Factors influencing epiphytic bryophyte and lichen species richness at different spatial scales in managed temperate forests

The effect of management related factors on species richness of epiphytic bryophytes and lichens was studied in managed deciduous-coniferous mixed forests in Western-Hungary. At the stand level, the potential explanatory variables were tree species composition, stand structure, microclimate and light conditions, landscape and historical variables; while at tree level host tree species, tree size and light were studied. Species richness of the two epiphyte groups was positively correlated. Both for lichen and bryophyte plot level richness, the composition and diversity of tree species and the abundance of shrub layer were the most influential positive factors. Besides, for bryophytes the presence of large trees, while for lichens amount and heterogeneity of light were important. Tree level richness was mainly determined by host tree species for both groups. For bryophytes oaks, while for lichens oaks and hornbeam turned out the most favourable hosts. Tree size generally increased tree level species richness, except on pine for bryophytes and on hornbeam for lichens. The key variables for epiphytic diversity of the region were directly influenced by recent forest management; historical and landscape variables were not influential. Forest management oriented to the conservation of epiphytes should focus on: (i) the maintenance of tree species diversity in mixed stands; (ii) increment the proportion of deciduous trees (mainly oaks); (iii) conserving large trees within the stands; (iv) providing the presence of shrub and regeneration layer; (v) creating heterogeneous light conditions. For these purposes tree selection and selective cutting management seem more appropriate than shelterwood system.     

Implications of shifts in coffee production on tree species richness, composition and structure on small farms around Mount Kenya

Small coffee farms around Mount Kenya in Kenya contain many planted and remnant tree species but little is known in the region about the relationship between trees on farms and the methods and dynamics of coffee production. Shifts in production may alter tree diversity and potentially impact on future biodiversity conservation efforts by affecting niches available for indigenous trees on farms. Here, knowledge was gathered on how changes in coffee production on 180 small farms around Mount Kenya may affect tree diversity, categorizing farms according to coffee yield levels over a period of five years as increasing, decreasing or stable production. Tree species richness, abundance and composition were analyzed using species accumulation curves, Rènyi diversity profiles, rank abundance and ecological distance ordinations, and the effects of coffee production examined using quasi-Poisson generalized linear regressions. Species richness were positively correlated with tree basal area but negatively related to coffee, banana and maize yields value. A difference in average tree species richness, abundance and basal area on increasing farms was observed compared to the decreasing and stable farms, even though formal tests on richness and densities differences were inconclusive. These dynamics do not significantly influence vegetation structure but seem to have a bearing on species composition on farms of different coffee production. The overall low abundance (23 % of trees) but high richness (78 % of species) of indigenous trees on coffee farms could change markedly if the dynamics observed in the current study persist, indicating the need for the development of intensified multi-species cropping systems.     

Diversity and composition of arboreal beetle assemblages in tropical pasture afforestations: effects of planting schemes and tree species identity

Timber tree plantations are considered for rehabilitating forest biodiversity in the tropics, but knowledge on determinants of faunal diversity patterns in such human-modified forest landscapes is scarce. We quantified the composition of beetle assemblages on three native timber species (Anacardium excelsum, Cedrela odorata and Tabebuia rosea) planted on former pasture to assess effects of tree species identity, tree species diversity, and insecticide treatment on a speciose group of animals in tropical plantations. The beetle assemblage parameters ‘abundance’, ‘species richness’, ‘Chao1 estimated species richness’ and ‘Shannon diversity’ were significantly reduced by insecticide treatment for each tree species. Shannon diversity increased with stand diversification for T. rosea but not for A. excelsum and C. odorata. Species similarity was highest (lowest species turnover) between beetle assemblages on T. rosea, and it was lowest (highest species turnover) for assemblages on insecticide-treated trees of all timber species. Considering trophic guilds, herbivorous beetles dominated on all tree species and in all planting schemes. Herbivores were significantly more dominant on T. rosea and C. odorata than on A. excelsum, suggesting that tree species identity affects beetle guild structure on plantation trees. Insecticide-treated stands harbored less herbivores than untreated stands, but exhibited a high abundance of predator beetle species. Our study revealed that even young pasture-afforestations can host diverse beetle assemblages and thus contribute to biodiversity conservation in the tropics. The magnitude of this contribution, however, may strongly depend on management measures and on the selected tree species.     

