Preprints
https://doi.org/10.5194/egusphere-2023-1932
https://doi.org/10.5194/egusphere-2023-1932
05 Oct 2023
 | 05 Oct 2023

Drivers of ecosystem water use efficiency in a temperate rainforest and a peatland in southern South America

Jorge F. Perez-Quezada, David Trejo, Javier Lopatin, David Aguilera, Bruce Osborne, Mauricio Galleguillos, Luca Zattera, Juan L. Celis-Diez, and Juan J. Armesto

Abstract. The variability and drivers of carbon and water fluxes and their relationship to ecosystem water use efficiency (WUE) in natural ecosystems of southern South America are still poorly understood. For eight years (2015–2022), we measured water and carbon fluxes using eddy covariance towers in a temperate rainforest and a peatland in southern Chile. Different expressions for ecosystem WUE were derived from estimates of gross primary productivity (GPP) and evapotranspiration (ET), which was further partitioned into evaporation (E) and transpiration (T). We then used the correlation between detrended time series and structural equation modeling to identify the main environmental drivers of WUE, GPP, ET, E and T. The results showed that WUE is low in both ecosystems, and likely explained by the high annual precipitation in this region (∼2100 mm). Only expressions of WUE that included atmospheric water demand showed seasonal variation. Variations in WUE were related more to changes in ET than to changes in GPP, while T remained relatively stable accounting for around 47 % of ET for most of the study period. For both ecosystems, E increased with higher global radiation, higher surface conductance and when the water table was closer to the surface. Higher values for E were also found with increased wind speeds in the forest and higher air temperatures in the peatland. The absence of a close relationship between ET and GPP is likely related to the dominance of plant species that either do not have stomata (i.e., mosses in the peatland or epiphytes in the forest) or have poor stomatal control (i.e., anisohydric tree species in the forest). The observed increase in potential ET in the last two decades and the projected drought in this region suggests that WUE could increase in these ecosystems, particularly in the forest, where stomatal control may be more significant.

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Journal article(s) based on this preprint

18 Mar 2024
Comparison of carbon and water fluxes and the drivers of ecosystem water use efficiency in a temperate rainforest and a peatland in southern South America
Jorge F. Perez-Quezada, David Trejo, Javier Lopatin, David Aguilera, Bruce Osborne, Mauricio Galleguillos, Luca Zattera, Juan L. Celis-Diez, and Juan J. Armesto
Biogeosciences, 21, 1371–1389, https://doi.org/10.5194/bg-21-1371-2024,https://doi.org/10.5194/bg-21-1371-2024, 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
For 8 years we sampled a temperate rainforest and a peatland in Chile to estimate their...
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