Enhanced seed dispersal of Prunus africana in fragmented and disturbed forests?

Forest destruction and disturbance can have long-term consequences for species diversity and ecosystem processes such as seed dispersal. Understanding these consequences is a crucial component of conserving vulnerable ecosystems. In the heavily fragmented and disturbed Kakamega Forest, western Kenya, we studied seed dispersal of Prunus africana (Rosaceae). In the main forest, five forest fragments, and differently disturbed sites, we quantified the overall frugivore community as an indicator for species diversity. Furthermore, we determined the frugivores on 28 fruiting P. africana trees, estimated seed dispersal, crop size and the general fruit availability of surrounding trees. During the overall frugivore census we recorded 49 frugivorous species; 36 of them were observed visiting P. africana trees and feeding on their fruits. Although overall frugivore species richness was 1.1 times lower in fragments than in main forest sites and 1.02 times higher in highly disturbed than in less disturbed sites, P. africana experienced 1.1 times higher numbers of frugivores in fragments than in main forest sites and 1.5 times higher numbers of frugivores in highly disturbed than in less disturbed sites. Correspondingly, seed dispersal was 1.5 times higher in fragments than in main forest sites and 1.5 times higher in more disturbed than less disturbed sites. Fruit availability of surrounding trees and crop size influenced the number of visitors to some degree. Thus, the number of dispersed seeds seemed to be slightly higher in fragmented and highly disturbed sites. This indicates that loss of single species does not necessarily lead to a decrease of ecosystem services. However, loss of diversity could be a problem in the long term, as a multitude of species might act as buffer against future environmental change.     

Fluxes and concentrations of dissolved organic carbon and nitrogen – a synthesis for temperate forests

Dissolved organic carbon (DOC) and nitrogen (DON)represent an important part of the C and N cycles inforest ecosystems. Little is known about the controlson fluxes and concentrations of these compounds insoils under field conditions. Here we compiledpublished data on concentrations and fluxes of DOC andDON from 42 case studies in forest ecosystems of thetemperate zone in order to evaluate controls on alarger temporal and spatial scale. The focus was onannual fluxes and concentrations in throughfall,forest floor leachates and soil solutions. In allcompartments considered, concentrations and fluxesdiffered widely between the sites. Highestconcentrations of DOC and DON were generally observedin forest floor leachates and in A horizons. Highestfluxes occurred in forest floor leachates. The fluxesof DOC and DON in forest floor leachates increasedwith increasing annual precipitation and were alsopositively related to DOC and DON fluxes withthroughfall. Variation in throughfall fluxes couldexplain 46% and 65% of the variation in DOC and DONfluxes from the forest floor, respectively. No generaldifference in DOC and DON concentrations and fluxes inforest floor leachates was found when comparingconiferous and hardwood sites. Concentrations of DOCin forest floor leachates were positively correlatedto the pH of the forest floor. Furthermore, there wasno relationship between organic C and N stocks, soilC/N, litterfall or mineral N inputs and concentrationsand fluxes of DOC and DON in forest floor leachates.Including all compartments, fluxes of DOC and DON werehighly correlated. Ratios of DOC to DON calculatedfrom fluxes from the forest floor were independent ofthe amount of annual precipitation, pointing to asimilar response of DOC and DON to precipitationconditions. A decrease in the ratio of DOC to DON withsoil depth as observed on a plot-scale, was notconfirmed by data analysis on a large scale. Thecontrols observed on annual fluxes and concentrationsof DON and DOC at regional scale differed from thosereported for smaller time and space scales.     

Old‐growth forests,carbon and climate change: Functions and management for tall open‐forests in two hotspots of temperate Australia

