Nature conservation in the Carpathians focuses on primary forest remnants as biodiversity hotspots. They are often recognized by structural attributes such as tree size heterogeneity and the ...occurrence of ancient trees. Studies from managed forests or on gradients from managed to unmanaged forests suggest that structure heterogeneity increases herb layer diversity. We have focused on mountain beech primary forests and tested the effect of tree-stand structure, and natural disturbance history on the herb vegetation composition and richness in 150 plots across Slovakia to complement the recent evidence. The overall herb species richness is declining with the increase of recent tree and shrub layer cover, and this decline was also observed for the richness of forest specialists, although their proportion to the other species is growing. Interestingly, we did not find any effect of canopy continuity or time since the last disturbance in the plot on the forest specialist's proportion. Our results suggest that species rich understory of primary mountain beech forests are characterized by relatively low structural complexity and low tree and shrub layer cover, and this is true also if only forest specialist species are considered. These outcomes emphasize the need for tailored strategies in monitoring and managing protected forests. With the recent landscape changes in Europe, they are important for understanding herbaceous vegetation development after the abandonment of forest use.
•The herb layer of primary beech-dominated forests is shaped by forest structure.•Lighter, less structured natural forests host more herb species.•Time since the last natural disturbance does not affect herb richness or composition.•Forest specialists do not prefer undisturbed primary forests with closed canopies.
•High structural heterogeneity reduces the diurnal temperature range (DTR).•Effects of stand structure on DTR are more pronounced in regions with low precipitation.•DTR is lower in unmanaged than in ...managed uneven-aged and even-aged stands.•Terrestrial laser scanning based approaches explain 79.4% of variance in DTR.
The microclimate in forest ecosystems can be altered by modifications of stand structure due to forest management or natural forest development. Current forest management practices in Central Europe and North America aim to promote structural heterogeneity and maintain forest canopy cover, which is known to be a major driver of forest microclimate. Here, we investigated the impacts of forest management and structural heterogeneity on the diurnal temperature range (DTR) in 128 managed forest stands in three climatically different locations (Swabian Alb, Hainich-Dün and Schorfheide-Chorin) in Central Europe. Increasing structural heterogeneity by promoting tree size diversity and differentiation increased vertical stratification and resulted in an impaired DTR during the vegetation period. Linear regression models with geographic location, elevation above sea level, canopy openness and measures of structural heterogeneity as explanatory variables explained 79.4–80.9% of variance in DTR. However, the overall effect of structural heterogeneity on DTR was small. Differences in DTR between plots of different main tree species could be attributed to differences in canopy openness and light transmission, whereas tree species diversity had no significant effect on DTR. Unmanaged forests were characterized by a significantly lower DTR than managed, even-aged forests. DTR in uneven-aged stands managed under single tree selection was comparable to unmanaged stands. Terrestrial laser scanning (TLS) derived measures of canopy openness and vertical structure allowed to explain 79.4% of variance in DTR considering geographic location and elevation, which can also be assessed by TLS with integrated GPS and an altimeter. We conclude that structural characteristics of forest stands other than canopy openness contribute marginally to variation in forest microclimate. However, the analyses of structure-microclimate analyses indicate that effects of stand structure on DTR might be more pronounced in regions with low precipitation during the vegetation period.
•Assessment of tree species composition effects on communities of 13 species groups.•Oak, pine or spruce admixtures to beech affect diversity and community composition.•Effects often depend on tree ...species identity and on the proportion of admixture.•Admixture increases gamma diversity through heterogeneity and associated species.•Forest managers can assess ecological effects of altering tree species composition.
Central Europe's temperate forests are heavily shaped by centuries of human activity. Their natural vegetation, mainly consisting of beech-dominated (Fagus sylvatica) deciduous forests, has been widely replaced by more profitable species grown outside of their natural ranges. This has strongly influenced forest-dwelling communities. Necessary adaptations to changing climatic conditions and the increasing demand for forest ecosystem multifunctionality are reversing these shifts in tree species composition. Integrative approaches that seek to balance production and conservation goals promote mixed forests of beech with spruce (Picea abies), pine (Pinus sylvestris), or oak (Quercus spp.). These mixed forests more closely resemble the natural vegetation and have reduced vulnerability to disturbances compared to coniferous monocultures, but higher commercial value compared to pure beech forests. However, our understanding of how different levels of admixture of commercially relevant tree species to beech forests affect multi-trophic diversity and community composition remains limited.
