Australian Tropical and Subtropical Rain Forest Community Assembly: Phylogeny,Functional Biogeography,and Environmental Gradients

To compare community assemblage patterns in tropical northeastern and subtropical central eastern Australia across selected gradients and scales, we tested the relationship of species traits with phylogenetic structure, and niche breadth. We considered phylogenetic relationships across current‐day species in assemblages in relation to rain forest species pool sizes, and trait values along gradients including elevation and latitude. Trait values were quantified across scales for seed size, leaf area, wood density and maximum height at maturity for 1137 species and 596 assemblages using trait gradient analysis (TGA). Local assemblages of subtropical species had narrower trait ranges, and higher niche breadth values than corresponding assemblages of tropical species. Leaf size and seed size increased at low latitudes, and community phylogenetic structure was most strongly correlated with seed traits in the subtropics, reflecting dispersal and re‐colonization processes. Elevation accounted for little of the variance in community phylogenetic structure or trait variation across local and regional scales. Stable moist forest areas retained many species from ancestral rain forest lineages across a range of temporally conserved habitats; species within assemblages were less related; and rain forest assemblages had higher functional diversity, but lower niche breadth. This suggests that on average, assemblages of species in stable areas had greater trait variation and narrower distributions. Historic and recent rain forest contraction and re‐expansion can result in recolonized areas that are dominated by species that are more related (phylogenetically) than by chance, have smaller, widely dispersed seeds, and greater niche breadth (broader distributions).     

Tree Diversity,Environmental Heterogeneity,and Productivity in a Mexican Tropical Dry Forest1

Species diversity–environmental heterogeneity (D–EH) and species diversity–productivity (D–P) relationships have seldom been analyzed simultaneously even though such analyses could help to understand the processes underlying contrasts in species diversity among sites. Here we analyzed both relationships at a local scale for a highly diverse tropical dry forest of Mexico. We posed the following questions: (1) are environmental heterogeneity and productivity related?; (2) what are the shapes of D–EH and D–P relationships?; (3) what are individual, and interactive, contributions of these two variables to the observed variance in species diversity?; and (4) are patterns affected by sample size, or by partitioning into average local diversity and spatial species turnover? All trees (diameter at breast height ≥5 cm) within twenty‐six 0.2‐ha transects were censused; four environmental variables associated with water availability were combined into an environmental heterogeneity index; aboveground standing biomass was used as a productivity estimator. Simple and multiple linear and nonlinear regression models were run. Environmental heterogeneity and productivity were not correlated. We found consistently positive log‐linear D–EH and D–P relationships. Productivity explained a larger fraction of among‐transect variance in species diversity than did environmental heterogeneity. No effects of sample size were found. Different components of diversity varied in sensitivity to environmental heterogeneity and productivity. Our results suggest that species' differentiation along water availability gradients and species exclusion at the lowest productivity (driest) sites occur simultaneously, independently, and in a scale‐dependent fashion on the tree community of this forest.     

Environmental and Biotic Controls over Aboveground Biomass Throughout a Tropical Rain Forest

The environmental and biotic factors affecting spatial variation in canopy three-dimensional (3-D) structure and aboveground tree biomass (AGB) are poorly understood in tropical rain forests. We combined field measurements and airborne light detection and ranging (lidar) to quantify 3-D structure and AGB across a 5,016 ha rain forest reserve on the northeastern flank of Mauna Kea volcano, Hawaii Island. We compared AGB among native stands dominated by Metrosideros polymorpha found along a 600–1800 m elevation/climate gradient, and on three substrate-age classes of 5, 20, and 65 kyr. We also analyzed how alien tree invasion, canopy species dominance and topographic relief influence AGB levels. Canopy vertical profiles derived from lidar measurements were strong predictors (r ² = 0.78) of AGB across sites and species. Mean AGB ranged from 48 to 363 Mg ha⁻¹ in native forest stands. Increasing elevation corresponded to a 53–84% decrease in AGB levels, depending upon substrate age. Holding climate constant, changes in substrate age from 5 to 65 kyr corresponded to a 23–53% decline in biomass. Invasion by Psidium cattleianum and Ficus rubiginosa trees resulted in a 19–38% decrease in AGB, with these carbon losses mediated by substrate age. In contrast, the spread of former plantation tree species Fraxinus uhdei corresponded to a 7- to 10-fold increase in biomass. The effects of topographic relief at both local and regional scales were evident in the AGB maps, with poorly drained terrain harboring 76% lower biomass than forests on well-drained relief. Our results quantify the absolute and relative importance of environmental factors controlling spatial variation in tree biomass across a rain forest landscape, and highlight the rapid changes in carbon storage incurred following biological invasion. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author Contributions  GPA and RFH conceived of or designed the study. GPA, RFH, TAV, DEK, and TKB performed research and analyzed data. GPA, RFH, DEK, and TKB contributed new methods or models. GPA wrote the article.     

