Mature Forest Sites Research Articles

Hyperdiversity of ectomycorrhizal fungus assemblages on oak seedlings in mixed forests in the southern Appalachian Mountains

Diversity of ectotrophic mycobionts on outplanted seedlings of two oak species (Quercus rubra and Quercus prinus) was estimated at two sites in mature mixed forests in the southern Appalachian Mountains by sequencing nuclear 5.8S rRNA genes and the flanking internal transcribed spacer regions I and II (ITS). The seedlings captured a high diversity of mycorrhizal ITS-types and late-stage fungi were well represented. Total richness was 75 types, with 42 types having a frequency of only one. The first and second order jackknife estimates were 116 and 143 types, respectively. Among Basidiomycetes, tomentelloid/thelephoroid, russuloid, and cortinarioid groups were the richest. The ascomycete Cenococcum geophilum was ubiquitously present. Dominant fungi included a putative Tuber sp. (Ascomycetes), and Basidiomycetes including a putative Craterellus sp., and Laccaria cf. laccata. Diversity was lower at a drier high elevation oak forest site compared to a low elevation mesic cove--hardwood forest site. Fungal specificity for red oak vs. white oak seedlings was unresolved. The high degree of rarity in this system imposes limitations on the power of community analyses at finer scales. The high mycobiont diversity highlights the potential for seedlings to acquire carbon from mycelial networks and confirms the utility of using outplanted seedlings to estimate ectomycorrhizal diversity.

Differences in habitat quality explain nestedness in a land snail meta‐community

We set up two alternative hypotheses on how environmental variables could foster nestedness; one of “nested habitats” and another of “nested habitat quality”. The former hypothesis refers to situations where the nestedness of species depends on a nestedness of discrete habitats. The latter considers situations where all species in an assemblage increase in abundance along the same environmental gradient, but differ in specialisation or tolerance. We tested whether litter‐dwelling land snails (terrestrial gastropods) in boreal riparian forest exhibited a nested community structure, whether such a pattern was related to differences in environmental variables among sites, and which of the two hypotheses that best could account for the found pattern. We sampled litter from 100 m2 plots in 29 mature riparian forest sites along small streams in the boreal zone of Sweden. The number of snail species varied between 3 and 14 per site. Ranking the species‐by‐site matrix by PCA scores of the first ordination axis revealed a similarly significant nested pattern as when the matrix was sorted by number of species, showing that the species composition in this meta‐community can be properly described as nested. Several environmental variables, most notably pH index, were correlated with the first PCA axis. All but two species had positive eigenvectors in the PCA ordination and the abundance increased considerably along the gradient for most of the species implying that the hypothesis of “nested habitats” was rejected in favour of the “nested habitat quality” hypothesis. Analyses of nestedness have seldom been performed on equal sized plots, and our study shows the importance of understanding that variation in environmental variables among sites can result in nested communities. The conservation implications are different depending on which of our two hypotheses is supported; a conservation focus on species “hotspots” is more appropriate if the communities are nested because of “nested habitat quality”.

Importance of Non-Stand-Replacing Fire for Development of Forest Structure in the Pacific Northwest, USA

Abstract Old-growth forests have been the subject of much political concern and forestry research in the 20th century. Evidence that many old-growth stands of the western Oregon Cascade Range have experienced multiple low- to moderate-severity fires has led to the hypothesis that such fires have sustained structural complexity in certain temperate coniferous forests. Multiple regression analysis was used to assess the role of historical non-stand-replacing fire for 90 mature and old forest sites on a 450-km2 landscape of mixed-severity fire regime in western Oregon. The occurrence of non-stand-replacing fire was inferred from the relative frequency of fire scars on Pseudotsuga menziesii. Results suggest that in the central western Cascades, the occurrence of non-stand-replacing fire has favored variability in tree diameter sizes, larger trees, and a greater component of shade-tolerant tree species, after accounting for the effects of elevation, slope aspect, and stand age. However, the fire scar variable explained a relatively small percentage of the variance not explained by these effects, with partial R2 values ranging from 0.05 to 0.16. A path analysis suggested that the effects of stand age on forest structure can be partitioned into direct effects (gap dynamics and successional processes in the absence of disturbance) and indirect effects (older stands have had more time to experience non-stand-replacing fire), with the indirect effects explaining a large component of forest structural attributes that are typically associated with the old-growth seral stage. While the cumulative and long-term effects of non-stand-replacing fire in this region are likely complex, it would seem prudent to include such disturbances as a key ecosystem process, where management practices seek to emulate natural disturbance regimes or facilitate the development of old-growth forest structures. FOR. SCI. 50(2):245–258.

