Agricultural land-use change in a Mexican oligotrophic desert depletes ecosystem stability

Abstract

BackgroundGlobal demand for food has led to increased land-use change, particularly in dry land ecosystems, which has caused several environmental problems due to the soil degradation. In the Cuatro Cienegas Basin (CCB), alfalfa production irrigated by flooding impacts strongly on the soil.MethodsIn order to analyze the effect of such agricultural land-use change on soil nutrient dynamics and soil bacterial community composition, this work examined an agricultural gradient within the CCB which was comprised of a native desert grassland, a plot currently cultivated with alfalfa and a former agricultural field that had been abandoned for over 30 years. For each site, we analyzed C, N and P dynamic fractions, the activity of the enzyme phosphatase and the bacterial composition obtained using 16S rRNA clone libraries.ResultsThe results showed that the cultivated site presented a greater availability of water and dissolved organic carbon, these conditions promoted mineralization processes mediated by heterotrophic microorganisms, while the abandoned land was limited by water and dissolved organic nitrogen. The low amount of dissolved organic matter promoted nitrification, which is mediated by autotrophic microorganisms. The microbial N immobilization process and specific phosphatase activity were both favored in the native grassland. As expected, differences in bacterial taxonomical composition were observed among sites. The abandoned site exhibited similar compositions than native grassland, while the cultivated site differed.DiscussionThe results suggest that the transformation of native grassland into agricultural land induces drastic changes in soil nutrient dynamics as well as in the bacterial community. However, with the absence of agricultural practices, some of the soil characteristics analyzed slowly recovers their natural state.

Tetracycline and Sulfonamide Antibiotic Resistance Genes in Soils From Nebraska Organic Farming Operations

“…Samples were collected at two depths (0.0–7.6 cm and 7.6–15.2 cm), homogenized by hand-mixing of the bag, and stored at -80°C, resulting in a total of 196 soil samples that were evaluated for ARG targets. Soil analyses, including determination of coarse particular organic matter (CPOM), fine particulate organic matter (FPOM), microaggregates (MicAg), large and small macroaggregates (Lmac, Smac), pH, electrical conductivity (EC), and fatty acid profiles were performed as part of a separate study, using methods that have previously been described ( Cambardella and Elliott, 1994 ; Drijber et al, 2000 ; Cambardella et al, 2001 ; Grigera et al, 2006 ). Chemical analyses were performed at Ward Laboratories, Kearney, NE, United States.…”

Archaeal Communities: The Microbial Phylogenomic Frontier

“…Archaeal Domes (AD) are, so far, the most diverse microbial community found in CCB, despite the extreme conditions. Since this area is subject to water exploitation by intensive agricultural practices, desiccation and soil nutrient loss have become common in numerous ponds ( Hernandez-Becerra et al, 2016 ). Our research group prioritizes investigating the ecology of these highly diverse Archaeal-rich microbial communities to fluctuating temperature and rainfall conditions.…”

Ecosystem science: a new approach in the analysis of functional processes in natural and human transformed terrestrial ecosystems

“…This latter definition therefore incorporates a dynamic concept of ecosystem resilience. Most of the papers related to ecosystem resilience analyzed changes of biological diversity following disturbance (MacGillivray et al 1995, Tilman 1996, Griffiths et al 2000, Wardle et al 2000, but a few studies analyzed the recovery of functional processes (Herbert et al 1999, Orwin & Wardle 2004, Hernández-Becerra et al 2016). In addition, some authors proposed a quantitative index of ecosystem resilience (Herbert et al 1999, Griffiths et al 2001, Orwin & Wardle 2004.…”

“…Most studies are focused on a few variables, limiting the conclusions that can be made regarding the resilience capacity of ecosystems. For illustrative purposes, we present a resilience study conducted in a desert ecosystem in northern Mexico published by Hernández-Becerra et al (2016). These authors analyzed soil microbial composition and soil nutrient dynamics in three plots with different management conditions (natural desert grassland, plot cultivated with alfalfa and plot abandoned for over 30 years) in the Cuatro Ciénegas Basin in northern Mexico.…”

“…These authors analyzed soil microbial composition and soil nutrient dynamics in three plots with different management conditions (natural desert grassland, plot cultivated with alfalfa and plot abandoned for over 30 years) in the Cuatro Ciénegas Basin in northern Mexico. Briefly, the management consisted of cultivation of alfalfa (Medicago sativa L.) by flooding the fields and introducing large quantities of fertilizer, but the agriculture plots were abandoned because of soil degradation, mainly salinization (Hernández-Becerra et al 2016, Tapia-Torres et al 2018. Figure 1 shows the variables with the greatest differences among the three plots.…”