珠三角丘陵区耕地质量综合评价及指标权重敏感性分析

Comprehensive evaluation of cultivated land quality and sensitivity analysis of index weight in hilly region of Pearl River Delta

快速工业化和城市化给珠三角地区的耕地造成一系列土壤环境污染问题,合理评价这些区域耕地质量对指导耕地的有效利用和保护以及实现耕地数量-质量综合平衡与管理具有重要意义。目前耕地质量评价中,较少考虑土壤污染因素,并且缺乏对指标的权重敏感性分析验证评价结果的可靠性。因此该文以珠三角土壤受污染区之一的增城区为例,综合考虑土壤肥力因素以及土壤环境评价指标,从土壤理化性质、农业生产条件、区位条件、土壤环境4个方面构建耕地质量综合评价指标体系,分析增城区耕地质量总体特征及空间布局与行政区域分布规律,在此基础上基于OAT(one-at-a-time)法来评估各指标权重的不确定性对评价结果的影响程度。结果表明:增城区耕地整体质量较高但优质耕地较少。在耕地质量综合评价中融入土壤污染因素,并对其进行微观定量分析,使得评价体系更全面。不同指标权重变化对耕地质量变化率影响的空间差异较大;对于同一指标,权重增加或减少的值相同时,其对耕地质量评价结果的敏感性相同。最大的MACR(mean absolute change rate)值3.558 2%远低于相应的权重变化率30%,表明评价结果总体相对稳定,该文初始确定的权重是合理的。该研究有助于国土相关部门更好地掌握土壤受污染区域的耕地质量,在空间多准则决策中减少不确定性影响。

Rapid industrialization and urbanization have brought a series of environmental problems related to soil pollution in the Pearl River Delta region. A systematic and synthetic evaluation of the cultivated land quality is of great significance to guide the rational utilization and protection of cultivated land, as well as to realize the comprehensive balance and management of cultivated land. However, the soil pollution factors have seldom been considered in cultivated land quality evaluation system, which was also short of a sensitivity analysis of the index weight. Based on GIS （geographic information system） multi-objective decision analysis, the paper conducted a study on the evaluation of cultivated land quality and the sensitivity analysis of index weight by taking Zengcheng District of Pearl River Delta as an example. With soil fertility factor and environmental assessment index taken into consideration, the comprehensive evaluation index system of cultivated land quality was constructed from 4 aspects： Soil physical and chemical properties, agricultural production conditions, location conditions and soil environment, so as to analyze the general characteristics of cultivated land quality and the spatial layout rule in Zengcheng District, and the weight sensitivity analysis of OAT （one-at-a-time） method was adopted to evaluate the influence degree of each index weight＇s uncertainty on the evaluation results. In order to reflect the trend and regularity of the changon cultivated land quality and its spatial pattem, the weight value of only one factor changed at a time while the other factors remained unchanged. When the value of RPC （range of percent change） and IPC （increment of percent change） were at ±30% and ＋2% respectively, and every criterion factor was applied to all the evaluation indicators as the main change factor, a total of 420 groups of weight values were generated, among which every group of weights were calculated to produce a new evaluation result of the comprehensive quality of cultivated land. The main results of the study were as follows： 1） The cultivated land in Zengcheng District had a good overall quality, but high quality cultivated land was lacked. The grades of cultivated land quality were mainly concentrated at the 2nd and 3rd grade, which accounted for 30.88% and 31.69%, respectively. The proportion of middle and low yield field was relatively large. 2） From the perspective of the spatial distribution, the cultivated land with better quality was mainly distributed in the southern plains, the basins with better irrigation conditions like Zengjiang River basin, East River basin and Xifu River basin, as well as North River valley. The comprehensive quality of most cultivated land in Zhengguo, Xiaolou and Paitan was not high, and the overall quality of cultivated land in Xintang Town was poor. 3） The changes of weights had a certain influence on the quality distribution of cultivated land. Seen from the spatial distribution of change rate of cultivated land quality generated from different weight distribution, the spatial differences of the calculated results were rather big. When the weight increased or decreased by the same value, the same factor showed the same sensitivity to the quality evaluation results of cultivated land. 4） The maximum MACR （mean absolute change rate） value of 3.558 2% was much lower than the corresponding weight change rate of 30%, showing that the evaluation results were relatively stable, and the quality of cultivated land in Zengcheng District was overall stable. In conclusion, in the comprehensive evaluation of cultivated land quality, the soil environmental factors should be taken into consideration, and a quantitative analysis of micro-data of the soil pollution situation should be conducted to make the evaluation system more comprehensive and more scientific. The sensitivity analysis of the index weight can verify the reliability of the evaluation results, which can help the relevant departments make better decisions, and reduce the uncertainty in the spatial multi-criterion decision-making.