中国典型森林生态系统土壤水分时空分异及其影响因素

森林土壤水分作为物质与能量循环的载体影响林木生长与发育，并通过影响水分在陆气之间的循环与分配影响区域气候。基于我国不同气候带的9个森林生态系统定位观测站的长期观测数据，探究了2005-2016年中国典型森林生态系统土壤水分的空间分异及其时间动态，并进一步分析了影响其时空分异的环境因素。主要研究结论如下：（1）9个森林生态系统的土壤水分多年均值介于12.45%-36.30%之间，空间上呈现中温带、亚热带、热带土壤水分较高，暖温带土壤水分较低的分布特征。降水蒸散差（降水与蒸散的差值）可以解释我国森林生态系统土壤水分空间分异的62%（P<0.05）；（2）我国北部与东部季风区森林区域土壤水分呈上升趋势，降水上升是主因，其中暖温带北京、南亚热带鼎湖山与鹤山森林土壤水分上升趋势显著，增幅分别为0.67%/a、1.72%/a与0.69%/a；西南地区森林生态系统土壤水分呈下降趋势，该趋势由降水下降与蒸散上升共同导致，其中中亚热带贡嘎山及哀牢山森林生态系统土壤水分下降趋势显著，降幅分别为-1.77%/a与-0.94%/a；土壤水分时间分异与降水蒸散差的相关性最高（R=0.59，P<0.01）；（3）土壤水分呈下降趋势的森林生态系统中，春季土壤水分变化主导了年际变化，土壤水分上升的森林生态系统中，年际变化则是由秋、冬季主导。（4）与ERA-interim土壤水分再分析数据比较得出，两者在空间格局与变化趋势上均具有较高的一致性。CERN土壤水分观测数据反映了无人为干扰的自然条件下森林土壤-植被-气候之间的反馈作用，可为基于模型的土壤水分研究提供长时序的验证数据。

Spatio-temporal variation of soil moisture and its influencing factors in Chinese typical forest ecosystems

Soil moisture of forest ecosystems acts as a carrier of matter and energy cycle, affecting growth and development of vegetation, and affecting regional climate by changing the circulation and distribution of water between land and atmosphere. Based on the long-term observation data of 9 forest ecosystem sites in different climatic zones in China, this study explores the spatial pattern and temporal dynamics of soil moisture in Chinese typical forest ecosystems from 2005 to 2016, and further analyzes its influencing environmental factors. The main research conclusions are as follows: (1) the multi-year mean of soil moisture in 9 forest ecosystems ranges from 12.45% to 36.30%. The spatial distribution is that soil moisture in the temperate zone, subtropical zone and tropical zone is relatively high, while that in the warm temperate zone is relatively low. Precipitation minus evapotranspiration (P-ET) can explain 62% (P<0.05) of the spatial pattern of soil moisture of forest ecosystems in China. (2) Soil moisture shows an upward trend in north China and east monsoon area in China and the increase of precipitation is the main cause. Soil moisture of Beijing Forest Ecosystem(BJF), Dinghushan Forest Ecosystem(DHF), Heshan Forest Ecosystem(HSF) increases significantly by 0.67%/a, 1.72%/a and 0.70%/a, respectively. Soil moisture shows a downward trend in Southwest China which is caused by both the decrease of precipitation and the increase of ET. Soil moisture of Gonggashan Forest Ecosystem(GGF) and Ailaoshan Forest Ecosystem (ALF) shows a significant downward trend with the decreases of -1.77%/a and -0.94%/a. The correlation between the temporal trend of soil moisture and P-ET was the highest (R=0.59, P<0.01). (3) In the forest ecosystem where soil moisture is decreasing, the change of soil moisture in spring dominates the interannual trend, while in the forest ecosystems where soil moisture is increasing, the interannual trend is dominated by autumn and winter. The CERN soil moisture observation data reflects the feedback effect between soil-vegetation-climate under undisturbed natural forest conditions, which can also provide long-term verification data for model-based soil moisture research.