基于“要素-需求-调控”的云南坡耕地质量评价

Quality evaluation of slope farmland in Yunnan Province based on“element-demand-regulation”framework

坡耕地作为中国山丘区耕地资源的重要组成部分,科学评价其质量状况是实施坡耕地数量、质量、生态“三位一体”保护的基础。该文在分析坡耕地利用特征及质量内涵基础上,构建基于“要素-需求-调控”的坡耕地质量评价体系,对云南坡耕地质量进行定量化评价,分析坡耕地质量空间分布特征。结果表明:1)云南坡耕地质量评价最小数据集(MDS)指标体系由有效土层厚度、耕层厚度、土壤容重、土壤质地、土壤pH值、有机质、有效磷、速效钾、≥10℃积温、田块规整度、连片度、降雨量、灌溉保证率、田面坡度14个指标构成。2)坡耕地质量指数(Slope Farmland Integrated Fertility Index,SIFI)分布在0.36~0.81之间,均值为0.59,大部分评价单元SIFI<0.6,不同评价单元SIFI差异显著(P<0.05);5种坡耕地主要土壤类型SIFI从大到小依次为:赤红壤、红壤、紫色土、黄壤、黄棕壤;SIFI变化与高程有关,在0~1000 m高程范围内SIFI随高程增加呈增长趋势,而在>1000 m高程范围内SIFI随高程增加而减小。3)坡耕地质量等级以六等地、五等地、七等地、四等地为主,空间分布上呈现显著的聚集特征,不同分区坡耕地质量等级洛伦兹曲线均呈“S”型分布格局,云南坡耕地质量等级总体偏低。研究可为完善坡耕地质量评价体系,开展坡耕地质量调控提供科学依据。

Cultivated land being an essential natural resource,has been increasingly occupied in the last 60 years with the acceleration of urbanization.It is necessary to be careful in land use,in order to ensure food security and human existence.In addition,the quality degradation of cultivated land has seriously threatened to food security due to the misuse of land.Slope farmland,one type of cultivated land,is widely distributed in the plateau and mountain areas in the central and western China.Scientific quality evaluation of slope farmland is closely related to local food security and ecological environment,further to implement national protection schemes,such as the“Trinity”of quantity,quality and ecology.However,there are some features of slope farmland,such as wide distribution,large slope,soil erosion,frequent seasonal drought,low soil quality,to make accurate evaluation difficult.The evaluation index and model are also lacking.Taking the slope farmland in Yunnan as a research area,this study aims to construct a quality evaluation system of slope farmland based on the framework of“element demand regulation”.The 30 m×30 m grid(pixel)was selected as an evaluation unit for the comprehensive weight.The quality of slope farmland was evaluated quantitatively,together with its characteristics of spatial distribution.The results showed that:1)Index system of the Minimum Data Set(MDS)in quality evaluation of slope farmland consisted of 14 indexes,including the effective thickness of soil layer,arable layer thickness,bulk density of soil,soil texture,pH value of soil,organic matter,effective phosphorus,available potassium,accumulated temperature(≥10℃),field regularity,contiguity,amount of rainfall,assurance rate of irrigation,and field slope.2)Slope farmland Integrated Fertility Index(SIFI)was distributed between 0.36 and 0.81,with an average value of 0.59.Most evaluation units of SIFI was less than 0.6,showing a significant difference(P<0.05).The SIFI size relationship between five types of soil in slope farmland were ranked in order:Lateritic red earths,Red earths,Purplish soils,Yellow earths,Yellow-brown earths.SIFI increased with the elevation in the range of 0-1000 m,while decreased larger than 1000 m,indicating the variation of SIFI was related to the range of elevation.3)The quality of slope farmland can be Grade 6,5,7 and 4,according the national standard.Specifically,the quality of slope farmland was relatively high Grade 4 and 5 at the southern border,central,southeast,and western Yunnan,whereas,northeast and northwest Yunnan indicated low Grade 6 and 7.The Lorenz curve of quality grade showed a pattern of“S-type”distribution in different regions,indicating a low grade in Yunnan province.This finding can provide a scientific basis to improve the quality evaluation system of slope land,thereby to efficiently implement geological regulation of slope farmland.