Old-growth Areas Research Articles

Rolling down that mountain: microgeographical adaptive divergence during a fast population expansion along a steep environmental gradient in European beech

Forest tree populations harbour high genetic diversity thanks to large effective population sizes and strong gene flow, allowing them to diversify through adaptation to local environmental pressures within dispersal distance. Many tree populations also experienced historical demographic fluctuations, including spatial population contraction or expansions at various temporal scales, which may constrain their ability to adapt to environmental variations. Our aim is to investigate how recent contraction and expansion events interfere with local adaptation, by studying patterns of adaptive divergence between closely related stands undergoing environmentally contrasted conditions, and having or not recently expanded. To investigate genome-wide signatures of local adaptation while accounting for demography, we analysed divergence in a European beech population by testing pairwise differentiation among four tree stands at ~35k Single Nucleotide Polymorphisms from ~9k genomic regions. We applied three divergence outlier search methods resting on different assumptions and targeting either single SNPs or contiguous genomic regions, while accounting for the effect of population size variations on genetic divergence. We found 27 signals of selective signatures in 19 target regions. Putatively adaptive divergence involved all stand pairs. We retrieved signals both when comparing old-growth stands and recently colonised areas and when comparing stands within the old-growth area. Therefore, adaptive divergence processes have taken place both over short time spans, under strong environmental contrasts, and over short ecological gradients, in populations that have been stable in the long term. This suggests that standing genetic variation supports local, microgeographic divergence processes, which can maintain genetic diversity at the landscape level.

Estimating the amount of British Columbia’s “big-treed” old growth: Navigating messy indicators

British Columbia’s (BC) diverse forest ecosystems include highly productive old growth with global importance for carbon storage and biodiversity. Current estimates of the remaining amount of “big-treed” old growth vary 10-fold, creating uncertainty that challenges provincial attempts to shift management policy toward ecological integrity. This uncertainty arises from using different remotely sensed indicators and definitions of tree size. No ideal indicator exists. We attempt to improve clarity by evaluating the reliability of candidate indicators, calibrating selected indicators to improve consistency, and generating multiple estimates of the amount of big-treed old growth using calibrated indicators. To evaluate reliability, we compared inventory estimates of tree size and site productivity with measured tree size in 1,945 ground plots. To assess the amount of big-treed old growth, we determined an equivalent “big” size threshold for each indicator and calculated the area of old growth above the size threshold. Stand volume, tree density, basal area, and diameter estimates performed poorly; we selected tree height and two measures of site productivity for further analysis. Estimated tree height best indicated the current old growth size, followed by inventory-based site index and finally ecosystem-based site index. The calibrated indicators agreed that very little remaining old growth supports large trees (1.5–3.3% for the biggest trees; 6–13% including medium-sized trees that represent the largest growing trees in lower productivity interior ecosystems). Tree height cannot be used to compare the remaining area of big-treed old growth to the area expected naturally, an important input for ecological risk assessment and conservation planning because height data are lost from the inventory after harvest. The two calibrated site productivity indicators agreed that the amount remaining is less than 30% of the expected historical amount, posing a high risk to biodiversity and resilience. We recommend using estimated height to identify the biggest remaining old-growth stands for regional planning and calibrated inventory-based site index for risk assessment until a detailed ecosystem mapping has been verified to represent old-growth variability. To reduce uncertainty, we suggest that planning groups compare several indicators and analysis approaches, adjusted to ensure equivalence, and use precaution to avoid any unknowingly increasing risks.

