【作者】 王凯；

【导师】 王子龙；

【作者基本信息】 东北农业大学 ， 农业水土工程， 2023， 硕士

【摘要】 全球气候变暖问题日益严重,气候变化所引起积雪格局的变化深刻影响了土壤物理结构和生化过程,黑土是我国宝贵的土壤资源。我国的黑土资源多数集中在季节性冻土区。这些地区全年一半的时间都被雪覆盖。积雪的变化致使这些地区的黑土侵蚀流失现象加剧、土壤养分供给失衡,对黑土区粮食食品安全产生威胁。在此背景下,模拟积雪变化,探究未来气候变暖条件下土壤养分循环过程对于寒区农业水土资源高效利用及黑土生境保护模式构建具有重要实践意义。以往研究主要集中在冬季早期或深冬期对土壤水土环境以及有效养分与酶活性的动态变化特征的研究。而忽视了积雪变化情况下整个冬季土壤有效养分的变化特征以及其与酶活性间的响应关系,积雪变化对土壤结构的改变以及化学性质的影响是一个漫长的过程,所以短期内的研究很难揭示积雪变化影响土壤物质循环的机理,土壤酶作为土壤中最为活跃的组分之一,是土壤中极为重要的催化剂,因此探究积雪变化下土壤酶活性的影响因素以及其与土壤养分之间的响应关系具有重要意义。本研究为了进一步探索黑土有效养分和酶活性对积雪变化的季节性响应,采用人工增雪、减雪以及除雪的方法,设置了四个处理组,分别为增雪处理组(SA)、减雪处理组(SL)、除雪处理组(SR)以及正常积雪对照组(C)。通过分析土壤环境因子、有效碳氮、土壤酶活性的动态变化特征,探究积雪变化条件下土壤有效碳氮与酶活性两者间的潜在互馈机制。主要研究结论如下:(1)季节性冻土区积雪变化影响着土壤水土变化过程。本研究结果表明,表层土壤湿度对积雪量的响应较不明显,但对于30-100cm土层深度的土壤来说,积雪量的变化对其土壤湿度的影响较大,加雪处理显著增加了土壤温度,减雪处理以及除雪处理则与之相反,土壤温度关系到土壤中的水分迁移,土壤温度的变化势必会影响到土壤的冻融循环过程。结果显示,积雪量的减小增加了土壤在冻融时期的冻融循环次数,而频繁的冻融循环过程会导致基质势降低,在势能差的驱使下,土壤液态含水率及盐分会从高势能区向低势能区迁移聚集,导致土壤p H以及质量含水量下降。(2)季节性冻土区积雪变化影响着土壤碳素动态变化过程。本研究结果表明,不同处理下土壤TOC、DOC及MBC呈现出了不同的变化趋势,其中,TOC以及DOC呈现出先增大再减少后增大的趋势,MBC呈现出先减少后增加再减少的趋势。进入早雪期后,积雪量的减少显著增加了土壤碳素含量。在融雪期,土壤DOC以及MBC含量随积雪量的减小而增加,而土壤TOC含量则随积雪量的减小而减小。在作物生长早期,减雪处理以及除雪处理明显降低了土壤DOC含量,但却显著增加TOC以及MBC含量,加雪处理与之相反。积雪深度的增加增强了土壤有效碳素与土壤温度之间的响应关系,减弱了土壤有效碳素与土壤湿度、冻融循环次数之间的响应关系(3)季节性冻土区积雪变化影响着土壤氮素动态变化过程。本研究结果表明,不同处理下土壤无机氮、DON及MBN呈现出了不同的变化趋势,其中,DON以及MBN呈现出先增加再减少的趋势,土壤无机氮呈现出先减少再增加的趋势。进入早雪期后,积雪量的减少显著增加了土壤无机氮含量,但土壤DON以及MBN含量却随着积雪量的减少而逐渐增加。在深雪期以及融雪期,积雪深度的减少显著增加了DON以及MBN含量,显著降低了土壤无机氮含量;在作物生长早期,积雪深度的较少显著增加了土壤无机氮以及MBN含量,显著降低了DON含量,加雪处理与其相反。积雪深度的增加增强了土壤有效氮素与土壤质量含水率之间的响应关系,减弱了土壤氮素与土壤冻融循环次数之间的响应关系。(4)季节性冻土区积雪变化影响着土壤酶活性动态变化过程。本研究结果表明,不同处理下土壤脲酶活性以及蔗糖酶活性呈现出了不同的变化趋势,其中,脲酶活性呈现出先增加后减少再增加的趋势,蔗糖酶活性呈现出先减少后增加又减少再增加的趋势。积雪量的减少显著降低了冬季的土壤酶活性,土壤酶在土壤中是较为活跃的组分,土壤水热状态的微小改变可能都会影响土壤酶活性的来源。积雪深度的增加增强了土壤酶活性与土壤pH之间的响应关系,减弱了土壤酶活性与土壤温度之间的响应关系。(5)季节性冻土区土壤酶活性的控制因素及其与有效碳氮的互馈关系。基于试验过程中收集的土壤环境因子、有效碳氮以及酶活性的数据,首先,利用Person相关性分析探究了土壤酶活性、有效碳氮与环境因子的相关性差异。本研究结果表明,土壤酶活性及MBN与环境因子的相关关系具有一致性,而土壤有效碳氮与环境因子的相关关系则与其具有明显差异,这也在一定程度上解释了土壤酶活性及土壤有效碳氮的动态变化过程存在差异的原因。其次,本研究通过因子分析发现,土壤可溶性有机碳氮是控制两种土壤酶活性的主要因子。最后,通过建立土壤环境因子、酶活性及有效碳氮的结构方程发现,土壤酶活性与土壤有效碳素之间存在明显的互馈关系,而与有效氮素则无显著的闭环过程。综上所述,本研究通过长期野外试验证明了未来积雪变化将导致土壤有效碳氮的动态变化特征发生转变,揭示了土壤酶活性与有效碳氮之间的潜在关系。研究结果对气候变暖背景下我国东北黑土区的图样养分与酶活性之间关系的进一步研究在提供了一定理论基础。更多还原

【Abstract】 Global warming events are intensifying.The change of snow cover pattern caused by climate change has profoundly affected soil physical structure and biochemical process.Black soil is a precious soil resource in our country.Our country’s black soil resources mostly concentrated in seasonal frozen soil area.These areas are covered in snow for half the year.The change of snow cover leads to the aggravation of erosion and loss of black soil and the imbalance of soil nutrient supply in these areas,which poses a threat to the food safety in the black soil area.In this context,simulating snow cover change and exploring the soil nutrient cycling process under future climate warming are of great practical significance for the efficient utilization of agricultural water and soil resources and the construction of black soil habitat protection model in cold regions.Previous studies mainly focused on the dynamic change characteristics of soil and water environment,available nutrients and enzyme activities in early or late winter.However,the change characteristics of soil available nutrients and their response to enzyme activities in the whole winter under the condition of snow cover change are ignored.The influence of snow cover change on soil structure change and chemical properties is a long process,so it is