Shrub Layer Research Articles

Low understory condition in an oak forest in Hungary, 1972 and 2022 – Síkfőkút Project is 50 years old

erious oak decline was first detected in 1979-80 in a mixed sessile oak–Turkey oak forest (Quercetum petraeae-cerridis Soó 1963). This decline resulted important structural changes in the understory shrub layer. Despite of this, relatively few studies deal with shrub communities and shrub layer dynamics after oak death. The goals of this research were to determine the conditions of low shrubs and analyse the possible changes in this layer after 5 decades from the beginning of Síkfőkút research. Specimens which were lower than 1.0 m in height were categorized as low shrubs in the shrub community. In 1972 and in 2022, 16- 17 native low shrub species were observed in the understory; 15 species were present continuously in the forest. The density of low shrubs was 87401 and 17317 specimen ha-1. The most common low shrub species was Ligustrum vulgare and 5 decades later Quercus petraea with 24.1% and 37.8% ratio. The mean height and mean diameter of low shrub species changed among 10.3-67.0 cm and 1.5-7.5 mm. The mean cover of these shrubs fluctuated between 35 cm2 and 2026 cm2 based on the two measured year. Our results suggest that the low shrub layer responded negatively to the biotic and abiotic factors under 5 decades; this is especially true to the density, cover and diversity indices of species.

Trade-Offs and Synergies between Plant Species Diversity and Water Retention Capacity of Pinus massoniana Plantation Community in Danjiangkou Reservoir Area

In order to quantify the plant species diversity characteristics of Pinus massoniana plantations with different stand densities in the Danjiangkou reservoir area of Hubei Province and the relationship of their trade-offs and synergies with the water retention capacity in the reservoir area to give full play to the forest ecosystem services in the reservoir area and improve the level of sustainable management of plantations, we used the typical plot method, selected 35-year-old Pinus massoniana with low density (925–1000 plants·ha), medium density (1425–1625 plants·ha), and high density (2375–2525 plants·ha), and its community structure, species composition, and understory plant species diversity were studied, respectively, and the relationship of the trade-offs and synergies between the two services of water retention capacity and plant species diversity in Pinus massoniana plantations were calculated. We found that: (1) According to the survey statistics, there were 69 species of plants in the shrub and herb layers under forest including 32 species of shrubs and 37 species of herbs, belonging to 33 families and 62 genera. (2) The species richness of the shrub layer increased with the increase in the stand density, which was opposite in the herb layer. The Shannon–Wiener diversity index and Simpson dominance index of the shrub layer showed the regularity of high density > low density > medium density, while the herb layer decreased gradually with the increase in density. The Pielou evenness index of the shrub layer and herb layer was the highest in the high-density and medium-density stands, respectively. (3) Trunk flow, soil layer water storage and plant species diversity under medium and high density conditions, litter layer water storage and plant species diversity under low-medium density conditions showed synergistic relationships in the shrub layer and herb layer, everything else were trade-off relationships. As far as the Danjiangkou reservoir area is concerned, the low-density Pinus massoniana plantations have higher understory plant species diversity and more stable community structure, and there is a trade-off relationship between the water retention capacity and understory plant species diversity.

Population Density and Stability of Breeding Birds in English Oak Woodland Over a 32-Year Period in Relation to Habitat Structure and Edges

Long-term breeding bird censuses in Białowieża National Park (BNP), north-east Poland, have revealed rather low densities of birds and high community stability which may be features of near-natural forest conditions. This paper reports on a long-term census of breeding birds in 50 ha of oak woodland in central England which contained both managed and undisturbed areas. New information is provided on breeding bird density and its spatial variation within English mature broadleaved woodland to address two questions: Under what circumstances are English woods likely to support higher densities than those occurring in BNP? Is there evidence that population and community stability is lower in English woodland? The overall bird density was lower than in the BNP oak-hornbeam stands, at the scale of both the whole study area and the undisturbed stands. Densities of three of the five dominant species (Cyanistes caeruleus, Parus major, Troglodytes troglodytes) were lower in BNP, Fringilla coelebs was higher, while Erithacus rubecula was similar. Within the undisturbed stands, densities of seven of 12 species, including T. troglodytes, were similar to those in BNP, two were considerably higher (C. caeruleus, P. major) and one much lower (F. coelebs). Selection of the external woodland edge by several species resulted in relatively high overall densities in the edge zone. The broad composition of the bird community remained fairly stable with the exception of declines in tropical migrants and increases in shrub layer nesters. Temporal abundance patterns of species showed much individuality. Trends of several species appeared to be driven by changes in habitat structure. However, the same species remained numerically dominant or characteristic of the wood throughout the study period. This suggests there was a core of resilient species, much as proposed for BNP. Although caution is needed in drawing conclusions from a single site, with the exception of a small number of species, in recent decades there is unlikely to have been a general pattern of higher densities of birds in English woodland than in BNP. However, some English woods with highly complex vegetation structures, or a high proportion of edge habitat, do have exceptionally high densities (> 100 territories/10 ha).

