本文選題：紅壤干旱 + 植被�。� 參考：《華中農業(yè)大學》2017年碩士論文

【摘要】：我國熱帶亞熱帶的紅壤區(qū)降水分布不均,由此造成的水土流失和季節(jié)性干旱問題十分突出,嚴重制約了該區(qū)的農業(yè)生產和發(fā)展。紅壤坡地的土壤水分狀況影響農林生態(tài)系統(tǒng)的功能,也是導致季節(jié)性干旱形成的原因。然而,近年紅壤坡地上植被的種植結構改變對干濕季紅壤水分動態(tài)規(guī)律的影響機制還不清楚。本文研究干濕兩季紅壤坡地不同植被類型的土壤水分變化規(guī)律,為改善紅壤季節(jié)性干旱提供理論依據(jù)。本研究在湖北省咸寧市賀勝橋鎮(zhèn)江里頭的一個典型紅壤緩坡地(坡地面積約13667 m2,坡長約136 m,平均坡度約4°,坡向正南,第四紀紅色粘土母質)上開展,于2015年4月12日至2016年10月3日進行高頻連續(xù)定位監(jiān)測試驗。試驗設置在上坡、中坡、下坡三個坡位,植被類型分別是喬木(杉木)、小喬木(紅葉石楠)、作物(油菜),每個植被地塊中心埋設4個EC-5水分探針,分別監(jiān)測20、40、60、90 cm深度的土壤含水量(記錄間隔為30 min),坡地自然降雨量監(jiān)測與土壤含水量同步。2016年3月12日(進入濕季前)沿坡地縱向中心線,每個地塊均勻設置3~5個采樣點,采用烘干法測定土壤含水量。2016年4月21日,進行植物根系挖取及掃描試驗,獲取根長、根表面積、根體積等指標。得到以下研究結果:(1)不同植被類型的土壤水分宏觀特征不同。2016年濕季水澇、干季干旱分別都比2015年嚴重。喬木的土壤儲水量在兩年之間幾乎無差異,但是2016年小喬木的土壤儲水量明顯降低,而作物的土壤儲水量明顯增加。2015年,小喬木40 cm深度在干季的土壤平均含水量明顯相對濕季降低;喬木40 cm深度土壤平均含水量在兩季中都最小;作物60 cm深度土壤平均含水量在濕季最小。喬木淺層土壤水分在濕季的活躍程度(變異系數(shù))較大且大于干季,而小喬木的各深度土壤水分在干季的活躍程度大于濕季。喬木干季60 cm深度和作物干季20 cm深度、濕季60 cm深度的土壤水分時間穩(wěn)定性較弱,但水分活躍程度較大。作物60 cm深度存在一個頻率較小、但又跨度較大的高含水量集中區(qū)域,尤其是在2016年的高含水量區(qū)域明顯較大。(2)不同植被類型的根系特征與吸水能力密切相關。喬木和小喬木在土壤40 cm深度的RLD(總根長密度)大于20 cm深度且最大,60、90 cm深度的RLD隨著土壤深度增加而減小;小喬木在不同土壤深度上的RLD都大于喬木,尤其是土壤40 cm深度;作物20 cm深度的RLD、RSD(總根表面積密度)、RVD(總根體積密度)都最大且隨土壤深度增加而遞減。在濕季,這三種植被的根系相對吸水率在土壤剖面上的變化特征與細根根長量的分布特征基本一致。在2015、2016年的干旱期內,喬木和小喬木的根系相對吸水率變化規(guī)律幾乎相同,二者在2016年干旱早期的根系相對吸水率下降不是很穩(wěn)定,而在干旱后期則緩慢趨于平穩(wěn)且其變化規(guī)律與2015年干旱階段一致,這主要與干旱持續(xù)時間長短有關。(3)不同植被土壤20 cm深度的干旱強度和干旱程度的變化特征差異明顯。整體上,喬木的土壤干旱強度、干旱程度都隨著干旱天數(shù)的增加而增加,小喬木和作物的土壤干旱程度雖然在兩年干旱期中都呈增加趨勢,但二者的干旱強度變化在兩年干旱期中有不同的表現(xiàn),2016年的干旱強度大于2015年且總體呈下降趨勢。干旱期初始,喬木、小喬木的土壤干旱程度都大于作物,而在干旱過程中(除了2015年干旱期Ⅱ之外)的土壤干旱強度是作物小喬木喬木;作物和小喬木的表層土壤含水量在干旱過程中都較早降低到最小值,而喬木滯后。(4)不同植被土壤水分—降雨的響應過程在不同降雨事件中表現(xiàn)不同。在大暴雨、暴雨事件下,喬木、小喬木和作物的土壤水分—降雨的響應過程都主要受到優(yōu)先流(根系通道或地表裂縫)和壤中流(來自上坡的土壤水分補給)的共同影響,其中作物休閑期的表層土壤水分波動沒有喬木、小喬木劇烈。中、小雨事件對這三種植被土壤水分的影響相對減小,而作物種植期表層土壤水分對中雨的響應最明顯且迅速,含水量波動較喬木、小喬木更為劇烈。因此,濕季,喬木和小喬木的土壤水分—降雨響應過程相似,但作物種植期的表層土壤水分波動比喬木、小喬木明顯,而休閑期恰好相反;干季,不論土壤干旱程度高低,涵養(yǎng)水源能力最弱的植被都是喬木;小喬木和作物(休閑期)的涵養(yǎng)水源能力受土壤干旱程度的影響較大。總之,紅壤坡地水分時空分布,在濕季更大程度地受到植被和地形的協(xié)同影響;干季的植被因素影響仍重要,而地形因素影響程度減小。
[Abstract]:The distribution of precipitation in the red soil region of tropical and subtropical regions of our country is uneven, and the problems of soil and water loss and seasonal drought are very prominent, which seriously restrict the agricultural production and development in this area. The soil moisture status of the red soil slope land affects the function of the agroforestry system and causes the seasonal drought. The influence mechanism of the change of vegetation structure on the dynamic law of water dynamics in dry and wet red soil is not clear. This paper studies the soil moisture change law of different vegetation types in the dry and wet two season red soil slope, and provides a theoretical basis for the improvement of the seasonal drought in red soil. This study is a typical red soil in Zhenjiang, Xianning, Hubei province. The gentle sloping area (the slope area is about 13667 m2, the slope length is about 136 m, the average slope is about 4 degrees, the slope to the south, the Quaternary red clay matrix) is carried out on the high frequency continuous location monitoring test from April 12, 2015 to October 3, 2016. The experiment is set up on the slope, the middle slope and the lower slope, and the vegetation types are tree (Cunninghamia lanceolata) and small tree (red leaf stone). 4 EC-5 water probes were embedded in the center of each vegetation block. The soil water content of 20,40,60,90 cm depth was monitored respectively (the interval of record was 30 min). The natural rainfall monitoring on the slope land was synchronized with the soil water content in March 12th (before the wet season) in the longitudinal center line along the slope, and each plot was evenly set by 3~5 sampling points. The soil moisture content of the soil was measured by the drying method in April 21st.2016 years. The root length, the root surface area and the root volume of the plant were obtained. The following results were obtained: (1) the macroscopic characteristics of soil moisture in different vegetation types were different from the wet season in the wet season in.2016, and the dry season drought was more serious than that in 2015. There was almost no difference between two years, but the soil water storage of small trees decreased obviously in 2016, and the soil water content of the crop increased obviously in.2015 years, the average water content of the 40 cm