Influence of woodland management within interior forests on foliage arthropods and avian insectivores

Disentangling the confounded effects of edge and area in fragmented landscapes is a recurrent challenge for landscape ecologists, requiring the use of appropriate study designs. Here, we examined the effects of forest fragment area and plot location at forest edges versus interiors on native and exotic bird assemblages on Banks Peninsula (South Island, New Zealand). We also experimentally measured with plasticine models how forest fragment area and edge versus interior location influenced the intensity of avian insectivory. Bird assemblages were sampled by conducting 15 min point-counts at paired edge and interior plots in 13 forest fragments of increasing size (0.5–141 ha). Avian insectivory was measured as the rate of insectivorous bird attacks on plasticine models mimicking larvae of a native polyphagous moth. We found significant effects of edge, but not of forest patch area, on species richness, abundance and composition of bird assemblages. Exotic birds were more abundant at forest edges, while neither edge nor area effects were noticeable for native bird richness and abundance. Model predation rates increased with forest fragmentation, both because of higher insectivory in smaller forest patches and at forest edges. Avian predation significantly increased with insectivorous bird richness and foraging bird abundance. We suggest that the coexistence of native and exotic birds in New Zealand mosaic landscapes enhances functional diversity and trait complementation within predatory bird assemblages. This coexistence results in increased avian insectivory in small forest fragments through additive edge and area effects.

Tree diversity is increasingly acknowledged as an important driver of insect herbivory. However, there is still a debate about the direction of associational effects that can range from associational resistance (i.e., less damage in mixed stands than in monocultures) to the opposite, associational susceptibility. Discrepancies among published studies may be due to the overlooked effect of spatially dependent processes such as tree location within forests. We addressed this issue by measuring crown defoliation and leaf damage made by different guilds of insect herbivores on oaks growing among conspecific versus heterospecific neighbors at forest edges versus interior, in two closed sites in SW France forests. Overall, oaks were significantly less defoliated among heterospecific neighbors (i.e., associational resistance), at both forest edge and interior. At the leaf level, guild diversity and leaf miner herbivory significantly increased with tree diversity regardless of oak location within stands. Other guilds showed no clear response to tree diversity or oak location. We showed that herbivore response to tree diversity varied among insect feeding guilds but not between forest edges and interior, with inconsistent patterns between sites. Importantly, we show that oaks were more defoliated in pure oak plots than in mixed plots at both edge and forest interior and that, on average, defoliation decreased with increasing tree diversity from one to seven species. We conclude that edge conditions could be interacting with tree diversity to regulate insect defoliation, but future investigations are needed to integrate them into the management of temperate forests, notably by better understanding the role of the landscape context.

Associated endogenous hormones were affected by forest fragmentation and significantly correlated with aboveground biomass storage. Forest fragmentation threatens aboveground biomass (AGB) and affects biodiversity and ecosystem functioning in multiple ways. We ask whether and how forest fragmentation influences AGB in forest fragments. We investigated differences in AGB between forest edges and interiors, and how plant community characteristics and endogenous hormones influenced AGB. In six 40 m × 40 m plots spread across three forest fragments, AGB was significantly higher in plots in the forest interior than in those at the edge of forests. The proportion of individuals with a large diameter at breast height (DBH > 40 cm) in the forest edges is higher than that in the forest interiors. Further, trees within a 15–40 cm DBH range had the highest contribution to AGB in all plots. Trees in interior plots had higher abscisic acid (ABA) and lower indole-3-acetic acid (IAA) concentrations than those in edge plots. In addition, AGB was significantly positively and negatively correlated with ABA and IAA concentrations at the community scale. In this study, we provide an account of endogenous hormones’ role as an integrator of environmental signals and, in particular, we highlight the correlation of these endogenous hormone levels with vegetation patterns. Edge effects strongly influenced AGB. In the future, more endogenous hormones and complex interactions should be better explored and understood to support consistent forest conservation and management actions.

