Habitat preferences of oak-feeding xylophagous beetles in a temperate woodland: implications for forest history and management

Oaks host the richest fauna of saproxylic insect in Europe. We studied habitat preferences of two beetle families, Buprestidae and Cerambycidae, by rearing the beetles from standardised oak timber baits. Species density was higher in the understorey than in the canopy; and in sun-exposed baits if within the understorey. Insolation was the most important factor affecting the composition of reared assemblages (explaining ca. 30% of variation in the data), followed by vertical stratum (ca. 10%). Local dead wood volume had no effect. The high preference for sun-exposed wood located near the ground suggests that: (i) open-canopy woodlands had to be rather common in temperate Europe; (ii) oak-utilising xylophages would benefit from restoration of management practices such as coppicing or woodland pasture; (iii) the policy of increasing dead wood volume in commercial forests is principally correct, but its success will depend on dead wood location within the forests.     

Considerations regarding species distribution models for forest insects

1. Species distribution models, or SDMs, have become important decision support tools by answering fundamental questions about where species, including invasive species, are likely to survive and thrive based on environmental conditions.
2. For an inexperienced modeller or model reviewer, the terminology and technical aspects of SDMs can be overwhelming, and even well-trained modellers can struggle to understand the implications of various modelling choices.
3. Here, I outline some key considerations with respect to SDMs, focusing on their application to forest insects. Foremost, I assert that a model should be developed and evaluated with attention to relationships between an insect and its hosts, as those relationships determine much about the places the insect may occupy.
4. In my view, the most successful models are constructed carefully and incorporate honest assessments of their limitations, sources of error and uncertainty, and the degree of linkage between the model and the real-world circumstances it is meant to portray.

     

Diversity and biovolume of tree species in natural forest ecosystem in the bitumen-producing area of ondo state,Nigeria: a baseline study

Tree species diversity, biovolume and forest stand structure were investigated in natural forest ecosystem located around some selected communities in the bitumen-producing area of Ondo state, Nigeria. Two forest reserves and four free areas distributed in 4 Local Government Areas (LGA) of the state were selected for data collection, out of the total 6 LGAs in the bitumen belt of the state. The two forest reserves are Oluwa FR at Legge in Odigbo LGA and Eba Island FR in Ese-Odo LGA while the four free areas are located close to each of Omotoso community (Odigbo LGA), Ode-Aye community (Okitipupa), Igbo-Egunrin community (Ilaje) and Igbotako community (Okitipupa). Eight plots of equal size (20 × 20 m) were located in each of the selected location, using systematic line transect sampling design. In each plot, all living trees with dbh ≥ 10 cm were identified with their botanical names and their dbhs were also measured. The results of the study reveal that there were ninety nine (99) tropical hardwood timber species (range: 21 to 48 species per selected forest). These species were distributed among twenty nine (29) families. While Funtumia elastica has the highest population distribution across the selected communities’ forest, Euphorbiaceae was the dominant family in the entire area. Although there was a moderate variation in the biodiversity indices among the selected communities’ forest, the Shannon-Weiner diversity index of H¹ = 4.02 and species evenness of E = 0.88 were obtained for the entire study area. Tree density summing up to 2,740 trees/6 ha varied moderately, with a range of 361–609 tree/ha, among the communities. Though most of the trees encountered belonged to the lowest diameter size class, the mean basal area and biovolume were 26.69 m²/ha and 262.36 m³/ha respectively. Recommendations guiding the decision on the allocation of the communities’ forest to the bitumen exploratory industries are made and the need for good forest management of the prospective area of bitumen exploration of Ondo state is emphasized. This is to prevent the imminent loss of biological diversity that would eventually accompany the exploration.     

