In this study, tropical peat swamp soils from Giam Siak Kecil-Bukit Batu Biosphere Reserve (GSKBB) in Indonesia was evaluated to assess the impact of oil palm and rubber plantations on this unique organic soil through...In this study, tropical peat swamp soils from Giam Siak Kecil-Bukit Batu Biosphere Reserve (GSKBB) in Indonesia was evaluated to assess the impact of oil palm and rubber plantations on this unique organic soil through comparisons with soils from a natural forest using a polyphasic approach (chemical and molecular microbial assays). Changes in the ammonium, nitrate and phosphate concentration were observed in soils converted to agricultural use. Soil enzyme activities in plantation soils showed reduced β-glucosidase, cellobiohydrolase and acid phosphatase activities (50% - 55% decrease). PCR-DGGE based analysis showed that the soil bacterial community from agricultural soils exhibited the lowest similarity amongst the different microbial groups (fungi and Archaea) evaluated (34% similarity to the natural forest soil). Shannon Diversity index values showed that generally the conversion of tropical peatland natural forest to rubber plantation resulted in a greater impact on microbial diversity (ANOVA p < 0.05). Overall, this study indicated substantial shifts in the soil microbial activity and diversity upon conversion of natural peatland forest to agriculture, with a greater change being observed under rubber plantation compared to oil palm plantation. These findings provided important data for future peatland management by relating changes in the soil microbial community and activities associated to agricultural practices carried out on peatland.展开更多
Hainan Island is located in the northern periphery of the tropical world.The environment is suitable for a number of tropical economic crops.The content of soil organic matter under rubber plantation is around 10- 20 ...Hainan Island is located in the northern periphery of the tropical world.The environment is suitable for a number of tropical economic crops.The content of soil organic matter under rubber plantation is around 10- 20 g kg-1.Cu,Zn,Mn,As,Mg,Ca and K in the soil profile reflect the parent material and the intensive weathering and leaching in the area.Copper has noticeably accumulated in the lower horizon,whereas the concentrations of Ca,Mg and K.in rubber trees are 0.5- 4.9,2.2- 4.3 and 4.6-10.2 g kg-1 respectively.These three elements are mostly distributed in the plant roots and are particularly required during the development of new leaves early in the season.展开更多
This research was designed to help solve existing sustainable use problems such as soil nutrient loss and soil fertility decline in natural rubber plantations located in the hilly land of the south central mountainous...This research was designed to help solve existing sustainable use problems such as soil nutrient loss and soil fertility decline in natural rubber plantations located in the hilly land of the south central mountainous area of Hainan Island, China. Two different land management practices, sustainable and traditional, were adopted in a four-year experiment. Contour terraced fields and deep ditches for green manure were built in a sustainable way with a balanced, need-based application of complex fertilizer. Results of the four-year experiment showed that these sustainable measures compared to traditional measures improved available P and available K; had a 47.8% less soil erosion (an average of 3 663 t km-2 year-1) and a 15.9% lower runoff coefficient of 0.53; increased the dry rubber yield by 42.4%; and improved the economic benefit by 2.4 times. The sustainable land management scheme not only improved land utilisation efficiency, but also helped maintain soil fertility while increasing production in rubber plantations. It thereby offered a reasonable and sustainable use for land resources in the tropical mountainous areas.展开更多
The impacts of economic forest on global environmental change(GEC) are one of the hot issues in environmental study. Based on the 3 year observation data and 40 year climate data, GEC and analysis of the hydrological ...The impacts of economic forest on global environmental change(GEC) are one of the hot issues in environmental study. Based on the 3 year observation data and 40 year climate data, GEC and analysis of the hydrological dynamic characteristics of rubber plantations and estimate of the water balance in the rubber plantations in Hainan Island were made. The results showed that the rainfall intercepted by the canopy of the plantations accounted for 11 45% of the annual rainfall, the total runoff for 23 71%, the total evaporation and transpiration for 63 24%, the soil moisture storage for 1 6%. Analysis of the 40 year rainfall data in the 19 counties of Hainan Island during 1951—1990 showed that the large scale substitution of the natural vegetation with the rubber plantations had no significant effect on the local rainfall in Hainan Island. The main reasons are (1) 80% of the rainfall in Hainan is brought by typhoons; (2) the proportion of 11 6% rubber plantations in total forest coverage in Hainan is not enough to influence the local rainfall in Hainan Island; and (3) although the rubber plantation is artificial vegetation, it has the similar function to the tropical rain forest. Analysis of the total water resource and total GDP of Hainan in 1997 showed that the economic benefit resulted from the water resource was 1 0 RMB Yuan/m 3 The value of hydrological of the rubber plantation in Hainan was 113 9 million RMB Yuan/a when compared with the tropical rain forest. The paper reaches conclusion that the hydrological eco service function of rubber plantation has been enhanced after transformed from natural vegetation, which includes the natural service and powerful social service.展开更多
Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to ru...Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.展开更多
Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, ...Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, “CATAS7-20-59”, “PR107”, “RRIM600”, “GT1”, “INA873”, “93-114”in South China. The results showed that there were six kinds of existing plant types of rubber tree after planting of rubber plantations, which were available tapping trees, wind damaged trees, cold damaged trees, tapping panel dryness trees, absent trees and weak trees, respectively. These data investigated also showed rubber trees under available tapping, stoppage due to tapping panel dryness, absence, wind damage, cold damage and weakness were counted and calculated and made up for 72.21%, 14.75%, 5.61%, 3.86%, 2.68% and 1.89%. Tapping panel dryness trees, wind damage and absent trees are major factors for the loss of tapping rubber trees in the rubber plantations. Of these investigated varieties, available tapping trees per 100 trees of rubber plantation of “PR107”at the 1st, 12th, 14th, 16th, 20th, 24th tapping year were 96, 67, 70, 75, 66, 46 trees in Hainan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “RRIM600”at the 9th, 15th, 20th, 22nd tapping year were 88, 62, 55, 36 trees in Yunnan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “93-114” at the 10th, 19th, tapping year were 94, 62 trees in Guangdong planting zone. These results showed that available tapping trees of rubber plantation decreased with increasing tapping age under different planting zones in China.展开更多
