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Canopy Species (canopy + species)
Selected AbstractsRegeneration patterns and persistence of the fog-dependent Fray Jorge forest in semiarid Chile during the past two centuriesGLOBAL CHANGE BIOLOGY, Issue 1 2008ALVARO G. GUTIÉRREZ Abstract The persistence of rainforest patches at Fray Jorge National Park (FJNP) in semiarid Chile (30°40,S), a region receiving approximately 147 mm of annual rainfall, has been a source of concern among forest managers. These forests are likely dependent on water inputs from oceanic fog and their persistence seems uncertain in the face of climate change. Here, we assessed tree radial growth and establishment during the last two centuries and their relation to trends in climate and canopy disturbance. Such evaluation is critical to understanding the dynamics of these semiarid ecosystems in response to climate change. We analyzed forest structure of six forest patches (0.2,22 ha) in FJNP based on sampling within 0.1 ha permanent plots. For the main canopy species, the endemic Aextoxicon punctatum (Aextoxicaceae), we used tree-ring analysis to assess establishment periods, tree ages, growing trends and their relation to El Niño Southern Oscillation (ENSO), rainfall, and disturbance. The population dynamics of A. punctatum can be described by a continuous regeneration mode. Regeneration of A. punctatum was sensitive to different canopy structures. Growth release patterns suggest the absence of large scale human impact. Radial growth and establishment of A. punctatum were weakly correlated with rainfall and ENSO. If water limits forests patch persistence, patches are likely dependent on the combination of fog and rain water inputs. Forest patches have regenerated continuously for at least 250 years, despite large fluctuations in rainfall driven by ENSO and a regional decline in rainfall during the last century. Because of the positive influence on fog interception, forest structure should be preserved under any future climate scenario. Future research in FJNP should prioritize quantifying the long-term trends of fog water deposition on forests patches. Fog modeling is crucial for understanding the interplay among physical drivers of water inputs under climate change. [source] Avian distribution in treefall gaps and understorey of terra firme forest in the lowland AmazonIBIS, Issue 1 2005JOSEPH M. WUNDERLE JR We compared the bird distributions in the understorey of treefall gaps and sites with intact canopy in Amazonian terra firme forest in Brazil. We compiled 2216 mist-net captures (116 species) in 32 gap and 32 forest sites over 22.3 months. Gap habitats differed from forest habitats in having higher capture rates, total captures, species richness and diversity. Seventeen species showed a significantly different distribution of captures between the two habitats (13 higher in gap and four higher in forest). Gap habitats had higher capture rates for nectarivores, frugivores and insectivores. Among insectivores, capture rates for solitary insectivores and army ant followers did not differ between the two habitats. In contrast, capture rates were higher in gaps for members of mixed-species insectivore flocks and mixed-species insectivore,frugivore flocks. Insectivores, especially members of mixed-species flocks, were the predominant species in gap habitats, where frugivores and nectarivores were relatively uncommon. Although few canopy species were captured in gap or forest habitats, visitors from forest mid-storey constituted 42% of the gap specialist species (0% forest) and 46% of rare gap species (38% forest). Insectivore, and total, captures increased over time, but did so more rapidly in gap than in forest habitats, possibly as a response to gap succession. However, an influx of birds displaced by nearby timber harvest also may have caused these increases. Avian gap-use in Amazonian terra firme forests differs from gap-use elsewhere, partly because of differences in forest characteristics such as stature and soil fertility, indicating that the avian response to gaps is context dependent. [source] Effects of natural disturbance and selective logging on Nothofagus forests in south-central ChileJOURNAL OF BIOGEOGRAPHY, Issue 7 2002William Pollmann Aim Changes in stand structure, floristic composition and tree population dynamics during the last four centuries were described in southern temperate rain forests. The impacts of natural and anthropogenic disturbance since the late 1560s were examined for old-growth and logged forests. Location The study was conducted in montane Nothofagus alpina forests in the Andean Range of south-central Chile. Study sites were located at a range of altitudes between 1000 and 1250 m