The effect of hummingbird flower mites on nectar availability of two sympatric Heliconia species in a Brazilian Atlantic forest

BACKGROUND AND AIMS: Hummingbird flower mites feed and reproduce in flowers of host plants pollinated by hummingbirds, and use the nostrils and bill of the hummingbird to move from plant to plant. These mites compete with the pollinator for the nectar produced by flowers. An investigation was made of the relationship between the pattern of nectar production and the effects of hummingbird flower mites in the flowers of two sympatric species of Heliconia (Heliconiaceae). METHODS: Nectar production was sampled by carrying out two experiments: 2-hour intervals and accumulated nectar. Flowers with and without mites were used in both experiments. KEY RESULTS: Exclusion of mites increased nectar production, especially in accumulated daily production (a maximum of 49 % more nectar). Both Heliconia species had the same pattern of nectar production: a high concentration in the morning, which was progressively reduced as the day passed. This pattern of nectar production coincides with the behaviour of the pollinator, which makes more frequent visits in the morning, as observed in a previous study. CONCLUSIONS: The results suggest that the impact of mites on nectar availability of Heliconia is more important with regard to total volume of nectar produced irrespective of flower longevity. A high variation among individuals in nectar produced in the populations was also observed. Hummingbird flower mites strongly affect availability of nectar for hummingbirds.     

Edge effects on epiphytic communities in a Mediterranean Quercus pyrenaica forest

Question: What are the edge effect responses of epiphytic lichen communities in Mediterranean Quercus pyrenaica forest? Location: Central Spain. Methods: We established ten transects perpendicular to a road dissecting a well conserved remnant of Q. pyrenaica forest into two sections. Transects extended from the forest/road edge to 100 m into the forest. Data were collected from seven plots in each transect at different distances from the edge. Variables were grouped into stand scale variables (distance to edge, number of trees per plot, mean diameter per plot, irradiance) and tree scale variables (diameter and height of sampled trees, aspect of the sampled square and relative height of the square). We used General Mixed Linear Models and constrained ordination techniques to test the hypothesis that the spatio‐temporal heterogeneity of light and water controls the occurrence of lichens and bryophytes along the edge‐interior gradient in the Q. pyrenaica forest. Results: Microclimatic parameters vary in a non‐linear way; edge and interior stands showed the most divergent and extreme values. Although the micro‐environment within Mediterranean forests is heterogeneous, interior conditions are apparently suitable for the performance of some specific forest epiphytes. Consequently, species richness does not show significant differences along the gradient. Total epiphytic cover increases towards the forest interior, but distance to the edge together with other predictors at the tree scale (aspect and height of the square) are the most relevant predictors for the composition and structure of these communities. Conclusions: Composition and structure of epiphytic communities in a Mediterranean semi‐deciduous forest are affected by the edge between the forest and the road constructed. Since some extremely rare lichens only occur at interior stands, the conservation of these threatened elements requires urgent conservation measures because well preserved and unmanaged forests in the Mediterranean region are very rare.     

Charr truth: sympatric differentiation in Salvelinus species

Charrs, Salvelinus species, are characteristic fishes of northern freshwater lakes and rivers. They are highly variable in almost every aspect of their behaviour, morphology and life history. Several possible explanations have been proposed to account for this variability and resolve the taxonomic confusion in this genus. I propose that sympatric trophic polymorphism, in the ecological context of these species, can make sense of this variability. I use examples from charr in Canada and Iceland to construct an evolutionary scenario for this genus.     

Segregation of habitat and prey in two sympatric carnivorous plant species,Drosera rotundifolia and Drosera intermedia

Summary Labelled nitrogen was used to evaluate the effects of intensive forest management on soil nitrogen transformations. The total release of N into inorganic forms (ammonium plus nitrate) was much greater than net N mineralization in all treatments. Immobilization of N by microbes was greatest in minimally-treated harvested plots, while the turnover of N within soil microbes was greatest in intensively-treated plots. Ammonium was immobilized 2.4–3.2 times more rapidly than nitrate in havested plots; nitrification in disturbed sites could thus increase the availability of N to regrowing vegetation.     

