Phenolic control of plant nitrogen acquisition through the inhibition of soil microbial decomposition processes: a plant-microbe competition model

Incorporating the soil environment and microbial community into plant competition theory

Plants affect microbial communities and abiotic properties of nearby soils, which in turn influence plant growth and interspecific interaction, forming a plant-soil feedback (PSF). PSF is a key determinant influencing plant population dynamics, community structure, and ecosystem functions. Despite accumulating evidence for the importance of PSF and development of specific PSF models, different models are not yet fully integrated. Here, we review the theoretical progress in understanding PSF. When first proposed, PSF was integrated with various mathematical frameworks to discuss its influence on plant competition. Recent theoretical models have advanced PSF research at different levels of ecological organizations by considering multiple species, applying spatially explicit simulations to examine how local-scale predictions apply to larger scales, and assessing the effect of PSF on plant temporal dynamics over the course of succession. We then review two foundational models for microbial- and litter-mediated PSF. We present a theoretical framework to illustrate that although the two models are typically presented separately, their behavior can be understood together by invasibility analysis. We conclude with suggestions for future directions in PSF theoretical studies, which include specifically addressing microbial diversity to integrate litter- and microbial-mediated PSF, and apply PSF to general coexistence theory through a trait-based approach.

Effect of elevated CO2, O3, and UV radiation on soils

In this work, we have attempted to review the current knowledge on the impact of elevated CO2, O3, and UV on soils. Elevated CO2 increases labile and stabile soil C pool as well as efficiency of organic pollutants rhizoremediation and phytoextraction of heavy metals. Conversely, both elevated O3 and UV radiation decrease inputs of assimilates to the rhizosphere being accompanied by inhibitory effects on decomposition processes, rhizoremediation, and heavy metals phytoextraction efficiency. Contrary to elevated CO2, O3, or UV-B decreases soil microbial biomass, metabolisable C, and soil N t content leading to higher C/N of soil organic matter. Elevated UV-B radiation shifts soil microbial community and decreases populations of soil meso- and macrofauna via direct effect rather than by induced changes of litter quality and root exudation as in case of elevated CO2 or O3. CO2 enrichment or increased UV-B is hypothesised to stimulate or inhibit both plant and microbial competitiveness for soluble soil N, respectively, whereas O3 favours only microbial competitive efficiency. Understanding the consequences of elevated CO2, O3, and UV radiation for soils, especially those related to fertility, phytotoxins inputs, elements cycling, plant-microbe interactions, and decontamination of polluted sites, presents a knowledge gap for future research.

The impact of long-term CO2 enrichment on sun and shade needles of Norway spruce (Picea abies): photosynthetic performance, needle anatomy and phenolics accumulation

Norway spruce (Picea abies L. Karst) grown under ambient (365-377 μmol(CO(2)) mol(-1); AC) and elevated (700 μmol(CO(2)) mol(-1); EC) CO(2) concentrations within glass domes with automatically adjustable windows and on an open-air control site were studied after 8 years of treatment. The effect of EC on photosynthesis, mesophyll structure and phenolics accumulation in sun and shade needles was examined. Photosynthetic assimilation and dark respiration rates were measured gasometrically; the structural parameters of mesophyll were determined using confocal microscopy and stereological methods. The contents of total soluble phenolics and lignin were assessed spectrophotometrically, and localizations of different phenolic groups were detected histochemically on needle cross-sections. EC enhanced the light-saturated CO(2) assimilation rate and reduced dark respiration in the current-year needles. No effects of CO(2) enrichment on mesophyll structural parameters were observed. Similarly, the accumulation and localization of phenolics and lignin remained unaffected by EC treatment. Needles differentiated into sun and shade ecotypes in the same manner and to the same extent irrespective of CO(2) treatment. Based on these results, it is apparent that the EC-induced enhancement of photosynthesis is not related to changes in the examined structural parameters of mesophyll and accumulation of phenolic compounds.