a.s.l. Methods Temporal variation in species recruitment and annual dendroecological data were used to determine the historical development and disturbance history of three old-growth forests, and three stands after selective logging in the late 1880s to early 1900s. Considering the spatial structure of evergreen vs. deciduous elements, the forests are a mixture of deciduous and evergreen tree species. Results Stem density, maximum stem diameter and basal area differed between the old-growth and logged stands, but species composition did not. At lower altitudes, N. alpina was the dominant canopy species in both old-growth and logged stands, but regeneration of N. alpina was significantly different in these stands. At higher altitudes, N. alpina and N. dombeyi were the dominant canopy species in both old-growth and logged stands, and here regeneration patterns of these Nothofagus species were similar. After selective logging, in mixed forests of shade-intolerant Nothofagus and more shade-tolerant trees (such as Laurelia philippiana) there has been a shift in regeneration from more shade-tolerant resprouting species towards Nothofagus. Major and moderate releases in radial growth, indicative of disturbance, occurred in most of the older trees during the last four centuries, and especially during the last 100 years. Growth rates of N. alpina are higher than those of associated shade-tolerant trees, and apparently increase after disturbances. Main conclusions Results suggest that under disturbance regimes dominated by treefall gaps, and additionally canopy openings by selective logging, maintenance of Nothofagus species appears to be associated with complementary differences in growth rate, sprouting capacity, canopy residence time, and longevity. Such small-scale canopy openings may help explain the relative abundance of N. alpina in montane mixed rain forests in the Andean Range, where the maintenance of Nothofagus species in many stands has been attributed to a high frequency of coarse-scale disturbance. My results serve to emphasize that understanding the species coexistence and forest dynamics in Nothofagus forests may require attention to interspecific differences in life-history characteristics. [source] Maximum size distributions in tropical forest communities: relationships with rainfall and disturbanceJOURNAL OF ECOLOGY, Issue 3 2008Lourens Poorter Summary 1The diversity and structure of communities are partly determined by how species partition resource gradients. Plant size is an important indicator of species position along the vertical light gradient in the vegetation. 2Here, we compared the size distribution of tree species in 44 Ghanaian tropical forest communities, using data from 880 one-hectare plots and over 118 000 trees belonging to more than 210 species. 3The size distribution of forest species showed a continuous normal or log-normal distribution, with many canopy species and a few large species, and varied from community to community. Multiple regression showed that this variation is related to rainfall and to disturbance. 4Size distributions in wet forests were less skewed than those in dry forests, with a smaller proportion of big species and a smaller size range. At the same time they exhibited tighter species packing, resulting in higher species richness. Communities with high disturbance have less species packing and lower species richness. 5Synthesis. We conclude that the factors that constrain organism size and species coexistence in these tropical forest tree communities differ from those known to operate on a number of well-studied animal communities. [source] Ornithophilous canopy species in the Atlantic rain forest of southeastern BrazilJOURNAL OF FIELD ORNITHOLOGY, Issue 2 2008Márcia A. Rocca ABSTRACT In tropical ecosystems, birds play a relevant role in plant reproduction. Although hummingbirds are regarded as the most important vertebrate pollinators in the Neotropics, the possible role of perching birds as pollinators has been neglected. From 2003 to 2005, we observed 68 species of plants visited by birds in an Atlantic rainforest in southeastern Brazil, including three canopy species: Spirotheca rivieri (Malvaceae, Bombacoidea), Schwartzia brasiliensis (Marcgraviaceae), and Psittacanthus dichrous (Loranthaceae). Flowers of these three species were visited by 15 different species of perching birds and by hummingbirds. The flowers of these three plants are colorful, ranging from deep red or purple to orange. Spirotheca rivieri blooms during the austral winter and Schwartzia brasiliensis during the summer. The flowers of these two species produce copious amounts of dilute nectar in easily accessible structures and both species appear to depend primarily on