Abstract

The prognosis and utility under climate change are presented for two old‐growth, temperate forests in Australia, from ecological and carbon accounting perspectives. The tall open‐forests (TOFs) of south‐western Australia (SWA) are within Australia’s global biodiversity hotspot. The forest management and timber usage from the carbon‐dense old‐growth TOFs of Tasmania (TAS) have a high carbon efflux, rendering it a carbon hotspot. Under climate change the warmer, dryer climate in both areas will decrease carbon stocks directly; and indirectly through changes towards dryer forest types and through positive feedback. Near 2100, climate change will decrease soil organic carbon (SOC) significantly, e.g. by ～30% for SWA and at least 2% for TAS. The emissions from the next 20 years of logging old‐growth TOF in TAS, and conversion to harvesting cycles, will conservatively reach 66(±33) Mt‐CO₂‐equivalents in the long‐term – bolstering greenhouse gas emissions. Similar emissions will arise from rainforest SOC in TAS due to climate change. Careful management of old‐growth TOFs in these two hotspots, to help reduce carbon emissions and change in biodiversity, entails adopting approaches to forest, wood product and fire management which conserve old‐growth characteristics in forest stands. Plantation forestry on long‐cleared land and well‐targeted prescribed burning supplement effective carbon management.

Abbreviations: C, carbon; CBS, clearfell, burn and sow; CO₂‐e, CO₂ equivalents; CWD, coarse woody debris; DOC, dissolved organic carbon; GHG, greenhouse gas; Mt, megatonnes; SOC, soil organic carbon; SWA, south‐western Australia; SWAFR, Southwest Australian Floristic Region; TAS, Tasmania; TOF, tall open‐forest; t‐C ha^?1 yr^?1, tonnes of carbon per hectare per year     

Lichens and bryophytes as indicators of old‐growth features in Mediterranean forests

Abstract

This study is focused on the selection of variables affecting lichen and bryophyte diversity in Mediterranean deciduous forests. Plots representing two forest types (Fagus sylvatica and Quercus cerris forests) and two forest continuity categories (old‐growth (OG) and non‐OG forests) were selected in the Cilento and Vallo di Diano National Park (Italy). The presence and the abundance of bryophytes and epiphytic lichens were recorded. Structural variables of the forests and vascular plant species richness have been used as predictors. A strong positive correspondence between the two groups of organisms was found. Higher species richness and the distribution of rare species are related to OG stands, while a qualitative (species composition) rather than a quantitative (species richness) difference between the two forest types was observed. Some species elsewhere considered as indicators of forest continuity, such as Lobaria pulmonaria, Antitrichia curtipendula, and Homalothecium sericeum, are associated with OG forests, independently from forest type, suggesting that they can be regarded as suitable indicators also in Mediterranean forests. Finally, our results suggest that old trees, high levels of basal area, a broad range of diameter classes, and high understory diversity are the main structural features affecting cryptogamic communities, while no correlation was found with the occurrence of deadwood.     

Tree diversity and conservation value of Ngovayang’s lowland forests,Cameroon

The Ngovayang Massif of southern Cameroon is a range of small hills near the Atlantic coast, in the Lower Guinea floristic region. This region is known to harbor forests with high levels of biodiversity and endemism, but this Massif is botanically poorly known. We assessed tree species diversity, floristic composition and level of endemism of the Ngovayang forest, comparing it with other sites in Central Africa. Five 1-ha permanent plots within old-growth lowland forests of the Ngovayang Massif were censused. A total of 2,658 individuals with dbh ≥ 10 cm were recorded, belonging to 293 species, 170 genera and 60 families. The mean number of stems was 532 ± 75 stems ha⁻¹. Taking into account other data available, the list of vascular plants known in the Massif reaches a total of 450 species. We found 47 species of high conservation value, including Cameroon endemics and other rare and threatened species. Species richness and endemism are comparable to those of the richest known sites in Central African forests. The forests of Ngovayang were found to be particularly rich in Fabaceae-Caesalpinioideae. Topographic heterogeneity, high precipitation and atmospheric humidity owing to the proximity of the ocean, and permanence of a forest cover during past geological times probably all contribute to explaining the Massif’s high tree diversity and endemism. This study highlights the botanical importance of the poorly studied Ngovayang forest within the Lower Guinea region, justifying efforts for improved assessment of this value and for the development of suitable national conservation strategies.     

