Ecological contingency in species shifts: downslope shifts of woody species under warming climate and land-use change

Abstract

A predicted impact of a warming climate is an upslope shift of montane plant species. These upslope shifts may be amplified by land-use changes or attenuated by forest recoveries at low elevations where historical disturbances were ceased allowing for plant regrowth. Consequently, species may shift downslope back to low elevations where they had been previously harvested. The cessation-driven downslope shifts are hypothesized to dampen or even reverse climate-driven upslope shifts. We tested this hypothesis by a 20 year (1989-2009) forest inventory dataset from five mountainous areas in eastern China. In our study region, intense deforestation occurred mostly at low elevations until 1970, but was then ceased to facilitate natural forest recovery. Based on the analyses of 30 216 woody plants in 609 plots, we found that: (1) forest recovery occurred over the 20 year survey period, and increment rates of both recruitment and basal area increased up to 2004. However, in the last period (2004-2009), increment rates of basal area leveled off and recruitment was close to zero; (2) forest recovery was faster at lower elevations, as indicated by the higher increment rates there; (3) despite rising regional temperatures, the mean elevations of study species showed a downslope shift over the 20 years; and (4) the contribution of forest recovery to elevational shifts was supported by the fact that the species shifts were positively related to elevational changes in the recruitment increment, e.g. the negative (or downslope) shifts occurred in association with higher increments at lower elevations. These results suggest that, the cessation of disturbances and consequent lowland forest recovery had greater effects on the species distributions than did warming climate. In mountain systems that are being allowed to recover from historical disturbances, the effects of forest recovery on species distributions should be explicitly accounted for when assessing and predicting climate change impacts.

Stability in subtropical forests: The role of tree species diversity, stand structure, environmental and socio‐economic conditions

“…Our results suggest that this indirect effect of slope occurs mainly by modulating plant species richness and thereby has an indirect effect on stability. This analysis illustrates that the correlation often found between site conditions and ecosystem stability might be attributable, in part, to an indirect relationship reflecting changes in plant diversity (Nüchel et al., 2019; Zhang et al., 2019). Not surprisingly, slope steepness was also related to human modification (Nüchel et al., 2019).…”

“…Topography also governs geographical gradients in species diversity (Belote, 2018; Nüchel et al., 2019; Wang et al., 2009; Zhang et al., 2019). Slope is a common factor influencing both patterns of land use and species diversity.…”

“…Firstly, we divided stability into two components (mean and SD of productivity) and included direct paths from species richness and species asynchrony to the two components, which represent the underlying mechanisms of stability (Craven et al., 2018; Loreau & Hector, 2001). Secondly, we included indirect paths from climate (García‐Palacios et al., 2018; Mazzochini et al., 2019), slope (Nüchel et al., 2019; Zhang et al., 2019) and population density (Chen et al., 2018; Schulze et al., 2018) to stability because these factors could affect the forest stability via species and structural diversity (Supporting Information Table S1). We parameterized our structural equation model and tested its goodness‐of‐fit using the goodness‐of‐fit index (GFI), chi‐square test and standardized root mean square residual (SRMR).…”

Carrying Capacity of Spatially Distributed Metapopulations

“…As dispersal rates decline with habitat fragmentation, understanding the combined effect of heterogeneity and dispersal on the attainable population size will be essential for fostering population persistence of desired species [15][16][17] or limiting invasive species in these environments [18]. Additionally, general patterns of species range shifts (to higher elevations and latitudes) are anticipated with warming temperatures [19][20][21], so projecting shifting population dynamics along environmental gradients is essential.…”

Exposing wind stress as a driver of fine‐scale variation in plant communities

“…Freeman et al., 2018; Morueta‐Holme et al., 2015), exceptions have also been noted (e.g. Lenoir et al., 2010; Zhang et al., 2019), suggesting that some key factors or processes still need to be accounted for. Indeed, many studies forecasting ecological responses to climate change consider only temperature and precipitation as climatic variables, and do not account for other components of climate.…”