Understorey Layer Research Articles

Spatial patterns of infiltration vary with disturbance in a shrub-encroached woodland

Woody plant encroachment is known to have substantial effects on a range of ecosystem processes. Research worldwide indicates that the area around shrubs and trees has higher levels of infiltration than the interspaces. Little is known, however, about the hydrological consequences of shrub removal on infiltration, and how this might be influenced by grazing. We examined the spatial patterns of infiltration across three treatments relating to shrub removal and grazing: (i) undisturbed (ungrazed, unploughed), (ii) grazed but unploughed, and (iii) grazed and ploughed. In general we found that disturbance was associated with a greater cover of bare soil but lower infiltrability, our laboratory–based measure of infiltration. At the undisturbed site, bare soil was patchy and localized, with an autocorrelation range or connectivity of 1.4 m. The autocorrelation range of infiltrability at this site (A0=3 m) was larger than would be predicted from the size of the shrub canopy, and this was attributed to the presence of a well–developed understorey layer and biological soil crust community. At both grazed sites, infiltration was confined to the immediate canopy area of the remaining shrubs (A0=1.2 m in the unploughed–grazed site). Additionally, there was increasing connectivity of bare soil with disturbance, up to 6.8 m at the ploughed–grazed site. With increasing disturbance, resource-rich shrub patches are likely to become more developed, further reinforcing their growth and persistence at the expense of the bare interspaces. Our results indicate the importance of shrubs for maintaining landscape connectivity, and the long-term unsustainable practice of removal by ploughing, which is likely to promote shrub dominance rather than suppression.

Temporal changes in forest plant communities at different site types

AbstractAimsGiven the significance of the herbaceous understorey layer for temperate forest ecosystem biodiversity and functioning, it is important to have a thorough understanding of its dynamics in response to environmental change. However, site‐specific factors such as soil type may cause differential temporal herb layer changes within a single study area under comparable external pressure. Surprisingly, relatively few studies have examined herb layer changes on different site types within the same forest complex. The aim of this study is to determine the temporal differences in herb vegetation and to compare these for two differing site types in the same forest complex.LocationAncient broad‐leaved woodlands traditionally managed as coppice with standards in South Belgium, an area with secondary deposits and a mild temperate climate.MethodsIn 2008 we re‐inventoried 43 vegetation recordings from 1953 to 1954 in forests on two site types (acid and neutral forests). First, we described differences in soil pH, litter and overstorey characteristics between the sites. Next, multivariate analysis, Ellenberg indicator value and CSR signature were used to determine differences in herb layer diversity and composition between both the two survey times and the two site types. Finally, we analysed temporal differences in individual species abundances and frequencies.ResultsThe two site types clearly differed with respect to soil, litter and overstorey characteristics. Temporal changes between the surveys were mostly highly significant on the neutral sites and mostly not significant on the acid sites. On both site types, the species pool size declined. On the neutral site, the mean plot species richness also declined. Based on the plant‐derived characteristics (Ellenberg indicator values) of the plots, light availability decreased and nitrogen availability significantly increased on the neutral sites.ConclusionInput of eutrophying deposits and management changes are seen as key drivers of herb layer changes in the study area over the last half‐century. However, our study suggests that site characteristics such as parent material and soil pH should also be considered. Together with the key drivers, incorporating differences in site characteristics may improve our understanding of temporal shifts in herb layer vegetation in response to environmental change.

