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Contracting T asmanian montane grasslands within a forest matrix is consistent with cessation of A boriginal fire management
Author(s) -
Bowman D. M. J. S.,
Wood S. W.,
Neyland D.,
Sanders G. J.,
Prior L. D.
Publication year - 2013
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/aec.12008
Subject(s) - vegetation (pathology) , ecological succession , ecology , rainforest , geography , edaphic , soil water , biology , medicine , pathology
The persistence of treeless grasslands and sedgelands within a matrix of eucalypt and rainforest vegetation in the montane plateaux of northern T asmania has long puzzled ecologists. Historical sources suggest that T asmanian A borigines were burning these treeless patches and models seeking to explain their maintenance generally include fire, soil properties and A boriginal landscape burning. We aimed to provide a new historical perspective of the dynamics of the vegetation mosaics of S urrey H ills and P aradise P lains in north‐west and north‐east T asmania, respectively, and used vegetation surveys and soil sampling to explore the role of vegetation and soils in these dynamics. Sequences of historical maps (1832 and 1903) and aerial photography showed that many treeless patches have persisted in the landscape since E uropean settlement and that forests have rapidly expanded into the treeless patches since the early 1950s. Stand structure and floristic data described an expanding forest dominated by L eptospermum , which is consistent with vegetation succession models for the region. Soils under expanding forest boundaries did not have higher soil nitrogen or phosphorus than those under stable boundaries, signalling a lack of edaphic limitation to forest expansion. The magnitude of forest expansion at P aradise P lains (granite), S urrey H ills (basalt) and south‐west T asmania (quartzite) appears to follow a nutrient availability gradient and this hypothesis is backed by differences in soil phosphorus capital between the three systems. Given that existing vegetation boundaries in northern T asmania do not coincide with soil nutrient gradients, we suggest that treeless vegetation was maintained by A boriginal landscape burning and that the recent contraction of treeless vegetation is related to the breakdown of these fire regimes following E uropean settlement. The observed rates of forest expansion could result in a substantial loss of these grasslands if sustained through this century and therefore our work supports the continuation of prescribed burning to maintain this high conservation value ecosystem.