Termite diversity in Neotropical dry forests of Colombia and the potential role of rainfall in structuring termite diversity

Termites are ecosystem engineers that play an important role in the biotransformation and re‐distribution of nutrients in soil. The dry forests are endemic repositories, but at same time, they are most threatened by extensive livestock and crop farming, fires, and climate change. In Colombia, the best‐protected dry forests are located in the north. The termite fauna of dry forests are poorly known. The aim was to identify the termite species occurring in tropical dry forests of the Colombian Caribbean coast in relation to diet and precipitation, temperature, elevation, and soil properties. A total of 32 species in 1,103 occurrences were found. Termitidae accounted for 78% of the species richness with the Anoplotermes‐group, Microcerotermes, and Nasutitermes being the dominant genera. Differences in species composition and abundance were found across sites. These differences may be linked to anthropogenic disturbance and polygyny and polydomy. Strikingly, our highest elevation site (334 m) had the highest species richness much higher than the two lower elevation sites. This implies an inversion of the common elevation‐diversity gradient, also found for termites which can be explained by increasing precipitation with elevation in the dry forest. An analysis of termite species richness at the global scale confirms that termite species richness correlates positively with rainfall. Hence, rainfall seems to positively affect termite diversity. In line, the studied Colombian tropical dry forests had low diversity compared to rain forests. A decline of species‐rich soil‐feeding termites with increasing aridity may explain why the highest termite diversity occurs in humid tropical rain forests. Abstract in Spanish is available with online material.     

Diversity of terrestrial isopod species in the Chambi National Park (Kasserine,Tunisia)

Diversity of terrestrial isopods across habitats and altitude was studied in the National Park of Chambi (central Tunisia). Samples were collected over five years in seven sites (S1–S7), within an altitudinal range from 750 to 1,500 m a.s.l. Twelve species belonging to five families were identified, with one endemic species (Porcellio djahizi) to this area, and three species were present in all sites (P. djahizi, Leptotrichus panzerii and Armadillidium tunisiense). Agnaridae represented by Hemilepistus reaumurii species was the most abundant family (58.77%) and found in only one site. Our results showed differences in species richness between sites. Indeed, S2 and S3 (900 and 1,050 m) showed the highest species richness with 11 species each. This result validates the hypothesis of mid‐elevational richness peak and contradicts the theory of large sampling regimes in determining the relationship between species richness and elevation. Terrestrial isopod species richness in the Chambi Mountain tends to decrease with altitude: 11 species in S2 and S3 to four species in S7. The highest Shannon–Wiener diversity index value was observed in S2 (H′ = 3.21 bits). Canonical correspondence analysis revealed that H. reaumurii was positively correlated with temperature whereas A. tunisiense and P. djahizi were the only species positively correlated with altitude.     

Alternative pathways of liana communities in the forests of northwestern Argentina

Liana dynamics in secondary and mature forests are well known in tropical areas dominated by native tree species. Outside the tropics and in secondary forests invaded by exotic species, knowledge is scarce. In this study, we compare liana communities between secondary and mature forests dominated by native species in a subtropical montane area of Sierra de San Javier, Tucuman, Argentina. Additionally, we evaluate changes of liana communities in secondary forests with increasing densities of Ligustrum lucidum and Morus alba, two of the most invasive exotic trees of the area. We surveyed liana species richness and density in three 30-year secondary patches, four 60-year secondary patches, and four mature patches dominated by native tree species, to analyze changes in liana communities with forest age. Within each patch, we sampled 10–25 20 × 20 m quadrats. Additionally, we surveyed liana density and species richness in secondary forest patches with different densities of L. lucidum and M. alba. In native-dominated forests, liana species richness increased and showed a tendency of increasing basal area from 30-year secondary forests to mature forests. Liana density was highly variable, and most of the species were shared between native-dominated secondary and mature forests. Liana density and species richness decreased with L. lucidum density, whereas in secondary forests highly dominated by M. alba, lianas increased in density. Overall, lianas followed different pathways influenced by native forest succession and exotic tree invasions.     

