Tree Retention Research Articles

Bee Forage Tree Resources for Wild Honeybees: A Case Study from Kodagu's Sacred Groves and Coffee Agroecosystems

Wild honeybee populations are fundamental to biodiversity conservation and agricultural productivity, particularly as pollinators in tropical regions. This study investigated the diversity and seasonal availability of bee forage trees within sacred groves and coffee agro ecosystems in Kodagu, Karnataka, a biodiversity-rich area in the Western Ghats. Sacred groves, protected for cultural reasons, feature high floral diversity, providing continuous nectar and pollen resources, crucial for wild bee populations throughout the year. In contrast, coffee plantations, particularly in semi-evergreen systems, offer valuable yet seasonally limited forage, supplemented by selective native tree retention. By integrating traditional ecological knowledge associated with sacred groves and modern conservation practices, the research highlights how culturally protected landscapes contribute to year-round floral resources, crucial for sustaining wild bee populations. Sacred groves were found to consistently surpass coffee plantations in floral diversity and forage stability, particularly in semi-evergreen groves, which recorded the highest diversity and richness (H' = 3.75, 52 species). In contrast, coffee plantations, enhanced by selective retention of native trees, offer seasonally valuable but limited forage, with moderate diversity (H' = 3.35, 54 species). The study identifies key forage species unique to sacred groves and underscores their role in maintaining ecological resilience. These findings have practical implications for guiding community-based conservation programs, demonstrating that leveraging sacred groves and ecologically managed coffee agroecosystems can effectively balance biodiversity conservation with agricultural productivity. This integrated approach offers a model for sustaining pollinator populations vital to ecosystem health and crop yields.

Hostile environments, terminal habitat, and tomb trees: the impact of systemic failures to survey for mature-forest dependent species in the State forests of New South Wales

Context The Coastal Integrated Forestry Approval (CIFOA) areas of New South Wales (NSW), Australia include most populations of at least two threatened species of glider Petaurus australis australis (Yellow-bellied Glider [south-eastern]) and Petauroides volans (Greater Glider [Southern and Central]). The NSW Environmental Protection Authority (EPA) administers protocols to conserve gliders within forest compartments intensively managed for timber production by Forests Corporation NSW (FCNSW). These protocols include pre-logging surveys and retention of hollow-bearing trees (HBTs), den trees, and associated buffers. Citizen scientists have ground-truthed these protocols in some compartments. Aims We assessed the effectiveness of surveys by FCNSW and associated outcomes in the context of planned logging operations. Methods We used the publicly available EPA Native Forestry map viewer data for this analysis. Key results Although gliders have been detected and abundant HBTs retained in 10 State forests, no den trees were identified by FCNSW in any ‘active’ compartment (as at December 2023). Thus, isolated HBTs or tomb trees were retained without associated buffers. Several phases of EPA protocols have not improved the outcomes for glider conservation within logged compartments, even when complied with by FCNSW. Conclusions Based on the FCNSW data and on citizen science, surveys implemented by FCNSW under CIFOA protocols result in poor outcomes for gliders and other mature forest dependent species. Wholesale changes in process are likely required for effective conservation. Implications New approaches in monitoring and research commitment, administration, and oversight are likely required to halt the increasingly rapid decline of threatened gliders, as well as local forest communities in the State forests of NSW.

The Interactive Role of Climatic Transfer Distance and Overstory Retention on Douglas-Fir Seedling Survival and Height Growth in Interior British Columbia.

