Shrub Layer Research Articles

Soil seed burial and competition with surrounding plants determine the emergence and development of seedling of an endangered species Horsfieldia hainanensis Merr. in China

Three well-conserved Horsfieldia hainanensis Merr. populations were used to investigate their soil seed bank and seedling regeneration characteristics and their relationship to environmental factors. The results showed that the seed reserves were low in the H. hainanensis soil seed bank (16.93~24.74 seed/m2). The distribution pattern for the seeds and seedlings in the H. hainanensis populations was aggregated, and they were mainly found around 2–3 m from the mother plant. The seeds in the litter layer and the 5–10 cm soil layer showed no vigor, and only 25.7%~33.3% of the total seeds in the 0–5 cm soil layer were viable affected by the high temperature and humidity, the animals’ eating and poisoning. Affected by the height and coverage of the surrounding herbaceous layer and shrub layer, the seedlings of H. hainanensis could not obtain enough light and nutrients in the competition, resulting in the survival competitiveness of 1- to 3-year-old (1–3a) seedlings in the habitat had been in a weak position and a large number of seedlings died. It would take at least four years for seedlings to develop under the current environmental constraints. It can be concluded that the low seed reserve in the soil seed bank and high mortality of seedlings of H. hainanensis lead to slow or even stagnation of population regeneration, which was an important reason for the endangered of H. hainanensis. Therefore, the next research focus is to explore the influence mechanism of environmental factors on seed germination and seedling growth of H. hainanensis.

Dramatic altitudinal variations in leaf mass per area of two plant growth forms at extreme heights

Knowledge of how leaf mass per area (LMA) and its components, leaf thickness (LT) and leaf density (LD), and related leaf traits may vary with altitude concerning different plant life forms at extremely high altitudes is scarce. We measured LMA, leaf nitrogen (Nmass), LT, LD, and the related anatomical characteristics of an evergreen shrub (Rhododendron aganniphum var. schizopeplum, RAS) and a wintergreen herb (Bergenia purpurascen, BP) along an altitudinal gradient above 4200 m a.s.l. to disclose how LMA for two different growth forms may vary with altitude and which leaf attribute determines the within-species variation of LMA. LMA significantly increased with rising altitude, at a pace of 40 g m−2/100 m for RAS and 12 g m−2/100 m for BP, respectively. LT was mainly responsible for the variability in LMA for RAS, and the variation of LT and LD contributed almost equally for BP. Nmass tended to decrease with rising altitude, and was negatively related to LMA and LT for both species. Foliar δ13C showed significantly rising trends with altitude, and was positively correlated with LMA and LT. The results indicated that plants at the extremely high altitudes are adapted to possessing especially higher LMA and steeper slopes of the relationships between LMA and altitude, as well as lower leaf nitrogen concentrations and higher δ13C to cope with the low-temperature environment. Compared with many other studies, LMA for both species are assumed to be more sensitive to the changing environment (especially warming). Also, Rhododendron shrub displayed steeper slope compared with dwarf herbs beneath the shrub layer indicating the former species should be more sensitive to warming climate. In all, exploring the plant strategies via leaf functional traits is of importance to understand the geography of evergreen species in alpine regions and its responses to future climate change.

Communities of Soil Nematodes of Various Tundra Phytocenoses Differing in the Development Level of the Shrub Layer

In the series of phytocenoses from low bush to large-bushy tundra (Vorkuta district, Republic of Komi), with an increase in the shrub layer, the structure of nematode communities changes, as does their number and diversity. Among the trophic groups, a change in the number of bacterio-, myco-, and phytotrophs corresponded to the general tendency. Predators showed the opposite trend, while the abundance of polytrophs did not differ much in the studied areas. Differences in nematode communities are associated with changes in the hydrothermal regimen and chemical properties of the soil. Ecological and faunistic indices, calculated based on data on the abundance and diversity of nematodes, indicate a low level of organic matter in the soil food network and an equal proportion of fungal and bacterial decomposition patterns. However, additional verification of the efficiency of these indices in tundra ecosystems is required.

