县域耕地地力与农用地自然质量等级差异及关联性研究

Differences and relationships between farmland productivity and farmland natural quality

探寻县域耕地地力评价与农用地自然质量分等的联系与差异,有助于二者可比衔接。采用叠置法划分评价单元,系统聚类法确定评价的定量指标,特尔菲法筛选影响评价结果的定性指标,层次分析法确定评价指标权重,模糊数学法建立各参评指标与评价级别的关系模型,分别进行了湖南省衡东县县域耕地地力与农用地自然质量等级划分;采用GIS叠加分析法得到等别转移分布,并对等别转移分布规律及原因进行了研究。结果表明:衡东县农用地自然质量前5个级别所占面积比例达91.29%,而耕地地力只有74.37%,总体上耕地地力低于农用地自然质量1个级别;耕地地力和农用地自然质量高、中、低级别面积比例分别为32∶42∶26和33∶43∶24,均呈两头小、中间大的分布规律;耕地地力相应级别在水田和旱地的分布比例具有明显差异,高等级(1、2、3级)基本分布在水田,而农用地自然质量比例比较稳定;两种评价结果的等别转移量能清楚地显示二者对应地块级别的差异程度及空间分布,呈平地区>丘岗区>山地区的变化规律。评价对象的不同及布点采样的差异导致同一图斑上的评价结果出现一定差异,评价指标及权重的差异是二者评价结果差异的主要原因。

From comparisons and connections, the relationships and differences between farmland productivity classes and farmland natural quality grades were explored at county scale in this paper. The farmland productivity grades and farmland natural quality grades in Hengdong County were respectively evaluated by dividing evaluation units with overlay methods, determining quantitative indexes with system cluster analysis, choosing qualitative indicators affecting assessment results with Delphi, computing evaluation factor weights with analytic hierarchy process （AHP） and establishing relational models between indicators and grades with Fuzzy mathematical method. The grade transition distribution was recorded using GIS overlay analysis and the regularities and reasons discussed. The results indicated that farmland productivity grade was one degree lower than farmland natural quality grade in Hengdong County. The proportion of the area of the first five grades of farmland natural quality was 91.29%, but only 74.37% for farmland productivity. The ratio of the area of high, medium and low grades of farmland productivity was 32 ： 42 ： 26, but 33 ： 43 ： 24 for farmland natural quality. The distribution law of the proportion of area was respectively greater for medium grade field than for high and low grades fields. In terms of percent distribution, significant differences were observed between paddy field and dry land in farmland productivity, higher grades （1, 2 and 3） were mainly distributed in paddy fields. Even distribution among different grades was noted in farmland natural quality. Gradetransition percent between farmland productivity grades and farmland natural quality grades clearly showed the extent of dif- ferences and spatial distributions of corresponding grades fields. The distribution order of transition percent was plain areas 〉 hilly areas 〉 mountainous areas. Differences in evaluation indicators and weights were the main factors for the differences between two evaluation methods. However, the differences in evaluation objects and sample points also induced some differences in the evaluation results for similar blocks in the two evaluation methods.