Forest canopy in a deciduous forest has significant sheltering effects on the sub-canopy solar radiation,significantly influencing the energy balance of snow and permafrost beneath the forest and their spatial distrib...Forest canopy in a deciduous forest has significant sheltering effects on the sub-canopy solar radiation,significantly influencing the energy balance of snow and permafrost beneath the forest and their spatial distribution.This study employs a digital camera mounted with a fisheye lens to acquire photographs at various times in a growth cycle of the forest canopy at three selected sites in a deciduous forest near the Greater Khingan Mountains Forest Ecological Station,Northeast China.The vegetation types and conditions at the selected sites include P1 in Ledum-Claopodium-L.dahurica,P2 in Carex tato-L.dahurica,and P3 in Betula fruticosa-L.dahurica.After necessary image processing,these photographs were used to identify the canopy structure and its impacts on the sub-canopy solar radiation.Results show that fisheye photographs can successfully capture the forest canopy structure and are useful in estimating the sub-canopy solar radiation.The order of sheltering effects from the largest to the smallest on sub-canopy solar radiation at three selected sites is P3,P1,and P2,highly depending on the canopy density.Then sub-canopy solar radiation was calculated using fisheye photographs and an algorithm validated by in-situ observed solar radiation beneath the canopy at P1 and P3.The results are reasonable,although the accuracy seems compromised due to the mismatch of conditions for calculation and observation.Results also show that the mean annual solar radiation above the canopy was about 148.3 W/m2 in 2018,and the mean annual solar radiation values beneath the canopy were about 90.0,123.8,and 61.0 W/m2 at P1,P2,and P3,with only 60%,84%,and 42%of the total solar radiation penetrating through the canopy,respectively.Even in winter,when the trees are leafless,the canopy sheltering effects cannot be ignored in dense forests.Despite the limitations,fisheye photographs and related algorithms are useful in investigating the forest canopy structure and its impacts on sub-canopy solar radiation.展开更多
The optimal process conditions for solvent-free microwave extraction(SFME)of essential oils from Cinnamomum longepaniculatum deciduous leaves after moisture conditioning were established by response surface methodolog...The optimal process conditions for solvent-free microwave extraction(SFME)of essential oils from Cinnamomum longepaniculatum deciduous leaves after moisture conditioning were established by response surface methodology(RSM).A Box-Behnken design(BBD)was applied to evaluate the effects of three independent variables:moisture content(A:54%–74%),microwave power(B:300–500 W)and microwave time(C:20–40 min),on the extraction yield of essential oil.The compounds of the essential oils obtained by SFME,hydro-distillation and microwaveassisted hydro-distillation(MADE)were identified by gas chromatography-mass spectrometry(GC-MS),and the total lipids of C.longepaniculatum fresh leaves and deciduous leaves were analyzed.The correlation analysis of the response regression model indicated that quadratic polynomial model could be employed to optimize the extraction of essential oil.The optimal extraction condition was A:58%,B:400 W and C:28 min.In the optimal condition,the maximum extraction yield was 4.475 mL/100 g dw and higher than that by MADE.The main compound of the essential oil was eucalyptol(63.54%),and total oxygenated compounds was 78.95%,mainly caused by SFME and the metabolism of endophytic bacteria with decreasing content of phospholipids and fatty acids.Analysis of variance under the extraction condition illustrated high fitness of the model and the success of RSM for optimizing and reflecting the expected process condition.SFME combined with moisture regulation was an effective method for extracting essential oil from C.longepaniculatum deciduous leaves.展开更多
Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of ...Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of 57 plant species of MDF belonging to 28 families and 342 individuals and 25 plant species of DDF consist of 15 families and 285 individuals were identified. Plant species diversity was quantitatively higher in the MDF (H' = 3.68) compared to the DDF (H' = 2.39). Tectona grandis showed the highest density (30), dominance (4.40 m<sup>2</sup>) and IVI (27.01) of MDF and Dipterocarpus tuberculatus also composed the highest density (109), dominance (9.02 m<sup>2</sup>) and IVI (81.87) in DDF. The smallest diameter class (10 - 20 cm) comprised with 29 species, 103 individuals in MDF and 18 species, 85 individuals in DDF. The size class distribution displayed a reverse J-shaped pattern. The largest numbers of species were concentrated in the smallest height class in both investigated forests because of height and diameter distribution is closely related. The total densities of seedlings and saplings were 1219 and 531 ha<sup>-1</sup> in MDF and 988 and 444 ha<sup>-1</sup> in DDF respectively. Although soil texture of (40 - 50 cm) and (90 - 100 cm) were sandy clay loam in mixed deciduous forest, the other layers of both investigated forests were sandy loam.展开更多
Two types of forests in Northeast China is divided in this paper,that is,the decidu-ous forests in the northern part and the deciduous-evergreen forests in the eastern part.Both distri-butions of the two types of fore...Two types of forests in Northeast China is divided in this paper,that is,the decidu-ous forests in the northern part and the deciduous-evergreen forests in the eastern part.Both distri-butions of the two types of forests have also been pre sented.Meanwhile,the development and suc-cession as well as components of forests have been studied in detail.in the end,the vertical distribu-tion of the deciduous forests have been shown,in which,the near-temperate cold temperate decidu-ous coniferous forests are distributing in the low elevation area between 450m—600m from the northto the south,the typical siberian cold temperate deciduous coniferous forests are widely distributingfrom 450m—820m in the north to 600m—1050m in the south, the humid cold temperate deciduousconiferous forests can only be found in high elevation area from 820m—1100m in the north to1050m—1380m in the south,the cold temperate deciduous coniferous open forests can seldom ap-pear at the top of a few peaks.展开更多
AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been i...AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-andthrough defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue(P = 0.248), woven bone(P = 0.248) and compact bone(P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.展开更多
Background: The effect of forest fire on soil is complex and relatively less understood than its above ground effect.Understanding the effect of fire on forest soils can allow improving management of valuable forest e...Background: The effect of forest fire on soil is complex and relatively less understood than its above ground effect.Understanding the effect of fire on forest soils can allow improving management of valuable forest ecosystems as adequate and proper information is very important for efficient management. We have studied the recovery of soil properties after fire, using a chronosequence approach(two, five and fifteen years after fire and control). Soil samples were collected from each plot of four fire patches(B0, B2, B5 & B15) from three different depths viz. 0–10(Top), 10–20(Middle), and 20–30 cm(Bottom).Results: Soil organic carbon was lower than unburned plots after the fire and could not recover to the level of unburned plot(B0) even in 15 years. Total N, available P, and extractable K were lower 2-years and 5-years after the fire but are higher than unburned plot after 15-years. Available nitrogen(NO_3^- and NH_4^+) remain unchanged or higher than B0 in burned patches. Soil pH, Bulk Density, Water Holding Capacity, and Electrical Conductivity was lower initially after the fire. Forest fires have affected soil properties considerably. The response of soil properties varied with years after fire and soil depth.Conclusion: Forest fires occur very frequently in the study area. Significant quantities of carbon and total nitrogen are lost to the atmosphere by burning of litter, duff, and soil OM. Because nitrogen is one of the most important soil nutrients, the recapture of N lost by volatilization during a fire must receive special attention. Long-term studies are required to better understand the recovery of soil nitrogen.展开更多
