Forest Ecology and Management最新文献

Parasitic wood fungi are important to forest carbon cycles globally. However, whether or how they affect the flammability of coarse deadwood is poorly understood. Given the predicted climate-driven increase in wildfires and associated carbon emissions into the atmosphere, potentially amplifying climate warming, filling this knowledge gap should have high priority. We thereto investigated coastal plantations of the exotic black pine, Pinus nigra J.F. Arnold, in the Netherlands, which are widely suffering from Armillaria infection. We hypothesized that branches from forest stands with a visible Armillaria infection will burn differently compared with branches from stands without a visible Armillaria infection, due to Armillaria infection having an additional effect on the branch traits. We tested this hypothesis by burning coarse Pinus nigra branches across a range of densities from infected and uninfected forest patches under standardized conditions in a fire lab and by measuring Armillaria biomass (via ddPCR), deadwood traits and key flammability parameters. Armillaria infection did enhance the flammability of Pinus nigra branches (e.g. more ignitable, longer flame duration and higher percentage mass loss). This higher flammability originated from both direct Armillaria influences, e.g. via changing wood structure (before and/or after wood death), and indirect influences, e.g. by facilitating nitrogen fixation in wood, thereby increasing wood decomposability and consequently reducing wood density. Our findings also have important implications for understanding the role of pathogens in fire regimes more broadly.

We surveyed longleaf (Pinus palustris) and loblolly pine (P. taeda) stands burned within 0–7 years to examine the influence of prescribed fire on grassland-nesting passerines that overwinter in pine forests of central Louisiana, USA. We modeled occupancy and abundance of Bachman’s sparrows (Peucaea aestivalis), Henslow’s sparrows (Ammodramus henslowii), and sedge wrens (Cistothorus stellaris) in relation to stand type, years since burn, and site-scale vegetation conditions. We also used analysis of variance to compare vegetation conditions across study sites and detection points for these three species. Bachman’s sparrow occupancy was 3.7 times greater in longleaf stands compared to loblolly stands and decreased 30 % with every 10 % increase in canopy cover. We also found a positive relationship between Bachman’s sparrow density and the density of herbaceous plants in both stand types. Henslow’s sparrows used herbaceous vegetation within longleaf pine stands burned 0–2 years ago that was significantly taller than what we observed at the site scale, but the best fit models for Henslow’s sparrow occupancy (maximum vegetation height, bare ground, herbaceous cover) had overlapping confidence intervals. Henslow’s sparrow density was positively associated with bare ground and negatively associated with litter depth. Sedge wren occupancy decreased 50 % with every 10 % increase in canopy cover. Sedge wren density increased with increasing percent herbaceous cover, however, the 95 % confidence intervals for this relationship largely overlapped. Our study reiterated the importance of frequent (<3 years) prescribed fires to maintain habitat used by grassland-nesting passerines that overwinter in southeastern pine forests.

More frequent and severe droughts have affected forest ecosystems throughout Europe in recent decades. In Central Europe, large-scale dieback of Norway spruce has, for example, been observed, whereas Norway spruce decline was so far less widespread in Eastern Europe. To assess the potential future impacts of drought on Norway spruce in the southeastern part of its natural distribution, studies on drought resilience are urgently needed. Here, we use a tree-ring network consisting of more than 3000 trees from 158 managed Norway spruce stands of different ages distributed along elevational gradients in the Eastern Carpathians to assess growth responses to drought. Specifically, we analyzed differences in resilience components (e.g., resistance, recovery, resilience, recovery period) with elevation and tree age, and used the ‘line of full resilience’ concept to comprehensively assess drought resilience. Our results show that Norway spruce at low elevations (<800 m) is characterized by the lowest resistance to drought, though has a high recovery, while at high elevations (>1400 m), a higher resistance is associated with a low recovery. In general, older trees were found to need more time to recover. Resilience decreases with a higher water deficit, suggesting that Norway spruce is at risk in the Carpathians with ongoing climate change, urging the need for adaptative forest management.

