Precipitation Controls on Soil Biogeochemical and Microbial Community Composition in Rainfed Agricultural Systems in Tropical Drylands

Julio Campo,Morena Avitia,Ana E Escalante,Julieta A Rosell,Víctor Peña,Alberto Barrón-Sandoval,Karen Carrasco-Espinosa,Ulises Isaac Salazar Cabrera,Ana Wegier,Mariana Benítez,Rocío Cruz-Ortega,Thalita F Abbruzzini

doi:10.3390/su132111848

Abstract

The current and expected expansion of agriculture in the drylands of Mexico, together with the decrease in precipitation occurring in the country, likely affect ecosystem processes and will bring great challenges for the suitability of rainfed agriculture for smallholder farmers. Here, we assessed metrics of the soil C, N, and P cycles, as well as soil microbial diversity, under rainfed maize and common bean cropping in arid and semiarid regions of central Mexico. The soil enzymatic vector angles of cultivated plots in both regions were above 45°, suggesting P limitation for microbial growth and crop productivity. Although changes were not observed in the intensity of this P-limitation with aridity, we found a negative effect of drought increase on the concentration of soil organic C and total N, with consequences for the C, N, and P balance in soils. Increasing aridity leads to the homogenization of microbial diversity. Considering a scenario in which decreases in mean annual precipitation would uncouple the biogeochemical cycles and homogenize soil biodiversity, the ecological implications could be an increase in the vulnerability of agricultural ecosystems to drought, with negative consequences for the suitability of rainfed agriculture in the drylands of central Mexico.

Highlights

75% of the agricultural production in rural Mexico is rainfed
[54], alter the functions of tropical agricultural ecosystems and the yield of major crops [54], we sought to contribute to the understanding of how soil biogeochemistry and microbial we sought to contribute to the understanding of how soil biogeochemistry and microbial may be be sensitive sensitive to to differences differences in in precipitation precipitationregimes
Our study indicated that bacterial community composition remained stable under drier conditions, possibly due to attenuation of bacteria as a result of extended drought exposure [84] and/or altered functionality to build up resilience [85]

Summary

Introduction

75% of the agricultural production in rural Mexico is rainfed. This type of agriculture has seen rapid growth since the late 1980s [1], especially due to the expansion of maize and common bean cropping in the semiarid and arid regions of the country. Given its reliance on precipitation, this kind of agriculture is highly vulnerable to climate variability and climate change [2,3]. Precipitation variability does affect plant growth in the current year; it may have a strong effect on long-term food yields, considering the central role of precipitation in biogeochemical cycling and carbon (C) sequestration in agricultural soils [5,6]. Many measures have been suggested to reduce the vulnerability of smallholder farmers to climate change at a global scale [7], regional diagnoses of the effect of changes in

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