Fine root response to soil resource heterogeneity differs between grassland and forest
Pinno, B. D. and S. D.Wilson. 2013. Plant Ecology
Abstract
Soil resource heterogeneity has clear
effects on plant root development and overall plant
performance. Here we test whether contrasting vege-
tation types have similar or different responses to soil
patches of differing resource availability. We exam-
ined the fine root responses of grassland and forest
vegetation at the northern edge of the Great Plains to
transplanted patches of resource-poor and resource-
rich soils, using rhizotron imaging. Every aspect of
measured root behavior, including root length, pro-
duction, mortality, turnover, variability and size
distribution, varied significantly between patch types,
and most aspects also varied between vegetation types.
Most importantly, differential responses to patches
between grassland and forest were shown by signif-
icant interactions between patch type and vegetation
for two response variables. First, root length variabil-
ity was significantly lower in resource-rich compared
to resource-poor patches in forest but not grassland. Second, the proportion of very fine roots was signif-
icantly greater in resource-rich than resource-poor patches in forests but not grassland. Thus, compared to
grassland, forest more fully occupied resource-rich
patches relative to resource-poor patches by allocating
more growth to very fine roots. We report the first
example of significant differences between vegetation
types (grassland and forest) in root responses to soil
resource heterogeneity measured in a field experiment.
The relatively high ability of forest roots to more fully
occupy resource-rich patches is consistent with the
global expansion of woody vegetation and associated
increases in soil heterogeneity.
Key Words
Fine roots Forest-grassland interface Rhizotron imaging Soil heterogeneity Soil resource availability Woody expansion