Restoration Contributes to Maintain Ecosystem Services and Bio-Cultural Linkages Between Wetlands and Local Communities: a Case from a Botanical Diversity Hotspot in Japan.

The online version contains supplementary material available at 10.1007/s13157-022-01639-2.

Correlation between Vegetation Structure and Species Diversity in Traditional Villages in Karst Topographic Regions of the Zunyi City, China.

Studying the relationship between vegetation structure and diversity is important in an area having karst topography and unique traditional customs. We selected a total of six traditional villages in Zunyi City, China, to collect vegetation data. Additionally, using one-way ANOVA and the Pearson correlation coefficient analytic method to analyze, the results showed that, overall, plant communities were mostly regularly distributed. The overall differentiation degree was low aggregation, intensity, and the extreme intensity mixed state. Overall, competitive pressure, growth vigor and stability were better than the natural forest. The community stability index at lower altitude was significantly higher than that at higher altitude. The recorded plant communities in the living space were typically aggregated, the plant communities were randomly distributed in the production space, and the plant communities were uniformly distributed in the ecological space. In general, the diversity indexes, except the Jh index, were the highest in the herb layer; the second was in the shrub layer and the lowest was in the tree layer. Species diversity at the middle altitude was higher than that at low and high altitudes (except for the shrub at a high altitude of 1100-1160 m). The overall plant species diversity was highest in the living space, second highest in the ecological space and lowest in the production space. On the whole, there was a significant correlation between the spatial structure of plant communities and the species diversity of plant communities at different altitudes, and in PLE spaces. The main objective of this study was to reveal the plant community structure, species diversity, and their relationship under the dual effects of national traditional culture and karst landform. Additionally, we sought to provide theoretical guidance for the construction of plant community protection and biodiversity conservation in traditional villages in karst areas.

К синтаксономии искусственных лесов города Курска

Geobotanical survey and classification of communities of oak plantations of the city of Kursk has been carried out. The described phytocoenoses are attributed to the non-rank community Fraxinus pennsylvanica–Quercus robur within the order Carpinetalia betuli, whose species are most represented in the coenoflora of this syntaxon. Variants with thr differences in the species composition and habitat conditions have been established in the community: typica, Lonicera caprifolium, Robinia pseudoacacia. Lonicera caprifolium is dominant in the phytocoenoses of var. Lonicera caprifolium and has the characteristics of an aggressive invasive plant. It forms a dense cover in the grass layer and suppresses shrubs and woody growth. Communities of var. Robinia pseudoacacia are characterized by a high closeness of the crowns of the shrub layer formed by Robinia pseudoacacia. The grass layer in them is poorly developed due to the allelopathic effects of this invasive species. The conducted research makes it possible to assess the current state of the artificial forests of the city of Kursk and monitor changes in their composition and structure.

Changes in root chemical diversity along an elevation gradient of Changbai Mountain, China.

Root chemical traits play a critical role in plant resource use strategies and ecosystem nutrient cycling; however, the chemical diversity of multiple elements of fine root and community chemical assembly belowground are poorly understood. Here, we measured 13 elements (C, N, K, Ca, Mg, S, P, Al, Fe, Na, Mn, Zn, and Cu) in the fine roots of 204 plant species along elevational transect from 540 to 2357 m of Changbai Mountain, China to explore the variation, diversity, and community assembly of root chemical traits. At the species level, the concentrations of macronutrients (N, K, Ca, Mg, S, and P) decreased, whereas the trace metals (Fe, Mn, and Zn) increased with elevation. Root chemical traits at the community level systematically shifted along elevational gradients showing a pattern similar to that at the species level, which were mainly influenced by climate and soil rather than species diversity. In general, the interactions of climate and soil were the main drivers of root chemical assembly for woody layers, whereas soil factors played significant role for root chemical assembly for herb layer. The chemical assembly of rock-derived element P was mainly driven by soil factors. Meanwhile, root chemical diversities were mainly regulated by species diversity, the interactions of climate and soil, and soil factors in the tree, shrub, and herb layers, respectively. A better understanding of plant root chemical diversity and community chemical assembly will help to reveal the role of chemical traits in ecosystem functioning.