We investigated herbaceous plants, fungi, oribatid mites, springtails, true bugs, beetles, birds and bats in 41 mature forest stands differing in tree species composition. We assessed the effects of admixtures on abundances and alpha and gamma diversity, i.e. the total number of species per forest type, and a measure of multidiversity by comparing reference beech stands with stands containing varying proportions of admixed species. At the plot level, the proportion of admixtures was especially important regarding oak and pine. Increasing shares of oak positively affected birds, true bugs and herbivorous beetles. Increasing shares of pine benefitted herbivorous true bugs and understory plants but negatively affected other true bugs, bats, and litter-decomposing fungi. Spruce admixture resulted in higher saproxylic beetle and bird diversity. At the landscape level, admixture significantly increased gamma diversity in plants, mycorrhizal and litter decomposing fungi and herbivorous and saproxylic beetles. Only springtail gamma diversity decreased in the presence of admixture. Admixture also significantly altered community composition for six out of 13 taxa. Indicator species were found for all forest types, and seven species groups included species significantly associated with pure beech stands.
Our results indicate that forestry decisions determine forest biodiversity across trophic levels via tree species composition, combining habitat heterogeneity effects and tree species-specific associations. Even low shares of admixed species affect local abundances and diversity. By displacing some species while benefitting others, admixing also alters community composition. This study provides a basis for estimating how altering tree species composition in Central European forests changes the diversity and composition of forest communities.
Forest ecosystems are strongly impacted by continuing climate change and increasing disturbance activity, but how forest dynamics will respond remains highly uncertain. Here, we argue that a short ...time window after disturbance (i.e., a discrete event that disrupts prevailing ecosystem structure and composition and releases resources) is pivotal for future forest development. Trees that establish during this reorganization phase can shape forest structure and composition for centuries, providing operational early indications of forest change. While forest change has been fruitfully studied through a lens of resilience, profound ecological changes can be masked by a resilience versus regime shift dichotomy. We present a framework for characterizing the full spectrum of change after disturbance, analyzing forest reorganization along dimensions of forest structure (number, size, and spatial arrangement of trees) and composition (identity and diversity of tree species). We propose four major pathways through which forest cover can persist but reorganize following disturbance: resilience (no change in structure and composition), restructuring (structure changes but composition does not), reassembly (composition changes but structure does not), and replacement (structure and composition both change). Regime shifts occur when vegetation structure and composition are altered so profoundly that the emerging trajectory leads to nonforest. We identify fundamental processes underpinning forest reorganization which, if disrupted, deflect ecosystems away from resilience. To understand and predict forest reorganization, assessing these processes and the traits modulating them is crucial. A new wave of experiments, measurements, and models emphasizing the reorganization phase will further the capacity to anticipate future forest dynamics.
•Natural regeneration supports higher tree diversity as compared to restoration.•Restored mangrove stand attain higher biomass in a shorter period of time.•Natural regeneration and restoration ...follows mean tree weight-density trajectory.•Natural regeneration offers an excellent model system to examine stand dynamics.
Regeneration of mangroves that occurred within Straits of Malacca over the last 35 years offers an excellent model system to examine how stand dynamics change over time. With exact stand age known, assessment of forest structure, biodiversity and biomass along a natural mangrove development chronosequence provides valuable information to define how long it takes mangrove restoration to return to a natural baseline condition. In natural settings, it is hypothesized that forest structure, diversity and biomass increase with stand age and that these are highest and most complex in intact mangroves. Thus, the study analyzed dynamics in species composition, forest structure and biomass across intact as well as naturally regenerated (NR) stands from 3, 6, 12, 18, and 25 years of age. Intact mangrove stands were structurally more complex and more diverse than younger stands. The preponderance of A. marina regeneration that appear for succession gives rise to a high importance value in the study area. The mean for above-ground and below-ground biomass was 71.00 ± 2.30 and 36.07 ± 0.52 Mg ha−1, respectively. Mean individual tree mass to tree density relationship resembles the mean tree weight–density trajectory of self-thinning even-aged plant populations where mean individual tree mass increased with decreasing density. Naturally regenerated mangroves supported higher tree diversity with complex in stand structure compared to restored mangroves, which were basically comprised of Rhizophora species. Restored mangroves attain higher biomass in a shorter period of time compared to naturally regenerated mangroves. Mangrove restoration should focus on naturally regenerated mangroves in order to increase carbon sequestration and thus provide climate change mitigation. Ecosystem services, biodiversity and climate change mitigation values need to be considered for both mangrove types as restored mangroves lower tree diversity compared to naturally regenerated mangroves of the same age stand. Therefore it is suggested that sustainable management such as silviculture method might be suitable for naturally regenerated mangroves to absorb more carbon from atmosphere and maintain the higher diversity.
