59 research outputs found
Spatial patterns in species-rich sclerophyll shrublands of southwestern Australia
No full textQuestion: The drivers of spatial patterning among plant species and the implications of those patterns for the structure and function of plant communities are of ongoing interest and debate. Here we explore the spatial patterning shown by individual species in species-rich plant communities. We (1) compare the levels of aggregation in these communities to those observed in other species-rich communities, in particular tropical rain forests, and (2) consider how abiotic conditions might influence the levels of aggregation observed. Location: We describe the spatial structure of four species-rich Mediterranean-type shrubland communities near Eneabba, Western Australia. The four sites each contain > 10 000 plants and up to 113 species, and differ in substrate-type, species richness and composition. Methods: We analysed the spatial patterning of all species with more than 20 individuals (233 species patterns), and used point process models for aggregated patterns to separate first-order gradient effects from second-order clustering. Results: Aggregated distributions were most common at all sites, but especially at the site with the highest resource availability and heterogeneity and lowest species richness. APoisson cluster process best described the majority of aggregated species, suggesting that local interactions drive fine-scale patterns in these communities. Conclusions: As with many previous studies, we found that most species showed strong local aggregation. The proportion of species showing aggregation was less than has been described in species-rich tropical rainforests but was higher than observed in many temperate plant communities. The highest proportion of aggregated species was seen at the most resource-abundant site; this is in direct contrast to conceptual models that suggest that competition should be weakest, and aggregation most prevalent, in the most resource-limited sites
New Zealand grayling data
No full textData associated with Lee, F. & Perry, G.L.W. (2019). Assessing the role of
off-take and source-sink dynamics in the extinction of the amphidromous New
Zealand grayling (Prototroctes oxyrhynchus).</p
Lee_etal_2021_connectivity
No full textCode associated with manuscript Lee F., Simon K.S. & Perry, G.L.W. Network topology mediates freshwater fish metacommunity response to loss of connectivity
Retrieval of biomass combustion rates and totals from fire radiative power observations: FRP derivation and calibration relationships between biomass consumption and fire radiative energy release
No full textEstimates of wildfire aerosol and trace gas emissions are most commonly derived from assessments of biomass combusted. The radiative component of the energy liberated by burning fuel can be measured by remote sensing, and spaceborne fire radiative energy (FRE) measures can potentially provide detailed information on the amount and rate of biomass consumption over large areas. To implement the approach, spaceborne sensors must be able to derive fire radiative power (FRP) estimates from subpixel fires using observations in just one or two spectral channels, and calibration relationships between radiated energy and fuel consumption must be developed and validated. This paper presents results from a sensitivity analysis and from experimental fires conducted to investigate these issues. Within their methodological limits, the experimental work shows that FRP assessments made via independent hyperspectral and MIR radiance approaches in fact show good agreement, and fires are calculated to radiate 14 ± 3% [mean ± 1S.D.] of their theoretically available heat yield in a form capable of direct assessment by a nadir-viewing MIR imager. The relationship between FRE and fuel mass combusted is linear and highly significant (r2 = 0.98, n = 29, p < 0.0001), and FRP is well related to combustion rate (r2 = 0.90, n = 178, p < 0.0001), though radiation from the still-hot fuel bed can sometimes contribute significant FRP from areas where combustion has ceased. We conclude that FRE assessment offers a powerful tool for supplementing existing burned-area based fuel consumption measures, and thus shows significant promise for enhancing pyrogenic trace gas and aerosol emissions estimate
Shoot flammability is decoupled from leaf flammability, but controlled by leaf functional traits
No full textData associated with the manuscript:Alam, M.A., Wyse, S.V., Buckley, H.L., Perry, G.L.W., Sullivan, J.J., Mason, N.W.H., Buxton, R., Richardson, S.J., & Curran, T.J. (2019) Shoot flammability is decoupled from leaf flammability, but controlled by leaf functional traits. Journal of Ecology</div
Retrieval of biomass combustion rates and totals from fire radiative power observations: Application to southern Africa using geostationary SEVIRI imagery