A forest typology for monitoring sustainable forest management: The case of European Forest Types

Abstract

Sustainable forest management (SFM) is presently widely accepted as the overriding objective for forest policy and practice. Regional processes are in progress all over the world to develop and implement criteria and indicators of SFM. In continental Europe, a set of 35 Pan-European indicators has been endorsed under the Ministerial Conference on the Protection of Forests in Europe (MCPFE) to measure progress towards SFM in the 44 countries of the region. The formulation of seven indicators (forest area, growing stock, age structure/diameter distribution, deadwood, tree species composition, damaging agents, naturalness) requires national data to be reported by forest types. Within the vast European forest area the values taken by these indicators show a considerable range of variation, due to variable natural conditions and anthropogenic influences. Given this variability, it is very difficult to grasp the meaning of these indicators when taken out of their ecological background. The paper discusses the concepts behind, and the requirements of, a classification more soundly ecologically framed and suitable for MCPFE reporting than the three (un-informative) classes adopted so far: broadleaved forest, coniferous forest, mixed broadleaved and coniferous forest. We propose a European Forest Types scheme structured into a reasonably higher number of classes, that would improve the specificity of the indicators reported under the MCPFE process and its understanding.     

Bioacoustics for species management: two case studies with a Hawaiian forest bird

The management of animal endangered species requires detailed information on their distribution and abundance, which is often hard to obtain. When animals communicate using sounds, one option is to use automatic sound recorders to gather information on the species for long periods of time with low effort. One drawback of this method is that processing all the information manually requires large amounts of time and effort. Our objective was to create a relatively “user‐friendly” (i.e., that does not require big programming skills) automatic detection algorithm to improve our ability to get basic data from sound‐emitting animal species. We illustrate our algorithm by showing two possible applications with the Hawai'i ‘Amakihi, Hemignathus virens virens, a forest bird from the island of Hawai'i. We first characterized the ‘Amakihi song using recordings from areas where the species is present in high densities. We used this information to train a classification algorithm, the support vector machine (SVM), in order to identify ‘Amakihi songs from a series of potential songs. We then used our algorithm to detect the species in areas where its presence had not been previously confirmed. We also used the algorithm to compare the relative abundance of the species in different areas where management actions may be applied. The SVM had an accuracy of 86.5% in identifying ‘Amakihi. We confirmed the presence of the ‘Amakihi at the study area using the algorithm. We also found that the relative abundance of ‘Amakihi changes among study areas, and this information can be used to assess where management strategies for the species should be better implemented. Our automatic song detection algorithm is effective, “user‐friendly” and can be very useful for optimizing the management and conservation of those endangered animal species that communicate acoustically.     

Saproxylic hoverflies benefit by modern forest management (Diptera: Syrphidae)

Saproxylic organisms are regarded as threatened in many European countries. Nevertheless, there have been some signals indicating a recent increase of saproxylic hoverflies in the Netherlands. This paper examines the change in occurrence of saproxylic hoverflies compared to other ecological groups of the same family. The trend analysis is based on the database of an extensive recording programme carried out in the Netherlands. The results show an increase in occupied grid cells for a majority of saproxylic species in relation to other ecological groups. This positive trend occurs among all five ecological subcategories of saproxylic hoverflies recognized in this paper. It is suggested that this increase could be attributed to the changes in the Dutch forests during the past 50 years. Important aspects of these changes are: the increase in forest area (including an increase in area of forest with large and very large trees), the increase in age of forests and the changes in forest management in favour of a more natural approach towards dead and ill trees. In the discussion the possible influence of climate change and the method of trend calculation are discussed.     

Variation in allometry and tree architecture among<Emphasis Type="Italic"> Symplocos</Emphasis> species in a Japanese warm-temperate forest

We compared tree architecture and allometry among five Symplocos species (Symplocos myrtacea, Symplocos lancifolia, Symplocos lucida, Symplocos glauca, and Symplocos theophrastiifolia) in a Japanese warm-temperate forest to understand the causes of interspecific variations in these characteristics. S. lancifolia, S. glauca, and S. theophrastiifolia grew at elevations below 500 m, whereas S. lucida grew on ridges irrespective of elevations, and S. myrtacea grew at elevations above 590 m. The species that shared a habitat exhibited trade-offs between height growth and crown area extension that might reflect differentiation in their regeneration niches. S. lancifolia showed the lowest height growth and widest crown extension, whereas S. theophrastiifolia showed the greatest height growth and lowest crown extension. S. glauca was intermediate between these species. S. lucida grows on ridges characterized by strong winds and the absence of other Symplocos species; it had the thickest stem and second-narrowest crown of the five species, possibly due to mechanical stability constraints. S. myrtacea was smallest at the onset of reproduction, and its fruits developed under closed canopies. Its architecture and allometry may increase seed production. Variation in tree architecture and allometry among the five species appear to be related to differentiation among regeneration niches, mechanical stability, and reproduction constraints.     

