亚热带典型植被类型土壤水变化规律及影响机制研究

发布时间：2018-07-28 17:11

【摘要】：土壤水是植物生长和生存的重要物质基础,开展森林土壤水研究对于水土保持、生态保护、林业管理具有重要意义。森林植被类型差异导致了土壤容重、土壤有机碳总量、水稳性团聚体、土壤水饱和传导率等土壤性状的差异,并成为影响森林土壤水分特性变化的重要因素。本研究以浙江凤阳山国家级自然保护区内的常绿阔叶林、针阔混交林、竹林以及茶园为研究对象,通过野外调查、模拟实验、定点观测、室内分析等手段,研究了树木根系穿孔、土壤特征因子及剖面构造等对土壤水分传输和优先流特性的影响。在研究过程中,为表征土壤含水率变化特性及树木根系对优先流的影响,定义了“土壤含水率变化时间指数”、“土壤含水率变化幅度指数”、“细根根系渗透比”、“根系相对渗透面积”及“根系渗透影响指数”5个参数。研究结果如下:(1)植被类型对土壤性状及细根生物量影响显著。随土壤深度增加,4种植被类型土壤容重呈上升趋势,土壤总有机碳呈减少趋势。常绿阔叶林和针阔混交林中,土壤毛管孔隙度随土壤深度增加而减少,竹林和茶园中土壤毛管孔隙度变化不显著。土壤非毛管孔隙度在常绿阔叶林先下降后上升,在针阔混交林和竹林呈现上升趋势,在茶园中则呈下降趋势;常绿阔叶林、针阔混交林和竹林的土壤细根生物量呈现下降趋势,在茶园中先下降后上升。土壤大型团聚体含量在常绿阔叶林先增加后减少,在针阔混交林中先减少后增加,在竹林和茶园无显著差异。土壤中型团聚体含量在常绿阔叶林和竹林先减少后增加,在针阔混交林和茶园则先增加后减少。土壤小型水稳性团聚体含量在常绿阔叶林和茶园先下降后上升,在针阔混交林逐渐上升,而在竹林基本保持不变。水稳性团聚体组成结构的主要影响因素为土壤总有机碳、非毛管孔隙度,以及细根生物量。随土层深度的增加,土壤饱和导水率在常绿阔叶林呈上升趋势,在针阔混交林和竹林差异不显著,而在茶园先下降后上升;在土壤饱和导水率的各潜在影响因子中,非毛管孔隙度、土壤大型水稳性团聚体、中型水稳性团聚体对土壤饱和导水率的影响较大,其影响程度所占的比重分别为51.2%、17%、10.6%。(2)常绿阔叶林中,0-10cm及10-20cm土壤层土壤含水率接近,但低于20-30cm土层;针阔混交林与竹林中,各土壤层土壤含水率接近;茶园土壤层含水率与常绿阔叶林类似,但茶园不同土壤层含水率差异显著;2014年、2015年、2016年,4种植被类型各土壤层含水率最大值多出现于5-8月的春夏季节,而各土壤层含水率最小值则多出现于11月到次年1月的冬季。降雨对土壤含水率变化具有主导作用,降雨时间是影响“土壤含水率变化时间指数”最重要的正效应因素,“土壤含水率变化时间指数”与降雨时间之间的通径系数为0.699;总降雨量是影响“土壤含水率变化幅度指数”最重要的负效应因素,“土壤含水率变化幅度指数”与总降雨量之间的通径系数为0.549,此外,上述指数随着土壤温度升高都有增加的趋势。(3)随着降雨强度的增加,经由剖面产生的优先流量、经由枯根产生的优先流量,以及经由1mm与2mm根径细根产生的优先流量逐渐增加,并且增加的幅度随之增加。在同一降雨强度条件下,各土壤层之间经由剖面产生的优先流量、经由枯根产生的优先流量,以及经由1mm与2mm根径细根产生的优先流量均有较大差异,特别是在降雨强度为240mm h~(-1)时,10cm土壤层经由剖面产生的优先流量、经由枯根产生的优先流量,以及经由1mm与2mm根径细根产生的优先流量明显大于20cm与30cm。同一降雨强度条件下,10cm土壤层与30cm土壤层相比,经由剖面产生的优先流量与经由枯根产生的优先流量分别相差可达10倍,经由1mm与2mm根径细根产生的优先流量分别相差达70倍与20倍。“细根根系渗透比”受降雨强度及土壤深度影响规律各不相同。降雨强度为150 mm h~(-1),200 mm h~(-1)以及240 mm h~(-1)条件下,10 cm土壤层的枯根、1mm细根及2mm细根根系渗透比存在显著差异,20cm及30 cm土壤层,不同类型的细根根系渗透比差异不显著;在降雨强度分别为100 mm h~(-1),150 mm h~(-1),200 mm h~(-1)以及240 mm h~(-1)条件下,各根系相对渗透面积的差异主要体现在10 cm土壤层,在其余土壤层,根系相对渗透面积的差异并不显著;在降雨强度分别为150 mm h~(-1),200 mm h~(-1),240 mm h~(-1)条件下,不同类型细根根系渗透影响指数差异也表现在10 cm土壤层。对“根系渗透比”以及“根系渗透影响指数“进行了结构平衡方程模型分析后发现,全部因子可以解释73.2%“根系渗透影响指数”,其中降雨强度及“根系渗透比”对于“根系渗透影响指数”有显著的直接正效应。(4)在人工模拟降雨与自然降雨条件下,发现“土壤优先流产生过程中,流量逐渐减少甚至停止现象”的现象,本研究将其定义为“土壤栓塞”,简称“土栓”,该现象的消除称之为“土壤栓塞消除”,简称“土栓消除”。自然降雨条件下,随着时间的延伸,经由细根产生的土壤优先流总量呈现逐渐减少的趋势;产生优先流的细根数量总体上呈现阶梯下降的趋势;尽管产生优先流的细根数量总体上在减少,但就每次观测而言,会产生“部分原先产生优先流的细根不再产生优先流,原先并未观测到优先流产生的细根出现优先流”的情况。在人工模拟降雨条件下,经由土壤剖面、枯根、1mm与2mm细根所产生优先流过程中,均有不同程度的“土壤栓塞”以及“土壤栓塞消除”发生。“土壤栓塞”多出现于较大的降雨强度条件下,而且,在较大降雨强度条件下更容易产生“土壤栓塞消除”。
[Abstract]:Soil water is an important material basis for plant growth and survival. The study of forest soil water is of great significance to soil and water conservation, ecological protection and forestry management. The difference of forest vegetation types leads to the difference of soil bulk density, soil organic carbon amount, water stable aggregate, soil water saturation conductivity and so on. This study took the evergreen broad-leaved forest in Zhejiang Fengyang Mountain National Nature Reserve, the mixed forest of needle and broad-leaved forest, bamboo forest and tea garden as the research object. Through field investigation, simulation experiment, fixed observation, indoor analysis and so on, the paper studied the root perforation, soil characteristic factor and section structure of the tree. In the course of the study, in order to characterize the change characteristics of soil moisture content and the effect of tree root on the priority flow, the "time index of soil moisture content change", "soil water content change amplitude index", "root penetration ratio of fine