Patterns of habitat use by female brown long‐eared bats presage negative impacts of woodland conservation management

AbstractReinstating forestry practices, such as coppicing, thinning the understorey and grazing, has become a key element of proposals for improving the conservation value of broadleaved woodlands in Europe. However, the consequences of such woodland management for bats are poorly understood because of a lack of knowledge concerning their habitat requirements. We studied the brown long‐eared bat Plecotus auritus in South East England to determine how their patterns of habitat use could inform conservation management. Radio‐tracking of 38 adult females showed that they foraged primarily in woodland and that each had a foraging area (mean = 4.4 ha) that they returned to on successive nights. Core foraging areas (mean = 2.1 ha) were characterized by more cover and greater species diversity in the understorey layer than more peripheral areas. Hedgerows were also used for foraging in the late summer and autumn. Most conservation activities for this species have focused on protecting roosts in houses and other buildings. While such protection is important for bat conservation, efforts should also be made to protect foraging habitats in woodlands by maintaining cover of native species in the understorey layer and hedgerows that provide connectivity between woodland patches. Common conservation management practices, such as reinstating coppicing or grazing in semi‐natural broadleaved woodlands, could be detrimental for P. auritus and other woodland bats. Their impact on bats should be tested experimentally before they are widely promoted as a woodland conservation strategy.

Roles of thinning intensity in hardwood recruitment and diversity in a conifer, Criptomeria japonica plantation: A 5-year demographic study

To evaluate the role of thinning intensity in increasing hardwood diversity in managed coniferous forests, we investigated the effects of environmental changes caused by thinning on the seedling demography (i.e. seedling emergence, survival, and growth) of hardwood species for 5years after thinning in 67% thinned (Intensive), 33% thinned (Weak), and unthinned treatments (Control) in a Cryptomeria japonica plantation in northern Japan. Intensive thinning strongly increased light and soil temperature but reduced litter accumulation, thus facilitating seed germination, seedling emergence, and seedling survival of primarily early- and mid-successional species compared to late-successional species. As a result, more early- and mid-successional species were observed in Intensive compared to Weak and Control, whereas the number of late-successional species did not differ among thinning intensities. Thus, the number of species was greatest in Intensive but lowest in Control throughout the 5years. However, Shannon’s diversity index (H′) did not strongly differ among thinning intensities, largely due to the predominance of the mid-successional species Cornus controversa, particularly in Intensive. In Control and Weak, both seedling survival and height were often greater for advance regeneration than for seedlings newly emerged in the year following thinning, whereas neither variable differed between advance regeneration and seedlings newly emerged in Intensive, mainly due to selective predation of advance regeneration by mammalian herbivores. These results suggest that the future composition of hardwoods can be roughly predicted by the composition of advance regeneration in Weak but by the composition of both advance regeneration and seedlings newly emerged in Intensive. When comparing large individuals (height >1.5m), the number of species was greatest in Intensive in 2008, 5years post-thinning, primarily due to rapid vertical growth regardless of successional status. These results suggest that within a C. japonica plantation, a canopy-level mixed conifer-hardwood forest would be more probable and occur more rapidly in Intensive compared to Weak. In Weak, enhanced species diversity would likely be restricted to the understorey layer because of the slower growth rate and lower survival rate of hardwood seedlings caused by the more rapid deterioration of favourable environmental conditions.

Vegetation dynamics of ash-alder swamp forests in north-eastern Poland

Zmiany roślinności na siedlisku olsu jesionowego w lasach północno-wschodniej Polski

Restoration of three forest herbs in the Liliaceae family by manipulating deer herbivory and overstorey and understorey vegetation

Background: Research on herbaceous vegetation restoration in forests characterised by overstorey tree harvests, excessive deer herbivory, and a dominant fern understorey is lacking. Most of the plant diversity found in Eastern hardwood forests in the United States is found in the herbaceous understorey layer. Loss of forest herbaceous species is an indicator of declining forest conditions. Aims: The combined effects of deer herbivory, competitive understorey vegetation removal, and overstorey tree removal on the abundance and reproductive capacity of three understorey herbs in the Liliaceae family were evaluated. Methods: A split-plot randomised block design was used with three replicates. Treatments included three harvest intensities, fenced/unfenced, herbicide/no herbicide-treated, prescribed burn/no prescribed burn, and all combinations. A generalised linear model was used to compare treatment effects over 8 years. Results: Both fruit production and cover increased significantly in fenced areas for all three species. There was a significant 6-year recovery period for cover of the three species in response to herbicide. There was a significant 4-year recovery period of fire-treated plots for fruit production of the three species. The most intensively cut, fenced, and herbicide-treated plots had the greatest increases in sapling and Rubus spp. cover. Cover and fruit production of the three herbs were significantly greatest in the moderate-cut treatment. Conclusions: Restoration of these three liliaceous species is most likely to occur in Eastern deciduous forests and similar forests using a combined fenced and moderate-cut treatment.