difficult to reveal the mechanism of snow cover change affecting soil material cycling in a short period of time.Soil enzyme is one of the most active components in soil.Is an extremely important catalyst in soil,so it is of great significance to explore the influencing factors of soil enzyme activity under the change of snow cover and its response relationship with soil nutrients.In order to further explore the seasonal response of available nutrients and enzyme activities of black soil to snow cover changes,four treatment groups were set up,namely,snow increase group(SA),snow reduction group(SL),snow removal group(SR)and normal snow cover control group(C),using artificial snow increase,snow reduction and snow removal methods.By analyzing the dynamic change characteristics of soil environmental factors,available carbon and nitrogen,and soil enzyme activity,the potential mutual feeding mechanism between soil available carbon and nitrogen and soil enzyme activity under the condition of snow cover change was explored.The main research conclusions are as follows:(1)The change of snow cover in seasonal frozen soil affected the process of soil and water change.The results of this study showed that the response of surface soil moisture to snow cover was not obvious,but for the soil depth of 30-100 cm,the change of snow cover had a greater impact on soil moisture.Snow treatment significantly increased soil temperature,while snow reduction treatment and snow removal treatment were on the contrary.Soil temperature was related to the migration of water in soil.The change of soil temperature will certainly affect the freeze-thaw cycle of soil.The results showed that the decrease of snow cover increased the number of freeze-thaw cycles of soil during freeze-thaw period,and frequent freeze-thaw cycles would lead to the decrease of matrix potential.Driven by potential energy difference,soil liquid water content and salt would migrate and accumulate from high potential energy zone to low potential energy zone,resulting in the decrease of soil pH and mass water content.(2)The change of snow cover in seasonal frozen soil affected the dynamic change of soil carbon.The results of this study showed that TOC,DOC and MBC showed different trends under different treatments,among which TOC and DOC showed a trend of first increasing,then decreasing and then increasing,and MBC showed a trend of first decreasing,then increasing and then decreasing.After the early snowfall,the decrease of snow cover significantly increased soil carbon content.During the snowmelt period,soil DOC and MBC contents increased with the decrease of snow cover,while TOC contents decreased with the decrease of snow cover.In the early stage of crop growth,snow reduction and snow removal significantly reduced soil DOC content,but significantly increased TOC and MBC content,while snow treatment was on the contrary.The increasing of snow cover depth enhanced the response relationship between soil available carbon and soil temperature,but weakened the response relationship between soil available carbon and soil moisture and the number of freeze-thaw cycles(3)The change of snow cover in seasonal frozen soil affected the dynamic change of soil nitrogen.The results of this study showed that soil inorganic nitrogen,DON and MBN showed different trends under different treatments,among which,DON and MBN showed a trend of first increasing and then decreasing,while soil inorganic nitrogen showed a trend of first decreasing