Litter decomposition by slugs in mixed deciduous woodland

For the one year period considered, it is calculated that 683.5 g m^-2 plant litter entered the study area site. Of the six slugs studied, Arion intermedius Normand, the smallest species, had the highest overall consumption rate on the nine test foods (29.1 ± 0.9 mg dry wt g live wt^-1 d^-1) and the highest overall mean assimilation efficiency (72.0 + 0.9%). The mean faecal production for each of the six slug species was very similar, ranging from 8.4 to 9.9 mg dry wt g live wt^-1 d^-1. Using regression equations of food consumed on faeces produced, it is estimated that the slug fauna each year consumes 8.4% of the leaf litter input and 6.5% of the total available plant litter. Of the plant material consumed, 13.8 g dry wt m^-2 are deposited annually as faeces. The role of slugs in decomposition processes is discussed and compared with that of other soil organisms.     

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 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.     

Decomposition of deciduous leaf litter in a woodland stream

Microorganisms associated with decomposing deciduous leaf litter in a woodland stream were examined by scanning electron microscopy. The use of a critical point drying method allowed the preservation of a wide variety of microorganisms as well as the decomposing litter with a minimum of distortion. The micrographs provide evidence that the aquatic hyphomycetes are the major fungal flora present during decomposition. Two distinct groups of these fungi were found during the seasonal cycle with one group occurring only in the summer while the other occurred throughout the rest of the year. The presence of all developmental stages of these organisms in the environment is considered further evidence of their active role in the decomposition of litter.     

Restoration of a deciduous woodland in Western Norway formerly used for fodder production: effects on tree canopy and field layer

The rich deciduous woodland at Loi, Luster, Inner Sogn, 61° 20 N., was traditionally used for fodder production from both tree and field layer. After more than nearly 40 years of disuse and secondary forest succession, experimental efforts were made to restore the traditional agricultural meadow woodland. Following a detailed preliminary registration of the vegetation the following measures were taken:

Controls over leaf litter decomposition in a mixed evergreen and deciduous broad-leaved forest,Central China

Plant and Soil - Our understanding of the determinants of leaf litter decomposition is lacking for mixed evergreen and deciduous broad-leaved forests compared with tropical and temperate forests....     

Ecology of nematophagous fungi: vertical distribution in a deciduous woodland

Summary The distribution of nematophagous fungi in soil collected from a deciduous woodland is compared to various biotic and abiotic soil factors. The microfungi are isolated at all depths down to a maximum of 35 cm. Predators forming constricting rings, adhesive branches and adhesive knobs are restricted to the upper litter and humus layers. The net forming predators and endoparasites are isolated at all depths, although they are significantly more abundant in the lower mineral rich soils. A much greater species diversity of nematophagous fungi is recorded in the upper organic zones.Preliminary soil analysis indicates thatCephalosporium balanoides is independent of all soil variables, while predators able to form traps spontaneously are restricted to the organic soils which are rich in nematodes. Non-spontaneous trap forming predators, which are excellent saprophytes, are isolated from the deeper soils which are low in nutrients. The ecological significance of these results is discussed.     

Patterns and drivers of lichen species composition in a NW-European lowland deciduous woodland complex

We surveyed lichens in an extensive area of lowland deciduous oak and beech dominated forest under wood pasture management within the New Forest National Park, southern England. This provided the basis for an investigation of factors affecting the species density and composition of epiphytic lichen communities. Fifteen 1 hectare plots were established in the same sites as a parallel invertebrate survey, of which nine were in old growth forest and six in oak plantations of between c. 150 and 300 years old. In each plot 12 trees were identified for sampling and lichens were sampled on four aspects of each trunk. Results at the plot level showed that species density was significantly higher in the old growth woodland plots from those in plantations. Plot age had a significant effect on species on oak but this was not significant for lichen communities on beech. The species density of lichens associated with Trentepohliaceae photobionts on oaks showed a linear positive relationship with increasing plot age while the species density of species with other coccal green Chlorophyta decreased with age of the plot. A major part of the lichenised fungi with Trentepohliaceae photobionts includes indicator and notable species used in conservation evaluation and this component is most affected by fragmentation and isolation of forest sites. The results emphasise the importance of long term connectivity and ecological continuity in this extensive mosaic of lowland deciduous forest.     

