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•Mountain forest ecosystems (MFE) are significantly affected by human impact.•We examined patterns of tree species distributions in MFE in five national parks.•In natural MFE, tree ...species distributions depended on geomorphology and climate.•Geomorphology was more important than climate in driving species distributions.•Our results highlight which sites may be less vulnerable to climate change.
During changing climates, tree species distribution and productivity are subject of dynamic changes. However, two other factors can play a role in forest development: human impact and terrain properties. Furthermore, terrain properties can frequently modify climatic limitation of tree species growth both positively and negatively. Here, we chose to study five national parks in southern Poland. We tested the impact of climate, soil type and geomorphic indices on the occurrence and biomass of tree species using random forest models. We assumed that despite the presence of human impact, fundamental relationships between landscape properties and climate were still detectable in the selected parks. Elevation and valley depth were the most important individual predictors of tree species distribution; site-specificity was an additional important factor. In addition to the strong age-dependency of aboveground biomass (mainly for Norway spruce Picea abies (L.) Karst and European beech Fagus sylvatica L.), elevation negatively impacted the productivity of all tree species. Additionally, the topographic wetness index negatively affected the biomass of F. sylvatica, while the slope positively influenced its biomass. Using partial dependence plots, we described how geomorphic variables modify climate-dependent elevational patterns of species studied distributions and biomass. Due to protection and preservation of these sites as provided by the national park system, we could separate the effects of particular variables on tree species studied. Our results broaden understanding of the influence of geomorphological variability on species distributions under similar climatic and soil conditions. This allows for predicting sites with a higher probability of species persistence under changing climates. Therefore, our results might be used to identify sites less vulnerable to climate change, therefore important for conservation prioritization.
Forested hillslopes form a special geoecosystem, an environment of geomorphic processes that depend strongly on forest ecology, including the growth and decay of trees, changes in structure, ...disturbances and other fluctuations. Hence, the following various functions of trees are reviewed here: their role in both biomechanical and biochemical weathering, as well as their importance for the hillslope geomorphic subsystem and for transport of soil material via tree uprooting and root growth. Special attention is paid to tree uprooting, a process considered the most efficient and most frequent biogeomorphological indicator of bio-physical activity within forest in complex terrain. Trees have varied implications for soil formation in different environments (boreal to tropical forests) and altitudes. In this paper an attempt has been made to emphasize how trees not only modulate geomorphic processes, but also how they act as a direct or indirect agent of microrelief formation, the most striking example of which being widespread and long-lasting pit-and-mound microtopography. Based on the analyzed literature it seems that some problems attributed to forest ecology can have a fundamental effect on forested hillslope dynamics, a relationship which points to the need for its integration and interpretation within the field of geomorphology. The biology of individual trees has a key influence on the development of e.g. rock faces, weathering front migration and changes in the soil biomantle within upper and lower forest belts. Additionally, forms and sediments depend largely on the horizontal and vertical extent, volume and structure of root systems, as well as on active processes taking place in the root zone and rhizosphere. Furthermore, although trees to a large extent stabilize slope surfaces, their presence can also have a dual effect on slope stability due to tree uprooting, a process which in some circumstances can trigger mass movements (e.g. debris avalanches). So far, several attempts at quantifying the influence of trees on slopes have been made via the use of mathematical equations, enabling researchers to calculate: 1) the root plate volume of uprooted trees, 2) the amount of soil displacement due to tree root growth, and 3) rates of erosion, sedimentation and soil creep. In light of the reviewed literature, the most urgent issue appears to be the need for a thorough study of the interactions and feedbacks occurring between trees and geomorphic systems (e.g. soil mixing and biotransport by trees) in different climate zones, altitudes and time frames, especially in terms of the development of forest ecosystems during the Holocene.
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•We assessed drivers of stand biomass and its increment in Tatra National Park.•Combinations of tree stands, soil and geomorphic features allows biomass estimation.•Stand age, species ...composition, and elevation are the most important biomass drivers.•Valley depth and elevation have the most pronounced positive impact on tree biomass increment.•Our results support increase of carbon budget modeling for mountain forests.