and increasing.After the early snowfall,the decrease of snow cover significantly increased the soil inorganic nitrogen content,but the soil DON and MBN contents gradually increased with the decrease of snow cover.The decrease of snow depth significantly increased the content of DON and MBN,and significantly decreased the content of soil inorganic nitrogen during the deep snow period and the melting snow period.In the early stage of crop growth,less snow depth significantly increased soil inorganic nitrogen and MBN content,and significantly decreased DON content,while snow treatment was on the contrary.The increase of snow depth enhanced the response relationship between soil available nitrogen and soil mass water content,but weakened the response relationship between soil nitrogen and the number of freeze-thaw cycles.(4)The change of snow cover in seasonal frozen soil affected the dynamic change process of soil enzyme activity.The results of this study showed that soil urease activity and sucrase activity showed different trends under different treatments,among which,urease activity showed a trend of first increasing,then decreasing and then increasing,and sucrase activity showed a trend of first decreasing and then increasing and then decreasing and then increasing.The decrease of snow cover significantly reduced soil enzyme activity in winter.Soil enzyme is a relatively active component in soil,and small changes in soil hydrothermal state may affect the source of soil enzyme activity.The increase of snow cover depth enhanced the response relationship between soil enzyme activity and soil pH,but weakened the response relationship between soil enzyme activity and soil temperature.(5)The controlling factors of soil enzyme activity in seasonal frozen soil and its relationship with available carbon and nitrogen feed-back.Based on the data of soil environmental factors,available carbon and nitrogen and enzyme activities collected during the experiment,Person correlation analysis was used to explore the correlation differences between soil enzyme activities,available carbon and nitrogen and environmental factors.The results of this study showed that the correlation between soil enzyme activity and MBN and environmental factors was consistent,while the correlation between soil available carbon and nitrogen and environmental factors was significantly different,which also explained the reason for the difference in the dynamic change process of soil enzyme activity and soil available carbon and nitrogen to some extent.Secondly,through factor analysis,this study found that soil soluble organic carbon and nitrogen were the main factors controlling the activities of the two soil enzymes.Finally,through the structural equation of soil environmental factors,enzyme activity and available carbon and nitrogen,it was found that there was an obvious mutual feeding relationship between soil enzyme activity and available carbon,but no significant closed-loop process between soil enzyme activity and available nitrogen.In summary,this study proved that future snow cover changes will lead to changes in the dynamic change characteristics of soil available carbon and nitrogen,and revealed the potential relationship between soil enzyme activities and available carbon and nitrogen.The results provide a theoretical basis for further research on the relationship between nutrient patterns and enzyme activities in northeast black soil under the background of climate warming.更多还原