Reactivity of ectomycorrhizal communities of spruce and beech to recurrent years of severe summer drought
Dr. Karin PritschDate: January 23, 2019
Time: 2 pm (s.t.)
Place: F 01 (Büsgenweg 1)
Biodiversity assessments have been largely facilitated by next generation sequencing techniques. Yet, functional aspects related to biological diversity particularly in soil (micro-) organisms still are challenging to address and in most cases are not yet considered. In ectomycorrhizal communities, we can take advantage of the fact that ectomycorrhizae are morphologically distinct organs. Some of these functional traits such as exploration types are available from databases others are accessible through (bio-)chemical analyses. This facilitates to assess functional traits related to nutrient and water relations.
I will report on our analyzes of ectomycorrhizal community composition along with functional traits (enzyme activities, morphological traits) to identify mechanisms of drought adaptation in the ectomycorrhizal communities of the two tree species Fagus sylvatica and Picea abies. Fine root samples were collected at the Kranzberg Roof Experimental Site (KROOF) next to Freising, Germany, where 6 of 12 plots are equipped with retractable roofs to exclude precipitation throughout April-November. Soil samples were taken at the end of the vegetation period in late autumn since 2013 (before the experiment started) and in the years 2014-2017.
Results from 4 repeated years of summer drought show differences in the ECM community changes upon drought of spruce and beech which can be attributed to the different drought adaptation of fine roots of the two tree species. Community enzyme activities of seven extracellular enzyme activities remained remarkably stable in the surviving mycorrhizal communities but strongly declined – at the ecosystem level – upon repeated summer drought years because of the decline of vital fine roots. At the morphological level, long-distance exploration types of ectomycorrrhizae with structured rhizomorphs were less affected by decline than medium and short distance ECM types suggesting an enhanced capacity of water uptake and transport to increase survival of ectomycorrhizae under drought. Moreover, these results add evidence to decline the carbon starvation hypothesis under drought as the extensive mycelia of these plant carbon dependent fungi are still maintained even under severe drought.
Overall, both tree species and their ectomycorrhizae show still an enormous drought resistance considering an extreme drought scenario of four consecutive summer droughts at the KROOF sites particularly at the functional level.