【作者】 王涛；

【导师】 于雷；

【作者基本信息】 华中师范大学 ， 地理学， 2022， 硕士

【摘要】 稻虾综合种养模式(以下简称“稻虾模式”)自2015年以来规模扩大迅速,已成为我国长江中下游地区常见的耕地利用方式之一,稻虾田亦逐渐成为科学家们的研究对象。学者们早期主要关注单块稻虾田土壤有机碳的组成、剖面垂直分布,之后揭示了种养时间对稻虾田土壤有机碳的影响,进而探讨了稻虾模式对资源利用率、对水稻产量以及对生态环境的影响等,最后发现稻虾模式对土壤固碳具有促进作用。这符合全世界共同追求的目标——碳减排,对我国实现碳中和目标具有积极意义。然而,稻虾田多为农户自发开垦,地方政府难以掌握稻虾田的空间变化情况,更难以有效调控稻虾田的规模和科学引导稻虾产业发展,因此,亟需探索高精度识别稻虾田的方法。另外,学者们聚焦于稻虾模式和纯水稻种植对土壤有机碳含量的影响,却忽视了稻虾田转自地类的土壤特性,因此,有必要分析不同土地利用类型的地块转变为稻虾田后田面和虾沟土壤有机碳含量,尝试揭示不同转自地类稻虾田随时间变化对土壤有机碳的影响。本文基于谷歌地球引擎平台(Google Earth Engine,以下简称GEE),利用2016-2020年Sentinel-2多光谱成像仪的2A级遥感影像数据,逐年度构建光谱特征、纹理特征、地形特征等分类特征指标,采用随机森林分类方法得到了5个年度的湖北省潜江市土地利用分类结果,从中提取每个年份的稻虾田识别结果,获得稻虾田和其他地类的动态转换过程。选取转自于水稻田、无水田、水域、林地、建设用地的一年期、三年期、五年期稻虾田,采集稻虾田的田面和虾沟的土壤样品,采用重铬酸钾-外加热法测得土壤有机碳,分析不同转自地类稻虾田土壤有机碳含量的特性。本文研究得到以下结论:(1)2016-2020年潜江市土地利用分类结果的总体精度均在89%以上,其中2016、2017、2018、2020年超过90%;各年的Kappa系数均在87%以上,其中2016年和2017年超过88%。(2)潜江市稻虾田主要分布于全市的西北部、西部和中部地区,面积逐年增加。(3)水稻田集中分布在西部、南部、东南部,其面积占比一直最大;无水田主要分布在北部、东部,及东荆河两岸,其面积占比总体上在减少;林地主要分布在东荆河、田关河、西荆河等河流两岸,相较于其他地类,其面积占比最小;建设用地分布分散,主要集中分布在市区和乡镇中心,其占地面积变化幅度最小。(4)不同转自地类稻虾田在不同种养年份的田面和虾沟表层(0-20cm)土壤有机碳含量存在明显差异。且同一块稻虾田的田面和虾沟土壤有机碳含量差距明显。(5)各地类转变为稻虾田后,田面土壤有机碳含量高于原有地类的样地数量占总样地数量的70%,但不同转自地类对虾沟表层土壤有机碳含量都无显著性影响(p>0.05)。本研究在实现对稻虾田精确识别的基础上,创造性的提出了分析不同转自地类稻虾田在不同种养年份田面和虾沟表层土壤有机碳含量的差异,揭示稻虾田对土壤有机碳的影响。这对稻虾模式和稻虾产业的发展具有促进作用,有利于实现对稻虾田的动态监测和稻虾产业的市场预测、调控,可为后续相关研究和政策的规划提供借鉴。更多还原

【Abstract】 The rice crayfish comprehensive planting and breeding model has expanded rapidly since 2015,and has become one of the common cultivated land use modes in the middle and lower reaches of the Yangtze River in China.Rice crayfish field has gradually become the research object of scientists.In the early stage,scholars mainly focused on the composition and vertical distribution of soil organic carbon in a single rice crayfish field.Then they revealed the impact of planting and breeding time on soil organic carbon in rice crayfish field,and then discussed the impact of rice crayfish model on resource utilization,rice yield and ecological environment.Finally,they found that rice crayfish model promoted soil carbon sequestration.This is in line with the common goal of the world-carbon emission reduction,which is of positive significance for China to achieve the goal of carbon neutrality.However,rice crayfish fields are mostly reclaimed spontaneously by farmers,It is difficult for governments to grasp the spatial changes,and it is more difficult to effectively regulate the scale of rice crayfish field and scientifically guide the development of rice crayfish industry.Therefore,it is urgent to explore the method of high-precision identification of rice crayfish field.In addition,scholars focused on the impact of rice crayfish model and pure rice planting on soil organic carbon content,but ignored the soil characteristics of rice crayfish field transferred from land.Therefore,it is necessary to analyze the content of soil organic carbon on the field surface and shrimp ditch after the transformation of plots with different land use types into rice crayfish field,and try to reveal the impact of the change of rice crayfish field with time.Based on Google Earth engine,this paper uses the 2A remote sensing image data of sentinel-2 multispectral imager from 2016 to 2020,the classification indexes such as spectral features,texture features and topographic features are constructed year by year,and the land use classification results of Qianjiang City,Hubei Province in five years are obtained by using the random forest classification method,the recognition results of rice and shrimp fields in each year are extracted,and the dynamic transformation process between rice and shrimp fields and other land types is obtained.One year,threeyear and five-year rice crayfish fields transferred from fields without water,paddy field,water area,forest land and construction land were selected.The soil samples of field surface and shrimp ditch of rice crayfish field were collected.The content of soil organic carbon was measured by potassium dichromate external heating method,and the characteristics of soil organic carbon content of rice crayfish fields transferred from different land types were analyzed.The conclusions of this study are as follows:(1)From 2016 to 2020,the overall accuracy of land use classification results in Qianjiang City was more than 89%,of which more than 90%in 2016,2017,2018 and 2020;The kappa coefficient of each year is more than 87%,including more than 88%in 2016 and 2017.(2)Rice crayfish field in Qianjiang City is mainly distributed in the northwest,West and central regions of the city,with an area increasing year by year.(3)Paddy fields are concentrated in the west,South and Southeast,and their area proportion has always been the largest;Fields without water is mainly distributed in the north,East and both banks of Dongjing River,and its area proportion is decreasing on the whole;Forest land is mainly distributed on the banks of Dongjing River,Tianguan River,Xijing River and other rivers,and its area accounts for the smallest proportion compared with other land types;The distribution of construction land is scattered,mainly concentrated in urban areas and township centers,and the change range of its floor area is the smallest.(4)Soil organic carbon content of rice crayfish field transformed from different land types is significantly different in the field surface and shrimp ditch surface(020cm)in different planting and breeding years.The difference of soil organic carbon content between field surface and shrimp ditch in the same rice crayfish field is obvious.(5)After other land use types were transformed into rice crayfish field,the number of plots with higher soil organic carbon content than the original land type accounted for 70%of the total sample plots,but different land types had no significant effect on the content of surface soil organic carbon in shrimp ditch(P>0.05).Based on the accurate identification of rice crayfish field,this study creatively proposed to analyze the differences of soil organic carbon content on the field surface and shrimp ditch surface of rice crayfish field transformed from different land use types in different planting and breeding years,and reveal the impact of rice crayfish field on soil organic carbon.This will promote the development of rice crayfish model and rice crayfish industry,help to realize the dynamic monitoring of rice crayfish field and the market prediction and regulation of rice crayfish industry,and provide reference for subsequent relevant research and policy planning.更多还原