【作者】 王哲锋；

【导师】 李小刚；

【作者基本信息】 甘肃农业大学 ， 植物营养学， 2006， 硕士

【摘要】 围栏放牧是被广泛推荐的一种保护性草地利用方式,开垦是我国北方干旱、半干旱地带草原退化和沙漠化的主要原因之一,但是关于这两种利用方式在干旱农牧交错带对草原土壤有机碳及土壤结构稳定性影响的研究不多。本研究以自由放牧草地为对照,对围栏放牧和耕种两种利用方式下草原土壤有机碳动力学和团聚体稳定性进行了定量研究,以评价耕种和围栏放牧对农牧交错带草地可持续利用的影响。本研究的主要结果如下:1.与自由放牧草地相比较,围栏放牧22年草地土壤0-20 cm总有机碳含量增加了20%;土壤粗(0.1-2 mm )有机碳含量增加了16%,年轻(0.05-0.1 mm)有机碳含量降低了19%,稳定有机碳(0.05-0.1 mm)含量增加了27%;浓酸提取碳水化合物碳含量增加了22%,稀酸提取碳水化合物碳含量增加了15%,热水溶提取碳水化合物碳含量增加了16%;矿化碳(在51天培养期间释放出的碳)含量增加了30%,但是微生物量碳含量变化不明显。耕种40年后虽然土壤总有机碳含量变化不明显,但是粗(0.1-2 mm )有机碳含量降低了%,年轻(0.05-0.1 mm)有机碳含量降低了22%,土壤稳定有机碳(0.05-0.1 mm)含量增加了8%;浓酸提取碳水化合物碳含量降低了13%,稀酸提取碳水化合物碳含量降低了19%,热水溶提取碳水化合物碳含量降低了21%;矿化碳(在51天培养期间释放出的碳)含量降低了16%,微生物量碳含量降低了30%。上述结果说明,与传统放牧(自由放牧)相比较,围栏轮牧有利于土壤总有机碳、碳水化合物含量的增加以及微生物活性的增强,而开垦耕种虽然使干草原土壤的总有机碳含量变化不明显,但是碳水化合物含量和微生物活性显著降低。2.与自由放牧草地相比较,围栏放牧利用方式对>0.25 mm土壤水稳性团聚体含量影响不明显,耕种利用方式使>0.25 mm土壤水稳性团聚体含量降低了74%,团聚体稳定率降低了77%,平均重量直径降低了90%,表明干旱农牧交错带耕种对草原土壤结构稳定性产生毁灭性的影响。3.与总有机碳相比较,碳水化合物碳含量与土壤水稳性团聚体的含量、结构稳定率和平均重量直径更相关;而在所提取的三个碳水化合物组分中,稀酸提取碳水化合物与团聚体稳定性最相关,表明在本研究所涉及的土壤中,稀酸提取碳水化合物在水稳性团聚体的形成和稳定性上起主要作用。这一结果表明,更多还原

【Abstract】 Intensive grazing (fenced) is generally recommended a conservative use of grasslands, while cropping is one of major reasons relative to grassland degradation so as to desertification in arid and semi-arid regions. However, their effects on soil organic C pools and soil aggregates stability have not been well understood. This work was designed to investigate the changes in soil organic C dynamics and aggregates stability with relation to cultivation and intensive-grazing (fenced), compared with open-grazing (no-fenced) and therefore we evaluated the sustainability of these two types of grassland uses. The main conclusions as following:1. Compared with open grazing, intensive grazing for 22 years increased soil total organic C, coarse organic carbon and stable organic carbon contents by 20%,16% and 27% respectively, but decreased fine organic content by 19%. Intensive grazing increased soil concentrated-acid extracted carbohydrate C, diluted-acid extracted carbohydrate C, hot-water extracted carbohydrate C and mineralized C (in 51 incubation days ) by 22%,15%, 16% and 30%, respectively, but did not influence microbial C. Compared with open grazing, after 40 years cultivation did not influence total organic carbon, but decreased soil coarse organic carbon and fine organic carbon contents by 29% and 22% respectively, meanwhile, increased stable organic carbon content by 8%. Cultivation decreased concentrated-acid extracted carbohydrate carbon, diluted-acid extracted carbohydrate carbon, hot-water extracted carbohydrate carbon, microbial carbon and mineral carbon contents by 13%,19%,21%,30% and 16% respectively. Our work indicated intensive grazing is advantageous to the soil total organic carbon, the carbohydrate content increase as well as the microorganism activeness enhancement; although cultivation did not causes the grassland soil total organic carbon content significantly declining, the carbohydrate content and microorganism activeness remarkably reduce compared with open grazing.2 Compared with open grazing, intensive grazing has not significantly effect the content of >0.25 mm soil water stable aggregates, but cultivation decreased >0.25 mm soil water stable aggregates content, water stable aggregates ration and mean weight diameter by 74%,77% and 90% respectively. This results show cultivation had the ruinous influence to the grassland soil structure stability in the arid crisscross zones of agriculture and animal husbandry.3 Our research indicated with compared total organic carbon content, carbohydrate carbon concentration were more closed linear relationships to soil water stable aggregates content, stable aggregates ration and mean weight diameter. Between in withdraws in three carbohydrates components, the most linear relationship were found between diluted-acid extracted carbohydrate concentration and soil aggregates stability, It demonstrated diluted-acid extracted更多还原