Fire enhances litter decomposition and reduces vegetation cover influences on decomposition in a dry woodland

Dry woodlands frequently experience fire, and the heterogeneous spatial patterning of vegetation cover and fire behavior in these systems can lead to interspersed burned and unburned patches of different vegetation cover types. Biogeochemical processes may differ due to fire and vegetation cover influences on biotic and abiotic conditions, but these persistent influences of fire in the months or years following fire are not as well understood as the immediate impacts of fire. In particular, leaf litter decomposition, a process controlling nutrient availability and soil organic matter accumulation, is poorly understood in drylands but may be sensitive to vegetation cover and fire history. Decomposition is responsive to changes in abiotic drivers or interactions between abiotic conditions and biotic drivers, suggesting that decomposition rates may differ with vegetation cover and fire. The objective of this study was to assess the role of vegetation cover and fire on leaf litter decomposition in a semi-arid pinyon-juniper woodland in southern New Mexico, USA, where prescribed fire is used to combat increasing woody cover. A spatially heterogeneous prescribed burn led to closely co-located but discrete burned and unburned patches of all three dominant vegetation cover types (grass, shrub, tree). Decomposition rates of leaf litter from two species were measured in mesh litterbags deployed in factorial combination of the three vegetation cover types and two fire treatments (burned and unburned patches). For both litter types, decomposition was lower for unburned trees than for unburned grass or shrubs, perhaps due to greater soil–litter mixing and solar radiation away from tree canopies. Fire enhanced litter mass loss under trees, making decomposition rates similarly rapid in burned patches of all three vegetation cover types. Understanding decomposition dynamics in spatially heterogeneous vegetation cover of dry woodlands is critical for understanding biogeochemical process responses to fire in these systems.     

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.     

Factors affecting soil fauna feeding activity in a fragmented lowland temperate deciduous woodland

British temperate broadleaf woodlands have been widely fragmented since the advent of modern agriculture and development. As a result, a higher proportion of woodland area is now subject to edge effects which can alter the efficiency of ecosystem functions. These areas are particularly sensitive to drought. Decomposition of detritus and nutrient cycling are driven by soil microbe and fauna coactivity. The bait lamina assay was used to assess soil fauna trophic activity in the upper soil horizons at five sites in Wytham Woods, Oxfordshire: two edge, two intermediate and one core site. Faunal trophic activity was highest in the core of the woodland, and lowest at the edge, which was correlated with a decreasing soil moisture gradient. The efficiency of the assay was tested using four different bait flavours: standardised, ash (Fraxinus excelsior L.), oak (Quercus robur L.), and sycamore (Acer pseudoplatanus L.). The standardised bait proved the most efficient flavour in terms of feeding activity. This study suggests that decomposition and nutrient cycling may be compromised in many of the UK's small, fragmented woodlands in the event of drought or climate change.     

The distribution of leaf photosynthetic activity in a mixed grass-legume pasture canopy

The distribution of net photosynthetic activity of leaves was measured in a mixed grass (Setaria sphacelata var. sericea)-legume (Desmodium intortum) pasture stand using a method based on concurrent measurement of the rate of CO₂ exchange, and ¹⁴CO₂ dosing followed by rapid harvesting according to height strata. Comparisons were also made between plots which differed in the period of regrowth following defoliation. The usual superiority of leaf net photosynthetic rates of a C₄ grass, compared with C₃ legume leaves, was found in the upper, well illuminated strata. These rates were, however, much lower than those usually described for horizontally exposed leaves, primarily because leaves in the pasture stand were inclined to the horizontal. At greater depth in the canopies, the superiority of rates in the grass was less evident, and consequently the relative contributions of grass and legume to canopy photosynthesis became more dependent on their leaf area indices. Attention is drawn to the relative simplicity of the method for examining the contribution of leaves, which may differ according to species or position in the canopy, to productivity of the whole stand.     

