Estimation and analysis of the ratio of transpiration to evapotranspiration in forest ecosystems along the North-South Transect of East China

Journal of Geographical Sciences - The ratio of transpiration to evapotranspiration (T/ET) is a key parameter for quantifying water use efficiency of ecosystems and understanding the interaction...     

中国东部南北样带森林生态系统WUE和NUE空间格局及驱动因子(英文)

From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China (NSTEC). Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency (WUE) and nitrogen use efficiency (NUE), and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed: (1) vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. (2) Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE (p<0.001). While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE (p<0.001). Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. (3) There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC (p<0.001), indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.     

生态系统响应全球变化的陆地样带研究

为从机理上理解、评估和预测陆地生态系统对全球变化的响应,国际地圈生物圈计划在全球共启动了15条全球变化陆地样带,其中2条在中国,即中国东北样带和中国东部南北样带。从植物碳氮代谢、生物多样性、生态系统功能与碳收支及样带生态系统的变化趋势等方面较系统地总结了围绕中国这2条全球变化陆地样带的最新研究进展,加深了全球变化与陆地生态系统相互作用过程与机制的理解,提出未来中国全球变化陆地样带研究应充分利用我国特殊的生态与环境及区域特色,重点针对陆地生态系统对全球变化的适应性、地球系统相互作用的生物—物理—化学—社会过程与管理、土地利用变化的动力学过程与机制、灾害性天气气候的生态效应及其调控机制和全球变化模拟预警系统开展研究,做出一些在国际上既有显示度又服务于我国社会经济可持续发展的研究成果。     

NSTEC不同自然带土地利用/覆盖格局分析

采用≥10℃积温为指标划分的自然带，从土地利用结构和土地利用程度两方面，以垦殖率、土地产出、城市个数、城市建成区用地水平、土地利用程度和破碎度等为指标，构建了土地利用/覆盖格局分析的指标体系，通过自然单元和社会经济单元的数据匹配，量化土地利用/覆盖在不同自然带上的差异，从而分析中国东部南北样带上的土地利用/覆盖格局，以期为分析土地利用/覆盖变化及其驱动机制提供科学依据。     

Latitudinal patterns and influencing factors of soil humic carbon fractions from tropical to temperate forests

Soil humic carbon is an important component of soil organic carbon (SOC) in terrestrial ecosystems. However, no study to date has investigated its geographical patterns and the main factors that influence it at a large scale, despite the fact that it is critical for exploring the influence of climate change on soil C storage and turnover. We measured levels of SOC, humic acid carbon (HAC), fulvic acid carbon (FAC), humin carbon (HUC), and extractable humus carbon (HEC) in the 0–10 cm soil layer in nine typical forests along the 3800-km North-South Transect of Eastern China (NSTEC) to elucidate the latitudinal patterns of soil humic carbon fractions and their main influencing factors. SOC, HAC, FAC, HUC, and HEC increased with increasing latitude (all P<0.001), and exhibited a general trend of tropical < subtropical < temperate. The ratios of humic C fractions to SOC were 9.48%–12.27% (HAC), 20.68%–29.31% (FAC), and 59.37%–61.38% (HUC). Climate, soil texture, and soil microbes jointly explained more than 90% of the latitudinal variation in SOC, HAC, FAC, HEC, and HUC, and interactive effects were important. These findings elucidate latitudinal patterns of soil humic C fractions in forests at a large scale, and may improve models of soil C turnover and storage.     

中国东部南北样带森林生态系统蒸腾与蒸散比值(T/ET)时空变化

植被蒸腾与蒸散的比值(transpiration/evapotranspiration, T/ET)表征了植被蒸腾对生态系统蒸散的贡献率,是准确量化生态系统水分利用效率的关键参数,对研究植被水分运移的生理生态机理以及碳水循环关系具有重要意义。基于站点数据验证PT-JPL模型(Priestly-Taylor JetPropulsion Laboratory Model)模拟精度,集成遥感数据和气象栅格数据模拟中国东部南北样带森林生态系统2001-2010年T/ET,并分析其时空变化及影响因子。结果表明:①PT-JPL模型适用于中国东部森林生态系统蒸散及其组分模拟,具有较高的稳定性和可靠性;②中国东部南北样带森林生态系统T/ET空间差异显著,整体呈南部低、北部高,主要由夏季T/ET空间格局主导;样带整体T/ET均值为0.69,2001-2010年呈显著缓慢上升趋势,增幅为0.007/yr(p <0.01);③T/ET季节和年际变异的主控因子不同:温度和EVI是影响T/ET季节变异的关键因子,两者均可解释T/ET季节变异的90%左右(p <0.01);而T/ET的年际变异则主要受EVI影响,解释率为53%(p <0.05)。