Defoliation reduces soil biota – and modifies stimulating effects of elevated CO2

Ecology and Evolution

Marie Dam¹ 

[1]Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark

关键词: Deschampsia;    global change;    grass;    growing season;    microbial biomass;    microbial loop;    nematodes;    nutrient;    rhizodeposition;    soil;   

DOI  :  10.1002/ece3.1739

来源: Wiley

【 摘 要 】

Abstract

To understand the responses to external disturbance such as defoliation and possible feedback mechanisms at global change in terrestrial ecosystems, it is necessary to examine the extent and nature of effects on aboveground–belowground interactions. We studied a temperate heathland system subjected to experimental climate and atmospheric factors based on prognoses for year 2075 and further exposed to defoliation. By defoliating plants, we were able to study how global change modifies the interactions of the plant–soil system. Shoot production, root biomass, microbial biomass, and nematode abundance were assessed in the rhizosphere of manually defoliated patches of Deschampsia flexuosa in June in a full-factorial FACE experiment with the treatments: increased atmospheric CO₂, increased nighttime temperatures, summer droughts, and all of their combinations. We found a negative effect of defoliation on microbial biomass that was not apparently affected by global change. The negative effect of defoliation cascades through to soil nematodes as dependent on CO₂ and drought. At ambient CO₂, drought and defoliation each reduced nematodes. In contrast, at elevated CO₂, a combination of drought and defoliation was needed to reduce nematodes. We found positive effects of CO₂ on root density and microbial biomass. Defoliation affected soil biota negatively, whereas elevated CO₂ stimulated the plant–soil system. This effect seen in June is contrasted by the effects seen in September at the same site. Late season defoliation increased activity and biomass of soil biota and more so at elevated CO₂. Based on soil biota responses, plants defoliated in active growth therefore conserve resources, whereas defoliation after termination of growth results in release of resources. This result challenges the idea that plants via exudation of organic carbon stimulate their rhizosphere biota when in apparent need of nutrients for growth.

【 授权许可】

CC BY   
© 2015 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

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