depth in the dry season decreased obviously in the dry season, and the average water content of the 40 cm depth soil in the tree was the lowest in the two season, and the average crop 60 cm depth soil was average. The water content in the wet season is the smallest. The activity of soil moisture in the wet season is larger and larger than the dry season, but the depth of soil moisture in the dry season is greater than that in wet season. The depth of 60 cm in the dry season and 20 cm depth in the dry season of the tree, and the soil moisture time of 60 cm depth in the wet season are weak, but the water activity is less than that of the wet season. The degree of leaping was larger. There was a small, high water content area with a larger span of 60 cm depth, especially in the high water content area in 2016. (2) the root characteristics of different vegetation types were closely related to the water absorption capacity. The RLD (total root length density) of trees and small trees in soil 40 cm depth (total root length) was greater than 20 cm depth. And the maximum RLD of 60,90 cm depth decreased with soil depth increasing, and the RLD of small trees in different soil depth was greater than that of trees, especially soil 40 cm depth; RLD, RSD (total root surface area density) at 20 cm depth of crops, RVD (total root volume density) were all largest and decreased with soil depth. In wet season, these three roots were planted roots. In the 20152016 year drought period, the relative water absorption of the roots of the trees and the small trees is almost the same, the two in the early drought in the early 2016, the relative water absorption of the root is not very stable, but in the late period of drought it tends to be slow. The regularity is consistent with the drought stage in 2015, which is mainly related to the duration of drought duration. (3) the variation characteristics of drought intensity and drought degree of different vegetation soils at 20 cm depth are distinctly different. Although the degree of soil drought was increasing during the two years' drought period, the drought intensity of the two had different performance during the drought period in two years. In 2016, the drought intensity was greater than that in 2015 and generally declined. The soil drought degree of trees and small trees was greater than that of crops in the beginning of drought period, but in the drought process (except 2015). The soil drought intensity outside the drought period is small arbor trees; the water content in the surface soil of the crops and small trees decreased early to the minimum, while the trees lagged. (4) the response process of soil moisture to rainfall in different vegetation was different in different rainfall events. Under heavy rain and rainstorm events, trees and small Joe The response of soil moisture to rainfall in wood and crops is mainly influenced by the priority flow (root channel or surface fissure) and soil water supply from the upper slope (from the soil water supply from the upper slope). There is no tree in the surface soil water fluctuation in the crop leisure period, and the small trees are violent. The effect of the rain event on the soil moisture of the three plants is affected by the small rain events. The response of soil moisture to medium rain was most obvious and rapid in crop planting period, and the fluctuation of water content was more intense than that of trees and small trees. Therefore, in wet season, the soil moisture and rainfall response process of trees and small trees was similar, but the fluctuation of surface soil moisture in crop planting period was more obvious than that of trees and small trees, while the leisure period was just right. On the contrary, dry season, no matter the degree of soil drought, the weakest vegetation of water conservation is arbor; the water conservation ability of small Qiao Muhe crops (leisure period) is greatly influenced by the degree of soil drought. In a word, the spatial and temporal distribution of water in the red soil slope is influenced by the synergistic effect of vegetation and terrain in the wet season; the vegetative factors of the dry season The impact is still important, while the impact of topographic factors is reduced.
【學位授予單位】：華中農業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S152.7

【參考文獻】

相關期刊論文 前10條

1 陳姍姍;劉康;包玉斌;陳海;;商洛市水源涵養(yǎng)服務功能空間格局與影響因素[J];地理科學;2016年10期

2 龔詩涵;肖洋;鄭華;肖q，

本文編號：2048901