Niche characteristics of understory dominant species of talus slope in degraded tiankeng

We carried out niche monitoring and analysis of plant populations under the forest community in the talus slope ecotone of a typical moderate-degraded Bajiaxiantang tiankeng to provide scientific references for biodiversity conservation and vegetation restoration in degraded tiankeng area. The results showed that soil ammonium, available potassium, and available phosphorus signifi-cantly affected species distribution, which explained 37.4%, 32.8%, 29.3% of the total variation, respectively. With the change of talus slope of tiankeng (pit, uphill, mid-slope, downhill and pit bottom), life form of understory plants changed from evergreen and xerophytes to evergreen and hygro-mesophytes, with the niche overlap of herbs being larger than that of shrubs. Shrubs of Viburnum congestum and Campylotropis polyantha, and herbs of Arisaema erubescens and Arthraxon hispidus had wide ecological amplitude and strong resistance, which occupied the upper layer of the shrub and herb layers. Shrub Cornus oblonga and herb Geranium nepalense, Agrimonia pilosa lost the competitiveness with increasing soil alkalinity. Niche characteristics of understory dominant species in Bajiaxiantang were closely related to the canopy structure of mixed trees, ecological strategies of shrub and herb species, unique habitat of tiankeng, and the importance value of dominant species.

Mapping post fire recovery in Bakchar bog with Landsat time series data

The aim of this research was to assess the pyrogenic load and recovery processes after the fire event of 2016 within the drained site of Bakchar bog. Satellite remote sensing data and field data were collected for this study. The specific objectives of this study were: 1) to conduct field studies in key sites with different pyrogenic load keys in order to assess projective cover and species composition of the vegetation cover and 2) to compare field data with satellite image data using the vegetation index and perform spatial assessment of vegetation post-pyrogenic recovery in the first three years after the fire. The area of fire spread was 5.54 km2, including 4.44 km2 within the mire. The intensity and character of the vegetation recovery are differed between sites pyrogenic load classes. The first and second classes of the pyrogenic load are characteristic by the most intensive recovery process. These classes occupy 78 % of the burned area. NDVI values in three years after the fire become close and even exceed the values characteristic for drained pine-dwarf shrubs-sphagnum bogs mainly due to the intensive renewal of dwarf shrub layer. The emergence of deciduous trees will lead to a significant increase in the vegetation index in subsequent years.

Changes in vegetation structure and composition of urban and rural forest patches in Baltimore from 1998 to 2015

Urban forests often occur as highly fragmented patches with many non-native plant species, altered disturbance regimes, environmental pollutants, and uncertain trajectories of plant community composition. In 1998, the Baltimore Ecosystem Study, a U.S. National Science Foundation-funded Long-Term Ecological Research (LTER) program, established eight forested plots to investigate long-term impacts of urbanization on natural ecosystems. All plots were located in the Baltimore metropolitan area with four in urban forest patches and four in a rural forest. In 1998, these forest patches had closed canopies with well-developed tree, shrub and vine layers, and extensive herbaceous cover. The 1998 alpha diversity (species richness) was higher in urban plots than in rural plots, whereas both plot types had similar forest structure and a relatively small number of non-native species. In 2015, we resampled these plots to investigate changes in plant structure, composition, and diversity based on the abundance, cover, and size of plant species. Trees and vines experienced minimal structural changes in all the plots. Sapling, shrub, and herbaceous abundances all declined over time in the rural plots. In the urban plots, however, only the sapling and herbaceous layers experienced declines. Despite having fewer structural changes, urban plots showed a greater shift in species composition than did rural plots. As in 1998, alpha diversity was lower in the rural plots. Beta diversity (community dissimilarity) decreased among rural plots but remained nearly unchanged in the urban plots, whereas beta turnover (species turnover) was much higher in the urban plots. These data suggest that the urban plots may have divergent compositional trajectories from the rural plots, which may help urban forests retain structural similarities through functional redundancy.