Tree diversity and population structure in undisturbed and human-impacted stands of tropical wet evergreen forest in Arunachal Pradesh, Eastern Himalayas, India

Tree species richness, tree density, basal area, population structure and distribution pattern were investigated in undisturbed, mildly disturbed, moderately disturbed and highly disturbed stands of tropical wet evergreen forests of Arunachal Pradesh. The forest stands were selected based on the disturbance index (the basal area of the cut trees measured at ground level expressed as a fraction of the total basal area of all trees including felled ones): (i) undisturbed stand (0% disturbance index), (ii) mildly disturbed (20% disturbance index), (iii) moderately disturbed (40% disturbance index), and (iv) highly disturbed stand (70% disturbance index). Tree species richness varied along the disturbance gradient in different stands. The mildly disturbed stand showed the highest species richness (54 of 51 genera). Species richness was lowest (16 of 16 genera) in the highly disturbed stand. In the undisturbed stand, 47 species of 42 genera were recorded while in the moderately disturbed stand 42 species of 36 genera were found. The Shannon–Wiener diversity index for tree species ranged from 0.7 to 2.02 in all the stands. The highest tree diversity was recorded in the undisturbed stand and the lowest in the highly disturbed stand. The stands differed with respect to the tree species composition at the family and generic level. Fagaceae, Dipterocarpaceae and Clusiaceae dominated over other families and contributed 53% in the undisturbed, 51% in the mildly disturbed, 42% in the moderately disturbed and 49% in the highly disturbed forest stands to the total density of the respective stand. Stand density was highest (5452 stems ha^–1) in the undisturbed stand, followed by the mildly disturbed stand (5014), intermediate (3656) in the moderately disturbed stand and lowest (338) in the highly disturbed stand. Dominance, calculated as the importance value index of different species, varied greatly across the stands. The highest stand density and species richness were represented in the medium girth class (51–110 cm) in all the stands. In the undisturbed stand, the highest density was found in the 111–140 cm girth class, while in the mildly disturbed stand the 51–80 cm girth range recorded the highest density. About 55, 68 and 52% species were found to be regenerating in the undisturbed, mildly disturbed and moderately disturbed stands, respectively. No regeneration was recorded in the highly disturbed stand. Variation in species richness, distribution pattern and regeneration potential is related to human interference and the need for forest conservation is emphasized.     

Tree and stand level variables influencing diversity of lichens on temperate broad-leaved trees in boreo-nemoral floodplain forests

Tree and stand level variables affecting the species richness, cover and composition of epiphytic lichens on temperate broad-leaved trees (Fraxinus excelsior, Quercus robur, Tilia cordata, Ulmus glabra, and U. laevis) were analysed in floodplain forest stands in Estonia. The effect of tree species, substrate characteristics, and stand and regional variables were tested by partial canonical correspondence analysis (pCCA) and by general linear mixed models (GLMM). The most pronounced factors affecting the species richness, cover and composition of epiphytic lichens are acidity of tree bark, bryophyte cover and circumference of tree stems. Stand level characteristics have less effects on the species richness of epiphytic lichens, however, lichen cover and composition was influenced by stand age and light availability. The boreo-nemoral floodplain forests represent valuable habitats for epiphytic lichens. As substrate-related factors influence the species diversity of lichens on temperate broad-leaved trees differently, it is important to consider the effect of each tree species in biodiversity and conservation studies of lichens. Nomenclature Randlane et al. (2007) for lichens; Leht (2007) for vascular plants.     

The effects of genetic diversity,climate and defoliation events on trembling aspen growth performance across Canada