A new model for predicting understorey leaf area from biomass in eucalypt forest to test the ecohydrological equilibrium theory

Summary 1. Ecohydrological equilibrium theory predicts that vegetation leaf area approaches a maximum dictated by climate and available soil moisture, and that changes in the overstorey and understorey layers compensate such that combined leaf area is maintained. Thus, rapid recovery of understorey following overstorey thinning and burning can diminish catchment water yield increases expected as a result of reductions in evapotranspiration losses. However, the understorey layer is rarely considered in management decisions, in part because methods to estimate understorey leaf area are poorly developed. Improved methods are needed to advance our understanding of ecological and hydrological processes involving forest understorey. 2. We developed models for accurately estimating leaf area of the biodiverse understorey layer of eucalypt forests. Models based on biomass as the independent variable were simpler and more general than models based on above-ground nitrogen or N/C ratios which were sensitive to the relative proportions of N2-fixing plants. We applied our model to compare understorey leaf area with overstorey leaf area in regrowth eucalypt forest, and to derive estimates of leaf area for the world’s forests. 3. In thinned and prescribed burnt forest, understorey leaf area was inversely proportional to overstorey leaf area such that combined stand leaf area after only 4·5 years was unaffected by treatment. This represents the first reported confirmation of the ecohydrological equilibrium theory that is described in terms of the leaf area of the two layers. In contrast, understorey leaf area did not respond to thinning in plots with no follow-up burning. We conclude that more attention should be paid to strategies for managing understorey recovery when manipulating regrowth eucalypt forests for increased catchment water yields. 4.Synthesis and applications. Recovery in vegetation leaf area after thinning in eucalypt forest can be rapid due to the response of the understorey layer. We show that understorey leaf area can completely compensate for reductions in overstorey leaf area, consistent with ecohydrological equilibrium theory, within 5 years of disturbance if thinning is followed by prescribed burning. Applying our model to published biomass data for the world’s forests, we also show that forest understorey can have a leaf area comparable with some forest overstorey. Without this new model, these increases in biological understanding would be much more difficult to obtain. By simplifying the estimation of understorey leaf area, the new model will enable researchers to progress rapidly towards greater understanding of understorey and overstorey interactions in natural and disturbed forest ecosystems.

Saproxylic beetle assemblages in the Mediterranean region: Impact of forest management on richness and structure

Forests cover almost 30% of the Mediterranean region today, yet forest management activities have influenced structure and composition of both natural and planted forests. To date no study has been conducted to evaluate the impact of forest management on saproxylic beetle assemblages, although it is known that the Mediterranean is a biodiversity hotspot with a long-lasting human pressure on natural habitats. We provide an overview of saproxylic beetle assemblages of three forest types (mature Pinus halepensis forests, mature Pinus brutia forests, young Quercus calliprinos forests) in the East Mediterranean region using a one-year sample from 12 forest plots located in the north of Israel. The studied forest types differed in forest structure, but we found no significant difference in saproxylic beetle species richness. Aleppo pine forests showed the largest number of saproxylic beetle species. Forests dominated by P. brutia, a non-native tree species in Israel, show the lowest species number of all three forest types. Species composition differs substantially between oak and pine forests. A third of the species found either in P. halepensis or in Q. calliprinos forests being unique to these habitats, while a smaller proportion of unique beetle species is found in P. brutia forests. Several beetle species that were found both in oak and pine plots in our study develop exclusively on broadleaved shrubs or trees. This may be explained by the small distances between the studied pine trees and oaks in their proximity. Biodiversity in pine forests can be increased when these are mixed with broad-leaved trees, e.g. oaks in the understorey layer, as can be observed the natural regrowth in most of the planted pine stands in our research area. There is some evidence from other studies that older successional stages of oak forests are likely to host more species overall than the mature pine forests studied here. In order to enhance structural diversity foresters should allow for aging of single trees or stands, regardless of the tree species.

