Fine roots play a crucial role in the biogeochemical cycles of terrestrial ecosystems.Patterns of fine roots biomass formation for broad geographical areas are still unclear.We use published estimates of characteristi...Fine roots play a crucial role in the biogeochemical cycles of terrestrial ecosystems.Patterns of fine roots biomass formation for broad geographical areas are still unclear.We use published estimates of characteristics of European pine and spruce stands to determine their productivity and calculate the needle biomass.Then,the relationship between the fine-root:needle biomass ratio of European pine and spruce forests and the stand quality index,which is a proxy of soil fertility,was determined.We show that a rise in soil fertility is accompanied by a decrease in this ratio.Moving from the northern edge of the boreal zone southwards,with the related rise in air and soil temperatures,we see a decline in the mass ratio of fine roots and needle.The change in the fine-root:needle biomass ratio is controlled by the change in specific water uptake by roots,which is related to the osmotic pressure of the solution in the absorbing root's central vascular cylinder.The fine-root:needle ratio does not vary among stands of the same age if the stand quality index and the geographical latitude(a proxy of air and soil temperatures)are constant.These findings may be useful for further in-depth analysis of forest ecosystem functioning in Europe.展开更多
The operation of biomass treatment devices such as gasifiers is based on the control of key parameters that play an important role in product formation. These include: temperature, excess oxygen, relative humidity and...The operation of biomass treatment devices such as gasifiers is based on the control of key parameters that play an important role in product formation. These include: temperature, excess oxygen, relative humidity and biomass composition. This work focuses on excess oxygen and temperature. Unfortunately, flue gas oxygen analyzers are expensive and not accessible to small industries. However, the equivalence ratio is linked to excess oxygen and has the advantage of not depending on biomass composition. This study therefore focuses on the design and development of a device for controlling this equivalence ratio by measuring oxygen concentration using a self-propelled Lambda probe, and a system for monitoring this equivalence ratio using an Arduino Uno 3 microcontroller. The temperature is recorded with an accuracy of ±1.5°C. For a heating time of 10 minutes, the response time to temperature change is around 3 seconds, which is sufficient for the device to function properly. This simple device is an efficient and cost-effective means of checking the equivalence ratio.展开更多
In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） c...In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin （Onobrychis viciaefolia Scop.） seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO2 concentrations （ambient or ambient＋350 μmol mol^-1 CO2） without adding nutrients to them. After 90 days exposure to CO2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO2 concentration, the elevated CO2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO2 concentration. However, the elevated CO2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO2 concentration. The elevated CO2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO2 concentration had no effect on the N content in the plants compared to the ambient CO2 concentration. The elevated CO2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO2 concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.展开更多
To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fire...To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fired </span><span style="font-family:Verdana;">boiler power generation system is studied. It is a challenge to achieve optimum performance for the coupled system. The models of biomass gasification coupled with co-firing of coal in a boiler have been established. A comparative study of three kinds of biomass (Food Rubbish, Straw and Wood Pellets) has </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">been </span></span></span><span><span><span><span style="font-family:Verdana;">done. The syngas produced in a 10 t/h gasifier is fed to a 330 MWe coal-fired boiler for co-combustion, and the co-firing performances have been compared with pure coal combustion case under the conditions of constant boiler load. Results show that co-firing decreases the furnace combustion temperature and raises the flue gas temperature for Food Rubbish and Straw, while, flue gases temperature decrease in case of Wood Pellets. At the same time NO<sub>x</sub> and SO<sub>x</sub> emissions have reduced. The system efficiencies at constant load for Food Rubbish, Straw and Wood Pellets are 83.25%, </span><span style="font-family:Verdana;">83.88% and 82.56% when the optimum conditions of gasification and co-firing </span><span style="font-family:Verdana;">process are guaranteed.展开更多
Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of me...Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of measured grassland biomass at regional scale or global scale with a unified survey method, particular for below-ground biomass. The present study, based on a total of 44 grassland sampling plots with 220 quadrats across Ningxia, investigated the characteristics of above-ground biomass （AGB）, below-ground biomass （BGB）, litter biomass （LB）, total biomass （TB） and root：shoot ratios （R：S） for six predominantly grassland types, and their relationships with climatic factors. AGB, BGB, LB and TB varied markedly across different grassland types, the median value ranging from 28.2-692.6 g m-2 for AGB, 130.4-2 036.6 g m-： for BGB, 9.2-82.3 g m2 for LB, and 168.0-2 681.3 g m-： for TB. R：S showed less variation with median values from 3.2 to 5.3 （excluding marshy meadow）. The different grassland types showed similar patterns of biomass allocation, with more than 70% BGB for all types. There is evidence of strong positive effects associated with mean annual precipitation （MAP） and negative effects associated with mean annual temperature （MAT） on AGB, BGB, and LB, although both factors have the opposite effect on R：S.展开更多
Addressing climate change has become a common issue around the world in the 21st century and equally an important mission in Chinese forestry.Understanding the development of monitoring and assessment of forest biomas...Addressing climate change has become a common issue around the world in the 21st century and equally an important mission in Chinese forestry.Understanding the development of monitoring and assessment of forest biomass and carbon storage in China is important for promoting the evaluation of forest carbon sequestration capacity of China.The author conducts a systematic analysis of domestic publications addressing＂monitoring and assessment of forest biomass and carbon storage＂in order to understand the development trends,describes the brief history through three stages,and gives the situation of new development.Towards the end of the 20th century,a large number of papers on biomass and productivity of the major forest types in China had been published,covering the exploration and efforts of more than 20 years,while investigations into assessment of forest carbon storage had barely begun.Based on the data of the 7th and 8th National Forest Inventories,forest biomass and carbon storage of the entire country were assessed using individual tree biomass models and carbon conversion factors of major tree species,both previously published and newly developed.Accompanying the implementation of the 8th National Forest Inventory,a program of individual tree biomass modeling for major tree species in China was carried out simultaneously.By means of thematic research on classification of modeling populations,as well as procedures for collecting samples and methodology for biomass modeling,two technical regulations on sample collection and model construction were published as ministerial standards for application.Requests for approval of individual tree biomass models and carbon accounting parameters of major tree species have been issued for approval as ministerial standards.With the improvement of biomass models and carbon accounting parameters,thematic assessment of forest biomass and carbon storage will be gradually changed into a general monitoring of forest biomass and carbon storage,in order to realize their dynamic monitoring in national forest inventories.Strengthening the analysis and assessment of spatial distribution patterns of forest biomass and carbon storage through application of remote sensing techniques and geostatistical approaches will also be one of the major directions of development in the near future.展开更多
Background: Forest productivity has a pivotal role in human well-being. Vegetation quantity, niche complementarity, mass-ratio, and soil resources are alternative/complementary ecological mechanisms driving productivi...Background: Forest productivity has a pivotal role in human well-being. Vegetation quantity, niche complementarity, mass-ratio, and soil resources are alternative/complementary ecological mechanisms driving productivity. One challenge in current forest management depends on identifying and manipulating these mechanisms to enhance productivity. This study assessed the extent to which these mechanisms control aboveground biomass productivity(AGBP) of a Chilean mediterranean-type matorral. AGBP measured as tree aboveground biomass changes over a 7-years period, was estimated for twelve 25 m × 25 m plots across a wide range of matorral compositions and structures. Variables related to canopy structure, species and functional diversity, species and functional dominance, soil texture, soil water and soil nitrogen content were measured as surrogates of the four mechanisms proposed. Linear regression models were used to test the hypotheses. A multimodel inference based on the Akaike’s information criterion was used to select the best models explaining AGBP and for identifying the relative importance of each mechanism.Results: Vegetation quantity(tree density) and mass-ratio(relative biomass of Cryptocarya alba, a conservative species) were the strongest drivers increasing AGBP, while niche complementarity(richness species) and soil resources(sand, %) had a smaller effect either decreasing or increasing AGBP, respectively. This study provides the first assessment of alternative mechanisms driving AGBP in mediterranean forests of Chile. There is strong evidence suggesting that the vegetation quantity and mass-ratio mechanisms are key drivers of AGBP, such as in other tropical and temperate forests. However, in contrast with other studies from mediterranean-type forests, our results show a negative effect of species diversity and a small effect of soil resources on AGBP.Conclusion: AGBP in the Chilean matorral depends mainly on the vegetation quantity and mass-ratio mechanisms.The findings of this study have implications for matorral restoration and management for the production of timber and non-timber products and carbon sequestration.展开更多
Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shal...Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.展开更多
Carbon （C） sequestration through plantations is one of the important mitigation measures for rising levels of carbon dioxide and other greenhouse gases in the atmosphere. This study aimed to assess C stocks and thei...Carbon （C） sequestration through plantations is one of the important mitigation measures for rising levels of carbon dioxide and other greenhouse gases in the atmosphere. This study aimed to assess C stocks and their sequestration rate, and to develop allometric models for estimation of C stocking in age-series young teak （Tectona grandis） planta- tions （1, 5, 11, 18, 24 and 30 years） by using biomass and productivity estimation and regression, respectively. These plantations were raised in tropical moist deciduous forests of Kumaun Himalayan tarai. Total C stocks estimated for these plantations were 1.6, 15.8, 35.4, 39.0, 61.5 and 73.2 Mg ha-1, respectively. Aboveground and belowground C storage in- creased with increasing plantation age; however, the range of their percentage contribution showed little variation （87.8-88.2 and 11.7-12.7 %, respectively）, The rate of C sequestration for these respective plantations was 1.06, 6.95, 5.46, 5.42, 3.39 and 5.37 Mg ha-1 a-1. Forty percent of the aboveground annual storage was retained in the tree while 60 % was released in the form of foliage, twigs, and fruit litter. In the case of total （tree） annual production, 43 % was retained while 57 % was released as litter including root. C stock, C sequestration rate, accumulation ratio （1.4-18.1）, root：shoot C ratio （0.61--0.13） and production efficiency （0.01-0.18） were comparable to some previous reports for other species and forests. These data could be useful in deciding the harvesting age for young teak with respect to C storage and sequestrationrate. Four allometric models using linear regression equations were developed between biomass （twice the C stock） and diameter, girth, and height of the tree at different ages. The diameter model was found more suitable for C stock predic- tion in similar areas.展开更多
The cluster planting pattern （3 plants per hole） for cotton （Gossypium hirsutum L.） may increase economic yield over those of the traditional planting pattern （1 plant per hole） in arid regions of China. This in...The cluster planting pattern （3 plants per hole） for cotton （Gossypium hirsutum L.） may increase economic yield over those of the traditional planting pattern （1 plant per hole） in arid regions of China. This increase in yield depends on either increased biomass production or greater partitioning to fruit. This study was conducted to determine whether differences in biomass accumulation or partitioning to reproductive growth contributed to higher yield in the cluster planting pattern compared with the traditional one. Growth parameters, biomass accumulation, crop growth rate and partitioning between cluster planting pattern and traditional planting pattern was compared in northwest of China. The biomass production and partitioning in cluster planting plot was higher than in traditional planting one. Biomass accumulation was faster early in the clustered treatment, and it was also higher at harvest time. Total dry matter production per unit area was significantly higher than in the traditional planting. On a per plant basis, dry matter accumulation was faster and total biomass production was significantly higher in the cluster planting pattern. Numbers of sympodia and boll sizes were also larger, indicating that facilitation among plants was promoting crop yield. The increase in yield in the cluster planting treatment occurred through increased partitioning of dry matter to fruits than in the traditional planting pattern, resulting in more bolls and increased lint yield in arid regions.展开更多
