黄土高原丘陵区退耕还林地土壤碳氮库的动态变化(英文)

Dynamics of soil carbon and nitrogen stocks following afforestation in gully region of Loess Plateau, China

为了揭示坡耕地退化土壤植被恢复后土壤中碳（C）、氮（N）运移规律,采用植被次生演替空间序列代替时间序列的方法,研究了黄土丘陵沟壑区纸坊沟流域不同植被恢复模式下的C、N库及其相互关系在土壤剖面的时空变化。结果表明退化农地的造林显著地促进了CO2的固存,恢复了土壤N的可获得性,进而降低了N不足对可持续的CO2固存的限制。植被恢复显著地促进了0~60 cm土壤有机碳（soil organic carbon,SOC）和总氮（total nitrogen,TN）的积累,而只有在高于一定的恢复时间阈值（如26 a）下,促进了SOC库和TN库间的线性相关性。在土壤剖面上,SOC和TN库、SOC/TN库比以及SOC-TN间的线性相关性均随着土壤深度的增加而降低。与自然恢复相比,人工林在短期内具有CO2固存的优势,但由于随着恢复时间的增加,SOC增幅越来越大于TN增幅的事实,表明造林对碳固存的可持续性需在一个较长的时段下来评估,尤其需要关注20 cm以下层土壤。研究结果为黄土高原的生态修复和减缓温室效应提供了理论依据。

The effect of vegetation restoration on soil carbon（C） and nitrogen（N） stocks is an important consideration during the remediation of degraded soil. The temporal variation and distribution of C and N stocks in the soil profile were studied in areas with different types of vegetation restoration in the Zhifanggou catchment of China＇s Loess Plateau. In this area, the ＂Grain-for-Green＂ project（GFGP） encouraged landscape scale habitat restoration during the last decade. Results showed that afforestation of degraded cropland significantly promoted CO2 sequestration and restored soil N availability, which consequently reduced N limitation and sustained C sequestration. Above a vegetation age threshold, i.e. 26 years, afforestation significantly improved the linear correlation relationship between soil organic C（SOC） and total N（TN） stocks in the 0~60 cm soil profile. This linear SOC-TN stock nexus decreased with increasing soil depth, and the potential of having improved SOC stock, TN stock and the ratio between them in deeper soil layers increased with increasing time after afforestation. Managed plantations provide superior CO2 sequestration and improvement in the SOC-TN correlation at a relatively short period after afforestation when compared to natural restoration where vegetation is established by natural colonization. So these results indicate that the C sequestration sustainability of afforestation should be assessed at a long-term scale, and a relative great attention should be focused on deeper soil.