The Influence Of Vegetation On Reflected Solar Radiation In Arid And Extra-Arid Zone Of Mongolian Gobi

Viktor P Dedkov,S Khadbaatar,Elena V Danzhalova,Peter D Gunin,Sergey N Tkachenko,Sergey N Bazha,E Ariunbold

doi:10.24057/2071-9388-2020-91

Abstract

Vegetation cover has a noticeable effect on surface reflectivity and local microclimate in arid areas of Mongolian Gobi. Over the past decades, various shrub species (Haloxylon ammodendron and Calligonum mongolicum) have appeared on the previously unvegetated hamada. The climatic consequences of bush encroachment are still poorly understood. Using the experimental data, this article estimates the reflectance of plants dominating in Mongolia’s dry steppe, desert-steppe, and desert ecosystems. The average values of the total reflection coefficient at visible and infrared wavelengths range from 19.7% ± 1.4% to 20.1% ± 1.7% in plants growing in desert-steppe ecosystems, and from 25.0% ± 0.9% to 24.8% ± 1.5% on the bare surface. The difference between the reflectance of vegetated and unvegetated surfaces reaches 5%. Therefore, in daylight hours, the vegetated day surface loses less solar energy than the non-vegetated surface does. This phenomenon may be defined as a quasi- or secondary greenhouse effect – in daylight hours, solar energy is retained on the surface by vegetation and this contributes to the temperature increase. Such an impulse, which seems to be insignificantly small at first glance, triggers a series of climatic variations leading to a change in the structure of the radiation and heat balance as well as the climate not only in the desert-steppe and desert ecosystems but also in Central Asia as a whole. All this may explain the 1.2-2.3°C increase in air temperatures in the Gobi observed over the last 25 years.

Highlights

The surface of the Earth is not uniform and climatic zones have different functions in the biosphere
Eurasia’s desert-steppe zone, which occupies approximately 4 b ha (Zalibekov and Novikova 2016), is a special type of landscape that is characterised by accelerated development
We worked during the maximum vegetation period, we can assume that the influence of vegetation on the surface reflectance during this period will the highest

Summary

INTRODUCTION

The surface of the Earth is not uniform and climatic zones have different functions in the biosphere. In 2016, the National Statistical Agency of Mongolia estimated the national livestock at 62 million animals (http://www.en.nso.mn/) This cannot but affect the structure of vegetation cover, surface reflectance, microclimate, and the radiation balance. Studying the spectral properties of plants and plant communities is important for analysing the surface radiation balance, identifying the current causes of climate change, modelling the energy-mass exchange processes, and solving other research problems Another urgent objective is estimating the contribution of invasive plant species to the changes in the radiation balance and microclimate structure. The analysis took into account weather and climate characteristics, phenological states, biotope ecology, etc Another objective was to measure the integrated spectra of steppe and desert communities (averaged a certain area) for its later use in classifying Landsat ETM and MODIS data

METHODOLOGY AND MATERIALS PROCESSING

Zygophyllum xanthoxylon

Findings

The data are presented in the form x