Lowland plant arrival in alpine ecosystems facilitates a decrease in soil carbon content under experimental climate warming

Abstract

Climate warming is releasing carbon from soils around the world1-3, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems4-9. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown10. Here we used two whole-community transplant experiments and a follow-up glasshouse experiment to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences soil carbon content under warming. We found that warming (transplantation to low elevation) led to a negligible decrease in alpine soil carbon content, but its effects became significant and 52% ± 31% (mean ± 95% CIs) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that decreases in soil carbon content likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration and CO2 release under warming. Our findings suggest that warming-induced range expansions of herbaceous plants have the potential to alter climate feedbacks from this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.

Biodiversity change under adaptive community dynamics

“…Counterfactuals present a logistical challenge but can be addressed in several ways. Experimental environment reversals and reciprocal transplant experiments at the level of whole assemblages (e.g., Cui et al, 2018; Walker et al, 2022), or analysis of natural experiments as described earlier, can be used to assess community‐level fitness (as well as resulting ecosystem‐level effects) in community–environment combinations that we do not expect to see once adaptive dynamics have caught up to environmental change (such as those depicted in Figure 2).…”

“…Studies using this experimental approach have, for example, assessed effects of climate and other environmental changes (e.g., salinity, inundation) on community composition and ecosystem function (Cui et al, 2018; Peterson‐Smith & Baldwin, 2006; Wetzel et al, 2004), finding environmental effects on species' relative abundances and community‐level productivity. Some reciprocal community transplants have also been used to study effects of community compositional change on soil carbon storage (Walker et al, 2022) and CO 2 production (Juottonen, 2020). These transplant studies do not report results that can easily be interpreted in terms of the adaptive community dynamics framework (this was not their aim), due to the temporal resolution and detail with which results were reported.…”

Biodiversity in mountain soils above the treeline

“…This holds especially true for barren or sparsely vegetated soils with low C and N content, where increased plant growth and primary production clearly outweigh temperature-driven increases in soil respiration (Hagedorn et al ., 2019). In contrast, distinct increases in C loss have also been reported as a consequence of increased temperatures allowing lowland plants to colonise alpine environments (Walker et al ., 2022). Thus, predictions about the amount and the dynamics of C and N cycling in response to global warming can only be made on a basis of a better understanding of the complex biotic and abiotic interactions in mountain soils (Fig.…”

Warming and altered precipitation independently and interactively suppress alpine soil microbial growth in a decadal-long experiment

“…Global climate change is threatening multi-dimensional ecosystem services, such as terrestrial primary productivity and soil carbon storage ( Jansson and Hofmockel, 2020 ; Walker et al, 2022 ; Zhou et al, 2022 ), especially in high-elevation ecosystems ( Ma et al, 2017 ; Liu et al, 2018 ). Of these, the effects of global climate change on microbial processes related to soil carbon cycling should receive more extensive attention, because carbon balance will have feedbacks on climate system, and further reinforce/diminish the net impact on ecosystem functioning ( Jansson and Hofmockel, 2020 ).…”