How Do Landscape Heterogeneity, Community Structure, and Topographical Factors Contribute to the Plant Diversity of Urban Remnant Vegetation at Different Scales?

In highly fragmented urban areas, plant diversity of remnant vegetation may depend not only on community structure and topographical factors, but also on landscape heterogeneity. Different buffer radius settings can affect the relative importance of these factors to plant diversity. The aim of this study was to examine the relative importance of landscape heterogeneity, community structure, and topographical factors on plant diversity under different buffer radii in biodiversity hotspots. We established 48 plots of remnant vegetation in Guangzhou city, one of the biodiversity hotspots. A buffer radius of 500 m, 1000 m, and 2000 m was established around the center of each sample plot, and 17 landscape heterogeneity indices in each buffer were calculated by FRAGSTATS 4.2 software. Combined with the community structure and topographical factors, the impact factors of plant diversity under different buffer radii were analyzed by multiple regression analysis. We found the following: (1) The combined explanatory power of the three factors accounted for 43% of the species diversity indices and 62% of the richness index at its peak. The three impact factors rarely act independently and usually create comprehensive cumulative effects. (2) Scale does matter in urban landscape studies. At a 500 m buffer radius, community structure combined with road disturbance indices was strongly related to diversity indices in herb and shrub layers. The stand age was negatively correlated with the tree-layer richness index. As the scale increased, the diversity indices and richness index in the three layers decreased or increased under the influence of comprehensive factors. (3) The richness index in the herb layer was more responsive to impact factors than other biodiversity indices. Except for the herb layer, the interpretation of landscape heterogeneity for each plant diversity index was more stable than that for the other two factors. Road disturbance indices, combined with the other six landscape pattern metrics, can well indicate species diversity and richness. We suggest that the vegetation area of remnant patches within a radius of 500-2000 m should be appropriately increased to protect plant diversity, and the negative effects of road disturbance should also be considered.

Spatio‐temporal variation in deep soil water use patterns of overstorey and understorey layers in subtropical plantations predicts community assembly

Abstract Deep soil water utilization allows plants to cope with drought stress. However, little is known about the roles of the understorey layers in driving spatio‐temporal variations of deep soil water in forests and how the patterns of deep soil water use among life‐forms contribute to community assembly processes. We assessed the spatio‐temporal patterns and determinants of deep water utilization of tree, shrub and herb layers in subtropical coniferous plantations and investigated associations between deep water use parameters and dominance and richness of understorey vegetation. We found that the understorey layer had a higher reliance on deep soil water in the dry season, a larger seasonal plasticity of deep soil water uptake, but lower spatial variability in deep soil water utilization than the tree layer. We showed that greater reliance of the tree layer on deep soil water was associated with decreased shrub layer diversity, whereas greater reliance of the shrub layer on deep water was associated with increased herb layer diversity. Synthesis. Our results highlight the roles of understorey layers in driving the temporal dynamics of deep soil water in forests and improve our understanding of how deep soil water use patterns among life‐forms shape community assembly in forests.

Impact of European Beaver (Castor fiber L.) on Vegetation Diversity in Protected Area River Valleys

The aim of the study was to evaluate the impact of European beaver (Castor fiber L.) on vegetation diversity and the expansion of non-native plant species in areas surrounding watercourses in Polesie National Park, Poland. The investigation was carried out within six watercourses inhabited by beavers and four comparison watercourses where beaver were absent. European beaver living in the park had a small excursion range, reaching a maximum distance of 25 m from the watercourse so that effects on vegetation diversity were limited to the immediate vicinity of the watercourse. Beaver significantly influenced diversity of the tall tree and forest floor vegetation, while it did not significantly modify the diversity of the low tree and shrub layer. Five alien plant species were documented. The alien species most strongly associated with beaver activity was devil’s beggartick (Bidens frondosa L.), which occurred in the immediate vicinity of beaver dams. Other alien species most benefiting from the presence of beaver were giant goldenrod (Solidago gigantea Aiton) and black cherry (Prunus serotina Ehrh.). Our study confirmed hypotheses found in literature according to which beaver activities that reduce the proportion of native species can promote the expansion of plant alien species.

