Influence of chronic ozone stress on carbon translocation pattern into rhizosphere microbial communities of beech trees (Fagus sylvatica L.) during a growing season

Abstract

The influence of long-term chronic ozone exposure on carbon fluxes from young beech trees (Fagus sylvatica L.) into the phospholipid fraction of microbial communities (PLFA) in the rhizosphere and into the dissolved organic carbon (DOC) fraction was studied in a lysimeter experiment using 13 C depleted CO 2 over one vegetation period to identify possible changes in below ground carbon translocation processes due to the plant stress. It could be shown that microbial biomass as well as individual microbial communities and their activity pattern in the rhizosphere of young beech trees are mainly driven by the vegetation period. An increase in total microbial biomass as well as individual microbial communities was detected during the vegetation period from June to September. However, also a clear ozone effect was visible mainly at the end of the vegetation period. Enzyme activities and PLFA data indicated earlier induced plant senescence as a response to the elevated ozone treatment. Furthermore higher microbial biomass and abundance of plant C utilizing microbes was observed in elevated ozone treatments over the whole vegetation period.Plant Soil (2009) 323:85-95

A continuous labelling approach to recover photosynthetically fixed carbon in plant tissue and rhizosphere organisms of young beech trees (Fagus sylvatica L.) using 13C depleted CO2

“…As the trees were relatively small (compared to adult forest trees), they probably incorporate a higher part of the assimilated carbon into the plant biomass than into exudates, and rhizosphere organisms were forced to degrade older carbon sources. This suggestion may be supported by a lysimeter study, using similar labelling techniques but older beech trees, where also significant label incorporation was detected in bacterial PLFA (Esperschütz et al 2009; this issue).…”

Microbial expression profiles in the rhizosphere of willows depend on soil contamination

“…These increases in the exudation are mechanisms by which plants reduce the toxicity of trace elements in soil, as organic acids can effectively bind many compounds. Stressed beech trees were also shown to have a larger microbial biomass in their rhizosphere (Esperschutz et al, 2009). Our contaminated soils did contain a range of trace elements, but at relatively low concentrations, in the same range as the non-contaminated soils (B Cloutier-Hurteau, M-C Turmel and F Courchesne, personal communication), which is unlikely to have caused significantly higher stress to the plants in the contaminated soils.…”

“…Interactions in the rhizosphere have evolved over millions of years and can be seen as a way for plants to reach a minimal stress level by, among others, deterring pathogens, increasing their nitrogen and phosphorus uptake and detoxifying the environment. Plants confronted with stressful environments normally respond by increasing root exudation (Jones et al, 2004;Qin et al, 2007;Naik et al, 2009), which leads to increased microbial biomass in the rhizosphere (Esperschutz et al, 2009).…”

Effects of elevated CO2 and O3 on N-cycling and N2O emissions: a short-term laboratory assessment

“…In contrast, decreases in gross N mineralization and N 2 O emissions associated with decreased inputs of organic C due to decreased plant biomass production have been observed in other ecosystems (Holmes et al 2006;Kanerva et al 2007). Interestingly, respiration was marginally increased by eO 3 (p=0.06) during our experiment, despite decreased above-and belowground standing biomass ; Nissen (Andersen 2001;Esperschutz et al 2009). Those mechanisms likely sustained C and N availability in SoyFACE, causing the lack of short-term responses of mineral N-transformations in our experiment.…”