Limits...
Relative effects of mammal herbivory and plant spacing on seedling recruitment following fire and mining.

Parsons MH, Rafferty CM, Lamont BB, Dods K, Fairbanks MM - BMC Ecol. (2007)

Bottom Line: We provide the first comparison between selective herbivory and plant competition effects among two post-mined forest ecosystems (primary succession) and one post-fire woodland ecosystem (secondary succession).Kangaroo density in the post-fire community declined from the beginning of the experiment, while numbers in the post-mined revegetation increased fourfold within one year.Differences in water and nutrient availability may explain why herbivores are more likely to be attracted to post-mined communities.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Ecosystem Diversity and Dynamics (CEDD) in the Department of Environmental Biology, Curtin University of Technology, PO Box U1987, Perth, WA, Australia. M.Parsons@curtin.edu.au

ABSTRACT

Background: There is much debate concerning which ecological constraints are the most limiting factors to seedling recruitment in disturbed communities. We provide the first comparison between selective herbivory and plant competition effects among two post-mined forest ecosystems (primary succession) and one post-fire woodland ecosystem (secondary succession). Animal exclosure assessments of nine common species across eight sites were performed for comparison within three locations separated by up to 200 km. Additionally, we asked whether pre-browsed plants differed in nutrient content between or within species in the separate systems.

Results: Among the nine common species, seven of these were affected by mammal herbivory while five shared a similar vulnerability to predation regardless of system. One species was limited by competition (planting density). There was a strong linear correlation between herbivore selectivity (% browsed) and impact (biomass loss) on the fertilized minesites, but not post-fire sites. Phosphorus and potassium were higher for most species in the post-mined system. Principal components analyses revealed that nutrients in shortest supply may be the most likely components of selection within each system. Among all locations, species with highest levels of phosphorus, ADF and leaf water content were often favoured, while high tannins and nitrogen content were generally selected against.

Conclusion: Herbivory, rather than seedling competition, was the limiting factor for plant performance among post-fire and post-mined reclamation areas. The post-fire seedlings were smaller and more water and nutrient limited, nevertheless browsing prevalence was equivalent at all locations with nearly all seedlings predated. Kangaroo density in the post-fire community declined from the beginning of the experiment, while numbers in the post-mined revegetation increased fourfold within one year. Differences in water and nutrient availability may explain why herbivores are more likely to be attracted to post-mined communities.

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Principal components analysis for nine plant species exposed to mammal herbivores at three locations. iHeight = pre-exclosure removal height; iMass = pre-exclosure removal biomass (g), impact = post harvest biomass (1 - P) – see Methods. a = Whiteman Park, b = Huntly, c = BBM. Names for species are shown in italics.
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Figure 2: Principal components analysis for nine plant species exposed to mammal herbivores at three locations. iHeight = pre-exclosure removal height; iMass = pre-exclosure removal biomass (g), impact = post harvest biomass (1 - P) – see Methods. a = Whiteman Park, b = Huntly, c = BBM. Names for species are shown in italics.

Mentions: PCA showed the likelihood of a species being browsed (% eaten) was related to impact (1 - P value) for the post mined systems, r(9) = 0.879, P < 0.001 at Huntly and r(9) = 0.846, P < 0.005 at BBM (Fig 2). Pearson's correlation revealed no relationship between impact and % eaten at Whiteman r(9) = 0.241, P > 0.5. There were very strong linear relations at Huntly r(9) = 0.879, P < 0.001 and BBM r(9) = 0.846, P < 0.005. Initial (pre-exclosure removal) height and initial biomass were inversely correlated with likelihood of being browsed in all systems. PCA showed phosphorus was more likely a selection candidate at BBM and Whiteman; it was not favoured at Huntly (where it was more prevalent). Leaf water content waspositively correlated with browsing in all systems. Tannins were negatively correlated in all systems.


Relative effects of mammal herbivory and plant spacing on seedling recruitment following fire and mining.

Parsons MH, Rafferty CM, Lamont BB, Dods K, Fairbanks MM - BMC Ecol. (2007)

Principal components analysis for nine plant species exposed to mammal herbivores at three locations. iHeight = pre-exclosure removal height; iMass = pre-exclosure removal biomass (g), impact = post harvest biomass (1 - P) – see Methods. a = Whiteman Park, b = Huntly, c = BBM. Names for species are shown in italics.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2200639&req=5

Figure 2: Principal components analysis for nine plant species exposed to mammal herbivores at three locations. iHeight = pre-exclosure removal height; iMass = pre-exclosure removal biomass (g), impact = post harvest biomass (1 - P) – see Methods. a = Whiteman Park, b = Huntly, c = BBM. Names for species are shown in italics.
Mentions: PCA showed the likelihood of a species being browsed (% eaten) was related to impact (1 - P value) for the post mined systems, r(9) = 0.879, P < 0.001 at Huntly and r(9) = 0.846, P < 0.005 at BBM (Fig 2). Pearson's correlation revealed no relationship between impact and % eaten at Whiteman r(9) = 0.241, P > 0.5. There were very strong linear relations at Huntly r(9) = 0.879, P < 0.001 and BBM r(9) = 0.846, P < 0.005. Initial (pre-exclosure removal) height and initial biomass were inversely correlated with likelihood of being browsed in all systems. PCA showed phosphorus was more likely a selection candidate at BBM and Whiteman; it was not favoured at Huntly (where it was more prevalent). Leaf water content waspositively correlated with browsing in all systems. Tannins were negatively correlated in all systems.

Bottom Line: We provide the first comparison between selective herbivory and plant competition effects among two post-mined forest ecosystems (primary succession) and one post-fire woodland ecosystem (secondary succession).Kangaroo density in the post-fire community declined from the beginning of the experiment, while numbers in the post-mined revegetation increased fourfold within one year.Differences in water and nutrient availability may explain why herbivores are more likely to be attracted to post-mined communities.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Ecosystem Diversity and Dynamics (CEDD) in the Department of Environmental Biology, Curtin University of Technology, PO Box U1987, Perth, WA, Australia. M.Parsons@curtin.edu.au

ABSTRACT

Background: There is much debate concerning which ecological constraints are the most limiting factors to seedling recruitment in disturbed communities. We provide the first comparison between selective herbivory and plant competition effects among two post-mined forest ecosystems (primary succession) and one post-fire woodland ecosystem (secondary succession). Animal exclosure assessments of nine common species across eight sites were performed for comparison within three locations separated by up to 200 km. Additionally, we asked whether pre-browsed plants differed in nutrient content between or within species in the separate systems.

Results: Among the nine common species, seven of these were affected by mammal herbivory while five shared a similar vulnerability to predation regardless of system. One species was limited by competition (planting density). There was a strong linear correlation between herbivore selectivity (% browsed) and impact (biomass loss) on the fertilized minesites, but not post-fire sites. Phosphorus and potassium were higher for most species in the post-mined system. Principal components analyses revealed that nutrients in shortest supply may be the most likely components of selection within each system. Among all locations, species with highest levels of phosphorus, ADF and leaf water content were often favoured, while high tannins and nitrogen content were generally selected against.

Conclusion: Herbivory, rather than seedling competition, was the limiting factor for plant performance among post-fire and post-mined reclamation areas. The post-fire seedlings were smaller and more water and nutrient limited, nevertheless browsing prevalence was equivalent at all locations with nearly all seedlings predated. Kangaroo density in the post-fire community declined from the beginning of the experiment, while numbers in the post-mined revegetation increased fourfold within one year. Differences in water and nutrient availability may explain why herbivores are more likely to be attracted to post-mined communities.

Show MeSH
Related in: MedlinePlus