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Using a Tropical Elevation Gradient to Evaluate the Impact of Land‐Use Intensity and Forest Restoration on the Microbial Use of Organic Matter Under Climate Change
Author(s) -
Leizeaga A.,
Duran C.,
Hicks L. C.,
Sandén H.,
Wondie M.,
Rousk J.
Publication year - 2022
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2021gb007109
Subject(s) - environmental science , mineralization (soil science) , nutrient , ecosystem , nutrient cycle , land use , climate change , organic matter , arid , subtropics , decomposer , land use, land use change and forestry , agronomy , ecology , soil water , soil science , biology
We investigated how legacies of land use and climate affected the microbial use of organic matter (OM) along a tropical climate gradient in Ethiopia. Four levels of land‐use intensity ranging from croplands to pristine forests were assessed along a gradient from cool and moist high altitude (MAT = 16°C, MAP = 2,200 mm) to hot and dry lowland sites (MAT = 20°C, MAP = 1,050 mm). We resolved the biomass, structure, and growth rates of microbial decomposer communities together with the rates of carbon (C) and nitrogen (N) transformation. To target the legacies of climate and land use, samples were assessed at optimal moisture and standardized temperature in the laboratory. Microbial biomass and the fungal‐to‐bacterial ratio increased with both legacies of drier climates and higher land‐use intensities. In contrast, fungal growth rates increased in humid climates, but were unaffected by land use. The ratio of C mineralization to gross N mineralization decreased with higher humidity and more intensive land use, suggesting a change in microbial resource use from more nutrient‐poor to nutrient‐rich OM. Mineralization of nutrient‐poor OM implied a lower nutrient availability to microbes in arid climates and low‐intensity land uses, while the mineralization of nutrient‐rich OM in humid sites and higher intensity land uses implied a higher microbial nutrient availability there. The difference in respiration between land uses increased with ecosystem aridity, suggesting that OM turnover and soil fertility were more impacted by land use in drier climates. Together, our results suggest that drier subtropical climates will exacerbate the negative effects of land‐use intensification on OM turnover and nutrient provisioning for plants.