浙北平原地区耕地非粮化时空演变特征及碳排放效应分析

    Spatiotemporal evolution and carbon emission on non-grain production of cultivated land in the Northern Plains of Zhejiang Province, China

    • 摘要: 掌握耕地非粮化的时空演变特征及其碳排放效应,对于保障粮食安全和发展低碳绿色农业具有重要意义。研究以东部浙江省平原县桐乡市为例,运用遥感技术和GIS空间分析探讨耕地非粮化类型和时空演变特征,并采用生命周期评价法评估不同耕地非粮化类型的碳排放效应。研究表明:1)桐乡市2005—2020年耕地非粮化率由1.56%提升至7.50%,非粮化面积净增加2 464.74 hm2,在空间上呈现团状集聚型格局,高值集聚区分布在西南远郊水网密布地区。2)耕地非粮化的坑塘养殖类型面积占比最大,其次为苗木种植和蔬菜大棚,2005—2020年耕地非粮化主导类型由苗木种植为主转变为多类型交错分布模式。3)2005—2020年桐乡市耕地非粮化导致的碳排放量由22 232.56 t增长至98 945.40 t,其中坑塘养殖对碳排放量的贡献最大,2020年达到83.7%;在空间上呈现西南远郊高值集聚、中部近郊低值环状分布的态势。在保障区域粮食安全的前提下,应结合不同非粮化类型的碳排放效应,分区域、分类别地实施耕地非粮化管控,实现耕地保护和低碳利用协同发展。

       

      Abstract: Non-grain production refers to the mode in which the farmland of grain cultivation is occupied by cash crops, forests, fruits, or the stock-breeding industry. It is very necessary to identify the spatial and temporal evolution of non-grain production and then to examine the carbon emission, particularly for the national food security and low-carbon green agriculture. However, it is still lacking in the different types and their carbon emission of non-grain production at a fine scale. Differentiated control and management have been hindered on the non-grain production from a low-carbon perspective. Taking the Tongxiang City of Zhejiang Province in east China as an example, this study aims to explore the different types of non-grain production in the cultivated land, including nursery plantation, pit-pond aquaculture, livestock and poultry farming, and greenhouse vegetable production. Their spatial and temporal evolution was also determined using remote sensing and GIS spatial analysis. Global Moran’s I index and local Moran’s I statistics were used to evaluate the spatial distribution and agglomeration of non-grain production types over the years. The life cycle and the opportunity cost method were then applied to assess the carbon emission using field survey data. The results showed that: 1) The non-grain production rate of cultivated land increased from 1.56% to 7.50% from 2005 to 2020, where the non-grain production area had a net increase of 2,464.74 hectares. In terms of the distribution of non-grain production, there was significant spatial clustering, where the high-value agglomerations were distributed in the far southwestern suburbs with a dense water network. 2) Pit-pond aquaculture accounted for the largest proportion of non-grain production, followed by nursery plantation and greenhouse vegetable production. The evolution of non-grain production was shifted from the dominant type of nursery plantation to the staggered distribution of multiple types in the end. 3) Carbon emissions due to non-grain production increased from 22 232.56 to 98 945.40 t from 2005 to 2020, of which pit-pond aquaculture contributed the most. Moreover, the carbon emission from the pit-pond aquaculture accounted for 83.7% of the total in 2020. The largest contributors to the carbon emissions of nursery plantation and greenhouse vegetable production were various fertilizer inputs and plastic film inputs, respectively, while the main sources of carbon emissions from the pit-pond aquaculture and livestock and poultry farming were direct emissions of CH4 and N2O. Meanwhile, the carbon emissions of non-grain production showed a trend of high-value agglomeration in the far southwest and low-value ring distribution in the central suburbs. The carbon emission should consider the different types of non-grain production for regional food security. The management of non-grain production should be implemented under the regional types. The synergistic development can be achieved in cultivated land protection and low-carbon emission reduction in agricultural production.

       

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