The future climatic niche of interior Douglas-fir (Pseudotsuga menziesii var. glauca [Mirb.] Franco) is expected to have little spatial overlap with its current range due to climate change. The resulting misalignment of the climatic niche and species distribution is expected to result in many forests becoming maladapted in their current location, thus increasing vulnerability to disturbance and reducing productivity. This novel study examined the individual and interactive effects of climatic transfer distance and silviculture systems on planted 3-year-old Douglas-fir seedlings across the natural range of interior Douglas-fir in British Columbia. Several climatic transfer distance variables were considered, and the silviculture systems tested comprised the following gradients of tree retention: 0% retention (clearcut), 10% dispersed retention (seed-tree), 30% aggregate retention, and 60% aggregate retention with thinning from below. Using linear mixed effect models, we found that survival and height were positively correlated with movements of seedlings to warmer, wetter, and more humid climates. Moisture availability had a stronger influence than temperature, indicating that seedlings transferred to warmer but more arid climates would experience decreased survival and height. Where seedlings were transferred to climates with greater frost frequency or decreased humidity, greater retention of overstory trees improved survival and height. Conversely, movements to more favorable climatic conditions (warmer and wetter) resulted in improved survival and height where overstory retention was low. Our findings suggest that genetic reshuffling of populations through assisted migration could benefit from overstory retention where stressful climatic conditions due to aridity or increased frost frequency occur.

Investigating physiological responses and fine particulate matter retention of urban trees in Budapest

The urban environment is posing substantial challenges to both human well-being and the growth of plantations. Deploying advanced urban trees that effectively interact with atmospheric pollution will be a crucial step in urban planning. However, there is a paucity of knowledge in Hungary regarding these aspects. We studied the photosynthesis activities of three commonly planted trees (Acer platanoides, Fraxinus excelsior, and Tilia tomentosa) from two locations in Budapest, as well as their potential of capturing fine particulate matter on leaf surfaces. Our results reveal that T. tomentosa has developed a denser canopy and better photosynthetic activities, hence enhancing its adaptation to the urban environment in Budapest. F. excelsior showed a higher amount of fine PM wash-off, as it has a smoother leaf surface and was subjected to influences from wind speed and precipitation, making the captured particles more easily dislodged. Whereas fine PM concentration of A. platanoides and T. tomentosa were influenced by ambient PM10 and PM2.5, which might retain on their rough and hairy leaf surfaces. Approximately 38.17 tons of fine PM could be retained on urban greenery of Budapest at any given moment, highlighting the significant ecological and economic benefits of urban greenery. However, more accurate and long-term modeling is needed to develop a sustainable strategy for maximizing these benefits.

Thinning-induced decrease in fine root biomass, but not other fine root traits in global forests

In forest ecosystems, changes in the expression of tree absorptive root traits following management interventions are expected to influence post-thinning forest structure and function. Fine root traits are expected to be especially responsive to forest thinning—one of the most common forest management interventions and the focus of our research here—influencing tree-level responses to environmental change, and thereby contributing to post-thinning stand-level dynamics and ecosystem processes. However, there remains limited understanding surrounding whether or not forest thinning influences the expression of root morphological, chemical, and physiological traits associated with belowground resource acquisition. We conducted a global meta-analysis to evaluate the response of 13 fine root traits to forest thinning. Our study included analysis of 769 paired observations of root traits values pre- and post-thinning, derived from 89 peer-reviewed publications. Our meta-analysis found that forest thinning leads to a decrease in fine root biomass by 11.7% on average, while other root traits including fine root length, root C and N concentrations, root lifespan, and root respiration rates, are largely unresponsive to thinning treatments. Thinning tended to reduce fine root biomass at early stand recovery stages, with increases in fine root biomass being detected at later seral stages, especially in heavy thinning experiments. The effect of thinning on fine root biomass was most pronounced in deeper soil horizons. The influence of thinning on fine root trait expression was not affected by ecosystem or stand type, with the exception of biomass which decreased in temperate and coniferous forests. Our results demonstrate variations of fine root traits to forest management, as well as the importance of stand recovery time and thinning intensity in regulating fine root trait expression in retention trees. These patterns may have strong implications for governing soil carbon stocks in managed forests associated with decreased root inputs into deeper soils. Overall, our findings can enhance our comprehension of how forest management affects fine root trait expression, and relationship between managed forests and belowground ecosystem structure and function.

