Species richness and substrate specificity of lignicolous fungi in the canopy of a temperate,mixed deciduous forest

In the more than twenty years in which long-term canopy research has been conducted, mycology has been largely disregarded. Our studies using a construction crane to gain access to the canopy of a forest in Leipzig, Germany are the first long term investigations assessing the diversity and ecology of wood-decaying fungi in a canopy. Thirty-seven individuals of nine different tree species with a large amount of dead wood were selected. Sampling focussed on the four most prominent tree species Acer pseudoplatanus, Fraxinus excelsior, Quercus robur and Tilia cordata. In the years 2002 and 2003 dead wood was collected in different canopy strata. Dead branches were removed and stored for two weeks in open boxes with high humidity to allow growth of fructifications in the laboratory. 118 different taxa were identified (108 species, 77 genera). Corticioid fungi (e.g., of Corticiaceae, Stereaceae, Hymenochaetaceae) dominated the fungal composition with 37 species, pyrenomycetes were present with 18 species. Agaric fungi (Agaricales and Cortinariales) were scarce. Species with minute basidiomes dominated the fungal composition of this systematic group. Agarics with larger sporomes were found only once and were restricted to strongly decayed branches in shaded canopy areas. Concerning species richness and fungal composition the four tree species mentioned above differed remarkably. As expected, many fungi that grew on bark or slightly decayed wood showed a distinct host and substratum specifity. It is noteworthy that fungi which are purportedly to be non-specific were found on single tree species only.     

Species richness and distribution patterns of leaf-inhabiting endophytic fungi in a temperate forest canopy

In 2005, researchers at the Leipzig Canopy Crane Research Facility collected living leaves of four temperate tree species at heights of between 15 and 33 m above the ground. Following surface sterilisation of the leaves, leaf-fragments were cultured on malt extract agar which allowed the growth of endophytic fungi into the surrounding medium. Isolated cultures were identified by morphology and sequence analysis of the D1/D2 region of the large subunit rDNA. Phylogenetic analysis established the taxonomic positions of the fungi. A total of 49 different taxa were identified, representing 20 families and ten orders. With the exception of one basidiomycetous yeast, all taxa belonged to filamentous ascomycetes. Species richness was highest on Tilia cordata and lowest on Quercus robur. Species-accumulation curves showed that the sampling effort was not sufficient to cover the majority of the likely species at the investigation site. Most endophytes proved to be ubiquitous within the canopy of the investigation site, but habitat preferences in terms of different tree species, different light regimes and season (sampling times) were obvious for some abundant endophytes. Apiognomonia errabunda and Aspergillus niger occurred predominantly on Q. robur, Diplodina acerina on Acer pseudoplatanus, one species of Phoma significantly prefered shaded leaves from the lower canopy layer whereas Sordaria fimicola prefered sun-exposed leaves from the upper tree crowns. Seasonal patterns were observed, for example, for A. errabunda, which was abundant in young leaves in the spring and almost completely absent in aged autumn-leaves, thus suggesting the accumulation of antifungal secondary plant metabolites during the growing season. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. Wilfried Morawetz died in March 2007.     

Factors influencing sapling composition in canopy gaps of a temperate deciduous forest

To detect the factors that affect sapling species composition in gaps, we investigated 55 gaps in an old-growth temperate deciduous forest in Ogawa Forest Reserve, central Japan. Gap size, gap age, gap maker species, topographic location, adult tree composition around gaps, and saplings of tree species growing in the gaps were censused. For gaps 5 m², mean gap size was 70 m² and the maximum was 330 m². Estimated ages of gaps had a tendency to be concentrated in particular periods relating to strong wind records in the past. The sapling composition in gaps was highly and significantly correlated to that under closed canopy, indicating the importance of advance regeneration in this forest. However, some species showed significant occurrence biases in gaps or under closed canopy, suggesting differences in shade tolerance. The result of MANOVA showed that gap size and topography were important factors in determining the sapling composition in gaps. Species of gap makers affected the sapling composition indirectly by influencing gap size. The existence of parent trees around gaps had effects on sapling densities of several species. Gap age did not have clear influences on sapling composition. Variations in gap size and topography were considered as important factors that contribute to maintenance of species diversity in this forest.     

