Changes In Tree Species Composition Research Articles

Tree species composition affects litter eco‐hydrological function in Pinus massoniana conifer‐broadleaf mixed forest stands in southwest China

AbstractAlthough changes in tree species composition profoundly affect the structure, function, and processes of mixed forest ecosystems, there is limited knowledge on the effects of these changes on the hydrological functions of the litter layer in Pinus massoniana conifer‐broadleaf mixed forests in subtropical mountains. Here, we investigated three typical P. massoniana forest stands in southwest China: P. massoniana‐Liquidambar formosana conifer‐deciduous broadleaf mixed forest (Pm + Lf), P. massoniana‐Castanopsis eyrei conifer‐evergreen broadleaf mixed forest (Pm + Ce), and P. massoniana plantation (Pm), and conducted field investigations (litter composition and mass) and indoor immersion experiments to analyse the litter water‐holding capacity (LWHC) of forest stands in their natural state and with artificial ratios combining mixed (needle‐leaf and broad‐leaf) litters. The total litter mass did not significantly differ among the three forest stands (p > 0.05), but significant differences were observed in the needle‐leaf (0.67–2.92 t hm−2), broad‐leaf (0.32–1.89 t hm−2) and bark (0.11–0.34 t hm−2) masses in the undecomposed layer. The LWHC of different stand types was in the order of Pm + Lf > Pm + Ce > Pm. The maximum water‐holding capacity of different artificial ratios of mixed litters was positively proportional to the broad‐leaf mass and inversely proportional to the needle‐leaf mass, and the P. massoniana‐L. formosana mixed litter had a higher maximum water‐holding capacity than the P. massoniana‐C. eyrei mixed litter. The LWHC of mixed forests is mainly influenced by stand structure (tree composition) and litter characteristics, and is positively correlated with leaf area, thickness, dry matter content, and surface roughness. This study revealed that the LWHC can be significantly affected by different P. massoniana stands in subtropical mountains. This study will aid the sustainable and ecological management of forest in subtropical mountains, and P. massoniana plantations should be gradually converted into mixed conifer‐broadleaf forests with greater LWHC and buffering capacity.

Biomass recovery along a tropical forest succession: Trends on tree diversity, wood traits and stand structure

Secondary forests recovering after disturbances currently comprise about half of the world′s tropical forests. A better understanding of the recovery of species composition, stand structure, and biomass stocks of these secondary forests is critical for the sustainable management of these ecosystems. The main objective of this research was to develop the successional trends in forest biomass, tree diversity, and species composition recovery. We monitored the changes in tree species composition, stand structural characteristics, and biomass growth in a chronosequence of tropical secondary forests in the Yucatan Peninsula of Southeastern Mexico. We used both linear and non-linear regressions to develop biomass growth models during forest succession. We calculated tree species diversity and similitude indices between forest successional groups (young, medium-aged, and old-growth forests). The aboveground biomass stocks ranged from 5.2 to 121 Mg C ha-1, which increased gradually with forest age. We observed a divergent trend of biomass accumulation between soft- and densewood species during succession. The contribution of densewood species on tree biomass stock increased (from 32 % to 81 %) with the increasing forest ages. However, the tree diversity indices did not change significantly with forest age and were a poor predictor of aboveground biomass growth during succession. Secondary forests (SFs) of advanced age were more similar to old-growth forests (OF) in their species composition compared to young ones, as evidenced by the Chao-Jaccard index. However, it may take more than a century for these secondary forests to recover to OF-level species composition. Furthermore, the structural equation model allowed us to infer the relative importance of forest age, tree diversity, soil properties, and stand structural attributes, including wood density on biomass growth along the forest chronosequence. Forest age-mediated effect of species composition shift and stand structural changes was a better predictor of biomass accumulation than the changes in tree diversity or soil properties during succession. However, the soil properties as a construct (latent variable), had a significant positive covariance with stand structure, indirectly influencing biomass growth. These biomass and species composition recovery models could be useful in forest management for biodiversity conservation, landscape restoration, and ecosystem services, including carbon sequestration.

