A study was conducted to assess the impact of different land use systems on soil organic carbon (SOC), its fractions and soil organic carbon stocks under different land use systems in a mixed watershed in the submontane region of north-west India. Soil samples were collected up to a depth of 120 cm from three locations each from maize-wheat, agro-horticulture and agroforestry (3 and 6-year plantation) land use systems. The results revealed that the surface soils (0–15 cm) under agroforestry had significantly higher SOC (5.3 mg g^− 1) than in soils under other cropping systems and varied from 4.3 to 5.3 mg g^− 1. The labile carbon (LC), aggregate associated carbon (AAC), particulate organic carbon (POC) and mineralizable carbon (MC) were also significantly higher in surface soils under agroforestry 6-year plantation than other three cropping systems and thereafter exhibited significantly lower content of SOC and its fractions in each of the depth as compared to the surface soil in all the cropping systems except maize-wheat system where LC increased significantly in the second depth and decreased gradually in the subsequent lower depths. The proportion of these fractions in relation to the soil organic carbon was lowest in soils under maize-wheat (10–70%) than the tree-based cropping systems (20–100%). The typical decrease of SOC content in the 3rd depth (30–60 cm) was the sharpest and thereafter it stabilized in lower depths in maize-wheat system. The SOC stock followed the trend: agroforestry 6-year (38 Mg ha^− 1) > agroforestry 3-year (30.5 Mg ha^− 1) > agrohorticulture or maize-wheat system (27.5 Mg ha^− 1). Up to 33% lower SOC stocks were recorded in maize-wheat or agrohorticulture cropping systems than under the agroforestry land use system, thereby suggesting that conversion of forest land to agroecosystems can contribute to losses of up to 10.5 Mg ha^− 1 SOC over time. Overall conclusion from this investigation is that SOC levels are strongly influenced by the prevailing land use systems.

中文翻译：

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印度西北部典型的Ustrochrepts不同土地利用方式下的土壤有机碳，其组分和土壤有机碳储量

进行了一项研究，以评估印度西北部山区一个分水岭下不同土地利用系统下不同土地利用系统对土壤有机碳（SOC），其组成和土壤有机碳储量的影响。从玉米，小麦，园艺和农林业（3年和6年人工林）土地利用系统的三个位置分别采集了深度达120厘米的土壤样品。结果表明，农林业下的表层土壤（0-15厘米）SOC显着高于其他耕作制度下的土壤有机碳（5.3 mg g ^-1），范围从4.3到5.3 mg g ^-1。农林6年种植下表层土壤中的不稳定碳（LC），聚集伴生碳（AAC），颗粒有机碳（POC）和可矿化碳（MC）也显着高于其他三种种植制度，其后的含量显着降低。与除玉米-小麦系统以外的所有耕作系统中表层土壤相比，SOC和其在每个深度中的比重均不同，在第二个深度中，LC显着增加，在随后的较低深度中，LC逐渐减小。这些部分相对于土壤有机碳的比例在玉米小麦下的土壤中最低（10–70％），比树木种植系统（20–100％）最低。在第三深度（30–60 cm）中，SOC含量的典型下降最为明显，此后在玉米-小麦系统中的较低深度中稳定下来。^{− 1}）> 3年农林业（30.5 Mg ha ^{− 1}）>农业园艺或玉米-小麦系统（27.5 Mg ha ^{− 1}）。与农林业土地利用系统相比，玉米-小麦或农用园艺种植系统的SOC储量减少了多达33％，这表明随着时间的流逝，林地向农业生态系统的转化可能导致高达10.5 Mg ha ^-1 SOC的损失。该调查的总体结论是，SOC水平受现行土地使用系统的强烈影响。