基于生物量的黄土丘陵沟壑区小流域生态恢复评价

发布时间：2018-07-29 08:33

【摘要】：灌草地上生物量是反映植被生长状况的重要指标,是评价区域植被恢复情况的重要手段,植被恢复又是区域生态恢复状况的直观体现,以灌草地上生物量为基础评价区域生态恢复情况是可行的。本文以位于黄土丘陵沟壑区第二副区的彭阳县不同生态分区8个典型小流域为研究区,以2005年、2014年两期高分辨率遥感影像为数据,基于RS、GIS技术,在R软件支持下,应用GAM模型、空间分析等方法,利用灌草地上生物量评价小流域生态恢复情况。首先,通过目视解译2005年和2014年高分辨率遥感影像,获取小流域两年的土地利用一级分类现状数据,在ArcGIS平台下,分析不同生态分区中小流域土地利用变化。其次,在ENVI软件支持下,提取各小流域植被指数,将实地调研数据与归一化植被指数(NDVI)进行回归分析,建立灌草地上生物量估测模型,估算小流域灌草地上生物量,分析在土地利用变化下灌草地上生物量变化情况,得到不同生态分区中各小流域灌草地上生物量变化情况。最后,根据小流域自身地貌特征,利用ArcGIS软件地形分析,提取各小流域海拔、坡度、坡向等地形因子,在R软件支持下,将地形因子与2014年实地调研得到灌草地上生物量构建GAM模型,分析灌草地上生物量与地形之间的关系。利用ENVI软件,制作灌草地上生物量空间分布图,分析各小流域灌草地上生物量空间分布异同,并根据各小流域不同的生态恢复措施、水土保持治理方式,分析灌草地上生物量与生态恢复措施、土地利用类型间的关系。研究从土地利用变化角度入手,分析小流域植被覆盖变化情况,利用NDVI估算小流域灌草地上生物量,显示其空间分布状况,最后通过研究灌草地上生物量与地形因子、生态恢复措施之间的关系,评价小流域生态恢复状况,为小流域植被恢复、水土保持治理、生态恢复提供支持。研究主要结论如下:(1)小流域土地利用变化方面,彭阳县8个典型小流域土地利用变化明显,耕地面积显著减少,草地、林地面积增加。对于处在不同生态分区的小流域土地利用变化各有特点:位于北部丘陵沟壑水土流失治理区的安家川流域,沟道纵横,传统耕作模式不仅效率低下,且易造成水土流失,通过实施退耕还林、坡改梯等生态恢复工程,耕地明显减少,林地增幅最大。位于中西部台地旱作农业保护区中的王洼沟、高建堡、李家沟流域,此区域地势相对平缓,草地面积增加的同时,根据区域特色,区域内园地面积有所增加;李家沟流域治理更多采用灌草混交的模式,林地面积转化为草地。位于南部河谷残塬农业耕作区罗堡子沟、后沟、茹河流域,受生态移民安置等方面影响,城镇村及工矿用地面积有所增加,未利用地等其他土地面积显著减少。位于西南部森林水源涵养区的红河流域,属六盘山山区,水源充足,土壤含水量较高,更宜乔木等大型树木生长,林地面积增加明显。(2)小流域灌草地上生物量变化方面,彭阳县8个典型小流域灌草地上生物量显著增加。其中,高建堡流域、王洼沟流域、罗堡子沟流域灌草地上生物量增加较为突出,增幅分别为48.87%、38.35%、28.19%;红河流域、后沟流域灌草地上生物量增长幅度最小,增幅分别为7.49%、8.92%。说明10年间彭阳县植被恢复整体较好,4个生态分区植被覆盖度均有增加。其中植被恢复程度最好的为中西部台地旱作农业保护区,在实施“88542”、水平阶等整地措施下,植被生境得到有效保护;北部丘陵沟壑水土流失治理区因其自然环境相对恶劣,在生态恢复措施实施下,灌草地上生物量也有增长;南部河谷残塬农业耕作区、西南部森林水源涵养区灌草地上生物量增幅较小,但其土壤水分条件相对较好,植被覆盖基础较好,在生态恢复措施的实施下,植被生境得到进一步保护,灌草地上生物量同样有所增加。(3)应用高分辨率遥感影像,分别提取2005年、2014年4个不同生态分区的8个小流域提取归一化植被指数(NDVI)。对两期影像NDVI值通过建立回归模型,探寻其函数关系,建立转换方程SPOTNDvI = 0.8983 ZY-3NDVI +0.0598(R2 = 0.805),减小不同传感器遥感影像由于定标参数不同产生的差异,为估算各小流域灌草地上生物量提供可靠数据。(4)小流域灌草地上生物量与地形因子相关性明显,地形因子影响灌草地上生物量分布大小依次为坡向、海拔、坡度。海拔在1470～1620m、1750～1840m之间正东坡区域植被生物量分布较多,植被生长情况较好:海拔在1620～1750m之间的正南、正北坡,灌草地上生物量分布较少,植被生长状况相对较差。这同时也反映出随地形变化,植被生长所需的光、水、热等要素也随之变化,进一步影响植被生长。(5)各小流域2014年灌草地上生物量均高于2005年,灌草地上生物量空间分布特点与小流域土地利用状况联系密切,土地利用方式决定区域灌草地上生物量分布情况,林地地上生物量最高,其次为草地,耕地。各小流域土地利用方式得到有效利用,林地、草地面积增加,植被覆盖度增加明显,流域生态环境得到较大改善,实施生态恢复措施对小流域生态恢复作用显著。
[Abstract]:The biomass on the grassland is an important indicator to reflect the vegetation growth, and it is an important means to evaluate the restoration of regional vegetation. The restoration of vegetation is an intuitive embodiment of the ecological restoration of the region. It is feasible to evaluate the ecological restoration of the region on the basis of the biomass of the grassland. This paper is located in the second sub regions of the Loess Hilly and gully region. 8 typical small watershed of different ecological areas in Pengyang county are the research areas. With 2005 and 2014, the two periods of high resolution remote sensing images are data. Based on RS, GIS technology and R software, GAM model and spatial analysis are applied to evaluate the biological recovery of small watershed using the biomass on the grassland. First, it is interpreted by visual interpretation in 2005 and 2014. The high resolution remote sensing image is used to obtain the status data of the first class classification of land use for two years. Under the ArcGIS platform, the land use change of small and medium watershed in different ecological areas is analyzed. Secondly, under the support of ENVI software, the vegetation index of each small watershed is extracted, and the field survey data and the normalized vegetation index (NDVI) are regressed and established. The biomass estimation model on the grassland is used to estimate the biomass on the irrigation grassland in the small watershed, and the biomass changes on the grassland under the land use change are analyzed. The changes in the biomass of the small watershed on the grassland are obtained. Finally, according to the characteristics of the small catchment's own geomorphology, the small watershed is extracted by the ArcGIS software topographic analysis. In the support of altitude, slope, slope direction and other topographic factors, under the support of R software, the GAM model was constructed by topographic factors and the field survey on the grassland in 2014. The relationship between biomass and terrain on the grassland was analyzed. The spatial distribution of biomass on the irrigation grassland was made by using ENVI software, and the spatial distribution of biomass on the irrigation grassland was analyzed. According to the different ecological restoration measures and the ways of soil and water conservation, the relationship between the biomass and ecological restoration measures and the relationship between land use types was analyzed. The change of vegetation coverage in small watershed was analyzed from the angle of land use change, and the biomass of the small watershed was estimated by NDVI. In the end, the relationship between the biomass and topographic factors and the ecological restoration measures on the grassland was studied, and the ecological restoration of the small watershed was