Differential roles of seed and sprout regeneration in forest diversity and productivity after disturbance

Natural regeneration after disturbances is a key phase of forest development, which determines the trajectory of successional changes in tree species composition and diversity. Regenerating trees can originate from either seeds or sprouts produced by disturbed trees with sprouting ability. Although both regeneration strategies often develop and co-occur after a disturbance, they tend to affect forest development differently due to significant functional differences. However, the origin of tree regeneration is rarely distinguished in post-disturbance forest surveys and ecological studies, and the differential roles of seed and sprout regeneration in forest productivity and diversity remain poorly understood. To address these research gaps, we explored the role of sprout and seed regeneration in the formation of woody species diversity and above-ground biomass (AGB) productivity in early-stage forest development. Data were collected in two experimental forest stands in the Czech Republic, where trees were cut with varying intensities with the density of residual (uncut) trees ranging from 0 to 275 trees per hectare. All trees were mapped and their sizes were measured before cutting and then, either as a stump with sprouts or a residual tree, remeasured 11 years later. In addition, all tree saplings were mapped and measured 11 years after logging, and their origin (sprout or seed) was identified. To assess abundances and productivity, we estimated AGB of all 2,685 sprouting stumps of 19 woody species and 504 generative (i.e., seed origin) individuals of 16 woody species, using allometric equations. Mixed-effects models were used to analyze the effects of each regeneration strategy on woody species diversity and the total AGB under varying densities of residual trees. Nonmetric multidimensional scaling was used to evaluate the effect of regeneration strategies on species composition. AGB and diversity of sprouts were significantly higher than those of seed regeneration. Sprouts formed on average 97.1% of the total regeneration AGB in Hády and 98.6% in Soběšice. The average species richness of sprouts was 4.7 in Hády and 2.2 in Soběšice, while the species richness of seed regeneration averaged 2.1 and 1.1 in Hády and Soběšice, respectively. Increasing density of residual trees reduced AGB and diversity of both sprouts and seed regeneration, but seed regeneration was affected to a greater extent. Residual trees had an especially strong inhibitory effect on the establishment of seed regeneration. Consequently, seed-originated saplings were nearly absent in plots with high residual tree density, and abundant sprouts accounted for most of the AGB and diversity. However, unlike sprouts whose species composition resembled that of the original stand, seed regeneration brought in new species, enriching the stand's overall species pool and beta diversity. Our results demonstrated differential roles of sprout and seed regeneration in the early stage of forest succession. Sprout regeneration was the main source of woody AGB productivity as well as species diversity, and its importance increased with the increasing density of standing mature trees. The results indicate the crucial yet previously underestimated role of sprout regeneration in post-disturbance forest dynamics. They suggest that the presence of residual mature trees, whether retained after partial cutting or undisturbed, can substantially suppress seed regeneration while the role of sprout regeneration in early succession becomes more distinctly evident.

Decomposability of leaf and wood litter are not correlated across species: effects of litter traits on decomposition in field and laboratory conditions

Changes in tree species composition have important effects on the overall rate of litter decomposition at a community level because litter decomposability varies among species and between leaf and wood litter. To understand how changes in tree species composition affect litter dynamics and carbon sequestration at the ecosystem level, it is important to clarify interspecific variations in leaf and wood litter decomposability, and the traits driving the variation. Using field data, field experiments, and laboratory experiments, we explored rates of leaf and wood litter decomposition and their relationships to traits of ten deciduous hardwood species in a temperate forest in Japan. Rates of leaf and wood litter decomposition at the community level were also estimated by considering species‐specific litter inputs and decomposition rates. Rates of leaf and wood litter decomposition were not correlated under either field or controlled laboratory conditions. This is probably because the traits that affect decomposition rate differ between leaf and wood litter. Interspecific variation in litter decomposability of leaves and wood was generally consistent between field conditions and laboratory experiments using a single fungus, suggesting that the decomposing fungi set the species‐specific decomposition rates. Moreover, the leaf and wood traits that affected decomposition by their specific fungi were different. The aboveground input of wood litter was less than half that of leaf litter, but its half‐life was > 3 times longer, suggesting that wood and leaves make similar contributions to litter accumulation. Focusing on either leaf or wood litter alone may produce misleading estimates of how species composition changes affect litter dynamics at the community level. Our results provide insight into predicting the response of carbon dynamics to future climate change.