Different response to environmental factors and spatial variables of two attributes (cover and diversity) of the understorey layers

We investigated the relationships among the vertical layers of a temperate forest and the power of environmental and spatial factors to explain the variation in two attributes of shrub and herbaceous layers: cover and diversity. In the study site, 102 square plots with sides of 20 m were established in a stratified random design. Among the environmental factors we studied overstorey related factors, soil attributes and topographic related variables. To use the space as an explanatory variable, we applied the Principal Coordinates of Neighbourhood Matrices method. Variation partitioning with regression analyses was used to discover which variables better explained variation in cover and diversity within the shrub and herbaceous layers. The spatial patterns displayed by cover and diversity in the shrub and herbaceous layer were more similar between both layers than within the same layer. Along the same lines, the amount of variance explained by all the environmental (overstorey, soil and topography) and spatial variables together was higher in the models of cover than in those of diversity. The differences in the explained variation were primarily due to the higher spatial fraction in the models of cover. In general, shrub and herbaceous cover was higher on southern slopes with a more diverse overstorey, high values of soil temperature and low values of litter cover. Otherwise, higher values of shrub and herbaceous diversity were found on steep slopes with low values of leaf litter cover. However, while higher values of shrub diversity were found on southern slopes, herbaceous values were more patchily distributed. The differences in the amount of variation explained by the spatial variables in both attributes (cover and diversity) indicate their different spatial arrangement at the scale which we considered. While values of cover were more continuous in space, those of diversity showed a patchy distribution of higher values. The presence of this spatial component could be interpreted as the importance of seed dispersal or unmeasured environmental variables. The results indicate that the lack of management in temperate forests allows species movement in a heterogeneous environment favouring higher values of cover and diversity in the understory layers.

Mapping the understorey of deciduous woodland from leaf-on and leaf-off airborne LiDAR data: A case study in lowland Britain

This study examines the understorey information present in discrete-return LiDAR (Light Detection And Ranging) data acquired for temperate deciduous woodland in mid summer (leaf-on) and in early spring when the understorey had mostly leafed out, but the overstorey had only just begun budburst (referred to here as leaf-off). The woodland is ancient, semi-natural broadleaf and has a heterogeneous structure with a mostly closed canopy overstorey and a patchy understorey layer. In this study, the understorey was defined as suppressed trees and shrubs growing beneath an overstorey canopy. Forest mensuration data for the study site were examined to identify thresholds (taking the 95th percentile) for crown depth as a percentage of crown top height for the six overstorey tree species present. These data were used in association with a digital tree species map and leaf-on first return LiDAR data, to identify the possible depth of space available below the overstorey canopy in which an understorey layer could exist. The leaf-off last return LiDAR data were then examined to identify whether they contained information on where this space was occupied by suppressed trees or shrubs forming an understorey. Thus, understorey was mapped from the leaf-off last return data where the height was below the predicted crown depth. A height threshold of 1 m was applied to separate the ground vegetation layer from the understorey. The derived understorey model formed a discontinuous layer covering 46.4 ha (or 31% of the study site), with an average height of 2.64 m and a 77% correspondence with field data on the presence/absence of suppressed trees and shrubs (kappa 0.53). Because the first return data in leaf-on and leaf-off conditions were very similar (differing by an average of just 0.87 m), it was also possible to map the understorey layer using leaf-off data alone. The resultant understorey model covered 39.4 ha (or 26% of the study site), and had a 72% correspondence with field data on the presence/absence of suppressed trees and shrubs (kappa 0.45). This moderate reduction in the area of understorey mapped and associated accuracy came with a saving of half of all data acquisition and pre-processing costs. Whilst the understorey modelling presented here undoubtedly benefited from the specific timing of LiDAR data acquisition and from ancillary data available for the study site, the conclusions have resonance beyond this case study. Given that the understorey and overstorey canopies in lowland broadleaf woodland can merge into one another, the modelling of understorey information from discrete-return LiDAR data must consider overstorey canopy characteristics and laser penetration through the overstorey. It is not adequate in such circumstances to apply simple height thresholds to LiDAR height frequency distributions, as this is unlikely to distinguish whether a return has backscattered from the lower parts of the overstorey canopy or from near the surface of the understorey canopy.

