Forest Dynamics Research Articles

Meta-analysis of spatial genetic patterns among European saproxylic beetles

AbstractThe phylogeography of many forest-dwelling species in Europe is well understood. However, our knowledge regarding the genetics of saproxylic beetles remains insufficient. This knowledge gap extends to understanding the influence of both quaternary history and contemporary forest dynamics on population genetics. To fill this gap, we conducted a systematic review and meta-analysis of recent literature concerning saproxylic beetle taxa with available genetic data. We include both threatened and common species in our study, which enabled us to generalize our findings to the whole saproxylic community. Results suggest a latitudinal decrease in diversity in most species, likely influenced by Pleistocene glaciation and subsequent population expansions from southern refugia. Additionally, we observed an east–west gradient in diversity, with threatened species exhibiting higher diversity towards the east. This may reflect historical forest dynamics and anthropogenic pressures, such as heavy wood logging in Western Europe. Similarly, we found a pattern along altitude, with populations in higher elevation forests, which are often more natural, exhibiting higher diversity. Furthermore, we identified distinct phylogenetic units or genetic clusters in southern Europe reflecting the distribution of glacial refugia. For some taxa, distinct units were also reported in eastern Europe where populations spread from Asian refugia. Central Europe showed a high number of phylogenetic units, although unique (private) clades or clusters were absent. Most likely it is an effect of the presence of beetles that originated from various refugia belonging to different phylogenetic units.This study brings insights into general phylogeographic patterns, which have previously been examined only for single representatives of saproxylic beetles. It should also help in the proper planning of conservation and management efforts for wood-dwelling beetles.

To the top or into the dark? Relationships between elevational and canopy cover distribution shifts in mountain forests

Numerous studies have reported that observed species shifts in mountain areas lag behind expectations under current warming trends, however, the mechanisms remain poorly understood. One important mechanism might be microclimatic heterogeneity causing migration of species to cooler conditions under closed forest canopies, but evidence is scarce. We here compared the distributions of 710 species (11 taxonomic groups including fungi, plants, and animals) along an elevation gradient (287–1419 m a.s.l.) in a temperate low mountain range between 2006–2008 and 2016–2017 to address this open question. We characterized each species' distribution (peak and breadth) based on their abundance along two environmental gradients: elevation and canopy cover. We then analysed changes in species' distribution peaks, asking whether shifts in canopy distribution and initial distribution characteristics explain variation in elevational distribution shifts. Across all taxa, the mean shift in elevational distribution peak was + 35.3 m (i.e. upslope). Species' baseline distribution peaks were strong predictors of elevational distribution shifts with stronger upslope shifts in low‐elevation and open‐forest species. Even though we observed considerable variation in the responses among species, canopy distribution shifts had a significant negative effect on elevational distribution shifts overall and in six taxonomic groups. We suggest that this is related to cooler microclimatic conditions under closed compared to open forest canopies. Shifts to closed‐canopy forests may thus partly compensate for elevational distribution shifts, highlighting the conservation value of heterogeneous landscapes featuring microclimatic refugia. Yet, it is likely that other mechanisms, such as habitat limitation, are also at play. Future studies need to quantify the potential of microclimatic refugia under accelerating forest dynamics, considering the interplay of canopy cover and other factors driving microclimate, and to illuminate the complex climate change response mechanisms among species and taxonomic groups.

Ecosystem transition due to deer overabundance: Insights from long‐term studies and future considerations

AbstractThe overabundance of certain deer species is emerging as a critical issue in many forested regions across the Northern Hemisphere, including those in Japan. In the field of deer impact studies, the prevailing notion has been that overabundant deer populations could cause drastic changes of ecosystem states. This study comprises a review of the historical discussion surrounding ecosystem changes caused by deer overabundance, from theoretical frameworks to in situ observations and experiments. The synthesis highlights the potential for state transitions, shifting ecosystems from forest to nonforest states, and in some scenarios to a so‐called alternative stable states. However, detecting these transitions poses challenges due to the enduring impacts of past deer activity and the nonequilibrium nature of forest dynamics. Furthermore, this study reveals additional multifield complexities arising from the interactive effects of deer overabundance and global changes on future forest dynamics. To address these challenges, new avenues for research are proposed, emphasizing the importance of sustained efforts in conducting valuable long‐term studies.

