Response of forest distribution to past climate change: An insight into future predictions

Abstract

Vegetation dynamics could lead to changes in the global carbon and hydrology cycle, as well as feedbacks to climate change. This paper reviews the response of forest dynamics to climate change. Based on palaeoecological studies, we summarized the features and modes of vegetation response to climate change and categorized the impacts of climate change on vegetation dynamics as three types: climate stress on vegetation, buffer effects by non-climatic factors, and perturbation of the vegetation distribution by stochastic events. Due to the openness of the vegetation system and the integrated effects of both climatic and non-climatic factors, the vegetation-climate relationship deviates far from its equilibrium. The vegetation distribution shows a non-linear response to climate change, which also makes it difficult to quantify the modern vegetation distribution in terms of specific climatic factors. Past analog, space-for-time-substitution and Dynamic Global Vegetation Models (DGVMs) are three approaches to predicting the future vegetation distribution, but they have all been established on the assumption of vegetation-climate equilibrium. We propose that improving DGVMs is a future task for studies of vegetation dynamics because these are process-based models incorporating both disturbance (e.g. fire) and the variability in Plant Functional Types (PFTs). However, palaeoecological results should be used to test the models, and issues like spatial and temporal scale, complexity of climate change, effects of non-climatic factors, vegetation-climate feedback, and human regulation on vegetation dynamics are suggested as topics for future studies. . Will global warming lead to the expansion or decline of forests in the future? Will measures taken to address climate change concerns, such as the forestation of grasslands, successfully expand the distribution of the forest or have the reverse effect? These scientific and practical questions have been the focus of extensive discussion in the scientific community [5]. In China, for example, as an adaptation to climate change, the area covered by forest will increase from the current 20% to 23% in 2020. Due to the lack of physical space in the wet climate zone, much planting is taking place in the current forest-steppe ecotone [6]. Will the future climate benefit forests in the current forest-steppe ecotone? To answer this question we need to make accurate predictions of future climate forcings of vegetation dynamics. Vegetation dynamics in the past and present are critical to predictions of vegetation response to climate change in the future [7]. Through a review of previous work, we have attempted to summarize the general principles and modes of vegetation response to climate change, and to explore how to accurately predict climate-induced changes in vegetation under the future climate change scenarios.

Fire facilitates warming-induced upward shifts of alpine treelines by altering interspecific interactions

“…The structure and position of alpine treelines are considered to be primarily thermally controlled (Körner 2012). In support of this hypothesis, global climatic warming has induced upward treeline encroachment and tree densification at some treeline ecotones (Camarero and Gutiérrez 2004;Chapin et al 2005;Liang et al 2011;Liu and Yin 2013;Greenwood et al 2014;Liang et al 2016;Wang et al 2016a). Many treelines globally, however, are relatively stable despite evidence of regional warming (Harsch et al 2009).…”

Increased stem density and competition may diminish the positive effects of warming at alpine treeline

“…Because low temperature often is the major constraint on tree regeneration, survival, and growth at alpine treelines (Wang et al. , Holtmeier and Broll , Liu and Yin , Renard et al. ), recent treeline densification at treelines has been linked to rising temperatures (Liang et al.…”

Moisture‐mediated responsiveness of treeline shifts to global warming in the Himalayas

“…Warmer conditions have been associated with increased tree regeneration and encroachment at treeline ecotones worldwide (Camarero & Gutiérrez, 2004;Liang et al, 2016;Liang, Wang, Eckstein, & Luo, 2011), and also with upward treeline shifts in many sites (Beckage et al, 2008;Du et al, 2018;Harsch et al, 2009;Huang et al, 2017;Peñuelas, Ogaya, Boada, & Jump, 2007). Changes in the patterns of distributional limits of tree species at treelines, however, are not homogenous and depend on many local-scale interactions (Camarero et al, 2017;Case & Duncan, 2014;Elliott, 2011;Kharuk, Ranson, Im, & Vdovin, 2010;Liu & Yin, 2013;Loranger, Zotz, & Bader, 2017;Wang, Camarero, Luo, & Liang, 2012;Wang, Liang, Sigdel, Liu, & Camarero, 2017;Zhu, Woodall, & Clark, 2012). For example, a global meta-analysis found that only about half of 166 treeline sites had shifted upward (Harsch et al, 2009), suggesting that the responses of alpine treelines to climatic warming are mediated by other factors such as biotic interactions (Harsch et al, 2012;Liang et al, 2016;Lyu, Zhang, Deng, & Mäkinen, 2016), geomorphic processes (Macias-Fauria & Johnson, 2013;Resler, Butler, & Malanson, 2005) or topography (Elliott & Cowell, 2015;Holtmeier & Broll, 2005;Li & Yang, 2004).…”