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Precipitation variability does not affect soil respiration and nitrogen dynamics in the understorey of a Mediterranean oak woodland
Authors:Marjan Jongen  Xavier Lecomte  Stephan Unger  David Fangueiro  João Santos Pereira
Affiliation:1. Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017, Lisbon, Portugal
2. Department of Experimental and Systems Ecology, University of Bielefeld, Universit?tsstr. 25, 33615, Bielefeld, Germany
Abstract:

Background and aims

Future climate scenarios for the Mediterranean imply increasing precipitation variability. This study presents a large-scale water manipulation experiment simulating changes in precipitation variability, aiming at a better understanding of the effects of rainfall patterns on soil C and N cycling and understorey productivity in a Mediterranean oak woodland.

Methods

We used rain-out shelters to achieve (1) a normal dry period (7 days), and (2) a dry period increased three-fold (21 days), without altering total annual precipitation inputs.

Results

The temporal patterns of soil respiration (R s) and soil inorganic N were not affected by treatment. However, water infiltration and N leaching increased with large infrequent watering events. R s and soil NH4 +-N correlated with soil temperature, with soil NO3 ?-N being influenced by leaching.

Conclusions

The lack of significant treatment effects on either R s or soil inorganic N can be explained by (1) minor differences in plant productivity between the treatments, suggesting equal plant N demand, and (2) the absence of moisture dependence of R s and soil NH4 +-N. Increased N leaching with large infrequent precipitation events may have longer-term consequences for ecosystem functioning. Our results contribute to an improved understanding of possible climate change effects on key ecosystem processes in Mediterranean ecosystems.
Keywords:
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