How are the Spatio-Temporal Patterns of Vegetation Coverage and Biomass of Temperate Deserts in Central Asia and relationship of Climate Factors and Biomass?

Deserts are an important component in the terrestrial ecosystems. Although temperate deserts occupy nearly a quarter of the total global deserts, many previously regional studies focused more attention on hot deserts’ biomass instead of biomass in temperate deserts. Some previously studies have used the remote-sensing derived vegetation indices to estimate the biomass in deserts based on vegetation fractional coverage (VFC). However, the challenge of the estimation in the large deserts is enhanced due to the relatively weak spectral response of sparse desert vegetation and lack of field observations. Thus, it is in urgent need to explore the distribution of VFC and biomass as well as the relationship between climate factors and biomass in temperate deserts, especially those in Central Asia where more than 80% of the total global deserts is distributed.  

Central Asia, coving an area of more than 1×10⁷ km², comprises the vast dryland of the northwestern China, southwestern Mongolia Republic and the five Central Asia states of the former Soviet Union (i.e. Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan). Combining the 168 field observations conducted from 2010 to 2014 and the MODIS (Moderate Resolution Imaging Spectroradiometer) data, Prof. ZHANG Chi et al. analyzed the spatio-temporal patterns of VFC and biomass in the periods of 2000-2004 and 2010-2014, and the relationship between climate factors (temperature, precipitation and aridity) and biomass of the temperate deserts in Central Asia. 

In Central Asia, the temperate desert vegetation has an area of 3.6×10⁶ km², which mainly covers by the temperate semi-shrubs and dwarf semi-shrubs (occupying 36% of the total desert biomass). The mean VFC of the temperate desert was 19%, and the mean biomass density was 280 gm^-2. Compared with biomass in the period 2000-2004, the biomass in the period 2010-2014 did not show significant change. 

Precipitation, aridity and growing season temperature all had significant effects on the biomass. Precipitation had a stronger effect on the plant growth than temperature. The higher is the precipitation, the higher is the biomass density. In Central Asia, as the precipitation was higher in the west than in the east, VFC and biomass density also decreased from west to east. The plants usually grew better on the windward slopes of the mountains. 

This study was published in Remote Sensing of Environment in 2016. 

Contact: ZHANG Chi 

E-mail: zc@ms.xjb.ac.cn 

State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography (http://english.egi.cas.cn/)