Strong resilience of soil respiration components to drought-induced die-off resulting in forest secondary succession

Barba J., Curiel Yuste J., Poyatos R., Janssens I.A., Lloret F. (2016) Strong resilience of soil respiration components to drought-induced die-off resulting in forest secondary succession. Oecologia. 182: 27-41.
Link
Doi: 10.1007/s00442-016-3567-8

Abstract:

How forests cope with drought-induced perturbations and how the dependence of soil respiration on environmental and biological drivers is affected in a warming and drying context are becoming key questions. The aims of this study were to determine whether drought-induced die-off and forest succession were reflected in soil respiration and its components and to determine the influence of climate on the soil respiration components. We used the mesh exclusion method to study seasonal variations in soil respiration (RS) and its components: heterotrophic (RH) and autotrophic (RA) [further split into fine root (RR) and mycorrhizal respiration (RM)] in a mixed Mediterranean forest where Scots pine (Pinus sylvestris L.) is undergoing a drought-induced die-off and is being replaced by holm oak (Quercus ilex L.). Drought-induced pine die-off was not reflected in RS nor in its components, which denotes a high functional resilience of the plant and soil system to pine die-off. However, the succession from Scots pine to holm oak resulted in a reduction of RH and thus in an important decrease of total respiration (RS was 36 % lower in holm oaks than in non-defoliated pines). Furthermore, RS and all its components were strongly regulated by soil water content-and-temperature interaction. Since Scots pine die-off and Quercus species colonization seems to be widely occurring at the driest limit of the Scots pine distribution, the functional resilience of the soil system over die-off and the decrease of RS from Scots pine to holm oak could have direct consequences for the C balance of these ecosystems. © 2016, Springer-Verlag Berlin Heidelberg.

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Effects of drought-induced forest die-off on litter decomposition

Barba J., Lloret F., Yuste J.C. (2016) Effects of drought-induced forest die-off on litter decomposition. Plant and Soil. 402: 91-101.
Link
Doi: 10.1007/s11104-015-2762-4

Abstract:

Aims: Drought-induced forest die-off and subsequent species replacement may modify environmental conditions and eventually affect litter decomposition. We aimed to disentangle the effects of tree species and die-off state on litter decomposition in a mixed forest where Pinus sylvestris populations experiencing severe drought-induced die-off are being replaced by Quercus ilex. Methods: Litter bags with leaves and fine roots from both species were placed under canopies representing three habitats of the die-off and replacement process (healthy and dead P. sylvestris and healthy Q. ilex). Mass was assessed over 3 years. Results: Species-specific chemistry of litter (C:N ratio) had a direct effect on mass loss, but also indirect effects, attributed to the decomposer microbial community associated with a given habitat-species. In their respective original habitats, oak leaves decomposed 44 % faster than pine needles, whereas oak roots decomposed 46 % slower than pine roots. Conclusions: Forest die-off and species replacement affected litter decomposition. This effect can have great implications in forest functioning, particularly if drought-induced die-off worsens in the next decades, according with the trend observed in the studied system. © 2015, Springer International Publishing Switzerland.

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