Improving bird abundance estimates in harvested forests with retention by limiting detection radius through sound truncation

ABSTRACT An inherent challenge with acoustically surveying birds is that the distance at which they can be detected depends on how far their song can be heard. We developed a distance-based sound detection space truncation method to correct for variable sampling radii due to surveying in forested or open conditions. The method was pivotal in evaluating bird responses to retention patches; without this methodological advancement, the impact of retention patches on songbird abundance was vastly underestimated. In the boreal forest, these patches of live trees are retained in regenerating harvested forests to provide ecological services for species adapted to natural disturbances. Although we did not verify our a priori assumption with ground observations, our findings suggest that limited-distance sampling better captures the effects of retention patches on bird use of harvested forests. When evaluated using unlimited distance surveys, retained trees had a negligible effect on bird abundance, whereas applying detection distance truncation highlighted the importance of retention on forest birds. We found that early to mid-seral forest songbirds benefited from retention patches, with notable increases in abundance after 10 years of regeneration. The size of retention patches, ranging from 0.1 to 1.2 ha, did not have a linear relationship with bird abundance. Instead, edge effects stemming from the configuration of these patches emerged as key determinants of abundance for the majority of the species studied. Retention patches that were nearest to unharvested forests were used the most, compared to further into harvest areas. Our research not only highlights the underestimated impact of small-scale live tree retention on forest songbirds but also introduces a significant methodological innovation in the field of acoustic monitoring.

Retention forestry can maintain epiphytic lichens on living pine trees, but provides impoverished habitat for deadwood‐associated lichens

Abstract Managing forests for timber yields reduces the amounts of old trees and deadwood, which has profound effects on species that are dependent on them. Retention forestry, where some trees are permanently left unharvested on clear‐cut sites, may enable the formation of deadwood and old trees in managed forests, but it is unresolved how well these practices facilitate the occurrence of species in managed forests, especially in the long term. We studied the capacity of tree retention practices to support the diversity of epiphytic lichens, a key group among threatened forest species. We compared lichen assemblages on retained trees in harvested sites to those on trees in unharvested control sites. The data were collected 21‐year post‐harvest and included living trees, snags (standing dead trees) and logs (fallen trees) of Pinus sylvestris (Scots pine). Living trees, snags and logs each hosted distinct lichen communities. The highest lichen diversity was found on snags. On living trees, species richness was similar in harvested and unharvested sites, but there was slight species turnover. In contrast, deadwood in unharvested sites hosted higher species richness and distinct species assemblages compared to deadwood in harvested sites. These differences were most pronounced on snags. Specifically, unharvested sites contained high‐longevity snags (kelo trees), which hosted unique lichen communities with higher lichen richness than any other studied substrate, including the highest numbers of red‐listed and deadwood‐dependent species. Synthesis and applications. Retention forestry can support lichen assemblages associated with living Pinus sylvestris. However, maintaining deadwood‐associated lichen diversity through retention practices entails significant challenges. Deadwood‐associated lichen diversity relies on high‐longevity snags and is not sustained by the habitats provided in retention forestry. Biodiversity maintenance in forest management requires comprehensive provision of the habitat features of unmanaged forests, such as a qualitatively representative deadwood profile, which can prove difficult.

Spatial scale of stand-replacing forest disturbance influences the amplitude of snowshoe hare population fluctuations in boreal forests of northwest Canada