In the southern mountain ranges of Yunnan province,China,deep valleys of several large rivers create rain shadows with hot dry summers,and are locally designated tropical;towards the north,notably in the Lancang(Upper...In the southern mountain ranges of Yunnan province,China,deep valleys of several large rivers create rain shadows with hot dry summers,and are locally designated tropical;towards the north,notably in the Lancang(Upper Mekong)valley,these regions may experience frost during winter.The woody forest canopy of these valleys is predominantly deciduous,with evergreen elements in the north,where the canopy is open and the forest savanna-like.However,we here present tall forest with a closed deciduous canopy and semi-evergreen subcanopy observed in hot dry valleys of these rivers and their tributaries in the tropical south.The structure and physiognomy of these forests resemble the tall(moist)deciduous forest formation widespread in South Asia and Indo-Burma.Furthermore,these forests are largely composed of tropical elements at both the generic(80%)and the species level(>70%),indicating that these forests are indeed tropical.We originally hypothesized that these isolated forests represent refugia of a pre-Holocene extension of tall(moist)deciduous forest formation of South Asia and Indo-Burma.The sample plot we established to test this hypothesis confirmed that these forests share the structure and physiognomy of the tall(moist)deciduous forest formation;however,the plots also showed that these forests lack the characteristic and dominant species of the formation's Indo-Burmese range.The tree flora,in particular,indicates that both deciduous and evergreen elements are instead mostly derived from the adjacent tropical semi-evergreen forests of tropical southern China;yet they also include an important endemic element,which implies that these forests have survived as refuges possibly since the Pliocene.The exceptional representation of evergreen elements in these forests indicates that they have rarely been subject to hot fires or domestic cattle browsing,adding to the unique nature of the forests and further justifying their strict conservation.展开更多
Spatial distribution is fundamental for understanding species coexistence mechanisms in forest communities.Here we comprehensively explored fine-scale spatial patterns of tree species in a secondary warm-temperate dec...Spatial distribution is fundamental for understanding species coexistence mechanisms in forest communities.Here we comprehensively explored fine-scale spatial patterns of tree species in a secondary warm-temperate deciduous broad-leaved forest community in north China.Aggregated distribution patterns were predominant.Species functional traits had no significant effects on their spatial patterns.The aggregation intensity decreased with increasing DBH and abundance.The multivariate linear stepwise regression showed that abundance and maximum DBH were correlated with the aggregation intensity.Our results partially confirm that species attributes(abundance,DBH)and habitat heterogeneity may primarily contribute to spatial patterns and species coexistence in this secondary forest.展开更多
BACKGROUND Autoimmune hepatitis is a serious autoimmune liver disease that threatens human health worldwide,which emphasizes the urgent need to identify novel treatments.Stem cells from human exfoliated deciduous teet...BACKGROUND Autoimmune hepatitis is a serious autoimmune liver disease that threatens human health worldwide,which emphasizes the urgent need to identify novel treatments.Stem cells from human exfoliated deciduous teeth(SHED),which are easy to obtain in a non-invasive manner,show pronounced proliferative and immunomodulatory capacities.AIM To investigate the protective effects of SHED on concanavalin A(ConA)-induced hepatitis in mice,and to elucidate the associated regulatory mechanisms.METHODS We used a ConA-induced acute hepatitis mouse model and an in vitro co-culture system to study the protective effects of SHED on ConA-induced autoimmune hepatitis,as well as the associated underlying mechanisms.RESULTS SHED infusion could prevent aberrant histopathological liver architecture caused by ConA-induced infiltration of CD3+,CD4+,tumor necrosis-alpha+,and interferon-gamma+inflammatory cells.Alanine aminotransferase and aspartate aminotransferase were significantly elevated in hepatitis mice.SHED infusion could therefore block ConA-induced alanine aminotransferase and aspartate aminotransferase elevations.Mechanistically,ConA upregulated tumor necrosisalpha and interferon-gamma expression,which was activated by the nuclear factor-kappa B pathway to induce hepatocyte apoptosis,resulting in acute liver injury.SHED administration protected hepatocytes from ConA-induced apoptosis.CONCLUSION SHED alleviates ConA-induced acute liver injury via inhibition of hepatocyte apoptosis mediated by the nuclear factor-kappa B pathway.Our findings could provide a potential treatment strategy for hepatitis.展开更多
Urban areas are a major source of anthropogenic carbon dioxide (CO<sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">) emissions ...Urban areas are a major source of anthropogenic carbon dioxide (CO<sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">) emissions because of road traffic and local heating with natural gas, oil or coal. Rome is among the largest European cities (129,000 ha) with a large volume of green areas (69.6% of the total Municipality area). The CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> sequestration (CS) capability for the greenery extending for about 300 km</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> inside the area delimited by the Great Ring Road (GRA) in Rome was calculated combining satellite data with CS data measured in the field. Data from Sentinel-2 were collected and the Normalized Difference Vegetation Index (NDVI) was computed on a pixel-base. Three plant classes homogeneous in terms of annual NDVI profile were identified: deciduous trees (DT), evergreen trees (ET) and meadows (M) covering an area of 14,142.027 ha within the GRA, of which M had the highest percentage (48%), followed by DT (27%) and ET (25%). CS ranged from 428,241</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;">492.9 </span><span style="font-family:Verdana;">T</span><span style="font-family:;" "=""><span style="font-family:Verdana;">ons CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> year</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> (ET) to 263,072</span></span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;">460.6 Tons CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> year</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> (M). The total CS of the greenery inside the GRA was 1049,490,355.4 Tons CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> year</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> resulting in an annual economic value of $772,424,901.6/ha. The CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> sequestration capability of the considered plant classes could be incorporated into the national greenhouse gas emission budget to calculate the contribution of CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> sequestration to the economy of Rome.</span></span>展开更多
