陕北黄土丘陵区不同土地利用方式下土壤碳剖面分布特征

黄土高原土层深厚,土壤剖面碳存储受土地利用方式影响明显.为探讨不同土地利用方式对深层土壤碳分布的影响,研究了人工经济林地(陕北米脂)、退耕还林地(神木)和防风固沙林地(榆林榆阳区)0~20.0 m土壤有机碳(SOC)和无机碳(SIC)的分布特征和差异.结果表明,在不同土地利用方式下SOC含量:矮化枣树(2.00 g·kg~(-1))未矮化枣树(1.54 g·kg~(-1))柠条林(0.97 g·kg~(-1))退化人工草地(0.81 g·kg~(-1))樟子松林(0.70 g·kg~(-1))荒草地(0.45 g·kg~(-1)),且各剖面之间SOC含量存在显著性差异(P0.05).在不同土地利用方式下SIC含量:矮化枣树(11.66 g·kg~(-1))≥未矮化枣树(11.59g·kg~(-1))柠条林(9.62 g·kg~(-1))退化人工草地(8.07 g·kg~(-1))樟子松林(4.32 g·kg~(-1))荒草地(0.47 g·kg~(-1));人工经济林和退耕还林(草)样地内所有土壤剖面之间SIC含量无显著性差异;人工经济林、退耕还林(草)剖面和防风固沙林地剖面SIC含量存在显著性差异(P0.05).矮化枣树、未矮化枣树、柠条林、退化人工草地、樟子松林和荒草地土壤剖面无机碳密度分别是有机碳密度的6.19、7.71、10.80、10.78、5.91和1.03倍.综上可见,不同土地利用方式之间土壤碳储量存在明显差异,无机碳的含量远高于有机碳.

Profile Distribution of Soil Organic and Inorganic Carbon Under Different Land Use Types in the Loess Plateau of Northern Shaanxi

Carbon storage in the Loess Plateau is affected by land use. In order to assess the differences in soil organic carbon (SOC) and soil inorganic carbon (SIC) under different land use patterns in deep soil profiles, we investigated the distribution characteristics of SOC and SIC at 0-20.0 m soil depth at three locations in the northern Shaanxi province (i.e., an economical plantation in Mizhi, a reforestation area in Shenmu, and a wind break and sand fixation forest district in Yuyang). The results showed that the order for SOC content was:pruning jujube tree (2.00 g·kg^-1) > jujube tree (1.54 g·kg^-1) > Caragana (0.97 g·kg^-1) > degraded artificial grassland (0.81 g·kg^-1) > pine forests (0.70 g·kg^-1) > natural grass field (0.45 g·kg^-1), which indicated significant differences between SOC content and land use types (P<0.05). Similarly, the order of SIC content was:pruning jujube tree (11.66 g·kg^-1) > jujube tree (11.59 g·kg^-1) > Caragana (9.62 g·kg^-1) > degraded artificial grassland (8.07 g·kg^-1) > pine forests (4.32 g·kg^-1) > natural grass field (0.47 g·kg^-1). There were no significant differences between SIC content and soil profiles under the economical plantation of Mizhi and the reforestation area of Shenmu. There were significant differences for SIC content between an artificial economic forest, an area returning farmland to a forest (grass) profile, and a windbreak and sand fixation forest (P<0.05). The SIC densities for pruning jujube tree, jujube tree, Caragana, degraded artificial grassland, pine forest, and natural grass field were 6.19, 7.71, 10.70, 10.78, 5.91, and 1.03 times that of its corresponding SOC density, respectively. It has been concluded that the soil carbon storage was significantly different for different land use patterns, and the SIC content was much higher than the SOC content in the soil profile.