Multiple Environmental Controls on Cockroach Assemblage Structure in a Tropical Rain Forest

Arthropod abundance and diversity are remarkable in tropical forests, but are also spatially patchy. This has been attributed either to resources, predators, abiotic conditions or disturbances, but whether such factors may simultaneously shape arthropod assemblage structure is little known. We used cockroaches to test for multiple environmental controls on assemblage structure in 25 km² of Amazonian forest. We performed nocturnal, direct searches for cockroaches in 30 plots (250 m × 2 m) during two seasons, and gathered data on biotic and abiotic factors from previous studies. Cockroach abundance increased with dry litter mass, a measure of resource amount, while species richness increased with litter phosphorus content, a measure of resource availability. Cockroach abundance and species richness decreased with ant relative abundance. Cockroach species composition changed along the gradient of: (1) soil clay content, which correlates with a broad differentiation between flood‐prone and non‐flooded forest; (2) soil relative moisture, consistent with known interspecific variation in desiccation tolerance; and (3) according to the abundance of ants, a potential predator. Turnover in species composition was correlated with abiotic conditions—sorting species according to physiological requirements and to disturbance‐related life history traits—and to ants' selective pressure. Cockroach abundance, diversity, and composition seem to be controlled by distinct sets of environmental factors, but predators which were represented by ants, emerged as a common factor underlying cockroach distribution. Such patterns of community structure may have been previously overlooked by undue focus on single or a few factors, and may be common to tropical forest arthropods.     

Facilitative-Competitive Interactions in an Old-Growth Forest: The Importance of Large-Diameter Trees as Benefactors and Stimulators for Forest Community Assembly

The role of competition in tree communities is increasingly well understood, while little is known about the patterns and mechanisms of the interplay between above- and belowground competition in tree communities. This knowledge, however, is crucial for a better understanding of community dynamics and developing adaptive near-natural management strategies. We assessed neighbourhood interactions in an unmanaged old-growth European beech (Fagus sylvatica) forest by quantifying variation in the intensity of above- (shading) and belowground competition (crowding) among dominant and co-dominant canopy beech trees during tree maturation. Shading had on average a much larger impact on radial growth than crowding and the sensitivity to changes in competitive conditions was lowest for crowding effects. We found that each mode of competition reduced the effect of the other. Increasing crowding reduced the negative effect of shading, and at high levels of shading, crowding actually had a facilitative effect and increased growth. Our study demonstrates that complementarity in above- and belowground processes enable F. sylvatica to alter resource acquisition strategies, thus optimising tree radial growth. As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics. We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes. This finding highlights the potential importance of the rarely examined relationship between the spatial aggregation pattern of large-diameter trees and the outcome of neighbourhood interactions, which may be central to community dynamics and the related forest ecosystem services.     

Making Forest of Bliss: Intention, Circumstance, and Chance in Nonflction Film

Making Forest of Bliss: Intention, Circumstance, and Chance in Nonflction Film. Robert Gardner and Ákos Östör. Cambridge, MA: Harvard University Press, 2002. 135 pp., DVD.     

Basement Membrane Proteins: Structure,Assembly, and Cellular Interactions

Abstract

Basement membranes are thin layers of a specialized extracellular matrix that form the supporting structure on which epithelial and endothelial cells grow, and that surround muscle and fat cells and the Schwann cells of peripheral nerves. One common denominator is that they are always in close apposition to cells, and it has been well demonstrated that basement membranes do not only provide a mechanical support and divide tissues into compartments, but also influence cellular behavior. The major molecular constituents of basement membranes are collagen IV, laminin-entactin/nidogen complexes, and proteoglycans. Collagen IV provides a scaffold for the other structural macromolecules by forming a network via interactions between specialized N-and C-terminal domains. Laminin-entactin/nidogen complexes self-associate into less-ordered aggregates. These two molecular assemblies appear to be interconnected, presumably via binding sites on the entactin/nidogen molecule. In addition, proteoglycans are anchored into the membrane by an unknown mechanism, providing clusters of negatively charged groups. Specialization of different basement membranes is achieved through the presence of tissue-specific isoforms of laminin and collagen IV and of particular proteoglycan populations, by differences in assembly between different membranes, and by the presence of accessory proteins in some specialized basement membranes. Many cellular responses to basement membrane proteins are mediated by members of the integrin class of transmembrane receptors. On the intracellular side some of these signals are transmitted to the cytoskeleton, and result in an influence on cellular behavior with respect to adhesion, shape, migration, proliferation, and differentiation. Phosphorylation of integrins plays a role in modulating their activity, and they may therefore be a part of a more complex signaling system.     