Tree genetic makeup may provide an important control of growth dynamics; however, no studies have previously attempted to evaluate its effects in natural trembling aspen stands. In this study, we examined the relative contribution of genetics (i.e. clonal diversity, observed heterozygosity) and environmental conditions (i.e. insects, climate) on aspen growth as represented by mean inter-tree correlation (RBAR), tree basal area increment (TBAI) and inter-annual growth variability (MS). We sampled 440 trees in 22 even-aged natural stands dominated by aspen along an east-west continental gradient of decreasing annual precipitation in the Canadian boreal forest. Linear and mixed-effect models tested the relationships between tree growth, genetics and environmental factors. We showed that clonal diversity and number of years with forest tent caterpillar (FTC) defoliation (N_FTC) reduced and increased the level of growth synchronicity (RBAR), respectively. Clonal diversity explained 30 % of variation in RBAR among sites. TBAI was positively influenced by high moisture conditions while N_FTC and climate explained the variation in MS among trees for each site. No genetic effect could explain either TBAI or the MS variation. Climate and N_FTC drive annual growth variability in trembling aspen at stand and subcontinental scales. Tree genetic makeup contributed to these dynamics, the annual growth dynamics of multi-clonal stands being less homogeneous than those of monoclonal stands. Maintaining diverse aspen stands may ensure a wider range of growth responses to environmental variability, which in turn may help maintain resilience of aspen stands under future climate.     

中条山中段木本植物群落植物种多样性分析

采用样方法取样,依据重要值指标运用双向指示种分析(TWINSPAN)法,将山西中条山中段植被群系分成16个群丛。应用丰富度指数（R₁、R₂）、Simpson指数（λ）,Shannon-Weiner指数(H′)和均匀度指数(E₁、E₅)研究了16个群丛的植物种多样性。结果表明：群系植物种多样性指数的大小受立地生境和人为活动的综合影响;森林群落的植物种多样性指数明显高于灌丛群落;群落植物种多样性在空间上的差异不仅决定于物种丰富度指数,更与各物种间的均匀度指数密切相关;进而影响不同层次的物种多样性对群落总体物种多样性的贡献。     

Competition and regeneration in quaking aspen–white fir (Populus tremuloides–Abies concolor) forests in the Northern Sierra Nevada,USA

Question: How does competition between quaking aspen (Populus tremuloides) and white fir (Abies concolor) affect growth and spatial pattern of each species? Location: The northern Sierra Nevada, California, USA. Methods: In paired plots in mixed aspen‐ (n=3) or white fir‐dominated (n=2) stands, we mapped trees and saplings and recorded DBH, height, species, and condition and took increment cores. We tallied seedlings by species. Tree ring widths were used as a measure of basal area change over the last decade, and canopy openness was identified using hemispherical photographs. Linear mixed models were used to relate neighborhood indices of competition, stand, and tree‐level variables to diameter increment. Spatial patterns of stems were identified using the Neighborhood Density Function. Results: White fir radial growth was higher in aspen‐ than white fir‐dominated plots. Individual‐level variables were more important for white fir than for aspen growth, while variables representing competitive neighborhood were important only for aspen. The forest canopy was more open in aspen‐ than white fir‐dominated stands, but ample aspen seedlings were observed in all stands. Canopy stems of aspen and white fir were randomly distributed, but saplings and small trees were clumped. Aspen saplings were repelled by canopy aspen stems. Conclusions: Variation in canopy openness explained more stand–stand variation in white fir than aspen growth, but high light levels were correlated with recruitment of aspen seedlings to the sapling class. Radial growth of aspen was predicted by indices of neighborhood competition but not radial growth of white fir, indicating that spacing and stem arrangement was more important for aspen than white fir growth. Fire suppression has removed a major disturbance mechanism that promoted aspen persistence and reduced competition from encroaching conifers, and current forests favor species that regenerate best by advance regeneration (white fir).     

Tree Diversity Limits the Impact of an Invasive Forest Pest

The impact of invasive herbivore species may be lower in more diverse plant communities due to mechanisms of associational resistance. According to the “resource concentration hypothesis” the amount and accessibility of host plants is reduced in diverse plant communities, thus limiting the exploitation of resources by consumers. In addition, the “natural enemy hypothesis” suggests that richer plant assemblages provide natural enemies with more complementary resources and habitats, thus promoting top down regulation of herbivores. We tested these two hypotheses by comparing crown damage by the invasive Asian chestnut gall wasp (Dryocosmus kuriphilus) on chestnut trees (Castanea sativa) in pure and mixed stands in Italy. We estimated the defoliation on 70 chestnut trees in 15 mature stands sampled in the same region along a gradient of tree species richness ranging from one species (chestnut monocultures) to four species (mixtures of chestnut and three broadleaved species). Chestnut defoliation was significantly lower in stands with higher tree diversity. Damage on individual chestnut trees decreased with increasing height of neighboring, heterospecific trees. These results suggest that conservation biological control method based on tree species mixtures might help to reduce the impact of the Asian chestnut gall.     