Species Abundance Distribution Patterns of a Toona ciliata Community in Xingdoushan Nature Reserve

With the goal of model fitting species abundance distribution patterns of the tree, shrub and herb layers of the natural Toona ciliata community in Xingdoushan Nature Reserve, Enshi Autonomous Prefecture, Hubei Province, we used the data collected from the field survey and employed different ecological niche models. The models tested were the broken stick model (BSM), the overlapping niche model (ONM) and the niche preemption model (NPM), as well as three statistic models, the log-series distribution model (LSD), the log-normal distribution model (LND) and the Weibull distribution model (WDM). To determine the fitted model most suitable to each layer, the fitting effects were judged by criteria of the lowest value of Akaike Information Criterion (AIC), Chi-square and the K-S values with no significant difference (P>0.05) between the theoretical predictions and observed species abundance distribution values. The result showed: (1) The fitting suitability and goodness of fit of the tree, shrub and herb layers by using the three ecological niche models were ranked as: NPM>BSM>ONM. Of the three statistical models, by accepting the fitting results of the three layers, WDM was the best fitting model, followed by LND. By rejecting the fitting tests of the herb layer, LSD had the worst fitting effect. The goodness of the statistical models was ranked as: WDM>LND>LSD. In general, the statistical models had better fitting results than the ecological models. (2) T. ciliata was the dominant species of the tree layer. The species richness and diversity of the herb layer were much higher than those of either the tree layer or the shrub layer. The species richness and diversity of the shrub layer were slightly higher than those of the tree layer. The community evenness accorded to the following order: herb>shrub>tree. Considering the fitting results of the different layers, different ecological niche models or statistical models with optimal goodness of fit and ecological significance can be given priority to in studying the species abundance distribution patterns of T. ciliata communities.

Plant community structure and species diversity in Lingang wetland park in Tianjin China

Lingang wetland park is a newly built wetland park in Lingang district, Tianjin, China. The community composition, community structure, frequency of occurrence of arbor and shrub layer and dominant species of plant community in lingang wetland park were investigated. The results showed that the community of Lingang wetland park was mainly characterized by the structure of trees-shrubs-lawns, and the ratio of species and number of evergreen trees to deciduous trees was 2:15 and 1:23. Wetland park is rich in plant diversity, the dominance index at park's east gate and “qushuihuajing” were 0.8183 and 0.8152, which were far higher than other quadrants and the dominant species is golden elm. Among the tall trees, Ulmus pumila, Salix babylonica, Aureus locustae with the highest application frequency accounted for 23.8%. For shrubs, lonicera japonica, Euonymus japonicus and Lonicera maackii had the highest frequency of application. Festuca elata and Hemerocallis fulva had highest application frequency in lawns. They accounted for only 13.2% in herbs. It indicated that only several plants in the park have high frequencies.

Резерви підвищення лісистості та продуктивності культур сосни у Центрально-придніпровській височинній області

Досліджено, що Центрально-Придніпровська височинна область відзначається надзвичайно низьким відсотком лісистості та майже суцільною розораністю. Встановлено, що за раціонального ведення лісового господарства у регіоні досліджень, резервом для підвищення лісистості є прирічкові землі, землі, непридатні для подальшого сільськогосподарського використання і землі покинутих людьми сіл, які були збудовані у басейнах водозборів великих і малих річок. Виявлено, що ліси водозбору представлені лісовими масивами, полезахисними, протиерозійними, придорожніми смугами, трапляються невеликими фрагментами на схилах долини, зрідка виходять на плакор, а серед зональної рослинності збереглися дубово-ясенево-грабові ліси. У чагарниковому ярусі має перевагу ліщина звичайна, рідше – клен татарський, бруслина бородавчаста та європейська. Водночас уздовж русла, особливо у пониззі, формуються заплавні вербово-тополеві ліси, а у верхів'ях водозабору – заплавні вільшняки. З'ясовано, що для підвищення продуктивності соснових насаджень Чигиринського бору у випадках, коли догляд своєчасно не здійснювався і лісостан формувався в умовах високої повноти, інтенсивність рубань для середньовікових і пристигаючих насаджень доцільно підвищити на 1015 %. Наступні прийоми доглядових рубань необхідно проводити традиційними селекційними методами через 4 роки, оскільки простежується зміна глобальної температури за останні 175 років у бік потепління. Висвітлено наслідки введення робінії псевдоакації як міжквартального бар'єру за залісення Чигиринських пісків. Пропонуємо як систему протипожежних заслонів проти поширення вогню у соснових культурах у ролі міжквартальних бар'єрів використовувати насадження берези повислої, а не робінії псевдоакації. Земельні наділи покинутих людьми сіл пропонуємо заліснювати деревостанами на типологічній основі з урахуванням головних лісотвірних порід місцевості.