Although aluminum itself was reported to prevent dental caries, previous in vitro studies reported that the aluminum level in the whole saliva of children was independent of caries prevalence. Purposes of this study w...Although aluminum itself was reported to prevent dental caries, previous in vitro studies reported that the aluminum level in the whole saliva of children was independent of caries prevalence. Purposes of this study were to compare the elution levels of aluminum and calcium from deciduous enamel into acidic artificial saliva, and determine whether the degree of aluminum elution reflects individual caries risk. One hundred and eleven extracted human deciduous teeth were collected. Concentrations of aluminum and calcium eluted from sound regions of enamel into artificial saliva (pH 6.2 or 5.5) were determined using atomic absorption spectrophotometry. One hundred and four and 108 available data samples were obtained for aluminum and calcium evaluation, respectively, and were compared based on the sex, tooth type, caries history, and the number of the donor’s carious teeth at each pH. Calcium elution was not affected by the sex;however, more aluminum was eluted from boys’ than from girls’ teeth at pH 5.5. The aluminum release depended on the tooth type, and was significantly higher in incisors than in molars at a pH of 5.5. In relation to the caries history, aluminum (at pH 5.5) and calcium (at pH 6.2) dissolved more from sound regions of the enamel of caries-experienced teeth than from the enamel of teeth without caries experience. Moreover, aluminum markedly dissolved from enamel in artificial saliva at both pH 6.2 and 5.5 when the donor had more carious teeth, regardless of the presence or absence of caries experience in the sampled teeth. There is a possibility that the rate of aluminum elution from enamel into acidic fluid reflects individual caries sensitivity.展开更多
Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change.Combined observations and analyse...Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change.Combined observations and analyses of plant ecophysiology and optical remote sensing would enable us to achieve these studies.In order to examine the utility of spectral vegetation indices(VIs)for assessing ecosystem-level photosynthesis,we investigated the relationships between canopy-scale photosynthetic productivity and canopy spectral reflectance over seasons for 5 years in a cool,temperate deciduous broadleaf forest at‘Takayama’super site in central Japan.Methods Daily photosynthetic capacity was assessed by in situ canopy leaf area index(LAI),(LAI×Vcmax[single-leaf photosynthetic capacity]),and the daily maximum rate of gross primary production(GPPmax)was estimated by an ecosystem carbon cycle model.We examined five VIs:normalized difference vegetation index(NDVI),enhanced vegetation index(EVI),green–red vegetation index(GRVI),chlorophyll index(CI)and canopy chlorophyll index(CCI),which were obtained by the in situ measurements of canopy spectral reflectance.Important Findings Our in situ observation of leaf and canopy characteristics,which were analyzed by an ecosystem carbon cycling model,revealed that their phenological changes are responsible for seasonal and interannual variations in canopy photosynthesis.Significant correlations were found between the five VIs and canopy photosynthetic capacity over the seasons and years;four of the VIs showed hysteresis-type relationships and only CCI showed rather linear relationship.Among the VIs examined,we applied EVI–GPPmax relationship to EVI data obtained by Moderate Resolution Imaging Spectroradiometer to estimate the temporal and spatial variation in GPPmax over central Japan.Our findings would improve the accuracy of satellite-based estimate of forest photosynthetic productivity in fine spatial and temporal resolutions,which are necessary for detecting any response of terrestrial ecosystem to meteorological fluctuations.展开更多
We compared the pollen assemblages of surface moss samples and corresponding vegetation inventory data from 34 sites in the Huangling region of the central Loess Plateau. Our aims were to determine the characteristics...We compared the pollen assemblages of surface moss samples and corresponding vegetation inventory data from 34 sites in the Huangling region of the central Loess Plateau. Our aims were to determine the characteristics of the pollen assemblages from the deciduous broadleaved forest climax community and its significance in terms of vegetation type and species composition. The pollen assemblages are dominated by woody plants such as Quercus(42% of total terrestrial pollen),Betula(16%) and Pinus(12%), with minor differences between different plant communities. The pollen assemblages of individual sampling sites differed from the vegetation composition within the 0–100 m scope and were more similar to the vegetation coverage within the 0–1000 m scope. This indicates that the surface pollen assemblages mainly reflect the comprehensive information from the vegetation composition of a large area, rather than the vegetation composition close to the sampling site. The contents of Quercus, Betula and Pinus pollen are high, and close to their vegetation coverage; whereas the contents of deciduous broadleaved arbor taxa(such as Malus and Acer) are lower, but their corresponding regional vegetation cover is higher. This suggests that the vegetation information conveyed by poorly-represented pollen taxa should be considered when interpreting stratigraphic pollen assemblages. Using the observed quantitative relationships between pollen and vegetation of the main taxa, we reconstructed the regional vegetation composition in the Gonghai Lake area of the northeastern Loess Plateau during the middle Holocene(7300–5000 yr BP). The results indicated that Quercus-dominated deciduous broadleaved forest climax community developed in the mountains surrounding the lake.展开更多
Introduction:This paper describes the leafing,flowering and fruiting phenology of canopy trees in the dry deciduous forest of Bhadra wildlife sanctuary from June 2004 to May 2006.Method:All the woody canopy individual...Introduction:This paper describes the leafing,flowering and fruiting phenology of canopy trees in the dry deciduous forest of Bhadra wildlife sanctuary from June 2004 to May 2006.Method:All the woody canopy individuals(>20 cm girth at breast height)were identified and tagged with a unique number along a transect of approximately 2 Km comprising 157 individuals of 22 species.Observations were made at monthly intervals from June 2004 to May 2006 for leafing,flowering and fruiting phenophases.Result:Leaf fall starts in September,with a peak in December and January.Leaf initiation begins in February,with a peak in April before the monsoon.Leaf expansion starts in February from pre-monsoon with a peak in May and July during the monsoon.Leaf senescence begins in September to November and peaks in January to March.Flower bud initiates in January with a peak in April and May,and pollination begins in April with a peak in May and July before the monsoon to onset of monsoon.Fruit bud initiates in May with a peak in September and October.Unripened fruit was observed in May with a peak in September and November.Fruit fall begins in November with a peak in March.Conclusion:Our results show that leafing and flowering activities occur in the summer or pre-monsoon.Fruiting patterns occur during the monsoon to post-monsoon season.Seasonality among various phenophases indicates that leaf senescence flower initiation and fruit fall have strong seasonality.展开更多