岷江冷杉林皆伐后次生群落结构和物种多样性的演替动态

为阐明岷江冷杉林皆伐后次生群落的演替过程,采用空间代替时间的方法,在川西米亚罗林区海拔3100—3600 m的阴坡选择岷江冷杉林皆伐后次生演替10、20、30、40和50a阶段的次生群落作为研究对象,对其群落结构和物种多样性的动态进行了研究。不同演替阶段的树木均呈显著聚集分布。按群落中优势种的重要值将该演替序列划分为3个类型:悬钩子-蔷薇灌丛、白桦阔叶林和桦木-岷江冷杉针阔混交林。随次生演替,乔木和灌木种的物种丰富度趋于增加,而草本种的物种丰富度趋于减少;乔木和灌木种的Shannon-Wiener多样性指数趋于增大,而草本的Shannon-Wiener多样性指数趋于减小;乔木、灌木和草本层的Pielou均匀度指数均趋于增大;乔木层的Simpson优势度指数趋于减小,灌木和草本层的Simpson优势度指数在演替0—40年阶段趋于增大,而在演替50a阶段趋于减小。在该演替序列中,乔木、灌木和草本层的物种组成均呈耐荫种替代非耐荫种的趋势。     

Population structure of the widespread species,Anogeissus leiocarpa (DC.) Guill. & Perr. across the climatic gradient in West Africa semi-arid area

In the climate change context, widely distributed plant species can serve as relevant barometers of ecosystems' sensitivity or resilience to disturbances. This study aimed at assessing the population structure and individual morphological traits of Anogeissus leiocarpa, a widespread tree species, across a broad strip of land, from the north to the south of Burkina Faso. We compared stands in four phytogeographical zones in order to analyze morphological variations in trees and recruits density, individual size and their spatial structure. Our results showed significant increase of tree density from the Sahel (77.1 trees/ha) to the South-Sudanian (166 trees/ha) while diameter, height and basal area had an opposite trend. No recruits were found in the Sahel stands, while their density increased from the Sub-Sahel (5.17 individuals/ha) to the South-Sudanian (6.46 individuals/ha). Tree diameters revealed positive asymmetric distributions in the Sudanian and Sub-Sahel whereas the Sahel stands showed a symmetric distribution. Height structure of saplings revealed “J reverse” shape in Sudanian stands while Sub-Sahelian ones exhibited Gaussian shape. Height–diameter relationships revealed thin trees towards the south-Sudanian. The spatial structure of trees indicated random distributions in all zones whereas recruits presented aggregative distribution trend in the Sudanian zones. A. leiocarpa's trees have a good ability to support broad climatic fluctuations but the populations' rejuvenation is unpredictable in the extreme harsh conditions. The species is fairly resilient to anthropogenic disturbances in Sub-Sahel and Sudanian zones. However, managing issues should pay attention to the species communities by considering its demographic behavior in the health state appreciation of ecosystems.     

Tree diversity drives abundance and spatiotemporal β‐diversity of true bugs (Heteroptera)

1. Spatiotemporal patterns of canopy true bug diversity in forests of different tree species diversity have not yet been disentangled, although plant diversity has been shown to strongly impact the diversity and distribution of many insect communities. 2. Here we compare species richness of canopy true bugs across a tree diversity gradient ranging from simple beech to mixed forest stands. We analyse changes in community composition by additive partitioning of species diversity, for communities on various tree species, as well as for communities dwelling on beech alone. 3. Total species richness (γ‐diversity) and α‐diversity, and abundance of true bugs increased across the tree diversity gradient, while diversity changes were mediated by increased true bug abundance in the highly diverse forest stands. The same pattern was found for γ‐diversity in most functional guilds (e.g. forest specialists, herbivores, predators). Temporal and even more, spatial turnover (β‐diversity) among trees was closely related to tree diversity and accounted for ～90% of total γ‐diversity. 4. Results for beech alone were similar, but species turnover could not be related to the tree diversity gradient, and monthly turnover was higher compared to turnover among trees. 5. Our findings support the hypothesis that with increasing tree diversity and thereby increasing habitat heterogeneity, enhanced resource availability supports a greater number of individuals and species of true bugs. Tree species identity and the dissimilarity of true bug communities from tree to tree determine community patterns. 6. In conclusion, understanding diversity and distribution of insect communities in deciduous forests needs a perspective on patterns of spatiotemporal turnover. Heterogeneity among sites, tree species, as well as tree individuals contributed greatly to overall bug diversity.     

