冻融作用对不同水分条件湿地土壤矿化过程的影响

发布时间：2018-04-15 17:52

本文选题：冻融作用 + meta分析　；参考：《中国科学院大学(中国科学院东北地理与农业生态研究所)》2017年硕士论文

【摘要】：全球气候变化可能导致地表雪被厚度变化,未来北半球中高纬度和海拔地区的冻融现象可能会越来越频繁的发生。冻融过程可以在很大程度上改变土壤碳氮循环过程。这里,我们收集了 46篇原始文献,评估了冻融作用影响下跟碳、氮循环相关的18个变量的效应比,通过随机效应模型检验冻融作用下不同土壤来源、影响阶段(包括初始影响和长期影响)、实验方法以及土壤层碳氮参数的效应比变化。土壤来源包括森林、灌丛、草地、农田、苔原和湿地。并且通过meta回归分析效应比与冻结温度、土壤pH、土壤碳氮比以及其他环境因子之间的关系。结果表明:冻融过程导致微生物氮和微生物碳氮比分别下降了 12.2%和8.5%,土壤可溶性有机碳(DOC)和可溶性有机氮(DON)分别上升了 27.5%和37.3%。冻融作用使NH4+、NO3-和可溶性无机氮(DIN)浓度上升了 84.1%、29.6%和35.4%。N2O排放量在冻融促进下上升了 95.0%。实验室模拟和野外观测结果在氮矿化速率、硝化速率和呼吸速率指标上存在矛盾。冻融作用对细根周转具有促进作用,但是对长期的地上生物量并没有显著影响。水分条件是湿地生态系统重要的生态属性。春季冻融期湿地土壤的水分条件常因冰雪融化而具有明显的时间波动。并且湿地的负地形特点常常使同一区域湿地土壤的水分条件具有显著的空间差异性。本文通过实验室冻融模拟土柱实验探讨了不同冻融频次下,湿地土壤在不同空间和时间水分条件下矿化过程的变化和响应。冻融作用可以破坏土壤大粒级团聚体(2 mm),使50%持水量和100%持水量容重降低,并增加这两种水分条件土壤的溶解氧浓度和氧化还原电位值,但是对10 cm上覆水的影响较小,10 cm上覆水的湿地土壤由于上覆水的缓冲和压实作用,导致土壤容重增大和2 mm水稳性大团聚体随时间增多。冻融作用能够增加不同水分条件土壤DOC含量、NH4+含量,减少土壤中DON含量,对土壤NO3-含量的影响与水分条件有关,冻融作用使50%持水量和100%持水量湿地土壤的NO3-含量增加,使10 cm上覆水湿地土壤NO3-含量减少。冻融作用显著增加各水分条件湿地土壤渗滤液中DOC含量、DON含量和NH4+含量,增加50%持水量湿地土壤渗滤液中NO3-含量,减少100%持水量和10 cm上覆水的湿地土壤渗滤液中NO3含量。冻融作用抑制了 50%持水量湿地土壤CH4的排放速率,促进了 100%持水量和10 cm上覆水的湿地土壤CH4排放速率。冻融作用抑制各水分条件土壤CO2的排放速率。冻融作用促进50%持水量和100%持水量湿地土壤N20的排放速率,抑制了 10 cm上覆水湿地土壤N2O排放速率。冻融作用促进了各水分条件湿地土壤在融化过程中的呼吸速率、反硝化速率。显著增加50%和100%持水量的湿地土壤融化过程中总硝化速率,10 cm上覆水湿地土壤总硝化速率增加较小。无论土壤由干变湿还是由湿变干,冻融作用都显著降低土壤中DOC和DON含量。冻融作用显著降低湿地土壤由干变湿过程中NH4+和NO3-含量,显著增加湿地土壤由湿变干过程中NH4+和NO3含量。冻融作用显著降低湿地由干变湿过程中渗滤液中DOC含量和NH4+含量,增加湿地土壤由湿变干过程中渗滤液中DOC含量和NH;含量。冻融作用增加湿地土壤由干变湿过程中渗滤液中NO3含量,显著减少湿地土壤由湿变干过程中渗滤液中NO3含量。无论由干变湿还是由湿变干,冻融作用都显著减少湿地渗滤液中DON含量,并对CH4和N2O排放起到显著促进作用,相反对C02排放起到显著抑制作用。本论文的meta分析结果可以帮助更好的理解不同环境下土壤碳氮循环对冻融过程的响应。另外基本阐述了冻融作用对湿地土壤在不同典型水分条件下矿化过程及结果的影响及差异。简要描述了土壤干湿变化与冻融作用叠加影响下土壤矿化过程结果的差异。有助于理解水分条件这一湿地土壤关键环境因子在冻融过程影响中的作用。
[Abstract]:Global climate change may lead to surface snow thickness changes, future high latitude and altitude in the northern hemisphere the freeze-thaw phenomenon may be more frequent. The freeze-thaw process can change soil carbon and nitrogen cycling in great extent. Here, we collected 46 articles of the original literature, evaluated the influence of freezing and thawing with carbon, nitrogen cycle effect of 18 variables related to the ratio of the random effect model test of freezing and thawing under different soil sources influence stage (including initial and long term influence), experimental methods and soil layer parameters the effect of carbon and nitrogen ratio changes. Soil sources including forest, shrub, grassland and farmland. The tundra and wetlands. And through meta regression analysis and effect than the freezing temperature, soil pH, the relationship between soil carbon and nitrogen ratio and other environmental factors. The results show that the freezing and thawing process lead to microbial nitrogen and microbial carbon and nitrogen. Don't drop by 12.2% and 8.5%, soil soluble organic carbon (DOC) and dissolved organic nitrogen (DON) were increased to NH4+ 27.5% and 37.3%. freezing and thawing, NO3- and dissolved inorganic nitrogen (DIN) concentration increased by 84.1%, 29.6% and 35.4%.N2O emissions increased by 95. In the simulation laboratory and field observations of nitrogen mineralization rate results in the freeze-thaw promoting, contradiction between nitrification rate and respiration rate index. The freeze-thaw action has a promoting effect on fine root turnover, but had no significant effect on long-term aboveground biomass. The water condition is the important attribute of ecological wetland ecosystem. The spring freeze thawing period of wetland soil moisture conditions because of the melting of ice and snow but with time fluctuation obviously. Negative terrain features and wetland water conditions often make the same area of the wetland soil had significant spatial variability. Through laboratory soil column simulation experiment of freezing and thawing Effects of different freeze-thaw frequency, wetland soil