A study was conducted at Msekera Regional Agricultural Research Station in eastern Zambia to （1） describe canopy branching properties of Acacia angustissima, Gliricidia sepium and Leucaena collinsii in short rotatio...A study was conducted at Msekera Regional Agricultural Research Station in eastern Zambia to （1） describe canopy branching properties of Acacia angustissima, Gliricidia sepium and Leucaena collinsii in short rotation forests, （2） test the existence of self similarity from repeated iteration of a structural unit in tree canopies, （3） examined intra-specifie relationships between functional branching characteristics, and （4） determine whether allometric equations for relating aboveground tree biomass to fractal properties could accurately predict aboveground biomass. Measurements of basal diameter （Din0） at 10em aboveground and total height （H）, and aboveground biomass of 27 trees were taken, but only nine trees representative of variability of the stand and the three species were processed for functional branching analyses （FBA） of the shoot systems. For each species, fractal properties of three trees, includ- ing fractal dimension （Dfract）, bifurcation ratios （p） and proportionality ratios （q） of branching points were assessed. The slope of the linear re- gression ofp on proximal diameter was not significantly different （P 〈 0.01） from zero and hence the assumption that p is independent of scale, a pre-requisite for use of fraetal branching rules to describe a fraetal tree canopy, was fulfilled at branching orders with link diameters 〉1.5 cm. The proportionality ration q for branching patterns of all tree species was constant at all scales. The proportion of q values 〉0.9 （fq） was 0.8 for all species. Mean fraetal dimension （Df^ct） values （1.5-1.7） for all species showed that branching patterns had an increasing magnitude of intricacy. Since Dfraet values were 〉1.5, branching patterns within species were self similar. Basal diameter （D10）, proximal diameter and Dfraet described most of variations in aboveground biomass, suggesting that allometric equa- tions for relating aboveground tree biomass to fractal properties could accurately predict aboveground biomass. Thus, assessed Acacia, Gliri- cidia and Leucaena trees were fractals and their branching propertiescould be used to describe variability in size and aboveground biomass.展开更多
基金funded by state order to the Karelian Research Centre of the Russian Academy of Sciences(Forest Research Institute of KarRC RAS)。
文摘Fine roots play a crucial role in the biogeochemical cycles of terrestrial ecosystems.Patterns of fine roots biomass formation for broad geographical areas are still unclear.We use published estimates of characteristics of European pine and spruce stands to determine their productivity and calculate the needle biomass.Then,the relationship between the fine-root:needle biomass ratio of European pine and spruce forests and the stand quality index,which is a proxy of soil fertility,was determined.We show that a rise in soil fertility is accompanied by a decrease in this ratio.Moving from the northern edge of the boreal zone southwards,with the related rise in air and soil temperatures,we see a decline in the mass ratio of fine roots and needle.The change in the fine-root:needle biomass ratio is controlled by the change in specific water uptake by roots,which is related to the osmotic pressure of the solution in the absorbing root's central vascular cylinder.The fine-root:needle ratio does not vary among stands of the same age if the stand quality index and the geographical latitude(a proxy of air and soil temperatures)are constant.These findings may be useful for further in-depth analysis of forest ecosystem functioning in Europe.
文摘The operation of biomass treatment devices such as gasifiers is based on the control of key parameters that play an important role in product formation. These include: temperature, excess oxygen, relative humidity and biomass composition. This work focuses on excess oxygen and temperature. Unfortunately, flue gas oxygen analyzers are expensive and not accessible to small industries. However, the equivalence ratio is linked to excess oxygen and has the advantage of not depending on biomass composition. This study therefore focuses on the design and development of a device for controlling this equivalence ratio by measuring oxygen concentration using a self-propelled Lambda probe, and a system for monitoring this equivalence ratio using an Arduino Uno 3 microcontroller. The temperature is recorded with an accuracy of ±1.5°C. For a heating time of 10 minutes, the response time to temperature change is around 3 seconds, which is sufficient for the device to function properly. This simple device is an efficient and cost-effective means of checking the equivalence ratio.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP200807181008)the Science Fund of Shaanxi Normal University for the Young Scholars,China
文摘In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin （Onobrychis viciaefolia Scop.） seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO2 concentrations （ambient or ambient＋350 μmol mol^-1 CO2） without adding nutrients to them. After 90 days exposure to CO2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO2 concentration, the elevated CO2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO2 concentration. However, the elevated CO2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO2 concentration. The elevated CO2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO2 concentration had no effect on the N content in the plants compared to the ambient CO2 concentration. The elevated CO2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO2 concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.