Silvopastoralism in New Zealand: review of effects of evergreen and deciduous trees on pasture dynamics

Complex interactions between livestock, trees and pasture occur in silvopastoral systems. Between trees and pasture, competition for soil resources (nutrients and water) occurs, becoming especially relevant when one of them is in scarce supply. Trees reduce light and water reaching the understorey layers according to tree density and canopy size. However, they may ameliorate extreme climatological features (reducing wind speed and evapotranspiration, and alleviating extreme temperatures), and improve soil properties, for example, deciduous tree litter may contribute to increased pH and soil nutrient concentrations. During tree establishment, there are generally negligible effects on pasture, irrespective of tree type. However, there is a decline in pasture production and nutritive value under shade with increasing tree age and higher stand density. Under the same conditions, deciduous trees affect pasture later (extinction point of pasture occurs at 85% of canopy closure) than evergreen trees (about 67% for Pinus radiata D. Don). This is mainly because deciduous trees have a leafless period that enables pasture recovery, and their litter smothers pasture less intensely because of its relatively fast decomposition. Silvopastoral studies conducted in New Zealand are reviewed to discuss these effects, and differences in the effects of evergreen and deciduous trees are shown using the examples of P. radiata, and Populus and Salix spp. respectively, which exist in many temperate countries. Future research needs are outlined.

A Survey of Lichens and Bryophytes in White Spruce, <em>Picea glauca</em>, Tree Islands on a Calcareous Beach Ridge in Northeastern Manitoba

Studies on the diversity of lichens and bryophytes in northern ecosystems have focused on open tundra and boreal forests. Krummholz tree islands have received little attention. This study examined species’ diversity of lichens and bryophytes among islands of White Spruce trees in northern Manitoba. Thirty-three species were found in the tree islands with 11 additional species forming the understorey layer. The trees were dominated by epiphytic lichens and the understorey was dominated by pleurocarpous mosses. The most common lichens were widespread species. Rare lichens in the study area included Protopannaria pezizoides and Alectoria nigricans growing in the shaded interior of the tree islands. The age and density of the tree islands may produce habitat conditions different from those in mature White Spruce boreal forests. Comparative studies between White Spruce krummholz and other White Spruce stands are needed.

Overstorey tree species regulate colonization by native and exotic plants: a source of positive relationships between understorey diversity and invasibility

ABSTRACTThe North American woody species, Prunus serotina Ehrh., is an aggressive invader of forest understories in Europe. To better understand the plant invasion process, we assessed understorey plants and Prunus serotina seedlings that have colonized a 35‐year‐old replicated common‐garden experiment of 14 tree species in south‐western Poland. The density and size of established (> 1 year old) P. serotina seedlings varied among overstorey species and were related to variation in light availability and attributes of the understorey layer. In a multiple regression analysis, the density of established P. serotina seedlings was positively correlated with light availability and understorey species richness and negatively correlated with understorey species cover. These results suggest that woody invader success is adversely affected by overstorey shading and understorey competition for resources. Simultaneously, however, invader success may generally be positively associated with understorey species richness because both native and invasive plant colonization respond similarly to environmental conditions, including those influenced by overstorey tree species. Identification of characteristics of forests that increase their susceptibility to invasion may allow managers to target efforts to detect invasives and to restore forests to states that may be less invasible.