Simulation and prediction of changes in tree species composition in subtropical forests of China using a nonlinear difference equation system model.

Changes in tree species composition are one of the key aspects of forest succession. In recent decades, significant changes have occurred in the tree species composition of subtropical forests in China, with a decrease in coniferous trees and an increase in broad-leaved trees. This study focuses on Zhejiang Province, located in the subtropical region of China, and utilizes seven inventories from the National Continuous Forest Inventory (NCFI) System spanning 30 years (1989-2019) for modeling and analysis. We categorized tree species into three groups: pine, fir, and broadleaf. We used the proportion of biomass in a sample plot as a measure of the relative abundance of each tree species group. A novel nonlinear difference equation system (NDES) model was proposed. A NDES model was established based on two consecutive survey datasets. A total of six models were established in this study. The results indicated that during the first two re-examination periods (1989-1994, 1994-1999), there was significant fluctuation in the trend of tree species abundance, with no consistent pattern of change. During the latter four re-examination periods (1999-2004, 2004-2009, 2009-2014, 2014-2019), a consistent trend was observed, whereby the abundance of the pine group and the fir group decreased while the abundance of the broad-leaved group increased. Moreover, over time, this pattern became increasingly stable. Although the abundances of the pine group and the fir group have been steadily declining, neither group is expected to become extinct. The NDES model not only facilitates short-term, medium-term, and even long-term predictions but also employs limit analysis to reveal currently obscure changing trends in tree species composition.

Inventory Results of 101 Natural Forests in the Middle Hills of Nepal over Two Decades

Repeated forest-resource inventories provide indispensable information to evaluate, for example, the mean growth rate of stands and changes in tree-species composition in an area.This paper presents a summary of such longitudinal forest inventory data in the Middle Hills of Nepal, where deforestation has been an issue. Our first inventory was implemented between 1997 and 1999 and measured 3839 plots of 100 square meters (m 2 ). Our second inventory was conducted between 2014 and 2016 and measured 3765 plots of 100 m 2 . We found that over these two decades, the number of trees per hectare (ha -1) significantly improved. The number of stands ha -1 with diameter at breast height (DBH) of 10 centimeters (cm) and above went from 361.2 in the first inventory to 466.2 in the second inventory. We also found that not only the number of stands but also the quality of stands significantly improved. The number of stands with DBH of 30 cm and above ha-1 increased from 72.9 to 99.6. The mean alpha diversity, the number of trees species in a plot, rose to 2.1 from 1.6 in the initial inventory. In sum,“green has made a bold comeback in the Middle Hills”. Our indices evaluating the intensities of human activities on the plots suggest that these improvements in forest-resource conditions may be due to the decreased use of forests in the Middle Hills over these two decades.

Vývoj vybraných zmiešaných ihličnato-listnatých porastov v režime bezzásahovosti

The climate change has an adverse impact on tree species and forest stands. Different tree species tolerance and changes in tree species composition are considered as one of the climate change consequences. The paper deals with assessment and comparison of tree species composition and basal area increment in mixed (spruce-fir-beech) stands, which were left to self-thinning during 45–55 years. The large-scale experimental basis of older thinning permanent research plots established, in the past, in mixed stands situated in the 5th and 6th altitudinal forest zone was used in the research. At the same time the detected changes were compared to long-range goal and tree species models specified for a given forest type. The results showed increased proportion of beech and sycamore maple contrary to decreased share of fir and spruce. At the same time, fir also recorded the highest percentage of loss by self-thinning. The comparison of the current tree species composition with the models showed slight differences in all areas in favour of spruce at the expense of beech. Similarly, the basal area increment of beech was the highest everywhere.