The natural disturbance model for ecosystem management of timber harvesting promotes the emulation of natural disturbance regimes in the patterns of tree removal. Wildfire is a prominent natural disturbance in boreal forests of western Canada, frequently removing most of the tree canopy from patches of 500–10,000 ha in stand-replacing events. However, fire suppression, coupled with a spatial pattern of timber harvesting dominated by small patch cuts of 10–160 ha, have changed the spatial scale of younger stands away from scales within which boreal organisms evolved. In two regions (Sub-Boreal Spruce biogeoclimatic zone of central British Columbia and Liard Basin of southeast Yukon), we tested the hypothesis that different spatial scales of stand-replacing forest disturbance (wildfire and timber harvesting) result in different amplitudes of change in abundance of snowshoe hare, a keystone boreal forest mammal for which mid-seral stand conditions provide optimal habitat. Landscapes with large patches (>2000 ha) of mid-seral forest following stand-replacing disturbance supported consistently and often significantly more hares, with wider amplitude in cyclic fluctuation, than small patches (20–200 ha) of mid-seral habitat and than mature forest landscapes. Densities of hares high enough to support reproduction by Canada lynx (a specialist hare predator) only occurred in landscapes disturbed at the scale of a moderate to large-sized wildfire (1000 – 10,000 ha). Landscapes unaffected by stand-replacing disturbance for at least 80 years (i.e. mature forests) supported very few hares and without cyclic fluctuations. We recommend that the recent pattern of cutting dominated by small patches (20–200 ha) be shifted to include many larger patches (2000–5000 ha). This can happen with incremental, contiguous patch cutting over a period of years short enough that the completed patch will supply high quality, mid-seral habitat for at least the period of one hare cycle (10 y). In designing relatively large patches, mature green tree retention would be desirable for various values, but would be best as small stands of mature forest dispersed within large patch cuts, similar to the legacy of fire. Silviculture (reforestation and stand tending) should create and sustain a mix of conifer and deciduous regeneration in the mid-seral stands. Emulating spatial patterns of stand-replacing natural disturbance appears necessary to sustain snowshoe hare cycles when most fires are suppressed in intensively managed western Canadian boreal forests.

Determinants of tree population temporal stability in a temperate mixed forest over a gradient of nitrogen addition

Nitrogen (N) deposition is a significant threat to the functioning of forests and negatively impacts the delivery of forest goods and services. Contemporary management approaches seek to adapt forests to such N-deposition stressors, but to date how plant populations in natural forests respond to N deposition and what factors determine the contrasting responses among populations are still unclear. Here, we investigated the impact of N-addition (control: 0 kg ha−1 yr−1; low: 25 kg ha−1 yr−1; medium: 50 kg ha−1 yr−1; high: 75 kg ha−1 ha yr−1) on tree population temporal stability and how initial tree size, mycorrhizal type, and leaf N content (LNC; as a surrogate for functional trait composition) mediate tree population responses to N-addition in a Korean pine and mixed broadleaved dominated temperate forest in northern China. We quantified tree species population temporal stability as the ratio of mean to standard deviation of the year-by-year stem increments recorded in individual trees from 2015 to 2022 experimental period. The results showed different temporal stabilities of tree species among four N-addition levels, with the highest population stability observed within the high N-addition plots. Furthermore, initial tree size had significantly (p < 0.001) positive effects on population temporal stability. The effect of LNC and initial tree size were also contingent on the level of N applied. Specifically, increase in tree population LNC reduced population temporal stability in all plots where N was added. Our results imply that retention of large-sized trees and species with resource-conservative strategies (e.g., low LNC) could enhance forest stability under N deposition.

Functional responses of understory plants to natural disturbance-based management in eastern and western Canada.