The breakdown and decomposition of sweet chestnut (Castanea sativa mill.) and beech (Fagus sylvatica L.) leaf litter in two deciduous woodland soils

Summary Changes in the carbon, hydrogen, nitrogen and polyphenol content of chestnut and beech leaves were measured during the first year after fall.Chestnut leaves had an initial carbon, hydrogen and nitrogen content (by weight) of 48.71%, 5.56% and 0.77% respectively; beech had a similar carbon and hydrogen content (47.77% and 5.36%) but less nitrogen (0.56%).Both leaf litter types showed percentage increases in nitrogen content during the study period but only the beech showed absolute increases in nitrogen content of up to 66.7% of the initial weight present in the leaves. The percentage increases in the nitrogen content of chestnut litter were largely attributable to more rapid losses of non-nitrogenous leaf constituents while the weight of nitrogen present in the leaves remained relatively constant.The percentage carbon and hydrogen contents of the chestnut and beech litter showed changes of less than 1% throughout the year, indicating that carbohydrate losses were directly proportional to weight losses.Soil animals fed on chestnut leaves to a far greater extent than beech leaves; this difference did not appear to be directly attributable to differences between the nitrogen contents or C/N ratios of the two leaf litter species. The gross polyphenol contents of chestnut and beech litter showed an intraspecific inverse correlation with the feeding activities of soil animals on the leaves, but did not account for interspecific differences in leaf palatability since chestnut leaves were eaten when they contained higher polyphenol concentrations than beech leaves. However, there was an interspecific negative correlation between palatability and the presence of protocatechuic and gallic acids.     

Utility of information in photographs taken upwards from the floor of closed-canopy deciduous broadleaved and closed-canopy evergreen coniferous forests for continuous observation of canopy phenology

Hemispherical photographs taken on forest floors are used to monitor seasonal changes in canopy openness or leaf area index in ecological studies. Those analyses usually use black and white images converted from the original colour images. Photographs taken by downwards-facing cameras installed on towers are used to provide detailed information on leaf expansion, maturation and senescence of various tree species through the analysis of red, green and blue ‘digital numbers’ (DN_RGB) extracted from those images. To examine the usefulness of colour information encoded in upwards hemispherical photographs in monitoring canopy phenological characteristics, we examined the consistency of DN_RGB values between downwards and upwards images in deciduous broadleaved and evergreen coniferous forests in Japan. In the deciduous broadleaved forest, the DN_RGB values in the upwards images were able to detect canopy phenology almost as well as those in the downwards images. However, we found the effects on DN_RGB of (1) the spatial heterogeneity among observed points, (2) low-vegetation (before the beginning of leaf-expansion and after the end of leaf-fall period) and (3) white balance settings. In the evergreen coniferous forest, in contrast, the DN_RGB values in the upwards images did not capture canopy phenology. These different results may be attributable to the light attenuation characteristics in the canopies due to the geometries of leaves and branches. Thus, the DN_RGB values obtained from upwards images are almost as good as those of downwards images for monitoring detailed canopy phenology in deciduous broadleaved forests with a closed canopy.     

Genet structure and determinants of clonal structure in a temperate deciduous woodland herb, Uvularia perfoliata

1 We used isozyme variation to examine the genet structure of Uvularia perfoliata patches in gap and closed canopy habitats in a temperate deciduous forest in Maryland, USA.
2 A large patch in a gap habitat was composed of a small number of widely spread genets with many ramets, and a large number of genets with more restricted distribution and few ramets. Genets with many ramets were patchily distributed at a metre scale. Analysis of genet structure on a scale of square centimetres, however, revealed that the genets were highly intermingled with no clear boundaries between them. The presence at both scales of sampling of many genets with unique multilocus genotypes indicated continuing genet recruitment within the population.
3 In the closed canopy habitat, the patches examined were each composed of a single unique multilocus genotype, suggesting that each had developed by asexual propagation following the establishment of a single genet.
4 The clonal structure of U. perfoliata patches in both gap and closed canopy habitats therefore appears to depend on recruitment patterns of genets. Populations in closed canopy habitats are characterized by a 'waiting' strategy, in which asexual ramet production maintains populations until genet recruitment by seed production can occur under the more optimal conditions associated with canopy gaps. Extended sampling suggests that the genetic diversity of U. perfoliata populations is primarily controlled by the disturbance regime of the forest canopy.