Proliferation of roots in a nutrient patch can occur either as a resul
t of an increase in root length (morphological response) or by a chang
e in root birth or death rates (demographic responses). In this study
we attempted to distinguish between these two mechanisms of response t
o nutrient patches and to compare the responses of four old-field plan
t species (two annuals, two perennials). For all four species combined
, there were significant increases in root numbers and root length in
fertilized patches. Root proliferation in fertilized patches was large
ly due to increased birth ( = branching) rates of new roots. However,
there was also a significant increase in root death rates in the ferti
lized patches which reduced the magnitude of the increase in net root
numbers. Plots for individual species suggested they differed in the m
agnitude and timing of root proliferation in fertilized patches due to
differences in root birth and death rates. However, because of the li
mited sample size in this study, there was only a marginally significa
nt difference among species in root birth rates, and no difference in
death rates. Further studies are currently underway to better quantify
species differences in the demographic mechanism, as well as magnitud
e, of response to nutrient patches and if this would affect the abilit
y to exploit small-scale heterogeneity in soil resources.