IMPACTS OF EARLY‐ AND LATE‐SERAL MYCORRHIZAE DURING RESTORATION IN SEASONAL TROPICAL FOREST, MEXICO

Disturbance of vegetation and soil may change the species composition of arbuscular mycorrhizal fungi (AMF), which may in turn affect plant species responses to AMF. Seasonal tropical forest in Mexico is undergoing rapid conversion to early‐successional forest because of increased wildfire and may require restoration. The responses of six early‐ and late‐successional tree species were tested using early‐ and late‐successional AMF inoculum. The plants were germinated in the shadehouse and received three inoculum treatments: (1) soil from a two‐year‐old burned site, (2) soil from a mature forest site, or (3) uninoculated controls. They were transplanted as seedlings to a site prepared by burning, and their growth was measured from September 1997 to November 2000. All six species had the greatest growth response to early‐seral inoculum, but the response to late‐seral inoculum varied. Two tree species, Ceiba pentandra and Guazuma ulmifolia, were smallest with late‐seral inoculum, even smaller than the uninoculated plants, and the other species, Brosimum alicastrum, Havardia albicans, Acacia pennatula, and Leucaena leucocephala, had intermediate growth with late‐seral inoculum. Of these, Brosimum, Havardia, and Ceiba occur in late‐successional forest, and the others are early seral. Of the several growth measurements (height, cover, biomass, stem diameter), stem‐diameter responses to inoculum were still significantly different into the third year for four of the species. The uninoculated plants became infected by residual inoculum in the burned experimental site within three months of transplanting, yet mycorrhizal responses persisted. The treatment size differences may be due to different species composition of the inocula. The early‐seral inoculum was dominated by small‐spored Glomus spp., while the late‐seral inoculum had a higher density of large‐spored Gigasporaceae. The latter are known from greenhouse experiments to promote a smaller plant‐growth response than Glomus. Mature forest trees may withstand the carbon drain from Gigasporaceae better than establishing seedlings, so the growth patterns we observed with inoculum source are consistent with a rapidly growing successional forest, followed by slower‐growing mature forest. The results suggest that early‐seral AMF should be used when seedlings are inoculated for restoration, even for late‐seral tree species.

A comparison of brachyuran crab community structure at four mangrove locations under different management systems along the Melaka Straits-Andaman Sea Coast of Malaysia and Thailand

Brachyuran crab community structure was compared between mangrove sites under different management systems from four locations along the Melaka Straits-Andaman Sea Coast. Klong Ngao, a mangrove estuary in Ranong Province of southern Thailand, lies within a Biosphere Reserve designated in 1997. Sites were positioned in plantations at a former charcoal concession forest, a disused tin mine, and an abandoned shrimp pond along this estuary. The Merbok estuary in Kedah, Malaysia, is partially managed: the mangroves are cut for charcoal and poles on a small scale and the forests are left to regenerate naturally. The Matang Mangrove Forest Reserve in Perak, Malaysia, is heavily exploited but well managed, forRhizophora wood to produce charcoal, and has been for 100 years. Sites were positioned in plantations of different ages. Kuala Selangor Nature Park, Selangor, Malaysia, was established as a nature reserve in 1987 and contains mature mangrove forest regenerating naturally from previous selective felling. At Klong Ngao and Matang, mature reserve forest sites were also studied for comparison with plantation sites. The sites included both upstream and downstream locations and were of similar area, minimizing effects from possible species-area relationships. Sites were chosen with similar environmental conditions and with a dominance ofRhizophora spp. At each site per location, the brachyuran crabs were sampled quantitatively in 100 m2 quadrats by three independent 15-min timed crab catches. The crab community recorded was analyzed by univariate and multivariate statistical techniques. Management history plays an important role in moderating the crab community structure. The crab community also changes with the age of the mangrove forest stand. Sesarmid crabs consistently dominated in mature forests, whereas young plantations were colonized mainly by ocypodid crabs. The findings show that heavily effected sites—e.g., disused tin mining areas, former concession forests, and abandoned shrimp ponds—can be rehabilitated by planting mangroves and that the crab community is a useful ecological indicator of habitat status.

