土壤有機碳（SOC）庫是陸地生物圈中最大的碳庫,，約占陸地生態(tài)系統(tǒng)總碳儲量的三分之二,，其中農(nóng)田土壤有機碳庫占全球陸地碳庫的8%—10%。然而,，由人類活動引起的土地利用/覆蓋變化已成為影響土壤碳庫動態(tài)的最直接原因,，其中最嚴重的干擾就是將自然植被轉變?yōu)楦亍Ｖ袊鞅备珊祬^(qū)具有獨特的山盆相間的地貌格局,，形成了典型的以“山地－綠洲－荒漠”為主體的流域生態(tài)系統(tǒng),，其結構完全不同于世界其它干旱區(qū)，如非洲Savanna稀樹草原地區(qū),、中東干旱沙漠區(qū)域,、澳洲中西部干旱區(qū)及北美干旱區(qū)等。中國西北干旱區(qū)流域生態(tài)系統(tǒng)一直受到人類活動的強烈影響,，半個世紀前人類大規(guī)模的水土開發(fā)使得流域下部的荒漠覆被土地轉變?yōu)槿斯ぞG洲,，以天山北坡為例，近50年耕地面積增幅約150%,，其后在不同農(nóng)業(yè)管理模式的影響下,，土壤碳庫發(fā)生了顯著變化。
中國科學院新疆生態(tài)與地理研究所陳曦研究團隊,，在國家重點基礎研究發(fā)展計劃（973計劃）（2009CB825105）的支持下,，以干旱區(qū)典型的三工河流域下部的人工綠洲為例，基于CENTURY模型,，研究了人工綠洲開發(fā)前后及農(nóng)業(yè)管理模式變化對表層土壤有機碳庫（0-20cm）的影響,。CENTURY模型模擬結果表明：（1）研究區(qū)荒漠灌木林地開墾為人工綠洲后，在最初的兩年土壤總有機碳（TOC）快速增加,，隨后呈逐漸下降的趨勢,；（2）研究區(qū)人工綠洲在被開發(fā)后50年的連續(xù)耕作下,，平均土壤TOC呈先增后減再增的“N”型變化趨勢，但最終土壤TOC超過了原始自然狀態(tài)下的TOC,，而且2008年土壤TOC比原始荒漠狀態(tài)增加7.74%,，說明研究區(qū)表層土壤有機碳總體呈“碳匯”趨勢。
尤其在研究區(qū)實施了免耕,、秸稈粉碎還田,、科學測土配方施肥等保護性耕作措施后，土壤固碳效應明顯,，這完全不同于熱帶森林,、中國北部溫帶半干旱草原及非洲Savanna半干旱稀樹草原開墾為耕地后土壤有機碳大量損失的結論。（生物谷Bioon.com）
生物谷推薦原文出處：
Ecological Complexity DOI： 10.1016/j.ecocom.2010.11.003
Using the CENTURY model to assess the impact of land reclamation and management practices in oasis agriculture on the dynamics of soil organic carbon in the arid region of North-western China
Wenqiang Xu, Xi Chen, Geping Luo and Qing Lin
Large-scale reclamation of arid land in North-western China over the past 50 years has converted the natural desert landscape into anthropogenic oasis, particularly in the lower part of watersheds. Drastic human activities may have caused the change of soil organic carbon (SOC) in anthropogenic oasis. This study employs the CENTURY model (Version 4.0) to investigate the effects of land reclamation and management practices in oasis agriculture on the dynamic of SOC at the lower part of Sangong river watershed, a typical anthropogenic oasis reclaimed at 50 years ago. Based on field investigation, history of crop rotations, and past farm practices in study area, land management practices were divided into five categories, corresponding five periods, 0–1958, 1959–1984, 1985–1992, 1993–1998 and 1999–2008. The model successfully simulated the SOC dynamics of the top layer soil (0–20 cm) in the different periods. The state of equilibrium of total SOC and the active, slow, and passive carbon pools were built by CENTURY model in 0–1959. Over the 50 years’ cultivation (1959–2008), the mean change in total SOC exhibited complex ways. SOC increased rapidly in the first 2 years (1959–1960) after shrubland reclamation, and declined slowly during the period 1961–1984 and then decreased rapidly from 1985 to 1992. Between 1993 and 1998, it remained relatively stable, and climbed rapidly again during 1999–2008. The trend in total SOC showed “N” shape, i.e., increase, decrease, then increase. Finally, total SOC is greater (8.2%) in 2008 than the original level of SOC under the natural desert shrub. The improvements of land management practices such as ploughing being replaced with no tillage, straw being crushed before returning it to soil, and reasonable application of fertilizers, played a key role in the change in total SOC. Especially, soil carbon sequestration was obviously increased since protective management practices were implemented in 1993, such as no tillage, straw returning to soil, and the balanced fertilization technique. The results were different from the conclusions that loss of soil organic carbon would happen due to reclamation and continuous farming in tropical forests, semiarid grasslands of northern China and Nigerian semiarid Savannah.
