Human impacts and aridity differentially alter soil N availability in drylands worldwide

MANUEL DELGADO-BAQUERIZO; FERNANDO T. MAESTRE; ANTONIO GALLARDO; DAVID J. ELDRIDGE; SANTIAGO SOLIVERES; MATTHEW A. BOWKER; ANA PRADO-COMESAÑA; JUAN GAITÁN; JOSÉ L. QUERO; VICTORIA OCHOA; BEATRIZ GOZALO; MIGUEL GARCÍA-GÓMEZ; PABLO GARCÍA-PALACIOS; MIGUEL BERDUGO; ENRIQUE VALENCIA; CRISTINA ESCOLAR; TULIO ARREDONDO; CLAUDIA BARRAZA-CEPEDA; BERTRAND R. BOEKEN; DONALDO BRAN; OMAR CABRERA; JOSÉ A. CARREIRA; MOHAMED CHAIEB; ABEL A. CONCEIÇÃO; MCHICH DERAK; CARLOS I. ESPINOSA; ADRIANA FLORENTINO; GABRIEL GATICA; WAHIDA GHILOUFI; SUSANA GÓMEZ-GONZÁLEZ; JULIO R. GUTIÉRREZ; ROSA M. HERNÁNDEZ; ELISABETH HUBER-SANNWALD; MOHAMMAD JANKJU; REBECCA L. MAU; MARIA MIRITI; JORGE MONERRIS; ERNESTO MORICI; MUCHAI MUCHANE; KAMAL NASERI; EDUARDO PUCHETA; ELIZABETH RAMÍREZ; DAVID A. RAMÍREZ-COLLANTES; ROBERTO ROMÃO; MATTHEW TIGHE; DUILIO TORRES; CRISTIAN TORRES-DÍAZ; JAMES VAL; JOSÉ P. VEIGA; DELI WANG; XIA JUAN; ELI ZAADY

Global Ecology and Biogeography

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 p. 36 - 45

1466-822X

Aims Climate and human impacts are changing the nitrogen (N) inputsand losses in terrestrial ecosystems. However, it is largely unknown howthese two major drivers of global change will simultaneously influence theN cycle in drylands, the largest terrestrial biome on the planet. We conducteda global observational study to evaluate how aridity and humanimpacts, together with biotic and abiotic factors, affect key soil variables ofthe N cycle.Location Two hundred and twenty-four dryland sites from all continentsexcept Antarctica widely differing in their environmental conditions andhuman influence.Methods Using a standardized field survey, we measured aridity, humanimpacts (i.e. proxies of land uses and air pollution), key biophysical variables(i.e. soil pH and texture and total plant cover) and six importantvariables related to N cycling in soils: total N, organic N, ammonium,nitrate, dissolved organic:inorganic N and N mineralization rates.We usedstructural equation modelling to assess the direct and indirect effects ofaridity, human impacts and key biophysical variables on the N cycle.Results Human impacts increased the concentration of total N, whilearidity reduced it. The effects of aridity and human impacts on the N cyclewere spatially disconnected,whichmay favour scarcity of N in the most aridareas and promote its accumulation in the least arid areas.Main conclusions We found that increasing aridity and anthropogenicpressure are spatially disconnected in drylands. This implies that whileplaces with low aridity and high human impact accumulate N, most aridsites with the lowest human impacts lose N. Our analyses also provideevidence that both increasing aridity and human impacts may enhance therelative dominance of inorganicNin dryland soils, having a negative impacton key functions and services provided by these ecosystems.