Patterns of foliar δ15N and their control in Eastern Asian forests

Foliar δ¹⁵N has been used increasingly in research on ecosystem nitrogen (N) cycling, because it can serve as an integrator of ecosystem N cycling and thus has a potential to reveal temporal and spatial patterns of N cycling as well as how the N cycle is altered by disturbances. However, the current understanding on controls of foliar δ¹⁵N is based principally on studies from America, Europe, Australia and Africa. Here we compiled data from 65 forests at 33 sites across East Asia to explore regional patterns and what controls foliar δ¹⁵N by linking it to climate, species composition, soil depth, slope position, N deposition, and soil N availability. In East Asia, foliar δ¹⁵N ranged from ?7.1 to +2.7‰. Mean foliar δ¹⁵N values for tropical, subtropical and temperate forests were all ?3.1‰, which was unexpected. The patterns of foliar δ¹⁵N with precipitation, temperature and altitude were not clear. The variation in foliar δ¹⁵N among species and between different slope positions appeared to be small within a given forest. The δ¹⁵N for both bulk soil N and extractable inorganic N generally increased with soil depth as expected, strengthening the idea that deep-rooted trees may have access to ¹⁵N-enriched N. Different from the positive correlations reported across America and Europe, in East Asia we found that foliar δ¹⁵N decreased with increasing N deposition and did not relate to soil N availability. These discrepancies deserve more research to elucidate the mechanisms by which foliar δ¹⁵N is affected by ecosystem N availability at a regional scale.     

Angola’s central scarp forests: patterns of bird diversity and conservation threats

Despite Angola’s central scarp forests being recognised as a critical global priority for bird conservation, fine-scale information on threatened bird distributions and patterns of bird diversity are lacking. These data are essential to identify sites within the Western Angola Endemic Bird Area that should be targeted for conservation. First endemic and near-endemic species and subspecies, and species with isolated populations along the Angolan scarp were identified to highlight taxa of greatest priority for conservation and for use in studying the evolutionary origins of the region. Thereafter survey data collected during 2005 from 13 forest sites along the central scarp was analysed. These data show that there are three distinct bird communities across the width of the escarpment, each associated with a distinctive forest type. Of note is the finding that threatened and Near Threatened endemic species occur almost exclusively in the dry forests adjacent to the main escarpment, rather than in the moistest forests found on the main escarpment, which instead are richer in Congo Basin forest birds. Based on these data, summaries of ranges, populations and conservation threats are given for the seven most threatened bird species. Attention is drawn to threats to the habitats of greatest importance to these species. A conservation area network should be established that encompasses the full spectrum of bird diversity described, to ensure survival of current unique taxa and the future evolutionary potential of the area.     

Where will the wood come from? Plantation forests and the role of biotechnology

Wood is almost as important to humanity as food, and the natural forests from which most of it is harvested from are of enormous environmental value. However, these slow-growing forests are unable to meet current demand, resulting in the loss and degradation of forest. Plantation forests have the potential to supply the bulk of humanity's wood needs on a long-term basis, and so reduce to acceptable limits the harvest pressures on natural forests. However, if they are to be successful, plantation forests must have a far higher yield of timber than their natural counterparts, on much shorter rotation times. To achieve this in reasonable time, biotechnology must be applied to the tree-improvement process, for which large increases in public and private capital investment are needed. However, additional obstacles exist in the form of opposition to plantations, some forest ecocertification schemes, and concerns about aspects of forest biotechnology, especially genetic engineering. It is the intention of this article to explain, in detail, why plantation forests are needed to sustainably meet the world's demand for wood, why they are not being developed fast enough, and why the application of biotechnology to tree improvement is essential to speeding up this process.     

Templates of food–habitat resources for the organization of soil animals in temperate and tropical forests

The functioning and structure of terrestrial ecosystems are shaped and maintained by plant–decomposer interactions. The food and habitat of animal populations are biogenic and are mainly of plant origin (plant litter) in terrestrial ecosystems. Primary resources of the food-habitat template for the organization of soil animals are provided by the primary production of plants, and are then modified through decomposition processes by microbial populations. In the microbial decomposition system, the efficiency of carbon utilization by microbial decomposers characterizes the decomposition processes between tropical and temperate forest ecosystems. Tropical forests show poor development of soil reservoir systems because of the high efficiency of lignin decomposition by microbial populations. The decomposition processes of leaf litter are described briefly for the understanding of organization of soil animal communities in tropical and temperate forests. A comparison of decomposition processes shows qualitative differences in decomposition between temperate and tropical forests. The composition of functional groups of soil animals is well explained by the decomposition processes in both forests.     