Managed forests represent a major fraction of the global forest area and are known to host impoverished biodiversity compared to natural forests. The effect of forest management has focused mainly on aggregated community metrics such as species richness of single taxa and on simplistic managed vs. unmanaged comparisons. However, the effect of forest management is expected to vary among species and taxa and to be contingent on site-specific conditions. In this study, we focus on fine-scale multi-taxon biodiversity patterns to disentangle the impact of forest management on the forest structure and the abiotic soil conditions of the stands. We base our comparisons on carefully selected pairs of managed and unmanaged stands to minimize regional differences that could confound the effects of management. We found that the total effect of forest management on alpha diversity was positive on plants and rove beetles, neutral on ground beetles and mosses, and negative on crane flies, fungi, and lichens. However, using joint species distribution modeling we show that individual species’ responses to the local underlying soil conditions can be as important as the forest structural changes induced by management, but this varied among the different taxa. Based on these responses we disclose synergies and trade-offs among some of the taxa. Our results indicate that the balance between forest management and abiotic conditions can shape the patterns of forest multi-taxon biodiversity. Considering these conditions can be important in predicting the response of biodiversity to forest management and act as key criteria when prioritizing areas for the conservation of biodiversity.

Maritime pine (Pinus pinaster Ait.) covers vast areas and is of economic importance in southwestern Europe, particularly in Galicia (NW Spain). Galicia is a heterogeneous region with an Atlantic climate in the coast and a Mediterranean-like climate in the inland, where forest reproductive materials (FRM) with proper adaptation, productivity and timber quality are not available. Thus, there is a need for tailored FRM recommendations for reforestation in this region. P. pinaster is particularly sensitive to environmental variation and shows significant intraspecific genetic variability in this sensitivity, so understanding population responses to environmental variation becomes crucial for proper selection of FRM. Taking advantage of volume growth and stem straightness 13 years after planting, assessed on c. 7500 trees from 25 P. pinaster populations established in seven common gardens across inland Galicia, we analyzed intraspecific variation in sensitivity to climate, geographic, edaphic and site quality factors. We used Mantel correlations and factorial regression models to distinguish the environmental parameters explaining the observed population × site interaction. We also estimated population phenotypic plasticity across sites and the existing genetic relationship between growth and stem straightness to define the optimal selection strategy for productivity purposes. Results showed a quantitatively significant population × site interaction for growth whereas it was almost negligible for stem straightness. In the case of growth, no specific environmental factor was able to explain the population relative performance across test sites, being site quality the only significant factor but with low power to describe the patterns found. Population differences were maximized in higher site quality conditions, where the largest gains from planting selected populations would be expected. Tree growth and straightness were not genetically correlated. Based on these results, subdividing inland Galicia for deployment of P. pinaster FRM throughout specific selections for each subregion is not recommended. Selecting FRM based on average growth and its phenotypic stability should be also avoided, as both properties were negatively correlated. We recommend selecting FRM based on the results from high quality sites, where Atlantic origin populations with high levels of genetic improvement showed the fastest growth. The inclusion of selection criteria based on stem straightness did not alter recommendations given that fast growing FRM showed intermediate or slightly above-average straightness. The limited explanatory power of climate factors for the population × site interaction prevents adjusting recommendations in light of the projected climate change.

Exotic woodboring insects, including some ambrosia beetles (Coleoptera: Curculionidae, Scolytinae, and Platypodidae), are threatening native forests worldwide. Longleaf pine (Pinus palustris Mill.) forest is an endangered habitat in the southeastern United States. One of the most important actions necessary for its conservation is prescribed fire, which maintains its savanna structure. However, prescribed fire is a forest disturbance, possibly creating new niches for colonization by exotic insects. The interaction between prescribed fire and exotic ambrosia species is understudied, especially in highly fire-dependent ecosystems. We carried out a two-year experiment in mixed longleaf pine forests in Alabama, USA. We compared ambrosia beetle communities in recently burned and unburned sites. We found that more than 66 % of total individuals in longleaf pine forests, regardless of fire management, were exotic species. Moreover, exotic ambrosia beetles were more abundant in burned stands, whereas native species showed no difference between burned or unburned stands. Fire management influenced stand species composition for native but not exotic ambrosia beetles. These results indicate that trade-offs exist in managing fire-dependent ecosystems, especially in the Anthropocene era, which is associated with rampant biological invasions. Fire is important to preserve the longleaf pine habitat, but it simultaneously acts as a disturbance, increasing the population density of those exotic species taking advantage of the presence of stressed or dying trees.