Driven by soil biochemistry and plant community composition,soil microbial communities reflect land management and environmental conditions.To evaluate the effects of land-use change on soil microbial diversity,we use...Driven by soil biochemistry and plant community composition,soil microbial communities reflect land management and environmental conditions.To evaluate the effects of land-use change on soil microbial diversity,we used denaturing gradient gel electrophoresis(DGGE)combined with sequencing to compare bacterial and fungal community profiles between rubber plantation(RP)and nearby seasonal rainforests(SR).Rainforest soil generally had higher soil total C and microbial biomass C concentration,smaller soil aggregate proportions,and a soil pH below rubber plantation soil.The bacterial and fungal richness and diversity were similar after converting primary forests to rubber plantations.However,the composition of bacterial and fungal communities has significantly changed in rubber plantations.Basidiomycota,the predominant group of fungi,was significantly different between primary forests and rubber plantations.However,Basidiomycota showed higher heterogenetic distribution in the rainforest under rubber plantations.In conclusion,land-use changes mainly affect soil microbial community composition and heterogeneity distribution patterns,especially for saprotrophic fungi,which consist of changes in litter inputs and soil C conditions.展开更多
Soil erosion by water is known to be a major driver of land degradation.Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land.Splash erosion ...Soil erosion by water is known to be a major driver of land degradation.Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land.Splash erosion may be exacerbated or mitigated by ongoing land use/cover change.To estimate the effects of various land use and management systems on splash erosion in the humid tropics,we measured the actual splash erosion under natural rainfall conditions in a tropical rainforest(TR),rubber monoculture(RM),and four rubber agroforestry ecosystems in Xishuangbanna,Southwestern China.The average cumulative splash mass in the RM was 48.7 times higher compared to that in the TR,indicating that the replacement of TR by RM results in severe splash erosion.In the rubber agroforestry systems,the throughfall kinetic energy and splash mass were 34-76%and 86-97%lower,respectively,than that in the RM,indicating that intercropping crops with rubber trees can effectively alleviate erosive power of throughfall and thus splash erosion.Under all land use regimes,in the plots where the litter layer was removed,splash erosion was significantly(2.0-12.1 times)higher and more spatially heterogeneous than in those with litter cover.This highlighted the key role of the forest litter layer in protecting the soil from raindrop detachment.In the study area,the actual splash erosion was strongly correlated with the conditions of precipitation(amount and intensity(I10)of rainfall)and the vegetation structure(especially the crown base height,leaf area index,and canopy cover),but weakly correlated with the soil properties.Given the importance of near-ground intercrops(height<5 m)for improving the vegetation structure,surface cover,and soil conditions,the intercropping of Camellia sinensis and Theobroma cacao with rubber trees is a promising approach for controlling splash erosion and also has benefits on the sus-tainable development of rubber plantation.展开更多
Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resista...Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.展开更多
Tree plantation and forest restoration are the major strategies for enhancing terrestrial carbon sequestration and mitigating climate change.The Grain for Green Project in China has positively impacted global carbon s...Tree plantation and forest restoration are the major strategies for enhancing terrestrial carbon sequestration and mitigating climate change.The Grain for Green Project in China has positively impacted global carbon sequestration and the trend towards fragmentation of plantation forests.Limited studies have been conducted on changes in plantation biomass and stand structure caused by fragmentation,and the effect of fragmentation on the carbon storage of plantation forests remains unclear.This study evaluated the differences between carbon storage and stand structure in black locust forests in fragmented and continuous landscape in the Ansai District,China and discussed the effects of ecological significance of four landscape indices on carbon storage and tree density.We used structural equation modelling to explore the direct and indirect effects of fragmentation,edge,abiotic factors,and stand structure on above-ground carbon storage.Diameter at breast height(DBH)in fragmented forests was 53.3%thicker,tree density was 40.9%lower,and carbon storage was 49.8%higher than those in continuous forests;for all given DBH>10 cm,the trees in fragmented forests were shorter than those in continuous forests.The patch area had a negative impact on carbon storage,i.e.,the higher the degree of fragmentation,the lower the density of the tree;and fragmentation and distance to edge(DTE)directly increased canopy coverage.However,canopy coverage directly decreased carbon storage,and fragmentation directly increased carbon storage and tree density.In non-commercial forests,fragmentation reduces the carbon storage potential of plantation,and the influence of patch area,edge,and patchy connection on plantation should be considered when follow-up trees are planted and for the plantation management.Thus,expanding the area of plantation patches,repairing the edges of complex-shaped patches,enhancing the connectivity of similar patches,and applying nutrients to plantation forests at regular intervals are recommended in fragmented areas of the Loess Plateau.展开更多
Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas.An im...Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas.An important species for afforestation in dry environments of northern China,Mongolian pine(Pinus sylvestris var.mongolica Litv.)has recently exhibited growth decline and dieback on many sites,particularly pronounced in old-growth plantations.However,changes in response to drought stress by this species with age as well as the underlying mechanisms are poorly understood.In this study,tree-ring data and remotely sensed vegetation data were combined to investigate variations in growth at individual tree and stand scales for young(9-13 years)and aging(35-52 years)plantations of Mongolian pine in a water-limited area of northern China.A recent decline in tree-ring width in the older plantation also had lower values in satellited-derived normalized difference vegetation indices and normalized difference water indices relative to the younger plantations.In addition,all measured growth-related metrics were strongly correlated with the self-calibrating Palmer drought severity index during the growing season in the older plantation.Sensitivity of growth to drought of the older plantation might be attributed to more severe hydraulic limitations,as reflected by their lower sapwood-and leaf-specific hydraulic conductivities.Our study presents a comprehensive view on changes of growth with age by integrating multiple methods and provides an explanation from the perspective of plant hydraulics for growth decline with age.The results indicate that old-growth Mongolian pine plantations in water-limited environments may face increased growth declines under the context of climate warming and drying.展开更多