Protecting a single endangered species and meeting multiple conservation goals: an approach with Guaiacum sanctum in Yucatan Peninsula,Mexico

Aim New protected areas should consider safeguarding high conservation value sites based on multiple criteria and not just the presence of a single endangered or charismatic species. However, the extent to which complementary criteria coincide is usually unknown. We use the case of Guaiacum sanctum (Zygopyllaceae), an endangered timber tree species, to explore whether the protection of forests where this species is most abundant would meet other complementary conservation goals, such as capturing regional plant biodiversity, protecting other threatened/endemic species or safeguarding ecosystem services. Location Yucatan Peninsula, southern Mexico. Methods We conducted an analysis of the structure, composition and diversity of tree communities (including stems ≥5 cm dbh) at eight G. sanctum forest sites. We identified endemic and threatened tree species and quantified above‐ground tree biomass and carbon storage in these G. sanctum forests. Results Guaiacum sanctum forests contain 35–59 tree species on plots as small as 1000 m². The species composition of tree communities changed rapidly (high β‐diversity) across soil boundaries and rainfall regimes. Twenty‐one endemic and eight threatened tree species were recorded in our inventories. Individuals of G. sanctum represented up to 55% of the above‐ground carbon for trees ≥5 cm dbh. The high basal area of G. sanctum forests plus the high wood density, abundance, large size and longevity (more than 500 years) of G. sanctum and other tree species enhance the potential importance of these forests for carbon storage. Main conclusions A conservation strategy focused on protecting important populations of G. sanctum in the Yucatan Peninsula would have significant co‐benefits for conservation of regional tree species biodiversity and provision of critical ecosystem services. Our study illustrates a multiple criteria approach useful for the selection of areas with high conservation value on the basis of endemic, threatened species, species richness and ecosystem services.     

Diversity of understory plants in undisturbed and disturbed tropical lowland forests of Little Andaman Island, India

Species richness and density of understory plants were investigated in eight 1 ha plots, distributed one each in undisturbed and disturbed tropical evergreen, semi-evergreen, deciduous and littoral forests of Little Andaman island, India, which falls under one of the eight hottest hotspots of Biodiversity in the world viz. the Indo-Burma. One hundred 1 m⁻² quadrats were established in each 1 ha plot, in which all the understory plants (that include herbs, undershrubs, shrubs and herbaceous climbers) were enumerated. The total density of understory plants was 6,812 individuals (851 ha⁻¹) and species richness was 108 species, representing 104 genera and 50 families. Across the four forest types and eight study plots, the species richness ranged from 10 to 39 species ha⁻¹. All the disturbed sites harbored greater number of species than their undisturbed counterparts. Herbs dominated by species (63%) and density (4,259 individuals). The grass Eragrostis tenella (1,860 individuals; IVI 40), the invasive climber Mikania cordata (803; IVI 20) and the shrub Anaxagorea luzonensis (481; IVI 17.5) were the most abundant species. Poaceae, Asteraceae, Acanthaceae, Orchidaceae and Euphorbiaceae constituted the species-rich families represented by 6 species each. The species-area curves attained an asymptote at 0.8 ha level except in sites DD and DL, indicating 1 ha plot is not sufficient to capture all the understory species in disturbed forests. The alien weeds formed about one-fourth of the species richness (31 species; 28%) and density (1,926 individuals; 28.3%) in the study sites, indicating the extent of weed invasion and the attention required for effective conservation of the native biodiversity of the fragile island forest ecosystem.     

Bryophyte Species Diversity in Secondary Forests Dominated by the Introduced Species Spathodea campanulata Beauv. in Puerto Rico

