本文選題：羊草 + 蓋度��； 參考：《西北農(nóng)林科技大學》2015年碩士論文

【摘要】：黃土高原地區(qū)植被覆蓋度低,土壤抗侵蝕能力弱,加之降雨分布集中,造成嚴重的水土流失,土地資源遭受破壞,導致土壤肥力下降,生態(tài)環(huán)境極為脆弱。植被對土壤侵蝕的影響具有不可忽視的作用,退耕建植人工草地可以明顯減輕土壤侵蝕程度,有利于土壤在雨季對降水的蓄積。羊草在我國集中分布于東北平原和內(nèi)蒙古高原東部,在陜西、寧夏、甘肅等省(自治區(qū))亦有分布,是禾本科牧草中分布最廣、利用價值最高的優(yōu)良禾草。因而分析羊草蓋度對產(chǎn)流產(chǎn)沙過程和風蝕過程的影響,明確羊草的水土保持效益,對羊草地的水土流失防治具有重要意義。通過人工降雨試驗和風洞試驗,研究了5種蓋度下羊草地的產(chǎn)沙產(chǎn)流特性和抗風蝕特性,探討了不同蓋度羊草地的水土保持效應。取得了如下主要結(jié)論:1.模擬降雨條件下,隨羊草蓋度的增加初始產(chǎn)流逐漸延后;坡度越大,產(chǎn)流時間越快;雨強越大,產(chǎn)流時間越快。當羊草蓋度小于60%時,蓋度對產(chǎn)流時間的影響相對較小,羊草蓋度為100%時,產(chǎn)流時間最慢。坡度為5°時,產(chǎn)流時間最慢,隨著坡度的逐漸增加,產(chǎn)流時間的增加率逐漸增大。黃綿土的初始產(chǎn)流時間快于風沙土的初始產(chǎn)流時間。羊草蓋度對不同土類的初始產(chǎn)流時間的影響比較穩(wěn)定,隨著羊草蓋度的逐漸增加,風沙土的初始產(chǎn)流時間相比黃綿土的平均滯后速率沒有明顯變化。2.相同坡度和雨強下,隨羊草蓋度的增加,累積徑流量呈持續(xù)減少的趨勢。坡度和雨強同樣是影響累積徑流量的重要因素。蓋度為20%時,平均累積徑流量76.15 L/(m2·h),當羊草蓋度增加到100%時,平均累積徑流量減少44%。坡度越大,累積徑流量越大,當坡度由5°增加到15°時,平均累積徑流量增大26%;雨強越大,累積徑流量越大,當雨強由90mm/h增大到120mm/h時平均累積徑流量增大42%。風沙土的累積徑流量小于黃綿土的累積徑流量,隨著羊草蓋度的逐漸增加,風沙土的累積徑流量相比黃綿土的平均減少速率先減小后增大,當羊草蓋度為60%時,其減少速率達到最小。3.羊草蓋度、坡度和雨強是影響累積產(chǎn)沙量的重要因素,累積產(chǎn)沙量與羊草蓋度呈反比,與坡度和雨強呈正比。當羊草蓋度由20%增加到100%時,平均累積產(chǎn)沙量減少65%;當坡度由5°增加到15°時,平均累積產(chǎn)沙量增加63%;當雨強由90mm/h增加到120mm/h時,平均累積產(chǎn)沙量增加79%。風沙土的累積產(chǎn)沙量大于黃綿土的累積產(chǎn)沙量,當羊草蓋度小于60%時,風沙土累積產(chǎn)沙量相比黃綿土累積產(chǎn)沙量的平均增加速率隨著羊草蓋度的增加緩慢上升;當羊草蓋度為大于60%時,其增加速率迅速增大。4.黃綿土羊草地和風沙土羊草地的產(chǎn)流趨勢均呈現(xiàn)在降雨初期產(chǎn)流率快速增長,在降雨中后期產(chǎn)流率保持穩(wěn)定;產(chǎn)沙趨勢呈現(xiàn)在降雨初期產(chǎn)沙率快速增長然后出現(xiàn)小幅回落,在降雨中后期產(chǎn)沙率保持穩(wěn)定。在降雨過程中的每一個階段,黃綿土的產(chǎn)流率高于相應條件下風沙土的產(chǎn)流率;黃綿土的產(chǎn)沙率低于相應條件下風沙土的產(chǎn)沙率,在雨強120mm/h、坡度15°和羊草蓋度為20%時這一特征表現(xiàn)最明顯。5.風蝕量與羊草蓋度呈反比,與風速呈正比,黃綿土的風蝕量低于相應條件下風沙土的風蝕量。當羊草蓋度從60%增加到80%時,風蝕量的減少率最大,由此可知,羊草抵抗風蝕的臨界蓋度介于60-80%之間。0-23cm高度內(nèi)這兩層的集沙儀收集到的風蝕物的質(zhì)量比較接近,主要是由蠕移顆粒和大部分的躍遷顆粒組成,這一高度內(nèi)收集到的風蝕物占整體風蝕量的70%以上。6.人工羊草地的蓋度比較大,從而有效的阻止了風力對土壤的侵蝕。與細竹蒿草相比,羊草的減蝕率達到37.47%。留茬可以有效防止水土流失,與深翻地相比,蕎麥留茬的減蝕率是62.01%,玉米留茬的減蝕率是70.99%,羊草留茬的減蝕率與玉米留茬的減蝕率比較接近。
[Abstract]:The vegetation coverage of the Loess Plateau is low, the soil erosion resistance is weak, and the distribution of rainfall is concentrated. The soil erosion is serious, the land resources are destroyed, the soil fertility is reduced and the ecological environment is extremely fragile. The effect of vegetation on soil erosion can not be ignored. The degree of erosion is beneficial to the accumulation of soil in the rainy season. In China, Leymus chinensis is distributed in the Northeast Plain and the eastern Inner Mongolia plateau, in Shaanxi, Ningxia, Gansu and other provinces (autonomous regions), which are the most widely distributed and best used grasses in the grasses. Therefore, the process of runoff and sediment yield and wind erosion are analyzed. The effect of water and soil conservation of Leymus chinensis is of great significance to the prevention and control of soil erosion in sheep and grassland. Through artificial rainfall experiment and wind tunnel test, the characteristics of sediment yield and wind erosion of sheep grassland under 5 kinds of coverage are studied, and the water and soil conservation effect of sheep grassland with different coverage is discussed. The following main conclusions are obtained: 1. simulation With the increase of the coverage of Leymus chinensis, the initial runoff was gradually postponed with the increase of the coverage of Leymus chinensis; the greater the slope, the faster the flow time, the greater the rain intensity, the faster the production time. When the cover of Leymus chinensis was less than 60%, the effect of the coverage on the production time was relatively small. When the cover of Leymus chinensis was 100%, the flow time was the slowest, and the flow time was the slowest and with the gradient of the gradient. The increase rate of the flow time increased gradually. The initial flow time of the yellow soil was faster than the initial flow time of the aeolian soil. The effect of Leymus chinensis coverage on the initial flow time of different soils was more stable. With the gradual increase of the coverage of Leymus chinensis, the initial flow time of the aeolian soil had no obvious change in the