Mycorrhizal and endophytic fungi structure forest below-ground symbiosis through contrasting but interdependent assembly processes

BackgroundInteractions between plants and diverse root-associated fungi are essential drivers of forest ecosystem dynamics. The symbiosis is potentially dependent on multiple ecological factors/processes such as host/symbiont specificity, background soil microbiome, inter-root dispersal of symbionts, and fungus–fungus interactions within roots. Nonetheless, it has remained a major challenge to reveal the mechanisms by which those multiple factors/processes determine the assembly of root-associated fungal communities. Based on the framework of joint species distribution modeling, we examined 1,615 root-tips samples collected in a cool-temperate forest to reveal how root-associated fungal community structure was collectively formed through filtering by host plants, associations with background soil fungi, spatial autocorrelation, and symbiont–symbiont interactions. In addition, to detect fungi that drive the assembly of the entire root-associated fungal community, we inferred networks of direct fungus–fungus associations by a statistical modeling that could account for implicit environmental effects.ResultsThe fine-scale community structure of root-associated fungi were best explained by the statistical model including the four ecological factors/processes. Meanwhile, among partial models, those including background soil fungal community structure and within-root fungus–fungus interactions showed the highest performance. When fine-root distributions were examined, ectomycorrhizal fungi tended to show stronger associations with background soil community structure and spatially autocorrelated patterns than other fungal guilds. In contrast, the distributions of root-endophytic fungi were inferred to depend greatly on fungus–fungus interactions. An additional statistical analysis further suggested that some endophytic fungi, such as Phialocephala and Leptodontidium, were placed at the core positions within the web of direct associations with other root-associated fungi.ConclusionBy applying emerging statistical frameworks to intensive datasets of root-associated fungal communities, we demonstrated background soil fungal community structure and fungus–fungus associations within roots, as well as filtering by host plants and spatial autocorrelation in ecological processes, could collectively drive the assembly of root-associated fungi. We also found that basic assembly rules could differ between mycorrhizal and endophytic fungi, both of which were major components of forest ecosystems. Consequently, knowledge of how multiple ecological factors/processes differentially drive the assembly of multiple fungal guilds is indispensable for comprehensively understanding the mechanisms by which terrestrial ecosystem dynamics are organized by plant–fungal symbiosis.

A Comprehensive Framework for Understanding Urban Forests as Social-Ecological Systems

AbstractUrban forest management is a multistakeholder, multi-objective situation whereby a surfeit of synergistic or competing goals may exist. Greater research and applied guidance for what works in which urban forest contexts could help improve urban tree and forest outcomes. The challenge in conducting research of this nature is systematic definitions of “what works” and “which contexts” across multidimensional, polycentric urban forest social-ecological systems. This paper presents a comprehensive framework for studying the complexities in urban forest systems (synthesized from numerous other frameworks in the field) that could be used to generate context-specific insights into urban forest management and dynamics. The logic of using frameworks and specific frameworks that already exist within the field are reviewed. Then, I present the urban forest social-ecological system (UFSES) framework. The UFSES framework specifies 5 first-tier factors: theCharacteristics of Trees in the Urban Forest (T); theSurrounding Growing Environment (E);Management & Institutions (M); andCharacteristics of the Human Community (H); which influenceUrban Forest Outcomes (O). A detailed set of second-tier variables nested within these factors are presented in tables at the end of the paper. The framework can foster holistic systems thinking in a systematic yet flexible way; provide a working draft of a common language for thinking about and studying urban forest systems; and enable comparative case research.

