Efford, M.G., Warburton, B., Coleman, M. C. and Barker R. J. 2005. A field test of two methods for density estimation. Wildlife Society Bulletin 33: 731–738.
Population density estimation with a new spatially explicit capture–recapture method was tested in the field and compared to distance analysis of data from trapping webs. Brushtail possums were trapped in pine forest at Waitarere, near Foxton. Capture–recapture with hollow trapping squares gave an estimate (1.9/ha) that was close to the result from nearly complete removal (2.3/ha). Trapping webs gave highly biased estimates (6.5–8.0/ha), consistent with Monte Carlo simulations. The spatially explicit capture–recapture method places few constraints on the spatial configuration of sampling; dispersed configurations (e.g. randomly sited trap clusters) may be used to estimate mean density across landscapes. See www.landcareresearch.co.nz/services/software/density for software and a pdf of the paper.
02 December, 2005
02 October, 2005
Urlich et al. (2005): Tree regeneration in a New Zealand rain forest influenced by disturbance and drainage interactions.
Urlich, S.C.; Stewart, G.H.; Duncan, R.P.; Almond, P.C. 2005. Tree regeneration in a New Zealand rain forest influenced by disturbance and drainage interactions. Journal of Vegetation Science 16: 423–432.
Question: Does canopy tree regeneration response to difference large disturbances vary with soil drainage?
Location: Old-growth conifer (Dacrydium and Dacrycarpus), angiosperm (Nothofagus and Weinmannia) rain forest, Mount Harata, South Island, New Zealand.
Methods: Trees were aged (1056 cores) to reconstruct stand history in 20 (0.12–0.2 ha) plots with different underlying drainage. Spatial analyses of an additional 805 tree ages collected from two (0.3–0.7 ha) plots were conducted to detect patchiness for five canopy tree species. Microsite preferences for trees and saplings were determined.
Results: There were clear differences in species regeneration patterns on soils with different drainage. Conifer recruitment occurred infrequently in even-aged patches (>1000 m2) and only on poorly drained soils. Periodic Nothofagus fusca and N. menziesii recruitment occurred more frequently in different sized canopy openings on all soils. Weinmannia recruitment was more continuous on all soils reflecting their greater relative shade-tolerance. Distinct periods of recruitment that occurred in the last 400 years matched known large disturbances in the region. These events affected species differently as soil drainage varied. Follow- ing earthquakes, both conifer and N. menziesii regenerated on poorly drained soils, while Nothofagus species and Weinmannia regenerated on well drained soils. However, Dacrydium failed to regenerate after patchy storm damage in the wetter forest interior; instead faster growing N. fusca captured elevated microsites caused by uprooting.
Conclusions: Underlying drainage influenced species composition, while variation in the impacts of large disturbance regulated relative species abundances on different soils.
Question: Does canopy tree regeneration response to difference large disturbances vary with soil drainage?
Location: Old-growth conifer (Dacrydium and Dacrycarpus), angiosperm (Nothofagus and Weinmannia) rain forest, Mount Harata, South Island, New Zealand.
Methods: Trees were aged (1056 cores) to reconstruct stand history in 20 (0.12–0.2 ha) plots with different underlying drainage. Spatial analyses of an additional 805 tree ages collected from two (0.3–0.7 ha) plots were conducted to detect patchiness for five canopy tree species. Microsite preferences for trees and saplings were determined.
Results: There were clear differences in species regeneration patterns on soils with different drainage. Conifer recruitment occurred infrequently in even-aged patches (>1000 m2) and only on poorly drained soils. Periodic Nothofagus fusca and N. menziesii recruitment occurred more frequently in different sized canopy openings on all soils. Weinmannia recruitment was more continuous on all soils reflecting their greater relative shade-tolerance. Distinct periods of recruitment that occurred in the last 400 years matched known large disturbances in the region. These events affected species differently as soil drainage varied. Follow- ing earthquakes, both conifer and N. menziesii regenerated on poorly drained soils, while Nothofagus species and Weinmannia regenerated on well drained soils. However, Dacrydium failed to regenerate after patchy storm damage in the wetter forest interior; instead faster growing N. fusca captured elevated microsites caused by uprooting.