•Current allometry has low sample size and excludes large trees.•Terrestrial LiDAR precisely and non-destructively estimates tree biomass.•We developed high sample size species-specific allometry ...with terrestrial LiDAR.•Measurements of large trees and sample size impact biomass prediction accuracy.•Future allometry and biomass estimation will be improved with terrestrial LiDAR.
Forests provide essential ecosystem services and hold approximately 45% of global terrestrial carbon. Estimates of the quantity and spatial distribution of global forest carbon are built on the assumption that regional- or national-scale allometry accurately captures growth form across the wide spectrum of plant size. Allometry is painstaking and costly to create: trees must be cut, dried, and weighed, over the span of months. This bottleneck has left most equations low in sample size and without large trees (>50 cm), which can contain over 40% of aboveground carbon. Terrestrial laser scanning (TLS) can potentially increase the range and sample size of allometric equations through non-destructive biomass estimation and must be evaluated in this context. We deployed TLS at the Center for Tropical Forest Science - Forest Global Earth Observatory (CTFS-ForestGEO) plot in Front Royal, Virginia and virtually reconstructed 329 trees with diameters up to 123 cm. Three-dimensional tree models were the basis for 22 local allometric relationships for comparison to the Jenkins et al. (2003) and Chojnacky et al. (2014) equations. Overall, TLS allometry had lower RMSE and predicted higher tree-level biomass compared to the equivalent national equations. We evaluated site-wide allometry for errors from insufficient sample size and diameter range. Allometric equations did not stabilize to a consistent set of parameters until 100–200 samples were reached and exclusion of large trees severely limited prediction accuracy. This work implies that current biomass equations may be inadequate and highlights TLS stem modeling as an appropriate method of non-destructive allometric equation development for updating allometry and reducing uncertainty in landscape-level biomass estimates.
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•Oak forests are of great economic and conservation importance.•We identify integrative management options for forestry and nature conservation.•Light availability is a strong link ...between forestry and conservation demands.•There is an urgent need for integrative oak forest planning approaches.•Ecological continuity should be secured in structural “sustainability units”.
Central European temperate oak woodlands are highly valued for their rich biodiversity. They are also of great economic importance and forest management aims to produce high quality timber, which demands high investments. The aim of this literature review is to identify management options for forestry and nature conservation that sustain both the ecological value of oak forests and the economic viability of oak silviculture.
We addressed three main questions: (a) Oaks and close-to-nature forestry – what are the key silvicultural challenges and options?, (b) What is the particular significance of ecological continuity and which structural features are of importance for biodiversity conservation in oak forests?, (c) What are the key elements and possible strategies of forest management that sustain the ecological values in oak forests in combination with viable forestry?
Light availability appeared to be a conspicuous link connecting the conservation and the silvicultural aspects of multifunctional oak forest management: Both young oak trees and multiple oak woodland specialist species are characterized by their need for increased sunlight exposure. This common denominator provides a sound basis for integrative management practices for forestry and nature conservation. The concept of retention forestry offers purposeful approaches. So the harvest of valuable timber oaks or the creation of canopy gaps for oak regeneration can be used to release the crowns and trunks of habitat oaks from shading and competition. When looking at the management of oak woodland biodiversity hotspots, the re-establishment of (modified) historical forest management techniques, which increase stand openness and create transitional habitats that provide suitable oak regeneration niches, seems to be necessary.
Not only the continuity of oak woodland cover and natural site conditions, but also the uninterrupted temporal continuity and availability of wood-related structural features turned out to be of particular importance for oak woodland specialist species. We identified an urgent need for systematic forest planning approaches that secure the long-term availability of these structural features within areas or “sustainability units” that are large enough to maintain viable populations of oak woodland specialist species. In particular, conservation-oriented forestry measures should mainly be implemented in those areas, where the greatest effectiveness is to be expected. In the sustainability units, oak regeneration measures ought to take place either in close vicinity to old oak stands or directly in these stands. The choice of one of these options should be based on a careful consideration of the needs and possibilities of both silvicultural and nature conservation management.
This paper presents an adaptive grid-based clustering algorithm called as “AGFC”, which uses a forest-like query structure to sequentially discovers multiple arbitrary-shaped clusters from the grid. ...The main advantage of AGFC is that it can effectively generate a reasonable grid division with a simple startup parameter. This method determines the appropriate grid division width through the minimum gap between the peaks and valleys of the density curve in a specific dimension, which depends on the distribution of the sample, to overcome the subjectivity of manual determination to a certain extent. Furthermore, in the forest-like query structure, it constructs a “Aggregation Judgment” criterion for high-density cells to find out the possible clusters through the merging of cells. Finally, using the “Re-clustering process” to eliminate very small clusters and further repairing the edge areas of the main clusters. The experimental results show that the proposed method can obtain competitive results under the premise of automatically determining the grid.