European Beech Forests in Austria—Current Distribution and Possible Future Habitat

A change in tree species composition in Central Europe to increase the resilience of forests when coping with climate change effects is imminent. We evaluated the present and expected future role of the European beech, (Fagus sylvatica L.), with respect to the expansion of its habitat and its stem. We assessed the current relevance of beech from data of the Austrian Forest Inventory 2007/09, and analyzed forest policies promoting the establishment of beech forests. We simulated forest growth with the model CALDIS, linked with the timber-market model FOHOW2. We used a business-as-usual (BAU) forest management strategy under moderate (RCP 4.5 BAU) or extreme (RCP 8.5 BAU) climate change. We also simulated an extreme climate change scenario with a forced change in the tree species composition (RCP 8.5 Change Species). Beech occurs in Austrian forests over the elevational gradient of 250 to 1600 m a.s.l. In low elevation, it forms beech-dominated forests, often for the supply of the domestic fuelwood demand. In mountain regions, beech enriches the diversity of Norway spruce, (Picea abies (L.) H. Karst.)-dominated forests. In a BAU setting, the habitat of beech increases only slightly in both climate scenarios. The scenario ‘RCP 8.5 Change Species’ increases the habitat of beech in the next 60 years considerably. With progressing warming, other broadleaved tree species gain relevance. The vulnerability to drought and pathogens are limiting factors for Austrian beech forests. The future habitat depends on many factors such as the ability of forests to cope with climate change, the confidence to arising market opportunities of beech timber in the wake of technological progress, and financial and non-financial incentives for the implementation of adaptive forest management.

Ecological Factors Driving Tree Diversity across Spatial Scales in Temperate Forests, Northeast China

Species diversity has been shown to be influenced by environmental factors, but the mechanism underlying their relationship remains unclear across spatial scales. Based on field investigation data collected from 3077 sample plots in temperate forest ecosystems, we compared tree species richness, evenness and dominance at 10 km × 10 km, 30 km × 30 km and 90 km × 90 km spatial scales. Then, we detected the scale dependence of changes in tree species composition on climate, topography and forest structure using variation partitioning and quantified their contribution to tree diversity with gradient–boosted models (GBMs) and fitted their relationships. The magnitude of tree richness, evenness and dominance significantly increased with spatial scale. Ecological factors jointly accounted for 24.3%, 26.5% and 38.5% of the variation in tree species composition at the three spatial scales, respectively. The annual mean temperature had a strong impact on tree richness, evenness and dominance and peaked at an intermediate scale. Tree evenness and dominance increased with the variation of temperature but had upper and lower limits. Tree richness obviously increased with annual precipitation on multiple scales and decreased with annual sunshine duration at large spatial scales. Tree richness, evenness and dominance obviously increased with the variation in elevation and diameter at breast height at large scales and small scales, respectively. Tree dominance decreased with tree height at a small scale. The dependence of tree diversity on ecological factors increased with spatial scales. Furthermore, different factors exert various controls on tree diversity at different spatial scales, representing a comprehensive mechanism regulating tree diversity.

From leaf litter to crowns: Response of animal biodiversity to native and non-native oak vegetation

The change in tree species composition is an important process influencing forest biodiversity worldwide. Therefore, it is important to reveal its actual impacts on forest biodiversity. We selected three animal groups (birds, beetles and soil macroinvertebrates) with different dispersal abilities to answer the following scientific question: how does the replacement of a native tree species, pedunculate oak (Quercus robur), by the non-native red oak (Q. rubra) affect the species richness and compositions of the analyzed animal groups?We selected ten lowland woodlands surrounding the city of Pardubice (Czech Republic). In total, forty patches with twenty in mature native oak and twenty in mature non-native oak were studied in the 2017 vegetation season.We found that the effect of the tree species on the species richness was mainly negative for both oak species. The samples with the highest species richness coincided with stands containing mixed native and non-native oak trees. The species composition results indicated that several species avoided red oak, but highly similar numbers of species indicated the same avoidance of the native oak.The results of our study revealed that the effect of non-native vegetation was not as profound as expected, compared to the effect of native vegetation. Neither native nor non-native vegetation significantly affected even flightless fauna. Nevertheless, the extensive planting of non-native trees is not advantageous for many known reasons (e.g., invasibility). An important approach when using non-native trees like red oak in forests is to plant these species admixed or interspersed. In these cases, the impacts of non-native species on the biota are not necessarily negative.

