杭州余杭区农田耕层土壤有机碳空间分布特征及其影响因素

Spatial distribution characteristics of topsoil organic carbon in farmland and its influencing factors in Yuhang District,Hangzhou City

利用杭州市余杭区耕地地力调查采集的2 814份土壤样品,基于GIS技术研究了余杭区耕层土壤有机碳(topsoil organic carbon,TOC)的空间分布状况,并探讨了影响该地区TOC的因素。结果显示,余杭区TOC密度大致以崇贤镇为中心、以仓前镇为副中心呈辐射状向周围递减,全区TOC密度达46.3 t·hm-2,高于全国平均水平。从立地条件看,TOC密度表现为水网平原>河谷平原>低山丘陵>滨海平原。从耕层理化性状来看,随着耕层黏粒量的增加,TOC密度逐渐增大,表现为砂土<壤土<黏壤土<黏土;近中性和中性的TOC密度较高,酸性和碱性的土壤都不利于土壤固碳;阳离子交换量(cation exchange capacity,CEC)较大的土壤固碳能力较强;在一定范围内TOC随着容重的增加而减少,但过高的容重也会增加TOC密度。从耕层养分看,全氮、速效钾均与TOC密度成正相关。在土地利用方面,耕地的TOC密度略高于园地。从土壤类型看,各类土壤的TOC密度存在差异,表现为水稻土>潮土>粗骨土>石灰(岩)土>红壤>紫色土>黄壤,水稻土TOC密度和有机碳库储量均最大,黄壤最小。

According to the farmland fertility survey sampling criterion,the spatial distribution of TOC（ topsoil organic carbon） density was depicted by GIS based on 2 814 soil samples collected in Yuhang District. Besides,potentially influencing factors TOC density were discussed. It was shown that the highest TOC density was found in the center of Chongxian Town and in the sub-centre of Cangqian Town in Yuhang District,and the spatial distribution of TOC density were radially decreasing from the center. The TOC density in Yuhang District was up to 46. 3 t·hm- 2,which was above the national average. From the perspective of site conditions,the TOC density was decreased as alluvial plain 〉 valley plain 〉 hilly 〉 coastal plain. From the view of topsoil physicochemical properties, the TOC density was gradually increasing with the elevated amount of clay in topsoil. The TOC density increased as sandy 〈 loam 〈 clay loam 〈 clay. The TOC density in near-neutral and neutral soil was higher, while acidic and alkaline soils were not conducive to soil carbon sequestration. Soils with larger CEC （ cation exchange capacty） possessed a stronger ca- pacity of soil carbon sequestration. Within a certain range, with the increasing of bulk density, the density of farm- land TOC was decreasing. But the relatively high bulk density would also increase TOC density. From the perspective of topsoil nutrients, total nitrogen and available potassium were all positively correlated with TOC density. In terms of land use, TOC density in farmland was slightly higher than those in gardens. From the perspective of soil types, TOC density decreased in the order of paddy soil 〉 alluvial soil 〉 skeletal soil 〉 limestone （rock） soil 〉 red soil 〉 purple soil 〉 yellow soil. Paddy soils exhibited the highest TOC density and the largest organic carbon storage, while the yellow soils showed the lowest TOC density and the smallest organic carbon storage.