Accuracy assessment of LAI, PAI and FCOVER from Sentinel-2 and GEDI for monitoring forests and their disturbance in Central Germany

ABSTRACT Forest monitoring benefits from biophysical parameters such as Leaf Area Index (LAI), Plant Area Index (PAI) and fractional vegetation cover (FCOVER) and can be obtained from optical and LiDAR remote sensing, such as Sentinel-2 (S2) and the Global Ecosystem Dynamics Investigation (GEDI). While GEDI-derived products consider all phyto-elements, those from S2 refer to green elements only. Apart from individual accuracies, systemic deviations among products are thus expectable. However, products from S2 and GEDI lack inter-comparison. We evaluated S2 and GEDI-derived LAI, PAI and FCOVER with digital hemispherical photography observations (DHP) in a forest disturbance hotspot in Germany across various forest conditions, including vital stands, standing deadwood and clearings. We found moderate to high agreement with in-situ data, with highest accuracy for S2-derived LAI (R2 = 0.54) and GEDI-derived FCOVER (R2 = 0.73). Agreements between S2 and GEDI products were low, which we attribute to systematic influences of woody components, GEDI’s limitations in sloped terrain, and saturation of optical signals in dense canopy. In conclusion, findings suggest that while GEDI is effective in dense canopies, S2 products are beneficial for monitoring forest recovery. We also see potential for synergistic use in monitoring standing deadwood for habitat mapping and fire risk assessment.

Southeastern Ohio Hemlock Stands Prior to Hemlock Woolly Adelgid Infestation: Baseline Conditions from 2 Surveys a Decade Apart

The Hocking Hills of southeastern Ohio are situated at the western range boundary of eastern hemlock, where this foundation species occurs in isolated pockets in ravines and on steep slopes. The goal of this study is to characterize these hemlock stands prior to infestation by hemlock woolly adelgid (HWA), which recently entered the state and is likely to cause high mortality if untreated. Individuals in 30 plots established from 2008 to 2011 were resurveyed in 2020, allowing determination of growth rates and mortality rates. Each plot was paired with an upslope transect in the resurvey to record non-hemlock species likely to seed in from above. Tree species diversity in the plots is low (Shannon H’ < 1), as eastern hemlock remained the dominant species in all plots; storm damage and competitive thinning appeared to account for most mortality across all species. Hemlock growth rates were comparable to deciduous species. Common co-occurring species are statistically associated with particular topographic and soil properties on the plots. Following future hemlock mortality, tulip-poplar, chestnut oak, white oak, sweet birch, and red maple may be among the first species to dominate the canopy; Japanese stiltgrass currently appears to be the invasive species of greatest concern. An understanding of pre-HWA composition, structure, and forest dynamics can inform restoration efforts, if in the future long-term, sustainable HWA control or host-tree resistance is developed; this understanding can also apprise management and conservation efforts in the unique hemlock stands of southeast Ohio.

Southeastern Ohio Hemlock Stands Prior to Hemlock Woolly Adelgid Infestation: Baseline Conditions from 2 Surveys a Decade Apart

The Hocking Hills of southeastern Ohio are situated at the western range boundary of eastern hemlock, where this foundation species occurs in isolated pockets in ravines and on steep slopes. The goal of this study is to characterize these hemlock stands prior to infestation by hemlock woolly adelgid (HWA), which recently entered the state and is likely to cause high mortality if untreated. Individuals in 30 plots established from 2008 to 2011 were resurveyed in 2020, allowing determination of growth rates and mortality rates. Each plot was paired with an upslope transect in the resurvey to record non-hemlock species likely to seed in from above. Tree species diversity in the plots is low (Shannon H’ < 1), as eastern hemlock remained the dominant species in all plots; storm damage and competitive thinning appeared to account for most mortality across all species. Hemlock growth rates were comparable to deciduous species. Common co-occurring species are statistically associated with particular topographic and soil properties on the plots. Following future hemlock mortality, tulip-poplar, chestnut oak, white oak, sweet birch, and red maple may be among the first species to dominate the canopy; Japanese stiltgrass currently appears to be the invasive species of greatest concern. An understanding of pre-HWA composition, structure, and forest dynamics can inform restoration efforts, if in the future long-term, sustainable HWA control or host-tree resistance is developed; this understanding can also apprise management and conservation efforts in the unique hemlock stands of southeast Ohio.