Structural and functional characterization of the dry forest in central Argentine Chaco

Here, we studied the composition, structure and functioning of the woody vegetation of a 1000-ha area of the Central Argentine Chaco. First, we identified, through Landsat satellite image processing, three different vegetation classes: two forest types and a savanna. Each class was field surveyed to analyze the composition and structure of the woody plant community. Functioning was assessed through the enhanced vegetation index – a proxy of productivity – obtained from the MODIS sensor. The forest classes showed no differences in composition but some differences in structural attributes, particularly in the density of the dominant tree species in the area, Aspidosperma quebracho-blanco. As expected, the savanna showed less density and basal area of woody plants, with a relative high proportion of tree species seedlings and heliophilous shrubs. The forest class with less density of A. quebracho-blanco presented higher productivity. This could be related to a higher ability of the shrub layer to intercept radiation because shrubs are under an open canopy, as has been noted for early successional stages. Additionally, we found that annual mean productivity for the three classes showed a negative trend in the period 2000-2014. Our results provide valuable information since there are no studies addressing relationships between structural and functional attributes at local level in the Chaco Region.

Ecological indicators of near-surface permafrost habitat at the southern margin of the boreal forest in China

Abstract The most dramatic permafrost degradation is expected to occur at the southern edge of permafrost distribution, which is difficult to detect directly on a large scale. Ecological indicators can be used to provide an early signal of changes in terrestrial ecosystems for regional near-surface permafrost habitats and potentially to monitor near-surface permafrost degradation. In this study, plant composition and community structure indicate the near-surface permafrost distribution at the southern edge of the boreal forest and permafrost in northeastern China. The plant species composition and structure of aboveground vegetation were linked to the belowground near-surface permafrost distribution in order to find indicators of changes in vegetation features from permafrost melting. These indicators are essential for assessing changes in permafrost vegetation systems under climate change. Carex schmidtii and C. appendiculata in the herb layer and Betula fruticosa in the shrub layer were found to be specific near-surface permafrost plant indicator species, especially for the wetland permafrost. Shrub cover, moss mat thickness and tree canopy cover are also strongly correlated with near-surface permafrost distribution. The active layer thickness (ALT) showed negative correlations with moss thickness and shrub cover because these features may act as buffers for regional climate warming. We chose the cover of each indicator species, near-surface permafrost-specific community features and geographical information as independent variables to predict the possible distribution of near-surface permafrost in our study region using logistic regression. The results showed that the prediction model had good performance and accuracy. Our study sheds light on early caution of deepening of regional-scale permafrost active layer with vegetation indicators that can further be identified from satellite images.

Forest structure determines spatial changes in avian communities along an elevational gradient in tropical Africa

AbstractAimTo test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters.LocationA 2,000‐m long elevational gradient of tropical forest on Mt. Cameroon, west‐central Africa.TaxonBirds and trees.MethodsWe performed bird censuses and vegetation mapping at the same plots across six forested sites at elevations of 350, 650, 1,100, 1,500, 1,850, and 2,200 m a.s.l., with 16 plots per elevation. We tested the effects of elevation, forest structure and tree diversity on the species richness, functional diversity and β‐diversity of birds (Bray–Curtis dissimilarity). We used conditional inference trees based on random forests (RF) to investigate these relationships across all elevation sites as well as within elevations.ResultsBoth tree and bird species richness declined monotonically with elevation. Vegetation structure correlated with elevation, and all vegetation attributes significantly differed among elevations. The RF explained 70% of the variance in avian species richness, with the most important predictors being elevation, proportion of dead trees, tree species richness and herb layer coverage. We found that elevation (and shrub layer) was a particularly important predictor of avian functional diversity. We identified no important predictor of bird species richness after standardization within elevations, and the proportion of dead trees was the sole important predictor of functional diversity. Within‐elevation β‐diversity in avian community composition was determined by the dissimilarity of the tree community and differences in leaf area index, solar radiation and spatial distance. The functional dissimilarity was best explained by leaf area index.Main conclusionsApart from elevation itself, spatial distance even within elevations correlated with compositional and functional variation among avian assemblages. Forest structural traits can have a significant influence on distribution of birds. Thus, gaps in the spatial distribution of species such as along elevations might be caused by fine‐scale recognition of suitable habitats.