moisture conditions in different space and time change and response. The mineralization process of freezing and thawing can destroy soil aggregates (2 mm), the 50% water holding capacity and water holding capacity of 100% bulk density reduced, and increase the concentration of dissolved oxygen and oxidation of these two kinds of soil moisture conditions the soil oxidation-reduction potential value, but the impact on the 10 cm of the overlying water is small, 10 cm on wetland soil overlying water due to overlying water and buffer compaction, resulting in an increase in soil bulk density and 2 mm water stable aggregates increases with time. Freezing and thawing can increase with the DOC content, the soil moisture conditions the content of NH4+, reduce the content of DON in soil, effects on soil NO3- content and moisture conditions, freezing and thawing NO3- content to 50% moisture and 100% of water holding capacity of wetland soil increased to 10 cm in overlying water wetland soil NO3- content decreased. Freezing and thawing significantly The increasing water conditions of wetland soil infiltration DOC content in filtrate, DON content and NH4+ content, increase the water holding capacity of 50% wetland soil infiltration NO3- content in filtrate, wetland soil decreased 100% capacity and 10 cm of overlying water permeability and NO3 content in the filtrate. The freeze-thaw inhibited the 50% water holding capacity of wetland soil CH4 emissions rate, promote wetland soil CH4 emission rate of 100% capacity and 10 cm of overlying water. The suppression of freezing and thawing soil CO2 emission rate. The freeze-thaw action to promote the 50% capacity and 100% to N20 soil water wetland emission rate, inhibited 10 cm of overlying water wetland soil N2O emission rate. Freezing and thawing promoted respiration rate during the water conditions of wetland soil, soil nitrification denitrification rate. The total melting process of wetland was significantly increased by 50% and 100% in the water holding rate, 10 cm gross nitrification rate increased with water in wetland soil Add small. Whether soil from dry to wet or wet dry, freezing and thawing were significantly decreased DOC and DON content in soil. The freeze-thaw effect was significantly reduced by dry wetland soil NH4+ and NO3- content in wet process, significant increase in wetland soil from wet to dry NH4+ and NO3 content in the process of freeze-thaw. With the DOC content decreased significantly and the content of NH4+ in leachate infiltration wetland from dry to wet process, the content of DOC and NH in leachate infiltration wetland soil increased by wet dry process; content. NO3 content in leachate infiltration of freezing and thawing of wetland soil increased from dry to wet process, significantly reduce the content of NO3 in leachate infiltration wetland the soil from wet to dry in the process. No matter from dry to wet or wet dry, freezing and thawing are significantly reduced the content of DON in leachate infiltration wetland, and to promote effect on CH4 and N2O emissions, contrary to the C02 emissions play a significant inhibitory effect. The meta analysis. The fruit can help better understanding of soil carbon and nitrogen cycle in different environments in response to freezing and thawing process. Also basically illustrates the influence of freezing thawing on the mineralization process and results of wetland soil under different moisture conditions and differences. A brief description of the differences in soil moisture change and freezing thawing process of the soil mineralization superimposed under the influence contribute to the understanding of water conditions. The wetland soil key environment factors in the freezing and thawing process is studied.

【学位授予单位】：中国科学院大学(中国科学院东北地理与农业生态研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S153

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