Gini coefficient predictions from airborne lidar remote sensing display the effect of management intensity on forest structure

In this study, two forest sites located in Finland were compared by means of predictions of Gini coefficient (GC) obtained from airborne laser scanning (ALS). We discuss the potential of the proposed method for identifying differences in structural complexity in relation with the management history of forests. The first study site (2200 ha), the Koli National Park (NP), includes areas where human intervention was restricted after 1907, in addition to forests which were protected only after the 1990s. The second study site in the municipality of Kiihtelysvaara (800 ha) has been under intensive management. These are commercial forests which include areas with different types of ownership: a large estate owned by an industrial company together with smaller private properties. We observed that GC predictions may be used to evaluate the effects of management practice on forest structure. Conservation and commercial forests showed significant differences, with the old-protected area of Koli having the highest, and the most intensively managed area in Kiihtelysvaara the lowest GC values. The effect of management history was revealed, as the 1990s’ extensions of Koli NP were more similar to unprotected areas than to forests contained within the original borders of the 1907s’ state property. Yet, their conservation status for almost two decades has been sufficient for developing significant differences against the outside of the NP. In Kiihtelysvaara, we found significant differences in GC according to the type of ownership. Moreover, the ALS predictions of GC also detected differences near lakeshores, which are driven by limitations on logging governed by Finnish law. Estimating this indicator with ALS remote sensing allowed to observe its spatial distribution and to detect peculiarities which would otherwise be unavailable from field plot sampling. Consequently, the method presented appears to be well suited for monitoring the effects of management practice, as well as verifying its compliance with legal restrictions.     

Wildfires in the western Canadian boreal forest: Landscape patterns and ecosystem management

Abstract. Mimicking of natural disturbance for ecosystem management requires an understanding of the disturbance processes and the resulting landscape patterns. Since fire is the major disturbance in the boreal forest, three widely held beliefs about fire behavior and resulting landscape patterns are examined in light of the empirical evidence available. These beliefs are: (1) that there is a ‘natural’ fire frequency for boreal ecosystems; (2) that the landscape mosaic created by wildfire is generally one of small, younger patches embedded within a matrix of older forest; and (3) that forest flammability is largely controlled by fuel accumulation. Despite the apparently logical basis for such beliefs, they are not well supported by empirical evidence. This discrepancy is explained by problems such as failure to appreciate the relationship between number of fires and area burned and inappropriate extrapolations or generalizations from other regions and vegetation types. The most important implications for management are that the natural disturbance processes producing landscape patterns in the boreal forest generally operate at much larger scales than management units, and that humans may have more indirect (through landuse change) rather than direct (through fire suppression) effects on the frequency of wildfires.     

Size-specific reproductive parameters in red algae: a comparative analysis for two sympatric species from Central Chile

Ahnfeltia durvillaei and Gymnogongrus furcellatus, two intertidal red algae from central Chile, often grow sympatrically and their gametophytic phases are dominant in the field, but recruitment is low. A shortterm comparative analysis of the reproductive behavior of their gametophytes was carried out to determine quantitative levels of reproduction and their degree of functional similarity. Size, rather than age, was evaluated as predictor of fecundity. Both species showed the same qualitative patterns, although maintaining quantitative differences. Reproductive plants were recorded throughout the size range, and fecundity increased continuously and directly with size. A size-independent threshold in reproductive effort was found for each species, and the variance of effort values decreased inversely with size. Vertical, size-specific life tables revealed low dependence of survivorship with size, and reproductive values exhibited a maximum at the same size class for both species. This last pattern, and a negative relationship found between fecundity and survivorship, suggest the existence of costs or trade-offs operating at the phenotypic level, but they would not be supported in a selective context.     

