本文選題：森林土壤　切入點：中微量元素　出處：《華南農(nóng)業(yè)大學》2016年碩士論文

【摘要】：森林不僅具有改善人類居住環(huán)境、涵養(yǎng)水源、防止水土流失的作用,還與森林土壤二者相互作用,影響土壤的發(fā)育與形成。因此,分析森林土壤中量與微量元素空間分布,對森林恢復與更新具有重要意義。本文以廣東省云浮市云城區(qū)云安區(qū)為研究區(qū)域,運用BP人工神經(jīng)網(wǎng)絡(luò)預(yù)測模型,預(yù)測森林土壤中量及微量元素的空間分布,分析研究區(qū)內(nèi)森林土壤中量與微量元素含量的空間分布特征,以期揭示當前環(huán)境條件下云城區(qū)云安區(qū)森林土壤中量與微量元素含量的分布現(xiàn)狀,為該區(qū)森林的經(jīng)營管理提供參考。本研究主要結(jié)論如下:1.對森林土壤中量及微量元素含量而言,整個研究區(qū)中量元素交換鈣的含量相對較高,其次為全硫,交換鎂含量最低;微量元素中,總鉛的含量最高,其次為總鋅,總鎘含量最低�？傛k、總鋅的含量均在土壤環(huán)境質(zhì)量標準一級標準的范圍內(nèi),總鉛的含量在二級標準的范圍內(nèi)。交換鈣、交換鎂、總鎘、總鋅的含量均小于全國背景值,總鉛的含量大于全國背景值。2.通過土壤中量與微量元素變異系數(shù)的比較,云城區(qū)6個土壤中量及微量元素的變異系數(shù)分別在33.04%~98.19%之間,云安區(qū)的6個土壤中量及微量元素的變異系數(shù)在33.43~106.34%之間。其中云安區(qū)交換鈣屬于強變異,其余均屬于中等變異,云城區(qū)與云安區(qū)交換鈣的變異系數(shù)最大,分別為98.19%、106.34%。云城區(qū)總鎘的變異系數(shù)最低,為33.04%。3.插值方法的比較,通過建模點與驗證點的均方根誤差與平均絕對誤差的精度比較,可以看出泛克里格插值法比反距離加權(quán)插值法的精度高,進一步通過預(yù)測值與實測值的相關(guān)性顯著度比較,發(fā)現(xiàn)泛克里格插值方法與反距離加權(quán)插值法建模點的預(yù)測值與實測值相關(guān)性都呈現(xiàn)出顯著性,但是兩種插值法的預(yù)測值與實測值相關(guān)系數(shù)差值不同,其中泛克里格的差值最小,但6個元素中泛克里格插值法對交換鎂的預(yù)測性較好,對其他5個元素預(yù)測性欠佳。4.從模型的選取上來看,通過建模點與驗證點實測值與預(yù)測值相關(guān)性顯著度分析,結(jié)果發(fā)現(xiàn)交換鈣、交換鎂、全硫、總鎘、總鋅的預(yù)測,BP人工神經(jīng)網(wǎng)絡(luò)模型最好;總鉛的預(yù)測,雖然泛克里格方法優(yōu)于BP人工神經(jīng)網(wǎng)絡(luò)模型,仍需深入研究其最適模型。從空間預(yù)測分布圖上來看,BP人工神經(jīng)網(wǎng)絡(luò)能更好的體現(xiàn)明顯的地形之間的變化,與泛克里格插值法相比,更具有推廣性,即BP人工神經(jīng)網(wǎng)絡(luò)最優(yōu)。5.土壤中量與微量元素空間分布呈現(xiàn)出規(guī)律性,微量元素總鎘、總鉛、總鋅的分布在整個研究區(qū)呈自西向東逐漸遞減的空間分布趨勢;交換鈣總體呈自西向東逐漸增加再降低再增加的趨勢,交換鎂與全硫總體呈自西向東逐漸遞減再增加的趨勢,交換鈣與交換鎂的低值區(qū)呈一條不規(guī)則的帶狀由北向南從中部插整個研究區(qū)。中量元素受淋溶作用強,元素流失量多;微量元素受到人為干擾影響較大,包括施肥、農(nóng)藥、汽車尾氣等影響。
[Abstract]:Forest not only has the function of improving human living environment, conserving water source and preventing soil erosion, but also interacts with forest soil, which affects the development and formation of soil. Therefore, the spatial distribution of trace elements and quantity in forest soil is analyzed. This paper takes Yunan District, Yunfu City, Guangdong Province as the research area, and uses BP artificial neural network to predict the spatial distribution of trace elements and quantity in forest soil. The spatial distribution characteristics of forest soil quantity and trace element content in Yunan district were analyzed in order to reveal the distribution status of forest soil quantity and trace element content in Yunan district under the current environmental conditions. The main conclusions of this study are as follows: 1. In terms of the amount of forest soil and the content of trace elements, the content of exchangeable calcium in the whole study area is relatively high, followed by total sulfur and the lowest content of exchange magnesium; Among trace elements, total lead content is the highest, followed by total zinc, total cadmium content is the lowest. Total cadmium and total zinc content are within the range of the first class standard of soil environmental quality standard, the total lead content is within the range of the second grade standard. The contents of total cadmium and zinc were all lower than the national background value, and the content of total lead was larger than the national background value. 2. By comparing the variation coefficient of soil quantity and trace elements, the variation coefficients of soil quantity and trace elements in six soils of Yuncheng District were 33.04 ~ 98.19%, respectively. The coefficient of variation of the six soils in Yunan area was 33.43 ~ 106.34%, in which the exchangeable calcium in Yunan area was a strong variation, while the others were medium variation, and the coefficient of variation between Yunan and Yunan was the largest. Respectively 98.19 and 106.34.The coefficient of variation of total cadmium in Yuncheng District is the lowest, 33.04k.3.Compared with the interpolation method, the accuracy of the root mean square error and the mean absolute error of the modeling point and the verification point are compared. It can be seen that the accuracy of the pan Kriging interpolation method is higher than that of the inverse distance weighted interpolation method, and the correlation significance between the predicted value and the measured value is further compared. It is found that the correlation between the predicted values and the measured values of the modeling points of the pankriging interpolation method and the inverse distance weighted interpolation method is significant, but the difference between the predicted values of the two interpolation methods and the measured values is different, in which the pan kriging method has the smallest difference. However, the Pan-Kriging interpolation method has a good predictability for the exchange magnesium, and the other five elements are not predictable. 4. From the model selection, the correlation significance between the measured values and the predicted values of the modeling points and the verification points is analyzed. The results show that the BP artificial neural network model is the best in predicting calcium exchange, magnesium exchange, total sulfur, total cadmium and total zinc, while the Pan-Kriging method is better than the BP artificial neural network model in the prediction of total lead. From the spatial prediction map, BP artificial neural network can better reflect the obvious terrain changes, compared with the pan Kriging interpolation method, it is more extensible. That is, BP artificial neural network is the best. 5. The spatial distribution of soil quantity and trace elements is regular. The distribution of trace elements, total cadmium, total lead and total zinc in the whole study area is gradually decreasing from west to east. The total exchangeable calcium increased gradually from west to east, then decreased and increased again from west to east, and the exchange magnesium and total sulfur decreased gradually from west to east, and then increased again. The low value region of exchangeable calcium and magnesium intercalated from north to south into the whole study area from north to south. The medium amount of elements was strongly eluted, the amount of elements lost was much, and the trace elements were affected greatly by human interference, including fertilization and pesticide. Automobile exhaust, etc.
【學位授予單位】：華南農(nóng)業(yè)大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：S714.5

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