Aims The study of deciduous phenology over boreal forest is important for understanding forest ecology and better management.In this paper,our objective was to determine the phenological stages of deciduous leaf out(D...Aims The study of deciduous phenology over boreal forest is important for understanding forest ecology and better management.In this paper,our objective was to determine the phenological stages of deciduous leaf out(DLO)over the deciduous-dominant[i.e.trembling aspen(Populus tremuloides)]stands in the Canadian Province of Alberta.Methods During the period 2006–08,we used Moderate Resolution Imaging Spectroradiometer(MODIS)-based 8-day surface temperature(TS)images to calculate accumulated growing degree days(AGDD:a favourable temperature regime for plant growth).The temporal dynamics of AGDD in conjunction with in situ DLO observations were then analysed in determining the optimal threshold for DLO in 2006(i.e.80 degree days).Important Findings The implementation of the above-mentioned optimal threshold revealed reasonable agreements(i.e.on an average 91.9%of the DLO cases within ±2 periods or ±16 days of deviations during 2007–08)in comparison to the in situ observed data.The developments could be useful in various forestry-related applications,e.g.plant growth and its ability of exchanging atmospheric carbon dioxide,forest ecohydrology,risk of insect infestation,forest fire and impact of climate change,among others.展开更多
Introduction:The study was conducted in Mudumalai Tiger Reserve,in the Western Ghats to understand the effect of a single fire event on tree diversity and regeneration status.Four forest patches were selected which we...Introduction:The study was conducted in Mudumalai Tiger Reserve,in the Western Ghats to understand the effect of a single fire event on tree diversity and regeneration status.Four forest patches were selected which were unburned,2-year-old burn,5-year-old burn,and 15-year-old burn.Three 0.1 ha square plots were laid randomly in all four patches and analyzed for tree diversity,stand structure,and regeneration of tree species.Results:A total of 4129 individuals of tree species were recorded in field surveys,comprising 3474 seedlings,121 saplings,and 534 trees.Totally,40 tree species were recorded in study plots,from which 28 species were seedlings,16 species were saplings,and 37 species were at tree stages.Conclusions:Tree diversity decreased in 2-year-old and 5-year-old burnt plots and was reached to the level of unburnt plots in 15 years of interval.Stems of small size classes started increasing after the fire.Seedling density increased linearly in subsequent years after fire but sapling and tree density recorded less than control in B2 but was higher in B5 and B15.The overall fire affected diversity,but regeneration showed a positive trend.展开更多
Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to...Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to retrieve spring phenology metrics from four Moderate Resolution Imaging Spectro-radiometer(MODIS)products,including fraction of Absorbed Photosyntheti-cally Active Radiation(fAPAR),Leaf Area Index(LAI),Normalized Difference Vegetation Index(NDVI),and Enhanced Vegetation Index(EVI)for three temperate deciduous broadleaf forests in North America between 2001 and 2009.These MODIS-based spring phenology metrics were subsequently linked to the photosynthetic curves(daily gross primary productivity,GPP)measured by an eddy covariance flux tower.The 20% dynamic threshold spring onset metrics from MODIS products were closer to the photosynthesis onset metrics at the date of 2% GPP increase for NDVI and fAPAR,and closer to the date of 5%and 10% increase of GPP for EVI and LAI,respectively.The 50% dynamic threshold onset metrics were closer to the photosynthesis onset metrics at the date of 10%GPP increase for NDVI,and closer to the date of 20% GPP increase for fAPAR,LAI and EVI,respectively.These results can improve our knowledge on the photosynthesis activity status of remotely sensed spring phenology metrics.展开更多
Background:Ongoing climate change is anticipated to increase the frequency and intensity of drought events,thereby affecting forest recovery dynamics and elevating tree mortality.The drought of 2018,with its exception...Background:Ongoing climate change is anticipated to increase the frequency and intensity of drought events,thereby affecting forest recovery dynamics and elevating tree mortality.The drought of 2018,with its exceptional intensity and duration,had a significant adverse impact on tree species throughout Central Europe.However,our understanding of the resistance to and recovery of young trees from drought stress remains limited.Here,we examined the recovery patterns of native deciduous tree sapling species following the 2018 drought,and explored the impact of soil depth,understory vegetation,and litter cover on this recovery.Methods:A total of 1,149 saplings of seven deciduous tree species were monitored in the understory of old-growth forests in Northern Bavaria,Central Germany.The vitality of the saplings was recorded from 2018 to 2021 on 170 plots.Results:Fagus sylvatica was the most drought-resistant species,followed by Betula pendula,Acer pseudoplatanus,Quercus spp.,Corylus avellana,Carpinus betulus,and Sorbus aucuparia.Although the drought conditions persisted one year later,all species recovered significantly from the 2018 drought,albeit with a slight decrease in vitality by 2021.In 2018,the drought exhibited a more pronounced adverse effect on saplings in deciduous forests compared to mixed and coniferous forests.Conversely,sapling recovery in coniferous and mixed forests exceeded that observed in deciduous forests in 2019.The pivotal factors influencing sapling resilience to drought were forest types,soil depth,and understory vegetation,whereas litter and forest canopy cover had a negative impact.Conclusion:Long-term responses of tree species to drought can be best discerned through continuous health monitoring.These findings demonstrate the natural regeneration potential of deciduous species in the context of climate change.Selective tree species planting,soil management practices,and promoting understory diversity should be considered when implementing adaptive management strategies to enhance forest resilience to drought events.展开更多
We analyzed national forest inventory data collected from circa 2000–2018 across 37 states in the eastern United States to better understand the influence of forest health related canopy disturbances on the regenerat...We analyzed national forest inventory data collected from circa 2000–2018 across 37 states in the eastern United States to better understand the influence of forest health related canopy disturbances on the regeneration and recruitment dynamics of upland oaks(Quercus).We found low levels of oak recruitment across all disturbance types examined but limited evidence of any direct effects from the type of disturbance on the population of regenerating oaks.The general lack of differences in oak regeneration response between forest health disturbances and disturbances caused by harvested or non-disturbed plots does not indicate that the effects of forest health disturbances were benign,however.Instead,low level of oak recruitment across all disturbance types highlights the pervasiveness of the trend of shifting composition in once oak-dominated forests where oak is absent or sparse in the regeneration layer.Our results show that oak recruitment was higher when oak was present as advance reproduction prior to disturbance from any cause examined.Collectively,these results lead us to conclude that the widespread inadequacy of oak advance reproduction in mature oak-dominated forests is the prevailing threat to oak forest health and sustainability.We suggest the status of advance reproduction be treated as a co-morbidity when weighing the risk and potential outcomes from other threats to upland oak forests in the eastern United States.展开更多
基金the National Natural Science Foundation of China(Grant Nos.41971079 and 41671059,41975081).