Vegetation restoration through artificial plantation is an effective method to combat desertification,especially in arid and semi-arid areas.This study aimed to explore the ecological effect of the plantation of Sabin...Vegetation restoration through artificial plantation is an effective method to combat desertification,especially in arid and semi-arid areas.This study aimed to explore the ecological effect of the plantation of Sabina vulgaris on soil physical and chemical properties on the southeastern fringe of the Mu Us Sandy Land,China.We collected soil samples from five depth layers(0-20,20-40,40-60,60-80,and 80-100 cm)in the S.vulgaris plantation plots across four plantation ages(4,7,10,and 16 years)in November 2019,and assessed soil physical(soil bulk density,soil porosity,and soil particle size)and chemical(soil organic carbon(SOC),total nitrogen(TN),available nitrogen(AN),available phosphorus(AP),available potassium(AK),cation-exchange capacity(CEC),salinity,p H,and C/N ratio)properties.The results indicated that the soil predominantly consisted of sand particles(94.27%-99.67%),with the remainder being silt and clay.As plantation age increased,silt and very fine sand contents progressively rose.After 16 years of planting,there was a marked reduction in the mean soil particle size.The initial soil fertility was low and declined from 4 to 10 years of planting before witnessing an improvement.Significant positive correlations were observed for the clay,silt,and very fine sand(mean diameter of 0.000-0.100 mm)with SOC,AK,and p H.In contrast,fine sand and medium sand(mean diameter of 0.100-0.500 mm)showed significant negative correlations with these indicators.Our findings ascertain that the plantation of S.vulgaris requires 10 years to effectively act as a windbreak and contribute to sand fixation,and needs 16 years to improve soil physical and chemical properties.Importantly,these improvements were found to be highly beneficial for vegetation restoration in arid and semi-arid areas.This research can offer valuable insights for the protection and restoration of the vegetation ecosystem in the sandy lands in China.展开更多
Rubber trees (Hevea brasiliensis Müll. Arg.) have been commercially cultivated for a century and a half in Asia, particularly in China, and they constitute a common element of plantation ecosystems in tropical re...Rubber trees (Hevea brasiliensis Müll. Arg.) have been commercially cultivated for a century and a half in Asia, particularly in China, and they constitute a common element of plantation ecosystems in tropical regions. Soil health is fundamental to the sustainable development of rubber plantations. The objective of the study is to explore the influence of different complex ecological cultivation modes on the stability of soil aggregates in rubber based agroforestry systems. In this study, the ecological cultivation mode of rubber—Alpinia oxyphylla plantation, the ecological cultivation mode of rubber—Phrynium hainanense plantations, the ecological cultivation mode of rubber—Homalium ceylanicum plantations and monoculture rubber plantations were selected, and the particle size distribution of soil aggregates and their water stability characteristics were analyzed. The soil depth of 0 - 20 cm and 20 - 40 cm was collected for four cultivation modes. Soil was divided into 6 particle levels > 20 cm. soil was divided into 6 particle levels > 5 mm, 2 - 5 mm, 1 - 2 mm, 0.5 - 1 mm, 0.25 - 0.5 mm, and 0.053 - 0.25 mm according to the wet sieve method. The particle size proportion and water stability of soil aggregates were determined by the wet sieve method. The particle size proportion and water stability of soil aggregates under different ecological cultivation modes were analyzed. The results showed that under different ecological cultivation modes in the shallow soil layer (0 - 20 cm), the rubber—Alpinia oxyphylla plantation and the rubber—Phrynium hainanense plantation promoted the development of dominant soil aggregates towards larger size classes, whereas the situation is the opposite for rubber—Homalium ceylanicum plantation. In soil layer (20 - 40 cm), the ecological cultivation mode of rubber—Phrynium hainanense plantation developed the dominant radial level of soil aggregates to the diameter level of large aggregates. Rubber—Alpinia oxyphylla plantation and rubber—Homalium ceylanicum plantation, three indicators, including the water-stable aggregate content R<sub>0.25</sub> (>0.25 mm water-stable aggregates), mean weight diameter (MWD), and geometric mean diameter (GMD), were all lower than those in the rubber monoculture mode. However, in the rubber—Phrynium hainanense plantation, the water-stable aggregate content R<sub>0.25</sub>, mean weight diameter, and geometric mean diameter were higher than in the rubber monoculture mode, although these differences did not reach statistical significance.展开更多
Rubber(Hevea brasiliensis) plantations have been expanded rapidly in tropical regions of Southwest China and cover more than20% of land area in Xishuangbanna.Several studies have addressed changes of soil C stocks in ...Rubber(Hevea brasiliensis) plantations have been expanded rapidly in tropical regions of Southwest China and cover more than20% of land area in Xishuangbanna.Several studies have addressed changes of soil C stocks in rubber plantations;however,estimates of total ecosystem C stocks and their temporal changes in rubber plantations have been inadequately studied.This study calculated C stocks in soil,biomass,litter,and dry rubber(latex),and estimated the total ecosystem C stocks of rubber plantations in an age sequence of 3-,7-,9-,21-,27-,and 34-year-old in Xishuangbanna,Southwest China.The total C stocks in rubber plantations ranged from 150.3 to 283.7 Mg C ha^(-1),with a mean of 213.4 Mg C ha^(-1).The plantations≤9-year-old had significantly lower(P<0.05)total C stocks than those older than 9 years.Carbon stocks in soil(mass equivalent) were between 107.1–170.5 Mg C ha^(-1) and in living biomass were between 2.8–95.7 Mg C ha^(-1),representing the largest and the second largest C components in a rubber plantation ecosystem.Neglect of dry rubber C stock resulted in an underestimate of 7.8%–14.2% of the total C stock in the rubber plantations older than 9 years,which was much larger than the contribution of litter C stock(less than 2%).展开更多
The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focus...The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.展开更多
