【作者】 尹萍；

【导师】 李小刚；

【作者基本信息】 甘肃农业大学 ， 植物营养学， 2008， 硕士

【摘要】 开垦对土壤有机碳库和土壤团聚体稳定性有很大的影响,但随着开垦年限的增加,土壤性质如何变化到目前为止还不太清楚。因而,本研究选取亚高山草甸土壤6个不同开垦年限:未开垦,开垦5年,开垦13年,开垦20年,开垦33年,开垦大于70年土壤作为研究对象,研究开垦年限对亚高山草甸土壤有机碳、氮、碳水化合物、腐殖质、矿化碳和团聚体稳定性的影响。以期探讨土壤有机碳库和土壤团聚体稳定性随着开垦年限的变化有何变化。主要研究结论如下:1.该区土壤质地为粉壤。亚高山草甸土壤开垦后,在0~15cm深度,土壤pH值与未开垦土壤相比较,差异不显著。土壤中粉粒和砂粒含量变化亦不显著,但粘粒含量在开垦33年内(主要出现在20～33年间)有上升趋势,这可能与耕作扰动使土壤颗粒的细化有关;开垦33年以后粘粒含量开始下降,这可能与风蚀有关。0~15cm土层的CaCO3含量呈增加的趋势,但是变化不明显。2.亚高山草甸土壤开垦5年后,0~15cm层土壤有机碳含量与未开垦草甸土相比呈显著下降趋势,之后的33年内也下降,但是趋势不明显。开垦70年以上总有机碳含量与未开垦草甸土壤相比下降了34%。颗粒有机碳在开垦5~70年以上差异不显著,但与未开垦草甸土相比下降显著。而矿物结合态有机碳含量只是在开垦70年以上呈显著下降趋势。土壤中全氮的含量呈下降趋势,开垦5年后全氮含量与未开垦土壤相比差异显著,之后13~20年差异不显著,在33年和70年以上时又呈显著下降趋势。颗粒有机氮和矿物结合态有机氮含量的变化趋势分别与颗粒有机碳和矿物结合态有机碳含量变化趋势一致。3.亚高山草甸土壤开垦后,0~15cm层土壤碳水化合物碳随着开垦年限的增加呈下降趋势。开垦5年后碳水化合物碳含量显著下降了29%,开垦5~33年土壤碳水化合物碳含量在4.3~4.2g/kg之间,变化不显著。开垦70年以上碳水化合物碳比开垦33年土壤下降显著。土壤腐殖质碳含量在开垦5年后下降显著,之后的几十年中也呈下降趋势,但在33年后腐殖质碳含量有所升高,但是在开垦70年以上土壤腐殖质碳又下降,与未开垦草甸土壤相比下降了36%。土壤中可矿化碳的含量在5年后也显著下降,与未开垦草甸土壤相比下降了35%。开垦5~70年以上土壤可矿化碳含量没有显著性差异。4.亚高山草甸土壤开垦耕种后,随着开垦年限的增加,土壤全磷含量不断增加。但在开垦20年之内全磷含量变化不显著,在开垦20年到70年以上土壤全磷含量下降显著。速效磷含量变化波动很大,随着开垦年限的增加而增加,但是在开垦13年后有所下降,之后又随之上升。5.土壤结构稳定性在亚高山草甸土壤开垦后显著下降,主要表现在开垦5年之内。在不同的开垦年限之间,团聚体的稳定性差异不显著。开垦5~33年团聚体稳定率与未开垦草甸土相比降低了66~84%,开垦70年以上降低了86%。更多还原

【Abstract】 It is great effects of reclamation on soil organic carbon pool and soil aggregate stability, but, we cannot know how soil property change clearly with the increase of reclamation years after reclamation. We selected six different sub-alpine meadow reclamation soil: uncultivated, cultivated for 5 years, cultivated for 13 years, cultivated for 20 years, cultivated for 33 years, cultivated over 70 years. We analysis the effects of different reclamation years on soil organic carbon,nitrogen,carbohydrate,humus,mineralization-carbon and soil aggregate stability. The aims were to investigate changes of soil organic carbon and soil aggregate stability under different years of reclamation. The main conclusions of the study are summarized as follows:1. Sub-alpine meadow is predominated by silty loam. There is no obvious difference of the soil pH (0-15cm) between the uncultivated site and the after reclamation sites. The changes of silt and sand content are not significant too, but there is an upward trend of the clay content in the sample of cultivated for 33 years (mainly from cultivated for 20 years to cultivated for 33 years), which may be related to farming disturbance which could refine the soil particles; after cultivated 33 years, the clay content start to decline, which may be related to wind erosion. The CaCO3 content at 0~15cm depth layer present increasing trend, but there is no significant.2. There is significant decrease of soil organic carbon content at 0-15cm depth after cultivated 5 years in the sub-alpine meadow; there is decrease during the samples of cultivated 5 years to 33 years too, but no significant. Compared to the sample of uncultivated, total organic carbon content of the sample of cultivated over 70 years decreased by 34 percent. There is no significant difference of the particulate organic carbon during the samples of cultivated 5 years to over 70 years, but lower than that of the sample of uncultivated significantly. The mineral-associated organic carbon presented significantly declining trend only in the sample of cultivated over 70 years. Total nitrogen presented significantly declining trend, there is significant difference between the samples of after cultivated 5 years and uncultivated, no significant between the samples during cultivated 13~20 years, significantly declining during the samples of cultivated 33 years to over 70 years. The particulate organic nitrogen and the mineral-associated organic nitrogen have the same tend with the particulate organic carbon and the mineral-associated organic carbon separately.3. The soil carbohydrate carbon at 0-15cm depth decrease with the reclamation year increase after reclamation in the sub-alpine meadow. It decrease 29% significantly after cultivated 5 years, which is 4.3~4.2g/kg during the samples of cultivated 5~33 years, and no significant. There is significant decrease in the soil carbohydrate carbon of the sample of cultivated over 70 years than that of the samples of cultivated for 33 years. The soil humus carbon significant decrease after cultivated 5 years, but there is increase from cultivated 33 years, and the soil humus carbon decrease in the sample of cultivated over 70 years, decreased by 36 % compared to the uncultivated land. Mineralization in soil carbon content also decreased significantly in samples of after cultivated 5 years, decreased by 35 % compared to the uncultivated land. There is no significant difference of the mineralization in soil carbon content of the samples of cultivated 5~70 years.4. The total soil phosphorus content increases continuously with the reclamation year increase after reclamation in the sub-alpine meadow. But there is no significant during the samples of cultivated 5~20 years and significantly decreasing during the samples of cultivated 20~70 years. The fluctuation of available phosphorus is great, and which increase with the reclamation year increase, but decreased after 13 years and then went up again.5. Soil structure stability significantly decreased in the sub-alpine meadow, mainly in the sample of cultivated for 5 years. There is no significant difference in the soil structure stability under different years of reclamation. The aggregate stability rate decreased 66~84% during cultivated 5~33 years, and decreased 86% of the sample of cultivated over 70 years.更多还原