文摘Forest canopy in a deciduous forest has significant sheltering effects on the sub-canopy solar radiation,significantly influencing the energy balance of snow and permafrost beneath the forest and their spatial distribution.This study employs a digital camera mounted with a fisheye lens to acquire photographs at various times in a growth cycle of the forest canopy at three selected sites in a deciduous forest near the Greater Khingan Mountains Forest Ecological Station,Northeast China.The vegetation types and conditions at the selected sites include P1 in Ledum-Claopodium-L.dahurica,P2 in Carex tato-L.dahurica,and P3 in Betula fruticosa-L.dahurica.After necessary image processing,these photographs were used to identify the canopy structure and its impacts on the sub-canopy solar radiation.Results show that fisheye photographs can successfully capture the forest canopy structure and are useful in estimating the sub-canopy solar radiation.The order of sheltering effects from the largest to the smallest on sub-canopy solar radiation at three selected sites is P3,P1,and P2,highly depending on the canopy density.Then sub-canopy solar radiation was calculated using fisheye photographs and an algorithm validated by in-situ observed solar radiation beneath the canopy at P1 and P3.The results are reasonable,although the accuracy seems compromised due to the mismatch of conditions for calculation and observation.Results also show that the mean annual solar radiation above the canopy was about 148.3 W/m2 in 2018,and the mean annual solar radiation values beneath the canopy were about 90.0,123.8,and 61.0 W/m2 at P1,P2,and P3,with only 60%,84%,and 42%of the total solar radiation penetrating through the canopy,respectively.Even in winter,when the trees are leafless,the canopy sheltering effects cannot be ignored in dense forests.Despite the limitations,fisheye photographs and related algorithms are useful in investigating the forest canopy structure and its impacts on sub-canopy solar radiation.
基金supports of the Wuhan Scientific and Technical Payoffs Transformation Project(2019030703011505)Enterprise Technology Innovation and Development Projects(2021BLB151)Agricultural Science and Technology Innovation Project of Chinese Academy of Agricultural Sciences(CAAS-ASTIP-2021-OCRI).
文摘The optimal process conditions for solvent-free microwave extraction(SFME)of essential oils from Cinnamomum longepaniculatum deciduous leaves after moisture conditioning were established by response surface methodology(RSM).A Box-Behnken design(BBD)was applied to evaluate the effects of three independent variables:moisture content(A:54%–74%),microwave power(B:300–500 W)and microwave time(C:20–40 min),on the extraction yield of essential oil.The compounds of the essential oils obtained by SFME,hydro-distillation and microwaveassisted hydro-distillation(MADE)were identified by gas chromatography-mass spectrometry(GC-MS),and the total lipids of C.longepaniculatum fresh leaves and deciduous leaves were analyzed.The correlation analysis of the response regression model indicated that quadratic polynomial model could be employed to optimize the extraction of essential oil.The optimal extraction condition was A:58%,B:400 W and C:28 min.In the optimal condition,the maximum extraction yield was 4.475 mL/100 g dw and higher than that by MADE.The main compound of the essential oil was eucalyptol(63.54%),and total oxygenated compounds was 78.95%,mainly caused by SFME and the metabolism of endophytic bacteria with decreasing content of phospholipids and fatty acids.Analysis of variance under the extraction condition illustrated high fitness of the model and the success of RSM for optimizing and reflecting the expected process condition.SFME combined with moisture regulation was an effective method for extracting essential oil from C.longepaniculatum deciduous leaves.
文摘Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of 57 plant species of MDF belonging to 28 families and 342 individuals and 25 plant species of DDF consist of 15 families and 285 individuals were identified. Plant species diversity was quantitatively higher in the MDF (H' = 3.68) compared to the DDF (H' = 2.39). Tectona grandis showed the highest density (30), dominance (4.40 m<sup>2</sup>) and IVI (27.01) of MDF and Dipterocarpus tuberculatus also composed the highest density (109), dominance (9.02 m<sup>2</sup>) and IVI (81.87) in DDF. The smallest diameter class (10 - 20 cm) comprised with 29 species, 103 individuals in MDF and 18 species, 85 individuals in DDF. The size class distribution displayed a reverse J-shaped pattern. The largest numbers of species were concentrated in the smallest height class in both investigated forests because of height and diameter distribution is closely related. The total densities of seedlings and saplings were 1219 and 531 ha<sup>-1</sup> in MDF and 988 and 444 ha<sup>-1</sup> in DDF respectively. Although soil texture of (40 - 50 cm) and (90 - 100 cm) were sandy clay loam in mixed deciduous forest, the other layers of both investigated forests were sandy loam.
文摘Two types of forests in Northeast China is divided in this paper,that is,the decidu-ous forests in the northern part and the deciduous-evergreen forests in the eastern part.Both distri-butions of the two types of forests have also been pre sented.Meanwhile,the development and suc-cession as well as components of forests have been studied in detail.in the end,the vertical distribu-tion of the deciduous forests have been shown,in which,the near-temperate cold temperate decidu-ous coniferous forests are distributing in the low elevation area between 450m—600m from the northto the south,the typical siberian cold temperate deciduous coniferous forests are widely distributingfrom 450m—820m in the north to 600m—1050m in the south, the humid cold temperate deciduousconiferous forests can only be found in high elevation area from 820m—1100m in the north to1050m—1380m in the south,the cold temperate deciduous coniferous open forests can seldom ap-pear at the top of a few peaks.
文摘AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-andthrough defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue(P = 0.248), woven bone(P = 0.248) and compact bone(P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.
基金the University Grants Commission, New Delhi for providing the financial support for the Ph.D. research through Junior Research Fellowship (UGC letter No. F. 17-115/98 (SA-I) dated-11 June 2013)
文摘Background: The effect of forest fire on soil is complex and relatively less understood than its above ground effect.Understanding the effect of fire on forest soils can allow improving management of valuable forest ecosystems as adequate and proper information is very important for efficient management. We have studied the recovery of soil properties after fire, using a chronosequence approach(two, five and fifteen years after fire and control). Soil samples were collected from each plot of four fire patches(B0, B2, B5 & B15) from three different depths viz. 0–10(Top), 10–20(Middle), and 20–30 cm(Bottom).Results: Soil organic carbon was lower than unburned plots after the fire and could not recover to the level of unburned plot(B0) even in 15 years. Total N, available P, and extractable K were lower 2-years and 5-years after the fire but are higher than unburned plot after 15-years. Available nitrogen(NO_3^- and NH_4^+) remain unchanged or higher than B0 in burned patches. Soil pH, Bulk Density, Water Holding Capacity, and Electrical Conductivity was lower initially after the fire. Forest fires have affected soil properties considerably. The response of soil properties varied with years after fire and soil depth.Conclusion: Forest fires occur very frequently in the study area. Significant quantities of carbon and total nitrogen are lost to the atmosphere by burning of litter, duff, and soil OM. Because nitrogen is one of the most important soil nutrients, the recapture of N lost by volatilization during a fire must receive special attention. Long-term studies are required to better understand the recovery of soil nitrogen.
