不同沙地生境下柠条灌丛化对草地土壤有机碳含量及分布的影响

为揭示不同沙地生境下灌丛化草地土壤有机碳及其组分的分布特征,以宁夏盐池县沙化草原不同沙地生境(丘间低地、固定沙地、半固定沙地、流动沙地)下不同发育期的柠条灌丛斑块及其对应的草地斑块为研究对象,对土壤颗粒组成、土壤有机碳(soil organic carbon,SOC)、颗粒有机碳(particulate organic carbon,POC)及易氧化有机碳含量(labile organic carbon,LOC)进行分析。结果表明:1)各沙地生境发育中期灌丛斑块的SOC、POC、LOC及POC/SOC极显著高于草地斑块(P0.01),而LOC/SOC在灌丛和草地斑块间差异性不显著;2)从丘间低地、固定沙地、半固定沙地到流动沙地,灌丛斑块及其对应的草地斑块SOC、POC、LOC及LOC/SOC均在固定沙地出现峰值,然后呈下降趋势,表明固定沙地及不同沙地生境发育中期的灌丛斑块和草地斑块是SOC、LOC及POC变化的临界点;3)相关分析发现,发育中期2种斑块SOC与POC及LOC间及SOC与LOC/SOC间均呈极显著相关(P0.01),但土壤黏粉粒与各组分有机碳及其分配比率间没有显著相关,因此LOC和POC可作为表征草地退化最敏感的指标。研究可为沙化草原土壤恢复研究提供理论依据。

Effect of shrub (Caragana intermedia) encroachment under different sandy habitats on content and distribution of soil organic carbon in desert grassland

Shrub encroachment is one of the serious ecological problems in arid and semiarid regions of Northwest China. In order to explore the distribution of organic carbon fractions of sandy sierozem during the process of shrubs encroachment, soil samples at the depth of 10 cm were collected in April 2015 from different development stages of shrub patches and grassland patches of degraded sandy grassland in 4 different sandy habitats(interdunal lowland, fixed sand, semi-fixed and shifting) by shrub, Caragana intermedia, in Yanchi County of Ningxia, Northwest China. Soil organic carbon(SOC), labile organic carbon(LOC), and particulate organic carbon(POC) contents and soil particle composition were analyzed. In addition, we analyzed the soil organic matter, total N, total P and soil particle composition from 4 different sandy habitats. Results showed that the SOC fractions in 4 sandy habitats had significantly differences between the medium development stages of shrub patches and grassland patches(P<0.01), which showed that the SOC, POC, LOC and POC/SOC in shrub patches were significantly higher(P<0.01) than that of grassland patches in 4 sandy habitats. However, there was not significant differences in LOC/SOC between the medium development stages of shrub patches and grassland patches. The SOC in the medium development stages of shrub patches and grassland patches appeared a peak in fixed sand, similarly, the LOC, POC and LOC/SOC appeared peaks of the various developmental stages in fixed sand, and then reduced gradually from fixed to shifting sand. Correlation analysis showed a significant correlation(P<0.01) among SOC, LOC to POC of the medium development stages of shrub patches and grassland patches, and between SOC and LOC/SOC. However, there was no relevance between soil clay and silt fractions and the organic carbon fractions and their distribution ratios. In summary, the labile organic carbon fractions and POC can be characterized as more sensitive indicators of shrub encroachment and degradation grassland. Study above reveals the distribution of soil resources caused by shrub encroachment in arid and semiarid region of North China, and it provides the important infromation for soil restoration in desert grassland.