Toward diverse seed sourcing to upscale ecological restoration in the Brazilian Cerrado

Seed markets are vital to scaling up ecosystem restoration in the Brazilian Cerrado, home of the world’s most species-rich grasslands and savannas. We compiled lists of species traded by four major Cerrado seed supply systems to investigate the representativeness of the species currently available for seed-based restoration. We also identified whether dominant ground-layer species are being sourced for seed production. Seeds from 263 Cerrado species can be purchased for restoration, of which 68% are trees, particularly legumes (24%). 63% of the traded species were found in only one seed supply system. The five most dominant graminoids of the Cerrado ground layer were available for sale, but two additional species uncommon in old-growth areas represented 44% of the sales of a key seed trader in Central Brazil. The expansion of Cerrado seed supply systems should be supported to further increase the number of species on the market. Sourcing seeds from a diversity of herbaceous species is central to facilitating the restoration of species-rich grasslands and savannas in the Cerrado. Recovering the diversity and functioning of old-growth open ecosystems through seeds will depend on increasing the supply and demand for species typical of Cerrado’s ground layer.

Extensive recent wildfires demand more stringent protection of critical old growth forest

Old growth forests have many key values, but temporal changes across their spatial extent are poorly understood. This includes large parts of Australia and is a major knowledge gap given the extent of human and natural disturbances in the Australian forest estate over past decades. We integrated spatial data on the timing and extent of fire and logging across mapped forest and woodland cover in different Ecological Vegetation Class (EVC) groups to quantify disturbance of the old growth forest and woodland estate in Victoria since 1995, including after the 2019–20 wildfires. We found ~77% of old growth forest and woodlands have been disturbed by fire and logging over the past 25 years. Disturbance was particularly marked in some EVCs, such as the Wet and Damp Forest and the Subalpine Woodlands. In contrast, relatively little of the Modelled Old Growth Forest and Woodland has been disturbed between 1995 and 2020 in other EVCs such as in Plains Woodlands and Heathy Woodlands. Wildfire was the primary driver of disturbance in Modelled Old Growth Forest and Woodland. We argue that a range of strategies is critical to increase protection of undisturbed old growth forest. These include re-assessing disturbance data layers to ensure that areas of old growth that have been burned at low severity are protected, and reducing the size of old growth patches to be conserved. There is also a need to increase levels of protection of young forests to enable them to grow through to an old growth state.

Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees.

Logging, pervasive across the lowland tropics, affects millions of hectares of forest, yet its influence on nutrient cycling remains poorly understood. One hypothesis is that logging influences phosphorus (P) cycling, because this scarce nutrient is removed in extracted timber and eroded soil, leading to shifts in ecosystem functioning and community composition. However, testing this is challenging because P varies within landscapes as a function of geology, topography and climate. Superimposed upon these trends are compositional changes in logged forests, with species with more acquisitive traits, characterized by higher foliar P concentrations, more dominant. It is difficult to resolve these patterns using traditional field approaches alone. Here, we use airborne light detection and ranging‐guided hyperspectral imagery to map foliar nutrient (i.e. P, nitrogen [N]) concentrations, calibrated using field measured traits, over 400 km2 of northeastern Borneo, including a landscape‐level disturbance gradient spanning old‐growth to repeatedly logged forests. The maps reveal that canopy foliar P and N concentrations decrease with elevation. These relationships were not identified using traditional field measurements of leaf and soil nutrients. After controlling for topography, canopy foliar nutrient concentrations were lower in logged forest than in old‐growth areas, reflecting decreased nutrient availability. However, foliar nutrient concentrations and specific leaf area were greatest in relatively short patches in logged areas, reflecting a shift in composition to pioneer species with acquisitive traits. N:P ratio increased in logged forest, suggesting reduced soil P availability through disturbance. Through the first landscape scale assessment of how functional leaf traits change in response to logging, we find that differences from old‐growth forest become more pronounced as logged forests increase in stature over time, suggesting exacerbated phosphorus limitation as forests recover.