AVIAN COMMUNITY RESPONSE TO SOUTHERN PINE ECOSYSTEM RESTORATION FOR RED-COCKADED WOODPECKERS

The effects of Red-cockaded Woodpecker (Picoides borealis) management on nontarget birds is not widely known. Intensive management for pine specialists such as the Red-cockaded Woodpecker may negatively impact both Nearctic-Neotropical and Temperate Zone migrants associated with hardwood vegetation. To evaluate possible positive and negative associations, we surveyed avian communities from 1995–1997 using point counts within managed Red-cockaded Woodpecker cavity tree clusters and mature forest control sites in longleaf pine (Pinus palustris) and loblolly (P. taeda)-shortleaf (P. echinata) pine habitats. In general, sites managed for Red-cockaded Woodpeckers supported more diverse and numerous bird populations than mature forest control sites. During the breeding season in loblolly-shortleaf and longleaf pine habitats, respectively, species richness was 47% and 23% greater, avian abundance was 57% and 65% greater, and bird species diversity was 25% and 21% greater within managed Red-cockaded Woodpecker cluster sites than within control sites. During winter, species richness and avian abundance each were 52% higher within managed Red-cockaded Woodpecker cluster sites than control sites in loblolly-shortleaf pine habitat.

Mangrove Rehabilitation and Intertidal Biodiversity: a Study in the Ranong Mangrove Ecosystem, Thailand

The diversity, abundance, biomass and community structure of crustacean and molluscan macrofauna were studied in the Ranong mangrove forest ecosystem on the Andaman Sea coast of southern Thailand. After a history of commercial exploitation the mangroves along the Klong Ngao tidal creek have been assigned conservation status within a new Ranong Biosphere Reserve established in 1997. Over the past 12 years, several areas of mangrove destroyed or degraded by wood harvesting, tin mining and aquaculture, have been rehabilitated on a pilot basis by planting monocultures of mangrove seedlings using four common local species (Rhizophora apiculata, R. mucronata, Bruguiera cyclindrica and Ceriops tagal). These plantation forests with different past management histories were compared with a natural, mixed, mature mangrove forest which has been conserved for about 40 years. Macrofauna were sampled within a 100m2 vegetation quadrat in each study site. Crustaceans were sampled quantitatively by 3×15min timed hand catches per site. Molluscs were sampled in 3×m2 quadrats positioned around three randomly selected trees in each vegetation quadrat. The lowest crustacean and molluscan diversity was recorded from the former tin mining site. The highest diversity was recorded from aRhizophora plantation in the natural mixed forest area for both crustaceans and molluscs. The vegetation community structure was not correlated with the environmental variables measured, or with macrofauna community structure. Of the environmental parameters chosen, the crustacean community structure was best expressed by shore level, while for molluscan diversity and abundance it was soil moisture content. The macrofauna community structure at the tin mining site was significantly different to the other sites, and was dominated by a single species of crab, Metaplax elegans. Grapsid crabs, especially sesarmid species, dominated over ocypodid crabs in the mature forest site, whereas Uca species and other ocypodids were more abundant than grapsids in the degraded concession forest area. Snails of the families Neritidae and Ellobiidae were the most abundant molluscs in the mature forest, whereas Littoriinidae, Assimineidae and Potamidae species were more representative of the younger plantation sites. The findings from this study suggest that some of these well represented families of mangrove macrofauna could be used as indicators of ecological change as part of a long term environmental monitoring programme in Ranong and other areas in Southeast Asia where mangroves are being rehabilitated.