root", "relative osmosis area of root system" and "root" were defined. The results are as follows: (1) the vegetation types have significant influence on soil properties and fine root biomass. With the increase of soil depth, the soil bulk density of 4 types of soil is on the rise, and the total organic carbon in soil decreases. The soil capillary porosity increases with the soil depth in the evergreen broad-leaved forest and the coniferous and broad-leaved mixed forest. The porosity of soil capillary in the bamboo forest and the tea garden was not significant. The soil non capillary porosity increased after the evergreen broad-leaved Lin Xian descended, and increased in the coniferous and broad-leaved mixed forest and bamboo forest, and decreased in the tea garden; the evergreen broad-leaved forest, the mixed forest and bamboo forest of the broad-leaved forest and the bamboo forest showed a declining trend in the tea garden. The content of large soil aggregate in the evergreen broad-leaved forest decreased first and then decreased in the coniferous broad-leaved forest. There was no significant difference between the bamboo forest and the tea garden. The soil medium aggregate content increased first in the evergreen broad-leaved forest and bamboo forest, and then increased in the coniferous broad-leaved forest and the tea garden. The soil small water stability was reduced. The aggregate content increased first in evergreen broad-leaved forest and tea garden, and increased gradually in the coniferous and broad-leaved mixed forest, but remained unchanged in the bamboo forest. The main influencing factors of the composition structure of water stable aggregates were soil total organic carbon, non capillary porosity, and fine root biomass. With the increase of soil depth, the soil saturated water conductivity was evergreen broad-leaved. There is an upward trend in the forest and bamboo forest, but in the tea garden, the difference is not significant, but in the tea garden, the soil saturated water stability aggregate and the medium water stable aggregate have great influence on the soil saturated water conductivity, and the proportion of the influence degree is 5, respectively. In 1.2%, 17%, 10.6%. (2) evergreen broad-leaved forests, soil moisture content in soil layer 0-10cm and 10-20cm is close, but lower than that in 20-30cm soil layer; the soil water content of soil layer is close to that of the mixed forest and bamboo forest. The water content of the soil layer in the tea garden is similar to that of the evergreen broad-leaved forest, but the water content of different soil layers in the tea garden is significant. In 2014, 2015, 2016, 4 plants were planted. The maximum water content of each soil layer appeared in the spring and summer season of 5-8 months, while the minimum water content of each soil layer appeared in the winter from November to January of the following year. The rainfall has a leading role in the change of soil moisture content, and the rainfall time is the most important positive effect factor affecting the time index of soil water content, "soil water content" The path coefficient between the rate of change time index and the rainfall time is 0.699, and the total rainfall is the most important negative effect factor affecting the change amplitude index of soil water content, and the path coefficient between the change amplitude index of soil moisture content and the total rainfall is 0.549, in addition, the