降雨变化对内蒙古半干旱草地土壤活性氮库及净氮矿化的影响

发布时间：2018-08-25 09:36

【摘要】：目前,降雨变化对半干旱草原生态系统的影响机制还不明确。为了研究降雨变化对内蒙古半干旱草原生态系统功能及过程的影响,我们在内蒙古锡林浩特设置了两个不完全相同的降雨格局及降雨量分配改变的人工控制实验,包括锡林浩特市西乌珠穆沁旗挡雨板控制降雨实验平台(处理包括5个降雨梯度：生长季减少降雨60%和30%,对照,增加降雨30%和60%;以及两种改变降雨分布处理,在生长季6月-9月内每个月初将上个月应增加的30%和60%降雨量一次性灌溉到相应样地)和中国科学院内蒙古草原生态定位站防雨棚控雨实验平台(包括8个降雨梯度处理：生长季降雨量100mm、150mm、 200mm、300mm、350mm、400mm、450mm、500mm,在生长季前、中、后期分别以30%、50%、20%的比例分配降雨;4个降雨格局处理：生长季降雨量275mm在生长季前、中期分别以1:1、1：2、1：4和1：8的比例分配降雨；以及4个极端降雨格局处理：极端干旱(100mm)和极端降雨(500mm)在生长季前、中期分别以1：1和1：8的比例分配降雨),探讨了生长季不同降雨量和降雨分布格局对内蒙古半干旱草原生态系统土壤含水量、草地生产力、土壤活性氮库以及土壤净氮矿化速率的影响。两个降雨控制实验得到如下结论：(1)降雨量控制实验①土壤含水量随着降雨量的增加而增加。改变降雨量分布处理对土壤含水量没有显著影响。②地上净初级生产力随着降雨量的增加而增加,地下净初级生产力对降雨量的变化响应不明显;改变降雨量分布处理对地上、地下净初级生产力没有显著影响。地上、地下净初级生产力与土壤含水量间具有显著正相关关系。③增加降雨量处理降低了土壤无机氮的浓度,减少降雨量处理虽然显著增加了铵态氮浓度,但同时也显著降低了硝态氮和无机氮库的浓度：改变降雨分布对无机氮浓度没有显著影响。在降雨量变化处理下,土壤铵态氮的浓度与土壤含水量呈显著负相关关系,硝态氮和无机氮库的浓度与土壤含水量呈显著正相关关系。④降雨量增加和改变降雨分布处理对土壤微生物生物量碳没有影响,降雨量减少降低了土壤微生物生物量碳;降雨量增加对土壤微生物生物量氮没有影响,但是降雨量减少降低了土壤微生物生物量氮。改变降雨分布处理增加了土壤微生物生物量氮;增加降雨量和改变降雨分布处理对土壤微生物生物量碳氮比没有影响,但是减少降雨量显著提高了土壤微生物生物量碳氮比,并且随着降雨量的减少而增加。降雨量变化处理下土壤微生物生物量碳与土壤含水量没有显著相关性,土壤微生物生物量氮与土壤含水量呈显著正相关关系,土壤微生物生物量碳氮比与土壤含水量呈显著负相关关系。说明改变降雨量改变了土壤微生物群落的组成和结构。(2)降雨格局控制实验①土壤含水量随着生长季降雨量的增加而增加;降雨格局和极端降雨格局的改变对土壤含水量没有显著影响。②地上净初级生产力随着生长季降雨量的增加而增加,与土壤含水量具有显著的正相关关系。降雨量和降雨格局的变化对地下净初级生产力没有影响。极端降雨处理的地上、地下净初级生产力都显著高于极端干旱处理。降雨格局处理下除了地下净初级生产力与土壤含水量没有显著相关关系外,降雨量和降雨格局的变化处理下,地上、地下净初级生产力与土壤含水量都呈显著正相关关系。③2014年生长季中后期(7-10月)土壤铵态氮的浓度随降雨量的增加而增加,2014年生长季中后期(7-10月)降雨量变化对土壤硝态氮和无机氮库没有显著影响；2015年生长季降雨量变化对土壤无机氮的浓度没有显著影响。降雨格局和极端降雨格局(极端干旱和极端降雨)处理对土壤的无机氮的浓度没有显著影响。降雨量和降雨格局变化下土壤总无机的浓度与土壤含水量都呈显著的正相关关系。④降雨量变化对土壤微生物生物量没有影响,2015年生长季500mm降雨量处理的土壤微生物生物量碳氮比显著低于其他四个处理。降雨格局和极端降雨格局变化对土壤微生物生物量没有影响。降雨量变化处理下土壤微生物生物量碳、氮,降雨格局变化处理下微生物生物量碳和微生物生物量碳氮比与土壤含水量都显著呈正相关关系。⑤降雨量、降雨格局和极端降雨格局(极端干旱和极端降雨)处理对土壤的净氨化速率、净硝化速率和净氮矿化速率都没有影响。降雨量和降雨格局变化处理下净氨化速率、净硝化速率和净氮矿化速率与土壤含水量相关关系不显著。综上,降雨变化背景下草地土壤活性氮库及净氮矿化速率的变化可能是枯落物、植物、土壤环境及其土壤微生物等多因素相互作用的结果。对于生态系统中变化缓慢但将会产生深远影响的过程,在未来降雨变化情况下会发生怎么样的改变还需要长期的实验研究。
[Abstract]:In order to study the effect of rainfall change on the function and process of semi-arid grassland ecosystem in Inner Mongolia, we set up two different artificial control experiments in Xilinhaote, Inner Mongolia. Rainfall control experiment platform of Xiwu Zhumqin Banner in Haot City (treatment includes five rainfall gradients: reducing rainfall by 60% and 30% in growing season, increasing rainfall by 30% and 60% in contrast; and two kinds of treatment of changing rainfall distribution, irrigating 30% and 60% of rainfall which should be increased in last month to corresponding sample plots in June-September of growing season) Rainfall control experiment platform of Inner Mongolia Grassland Ecological Positioning Station, Chinese Academy of Sciences (including 8 rainfall gradient treatments: rainfall in growing season is 100 mm, 150 mm, 200 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, and rainfall is allocated by 30%, 50% and 20% before, in middle and late growing season respectively; Rainfall was allocated at the ratio of 1:1,1:2,1:4 and 1:8 respectively in the pre-season and middle-season, and four extreme rainfall patterns, extreme drought (100mm) and extreme rainfall (500mm), were allocated at the ratio of 1:1 and 1:8 respectively in the pre-season and middle-season of the growing season. The effects of ecosystem soil water content, grassland productivity, soil active nitrogen pool and soil net nitrogen mineralization rate were studied. Two rainfall control