Early Inhabitants of the Amazonian Tropical Rain Forest: A Study of Humans and Environmental Dynamics

Early Inhabitants of the Amazonian Tropical Rain Forest:. Study of Humans and Environmental Dynamics . Santiago Mora. Pittsburgh: University of Pittsburgh Press, 2003. 211 pp.     

Seed Banks in Savanna,Forest Fragments,and Continuous Forest Edges Differ in a Tropical Dry Forest in Madagascar

Rapid deforestation has fragmented habitat across the landscape of Madagascar. To determine the effect of fragmentation on seed banks and the potential for forest regeneration, we sampled seed viability, density and diversity in 40 plots of 1 m² in three habitat types: forest fragments, the near edge of continuous forest, and deforested savanna in a highly fragmented dry deciduous forest landscape in northwestern Madagascar. While seed species diversity was not different between forest fragments and continuous forest edge, the number of animal‐dispersed seeds was significantly higher in forest fragments than in continuous forest edge, and this pattern was driven by a single, small‐seeded species. In the savanna, seeds were absent from all but three of the 40 plots, indicating that regeneration potential is low in these areas. Several pre‐ and post‐dispersal biotic and abiotic factors, including variation in the seed predator communities and edge effects could explain these findings. Understanding the extent to which seed dispersal and seed banks influence the regeneration potential of fragmented landscapes is critical as these fragments are the potential sources of forest expansion and re‐connectivity.     

Forest Structure and Biomass of a Tropical Seasonal Rain Forest in Xishuangbanna,Southwest China1

Xishuangbanna is a region located at the northern edge of tropical Asia. Biomass estimates of its tropical rain forest have not been published in English literature. We estimated forest biomass and its allocation patterns in five 0.185–1.0 ha plots in tropical seasonal rain forests of Xishuangbanna. Forest biomass ranged from 362.1 to 692.6 Mg/ha. Biomass of trees with diameter at 1.3 m breast height (DBH) ≥ 5 cm accounted for 98.2 percent of the rain forest biomass, followed by shrubs (0.9%), woody lianas (0.8%), and herbs (0.2%). Biomass allocation to different tree components was 68.4–70.0 percent to stems, 19.8–21.8 percent to roots, 7.4–10.6 percent to branches, and 0.7–1.3 percent to leaves. Biomass allocation to the tree sublayers was 55.3–62.2 percent to the A layer (upper layer), 30.6–37.1 percent to the B layer (middle), and 2.7–7.6 percent to the C layer (lower). Biomass of Pometia tomentosa, a dominant species, accounted for 19.7–21.1 percent of the total tree biomass. The average density of large trees (DBH ≥100 cm) was 9.4 stems/ha on two small plots and 3.5 stems/ha on two large plots, illustrating the potential to overestimate biomass on a landscape scale if only small plots are sampled. Biomass estimations are similar to typical tropical rain forests in Southeast Asia and the Neotropics.     

Dead Wood Necromass in a Moist Tropical Forest: Stocks,Fluxes, and Spatiotemporal Variability

Ecosystems - Woody debris (WD) stocks and fluxes are important components of forest carbon budgets and yet remain understudied, particularly in tropical forests. Here we present the most...     

Hurricane Disturbance,Plant-Animal Interactions,and the Reproductive Success of a Tropical Shrub1

Hurricane disturbance may have strong effects on plant-animal interactions important in plant reproductive success. Components of reproductive success (flowering, pollination, seed predation) in the tropical shrub Ardisia escallonioides (Myrsinaceae) were examined from 1991–1994 in four southern Florida populations. Hurricane Andrew struck three of the four populations on 24 August 1992. Hurricane Andrew delayed flowering by two months in 1992. In 1993 and 1994, the three hurricane-damaged populations had increased flowering and inflorescence production compared to 1991 and 1992, while the undamaged population had no flowering. Hurricane disturbance had different effects on generalist versus specialist plant-animal interactions. Species composition and relative abundance of the generalist pollinator community that visits A. escallonioides was similar before and after the hurricane, indicating little effect of the disturbance on this interaction. In contrast, populations of a specialist flower galling moth (Periploca sp., Cosmopterigidae) declined in 1992 following Hurricane Andrew. Although moth populations increased at two of the three sites in 1993, the relative impact of moth predation on seed production was low due to extensive flower production. One moth population suffered local population extirpation for two years, reestablishing itself in November 1994. Hurricane disturbance resulted in a window of opportunity for massive seed production of Ardisia escallonioides in south Florida. Total seed production in 1993 increased twelve to seventy-three times the 1992 levels. Total seed production declined in 1994, but remained high compared to prehurricane levels.     