Macrofungal diversity and community ecology in mature and regrowth wet eucalypt forest in Tasmania: A multivariate study

Abstract The biodiversity of macrofungi in mature and young regrowth Tasmanian wet forests is described at the species level and at the community level. The macrofungal communities studied were much more species‐rich than their vascular plant counterparts, with the total number of macrofungal taxa outnumbering vascular plants by four to one. This ratio applied in both mature and young regrowth forest sites. Some 242 taxa of macrofungi were recorded, of which 132 were identified to species level, the remainder to species groups or higher taxa. Distinct communities could be discerned from multivariate analysis (ordination and classification) of vascular plant and macrofungal data from the mature and regrowth sites. The two vascular plant communities had different fire histories, and this difference is also assumed to account for the separation of the macrofungal communities of the two forest types. There was generally a high level of congruence between the vascular plant and the macrofungal communities. However, one young regrowth site, which was relatively close to the mature sites in the ordination space for the analysis of vascular plants, was distant from the mature forest sites for the analysis of macrofungi. Another regrowth site, which had experienced wildfire rather than silvicultural regeneration, clustered with mature sites for some analyses of the macrofungal assemblage. Variation in the macrofungal communities was correlated with a different set of the measured environmental variables than was variation in the vascular plant communities. Mature and young regrowth forests were found to have distinctly different macrofungal floras, with approximately 40% of the taxa in each forest type being restricted to that type of site. Suitable indicator taxa (restricted or preferential to particular forest types) for use in further studies are suggested.

Impacts of a Flood on Small Mammal Populations of Lower Missouri River Floodplain Forests

Small mammal responses to flooding in the lower Missouri River floodplain are poorly understood. Our study examined the survival of marked populations of small mammals in mature and regenerating forest seral stages in response to a brief flood. Peromyscus spp. were the most abundant species captured before (94% of individuals captured) and after (98%) the flood and survival in inundated mature forest sites did not significantly differ from unflooded reference sites. However, the lowest number (n = 14) and percentage (29%) of Peromyscus spp. recaptures occurred in a young regenerating forest site. Elliot's short-tailed shrews (Blarina hylophaga), which are less adapted for arboreal habitats, declined in abundance after the flood.

Patterns of leaf‐pathogen infection in the understory of a Mexican rain forest: incidence, spatiotemporal variation, and mechanisms of infection

This study assessed the levels of damage by leaf pathogens and their variability in terms of host species, space (four mature forest sites) and season of the year (dry and rainy), and the mechanisms of infection in the understory of the Los Tuxtlas tropical rain forest. Sixty-five percent of the species surveyed in the dry season (N = 49) and 64.9% of those surveyed in the rainy season (N = 57) were damaged by fungi. Leaf area damaged per plant, on average, was <1% (range: 0.25-20.52%). There was considerable variation in the degree of infection among species, but not among sites and seasons. The survey showed that 43% of the leaves were damaged by herbivores and pathogens concurrently, 16% showed damage by insect herbivory alone, and only 1.4% of the sampled leaves showed damage by pathogens alone. Pathogenicity assays experimentally confirmed that the predominant mechanism of fungal establishment was wounding, such as that caused by herbivory (or other similar sources), and only rarely did infection occur through direct contact (without wounds). The results revealed the omnipresence of leaf fungal infection, although with low damage per plant, and the importance of herbivorous insects in the facilitation of fungal infection in tropical understory plants.

Paired‐tower measurements of carbon and energy fluxes following disturbance in the boreal forest