Impacts of Moso bamboo (Phyllostachys pubescens) invasion on species diversity and aboveground biomass of secondary coniferous and broad-leaved mixed forest.

In recent decades, Moso bamboo has been largely increasing in the subtropical area of China, raising ecological concerns about its invasion into other native forest ecosystems. One concern is whether the invasion of Moso bamboo significantly simplifies forest community composition and structure and declines biomass. This study adopted the space-for-time method to investigate a secondary coniferous and broad-leaved mixed forest (SF) being invaded by an adjacent Moso bamboo forest (MB) in the Wuxie forest reserve, Zhejiang Province. Three plots were established in each SF, MB, and transitional forest. The results showed that the species composition and species dominance of the arborous layer changed significantly (P < 0.05), which was indicated by the significantly decreased species richness (Margalef index, Shannon–Wiener index, and Simpson index) and evenness (Pielou evenness index). In contrast, the species richness of the shrub and herbaceous layers had two divergent indications (increasing or unchanged), and the evenness remained unchanged. The total and arborous-layer aboveground biomass of the forest community has had no noticeable change (P < 0.05). However, the biomass of the shrub and herbaceous layers showed an increasing trend (shrub significant but herbaceous not), but they only occupied a small proportion (∼1%) of the total biomass. Finally, the aboveground biomass and the diversity index had no significant correlation in each layer and overall stands. We hope that the findings could provide a theoretical basis for the invasion mechanism and ecological consequences of the Moso bamboo invasion.

Effects of Post-Fire Timber Harvest and Mastication on Shrub Regrowth in the Sierra Nevada Mountains: A Lake Tahoe Case Study

Increasingly large high-severity wildfires in dry forests of the western United States have led to concern about how best to regenerate new forests after wildfires. Harvesting fire-killed trees, burning woody debris, and tree planting are commonly used reforestation strategies. This study evaluated the effects of a novel forest restoration approach that involved masticating un-merchantable dead trees and spreading the woody debris generated across the site to prevent erosion from the 2007 Angora Fire in Lake Tahoe, California. Woody material covered 82% of the site after treatment, with an average depth of 6.6 cm, and volume of 190 tonnes per hectare. We found that this treatment reduced shrub regrowth, compared to an untreated area nearby, and that shrub regrowth was inversely related to fuel depth. Seven years after the fire, shrub cover averaged only 50% on treated plots compared to 92% on untreated plots. The tallest shrubs averaged 69 cm in height on the treated site compared to 114 cm on nearby untreated sites. Tree seedlings planted on the treated site averaged 141 cm in height, well above the height of the shrubs. Advantages of this approach include controlling erosion while reducing drought stress, reducing the potential for weed introduction, and reducing the need for herbicide to control shrub competition. Although leaving a layer of woody material where new trees have been planted does constitute a fire hazard, so too does a vigorous shrub layer. Managers should consider and weigh these factors when deciding on a post-fire reforestation strategy.

Seasonal Water Uptake Patterns of Different Plant Functional Types in the Monsoon Evergreen Broad-Leaved Forest of Southern China

The precipitation changes induced by climate warming have substantially increased extreme precipitation and seasonal drought events. Different plant functional types (PFTs) could exert an important role in resisting extreme climate. However, the patterns of plant water uptake in different PFTs remain uncertain, especially under different magnitudes of rainfall events. Here, we employed a stable hydrogen isotope (δD) to determine the water sources of different PFTs, including Castanopsis chinensis in the canopy layer, Schima superba in the canopy sublayer, Psychotria asiatica in the shrub layer, and Blechnum orientale on the forest floor in the monsoon evergreen broad-leaved forest in Dinghushan Biosphere Reserve, China. We further used a two-end linear mixing model to explore the water utilization among different PFTs. Our results revealed that precipitation and soil water before rainfall were the water sources of different PFTs. Furthermore, the proportions of precipitation utilized by S. superba in the canopy sublayer under light and moderate rainfalls were 6.9%–59.4% and 30.5%–66.3%, respectively, which were significantly higher than those of other species in both the dry and wet seasons. After heavy rainfall, the proportion of precipitation utilized by S. superba was the lowest (4.7%–26.5%), while B. orientale had the highest proportion of precipitation utilization (31.6%–91.5%), whether in the dry or wet season. These findings imply that different PFTs would compete with one another for water uptake. Especially under climate warming, the uneven distribution of precipitation would intensify the water competition among species, ultimately resulting in the plant community structure becoming much more unstable than before.

