Canopy interception of incident precipitation, as a critical component of a forest＇s water budget, can affect the amount of water available to the soil, and ultimately vegetation distribution and function. In this pa...Canopy interception of incident precipitation, as a critical component of a forest＇s water budget, can affect the amount of water available to the soil, and ultimately vegetation distribution and function. In this paper, a statistical-dynamic approach based on leaf area index and statistical canopy interception is used to parameterize the canopy interception process. The statistical-dynamic canopy interception scheme is implemented into the Community Land Model with dynamic global vegetation model （CLM-DGVM） to improve its dynamic vegetation simulation. The simulation for continental China by the land surface model with the new canopy interception scheme shows that the new one reasonably represents the precipitation intercepted by the canopy. Moreover, the new scheme enhances the water availability in the root zone for vegetation growth, especially in the densely vegetated and semi-arid areas, and improves the model＇s performance of potential vegetation simulation.展开更多
Leaf growth and its interaction with the growing environment critically affect leaf area, distribution, and function, and ultimately affects grain yield of maize(Zea mays L.). To detect the effects of leaf area dynami...Leaf growth and its interaction with the growing environment critically affect leaf area, distribution, and function, and ultimately affects grain yield of maize(Zea mays L.). To detect the effects of leaf area dynamics, growth periods, and the environment on maize grain yield, a three-year field experiment was conducted using two maize varieties, medium plant-size variety Zhengdan 958(ZD958) and large plant-size variety Zhongnongda 4(ZND4), and three to five sowing dates. The sowing date significantly affected maize yield as a result of changes in leaf area, growth stage, and growing environment. Prior to the 12 th leaf stage, significant correlations between leaf area dynamics, environment, and yield were seldom detected. The expansion of leaf area from 12 th leaf stage to silking stage was significantly positively correlated with growing degree days(GDD), solar radiation, and grain yield, indicating the importance of leaf area dynamics during this period. After silking, solar radiation played a more important role in inducing leaf senescence than GDD, particularly in the 2 nd half of the grain filling stage. Accelerated leaf senescence in late growth period can increase maize yield. The environment affected leaf area dynamics and yield of the large plant-size variety(ZND4) more easily than the medium plant-size variety(ZD958) at the optimum plant density, reflecting the difference in varietal capacity to adapt to the growing environment. This study indicates that optimizing the interaction among leaf area dynamics, growth periods, and environment is a sound strategy to increase maize yield. Favorable interactions are useful to determine the optimal sowing date of a given variety.展开更多
以粤北车八岭2008年受冰灾破坏的山地常绿阔叶林为研究对象，设置2 hm2固定样地开展连续3 a （2008-2010年）的乔木群落调查，研究冰灾对亚热带森林更新演替的影响。结果发现：（1）样地优势乔木树种受灾程度由高到低依次为：栲树＞鸭...以粤北车八岭2008年受冰灾破坏的山地常绿阔叶林为研究对象，设置2 hm2固定样地开展连续3 a （2008-2010年）的乔木群落调查，研究冰灾对亚热带森林更新演替的影响。结果发现：（1）样地优势乔木树种受灾程度由高到低依次为：栲树＞鸭公树＞米槠＞石栎＞木荷＞栓叶安息香＞微毛山矾＞华南桂＞香楠＞尾尖叶柃；2）冰灾后3 a冠层乔木群落总个体数先增加后减少，其变动主要来源于乔木幼树，但区系成分和多样性变化不大；3）乔木径级越小其个体数越多、年间变化越大，乔木从小径级到大径级的成长过程中死亡率的总体趋势在下降；4）样地中整个乔木群落是呈聚集分布的，乔木从小树到大树是从聚集分布到随机分布再到均匀分布的变化过程，并且2009和2010年的乔木群落分布格局更相近。展开更多
Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when ...Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when they fall from the canopy,which limits our understanding of their role in forest carbon sequestration and nutri-ent cycling.In the temperate rainforest of the Quinault River Valley,Washington State,our aim was to test hypotheses regarding four elements of disturbance that might contribute to their decline.Methods We established set of experiments in which we placed samples of canopy epiphytes and their branch segments:(i)in the canopy versus forest floor microenvironment(stratum);(ii)attached to live versus dead branch substrates;(iii)subjected to physical disruption and‘jarring’;and(iv)in direct versus indirect con-tact with the forest floor.Over the 2-year study,we assigned a non-destructive‘vitality index’(based on color and appar-ent mortality and dryness)to each sample every 2-3 months to compare effects of the experimental treatments and analyzed with a statistical model and post hoc pairwise comparisons of treatments.Important Findings The canopy versus ground stratum and live/dead branch status sig-nificantly affected epiphyte vitality.Effects of physical disruption and ground contact were not significant.There were seasonal effects(low vitality during the sampling times in the summer,revitalization upon sampling times in the winter)for all treatments except samples in contact with the ground.One implication of these results relates to effects of climate change,which is predicted to shift to hotter,drier summers and wetter winters.Climate change may affect forest dynamics and nutrient cycling in unpredictable ways.Results also point to future experiments to understand biotic and abiotic effects on epiphyte disturbance and dynamics.展开更多
文摘Canopy interception of incident precipitation, as a critical component of a forest＇s water budget, can affect the amount of water available to the soil, and ultimately vegetation distribution and function. In this paper, a statistical-dynamic approach based on leaf area index and statistical canopy interception is used to parameterize the canopy interception process. The statistical-dynamic canopy interception scheme is implemented into the Community Land Model with dynamic global vegetation model （CLM-DGVM） to improve its dynamic vegetation simulation. The simulation for continental China by the land surface model with the new canopy interception scheme shows that the new one reasonably represents the precipitation intercepted by the canopy. Moreover, the new scheme enhances the water availability in the root zone for vegetation growth, especially in the densely vegetated and semi-arid areas, and improves the model＇s performance of potential vegetation simulation.