Large-scale synchrony of gap dynamics and the distribution of understory tree species in maple–beech forests

Large-scale synchronous variations in community dynamics are well documented for a vast array of organisms, but are considerably less understood for forest trees. Because of temporal variations in canopy gap dynamics, forest communities—even old-growth ones—are never at equilibrium at the stand scale. This paucity of equilibrium may also be true at the regional scale. Our objectives were to determine (1) if nonequilibrium dynamics caused by temporal variations in the formation of canopy gaps are regionally synchronized, and (2) if spatiotemporal variations in canopy gap formation affect the relative abundance of tree species in the understory. We examined these questions by analyzing variations in the suppression and release history of Acer saccharum Marsh. and Fagus grandifolia Ehrh. from 481 growth series of understory saplings taken from 34 mature stands. We observed that (1) the proportion of stems in release as a function of time exhibited a U-shaped pattern over the last 35 years, with the lowest levels occurring during 1975–1985, and that (2) the response to this in terms of species composition was that A. saccharum became more abundant at sites that had the highest proportion of stems in release during 1975–1985. We concluded that the understory dynamics, typically thought of as a stand-scale process, may be regionally synchronized.     

What is the impact of Impatiens parviflora on diversity and composition of herbal layer communities of temperate forests?

The aim was to estimate the impacts of invasive Impatiens parviflora on forests' herbal layer communities. A replicated Before-After-Control-Impact field experiment and comparisons with adjacent uninvaded plots were used. The alien's impact on species richness was tested using hierarchical generalized mixed effect models with Poisson error structure. Impact on species composition was tested using multivariate models (DCA, CCA, RDA) and Monte-Carlo permutation tests. Removal plots did not differ in native species richness from neither invaded nor adjacent uninvaded plots, both when the treatment's main effect or its interaction with sampling time was tested (Chi(2)?=?0.4757, DF?=?2, p?=?0.7883; Chi(2)?=?7.229, DF?=?8, p?=?0.5121 respectively). On the contrary, ordination models revealed differences in the development of plots following the treatments (p?=?0.034) with the invaded plots differing from the adjacent uninvaded (p?=?0.002). Impatiens parviflora is highly unlikely to impact native species richness of invaded communities, which may be associated with its limited ability to create a dense canopy, a modest root system or the fact the I. parviflora does not represent a novel and distinctive dominant to the invaded communities. Concerning its potential impacts on species composition, the presence of native clonal species (Athyrium filix-femina, Dryopteris filix-mas, Fragaria moschata, Luzula luzuloides, Poa nemoralis) on the adjacent uninvaded plots likely makes them different from the invaded plots. However, these competitive and strong species are more likely to prevent the invasion of I. parviflora on the adjacent uninvaded plots rather than being themselves eliminated from the invaded communities.     

Are Sebacinaceae common and widespread ectomycorrhizal associates of Eucalyptus species in Australian forests?

A molecular survey of basidiomycete ectomycorrhizal fungi colonising root tips at a site in Eucalyptus marginata (jarrah) forest revealed the presence of many fungal species which could not be identified from a database of ITS-PCR-RFLP profiles from morphologically identified species. Three of these unidentified taxa were among the six most frequently encountered profiles. Phylogenetic analyses of ITS and nuclear LSU sequences revealed a close relationship among the three fungi and that they belong to the family Sebacinaceae (sensu Weiss and Oberwinkler 2001). The possibility that DNA of non-ectomycorrhizal rhizosphere or endophytic fungi had been amplified selectively by the basidiomycete-specific primers was tested by amplification with fungal-specific primers. A single PCR fragment was amplified in all but two of the 24 samples tested and digestion with two restriction enzymes produced RFLP profiles which matched those from the Sebacinoid sequence. We conclude, therefore, that at least three species of Sebacinaceae are common ectomycorrhizal associates of E. marginata.     

Sources or sinks? The responses of tropical forests to current and future climate and atmospheric composition.