Demographic trade-offs and functional shifts in a hurricane-impacted tropical forest.

Understanding shifts in the demographic and functional composition of forests after major natural disturbances has become increasingly relevant given the accelerating rates of climate change and elevated frequency of natural disturbances. Although plant demographic strategies are often described across a slow-fast continuum, severe and frequent disturbance events influencing demographic processes may alter the demographic trade-offs and the functional composition of forests. We examined demographic trade-offs and the shifts in functional traits in a hurricane-disturbed forest using long-term data from the Luquillo Forest Dynamics Plot (LFPD) in Puerto Rico. We analysed information on growth, survival, seed rain and seedling recruitment for 30 woody species in the LFDP. In addition, we compiled data on leaf, seed and wood functional traits that capture the main ecological strategies for plants. We used this information to identify the main axes of demographic variation for this forest community and evaluate shifts in community-weighted means for traits from 2000 to 2016. The previously identified growth-survival trade-off was not observed. Instead, we identified a fecundity-growth trade-off and an axis representing seedling-to-adult survival. Both axes formed dimensions independent of resprouting ability. Also, changes in tree species composition during the post-hurricane period reflected a directional shift from seedling and tree communities dominated by acquisitive towards conservative leaf economics traits and large seed mass. Wood specific gravity, however, did not show significant directional changes over time. Our study demonstrates that tree demographic strategies coping with frequent storms and hurricane disturbances deviate from strategies typically observed in undisturbed forests, yet the shifts in functional composition still conform to the expected changes from acquisitive to conservative resource-uptake strategies expected over succession. In the face of increased rates of natural and anthropogenic disturbance in tropical regions, our results anticipate shifts in species demographic trade-offs and different functional dimensions.

Forest management affects saproxylic beetles through tree species composition and canopy cover

Forest management has been shown to affect biodiversity, but the effects vary among taxa and studies. Due to their host-tree preferences, many saproxylic, i.e. deadwood-dependent, beetle species are likely affected by forest management via changes in tree species composition. However, further structural differences caused by forest management, such as microclimatic conditions, may interfere with effects of tree species. We lack a more detailed understanding of how forest management intensity influences saproxylic beetles through tree species composition and structural properties.We analyzed the effect of forest management on saproxylic beetles using an eight-year dataset collected from 379 experimental logs of 13 different tree species, which were exposed in forests of different management intensity in three regions of Germany. To quantify forest management intensity, we first used a composite index (ForMI) which considers the share of locally non-native tree species, the origin of deadwood and the harvesting rate and then replaced it by five forest structural and compositional properties. This two-step approach allowed to assess the overall effects of management summarizing different aspects and to identify the main forest attributes driving these overall effects. We further investigated whether the effects differ between beetle assemblages emerging from conifer and broadleaf logs (host level), and between generalists, conifer-specialists, and broadleaf-specialists (beetle specialization level).Abundance and species richness increased with increasing ForMI for all beetles, generalists, and conifer-specialists, but not for broadleaf-specialists.Effects of ForMI were stronger for assemblages emerging from conifer than broadleaf logs. Among the evaluated structural and compositional variables, strongest effects were observed for conifer share at stand level and canopy cover. Conifer share positively affected the species richness of all beetles, generalists and conifer specialists, but not of broadleaf specialists. Canopy cover negatively affected all beetles, generalists and conifer specialists, but did not affect broadleaf specialists.Our results show that major drivers behind effects of forest management on saproxylic beetles are differences in tree species composition and canopy cover. Effects differ between beetle groups depending on their host specialization. Forest management decisions regarding tree species composition should therefore more strongly consider their effects on saproxylic beetle diversity to meet conservation goals also in the future.