Oil palm plantations have dramatically expanded in tropical Asia over the past decades.Although their establishment has been projected to increase nitrous oxide(N_(2)O)emissions,earlier reports have shown inconsistent...Oil palm plantations have dramatically expanded in tropical Asia over the past decades.Although their establishment has been projected to increase nitrous oxide(N_(2)O)emissions,earlier reports have shown inconsistent results.This study analyzed these previously published data to compare N_(2)O emissions in oil palm plantations to reference forests.A linear mixed-eff ects model was used to examine the signifi cance of the eff ect of establishing oil palm plantations on N_(2)O emissions,rather than to calculate mean eff ect sizes because of limitations in the data structure.The results indicated that N_(2)O emissions were signifi cantly greater from oil palm plantations than from reference forests,as expected.This is the fi rst study to report the eff ect of oil palm plantations on N_(2)O emissions by synthesizing previously published data.To quantify the size of this eff ect,additional studies with frequent and long-term monitoring data are needed.展开更多
Biochar can enhance crop production and sequester carbon,but there have been few studies with tree crops.Rubber plantations cover more than 8 million hectares in Southeast Asia,so we assessed the feasibility of biocha...Biochar can enhance crop production and sequester carbon,but there have been few studies with tree crops.Rubber plantations cover more than 8 million hectares in Southeast Asia,so we assessed the feasibility of biochar application in these plantations with a pot trial.Rubber seedlings were planted in soil with four concentrations(0,1.25%,2.5% and 5%,w/w)of biochar combined with two concentrations of compound fertilizer(0 kg/ha and 300 kg/ha).Soil properties and seedling growth were measured,and a leaching experiment was conducted in the rainy season.Our results show that biochar increased pH,water content(27.4-65.1%),total carbon(25.4-53.6%),nitrate nitrogen,and available phosphorus in the soil,and decreased bulk density(3.2-23.9%).Biochar treatment reduced leaching of ammonium nitrogen and ortho-P.Biochar increased seedling nutrient uptake(C,N,P and K),with 2.5% and 5% biochar showing the largest effects,but seedling biomass was the highest with 1.25%,and declined in 2.5% and 5%.Our results suggest that biochar addition is an effective way to improve rubber plantation soils,sequester more carbon and decrease nutrient leaching,but the optimum application rate under field conditions needs further research.展开更多
The research on asphalt performance mainly focused on the macro performance and micro mechanism.Mesoscopic analysis was introduced to study the effect of rubber powder movement on asphalt rubber properties.After the p...The research on asphalt performance mainly focused on the macro performance and micro mechanism.Mesoscopic analysis was introduced to study the effect of rubber powder movement on asphalt rubber properties.After the preparation parameters and the preparation process of asphalt rubber were determined,the modification mechanism and rheological properties were analyzed which revealed the compatible stability mechanism.Then,the analysis model of asphalt rubber was established to focus on simulating the effect of rubber powder and the spatial movement on its mechanical properties.The experimental results show that rubber powder can make the asphalt rubber bear more uniform stress distribution and enhance the ability to resist deformation.Meanwhile,the rotational motion and final distribution of rubber powder have an obvious impact on the mechanical properties of asphalt rubber.In the selected feature points,the average stress of rubber powder at 0°space angle is only 34.1%of that at90°space angle.When the rubber powders are all in parallel in the ideal state,it enhances the mechanical properties the most.This study supplements the“mesoscopic”scale between macro and micro research.The relationship between micro mechanism and macro properties of asphalt rubber will be established from the mesoscopic perspective.It is also an effort to realize the effective correlation from micro,mesoscopic to macro in asphalt.展开更多
Environmental problems caused by waste tires are becoming increasingly prominent.There is an urgent need to find a green way to dispose of waste tires,and scholars have made considerable efforts in this regard.In the ...Environmental problems caused by waste tires are becoming increasingly prominent.There is an urgent need to find a green way to dispose of waste tires,and scholars have made considerable efforts in this regard.In the construction industry,rubber extracted from waste tires can be added to concrete to alleviate environmental problems to a certain extent.As a new building material,rubber concrete has superior properties compared to ordinary concrete and has been widely used in many fields.Numerous studies have been conducted worldwide to investigate the effect of waste tire rubber on the performance of concrete.It has been reported that the addition of waste tire rubber has a significant influence on the performance of concrete.Workability influences the hardened performance of rubber concrete,especially the durability.Based on the current research results,the workability and durability of concrete manufactured with waste tire rubber,including water absorption and permeability,carbonation resistance,chloride ion permeability resistance,and freeze-thaw resistance,are summarized in this paper.It is concluded that the addition of waste tires has a negative effect on the workability of concrete.In terms of durability,concrete exhibits better chloride ion penetration resistance and frost resistance,with a higher water absorption rate,and lower anti-permeability and carbonation resistance owing to the addition of waste tire rubber.展开更多
文摘In this study, tropical peat swamp soils from Giam Siak Kecil-Bukit Batu Biosphere Reserve (GSKBB) in Indonesia was evaluated to assess the impact of oil palm and rubber plantations on this unique organic soil through comparisons with soils from a natural forest using a polyphasic approach (chemical and molecular microbial assays). Changes in the ammonium, nitrate and phosphate concentration were observed in soils converted to agricultural use. Soil enzyme activities in plantation soils showed reduced β-glucosidase, cellobiohydrolase and acid phosphatase activities (50% - 55% decrease). PCR-DGGE based analysis showed that the soil bacterial community from agricultural soils exhibited the lowest similarity amongst the different microbial groups (fungi and Archaea) evaluated (34% similarity to the natural forest soil). Shannon Diversity index values showed that generally the conversion of tropical peatland natural forest to rubber plantation resulted in a greater impact on microbial diversity (ANOVA p < 0.05). Overall, this study indicated substantial shifts in the soil microbial activity and diversity upon conversion of natural peatland forest to agriculture, with a greater change being observed under rubber plantation compared to oil palm plantation. These findings provided important data for future peatland management by relating changes in the soil microbial community and activities associated to agricultural practices carried out on peatland.