How tropical rainforests are responding to the ongoing global changes in atmospheric composition and climate is little studied and poorly understood. Although rising atmospheric carbon dioxide (CO2) could enhance forest productivity, increased temperatures and drought are likely to diminish it. The limited field data have produced conflicting views of the net impacts of these changes so far. One set of studies has seemed to point to enhanced carbon uptake; however, questions have arisen about these findings, and recent experiments with tropical forest trees indicate carbon saturation of canopy leaves and no biomass increase under enhanced CO2. Other field observations indicate decreased forest productivity and increased tree mortality in recent years of peak temperatures and drought (strong El Niño episodes). To determine current climatic responses of forests around the world tropics will require careful annual monitoring of ecosystem performance in representative forests. To develop the necessary process-level understanding of these responses will require intensified experimentation at the whole-tree and stand levels. Finally, a more complete understanding of tropical rainforest carbon cycling is needed for determining whether these ecosystems are carbon sinks or sources now, and how this status might change during the next century.     

A genome-wide association study of Alzheimer’s disease using random forests and enrichment analysis

Alzheimer??s disease (AD) is a serious neurodegenerative disorder and its cause remains largely elusive. In past years, genome-wide association (GWA) studies have provided an effective means for AD research. However, the univariate method that is commonly used in GWA studies cannot effectively detect the biological mechanisms associated with this disease. In this study, we propose a new strategy for the GWA analysis of AD that combines random forests with enrichment analysis. First, backward feature selection using random forests was performed on a GWA dataset of AD patients carrying the apolipoprotein gene (APOE?4) and 1058 susceptible single nucleotide polymorphisms (SNPs) were detected, including several known AD-associated SNPs. Next, the susceptible SNPs were investigated by enrichment analysis and significantly-associated gene functional annotations, such as ??alternative splicing??, ??glycoprotein??, and ??neuron development??, were successfully discovered, indicating that these biological mechanisms play important roles in the development of AD in APOE?4 carriers. These findings may provide insights into the pathogenesis of AD and helpful guidance for further studies. Furthermore, this strategy can easily be modified and applied to GWA studies of other complex diseases.     

Development policy,forests, and peasant farms: Reflections on Huastec-managed forests’ contributions to commercial production and resource conservation

The Huastec Indians of northeastern Mexico manage their forests in an indigenous system that integrates commercial and subsistence production. Elements of primary and secondary forest coexist with introduced species in this diverse silvicultural structure which complements the swidden and permanent agriculture fields of the Huastec farmstead. The forest’s direct production of the food, timber, and fuel resources discussed here buffers the Huastec peasant family against market fluctuations and the failed harvest of a single crop. The Huastec system of forest management offers an alternative pattern to the agroforestry and plantation schemes now being suggested for development in the tropics. It is an alternative that provides protection for wild genetic resources while it contributes to the combination of commercial and subsistence agriculture so important for the successful modernization of peasant agriculture. The documentation of this system demonstrates that ethnobotanists and economic botanists have an important but unrealized role to play in the protection of biotic resources and in the development of sustained yield agroecosystems for peasants. The contributions of ethnobotanists are particularly valuable because they can find where and why useful wild species persist in agroecosystems. A greater effort to direct the attentions of policy makers to the value of ethnobotanical knowledge is needed.     

Plantation forests and biodiversity: oxymoron or opportunity?

Losses of natural and semi-natural forests, mostly to agriculture, are a significant concern for biodiversity. Against this trend, the area of intensively managed plantation forests increases, and there is much debate about the implications for biodiversity. We provide a comprehensive review of the function of plantation forests as habitat compared with other land cover, examine the effects on biodiversity at the landscape scale, and synthesise context-specific effects of plantation forestry on biodiversity. Natural forests are usually more suitable as habitat for a wider range of native forest species than plantation forests but there is abundant evidence that plantation forests can provide valuable habitat, even for some threatened and endangered species, and may contribute to the conservation of biodiversity by various mechanisms. In landscapes where forest is the natural land cover, plantation forests may represent a low-contrast matrix, and afforestation of agricultural land can assist conservation by providing complementary forest habitat, buffering edge effects, and increasing connectivity. In contrast, conversion of natural forests and afforestation of natural non-forest land is detrimental. However, regional deforestation pressure for agricultural development may render plantation forestry a ‘lesser evil’ if forest managers protect indigenous vegetation remnants. We provide numerous context-specific examples and case studies to assist impact assessments of plantation forestry, and we offer a range of management recommendations. This paper also serves as an introduction and background paper to this special issue on the effects of plantation forests on biodiversity.

