Browsing by Autor "Aurora Gaxiola"

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Exclusion of small mammals and lagomorphs invasion interact with human-trampling to drive changes in topsoil microbial community structure and function in semiarid Chile
(Elsevier BV, 2018) Fernando D. Alfaro; Marlene Manzano; Sebastián Abades; Nicole Trefault; Rodrigo De la Iglesia; Aurora Gaxiola; Pablo A. Marquet; Julio R. Gutiérrez; Peter L. Meserve; Douglas Kelt
Microbial communities in soil chronosequences with distinct parent material: the effect of soil <scp>pH</scp> and litter quality
(Wiley, 2017) Fernando D. Alfaro; Marlene Manzano; Pablo A. Marquet; Aurora Gaxiola
Summary During soil development, bacteria and fungi can be differentially affected by changes in soil biogeochemistry. Since the chemistry of parent material affects soil pH , nutrient availability, and indirectly litter quality, we hypothesize that parent material has an important influence on microbial community patterns during long‐term soil development. In this paper, we tested for the effect of parent material, as well as, soil and litter properties upon microbial community patterns in three c. 20 000‐year‐old semi‐arid chronosequences developed on sedimentary and volcanic (i.e. Andesitic and Dacitic) soils in the Dry Puna of Bolivia. We evaluated microbial patterns by analysing the terminal restriction fragment length polymorphism from amplified bacterial 16S rRNA genes, and the fungal internal transcribed spacer region, and quantitative real‐time polymerase chain reaction. Soil and litter characteristics differed significantly between the Sedimentary and volcanic chronosequences. In particular, soil pH was alkaline in all stages of the Sedimentary chronosequence; whereas it changed from alkaline to near neutral across stages in both volcanic chronosequences. Composition of bacterial communities changed across volcanic chronosequences, and this change was associated with a reduction in soil pH and increases in litter quality, whereas no differences were found in the Sedimentary chronosequence. Fungal community composition, in contrast, did not change across any chronosequence. Relative microbial abundance, expressed as the fungal:bacterial ratio, declined across stages of the Sedimentary chronosequence in association with decreases in TC and TP , whereas in the Andesitic chronosequence decreases in fungal:bacterial ratios were related with increases in litter quality and declines in soil pH . Synthesis . Our results show the importance of parent material in affecting bacterial and fungal communities during soil development. Further, in semi‐arid chronosequences, fungal:bacterial ratios tend to decline given that soil pH in young soils is rather alkaline. Our results also are consistent with the general framework that highlights the importance of above‐ground (i.e. litter quality) and below‐ground (i.e. soil properties) in affecting microbial relative abundance and community composition during soil development.
Species interactions across trophic levels mediate rainfall effects on dryland vegetation dynamics
(Wiley, 2020) Ariel A. Farías; Cristina Armas; Aurora Gaxiola; Patricia Agudelo‐Romero; Jose Luis Cortés; Ramiro Pablo López; Fernando Casanoves; Milena Holmgren; Peter L. Meserve; Julio R. Gutiérrez
Abstract Arid ecosystems are strongly limited by water availability, and precipitation plays a major role in the dynamics of all species in arid regions, as well as the ecosystem processes that occur there. However, understanding how biotic interactions mediate long‐term responses of dryland ecosystems to rainfall remains very fragmented. We report on a unique large‐scale field experiment spanning 25 yr and three trophic levels (plants, small mammal herbivores, predators) in a dryland ecosystem in the northern Chilean Mediterranean Region where we assessed how biotic interactions influence the long‐term plant community responses to precipitation. As the most persistent ecological changes in dryland systems may result from changes in the structure, cover, and composition of the perennial vegetation, we emphasized the interplay between bottom‐up and top‐down controls of perennial plants in our analyses. Rainfall was the primary factor affecting the dynamics of, and interactions among, plants and small mammals. Ephemeral plant cover dynamics closely tracked short‐term annual rainfall, but seemed unaffected by top‐down controls (herbivory). In contrast, the response of the perennial plant cover to precipitation was mediated by (1) a complex interplay between subtle top‐down (herbivory) controls that become more apparent in the long‐term, (2) competition with ephemeral plants during wet years, and (3) an indirect effect of predators on subdominant shrubs and perennial herbs. This long‐term field experiment highlights how climate‐induced responses of arid perennial vegetation are influenced by interactions across trophic levels and temporal scales. In the face of global change, understanding how multi‐trophic controls mediate dryland vegetation responses to climate is essential to properly managing the conservation of biodiversity in arid systems.