Endangered lowland oak forest steppe remnants keep unique bird species richness in Central Hungary

The biodiversity of natural or semi-natural native, old oak woodlands have high conservation importance, especially in landscapes of monocultural forest plantations and arable fields. With a wider variety of microhabitats and foraging sources, such old oak forests can provide essential habitat for native forest bird communities. We conducted a study using bird point counts to compare the forest bird communities of old pedunculate oak (Quercus robur) remnants with native and non-native plantations in central Hungary in a landscape of mostly arable fields, settlements, and monocultural plantations. Avian surveys were carried out in old oak forest remnants, middle-aged oak, white poplar (Populus alba), hybrid poplar (Populus × euramericana), black locust (Robinia pseudoacacia), and pine (Pinus spp.) plantations. Fieldwork has been carried out in nine study sites, where all six habitat types were represented (with a few exceptions), to determine total abundance, species richness, Shannon–Wiener diversity, species evenness, dominant and indicator species, and guild abundances. We found that old oak forest remnants were the most diverse habitats among the studied forest types, while hybrid poplar and pine plantations exhibited the lowest avian biodiversity. The avian guilds most sensitive to the loss of old oak forest remnants were ground foragers, bark foragers, cavity-nesters, residents, and Mediterranean migratory birds. Native habitats were more diverse than non-native plantations. Our results suggest that it is important to conserve all remaining high biodiversity old oak stands and to avoid clear-cutting of monocultural plantations in favour of practices such as mixed-species plantations, longer rotation lengths, or retention forestry.

Potential Recolonization Benefits of Retention Forestry Practices

Tree retention after forest harvest is often used to enhance biodiversity in forests that are otherwise managed using even-aged systems. It remains unclear to what extent scattered trees and residual patches (i.e., retained structures) actually facilitate recolonization of species in logged areas. For assessing recolonization benefits, it is necessary to consider both survival in retained structures postharvest and recolonization in cleared areas. We conducted a literature review to assess recolonization responses of birds, mammals, reptiles, amphibians, vascular plants, invertebrates, lichens/bryophytes, and mycorrhizal fungi. The clearest benefits of retention were for poorly dispersing plants. Seed dispersal type may be a key life-history trait relative to effectiveness of recolonization, with animal-dispersed seeds having the greatest dispersal range. We found that lichens/bryophytes are likely not dispersal limited (with possible exceptions) but are slow growing and require the development of moist microsite conditions. Significant literature gaps exist for amphibians, nonvolant invertebrates, and mycorrhizal fungi. Overall, recolonization success postharvest is taxon specific, where the benefits of implementing retention systems will depend on the region and species within that region. Species that require a long growth period (some lichens) or are poor dispersers (some herbaceous species) may benefit more from the creation of forest reserves than from retention practices.

The Use of Tree-Related Microhabitats as Forest Biodiversity Indicators and to Guide Integrated Forest Management

Purpose of the Review The concept of tree-related microhabitats (TreMs) is an approach to assess and manage multi-taxon species richness in forest ecosystems. Owing to their provision of special habitat features, TreMs are of special interest as a surrogate biodiversity indicator. In particular, in retention forestry, TreMs have gained attention over the past decade as a selection criterion for retained structural elements such as habitat trees. This review seeks to (a) address the suitability of TreMs as biodiversity indicator in the context of retention forestry, (b) summarize drivers of TreM occurrence and the status quo of the implementation of TreM-based retention concepts in forest management, and (c) discuss current and future challenges to the use of TreMs as biodiversity indicator. Recent Findings The TreM concept originated in Europe where it is now increasingly implemented. Most studies of the quantity, quality, and diversity of TreMs are focused on tree species from this region, although it is increasingly applied in other contexts. In addition to tree species, tree dimensions and live status have been identified as the main drivers of TreM occurrence. One major remaining research challenge is to verify relationships between the occurrence and abundance of forest-dwelling species from different taxonomic groups and TreMs to improve the evidence basis of this concept and thus increase its integration in forest conservation approaches. Summary TreMs are not the “silver bullet” indicator to quantify biodiversity of forest dwelling species, but they provide an important tool for forest managers to guide the selection of habitat trees for the conservation of the associated biodiversity.

