农牧交错带牧业系统波动性及影响因子分析

牧业系统波动是影响到农牧交错带农户生计和生态安全的重大问题。该研究以羊只总数为牧业系统特征变量,选取年降水量、年平均气温、有效灌溉面积、粮食播种面积、粮食总产量、当年造林面积、草地面积、植被指数、农业劳动力人数和农民人均纯收入为影响因子。用经验模态分解法获得羊只总数及其10个影响因子的波动分量和趋势量;进而运用集对分析法对羊只总数与其影响因子的相应波动分量进行对比分析。结果表明,1954—2013年盐池县羊只总数波动较大,羊只总数及其10个影响因子存在3~4、7~15、22~26、40~45 a的准周期性波动,22~26 a准周期是羊只总数波动中最重要的。对羊只总数波动影响最大的因子是粮食播种面积,其次是年降水量,二者的综合影响率占75%。年平均气温、粮食总产量和造林面积也有一定影响。羊只总数波动分量的周期越长,受农业的影响越大;越短则受气候的影响越大。经济社会对羊只总数的波动影响很小。气候因子在3、7~9和30 a准周期上影响羊只总数波动,是其主控因子;而粮食总产量、当年造林面积是羊只总数波动的反向调节因子,其他6个因子兼有主控和反向调节两方面的作用。基于以上各主要影响因子的作用机理,构建有效的农林牧复合系统将是实现盐池县牧业系统稳定发展的必然出路。

Fluctuation of animal husbandry system and its driving factors analysis in agro-pastoral transitional zone

Abstract: Fluctuation of animal husbandry system (FAHS) can affect not only the sustainability of farmers' livelihood, but also the stability of regional ecosystem. Characteristics of FAHS and its driving factors in Yanchi County, Ningxia Hui Autonomous Region, which was a typical agro-pastoral zone, were studied and discussed in this paper. According to previous research results and our surveys, total number of sheep was defined as the dependent variable and 10 driving factors were defined as the independent variables, namely, average annual precipitation, average annual temperature, effective irrigated area, grain acreage, gross output of grain, afforestation area, grassland area, vegetation index, agricultural labor force and per capita net income of farmers. Then, the empirical mode decomposition (EMD), which is a powerful method for analyzing the nonlinear and non-stationary time series data, was used to analyze the variability of animal husbandry system and its driving factors. The time series data of total number of sheep and its 10 driving factors from 1954 to 2013 were decomposed into several intrinsic mode functions (IMFs) and a residual trend respectively. Meanwhile, the set pair analysis (SPA) method was used to analyze the contribution of each driving factor to FAHS. Here, 3 IMFs that were decomposed from total number of sheep and the corresponding IMFs that were decomposed from each driving factor were input in the set pair analysis model, and the relationship between FAHS and its driving factors was obtained by this method. The results showed: 1) The total number of sheep increased significantly with an annual fluctuation during the past 60 years and its coefficient of variation was moderate. The total number of sheep had 3 IMFs and its 10 driving factors had 2-5 IMFs. The most of IMFs had the fluctuant periods of 3-4, 7-15, 22-26 and 40-45 years respectively. The IMFs that had the fluctuant period of 22-26 years and the biggest variance contribution were the most important components that were decomposed from the total number of sheep. 2) The fluctuation of the total number of sheep mainly depended on grain acreage, followed by average annual precipitation, and the contribution rate of both driving factors accounted for 75%. The fluctuation of the number of sheep was also weakly affected by average annual temperature, gross output of grain and total output and afforestation area. 3) In these IMFs that were decomposed from total number of sheep, the one that had a longer fluctuation period was affected more seriously by agriculture. In contrast, the one that had a shorter fluctuation period was affected more seriously by climatic factors. Economic and social factors had limited effect on the fluctuations of the total number of sheep. 4) Climatic factors such as average annual precipitation and average annual temperature mainly drove the fluctuation of the total number of sheep. In contrast, grain total output and annual afforestation area had a reverse effect to the total number of sheep. Other 6 factors including effective irrigated area, grain acreage, grassland area, vegetation index, agricultural labor force and per capita net income of farmers had bi-directional effects on the total number of sheep. Based on above analyses, we suggest that the sustainable development for animal husbandry system in Yanchi County is constructing an effective agro-forestry-animal composite husbandry system in this typical agro-pastoral zone. In particular, developing appropriate scale and efficient farmland and feed shrub stands is very important to maintain the stability of animal husbandry system.