Plant demography and grassland community balance: the contribution of population regulation mechanisms
Briske, D.D.; Silvertown, J.W.
Grasslands for our world: 105-111
1993
Document Number: 512190
Processes that contribute to the stability of grassland communities were discussed in relation to grassland organization. At the individual plant level, apical dominance did not explain the response of tiller recruitment to defoliation. At the population level, radiation quality and axillary bud longevity did not explain tiller recruitment. Competition appeared to exert the greatest regulation on tiller populations. At the community level, grazing modified the balance of competitive interactions in favour of the smaller, earlier and mid-seral species that avoid grazing; these species replace the larger, competitive, late-seral species within the community. It was suggested that these compositional shifts in response to grazing were best understood through the underlying population processes. Late-seral dominants frequently exhibited a decrease in basal area and tiller density/plant and /unit area while the more leniently grazed early or mid-seral species exhibited an increase in these population parameters. This shift in population structure enabled the more grazing-resistant early and mid-seral species to acquire a greater proportion of the available resources and eventually dominate the community as long as intensive grazing continued. Greater insight into the demographic changes that accompany community degradation will provide a more predictive model for the assessment of ecological disturbances and a potentially effective procedure for monitoring grassland responses to disturbance.