The role of biomass allocation strategy in diversity loss due to fertilization

Proposed mechanisms for explaining biodiversity loss due to fertilization include interspecific competition and assemblage-level thinning. The interspecific competition hypothesis (ICH) assumes a link between population changes and species competitive ability, which is related to functional traits such as biomass allocation patterns. Based on a 2-year fertilization experiment in an alpine meadow on the Tibetan Plateau, we attempted to explore the relationships between individual and population responses. Individual response was measured by changes in plant biomass and biomass allocation, and population response was estimated by changes in species abundance. The results suggested that following fertilization (1) changes in individual biomass differ among species and functional groups, (2) reproductive allocation tends to decrease for all species whereas leaf allocation generally increases for grasses but decreases for forbs, (3) a strong positive correlation exists between species relative abundance change and individual biomass response, and (4) species relative abundance change has a positive correlation with leaf allocation response, a negative correlation with stem allocation response, and no significant correlation with reproductive allocation response. We conclude that the individual biomass responses and biomass allocation strategy can partly explain diversity loss due to fertilization, a result consistent with the ICH.