Canopy surface topography in a French Guiana forest and the folded forest theory

The canopy surface is an undulating surface that follows the irregular contours of the upper tree crowns and defines the inner and the outer limits of the forest volume. In French Guiana, the height of the canopy surface was surveyed in both a primary and a 20-years old clear-felled secondary forest plot. The topographic surface was displayed in a three-dimensional mesh, where X and Y are horizontal co-ordinates, and Z is the canopy height measured from the ground with an optical telemeter. The statistical dispersion of Z-data, and the spatial tree height variations, are interpreted at different levels of ecosystem organisation, from forest type (primary or secondary forest) to the trees themselves, following the folded forest model theory (Oldeman 1992, 1994). The vertical growth of trees creates a convex pattern in the relief of canopy surface, whereas gaps make concavities which delimit impact of perturbation on the forest structure. These events are either the result of the dynamic of single trees (emergent and decayed trees), or arise from the dynamic of a group of trees working together (group of emergent trees or complex gaps). At the plot scale, the elementary events, convexities and concavities, are gathered on similar topo-sequences, and form canopy units either higher or lower than the average canopy height. This study suggests that the topography of the canopy surface is defined by a complex nested system from trees, to groups of trees, to canopy units, within a delimited floristic and physical environment.     

Comparing Juniperus virginiana tree-ring chronologies from forest edge vs. forest interior positions in the Cedars Natural Area Preserve in Virginia, USA

We created two eastern red cedar master chronologies, one from trees growing along the edge of grassy openings and another from trees growing within the intact forest canopy. Correlation coefficients were calculated between ring width indices from two time periods (1895–1949 and 1950–2001) of the residual chronology and temperature, precipitation, and Palmer Drought Severity Indices (a standardized measure of dryness). The two time periods represented younger and older eastern red cedar. The younger, interior eastern red cedar had significant, positive correlations between ring width index (RWI) and June and November precipitation, March temperature, and Palmer Drought Severity Index (PDSI) from May through December. There were significant, negative correlations between RWI and May, June, and December temperature and May through July PDSI from the previous year. For the older, interior eastern red cedar significant, positive correlations existed between RWI and precipitation from the previous June, October, and December, and PDSI from July. Significant, negative correlations existed between RWI and January precipitation and May temperature. For the edge eastern red cedar within the earlier time segment (1895–1949) there was only one significant dendroclimatic correlation and this was a negative correlation with December temperature. For the edge eastern red cedar within the later time segment (1950–2001) there were significant, positive correlations between RWI and precipitation from June, September, October, and December of the previous year, March precipitation from the current growing season, and PDSI from July. There were significant, negative correlations between RWI and precipitation from January and November, temperature from the previous June, temperature from May and December, and PDSI from June of the previous year. Thus, eastern red cedar from the interior had more significant correlations to climate than trees growing along the edge. This result does not match other studies that have found edge trees to be more responsive to climate than interior trees. Perhaps this difference can be explained by some of the variations in the significant dendroclimatic correlations between the earlier and later time periods. The differences between the two time periods (within a single site) imply that the environmental conditions of trees changed over time. These differences may be a result of tree encroachment into the forest openings which creates a constantly changing environment for the eastern red cedar and results in some of the high variability of dendroclimatic relationships identified in this study. These results imply that trees growing in communities without stable edges, i.e. where the environment around the trees is in a constant state of flux, would be unsuitable for climatic reconstruction because they do not conform to the uniformitarian principle.     

森林管理在全球CO2减排中的作用

综述了各种森林管理措施在全球CO₂减排中的作用.这些管理措施主要包括减少森林砍伐速度,增加森林覆盖面积,加强对现存森林的肥料、火灾及病虫害管理,以薪材替代化石燃料等.同时探讨了中国的森林管理存在的优势和不足.目前中国森林生态系统主要是植被碳库,在全球碳循环过程中扮演着“碳汇”的角色,但其“碳汇”功能较小.因此,如何加强对新建人工林的抚育、病虫害和火灾管理,增强中国森林的“碳汇”功能,充分发挥其在CO₂减排中的作用,是我们面临的重要工作     

Effects of fire regime on plant species richness and composition differ among forest,woodland and heath vegetation

Question

Do the effects of fire regimes on plant species richness and composition differ among floristically similar vegetation types?

Location

Booderee National Park, south‐eastern Australia.

