Bl. Foster et Kl. Gross, PARTITIONING THE EFFECTS OF PLANT BIOMASS AND LITTER ON ANDROPOGON GERARDI IN OLD-FIELD VEGETATION, Ecology, 78(7), 1997, pp. 2091-2104
We examined the effects of living plant neighbors and litter on the pe
rformance of a native C-4 grass, Andropogon gerardi, at five old-field
sites that differ in community biomass and soil fertility. We used pl
ant removal experiments in which both living neighbors and litter were
manipulated in a factorial arrangement of treatments over one growing
season. Andropogon was added to treatment plots as seeds and as estab
lished transplants to examine the effects of the surrounding plant com
munity on the recruitment and established phases of its life history.
Neighbors negatively affected Andropogon performance at all sites, ind
icating that resource exploitation by living plants was an important c
onstraint to seedling recruitment and growth across the range of commu
nity biomass examined. Plant litter negatively affected recruitment at
sites with the greatest community biomass, but had no effect on the g
rowth of established transplants at any of the sites. The total effect
of the surrounding plant community on recruitment was positively corr
elated with community biomass due to an increasing impact of plant lit
ter. However, the total effect of the surrounding community on the gro
wth of established transplants was unrelated to community biomass. The
results suggest that it may be during the recruitment phase of the li
fe history, when seeds and seedlings are especially susceptible to the
effects of both litter and living neighbors, that Andropogon is most
sensitive to variation in community biomass. Variation in the effects
of litter on recruitment may be important in regulating plant species
diversity and the distribution of native C-4 grasses along old-field b
iomass gradients in southwest Michigan.