The introduced tree species Spathodea campanulata (Bignoniaceae) forms novel forests in Puerto Rico, these having emerged after the abandonment of fields in the mid‐20th century and resulting in forests with a new species composition. We assessed bryophyte species richness in these novel forests and sought correlations with geological substrate, past land use, forest edge and patch area, forest structure, elevation, microhabitat diversity, tree species richness, and microclimatic conditions. Transects were established (edge and forest interior) in nine moist forest patches dominated by Spathodea in north‐central Puerto Rico. These Spathodea forest patches ranged from 0.6 to 9 ha. ANOVA, Chi‐square, correlation, and cluster analyses were used in data analyses. We found 57 bryophyte species. There was a significant difference in bryophyte richness among patches. Those on karst exhibited highest bryophyte richness due to microhabitat diversity, past land use, and shorter hydroperiods. Alluvial sites scored lowest in bryophyte species richness, and forest structure was important for bryophyte communities on these sites. Significant differences in temperature, relative humidity, and light intensity were observed between edge and forest interior. These appeared important for establishing bryophyte species cover but not richness and composition. Microhabitat diversity, patch area, and forest age were more related to bryophyte species richness than elevation, exposed edge, and tree species richness, regardless of geologic substrate. Collectively, Spathodea patches were similar to mature forests on the Island with respect to bryophyte species richness and composition. Novel Spathodea forests have conservation value due to their habitat suitability for bryophyte communities.     

Assessing the effectiveness of protected areas for conserving range-restricted rain forest butterflies in Sabah,Borneo

Rain forests on Borneo support exceptional concentrations of endemic insect biodiversity, but many of these forest-dependent species are threatened by land-use change. Totally protected areas (TPAs) of forest are key for conserving biodiversity, and we examined the effectiveness of the current TPA network for conserving range-restricted butterflies in Sabah (Malaysian Borneo). We found that mean diurnal temperature range and precipitation of the wettest quarter of the year were the most important predictors of butterfly distributions (N = 77 range-restricted species), and that species richness increased with elevation and aboveground forest carbon. On average across all species, TPAs were effective at conserving ~43% of species’ ranges, but encompassed only ~40% of areas with high species richness (i.e., containing at least 50% of our study species). The TPA network also included only 33%–40% of areas identified as high priority for conserving range-restricted species, as determined by a systematic conservation prioritization analysis. Hence, the current TPA network is reasonably effective at conserving range-restricted butterflies, although considerable areas of high species richness (6,565 km²) and high conservation priority (11,152–12,531 km²) are not currently protected. Sabah's remaining forests, and the range-restricted species they support, are under continued threat from agricultural expansion and urban development, and our study highlights important areas of rain forest that require enhanced protection.     

Alien dominance of the parasitoid wasp community along an elevation gradient on Hawai’i Island

Through intentional and accidental introduction, more than 100 species of alien Ichneumonidae and Braconidae (Hymenoptera) have become established in the Hawaiian Islands. The extent to which these parasitoid wasps have penetrated native wet forests was investigated over a 1,765 m elevation gradient on windward Hawai’i Island. For >1 year, malaise traps were used to continuously monitor parasitoid abundance and species richness in nine sites over three elevations. A total of 18,996 individuals from 16 subfamilies were collected. Overall, the fauna was dominated by aliens, with 44 of 58 species foreign to the Hawaiian Islands. Ichneumonidae was dominant over Braconidae in terms of both diversity and abundance, comprising 67.5% of individuals and 69.0% of species collected. Parasitoid abundance and species richness varied significantly with elevation: abundance was greater at mid and high elevations compared to low elevation while species richness increased with increasing elevation, with all three elevations differing significantly from each other. Nine species purposely introduced to control pest insects were found, but one braconid, Meteorus laphygmae, comprised 98.0% of this assemblage, or 28.3% of the entire fauna. Endemic species, primarily within the genera Spolas and Enicospilus, were collected almost exclusively at mid- and high-elevation sites, where they made up 22.1% and 36.0% of the total catch, respectively. Overall, 75.9% of species and 96.0% of individuals are inferred to parasitize Lepidoptera larvae and pupae. Our results support previous data indicating that alien parasitoids have deeply penetrated native forest habitats and may have substantial impacts on Hawaiian ecosystems.     