Value-added forest management planning: A new perspective on old-growth forest conservation in the fire-prone boreal landscape of Canada

The maintenance of old-growth stands is important for sustaining natural forest ecosystems, but fire disturbances and commonly-used timber harvest practices exert adverse impacts on the retention of old-growth forests. Forest management planning prescribes harvest levels based on the planning policy and models, but the impact of the management strategies on the retention of old-growth forests has not been well studied. The objectives of this study were to examine: a) the impact of implementing three different harvest policies on the retention of old-growth forest and b) the impact of implementing a policy of maintaining a targeted minimum of 20% old-growth area on the harvest revenue that would be generated over a long planning horizon. To simulate the implementation of these policies, we developed three strategic timber harvest-scheduling models. The first model (Model 1) maximizes harvest timber volume; Model 2 maximizes the net present value (NPV) of the timber harvested; and Model 3 maximizes the NPV of value-added products at the primary processing mills. The value-added products we considered were lumber, chips and sawdust. The models were solved for three forest management units with different fire regimes. Solutions to models that did not include a strict constraint on old-growth forest area retention did not retain the targeted level of old-growth forest over a 150-year planning horizon. When an old-growth constraint was implemented, Model 3 produced the greatest revenue with the least variation by 5-year period over the planning horizon. The probability of finding a feasible solution to our optimization Model 3 with an old-growth forest constraint increased to 0.87–1.0 compared with 0.71–0.83 using Model 1, and 0.78–0.87 using Model 2. We conclude that the value-added policy model increases the probability of sustaining the bioeconomy while preserving forest ecosystems initiated by disturbance.

Effects of bamboo dominance and palm-heart harvesting on the phylogenetic structure of the seed and seedling communities in an old-growth Atlantic Forest

Abstract:A comprehensive assessment of the effect of disturbances on tropical and subtropical forests is needed to better understand their impacts on forest structure and diversity. Although taxonomic and functional diversity measures have been successfully adopted in this context, phylogenetic diversity metrics are still poorly explored. We compared the phylogenetic structure of the seed rain and regenerating seedling community in patches of an old-growth Atlantic Forest remnant dominated or not by a ruderal bamboo species,Guadua tagoara. We sampled those patches before and after illegal harvesting of the palmEuterpe edulisthus assessing if the harvesting led to changes in the phylogenetic structure of the seed rain and the regenerating community in both patches. Bamboo-dominated patches showed a significantly higher presence of species in the seed rain that were more distantly related to each other in the phylogeny than expected by chance compared with patches without bamboos, but this difference disappeared after palm-heart harvesting. Contrary to what we expected, we did not find significant changes in the phylogenetic structure of seedlings before or after palm-heart harvesting. The phylogenetic structure at the tips of the phylogeny was random overall. The maintenance of a higher presence of far relatives in the phylogeny of the seedling community suggests, assuming trait conservatism, that despite bamboo dominance and palm-heart harvesting, functional diversity is being preserved at least in the early regenerating stages and in the time frame of the study. However, higher presence of pioneer taxa after palm-heart harvest indicates that this disturbance may lead old-growth areas to earlier successional stages.

Risk aversion and risk seeking in multicriteria forest management: a Markov decision process approach

Markov decision process models were extended to reflect some consequences of the risk attitude of forestry decision makers. One approach consisted of maximizing the expected value of a criterion subject to an upper bound on the variance or, symmetrically, minimizing the variance subject to a lower bound on the expected value. The other method used the certainty equivalent criterion, a weighted average of the expected value and variance. The two approaches were applied to data for mixed softwood–hardwood forests in the southern United States with multiple financial and ecological criteria. Compared with risk neutrality or risk seeking, financial risk aversion reduced expected annual financial returns and production and led to shorter cutting cycles that lowered the expected diversity of tree species and size, stand basal area, stored CO2e, and old-growth area.

Habitat Structure Influences the Diversity, Richness and Composition of Bird Assemblages in Successional Atlantic Rain Forests

This study evaluated the influence of vegetation structure on bird diversity, guilds, and the richness and composition of species in different successional stages of the subtropical Atlantic rain forest. Much of the land that was formerly agricultural in the Brazilian Atlantic rain forest region is now given over to secondary forests. The habitat structure of these successional forests vary and are influenced by time, historical use and local variables, all of which affect bird assemblies. Sampling of bird species was carried out through audio-visual point counts conducted in forests varying from six years after abandonment to old-growth areas. Forests in which the point counts were conducted were further classified into initial, intermediate and advanced stages according to 11 vegetation structural variables, through cluster analyses. The study found that bird richness and diversity were similar between initial and intermediate stages, but higher in advanced areas. Bird species composition differed betwe...