SummaryDisturbances by fire and harvesting are thought to regulate the carbon balance of the Canadian boreal forest over scales of several decades. However, there are few direct measurements of carbon fluxes following disturbances to provide data needed to refine mathematical models. The eddy covariance technique was used with paired towers to measure fluxes simultaneously at disturbed and undisturbed sites over periods of about one week during the growing season in 1998 and 1999. Comparisons were conducted at three sites: a 1‐y‐old burned jackpine stand subjected to an intense crown fire at the International Crown Fire Modelling Experiment site near Fort Providence, North‐west Territories; a 1‐y‐old clearcut aspen area at the EMEND project near Peace River, Alberta; and a 10‐y‐old burned, mixed forest near Prince Albert National Park, Saskatchewan. Nearby mature forest stands of the same types were also measured as controls. The harvested site had lower net radiation (Rn), sensible (H) and latent (LE) heat fluxes, and greater ground heat fluxes (G) than the mature forest. Daytime CO2 fluxes were much reduced, but night‐time CO2 fluxes were identical to that of the mature aspen forest. It is hypothesized that the aspen roots remained alive following harvesting, and dominated soil respiration. The overall effect was that the harvested site was a carbon source of about 1.6 gC m−2 day−1, while the mature site was a sink of about −3.8 gC m−2 day−1. The one‐year‐old burn had lower Rn, H and LE than the mature jackpine forest, and had a continuous CO2 efflux of about 0.8 gC m–2 day−1 compared to the mature forest sink of − 0.5 g C m−2 day−1. The carbon source was likely caused by decomposition of fire‐killed vegetation. The 10‐y‐old burned site had similar H, LE, and G to the mature mixed forest site. Although the diurnal amplitude of the CO2 fluxes were slightly lower at the 10‐y‐old site, there was no significant difference between the daily integrals (− 1.3 gC m−2 day−1 at both sites). It appears that most of the change in carbon flux occurs within the first 10 years following disturbance, but more data are needed on other forest and disturbance types for the first 20 years following the disturbance event.

Variation in Post-dispersal Seed Predation in Mature Peruvian Lowland Tropical Forest and Fallow Agricultural Sites1

Variation in post-dispersal seed predation between mature forest and fallow swidden agriculture sites (young forest) was examined for 26 tree and liana species in Peruvian lowland tropical forest. Exclosures were also used to determine the relative importance of vertebrate and invertebrate seed predators. Although species differed significantly in levels of predation, predation of seeds exposed to vertebrates was high (>75%) for all species, while seed predation by invertebrates was lower and more variable. Seed and seedling predation by insects was significantly higher in mature forest, while seed predation by rodents was higher in fallow areas. Other sources of mortality (primarily desiccation) were higher for seeds in fallow areas. The percentage of seeds moved was significantly different among species but not between forests.

Evaporation from Scots pine (Pinus sylvestris) following natural re-colonisation of the Cairngorm mountains, Scotland

Abstract. Recently, changing land-use practices in the uplands of Scotland have resulted in increased re-colonisation of wet heath moorland by natural Scots pine (Pinus sylvestris) woodland. The simple semi-empirical water use model, HYLUC, was used to determine the change in water balance with increasing natural pine colonisation. The model worked well for 1996. However, values of soil moisture deficit simulated by HYLUC diverged significantly from measurements in 1997 when rainfall quantity and intensities were less. Measured interception by the forest canopy (interception by the undergrowth was not measured) was very different from HYLUC simulated values. By changing interception parameters to those optimised against measured canopy interception, HYLUC simulated changing soil moisture deficits better and gave more confidence in the resulting transpiration values. The results showed that natural pine woodland interception may be similar to plantation stands although the physical structure of the natural and plantation forests are different. Though having fewer storage sites for interception in the canopy, the natural pine woodland had greater ventilation and so evaporation of intercepted rainfall was enhanced, especially during low intensity rainfall. To understand the hydrological changes that would result with changing land-use (an expansion of natural forests into the wet heath land), the modelled outputs of the wet heath and mature forest sites were compared. Evaporation, a combination of transpiration and interception, was 41% greater for the forest site than for the wet heath moorland. This may have significant consequences for the rainfall-runoff relationship and consequently for the hydrological response of the catchment as the natural woodland cover increases Keywords: Evaporation; interception; transpiration; water balance; Scots pine; forest

The biology of kauri (Agathis australis) in New Zealand 11. Nitrogen cycling in four kauri forest remnants

