Responses of Vegetation Growth to Climatic Factors in Shule River Basin in Northwest China: A Panel Analysis

Abstract

Abstract:The vegetation response to climatic factors is a hot topic in global change research. However, research on vegetation in Shule River Basin, which is a typical arid region in northwest China, is still limited, especially at micro scale. On the basis of Moderate-resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data and daily meteorological data, employing panel data models and other mathematical models, the aim of this paper is to reveal the interactive relationship between vegetation variation and climatic factors in Shule River Basin. Results show that there is a widespread greening trend in the whole basin during 2000-2015, and 80.28% of greening areas (areas with vegetation improvement) are distributed over upstream region, but the maximum vegetation variation appears in downstream area. The effects of climate change on NDVI lag about half to one month. The parameters estimated using panel data models indicate that precipitation and accumulated temperature have positive contribution to NDVI. With every 1-mm increase in rainfall, NDVI increases by around 0.223‰ in upstream area and 0.6‰ in downstream area. With every 1-• C increase in accumulated temperature, NDVI increases by around 0.241‰ in upstream area and 0.174‰ in downstream area. Responses of NDVI to climatic factors are more sensitive when these factors are limiting than when they are not limiting. NDVI variation has performance in two seasonal and inter-annual directions, and the range of seasonal change is far more than that of inter-annual change. The inverted U-shaped curve of the variable intercepts reflects the seasonal change. Our results might provide some scientific basis for the comprehensive basin management.

Spatio-Temporal Variation of Land-Use Intensity from a Multi-Perspective—Taking the Middle and Lower Reaches of Shule River Basin in China as an Example

“…After 1996, because of the implementation of policies such as "Integrated Development of Agricultural Irrigation and Immigrant Settlement in Shule River Basin (1996-2006)", "Reconstruction of Hexi (1997)", and "Western Development (2000)", as well as the progression of industrialization and urbanization, the population increased rapidly and gradually transferred to urban areas. This led to the expansion of the urban construction area and increase in HAL-AL [37][38][39]44]. Meanwhile, because of the immigrant project, people's needs for food and profits increased.…”

“…As the global climate changes, interference from human activities has exacerbated the regional land use and land coverage, which influences the intensity of land use. However, human activities are mainly affected by the policies as the result of natural background superimposition and artificial influence [38]. From the investigation of three inland river basins in the Hexi Corridor of Gansu Province, development intensity of land resources is different from east to west (Shiyang River development and utilization up to 171%, Hei River development and utilization rate to 92%, Shule River development and utilization rate to 75%), the contradiction between "man and land" also gradually gets slow from the east to the west [39,40,60].…”

“…Meanwhile, no large-scale immigrant development in the two major basins is constructed, and land resources are in a state of incremental development after the founding of the People's Republic of China. On the contrary, large-scale migration development in the middle and lower reaches of the Shule River basin has been carried out under the promotion of national policies [38,39,44,45]. "The comprehensive development project for agricultural irrigation and resettlement in the Shule River" lasted 10 years, and was initiated in 1996, which was the most recent and largest organized migration to the basin [37].…”

“…Additionally, the areas of infrastructure, public service facilities, and residential land for immigrant housing are also increasing, with expected increases of 5.62 hm 2 in ten years due to a large number of immigrants. Large-scale immigration and land development changed the ways of land use [37][38][39][40]. Artificial and semi-artificial lands gradually replaced some part of the natural and semi-natural lands.…”

“…They include land-cover change and land-use "Grain for Green Project", etc., which directly or indirectly influenced land use in Shule River Basin. Recently, a lot of research on Shule River Basin has been carried out from perspectives of land use/cover changes, quality of ecosystem, ecological and environmental effects and so on [37][38][39][40]. Nonetheless, these studies do not consider spatio-temporal variation of land-use intensity and variation caused by immigration, national policies, technologies, and other human activities.…”