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•No ubiquitous relationship exists between forest stand structure and functioning.•Stand structure often increases aboveground biomass through niche complementarity.•Stand structure ...has either negative, positive or non-significant effects on stand productivity.•Negative effect may be attributable to the asymmetric competition for light.•Further multivariate studies are needed for forest stand structure and functioning.
Species diversity is a part of (forest) stand structure but tree diameter diversity and height diversity alone or combined are typically defined as stand structural diversity or complexity or attribute(s). There is increasing evidence that stand structural attributes determine forest functioning. Here, I provide a review of forest stand structure and functioning (e.g. aboveground biomass, carbon storage and productivity) in order to explore the current knowledge across worldwide forest ecosystems including (sub-) tropical, temperate and boreal forests, as well as agroforests and experimental plantations or forests. A total of 31 original studies were selected, based on the hypothesized relationships between forest stand structure and functioning, through the systematic literature search in the Web of Science and Google Scholar. Hypothesized studies on forest stand structure and functioning, as compared to species diversity, are under-represented in the highly skewed ecological literature. The synthesis of this review indicates that stand structural attributes often increase aboveground biomass or carbon storage through the positive plant-plant interactions under the niche complementarity effect. Whereas, the influences of stand structural attributes on stand productivity are either negative, positive or nonsignificant. Here, the negative influence is attributable to the asymmetric competition for light, competitive exclusion and selection effect, whereas the nonsignificant effect is attributable to the absolute superiority of specific trees on stand growth. This review highlights that there is no ubiquitous relationship between stand structure and forest functioning, but this relationship greatly depends on the environmental conditions, biotic interactions, stand age and disturbance intensities within a specific forest ecosystem. I anticipate that this review might encourage further studies on the multivariate relationships between stand structural attributes and forest functioning while considering for the effects of other abiotic and biotic factors of the forests.
Mangroves are under immense anthropogenic pressures globally which are further exacerbated by their accessibility to humans. To minimize human access hence pressures to the ecosystem, establishment ...of protected areas is often employed. However, the ecological effectiveness of protected areas, which influences their legal durability, is rarely assessed beyond curbing deforestation. Furthermore, little is known about whether protection could still provide a positive ecological impact if the sites are easily accessible, i.e., adjacent to urban areas, near roads, small in area and/or fragmented. To improve our understanding thereon, this study compares anthropogenic disturbance severity, forest structures and ecosystem carbon (C) stocks of protected and unprotected mangroves near Barranquilla, Colombia’s largest coastal city. The outcomes suggest that accessible, yet protected mangrove has a mean disturbance index of 5.3, lower than unprotected mangrove (mean 11). Protected mangrove also has higher mean (± SD) tree basal area (26.5 ± 15.6 m2 ha−1), mean densities of tree, sapling and seedling (899 ± 398, 5155 ± 7860, and 68,837 ± 73,899 individual ha−1, respectively) and biomass C stock (mean 89.5 ± 39 Mg ha−1) than those of accessible unprotected mangrove (mean basal area 19.3 ± 5 m2 ha−1; mean tree, sapling and seedling densities 823 ± 215, 749 ± 94, and 33,727 ± 44,882 individual ha−1, respectively; mean biomass C stock 60.2 ± 14.5 Mg ha−1). Results suggest that the current sediment C stocks, that is higher in unprotected than protected mangroves (396.8 ± 552.6 and 142.4 ± 205.7 Mg ha−1, respectively), are not primarily driven by conservation status, but by long-term processes that likely pre-date the protected status designation. Mangrove protection, however, could help maintain carbon stocks in soils and biomass and the potential for further soil carbon sequestration, and thus are pivotal in determining future trajectories of mangrove climate mitigation potential. This study shows that even imperfect protection offers ecological benefits to highly accessible ecosystems. Hence, focus should be placed on optimizing these benefits and minimizing their vulnerability to downgrading, downsizing and degazettement.
•influence of protection on mangroves is assessed beyond curbing deforestation.•protection effectively limit anthropogenic disturbance on mangroves.•protection promotes mangrove biomass C and regeneration potential.•mangrove sediment C stocks is largely influenced by sediment properties.•mangrove protection is ecologically beneficial even for highly accessible systems.
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