The stands and soils of forest ecosystems are one of the most important carbon sinks in the terrestrial environment; thus, proper estimation of forest biomass increment is crucial to understand the rate of atmospheric CO2 sequestration. Here, we propose a biomass and biomass increment estimation methodology using forest inventory data from 1991 to 2006 from the Tatra National Park (TNP), Western Carpathians, Poland. Using machine learning techniques (random forest), we showed, for the first time, that stand age, the proportion of Abies alba, Picea abies, and Pinus mugo, and elevation are the most important predictors of aboveground stand biomass. Stand biomass increment is driven by the proportion of P. mugo, A. alba, and P. abies, stand age, elevation, and valley depth. Our results showed that the primary drivers of forest biomass (stand age and species composition) could be modified by the geomorphic properties of the terrain, indicating their importance in the mitigation of negative climate change trends in forest landscapes. Additionally, we showed that the biomass increment assessment using repeated measurements differed from trends of age-based biomass models, indicating the need to consider site-specific factors (e.g., slope and aspect). The potential applicability of these results improves the accuracy of carbon budget modeling and supports decision-making in nature conservation and forest management.
•A new method of automatic unsupervised pit–mound topography detection is presented.•Pit–mound topography is an indicator of abiotic disturbances in forests.•LiDAR data support the recognition of ...biological activity imprints on hillslopes.•The contour method (CM) can be implemented in various types of ecological and geomorphic modeling.•The CM can aid in responsible forest management.
Pit-and-mound topography is a result of tree uprooting caused by hurricane-force wind events and hence can act as a bioindicator of forest disturbance. The occurrence and evolution of pit–mound topography can be analyzed using detailed elevation data, such as point clouds from Light Detection and Ranging (LiDAR) surveys. The objective of this study was to develop an automatic method of pit–mound topography detection. We propose the usage of closed contour lines to extract the locations of pits and mounds. We performed analyses in two study areas (Markowa and Stonów) located on the Babia Góra Massif (southern Poland). We computed the digital elevation model (DEM), extracted contour lines, calculated the length of each contour line and selected only closed contours belonging to a specified length interval. Then, we created polygons from the outermost closed contour lines. We classified polygons into “pits” and “mounds” by investigating the location of the highest and lowest altitudes within the polygon. We tested 27 variants of our method using different DEM spatial resolutions, contour intervals and contour length intervals. To estimate the accuracy of our method, we created a validation dataset by performing manual recognition of pit–mound pairs based on the topographic position index (TPI). One of the highest accuracies, obtained for the 1st variant of our method, reached 96.9 % for pits, 93.8 % for mounds and 90.6 % for pit–mound pairs in the Stonów area. In the Markowa area, this variant achieved an accuracy of 95.2 % for pits, 90.5 % for mounds and 85.7 % for pit–mound pairs. Our method can be used as an important step in analyses conducted in forest ecology, geomorphology or soil science.
The role of trees and forests as a critical component of the biosphere and critical zone, and of the Earth system more generally, is widely appreciated. Less known and acknowledged are the ...geomorphological functions of tree roots, although their importance has been widely referred to in soil studies, paleopedology, and paleobotany. Tree roots and their impact on weathering processes and soil production were incorporated in the Devonian plant hypothesis and tree root casts served as a key evidence of recognition of past soils in geology, sedimentology, and paleopedology. However, knowledge of biomechanical and biochemical weathering induced by vascular plant roots (mainly trees) has been rarely utilized in geomorphic studies. Biogeomorphic and pedologic studies in recent decades have highlighted the importance of tree uprooting, in which roots play a primary role, in soil development, regolith disturbance and bedrock mining. Other important functions of roots were also recognized, e.g., soil displacement by growing roots, infilling of stump holes and root cavities, root groove development, direct and indirect effects taking place in the rhizosphere and mycorrhizosphere (mainly biochemical weathering of minerals, support by microbial communities and symbiotic fungi), and changes in porosity, permeability, and hydrology of soils in the root zone. However, further studies are urgently needed because many aspects of biochemical and biomechanical weathering are not well understood. This is especially true with respect to taxa-specific impacts. Variations in root architectures, edaphic settings, ecological relationships, and geographic ranges result in substantially different biogeomorphic impacts of different tree species. Additionally, the same species in different environmental settings may have different effects.
