Optimal management of a flammable forest providing timber and carbon sequestration benefits: an Australian case study

In deciding to keep or fell a forest stand given its age, the risk of loss of timber through wildfire is an important consideration. If trees also have value from sequestration of carbon, another effect of fire is the unplanned loss of stored carbon. Factors affecting the decision to keep or fell trees, and how much to spend on fire protection, are investigated using stochastic dynamic programming, using carbon sequestration in stands of mountain ash in Victoria as a case study. The effect of treating sawlogs as a permanent carbon sink after harvesting is explored.Forest management, timber, carbon, dynamic, programming, Resource /Energy Economics and Policy,

Despotic, high-impact species and the subcontinental scale control of avian assemblage structure

Some species have disproportionate influence on assemblage structure, given their numbers or biomass. Most examples of such "strong interactors'' come from small-scale experiments or from observations of the effects of invasive species. There is evidence that entire avian assemblages in open woodlands can be influenced strongly by individual species over very large areas in eastern Australia, with small-bodied species (2000 km). A series of linked Bayesian models was used to identify large-bodied (>= 50 g) bird species that were associated with changes in occurrence and abundance of small-bodied species. One native species, the Noisy Miner (Manorina melanocephala; family Meliphagidae), was objectively identified as the sole large-bodied species having similar detrimental effects in all districts, depressing occurrence of 57 of 71 small-bodied species. Adverse effects on abundances of small-bodied species were profound when the Noisy Miner occurred with mean site abundances >= 1.6 birds/2 ha. The Noisy Miner may be the first species to have been shown to influence whole-of-avifauna assemblage structure through despotic aggressiveness over subcontinental scales. These substantial shifts in occurrence rates and abundances of small-bodied species flow on to alter species abundance distributions of entire assemblages over much of eastern Australia

Responses of floodplain birds to high-amplitude precipitation fluctuations over two decades

Globally, high-amplitude variation in weather (e.g. precipitation) is increasing in frequency and magnitude. This appears to be so for the southern Murray-Darling Basin, Australia, where droughts of unprecedented (in the instrumental record, extending back to the mid-1800s) depth and duration (1997–first half of 2010; second half of 2012–) are being punctuated by extreme wet periods, albeit of shorter duration (‘Big Wet’, second half of 2010–first half of 2012). We have previously reported on the responses of floodplain-forest birds to the cessation of the longest recorded drought (‘Big Dry’, 1997–first half of 2010), but we found little evidence of a rebound, at least shortly after the Big Wet. However, we reasoned that there may have been insufficient time for the birds to have responded in that short time, so we repeated the survey program 5 years after the end of the Big Wet (2017). Bird occurrences, reproductive activity and success were substantially greater compared with late in the Big Dry (2009) than they had been soon after the Big Wet (2013). However, bird occurrences still fell well below measurements in the early-Big Dry (1998), so that the avifauna appears to be in decline, most probably because the length of drought periods far exceeds that of wet periods giving the birds too little time to recover fully. © 2022 The Authors. Austral Ecology published by John Wiley & Sons Australia, Ltd on behalf of Ecological Society of Australia

How well do ecosystem-based planning units represent different componenets of biodiversity?

There are many proposals for managing biodiversity by using surrogates, such as umbrella, indicator, focal, and flagship species. We use the term biodiversity management unit for any ecosystem-based classificatory scheme for managing biodiversity. The sufficiency of biodiversity management unit classification schemes depends upon (1) whether different biotic elements (e.g., trees, birds, reptiles) distinguish between biodiversity management units within a classification (i.e., coherence within classes}; and (2) whether different biotic elements agree upon similarities and dissimilarities among biodiversity management unit classes (i.e., conformance among classes). Recent evaluations suggest that biodiversity surrogates based on few or single taxa are not useful. Ecological vegetation classes are an ecosystem-based classification scheme used as one component for biodiversity management in Victoria, Australia. Here we evaluated the potential for ecological vegetation classes to be used as biodiversity management units in the box-ironbark ecosystem of central Victoria, Australia. Eighty sites distributed among 14 ecological vegetation classes were surveyed in the same ways for tree species, birds, mammals, reptiles, terrestrial invertebrates, and nocturnal flying insects. Habitat structure and geographic separations also were measured, which, with the biotic elements, are collectively referred to as variables. Less than half of the biotic element-ecological vegetation class pairings were coherent. Generalized Mantel tests were used to examine conformance among variables with respect to ecological vegetation classes. While most tests were not significant, birds, mammals, tree species, and habitat structure together showed significant agreement on the rating of similarities among ecological vegetation classes. In this system, use of ecological vegetation classes as biodiversity management units may account reasonably well for birds, mammals, and trees; but reptiles and invertebrates would not be accommodated. We conclude that surrogates will usually have to be augmented or developed as hierarchies to provide general representativeness