above index increases with the increase of soil temperature. (3) (3) with the increase of rainfall intensity, the priority flow generated by the section, the priority flow generated by the dry root, and the priority flow generated by the fine roots of the 1mm and the 2mm root diameter increase gradually, and the increase is increased. The preferential flow generated by the root and the preferential flow generated by the 1mm and the root diameter of 2mm are greatly different, especially when the rainfall intensity is 240mm h~ (-1), the priority flow generated by the 10cm soil layer via the section, and the priority flow generated by the root diameter of the 1mm and the 2mm root diameter are obviously greater than 20cm and 30cm. Under the same rainfall intensity, compared with the 30cm soil layer, the difference between the preferential flow produced by the 10cm soil layer and the priority flow generated by the dry root can reach 10 times respectively. The difference of the priority flow produced by the fine root diameter of the 1mm and the 2mm root is 70 and 20 times respectively. The regularity is different. The rainfall intensity is 150 mm h~ (-1), 200 mm h~ (-1) and 240 mm h~ (-1), and there is a significant difference in the root penetration ratio of the 10 cm soil layer, the 1mm root and the root root penetration ratio of 2mm fine root, and the difference of the root penetration ratio of the different types of root roots is not significant, and the rainfall intensity is 100, 150, 200, respectively. Under the conditions of mm h~ (-1) and 240 mm h~ (-1), the difference of the relative permeation area of each root system is mainly reflected in the 10 cm soil layer, and the relative permeability area of the root system is not significant in the rest of the soil layer. Under the condition of the rainfall intensity of 150 mm h~ (-1), 200 mm h~, and 240 Now 10 cm soil layer. After analyzing the structural equilibrium equation model of "root penetration ratio" and "root penetration influence index", it is found that all factors can explain the 73.2% "root penetration influence index", in which the rainfall intensity and "root penetration ratio" have significant direct positive effects on the "root permeability influence index". (4) Under the conditions of artificial rainfall and natural rainfall, the phenomenon that the flow of soil priority flow is gradually reduced or even stopped is found. This study defines it as "soil embolism", referred to as "soil embolus", which is called "soil embolism elimination", referred to as "soil suppository elimination". With the extension of time, the total amount of soil preferential flow generated by the fine roots is gradually decreasing; the number of fine roots producing priority flow presents a downward trend in general; although the number of fine roots that produces the priority flow is generally decreasing, the fine roots that produce a partial first flow of flow will no longer produce an advantage over each observation. "Soil embolism" and "soil embolism elimination" occurred in the process of preferential flow generated by soil profiles, dry roots, 1mm and 2mm fine roots in the simulated rainfall conditions. Under the condition of rainfall intensity, soil embolism can be eliminated more easily under the condition of greater rainfall intensity.
【学位授予单位】：南京林业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S714

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