文摘To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fired </span><span style="font-family:Verdana;">boiler power generation system is studied. It is a challenge to achieve optimum performance for the coupled system. The models of biomass gasification coupled with co-firing of coal in a boiler have been established. A comparative study of three kinds of biomass (Food Rubbish, Straw and Wood Pellets) has </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">been </span></span></span><span><span><span><span style="font-family:Verdana;">done. The syngas produced in a 10 t/h gasifier is fed to a 330 MWe coal-fired boiler for co-combustion, and the co-firing performances have been compared with pure coal combustion case under the conditions of constant boiler load. Results show that co-firing decreases the furnace combustion temperature and raises the flue gas temperature for Food Rubbish and Straw, while, flue gases temperature decrease in case of Wood Pellets. At the same time NO<sub>x</sub> and SO<sub>x</sub> emissions have reduced. The system efficiencies at constant load for Food Rubbish, Straw and Wood Pellets are 83.25%, </span><span style="font-family:Verdana;">83.88% and 82.56% when the optimum conditions of gasification and co-firing </span><span style="font-family:Verdana;">process are guaranteed.
基金supported by the Strategic-Leader Sci-Tech Projects of Chinese Academy of Sciences(XDA05050403)the Important Direction Project of Innovation of Chinese Academy of Sciences(CAS)(KSCX1-YW-12)
文摘Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of measured grassland biomass at regional scale or global scale with a unified survey method, particular for below-ground biomass. The present study, based on a total of 44 grassland sampling plots with 220 quadrats across Ningxia, investigated the characteristics of above-ground biomass （AGB）, below-ground biomass （BGB）, litter biomass （LB）, total biomass （TB） and root：shoot ratios （R：S） for six predominantly grassland types, and their relationships with climatic factors. AGB, BGB, LB and TB varied markedly across different grassland types, the median value ranging from 28.2-692.6 g m-2 for AGB, 130.4-2 036.6 g m-： for BGB, 9.2-82.3 g m2 for LB, and 168.0-2 681.3 g m-： for TB. R：S showed less variation with median values from 3.2 to 5.3 （excluding marshy meadow）. The different grassland types showed similar patterns of biomass allocation, with more than 70% BGB for all types. There is evidence of strong positive effects associated with mean annual precipitation （MAP） and negative effects associated with mean annual temperature （MAT） on AGB, BGB, and LB, although both factors have the opposite effect on R：S.
基金funded by the State Forestry Administration of China
文摘Addressing climate change has become a common issue around the world in the 21st century and equally an important mission in Chinese forestry.Understanding the development of monitoring and assessment of forest biomass and carbon storage in China is important for promoting the evaluation of forest carbon sequestration capacity of China.The author conducts a systematic analysis of domestic publications addressing＂monitoring and assessment of forest biomass and carbon storage＂in order to understand the development trends,describes the brief history through three stages,and gives the situation of new development.Towards the end of the 20th century,a large number of papers on biomass and productivity of the major forest types in China had been published,covering the exploration and efforts of more than 20 years,while investigations into assessment of forest carbon storage had barely begun.Based on the data of the 7th and 8th National Forest Inventories,forest biomass and carbon storage of the entire country were assessed using individual tree biomass models and carbon conversion factors of major tree species,both previously published and newly developed.Accompanying the implementation of the 8th National Forest Inventory,a program of individual tree biomass modeling for major tree species in China was carried out simultaneously.By means of thematic research on classification of modeling populations,as well as procedures for collecting samples and methodology for biomass modeling,two technical regulations on sample collection and model construction were published as ministerial standards for application.Requests for approval of individual tree biomass models and carbon accounting parameters of major tree species have been issued for approval as ministerial standards.With the improvement of biomass models and carbon accounting parameters,thematic assessment of forest biomass and carbon storage will be gradually changed into a general monitoring of forest biomass and carbon storage,in order to realize their dynamic monitoring in national forest inventories.Strengthening the analysis and assessment of spatial distribution patterns of forest biomass and carbon storage through application of remote sensing techniques and geostatistical approaches will also be one of the major directions of development in the near future.