Drought acclimation of two deciduous tree species of different layers in a temperate forest canopy

Water-use strategies of Populus tremula and Tilia cordata, and the role of abscisic acid in these strategies, were analysed. P. tremula dominated in the overstorey and T. cordata in the lower layer of the tree canopy of the temperate deciduous forest canopy. Shoot water potential (), bulk-leaf abscisic acid concentration ([ABA]_leaf), abscisic acid concentration in xylem sap ([ABA]_xyl), and rate of stomatal closure following the supply of exogenous ABA (v) decreased acropetally through the whole tree canopy, and foliar water content per area (w), concentration of the leaf osmoticum (c), maximum leaf-specific hydraulic conductance of shoot (L), stomatal conductance (g_s), and the threshold dose per leaf area of the exogenous ABA (d_a) required to reduce stomatal conductance increased acropetally through the tree canopy (from the base of the foliage of T. cordata to the top of the foliage of P. tremula) in non-stressed trees. The threshold dose per leaf dry mass of the exogenous ABA (d_w) required to reduce stomatal conductance, was similar through the tree canopy. After a drought period (3 weeks), the , w, L, g_s, d_a and d_w had decreased, and c and v had increased in both species. Yet, the effect of the drought period was more pronounced on L, g_s, d_a, d_w and v in T. cordata, and on , w and c in P. tremula. It was concluded that the water use of the species of the lower canopy layer—T. cordata, is more conservative than that of the species of the overstorey, P. tremula. [ABA]_leaf had not been significantly changed in these trees, and [ABA]_xyl had increased during the drought period only in P. tremula. The relations between [ABA]_leaf, [ABA]_xyl and the stomatal conductance, the osmotic adjustment and the shoot hydraulic conductance are also discussed.     

Drought during canopy development has lasting effect on annual carbon balance in a deciduous temperate forest

* Climate change projections predict an intensifying hydrologic cycle and an increasing frequency of droughts, yet quantitative understanding of the effects on ecosystem carbon exchange remains limited. * Here, the effect of contrasting precipitation and soil moisture dynamics were evaluated on forest carbon exchange using 2 yr of eddy covariance and microclimate data from a 50-yr-old mixed oak woodland in northern Ohio, USA. * The stand accumulated 40% less carbon in a year with drought between bud-break and full leaf expansion (354 +/- 81 g C m(-2) yr(-1) in 2004 and 252 +/- 45 g C m(-2) yr(-1) in 2005). This was caused by greater suppression of gross ecosystem productivity (GEP; 16% = 200 g) than of ecosystem respiration (ER; 11% = 100 g) by drought. Suppressed GEP was traced to lower leaf area, lower apparent quantum yield and lower canopy conductance. The moisture sensitivity of ER may have been mediated by GEP. * The results highlight the vulnerability of the ecosystem to even a moderate drought, when it affects a critical aspect of development. Although the drought was preceded by rain, the storage capacity of the soil seemed limited to 1-2 wk, and therefore droughts longer than this are likely to impair productivity in the region.     

Long-term succession in a Danish temperate deciduous forest

Forest successional trajectories covering the last 2000 yr from a mixed deciduous forest in Denmark show a gradual shift in dominance from Tilia cordata to Fagus sylvatica and a recent increase in total forest basal area since direct management ceased in 1948. The successions are reconstructed by combining a fifty-year record of direct tree observations with local pollen diagrams from Draved Forest, Denmark. Five of the seven successions record a heathland phase of Viking Age dating from 830 AD. The anthropogenic influence is considerable throughout the period of study even though Draved contains some of the most pristine forest stands in Denmark. Anthropogenic influence including felling masks the underlying natural dynamics, with the least disturbed sites showing the smallest compositional change. Some effects of former management, such as loss of Tilia cordata dominance, are irreversible. Artificial disturbance, particularly drainage, has accelerated and amplified the shift towards Fagus dominance that would have occurred on a smaller scale and at a slower rate in the absence of human intervention.     