Methods

We completed floristic surveys of 87 sites in Sydney Coastal dry sclerophyll vegetation, where fire history records have been maintained for over 55 years. We tested for associations between different aspects of the recent fire history and plant species richness and composition, and whether these relationships were consistent among structurally defined forest, woodland and heath vegetation types.

Results

The relationship between fire regime variables and plant species richness and composition differed among vegetation types, despite the three vegetation types having similar species pools. Fire frequency was positively related to species richness in woodland, negatively related to species richness in heath, and unrelated to species richness in forest. These different relationships were explained by differences in the associations between fire history and species traits among vegetation types. The negative relationship between fire frequency and species richness in heath vegetation was underpinned by reduced occurrence of resprouting species at high fire frequency sites (more than four fires in 55 years). However, in forest and woodland vegetation, resprouting species were not negatively associated with fire frequency.

Conclusions

We hypothesize that differing relationships among vegetation types were underpinned by differences in fire behaviour, and/or biotic and abiotic conditions, leading to differences in plant species mortality and post‐fire recovery among vegetation types. Our findings suggest that even when there is a high proportion of shared species between vegetation types, fires can have very different effects on vegetation communities, depending on the structural vegetation type. Both research and management of fire regimes may therefore benefit from considering vegetation types as separate management units.     

Availability of coarse woody debris in a boreal old‐growth Picea abies forest

Abstract. This study reports temporal (based on cross‐dated dead trees) and spatial patterns of availability of coarse woody debris (CWD) from Picea abies in a Swedish boreal landscape with discrete old‐growth forest patches in a wetland matrix. Data were collected from 29 patches ranging in size from 0.3 to 28 ha. A total of 897 dead trees with a minimum diameter of > 15 cm occurred on the 7.2 ha area analysed. The year of death was established for 50% of these trees. CWD volume ranged from 17 to 65 m³/ha for downed logs and from 0.5 to 13 m³/ha for standing snags. CWD of all decay stages and diameter classes occurred abundantly and the probability of finding logs of all decay stages and sizes was very high at the scale of single hectares. Tree mortality differed among 5 yr periods. However, during the last 50 yr no 5 yr period produced less than 3 logs/ha. Decay rates were highly variable among different logs. Logs with soft wood and some wood pieces lost (decay stage 5) died ca. 34 years ago. This suggests a fairly rapid decay in this northern forest. The data indicate a high and continuous availability of CWD of all types. It is likely, therefore, that selection pressures for efficient dispersal among CWD dependent species may not be very high. Consequently, species with narrow habitat demands and/or low dispersal ability may have evolved and this may contribute to the decrease of certain species in the managed landscape.     

Idiosyncratic soil-tree species associations and their relationships with drought in a monodominant Amazon forest

Monodominant forests are characterized by the strong influence of a single species on the structure and diversity of the community. In the tropics, monodominant forests are rare exceptions within the generally highly diverse tropical forest biome. Some studies have shown that tree monodominance may be a transient state caused by successional and demographic variation among species over time. Working in a Brosimum rubescens Taub. (Moraceae) monodominant forest at the southern edge of Amazonia, we tested the hypotheses that local-scale variation in intra- and interspecific spatial patterns of dominant tree species is affected by i) demographic rates of recruitment and mortality following severe droughts, ii) local variation in edaphic properties, and iii) occupation of species in the vertical layer of the forest. We quantified intra- and interspecific spatial patterns and edaphic associations of the five most abundant species using aggregation and association distance indices, and examined changes over time. We found some support for all hypotheses. Thus, intra- and interspecific spatial patterns of most species varied over time, principally after severe drought, emphasizing species-level variability and their interactions in sensitivity to this disturbance, even as B. rubescens monodominance was maintained. While positive and negative spatial associations with edaphic properties provide evidence of habitat specialization, the absence of negative spatial associations of B. rubescens with edaphic properties indicates that this species experiences little environmental restriction, and this may be one of the factors that explain its monodominance. Spatial repulsion and attraction between species in the same and in different vertical layers, respectively, indicates niche overlap and differentiation, while changes over time indicate that the relationships between species are dynamic and affected by drought disturbance.