The response of litter decomposition to extreme drought modified by plant species, plant part, and soil depth in a temperate grassland

Abstract

Plant litter decomposition is a key ecosystem process in carbon and nutrient cycling, and is heavily affected by changing climate. While the direct effects of drought on decomposition are widely studied, in order to better predict the overall drought effect, indirect effects associated with various drought-induced changes in ecosystems should also be quantified. We studied the effect of an extreme (5-month) experimental drought on decomposition, and if this effect varies with two dominant perennial grasses, plant parts (leaves vs. roots), and soil depths (0-5 cm vs. 10-15 cm) in a semiarid temperate grassland. After 12 months, the average litter mass loss was 43.5% in the control plots, while only 25.7% in the drought plots. Overall, mass loss was greater for leaves (44.3%) compared to roots (24.9%), and for Festuca vaginata (38.6%) compared to Stipa borysthenica (30.5%). This variation was consistent with the observed differences in nitrogen and lignin content between plant parts and species. Mass loss was greater for deep soil (42.8%) than for shallow soil (26.4%). Collectively, these differences in decomposition between the two species, plant parts, and soil depths were similar in magnitude to direct drought effect. Drought induces multiple changes in ecosystems, and our results highlight that these changes may in turn modify decomposition. We conclude that for a reliable estimate of decomposition rates in an altered climate, not only direct but also indirect climatic effects should be considered, such as those arising from changing species dominance, root-to-shoot ratio, and rooting depth.

The role of drought, disturbance, and seed dispersal in dominance shifts in a temperate grassland

“…One of the ways in which a dominance change from Festuca to Stipa may have a considerable impact relates to decomposition and, consequently, carbon and nutrient cycling. In a recent study, Seres et al (2022) found that leaf and root litter from Festuca vaginata is decomposed by the local microbial community at a faster rate than the respective plant parts from Stipa borysthenica . In the case of leaves, this is due to higher lignin and lower N content in Stipa , making the litter from this species harder to break down.…”

Macro-environment strongly interacts with warming in a global analysis of decomposition

“…In other places, climate warming is predicted to increase the frequency and intensity of droughts, which could in turn reduce decomposition by limiting the biological activity of decomposer organisms, as has been shown in temperate grasslands (Vogel et al 2013;Walter et al 2013). Therefore, in warmer systems and systems with high variability in precipitation (e.g., savannahs), the warming response is likely to depend strongly on concurrent moisture conditions (Aerts 1997;Seres et al 2022). Our study should lead to a better understanding of the interaction between the prevailing macro-environmental conditions and the changes in decomposition caused by warming.…”

“…2013). Therefore, in warmer systems and systems with high variability in precipitation (e.g., savannahs), the warming response is likely to depend strongly on concurrent moisture conditions (Aerts 1997; Seres et al . 2022).…”