【作者】 王莹；

【导师】 陶晓；

【作者基本信息】 安徽农业大学 ， 风景园林学， 2023， 硕士

【摘要】 土壤氮素矿化调控土壤氮素有效性,影响植物根系对氮素的吸收利用,其周转效率是限制植物营养吸收和陆地生产力提升的关键因素。长期氮沉降可以改变土壤养分状况及微生物群落结构,影响土壤氮素矿化。目前,我国城市化进程正处于加速发展阶段,对城市区域内外的森林生态系统结构和功能产生直接和间接影响,并导致诸多生态环境要素在城-乡间呈现明显变化。因此,氮沉降对城-乡森林土壤氮素矿化的影响可能不同。本研究通过对安徽城郊森林和乡村森林样地进行模拟氮沉降下(0,50和100 kg N·ha^-1·yr^-1)土壤氮素原位矿化实验,研究氮沉降对城郊和乡村森林土壤氮素矿化的季节和年际变化,分析氮沉降下土壤氮素矿化在不同季节、年际、土层、处理和区位的差异,以期为氮沉降下城-乡森林氮素循环过程提供科学依据。主要结论如下:（1）从季节动态来看,氮沉降下城郊和乡村森林土壤无机氮库（铵态氮、硝态氮和无机氮）总体上表现为生长季末期高,生长季后期低,且乡村森林季节动态变化波动较大。氮沉降下城郊森林土壤净氮矿化速率（净氨化、硝化和矿化速率）季节动态主要表现为“双峰曲线”,而乡村森林表现为“单峰曲线”。（2）从年际动态来看,模拟氮沉降第一年,氮沉降对城郊森林土壤硝态氮、无机氮和净氮矿化速率呈抑制作用;对乡村森林土壤无机氮库含量和净氮矿化速率主要为促进作用。模拟氮沉降第五年,氮沉降促进城郊森林土壤无机氮库及净氮矿化速率;氮沉降促进乡村森林土壤无机氮库含量,抑制土壤净氮矿化速率。（3）在垂直分布上,氮沉降下城郊和乡村森林土壤0-10 cm土层土壤无机氮库含量均大于10-30 cm土层;城郊森林0-10 cm土层土壤净氮矿化速率大于10-30 cm土层,乡村森林0-10 cm与10-30 cm土层土壤净氮矿化速率相近。（4）各氮沉降处理均能有效改善城-乡森林土壤氮有效性。综合分析,城-乡森林氮沉降量为50 kg N·ha^-1·yr^-1促进土壤氮矿化作用,土壤氮有效性达到最佳,从而为植被提供较充足的可被直接吸收利用的氮素,进而利于打造优美、稳定、可持续的城-乡园林绿化空间。综上所述,氮沉降对城-乡森林土壤氮素矿化的影响有所差异。本研究为完善森林生态系统氮循环理论提供科学依据,并为区域城市化进程绿化空间土壤改良提供技术支撑。更多还原

【Abstract】 Soil nitrogen mineralization regulates soil nitrogen availability and affects the absorption and utilization of nitrogen by plant roots.Its turnover efficiency is a key factor limiting plant nutrient uptake and land productivity improvement.Long-term nitrogen deposition can change soil nutrient status and microbial community structure,and affect soil nitrogen mineralization.At present,China’s urbanization process is in a stage of accelerated development,which has direct and indirect impacts on the structure and function of forest ecosystems around urban areas,and leads to significant changes in many ecological environment factors.Therefore,the effects of nitrogen deposition on nitrogen mineralization in urban-rural forest soils may be different.In order to provide a scientific basis for the nitrogen cycle process of urban-rural forest under nitrogen deposition,in this study,the in-situ mineralization experiments of soil nitrogen under simulated nitrogen deposition(0,50and 100 kg N·ha^-1·yr^-1)were carried out in suburban and rural forest plots in Anhui Province.The seasonal and interannual changes of soil nitrogen mineralization in suburban and rural forests were studied,and the differences of soil nitrogen mineralization under nitrogen deposition in different seasons,years,soil layers,treatments and locations were analyzed.The main conclusions are as follows:（1）From the perspective of seasonal dynamics,the soil inorganic nitrogen pools（ammonium nitrogen,nitrate nitrogen and inorganic nitrogen）in suburban and rural forests under nitrogen deposition were generally high at the end of the growing season and low at the end of the growing season,and the seasonal dynamic changes of rural forests fluctuated greatly.The seasonal dynamics of soil net nitrogen mineralization rate（net ammonification,nitrification and mineralization rate）in suburban forests under nitrogen deposition mainly showed a“bimodal curve”,while that in rural forests showed a“unimodal curve”.（2）From the perspective of interannual dynamics,in the first year of simulated nitrogen deposition,nitrogen deposition inhibited the mineralization rate of nitrate nitrogen,inorganic nitrogen and net nitrogen in suburban forest soil.It mainly promoted the content of inorganic nitrogen pool and net nitrogen mineralization rate in rural forest soil.In the fifth year of simulated nitrogen deposition,nitrogen deposition promoted the inorganic nitrogen pool and net nitrogen mineralization rate of suburban forest soil.Nitrogen deposition promoted the content of inorganic nitrogen pool in rural forest soil and inhibited the net nitrogen mineralization rate of soil.（3）In the vertical distribution,the content of soil inorganic nitrogen pool in 0-10 cm soil layer of suburban and rural forest soil under nitrogen deposition was higher than that in 10-30 cm soil layer.The net nitrogen mineralization rate of 0-10 cm soil layer in suburban forest was higher than that of 10-30 cm soil layer,and the net nitrogen mineralization rate of 0-10cm and 10-30 cm soil layer in rural forest were similar.（4）All nitrogen deposition treatments can effectively improve the nitrogen availability of urban-rural forest soil.Comprehensive analysis showed that the nitrogen deposition of urban-rural forest was 50 kg N·ha^-1·yr^-1 to promote soil nitrogen mineralization,and the soil nitrogen availability was the best,thus providing sufficient nitrogen for vegetation to be directly absorbed and utilized,which was conducive to creating beautiful,stable and sustainable urban-rural landscaping space.In summary,the effects of nitrogen deposition on nitrogen mineralization in urban-rural forest soils are different.This study provides a scientific basis for improving the theory of nitrogen cycle in forest ecosystems,and provides technical support for soil improvement in green space during regional urbanization.更多还原