Tree turnover in a premontane neotropical forest (1998–2009) in Costa Rica

Tropical premontane forests between 700 and 1,400 m.a.s.l. represent a particular component of the gamma diversity of neotropical ecosystems; however, the extent of information about their dynamics lags behind the more studied lowland rain forests. Data from three 1-ha permanent plots in a premontane forest in Costa Rica collected during an 11-year period (1998–2009) suggested a high tree turnover rate for this ecosystem (high mortality rate, λ = 2.4% and annual recruitment, μ = 2.6%). The floristic composition did not significantly change during the study period, but its high dynamism (2.4%) exceeded that of several reported values from highly diverse neotropical lowland rain forests. The documented decrease in abundance (8.6%) and basal area (14.3%) of trees ≥10 cm in DBH differs from the general trend of increase described for several lowland tropical rain forests in recent decades. We detected a significant population reduction (>15% of individuals from 1998 to 2009) in several relatively abundant tree species, whereas the populations of the three most dominant species remained nearly constant. The high tree turnover recorded for this premontane forest might not have affected tree diversity; but it might be promoting recruitment and growth of some tree species that may eventually become over-dominant in this ecosystem.     

Seasonal variations in moisture use in a piñon–juniper woodland

In water-limited environments of the intermountain region of North America, summer precipitation may play a role in the structure and function of aridland communities and ecosystems. This study examined the potential reliance on summer precipitation of two widespread, coexisting woody species in the southwestern United States, Pinus edulis Englmn. (Colorado piñon) and Juniperus osteosperma (Torr) Little (Utah juniper). The current distributions of P. edulis and J. osteosperma are highly suggestive of different dependencies on summer rainfall. We hypothesized that P. edulis was dependent on summer precipitation, utilizing summer precipitation even during extremely dry summers, whereas J. osteosperma was not dependent, using summer precipitation only when amounts were above some minimum threshold. Using sap flux and stable isotopic methods to assess seasonal water sources and water use efficiency, we examined the response of these two species to seasonal variations in moisture at a site located near the northern limits of the North American monsoon. Both sap flux and isotopic results indicated that P. edulis was responsive to summer rain, while J. osteosperma was not. Following summer rain events, sap flux density increased in P. edulis for several days, but not in J. osteosperma. Isotopic evidence indicated that P. edulis took up summer-derived moisture to a greater extent than J. osteosperma. Values of the natural abundance stable isotope ratio of carbon of leaf soluble carbohydrates increased over the summer for P. edulis, indicative of assimilation at higher water use efficiency, but were invariant for J. osteosperma. Our results supported the hypothesis that P. edulis and J. osteosperma are differentially sensitive to summer precipitation and are discussed in the light of potential changes in the seasonality of precipitation associated with climate change.     

Tree population changes in a tropical dry evergreen forest of south India over a decade (1992–2002)

Changes in species composition and density of trees >10 cm gbh in a tropical dry evergreen forest in Puthupet, south India are interpreted for the period between 1992 and 2002. A 1-ha plot was inventoried in 1992 and was recensused in 2002. During the 10-year interval tree taxa diversity as well as stand density increased, but the basal area value decreased. Tree species richness increased by 21% (from 24 to 29 species) by an addition of eight species and local extinction of three species. The tree density increased just by eight individuals (from 1330 stems ha⁻¹ in 1992 to 1338 ha⁻¹ in 2002), but the basal area decreased by 8% (from 37.5 to 34.5 m² ha⁻¹). Many species (11 numbers) have increased in abundance rather than decreased. Many surviving species seem to have considerable stability in abundance at the local scale. The density of smaller stems (10 29 cm gbh) increased by 15.3%, while that of the larger trees decreased drastically (81.6%). Ninety percent of the missing stems were from the middlestorey of the forest. Tree density changes among the three ecological guilds revealed a decrease in stem density and an increase in basal area in the lowerstorey; while the middlestorey exhibited a reverse trend. Family-wise, tree density changes revealed that the majority of families (67%) showed an increase in stem density. Long-term studies on tree population changes are essential to estimate tree mortality and recruitment rates, which will provide a greater insight in tropical forest dynamics.     