基金funded by The National Natural Science Foundation of China(41471051,31970223)the major project of Yunnan Science and Technology Department-Yunnan University joint fund(2018FY001(-002))“Yunnan Vegegraphy Research”.Fig.1 was made by Yang Jianbo from GIS Lab in Xishuangbanna Tropical Botanical Garden,Chinese Academy of Sciences.
文摘In the southern mountain ranges of Yunnan province,China,deep valleys of several large rivers create rain shadows with hot dry summers,and are locally designated tropical;towards the north,notably in the Lancang(Upper Mekong)valley,these regions may experience frost during winter.The woody forest canopy of these valleys is predominantly deciduous,with evergreen elements in the north,where the canopy is open and the forest savanna-like.However,we here present tall forest with a closed deciduous canopy and semi-evergreen subcanopy observed in hot dry valleys of these rivers and their tributaries in the tropical south.The structure and physiognomy of these forests resemble the tall(moist)deciduous forest formation widespread in South Asia and Indo-Burma.Furthermore,these forests are largely composed of tropical elements at both the generic(80%)and the species level(>70%),indicating that these forests are indeed tropical.We originally hypothesized that these isolated forests represent refugia of a pre-Holocene extension of tall(moist)deciduous forest formation of South Asia and Indo-Burma.The sample plot we established to test this hypothesis confirmed that these forests share the structure and physiognomy of the tall(moist)deciduous forest formation;however,the plots also showed that these forests lack the characteristic and dominant species of the formation's Indo-Burmese range.The tree flora,in particular,indicates that both deciduous and evergreen elements are instead mostly derived from the adjacent tropical semi-evergreen forests of tropical southern China;yet they also include an important endemic element,which implies that these forests have survived as refuges possibly since the Pliocene.The exceptional representation of evergreen elements in these forests indicates that they have rarely been subject to hot fires or domestic cattle browsing,adding to the unique nature of the forests and further justifying their strict conservation.
基金This study was supported by the National Key R&D Program of China(2017YFC0505601)the National Natural Science Foundation of China(31570630)State Key Laboratory of Forest and Soil Ecology(LFSE2015-13).
文摘Spatial distribution is fundamental for understanding species coexistence mechanisms in forest communities.Here we comprehensively explored fine-scale spatial patterns of tree species in a secondary warm-temperate deciduous broad-leaved forest community in north China.Aggregated distribution patterns were predominant.Species functional traits had no significant effects on their spatial patterns.The aggregation intensity decreased with increasing DBH and abundance.The multivariate linear stepwise regression showed that abundance and maximum DBH were correlated with the aggregation intensity.Our results partially confirm that species attributes(abundance,DBH)and habitat heterogeneity may primarily contribute to spatial patterns and species coexistence in this secondary forest.
基金Supported by The National Natural Science Foundation of China,No.81970940 and No.81600865Beijing Natural Science Foundation,No.7182182and the National Science and Technology Major Project of the Ministry of Science and Technology of China,No.2018ZX10302207.
文摘BACKGROUND Autoimmune hepatitis is a serious autoimmune liver disease that threatens human health worldwide,which emphasizes the urgent need to identify novel treatments.Stem cells from human exfoliated deciduous teeth(SHED),which are easy to obtain in a non-invasive manner,show pronounced proliferative and immunomodulatory capacities.AIM To investigate the protective effects of SHED on concanavalin A(ConA)-induced hepatitis in mice,and to elucidate the associated regulatory mechanisms.METHODS We used a ConA-induced acute hepatitis mouse model and an in vitro co-culture system to study the protective effects of SHED on ConA-induced autoimmune hepatitis,as well as the associated underlying mechanisms.RESULTS SHED infusion could prevent aberrant histopathological liver architecture caused by ConA-induced infiltration of CD3+,CD4+,tumor necrosis-alpha+,and interferon-gamma+inflammatory cells.Alanine aminotransferase and aspartate aminotransferase were significantly elevated in hepatitis mice.SHED infusion could therefore block ConA-induced alanine aminotransferase and aspartate aminotransferase elevations.Mechanistically,ConA upregulated tumor necrosisalpha and interferon-gamma expression,which was activated by the nuclear factor-kappa B pathway to induce hepatocyte apoptosis,resulting in acute liver injury.SHED administration protected hepatocytes from ConA-induced apoptosis.CONCLUSION SHED alleviates ConA-induced acute liver injury via inhibition of hepatocyte apoptosis mediated by the nuclear factor-kappa B pathway.Our findings could provide a potential treatment strategy for hepatitis.
文摘Urban areas are a major source of anthropogenic carbon dioxide (CO<sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">) emissions because of road traffic and local heating with natural gas, oil or coal. Rome is among the largest European cities (129,000 ha) with a large volume of green areas (69.6% of the total Municipality area). The CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> sequestration (CS) capability for the greenery extending for about 300 km</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> inside the area delimited by the Great Ring Road (GRA) in Rome was calculated combining satellite data with CS data measured in the field. Data from Sentinel-2 were collected and the Normalized Difference Vegetation Index (NDVI) was computed on a pixel-base. Three plant classes homogeneous in terms of annual NDVI profile were identified: deciduous trees (DT), evergreen trees (ET) and meadows (M) covering an area of 14,142.027 ha within the GRA, of which M had the highest percentage (48%), followed by DT (27%) and ET (25%). CS ranged from 428,241</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;">492.9 </span><span style="font-family:Verdana;">T</span><span style="font-family:;" "=""><span style="font-family:Verdana;">ons CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> year</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> (ET) to 263,072</span></span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;">460.6 Tons CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> year</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> (M). The total CS of the greenery inside the GRA was 1049,490,355.4 Tons CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> year</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> resulting in an annual economic value of $772,424,901.6/ha. The CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> sequestration capability of the considered plant classes could be incorporated into the national greenhouse gas emission budget to calculate the contribution of CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> sequestration to the economy of Rome.</span></span>
文摘Although aluminum itself was reported to prevent dental caries, previous in vitro studies reported that the aluminum level in the whole saliva of children was independent of caries prevalence. Purposes of this study were to compare the elution levels of aluminum and calcium from deciduous enamel into acidic artificial saliva, and determine whether the degree of aluminum elution reflects individual caries risk. One hundred and eleven extracted human deciduous teeth were collected. Concentrations of aluminum and calcium eluted from sound regions of enamel into artificial saliva (pH 6.2 or 5.5) were determined using atomic absorption spectrophotometry. One hundred and four and 108 available data samples were obtained for aluminum and calcium evaluation, respectively, and were compared based on the sex, tooth type, caries history, and the number of the donor’s carious teeth at each pH. Calcium elution was not affected by the sex;however, more aluminum was eluted from boys’ than from girls’ teeth at pH 5.5. The aluminum release depended on the tooth type, and was significantly higher in incisors than in molars at a pH of 5.5. In relation to the caries history, aluminum (at pH 5.5) and calcium (at pH 6.2) dissolved more from sound regions of the enamel of caries-experienced teeth than from the enamel of teeth without caries experience. Moreover, aluminum markedly dissolved from enamel in artificial saliva at both pH 6.2 and 5.5 when the donor had more carious teeth, regardless of the presence or absence of caries experience in the sampled teeth. There is a possibility that the rate of aluminum elution from enamel into acidic fluid reflects individual caries sensitivity.
