Grassland responses to multiple disturbances on the New England Tablelands in NSW, Australia

Abstract

Disturbances have played a significant role in shaping vegetation patterns following European settlement and agricultural development in Australia, particularly over the last 100 years. However, little is known about the temporal dynamics of plant communities in relation to disturbances and their interactions. In this study we examined the response and recovery of temperate grassland communities to disturbance, using a multi-factorial experiment involving grazing exclusion (absent and present), fire (absent and present), soil cultivation (none, 5 and 20 cm) and soil amendment (none, fertiliser and fertiliser plus clover seeds) on the New England Tablelands in NSW, Australia. Temporal patterns of plant communities were analysed using detrended correspondence analysis for eight surveys over 24 months. Vegetation patterns at each survey were analysed using principal components analysis. The effects of treatments on malleability (Bray-Curtis dissimilarity) of plant communities were analysed using a linear mixed model, and the relationships between malleability and plant species groups were depicted using a generalised additive model and further analysed using a linear model. Perennial native grasses and a non-native forb (Hypochaeris radicata) initially dominated the vegetation, but after the disturbances H. radicata and other non-native species dominated. Compositional changes from the initial states were greatest in the first spring (7 months after treatment application), and then the vegetation tended to recover towards its original state. Soil cultivation resulted in the greatest deviation in community composition, followed by soil amendment, fire, with grazing exclusion the least. The recovery process and rate of recovery varied with treatment reflecting the dominance of soil cultivation and its interactions with other forms of disturbances. Soil amendment and grazing exclusion tended to reduce the effects of soil cultivation. Malleability was negatively related to perennial native grasses; positively to other nonnative species, annual native grasses and perennial native sedges/rushes; and negatively to H. radicata when its cover was below 18%, but positively when above 18%. The degree of malleability reflected the high resilience of the vegetation to disturbance, and was mainly due to the recovery of perennial native grasses and H. radicata. This resilience demonstrated that the small-scale disturbances did not cause vegetation to cross an ecological threshold and that the present vegetation is resilient to common disturbances occurring at small scales. The results also suggest (1) that the present vegetation has developed mechanisms to adapt to these disturbances, (2) the importance of disturbance scale or (3) that the ecological threshold had already been crossed and the present vegetation is in a degraded state compared with its original state before the end of the 19th century.

Effects of a tropical cyclone on salt marsh insect communities and post‐cyclone reassembly processes

“…Thus, taxon replacement was not the dominant driver of dissimilarity over time among coastal salt marsh insect communities affected by Hurricane Isaac. Similar patterns have been noted after disturbances in other ecosystems (Li et al , Robinson , Feckler et al ).…”

Vegetation dynamics in a novel ecosystem: agroforestry effects on grassland vegetation in Uruguay

“…Composition, however, began to converge; PH sites had similar vegetation community composition to YF sites. Vegetation in the Campos ecoregion may be more resilient to impacts of afforestation than in other regions, given that plants have already adapted to long-term grazing (Greenberg et al 1995, Li et al 2007). Many traits that are beneficial in grazed systems, such as wind-dispersed seeds and a rosette morphology, also serve plants well in afforested systems, where wind dispersed seeds can colonize open spaces, and the versatile architecture of rosettes (flat structure when not flowering) can take better advantage of resources, like reduced light (McIntyre et al 1995).…”

Restoring biopedturbation in grasslands with anthropogenic focal disturbance

“…Many grasslands lack resilience under extensive soil disturbance yet are resilient under focal soil disturbance. Mechanized focal soil disturbance in Australian grasslands was more influential on plant species composition than defoliation and water availability (McIntyre and Lavorel 1994) and one-time cultivation on small plots was more influential than grazing or fire, but recovery was relatively rapid (Li et al 2007). Following prairie dog removal, plant community composition and herbaceous production were similar within two years to areas grazed by bison (Silva et al 1991).…”