Species diversity and community structure in sal (<Emphasis Type="Italic">Shorea robusta</Emphasis>) forests of two different rainfall regimes in West Bengal,India

Knowledge on the structure and composition of the plant communities has enormous significance in conservation and management of forests. The present study aimed to assess the community attributes, viz., structure, composition and diversity in the moist and dry sal (Shorea robusta) forests in the West Bengal province of India and compare them with the other sal forests of India. The phytosociological data from these forests were quantitatively analysed to work out the species richness, diversity, evenness, dominance, importance value, stand density and the basal area. The analysis showed that plant richness and diversity in moist sal forests of northern West Bengal are higher than the dry sal forests of south-west Bengal; a total of 134 tree (cbh ≥30 cm), 113 shrub and 230 herb species were recorded in the moist sal forest compared to 35 tree, 41 shrub and 96 herb species in dry sal forest. Papilionaceae was observed to be the dominant family. Dry sal forests had higher tree dominance (0.81) and stand density (1,006 stems ha⁻¹) but lower basal area (19.62 m²ha⁻¹) while moist sal forest had lower tree dominance (0.18) and stand density (438 stems ha⁻¹) but higher basal area (56.52 m²ha⁻¹). Tree species richness and stem density across girth classes in both the types decreased from the smallest to largest trees, while the occurrence rate of species increased with increase in girth class. A t-test showed significant differences in species richness, basal area and the stand density at 95% confidence level (p = <0.05) in the two forest types. The CCA indicated very low overall match (canonical correlation value = 0.40) between the two sets of variables from moist and dry sal types. The differences in these forests could be attributed to the distinct variations in climatic conditions- mainly the rainfall, disturbance regimes and the management practices.     

Relationships between the density of two potential restoration tree species and plant species abundance and richness in a degraded Afromontane forest of Kenya

In recent years, there have been considerable efforts to restore degraded tropical montane forests through active restoration using indigenous tree species. However, little is known about how these species used for restoration influence other species. In this study, two potential restoration species, Albizia gummifera and Neoboutonia macrocalyx, are investigated with regard to the relationship between their density and the abundance and richness of other plant species. The study was conducted in a degraded forest consisting of disturbed transition zones and secondary forest. Our results show positive relationships between the density of A. gummifera and the abundance of tree seedling and sapling richness in the transition zones and in the secondary forest. Shrub richness was negatively related to the density of A. gummifera. Abundance and richness of tree saplings and shrubs were positively related to N. macrocalyx density both in the transition zones and in the secondary forest. Herb species richness declined with N. macrocalyx density in the transition zones but increased with N. macrocalyx density in the secondary forest. The positive relationships between the density of the two tree species and species richness of other woody species suggest that both A. gummifera and N. macrocalyx can be suitable for active restoration of degraded mountain forests within their natural range.     

Agricultural land use and black fly (Diptera,Simuliidae) species richness and species assemblages in tropical streams,Northeastern Thailand

Habitat degradation through agricultural land use is the major factor threatening lotic ecosystems. Although black flies are major components of these ecosystems, the impact of agricultural land use on species diversity and species assemblages has been largely ignored in tropical streams of the Oriental region. The objectives of this study are to examine patterns of species distribution and species richness and to compare black fly species richness and species assemblages in forest and agricultural streams in Thailand. A total of 143 collections were made from 70 stream sites between June 2007 and May 2008. Whereas 19 black fly species found in these collections were all found in forest sites, only 13 species were found in agricultural sites. High species richness was associated with larger, faster, and cooler streams with larger streambed particles and the presence of riparian trees. Logistic regression analyses revealed that stream size, velocity, and riparian vegetation are among the most important factors determining patterns of spatial distribution. The results are largely consistent with studies in other zoogeographic regions, suggesting the existence of general rules for black fly species distributions. Comparisons of the physicochemical conditions between forest and agricultural streams indicated that streams in agricultural areas are warmer, with higher conductivity and fewer riparian trees. Species richness was significantly higher in forest than in agricultural streams (t = 3.61, P < 0.001). Streams in forest areas were predominantly occupied by S. siamense (73%) but other species were also found at a relatively high frequency (>20%) of the sampling sites. In contrast, streams in agricultural areas were predominantly occupied by S. aureohirtum (>80%) among the sole black fly species at 27% of the sites. The results indicate that agricultural land use has a significantly detrimental impact on black fly diversity and species assemblages. Handling editor: D. Dudgeon     

Distribution of vascular plant species richness and endemic richness along the Himalayan elevation gradient in Nepal

