Secondary succession and breeding bird community structure: Patterns of resource utilization

A successional shift enhances stability in ant symbiont communities

Throughout succession, communities undergo structural shifts, which can alter the relative abundances of species and how they interact. It is frequently asserted that these alterations beget stability, i.e. that succession selects for communities better able to resist perturbations. Yet, whether and how alterations of network structure affect stability during succession in complex communities is rarely studied in natural ecosystems. Here, we explore how network attributes influence stability of different successional stages of a natural network: symbiotic arthropod communities forming food webs inside red wood ant nests. We determined the abundance of 16 functional groups within the symbiont community across 51 host nests in the beginning and end stages of succession. Nest age was the main driver of the compositional shifts: symbiont communities in old nests contained more even species abundance distributions and a greater proportion of specialists. Based on the abundance data, we reconstructed interaction matrices and food webs of the symbiont community for each nest. We showed that the enhanced community evenness in old nests leads to an augmented food web stability in all but the largest symbiont communities. Overall, this study demonstrates that succession begets stability in a natural ecological network by making the community more even.

Do Review Papers on Bird–Vegetation Relationships Provide Actionable Information to Forest Managers in the Eastern United States?

Forest management planning requires the specification of measurable objectives as desired future conditions at spatial extents ranging from stands to landscapes and temporal extents ranging from a single growing season to several centuries. Effective implementation of forest management requires understanding current conditions and constraints well enough to apply the appropriate silvicultural strategies to produce desired future conditions, often for multiple objectives, at varying spatial and temporal extents. We administered an online survey to forest managers in the eastern US to better understand how wildlife scientists could best provide information to help meet wildlife-related habitat objectives. We then examined more than 1000 review papers on bird–vegetation relationships in the eastern US compiled during a systematic review of the primary literature to see how well this evidence-base meets the information needs of forest managers. We identified two main areas where wildlife scientists could increase the relevance and applicability of their research. First, forest managers want descriptions of wildlife species–vegetation relationships using the operational metrics of forest management (forest type, tree species composition, basal area, tree density, stocking rates, etc.) summarized at the operational spatial units of forest management (stands, compartments, and forests). Second, forest managers want information about how to provide wildlife habitats for many different species with varied habitat needs across temporal extents related to the ecological processes of succession after harvest or natural disturbance (1–2 decades) or even longer periods of stand development. We provide examples of review papers that meet these information needs of forest managers and topic-specific bibliographies of additional review papers that may contain actionable information for foresters who wish to meet wildlife management objectives. We suggest that wildlife scientists become more familiar with the extensive grey literature on forest bird–vegetation relationships and forest management that is available in natural resource management agency reports. We also suggest that wildlife scientists could reconsider everything from the questions they ask, the metrics they report on, and the way they allocate samples in time and space, to provide more relevant and actionable information to forest managers.

Does post-mining rehabilitation restore habitat equivalent to that removed by mining? A case study from the monsoonal tropics of northern Australia

Context Rehabilitation is increasingly being promoted as a strategy for minimising and even reversing biodiversity loss. Many rehabilitation strategies that aim to provide habitat focus entirely on establishing vegetation. Successful vegetation establishment, however, does not necessarily provide habitat that is ecologically equivalent to that removed by vegetation clearing. Quantitative understanding of faunal responses to rehabilitation is required if rehabilitation techniques are to be refined and deliver desired biodiversity outcomes. Aims I aimed to assess the extent to which post-mining rehabilitation restores bird habitat equivalent to that removed in the mining process on the Weipa bauxite plateau. Methods The composition, abundance and richness of bird assemblages were compared between native forest sites and a 23-year chronosequence of post-mining rehabilitation sites. Native forest sites were made up of three Weipa bauxite plateau land units, including the land unit that represents pre-mining native forest, and two land units that are considered to be potential analogues for the post-mining landscape. Key results Bird abundance and bird species richness increased with rehabilitation age. Bird species richness in the two oldest age classes of mine rehabilitation was similar to values obtained from pre-mining native forest and post-mining landscape analogue sites. The composition of bird assemblages, however, was significantly different. Of all the bird species observed, 25% occurred exclusively in native forest sites, 19% occurred exclusively in mine-rehabilitation sites, and the remaining 56% were recorded in both native forest and mine-rehabilitation sites. Site bird-detection rates were significantly related to site vegetation structure, with inter-specific differences in bird response. Conclusions Post-mining rehabilitation at Weipa has partially made up for the loss of habitat caused by clearing for mining. Twenty-three years after rehabilitation commenced, however, a clear residual impact on biodiversity remains, with a third of native forest birds absent from mine rehabilitation, including several native forest specialists. Implications Rehabilitation can partially make up for biodiversity losses caused by the initial loss of habitat. There is no evidence, however, that rehabilitation can achieve ‘no net loss’. Reliance on rehabilitation to achieve conservation outcomes does not address the fact that many fauna species require resources that are found only in mature forest.