文摘Hainan Island is located in the northern periphery of the tropical world.The environment is suitable for a number of tropical economic crops.The content of soil organic matter under rubber plantation is around 10- 20 g kg-1.Cu,Zn,Mn,As,Mg,Ca and K in the soil profile reflect the parent material and the intensive weathering and leaching in the area.Copper has noticeably accumulated in the lower horizon,whereas the concentrations of Ca,Mg and K.in rubber trees are 0.5- 4.9,2.2- 4.3 and 4.6-10.2 g kg-1 respectively.These three elements are mostly distributed in the plant roots and are particularly required during the development of new leaves early in the season.
基金1Project supported by the United Nations Development Program.
文摘This research was designed to help solve existing sustainable use problems such as soil nutrient loss and soil fertility decline in natural rubber plantations located in the hilly land of the south central mountainous area of Hainan Island, China. Two different land management practices, sustainable and traditional, were adopted in a four-year experiment. Contour terraced fields and deep ditches for green manure were built in a sustainable way with a balanced, need-based application of complex fertilizer. Results of the four-year experiment showed that these sustainable measures compared to traditional measures improved available P and available K; had a 47.8% less soil erosion (an average of 3 663 t km-2 year-1) and a 15.9% lower runoff coefficient of 0.53; increased the dry rubber yield by 42.4%; and improved the economic benefit by 2.4 times. The sustainable land management scheme not only improved land utilisation efficiency, but also helped maintain soil fertility while increasing production in rubber plantations. It thereby offered a reasonable and sustainable use for land resources in the tropical mountainous areas.
文摘The impacts of economic forest on global environmental change(GEC) are one of the hot issues in environmental study. Based on the 3 year observation data and 40 year climate data, GEC and analysis of the hydrological dynamic characteristics of rubber plantations and estimate of the water balance in the rubber plantations in Hainan Island were made. The results showed that the rainfall intercepted by the canopy of the plantations accounted for 11 45% of the annual rainfall, the total runoff for 23 71%, the total evaporation and transpiration for 63 24%, the soil moisture storage for 1 6%. Analysis of the 40 year rainfall data in the 19 counties of Hainan Island during 1951—1990 showed that the large scale substitution of the natural vegetation with the rubber plantations had no significant effect on the local rainfall in Hainan Island. The main reasons are (1) 80% of the rainfall in Hainan is brought by typhoons; (2) the proportion of 11 6% rubber plantations in total forest coverage in Hainan is not enough to influence the local rainfall in Hainan Island; and (3) although the rubber plantation is artificial vegetation, it has the similar function to the tropical rain forest. Analysis of the total water resource and total GDP of Hainan in 1997 showed that the economic benefit resulted from the water resource was 1 0 RMB Yuan/m 3 The value of hydrological of the rubber plantation in Hainan was 113 9 million RMB Yuan/a when compared with the tropical rain forest. The paper reaches conclusion that the hydrological eco service function of rubber plantation has been enhanced after transformed from natural vegetation, which includes the natural service and powerful social service.
基金the BMZ/GIZ “Green Rubber” (Project No. Project No. 13.1432.7-001.00)the CGIAR (Consultative Group for International Agricultural Research) Research Program 6: Forests, Trees and Agroforestry+2 种基金financially supported by the Federal Ministry for Economic Cooperation and Development, Germanyfunded by the National Natural Science Foundation of China (Grant No. 31450110067) the Chinese Academy of Science funded the Chinese Academy of Science funded the post-doc fellowship for Stefanie Goldberg (Grant No. 2013Y2SB0007)
文摘Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.
文摘Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, “CATAS7-20-59”, “PR107”, “RRIM600”, “GT1”, “INA873”, “93-114”in South China. The results showed that there were six kinds of existing plant types of rubber tree after planting of rubber plantations, which were available tapping trees, wind damaged trees, cold damaged trees, tapping panel dryness trees, absent trees and weak trees, respectively. These data investigated also showed rubber trees under available tapping, stoppage due to tapping panel dryness, absence, wind damage, cold damage and weakness were counted and calculated and made up for 72.21%, 14.75%, 5.61%, 3.86%, 2.68% and 1.89%. Tapping panel dryness trees, wind damage and absent trees are major factors for the loss of tapping rubber trees in the rubber plantations. Of these investigated varieties, available tapping trees per 100 trees of rubber plantation of “PR107”at the 1st, 12th, 14th, 16th, 20th, 24th tapping year were 96, 67, 70, 75, 66, 46 trees in Hainan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “RRIM600”at the 9th, 15th, 20th, 22nd tapping year were 88, 62, 55, 36 trees in Yunnan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “93-114” at the 10th, 19th, tapping year were 94, 62 trees in Guangdong planting zone. These results showed that available tapping trees of rubber plantation decreased with increasing tapping age under different planting zones in China.