Natural disturbance-based management (NDBM) is hypothesized to maintain managed forest ecosystem integrity by reducing differences between natural and managed forests. The effectiveness of this approach often entails local comparisons of species composition or diversity for a variety of biota from managed and unmanaged forests. Understory vegetation is regularly the focus of such comparison because of its importance in nutrient cycling, forest regeneration, and for wildlife. However, larger scale comparisons between regions with distinct species assemblages may require a trait-based approach to better understand understory responses to disturbance. We compared the long-term effects of retention harvesting on understory vegetation in two large experimental study sites located in eastern and western regions of the Canadian boreal forest. These sites included the Sylviculture en Aménagement Forestier Ecosystémique (SAFE) experiment and the Ecosystem Management Emulating Natural Disturbance (EMEND) experiment, located in the eastern and western regions of Canada, respectively. EMEND and SAFE share common boreal understory species but have distinct tree communities, soils, and climate. Both experiments were designed to evaluate how increasing tree retention after harvest affects biodiversity. Here, we examined taxonomic richness, functional diversity, and functional composition (using community trait mean values) of understory plant communities, and also examine intraspecific trait variability (ITV) for five species common and abundant in both experiments. We observed the limited impacts of retention level on richness, functional diversity, and functional composition of understory plants 20 years postharvest. However, ITV of leaf morphological traits varied between retention levels within each experiment, depending on the species identity. Common species had different functional responses to retention level, showing species-specific reactions to environmental variation. Our result suggests that understory plant communities in the boreal forest achieve resilience to disturbance both in terms of interspecific and intraspecific functional trait diversity. Such diversity may be key to maintaining understory biodiversity in the face of future disturbances and environmental change. Our results reveal the significance of ITV in plant communities for understanding responses to forest harvesting and the importance of choosing appropriate traits when studying species responses to the environment.

Deadwood enrichment in Fennoscandian spruce forests – New results from the EVO experiment

In Fennoscandian forests, evidence on the effects of variable tree retention, prescribed burning and deadwood creation on deadwood quantity and quality is still scarce. We studied the effects of prescribed burning, tree retention and downed wood creation on the deadwood profile in managed boreal Norway spruce forest stands over a 16-year period. The stand scale treatments of the experiment included cuttings with a constant volume of dispersed retention trees (50 m3 ha-1, ca. 200 trees per ha), and three levels of downed deadwood creation (5, 30 and 60 m3 ha-1), in both upland and paludified biotopes of Myrtillus site type, with or without prescribed burning, with three replicates each.After 16 years since the treatments, the diverse deadwood profiles with varying distribution by decay class were formed. The volume of deadwood varied from 9 to 107 m3 ha-1 with a mean of 65 m3 ha-1. The index of deadwood diversity was positively influenced by prescribed burning and negatively influenced by deadwood creation. The volume of all deadwood and coarse woody debris (CWD), volume and number of logs, as well as dead to live volume ratio increased after prescribed burning and with the level of deadwood creation. The positive effect of deadwood creation on the total CWD volume was higher in the upland biotopes than in the paludified ones. The highest amounts of all deadwood, CWD and logs were recorded in the upland biotopes after prescribed burning without deadwood creation. Our findings highlight the impact of tree retention with prescribed burning and deadwood creation in diversifying deadwood profile and maintaining deadwood continuum for decades.

Secondary Amazon rainforest partially recovers tree cavities suitable for nesting birds in 18–34 years

Abstract Passive restoration of secondary forests can partially offset loss of biodiversity following tropical deforestation. Tree cavities, an essential resource for cavity-nesting birds, are usually associated with old forest. We investigated the restoration time for tree cavities suitable for cavity-nesting birds in secondary forest at the Biological Dynamics of Forest Fragments Project (BDFFP) in central Amazonian Brazil. We hypothesized that cavity abundance would increase with forest age, but more rapidly in areas exposed to cutting only, compared to areas where forest was cut and burned. We also hypothesized that cavities would be lower, smaller, and less variable in secondary forest than in old-growth forest, which at the BDFFP is part of a vast lowland forest with no recent history of human disturbance. We used pole-mounted cameras and tree-climbing to survey cavities in 39 plots (each 200 × 40 m) across old-growth forests and 11–34-year-old secondary forests. We used generalized linear models to examine how cavity supply was related to forest age and land-use history (cut only vs cut-and-burn), and principal components analysis to compare cavity characteristics between old-growth and secondary forest. Cavity availability increased with secondary forest age, regardless of land-use history, but the oldest secondary forest (31–34 years) still had fewer cavities (mean ± SE = 9.8 ± 2.2 cavities ha–1) than old-growth forest (20.5 ± 4.2 cavities ha–1). Moreover, secondary forests lacked cavities that were high and deep, with large entrances—characteristics likely to be important for many species of cavity-nesting birds. Several decades may be necessary to restore cavity supply in secondary Amazonian forests, especially for the largest birds (e.g., forest-falcons and parrots &amp;gt; 190 g). Retention of legacy trees as forest is cleared might help maintain a supply of cavities that could allow earlier recolonization by some species of cavity-nesting birds when cleared areas are abandoned. A Portuguese version of this article is available in Supplementary Material 1.

