Temperature factors are a primary driver of the forest bryophyte diversity and distribution in the southeast Qinghai-Tibet Plateau

Abstract

The Qinghai-Tibet Plateau (QTP) is an amplifier of global climate change, where the climate change is happening faster or more dramatically. Bryophytes play an important role in forest communities, and they are sensitive to climate change. In this study, we selected 75 sites in locations in the southeast QTP with well-developed forests and collected bryophytes from soils, stones, trees, and dead wood. By utilizing the large sample set obtained, we investigated the responses of the forest bryophyte diversity and distribution to climate change. We extracted and measured 10 climate factors, including nine macroclimate factors: humidity-, temperature-, solar radiation-related factors, and one microclimate factor, canopy density. We used the ordinary least squares (OLS) to establish simple and multiple regression models between the Shannon diversity index and climate factors and utilized the canonical correspondence analysis (CCA) to investigate the response of the total bryophyte distribution and the differential response of bryophytes growing on soils, stones, trees, and dead wood to climate. We found that most climate factors showed unimodal patterns with the forest bryophyte diversity, and when climate change exceeded the optimal threshold for bryophyte growth, with even small increases, this led to a decrease in the bryophyte diversity. In contrast to previous studies on the response of bryophytes to the climate in other regions, we found temperature factors (i.e., minimal temperature and daily temperature range) were the most influential drivers of the forest bryophyte diversity and distribution, regardless of the growth substrate in the southeast QTP. According to the total explained variance of climate factors to the bryophyte distribution, the bryophytes growing on trees (10.6%) and dead wood (14.3%) were more sensitive to climate than those growing on soils (6.9%) and stones (7.7%). Therefore, with continued global warming, the forest bryophytes of the QTP will face a great threat, as they are most effected by temperature change among all of the climate factors.