Biomechanical and biochemical effects recorded in the tree root zone - soil memory, historical contingency and soil evolution under trees

Background and aims The changing soils is a neverending 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, aswell 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 (14C), 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 Bbasket^ 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)

The Effect of Tree-Uprooting on the Soil Spatial Complexity in an Old-Growth Temperate Forest, Central Europe

The formation of spatial pedocomplexity in forested landscapes is an issue that has not yet been comprehensively resolved. This study analysed the effects of tree disturbances on the spatial variability of soil chemical properties in order to explain the spatial pedocomplexity in one of the oldest forest reserves in Europe. A total of 1545 sites over an area of 74 ha were assessed in terms of soil taxonomy, morphology, and profiles. We quantified the spatial autocorrelation of soil chemical properties and analysed the effects of soil disturbance regimes on soil chemical properties in both the surface and subsurface layers using geostatistics and redundancy analysis, respectively. A paired difference test revealed that the factors involved in the soil formation of the two layers are different. The neoformation of the surface layer proceeds rapidly after soil disturbance and, therefore, some formerly disturbed surface layers become mature above immature subsurface layers. The effect of tree disturbances on soil chemical properties was significant for totally decomposed treethrows. Treethrow density partially explained the variation in soil chemical properties in both layers, but even more so in the subsurface layer. This study further elucidates the impact of treethrows on soils and shows that they are an important driver of soil spatial pedocomplexity

Dead or Alive: Drivers of Wind Mortality Initiate Multiple Disturbance Regime in a Temperate Primeval Mountain Forest

The driving forces of tree mortality following wind disturbances of mountain mixed European temperate forests belongs among issues not comprehensively resolved. Hence, we aimed to elucidate the key factors of tree resistance to historical severe disturbance events in the Boubínský Primeval Forest, one of the oldest forest reserves in the Czech Republic. By using spatially explicit tree census, dendrochronological and soil data, we study spatial and temporal patterns of past disturbances and mathematically compared selected characteristics of neighboring trees that were killed by a severe storm in 2017 and those that remained undisturbed. The tendency of trees toward falling was primarily driven edaphically, limiting severe events non-randomly to previously disturbed sites occupied by hydromorphic soils and promoting the existence of two spatially-separated disturbance regimes. While disturbed trees usually recruited in gaps and experienced only one severe release event, surviving trees characteristically regenerated under the canopy and were repeatedly released. Despite the fact that disturbed trees tended to reach both lower ages and dimensions than survivors, they experienced significantly higher growth rates. Our study indicates that slow growth with several suppression periods emerged as the most effective tree strategy for withstanding severe windstorms, dying of senescence in overaged life stage. Despite the selective impact of the Herwart storm on conifer population, we did not find any difference in species sensitivity for most characteristics studied. We conclude that the presence of such ancient, high-density wood trees contributes significantly to the resistance of an entire stand to severe storms

Impact of trees and forests on the Devonian landscape and weathering processes with implications to the global Earth's system properties – A critical review

Evolution of terrestrial plants, the first vascular plants, the first trees, and then whole forest ecosystems had far reaching consequences for Earth system dynamics. These innovations are considered important moments in the evolution of the atmosphere, biosphere, and oceans, even if the effects might have lagged by hundreds of thousands or millions of years. These fundamental changes in the Earth's history happened in the Paleozoic: from the Ordovician, the time of the first land plants, to the Carboniferous, dominated by forest ecosystems. The Devonian Plant Hypothesis (DPH) was the first concept to offer a full and logical explanation of the many environmental changes associated with the evolution of trees/forests that took place during this time period. The DPH highlighted the impact of deep-rooted vascular plants, particularly trees on weathering processes, pedogenesis, nutrient transport, CO2 cycling, organic and inorganic carbon deposition, and suggests further possible consequences on the marine realm (oceanic anoxia and extinction during the Late Devonian). Here we attempt to combine the DPH and the related expansion in biodiversity, the Devonian Plant Explosion (DePE), with the Biogeomorphic Ecosystem Engineering (BEE) concept. This idea connects tree growth and activity with initiation and/or alteration of geomorphic processes, and therefore the creation or deterioration of geomorphic landforms. We focus on trees and forest ecosystems, as the assumed dominant driver of plant-initiated change. We find that whereas there is a broad evidence of trees as important biogeomorphic ecosystem engineers, addressing the DPH is difficult due to limited, difficult to interpret, or controversial data. However, we argue the concept of BEE does shed new light on DPH and suggest new data sources that should be able to answer our main question: were Devonian trees Biogeomorphic Ecosystem engineers

ZMĚNY FOREM Fe A Al V RÁMCI PEDOGENEZE VÝVRATIŠŤ V PŘIROZENĚ SE VYVÍJEJÍCÍM JEDLO-BUKOVÉM PRALESE

The study is focused on changes of Fe and Al behaviour in naturally developing fir–beech forest Razula (Western Carpathians) with respect to time – in the scope of pedogenic processes. Soil samples from 14 different windthrow sites, of known age (19–192 years), were tested. Samples were taken from five depths from three parts of the windthrow – pit, mound and undisturbed part as a control. Exchangeable (“ free”), oxalate extractable and dithionate-citrate extractable forms of Al and Fe were measured. It was found that contents of Fe and Al forms significantly differed with respect to age and location (pit, mound and control). Moreover, Fe and Al forms also significantly differed in disturbed and undisturbed parts of the windthrow

Joint effects of climate, tree size, and year on annual tree growth derived from tree-ring records of ten globally distributed forests

Tree rings provide an invaluable long-term record for understanding how climate and other drivers shape tree growth and forest productivity. However, conventional tree-ring analysis methods were not designed to simultaneously test effects of climate, tree size, and other drivers on individual growth. This has limited the potential to test ecologically relevant hypotheses on tree growth sensitivity to environmental drivers and their interactions with tree size. Here, we develop and apply a new method to simultaneously model nonlinear effects of primary climate drivers, reconstructed tree diameter at breast height (DBH), and calendar year in generalized least squares models that account for the temporal autocorrelation inherent to each individual tree\u27s growth. We analyze data from 3811 trees representing 40 species at 10 globally distributed sites, showing that precipitation, temperature, DBH, and calendar year have additively, and often interactively, influenced annual growth over the past 120 years. Growth responses were predominantly positive to precipitation (usually over ≥3-month seasonal windows) and negative to temperature (usually maximum temperature, over ≤3-month seasonal windows), with concave-down responses in 63% of relationships. Climate sensitivity commonly varied with DBH (45% of cases tested), with larger trees usually more sensitive. Trends in ring width at small DBH were linked to the light environment under which trees established, but basal area or biomass increments consistently reached maxima at intermediate DBH. Accounting for climate and DBH, growth rate declined over time for 92% of species in secondary or disturbed stands, whereas growth trends were mixed in older forests. These trends were largely attributable to stand dynamics as cohorts and stands age, which remain challenging to disentangle from global change drivers. By providing a parsimonious approach for characterizing multiple interacting drivers of tree growth, our method reveals a more complete picture of the factors influencing growth than has previously been possible

Carbon carrying capacity in primary forests shows potential for mitigation achieving the European Green Deal 2030 target

13 Pág.Carbon accounting in the land sector requires a reference level from which to calculate past losses of carbon and potential for gains using a stock-based target. Carbon carrying capacity represented by the carbon stock in primary forests is an ecologically-based reference level that allows estimation of the mitigation potential derived from protecting and restoring forests to increase their carbon stocks. Here we measured and collated tree inventory data at primary forest sites including from research studies, literature and forest inventories (7982 sites, 288,262 trees, 27 countries) across boreal, temperate, and subtropical Global Ecological Zones within Europe. We calculated total biomass carbon stock per hectare (above- and below-ground, dead biomass) and found it was 1.6 times larger on average than modelled global maps for primary forests and 2.3 times for all forests. Large trees (diameter greater than 60 cm) accounted for 50% of biomass and are important carbon reservoirs. Carbon stock foregone by harvesting of 12–52% demonstrated the mitigation potential. Estimated carbon gain by protecting, restoring and ongoing growth of existing forests equated to 309 megatons carbon dioxide equivalents per year, additional to, and higher than, the current forest sink, and comparable to the Green Deal 2030 target for carbon dioxide removals.We thank the many people involved with the collection and provision of the site data and recognise the significant resources, people and time required to collect this invaluable data. The research for the synthesis, analysis and writing (H.K., Z.K., S.H., B.M.) was supported by a grant from a charitable organisation which neither seeks nor permits publicity for its efforts. The funder had no involvement in the study design, results or publication of the paper. Site data from Spain was funded by the Spanish Ministry of Science, Innovation and Universities [AGL2016-76769-C2-2-R]. C.P.C. was supported by the Spanish Ministry of Science and Innovation [RYC2018-024939-I]. J.A.M.V. was supported by the Ramón Areces Foundation Grants for Postdoctoral Studies. Contribution of D.A., K.K. and P.S. as well as data collection and processing from Czech natural forests was supported by Czech Science Foundation, project no. 24-11119S. D.M.-B. was funded by projects AGL2015-73190-JIN, PID2019-110273RB-I00 and contract RYC-2017-23389 by the Spanish Ministry of Science and Innovation MCIN/AEI. V.B. and I.D. were supported by the FORCLIMIT project funded in the frame of the ERA-NET FACCE ERA-GAS and with national support from Romanian National Authority for Scientific Research and Innovation, CCCDI \u2013 UEFISCDI [grant number 82/2017]. FACCE ERA-GAS has received funding from the European Union\u2019s Horizon 2020 research and innovation programme [grant agreement 696356. T.Z. was funded by The WWF Bulgaria through the project IKEA \u2116 9E0710.05 and by The National Roadmap for Research Infrastructure (2020-2027), Ministry of Education and Science of Republic of Bulgaria, through agreements No DO1-405/18.12.2020 and DO1-163/28.07.2022 (LTER-BG). L.D. was funded by the project of the National Research, Development and Innovation Office NKFIH K 131837. T.N. received support from the Slovenian Research Agency (Project No. J4-1765). For additional assistance with site data, we thank Dr. Ra\u00FAl Sanchez-Salguero and Dr. Andrea Hevia for evaluating the age in the dendrochronological samples in Spain, and Nesibe K\u00F6se, Mehmet Do\u011Fan, Daniel Bishop, Marco Mina, Timothy Thrippleton, Neil Pederson, Guillermo Gea-Izquierdo and Macarena F\u00E9rriz for their help during fieldwork, and Cengiz Cihan and the Turkish General Directorate of Forestry (OGM) in Bor\u00E7ka (Artvin) for their assistance in the field in Turkey.Peer reviewe

Major axes of variation in tree demography across global forests

The future trajectory of global forests is closely intertwined with tree demography, and a major fundamental goal in ecology is to understand the key mechanisms governing spatio-temporal patterns in tree population dynamics. While previous research has made substantial progress in identifying the mechanisms individually, their relative importance among forests remains unclear mainly due to practical limitations. One approach to overcome these limitations is to group mechanisms according to their shared effects on the variability of tree vital rates and quantify patterns therein. We developed a conceptual and statistical framework (variance partitioning of Bayesian multilevel models) that attributes the variability in tree growth, mortality, and recruitment to variation in species, space, and time, and their interactions – categories we refer to as organising principles (OPs). We applied the framework to data from 21 forest plots covering more than 2.9 million trees of approximately 6500 species. We found that differences among species, the species OP, proved a major source of variability in tree vital rates, explaining 28–33% of demographic variance alone, and 14–17% in interaction with space, totalling 40–43%. Our results support the hypothesis that the range of vital rates is similar across global forests. However, the average variability among species declined with species richness, indicating that diverse forests featured smaller interspecific differences in vital rates. Moreover, decomposing the variance in vital rates into the proposed OPs showed the importance of unexplained variability, which includes individual variation, in tree demography. A focus on how demographic variance is organized in forests can facilitate the construction of more targeted models with clearer expectations of which covariates might drive a vital rate. This study therefore highlights the most promising avenues for future research, both in terms of understanding the relative contributions of groups of mechanisms to forest demography and diversity, and for improving projections of forest ecosystems

Mycorrhizal feedbacks influence global forest structure and diversity

One mechanism proposed to explain high species diversity in tropical systems is strong negative conspecific density dependence (CDD), which reduces recruitment of juveniles in proximity to conspecific adult plants. Although evidence shows that plant-specific soil pathogens can drive negative CDD, trees also form key mutualisms with mycorrhizal fungi, which may counteract these effects. Across 43 large-scale forest plots worldwide, we tested whether ectomycorrhizal tree species exhibit weaker negative CDD than arbuscular mycorrhizal tree species. We further tested for conmycorrhizal density dependence (CMDD) to test for benefit from shared mutualists. We found that the strength of CDD varies systematically with mycorrhizal type, with ectomycorrhizal tree species exhibiting higher sapling densities with increasing adult densities than arbuscular mycorrhizal tree species. Moreover, we found evidence of positive CMDD for tree species of both mycorrhizal types. Collectively, these findings indicate that mycorrhizal interactions likely play a foundational role in global forest diversity patterns and structure

Variation in Downed Deadwood Density, Biomass, and Moisture during Decomposition in a Natural Temperate Forest

Deadwood is a resource of water, nutrients, and carbon, as well as an important driving factor of spatial pedocomplexity and hillslope processes in forested landscapes. The applicability of existing relevant studies in mountain forests in Central Europe is limited by the low number of data, absence of precise dating, and short time periods studied. Here, we aimed to assess the decomposition pathway in terms of changes and variability in the physical characteristics of deadwood (wood density, biomass, and moisture) during the decomposition process, and to describe differences in decomposition rate. The research was carried out in the Žofínský Primeval Forest, one of the oldest forest reserves in Europe. Samples were taken from sapwood of downed logs of the three main tree species: Fagus sylvatica L., Abies alba Mill., and Picea abies (L.) Karst. The time since the death of each downed log was obtained using tree censuses repeated since 1975 and dendrochronology. The maximal time since the death of a log was species-specific, and ranged from 61–76 years. The rate of change (slope) of moisture content along the time since death in a linear regression model was the highest for F. sylvatica (b = 3.94) compared to A. alba (b = 2.21) and P. abies (b = 1.93). An exponential model showing the dependence of biomass loss on time since death revealed that F. sylvatica stems with a diameter of 50–90 cm had the shortest decomposition rate—51 years—followed by P. abies (71 years) and A. alba (72 years). Our findings can be used in geochemical models of element cycles in temperate old-growth forests, the prediction of deadwood dynamics and changes in related biodiversity, and in refining management recommendations