Effects of population density on forest structure and species richness and diversity of trees in Kampong Thom Province, Cambodia

This study examined differences in stand structure, tree species richness, and tree species diversity in relation to population density in Kampong Thom Province, Cambodia. Tree data were obtained from a 1997 forest inventory involving 60 clusters (540 plots) systematically distributed over 30% of the provincial forest area. Spatially referenced population data were obtained from the 1998 national population census. The average number of trees per cluster was 356/ha, the average basal area, 23 m²/ha, the average stand volume, 217 m³/ha, and the average aboveground biomass, 273 Mg/ha for all trees of DBH 10 cm and larger. The average species richness per cluster was 37 species, while average species diversity was measured as 0.916 using Simpson’s index and 2.98 by Shannon’s index. Significant negative correlations were generally found between population density surrounding clusters and tree density, basal area, stand volume, aboveground biomass, and species richness and diversity for three examined diameter classes (DBH of 10–30, ≥30, and ≥10 cm). As the distance from clusters for calculating population density increased, the correlation levels increased up to 5 or 7 km, depending on the variables and diameter class, and then stayed relatively constant for stand structure variables and decreased for species richness and diversity. The results indicate that evidence of disturbance was more pronounced at higher population density up to around 5 to 7 km. We suggest that introduction of greater controls on human disturbance should be a high priority for resource management and conservation in Kampong Thom Province and, presumably, Cambodia as a whole.     

Spatiotemporal changes of beetle communities across a tree diversity gradient

Aim Plant and arthropod diversity are often related, but data on the role of mature tree diversity on canopy insect communities are fragmentary. We compare species richness of canopy beetles across a tree diversity gradient ranging from mono‐dominant beech to mixed stands within a deciduous forest, and analyse community composition changes across space and time. Location Germany’s largest exclusively deciduous forest, the Hainich National Park (Thuringia). Methods We used flight interception traps to assess the beetle fauna of various tree species, and applied additive partitioning to examine spatiotemporal patterns of diversity. Results Species richness of beetle communities increased across the tree diversity gradient from 99 to 181 species per forest stand. Intra‐ and interspecific spatial turnover among trees contributed more than temporal turnover among months to the total γ‐beetle diversity of the sampled stands. However, due to parallel increases in the number of habitat generalists and the number of species in each feeding guild (herbivores, predators and fungivores), no proportional changes in community composition could be observed. If only beech trees were analysed across the gradient, patterns were similar but temporal (monthly) species turnover was higher compared to spatial turnover among trees and not related to tree diversity. Main conclusions The changes in species richness and community composition across the gradient can be explained by habitat heterogeneity, which increased with the mix of tree species. We conclude that understanding temporal and spatial species turnover is the key to understanding biodiversity patterns. Mono‐dominant beech stands are insufficient to conserve fully the regional species richness of the remaining semi‐natural deciduous forest habitats in Central Europe, and analysing beech alone would have resulted in the misleading conclusion that temporal (monthly) turnover contributes more to beetle diversity than spatial turnover among different tree species or tree individuals.     