Importance of climate‐induced tree species composition changes in forecasting the amount of reachable habitat for forest birds

AbstractAimBird and tree species distributions will shift along with future climatic conditions through direct effects related to species responses to bioclimatic variables. In addition, tree species composition changes should indirectly drive changes in forest bird habitats. Here, we predicted the effects of climate changes on the amount of reachable habitat for forest birds and teased apart the role of the indirect effects.LocationFrance.MethodsWe projected tree and bird species distributions (2020 and 2050) using generalized additive models which accounted for climatic conditions at a large scale (France) and local environmental conditions at regional scale. The projections combined two scenarios of climate changes (RCP 2.6 and 8.5) and two scenarios of forest management (increase in either deciduous or coniferous stands). We modelled the amount of reachable habitat with landscape graphs and the equivalent connectivity index (EC) for five birds associated to the main forest types of the study area. To differentiate the sources of EC change between 2020 and 2050, we compared two future landscape graphs including only the indirect effect, or the direct and indirect effects of climate changes.ResultsFor birds with low and intermediate thermal maxima, climate‐based distributions were nearly stable over time (absence of direct effects), EC change was only attributed to indirect effects. In contrast, for bird species with high thermal maximum, EC change was mostly driven by direct effects (more favourable climatic conditions) and little by indirect effects.Main conclusionsUsing an innovative modelling framework that bind species distribution and connectivity models with climate and land use changes in forest, we showed that EC dynamics could be completely due to climate‐driven changes in tree species composition. Our results highlight the importance of accounting for the indirect effects of climate changes, especially in forests where major shifts in tree species composition are expected.

Changes in tree layer and altitudinal distribution of herbaceous species in temperate old-growth forests over 30 years

Temperate forest ecosystems, including old-growth fragments, are subject to increasing pressures, both from biotic and abiotic factors. Frequent disturbance events, rising mean annual temperatures and longer-lasting droughts are causing changes in tree species composition, probably shifting the altitudinal distribution of herbaceous species as well. Our goal was to examine whether such shifts can be observed even in old-growth temperate forests, and if the changes in the species composition and spatial distribution of trees is reflected in the herbaceous layer. Our study was based on a survey of several old-growth forests from the 1970s that was repeated after 30 years. Using spatial point pattern methods and generalized linear mixed effect models, repeated measurements of mapped phytosociological relevés and detailed maps of tree positions from two survey periods allowed us to examine how the species composition of the herb layer and the spatial distribution of trees ≥ 10 cm DBH (diameter at breast height) changed over 30 years. On most of the studied sites, the total number of trees declined and the proportion of broadleaves increased between the two surveys. Analyses of tree spatial distribution showed a general shift from a regular spatial distribution in the 1970s to a clustered spatial distribution of trees in the 2000s. In the 2000s, herbaceous species showed an upwards shift in their distribution compared to the 1970s, even after accounting for the effect of changing tree spatial distributions in both survey periods. These effects could be an outcome of warmer and drier weather conditions during the past decades. Further investigation is needed to examine whether this trend is related to changes in climatic conditions.

Tree stratum alteration decreases C use efficiency and the stability of litter decomposition in a sacred fir ( Abies religiosa ) forest

Background: There is limited information to predict the direction in which canopy modification affects the microbial carbon use efficiency (CUE) and, consequently, the magnitude and stability of litter decomposition in monodominant sacred fir ( Abies religiosa ) forests.
 Questions: What is the effect of tree stratum alteration on CUE and stability of litter decomposition in an A. religiosa forest?
 Study sites and dates: Two conditions inside a sacred fir forest were selected: A) a naturally monodominant homogeneous condition, and B) a heterogeneous condition with a non-monospecific tree stratum derived from local disturbances (wildfire and reforestation) occurred on a single occasion 18 years ago.
 Methods: In each condition (homogeneous and heterogeneous), the Importance Value Index (IVI) was calculated in the tree stratum, while chemical composition, microbial carbon (C) concentration, enzyme activities and C mineralization were measured in litter samples. The specific enzymatic activity and the metabolic quotient were calculated as CUE indicators, and the coefficient of variation as a proxy for litter decomposition stability.
 Results: A change in tree species composition and an increase in tree species richness in the heterogeneous condition was found, which decreased litter phosphorous (P) concentration. This promoted a high microbial activity and low CUE, favoring C mineralization. Furthermore, low stability during litter decomposition was observed as tree species richness increased.
 Conclusions: Tree stratum heterogeneity, as a consequence of past disturbances, decreases CUE and the stability of litter decomposition in an A. religiosa forest.