Aim Species richness and endemic richness vary along elevation gradients, but not necessarily in the same way. This study tests if the maxima in gamma diversity for flowering plants and the endemic subset of these plants are coherent or not. Location The study was conducted in Nepal, between 1000 and 5000 m a.s.l. Methods We used published data on distribution and elevational ranges of the Nepalese flora to interpolate presence between maximum and minimum elevations. Correlation, regression and graphical analyses were used to evaluate the diversity pattern between 1000 and 5000 m a.s.l. Results The interval of maximum species endemic to Nepal or the Himalayas (3800–4200 m) is above the interval of maximum richness (1500–2500 m). The exact location of maximum species density is uncertain and its accuracy depends on ecologically sound estimates of area in the elevation zones. There is no positive statistically significant correlation between log‐area and richness (total or endemic). Total richness is positively correlated with log‐area‐adjusted, i.e. estimated area adjusted for the degree of topographic heterogeneity. The proportion of endemic species increases steadily from low to high elevations. The peak in endemism (c. 4000 m) corresponds to the start of a rapid decrease in species richness above 4000 m. This may relate to the last glacial maximum (equilibrium line at c. 4000 m) that penetrated down to 2500–3000 m. This dynamic hard boundary may have caused an increase in the extinction rate above 4000 m, and enhanced the probability of isolation and facilitated speciation of neoendemics, especially among genera with a high proportion of polyploids. Main conclusions The results reject the idea of corresponding maxima in endemic species and species richness in the lowlands tentatively deduced from Stevens’ elevational Rapoport effect. They confirm predictions based on hard boundary theory, but hard‐boundaries should be viewed as dynamic rather than static when broad‐scale biogeographical patterns with a historical component are being interpreted.     

Effectiveness of passive restoration on density and diversity of regenerating tree species in mixed Dipterocarp forests of Nepal

In many developing countries, the only affordable approach to recover ecosystem structure and function is through passive restoration. We conducted a 3 year study of passive restoration in mixed Dipterocarp forests dominated by Shorea robusta to examine the effectiveness of exclusion (fencing and fire suppression) on diversity, density, and richness of regenerating tree seedlings and saplings. We analyzed excluded and disturbed paired sites. We observed exclusion was effective in increasing seedling richness and occurrence of S. robusta and Syzygium cumini. A significant improvement in sapling strata (diversity, density, and richness) from excluding the disturbances was observed. Mean sapling density estimated was about 500% higher in excluded compared to disturbed sites. Probability of occurrence of S. robusta and Dalbergia latifolia saplings increased due to exclusion. That said, presence of exotic species Chromolaena odorata was higher in excluded sites reflecting the need for assisted natural regeneration in forests. This study has demonstrated passive restoration as an effective approach for improving natural regeneration in mixed Dipterocarp forest ecosystems and possibly other similar forest types, and will serve as a reference document for future restoration interventions.     

Woody vegetation dynamics in the tropical and subtropical Andes from 2001 to 2014: Satellite image interpretation and expert validation

The interactions between climate and land‐use change are dictating the distribution of flora and fauna and reshuffling biotic community composition around the world. Tropical mountains are particularly sensitive because they often have a high human population density, a long history of agriculture, range‐restricted species, and high‐beta diversity due to a steep elevation gradient. Here we evaluated the change in distribution of woody vegetation in the tropical Andes of South America for the period 2001–2014. For the analyses we created annual land‐cover/land‐use maps using MODIS satellite data at 250 m pixel resolution, calculated the cover of woody vegetation (trees and shrubs) in 9,274 hexagons of 115.47 km², and then determined if there was a statistically significant (p < 0.05) 14 year linear trend (positive—forest gain, negative—forest loss) within each hexagon. Of the 1,308 hexagons with significant trends, 36.6% (n = 479) lost forests and 63.4% (n = 829) gained forests. We estimated an overall net gain of ~500,000 ha in woody vegetation. Forest loss dominated the 1,000–1,499 m elevation zone and forest gain dominated above 1,500 m. The most important transitions were forest loss at lower elevations for pastures and croplands, forest gain in abandoned pastures and cropland in mid‐elevation areas, and shrub encroachment into highland grasslands. Expert validation confirmed the observed trends, but some areas of apparent forest gain were associated with new shade coffee, pine, or eucalypt plantations. In addition, after controlling for elevation and country, forest gain was associated with a decline in the rural population. Although we document an overall gain in forest cover, the recent reversal of forest gains in Colombia demonstrates that these coupled natural‐human systems are highly dynamic and there is an urgent need of a regional real‐time land‐use, biodiversity, and ecosystem services monitoring network.     