Four sites, two of which are dominated by kauri poles and two dominated by mature kauri trees, were investigated for total nitrogen content, nitrogen fixation, and nitrogen turnover. All sites have low foliage nitrogen concentration, and in most cases this is below the critical deficiency level of 0.81–0.92% N. Leaves may be retained on trees for up to 12 years and contain decreasing amounts of nitrogen as they age. Above‐ground kauri biomass contains &om 61 kg N ha‐1 in a young pole stand to 900 kg N ha‐1 in a mature stand. A large amount of nitrogen is contained in the forest floor, with up to 6.5 t N ha‐1 in the mature forest site. Mean residence time for nitrogen ranges from 9 to 192 years. Total ecosystem nitrogen of as much as 14 t ha‐1 was recorded in the oldest site, representing an extreme level of N storage and immobilisation. Nitrogen fixation by he living heterotrophs in decaying litter can account for at least 5 kg N ha‐1 yr‐1, which, when integrated over the life of the forest, accounts for the large build‐up in ecosystem N. Nitrogen use efficiency averages 155 g dry matter per g N, which is almost twice that of other forests reported. Overall N‐cycling models are produced for the two mature kauri sites and show that only 0.3% and 0.7% of total ecosystem N is mobilised in any year. There is a close linear relationship between both stem productivity and litter production and maximum foliage N in any stand and this has important implications for management of kauri forest.

Assessing the Success of Restoration Plantings in a Temperate New Zealand Forest

AbstractThe success of restoration plantings in restoring indigenous forest vascular plant and ground invertebrate biodiversity was assessed on previously grass‐covered sites in the eastern South Island, New Zealand. The composition and structure of grassland, three different aged restoration plantings (12, 30, and 35 years old), a naturally regenerating forest (100 years old), and a remnant of the original old‐growth forest of the area were measured. The restoration plantings are dominated by the native tree Olearia paniculata, which is not indigenous to the study area. Despite this, indigenous forest invertebrate and plant species are present in all three restoration sites and with increasing age the restoration sites become compositionally more similar to the naturally regenerating and mature forest sites. In particular the regenerating vegetation of the restoration sites is very similar floristically to the regenerating vegetation of the naturally regenerating and mature forest sites, despite marked differences in the current canopy vegetation reflecting the presence of the planted O. paniculata. The presence of regeneration in all three restoration sites indicates that the functional processes that initiate regeneration, such as dispersal, are present. The majority of regenerating tree species (71%) are bird dispersed and it is clear that birds play an important role in the recolonization of plant species at these sites despite the absence of edible fruit attractive to frugivorous birds on O. paniculata, a wind‐dispersed species. The strong correlations between plant and invertebrate community composition and study‐site age (r = 0.80, −0.24, −0.68 for plants, beetles, and spiders, respectively) suggest that the restoration site plant and invertebrate communities are undergoing change in the direction of the naturally regenerating and mature forest communities. Without restoration, colonization of grassland by forest plants is very slow in the study area and the restoration plantings studied here have been successful because they have considerably accelerated the return to forest at these sites.

Impacts of disturbance initiated by road construction in a subtropical cloud forest in the Luquillo Experimental Forest, Puerto Rico

The impacts of road construction and the spread of exotic vegetation, which are common threats to upper elevation tropical forests, were evaluated in the subtropical cloud forests of Puerto Rico. The vegetation, soil and microclimate of 6-month-old roadfills, 35-year-old roadfills and mature forest with and without grass understories were compared. Recent roadfills had higher light levels, soil temperatures, bulk densities, larger pools of exchangeable soil nutrients and higher soil oxygen concentrations; but lower soil moisture, soil organic matter and total soil N than the mature forest. On the 35-year-old roadfills, bulk density, soil pH and P pools were statistically similar to the mature forest while soil moisture, total N and base cations were different. The total aboveground biomass of 6-month-old roadfills was about 2 Mg/ha and dominated by a variety of monocot and herbaceous species. The 35-year-old roadfill areas had a biomass of 10.5 Mg/ha, 77% of which was non-woody. Seedling density, tree density and total woody biomass were 12, 28 and 2% of mature forest sites, respectively. In these areas, where soils were disturbed during construction, accumulation of biomass is the slowest known for the LEF. It may take 200–300 years for biomass to attain mature forest levels. In areas that were not directly disturbed during construction, the road has had little effect on the vegetative composition beyond a 5–10 m zone immediately adjacent to the pavement. Although non-native monocots, one of which had been planted along the road 35 years earlier, were copious along the disturbed roadside, they were generally absent from the mature forest and only abundant in habitats of anthropogenic origin.