Rill Erosion Due to Wildfire or Deforestation in Forestlands of Northern Iran

Rill erosion, mostly affecting steep and long hillslopes, is one of the most severe effects of deforestation and wildfires in natural ecosystems. Specific monitoring and accurate but simple models are needed to assess the impacts of these forest disturbances on the rill detachment process. To address this need, this study has simulated the rill detachment capacity (Dc) through flume experiments on samples of soils collected in hillslopes after deforestation and severe burning. The associations between Dc and organic matter (OM) and the aggregate stability of soil (WSA), two key parameters influencing the rill detachment process, have also been explored under the two soil conditions (deforested and burned soils) using multivariate statistical techniques. Finally, linear regression models to predict Dc from these soil parameters or the hydraulic and morphological variables (water flow rate, WFR, and soil slope, S), set in the flume experiments, have been proposed for both soil conditions. Higher Dc in samples from deforested sites compared to the burned soils (+35%) was measured. This Dc increase was associated with parallel decreases in OM (−15%) and WSA (−34%) after deforestation compared to the wildfire-affected sites. However, the discrimination in those soil properties between the two soil conditions was not sharp. Accurate linear equations (r2 > 0.76) interpolating Dc and the shear stress (τ) have been set to estimate the rill erodibility (Kr) to evaluate soil resistance in erosion models to be applied in deforested or burned sites.

Transient Post-Fire Growth Recovery of Two Mediterranean Broadleaf Tree Species

Fires affect forest dynamics in seasonally dry regions such as the Mediterranean Basin. There, fire impacts on tree growth have been widely characterized in conifers, particularly pine species, but we lack information on broadleaf tree species that sprout after fires. We investigated post-fire radial growth responses in two coexisting Mediterranean hardwood species (the evergreen Quercus ilex, the deciduous Celtis australis) using tree-ring width data. We compared growth data from burnt and unburnt stands of each species subjected to similar climatic, soil and management conditions. We also calculated climate–growth relationships to assess if burnt stands were also negatively impacted by water shortage, which could hinder growth recovery. Tree-ring data of both species allowed us to quantify post-fire growth enhancements of +39.5% and +48.9% in Q. ilex and C. australis, respectively, one year after the fire. Dry spring climate conditions reduced growth, regardless of the fire impact, but high precipitation in the previous winter enhanced growth. High June radiation was negatively related to the growth of unburnt Q. ilex and burnt C. australis stands, respectively. Post-fire growth enhancement lasted for five years after the fire and it was a transitory effect because the growth rates of burnt and unburnt stands were similar afterwards.

Light-demanding canopy tree species do not indicate past human disturbance in the Yangambi rainforest (Democratic Republic of the Congo)

Key messageIn a former paper, we investigated whether the presence of light-demanding tree species in the forest canopy of the Yangambi Biosphere Reserve (central Congo basin) might be a result of past human disturbances (Luambua et al., Ecol Evol 11:18691–18707, 2021). We focussed on the spatial distribution of the most abundant light demanders, but this approach did not yield conclusive results. In the present study, we focus on all species in the forest and conclude that light demanders are not a transient feature of successional tropical forests but an intrinsic component of old-growth forests in Yangambi.ContextCentral African rainforests are characterised by an abundance of light-demanding tree species, which are aggregated in the canopy but underrepresented in the understorey. A popular explanation is that these forests are recovering from slash-and-burn farming activities preceding the relocation of settlements during the colonial era. In a former paper, we showed that the abundance of light-demanding tree species in the Yangambi Biosphere Reserve (central Congo basin) cannot be unambiguously attributed to past human disturbances, using an approach that focused on the spatial distribution of the most abundant light demanders (Luambua et al., Ecol Evol 11:18691–18707, 2021).AimsAs the former study was inconclusive, the present study aims to further test the assumptions behind the ‘recovery from human disturbance hypothesis’, by considering all species in the forest of Yangambi. We addressed four specific research questions: (i) do light demanders occur in large ‘pockets’ occupying large areas of forest? (ii) Are light demanders abundant? (iii) Do they exhibit a regeneration deficit? (iv) Is species composition in pockets of light demanders different from the surrounding forests?MethodsWe identified the location and size of pockets of light demanders in several transects cumulating to 50 km. We installed permanent inventory plots within and outside these pockets and calculated the diameter and age distributions of light demanders within each pocket. We assessed whether pockets of light demanders are different from surrounding forests, using plot clustering analysis.ResultsOur results showed that light demanders were aggregated, but the pockets were small, scarce, and represent a minor fraction of the total forest area. Furthermore, light demanders were not abundant, even in pockets where they were aggregated. Their age distributions did not show a regeneration deficit. Finally, species composition in pockets of light demanders did not differ substantially from surrounding forests where they were scarce or absent.ConclusionsWe conclude that light-demanding canopy species do not indicate past human disturbance in Yangambi and that they are an intrinsic component of old-growth forests rather than a transient feature of successional forests. Our insights show that the large carbon sink observed in mature forests in this region is not driven by successional forest dynamics.

