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

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. Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) noted that recent climate changes have generated widespread impacts on human and natural systems. The atmosphere and oceans are getting warmer, and the amounts of snow and ice are decreasing. 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]. In addition, the ecosystem is facing unprecedented pressure, which will restrict regional sustainable development in different regions. Consequently, 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.Many researchers have carried out relevant studies on the alpine tree line related to the formation and restriction mechanisms, location fluctuations under climate change, vegetation community diversity patterns, and demarcation elevation identification. Some studies have taken the limitations o...

High Mountains Becoming Wetter While Deserts Getting Drier in Xinjiang, China since the 1980s

“…We merged the different types of needle leaf forest (evergreen needle leaf and deciduous needle leaf) into one category, namely the coniferous forest belt. The grassland higher than the altitude of the coniferous forest belt is named alpine meadow [22]. The grasslands below the elevation of the coniferous forest belt are named montane steppe [23].…”