The abundance of epiphytic liverworts on the bark of Cryptomeria japonica in relation to different physical and biochemical attributes, found in Senchal Wildlife Sanctuary, Darjeeling, Eastern Himalaya

BackgroundMaintenance of biodiversity is an integral part of sustainable forest management. Epiphytic bryophytes are an important element of biodiversity. Thus, this work aims to study the role of different physical and biochemical factors in affecting the growth and proliferation of epiphytic liverworts. Fifty trees in three different plots, distributed in Senchal wildlife sanctuary, Darjeeling, were surveyed. Factors such as light intensity, moisture, and diameter at breast height (DBH) of the tree were studied to evaluate their possible role in affecting epiphytic liverworts. The effect of bark biochemical characteristics on the abundance of epiphytic liverworts was also studied by undertaking a quantitative test of pH, phenol, flavonoid, ortho-dihydric phenol, terpene, total sugar, and tannin. Multiple regression analysis and principal component analysis (PCA) were carried out to test the effects of these parameters.ResultsLight intensity, moisture, and DBH highly influenced the abundance of liverworts. Old trees had higher epiphytic liverwort cover than younger ones. Bark biochemical properties like pH, phenol, flavonoid, ortho-dihydric phenol, tannin and sugar did not have a significant effect on the epiphytic liverwort cover, while the terpenoid content of the bark reduced liverworts cover.ConclusionTo sustain the occurrence of epiphytic liverworts in ecosystems, forest management should ensure the presence of old trees. Light intensity and moisture had a large effect on the distribution and abundance of liverworts, so it is important to maintain tree cover, shrub layer, and tree density.

Флороценотическое разнообразие лесостепного комплекса урочища «Бойцы» (Ставропольская возвышенность, Прикалаусские высоты)

В настоящей работе приведен обзор флористического разнообразия лесостепного комплекса урочища «Бойцы» Прикалаусско-Буйволинского ландшафта. Дано описание рельефа территории и его форм, отмечены коренные породы, типы почв и др. Несмотря на свое фиторазнообразие, в ботаническом отношении территория является не изученной. Впервые приводятся описание растительного покрова равнинных участков, склонов, балок, потяжин с соответствующими флористическим рядами. Указаны основные доминанты древесного и кустарникового яруса, а также виды с широкой экологической валентностью. На территории района исследования выявлены ксерофильные и петрофильные группировки, составляющие основу раритетной флоры урочища.

Quantifying the Relationship among Impact Factors of Shrub Layer Diversity in Chinese Pine Plantation Forest Ecosystems

Shrub layer diversity is an essential component of the forest ecosystem diversity, that contributes significantly to structuring the community and maintaining diversity, especially in plantation forests. In previous studies, researchers have reported the strong relationship among various factors (i.e., soil composition, mean annual temperature, etc.) and shrub diversity. However, how these factors jointly influence shrub diversity and which factors could be considered the key factors is still unknown. In this study, we attempted to quantify the effect among environmental factors, soil factors and forest stand factors on shrub diversity. Twenty-seven variables were selected from 57 Chinese pine plantation plots in Huanglong Mountain, Yanan City, Shaanxi Province, China. The path models showed that latent variable of soil properties is the main effective factor of latent variable of shrub diversity (directly effect, path coefficient = 0.344) and the latent variable of site conditions is another effective factor of latent variable of shrub diversity (indirectly effect, path coefficient = 0.177); Besides, the latent variable of site conditions and forest properties directly affect the latent variable of soil properties (path coefficient = 0.514 and 0.326, respectively). Among the latent variable of soil properties, soil water content (SWC) has the biggest weight of 0.666, which indicated the most significant contribution of SWC to latent variables of shrub diversity. Total nitrogen, weighted 0.375, and total phosphorus, weighted 0.308, are also important factors and make a similar contribution to latent variable of shrub diversity. Soil organic matter (SOM) has a minimal impact (lowest weight, 0.059); among the objective variables of site condition, altitude contributes the most and is followed by litter thickness, weighted at 0.722 and 0.448, respectively. Furthermore, among all the variables affecting the latent variable of forest properties, forest age is recognized as the maximum impactor of soil property change, which weighted −0.941; and is followed by forest stock volume and diameter at breast height (DBH), weighted 0.795 and 0.788, respectively. The crowding index (C) has the lowest weight (−0.235) and demonstrated that spatial distribution and crowding of trees have minimal impact on the latent variable of Soil properties. diversity Overall, our study provides new insights into quantifying the relationships among different driving factors that potentially play a significant role in determining shrub layer diversity within the plantation forest.