Conclusions: Underlying drainage influenced species composition, while variation in the impacts of large disturbance regulated relative species abundances on different soils.
Gillman and Ogden (2005): Microsite heterogeneity in litterfall risk to seedlings.
Gillman, L. N., and J. Ogden. 2005. Microsite heterogeneity in litterfall risk to seedlings. Austral Ecology 30:497–504.
Litterfall is an important cause of damage and mortality to seedlings in many forests. However, this study is the first to demonstrate variable risks of litterfall damage among different microsites. Artificial seedlings were ‘planted’ along transects in each of two New Zealand forests, and the overhead species recorded. The artificial seedlings were monitored monthly for damage over two years. The risk of damage differed significantly among microsites from 2% to 30% per y (P < 0.0005). Seedlings differ in resilience to litterfall (Gillman et al. 2003) and, therefore, microsites with different litterfall risks provide the potential for regeneration niche differentiation.
Litterfall is an important cause of damage and mortality to seedlings in many forests. However, this study is the first to demonstrate variable risks of litterfall damage among different microsites. Artificial seedlings were ‘planted’ along transects in each of two New Zealand forests, and the overhead species recorded. The artificial seedlings were monitored monthly for damage over two years. The risk of damage differed significantly among microsites from 2% to 30% per y (P < 0.0005). Seedlings differ in resilience to litterfall (Gillman et al. 2003) and, therefore, microsites with different litterfall risks provide the potential for regeneration niche differentiation.
02 June, 2005
Willis and Millar (2005): Using marine reserves to estimate fishing mortality.
Willis, T.J. & R.B. Millar (2005) Using marine reserves to estimate fishing mortality. Ecology Letters 8: 47–52.
The pervasive effects of fishing mean that what is generally seen on our coasts is not ‘natural’. Here we demonstrate how no-take marine reserves, where all forms of human-induced disturbance are forbidden, can be used to estimate fishing mortality independently of the fishery. We suggest that reserves can be used to estimate other important population parameters in exploited marine species. Reserves can be used to combat the ‘shifting baseline’ syndrome and provide controls for determining what is natural in the oceans.
The pervasive effects of fishing mean that what is generally seen on our coasts is not ‘natural’. Here we demonstrate how no-take marine reserves, where all forms of human-induced disturbance are forbidden, can be used to estimate fishing mortality independently of the fishery. We suggest that reserves can be used to estimate other important population parameters in exploited marine species. Reserves can be used to combat the ‘shifting baseline’ syndrome and provide controls for determining what is natural in the oceans.
Efford and Cowan (2004): Long-term population trend of Trichosurus vulpecula in the Orongorongo Valley, New Zealand.
Efford, M. G.; Cowan, P. E. 2004. Long-term population trend of Trichosurus vulpecula in the Orongorongo Valley, New Zealand. In: R. L. Goldingay and S. M. Jackson (eds.) The biology of Australian possums and gliders. Surrey Beatty & Sons, Chipping Norton. Pp. 471–483.
Browsing by introduced brushtail possums has been predicted to shift the species composition of native forests away from palatable species, and thereby to reduce the density of possums those forests support. We tested this prediction with data from a population of possums monitored by capture–recapture over 35 years. Annual density varied within a relatively narrow band (6.5–13.7/ha) and the overall trend was slightly positive (+0.04 ± 0.025 /ha/year), despite the decline of some ‘preferred’ plant species. We speculate that possum carrying capacity was buffered against the loss of palatable plants because these were replaced by more resilient and fast-growing palatable species.
Browsing by introduced brushtail possums has been predicted to shift the species composition of native forests away from palatable species, and thereby to reduce the density of possums those forests support. We tested this prediction with data from a population of possums monitored by capture–recapture over 35 years. Annual density varied within a relatively narrow band (6.5–13.7/ha) and the overall trend was slightly positive (+0.04 ± 0.025 /ha/year), despite the decline of some ‘preferred’ plant species. We speculate that possum carrying capacity was buffered against the loss of palatable plants because these were replaced by more resilient and fast-growing palatable species.