The foliage palatability hypothesis predicts that avian insectivores will preferentially forage in tree species with the greatest abundance of their arthropod prey, which in turn are associated with the tree’s foliage nutrition and palatability. We tested this hypothesis in a novel Prosopis–Leucaena woodland in Puerto Rico by determining foraging preferences of five insectivorous bird species for six tree species (five alien, one native) and relating preferences to foliage arthropod biomass and leaf chemistry. The most frequently preferred tree species for foraging were the alien Prosopis juliflora (preferred by five bird species) and Pithecellobium dulce (preferred by four bird species). Both species had high foliage arthropod biomass, high N content, low lignin/N ratios, and low hemicellulose content. Compounds, previously known to affect herbivore responses to Albizia lebbeck and Leucaena leucocephala, may explain low arthropod biomass despite high N content in Albizia and avoidance of Leucaena by four bird species despite its high arthropod biomass. The native Bucida buceras had tough leaves with low N content, low arthropod biomass, and only one bird species showed a weak preference for foraging in it. Biomass of predaceous arthropods showed strong negative correlations with the ratios of lignin/N and hemicellulose/N. Some alien tree species had highly palatable foliage with high arthropod biomass and hence were preferred for foraging by avian insectivores as predicted by the foliage palatability hypothesis. High foliage palatability of some alien tree species may weaken the effect of enemy release in some novel plant communities.

Retention forestry is increasingly adopted as an alternative to clearcutting practices and involves retaining structural and compositional complexity (e.g., living and dead trees) from preharvest to postharvest. Past studies have examined the role of retention forestry in supporting various ecosystem functions and biodiversity, whilst its microclimate buffering capacity has been largely neglected. We investigated the microclimates and the underlying mechanisms of retention forests relative to clearcuts and old forests in a boreal forest landscape in central Sweden. We found that both air temperature and vapour pressure deficit (VPD) differed significantly between the forest types. Old forests consistently exhibited the most buffered forest microclimates, followed by retention forests, while clearcuts displayed the lowest. Basal area and canopy cover were identified as the key determinants influencing air temperature and VPD across the forest types. Retention practices can also impact a stand's microclimates. Specifically, maintaining diverse tree species had the potential to lower the stand's maximum temperature, given its positive association with canopy cover. Large volumes of lying deadwood were found to be negatively correlated with both basal area and canopy cover, likely contributing to increased maximum temperatures. Furthermore, standing deadwood directly lowered the maximum temperature within forest stands. Finally, edge effects were observed in the retention forests, with south-facing edges experiencing significantly higher maximum temperature and VPD compared to north-facing edges and forest interiors. These south-facing edge effects were positively associated with the difference in lying deadwood volumes between forest edges and interiors. Our findings support the positive influence of retention practices on a stand's microclimate buffering, achieved through preserving diverse tree species, standing deadwood, and implementing measures to prevent severe wind-induced tree mortality, particularly in south-facing edges (e.g. creating south-facing buffer zones). Forest managers and policy makers can utilize these results to minimize the climate-change impacts on below-canopy biodiversity and functioning.

Enhanced forest interior estimations utilizing lidar-assisted 3D forest cover map

