Nitrogen availability and summer drought, but not N:P imbalance, drive carbon use efficiency of a Mediterranean tree-grass ecosystem.

Autor: Nair R; Discipline of Botany, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland.; Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany., Luo Y; Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland., El-Madany T; Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany., Rolo V; Forest Research Group, INDEHESA, University of Extremadura, Plasencia, Cáceres, Spain., Pacheco-Labrador J; Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, Maryland, USA.; Environmental Remote Sensing and Spectroscopy Laboratory (SpecLab), Spanish National Research Council, Madrid, Spain., Caldararu S; Discipline of Botany, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland., Morris KA; Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, Maryland, USA., Schrumpf M; Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany.; Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany., Carrara A; Fundación Centro de Estudios Ambientales del Mediterráneo (CEAM), Valencia, Spain., Moreno G; Forest Research Group, INDEHESA, University of Extremadura, Plasencia, Cáceres, Spain., Reichstein M; Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany., Migliavacca M; Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany.; European Commission Joint Research Centre, Ispra, VA, Italy.
Jazyk: angličtina
Zdroj: Global change biology [Glob Chang Biol] 2024 Sep; Vol. 30 (9), pp. e17486.
DOI: 10.1111/gcb.17486
Abstrakt: All ecosystems contain both sources and sinks for atmospheric carbon (C). A change in their balance of net and gross ecosystem carbon uptake, ecosystem-scale carbon use efficiency (CUE ECO ), is a change in their ability to buffer climate change. However, anthropogenic nitrogen (N) deposition is increasing N availability, potentially shifting terrestrial ecosystem stoichiometry towards phosphorus (P) limitation. Depending on how gross primary production (GPP, plants alone) and ecosystem respiration (R ECO , plants and heterotrophs) are limited by N, P or associated changes in other biogeochemical cycles, CUE ECO may change. Seasonally, CUE ECO also varies as the multiple processes that control GPP and respiration and their limitations shift in time. We worked in a Mediterranean tree-grass ecosystem (locally called 'dehesa') characterized by mild, wet winters and summer droughts. We examined CUE ECO from eddy covariance fluxes over 6 years under control, +N and + NP fertilized treatments on three timescales: annual, seasonal (determined by vegetation phenological phases) and 14-day aggregations. Finer aggregation allowed consideration of responses to specific patterns in vegetation activity and meteorological conditions. We predicted that CUE ECO should be increased by wetter conditions, and successively by N and NP fertilization. Milder and wetter years with proportionally longer growing seasons increased CUE ECO , as did N fertilization, regardless of whether P was added. Using a generalized additive model, whole ecosystem phenological status and water deficit indicators, which both varied with treatment, were the main determinants of 14-day differences in CUE ECO . The direction of water effects depended on the timescale considered and occurred alongside treatment-dependent water depletion. Overall, future regional trends of longer dry summers may push these systems towards lower CUE ECO .
(© 2024 The Author(s). Global Change Biology published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
Externí odkaz: