Effects Of Tree Species Composition Research Articles

Effects of Afforestation Patterns on Soil Nutrient and Microbial Community Diversity in Rocky Desertification Areas

Karst ecosystems are characterized by the dissolution of soluble rocks, displaying distinctive landscape features such as rugged peaks, steep slopes, and deep valleys. Afforestation is an effective approach for improving soil quality in rocky desertification areas because plants have evolved unique adaptations to thrive in such environments. However, the effects of tree species composition and cultivation patterns on the soil quality, microbial diversity, stability, and functions in rocky desertification areas remain unclear. In this work, four study plots including three types of forests—pure Pinus massoniana plantations, Toona sinensis plantations, mixed coniferous and broadleaf plantations (Pinus massoniana–Betula luminifera forests), and unforested area as the control—were established in a karst desertification area in the Hunan province of China. Soil properties including soil bulk density, soil organic carbon, total nitrogen, total phosphate, soil ammonium nitrogen, nitrate, available phosphate, soil pH, and soil microbial diversity were investigated in the study area. The results showed that the forests significantly increased the soil organic carbon, total nitrogen, and ammonium nitrogen compared to the unforested area. The microbial diversity indicators in mixed forests were significantly higher than those in the Pinus massoniana forests. The dominant bacteria phyla included Proteobacteria, Acidobacteria, and Actinobacteria, while fungi species such as Ascomycota and Basidiomycota were identified in all study plots. In addition, the AVD index evaluation revealed that the mixed forests enhanced the stability of the soil microbial communities compared to the monoculture plantations and unforested plots in rocky desertification areas. The research results indicated that, among the various forest types, the mixed forest was the most effective choice for afforestation in terms of improving the soil quality by changing the soil’s physiological properties in rocky desertification areas. Our study provided guidance and insights for afforestation technology and the optimal allocation of different tree species in the cultivation and management of plantation forests in rocky desertification regions.

Infestation intensity by the invasive oak lace bug, Corythucha arcuata (Say) in mixed and pure oak stands

AbstractThere has been accumulating evidence for effects of tree species composition on herbivory with many examples of lower damage by specialist feeders in tree species rich forests. In a joint study in five Central and Southeastern European countries, we studied the effect of tree species richness on infestation intensity of the oak lace bug, Corythucha arcuata (Say) (Heteroptera, Tingidae), an invasive pest on oak trees that has spread rapidly across the Balkan Peninsula and Central Europe. Intensity of infestation by C. arcuata on oaks was assessed on three or four study plots with high (pure stands) and three or four plots with low percentage of oak (mixed stands) in each country. Ordinal regression analysis showed that intensity of infestation of trees by C. arcuata differed between countries; no significant effect of stand type (mixed or pure) on infestation levels was detected. When analysing the percentage of trees in the highest infestation class, stand type had a significant effect with more intensive infestation in pure stands. We conclude that mixed stands will not prevent severe infestation but may help mitigating the impact of established C. arcuata populations.

Research progress on productivity of mixed forest.

One of the effective ways to improve the productivity of mixed forests is enhancing resource use efficiency based on the biological characteristics of afforestation tree species. Resource use efficiency is affected by tree species interactions and environmental conditions through applying appropriate cultivation patterns. In this study, we evaluated two estimating methods for the productivity of mixed forest, analyzed the internal mechanism of interspecific tree competition and complementary effects on mixed forest productivity, clarified external factors of growth space and habitat factors control over productivity of mixed forest, discussed the effects of tree species composition, stand density and site quality on productivity, and illustrated the productivity trajectory during the development of mixed forests. Finally, based on the knowledge of the internal mechanism and habitat factors affecting the formation of mixed forest productivity, we focused on the key scientific issues that urgently need to be solved in the construction of the current mixed forests cultivation patterns, and put forward future research directions, including improving the productivity estimation system, establishing long-term mixed forest observation field, enhancing the research on the comprehensive effect of various cultivation measures, and reinforcing research of the growth and development dynamics in mixed forests.

Key structural factors and their thresholds for promoting bird diversity in spruce-dominated production forests of central Europe

Many of native forests in Europe have been transformed into even-aged production forests of commercially attractive conifers. In recent decades, a moderate shift back to a more native tree species composition accompanied by the maturation of some close natural stands has been evident in the Czech Republic. We aimed to investigate the effects of increasing age and contribution of native tree species on bird species and to identify the potential critical thresholds of these factors in central European forests. For this purpose, bird monitoring and forest structure measurements were carried out at 120 plots in production forests and 20 forest reserves located on 20 study sites throughout the Czech Republic. These plots covered gradients of native tree species contribution and stand age. Birds were counted during the 2018, 2019 and 2020 breeding seasons using passive acoustic monitoring, followed by subsequent computer analysis of the recordings. We assessed relationships between differences in bird species composition and structural and environmental factors. We also used generalised additive models (GAMs) to investigate the effects of individual structural and environmental factors on birds, taking into account their occurrence frequencies and habitat preferences. Our results convincingly documented, that dissimilarities in bird species composition, especially species turnover, strongly coincided with differences in the share of conifer basal area and stand age. The effect of tree species composition on the bird species turnover reflected the habitat preferences of individual species. In addition, we found that some cavity-nesting species were strictly associated with stands with a low contribution of conifers and high stand age. The presence of forest older than at least 125, but sometimes up to 280 years is a critical factor for rare and old-growth bird species. Conversely, the high contribution of conifers (more than app. 60 % of basal area) inhibited the occurrence of the species-rich communities, especially the birds associated with close natural stands. Therefore, increasing the area of mature close-natural stands would be beneficial for bird diversity, especially for rare species. In central Europe, however, the rotation length of forest stands is usually less than 120 years in order to maximise timber production. Forest management practices should therefore support the maturation of forest stands and the transformation of tree species composition towards more native broadleaved forest stands. These measures are essential for the protection of species-rich bird communities, especially old-growth-associated birds, in central Europe.

More than trees: Stand management can be used to improve ecosystem diversity, structure and functioning 20 years after forest restoration in drylands

In Mediterranean drylands, extensive areas have been restored by reforestation over the past decades to improve diversity, soil fertility, and tree natural regeneration, contributing to halting desertification and land degradation. However, evaluating reforestation success usually relies on tree survival, while holistic and long-term evaluations of reforestation success based on ecosystem diversity, structure and functioning are scarce. In this work, we provide the first assessment that combines the evaluation of planted trees and indicators of ecosystem diversity, structure, and functioning in established reforestations with three native Mediterranean species along a climatic gradient. We sampled 43 20-year-old stands with umbrella pine, holm oak and cork oak in Portugal, and tested the effects of tree species composition, stand management (i.e., differences in tree density and shrub cover), and edaphoclimatic conditions, on the size of planted trees, species diversity, structural complexity and indicators of ecosystem functioning related to productivity, soil nutrients and tree natural regeneration.Our results show that, after 20 years of reforestation, stand management was an essential driver of plant diversity and ecosystem functioning. Higher tree density, particularly of oaks, and higher shrub cover improved plant diversity, ecosystem productivity, and oak regeneration. The latter was also improved by structural complexity. Tree composition effects highlighted the importance of pine management to avoid competition. Since we evaluated these reforestations along a climatic gradient, we also conclude that climate influenced pine and holm oak size, ecosystem productivity, and soil C/N. Our research, by being based on assessing the long-term reforestation success in a more holistic way, highlighted the importance of stand management for improving ecosystem diversity and functioning in these restored systems. Practices such as increasing tree density up to ~800 trees/ha and allowing a shrub cover of ca. 30 %, may improve the ecological condition of future and currently reforested areas across the Mediterranean region.

Effect of Tree Species Composition and Food Selectivity on the Population Density of Sclater’s Guenon (Cercopithecus sclateri Pocock 1904) in Forest Patches of Lagwa, Aboh-Mbaise, Imo State, Nigeria

Aims: Effect of tree species composition and food selectivity on the population density of the Sclater’s guenon was carried out to determine how habitat composition and food preferences affect population density of the Sclater’s monkeys in the study area.
 Place and Duration of Study: The study was carried out in forest patches of Lagwa community in Aboh-Mbaise Local Government Area, Imo State (December 2019-November 2021).
 Study Design: The point centered quarter method was used to collect data on trees species, while the visual observation and line transect methods was used to collect data on food preference and population density of the monkeys.
 Methodology: The research was carried out within the wet and dry season. Faecal examination was used for collecting information on plant and fruit species consumed.
 Results: The most dominant tree species were Khaya ivorensis and Treculia africana with important value index (IVI) of 35.13 and 26.73 respectively, while Bosqueia angolensis was the least dominant species with IVI of 0.99. Tree species with diameter at breast height class of 41cm and above were absent in Eziudo, Obo and Umunekere communities. Dacryodes edulis, Elaeis guinensis, Mangifera indica and Musa balbisiana were the most consumed plant species. The mean troop sizes were 3.21±1.42 for the dry season and 2.78±1.25 for the wet season, with troop density for both seasons as 0.03±0.02.
 Conclusion: The findings presents the relationship between the Sclater’s monkey’s diet and their habitat, and how habitat changes can cause changes in the feeding pattern, type of food and meals consumed. Sensitization campaigns and provision of alternative food sources for humans can reduce disturbance of the habitat and further sustain the population of the monkeys.

Effect of forest structures and tree species composition on common tick (Ixodes ricinus) abundance—Case study from Czechia

Tick-borne diseases are a significant health problem worldwide and have become even more pervasive in Europe due to the increasing abundance of tick species, especially the common tick (Ixodes ricinus L.). Moreover, in recent years, there have been changes in tick geographical distribution, the occurrence of new tick species, and an expansion in abundance driven by changes in forest management and climate change. Therefore, this paper’s objective is to determine the effect of tree species composition and forest structure on the abundance of I. ricinus in various forest stands in Czechia. Altogether, we analyzed 4195 collected ticks on 56 monitored research plots, of which 4182 individuals were I. ricinus, 4 individuals were Dermacentor reticulatus Fabricius, and 7 individuals were Haemaphysalis concinna C. L. Koch. The average density reached 1.21 ticks per 10 m2. The highest I. ricinus abundance was observed in coniferous stands (especially in Scotch pine—Pinus sylvestris L.) and forest edges with a high incidence of wild ungulate habitat signs. Contrarily, the lowest tick numbers were in clear-cut biotopes and mixed stands. Increasing vertical structure had a significant (p < 0.05) negative effect on I. ricinus abundance, similar to tree species diversity (richness, evenness, heterogeneity) and complex stand diversity on nymph stage abundance. Close-to-nature silviculture of mixed forests, which are resistant to climate extremes, could reduce the tick abundance, as well as the presence of tick-borne diseases compared to standard coniferous monocultures, which are receding now due to climate change. Based on this knowledge, it should be possible to predict the I. ricinus abundance under changing environmental conditions in the Central European region.

Neighboring plants and core herbivores determine the importance of Swietenia macrophylla in the plant–herbivore network

Species contribute differently to the structure and stability of networks of interacting species. However, species contributions to the importance of other species is usually neglected, thus limiting our understanding of species dynamics beyond the general network structure. We combined knowledge on diversity effects on focal species and network ecology to analyze the influence of plants and herbivores on big-leaf mahogany's (Swietenia macrophylla) importance in the plant–herbivore network. To this end, we built interaction networks using information from a large-scale tree diversity experiment and performed computer simulations of species removal with redistribution of interactions. We compared the importance of big-leaf mahogany in the observed networks to simulated networks where we removed: (a) tree species with similar beetle assemblages to mahogany, (b) the most interconnected (core) tree species and (c) the core beetle species. Removal of the core and similar tree species increased the importance of mahogany, whereas eliminating core beetle species decreased it. Interestingly, the effect of core tree species on mahogany’s importance was mediated by core beetles (R2 = 0.46). Neither tree nor core beetle species’ effects were contingent on tree species richness or abundance. These results indicate that highly connected tree and herbivore species jointly determine the role of mahogany in the plant–herbivore network. Likewise, these results provide insight into the effect of tree species composition and highly interactive herbivores in shaping the role of species in the herbivore network.

Interactive effects of tree species composition and water availability on growth and direct and indirect defences in Quercus ilex

Plant diversity has often been reported to decrease insect herbivory in plants. Of the numerous mechanisms that have been proposed to explain this phenomenon, how plant diversity influences plant defences via effects on growth has received little attention. In addition, plant diversity effects may be contingent on abiotic conditions (e.g. resource and water availability). Here, we used a long‐term experiment to explore the interactive effects of tree species composition and water availability on growth, direct (i.e. phenolics) and indirect (i.e. volatile organic compounds – VOCs) defences and leaf herbivory in Quercus ilex. We quantified herbivory by chewing insects, phenolic compounds and VOCs in Q. ilex trees growing in stands differing in tree species composition (Q. ilex, Q. ilex + Betula Pendula, Q. ilex + Pinus pinaster and Q. ilex + B. pendula + P. pinaster) and water availability (irrigated versus control). Both direct and indirect defences were affected by tree species composition, but such changes were not mediated by changes in tree stem diameter. Quercus ilex trees growing in stands with P. pinaster had the lowest concentration of both direct and indirect defences. Importantly, the effects of tree species composition on VOCs were exacerbated on irrigated blocks. Despite variation in defences, tree species composition did not affect herbivory in Q. ilex. Accordingly, we did not find any association between defences and insect herbivory. Our results suggest that changes in the micro‐environment rather than growth‐defence associations may mediate tree diversity effects on defences. In addition, reduced defensive investment in more diverse stands could negatively impact tree resistance masking the beneficial effects of species diversity at reducing insect herbivory.

Do tree species affect decadal changes in soil organic carbon and total nitrogen stocks in Danish common garden experiments?

AbstractTemperate forest soils are often considered as an important sink for atmospheric carbon (C), thereby buffering anthropogenic CO2 emissions. However, the effect of tree species composition on the magnitude of this sink is unclear. We resampled a tree species common garden experiment (six sites) a decade after initial sampling to evaluate whether forest floor (FF) and topsoil organic carbon (Corg) and total nitrogen (Nt) stocks changed in dependence of tree species (Norway spruce—Picea abies L., European beech—Fagus sylvatica L., pedunculate oak—Quercus robur L., sycamore maple—Acer pseudoplatanus L., European ash—Fraxinus excelsior L. and small‐leaved lime—Tilia cordata L.). Two groups of species were identified in terms of Corg and Nt distribution: (1) Spruce with high Corg and Nt stocks in the FF developed as a mor humus layer which tended to have smaller Corg and Nt stocks and a wider Corg:Nt ratio in the mineral topsoil, and (2) the broadleaved species, of which ash and maple distinguished most clearly from spruce by very low Corg and Nt stocks in the FF developed as mull humus layer, had greater Corg and Nt stocks, and narrow Corg:Nt ratios in the mineral topsoil. Over 11 years, FF Corg and Nt stocks increased most under spruce, while small decreases in bulk mineral soil (esp. in 0–15 cm and 0–30 cm depth) Corg and Nt stocks dominated irrespective of species. Observed decadal changes were associated with site‐related and tree species‐mediated soil properties in a way that hinted towards short‐term accumulation and mineralisation dynamics of easily available organic substances. We found no indication for Corg stabilisation. However, results indicated increasing Nt stabilisation with increasing biomass of burrowing earthworms, which were highest under ash, lime and maple and lowest under spruce.Highlights We studied if tree species differences in topsoil Corg and Nt stocks substantiate after a decade. The study is unique in its repeated soil sampling in a multisite common garden experiment. Forest floors increased under spruce, but topsoil stocks decreased irrespective of species. Changes were of short‐term nature. Nitrogen was most stable under arbuscular mycorrhizal species.

Intra-specific leaf trait variability of F. sylvatica, Q. petraea and P. abies in response to inter-specific competition and implications for forest functioning.

Variability in functional traits (FT) is increasingly used to understand the mechanisms behind tree species interactions and ecosystem functioning. In order to explore how FT differ due to interactions between tree species and its influence on stand productivity and other ecological processes, we examined the effects of tree species composition on the intra-specific variability of four widely measured FT: specific leaf area, leaf nitrogen content, leaf angle and stomatal conductance response to vapor pressure deficit. This study focused on three major central European tree species: European beech (Fagus sylvatica L.), Sessile oak (Quercus petraea Liebl.) and Norway spruce (Picea abies [L.] H. Karst.). Each species was examined in monoculture and two-species mixtures in the 13-year-old tree biodiversity experiment BIOTREE-Kaltenborn. Trait distributions and linear mixed models were used to analyze the effect of species mixing, tree size and stand variables on the intra-specific FT variability. A significant effect of branch height on most traits and species indicated a vertical gradient of foliar trait frequently related to light availability. Beech and oak showed a high overall trait variability and sensitivity to species mixing and stand basal area, while the trait variability of spruce was limited. Greater shifts in trait distributions due to mixing were found in specific leaf area for oak and leaf nitrogen content for beech. Thus intra-specific variability of key leaf traits was already influenced at this young development stage by inter-specific interactions. Finally, we used the 3-PG (Physiological Processes Predicting Growth) process-based forest growth model to show that the measured intra-specific variability on single FT values could influence stand productivity, light absorption and transpiration, although the net effect depends on the considered trait and the species composition of the mixture. The results of this study will aid better understanding of the effects of inter-specific competition on intra-specific FT variability, which has implications for the parameterization of process-based forest growth models and our understanding of ecosystem functioning.

The Effect of Tree Species Composition on Soil C and N Pools and Greenhouse Gas Fluxes in a Mediterranean Reforestation

The shift of tree species composition from conifers to mixed stands as a silvicultural management option for substituting pure plantations can have consequences for the greenhouse gas (GHG) budgets and climate impact. In this context, the main objective of the study was to assess the effect of tree species composition on GHG fluxes, organic matter of forest floor and soil in a degraded conifers plantation in Central Italy. Field-chamber GHG fluxes, litter, and total concentrations of soil C and N, soil temperature, and soil moisture were analyzed, assessing their relationships, under mixed and pure conifer species composition during three monitoring years. Carbon and nitrogen contents were higher under mixed than pure conifer species composition, both in forest floor and mineral soil. Soil carbon dioxide under litter of mixed tree species was significantly higher than that of pure conifers (+17.5%). Methane uptake was higher in the mixed plots than in the pure ones (+12.4%), especially in summer and autumn. Nitrous oxide fluxes were characterized by very low emissions, higher under mixed tree-species than pure conifers during winter. The relevant role of seasonality was confirmed by including in the linear mixed-effects model (LMM) the seasons as an additional random effect that produced a significant interaction between the soil moisture and soil temperature, especially on soil carbon dioxide and methane fluxes. Overall, the GHG budget was driven by organic matter availability, higher under mixed species. Our findings are a first step to help the understanding of the role of tree species composition on GHG emissions in the Mediterranean forest ecosystems.

Response of soil microbial communities to mixed beech-conifer forests varies with site conditions

Tree - soil interactions depend on environmental conditions. Planting trees may affect soil microbial communities and compromise their functioning, particularly in unfavorable environments. To understand the effects of tree species composition on soil microbial communities, we quantified structural and functional responses of soil microorganisms to tree species planted in various environments using substrate-induced respiration and phospholipid fatty acid analyses. Five forest types were studied including pure stands of native European beech (Fagus sylvatica), range expanding Norway spruce (Picea abies), and non-native Douglas-fir (Pseudotsuga menziesii), as well as the two conifer - beech mixtures. We found that microbial functioning depends strongly on soil nutrient concentrations in the studied forest sites. At nutrient-poor sites, soil microorganisms were more stressed in pure and mixed coniferous forests, especially in Douglas-fir, compared to beech forests. By contrast, microbial structure and functional indicators in beech forests varied little with site conditions, likely because beech provided ample amounts of root-derived resources for microbial growth. Since soil microbial communities are sensitive to Douglas-fir, planting Douglas-fir may compromise ecosystem functioning, especially at nutrient-poor sites. Overall, root-derived resources are important for determining the structure and functioning of soil microbial communities, so soil microbial responses to tree species will depend upon the provisioning of these resources as well as site-specific environmental conditions.

Vegetation composition and structure determine wild bee communities in a tropical dry forest

Understanding the factors that influence the composition and structure of bee communities in natural habitats is critical for conservation and restoration efforts, mainly in disturbed ecosystems that are widely used for agricultural crop production, such as tropical dry forests (TDF). The aim of this study was to evaluate the effects of tree species composition and vegetation structure on the composition, abundance and species richness of eusocial and non-eusocial wild bee assemblages. Bees (19.909 individuals of 96 species) were collected in fifteen plots in different secondary succession stages in a TDF in the state of Minas Gerais, Brazil. We found a positive relationship between tree community similarity and bee community similarity, for both eusocial and non-eusocial bees. Average tree height positively affected the abundance and species richness of eusocial bees, while the abundance of non-eusocial bees was negatively affected by tree species richness. Similar tree species composition and vegetation structure between plots at the same stage of secondary succession probably determined more similar bee communities than dissimilar tree communities. Most eusocial bee species are dependent on cavities in large trees to house their colonies, while most non-eusocial bees probably prefer open habitats because they provide a greater density and diversity of floral resources, and suitable areas for ground-nesting species. Since eusocial bees represented 94% of the individuals sampled, the conservation and restoration of mature forests is of primary importance in order to increase eusocial bee diversity, and the maintenance of these areas in the vicinity of agricultural systems is crucial to increase the ecosystem service of pollination.

Soil heterogeneity in tree mixtures depends on spatial clustering of tree species

Heterogeneity in soil characteristics promotes and maintains coexistence between a diverse set of species. In forests, trees have species-specific impacts on soil abiotic characteristics and mixing of tree species is being promoted as a tool to ensure high levels of diversity and functioning. Yet, limited knowledge is available on the effect of tree species composition and spatial clustering on heterogeneity in soil characteristics. In this paper we derived heterogeneity of key characteristics of the leaf litterfall, the forest floor and the mineral topsoil (C, N and base cation concentration, C:N ratio and mass) in 53 plots of 7 different tree species compositions. We found that heterogeneity increased from the leaf litterfall, through the forest floor down to the mineral topsoil. Mixing tree species did not lead to an increased heterogeneity in the forest floor and topsoil compared to monocultures. However, we did find that mixed plots where conspecific trees stand in groups are more heterogeneous than plots where species are intimately mixed. Our results imply that heterogeneity in soil characteristics does not necessarily increase with tree diversity, but that within mixed stands the spatial organization of tree species should be considered in relation to the scale at which heterogeneity is desired.

Tree Species Shape Soil Bacterial Community Structure and Function in Temperate Deciduous Forests.

Amplicon-based analysis of 16S rRNA genes and transcripts was used to assess the effect of tree species composition on soil bacterial community structure and function in a temperate deciduous forest. Samples were collected from mono and mixed stands of Fagus sylvatica (beech), Carpinus betulus (hornbeam), Tilia sp. (lime), and Quercus sp. (oak) in spring, summer, and autumn. Soil bacterial community exhibited similar taxonomic composition at total (DNA-based) and potentially active community (RNA-based) level, with fewer taxa present at active community level. Members of Rhizobiales dominated at both total and active bacterial community level, followed by members of Acidobacteriales, Solibacterales, Rhodospirillales, and Xanthomonadales. Bacterial communities at total and active community level showed a significant positive correlation with tree species identity (mono stands) and to a lesser extent with tree species richness (mixed stands). Approximately 58 and 64% of indicator operational taxonomic units (OTUs) showed significant association with only one mono stand at total and active community level, respectively, indicating a strong impact of tree species on soil bacterial community composition. Soil C/N ratio, pH, and P content similarly exhibited a significant positive correlation with soil bacterial communities, which was attributed to direct and indirect effects of forest stands. Seasonality was the strongest driver of predicted metabolic functions related to C fixation and degradation, and N metabolism. Carbon and nitrogen metabolic processes were significantly abundant in spring, while C degradation gene abundances increased from summer to autumn, corresponding to increased litterfall and decomposition. The results revealed that in a spatially homogenous forest soil, tree species diversity and richness are dominant drivers of structure and composition in soil bacterial communities.

Effects of tree species composition on soil properties and invertebrates in a deciduous forest

A comprehensive understanding of factors that influence soil properties and soil biota, such as tree composition, is essential for the management and conservation of biodiversity. This study was conducted to explore the effects of tree composition on a number of properties and invertebrates of soil in the forest ecosystem of northern Iran. Eleven plots were selected differing in the composition of the following tree species: Persian ironwood (Parrotia persica V.), maple (Acer velutinium B.), and hornbeam (Carpinus betulus L.). In each plot, we measured pH, particle size distribution, electrical conductivity (EC), calcium carbonate equivalent (CCE), organic carbon (OC), total nitrogen (TN), and soil microbial respiration rate (Resp), at depths of 0–10 cm and 10–20 cm. In addition, abundance, Shannon index, richness, and evenness of the soil invertebrates, at both depths, were determined. Accordingly, a total number of 636 and 312 invertebrates were recorded from the topsoil and subsoil, respectively. EC, pH, CCE, C/N, silt, sand, abundance, and richness of the soil invertebrates had a significant correlation with the tree abundance. The soil properties significantly differed among the plots having different tree species composition (P ≤ 0.05). The depths of the soil also had significant effects on the soil properties. The study revealed that the plot including single tree species (maple) had the highest invertebrate abundance (24.67), while the highest OC (6.06%), the greatest TN (0.40%), and the uppermost soil resp. (434 mg CO2 kg−1 day−1) were observed in the Persian ironwood-maple, which has two tree species. In addition, hornbeam-maple-Persian ironwood plot had the highest Shannon index (1.48) and the greatest richness of invertebrates (6.17), while the Persian ironwood-hornbeam-maple plot had the highest invertebrate evenness. However, the hornbeam plot had the lowest abundance, Shannon index, and richness of invertebrates (0.93). Overall, the results revealed that soil properties and soil invertebrate communities were affected by the dominant tree species, and their effects could be lowered or intensified by varying the proportion of different tree species.