文摘Driven by soil biochemistry and plant community composition,soil microbial communities reflect land management and environmental conditions.To evaluate the effects of land-use change on soil microbial diversity,we used denaturing gradient gel electrophoresis(DGGE)combined with sequencing to compare bacterial and fungal community profiles between rubber plantation(RP)and nearby seasonal rainforests(SR).Rainforest soil generally had higher soil total C and microbial biomass C concentration,smaller soil aggregate proportions,and a soil pH below rubber plantation soil.The bacterial and fungal richness and diversity were similar after converting primary forests to rubber plantations.However,the composition of bacterial and fungal communities has significantly changed in rubber plantations.Basidiomycota,the predominant group of fungi,was significantly different between primary forests and rubber plantations.However,Basidiomycota showed higher heterogenetic distribution in the rainforest under rubber plantations.In conclusion,land-use changes mainly affect soil microbial community composition and heterogeneity distribution patterns,especially for saprotrophic fungi,which consist of changes in litter inputs and soil C conditions.
基金supported by Yunnan Fundamental Research Projects(grant NO.202101AT070056 and 202101AS070010)the National Natural Science Foundation of China(32101380,32171557,and 31570622)the Youth Innovation Promotion Association CAS(2021397).
文摘Soil erosion by water is known to be a major driver of land degradation.Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land.Splash erosion may be exacerbated or mitigated by ongoing land use/cover change.To estimate the effects of various land use and management systems on splash erosion in the humid tropics,we measured the actual splash erosion under natural rainfall conditions in a tropical rainforest(TR),rubber monoculture(RM),and four rubber agroforestry ecosystems in Xishuangbanna,Southwestern China.The average cumulative splash mass in the RM was 48.7 times higher compared to that in the TR,indicating that the replacement of TR by RM results in severe splash erosion.In the rubber agroforestry systems,the throughfall kinetic energy and splash mass were 34-76%and 86-97%lower,respectively,than that in the RM,indicating that intercropping crops with rubber trees can effectively alleviate erosive power of throughfall and thus splash erosion.Under all land use regimes,in the plots where the litter layer was removed,splash erosion was significantly(2.0-12.1 times)higher and more spatially heterogeneous than in those with litter cover.This highlighted the key role of the forest litter layer in protecting the soil from raindrop detachment.In the study area,the actual splash erosion was strongly correlated with the conditions of precipitation(amount and intensity(I10)of rainfall)and the vegetation structure(especially the crown base height,leaf area index,and canopy cover),but weakly correlated with the soil properties.Given the importance of near-ground intercrops(height<5 m)for improving the vegetation structure,surface cover,and soil conditions,the intercropping of Camellia sinensis and Theobroma cacao with rubber trees is a promising approach for controlling splash erosion and also has benefits on the sus-tainable development of rubber plantation.
基金funded by the Science and Technology Research and Development Plan of the China State Railway Group Company Limited(No.N2023J053).
文摘Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.
基金supported by the National Natural Science Foundation of China(32201429)the College of Landscape Architecture and Art,Northwest A&F University,China.
文摘Tree plantation and forest restoration are the major strategies for enhancing terrestrial carbon sequestration and mitigating climate change.The Grain for Green Project in China has positively impacted global carbon sequestration and the trend towards fragmentation of plantation forests.Limited studies have been conducted on changes in plantation biomass and stand structure caused by fragmentation,and the effect of fragmentation on the carbon storage of plantation forests remains unclear.This study evaluated the differences between carbon storage and stand structure in black locust forests in fragmented and continuous landscape in the Ansai District,China and discussed the effects of ecological significance of four landscape indices on carbon storage and tree density.We used structural equation modelling to explore the direct and indirect effects of fragmentation,edge,abiotic factors,and stand structure on above-ground carbon storage.Diameter at breast height(DBH)in fragmented forests was 53.3%thicker,tree density was 40.9%lower,and carbon storage was 49.8%higher than those in continuous forests;for all given DBH>10 cm,the trees in fragmented forests were shorter than those in continuous forests.The patch area had a negative impact on carbon storage,i.e.,the higher the degree of fragmentation,the lower the density of the tree;and fragmentation and distance to edge(DTE)directly increased canopy coverage.However,canopy coverage directly decreased carbon storage,and fragmentation directly increased carbon storage and tree density.In non-commercial forests,fragmentation reduces the carbon storage potential of plantation,and the influence of patch area,edge,and patchy connection on plantation should be considered when follow-up trees are planted and for the plantation management.Thus,expanding the area of plantation patches,repairing the edges of complex-shaped patches,enhancing the connectivity of similar patches,and applying nutrients to plantation forests at regular intervals are recommended in fragmented areas of the Loess Plateau.
基金financially supported by the National Natural Science Foundation of China(31901093,32220103010,32192431,31722013)National Key R&D Program of China(2020YFA0608100,2022YFF1302505)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(ZDBS-LY-DQC019)。
文摘Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas.An important species for afforestation in dry environments of northern China,Mongolian pine(Pinus sylvestris var.mongolica Litv.)has recently exhibited growth decline and dieback on many sites,particularly pronounced in old-growth plantations.However,changes in response to drought stress by this species with age as well as the underlying mechanisms are poorly understood.In this study,tree-ring data and remotely sensed vegetation data were combined to investigate variations in growth at individual tree and stand scales for young(9-13 years)and aging(35-52 years)plantations of Mongolian pine in a water-limited area of northern China.A recent decline in tree-ring width in the older plantation also had lower values in satellited-derived normalized difference vegetation indices and normalized difference water indices relative to the younger plantations.In addition,all measured growth-related metrics were strongly correlated with the self-calibrating Palmer drought severity index during the growing season in the older plantation.Sensitivity of growth to drought of the older plantation might be attributed to more severe hydraulic limitations,as reflected by their lower sapwood-and leaf-specific hydraulic conductivities.Our study presents a comprehensive view on changes of growth with age by integrating multiple methods and provides an explanation from the perspective of plant hydraulics for growth decline with age.The results indicate that old-growth Mongolian pine plantations in water-limited environments may face increased growth declines under the context of climate warming and drying.