基金Funding for this research was obtained from CONICy T(Comisión Nacional de Investigación Científica y Tecnológica)for the grant Fondecyt No1150877funding was derived from the CONICy T doctoral grant No 21150802
文摘Background: Forest productivity has a pivotal role in human well-being. Vegetation quantity, niche complementarity, mass-ratio, and soil resources are alternative/complementary ecological mechanisms driving productivity. One challenge in current forest management depends on identifying and manipulating these mechanisms to enhance productivity. This study assessed the extent to which these mechanisms control aboveground biomass productivity(AGBP) of a Chilean mediterranean-type matorral. AGBP measured as tree aboveground biomass changes over a 7-years period, was estimated for twelve 25 m × 25 m plots across a wide range of matorral compositions and structures. Variables related to canopy structure, species and functional diversity, species and functional dominance, soil texture, soil water and soil nitrogen content were measured as surrogates of the four mechanisms proposed. Linear regression models were used to test the hypotheses. A multimodel inference based on the Akaike’s information criterion was used to select the best models explaining AGBP and for identifying the relative importance of each mechanism.Results: Vegetation quantity(tree density) and mass-ratio(relative biomass of Cryptocarya alba, a conservative species) were the strongest drivers increasing AGBP, while niche complementarity(richness species) and soil resources(sand, %) had a smaller effect either decreasing or increasing AGBP, respectively. This study provides the first assessment of alternative mechanisms driving AGBP in mediterranean forests of Chile. There is strong evidence suggesting that the vegetation quantity and mass-ratio mechanisms are key drivers of AGBP, such as in other tropical and temperate forests. However, in contrast with other studies from mediterranean-type forests, our results show a negative effect of species diversity and a small effect of soil resources on AGBP.Conclusion: AGBP in the Chilean matorral depends mainly on the vegetation quantity and mass-ratio mechanisms.The findings of this study have implications for matorral restoration and management for the production of timber and non-timber products and carbon sequestration.
基金sponsored by China Postdoctoral Science Foundation (Grant No.20090461149)the Postdoctoral Science Foundation of Jiangsu Province (Grant No. 0802029C)the Youth Science Foundation of JINAN Univeristy (Grant No. 51208026)
文摘Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.
文摘Carbon （C） sequestration through plantations is one of the important mitigation measures for rising levels of carbon dioxide and other greenhouse gases in the atmosphere. This study aimed to assess C stocks and their sequestration rate, and to develop allometric models for estimation of C stocking in age-series young teak （Tectona grandis） planta- tions （1, 5, 11, 18, 24 and 30 years） by using biomass and productivity estimation and regression, respectively. These plantations were raised in tropical moist deciduous forests of Kumaun Himalayan tarai. Total C stocks estimated for these plantations were 1.6, 15.8, 35.4, 39.0, 61.5 and 73.2 Mg ha-1, respectively. Aboveground and belowground C storage in- creased with increasing plantation age; however, the range of their percentage contribution showed little variation （87.8-88.2 and 11.7-12.7 %, respectively）, The rate of C sequestration for these respective plantations was 1.06, 6.95, 5.46, 5.42, 3.39 and 5.37 Mg ha-1 a-1. Forty percent of the aboveground annual storage was retained in the tree while 60 % was released in the form of foliage, twigs, and fruit litter. In the case of total （tree） annual production, 43 % was retained while 57 % was released as litter including root. C stock, C sequestration rate, accumulation ratio （1.4-18.1）, root：shoot C ratio （0.61--0.13） and production efficiency （0.01-0.18） were comparable to some previous reports for other species and forests. These data could be useful in deciding the harvesting age for young teak with respect to C storage and sequestrationrate. Four allometric models using linear regression equations were developed between biomass （twice the C stock） and diameter, girth, and height of the tree at different ages. The diameter model was found more suitable for C stock predic- tion in similar areas.