Are degraded karst tiankengs coupled with microclimatic underground forests the refugia of surface flora? Evidence from China’s Yunnan

Karst tiankengs, as one of the most magnificent negative topographies, are capable of forming a bank for species diversity conservation easily. More than 300 karst tiankengs have been discovered and identified worldwide. Given its treacherous terrain, although original karst tiankeng were identified as species refuges, the broader distribution of degraded karst tiankeng has not been systematically studied. Our study area comprised the degraded karst tiankeng cluster immersed in the fragmented karst forests of Yunnan, China. Fifty-eight plant samples were selected from karst tiankengs and surface. We compared species composition, and analyzed diversity indices and similarity coefficients to verify the isolation effect of karst tiankengs on floras. The results indicated that: (1) In the degraded karst tiankeng, there were 24 families, 37 genera and 48 species in the tree layer and 27 families, 43 genera and 49 species in the shrub layer. Outside the degraded karst tiankengs, 20 families, 31 genera and 39 species were in the tree layer, and the shrub layer included 26 families, 44 genera and 55 species. (2) The species composition reached significant differences within and outside degraded karst tiankeng (p &amp;lt; 0.05) based on the analysis of variance (ANOVA). (3) In the degraded karst tiankeng, species richness/diversity in trees were higher than those in the shrub layer, while at the surface, shrubs had higher richness and lower diversity than trees by Alpha-diversity index. And for Beta-diversity index, species similarity among degraded karst tiankengs (0.215) was extremely dissimilar, which was even lower than the contrast within and outside the degraded karst tiankengs (0.272). (4) Shared species ranged from 1 to 5 among the four habitats, with high variability in plant species across the habitat matrices. Through a comparative analysis of systematic biodiversity methods, we found that the degraded karst tiankengs, an independent type of karst tiankeng, are the unreported refugia. Species records in degraded karst tiankeng cluster will contribute to plant diversity conservation and resource management, and to the linkage with broader China’s karst floras. Karst tiankeng botanical habitats possess not only biodiversity value for in situ conservation, but will further support the ecological recovery of surface flora. While its mechanism needs to be further revealed.

Bird response to forest disturbance size in mountain spruce forests in Central Europe

Although natural disturbances are likely to occur more frequently and be more severe in future as a result of climate change, we have little evidence concerning the effect of disturbance size and severity on species diversity. We aimed to compare effects of varying size and severity of natural disturbances on bird species composition in the non-intervention area of Šumava National Park, Czech Republic. For this purpose, we surveyed bird communities in 1) small- and 2) large-scale disturbance, 3) enclaves of live trees in large-scale disturbance areas, and 4) non-disturbed forests. Furthermore, we used habitat characteristics to identify structural factors affecting species composition of bird communities. Birds were sampled by the point count method during the 2021 breeding season and analysed using linear models. Additionally, we use principal component analysis (PCA) to characterize four defined disturbance classes using habitat characteristics. The most important habitat characteristics for bird communities are structural complexity, live tree density, and understorey cover. Small-scale disturbances increased structural complexity of a forest and had a generally positive effect on birds. Both small- and large-scale disturbances supported species nesting on the ground and shrub layer. In contrast, large-scale disturbances negatively affected canopy nesting and specialist species. This likely was due to a reduction of small-scale habitat heterogeneity with increasing disturbance severity. High-severity disturbance changes structurally rich forests to rather uniform, open-canopy habitats that are temporally unsuitable for closed-canopy birds. On the other hand, low-severity disturbance enhances large-scale habitat heterogeneity and maintains suitable habitat for species of closed-canopy forest, including some specialist species.

