Growth rate, root development and nutrient uptake of 55 plant species from the Great Plains Grasslands, USA

Abstract

Empirical and theoretical studies have highlighted that plantcompetition and species diversity are substantially affected by interactionsamong plant growth and nutrient uptake rates, root lateral spread, rootplasticity, and small scale soil nutrient heterogeneity. This study wasdesignedto (a) experimentally estimate parameters regarding rootscaling patterns, root biomass allocation, growth rates, nutrient productivity,and root nutrient influx rates of 55 plant species common to Great Plainsgrasslands; and (b) determine if grasses and forbs can beclassified into statistically distinct groups based on these characteristics.Wefound that: (1) In all species root lateral spread, rootlength, and root surface area had significant allometric scaling relationshipswith root biomass, but that the relationships were unaffected by Navailability.(2) Reductions in the supply of N increased the root:shootratio in 62% of the species. (3) The frequency distributionandmean values of maximum relative growth rates were very similar for grasses andforbs/shrubs, but mid successional grasses had a higher relative growth ratethan late successional ones. (4) In 78% of the species tested,N productivity was increased by reductions in the N supply.(5)When subjected to a high N supply, the N and P productivity of grasses was, onaverage, higher than that of forbs/shrubs, and the N and P productivity ofC4 grasses was, on average, higher than that of C3grasses. No differences were found under a low N supply. (6)Nodifferences on the average maximum N and P influx rates per unit of rootsurfacearea were found between grasses and forbs or between C3 andC4 grasses, but both were correlated with maximum relative growthrate. (7) The set of parameters we measured were able toseparate grasses and forbs/shrubs into statistically distinct groups that tendto follow in broad terms the “coarse” vs. “fine” scaleforaging strategies hypothesis.