average lag rate of the yellow soil. Under the same slope and rain intensity, the cumulative runoff decreased continuously with the increase of the coverage of Leymus chinensis. The gradient and the rain intensity were also the important factors affecting the cumulative runoff. The average cumulative runoff was 76.15 L/ (m2. H) when the coverage was 20%. When the coverage of Leymus chinensis increased to 100%, the average cumulative runoff decreased the greater the 44%. gradient and the cumulative runoff. The larger the gradient increased from 5 to 15 degrees, the average cumulative runoff increased by 26%, the greater the rainfall intensity, the larger the cumulative runoff, the cumulative runoff of the 42%. wind sandy soil when the intensity of the rain increased from 90mm/h to 120mm/h was smaller than the cumulative runoff of the yellow soil, and the cumulative runoff phase of the aeolian sandy soil was gradually increased with the increase of the cover of the sheep and grass. The average reduction rate of the yellowish soil decreased first and then increased. When the coverage of Leymus chinensis was 60%, the decrease rate reached the minimum.3. Leymus chinensis coverage. The slope and rain intensity were the important factors affecting the cumulative sediment yield. The cumulative sediment yield was inversely proportional to the coverage of Leymus chinensis, and was proportional to the slope and rain intensity. The average cumulative sediment yield was increased when the coverage of Leymus chinensis was increased from 20% to 100%. The average cumulative sediment yield increased by 63% when the slope increased from 5 to 15. When the rain intensity increased from 90mm/h to 120mm/h, the cumulative sediment yield increased in 79%. aeolian sandy soil than the cumulative sediment yield of the yellow soil. When the coverage of Leymus Leymus was less than 60%, the cumulative sediment yield of the aeolian soil was compared with the average sediment yield of the yellow soil. The increase rate increased slowly with the increase of the coverage of Leymus chinensis; when the coverage of Leymus chinensis was greater than 60%, the rate of increase in the growth rate of.4. yellow meadow and aeolian sheep grassland increased rapidly in the early period of rainfall, and the rate of yield remained stable in the middle and late period of rainfall, and the trend of sediment yield in the early period of rainfall was faster. At each stage of the rainfall process, the yield of the yellow soil is higher than that of the corresponding wind sand soil, and the yield of the yellow soil is lower than that of the corresponding wind sand soil under the corresponding conditions, in the rainfall intensity 120mm/h, the slope 15 degree and the Leymus chinensis coverage at 20%. The most obvious sign of.5. wind erosion is inversely proportional to the coverage of Leymus chinensis, which is proportional to the wind speed, and the wind erosion of the yellow soil is lower than that of the wind sand soil under the corresponding conditions. When the coverage of Leymus chinensis increases from 60% to 80%, the reduction rate of wind erosion is the largest. Therefore, the critical coverage of Leymus chinensis resistance to wind erosion is between the two layers within the height of 60-80% between the two layers. The quality of the wind erosion objects collected by the sand instrument is close, mainly composed of vermicular particles and most of the transition particles. The wind erosion collected in this height accounts for more than 70% of the total wind erosion of the.6. artificial sheep grassland, which effectively prevents the erosion of the wind to the soil. 37.47%. stubble can effectively prevent soil erosion. Compared with deep ground, the erosion rate of buckwheat stubble is 62.01%, the erosion rate of corn stubble is 70.99%, and the erosion rate of stubble of Leymus chinensis is close to that of corn stubble.
【學位授予單位】：西北農(nóng)林科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：S157

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