天山北坡草甸草原碳过程及其对围栏封育的响应

发布时间：2018-11-14 17:59

【摘要】：草地生态系统是陆地生态系统的重要组成部分,研究其碳循环的变化规律对于了解整个陆地生态系统的物质循环具有重要的意义,随着全球变化进程的加剧,草地生态系统碳循环已成为热点研究议题。目前对碳过程的研究主要集中在荒漠草原、高山草原、亚高山草原、高寒草原,而对中低山地草甸草原生态系统的观测则比较匮乏。本研究采用Li-8100开路式土壤碳通量测量系统和静态箱法(Li-840 CO2/H2O红外分析仪),在乌鲁木齐市西南50 km的甘沟乡,对山地草甸草原围栏内外的土壤呼吸和生态系统呼吸进行了原地观测,同时对围栏内外的土壤、根系、植被进行了调查,并观测了气温、地温、含水量等环境要素,得出了结论如下:1.对比分析了围封与放牧山地草甸草原的土壤碳密度、地上植被碳密度及根系碳密度,结果表明,围封9年后的山地草甸草原土壤碳密度和根系碳密度在不同土层均高于放牧区,尤其是在0~10 cm土层差异达到极显著水平(P0.01);围封区各月地上植物碳密度均极显著高于放牧区(P0.01)。因此,围栏封育促进了山地草甸草原的碳截存能力,显著增加了山地草甸草原土壤和植物碳蓄积量。2.山地草甸草原,不论围栏内还是围栏外,土壤呼吸都表现为明显的日变化和季节变化规律,均呈单峰曲线,放牧并没有改变土壤呼吸速率的变化规律,5~8月峰形比较明显,4、9、10月份无明显峰形,碳排放大小夏季明显高于其他月份,尤其是6、7月份土壤呼吸对总的碳排放量贡献最大。总的来说,围封后碳排放显著高于围栏外。3.温度与湿度是影响土壤呼吸的两个重要因子,但温度起主导作用。在山地草甸草原,土壤呼吸与土壤含水量的相关性不显著;土壤呼吸与地温有着显著的正相关关系,温度是决定该山地草甸草原土壤呼吸的主导因子。围栏内外浅层土壤(0~5cm)相关性要高于其它深度的土壤,并且在各个层次的土壤,围栏内土壤呼吸与温度的相关性要高于围栏外,5 cm的地温能更好的反映土壤呼吸的变化情况。4.山地草甸草原,不论围栏内还是围栏外,生态系统碳交换都表现为明显的日变化和季节变化规律,均呈单峰曲线,放牧并没有改变碳通量的变化规律,5~8月明显表现为碳汇,但围栏内碳吸收明显高于围栏外,其他月份则表现为碳源,由于围栏内5~8月份在生态系统碳吸收中贡献较大,因此围封后的山地草甸草原在年季上表现为碳汇。而围栏外则因夏季在碳吸收中贡献小,因此表现为碳源。5.温度与湿度是影响生态系统碳交换的两个重要因子,但温度起主导作用。在山地草甸草原,生态系统碳交换与土壤含水量的相关性不显著;生态系统碳交换与温度有着显著的线性相关关系,温度是决定该山地草甸草原碳交换的主导因子。
[Abstract]:Grassland ecosystem is an important part of terrestrial ecosystem. It is of great significance to understand the material cycle of the whole terrestrial ecosystem by studying its carbon cycle. Grassland ecosystem carbon cycle has become a hot research topic. At present, the study of carbon process mainly focuses on desert steppe, alpine steppe, subalpine steppe, alpine steppe, and alpine steppe. In this study, Li-8100 open-circuit soil carbon flux measurement system and static box method (Li-840 CO2/H2O infrared analyzer) were used in Gangou Township, 50 km southwest of Urumqi. The soil respiration and ecosystem respiration inside and outside the enclosure of mountain meadow grassland were observed in situ. At the same time, the soil, root system and vegetation inside and outside the fence were investigated, and the environmental factors such as temperature, ground temperature, water content and other environmental factors were observed. The conclusions are as follows: 1. The soil carbon density, aboveground vegetation carbon density and root carbon density of enclosed and grazing mountain meadow steppe were compared. The results showed that the soil carbon density and root carbon density of mountain meadow steppe after 9 years of enclosure were higher than those of herding area in different soil layers. Especially at 10 cm, the soil layer difference reached a very significant level (P0.01). The carbon density of aboveground plants in enclosed area was significantly higher than that in herding area (P0.01). Therefore, fencing promoted the carbon sequestration capacity of mountain meadow steppe, and significantly increased the soil and plant carbon accumulation of mountain meadow grassland. 2. In mountain meadow grassland, both inside and outside the fence, soil respiration showed obvious diurnal variation and seasonal variation, and all of them showed a single peak curve. Grazing did not change the variation of soil respiration rate. The peak form of May to August was obvious. There was no obvious peak in October, and the carbon emission in summer was obviously higher than that in other months, especially in June and July, soil respiration contributed the most to the total carbon emissions. Overall, carbon emissions after containment were significantly higher than those outside the fence. Temperature and humidity are two important factors affecting soil respiration, but temperature plays a leading role. There was no significant correlation between soil respiration and soil moisture content in mountain meadow grassland, and there was a significant positive correlation between soil respiration and soil temperature, and temperature was the leading factor to determine soil respiration in mountain meadow grassland. The correlation between soil respiration and temperature inside and outside the enclosure is higher than that outside the fence, and the correlation of soil 0~5cm is higher than that of other depth soil, and the correlation between soil respiration and temperature in each layer of soil is higher than that outside the fence. The soil temperature of 5 cm can better reflect the change of soil respiration. 4. In mountain meadow grassland, both inside and outside the enclosure, the carbon exchange of ecosystem showed obvious diurnal variation and seasonal variation, all of them showed a single peak curve, grazing did not change the change rule of carbon flux, and from May to August, carbon sink was obvious. However, the carbon uptake in the enclosure was significantly higher than that outside the fence, and the other months were carbon source. The enclosed mountain meadow steppe was a carbon sink in the annual season because it contributed a lot to the carbon sequestration of the ecosystem in May and August. But outside the fence because of the summer carbon absorption contribution is small, so the performance of carbon source. 5. 5. Temperature and humidity are two important factors affecting carbon exchange in ecosystem, but temperature plays a leading role. In mountain meadow steppe, the correlation between ecosystem carbon exchange and soil water content is not significant, but there is a significant linear correlation between ecosystem carbon exchange and temperature, temperature is the dominant factor to determine carbon exchange in mountain meadow grassland.
【学位授予单位】：新疆农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S812

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