Effects of Silvicultural Adaptation Measures on Carbon Stock of Austrian Forests

We present the results of a simulation experiment that evaluated three scenarios of forest management in the context of climate change mitigation. Two scenarios refer to climate change adaptation measures. The third scenario was a business-as-usual scenario representing the continuation of current forest management. We wanted to know whether a change in tree species composition or the implementation of shorter rotation cycles is in accordance with the objectives of climate change mitigation. Our simulation experiment was based on data of the Austrian National Forest Inventory. A forest sector simulation model was used to derive timber demand and potential harvesting rates. Forest dynamics were simulated with an individual-tree growth model. We compared carbon stocks, harvesting rates, current annual increment, salvage logging, and forest structure. Compared to the business-as-usual scenario, a change in tree species composition and shorter rotation cycles reduce salvage logging by 14% and 32%, respectively. However, shorter rotation cycles reduce the carbon stock by 27%, but increase the harvesting rate by 4.8% within the simulation period of 140 years. For changes in the tree species composition, the results were the opposite. Here, the carbon stock is increased by 47%, but the harvesting rate is reduced by 15%. Thus, there are clear tradeoffs between the different ecosystem services depending on the climate change adaptation scenario. We also show that a fundamental change in forest management must be accompanied by a transformation in wood processing technology and innovation in wood utilization.

‘Back to the Future’—Oak wood-pasture for wildfire prevention in the Mediterranean

In the summer of 2021, enormous wildfires in the Mediterranean eliminated huge areas of mainly coniferous forest, destroyed adjacent settlements and claimed the lives of many people. The fires indicate effects of climate change and expose consequences of rural demographic changes, deficits in regional and touristic development planning and shortcomings in forest policy. This forum article highlights the dimensions of the problem, calls for a paradigm shift and shows solutions. Land abandonment, woody plant encroachment and non-reflective afforestation are leading to increasing amounts of combustible biomass. To prevent disastrous fires in future, fundamental changes in tree species composition, forest structure and management are essential. Plantations of reseeding pines are to be substituted by spacious or periodically open woodlands of long-lived trees with resprouting capacity such as Mediterranean oaks. Biomass-reducing practices including wood-pasture have to be revived in rural and peri-urban areas. Exemplary fire-resistant multifunctional oak woodlands occur throughout the Mediterranean. Urgent and medium-term measures in the burnt areas include promoting natural ecosystem regeneration, developing regionalized seed banks and nurseries to support native genetic resources, fostering vegetation mosaics of groves and multiple-use open and coppice woodland maintained by traditional practices, and in general forest management aiming at fuel biomass reduction and a policy counteracting land abandonment.

Tree Species Classification in a Temperate Mixed Mountain Forest Landscape Using Random Forest and Multiple Datasets