Windstorms are one of the most important disturbance factors in European forest ecosystems. An understanding of the major drivers causing observed changes in forests is essential to improve ...prediction models and as a basis for forest management. In the present study, we use machine learning techniques in combination with data sets on tree properties, bioclimatic and geomorphic conditions, to analyse the level of forest damage by windstorms in the Sudety Mountains over the period 2004–2010. We tested four scenarios under five classification model frameworks: logistic regression, random forest, support vector machines, neural networks, and gradient boosted modelling. Gradient boosted modelling and random forest have the best predictive power. Tree volume and age are the most important predictors of windstorm damage; climate and geomorphic variables are less important. Forest damage maps based on forest data from 2020 show lower probabilities of damage compared to the end of 20th and the beginning of 21st century.
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•Five machine learning models give consistent predictions of what controls wind damage.•Tree volume and age are the most important predictors of forest damage caused by wind.•Geomorphic and climate predictors are less important.•Random forest algorithm and gradient boosting modelling offer the best accuracy of prediction.•Forest stand features might significantly influence probability of forest damage.
Soil and regolith creep have been analyzed for at least the last 140 years, using many methodological configurations and temporal and spatial scales. The general concept of creeping soil and its ...mechanism, first proposed by W.M. Davis and G.K. Gilbert at the end of the 19th century, evolved since the 1940s towards theoretical models and precise short- and long-term field measurements. This fruitful epoch continued with results enhanced at the turn of the 20th century by the application of new research methods (e.g. radiometry) and a redefinition of the term soil creep to encompass the sum of stochastic shallow subsurface and near-surface processes causing net downslope movement of soil or regolith. Simultaneously, another possibility of creep detection was noticed in dendrochronology, and since the 1970s, in the formally defined discipline of dendrogeomorphology, indirect evaluations of creep activity were performed based on tree-ring analyses of bent trees. This method found many followers, but was also heavily criticized as imprecise and lacking in evidence of which kind of tree trunk curvature (e.g. “pistol-butt”- like deformation, S-shape curvature) could be ascribed to creep movement.
From the beginning, soil creep was associated with the activity of living organisms on hillslopes. However, this aspect of creep studies has never been fully developed, in spite of the solid foundations and directions of potential studies pointed out by Charles Darwin at the end of the 19th century.
In this paper we focus on the historical context of soil creep studies, and highlight forest ecosystems as probably the most active environment of biogenic creep, mainly due to tree uprooting and other biomechanical effects of living and dead trees (root channel infilling, tree root mounding etc.) that are a factors in biotransport. In the final sections the position of biogenic creep in the structure of biogeomorphic systems is discussed in relation to such important conceptual frameworks as the biogeomorphic ecosystem, biogeomorphic feedback window and ecosystem engineering. We also describe several hypotheses that should be carefully tested in the future, and propose several research methods that have the ability to further our knowledge about soil creep: radiometry, laser scanning and soil micromorphology.
Following previous findings regarding the influence of vascular plants (mainly trees) on weathering, soil production and hillslope stability, in this study, we attempted to test a hypothesis ...regarding significant impacts of tree root systems on soil and regolith properties. Different types of impacts from tree root system (direct and indirect) are commonly gathered under the key term of “biomechanical effects”. To add to the discussion of the biomechanical effects of trees, we used a non-invasive geophysical method, electrical resistivity tomography (ERT), to investigate the profiles of four different configurations at three study sites within the Polish section of the Outer Western Carpathians. At each site, one long profile (up to 189m) of a large section of a hillslope and three short profiles (up to 19.5m), that is, microsites occupied by trees or their remnants, were made. Short profiles included the tree root zone of a healthy large tree, the tree stump of a decaying tree and the pit-and-mound topography formed after a tree uprooting.
The resistivity of regolith and bedrock presented on the long profiles and in comparison with the short profiles through the microsites it can be seen how tree roots impact soil and regolith properties and add to the complexity of the whole soil/regolith profile. Trees change soil and regolith properties directly through root channels and moisture migration and indirectly through the uprooting of trees and the formation of pit-and-mound topography. Within tree stump microsites, the impact of tree root systems, evaluated by a resistivity model, was smaller compared to microsites with living trees or those with pit-and-mound topography but was still visible even several decades after the trees were windbroken or cut down.
The ERT method is highly useful for quick evaluation of the impact of tree root systems on soils and regolith. This method, in contrast to traditional soil analyses, offers a continuous dataset for the entire microsite and at depths not normally reached by standard soil excavations. The non-invasive nature of ERT studies is especially important for protected areas as it was shown in the present study.