基金supported by the National Key Research and Development Program of China(2017YFD0300603)the Special Fund for Agro-scientific Research in the Public Interest of China(201203031)。
文摘Leaf growth and its interaction with the growing environment critically affect leaf area, distribution, and function, and ultimately affects grain yield of maize(Zea mays L.). To detect the effects of leaf area dynamics, growth periods, and the environment on maize grain yield, a three-year field experiment was conducted using two maize varieties, medium plant-size variety Zhengdan 958(ZD958) and large plant-size variety Zhongnongda 4(ZND4), and three to five sowing dates. The sowing date significantly affected maize yield as a result of changes in leaf area, growth stage, and growing environment. Prior to the 12 th leaf stage, significant correlations between leaf area dynamics, environment, and yield were seldom detected. The expansion of leaf area from 12 th leaf stage to silking stage was significantly positively correlated with growing degree days(GDD), solar radiation, and grain yield, indicating the importance of leaf area dynamics during this period. After silking, solar radiation played a more important role in inducing leaf senescence than GDD, particularly in the 2 nd half of the grain filling stage. Accelerated leaf senescence in late growth period can increase maize yield. The environment affected leaf area dynamics and yield of the large plant-size variety(ZND4) more easily than the medium plant-size variety(ZD958) at the optimum plant density, reflecting the difference in varietal capacity to adapt to the growing environment. This study indicates that optimizing the interaction among leaf area dynamics, growth periods, and environment is a sound strategy to increase maize yield. Favorable interactions are useful to determine the optimal sowing date of a given variety.
文摘以粤北车八岭2008年受冰灾破坏的山地常绿阔叶林为研究对象，设置2 hm2固定样地开展连续3 a （2008-2010年）的乔木群落调查，研究冰灾对亚热带森林更新演替的影响。结果发现：（1）样地优势乔木树种受灾程度由高到低依次为：栲树＞鸭公树＞米槠＞石栎＞木荷＞栓叶安息香＞微毛山矾＞华南桂＞香楠＞尾尖叶柃；2）冰灾后3 a冠层乔木群落总个体数先增加后减少，其变动主要来源于乔木幼树，但区系成分和多样性变化不大；3）乔木径级越小其个体数越多、年间变化越大，乔木从小径级到大径级的成长过程中死亡率的总体趋势在下降；4）样地中整个乔木群落是呈聚集分布的，乔木从小树到大树是从聚集分布到随机分布再到均匀分布的变化过程，并且2009和2010年的乔木群落分布格局更相近。
基金National Science Foundation(EHR 15-14494 and DEB 11-41833 to N.M.N.and DBI 1400456 to K.D.K.).
文摘Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes.Little is known about the processes and rates of their death and decomposition when they fall from the canopy,which limits our understanding of their role in forest carbon sequestration and nutri-ent cycling.In the temperate rainforest of the Quinault River Valley,Washington State,our aim was to test hypotheses regarding four elements of disturbance that might contribute to their decline.Methods We established set of experiments in which we placed samples of canopy epiphytes and their branch segments:(i)in the canopy versus forest floor microenvironment(stratum);(ii)attached to live versus dead branch substrates;(iii)subjected to physical disruption and‘jarring’;and(iv)in direct versus indirect con-tact with the forest floor.Over the 2-year study,we assigned a non-destructive‘vitality index’(based on color and appar-ent mortality and dryness)to each sample every 2-3 months to compare effects of the experimental treatments and analyzed with a statistical model and post hoc pairwise comparisons of treatments.Important Findings The canopy versus ground stratum and live/dead branch status sig-nificantly affected epiphyte vitality.Effects of physical disruption and ground contact were not significant.There were seasonal effects(low vitality during the sampling times in the summer,revitalization upon sampling times in the winter)for all treatments except samples in contact with the ground.One implication of these results relates to effects of climate change,which is predicted to shift to hotter,drier summers and wetter winters.Climate change may affect forest dynamics and nutrient cycling in unpredictable ways.Results also point to future experiments to understand biotic and abiotic effects on epiphyte disturbance and dynamics.