Existing fire behaviour models under-predict the rate of spread of summer fires in open jarrah (Eucalyptus marginata) forest

SummaryFire behaviour data from Project Vesta experimental fires were used to evaluate the fire behaviour relationship on the Forest Fire Danger Meter (FFDM), the Forest Fire Behaviour Tables (FFBT) for Western Australia and the fire spread model of Burrows (1999) for predicting the rate of spread of fires in jarrah (Eucalyptus marginata) forest under dry summer conditions. Experimental fires were conducted at two sites in south-western Australia under conditions of moderate to high forest fire danger with fine fuel moisture contents of 6–9% oven dry weight and wind speeds up to 20 km h−1 (at 10 m in the open). Fuels ranged in age from 2 to 22 y since the last fire and had understorey shrub layers from 0.5 to 2.0 m tall. Mean rates of spread for experimental fires were 392 m h−1 and 405 m h−1 at the low and tall shrub sites respectively, with the fastest fires spreading at close to 1200 m h−1. Fires spread two to three times faster than predicted by the FFDM and FFBT fire spread models, and up to five times faster than predicted by the spread model of Burrows. Both the FFDM and FFBT models predicted fire spread better at the low shrub fuel site and when wind speeds were <12.5 km h−1. All models under-predicted fire spread at the tall shrub site and grossly under-predicted fire spread when wind speeds were >12.5 km h−1. We argue that existing fire behaviour models under-predict because they were developed using data from fires that had not achieved a quasi-steady rate of spread, whereas the line ignition technique used during Project Vesta experiments resulted in fires travelling at a speed closer to their potential rate of spread for the prevailing conditions. Existing guides remain valid for predicting spread during the early stages of fire growth when fires are developing from a point ignition and the headfire remains narrow.

Recovery of pristine boreal forest floor community after selective removal of understorey, ground and humus layers

In boreal spruce forests that rarely experience extensive disturbances, fine-scale vegetation gaps are important for succession dynamics and species diversity. We examined the community implications of fine-scale gap disturbances by selective removal of vegetation layers in a pristine boreal spruce forest in Northern Finland. The aim was to investigate how the speed of recovery depends on the type of disturbance and the species growth form. We also wanted to know if there appeared changes in species composition after disturbance. Five different treatments were applied in the study: Control, removal of the ground layer (bryophytes and lichens), removal of the understorey layer (dwarf shrubs, herbs and graminoids), removal of both the ground and understorey layers, and complete removal of the vegetation and humus layers above the mineral soil. The vegetation recovery was monitored in terms of cover and species numbers over a 5-year period. Understorey layer cover, composed mainly of clonal dwarf shrubs, recovered completely in 4 years in treatments where the humus layer remained intact, whereas ground layer cover did not reach the control level in plots from where bryophytes and lichens were removed. Recovery was faster in terms of species number than species cover. Bryophytes, graminoids and dominant dwarf shrubs appeared in all disturbed plots quickly after disturbance. Seedlings of trees appeared exclusively in disturbed plots. Graminoids dominated after the removal of humus layer. The results indicate that the regeneration of forest floor after small gap disturbance occurs mainly by re-establishment of the dominant species. Although destruction of the humus layer leaves a long-lasting scar to the forest floor, exposing of mineral soil may enhance the sexual reproduction of dominant species and the colonization of weaker competitors.