Landscape-level analysis of disturbance regimes in Chinnar Wildlife Sanctuary, a protected area of Western Ghats, India

ABSTRACT The degradation, fragmentation, and depletion of forests have occurred all over the world, simultaneously, with the exponential growth of the human population. The present study assesses the forest disturbance regime of Chinnar Wildlife Sanctuary (CWS), an ecologically significant biodiversity hotspot of Western Ghats (WG) through satellite image-based forest and land cover mapping and landscape metric analysis. The on-screen analysis based on field knowledge, facilitated, mapping of seven types of vegetation cover. The majority of forest area was covered by dry deciduous forest (39.2 km2 or 43.15%), whereas the minimum area was covered by disturbed forest (2.05 km2 or 2.26%). The disturbance index (DI) was calculated by linearly combining the land use land cover (LULC), road and settlement closeness, fire risk, porosity, patchiness interspersion, normalized difference vegetation index (NDVI), and fragmentation through a probabilistic weight-based linear additive model. The values of the DI (120–310) reclassified into four classes viz. low, moderate, high, and very high. The results revealed that 74.62 km2 (82.52%) of the forest area has low to moderate disturbance, while the rest of the forest area that is 15.8 km2 (17.48%) has high to very high disturbance. These analyses are based on remote sensing and GIS crucial for forest conservation and management strategies formulation.

Long‐Term Impacts of Selective Logging in a Tropical Rainforest in the East Region of Cameroon

ABSTRACTAlthough selective logging has become the primary cause of degradation in many African countries, little is known about its long‐term effects. This study investigated the long‐term effects of selective logging on forest tree species diversity and dynamics in the East Region of Cameroon. Six permanent monitoring plots of 1 ha each in unlogged and logged forests were established in 2005 and a recensus in 2011. Each 1 ha plot was divided into 25, 20 × 20 m quadrats. Each 20 × 20 m quadrat was further divided into 16, 5 × 5 m subquadrats, where the diameter at breast height (DBH) of all trees ≥ 2 cm was measured. There was a decrease in plant species density and richness in all forest types. Sloetiopsis usambarensis was the most important species in the unlogged forests and forests logged 21 years ago. The most important family was Putrangivaceae, Euphorbiaceae and Violaceae in the unlogged forests and forests logged 11 and 21 years ago, respectively. The frequency distribution of stem size classes indicated a reversed J‐shape of tropical forests. The above ground biomass (AGB) recovered more than 50% in all forests, and the unlogged forest had the highest AGB (961.8 Mg/ha). Larger stems indicated a forest at a stage of recovery from disturbance. Silvicultural management should be considered.

Linking individualistic growth stability of trees to the complexity of understorey layers

Abstract Tree‐growth stability is crucial in upholding forest ecosystem services. Despite extensive research on the correlation between tree growth and climate, the influence of forest understorey on tree‐growth stability remains understudied. We surveyed forest plots and collected tree‐ring samples along two elevational gradients, ranging from 3600 to 4400 m a.s.l., in the southeastern Tibetan Plateau. An index was developed to quantify individualistic growth stability of trees, and its linkage with the complexity of forest understorey structure was examined. We found that tree‐growth stability is more pronounced in complex forest communities. In forests with higher understorey complexity, the proportion of trees experiencing growth release increased during wet years, while those with growth suppression augmented during dry years. Interestingly, a subset of trees exhibits abnormal growth increases even during the driest years, whereas another subset shows abnormal growth reductions during the wettest years. Furthermore, forests with more complex understorey structures exhibited a higher proportion of trees showcasing these two types of ‘anti‐phase’ growth statuses. Synthesis. Our study underscores the linkage between individualistic growth stability of trees and the complexity of understorey structures. The growth stability of the overstorey layer is conveyed at the expense of individual‐level growth stability and synchrony in forests with complex understorey structures. These findings emphasize the necessity for attention to the interplay between tree growth and understorey community structures when assessing the impacts of future climate change on forest dynamics.

