Abstract
The sustainability of vulnerable eco-environment over the Silk Road Economic Belt is under threat of climate change, and the identification of vegetation constraints by sub-optimum climatic conditions is critically essential to maintain existing dryland ecosystems. To better understand how the vegetation varies at monthly scale and its effect by climate conditions in different desert areas, this study first investigated the seasonal variation of the normalized difference vegetation index (NDVI). Then, we analyzed the time effects of diverse climatic factors (air temperature, solar radiation, precipitation) on NDVI and estimated the limitation of NDVI by these climatic factors in different desert areas. The result showed that the mean monthly NDVI during 1982–2015 showed a unimodal variation in most desert areas, with high values in late spring and summer over cold arid areas, in early spring or early autumn over hot arid areas, and in summer over polar areas, respectively. Solar radiation and precipitation in cold arid areas presented 1–2 month lag or accumulation effect on NDVI, while precipitation in most hot arid areas showed no remarkable time-lag but 3 month accumulation effect, and all three climate factors in polar areas exhibited 1–3 month accumulation effect. The explanatory power of climatic conditions for vegetation dynamics considering time effects increased by 3.4, 10.8, and 5.9% for the cold arid areas, hot arid areas, and polar areas (i.e., relative increase of 4.1, 25.4, and 8.2%), respectively. The main climatic constraints to vegetation dynamics were the water condition in hot arid areas (>78%) and the temperature condition in polar areas (>67%), while cold arid areas were simultaneously limited by the water and temperature conditions (>76% in total). These results provide a detailed understanding of vegetation variation and ecological projection, which are very important to implement adaption measures for dryland ecosystems over the Silk Road Economic Belt.
Highlights
Vegetation growth is frequently constrained by sub-optimum climatic conditions, such as inadequate precipitation, low temperatures, and high cloudiness
Two fundamental questions remain: (i) How do the vegetation vary with climate conditions considering the time effects? (ii) To what extent do diverse climatic factors limit vegetation growth in different desert areas? the objective of our study was to investigate the spatiotemporal characteristics of vegetation dynamics and quantify its effect by climatic conditions over the Silk Road Economic Belt
In the whole study region, most of the minimum normalized difference vegetation index (NDVI) appeared in winter and early spring; it is interesting that both the hot arid desert semi-desert area and the hot arid desert shrub area had the lowest
Summary
Vegetation growth is frequently constrained by sub-optimum climatic conditions, such as inadequate precipitation, low temperatures, and high cloudiness. Precipitation represents the maximum amount of accessible water to natural vegetation, especially in the arid and semi-arid regions [1]. Temperature partly determines the photosynthetic rates of vegetation, and plants that grow in cold climates usually have lower productivity than these in the warmer environments [2]. Cloudiness will affect solar radiation and further influence the vegetation growth, because the photosynthesis only occurs in environments with sufficient light [3]. Previous studies revealed that water availability, temperature, and radiation limited vegetation growth over 40–52%, 31–33%, and 5–27%. Of the land areas, respectively [4,5]. The grassland regions of Asia and Remote Sens.
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