The forest structure and ecosystem quality in conditions of anthropogenic disturbance along productivity gradient

Forest structure and diversity have generally been well studied, but the effects of anthropogenic disturbance on structural differences of hemi-boreal old-growth and managed mature stands have not been quantified along a wide range of the productivity gradient. This study compared 39 quantitative or qualitative characteristics and various widely accepted biodiversity indicators of a stand, its understorey and the forest floor in old-growth and conventionally managed mature stands of dry alvar and fresh boreo-nemoral forests. This study has to produce a statistically supported set of indicators for evaluating of forest “naturalness”. We examined 154 stands over a wide biogeographical range in Estonia. Many forest structural characteristics, including stand basal area and composition, amount of dead wood, and coverage of understorey layers (shrub, herb and moss layers) followed productivity and/or biogeographical gradients. Old-growth forests had higher proportions of deciduous trees, a larger amount of coarse woody debris (CWD, consisting of logs and snags), a higher frequency of logs in each decay class, a denser understorey and herb layer, and a more heterogeneous pattern of herb layer diversity than mature managed forests. We found a correlation between live trees greater than 40 cm in diameter and forest age. The effects of forest management on the forest floor are both direct and indirect. Anthropogenic disturbance directly decreased shrub and herb layer coverage. Indirectly forest management increased herb layer coverage, proportion of graminoids, and species richness of the herb layer by improving light conditions as stand canopy was opened. The sets of indicators for assessing ecosystem quality in each forest site-type have overlapping features, such as the amount of dead wood, canopy closure of the stand and the presence of woodpeckers and specific lichens. Several other old-growth or disturbance indicators are forest-type specific, related to the composition of shrub and herb layer vegetation. Results suggest that stands managed with an extended rotation can be compositionally very similar to old-growth forests. Stands differ quantitatively in structural features, but these differences are confounded by other environmental factors, such as soil productivity, forest age or biogeography. Mature and old-growth forests still enclose features created by the mid-term (decades) and long-term (centuries) history of forest management practices.

Ecological interactions between fungi, other biota and forest litter composition in a unique Scottish woodland

The composition of forest litter and understorey layer, and fungal biomass (in terms of ergosterol) were measured in eight subplots over a winter–spring period (January to April). The sampling site was positioned in a range of woodland habitats (variously dominated by beech, Fagus sylvatica; birch, Betula pendula × pubescens, and oak Quercus petraea) and a clear area covered with grass (dominated by Holcus lanatus). The results were analysed together with data on bacteria and microinvertebrates available from parallel research. Levels of ergosterol in individual subplots ranged between 50 and 160 μg g−1 DW. Fungal biomass decreased in March, and then increased significantly in April. Stepwise regression models for ergosterol indicated positive relationships with moisture content (February), bacteria (all but February and March), flagellates (February) and plant-feeding nematodes and flies (January, overall). The relationships with roots, seeds, the collective variable ‘other microinvertebrates’ (all March), amoebae (February) and fragments (March, overall) were negative, while the relationship between fungi- and microbial-feeding nematodes changed sign between February (−) and March (+). Results of analysis of covariance for fungal ergosterol were significant only for January and the combined dataset. In January, fungi were shown to be significantly related to amoebae, bacteria and a collembolan Folsomia candida, while the only significant predictor returned by the overall model was bacteria. Correlation analysis confirmed some effects already noted, and revealed a number of further interactions. The results highlighted the complexity of factors influencing temporal dynamics and spatial variability of fungal biomass in forest litter. Most of the registered interactions appeared to be transient, and this should be taken into account while interpreting environmental observations. Interpretation of the specific relationships is given and implications for further research and overall ecosystem functioning are discussed.

Does resource availability govern vertical stratification of small mammals in an Australian lowland tropical rainforest?

Mammal assemblages of rainforest communities are commonly vertically stratified. This can be associated with competition for, or access to, resources in the upper canopy layers of the forest. This study investigated the extent of vertical stratification in a small mammal community of a tropical rainforest and whether any structure was related to resource abundance. The mammal community was vertically stratified, with Pogonomys mollipilosus and Cercartetus caudatus found only in the upper canopy layers and Rattus sp., Isoodon macrourus and Antechinus flavipes rubeculus on the ground and in the understorey layer. Melomys cervinipes and Uromys caudimaculatus were found at all four height layers. Total rodent captures were not significantly correlated with the abundance of fruit and flower resources, but arboreal captures of M. cervinipes and P. mollipilosus were correlated with the number of individual canopy trees of four prominent flower- and fruit-yielding species: Syzigium sayeri, Acmena graveolens, Argyrodendron perelatum and Castanospermum australe. We suggest that arboreal behaviour in these rodents serves to provide the advantages of first access to food resources, the availability of abundant resources in the canopy, and, ultimately, reduced competition in the upper strata.

