Overyielding of fine root biomass as increasing plant species richness in subtropical forests in central southern China
中亚热带森林植物多样性增加导致细根生物量"超产"

Aims The objectives were to compare the fine root biomass, necromass and their distributions in the soil profile and examine the effects of plant species diversity on the morphological properties of live fine roots at different soil depths among four forests along a gradient of increasing plant species richness in subtropical southern China. Methods The fine root samples were collected in March 2010 in four forests: coniferous monoculture (Cunninghamia lanceolata), coniferous pioneer species (Pinus massoniana-Lithocarpus glaber), deciduous (Choerospondias axillaris) and evergreen broadleaved (Cyclobalanopsis glauca-Lithocarpus glaber). In each forest, three soil cores containing fine roots were taken at each of three soil depth (0–10, 10–20 and 20–30 cm) at each of upper, middle and lower slope positions. Living and dead roots were manually separated and then oven dried at 75°C to constant mass to determine weight. Living roots were scanned with a Win-RHIZO 2005C to measure morphological parameters, including total root length, total root volume, number of root tips and forks. Important findings Fine root biomass tended to increase along the gradient from the plantation to evergreen broadleaved forest. Total fine root biomass within the 0–30 cm soil depth differed significantly among the forests, but there were no significant differences in living root biomass. Fine root biomass density decreased exponentially with soil depth at similar rates among the forests. With exception of the plantation, fine root biomass showed clear differences in their distribution in the soil layers, indicating significant belowground spatial niche segregation of the vertical root distribution patterns in the more species-rich stands. Differences in root biomass did not lead to significant differences in fine root morphology on a stand area basis.