Forest/environment relationships in Yosemite National Park,California, USA

Forest compositional patterns in Yosemite National Park, California, were related to environmental factors through numerical classification of forest types, arrangement of forest types along elevational and topographic gradients, and development of regression models relating basal area of common tree species to environmental variables. The eight forest types are differentiated primarily by elevation zone and secondarily by topographic setting. Lower montane forests (1200–1900 m) were divided into the Abies concolor/Calocedrus type occurring primarily on mesic sites and the Pinus ponderosa/Calocedrus type predominantly on xeric sites. Upper montane forests (1900–2500 m) included the Abies concolor/Abies magnifica type on mesic sites, the Abies magnifica/Pinus type on somewhat more xeric sites, and Juniperus occidentalis/Pinus jeffreyi woodlands on granitic domes. Subalpine forests (2500–3300 m) embraced three types: Tsuga mertensiana/Pinus forests on mesic sites, monotypic Pinus contorta forests on drier sites, and Pinus albicaulis/Pinus contorta groves at treeline. Regression models consistently included elevation and soil magnesium content as explanatory variables of species basal area totals. The two Abies spp. were negatively correlated with soil magnesium levels, whereas other montane species (e.g. Calocedrus decurrens, Pinus lambertiana, and Pinus ponderosa) exhibited positive correlation with soil magnesium. Topography and soil physical properties were only infrequently incorporated into species regression models.Abbreviations DBH= diameter at breast height (1.4 m) - DCA= detrended correspondence analysis - TWINSPAN= two-way indicator species analysis     

Diversity patterns of vascular epiphytes along an elevational gradient in the Andes

Aim To document the elevational pattern of epiphyte species richness at the local scale in the tropical Andes with a consistent methodology. Location The northern Bolivian Andes at 350–4000 m above sea level. Methods We surveyed epiphytic vascular plant assemblages in humid forests in (a) single trees located in (b) 90 subplots of 400 m² each located in (c) 14 plots of 1 ha each. The plots were separated by 100–800 m along the elevational gradient. Results We recorded about 800 epiphyte species in total, with up to 83 species found on a single tree. Species richness peaked at c. 1500 m and declined by c. 65% to 350 m and by c. 99% to 4000 m, while forests on mountain ridges had richness values lowered by c. 30% relative to slope forests at the same elevations. The hump‐shaped richness pattern differed from a null‐model of random species distribution within a bounded domain (the mid‐domain effect) as well as from the pattern of mean annual precipitation by a shift of the diversity peak to lower elevations and by a more pronounced decline of species richness at higher elevations. With the exception of Araceae, which declined almost monotonically, all epiphyte taxa showed hump‐shaped curves, albeit with slightly differing shapes. Orchids and pteridophytes were the most species‐rich epiphytic taxa, but their relative contributions shifted with elevation from a predominance of orchids at low elevations to purely fern‐dominated epiphyte assemblages at 4000 m. Within the pteridophytes, the polygrammoid clade was conspicuously overrepresented in dry or cold environments. Orchids, various small groups (Cyclanthaceae, Ericaceae, Melastomataceae, etc.), and Bromeliaceae (below 1000 m) were mostly restricted to the forest canopy, while Araceae and Pteridophyta were well represented in the forest understorey. Main conclusions Our study confirms the hump‐shaped elevational pattern of vascular epiphyte richness, but the causes of this are still poorly understood. We hypothesize that the decline of richness at high elevations is a result of low temperatures, but the mechanism involved is unknown. The taxon‐specific patterns suggest that some taxa have a phylogenetically determined propensity for survival under extreme conditions (low temperatures, low humidity, and low light levels in the forest interior). The three spatial sampling scales show some different patterns, highlighting the influence of the sampling methodology.     

