Native herbivore browsing alters plant physical and chemical traits in a eucalypt forest understory

Abstract

Macropods exhibit selective herbivory on plant traits within and between species and hence can alter plant trait variation. In this study, we asked what are the effects of macropod herbivory on intraspecific variation in plant traits of forest understory species? We tested the effects of herbivory by macropods on eight plant traits, in nine understory species using a herbivore exclusion experiment. Generalized linear mixed models were used to test for differences between herbivory treatments in trait means as well as variation within species and at the community level. Macropod herbivory resulted in differences in either the mean trait value or trait variance within a species for seven of the eight tested plant traits. Macropod exclusion resulted in larger dimensions of size for most species, as well as changes in specific leaf area, moisture content, and carbon content of leaves. Further, community‐weighted means of specific leaf area, moisture content, and leaf nitrogen were lower in the presence of macropods. Plant trait variance was altered for three of the seven community‐weighted traits. This study demonstrates a mechanism through which macropods can drive changes in the traits of understory plant species. Plant traits have been linked to various larger scale ecological processes including ecosystem flammability, nutrient cycling, response to global change, and habitat suitability for other organisms. Therefore, herbivore‐induced changes in plant trait variation and community composition could have important flow‐on effects for other environmental processes and hence should be considered in management decisions regarding fire‐prone ecosystems.