К проблеме повышения устойчивости насаждений Воронежской нагорной дубравы

The article is devoted to the definition of forest pathology condition of plantations of biology (for-est) nature monument "Old-growth areas of upland oak forests", located in the quarter 52 of Pravobe-rezhnoe forestry of Prigorodny district forest, Voronezh region. Definition of certain classes of biological sustainability of forests and evaluation of its sanitary condition during the examination of trees on test plots is carried out. The factors reducing the stability of oak trees are indentified and analyzed. Forest pa-thology plants condition were evaluated for three classes of biological sustainability. Sanitary condition of plantations is evaluated.

Mangrove rehabilitation in high erosion areas: Assessment using bioindicators

This study identifies a potentially effective rehabilitation technique for implementation in high erosion areas through the use of bioindicators. This is significant given that one third of mangroves have been cleared globally with clearing continuing at a rate of 1–2% per annum. There have been various attempts to rehabilitate degraded mangrove forests, however the success or failure of these is mostly unclear due to a lack of assessment. The two rehabilitation techniques assessed in this study were a basic fence system and another more elaborate fence technique designed by the Kien Giang Biosphere Reserve Project (KGBRP), Vietnam. The assessment was conducted by comparing vegetation and faunal communities in rehabilitation areas to those in adjacent old-growth areas. The indicators included: tree and understory plant diversity and density; forest cover and the density of crabs, mudskippers and gastropods. The results show the KGBRP rehabilitation fence technique delivered tree diversity, plant diversity, tree density and forest cover that most closely resembled old-growth areas. This suggests that the additional protection provided by the KGBRP fence was instrumental in achieving these results. In terms of total mudskipper, Boleophthalmus spp., Periophthalmodon spp. and ocypodid crab density, the KGBRP rehabilitation was most similar to the old-growth areas. This similarity is thought to be related to the comparable forest cover at these sites. The density of large crab holes was much higher in old-growth areas than in basic or KGBRP rehabilitation areas. The disparity between large crab hole density at KGBRP rehabilitation and old-growth areas, despite similar levels of forest cover, is thought to be linked to the immaturity of the KGBRP rehabilitation sites. As the KGBRP rehabilitation is most similar in terms of vegetation and faunal communities to the old-growth areas, it appears to be the most successful rehabilitation.

Impact of maximum opening area constraints on profitability and biomass availability in forestry – a large, real world case

The nature areas surrounding the capital of Norway (Oslomarka), comprising 1 700 km of forest land, are the recreational home turf for a population of 1.2 mill. people. These areas are highly valuable, not only for recreational purposes and biodiversity, but also for commercial activities. To assess the impacts of the challenges that Oslo municipality forest face in their management, we developed four optimization problems with different levels of management constraints. The constraints consider control of harvest level, guarantee of minimum old-growth forest area and maximum open area after final harvest. For the latter, to date, no appropriate analyses quantifying the impact of such a constraint on economy and biomass production have been carried out in Norway. The problem solved is large due to both the number of stands and number of treatment schedules. However, the model applied demonstrated its relevance for solving large problems involving maximum opening areas. The inclusion of maximum open area constraints caused 7.0% loss in NPV compared to the business as usual case with controlled harvest volume and minimum old-growth area. The estimated supply of 20-30 GWh annual energy from harvest residues could provide a small, but stable supply of energy to the municipality.2

Female red colobus monkeys maintain their densities through flexible feeding strategies in logged forests in Kibale National Park, Uganda