<Emphasis Type="Italic">Grias angustipetala</Emphasis> and <Emphasis Type="Italic">G. ecuadorica</Emphasis>, two new species of Lecythidaceae from western Ecuador

Grias angustipetala and G. ecuadorica, two new species from the wet forests of western Ecuador are described. Grias angustipetala occurs in the Awá Indígenous Territory and Reserva Ecológica Cotacachi-Cayapas in the Esmeraldas and adjacent Carchi Provinces between 50–1800 m elevation. Grias ecuadorica is found in the Los Ríos and Bolívar Provinces between 70–600 m elevation. The new species are illustrated and their relationships with related species are discussed.     

Abundance,richness and composition of lianas in forest communities along an elevation gradient in New Caledonia

Background: Lianas are an abundantand dynamic component of tropical forests, and their abundance ispredicted to increase with global change. A better understandingof factors that explain their distribution is required, especially onoceanic islands for which few data are available.

Aims: Identifythe environmental factors that shape liana communities in NewCaledonian forests

Methods: We studied liana abundance,basal area, richness and climbing modes in 27 forest plots (20m × 20 m) along an elevation gradient (sea level to ca. 1000 ma.s.l.) that covers different forest types and precipitation regimes.

Results: We inventoried 992 lianas belonging to 71 species. The abundance and basal area decreased logarithmically withincreasing elevation while species richness tended to peak at midelevations.Twining lianas were the most abundant and species-richfunctional group. We found no clear relationship between climbingmodes and forest structure.

Conclusions: Our results show thatliana abundance decreases with increasing elevation in responseto lower precipitation in seasonal dry forest. At high elevation (600–1000 m a.s.l.), climbing secondary hemi-epiphytes replace lianasprobably as a result of climate-based niche differentiation. Variationof species richness along the gradient could not be explained byprecipitation or by forest structural parameters.     

Influence of niche characteristics and forest type on fern species richness,abundance and plant size along an elevational gradient in Costa Rica

An analysis of the fern vegetation on 156 plots along an elevational gradient (45-3400 m) in undisturbed forests in Costa Rica, Central America, showed a hump-shaped pattern of species richness with a maximum of up to 68 species per 400 m2 at mid-elevations. This study documents the contribution of specific habitats (forest types: ridges, ravines) and niches within them (dead wood, rocks, growth zones in trees) to the local fern richness and the relation of species richness to elevation and climatic variables. Forests along ravines showed significantly higher species richness, presumably caused by high environmental humidity. The mean number of individuals of occupied niches per species increased significantly with elevation, suggesting that the niche breadth of species increased and that the differentiation of niches decreased with elevation. Both findings may explain the reduced fern species richness towards and above the upper treeline, but not at low elevations. The key factors for the decreases of species richness at the extremes of the gradient are likely to involve climatic conditions.     

The Influence of Habitat,Season, and Detectability on Abundance Estimates across an Amazonian Parrot Assemblage

The Amazon basin holds very high parrot species richness but almost nothing is known of parrot population densities in the region or how these vary between species, habitats, sites, and seasons. Such data are becoming important as humans impact on increasing areas of the region. Seventeen parrot species were surveyed using a line transect distance sampling method over 3 yr in floodplain and terra firme forests at two sites in the Tambopata region of southeast Peru. Density estimates for most species were in the range of 3.3–7.8/km², with Brotogeris cyanoptera and Amazona farinosa reaching densities of 22 and 23/km² in floodplain forest during the dry season. Parrot densities were higher in floodplain forest than in terra firme forest at both sites. The parrot communities of terra firme forests were similar across sites and seasons, but those in floodplain forests differed widely across sites and across seasons. Upper canopy birds are notoriously difficult to survey. We introduce a procedure to correct for the likely violation of the assumption that all birds on the transect line are detected (distance sampling assumption g(0) = 1). We correct g(0) based on calling rates of birds using a cue‐counting technique. Multipliers for g(0) differ across species and site, but not season. This method yielded density estimates on average 22 percent higher (6–40% higher in individual species) than those from the standard method.