The productivity and composition of mangrove forests,Laguna de Términos,Mexico

The composition and productivity of two mangrove sites surrounding the Laguna de Términos, Mexico, were studied from March 1979 to January 1984. Measurements were made of the tree composition, above-ground woody biomass changes, and litterfall production at a high-salinity fringing site and a low-salinity riverine site. Rhizophora mangle L. was the dominant tree at the fringing site, but occurred only at the water's edge at the riverine site. Avicennia germinans L. dominated the inland area of the riverine site. Laguncularia racemosa Gaertn. f. had a more even distribution from shore to inland and from site to site. Average diameter at breast height (DBH) was greater at the riverine site for each of the three species; however, tree density (trees > 2.5 cm DBH) was more than twice as high at the fringing site (7510 ha⁻¹) than at the riverine site (3360 ha⁻¹). Wood production (1206 g m⁻² year⁻¹ vs. 772 g m⁻² year⁻¹) and litterfall (1252 g m⁻² year⁻¹ vs. 835 g m⁻²) were higher at the riverine site than at the fringing site. Total estimated above-ground net production was 2458 g m⁻² year⁻¹ at the riverine site and 1607 g m⁻² year⁻¹ at the fringing site.     

Co-variation and indicators of species diversity: Can richness of forest-dwelling species be predicted in northern boreal forests?

Design and establishment of ecologically good networks of conservation areas often requires quick assessments of their biodiversity. Reliable indicators would be useful when doing such assessments. In order to explore the potential indicators for species richness in boreal forests, we studied (1) the co-variation of species richness and composition of species assemblages among beetles, polypores, birds and vascular plants, (2) the relationships between species richness and four boreal forest site types, (3) the relationship between species richness and forest physical structure and (4) the suitability of potential indicator groups within the four taxa to predict the species richness generally. The data show that there are probably not a single taxonomic or forest structural characteristic to be used as a general biodiversity indicator or surrogate for all the species. The correlations in species richness among the four taxa studied were low. However, group-specific indicators were obvious: forest site type was a good surrogate for vascular plant richness, and quantity and quality of dead wood predicted the species richness of polypores. The results support the view that different indicators shall be used for different forest types and taxonomic groups. These indicators should facilitate relatively rapid methods to assess biodiversity patterns at the forest stand level.     

Distribution of sulphur forms in soils from beech and spruce forests of Mont Lozère (France)

From a quantitative inventory of sulphur forms and sulphur budget, the relation between the distribution of the various sulphur forms and the sulphate fluxes in three soil profiles has been addressed. These profiles are located in two forested watersheds at Mont Lozère. One has been sampled in a beech forest and the other two in a spruce forest and in a harvested plot of this spruce forest, respectively. The mean annual input-output budgets showed a sulphur immobilization in the soil cover of the three plots. In the preserved spruce forest plot, because of larger dry depositions, the sulphur immobilization is much greater than in other plots and occurs essentially in the B horizons. In the other two profiles, the dominant immobilization occurs in the parent material.The total sulphur content is very high in the forest floor reaching 2065 g S g^-1 in the litter of one of the soils under spruce. In the organo-mineral horizons of soils under spruce, the total sulphur content decreases with depth and ranges from 310 to 520 g S g^-1 in the A horizons to 100–200 g S g^-1 in the parent material. In the profile under beech, the total sulphur content is lower except in the parent material. In all cases, the organic sulphur is the major part of sulphur often representing more than 90% of total sulphur. In organo-mineral soil horizons of the spruce forest, the part of the sulphateesters is more important than in the soil of the beech forest, probably related to the different nature of the microbial activity in the spruce forest. In contrast, the humification processes are more efficient in the soil under beech, which can be due to the greater input of organic sulphur by litterfall. It appears that the dominant organic sulphur form varies as a function of microbial ecology and sulphate flux. The maximum of the inorganic sulphate is located at the base of the B horizons in the soil of the spruce forest and in the parent material of the soil under beech. In these horizons, the high content of inorganic sulphate can be related to the higher amounts of amorphous Fe and Al phases.