There are two different options to manage forests in the era of global climate warming, with partly opposing inferences. One is to reduce management or abandon it, as undisturbed forest ecosystems effectively store carbon and usually are relatively resilient against disturbance effects (Naeem 1998, Peterson et al. 1998, Bengtsson et al. 2000). Leaving forests untouched thus is an efficient climate change mitigation option. Another option is to reduce CO2 emissions by the replacement of fossil fuels through timber-derived raw materials. Expanded use of forest products however entails a more intense forest management. These two opposing management perspectives need to be intertwined to define a compromise leading to truly climate-smart forestry (Verkerk et al. 2020). Most temperate bats rely on forested habitats for hunting or roosting. As three-dimensionally moving animals, they are especially sensitive to habitat alterations and are directly affected by forest management. Indeed, vegetation structure and species composition determine species-specific habitat use, arthropod prey occurrences and the availability of natural tree roosts. Forest bats are thus sensitive indicators of forest biodiversity. The present thesis aimed at analysing horizontal and vertical activity patterns of temperate forest bats in a coherent temperate old-growth forest. The Belovezhskaya Pushcha (BP) lowland woodland complex can serve as a reference for the study of old-growth dynamics through the number of untouched forest patches present and its size stretching beyond the Polish-Belarusian border. Bat diversity in unmanaged stands was compared to managed stands in the Economic Activity Zone of the Belovezhskaya Pushcha National Park (BPNP). Moreover, species-specific preferences for natural tree roost attributes were extracted in a meta-analytical framework combining own data with datasets from literature. We used automatically recording devices (batcorder) whose omnidirectional ultrasonic microphones are triggered by calls of echolocating or hunting bats. Bats were monitored simultaneously in natural canopy gaps and the adjacent forest interior within two forest communities in the Strictly Protected Zone of BP, namely Tilio-Carpinetum (broadleaved) and Querco-Pinetum (mixed-coniferous) stands. The impact of management was analysed by acoustically sampling managed Peucedano-Pinetum stands in the Economic Activity Zone of BPNP. A vertical batcorder setup in three forest heights analysed vertical stratification patterns of forest bats in canopy gaps and the adjacent forest interior. Bat activity in canopy gaps was slightly higher for edge-space foraging bats compared to the forest interior, while bat richness was higher in gaps only in the species-poor mixed-coniferous stands. Vertical stratification was more pronounced in the forest interior than in canopy gaps, and vertical forest use clearly showed species-specific and seasonal differences. Bat diversity in BPNP was impacted by management with especially evenness being lower in homogenized human-altered managed coniferous forests. The activity levels of four strict forest species in the forest interior were negatively influenced by tree basal area (B. barbastellus, P. pygmaeus, M. brandtii) and positively influenced by the proportion of broadleaved trees (P. pygmaeus, M. brandtii, M. nattereri). B. barbastellus and M. nattereri were furthermore found to be tree roost specialists. While B. barbastellus favours loose bark of dead trees as day roosts, M. nattereri preferentially roosts in cavities or crevices in vital broadleaved trees. Near-natural broadleaved forests are important habitats for temperate forest bat assemblages. The emulation of canopy gaps as a forest management strategy creates structurally heterogeneous forest stands that support a higher bat diversity through an increase in physical niches and foraging opportunities. Both the retention of snags and of large-sized vital trees offer essential roosting opportunities for forest bats and need to be integrated in close-to-nature forest management practices.

上海环城林带景观美学评价及优化策略

Raumzeitliche Dynamik der Parameter des Energie-, Wasser und Spurengashaushalts nach Kleinkahlschlag

Clearcuts are one of the results of forest management. The aim of this study was to assess the effect of clearcuts on bird communities in a managed forest in Western Poland. I applied the method of point transect counts. 20 points were located near clearcuts (less than 100 m from the nearest clearcut) and 25 points in the forest interior. In total, 36 bird species were recorded. On average, I found 9.20 bird species at points located near clearcuts and 6.72 species at points situated in the forest interior, and the difference was significant. The cumulative number of bird species for a given number of sampling points in the vicinity of clearcuts was higher than in the forest interior. The obtained results indicate that in managed, even-aged forests the generation of clearcuts can lead to an increase in local bird species richness.