基金supported by the National Natural Sciences Foundation of China(31300323)China Postdoctoral Science Foundation Funded Project(2014M552515)
文摘The cluster planting pattern （3 plants per hole） for cotton （Gossypium hirsutum L.） may increase economic yield over those of the traditional planting pattern （1 plant per hole） in arid regions of China. This increase in yield depends on either increased biomass production or greater partitioning to fruit. This study was conducted to determine whether differences in biomass accumulation or partitioning to reproductive growth contributed to higher yield in the cluster planting pattern compared with the traditional one. Growth parameters, biomass accumulation, crop growth rate and partitioning between cluster planting pattern and traditional planting pattern was compared in northwest of China. The biomass production and partitioning in cluster planting plot was higher than in traditional planting one. Biomass accumulation was faster early in the clustered treatment, and it was also higher at harvest time. Total dry matter production per unit area was significantly higher than in the traditional planting. On a per plant basis, dry matter accumulation was faster and total biomass production was significantly higher in the cluster planting pattern. Numbers of sympodia and boll sizes were also larger, indicating that facilitation among plants was promoting crop yield. The increase in yield in the cluster planting treatment occurred through increased partitioning of dry matter to fruits than in the traditional planting pattern, resulting in more bolls and increased lint yield in arid regions.
基金funded by the Gates Cambridge Trust at Cambridge University
文摘A study was conducted at Msekera Regional Agricultural Research Station in eastern Zambia to （1） describe canopy branching properties of Acacia angustissima, Gliricidia sepium and Leucaena collinsii in short rotation forests, （2） test the existence of self similarity from repeated iteration of a structural unit in tree canopies, （3） examined intra-specifie relationships between functional branching characteristics, and （4） determine whether allometric equations for relating aboveground tree biomass to fractal properties could accurately predict aboveground biomass. Measurements of basal diameter （Din0） at 10em aboveground and total height （H）, and aboveground biomass of 27 trees were taken, but only nine trees representative of variability of the stand and the three species were processed for functional branching analyses （FBA） of the shoot systems. For each species, fractal properties of three trees, includ- ing fractal dimension （Dfract）, bifurcation ratios （p） and proportionality ratios （q） of branching points were assessed. The slope of the linear re- gression ofp on proximal diameter was not significantly different （P 〈 0.01） from zero and hence the assumption that p is independent of scale, a pre-requisite for use of fraetal branching rules to describe a fraetal tree canopy, was fulfilled at branching orders with link diameters 〉1.5 cm. The proportionality ration q for branching patterns of all tree species was constant at all scales. The proportion of q values 〉0.9 （fq） was 0.8 for all species. Mean fraetal dimension （Df^ct） values （1.5-1.7） for all species showed that branching patterns had an increasing magnitude of intricacy. Since Dfraet values were 〉1.5, branching patterns within species were self similar. Basal diameter （D10）, proximal diameter and Dfraet described most of variations in aboveground biomass, suggesting that allometric equa- tions for relating aboveground tree biomass to fractal properties could accurately predict aboveground biomass. Thus, assessed Acacia, Gliri- cidia and Leucaena trees were fractals and their branching propertiescould be used to describe variability in size and aboveground biomass.