Tree holes in a mixed broad-leaf?podocarp rain forest, New Zealand

Despite the ecological importance of tree holes as habitat for many species in New Zealand, few studies have quantified the abundance, distribution or structural characteristics of tree holes in native forests. We recorded a total of 364 tree holes in ground-to-canopy surveys on 50 trees of five endemic species in the families Fagaceae and Podocarpaceae within Orikaka Ecological Area, Buller District, New Zealand. Tree holes were not uniformly distributed throughout the forest, with more holes in the three podocarp species Prumnopitys ferruginea, P. taxifolia and Dacrycarpus dacrydioides than in Nothofagus fusca or N.?menziesii. However, N. fusca had the largest tree holes of any of the tree species sampled. Tree-hole volume and tree-hole opening both increased with tree size. Tree-hole opening was strongly positively correlated with internal volume, especially for the podocarps. It therefore potentially provides a useful surrogate measure for quantifying the abundance of large tree holes from cost-effective ground surveys. We estimated there might be as many as 771 tree holes per hectare of forest at this site, but fewer of these were thought to be large enough for obligate hole-dwelling vertebrate species. Our findings differ from those of previous researchers in native forests around New Zealand because earlier studies use ground-based surveys to sample the abundance of tree holes suitable for specific fauna, whereas we used climbed inspections where all tree holes were recorded. This could be particularly important for the conservation management of native vertebrate and invertebrate species.     

Predator-prey relationships in the southeastern Ozarks–A.D. 1300

Archeological findings provide the basis for analyzing the exploitation of deer by Powers Phase Indian hunters in the southeastern Ozarks circaA.D. 1300. Predatory patterns of wolves have been documented. It is hypothesized that men and wolves were complementary, noncompetitive predators and that their predation functioned to keep the deer population within the carrying capacity of the southeastern Ozarks. A model is developed to illustrate the predator-prey relationships in the area.Powers Phase Research Project is financed by National Science Foundation Grant GS-3215 to James B. Griffin, University of Michigan.The term Powers Phase has been applied to a pre-Columbian American Indian population of Middle Mississippian cultural affiliation which occupied an area in southeast Missouri for a relatively short period of timecirca A.D. 1300.     

A preliminary reconstruction (A.D. 1635–2000) of spring precipitation using oak tree rings in the western Black Sea region of Turkey

Tree-ring data for Turkey are crucial to the understanding of the climatological effect of drought and rainfall from one era to the next. To this end, the present study reconstructed precipitation patterns in the western Black Sea region of Turkey. Tree-ring widths of oak trees were used to reconstruct March–June precipitation patterns for the years A.D. 1635–2000. According to the findings, during the past four centuries drought events in this region persisted for no more than 2 years, and extreme dry and wet events occurred generally in 1-year intervals. Historical records of droughts in Anatolia and neighboring countries corroborate the data furnished by tree-ring widths to indicate that major droughts and famine events occurred in 1725, 1757, 1887, 1890–1891, 1893–1894 and 1927–1928.     

Tree species regeneration in a mid-elevation,temperate rain forest in Isla de Chiloé, Chile

The regeneration of canopy and subeanopy species in a mid-elevation, primary rain forest in the Coastal Range of Isla de Chiloé (42°30S), in the cold-temperate region of Chile, was studied by comparing seedling and sapling abundances under the forest canopy, and within 36 tree-fall gaps. The forest was dominated byAmomyrtus luma andLaurelia philippiana (33 and 32% of the main canopy individuals), and two subcanopy species (Myrceugenia ovata, andMyrceugenia planipes) were also important. Uncommon species in the canopy wereDrimys winteri, Amomyrtus meli, andRaphithamnus spinosus. Tree-fall gaps were created generally by the fall of several trees, and the main canopy species were the principal gap-makers. Gap sizes varied between 28 and 972 m², with a mean of 197 m². Seedling and sapling abundances indicate that the dominant species are capable of regenerating below the canopy, but they also germinate and show enhanced growth within small light gaps. For one of the common subcanopy species (M. planipes) and the two infrequent canopy species (D. winteri, andA. meli) regeneration seems to depend entirely on tree-fall gaps. Thus, in this forest, light gaps allow the persistence of infrequent canopy species, but seem less important for the regeneration and maintenance of dominant canopy species.     