The Effect of Pine Forest Structure on Bird-Mobbing Behavior: From Individual Response to Community Composition

Pine-forest bird communities are affected by the forest structure and the density and composition of its understory vegetation. In this study, we focused on the combined effects of vegetation structure and caller identity on the mobbing behavior of birds in breeding and non-breeding seasons. We examined the effect of the understory structure and the density of three types of conifer forest habitats on bird behavior by broadcasting three different types of mobbing calls: Those of two all-year resident species in the state Israel (Sardinian warbler Sylvia melanocephala Gmelin and great tit Parus major L.) and one European species (coal tit Periparus ater L.), which is absent from these habitats. The mobbing call attracted 689 birds of 17 species, which represented 31% to 95% of the forest bird species that we detected in point counts at the same study plots. Bird reactions to mobbing calls were affected by the status and season, depending on forest type. Our results show that responses were stronger in forests with developed understory in comparison to forests with no understory, especially in winter. The highest number of responders and highest species richness of responders were observed in winter. P. major calls generated more interspecific than intraspecific responses, whereas S. melanocephala calls generated equal levels of inter- and intraspecific reactions. Both species generated different response patterns across the three forest habitat types. The response level of responders is higher when the mobbing calls are issued by local species rather than the P. ater. In winter, the response of non-resident species was higher than of resident species. Based on these results, we encourage the managers to maintain well-established understory vegetation, with special attention to the shrubs layer, to promote species diversity and rich behavioral responses of birds in the conifer forests in the eastern Mediterranean region.

Impact of an invasive tree on arthropod assemblages in woodlots isolated within an intensive agricultural landscape

AbstractAimLandscape simplification and the spread of invasive species are considered beyond the main threats to global biodiversity. It is well recognized that non‐crop habitats bring complexity to farmland and provide refuge for a wide range of organisms, including arthropods. However, knowledge about the effects of invasive trees on arthropods in non‐crop habitats in intensive agricultural landscapes is still weak. Therefore, we examined differences in the arthropod assemblages between woodlots formed by the invasive black locust (Robinia pseudoacaciaL.) and by native deciduous tree species in the intensive agricultural landscape.LocationCzech Republic, Central Europe.MethodsWe used a multi‐taxonomic approach to record arthropod assemblages using various sampling methods. The impacts of woodlot habitat structure were investigated across 13 arthropod taxa from different trophic levels.ResultsTotal abundance and species richness of all arthropods and the majority of the herbivore taxa were lower inR. pseudoacaciawoodlots, likely due to losses of the forest canopy specialists. The forest specialists were associated with the native woodlots with more developed canopy and shrub layers. The impoverished diversity of the forest specialists and canopy herbivores in theR. pseudoacaciawoodlots was partly compensated by the higher presence of species exploiting a well developed herb layer and open‐habitat specialists, including threatened species.Main conclusionsNative woodlots and those formed byR. pseudoacaciadiffer in vegetation structure and host different assemblages of arthropods. Therefore, parallel presence of both types of woodlots supports arthropod diversity in otherwise simplified agricultural landscapes through creating more complex mosaic of habitats.

Response of carabid and arachnid assemblages on plant invasion in woodlots within an agricultural landscape

Landscape simplification and the spread of invasive species are considered the main threats to global biodiversity. It is well recognized that non-crop habitats bring complexity to farmland and provide refuge for arthropods. However, knowledge about the effects of invasive trees on arthropods in non-crop habitats in intensive agricultural landscapes is still weak. Therefore, we examined differences in the carabid and arachnid assemblages between woodlots formed by the invasive black locust (Robinia pseudoacacia L.) and by native deciduous tree species in the intensive agricultural landscape in the Czech Republic, Central Europe. We sampled carabids, harvestmen and spiders by using pitfall traps, sweeping the vegetation and light trapping. Effects of woodlot’s habitat structure, land cover composition in the surroundings and the area of woodlots were included to the analyses. The abundance of carabids was lower in R. pseudoacacia woodlots. Carabid individuals could benefit from the more favourable microclimate in the native woodlots, in which relatively greater humidity may support more ample food resources. On the contrary, species richness of carabids did not differ between the woodlot types. The abundance and species richness of arachnids did not differ between the woodlot types. Number of individuals increased with increasing woodlot’s area and the species richness increased with the more open woodlot’s habitat structure. The forest specialists of both groups were associated with the native woodlots with more developed canopy and shrub layers. The diversity losses of the arachnid forest specialists in the R. pseudoacacia woodlots were replaced by the species exploiting well-developed herb layer, and open-habitat specialists, including threatened species. Conversely, carabids of open habitats had no affinity to woodlot types. Native woodlots and those formed by R. pseudoacacia differed in vegetation structure and hosted different arachnid and carabid assemblages. Therefore, parallel presence of both types of woodlots supports arthropod diversity in otherwise simplified agricultural landscapes through creating more complex mosaic of habitats.

