基于GA-BP的樟树林土壤呼吸对施氮的响应研究

发布时间：2018-03-07 14:25

  本文选题：土壤呼吸　切入点：施氮　出处：《中南林业科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前施氮对土壤呼吸影响的研究大多基于实验观测结果,受试验地自然条件的限制,不能研究在一定条件范围内土壤呼吸对施氮响应的连续变化过程。通过喷洒NH4NO3水溶液,设置对照(C,no N added),低氮(L,5gNm-2a-1),中氮(M,15gNm-2a-1),高氮(H,30gNm-2a-1)4种处理水平,使用GA-BP(人工神经网络)建立樟树林土壤呼吸对施氮响应的模型,通过模型模拟揭示了土壤呼吸对施氮响应的变化。结果如下:(1)GA-BP人工神经网络可以较好的模拟亚热带樟树林土壤呼吸在不同施氮量条件下的响应过程。通过模型仿真得到的结果连续、完整,解释了0.70-0.74的施氮水平、土壤温度、土壤湿度交互作用下的土壤呼吸过程。(2)绘制了 土壤呼吸与土壤湿度和土壤温度的响应曲面图及对应的等高线图。通过响应曲面图和变动率图直观的描述了不同施氮水平下土壤呼吸关于土壤温湿度的连续完整的变化过程。施氮在总体上抑制了土壤呼吸速率,但在高氮处理下土壤呼吸速率较低氮与中氮处理出现了增加,但未达到对照处理的水平。较低的土壤呼吸速率主要出现在土壤温度降较低区域,随着施氮量变化出现在不同的土壤湿度上;而较高的土壤呼吸速率主要出现在土壤湿度较高的区域,并随着施氮量的变化出现在不同的土壤温度上。(3)土壤呼吸总速率、低土壤湿度范围的土壤呼吸速率和高土壤湿度范围的土壤呼吸速率,三者比例从对照处理的1:0.83:1.29,到低氮处理的1:0.84:1.18,再至中氮处理的1:0.95:1.08,最后到高氮处理的1:1.04:0.96,随着施氮量的增加,不同湿度范围内土壤呼吸有向均值趋近的现象。(4)利用GA-BP人工神经网络特点,结合输入层-隐含层-输出层之间的权值,通过Garson算法计算求出影响土壤呼吸各因素的程度。从计算结果中可以发现,凋落物水平对土壤呼吸的影响贡献率最大,其余三个因素对土壤呼吸贡献率基本一致。
[Abstract]:At present, most of the studies on the effects of nitrogen application on soil respiration are based on the results of experimental observation. Limited by the natural conditions of the experimental site, the continuous variation process of soil respiration response to nitrogen application in a certain range of conditions can not be studied. NH4NO3 aqueous solution is sprayed. The response of soil respiration to nitrogen application in camphor forest was established by using GA-BP- (artificial neural network) at four treatment levels, namely, no N added, low nitrogen (Ln) 5g Nm-2a-1, medium N ~ (2 +) ~ (15) g Nm ~ (-2) -1a ~ (-1), high N ~ (2 +) H ~ (2 +) ~ (30) Nm ~ (-2) ~ (-1) ~ (-1). The response of soil respiration to nitrogen application was revealed by model simulation. The results are as follows: 1: 1 + GA-BP artificial neural network can better simulate the response process of soil respiration in subtropical camphor forest under different nitrogen application rates. The true result is continuous, Complete, explaining the N application level of 0.70-0.74, soil temperature, Soil respiration process under the interaction of soil moisture. 2) the response surface map of soil respiration, soil moisture and soil temperature and the corresponding contour map are drawn. The different responses are intuitively described by the response surface map and the change rate map. The continuous and complete variation of soil respiration in soil temperature and humidity at nitrogen application level. However, the soil respiration rate increased under high nitrogen treatment, but it did not reach the level of the control treatment. The lower soil respiration rate mainly occurred in the lower soil temperature drop area, but it did not reach the level of the control treatment, but the soil respiration rate increased under the condition of high nitrogen treatment, but it did not reach the control level. The higher soil respiration rate appeared in the higher soil moisture area, and the higher nitrogen application rate appeared in the different soil temperature, and the higher soil respiration rate appeared in different soil temperature, but the higher soil respiration rate appeared in the higher soil moisture area, and the higher soil respiration rate appeared in the different soil temperature with the change of nitrogen application rate, and the higher soil respiration rate appeared in the area with higher soil moisture content. The soil respiration rates in low soil moisture range and high soil moisture range ranged from 1: 0.83: 1.29 in control, 1: 0.84: 1.18 to 1: 0.84: 1.18 in low nitrogen treatment, 1: 0.95 to 1.08 in medium nitrogen treatment, and finally to 11.0: 4: 0.96 in high nitrogen treatment. With the increase of nitrogen application rate, In the range of different moisture, the phenomenon that the average value of soil respiration approaches to the average value. (4) using the characteristics of GA-BP artificial neural network, combining the weights between input layer, hidden layer and output layer, The degree of influencing factors of soil respiration was calculated by Garson algorithm. The results showed that litter level had the largest contribution to soil respiration, while the other three factors had the same contribution to soil respiration.
【学位授予单位】：中南林业科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S714
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本文编号：1579669