Zoo Basel Newsletter. 2013, Juli

Climate change alters the frequency and severity of extreme events, such as drought. Such events will be increasingly important in shaping communities as climate change intensifies. The ability of species to withstand extreme events (resistance) and to recover once adverse conditions abate (resilience) will determine their persistence. We estimated the resistance and resilience of bird species during and after a 13-year drought (the \u27Big Dry\u27) in floodplain forests in south-eastern Australia. We conducted bird surveys at the beginning and end of the Big Dry, and after the abrupt end to the drought (the \u27Big Wet\u27), to evaluate species-specific changes in reporting rates among the three periods. We assessed changes in bird-breeding activity before and after the Big Wet to estimate demographic resilience based on breeding. Between the start and the end of the Big Dry (1998 vs. 2009), 37 of 67 species declined substantially. Of those, only two had increased reporting rates after the Big Wet (2009 vs. 2013) that were equal to or larger than their declines, while three partially recovered. All other declining species showed low resilience: 25 showed no change in reporting rates and seven declined further. The number of breeding species and total breeding activity of all species declined after the Big Wet, and there was no change in the number of young produced. The Big Dry caused widespread declines in the floodplain avifauna. Despite the drought being broken by 2 years of well-above-average rainfall and subsequent near-average rainfall, most species showed low resilience and there was little indication that overall breeding had increased. The effects of drought appeared to be pervasive for much of the floodplain avifauna, regardless of species traits (species body mass, fecundity, mobility or diet). Ecosystems such as these are likely to require active management and restoration, including reinstatement of natural flooding regimes, to improve ecological condition, to enhance resistance and resilience to extreme climate events

Multi-scale assessment of human-induced changes to Amazonian instream habitats

Context Land use change and forest degradation have myriad effects on tropical ecosystems. Yet their consequences for low-order streams remain very poorly understood, including in the world´s largest freshwater basin, the Amazon. Objectives Determine the degree to which physical and chemical characteristics of the instream habitat of low-order Amazonian streams change in response to past local- and catchment-level anthropogenic disturbances. Methods To do so, we collected field instream habitat (i.e., physical habitat and water quality) and landscape data from 99 stream sites in two eastern Brazilian Amazon regions. We used random forest regression trees to assess the relative importance of different predictor variables in determining changes in instream habitat response variables. Results Multiple drivers, operating at multiple spatial scales, were important in determining changes in the physical habitat and water quality of the sites. Although we found few similarities in modelled relationships between the two regions, we observed non-linear responses of specific instream characteristics to landscape change; for example 20 % of catchment deforestation resulted in consistently warmer streams. Conclusions Our results highlight the importance of local riparian and catchment-scale forest cover in shaping instream physical environments, but also underscore the importance of other land use changes and activities, such as road crossings and upstream agriculture intensification. In contrast to the property-scale focus of the Brazilian Forest code, which governs environmental regulations on private land, our results reinforce the importance of catchment-wide management strategies to protect stream ecosystem integrity

Integrating plant- and animal-based perspectives for more effective restoration of biodiversity

Ecological restoration of modified and degraded landscapes is an important challenge for the 21st century, with potential for major gains in the recovery of biodiversity. However, there is a general lack of agreement between plant- and animal-based approaches to restoration, both in theory and practice. Here, we review these approaches, identify limitations from failing to effectively integrate their different perspectives, and suggest ways to improve outcomes for biodiversity recovery in agricultural landscapes. We highlight the need to strengthen collaboration between plant and animal ecologists, to overcome disciplinary and cultural differences, and to achieve a more unified approach to restoration ecology. Explicit consideration of key ecosystem functions, the need to plan at multiple spatial and temporal scales, and the importance of plant–animal interactions can provide a bridge between plant- and animal-based methods. A systematic approach to restoration planning is critical to achieving effective biodiversity outcomes while meeting long-term social and economic needs

How pervasive is biotic homogenization in human‐modified tropical forest landscapes?

Land-cover change and ecosystem degradation may lead to biotic homogenization, yet our understanding of this phenomenon over large spatial scales and different biotic groups remains weak. We used a multi-taxa dataset from 335 sites and 36 heterogeneous landscapes in the Brazilian Amazon to examine the potential for landscape-scale processes to modulate the cumulative effects of local disturbances. Biotic homogenization was high in production areas but much less in disturbed and regenerating forests, where high levels of among-site and among-landscape β-diversity appeared to attenuate species loss at larger scales. We found consistently high levels of β-diversity among landscapes for all land cover classes, providing support for landscape-scale divergence in species composition. Our findings support concerns that β-diversity has been underestimated as a driver of biodiversity change and underscore the importance of maintaining a distributed network of reserves, including remaining areas of undisturbed primary forest, but also disturbed and regenerating forests, to conserve regional biota

Predicting Landscape-Genetic Consequences of Habitat Loss, Fragmentation and Mobility for Multiple Species of Woodland Birds

Inference concerning the impact of habitat fragmentation on dispersal and gene flow is a key theme in landscape genetics. Recently, the ability of established approaches to identify reliably the differential effects of landscape structure (e.g. land-cover composition, remnant vegetation configuration and extent) on the mobility of organisms has been questioned. More explicit methods of predicting and testing for such effects must move beyond post hoc explanations for single landscapes and species. Here, we document a process for making a priori predictions, using existing spatial and ecological data and expert opinion, of the effects of landscape structure on genetic structure of multiple species across replicated landscape blocks. We compare the results of two common methods for estimating the influence of landscape structure on effective distance: least-cost path analysis and isolation-by-resistance. We present a series of alternative models of genetic connectivity in the study area, represented by different landscape resistance surfaces for calculating effective distance, and identify appropriate null models. The process is applied to ten species of sympatric woodland-dependant birds. For each species, we rank a priori the expectation of fit of genetic response to the models according to the expected response of birds to loss of structural connectivity and landscape-scale tree-cover. These rankings (our hypotheses) are presented for testing with empirical genetic data in a subsequent contribution. We propose that this replicated landscape, multi-species approach offers a robust method for identifying the likely effects of landscape fragmentation on dispersal