No full textSouthern African wildfires are a globally significant source of trace gases and aerosols. Estimates of southern African wildfire fuel consumption have varied from hundreds to thousands of teragrams (Tg), and better-constrained estimates are required to properly assess the effects of the pollutant emissions. A new approach for providing such estimates is via remote sensing observations of fire radiative power (FRP), a variable proportional to the rate of fuel consumption. The launch of the SEVIRI radiometer onboard the geostationary Meteosat-8 platform presents a unique opportunity to monitor FRP at 15 min intervals, allowing analysis of the complete diurnal cycle of biomass burning and calculation of the total fire radiative energy. Here we present the first FRP retrievals from SEVIRI and compare them to those derived from near-coincident MODIS overpasses. Strong agreement is achieved on a per-fire basis (r2 = 0.83, n = 139, p < 0.0001), although at the regional scale SEVIRI typically underestimates FRP with respect to MODIS due primarily to its inability to confidently detect fire pixels with FRP < 100 MW. Using relationships developed during ground-based experiments, SEVIRI-derived FRP measures are converted into estimates of the rate and total quantity of biomass combusted in southern Africa. During a 4.5 day monitoring period, and based on only the observed FRP recorded by SEVIRI, we infer that as a minimum estimate, peak combustion rates reached 50 tons/s and a total of 3.2 Tg of fuel was burnt in southern Africa. While provisional, we calculate that these figures maybe potentially increased upward by a factor of ~3 to account for atmospheric absorption of the upwelling radiation and for fires that were potentially cloud covered or too weakly emitting to be detected by the geostationary imager. The new tool of SEVIRI-derived FRP provides an insight into biomass burning on the African continent at a hitherto unobtainable temporal frequency, highly suited to the linking of pollutant emissions estimates to models of atmospheric transport.<br/
Data and code needed to create Fig. 5 in McWethy et al. 2013, Global Ecology and Biogeography
No full text<p>Publication and files needed to recreate Fig. 5 in:</p>
<p>McWethy, D.B., P.E. Higuera, C. Whitlock, T.T. Veblen, D.M.J.S. Bowman, G. Cary, S.G. Haberle, R.E. Kean, B.D. Maxwell, M.S. McGlone, G.L.W. Perry, J.M. Wilmshurst, A. Holz, and A. Tepley. 2013. A conceptual framework for predicting temperate ecosystem sensitivity to human impacts on fire regimes. Global Ecology & Biogeography, 22: 900-912.</p
McWethy et al. 2013. Global Ecology and Biogeography
No full text<p>McWethy, D.B., P.E. Higuera, C. Whitlock, T.T. Veblen, D.M.J.S. Bowman, G. Cary, S.G. Haberle, R.E. Kean, B.D. Maxwell, M.S. McGlone, G.L.W. Perry, J.M. Wilmshurst, A. Holz, and A. Tepley. 2013. A conceptual framework for predicting temperate ecosystem sensitivity to human impacts on fire regimes. Global Ecology & Biogeography, 22: 900-912.</p
Spatial modelling of "alternative" future landscapes under climate change and fire suppression, Mont Do, New Caledonia
No full textThe vegetation dynamics and disturbance regimes of the south-west Pacific have been significantly altered following human settlement. Previously forested landscapes are now dominated by a matrix of flammable early successional vegetation within which patches of mesic, fire-sensitive forest are embedded. Future environmental change, and in particular climate change, will further affect disturbance regimes in these ecosystems. If ignition frequency and fire extent increase, then the persistence of these landscapes in their current composition and structure is uncertain. Using a spatially explicit landscape ecological model, we explored the implications of climatically altered fire regimes for landscape composition and structure in a mountain-top reserve in New Caledonia. The outcomes of the modeling suggest that increased ignition probability and vegetation flammability would lead to a maquis (heathland)-dominated landscape structurally simpler than that seen today. The feasibility of fire suppression as a means of managing altered fire regimes was explored using a series of model experiments. Fire suppression has been problematic in some systems, especially those where fire hazard increases over time. However, in this ecosystem, and others in the south-west Pacific, it may be a viable alternative for managing fire because fire hazard, in terms of flammability, peaks early in the succession and then decreases over successional time
McWethy et al. 2013: Figure 5
No full text<p>Figure 5 from:</p>
<p>McWethy, D.B., P.E. Higuera, C. Whitlock, T.T. Veblen, D.M.J.S. Bowman, G. Cary, S.G. Haberle, R.E. Kean, B.D. Maxwell, M.S. McGlone, G.L.W. Perry, J.M. Wilmshurst, A. Holz, and A. Tepley. 2013. A conceptual framework for predicting temperate ecosystem sensitivity to human impacts on fire regimes. Global Ecology & Biogeography, 22: 900-912.</p
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