Application of the Conservation Planning Tool Zonation to Inform Retention Planning in the Boreal Forest of Western Canada

Retention forestry is an approach in which live trees and other components of forest structure are retained within harvested areas. A primary objective of retention forestry is to maintain biodiversity and to hasten post-harvest recovery of forest structure and function. Retention is now a key element in sustainable forest management practices in many regions of the world. However, locating where retention should be placed to best achieve management objectives is a challenging problem, and evidence-based approaches to operational applications are rare. We suggest here that harvest planners could benefit from the use of systematic conservation planning principles and methods to inform retention design. Specifically, we used a conservation planning—or prioritization—tool, Zonation, to create spatially-explicit scenarios of retention harvesting in a boreal mixedwood forest in northwestern Alberta, Canada. Scenarios were informed by several environmental variables related to site productivity; in particular, we used a metric of wetness (depth-to-water from the Wet Areas Mapping algorithm) that is based on airborne lidar-derived terrain models previously shown to correlate with patterns in post-harvest forest regeneration and biodiversity. The nine retention scenarios examined here related to the placement of retention focused to drier, mesic, or wetter sites in combination with other prioritization constraints. Results were compared with an existing harvest plan to assess differences in the spatial pattern of retention (e.g., percent overlapping area, number of patches, size of the patches). We also tested for the homogeneity of forest attributes (e.g., tree species, deciduous density) between scenarios and the existing harvest plan using multivariate dispersion analysis. Our results showed limited commonalities among scenarios compared to the existing harvest plan; they were characterized as having limited spatial overlap, and more and smaller patches with the use of a timber-cost constraint further affecting retention patterns. While modeling results significantly differed from current retention practices, the approach presented here offers flexibility in testing different scenarios and assessing trade-offs between timber production and conservation goals using a standardized conservation planning toolkit.

Long-term effects of prescribed burning, tree retention, and browsing on deciduous tree recruitment in European boreal forests

Silvicultural practices, effective fire suppression, and increased browser densities have profoundly altered structural diversity in boreal forests. Prescribed burning and retention forestry may counteract losses in structural diversity in managed forests, by maintaining higher deciduous admixture. We constructed an experiment on 18 sites with three types of timber harvesting (uncut, cut with retention, and clearcut) and burned half these sites. Subsequently, we established a herbivore treatment with three compartments (unfenced, fenced excluding moose (Alces alces), and fenced excluding moose and hares (Lepus spp.)). In these compartments, we planted rowan (Sorbus aucuparia), European aspen (Populus tremula), and silver birch (Betula pendula) seedlings, and monitored these for 17 years. Birch and rowan mortality were lower on cut and burned sites, with retention further enhancing birch survival on these sites. Retention without burning did not lower seedling mortality of any tree species. While browsing resulted in greater mortality on cut sites, burning appeared to greatly reduce browsing on birch and rowan. On mature uncut sites, seedlings of all tree species exhibited high mortality. Our findings show that deciduous tree recruitment can be improved through prescribed burning, particularly for birch and rowan, and that browsing impacts on deciduous trees depend on forest age.

The effects of variable retention forestry on coarse woody debris dynamics and concomitant impacts on American marten habitat after 27 years

Coarse woody debris (CWD) in the form of logs, downed wood, stumps and large tree limbs is an important structural habitat feature for many small mammal species, including the American marten (Martes americana). At a long-term experimental trial in northern temperate hemlock-cedar forests of British Columbia, Canada, we analysed the impact of varying amounts of overstory basal area retention: 0% (clearcut), 40%, 70%, and 100% (unharvested) on CWD volume, decay class, and inputs from windthrow over 27 years. We used CWD attributes (diameter, length, decay class, and height above the ground) known to be favourable for martens to create an index for assessing the impact of harvesting intensity on CWD habitat features. Stands with 70% retention had CWD attributes that resulted in CWD habitat features similar to unharvested stands. Clearcuts contained pieces that were smaller, more decayed, and closer to the ground, which contributed to a habitat that was less valuable, compared with stands that had higher retention. Over the 27-year period, windthrown trees were the majority of CWD inputs, and volume change was positively related to percent retention. Our results highlight that forest management influences CWD size and input dynamics over multiple decades, and the need for consideration of these impacts when undertaking long-term multiple-use forestry planning.