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On the interaction between tree canopy position and environmental effects on soil attributes and plant communities
Author(s) -
Soliveres Santiago,
Eldridge David J.,
Müller Jonathan D.,
Hemmings Frank,
Throop Heather L.
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.12312
Subject(s) - canopy , tree (set theory) , plant community , position (finance) , geography , ecology , tree canopy , environmental science , agroforestry , environmental resource management , ecological succession , biology , mathematics , business , mathematical analysis , finance
Questions Understanding how trees affect their understorey plants and soils is crucial to understand savanna ecosystems. Most studies focus on the differences between canopy and open microsites, but how do different positions within large tree canopies influence soils and plants? Are these potential differences likely to change depending on environmental conditions (i.e. annual rainfall and grazing)? Location One hundred sites across a rainfall gradient (220–1400 mm) in NSW, Australia. Methods We measured the cover, richness and community composition of understorey plants and 12 soil attributes related to infiltration, erodibility and fertility across three positions within the canopy of large eucalypts (trunk, mid‐canopy and edge) and in open areas. We also estimated the percentage similarity in plant communities across microsites, and the percentage species within the landscape occurring solely in one of the four microsites assayed. We tested the interactions between the effect of environmental conditions (rainfall and grazing) and canopy position on all these soil and vegetation attributes. Results Soil attributes explained ~50% of the effect of trees on understorey plants, and soil attributes improved with proximity to the trunk and increasing rainfall. The effect of canopy position × rainfall interactions depended on the response variable considered. These interactions did not affect soil attributes, the percentage of facilitation‐obligate species or species richness, and weakly affected plant composition. However, we found a strong reduction in similarity among plant communities within edge and mid‐canopy compared with open sites towards drier environments, and canopy position × rainfall interactions also significantly affected plant cover. We attribute these weak interactions between canopy position and environmental conditions to richness or the frequency of facilitation to the high turnover of facilitated species across microsites and across different environmental conditions. Conclusions Our study can be used to better understand community dynamics in ecosystems with scattered trees by showing the differential effects of trees on their understorey. Our results also contribute to the body of research on the relationships between plant–plant interactions and the environment by illustrating the importance of gradient length and the number of different microsites considered.