Species diversity of butterflies in Changbai Mountain in China

Using a modified belt transect method, we investigated the butterfly communities in five different vertical vegetation belts of Changbai Mountain in China from 1992 to 2009; these belts were broadleaf deciduous forest, coniferous–deciduous mixed forest, coniferous forest, erman’s birch forest and alp tundra. We determined the number of species and abundance of butterflies in each belt and in the coniferous–deciduous mixed forest belt, we also compared these parameters among different months. Preston’s lognormal distribution was used to model the species abundance distributions and five indicators (Shannon–Wiener diversity index (H′), Pielou uniformity index (J), Simpson predominance centralization index (C), Margalef abundance index (E) and Jaccard similarity coefficients) were used to analyze the butterfly community diversity. We found four main results. (1) Across all five vertical vegetation belts, 9641 butterflies were collected, belonging to 7 families, 98 genera and 196 species. As altitude increased, the number of butterfly genera and species gradually reduced. There was a relationship between the distribution of dominant species and the total species between each belt and the distribution of vascular plants. (2) The species abundance distribution was successfully modeled as a Preston’s lognormal distribution; the best fit was obtained when α = 0.326, the determinant coefficient of the equation was 0.74798. The species abundance distribution indicates that Changbai Mountain provides a suitable environment for butterflies; there was high species richness and an even distribution of butterfly species. There were few very common and very rare species, with most species having an intermediate abundance. (3) As altitude increased, H′ and E gradually became smaller, while C showed the opposite pattern, and J did not significantly change. The similarity coefficients analysis demonstrated a clear difference among belts; the farther apart any two belts, the smaller the similarity coefficient, indicating less similarity in the butterfly communities. The similarity coefficient between the deciduous forest and the coniferous–deciduous mixed forest belt was the largest (0.651) while that between the deciduous forest and the alp tundra was the smallest (0.141). (4) Comparison of the butterfly species communities among different months in the coniferous–deciduous mixed forest found that H′ and E showed similar directional changes, while the opposite pattern was found with C; the changes in J did not necessarily reflect the actual change in diversity.     

Factors affecting species richness of tree regeneration in mixed‐wood stands of central Maine

Question: Two questions about within‐stand spatial variability are addressed in this paper. How does species richness of tree regeneration respond to small‐scale ecological gradients, and what effect does natural Abies balsamea abundance have on the species richness of other tree regeneration? Location: A long‐term, gap‐silviculture experiment, Acadian mixed‐wood forest, Maine, USA. Methods: Eight stands treated with and without gap harvesting were sampled to capture sub‐stand heterogeneity of understorey tree regeneration concurrently with patterning of local stand conditions. Spatial and non‐spatial models were developed to test the relationships between two response variables [species richness of small (height ≥0.1 m, but <0.75 m) and large (height ≥0.75 m, but <1.4 m) regeneration] and five explanatory variables (depth to water table, percentage canopy transmittance, A. balsamea regeneration density, and overstorey basal area and species richness). Results: Despite high unexplained variance for all models, consistent associations among variables were found. Negative associations were found between: (1) the species richness of small regeneration and A. balsamea regeneration density and (2) the species richness of large regeneration and overstorey basal area. Positive associations were found between: (1) the species richness of small regeneration and both overstorey basal area and species richness and (2) the species richness of small and large regeneration and canopy transmittance. Conclusions: Promoting tree species diversity in Acadian mixed‐wood stands may not be achievable through the use of gap‐harvesting alone if the density of understorey Abies balsamea is not reduced either naturally or through silvicultural intervention.     

宝天曼地区栓皮栎林恢复过程中高等植物物种多样性变化

对宝天曼地区不同恢复阶段栓皮栎林的高等植物物种多样性特征进行了初步分析。结果表明,各层物种丰富度和多样性指数在不同恢复阶段栓皮栎林表现出草本层＞灌木层＞乔木层的趋势。乔木层物种丰富度和多样性指数基本上随恢复时间的增加而增加;灌木层在未破坏的栓皮栎林内较低,而在其他恢复阶段的栓皮栎林内基本相同;草本层在恢复５年、１５年和２５年的栓皮栎林中较高,而在恢复４５年和未破坏的栓皮栎林内较低。乔木层物种均匀度指数在未破坏的栓皮栎林中较高,在恢复２５年的栓皮栎林中较低;灌木层在恢复４５年的栓皮栎林中较高,在恢复１５年的栓皮栎林较低;草本层在恢复５年的栓皮栎林中较高,在恢复１５年的栓皮栎林中较低。不同恢复阶段栓皮栎林各层次间的物种多样性差异大多不显著,只有乔木层和草本层及灌木层和草本层之间的物种丰富度指数有显著差异。不同恢复阶段栓皮栎林在乔木层物种多样性特征上的差异最大,在灌木层物种多样性特征上有一定差异,在草本层物种多样性特征上没有明显的差异。     

Silver fir and Douglas fir are more tolerant to extreme droughts than Norway spruce in south‐western Germany