东灵山暖温带落叶阔叶次生林动态监测样地:物种组成与群落结构

群落结构状态是植被演替进程中的重要体现之一,同时也是下一步演替过程发生的基础.暖温带落叶阔叶次生林是中国暖温带森林植被的主要类型.为了更好地研究其演替动态、生物多样性维持机制,我们参照巴拿马Barro Colorado Island(BCI)50 ha热带雨林样地的技术规范,于2009年11月至2010年9月在北京门头沟区小龙门森林公园的暖温带落叶阔叶次生林内建立了一块20 ha的固定样地(简称DLS),对样地内胸径≥1 cm的所有木本植物进行了鉴定、调查及定位,分析了群落的组成和结构.结果表明,样地内木本植物有58种,隶属于18科33属.独立个体的总数为52,136,包括独立个体分枝的总数为103,284,全部为落叶树种.群落的区系类型以北温带成分居多,同时混有一些亚热带和热带成分,属典型的温带森林类型.群落优势种明显,个体数最多的前5个种的个体数占到总个体数的61%,前20个种占到92%,而其余38个种只占8%.群落成层现象明显,垂直结构由主林层(19个种)、次林层(18个种)和灌木层(21个种)组成.样地所有木本植物个体总径级分布呈倒"J"型,群落更新良好.主林层树种的径级结构近似于双峰或正态分布,而次林层和灌木层树种则表现出倒"J"型或"L"型.几个主要树种的空间分布表现出不同的分布格局,随着径级增大,聚集程度降低.空间分布格局显示主要优势种自身个体在其径级大小的空间分分布上互补,不同径级的个体占据了样地内不同的空间位置.     

Intra- and inter-specific variation in canopy photosynthesis in a mixed deciduous forest

 Within the same forest, photosynthesis can vary greatly among species and within an individual tree. Quantifying the magnitude of variation in leaf-level photosynthesis in a forest canopy will improve our understanding of and ability to model forest carbon cycling. This information requires extensive sampling of photosynthesis in the canopy. We used a 22-m-tall, four-wheel-drive aerial lift to reach five to ten leaves from the tops of numerous individuals of several species of temperate deciduous trees in central Massachusetts. The goals of this study were to measure light-saturated photosynthesis in co-occurring canopy tree species under field conditions, and to identify sampling schemes appropriate for canopy tree studies with challenging logistics. Photosynthesis differed significantly among species. Even though all leaves measured were canopy-top, sun-acclimated foliage, the more shade-tolerant species tended to have lower light-saturated photosynthetic rates (P _max) than the shade-intolerant species. Likewise, leaf mass per area (LMA) and nitrogen content (N) varied significantly between species. With only one exception, the shade-tolerant species tended to have lower nitrogen content on an area basis than the intolerant species, although the LMA did not differ systematically between these ecological types. Light-saturated P _max rates and nitrogen content, both calculated on either an area or a mass basis, and the leaf mass to area ratio, significantly differed not only among species, but also among individuals within species (P<0.0001 for both). Differences among species accounted for a greater proportion of variance in the P _max rates and the nitrogen content than the differences among individuals within a species (58.5–78.8% of the total variance for the measured parameters was attributed to species-level differences versus 5.5–17.4% of the variance was attributed to differences between individual trees of a given species). Furthermore, more variation is accounted for by differences among leaves in a single individual tree, than by differences among individual trees of a given species (10.7–30.4% versus 5.5–17.4%). This result allows us to compare species-level photosynthesis, even if the sample size of the number of trees is low. This is important because studies of canopy-level photosynthesis are often limited by the difficulty of canopy access. As an alternative to direct canopy access measurements of photosynthesis, it would be useful to find an ”easy-to-measure” proxy for light-saturated photosynthetic rates to facilitate modeling forest carbon cycling. Across all species in this study, the strongest correlation was between nitrogen content expressed on an area basis (mmol m^–2, N _area) and light-saturated P _max rate (μmol m^–2 s^–1, P _maxarea) (r ²=0.511). However, within a given species, leaf nitrogen was not tightly correlated with photosynthesis. Our sampling design minimized intra-specific leaf-level variation (i.e., leaves were taken only from the top of the canopy and at only one point in the season). This implies that easy-to-measure trends in nitrogen content of leaves may be used to predict the species-specific light-saturated P _max rates. Received: 16 March 1996 / Accepted: 16 August 1996     