Land covers associated with forest expansion hot spots in the Nepal Himalaya

Abstract Many regions of the Himalaya are experiencing forest expansion, signifying a widespread forest transition across this fragile mountain system. In the Nepal Himalaya, forest expansion is increasingly attributed to the narrative of cropland abandonment driven by rural outmigration. Understanding forest change dynamics as consequences of land use changes is critical in the context of rural mountain societies such as Nepal, which exhibit complex interactions between forest, agriculture, and livelihoods. We analysed forest gain in Nepal from 2000–2019 to inquire where and when forests have expanded and what land covers transitioned into forests. We integrated spatiotemporal analysis of national land cover maps and photointerpretation of very high resolution (VHR) imagery to improve analytical estimates. The Middle Mountain physiographic region experienced the strongest hot spots of forest gains relative to the high mountains or lowlands. Visual interpretation of VHR showed that 68.8% of forest gains since 2000 occurred on shrubland, and 26.5% on cropland. The dominance of shrubland-forest transitions implied that shrubland is an intermediate stage in a multi-decadal succession process, or a semi-permanent state such as arrested succession. Notably however, we also detected cropland-forest transitions occurring as fast as 6–10 years, indicating the potential for rapid forest succession if biophysical conditions permit. Thus, variations in land cover transitions to forests in the hills implicated multiple pathways of forest regeneration, reflecting a variety of spatiotemporally explicit drivers. Our results differ from previous studies because VHR image analysis accounted for land cover classification errors and improved land cover quantification. Further research on spatially explicit mechanisms and drivers of forest gain are needed to understand the synergies of forest, agriculture, and livelihoods to inform land use land cover policies that could be leveraged to enhance rural mountain livelihoods.

Advancing Knowledge in Forest Water Use Efficiency Under Global Climate Change Through Scientometric Analysis

Forests are critical in regulation of carbon and water cycles and mitigation of climate change. Forest water-use efficiency (WUE) refers to the ratio of biomass produced (or assimilated carbon) to the amount of water used by forests, which indicates how effectively a forest utilizes water to achieve productivity. Climate change and its impact on forest WUE are important research directions that explore the complex relationship between global environmental change and the forest ecosystem dynamics. The global intensification of climate change underscores the need for an inclusive understanding of forest water use and makes it crucial to know how forests balance carbon and water resources, which is essential for effective forest management and predicting ecosystem responses to climate change. This study aims to comprehensively and objectively analyze current research trends and future directions related to the response of forest WUE to climate change. Our database included 1755 research papers from the Web of Science Core Collection, spanning from 2000 to 2023. Our analysis included cooperative networks of countries, authors, and institutions, as well as the most frequently cited journals and articles, keyword co-occurrence analysis, and a keyword burst analysis. The results showed that the top cooperative country, author, and institution is PR China, Prof. Dr. Jesús Julio Camarero from the Consejo Superior de Investigaciones Científicas (CSIC), and the Chinese Academy of Sciences, respectively. The leading journal in this field is “Global Change Biology”. Critical research hot topics include gas exchange, modeling, altitudinal gradients, tree growth dynamics, net carbon exchange, global change drivers, tropical forests, nitrogen stoichiometry, Northern China plains, and extreme drought conditions. Frontier topics that have emerged in recent years include studies on China’s Loess Plateau, stable isotopes, radial growth, gross primary productivity, and Scots pine. The insights from this analysis are vital for researchers, decision-makers, and forestry professionals aiming to mitigate the impacts of climate change on forest WUE and overall ecosystem health and resilience. This study emphasizes the importance of sustained research efforts and global research collaboration in addressing the intricate challenges posed by climate change to forest ecosystems.