evaluated, which provided support for the vegetation restoration, soil and water conservation and ecological restoration. The main conclusions are as follows: (1) 8 typical small streams in Pengyang county with the change of land use in small watershed. The land use change is obvious, the area of cultivated land is reduced significantly, and the area of grassland and woodland is increased. The ecological restoration projects such as returning farmland to forest, slope change and other ecological restoration projects, the cultivated land is obviously reduced and the forest land has the greatest increase. It is located in Wang Wa gully, high building fort and Lijia gully Valley in the dry farming protection area of central and Western Taiwan. The area is relatively flat, the area of grassland is increased, and the area of garden area has increased in the area according to the regional characteristics; the treatment of Li Jia gully basin. The land area in the agricultural and tillage areas of the Southern River Valley, the rear gully and the Ru River Basin, is affected by the ecological resettlement, and the area of urban villages and industrial and mining land has been increased, and the area of other soil and land in the unused land has been significantly reduced. It is located in the water conservation area of the southwest forest. The Honghe River Basin, which belongs to the six Panshan mountain area, has abundant water source, higher soil water content, more suitable trees and other large trees, and the forest area increases obviously. (2) the biomass of the 8 typical small basins in Pengyang county is significantly increased in the irrigation area of the small watershed. The increase of biomass on grassland was more prominent, the increase was 48.87%, 38.35%, 28.19%, and the minimum growth rate of biomass in the Red River Basin was 7.49%. 8.92%. indicated that the restoration of vegetation in Pengyang county was better in 10 years, and the vegetation coverage of 4 ecological areas increased. Under the implementation of the "88542", the horizontal order and other measures, the vegetation habitat is effectively protected. In the northern hilly and gully soil erosion control area, the natural environment is relatively bad, and the biomass of the grassland is increased under the implementation of ecological restoration measures; the agricultural cultivation area in the Southern Valley of the tableland, the south-west forest water. In the source conservation area, the growth of the biomass on the grassland was relatively small, but the soil moisture conditions were relatively good, the vegetation cover foundation was better. Under the implementation of the ecological restoration measures, the vegetation habitat was further protected and the biomass of the grassland was increased. (3) the high resolution remote sensing images were used to extract 4 different ecological zones in 2005 and 2014 respectively. 8 small basins are extracted and normalized vegetation index (NDVI). The NDVI values of the two phase images are established by establishing regression models to explore the function relationship, and the transformation equation SPOTNDvI = 0.8983 ZY-3NDVI +0.0598 (R2 = 0.805) is established to reduce the difference of the different sensor images due to the different calibration parameters, so as to estimate the biomass on the irrigation grassland of each small watershed. Provide reliable data. (4) the correlation between biomass and topographic factors on the irrigation grassland of small watershed is obvious, and the topographic factors affect the distribution of biomass on the grassland in order of slope direction, elevation, slope, elevation from 1470 to 1620m, and the vegetation biomass distribution in the east slope area between 1750 and 1840m, and the vegetation growth is better: from 1620 to 1750m In the South and the north slope, the biomass distribution on the grassland is less and the growth of vegetation is relatively poor. This also reflects the changes of the light, water and heat as the terrain changes, and further affect the vegetation growth. (5) the biomass of each small watershed in 2014 was higher than that in 2005, and the biomass space on the grassland was divided. The characteristics of the cloth are closely related to the land use status of small watershed. The land use mode determines the distribution of biomass on the grassland, the highest biomass on the woodland, followed by the grassland and the cultivated land. The land use mode of each small watershed is effectively utilized, the forest land, the grassland area is increased, the vegetation coverage is increased obviously, and the ecological environment of the basin has been compared. Great improvement and implementation of ecological restoration measures played a significant role in ecological restoration of small watershed.
【学位授予单位】：宁夏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X171.4;X826

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