Rainfall, Biomass Variation, and Community Composition in the Park Grass Experiment

Abstract

We used data on grassland plant community composition over a 90—yr period in the history of the Park Grass Experiment, England to look for relationship between variation in composition and annual variation in rainfall and biomass. This was investigated by regressions of biomass and rainfall on each other, and of these variables separately on each of three different measures of variation in plant community composition. Two of these measures, principal components analysis scores based on variation in species abundance and the ratio by mass of nongrass/grass species, showed significant relationships with biomass variation on many experimental plots, although relationships with rainfall were relatively slight or nonexistent. The third measure employed similarity indices to detect changes in species composition in response to variation in biomass, but failed to find any. Biomass was significantly increased by rainfall on all plots. We propose that variation in community composition was more closely related to biomass variation than to rainfall because rainfall selectively favored the grasses in the community, which we believe competed asymmetrically (for light) with the other species when rainfall was high. The severity of this competition would depend upon biomass more directly than upon rainfall, although it is rainfall that enhanced grass growth. In effect, asymmetric competition magnified the effect of rainfall on community composition.

Pasture production from a long-term fertiliser trial under irrigation

“…Such annual fluctuations have been noted in other long-term experiments (e.g. the Park Grass continuous hay experiment; Jenkinson et al 1994) where they have been attributed in part to changes in annual climatic (rainfall) conditions (Silvertown et al 1994). Some of the variance in our annual yields could be similarly explained by insufficient water for irrigation in dry years, such as 1954 (Rickard & McBride 1987).…”

Functional- and abundance-based mechanisms explain diversity loss due to N fertilization

“…Theory predicts that, above a certain level of primary productivity, local species diversity declines as production increases (2)(3)(4). Observational studies across N deposition gradients (5) and numerous Nfertilization experiments (6,7) provide support for this theory. After land use change, N deposition and climate change have been predicted to be major drivers of diversity loss (8).…”

Combining livestock production information in a process-based vegetation model to reconstruct the history of grassland management

“…The relatively low correlation for annual total precipitation may cause inaccuracy in the model simulations of productivity, because water availability could be a major factor limiting grass growth (e.g. in temperate regions; Le Houerou et al, 1988;Silvertown et al, 1994;Briggs and Knapp 1995;Knapp et al, 2001;Nippert et al, 2006;Harpole et al, 2007). Further, a similar mean belowground NPP and an overestimation of mean aboveground NPP by ORCHIDEE-GM v3.1 is found in Sect.…”