Understory plant diversity and soil physicochemical properties of Pinus tabuliformis artificial water conservation forests in the upper reaches of Miyun Reservoir, China

We examined the characteristics of understory plant diversity and physicochemical properties and analyzed the correlation between understory plant diversity and soil factors across four Pinus tabuliformis artificial water conservation forests (P. tabuliformis × Larix gmelinii plantation, P. tabuliformis × Quercus mongolica plantation, P. tabuliformis × Armeniaca sibirica plantation, and P. tabuliformis plantation) in Fengning County, upstream of Miyun reservoir. The results showed that the composition and structure of understory community of the four forests were significantly different. The understory community in the P. tabuliformis × A. sibirica plantation was the richest in species composition, with Spiraea salicifolia, Ostryopsis davidiana, and Carex lanceolata as the main dominant species. In terms of species richness, Simpson index, Shannon diversity index, and Pielou index, plant diversity in the P. tabuliformis × A. sibirica plantation was the highest. Species diversity in the shrub layer and the herb layer was the highest in the P. tabuliformis × Q. mongolica plantation and the P. tabuliformis × Q. mongolica plantation, respectively. All physical and chemical indicators except total phosphorus differed significantly among the four forests. Soil physical and chemical properties of the P. tabuliformis × A. sibirica plantation were the best overall, and that in the P. tabuliformis × Q. mongolica plantation was the worst. Soil capillary porosity, pH, and organic matter were the main factors affecting species diversity in the shrub layer, while soil pH and capillary moisture capacity were the main factors affecting plant species diversity in the herb layer. The construction of P. tabuliformis × A. sibirica plantation was more conducive to increasing the diversity of understory plants and promoting soil improvement. Soil pH, organic matter, capillary porosity, and capillary moisture capacity were the dominant soil factors affecting the diversity of understory plants in the study area.

Survival in the understorey: Testing direct and indirect effects of microclimatological changes on Ixodes ricinus

The distribution of ticks in the Ixodes ricinus species complex is partly driven by climate, with temperature and relative humidity affecting survival. These variables are driven by macroclimate, but vary locally due to microclimate buffering. This buffering has been suggested to be one of the driving forces behind variation in tick survival and density in time and space. In order to understand the role of the herb layer with respect to this variation, we deployed I. ricinus within an existing experimental setup studying the response of forest understorey to micrometeorological changes. This allowed for the analysis of both direct effects of warming on tick survival in controlled field conditions, as well as indirect effects through changes in herb layer biomass. Herb layer biomass estimates were observed to be higher in plots that had been experimentally warmed, with a trend towards higher survival in these warmed plots. This marginal increase in survival rate may be due to increased microclimate buffering. Comparing our results to literature implies that canopy and shrub layer vegetation have a larger effect on climate buffering, and therefore also on tick survival. Since the herb layer biomass is expected to increase due to global warming and increased frequency of disturbance-induced canopy gaps, survival in forested habitats may increase in the future. This would increase the difference in survival compared to that in open habitats.

Forest gaps alter the soil bacterial community of weeping cypress plantations by modulating the understory plant diversity.

Weeping cypress is an endemic tree species that is widely planted in China, and the simple stand structure and fragile ecosystem of its plantation are common issues. Exploring the effect of different gap sizes on the soil bacterial community structure of weeping cypress plantations can provide a theoretical basis for the near-natural management of forest plantations. We, therefore, constructed three kinds of forest gaps with different sizes in weeping cypress plantations, namely, small (50–100 m2), medium (100–200 m2), and large gaps (400–667 m2), for identifying the key factors that affect soil bacterial communities following the construction of forest gaps. The results suggested that the herb layer was more sensitive than the shrub layer, while the Simpson, Shannon, and richness indices of the herb layer in plots with gaps were significantly higher than those of designated sampling plots without any gaps (CK). The presence of large gaps significantly increased the understory plant diversity and the Shannon and Simpson indices of the soil bacterial alpha diversity. There were obvious changes in the community composition of soil bacteria following the construction of forest gaps. The dominant bacterial phyla, orders, and functions were similar across the plots with different gap sizes. Of the indicator bacterial species, the abundance of the nitrogen-fixing bacteria, Lysobacter_ yangpyeongensis, and Ensifer_meliloti, was significantly different across plots with different gap sizes and accounted for a large proportion of the bacterial population of plots with medium and large gaps. The understory plant diversity was mostly related to the soil bacterial community than to other soil factors. The results of structural equation modeling indicated that the understory plant diversity was the most important environmental factor in driving the composition and diversity of bacterial communities. The construction of forest gaps significantly improved the understory plant diversity, physicochemical properties of the soil, and bacterial diversity in weeping cypress plantations, and the results of the comprehensive evaluation were in the order: large gaps > small gaps > medium gaps > CK. Our results suggested that large gaps are beneficial for the diversity of above-ground plant communities and underground soil bacterial communities.

