Is intensity of plant root mycorrhizal colonization a good proxy for plant growth rate, dominance and decomposition in nutrient poor conditions?

Questions: Mycorrhizae may be a key element of plant nutritional strategies and of carbon and nutrient cycling. Recent research suggests that in natural conditions, intensity of mycorrhizal colonization should be considered an important plant feature. How are inter-specific variations in mycorrhizal colonization rate, plant relative growth rate (RGR) and leaf litter decomposability related? Is (arbuscular) mycorrhizal colonization linked to the dominance of plant species in nutrient-stressed ecosystems? Location: Teberda State Biosphere Reserve, northwest Caucasus, Russia. Methods: We measured plant RGR under mycorrhizal limitation and under natural nutrition conditions, together with leaf litter decomposability and field intensity of mycorrhizal colonization across a wide range of plant species, typical for alpine communities of European mountains. We applied regression analysis to test whether the intensity of mycorrhizal colonization is a good predictor of RGR and decomposition rate, and tested how these traits predict plant dominance in communities. Results: Forb species with a high level of field mycorrhizal colonization had lower RGR under nutritional and mycorrhizal limitation, while grasses were unaffected. Litter decomposition rate was not related to the intensity of mycorrhizal colonization. Dominant species mostly had a higher level of mycorrhizal colonization and lower RGR without mycorrhizal colonization than subordinate species, implying that they were more dependent on mycorrhizal symbionts. There were no differences in litter decomposability. Conclusions: In alpine herbaceous plant communities dominated by arbuscular mycorrhizae, nutrient dynamics are to a large extent controlled by mycorrhizal symbiosis. Intensity of mycorrhizal colonization is a negative predictor for whole plant RGR. Our study highlights the importance of mycorrhizal colonization as a key trait underpinning the role of plant species in carbon and nutrient dynamics in nutrient-limited herbaceous plant communities. [ABSTRACT FROM AUTHOR]