The intensity of forest management affects the nest cavity production of woodpeckers and tits in mature boreal forests

Cavities made by birds are an important microhabitat for many taxa in forests. Long-term dynamics of cavity patterns and the effect of forest management on cavities are, however, largely unknown. We studied cavity production, measured as nest cavity production rates (CPR = no. of new cavities/km2/year), of woodpeckers and tits in forests with different management intensity in southern Finland, based on a data from 37 years. Forests were divided into managed, seminatural and natural stands. The data covered 56 forest stands with the total area of 1690 ha. Stands were inventoried annually for new cavities. The total numbers of woodpecker and tit cavities were 2238 and 329, respectively. There were large differences in CPRs between forest stands with different management intensity. For woodpeckers, the CPR was highest in natural forests (5.7) and lowest in managed forests (1.5). For the tit species, the respective numbers were 0.9 and 0.3. The CPRs of different cavity-making bird species and cavity tree characteristics (e.g. tree condition and species) were consistent, suggesting that different cavity-makers benefit from similar forest and tree characteristics. The results also suggest that forests managed with currently prevailing methods limit the production of cavities. To promote cavities, the results from this and other studies suggest that managed forests should include more features of natural forests, such as more diverse tree species and within-stand structural variability distribution (tree-level heterogeneity), larger amount of decayed wood, more retention trees and snags and longer rotation periods.

Gliding performance in the inland sugar glider in low-canopy forest

Knowledge of the gliding performance of gliding mammals provides important insight into how these species have evolved to use their environment but it can also be used to guide tree retention and habitat restoration. We investigated the glide performance of the inland sugar glider (Petaurus notatus) in central Victoria. We measured 40 glides from untagged individuals during nest box monitoring. On average, gliders launched into a glide from a height of 14.7 m above the ground and landed at 6.2 m above the ground. The average horizontal glide distance was 18.1 m (range 8–41 m). The glide ratio (horizontal glide distance/height dropped) and glide angle averaged 2.2 and 26.4°, respectively. These values represent a better average glide performance than any previously measured for an Australian gliding mammal. These data are contrasted with those of other gliding mammals to explore the hypothesis that smaller species may be more capable gliders than larger related species.

Effectiveness of conservation measures to support biodiversity in boreal timber-production forests

Large parts of the boreal forest ecosystems have been greatly affected by human use, and the current timber-oriented forest management practice that dominates boreal forests is proven to cause biodiversity and ecosystem services declines. These negative effects are mitigated in various ways, including in-situ measures implemented upon harvest. The measures comprise trade-offs between economic and ecological aims; thus, requiring solid knowledge of their effectiveness. However, comprehensive literature review of the effectiveness of such measures is scarce. We aim to fill part of this void by reviewing the scientific literature that have gauged effects of four in-situ conservation measures: green tree retention (GTR), patch retention (PR), dead wood retention (DW) and riparian buffer zones (RB). Two outcomes were considered, species richness and species abundance across taxa. From a total of 3012 initial papers, 48 met our inclusion criteria that generated 238 unique results. Results were grouped according to control. 178 studies used mature, unlogged forest as control. Out of those, 68% of the findings were not significant, i.e., suggesting no significant impact of harvest with biodiversity measures on species richness and species abundance compared to no harvest. Eighteen percent of the observations showed negative effects and 14% of the observations showed positive effects compared to no harvest. Sixty studies used harvest with no measures as control, of which 45% showed significant positive effects, meaning that compared to harvest with no measures, harvest with conservation measures has positively effects on species richness and abundance. However, 43% of the studies found no significant effect of the implemented conservation measures compared to harvest with no measures taken. The relatively few significant results reported restrain distinct conclusions on the effectiveness of the assessed conservation measures, but some degree of conservation measure is likely to have positive effects on biodiversity in timber-production forest. However, the scientific basis does not allow for pointing to threshold levels. Higher transparency of study design and statistical results would allow us to include more studies. There is a clear need for more research of effectiveness of common conservation measures in timber-production forests in order to strengthen the knowledge basis. In particular, there are few studies that employ harvest without any conservation measure as control. This is pivotal knowledge for forest managers as well as for policymakers for preserving biodiversity and the ecosystems in forest.