Behavioral flexibility allows primates to cope with environmental variability. Quantifying primate responses to human habitat modifications allows an effective means of assessing coping mechanisms. Within Kibale National Park, Uganda, logging led to reduced primate food availability that still exists almost 50 years after the harvest. Following the predictions of the ideal free distribution theory, primate densities are expected to decrease in areas of lower resource availability so that the resources available per individual are equivalent in logged and old-growth areas. However, counter to what would be predicted by the ideal free distribution theory, red colobus monkeys (Procolobus rufomitratus) occur at similar densities in logged and old-growth areas of Kibale. This suggests that either the ecological differences between the two areas are not sufficient to impact red colobus densities or that animals in logged areas are compensating to changes in resource availability by using different foraging strategies. To test between these hypotheses, we examined four groups of red colobus, two in logged and two in old-growth forests, and compared feeding behavior, feeding tree size, and tree productivity. Females in logged areas fed on resources from a greater number of plant species, fed on fewer resources from each species, and spent more time feeding than those in old-growth areas. By expanding their diet, females in logged areas effectively increased the resources available to them, which may contribute to their ability to maintain similar densities to females in old-growth areas. These findings have implications for an evolutionary understanding of how species deal with environmental change and considerations for conservation practices that determine what areas should be prioritized for protection.

Timing is everything: expanding the cost of sexual attraction hypothesis

Anthropogenic disturbances present challenges to animals. Behavioural plasticity is one way that animals adjust to degraded habitats. In the present study, we examined how ecological conditions impact reproduction of female red colobus monkeys, Procolobus rufomitratus, in Kibale National Park, Uganda. Wrangham (2002, Behavioural diversity in chimpanzees and bonobos, pp. 204–215) proposed the ‘cost of sexual attraction’ hypothesis to explain the relationship between ecology and female reproduction. Here for the first time we test and expand on this hypothesis in a folivorous species, the red colobus monkey. We compared four groups of red colobus, two in previously logged areas and two in old-growth areas, to examine differences in female reproductive behaviours and physiologies. We predicted that, because of differences in food availability, females living in logged areas would (1) have a shorter duration of genital tumescence, (2) mate less frequently and (3) constrain mating behaviours more to periods of maximal genital tumescence compared to females in old-growth areas. As predicted, females in logged areas were fully tumescent for a significantly shorter period, copulated significantly less frequently and showed mating behaviours when fully inflated significantly more than females in old-growth areas. This behavioural plasticity contributes to the maintenance of female reproductive function in the face of environmental constraints associated with anthropogenic disturbance that influences food resources.

Are silvopastoral systems compatible with forest regeneration? An integrative approach in southern Patagonia

We used an integrated approach to analyze the influence of silvopastoral management on the biotic and abiotic factors influencing on the natural recruitment of native forests in Tierra del Fuego (Argentina). The probabilities of transition from flowers to seeds to seedlings were estimated in forests with silvopastoral management (i.e., stands that had been both grazed and thinned), secondary growth stands, and unmanaged old-growth areas. Pre-dispersal losses were caused by microclimate and insect predation acting on flowers and immature fruits. Post-dispersal losses resulted from the impact of reduced litterfall and microclimate. But the most critical stage of the overall cycle was seedling establishment. Silvopastoral practices and stand age modified the main drivers of regeneration. While flowering was unaffected by management, fruiting and seed production were more successful in unmanaged forests. Seedling establishment and survival were favored by canopy cover reduction in silvopastoral stands. The increase of solar radiation and soil moisture in managed forests positively influenced the seedling establishment and survival, while in second-growth forests it was limited by suitable micro-site availability. Thinning practices aimed at increasing the understory heterogeneity in mature forests and restoring canopy complexity of second-growth stands could be suitable for sustainable management of these temperate forests.

Oribatid Mite Community Decline Two Years after Low-Intensity Burning in the Southern Cascade Range of California, USA

To assess effects of low-intensity fire, we combined two silvicultural prescriptions with prescribed fire in the California Cascade Range. In the first treatment, two 100-ha stands were thinned to reduce density while retaining old-growth structural characteristics, yielding residual stands with high structural diversity (HSD). Two other 100-ha plots were thinned to minimize old growth structure, producing even-aged stands of low structural diversity (LSD), and one 50-ha split-plot from each treatment was burned. In addition, two 50 ha old-growth Research Natural Areas (RNA) were selected as untreated reference plots, one of which was also burned. Fire treatments profoundly altered mite assemblages in the short term, and forest structure modification likely exacerbated that response. Sampling conducted two years following treatment confirmed a continuing decline in oribatid mite abundance. Oribatid species richness and assemblage heterogeneity also declined, and community dominance patterns were disrupted. Oribatid responses to fire were either more intense or began earlier in the LSD treatments, suggesting that removal of old-growth structure exacerbated mite responses to fire. Prostigmatids recovered quickly, but their populations nonetheless diminished significantly in burned split-plots. Mite assemblage responses to prescribed fire were continuing nearly two years later, with no clear evidence of recovery.

