The stability of Qinghai-Tibet Plateau ecosystem to climate change

Highlights

• The coniferous and hylaea on the QTP have a high resilience but low resistance to climate change.

• Temperature is the driving factor affecting the ecosystem of grasslands on the QTP.

• Precipitation is the driving factor for the forests and shrubs on the QTP.

Abstract

Climate change and simultaneous increases in extreme events have significant impacts on the structure and function of the global ecosystem. The response of the ecosystem on the Qinghai–Tibet Plateau (QTP) to climate change has drawn increasing attention for its prominent elevation. In this study, resistance and resilience were selected as two stability indicators of ecosystems to analyze the response of the QTP ecosystem to climate change over the past 34 years. We explored the main climate drivers that affect vegetation change, and predicted the stability of the ecosystem in the future. The results showed that the coniferous and Hylaea coniferous and hylaea forests of the QTP had high resilience, whereas the steppe and meadow had poor resilience. Shrubs and coniferous and hylaea coniferous and hylaea forests were with less resistance to climate change, whereas steppe and meadow showed more resistance to climate change. Temperature (TEMP) was the driving factor that affected the stability of steppe and meadow; however, precipitation (PRE) had a greater impact on stability of coniferous and hylaea forests and shrubs. Based on the CMIP5 results, TEMP and PRE on the QTP will significantly increase (p < 0.01) in the next 85 years, and 50.48% of the QTP will become more suitable for vegetation growth, mainly distributing in the southern meadow, part of the Hylaea, and areas bordering the southeastern coniferous and hylaea forests and shrubs. However, the ecosystem degradation might occurr in the central and eastern meadow regions.

Introduction

The global climate has been changing in recent decades, including increases in temperature, shifts in precipitation patterns and increases in carbon dioxide concentrations worldwide. These changes may likely have profound impacts on the composition and physical structure of vegetation (Klein et al., 2007; Parry et al., 2007; Scholze and Arnell, 2006) and govern the functioning of Earth's ecosystems (Cramer et al., 2001). However, the speed and nature of ecosystem responses to climate change remain highly divergent (Walker, 1991). It's caused by the different evapotranspiration, decomposition, and photosynthesis processes of species in each ecosystem (De Keersmaecker et al., 2018, Potts et al., 2006). Ecosystems are the important parts to maintain the global cycle of matter and energy, assessing its stability is the mission of assessing climate risk. Given the importance of ecosystem, a key knowledge gap exists in how to identify and then prioritize those ecosystems that are most sensitive to climate change, especially in climate change sensitive regions.

Resilience and resistance are often used to assess the stability of ecosystem under rapid climate change. Resilience is described as the ability of a community to return to its original state or another stable state after being disturbed (Beisner et al., 2003; Holling, 1973). When an ecosystem is approaching critical transitions, its recovery will slow down, and systems with lower resilience experience amplified responses to disturbance (De Keersmaecker et al., 2015, 2018; Seddon et al., 2016). Resistance is described as the ability of a community to maintain its stable state when the external environment changes (Chapin et al., 2011; Westman, 1978). Resistance was defined as the correlation between variance of climate components and vegetation index, which was used to characterize the extent to which ecosystems are affected by climate change. Higher correlation means the more changes of ecosystem caused by the disturbance of climate change, which means the lower resistance of the ecosystem to the climate change. Both resilience and resistance describe ecosystems' feedback to climate change from time series assessment, threw sight on ecosystems’ functional response from temporal variability but not its mean state. It is avail to assess the likely extent of ecosystem transformation and understand the full potential magnitude of impact should current climate change continue unabated.

The Qinghai–Tibet Plateau (QTP) is one of the most sensitive areas to global climate change (Peng et al., 2012; Yuke, 2019) and has an average altitude of about 4000 m (Yang et al., 2009). It was reported that the climate changes on the QTP exceed those in most of the northern hemisphere and even the world (Feng et al., 1998; Liu, 2000). The QTP has shown a clear warming trend and increased precipitation in past decades (Gao et al., 2016; Niu et al., 2004; Shaohong et al., 2007), which exerted great pressure on the local ecosystems. Researches, including field experiments, remote sensing, observations, and model simulations, has been conducted on the QTP ecosystems (Ding et al., 2007; Klein et al., 2007; Li et al., 2007; Zhang et al., 2013; Shen et al., 2015; Fu et al., 2018), and showed different feedback among the ecosystems. For example, it was reported that increasing temperature but not precipitation affected the temporal stability of biomass (Ma et al., 2017), while the observation of an alpine meadow in the northern QTP showed a stronger effect of the increased precipitation on ecosystem stability (Ding et al., 2007; Zhang et al., 2013). Warming has different impacts on steppe and meadow on the QTP, it can significant promote the growth of alpine meadow but may inhibit the growth of alpine meadow plants (Ganjurjav and Gao, 2016). Tree-ring width recorded that the resilience of trees generally increased in the past decades (Fang and Zhang, 2018). Beyond scattered observations and conflicting results, there has been little integrated research on the resilience and resistance of all alpine ecosystems on the QTP. Identification ecosystems of the QTP with low stability is an important step for understanding ecological adaptation to climate change.

Here, we presented resilience and resistance indices to assess the relative stability of ecosystems to climate change on the QTP to: (1) identify ecosystems and areas that exhibited amplified responses to climate change; (2) quantify climate drivers of ecosystem variation; and (3) predict the change trend of the QTP ecosystems in the future based on simulated climate data.