Carbon–biodiversity relationships in a highly diverse subtropical forest

Carbon-focused climate mitigation strategies are becoming increasingly important in forests. However, with ongoing biodiversity declines we require better knowledge of how much such strategies account for biodiversity. We particularly lack information across multiple trophic levels and on established forests, where the interplay between carbon stocks, stand age, and tree diversity might influence carbon–biodiversity relationships. Using a large dataset (>4600 heterotrophic species of 23 taxonomic groups) from secondary, subtropical forests, we tested how multitrophic diversity and diversity within trophic groups relate to aboveground, belowground, and total carbon stocks at different levels of tree species richness and stand age. Our study revealed that aboveground carbon, the key component of climate-based management, was largely unrelated to multitrophic diversity. By contrast, total carbon stocks—that is, including belowground carbon—emerged as a significant predictor of multitrophic diversity. Relationships were nonlinear and strongest for lower trophic levels, but nonsignificant for higher trophic level diversity. Tree species richness and stand age moderated these relationships, suggesting long-term regeneration of forests may be particularly effective in reconciling carbon and biodiversity targets. Our findings highlight that biodiversity benefits of climate-oriented management need to be evaluated carefully, and only maximizing aboveground carbon may fail to account for biodiversity conservation requirements.     

Raoul Combes (1883–1964) et la S.I.G.M.A.

Sans résumé     

Microchips in the laboratory of A.D. Mirzabekov: 1988–2007

The paper reviews the last period in the research work of A.D. Mirzabekov, when gel-based biochips were invented, studied, and introduced in practice. This work, starting from the early stages of the Human Genome Project up to the recent development of diagnostic and protein biochips, is considered in the context of the worldwide development of microarray technologies.     

Sexual reproduction of clonal dwarf shrubs in a forest–tundra ecotone

Successful sexual reproduction may be more important for regeneration of clonal species in high-latitude and -altitude areas than has been previously suggested. We investigated the potential of Vaccinium myrtillus, V. vitis-idaea and Empetrum nigrum ssp. hermaphroditum (E. hermaphroditum) for sexual reproduction at three sites in the forest–tundra ecotone in Finnish Lapland. We studied whether the potential differs between plant communities, whether disturbance enhances germination, and whether seedling emergence is limited by seed availability. We established a field experiment with disturbance and sowing treatments, and monitored seed and seedling numbers and survival rates for two years. The number of mature seeds of V. myrtillus was higher in plants from the tundra heath than in those from the coniferous and mountain birch forests. The number of mature seeds and seedlings emerging from the seed bank of E. hermaphroditum tended also to be higher in the tundra heath. Disturbance marginally increased the seedling emergence of V. myrtillus and E. hermaphroditum, whereas sowing generally increased the seedling numbers. The seedling number of V. myrtillus was lower in the tundra heath and that of E. hermaphroditum was lower in the coniferous forest than at the other sites. Seedling survival was equal for all plant species at all sites. We conclude that the capacity for sexual reproduction varies among plant communities, and seed availability is a stronger constraint than microsite availability for the studied species. Once the crucial early phase of seedling establishment is overcome, seedling survival enables successful recruitment of V. myrtillus, V. vitis-idaea and E. hermaphroditum in the subarctic area.     

Gap-phase regeneration in a semideciduous mesophytic forest, south–eastern Brazil

The study was carried out in ten natural canopy gaps in the SantaGenebra County Reserve (22°4945S, 47°0633W)in the county of Campinas, São Paulo State, Brazil. The size and canopyopenness of the gaps were studied using hemispherical photographs. Thevegetation survey included all shrubs and trees with height 0.50m in the gaps interiors and all the individuals with PBH(perimeterat breast height) 15 cm in a 3 m surroundingborder of the gaps. The similarity among the gaps and among their surroundingareas was assessed by the Jaccard similarity index and by cluster analyzes. Thegap size varied from 20.09 to 468 m², with apredominance of small gaps. The families with the greatest species richness inthe gaps were Rutaceae, Rubiaceae and Euphorbiaceae. The species with thegreatest number of individuals in the gaps were Coffeaarabica L., Hybanthus atropurpureus (St. Hil.)Taub. and Actinostemon klotschii (Muell. Arg.) Pax, allwidely distributed in the understorey. Shade-tolerant species (late secondaryspecies) predominated in function of the predominance of small gaps. The highnumber of species found in the gaps reflects the importance of thesedisturbances in the maintenance of species diversity in the studied forest.     