For monitoring protected forest landscapes over time it is essential to follow changes in tree species composition and forest dynamics. Data driven remote sensing methods provide valuable options if terrestrial approaches for forest inventories and monitoring activities cannot be applied efficiently due to restrictions or the size of the study area. We demonstrate how species can be detected at a single tree level utilizing a Random Forest (RF) model using the Black Forest National Park as an example of a Central European forest landscape with complex relief. The classes were European silver fir (Abies alba, AA), Norway spruce (Picea abies, PA), Scots pine (Pinus sylvestris, PS), European larch (Larix decidua including Larix kampferii, LD), Douglas fir (Pseudotsuga menziesii, PM), deciduous broadleaved species (DB) and standing dead trees (snags, WD). Based on a multi-temporal (leaf-on and leaf-off phenophase) and multi-spectral mosaic (R-G-B-NIR) with 10 cm spatial resolution, digital elevation models (DTM, DSM, CHM) with 40 cm spatial resolution and a LiDAR dataset with 25 pulses per m2, 126 variables were derived and used to train the RF algorithm with 1130 individual trees. The main objective was to determine a subset of meaningful variables for the RF model classification on four heterogeneous test sites. Using feature selection techniques, mainly passive optical variables from the leaf-off phenophase were considered due to their ability to differentiate between conifers and the two broader classes. An examination of the two phenological phases (using the difference of the respective NDVIs) is important to clearly distinguish deciduous trees from other classes including snags (WD). We also found that the variables of the first derivation of NIR and the tree metrics play a crucial role in discriminating PA und PS. With this unique set of variables some classes can be differentiated more reliably, especially LD and DB but also AA, PA and WD, whereas difficulties exist in identifying PM and PS. Overall, the non-parametric object-based approach has proved to be highly suitable for accurately detecting (OA: 89.5%) of the analyzed classes. Finally, the successful classification of complex 265 km2 study area substantiates our findings.

Accelerating Mountain Forest Dynamics in the Alps

Climate change alters forest development pathways, with consequences for ecosystem services and biodiversity. As the rate of warming increases, ecosystem change is expected to accelerate. However, ecosystem dynamics can have many causes unrelated to climate (for example, disturbance and stand development legacies). The compound effects of multiple drivers remain largely unclear. Here, we assessed forest dynamics over 28 years at Berchtesgaden National Park (BGNP), Germany, quantifying the spatiotemporal patterns and unraveling the drivers of forest change. We analyzed high-density forest inventory data, consisting of three consecutive censuses of 3759 permanent sample plots (132,866 tree records in total). We used semi-variograms to analyze spatial patterns of change, and boosted regression trees to quantify the effect of 30 covariates on changes in nine indicators of forest structure and composition. Over the 28 years investigated, the forests of BGNP were becoming denser, structurally more complex, and more species rich. Changes in forest structure were more pronounced and spatially correlated on the landscape than changes in tree species composition. Change rates of all indicators increased over time, signifying an acceleration of forest dynamics since the 1980s. Legacies and climate were the most important drivers of change, but had diverging impacts. Although forest change accelerated with increasing temperature, high legacy levels typical for late development stages dampened it. We here provide evidence for accelerating forest dynamics in mountain forests of the Alps, with potentially far-reaching consequences for biodiversity and ecosystem processes. We highlight that unmanaged forest development toward old-growth conditions could counteract climate-mediated acceleration of forest change.

Canopy Disturbances Catalyse Tree Species Shifts in Swiss Forests

Widely observed inertia of forest communities contrasts with climate change projections that suggest dramatic alterations of forest composition for the coming decades. Disturbances might be a key process to catalyse changes in tree species composition under environmental change by creating opportunities for ‘new’ species to establish. To test this assumption, we compared two assessments (1993–1995, 2009–2017) from the Swiss National Forest Inventory to evaluate which forests were opened by natural canopy disturbance (that is, wind, insect outbreaks, fire and drought) and if these disturbances altered tree species composition both in terms of species-specific basal area and recruitment densities. Natural disturbances affected 14% of the Swiss forests within 25 years, with wind and insect outbreaks being the most frequent (75%) and fire and drought being rare (< 1.5%). Disturbances led to a shift from conifer to broadleaf tree species at low elevation, in particular in dense Picea abies stands, but no change was observed at higher elevations. The composition of undisturbed sites persisted during the same period. Our results demonstrate that undisturbed forests widely resist changes in tree species composition as an effect of direct ingrowth by stand-forming species. Disturbance events seem necessary to create opportunities for climatically ‘better suited and site-adapted’ species to (re-)establish and therefore potentially catalyse tree species turnover under environmental changes. We detected a reduction of tree species that were—centuries ago—cultivated outside their primary natural range, in particular P. abies, or depended on traditional management practices (Pinus sylvestris, Castanea sativa), which may inform us on how the projected increase in disturbance frequency and severity might filter tree species composition and hereby alter forest structure.