ABSTRACT: Forest buffers adjacent to water bodies are widely prescribed in forest management to protect ecological functions of riparian systems. To date, buffers have been applied on the landscape uniformly without quantifying their effectiveness or the effects they have on landscape characteristics. Our objective was to quantify landscape characteristics (amount of edge and interior forest) when buffers were applied to water bodies in a 100 by 100 km area of northern Minnesota. We used a Landsat classified image in a geographic information system platform to apply two buffer widths −28.5 m and 57 m — to water bodies, including nonforested wetlands, intermittent or perennial streams, and lakes. A total of 107,141 ha (18.3 percent) of the forest area was adjacent to and within 28.5 m of these water bodies, while 201,457 ha of forest was within 57 m, representing 34.4 percent of the total forest area. Imposing a 28.5 m buffer on water bodies increased the amount of edge and interior forest in the study area. When water bodies were buffered with a 57 m forest strip, we found a slight increase in forest edge from the current condition, and this buffer width resulted in the largest amount of interior forest. Interior forest increased with the 57 m buffer due to the density of water bodies in this region; adjacent water bodies coalesced when buffers were applied and formed isolated forest islands that contained forest interior habitat. Instead of wholesale application of set width riparian buffers, we suggest that ecological conditions of riparian areas be evaluated on a site level and that areas that currently provide important riparian conditions be maintained on the landscape with appropriate management practices.

Does the effect of forest roads extend a few meters or more into the adjacent forest? A study on understory plant diversity in managed oak stands

This dissertation focuses on the effects of various young forest habitat management techniques on the avian and salamander community in West Virginia. Wildlife species associated with the nascent stage of forest succession are experiencing precipitous population declines throughout much of the eastern United States due to decreases in the amount of young forest area which have been brought on by changes in disturbance regimes over the past century. As a result, the need to find novel approaches for creating young forest habitats to sustain young forest wildlife populations is necessary. However, young forest habitat creation often negatively affects species that are considered disturbance-avoidant. As a result, I assessed the tradeoffs between creating young forest habitat for disturbance-associated species with the potential negative effects of reducing habitat suitability for disturbance-avoidant species throughout this dissertation. In Chapter 1, I summarize how historical land use practices in West Virginia have created current young forest conditions and the effects that these conditions have had on wildlife species that are specialized in exploiting young forest areas. I also introduce the study sites where this research was conducted and provide chapter objectives and topics of this dissertation. The recent proliferation of linear energy infrastructure throughout the central Appalachian region has prompted managers to explore ways of managing the young forest bird community in association with these long, linear openings but little empirical data exist. At the same time, forest interior songbirds and woodland salamanders are often negatively affected by energy infrastructure within forest dominated landscapes and any young forest management in these landscapes may further degrade habitats for forest interior species. In chapter 2 we studied how harvest size (15 m, 30 m, and 45 m wide) and intensity (14 m2/ha and 4.5 m2/ha residual basal area) of cut-back borders, which are linear tree cuttings adjacent to gas/oil pipeline and utility powerline rights-of-way (ROWs) or wildlife openings, influenced habitat suitability along ROWs and wildlife openings for the young forest and forest interior communities. The objectives of this chapter were to examine whether the implementation of cut-back borders increased habitat suitability for wildlife species and which cut-back border treatments optimized the tradeoff between maximizing positive responses of disturbance-dependent species (i.e., young forest species) while minimizing negative responses of disturbance-avoidant species (i.e., forest interior species). We found that young forest species’ abundances and species richness increased one-year and two-years after treatment, particularly in the 15-m wide borders, likely

Deforestation and forest degradation around the world endanger the functioning of ecosystems, climate stability, and conservation of biodiversity. We assessed the spatial and temporal dynamics of forest cover in Myanmar’s Hkakabo Razi Landscape (HRL) to determine its integrity based on forest change and fragmentation patterns from 1989 to 2016. Over 80% of the HRL was covered by natural areas, from which forest was the most prevalent (around 60%). Between 1989 and 2016, forest cover declined at an annual rate of 0.225%. Forest degradation occurred mainly around the larger plains of Putao and Naung Mung, areas with relatively high human activity. Although the rate of forest interior loss was approximately 2 to 3 times larger than the rate of total forest loss, forest interior was prevalent with little fragmentation. Physical and environmental variables were the main predictors of either remaining in the current land-cover class or transitioning to another class, although remaining in the current land cover was more likely than land conversion. The forests of the HRL have experienced low human impact and still constitute large tracts of contiguous forest interior. To ensure the protection of these large tracts of forest, sustainable forest policies and management should be implemented.

Structural variation of forest edges across Europe