Nutrient cycling in forest ecosystems can be sensitive to disturbances that change the availability of one nutrient relative to others, altering the synchrony in nutrient cycles that is expected to develop in undisturbed systems. We asked whether the relative availabilities of nitrogen (N) and phosphorus (P) differ with forest successional age after harvest, and tested effects of adding one nutrient on availability and recycling of the other, in a factorial nitrogen (N) × phosphorus (P) fertilization study in multiple early- and mid-successional and mature northern hardwood forest stands in central NH, USA. We did not find effects of forest age on resin-available N:P ratios, which varied widely among successional forest stands and were related to net N mineralization potentials in the forest floor of each stand. P addition suppressed resin-N availability by 31 % and lowered litterfall N recycling by 10 %, but we detected no effects on net N mineralization potentials. P addition also increased nitrification potentials in the organic horizon by up to 60 %, mostly in combination with added N. The effects of added N depended on P; lower resin-P in mature stands and lower litterfall P recycling in stands of all ages were detected only when P was added with N. We conclude that P limitation influences N recycling across forest age classes in these northern hardwoods, with some indication of stronger effects in successional stands. However, net N mineralization potentials better predicted the resin-N response to added P than did stand age. Our results suggest that alleviating P limitation promotes N limitation over time, especially in more rapidly growing successional forests, by increasing biotic demand for N, reducing its recycling in litterfall, and potentially by reducing net N mineralization.

Mangrove forests play a vital role in carbon sequestration, typhoon-induced wave attenuation, and the provision of ecological services. However, mangrove ecosystems have experienced large-scale loss globally due to rising sea levels and anthropogenic activities. This study investigates the dynamic changes in mangrove cover within the mega-Indus delta, the largest delta in Pakistan and Southern Asia, using multi-temporal remote sensing data and machine learning techniques from 1988 to 2023. The results indicate an increasing trend in mangrove areas in the Indus Delta, with an average annual growth rate of 18.72 %. The spatial distribution of mangrove forests tends to concentrate towards the landward areas, extending along tidal channels, while losses primarily occur in the seaward regions. Rising sea levels pose a potential threat to the survival of these mangroves. The strong southwest monsoon-driven waves are the leading cause of shoreline erosion of the Indus Delta mangroves. Meanwhile, the reduction in riverine sediment discharge is not associated with the increase in mangrove area. Instead, the tidal currents influenced by the southwest monsoon carry sediments into the delta’s tidal channels, causing them to fill and create suitable habitats for mangroves, which are the primary drivers of the observed mangrove expansion in the Indus Delta. Additionally, afforestation activities observed in the northwest and southwest parts of the study area have contributed to the restoration of mangroves. The loss of mangroves in the northernmost part of the northwest region was attributed to an oil spill incident. This study highlights the dynamic nature of mangrove ecosystems in the Indus Delta, characterized by an arid climate and low population density. The findings provide valuable insights into the factors influencing mangrove gain and loss and can inform management strategies for global mangrove restoration efforts.

Forested headwaters, particularly in the Pacific Northwest, USA, are typically heavily shaded by dense stands of riparian vegetation. Reduced riparian cover can occur from natural or anthropogenic events, resulting in increased light which can increase fish biomass by promoting in-stream food resources. We conducted a 5 y before-after-control-impact (BACI) study on 10 small streams in the Oregon Coast Range, USA, and investigated how changes to the magnitude of stream light, mediated by conventional and alternative riparian buffer configurations adjacent to upland timber harvest, changed Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) abundance, biomass, bioenergetics, diet composition, and the availability of aquatic food resources. Riparian buffer treatments reduced canopy cover as much as 34 % cover (98–99 % pre; 64–98 % post-treatment) and enhanced total available sunlight reaching the stream surface by 8–31 % relative to unharvested references that only changed by 3–4 %. In the first year following the treatments, young-of-year trout (YOY, age 0) densities changed by between +0.1 and +0.78 #/m² in treatment streams while densities changed by –0.001 and +0.02 #/m² at reference streams. Although change in YOY densities was positively correlated with change in stream light (r_s=0.81, p=0.02), changes in basal resources (periphyton and macroinvertebrates) were both positive and negative and did not increase with change in stream light. Adult (age 1+) trout responses were mixed in the first year post-treatment, but changed by –0.14 to +0.24 #/m² at treatment sites (–0.02 to –0.05 at reference sites) in the second year post-treatment, likely due to increased recruitment from the strong cohort of YOY in the first year. Bioenergetics analysis in one post-treatment year showed that adult trout did not experience greater summer growth (–0.003 to +0.0005 g g⁻¹ d⁻¹) or proportions of maximum consumption (0.18–0.25) in streams with more light than at reference streams (–0.001 and +0.001 g g⁻¹ d⁻¹, 0.19 and 0.23). Overall, while standing stock assessments suggest that fish showed some increases after experimental treatments that increased light, our data did not provide the clear mechanistic evidence for bottom-up drivers that was expected. The relationship between canopy removal and fish production is not always predictable in small headwater streams, and even though fish populations were generally resilient to riparian manipulation, evaluations of terrestrial food resources, the dynamic between canopy cover and light reaching the stream, and changes to temperature may lend valuable insight on the impacts to fish populations.