Altered precipitation and root herbivory affect the productivity and composition of a mesic grassland

Background Climate change models predict changes in the amount, frequency and seasonality of precipitation events, all of which have the potential to affect the structure and function of grassland ecosystems. While previous studies have examined plant or herbivore responses to these perturbations, few have examined their interactions; even fewer have included belowground herbivores. Given the ecological, economic and biodiversity value of grasslands, and their importance globally for carbon storage and agriculture, this is an important knowledge gap. To address this, we conducted a precipitation manipulation experiment in a former mesic pasture grassland comprising a mixture of C4 grasses and C3 grasses and forbs, in southeast Australia. Rainfall treatments included a control [ambient], reduced amount [50% ambient] and reduced frequency [ambient rainfall withheld for three weeks, then applied as a single deluge event] manipulations, to simulate predicted changes in both the size and frequency of future rainfall events. In addition, half of all experimental plots were inoculated with adult root herbivores (Scarabaeidae beetles). Results We found strong seasonal dependence in plant community responses to both rainfall and root herbivore treatments. The largest effects were seen in the cool season with lower productivity, cover and diversity in rainfall-manipulated plots, while root herbivore inoculation increased the relative abundance of C3, compared to C4, plants. Conclusions This study highlights the importance of considering not only the seasonality of plant responses to altered rainfall, but also the important role of interactions between abiotic and biotic drivers of vegetation change when evaluating ecosystem-level responses to future shifts in climatic conditions.

Silicon and Plant–Animal Interactions: Towards an Evolutionary Framework

Herbivory is fundamental in ecology, being a major driver of ecosystem structure and functioning. Plant Si and phytoliths play a significant antiherbivory role, the understanding of which and of its evolutionary context will increase our understanding of this phenomenon, its origins, and its significance for past, extant, and future ecosystems. To achieve this goal, we need a superdisciplinary evolutionary framework connecting the role of Si in plant–herbivore interactions, in global processes, and in plant and herbivore evolution. To do this properly, we should acknowledge and incorporate into our work some basic facts that are too often overlooked. First, there is great taxonomic variance both in plant Si contents, forms, and roles, but also in herbivore responses, dietary preferences, and in fossil evidence. Second, species and their traits, as well as whole ecosystems, should be seen in the context of their entire evolutionary history and may therefore reflect not only adaptations to extant selective factors but also anachronistic traits. Third, evolutionary history and evolutionary transitions are complex, resulting in true and apparent asynchronisms. Fourth, evolution and ecology are multiscalar, in which various phenomena and processes act at various scales. Taking these issues into consideration will improve our ability to develop this needed theoretical framework and will bring us closer to gaining a more complete understanding of one of the most exciting and elusive phenomena in plant biology and ecology.

Vegetation management influences habitat use by mammalian herbivores in shrub-encroached grassy woodland

Context Restoration of disturbed vegetation communities commonly involves altering vegetation composition and structure, attributes that can influence the suitability of habitat for fauna. Feedbacks may occur whereby changes to the vegetation affect mammalian herbivores, and unintended changes may prevent managers from achieving conservation goals. Aims To understand how vegetation management affects habitat use by five mammalian herbivores, namely eastern grey kangaroo (Macropus giganteus), swamp wallaby (Wallabia bicolor), common wombat (Vombatus ursinus), European rabbit (Oryctolagus cuniculus) and hog deer (Axis porcinus). Methods A management experiment (mechanical slashing of the encroaching shrub Leptospermum laevigatum) at Wilsons Promontory National Park, Australia, created slashed swales in addition to untreated dune and scrub woodland. In each vegetation stratum, we estimated the cover of L. laevigatum and quantified herbivore abundance by counting the standing crop of faecal pellets. Key results Relative to untreated vegetation, mechanical slashing of L. laevigatum substantially reduced cover of this species above 200 cm, but increased its cover below 30 cm. On the basis of faecal-pellet counts, multispecies use of managed and unmanaged parts of the landscape differed substantially, with the differences principally driven by higher abundance of European rabbits and eastern grey kangaroos at slashed sites. Conclusions The responses of three grazing species (kangaroo, rabbits and wombats) to vegetation management were predicted well by prior knowledge of diet and habitat preferences. This was not the case for the browser (swamp wallaby), nor for the grazer that consumes substantial amounts of browse in the study area (hog deer), and additional knowledge of the processes underlying their responses to vegetation change is required. Implications Our findings highlighted that vegetation management can influence herbivore abundances in the managed system. An improved understanding of these associations will allow vegetation management plans to incorporate herbivore responses.