Understorey phylogenetic diversity in thermophilous deciduous forests: overstorey species identity can matter more than species richness

BackgroundUnderstorey vegetation is a key biodiversity component of forest ecosystems. Previous studies examined its relations with the overstorey mainly in terms of taxonomic diversity, composition or productivity. So far, none focused on the phylogenetic aspect, which represents the deepest component of diversity in a community. Here, we explored the relations between overstorey species richness and identity and the phylogenetic structure of the understorey vegetation. As a model system we used a network of 36 plots in thermophilous deciduous forests of central Italy that are part of a European project on forest biodiversity and functions. The plots, characterized by similar site conditions, represent a gradient of overstorey richness from 1 to 4-species mixtures, with variable composition. After surveying the understorey in each plot, measures of phylogenetic diversity and structure (Phylogenetic Diversity, PD; Net Relatedness Index, NRI; and Nearest Taxon Index, NTI) were calculated from a fully resolved seed-plant phylogeny obtained from a ITS-5.8S nrDNA dataset including original sequences from local plant material.ResultsThe resulting understorey phylogenetic tree allowed reliable estimation of PD, NRTI and NTI. Phylogenetic diversity was dependent on species richness and the strength of this relationship did not change along the gradient of overstorey tree species richness. Net Relatedness and Nearest Taxon indices were both mostly positive but non-significant, indicating random phylogenetic structure of the understorey. The presence of Quercus petraea, usually found in more favorable site conditions, was associated with a significant phylogenetic clustering at the species level.ConclusionsOverstorey species richness was not related to understorey phylogenetic structure, while species identity (Q. petraea) was associated with an increase in evolutionary relatedness in this forest layer, possibly due to competitive exclusion in favorable site conditions. Further studies should examine whether and how understory phylogenetic structure is affected by variables such as small scale variations in site conditions and presence of a shrub layer, both present but not accounted for in our model system. A better understanding of the role of these variables and their interaction may contribute to fill the current gap between the theoretical field of phylogenetic ecology and forest management.

The Effect of Non-Native Black Pine (Pinus nigra J. F. Arnold) Plantations on Environmental Conditions and Undergrowth Diversity

The cover of introduced tree species in Europe has recently increased, due to several factors. Attempts to understand the impact of non-native edificator trees on the environmental conditions and diversity of undergrowth have so far been limited to a few studies. In this paper, we analyse the effect of one of the most commonly planted non-native tree species–black pine (Pinus nigra J. F. Arnold) in the Carpathian-Pannonian region, north of the border of its native occurrence. The objectives of our study were to determine the following: (i) How does black pine, as a non-native edificator, change the forest structure and environmental conditions in comparison to those of native communities? (ii) How does black pine change the species composition of undergrowth in comparison to that of native communities? (iii) Which factors are associated with the impact of black pine on diversity? To answer these questions, we used the twin plot method, sampling two neighbouring plots with the same environmental conditions in which one plot of the pair is in a forest with native tree species composition and the second plot is in a planted non-native Pinus nigra plantation. We found that in forests dominated by the non-native black pine, (a) the tree canopy is significantly more open; (b) the cover of the shrub layer is significantly higher; (c) the needles of black pine form a significantly thicker litter layer and (d) the cover of the herb layer is significantly lower than that in the native forest. (e) Black pine plays a vital role in modifying local climate by altering air temperature and humidity; (f) there were no significant differences in the soil pH between black pine plantations and native forests; (g) the plantations of black pine cause changes in diversity at both the species and the community level and (h) the dissimilarity between black pine plantations and neighbouring native forests decreases at higher altitudes.