Soil moisture storage in mature and replanted sub-humid boreal forest stands

Soil moisture profiles at two mature forest sites (Pine and Mixed-Wood) and two plantations (1981 Pine and 1992 Mixedwood) in central Saskatchewan were studied in conjunction with soil properties, precipitation, interception and evapotranspiration. Sampling locations within each stand were chosen to highlight differences in soil moisture due to interception, evapotranspiration and soil physical properties.Soil moisture storage to 1-m depth was greatest on the 92-Plantation where transpiration and interception of precipitation were less than the other sites. Moisture storage in the 81-Plantation was similar to that in the mixed-wood stand. The Pine stand had the lightest textured soils and stored least water to 1-m depth. Variability in moisture storage was also observed within stands and was associated with canopy structure and density, water extraction patterns and mechanical site preparation. In the furrows at the 92-Plantation, wet soils in combination with low infiltration rates and transpiration may have lead to the generation and channelling of rainfall runoff during a major rainfall event. Key words: Boreal forest, hydrological pathways, soil moisture, infiltration, interception, evapotranspiration

Succession in Bird Assemblages over a Seven-year Period in Regrowth Dry Sclerophyll Forest in South-east Tasmania

SummaryThe Tasmanian Parks and Wildlife Service monitored bird populations in a clearfell coupe and an adjacent unlogged forest in dry sclerophyll forest in the south-east of Tasmania for one and a half years in 1977–78. The mature forest was subsequently logged and another unlogged mature forest control site was added to the north. Monitoring by Forestry Tasmania continued for a further seven years, using a modified method. Numbers of birds and numbers of species were greatest in the mature forest and greater in the young regrowth than in the older regrowth. The higher numbers and species in the younger regrowth compared with the older regrowth are probably a result of the influence of older trees that were retained in sections of the young regrowth, the greater diversity of habitats in the young regrowth and the greater visibility in young regrowth. The bird faunas of the mature forest, older regrowth and young regrowth differed from each other. Individual species showed a range of responses to logging. Three species (Golden Whistler, Spotted Quail-thrush and Satin Flycatcher) that occurred in mature forest were virtually absent from regrowth.

Long-term environmental change in tropical forests: increasing tree turnover

SummaryAnalyzing permanent plot data from 40 tropical forest sites, Phillips and Gentry (1994) found that there has been a significant tendency for tree turnover – as measured by tree mortality and recruitment – to increase since the 1950s. The dataset is now substantially improved, and includes 67 mature forest sites with turnover data representing most of the major tropical forest regions of the world. This paper presents an updated and expanded analysis of the latest data, and confirms that tree turnover has increased in mature tropical forest plots. Several artifactual explanations have been suggested but none are supported by the available data, suggesting that surviving mature tropical forests have been recently affected by large-scale anthropogenic or natural change. The effects of increased turnover may include impacts on future global atmosphere, climate, and biodiversity. Better understanding of the ecological changes in mature tropical forests depends on progress in two critical research areas – a ground-based monitoring network of long-term, fully identified tropical forest plots, and controlled manipulation of atmospheric conditions in forest experiments. Research activity in both areas needs to be substantially increased if we are to understand and predict the complex interactions between tropical forest ecology and global environmental change.

Density of organic carbon in soil at coniferous forest sites in southern Finland

More detailed knowledge of the density of organic carbon in soils of boreal forests is needed for accurate estimates of the size of this C stock. We investigated the effect of vegetation type and associated site fertility on the C density at 30 mature coniferous forest sites in southern Finland and evaluated the importance of deep layers to the total C store in the soil by extending the sampling at eight of the sites to the depth of ground water level (2.4–4.6 m). The C density in the organic horizon plus 1 m thick mineral soil layer ranged from 4.0 kg/m2 to 11.9 kg/m2, and, on the average, increased towards the more productive vegetation types. Between the depth of 1 m and the ground water level the C density averaged 1.3–2.4 kg/m2 at the studied vegetation types and these layers represented 18–28% of the total stock of C in the soil. The results emphasize the importance of also considering these deep layers to correctly estimate the total amount of C in these soils. At the least fertile sites the soil contained about 30% more C than phytomass, whereas at the more fertile sites the amount of C in soil was about 10% less than the amount bound in vegetation.