Forest fragmentation and tree species composition jointly shape breeding performance of two avian insectivores

Habitat fragmentation and forestry practices affect forest structure and composition, and hence, their intrinsic value for biodiversity conservation. While higher tree species diversity is commonly proposed to result in habitat of higher quality for forest species, how these tree diversity and tree composition effects interact with forest fragmentation in terms of critical resources and demographic effects on forest birds remains poorly understood. We investigated here possible synergistic effects of forest fragmentation and tree species composition on the breeding performance of two common, insectivorous forest birds in a human-dominated landscape in northern Belgium. We monitored the breeding performance of Great Tits and Blue Tits in 53 plots across independent gradients of tree species composition and forest fragmentation. In addition, data on the biomass of the main food source of these two species (i.e. caterpillars) was collected during the breeding season. Both tree composition and habitat fragmentation impacted the breeding performance of Great and Blue Tits. Effects of tree species composition were mainly driven by tree species identity, rather than by tree species diversity, and the highest breeding performance was obtained in monocultures of Pedunculate Oaks. Fragmentation effects were only observed in resource-poor Beech monocultures with breeding performance declining with reduction in forest area. Structural Equation Modelling revealed diverse and species-specific pathways: for Great Tits tree composition effects on breeding performance were driven by resource availability while for Blue Tits these effects were driven by variation in clutch size. Thus, forestry practices aiming at promoting forest-dependent birds could benefit from including tree species that support high arthropod numbers and by maintaining forest patches of larger sizes.

Assessing horizontal accuracy of inventory plots in forests with different mix of tree species composition and development stage

Global navigation satellite systems (GNSS) have a wide range of applications in forest industry, including forest inventory. In this study, the horizontal accuracy of 45 inventory plots in different forest environments and 5 inventory plots under open sky conditions were examined. The inventory plots were located using a mapping-grade GNSS receiver during leaf-on season in 2017. True coordinates of the plot centres were acquired using a survey-grade GNSS receiver during leaf-off season in 2018. A study was conducted across a range of forest conditions in the forest unit Vígľaš, which is located in Slovakia (Central Europe). Root mean square error of horizontal accuracies was 8.45 m in the plots under forest canopy and 6.61 m under open sky conditions. We note decreased positional errors in coniferous forests as well as in younger forests. However, results showed that there is no statistically significant effect of tree species composition and stand age on horizontal accuracy.

Tree diversity promotes generalist herbivore community patterns in a young subtropical forest experiment.

Stand diversification is considered a promising management approach to increasing the multifunctionality and ecological stability of forests. However, how tree diversity affects higher trophic levels and their role in regulating forest functioning is not well explored particularly for (sub)tropical regions. We analyzed the effects of tree species richness, community composition, and functional diversity on the abundance, species richness, and beta diversity of important functional groups of herbivores and predators in a large-scale forest biodiversity experiment in south-east China. Tree species richness promoted the abundance, but not the species richness, of the dominant, generalist herbivores (especially, adult leaf chewers), probably through diet mixing effects. In contrast, tree richness did not affect the abundance of more specialized herbivores (larval leaf chewers, sap suckers) or predators (web and hunting spiders), and only increased the species richness of larval chewers. Leaf chemical diversity was unrelated to the arthropod data, and leaf morphological diversity only positively affected oligophagous herbivore and hunting spider abundance. However, richness and abundance of all arthropods showed relationships with community-weighted leaf trait means (CWM). The effects of trait diversity and CWMs probably reflect specific nutritional or habitat requirements. This is supported by the strong effects of tree species composition and CWMs on herbivore and spider beta diversity. Although specialized herbivores are generally assumed to determine herbivore effects in species-rich forests, our study suggests that generalist herbivores can be crucial for trophic interactions. Our results indicate that promoting pest control through stand diversification might require a stronger focus on identifying the best-performing tree species mixtures.