Elevation alters ecosystem properties across temperate treelines globally

Abstract

Temperature is a primary driver of the distribution of biodiversity as well as of ecosystem boundaries. Declining temperature with increasing elevation in montane systems has long been recognized as a major factor shaping plant community biodiversity, metabolic processes, and ecosystem dynamics. Elevational gradients, as thermoclines, also enable prediction of long-term ecological responses to climate warming. One of the most striking manifestations of increasing elevation is the abrupt transitions from forest to treeless alpine tundra. However, whether there are globally consistent above- and belowground responses to these transitions remains an open question. To disentangle the direct and indirect effects of temperature on ecosystem properties, here we evaluate replicate treeline ecotones in seven temperate regions of the world. We find that declining temperatures with increasing elevation did not affect tree leaf nutrient concentrations, but did reduce ground-layer community-weighted plant nitrogen, leading to the strong stoichiometric convergence of ground-layer plant community nitrogen to phosphorus ratios across all regions. Further, elevation-driven changes in plant nutrients were associated with changes in soil organic matter content and quality (carbon to nitrogen ratios) and microbial properties. Combined, our identification of direct and indirect temperature controls over plant communities and soil properties in seven contrasting regions suggests that future warming may disrupt the functional properties of montane ecosystems, particularly where plant community reorganization outpaces treeline advance.

Impact of Water-Induced Soil Erosion on the Terrestrial Transport and Atmospheric Emission of Mercury in China

“…64–66 The most remarkable correlation was found in the Tibetan region (R 2 = 0.3619, P < 0.0001**), which may be attributed to the significant change in ecosystem properties with temperatures associated with the elevation changes. 67 Further study is needed to improve the understanding of the interactions between the changing climate conditions and THg release into aquatic environments.…”

Impact of climate change on alpine vegetation of mountain summits in Norway

“…Hence, these ecosystems can also be used as indicators for the impacts of climate change (Grabherr et al 2010;Malanson et al 2011), and they provide an excellent base for detection of its early-warning signals (Wolf et al 2012). Over the past decades, widespread implications of warming on tundra vegetation have been reported (Post et al 2009;Mayor et al 2017), including an upslope migration and increasing species richness of vascular plants (Pauli et al 2007) and a progressive shrub expansion (Myers-Smith et al 2011).…”

Treelines—Approaches at Different Scales

“…While soils in the treeline ecotone and in the adjacent lower alpine zone (i.e., potential treeline) have developed with the limits set by the general elevational gradients of temperature and precipitation, they vary considerably depending on the local parent material, substrate (physical and chemical properties), vegetation, and on climate history (e.g., [51,[59][60][61][62]). Thus, a locally varying mosaic of soils (soil types) is typical of the treeline ecotone, whereas no real treeline-specific soils exist [5].…”