Species turnover in deciduous forest vegetation

Summary Permanent quadrats were marked out in two areas of hardwood forest vegetation in 1969, and listings of their vascular plant species were taken on several occasions over the snow-free seasons of 1969, 1970, 1971 and 1976. Over the period of study, mean numbers of species per m² remained virtually constant, but variations in the species compositions of individual quadrats were such that mean turnover ratios of 0.115 and 0.085, respectively, were computed for the two stands. Between 1969 and 1976 averages of 20% and 14%, respectively, of the species found in individual quadrats were replaced. This was not accomplished by qualitative changes in the floras of the two stands. Rather, it reflects the operation of a system of continuous rearrangements of species in the small quadrats of both sample areas.Taxonomical nomenclature and life-form system used in this study are according to Gleason & Cronquist (1963).William Phillips, Ian Sutherland and Sheila Thompson helped in the field; Professor Keith Wade commented on the material; Abal Sen drafted the diagram; and the research is part of that funded by the National Research Council of Canada.     

Species richness and canopy productivity of Australian plant communities

The species richness (number of vascular plants per hectare) of Australian plant communities (containing a mosaic of gap, regeneration, maturation and senescent phases) is correlated with the annual biomass productivity of the overstorey canopy.The annual production of leaves and stem in the canopy of the plant community is shown to be limited by the requirements of photosynthesis (particularly light and the availability of water) and the length of the growing season.The species richness of Australian plant communities is the product of the blance between the dominance of the overstorey and the response of the understorey to the shading of the overstorey. For all climatic regions and zones the species richness of the overstorey of the plant community is shown to be exponentially related to the annual shoot growth of the overstorey canopy, until the latitudinal or altitudinal tree line is reached. With latitudinal increase outside the tropics, overstorey canopies of forest communities absorb increasingly more of the incident solar radiation. markedly reducing the species richness of the understorey strata. In contrast, in these latitudes the overstorey of plant communities with widely spaced trees or tall shrubs will absorb far less solar radiation, thus enabling the species richness of the understorey to be maintained.     

Species coexistence in temperate, mixed deciduous forests

The response of tree life-history traits to community profiles (horizontal and vertical heterogeneity, disturbances and biotic interactions) determines community assembly rules, which are currently a hot issue in community ecology. Important mechanisms of coexistence differ throughout the developing stages of tree life history. Many processes of niche partitioning and tradeoffs that potentially enable tree coexistence have been reported to be present in temperate forests, although some of these life-history traits are either correlated with each other or are not independent. Not all of the proposed mechanisms explain coexistence equally well; some could predominate in determining the community organization of forest communities. Population studies need to concentrate more on the component species of a target community to detect the ecological assembly rule. These approaches can also address how chance factors contribute to the composition of temperate tree communities, which might be less dependent on chance than are tropical ones.     

Soil seed bank composition and diversity in a managed temperate deciduous forest

Little is known about the influence of forest management on the interaction between seed bank and aboveground vegetation. We surveyed seed banks and vegetation in 10 forest stands under similar abiotic conditions but submitted either to a coppice-with-standards treatment (n=5) or to a selective-cutting system (n=5). We analyzed species composition and diversity, community ecological profile, and distribution of taxa among different life forms, strategy, morphology and functional type categories. A total of 2085 seedlings (8296 seedsm^–2) germinated-corresponding to 28 species, among which Juncus effusus was the most abundant. Fifty-seven percent of the species were also recorded in the aboveground vegetation, the dominant species being Rubus fruticosus agg., but only 28% of the aboveground species were present in the seed bank. Our results suggest that (1) vernal geophytes and shade-tolerant perennials, which group most true forest species, are not incorporated in the seed bank, (2) parent plants of most seeds were present either in the stand in an earlier dynamic stage or apart from the stand and long-distance dispersed, (3) as expected, early-successional species are well represented in the seed bank, (4) forestry vehicles seem to be a major means of dispersion for stress-tolerant species normally found in forest lanes and wheel tracks. We conclude that seed banks contain species that have a potentially negative impact on the true forest flora and, thus, forest management should minimize soil disturbance and retain remnants of old-coppice woods to conserve disturbance-sensitive true forest species.     