experiments were carried out and the results were as follows: (1) Rainfall control experiment (1) Soil water content increased with the increase of rainfall. The change of rainfall distribution had no significant effect on soil water content. The net primary productivity (NPP) increased with the increase of rainfall, but the response of NPP to the change of rainfall was not obvious. The change of rainfall distribution had no significant effect on the above ground NPP. The concentration of inorganic nitrogen in soil was significantly increased, but the concentration of nitrate nitrogen and inorganic nitrogen pool was also significantly decreased by reducing rainfall. The concentration of inorganic nitrogen was not significantly affected by changing rainfall distribution. The concentrations of nitrate and inorganic nitrogen pools were positively correlated with soil water content. The soil microbial biomass C/N ratio was not affected by increasing rainfall and changing rainfall distribution, but the soil microbial biomass C/N ratio was significantly increased by reducing rainfall, and the rainfall increased with decreasing rainfall. There was no significant correlation between soil microbial biomass carbon and soil water content under different rainfall treatments, and there was a significant positive correlation between soil microbial biomass nitrogen and soil water content. (2) Rainfall pattern control experiment: (1) Soil water content increased with the increase of rainfall in growing season; the change of rainfall pattern and extreme rainfall pattern had no significant effect on soil water content. The net primary productivity (NPP) under extreme rainfall treatment was significantly higher than that under extreme drought treatment. There was no significant correlation between NPP and soil water content under rainfall pattern treatment except that there was no significant correlation between NPP and soil water content. (3) The concentration of soil ammonium nitrogen increased with the increase of rainfall in the middle and late growing season of 2014 (July-October), and the change of rainfall in the middle and late growing season of 2014 (July-October) had no significant effect on soil nitrate nitrogen and inorganic nitrogen pool; Rainfall pattern and extreme rainfall pattern (extreme drought and extreme rainfall) had no significant effect on soil inorganic nitrogen concentration. There was a significant positive correlation between soil total inorganic concentration and soil water content under rainfall and rainfall pattern changes. The C/N ratio of soil microbial biomass under 500 mm rainfall treatment in the growing season of 2015 was significantly lower than that under the other four treatments. _Rainfall, rainfall pattern and extreme rainfall pattern (extreme drought and extreme rainfall) had no effect on soil net ammonification rate, nitrification rate and net nitrogen mineralization rate. In summary, the changes of soil active nitrogen pool and net nitrogen mineralization rate under the background of rainfall change may be the result of interaction of litter, plant, soil environment and soil microorganisms. The processes that will have a far-reaching impact, and what changes will happen in future rainfall changes, will require long-term experimental studies.
【学位授予单位】：山西农业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S812

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