Understanding vegetation structures in green spaces to regulate atmospheric particulate matter and negative air ions

Green spaces can effectively reduce atmospheric particulate matter (PM) pollution and regulate negative air ions (NAI), this ecological function of green spaces is directly determined by their types and structures. However, the mechanism of the interactions among the types and structures of green spaces, PM, and NAI are still unclear. In the present study, we selected Dongling Park in Shenyang, China as an example of a typical green space. We ran field experiments to analyze the influences of various green space types and structures on PM10, PM2.5, and NAI. The results showed that green spaces had significantly lower PM10 and PM2.5 and higher NAI concentrations than non-green spaces. Among the four vegetation types (tree-shrub-herb, tree-herb, shrub-herb, and tree-shrub), the tree-shrub-herb type most effectively decreased atmospheric PM10 and PM2.5 concentrations (32.54 ± 8.14% and 21.26 ± 4.07%, respectively) and increased NAI concentrations (115.43 ± 10.00%) to a significantly greater extent than the other vegetation types (p < 0.05). Canopy density was strongly and significantly positively correlated with PM2.5 and PM10 concentrations (r = 0.84* and r = 0.86**, respectively). By contrast, shrub layer richness was significantly negatively correlated with PM2.5 and PM10 concentrations (r = −0.68* and r = −0.74*, respectively). Furthermore, significant positive correlations with NAI concentrations were detected in the canopy density and proportion of evergreen tree species significantly (r = 0.40* and r = 0.46*, respectively). The results illustrate that the green space vegetation types and structures, especially the density of tree canopy, the richness of shrub layer, and the proportion of evergreen tree species, can influence the airborne PM10, PM2.5 and NAI concentrations. Therefore, vegetation types and structures should be considered in the process of planning urban green spaces that perform the ecological function of improving air quality.

Ladybird communities in rural woodlands: Does an invader dominate?

The invasive alien species Harmonia axyridis (Coleoptera: Coccinellidae) was first observed in the UK in 2004. Previous studies have demonstrated the adverse effects on other species of H. axyridis during its early stages of establishment. However, habitat factors are important in determining distribution and population trends of ladybirds. Whilst the abundance of H. axyridis is well known in the UK within urban and other managed habitats, much less is known about its abundance in the wider countryside. Here we present the results of surveys from rural woodland habitats to assess whether or not H. axyridis dominates coccinellid communities in these rural habitats. Additionally, we explored the relationship between coccinellid and aphid abundance within these habitats. All field sites were in Cambridgeshire or Suffolk, East Anglia, UK and were surveyed between May and October 2016 and 2017. Three deciduous sites and three coniferous sites were included in the study. Surveys were conducted using a standardised approach involving sweep-netting within grass margins and tree beating to sample ladybirds from trees. Three distinct vegetation structures or layers were surveyed within both the coniferous and deciduous sites; tree, shrub and herb layer. All captured coccinellids were identified to species-level. Seventeen species of coccinellid and over 1300 individuals were recorded during the study period from two distinct site types (deciduous, coniferous). Species richness was lower at deciduous sites (n = 12) in comparison to coniferous (n = 16) sites. The coccinellid community also did not appear to be dominated by H. axyridis at rural sites, in contrast to urban areas. Deciduous woodland appeared to be a lesser preferred habitat of H. axyridis than coniferous woodland. Additionally, there was a distinct difference in the coccinellid community in relation to vegetation structure (across the tree, shrub and herb layers) between coniferous and deciduous sites. Our results indicate that there appear to be distinct native coccinellid communities at deciduous and coniferous sites. We discuss the way in which rural woodlands could act as a refuge for some native coccinellids.