基金funded by the National Natural Science Foundation of China(42171004)the Key Research and Development Program in Shaanxi Province,China(2021ZDLSF05-02)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0403)。
文摘Vegetation restoration through artificial plantation is an effective method to combat desertification,especially in arid and semi-arid areas.This study aimed to explore the ecological effect of the plantation of Sabina vulgaris on soil physical and chemical properties on the southeastern fringe of the Mu Us Sandy Land,China.We collected soil samples from five depth layers(0-20,20-40,40-60,60-80,and 80-100 cm)in the S.vulgaris plantation plots across four plantation ages(4,7,10,and 16 years)in November 2019,and assessed soil physical(soil bulk density,soil porosity,and soil particle size)and chemical(soil organic carbon(SOC),total nitrogen(TN),available nitrogen(AN),available phosphorus(AP),available potassium(AK),cation-exchange capacity(CEC),salinity,p H,and C/N ratio)properties.The results indicated that the soil predominantly consisted of sand particles(94.27%-99.67%),with the remainder being silt and clay.As plantation age increased,silt and very fine sand contents progressively rose.After 16 years of planting,there was a marked reduction in the mean soil particle size.The initial soil fertility was low and declined from 4 to 10 years of planting before witnessing an improvement.Significant positive correlations were observed for the clay,silt,and very fine sand(mean diameter of 0.000-0.100 mm)with SOC,AK,and p H.In contrast,fine sand and medium sand(mean diameter of 0.100-0.500 mm)showed significant negative correlations with these indicators.Our findings ascertain that the plantation of S.vulgaris requires 10 years to effectively act as a windbreak and contribute to sand fixation,and needs 16 years to improve soil physical and chemical properties.Importantly,these improvements were found to be highly beneficial for vegetation restoration in arid and semi-arid areas.This research can offer valuable insights for the protection and restoration of the vegetation ecosystem in the sandy lands in China.
文摘Rubber trees (Hevea brasiliensis Müll. Arg.) have been commercially cultivated for a century and a half in Asia, particularly in China, and they constitute a common element of plantation ecosystems in tropical regions. Soil health is fundamental to the sustainable development of rubber plantations. The objective of the study is to explore the influence of different complex ecological cultivation modes on the stability of soil aggregates in rubber based agroforestry systems. In this study, the ecological cultivation mode of rubber—Alpinia oxyphylla plantation, the ecological cultivation mode of rubber—Phrynium hainanense plantations, the ecological cultivation mode of rubber—Homalium ceylanicum plantations and monoculture rubber plantations were selected, and the particle size distribution of soil aggregates and their water stability characteristics were analyzed. The soil depth of 0 - 20 cm and 20 - 40 cm was collected for four cultivation modes. Soil was divided into 6 particle levels > 20 cm. soil was divided into 6 particle levels > 5 mm, 2 - 5 mm, 1 - 2 mm, 0.5 - 1 mm, 0.25 - 0.5 mm, and 0.053 - 0.25 mm according to the wet sieve method. The particle size proportion and water stability of soil aggregates were determined by the wet sieve method. The particle size proportion and water stability of soil aggregates under different ecological cultivation modes were analyzed. The results showed that under different ecological cultivation modes in the shallow soil layer (0 - 20 cm), the rubber—Alpinia oxyphylla plantation and the rubber—Phrynium hainanense plantation promoted the development of dominant soil aggregates towards larger size classes, whereas the situation is the opposite for rubber—Homalium ceylanicum plantation. In soil layer (20 - 40 cm), the ecological cultivation mode of rubber—Phrynium hainanense plantation developed the dominant radial level of soil aggregates to the diameter level of large aggregates. Rubber—Alpinia oxyphylla plantation and rubber—Homalium ceylanicum plantation, three indicators, including the water-stable aggregate content R<sub>0.25</sub> (>0.25 mm water-stable aggregates), mean weight diameter (MWD), and geometric mean diameter (GMD), were all lower than those in the rubber monoculture mode. However, in the rubber—Phrynium hainanense plantation, the water-stable aggregate content R<sub>0.25</sub>, mean weight diameter, and geometric mean diameter were higher than in the rubber monoculture mode, although these differences did not reach statistical significance.
基金National Natural Science Foundation of China, No.41271117 Strategy of Science and Technology Planning Project of Institute of Geographic Sciences and Natural Resources Research, CAS, No.2012SJ008
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA05050206)
文摘Rubber(Hevea brasiliensis) plantations have been expanded rapidly in tropical regions of Southwest China and cover more than20% of land area in Xishuangbanna.Several studies have addressed changes of soil C stocks in rubber plantations;however,estimates of total ecosystem C stocks and their temporal changes in rubber plantations have been inadequately studied.This study calculated C stocks in soil,biomass,litter,and dry rubber(latex),and estimated the total ecosystem C stocks of rubber plantations in an age sequence of 3-,7-,9-,21-,27-,and 34-year-old in Xishuangbanna,Southwest China.The total C stocks in rubber plantations ranged from 150.3 to 283.7 Mg C ha^(-1),with a mean of 213.4 Mg C ha^(-1).The plantations≤9-year-old had significantly lower(P<0.05)total C stocks than those older than 9 years.Carbon stocks in soil(mass equivalent) were between 107.1–170.5 Mg C ha^(-1) and in living biomass were between 2.8–95.7 Mg C ha^(-1),representing the largest and the second largest C components in a rubber plantation ecosystem.Neglect of dry rubber C stock resulted in an underestimate of 7.8%–14.2% of the total C stock in the rubber plantations older than 9 years,which was much larger than the contribution of litter C stock(less than 2%).