Improving our understanding of the potential of forest adaptation is an urgent task in the light of predicted climate change. Long‐term alternatives for susceptible yet economically important tree species such as Norway spruce (Picea abies) are required, if the frequency and intensity of summer droughts will continue to increase. Although Silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) have both been described as drought‐tolerant species, our understanding of their growth responses to drought extremes is still limited. Here, we use a dendroecological approach to assess the resistance, resilience, and recovery of these important central Europe to conifer species the exceptional droughts in 1976 and 2003. A total of 270 trees per species were sampled in 18 managed mixed‐species stands along an altitudinal gradient (400–1200 m a.s.l.) at the western slopes of the southern and central Black Forest in southwest Germany. While radial growth in all species responded similarly to the 1976 drought, Norway spruce was least resistant and resilient to the 2003 summer drought. Silver fir showed the overall highest resistance to drought, similarly to Douglas fir, which exhibited the widest growth rings. Silver fir trees from lower elevations were more drought prone than trees at higher elevations. Douglas fir and Norway spruce, however, revealed lower drought resilience at higher altitudes. Although the 1976 and 2003 drought extremes were quite different, Douglas fir maintained consistently the highest radial growth. Although our study did not examine population‐level responses, it clearly indicates that Silver fir and Douglas fir are generally more resistant and resilient to previous drought extremes and are therefore suitable alternatives to Norway spruce; Silver fir more so at higher altitudes. Cultivating these species instead of Norway spruce will contribute to maintaining a high level of productivity across many Central European mountain forests under future climate change.     

Tree diversity patterns in successive vegetation types along an elevation gradient in the Mountains of Eastern Mexico

Tree species richness changes along elevation gradients in response to underlying environmental conditions. Our hypothesis was that richness is associated with climatic variables and decreases with elevation. The objective was to identify trends in species, genus and family richness, diversity and vegetation structure in relation to climate variables along an elevation gradient with successive types of forest in Veracruz, Mexico. Trees were identified and measured in 0.1 ha at 15 sites located from 140 to 4000 m a.s.l. Generalized linear models were used to fit richness, diversity, basal area and density as a function of elevation; the best model was selected using Akaike’s Information Criterion. Multivariate analyses were used to explore climatic variables associated to composition of groups of sites along the gradient. Along the entire elevation gradient, species, genus and family richness decreased unimodally, and diversity decreased monotonically. Richness was positively correlated with temperature but not with precipitation. Basal area increased monotonically and highest basal area was associated with high humidity and certain tree species (Quercus and Abies). Ordinations indicated three groups of sites: lower elevation dry forest associated with temperature seasonality, mid-elevation cloud forest associated with precipitation-related variables, and coniferous forest at the top of the gradient associated with elevation. Our study shows that different plant communities are associated with certain climatic conditions and harbour different tree species, genera and families. The results support the hypothesis that species richness is associated with climate, and decreases with elevation.     

Seasonal occurrence and distribution of myxomycetes on different types of leaf litter in a warm temperate forest of western Japan

The seasonal occurrence and distribution of myxomycetes on different types of newly defoliated leaf litter were examined in a secondary forest in a warm temperate region of western Japan. The two types of leaf litter (deciduous trees, Prunus verecunda and Quercus variabilis, and evergreen trees, Q. glauca and Cinnamomum camphora) were incubated in trays on the forest floor. A total of 45 myxomycete species were recorded from 3021 collected samples that occurred at the July peak during the warmest and humidest season from April to November. The occurrence of species was significantly related to the changes in mean temperature and minimum temperature on both leaf types under humid conditions. Myxomycete assemblages were divided into three seasonal phases. Most of the species occurred in June–September, while a few species demonstrated characteristic distributions; i.e., Didymium melanospermum appeared in April– May and Diderma umbilicatum appeared in October– November. The respective leaf types supported the reproduction of myxomycetes with high species richness and diversity, with 34 species and H’ = 2.59 on deciduous trees and similarly 30 species and H’ = 2.49 on evergreen trees. Several species, however, exhibited a preference for either the deciduous tree or evergreen tree leaves. Thus, a mixed forest that defoliates during different two seasons yields a greater species diversity of myxomycete assemblage.