Remotely-Sensed Identification of a Transition for the Two Ecosystem States Along the Elevation Gradient: A Case Study of Xinjiang Tianshan Bogda World Heritage Site

Hong Wan,Xinyuan Wang,Peng Guo,Lei Luo,Yanchuang Zhao,Kai Wu,Hongge Ren

doi:10.3390/rs11232861

Abstract

The alpine treeline, as an ecological transition zone between montane coniferous forests and alpine meadows (two ecosystem states), is a research hotspot of global ecology and climate change. Quantitative identification of its elevation range can efficiently capture the results of the interaction between climate change and vegetation. Digital extraction and extensive analysis in such a critical elevation range crucially depend on the ability of monitoring ecosystem variables and the suitability of the experimental model, which are often restricted by the weak intersection of disciplines and the spatial-temporal continuity of the data. In this study, the existence of two states was confirmed by frequency analysis and the Akaike information criterion (AIC) as well as the Bayesian information criterion (BIC) indices. The elevation range of a transition for the two ecosystem states on the northern slope of the Bogda was identified by the potential analysis. The results showed that the elevation range of co-occurrence for the two ecosystem states was 2690–2744 m. At the elevation of 2714 m, the high land surface temperature (LST) state started to exhibit more attraction than the low LST state. This elevation value was considered as a demarcation where abrupt shifts between the two states occurred with the increase of elevation. The identification results were validated by a field survey and unmanned aerial vehicle data. Progress has been made in the transition identification for the ecosystem states along the elevation gradient in mountainous areas by combining the remotely-sensed index with a potential analysis. This study also provided a reference for obtaining the elevation of the alpine tree line quickly and accurately.

Highlights

As the ecological transition zone of montane coniferous forests and alpine meadows, the alpine tree line is extremely sensitive to environmental factors such as temperature, precipitation, and soil, which has great ecological vulnerability [1]
The shifts in land cover types with elevation is the outstanding universal value (OUV) of the Bogda [38], which is affected by the spatial variability of water resources and heat energy in elevation and aspect
The montane coniferous forests mainly grow on the northern-facing slope, and the aspect distribution map is illustrated in Figure 4a

Summary

Introduction

As the ecological transition zone of montane coniferous forests and alpine meadows, the alpine tree line is extremely sensitive to environmental factors such as temperature, precipitation, and soil, which has great ecological vulnerability [1]. With the change of environmental climatic factors, the vegetation distribution show a changing or narrowing position of the alpine tree line [2,3]. Many terrestrial species have shifted their geographic ranges, abundances, and species interactions in response to ongoing climate change [4]. As a “monitor” of climate change, the alpine tree line is sensitive to climate change and can help humans quickly understand the interaction between climate change and vegetation [5,6,7]. It is one of the hotspots to study the influence of climate change by obtaining the elevation range of the alpine tree line. At the same time, strengthening the study of the alpine tree line is significant for the protection and sustainable development of Natural Heritage Sites

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Conclusion