Department of Ecology, College of Urban and Environmental Sciences and MOE Laboratory for Earth Surface Processes, Peking University, 100871, Beijing, People's Republic of China.
J Plant Res. 2010 Jul;123(4):543-9. doi: 10.1007/s10265-010-0311-z. Epub 2010 Feb 20.
The projected recession of forests in the forest-steppe ecotone under projected climate drying would restrict the carbon sink function of terrestrial ecosystems. Previous studies have shown that the forest-steppe ecotone in the southeastern Inner Mongolia Plateau originally resulted from climate drying and vegetation shifts during the mid- to late-Holocene, but the interrelated processes of changing soil carbon storage and vegetation and soil shifts remain unclear. A total of 44 forest soil profiles and 40 steppe soil profiles were excavated to determine soil carbon storage in deciduous broadleaf forests (DBF), coniferous forests (CF) and steppe (ST) in this area. Carbon density was estimated to be 106.51 t/hm(2) (DBF), 73.20 t/hm(2) (CF), and 28.14 t/hm(2) (ST) for these ecosystems. Soil organic carbon (SOC) content was negatively correlated with sand content (R = -0.879, P < 0.01, n = 42), and positively correlated with silt (R = 0.881, P < 0.01, n = 42) and clay (R = 0.858, P < 0.01, n = 42) content. Consistent trends between fractions of coarse sand and a proxy index of relative aridity in sediment sequences from two palaeo-lakes further imply that climate drying reduced SOC through coarsening of the soil texture in the forest-steppe ecotone. Changes in carbon storage caused by climate drying can be divided into two stages: (1) carbon storage of the ecosystem was reduced to 68.7%, mostly by soil coarsening when DBF were replaced by CF at approximately 5,900 (14)C years before present (BP); and (2) carbon storage was reduced to 26.4%, mostly by vegetation shifts when CF were replaced by ST at approximately 2,900 (14)C years BP.
在预测的气候干燥下，森林-草原交错带的森林预计会衰退，这将限制陆地生态系统的碳汇功能。先前的研究表明，内蒙古高原东南部的森林-草原交错带原本是由于中晚全新世气候干燥和植被变化而形成的，但土壤碳储存和植被及土壤变化的相互关系过程仍不清楚。在该地区共挖掘了 44 个森林土壤剖面和 40 个草原土壤剖面，以确定落叶阔叶林 (DBF)、针叶林 (CF) 和草原 (ST) 的土壤碳储存。这些生态系统的碳密度估计分别为 106.51 t/hm(2) (DBF)、73.20 t/hm(2) (CF) 和 28.14 t/hm(2) (ST)。土壤有机碳 (SOC) 含量与砂含量呈负相关 (R = -0.879, P < 0.01, n = 42)，与粉砂 (R = 0.881, P < 0.01, n = 42) 和粘粒 (R = 0.858, P < 0.01, n = 42) 含量呈正相关。两个古湖泊沉积物序列中粗砂分数与相对干旱度代理指标之间的一致趋势进一步表明，气候干燥通过土壤质地变粗减少了森林-草原交错带的 SOC。气候干燥引起的碳储存变化可分为两个阶段：(1) 当 DBF 被 CF 取代时，碳储存减少到 68.7%，主要是由于土壤变粗，大约在距今 5900 年 (14)C 年前；(2) 当 CF 被 ST 取代时，碳储存减少到 26.4%，主要是由于植被变化，大约在距今 2900 年 (14)C 年前。