Effect of Stand Density on Growth and Allometry of Marri (Corymbia Calophylla) in the High Rainfall Zone of Southwest Western Australia

Marri (Corymbia calophylla), an endemic and keystone tree species of southwest Western Australia (SWWA), provides significant environmental, conservation, economic and cultural values. This study aims to analyse the effect of stand density, manipulated through thinning, on growth and allometry of marri-dominated forest. Although individual tree diameter (DHBUB, diameter at breast height under bark), basal area, height and crown-width (CW) growth was stimulated by thinning, stand basal-area growth was highest in denser (less thinned) stands. Stand density had a significant effect on the allometry between DBHUB and each of height and height-diameter ratio (HDR). Height and CW increased with an increase in DBHUB although the relationship with CW was not statistically significant; HDR was inversely related to DBHUB. Thinning has the potential to increase yields of merchantable timber, firewood, and enhance ecological values including tree hollows for arboreal fauna and marri-fruit production (important for cockatoos) that depend on retention of sufficient large old trees. Reduction of stand density through thinning reduces inter-tree competition and may help in reducing the risk of marri canker disease.

Ownership and governance of tree resources on cocoa farms: A case study in Brong-Ahafo and Western Regions of Ghana

Cocoa is important for the economy and rural development of Ghana. However, small-scale cocoa production is the leading agricultural product driver of deforestation in Ghana. Uncertain tree tenure disincentivizes farmers to retain and nurture trees on their farms. There is therefore the call for structures that promote tree retention and management within cocoa farming. We examined tenure barriers and governance for tree resources on cocoa farms. Data was collected from 200 cocoa farmers from two regions using multistage sampling technique. Information was gathered on tree ownership and fate of tree resources on cocoa farms, tree felling permit acquisition and associated challenges and illegal logging and compensation payments on cocoa farms. Results suggest 62.2% of farmers own trees on their farms. However, these farmers may or may not have ownership rights over the trees depending on the ownership of their farmlands. More than half of the farmers indicated they require felling permits to harvest trees on their farms, indicative of the awareness of established tree harvesting procedures. Seventy percent of the farmers have never experienced illegal logging on their farms. There is however the need to educate the remaining 30% on their rights and build their compensation negotiation powers for destructions to their cocoa crops. This study has highlighted ownership and governance issues with cocoa farming and it is important for the sustainability of on-farm tree resources and Ghana’s forest at large.

Diversification of forest management can mitigate wind damage risk and maintain biodiversity

Mitigating future forest risks, safeguarding timber revenues and improving biodiversity are key considerations for current boreal forest management. Alternatives to rotation forestry likely have an important role, but how they will perform under a changing climate remains unclear. We used a boreal forest growth simulator to explore how variations on traditional clear-cutting, in rotation length, thinning intensity, and increasing number of remaining trees after final harvest (green tree retention), and on extent of continuous cover forestry will affect stand-level probability of wind damage, timber production, deadwood volume, and habitats for forest species. We used business-as-usual rotation forestry as a baseline and compared alternative management adaptations under the reference and two climate change scenarios. Climate change increased overall timber production and had lower impacts on biodiversity compared to management adaptations. Shortening the rotation length reduced the probability of wind damage compared to business-as-usual, but also decreased both deadwood volume and suitable habitats for our focal species. Continuous cover forestry, and management with refraining from thinnings, and extension of rotation length represent complementary approaches benefiting biodiversity, with respective effects of improving timber revenues, reducing wind damage risk, and benefiting old-growth forest structures. However, extensive application of rotation length shortening to mitigate wind damage risk may be detrimental for forest biodiversity. To safeguard forest biodiversity over the landscape, shortening of the rotation length could be complemented with widespread application of regimes promoting old-growth forest structures.