Importance of the understory stratum to entomofaunal diversity in a temperate deciduous forest

The vertical stratification of lepidopteran and coleopteran communities in a cool-temperate deciduous forest in Japan was examined to evaluate the hypothesis of an expected uniform distribution of mobile flying insects between the canopy and understory of temperate forests. Lepidopteran and coleopteran insects were trapped using light traps at three sites in each of the canopy and understory for three consecutive nights each month from April to October 2001. For Lepidoptera, species richness, abundance, and family richness were significantly higher in the understory than in the canopy. For Coleoptera, only abundance was larger in the canopy relative to the understory; species and family richness did not differ between the strata. The beta diversity of the lepidopteran community was larger between the strata than among sites, but the coleopteran community showed an inverse pattern. These results imply the presence of vertical stratification within the lepidopteran community, but not within the coleopteran community, in the temperate forest. The understory contributes more than the canopy to lepidopteran diversity in the temperate forest, although this stratification may be relatively weak because, in contrast to the situation in tropical forests, the canopy and understory assemblages share many species.     

Species richness of Macrolepidoptera on Finnish deciduous trees and shrubs

Summary Species richness of Macrolepidoptera on Finnish trees and shrubs was analysed by means of stepwise regression analysis. The explaining variables were plant frequency, geographical range, plant height, number of relatives and leaf size.Total frequency of the host plant, which correlated strongly with range, explained 57% of the observed variance of lepidopteran species richness on deciduous trees and shrubs. Height of plant and number of relatives explained significantly the residual variation and altogether these three variables explained 71% of the variance of species richness.Analyses at the plant genus level gave similar results and frequency, height and number of relatives explained 78% of the variance of species richness of Macrolepidoptera on deciduous plant genera.When conifers were included in the analysis leaf size also becomes a significant variable. Leaf size can, however, act as a dummy variable which effectively distinguishes conifers from deciduous trees.The validity of different models explaining herbivore species richness on plants is discussed. The results of this study favoured more than earlier studies the importance of relatedness of host plants as a factor which determines the species richness of herbivores.     

Temperature-independent diel variation in soil respiration observed from a temperate deciduous forest

The response of soil respiration (R_s) to temperature depends largely on the temporal and spatial scales of interest and how other environmental factors interact with this response. They are often represented by empirical exponential equations in many ecosystem analyses because of the difficulties in separating covarying environmental responses and in observing below ground processes. The objective of this study was to quantify a soil temperature‐independent component in R_s by examining the diel variation of an R_s time series measured in a temperate deciduous forest located at Oak Ridge, TN, USA between March and December 2003. By fitting 2 hourly, continuous automatic chamber measurements of CO₂ efflux at the soil surface to a Q₁₀ function to obtain the temperature‐dependent respiration (R_t) and plotting the diel cycles of R_t, R_s, and their difference (R_i), we found that an obvious temperature‐independent component exists in R_s during the growing season. The diel cycle of this component has a distinct day/night pattern and agrees well with diel variations in photosynthetically active radiation (PAR) and air temperature. Elevated canopy CO₂ concentration resulted in similar patterns in the diel cycle of the temperature‐independent component but with different daily average rates in different stages of growing season. We speculate that photosynthesis of the stand is one of the main contributors to this temperature‐independent respiration component although more experiments are needed to draw a firm conclusion. We also found that despite its relatively small magnitude compared with the temperature‐dependent component, the diel variation in the temperature‐independent component can lead to significantly different estimates of the temperature sensitivity of soil respiration in the study forest. As a result, the common practice of using fitted temperature‐dependent function from night‐time measurements to extrapolate soil respiration during the daytime may underestimate daytime soil respiration.     