Habitat structure and food resources for wildlife across successional stages in a tropical forest

Tropical forests are experiencing an increase in the proportion of secondary forests as a result of the balance between the widespread harvesting of old-growth forests and the regeneration in abandoned areas. The impacts of such a process on biodiversity are poorly known and intensely debated. Recent reviews and multi-taxa studies indicate that species replacement in wildlife assemblages is a consistent pattern, sometimes stronger than changes in diversity, with a replacement from habitat generalists to old-growth specialists being commonly observed during tropical forest regeneration. However, the ecological drivers of such compositional changes are rarely investigated, despite its importance in assessing the conservation value of secondary forests, and to support and guide management techniques for restoration. By sampling 28 sites in a continuous Atlantic forest area in Southeastern Brazil, we assessed how important aspects of habitat structure and food resources for wildlife change across successional stages, and point out hypotheses on the implications of these changes for wildlife recovery. Old-growth areas presented a more complex structure at ground level (deeper leaf litter, and higher woody debris volume) and higher fruit availability from an understorey palm, whereas vegetation connectivity, ground-dwelling arthropod biomass, and total fruit availability were higher in earlier successional stages. From these results we hypothetize that generalist species adapted to fast population growth in resource-rich environments should proliferate and dominate earlier successional stages, while species with higher competitive ability in resource-limited environments, or those that depend on resources such as palm fruits, on higher complexity at the ground level, or on open space for flying, should dominate older-growth forests. Since the identification of the drivers of wildlife recovery is crucial for restoration strategies, it is important that future work test and further develop the proposed hypotheses. We also found structural and functional differences between old-growth forests and secondary forests with more than 80years of regeneration, suggesting that restoration strategies may be crucial to recover structural and functional aspects expected to be important for wildlife in much altered ecosystems, such as the Brazilian Atlantic forest.

Exploring adaptation to climate change in the forests of central Nova Scotia, Canada

The threat of climate change is now recognized as an imminent issue at the forefront of the forest sector. Incorporating adaptation to climate change into forest management will be vital in the continual and sustainable provision of forest ecosystem services. The objective of this study is to investigate climate change adaptation in forest management using the landscape disturbance model LANDIS-II. The study area was comprised of 14,000 ha of forested watersheds in central Nova Scotia, Canada, managed by Halifax Water, the municipal water utility. Simulated climate change adaptation was directed towards three components of timber harvesting: the canopy-opening size of harvests, the age of harvested trees within a stand, and the species composition of harvested trees within a stand. These three adaptation treatments were simulated singly and in combination with each other in the modeling experiment. The timber supply was found to benefit from climate change in the absence of any adaptation treatment, though there was a loss of target tree species and old growth forest. In the age treatment, all trees in a harvested stand at or below the age of sexual maturity were exempt from harvesting. This was done to promote more-rapid succession to climax forest communities typical of the study area. It was the most effective in maintaining the timber supply, but least effective in promoting resistance to climate change at the prescribed harvest intensity. In the composition treatment, individual tree species were selected for harvest based on their response to climate change in previous research and on management values at Halifax Water to progressively facilitate forest transition under the altered climate. This proved the most effective treatment for maximizing forest age and old-growth area and for promoting stands composed of climatically suited target species. The size treatment was aimed towards building stand complexity and resilience to climate change, and was the most influential treatment on the response of timber supply, forest age, and forest composition to timber harvest when it was combined with other treatments. The combination of all three adaptation treatments yielded an adequate representation of target species and old forest without overly diminishing the timber supply, and was therefore the most effective in minimizing the trade-offs between management values and objectives. These findings support a diverse and multi-faceted approach to climate change adaptation.