Effects of dispersed and aggregated retention on epiphytic microarthropod assemblages: A northern hardwood forest case study

Epiphytic lichens and bryophytes provide important habitat for microarthropods, yet little work has documented epiphytic microarthropod assemblages. Further, the response of epiphytes and their associated microarthropod communities to varying levels of forest disturbance and cutting intensity are not well known. We conducted a case study to provide an initial community description of epiphyte-dwelling microarthropods in Adirondack northern hardwoods, and to assess potential for impacts of aggregated and dispersed patterns of reserve tree retention to these communities. In total, 79 families of microarthropods were identified in the 0.14 m2 of samples. Late summer average daily maximum temperatures were 3.2 °C higher in the shelterwood, and three years following treatments the per-unit area dry weight of the bole-associated bryophyte Neckera pennata was 34 % lower in the shelterwood. Microarthropod richness and density were distinctly greater in epiphyte substrates at the base of trees, and were reduced in the shelterwood. Several indicator taxa were identified within the basal bryophytes in the reserve treatment, and in both bryophytes the microarthropod assemblages were more homogenous in the shelterwood. A few mobile and heavily sclerotized taxa persisted in shelterwood substrates, especially in the lichens which lacked 3-dimensional structure. This case study revealed a diverse community of microarthropods in northern hardwood forests that were structured by epiphyte type, height on tree and, potentially, by canopy removal, and suggests conservation value of aggregated tree retention when applying even-age regeneration methods with respect to epiphytic bryophytes, lichens, and their associated invertebrates.

Species identity and tree size drive residual tree mortality in island remnants in burned and harvested boreal forests

Ecosystem-based Forest Management (EBM) is a global paradigm with different forms of implementation. In North America, a key aspect of EBM is the emulation of natural disturbances such as wildfire, with retention forestry representing one dominant approach to implementation. Retention is intended to reduce the contrast between ecological legacies present in fire-disturbed and harvested stands by leaving unharvested patches or “island remnants”. These island remnants provide refugia for forest species, accelerate forest regeneration, and supply coarse woody material over time. However, the objectives of leaving retention patches could be compromised by excessive post-disturbance tree mortality, which may erode canopy cover in patches. Comparisons of residual tree mortality in dispersed retention or partial harvest to reference forests and clearcuts exist, but rarely have comparisons to island remnants created by wildfires been made, despite this being the model for these patches. Here, we sampled island remnants in burned and harvested areas in aspen-dominated mixedwood forests in Alberta, Canada, a decade after disturbance. We sought to: (i) test for differences in post-disturbance tree mortality in island remnants (fire versus harvest) (ii) determine if forest island edges experience higher tree mortality than plots located in the interior, and (iii) examine whether tree species, tree size, and stand density influence tree mortality patterns. Post-disturbance tree mortality was quantified using visual field surveys. Additionally, we dated a sub-sample of trees to quantify temporal patterns of tree mortality. We found that harvest-created island remnants did not exhibit higher residual tree mortality than similar-sized fire island remnants. Edge effects also had no impact on tree mortality, irrespective of disturbance type. Aspen (Populus tremuloides) had higher mortality than spruce (Picea glauca), and small-sized trees had a higher probability of mortality than large-sized trees. While previous studies have reported elevated rates of mortality for retention trees in relation to reference stands, we found similar mortality rates for trees in fire and harvest island remnants. These results support the continued implementation of retention forestry using island remnants within the scope of EBM in Alberta to promote forest recovery and resilience following disturbances.