Species richness and niche space for temperate and tropical folivores

We measured structural and chemical traits of the leaves of native, broad-leaved trees in two temperate localities [southern Ontario, Canada (34 species), and Missouri (36 species)] and one tropical locality [central Panama (samples of 21 and 23 species)] to test the hypothesis that the greater diversity of tree species and herbivore species in the tropics is associated with greater resource niche space for herbivores. Variables were leaf toughness, water content, dry mass per unit area, several structural and nutritional carbohydrates, common mineral elements, including nitrogen and phosphorus, and several defensive compounds, including tannins and alkaloids. The four samples were almost fully separable by discriminant analysis on the basis of these leaf traits. Variance in log-transformed trait values among species was lowest in the most northern sample, but did not differ significantly between Missouri and Panama. Niche space, estimated as the square root of the total variance in the log-transformed variables within each locality, varied approximately as Panama = 1, Missouri = 0.8, Ontario = 0.5. Although niche space decreases towards higher latitudes, the change does not match the ca. sixfold decrease in tree species richness or the ca. fourfold decrease in Lepidopteran species richness over the latitude range of our samples. Accordingly, tropical folivore diversity is associated with greater resource niche overlap, greater niche specialization, and/or more completely filled niches, or with variation in niche dimensions not measured in this study.     

Trade-offs between seedling growth and survival in deciduous broadleaved trees in a temperate forest

BACKGROUND AND AIMS: In spatially heterogeneous environments, a trade-off between seedling survival and relative growth rate may promote the coexistence of plant species. In temperate forests, however, little support for this hypothesis has been found under field conditions, as compared with shade-house experiments. Performance trade-offs were examined over a large resource gradient in a temperate hardwood forest. METHODS: The relationship between seedling survival and seedling relative growth rate in mass (RGR(M)) or height (RGR(H)) was examined at three levels of canopy cover (forest understorey, FU; small gap, SG; and large gap, LG) and at two microsites within each level of canopy cover (presence or absence of leaf litter) for five deciduous broad-leaved tree species with different seed sizes. KEY RESULTS: Within each species, both RGR(M) and RGR(H) usually increased with increasing light levels (in the order FU < SG < LG), whereas little difference was observed based on the presence or absence of litter. Seedling survival in FU was negatively correlated with both RGR(M) and RGR(H) in both LG and SG. The trade-off between high-light growth and low-light survival was more evident in the relationship with LG as compared with SG. An intraspecific trade-off between survival and RGR was observed along environmental gradients in Acer mono, whereas seedlings of Betula platyphylla var. japonica survived and grew better in LG. CONCLUSIONS: The results presented here strongly support the idea of light gradient partitioning (i.e. species coexistence) in spatially heterogeneous light environments in temperate forests, and that further species diversity would be promoted by increased spatial heterogeneity. The intraspecific trade-off between survival and RGR in Acer suggests that it has broad habitat requirements, whereas Betula has narrow habitat requirements and specializes in high-light environments.     

Seed demography of three co-occurring Acer species in a Japanese temperate deciduous forest

Abstract. Seed demography of three co-occurring Acer species in an old-growth mixed deciduous forest in Japan was studied. Almost all of the seeds of A. mono germinated in the first spring, while those of A. palmatum var. amoenum showed a delay in germination of almost one year. A. rufinerve showed a rather opportunistic germination habit. Both A. palmatum var. amoenum and A. rufinerve form short-term persistent seed banks, but without input of newly dispersed seeds they may become extinct in about one year. The seed bank for these two species is not as significant as for a typical pioneer species, and the seedling bank is important for all three species. Only a small proportion of the dispersed propagules contained viable embryos, mainly due to pollination failure or abortion (A. mono and A. palmatum var. amoenum), and invertebrate predation (A. rufinerve). For all three species, larger seed crops had a higher percentage of viable seeds. Even for these relatively small, wind-dispersed seeds, the predation pressure was very high. A large part of the dispersed seeds was eaten by wood mice during the first winter (30–80 %). Estimation from the 5-yr average of seed dispersal and seedling emergence showed that only 7–16 % of the dispersed viable seeds succeeded in germinating.