基金This long-term study was partly supported by the JSPS 21st Century COE Program at Gifu Universitythe JSPS-NRF-NSFS A3 Foresight Program,a Global Change Observation Mission(GCOM-C,PI#102)of the Japan Aerospace Exploration Agency(JAXA)+2 种基金the Global Environment Research Fund(S-1)and the Environment Research&Technology Development Fund(D-0909 and S-9)of the Ministry of Environment Japan,the JSPS KAKENHI(22310008)the JSPS‘Funding Program for Next Generation World-Leading Researchers(NEXT Program)’S.N.is supported by JSPS-KAKENHI(24710021,Grant-in-Aid for Young Scientists B).
文摘Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change.Combined observations and analyses of plant ecophysiology and optical remote sensing would enable us to achieve these studies.In order to examine the utility of spectral vegetation indices(VIs)for assessing ecosystem-level photosynthesis,we investigated the relationships between canopy-scale photosynthetic productivity and canopy spectral reflectance over seasons for 5 years in a cool,temperate deciduous broadleaf forest at‘Takayama’super site in central Japan.Methods Daily photosynthetic capacity was assessed by in situ canopy leaf area index(LAI),(LAI×Vcmax[single-leaf photosynthetic capacity]),and the daily maximum rate of gross primary production(GPPmax)was estimated by an ecosystem carbon cycle model.We examined five VIs:normalized difference vegetation index(NDVI),enhanced vegetation index(EVI),green–red vegetation index(GRVI),chlorophyll index(CI)and canopy chlorophyll index(CCI),which were obtained by the in situ measurements of canopy spectral reflectance.Important Findings Our in situ observation of leaf and canopy characteristics,which were analyzed by an ecosystem carbon cycling model,revealed that their phenological changes are responsible for seasonal and interannual variations in canopy photosynthesis.Significant correlations were found between the five VIs and canopy photosynthetic capacity over the seasons and years;four of the VIs showed hysteresis-type relationships and only CCI showed rather linear relationship.Among the VIs examined,we applied EVI–GPPmax relationship to EVI data obtained by Moderate Resolution Imaging Spectroradiometer to estimate the temporal and spatial variation in GPPmax over central Japan.Our findings would improve the accuracy of satellite-based estimate of forest photosynthetic productivity in fine spatial and temporal resolutions,which are necessary for detecting any response of terrestrial ecosystem to meteorological fluctuations.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41630753, 41702184 & 41611130050)the Hebei Key Laboratory of Environmental Change and Ecological Construction and Key discipline fund project in Hebei provincethe Science Foundation of Hebei Normal University (Grant No. L2018B29)
文摘We compared the pollen assemblages of surface moss samples and corresponding vegetation inventory data from 34 sites in the Huangling region of the central Loess Plateau. Our aims were to determine the characteristics of the pollen assemblages from the deciduous broadleaved forest climax community and its significance in terms of vegetation type and species composition. The pollen assemblages are dominated by woody plants such as Quercus(42% of total terrestrial pollen),Betula(16%) and Pinus(12%), with minor differences between different plant communities. The pollen assemblages of individual sampling sites differed from the vegetation composition within the 0–100 m scope and were more similar to the vegetation coverage within the 0–1000 m scope. This indicates that the surface pollen assemblages mainly reflect the comprehensive information from the vegetation composition of a large area, rather than the vegetation composition close to the sampling site. The contents of Quercus, Betula and Pinus pollen are high, and close to their vegetation coverage; whereas the contents of deciduous broadleaved arbor taxa(such as Malus and Acer) are lower, but their corresponding regional vegetation cover is higher. This suggests that the vegetation information conveyed by poorly-represented pollen taxa should be considered when interpreting stratigraphic pollen assemblages. Using the observed quantitative relationships between pollen and vegetation of the main taxa, we reconstructed the regional vegetation composition in the Gonghai Lake area of the northeastern Loess Plateau during the middle Holocene(7300–5000 yr BP). The results indicated that Quercus-dominated deciduous broadleaved forest climax community developed in the mountains surrounding the lake.
文摘Introduction:This paper describes the leafing,flowering and fruiting phenology of canopy trees in the dry deciduous forest of Bhadra wildlife sanctuary from June 2004 to May 2006.Method:All the woody canopy individuals(>20 cm girth at breast height)were identified and tagged with a unique number along a transect of approximately 2 Km comprising 157 individuals of 22 species.Observations were made at monthly intervals from June 2004 to May 2006 for leafing,flowering and fruiting phenophases.Result:Leaf fall starts in September,with a peak in December and January.Leaf initiation begins in February,with a peak in April before the monsoon.Leaf expansion starts in February from pre-monsoon with a peak in May and July during the monsoon.Leaf senescence begins in September to November and peaks in January to March.Flower bud initiates in January with a peak in April and May,and pollination begins in April with a peak in May and July before the monsoon to onset of monsoon.Fruit bud initiates in May with a peak in September and October.Unripened fruit was observed in May with a peak in September and November.Fruit fall begins in November with a peak in March.Conclusion:Our results show that leafing and flowering activities occur in the summer or pre-monsoon.Fruiting patterns occur during the monsoon to post-monsoon season.Seasonality among various phenophases indicates that leaf senescence flower initiation and fruit fall have strong seasonality.