153 Invasive Macroalgae on Tropical Reefs: Impacts, Interactions, Mechanisms and Management

Histories, patterns of introduction, management of impacts and predictable futures? Ecological impacts of weedy introduced and native marine algae have set Hawai'i apart from elsewhere in the tropics and offers a new show case for macroalgal blooms. Partly because of our isolation, impacts of non-indigenous species have been clearly identified, in some cases almost as quickly as introductions have occurred to Hawai'i. While hull fouling or intentional introductions may have been initial mechanisms for macroalgal introductions, spread among the Hawaiian Islands is not necessarily linked to the vector for arrival. Further, impacts of non-indigenous species are also not fully predictable, prior to introduction. This situation leads to challenging gaps in management strategies because few generalizations about the roles of nutrients or herbivory as drivers for macroalgal blooms can be supported at this time. Weedy native species represent a wide range of alternate impacts with other apparent combinations of forcing functions. Case histories for the most significant non-indigenous and weedy native algae will be presented with emphasis on potential new criteria to assess ecological impacts and provide resource biologists with critical new tools for the management of reef ecosystems.     

E-Commerce: Sorting Out the Environmental Consequences

The environmental effects of e‐commerce may be described in terms of first‐, second‐, and third‐order effects. Data for these effects are scarce, partly because research on environmental effects of e‐commerce and e‐business is still in its infancy, although it is evolving very rapidly. Until now, positive environmental consequences of e‐commerce have generally been coincidental. Two crucial questions that must be addressed are (1) How do we improve our understanding and management of the environmental effects of e‐commerce? and (2) Which approaches are best suited to the development of sustainable e‐solutions? Three approaches to developing sustainable e‐commerce solutions are discussed: the extension of environmental performance measurement and management to e‐commerce activities, the use of new cooperative forms of innovation management, and the provision of customer choice. Finally, an outlook on future research demands is presented. The technology itself (information and communication technologies, Internet) does not determine sustainability, but rather its design, use, and regulation does.     

中国热带森林水文生态功能

中国热带森林水文生态功能周光益（中国林科院热带林业研究所,广州５１０５２０）Ｅｃｏ＿ｈｙｄｒｏｌｏｇｉｃａｌＦｕｎｃｔｉｏｎｓｏｆＴｒｏｐｉｃａｌＦｏｒｅｓｔ,Ｃｈｉｎａ．ＺｈｏｕＧｕａｎｇｙｉ（ＴｈｅＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏｆＴｒｏｐｉ...     

Long-Term Environmental Correlates of Invasion by Lantana camara (Verbenaceae) in a Seasonally Dry Tropical Forest

Invasive species, local plant communities and invaded ecosystems change over space and time. Quantifying this change may lead to a better understanding of the ecology and the effective management of invasive species. We used data on density of the highly invasive shrub Lantana camara (lantana) for the period 1990–2008 from a 50 ha permanent plot in a seasonally dry tropical forest of Mudumalai in southern India. We used a cumulative link mixed-effects regression approach to model the transition of lantana from one qualitative density state to another as a function of biotic factors such as indicators of competition from local species (lantana itself, perennial grasses, invasive Chromolaena odorata, the native shrub Helicteres isora and basal area of native trees) and abiotic factors such as fire frequency, inter-annual variability of rainfall and relative soil moisture. The density of lantana increased substantially during the study period. Lantana density was negatively associated with the density of H. isora, positively associated with basal area of native trees, but not affected by the presence of grasses or other invasive species. In the absence of fire, lantana density increased with increasing rainfall. When fires occurred, transitions to higher densities occurred at low rainfall values. In drier regions, lantana changed from low to high density as rainfall increased while in wetter regions of the plot, lantana persisted in the dense category irrespective of rainfall. Lantana seems to effectively utilize resources distributed in space and time to its advantage, thus outcompeting local species and maintaining a population that is not yet self-limiting. High-risk areas and years could potentially be identified based on inferences from this study for facilitating management of lantana in tropical dry forests.