Plant–pollinator interactions in the understory of a lowland mixed dipterocarp forest in Sarawak

Pollination biology of 41 plants species of 21 families blooming in the forest understory was investigated in a lowland mixed diplerocarp forest in Lambir Hills National Park, Sarawak. Among these species, 29 species (71%) were pollinated by bees, four (10%) by nectariniid birds, three by small dipterans, and others by moths, butterflies, syrphid flies, wasps, and beetles. The 29 bee-pollinated species consisted of five distinct pollination guilds: ten species pollinated by medium traplining bees (two Amegilla species), nine by small traplining bees (three halictid and a xylocopine species), two by stingless bees and beetles, seven by stingless bees, and one by megachilid bees. The bees constituting the first two guilds were shade-loving, swiftly flying, long-tongued trapliners. Proboscis lengths of these pollinators correlated with flower depth of the host plant. Pollination systems in the forest understory were distinguished from that in the canopy by the prevalence of specific interactions, the number of traplining solitary bees, and lack of pollination systems by mass-recruiting eusocial bees, large Xylocopa bees, thrips, bats, and wind. These characteristics are largely similar between the Palaeotropics and the Neotropics through convergence of nectarivorous birds (spiderhunters vs. hummingbirds) and traplining bees (Amegilla vs. euglossine bees).     

Tree level indicators of species composition of saproxylic beetles in old-growth mountainous spruce–beech forest through variation partitioning

Forest reserves can serve as an opportunity for studying natural processes in the wild. We studied the effect of easy-to-see tree level indicators on saproxylic beetles (Coleoptera), using window traps. Our study was conducted in old-growth mountainous spruce–beech forest Bukacka in the Orlicke Mts. (Czech Republic). Our analyses showed that the species composition of the study group and its response to tree level indicators in the relatively homogenous environment of old-growth mountainous forest area could be explained reasonably well through variance partitioning. The results indicated that the decay stage was the category hosting the highest level of explained variance with respect to saproxylics, followed by diameter and tree. Red-listed beetle species were nearly the same associated with conifers and broadleaves. Our results highlighted the desirability of using tree level indicators to assess insect diversity, using window traps on tree trunk.     

Plant composition and diversity at edges in a semi-natural forest–grassland mosaic

Plant Ecology - As key components of landscapes, edges have received considerable scientific attention in anthropogenic ecosystems. However, edges in natural and semi-natural forest–grassland...     

Inter-annual variation in macroinvertebrate communities in a shallow forest lake in eastern Finland during 1990–2001

Cylindrospermopsis raciborskii undergoes characteristic morphological changes during its annual population development. Primary filaments (those that derive directly from the akinetes) possess the following morphological features: the trichomes have one or two acuminate ends; they are narrower (2.4–2.6 μm) tfhan older filaments, their lengths vary in a wide range (from 40 to 300 μm); some of them are straight but others are slightly coiled even in populations that later consist exclusively of straight filaments; cell walls between the cells are not or only hardly visible; the filaments have a fine granulation but no gas-vacuoles, polyphosphate- or any other contrasting bodies are seen. The secondary filaments deriving from the first division of primary filaments are similar but with only one acuminate end. This way, the number of germinating akinetes can be estimated as the number of primary filaments + 1/2 number of secondary filaments. The described morphological method to estimate inoculum size of C. raciborskii has limitations. (1) The number of akinetes that we get in this way is only a minimum number since germination is not synchronous under field conditions and probably not each akinete germinates that is present in the sediments. (2) The method is applicable only if germination occurs suddenly (relatively synchronously). This is often the case in a temperate region where germination is triggered by temperature. (3) The method cannot be used in tropical or subtropical lakes where water temperature is permanently rather high and akinetes do not develop or develop only very rarely. (4) Being an a posteriori method it cannot be used as predictive tool. Estimations for Lake Balaton are in a good agreement with results of studies with other methods (germination in laboratory cultures and direct counting) and have the advantage that they do not need time-consuming experimenting or difficult direct countings.