Seasonal shifts in depth-to-water uptake by young thinned and overstocked lodgepole pine (Pinus contorta) forests under drought conditions in the Okanagan Valley, British Columbia, Canada

Abstract. As drought and prolonged water stress become more prevalent in dry regions under climate change, preserving water resources becomes a focal point for maintaining forest health. Forest regeneration after forest loss or disturbance can lead to overstocked juvenile stands with high water demands and low water-use efficiency. Forest thinning is a common practice with the goal of improving tree health, carbon storage, and water use while decreasing stand demands in arid and semi-arid regions. However, little is known about the impacts of stand density on seasonal variation in depth-to-water uptake or the magnitude of the effect of growing season drought conditions on water availability. Existing reports are highly variable by climatic region, species, and thinning intensity. In this study, stable isotope ratios of deuterium (δ2H) and oxygen (δ18O) in water collected from various soil depths and from branches of lodgepole pine (Pinus contorta) under different degrees of thinning (control: 27 000 stems per hectare; moderately thinned: 4500 stems per hectare; heavily thinned: 1100 stems per hectare) over the growing season were analyzed using the MixSIAR Bayesian mixing model to calculate the relative contributions of different water sources in the Okanagan Valley in the interior of British Columbia, Canada. We found that under drought conditions the lodgepole pine trees shifted their depth-to-water uptake through the growing season (June to October) to rely more heavily on older precipitation events that percolated through the soil profile when shallow soil water became less accessible. Decreased forest density subsequent to forest thinning did not cause a significant difference in the isotopic composition of branch water but did cause changes in the timing and relative proportion of water utilized from different depths. Thinned lodgepole pine stands were able to maintain water uptake from 35 cm below the soil profile, whereas the overstocked stands relied on a larger proportion of deep soil water and groundwater towards the end of the growing season. Our results support other findings by indicating that, although lodgepole pines are drought-tolerant and have dimorphic root systems, they do not shift back from deep water sources to shallow soil water when soil water availability increases following precipitation events at the end of the growing season.

Rove beetle species diversity and the patterns of interactions with their host plants in primary and secondary tropical forests

AbstractIn tropical disturbed forests, it is relatively unknown the extent insect communities are experiencing shifts in species diversity and the consequences for ecosystem functions and services. In southern Mexico, we used the rove beetle community associated to Heliconia wagneriana bracts, as a model system, to investigate differences in community attributes and feeding habits between old-growth and human induced secondary forests. We tested if the beta diversity components of rove beetle communities were influenced by forest type and bract traits. Furthermore, we described the topology of individual-based heliconia-rove beetle ecological networks. Overall, we recorded 26 rove beetle species with significantly greater abundance in secondary forests. High compositional dissimilarity between forest types was observed with saprophagous species being more likely detected in old-growth forests; whereas predatory species in secondary forests. Heliconia-rove beetle networks showed a significant nested pattern with incidence data for old-growth forests and incidence and abundance data for secondary forests. Compared to old-growth forests, the rove beetle community in secondary forests showed strong shifts in species composition, diversity and differences in the detection probability of feeding habits, with consequences for ecosystem functioning. We further discuss these findings according to the forest disturbance and phytotelm systems. Implications for insect conservation: Individuals of H. wagneriana represent biodiversity reservoirs for invertebrates, especially in human-modified landscapes.

Reaction of Wood Ants to a Large-Scale European Spruce Bark Beetle Outbreak in Temperate Forests

In the Białowieża Forest, Norway spruce is the preferred host tree species for wood ants, both in coniferous and mixed stands; thus, spruce mortality as a consequence of a continuous spruce bark beetle outbreak in the Białowieża Forest since 2012 could have severe consequences for wood ant colonies, as well as their vitality and distribution. The main aim of this study was to assess whether the bark beetle outbreak had any effects on wood ant nest density and abundance and whether we could find any factors affecting the dead spruce distribution around ant nests. A re-inventory of active and abandoned wood ant nests in our study area was conducted from April to July 2022, using the same procedure as the previous inventory performed in 2016. The wood ant nest density was 0.11 per ha and remained practically the same relative to that determined in 2016. Our results indicate that, despite the importance of spruce for wood ants, in situations when only part of the spruce trees die, natural forest disturbances such as bark beetle outbreaks can actually have positive effects because more light can reach the forest floor, thereby promoting the establishment of new nests.

Forest disturbance and damage: Perspectives for forest monitoring and reporting

Forest disturbance and damage: Perspectives for forest monitoring and reporting