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Post‐grazing and post‐fire vegetation dynamics: long‐term changes in mountain bogs reveal community resilience
Author(s) -
Clarke Peter J.,
Keith David A.,
Vincent Ben E.,
Letten Andrew D.
Publication year - 2015
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.1111/jvs.12239
Subject(s) - sphagnum , bog , ecology , species richness , plant community , vegetation (pathology) , environmental science , geography , peat , biology , medicine , pathology
Questions Are Australian Sphagnum bogs compositionally stable or undergoing long‐term change in response to grazing legacies or environmental change along a climatic gradient? Are these Sphagnum bogs resilient to discrete fire events, and over what time scales does recovery from disturbance take place? How does fire disturbance influence species composition in the assembly of fire‐prone Australian bog communities? Location Alpine and subalpine bogs in mainland eastern Australia (Kosciuszko National Park). Method Full floristic sampling over ca. 50 yr (1960s, 1990, 2005, 2007, 2013) at 11 sites; each site sampled with 25 quadrats (0.1 m 2 ) haphazardly placed during each successive survey. Sites were stratified over alpine and subalpine elevations, in burned and unburned areas. Changes in species composition over space and time were examined with multivariate and univariate analyses. Results The Sphagnum bogs of the subalpine and alpine regions show progressive increases in cover of Sphagnum over the last 40–50 yr. Overall species richness and frequency of dominant woody species declined. These trends were not strongly related to the climate gradient. Fire temporarily reduced the frequency of most species but initial floristic composition was regained a decade after fire. There was fire‐dependent variation related to regeneration of hygrophyllous woody species through seed germination and seedling growth in open ground. Conclusion Our results show a degree of community resilience to both grazing and fire, although some observed changes appear directional and the recovery time for grazing was much longer than that for fire. The increase in Sphagnum frequency across subalpine and alpine bogs is likely to reflect progressive recovery of Sphagnum from the grazing era, possibly enhanced by the changing atmosphere. Concurrently, there have been declines in species richness and woody species frequency. The bogs exhibited resilience to infrequent pulse disturbance related to fires, which appear to drive community assembly through cycles of compositional change.