摘要:藏碳于土是减少温室气体排放的重要途径，紫云英等绿肥回田能显著促进土壤有机碳积累，且培肥地力，但至今有关其种植布局的研究极少结合用地适宜性和固碳培肥现实需求性进行探讨。本文以福建省浦城县为研究区，借助GIS与修正的加权指数和、动态聚类等数学模型集成技术，在基于1：5万比例尺的区域紫云英用地适宜性评价和耕层土壤碳密度分析的基础上，以适宜性和耕层土壤有机碳密度为指标，遵循最适宜生长和耕层土壤碳密度较低的耕地优先安排为种植用地的原则，将研究区紫云英优化种植区划分为优先、次优先和一般种植区。结果表明，研究区81.82%的耕地不同程度地适宜种植紫云英，耕层有机碳密度介于2.50~5.74 kg·m-2，空间差异较为明显。经优化布局的研究区紫云英用地面积占耕地总面积的59.72%，以优先种植区和次优先种植区占优势，分别占研究区紫云英优化布局用地总面积的25.72%和50.34%；其中耕地土壤固碳培肥需求较为强烈的莲塘、水北、古楼、永兴和忠信等乡镇可作为紫云英重点种植区，富岭、仙阳、石陂和九牧等乡镇可作为紫云英种植的后备种植区。基于土地适宜性和固碳需求，择优选取紫云英适宜种植区域，对于其高效种植利用、区域耕地土壤有机质提升计划的科学实施以及耕地质量的有效提高具有重要指导意义。
关键词:紫云英/
固碳/
适宜性/
土壤有机碳密度/
数学模型集成/
优化布局
Abstract:Soil carbon sequestration is an important way to reduce greenhouse gas emissions. Milk vetch and other green manures importantly impact annual variations of CO2 concentration in the atmosphere by promoting soil organic carbon accumulation and improving cropland soil fertility. However, research on the optimal arrangement of milk vetch plantation had to-date been hardly integrated with the suitability croplands for milk vetch plantation and realistic need for soil carbon sequestration. This study aimed to arrange milk vetch in the most suitable areas and fix as much CO2 as possible. Thus the suitability of milk vetch plantations in croplands was evaluated by analyzing soil organic carbon density (SOCD) in croplands based on the 1:50 000 scale database of land use/soil pattern in Pucheng County, Fujian Province. The optimal arrangement of milk vetch plantations in Pucheng was done using an integrative method in GIS environment. Then the modificatory weighted index sum method and dynamic clustering analysis were used for both land suitability and SOCD by dividing the index based on the principle of land suitability for milk vetch plantation and carbon sequestration needs of croplands. The priority, sub-priority and general plantation areas of milk vetch in Pucheng were optimally arranged based on the principles of preferential arrangement of croplands with low topsoil SOCD and high suitability for milk vetch growth. The results showed that 81.82% of the croplands in the study area had various suitability of milk vetch plantation. If milk vetch was planted in all the cultivated lands in the study area, the annual total yield of fresh milk vetch and application rate of green manure were 657 056.65 t and 27.75 t·hm-2, respectively; the annual carbon sequestration and the cultivated land area for which milk vetch pro-vided organic carbon sources would be 29 900.74 t and 23 677.72 hm2, respectively. The range of SOCD in the study area was 2.50-5.74 kg·m-2, differing sharply in space. On the basis of total cropland in Pucheng County, optimal area arrangement for milk vetch plantation was 59.72%, of which priority and sub-priority regions dominantly accounted for 25.72% and 50.34%, respectively. Priority region was mainly distributed in the basin area, sub-priority region distributed in the 200-400 m altitude range with gentle slope terraces, while general region was located in 250-800 m altitude range on slope terraces. The towns (including Liantang, Shuibei, Gulou, Yongxing and Zhongxin), which most needed soil carbon sequestration, were planned as the key developing areas. Then towns (e.g., Fuling, Xianyang, Shipi and Jiumu) were planned as the reserve areas for milk vetch plantation. The study provided the guide for the efficient planting and utilization of milk vetch. This showed the need to increase scientific implementation of soil organic matter programs and the continuous improvement of farmland quality by preferentially selecting suitable areas for milk vetch planting based on land suitability and carbon sequestration needs of croplands.
Key words:Milk vetch/
Carbon sequestration/
Suitability/
Soil organic carbon density/
Integration of mathematic models/
Optimal arrangement
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