•Biomechanical effects of tree roots evidenced by electrical resistivity tomography for the first time.•Tree roots have surprisingly long-term influence on soil and regolith properties.•Tree roots add to the complexity of soil/regolith continuity.•Electrical resistivity tomography has many advantages when applied to tree root zone studies.•The study documents limits and architecture of the Critical Zone.
Windstorms may have negative consequences on forest ecosystems, industries, and societies. Extreme events related to extra-tropical cyclonic systems remind us that better recognition and ...understanding of the factors driving forest damage are needed for more efficient risk management and planning. In the present study, we statistically modelled forest damage caused by the windstorm Klaus in south-west France. This event occurred on 24 January 2009 and caused severe damage to maritime pine (Pinus pinaster) forest stands. We aimed at isolating the best potential predictors that can help to build better predictive models of forest damage. We applied the random forest (RF) technique to find the best classifiers of the forest damage binary response variable. Five-fold spatial block cross-validation, repeated five times, and forward feature selection (FFS) were applied to the control for model over-fitting. In addition, variable importance (VI) and accumulated local effect (ALE) plots were used as model performance metrics. The best RF model was used for spatial prediction and forest damage probability mapping. The ROC AUC of the best RF model was 0.895 and 0.899 for the training and test set, respectively, while the accuracy of the RF model was 0.820 for the training and 0.837 for the test set. The FFS allowed us to isolate the most important predictors, which were the distance from the windstorm trajectory, soil sand fraction content, the MODIS normalized difference vegetation index (NDVI), and the wind exposure index (WEI). In general, their influence on the forest damage probability was positive for a wide range of the observed values. The area of applicability (AOA) confirmed that the RF model can be used to construct a probability map for almost the entire study area.
Background and aims
The changing soils is a never-ending process moderated by numerous biotic and abiotic factors. Among these factors, trees may play a critical role in forested landscapes by having ...a large imprint on soil texture and chemical properties. During their evolution, soils can follow convergent or divergent development pathways, leading to a decrease or an increase in soil spatial complexity. We hypothesized that trees can be a strong local factor intensifying, blocking or modifying pedogenetic processes, leading to local changes in soil complexity (convergence, divergence, or polygenesis). These changes are hypothetically controlled by regionally predominating soil formation processes.
Methods
To test the main hypothesis, we described the pedomorphological features of soils under tree stumps of fir, beech and hemlock in three soil regions: Haplic Cambisols (Turbacz Reserve, Poland), Entic Podzols (Žofínský Prales Reserve, Czech Republic) and Albic Podzols (Upper Peninsula, Michigan, USA). Soil profiles under the stumps, as well as control profiles on sites currently not occupied by trees, were analyzed in the laboratory for 20 physical and chemical properties. In total, we analyzed 116 soil samples. The age of trees and time of tree death were determined using the radiometry (
14
C), dendrochronology and repeated tree censuses. To process the data, we used multivariate statistics, namely, redundancy analyses (RDAs) and principal component analyses (PCAs). The statistical significance of variables was tested using Kruskal-Wallis, Dunn, and permutation tests. To reach the main aims of the present study, we examined the dataset at three levels of data complexity: 1) soil regions, 2) microsite (i.e., tree stump versus control site), and 3) soil horizon.
Results
Living tree roots and empty or infilled root channels were the most important pedogenic factors that affected the dimensions of soil horizons and the moisture in the root zone under tree stumps. Microsites explained almost 6% of the soil variability (
p
< 0.001, F = 13.99), demonstrating that trees significantly impacted soil chemical properties in the root zone in all regions. In the Albic Podzols soil region, we found evidence of “basket” podzolization. Our results suggest the rapid eluviation of organic matter-sesquioxide complexes under the stump, probably leading to local soil divergence in Albic Podzols. However, soil analyses under the stumps in the Haplic Cambisols soil region suggested local polygenetic changes in soils (e.g., hydromorphic processes). The thickness of the A and B horizons increased, and soil chemistry changed under trees in the Entic Podzol soil region compared to the control profiles.
Conclusions
In addition to regional environmental factors that manifest themselves in regional pedogenesis and that have a key role in modifying the influence of trees on the soil, the tree species can specifically modify pedogenic processes under standing trees. Trees may influence rate of pedogenesis (hemlock in Albic Podzol region) or even soil evolutionary pathways (beech in Haplic Cambisol region).
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