02 March, 2005
Joy and Death (2004): Predictive modelling and spatial mapping of freshwater fish and decapod assemblages.
Joy, M.K. & Death, R.G. (2004) Predictive modelling and spatial mapping of freshwater fish and decapod assemblages: an integrated GIS and neural network approach. Freshwater Biology, 49, 1036–1052.
We used stream fish and decapod spatial occurrence data extracted from the New Zealand Freshwater Fish Database combined with recent surveys and geospatial landuse data, geomorphologic, climatic, and spatial data in a geographical information system (GIS) to model fish occurrence in the Wellington Region, New Zealand. To predict the occurrence of each species at a site from a common set of predictor variables we used a multi- response, artificial neural network (ANN), to produce a single model to predict the entire fish and decapod assemblage in one procedure. The predictions from the ANN using this landscape scale data proved very accurate and four other evaluation metrics independent of species abundance or probability thresholds also confirmed the accuracy of the model. The geospatial data available for the entire regional river network were then used to create a habitat-suitability map for all 18 species over the regional river network using GIS. This prediction map has many potential uses including; monitoring and predicting temporal changes in fish communities caused by human activities and shifts in climate, identifying of areas in need of protection, biodiversity hotspots, and areas for the reintroduction of endangered or rare species.
We used stream fish and decapod spatial occurrence data extracted from the New Zealand Freshwater Fish Database combined with recent surveys and geospatial landuse data, geomorphologic, climatic, and spatial data in a geographical information system (GIS) to model fish occurrence in the Wellington Region, New Zealand. To predict the occurrence of each species at a site from a common set of predictor variables we used a multi- response, artificial neural network (ANN), to produce a single model to predict the entire fish and decapod assemblage in one procedure. The predictions from the ANN using this landscape scale data proved very accurate and four other evaluation metrics independent of species abundance or probability thresholds also confirmed the accuracy of the model. The geospatial data available for the entire regional river network were then used to create a habitat-suitability map for all 18 species over the regional river network using GIS. This prediction map has many potential uses including; monitoring and predicting temporal changes in fish communities caused by human activities and shifts in climate, identifying of areas in need of protection, biodiversity hotspots, and areas for the reintroduction of endangered or rare species.
Joy and Death (2004): Application of the Index of Biotic Integrity Methodology to New Zealand Freshwater Fish Communities.
Joy, M.K. & Death, R.G. (2004) Application of the Index of Biotic Integrity Methodology to New Zealand Freshwater Fish Communities. Environmental Management, 34, 415–428.
An index of biotic integrity (IBI) was developed for freshwater fish in New Zealand streams. Data on freshwater fish occurrence for 5007 sites over the entire country were obtained from the New Zealand freshwater fish database for the period 1980–2002. Corresponding environmental descriptors for the stream catchments above or at each of these sites were obtained from a number of databases using a geographic information system. Of the 12 original North American IBI metrics, only six were adapted and applied because of differences between the fish faunas of New Zealand and the United States of America. A number of evaluation methods showed all six metrics contributed to the overall IBI scores with high levels of consistency. The IBI assessment of sites sampled at different times showed high levels of temporal concordance. Overall, the results presented demonstrate the potential for New Zealand freshwater fish to be used to assess river condition at large spatial scales in New Zealand in the absence of specifically selected reference sites.
An index of biotic integrity (IBI) was developed for freshwater fish in New Zealand streams. Data on freshwater fish occurrence for 5007 sites over the entire country were obtained from the New Zealand freshwater fish database for the period 1980–2002. Corresponding environmental descriptors for the stream catchments above or at each of these sites were obtained from a number of databases using a geographic information system. Of the 12 original North American IBI metrics, only six were adapted and applied because of differences between the fish faunas of New Zealand and the United States of America. A number of evaluation methods showed all six metrics contributed to the overall IBI scores with high levels of consistency. The IBI assessment of sites sampled at different times showed high levels of temporal concordance. Overall, the results presented demonstrate the potential for New Zealand freshwater fish to be used to assess river condition at large spatial scales in New Zealand in the absence of specifically selected reference sites.
Subscribe to:
Posts (Atom)