Biomass and morphology of fine roots in temperate broad-leaved forests differing in tree species diversity: is there evidence of below-ground overyielding?

Biodiversity effects on ecosystem functioning in forests have only recently attracted increasing attention. The vast majority of studies in forests have focused on above-ground responses to differences in tree species diversity, while systematic analyses of the effects of biodiversity on root systems are virtually non-existent. By investigating the fine root systems in 12 temperate deciduous forest stands in Central Europe, we tested the hypotheses that (1) stand fine root biomass increases with tree diversity, and (2) ‘below-ground overyielding’ of species-rich stands in terms of fine root biomass is the consequence of spatial niche segregation of the roots of different species. The selected stands represent a gradient in tree species diversity on similar bedrock from almost pure beech forests to medium-diverse forests built by beech, ash, and lime, and highly-diverse stands dominated by beech, ash, lime, maple, and hornbeam. We investigated fine root biomass and necromass at 24 profiles per stand and analyzed species differences in fine root morphology by microscopic analysis. Fine root biomass ranged from 440 to 480 g m−2 in the species-poor to species-rich stands, with 63–77% being concentrated in the upper 20 cm of the soil. In contradiction to our two hypotheses, the differences in tree species diversity affected neither stand fine root biomass nor vertical root distribution patterns. Fine root morphology showed marked distinctions between species, but these root morphological differences did not lead to significant differences in fine root surface area or root tip number on a stand area basis. Moreover, differences in species composition of the stands did not alter fine root morphology of the species. We conclude that ‘below-ground overyielding’ in terms of fine root biomass does not occur in the species-rich stands, which is most likely caused by the absence of significant spatial segregation of the root systems of these late-successional species

Silviculture of mixed forests : a European overview of current practices and challenges

eISBN 9783319919539Currently, about 70% of the forest land in Europe is covered by stands composed of two or more tree species. The similar situation can be found outside Europe too. While forest management of monocultures is well described, multispecies forests still need a better understanding to develop appropriate forest practice. Managing mixed forests can be more complex than managing monocultures because of the need to optimize the provision of multiple benefits according to the societal demands including sustaining biodiversity and ecosystem functioning. In this chapter we are going to present (1) the most important and well-described tree species combinations found in each participating countries taking biogeographical region in Europe into account, (2) the main management objectives of those mixtures, (3) the silvicultural approaches that are available for the particular mixed-species forests and (4) the main challenges experienced in mixed-species forest management. We synthesized information about management of mixed-species forests based on questionnaires received from both European countries and few countries from outside Europe participating in COST Action ‘EuMIXFOR’. The survey revealed that (i) the main management objective in the analysed mixtures is valuable timber production followed by protection of soil and water and protection of forests against disturbances, (ii) the uniform shelterwood is the most widespread regeneration method followed by the clear-cutting and the irregular shelterwood system, (iii) the crown thinning followed by low thinning is the most frequent thinning method, and (iv) the main challenge of management is high game pressure and the lack of management rules covering mixture growth and taking into account both species functional traits and site conditionsVytauto Didžiojo universitetasŽemės ūkio akademij