Cyanobacteria of inselbergs in the Atlantic rainforest zone of eastern Brazil

Inselbergs of the Atlantic rainforest zone in south-eastern Brazil typically appear black because of the presence of a dense cyanobacterial film. We investigated this autotrophic, microorganism covering on the exposed rock surfaces of five selected inselbergs along a latitudinal gradient, from Parati Mirim in the south to Serra dos Amores in the north. The biofilm was 0.1–0.5 mm thick and consisted mainly of cyanobacteria and rarely cyanobacterial lichens, together with a few filamentous deuteromycete fungi. The biofilm itself was stratified, consisting of three strata: (1) an endolithic stratum, with chasmolithic Chroococcidiopsis sp. and Gloeocapsa sanguinea; (2) an epilithic understorey layer with unicellular forms like G. sanguinea and Xenotholos kerneri; and (3) an upper epilithic layer, composed of filamentous cyanobacteria like Scytonema myochrous, S. ocellatum, Stigonema mamillosum and S. hormoides. In total, 16 species of cyanobacteria, belonging to eight different genera were found on exposed rock surfaces uninfluenced by higher vegetation. The unicellular forms G. sanguinea and X. kerneri and the filamentous cyanobacterium Scytonema ocellatum were the most frequent species. When compared with the cyanobacterial flora of inselbergs in Venezuela, French Guyana and Ivory Coast, the Brazilian inselbergs showed the greatest similarities to those of Venezuela.

Responses of vertebrates to pastoralism, military land use and landscape position in an Australian tropical savanna

Abstract Despite the hegemony of pastoralism over most of Australia’s tropical savannas, its impacts upon biodiversity are poorly known. There is even less knowledge about the impacts of military training, a recent, but rapidly expanding, alternative land use. We compare impacts of these land uses upon mammals, birds, reptiles and frogs at a site in north‐eastern Australia, with sampling from 24 quadrats stratified by four landscape positions (upper slope to riparian) and three current land‐use types (pastoralism, military training and undisturbed). Prior to exclusion in 1967, the whole study area had been subjected to grazing over the course of approximately 100 years, so differences observed strictly reflect responses to changed land use (largely cessation from grazing) over the period of 32 years subsequent to the imposition of the present regime. The four classes of vertebrates showed contrasting responses. Frog distribution was unrelated to land use, but strongly associated with landscape position. Reptiles showed a very strong response to land‐use type but not to landscape position. The total abundance and richness of reptiles was greater in ungrazed (i.e. military and undisturbed) than in grazed quadrats. The total abundance and species richness of birds varied strongly with landscape position but was unrelated to land use. However, many individual bird species showed significant responses to land‐use type, and bird species composition was significantly related to both land‐use type and landscape position. The richness of the mammal fauna was weakly related to landscape position and not related to land‐use type. A few individual mammal species showed significant responses to either or both factors, but mammal species composition was significantly (albeit weakly) related only to land‐use type. With due regard to some interpretative constraints in the study design, and the history of the site prior to this study, these results suggest that pastoralism leads to a substantial rearrangement of the vertebrate fauna, and particularly so for reptiles and those mammals and birds associated with the ground and understorey layers. Given the extent of pastoralism across the tropical savannas, these results suggest that this industry has contributed to major and widespread change in the savanna fauna. In contrast to pastoralism, military land use (at least at the relatively low intensity examined here) produced little change in vertebrate assemblages.