No evidence of spatial root system segregation and elevated fine root biomass in multi-species temperate broad-leaved forests

Abstract

Differences in spatial rooting patterns among coexisting species have been recognized as an important mechanism for generating biodiversity effects on ecosystem functioning. However, it is not yet clear whether complementarity in root space exploration is a universal characteristic of multi-species woody communities. In a temperate broad-leaved forest with a mosaic of speciespoor and species-rich stands, we tested two hypotheses related to putative below-ground 'overyielding' in more diverse forests, (1) that species mixture results in a partial spatial segregation of the fine root systems of different species, and (2) that stand fine root biomass increases with tree species diversity. We investigated 12 stands either with one, three, or five dominant tree species (4 replicate stands each) under similar soil and climate conditions for stand fine root biomass and spatial root segregation in vertical and horizontal direction in the soil. Fine roots of different tree species were identified using a morphological key based on differences in colour, periderm surface structure, and branching patterns. In species-poor and species-rich stands, and in all tree species present, fine root density (biomass per soil volume) decreased exponentially with soil depth at very similar rates. Stand fine root biomass in the densely rooted upper soil (0-40 cm depth) was not significantly different between stands with 1, 3 or 5 dominant tree species. We conclude that 'below-ground overyielding' in terms of higher fine root biomasses in species-rich stands as compared to monospecific ones does not occur in these broad-leaved forests which most likely results from a missing complementarity in vertical rooting patterns of the present tree species.

Effects of beech (Fagus sylvatica), ash (Fraxinus excelsior) and lime (Tilia spec.) on soil chemical properties in a mixed deciduous forest

“…Fine root biomass of a single tree within the distance of 2 to 5 m (cluster radius) from the stem was approximately 400 to 600 gm −2 (0-40 cm depths) and did not differ between species. Meinen et al (2009b) found a high degree of root system overlap in mixed stands. The change of fine root biomass with increasing stem distance suggest that fine roots in our soil samples originated mainly from the three cluster trees.…”

“…Meinen et al (2009aMeinen et al ( , 2009b determined total root biomass and root distribution of different tree species close to our cluster sites. They found no evidence of spatial root system segregation or elevated root biomass in multi-species sites.…”

Diversity did not influence soil water use of tree clusters in a temperate mixed forest

“…Limestone already occurred at shallow soil depths (0.6-1.0 m) limiting the rooted soil volumes. Stand fine root biomass in the area decreased exponentially with soil depth with 63-77 % being concentrated in the upper 20 cm (Meinen et al, 2009).…”

European Mixed Forests: definition and research perspectives

“…However, few studies have examined belowground productivity in mixtures and even fewer have compared above-and belowground productivity (Forrester et al, 2006;Epron et al, 2013). Belowground overyielding has not been demonstrated to occur in mature temperate forests (Meinen et al, 2009a(Meinen et al, , 2009bJacob et al, 2013) although root differentiation led to higher fine root productivity in young stands (Lei et al 2012) whereas in boreal forests fine root overyielding was observed in mature stands originated after fire (Brassard et al, 2011). Interspecific competition can also have a strong impact on crown structure (Bayer et al, 2013) and crown allometry .…”