Global population decline of the Great Slaty Woodpecker ( Mulleripicus pulverulentus)

The Great Slaty Woodpecker ( Mulleripicus pulverulentus) of South and Southeast Asia, the third largest woodpecker species in the world, is currently in the IUCN Red List category of Least Concern. This woodpecker appears associated with old-growth forests, and the rapid reductions in forest cover and old-growth area in Southeast Asia urged examination of its global population trends. We assessed population densities, tree diameter use by the woodpecker, and logging disturbance at 21 transects in four regions across the range of the species: west Borneo, Lingga Island (Riau Archipelago, Indonesia), Tenasserim (Myanmar), and west-central Myanmar. Transect survey effort was 937 km. We assessed rates of deforestation and loss of old-growth forest in the range of the species from expert review reports. By combining population density and forest cover data sets we calculated the global population trend of the species. We found a preference for large diameter trees by foraging and nesting Great Slaty Woodpeckers, and a reduction of the frequency of such trees in logged forests. Across the four study regions, between old-growth forests and logged forests, densities of Great Slaty Woodpeckers were reduced by 80–94%. Although Great Slaty Woodpeckers occur in 15 countries, ca. 70% of the global population occurs in just four countries (Myanmar, Indonesia, Cambodia, and Malaysia), three of which have high annual rates of deforestation and loss of old-growth forest. Our population calculations show that over the past century at least 90% of the global population of the Great Slaty Woodpecker has been lost. At present 26,000–550,000 individuals remain. The current global decline rate of ca. 59% ± SD 17% in three generations justifies IUCN Vulnerable or Endangered status. Contributing factors to the steep decline rate of the species are a long generation time of 5.9–8.2 years and an association with old-growth, lower elevation forests. The Great Slaty Woodpecker case adds an Asian example to a global pattern of specialized woodpeckers that are associated with old or natural forests.

Efficacy of Audiovisual and Radar Surveys for Studying Marbled Murrelets in Inland Habitats

Radar and audiovisual surveys are important tools for identifying nesting habitat and developing inland conservation strategies for the marbled murrelet (Brachyramphus marmoratus), a threatened seabird that nests in old-growth forests in the Pacific Northwest, USA. Theoretically, counts from these 2 approaches (radar and audiovisual surveys) in different habitats depend on both habitat-specific densities and detection probabilities, which could result in spurious or mask differences among habitats if murrelets are more detectable in certain habitat types. Therefore, we used simultaneous audiovisual and radar surveys to estimate detection probabilities and quantify the relationship between detection probabilities and habitat in coastal redwood forests of northern California, USA. Radar and audiovisual counts were highly correlated (r = 0.65) based on 156 simultaneous surveys, but audiovisual surveys detected only 20.2% (2.6 SE) of murrelets detected by radar, whereas radar detected 75.6% (6.3 SE) of murrelets detected by audiovisual surveys. Murrelets tended to be easier to detect with both audiovisual and radar surveys when there were relatively large areas (>35 ha) of unharvested, old-growth forest at the survey site, probably because birds tended to fly slower and circled more over old growth. Detection probabilities were strongly affected by a variety of other factors including weather, time relative to sunrise, observer, and murrelet behavior. Murrelet counts were positively but weakly correlated to the area of unharvested old growth at the survey site for audiovisual and radar surveys, but this relationship disappeared when we corrected for the effect of habitat on detection probabilities. Our results indicate that raw counts should not be used as indices of nesting densities in different habitats and underscore the need to model heterogeneity in detection probabilities among habitats using available sampling designs and statistical methods. Nevertheless, we recommend using radar instead of audiovisual surveys for counting murrelets in forested areas because detection probabilities were much higher for radar than audiovisual surveys, radar is less likely to detect the same group of murrelets multiple times, and radar surveys can be conducted in poor viewing and hearing conditions.