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Simulated plant population responses to small‐scale disturbances in semi‐arid shrublands
Author(s) -
Wiegand Thorsten,
Dean W. Richard J.,
Milton Suzanne J.
Publication year - 1997
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 - 10.2307/3237345
Subject(s) - disturbance (geology) , guild , ecology , shrubland , population , seed dispersal , microsite , plant community , shrub , intermediate disturbance hypothesis , abundance (ecology) , biological dispersal , biology , environmental science , species diversity , ecological succession , ecosystem , habitat , agronomy , demography , paleontology , seedling , sociology
. We used a spatially explicit simulation model to examine the impact of small‐scale disturbance (created by the digging of aardvarks, Orycteropus afer , and bat‐eared foxes, Otocyon megalotis or as a management action) on the temporal and spatial dynamics of a typical Karoo shrub plant community, and to gather insight into the interplay between disturbance structure and population dynamics. Establishment, growth, mortality, seed dispersal and competitive interactions were modelled over long time‐scales in annual time‐steps under the influence of stochastic and unpredictable rainfall. Three disturbance regimes were included, varying the type, rate and size of the small‐scale disturbances. The impact of a disturbance regime on long‐term community dynamics depends on complex interactions between disturbance characteristics and life‐history attributes of component species. Plant density decreased with overall disturbance rates; this effect was independent of the type of disturbance. A given type and rate of disturbance did not influence all species within a guild (e.g. colonizer species) in the same way. The reason for these differences was that species responded not only to the disturbance but to changes in competition intensity from other species and changes in their reproductive potential relative to other species as well. Such interactions resulted in a sequential change in dominant species within guilds as disturbance rates increased. An increase in the overall disturbance rate did not always produce the trend in evenness expected from the intermediate disturbance hypothesis, but was influenced by the relative abundance of different types of disturbance.