基金financially supported by the Key Research Program of Frontier Sciences,the Chinese Academy of Sciences (No.QYZDY-SSW-SMC014)the National Natural Science Foundation of China (No.32171576)。
文摘The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.
基金supported by the Japan Society for the Promotion of Science(JSPS)KAKENHI(Grant Number 19H03008).
文摘Oil palm plantations have dramatically expanded in tropical Asia over the past decades.Although their establishment has been projected to increase nitrous oxide(N_(2)O)emissions,earlier reports have shown inconsistent results.This study analyzed these previously published data to compare N_(2)O emissions in oil palm plantations to reference forests.A linear mixed-eff ects model was used to examine the signifi cance of the eff ect of establishing oil palm plantations on N_(2)O emissions,rather than to calculate mean eff ect sizes because of limitations in the data structure.The results indicated that N_(2)O emissions were signifi cantly greater from oil palm plantations than from reference forests,as expected.This is the fi rst study to report the eff ect of oil palm plantations on N_(2)O emissions by synthesizing previously published data.To quantify the size of this eff ect,additional studies with frequent and long-term monitoring data are needed.
基金This research was supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(XDA05070304)the CAS 135 Program(XTBG-T03),Key program of NSF(31290221)the Science and Technology Service Network Initiative of Chinese Academy of Sciences(No.KFJ-EW-STS-084).
文摘Biochar can enhance crop production and sequester carbon,but there have been few studies with tree crops.Rubber plantations cover more than 8 million hectares in Southeast Asia,so we assessed the feasibility of biochar application in these plantations with a pot trial.Rubber seedlings were planted in soil with four concentrations(0,1.25%,2.5% and 5%,w/w)of biochar combined with two concentrations of compound fertilizer(0 kg/ha and 300 kg/ha).Soil properties and seedling growth were measured,and a leaching experiment was conducted in the rainy season.Our results show that biochar increased pH,water content(27.4-65.1%),total carbon(25.4-53.6%),nitrate nitrogen,and available phosphorus in the soil,and decreased bulk density(3.2-23.9%).Biochar treatment reduced leaching of ammonium nitrogen and ortho-P.Biochar increased seedling nutrient uptake(C,N,P and K),with 2.5% and 5% biochar showing the largest effects,but seedling biomass was the highest with 1.25%,and declined in 2.5% and 5%.Our results suggest that biochar addition is an effective way to improve rubber plantation soils,sequester more carbon and decrease nutrient leaching,but the optimum application rate under field conditions needs further research.
基金Funded by the Key Research and Development Projects in Shaanxi Province (2022SF-328)the Science and Technology Project of Henan Department of Transportation (2020J-2-3)the Science and Technology Project of Shaanxi Department of Transportation (Nos.19-10K and 19-28K)。
文摘The research on asphalt performance mainly focused on the macro performance and micro mechanism.Mesoscopic analysis was introduced to study the effect of rubber powder movement on asphalt rubber properties.After the preparation parameters and the preparation process of asphalt rubber were determined,the modification mechanism and rheological properties were analyzed which revealed the compatible stability mechanism.Then,the analysis model of asphalt rubber was established to focus on simulating the effect of rubber powder and the spatial movement on its mechanical properties.The experimental results show that rubber powder can make the asphalt rubber bear more uniform stress distribution and enhance the ability to resist deformation.Meanwhile,the rotational motion and final distribution of rubber powder have an obvious impact on the mechanical properties of asphalt rubber.In the selected feature points,the average stress of rubber powder at 0°space angle is only 34.1%of that at90°space angle.When the rubber powders are all in parallel in the ideal state,it enhances the mechanical properties the most.This study supplements the“mesoscopic”scale between macro and micro research.The relationship between micro mechanism and macro properties of asphalt rubber will be established from the mesoscopic perspective.It is also an effort to realize the effective correlation from micro,mesoscopic to macro in asphalt.
基金supported by the financial support received from Program for Innovative Research Team(in Science and Technology)in University of Henan Province of China(Grant No.20IRTSTHN009)National Natural Science Foundation of China(Grant Nos.U2040224,52179145)Natural Science Foundation of Henan(Grant Nos.212300410018,222300420081).
文摘Environmental problems caused by waste tires are becoming increasingly prominent.There is an urgent need to find a green way to dispose of waste tires,and scholars have made considerable efforts in this regard.In the construction industry,rubber extracted from waste tires can be added to concrete to alleviate environmental problems to a certain extent.As a new building material,rubber concrete has superior properties compared to ordinary concrete and has been widely used in many fields.Numerous studies have been conducted worldwide to investigate the effect of waste tire rubber on the performance of concrete.It has been reported that the addition of waste tire rubber has a significant influence on the performance of concrete.Workability influences the hardened performance of rubber concrete,especially the durability.Based on the current research results,the workability and durability of concrete manufactured with waste tire rubber,including water absorption and permeability,carbonation resistance,chloride ion permeability resistance,and freeze-thaw resistance,are summarized in this paper.It is concluded that the addition of waste tires has a negative effect on the workability of concrete.In terms of durability,concrete exhibits better chloride ion penetration resistance and frost resistance,with a higher water absorption rate,and lower anti-permeability and carbonation resistance owing to the addition of waste tire rubber.