文摘Aims The study of deciduous phenology over boreal forest is important for understanding forest ecology and better management.In this paper,our objective was to determine the phenological stages of deciduous leaf out(DLO)over the deciduous-dominant[i.e.trembling aspen(Populus tremuloides)]stands in the Canadian Province of Alberta.Methods During the period 2006–08,we used Moderate Resolution Imaging Spectroradiometer(MODIS)-based 8-day surface temperature(TS)images to calculate accumulated growing degree days(AGDD:a favourable temperature regime for plant growth).The temporal dynamics of AGDD in conjunction with in situ DLO observations were then analysed in determining the optimal threshold for DLO in 2006(i.e.80 degree days).Important Findings The implementation of the above-mentioned optimal threshold revealed reasonable agreements(i.e.on an average 91.9%of the DLO cases within ±2 periods or ±16 days of deviations during 2007–08)in comparison to the in situ observed data.The developments could be useful in various forestry-related applications,e.g.plant growth and its ability of exchanging atmospheric carbon dioxide,forest ecohydrology,risk of insect infestation,forest fire and impact of climate change,among others.
基金We thank the Tamil Nadu Forest Department for granting us permission and providing data to conduct this study at the Mudumalai Tiger Reserve.We acknowledge the support of field assistants and forest staff of Mudumalai Tiger Reserve for their help and cooperationThe first author thank the University Grants Commission,New Delhi for providing the financial support for the Ph.D.research through Junior Research Fellowship(UGC letter No.F.17-115/98(SA-I)dated 11 June 2013).
文摘Introduction:The study was conducted in Mudumalai Tiger Reserve,in the Western Ghats to understand the effect of a single fire event on tree diversity and regeneration status.Four forest patches were selected which were unburned,2-year-old burn,5-year-old burn,and 15-year-old burn.Three 0.1 ha square plots were laid randomly in all four patches and analyzed for tree diversity,stand structure,and regeneration of tree species.Results:A total of 4129 individuals of tree species were recorded in field surveys,comprising 3474 seedlings,121 saplings,and 534 trees.Totally,40 tree species were recorded in study plots,from which 28 species were seedlings,16 species were saplings,and 37 species were at tree stages.Conclusions:Tree diversity decreased in 2-year-old and 5-year-old burnt plots and was reached to the level of unburnt plots in 15 years of interval.Stems of small size classes started increasing after the fire.Seedling density increased linearly in subsequent years after fire but sapling and tree density recorded less than control in B2 but was higher in B5 and B15.The overall fire affected diversity,but regeneration showed a positive trend.
基金The authors gratefully acknowledge financial support provided for this research by the National Natural Science Foundation of China(41222008,91125003)the External Cooperation Program of the Chinese Academy of Sciences(GJH21123).
文摘Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to retrieve spring phenology metrics from four Moderate Resolution Imaging Spectro-radiometer(MODIS)products,including fraction of Absorbed Photosyntheti-cally Active Radiation(fAPAR),Leaf Area Index(LAI),Normalized Difference Vegetation Index(NDVI),and Enhanced Vegetation Index(EVI)for three temperate deciduous broadleaf forests in North America between 2001 and 2009.These MODIS-based spring phenology metrics were subsequently linked to the photosynthetic curves(daily gross primary productivity,GPP)measured by an eddy covariance flux tower.The 20% dynamic threshold spring onset metrics from MODIS products were closer to the photosynthesis onset metrics at the date of 2% GPP increase for NDVI and fAPAR,and closer to the date of 5%and 10% increase of GPP for EVI and LAI,respectively.The 50% dynamic threshold onset metrics were closer to the photosynthesis onset metrics at the date of 10%GPP increase for NDVI,and closer to the date of 20% GPP increase for fAPAR,LAI and EVI,respectively.These results can improve our knowledge on the photosynthesis activity status of remotely sensed spring phenology metrics.
文摘Background:Ongoing climate change is anticipated to increase the frequency and intensity of drought events,thereby affecting forest recovery dynamics and elevating tree mortality.The drought of 2018,with its exceptional intensity and duration,had a significant adverse impact on tree species throughout Central Europe.However,our understanding of the resistance to and recovery of young trees from drought stress remains limited.Here,we examined the recovery patterns of native deciduous tree sapling species following the 2018 drought,and explored the impact of soil depth,understory vegetation,and litter cover on this recovery.Methods:A total of 1,149 saplings of seven deciduous tree species were monitored in the understory of old-growth forests in Northern Bavaria,Central Germany.The vitality of the saplings was recorded from 2018 to 2021 on 170 plots.Results:Fagus sylvatica was the most drought-resistant species,followed by Betula pendula,Acer pseudoplatanus,Quercus spp.,Corylus avellana,Carpinus betulus,and Sorbus aucuparia.Although the drought conditions persisted one year later,all species recovered significantly from the 2018 drought,albeit with a slight decrease in vitality by 2021.In 2018,the drought exhibited a more pronounced adverse effect on saplings in deciduous forests compared to mixed and coniferous forests.Conversely,sapling recovery in coniferous and mixed forests exceeded that observed in deciduous forests in 2019.The pivotal factors influencing sapling resilience to drought were forest types,soil depth,and understory vegetation,whereas litter and forest canopy cover had a negative impact.Conclusion:Long-term responses of tree species to drought can be best discerned through continuous health monitoring.These findings demonstrate the natural regeneration potential of deciduous species in the context of climate change.Selective tree species planting,soil management practices,and promoting understory diversity should be considered when implementing adaptive management strategies to enhance forest resilience to drought events.
基金This project falls under Task Agreement 18-JV-11242311-084 with the USDA Forest ServiceNorthern Research Station,within master joint venture agreement 18-JV-11242311-093 under the Great Rivers Cooperative Ecosystems Studies Unit.
文摘We analyzed national forest inventory data collected from circa 2000–2018 across 37 states in the eastern United States to better understand the influence of forest health related canopy disturbances on the regeneration and recruitment dynamics of upland oaks(Quercus).We found low levels of oak recruitment across all disturbance types examined but limited evidence of any direct effects from the type of disturbance on the population of regenerating oaks.The general lack of differences in oak regeneration response between forest health disturbances and disturbances caused by harvested or non-disturbed plots does not indicate that the effects of forest health disturbances were benign,however.Instead,low level of oak recruitment across all disturbance types highlights the pervasiveness of the trend of shifting composition in once oak-dominated forests where oak is absent or sparse in the regeneration layer.Our results show that oak recruitment was higher when oak was present as advance reproduction prior to disturbance from any cause examined.Collectively,these results lead us to conclude that the widespread inadequacy of oak advance reproduction in mature oak-dominated forests is the prevailing threat to oak forest health and sustainability.We suggest the status of advance reproduction be treated as a co-morbidity when weighing the risk and potential outcomes from other threats to upland oak forests in the eastern United States.
