科尔沁沙地不同土地利用类型土壤化学计量特征

土壤碳(C)、氮(N)、磷(P)化学计量是衡量土壤质量及生态系统元素限制的重要指标,探讨土地利用和土层深度对土壤化学计量特征的影响有利于揭示科尔沁沙地土壤元素循环规律。本研究以科尔沁沙地5种土地利用类型(灌溉农田、旱作农田、沙质草地、固定沙丘、流动沙丘)土壤为对象,分析不同土地利用类型和不同土层土壤有机碳(SOC)、全氮(TN)、全磷(TP)含量及其化学计量特征。结果表明: 1)科尔沁沙地0～10 cm SOC(3.23 g·kg^-1)、TN(0.37 g·kg^-1)、TP(0.15 g·kg^-1)含量及化学计量比(C:N、C:P、N:P分别为9.07、25.56、2.97)远低于中国陆地土壤。2)土地利用变化显著改变了SOC、TN、TP含量及其化学计量特征,0～100 cm SOC、TN、TP含量均表现为灌溉农田>沙质草地>旱作农田>固定沙丘>流动沙丘;沙质草地、灌溉农田、旱作农田C:N显著高于固定沙丘和流动沙丘,沙质草地、固定沙丘、灌溉农田、旱作农田C:P显著高于流动沙丘,5种土地利用类型N:P无显著差异。3)随土层深度增加,沙质草地、固定沙丘、灌溉农田、旱作农田SOC和TN含量显著降低,流动沙丘SOC、TN含量和C:P在各土层间无显著差异;总体上,各土地利用类型TP含量和C:N受土层影响较小;沙质草地、固定沙丘、灌溉农田、旱作农田C:P和沙质草地N:P随土层深度增加而降低。4)SOC、TN、TP、C:N与中砂粒、细砂粒、土壤容重呈显著负相关,与黏粉粒和极细砂粒呈显著正相关。沙漠化导致科尔沁沙地SOC和养分流失,加剧土壤N缺乏,水肥投入有助于耕地维持相对较高的土壤养分水平。

Soil stoichiometry characteristics under different land use types in the Horqin Sandy Land,China

The stoichiometry characteristics of carbon (C), nitrogen (N), and phosphorus (P) is an important indicator of soil quality and ecosystem nutrient limitations. Exploring the effects of land use type and soil depth on soil nutrient stoichiometry can clarify soil nutrient cycling. In this study, we collected soil samples from sites with five different land use types (irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes) in the Horqin Sandy Land, and evaluated the influences of land use type and soil depth on the contents and stoichiometry characteristics of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP). We found that: 1) SOC (3.23 g·kg^-1), TN (0.37 g·kg^-1), and TP (0.15 g·kg^-1) contents and stoichiometry characteristics (C:N, C:P, N:P was 9.07, 25.56, 2.97, respectively) to a depth of 10 cm in the Horqin Sandy Land were significantly lower than the mean values of soils in China. 2) Soil stoichiometry characteristics differed significantly among land use types. The contents of SOC, TN, and TP to a depth of 100 cm were highest in irrigated cropland, followed by sandy grassland, rainfed cropland, fixed dunes, and mobile dunes. The C:N ratios in sandy grassland, irrigated cropland, and rainfed cropland were significantly higher than those in the fixed dune and mobile dune sites. C:P ratios in the sandy grassland, fixed dunes, irrigated cropland, and rainfed cropland were significantly higher than that in the mobile dunes. The N:P ratio differed little among the five land use types. 3) SOC and TN contents in the sandy grassland, fixed dunes, irrigated cropland, and rainfed cropland decreased with increasing soil depth. SOC, TN, and C:P in the mobile dunes and TP and C:N in all land use types showed no variation among depths. The C:P ratio of sandy grassland, fixed dunes, irrigated cropland, and rainfed cropland and the N:P ratio of sandy grassland decreased with increasing soil depth. 4) SOC, TN, and TP contents and the C:N ratio were significantly negatively correlated with the contents of medium and fine sands and with soil bulk density, but significantly positively correlated with silt+clay, and very fine sand contents. Desertification led to losses of SOC and nutrients in the Horqin Sandy Land, and exacerbated soil N deficiency. Inputs of water and ferti-lizer helped cropland to maintain a relatively high level of soil nutrients.