perching birds as pollinators, with hummingbirds being secondary or minor pollen vectors. The tubular, narrow flowers of P. dichrous are produced during the austral summer and are visited primarily by hummingbirds. Perching birds also visit the flowers, but destroy them. Our results suggest that previous estimates of the number of perching birds that feed on nectar may be too low and that flowers pollinated by perching birds may be more common in the canopy of Neotropical forests than previously thought. SINOPSIS En los ecosistemas tropicales, las aves desempeñan un papel importante en la reproducción de las plantas. Aunque se consideran a los colibríes como el grupo más importante de polinizadores en el neotrópico, este posible rol ha sido relegado en las aves de percha. De 2003,2005, observamos 68 especies de plantas visitadas por aves en el Bosque Pluvial del Atlántico en el sudeste de Brasil. Las flores en el dosel de Spirotheca rivieri (Malvaceae, Bombacoidea), Schwartzia brasiliensis (Marcgraviaceae) y Psittacanthus dichrous (Loranthaceae) fueron visitadas por 15 especies de aves, siendo colibríes y especies de aves de percha. Las flores de estas plantas son de gran colorido, desde rojo subido o púrpura hasta anaranjado. Spirotheca rivieri florece durante el invierno austral y Schwartzia brasiliensis durante el verano. Las flores de estas especies producen grandes cantidades de néctar y tienen estructuras de gran accesibilidad para las aves. Ambas especies parecen depender principalmente de aves de percha como polinizadores, siendo los colibríes polinizadores secundarios o vectores menores de polen. Las flores angostas y tubulares de P. dichrous se producen durante el verano austral y son visitadas, principalmente, por colibríes. Hay aves de perchas que también visitan a estas flores, pero al hacerlo las destruyen. Nuestros resultados sugieren que los estimados previos del número de aves de percha que se alimentan de néctar son muy bajos y que la polinización por aves de percha, parece ser más común en el dosel forestal de los bosques neotropicales que lo previamente pensado. [source] Dominance by a canopy forming seaweed modifies resource and consumer control of bloom-forming macroalgaeOIKOS, Issue 7 2007Britas Klemens Eriksson Degradation of ecological resources by large-scale disturbances highlights the need to demonstrate biological properties that increase resistance to change and promote the resilience of ecosystem regimes. Coastal eutrophication is a global-scale disturbance that drives ecosystem change by increasing primary production and favouring ephemeral and bloom-forming life-forms. Recent synthesis indicates that consumption processes increase the resistance of coastal communities to nutrient loading by controlling the responses of ephemeral macroalgae. Here we suggest a similar ecological function for canopy cover by demonstrating that the presence of a canopy species modifies both resource and consumer control of bloom-forming algae associated with nutrient enrichment. We tested effects of canopy presence on the interaction between consumer and resource control, by field-manipulations of a dominant canopy forming seaweed (Fucus vesiculosus), grazer presence (dominated by the gastropod Littorina littorea) and nutrient enrichment (common agricultural NPK fertilizer). Canopy cover and grazers jointly controlled strong increases of ephemeral bloom-forming algae (dominated by Ulva spp) from nutrient enrichment; nutrients increased ephemeral recruitment almost 10-fold, but only in the absence of both grazers and canopy cover. Recruitment success of the canopy-forming seaweed itself decreased additively with 56.1, 71.3 and 50.5% from independent effects of canopy cover, grazers and nutrient enrichment, respectively. A meta-analysis of nine nutrient enrichment experiments including seaweed, seagrass and stream communities, showed that in the presence of canopies average nutrient effects were reduced by more than 90% compared to without canopies. This corroborates the generality of our finding that dominating canopy species are important for aquatic ecosystems by increasing community resistance to the propagation of nutrient effects. [source] The effects of high temperature on isoprene synthesis in oak leavesPLANT CELL & ENVIRONMENT, Issue 7 2000E. L. Singsaas ABSTRACT Isoprene emission from plants is highly temperature sensitive and is common in forest canopy species that experience rapid leaf temperature fluctuations. Isoprene emission declines with temperature above 35 °C but the temperature at which the decline begins varies between 35 and 44 °C. This variability is caused by the rate at which leaf temperature is increased during measurement with lower temperatures associated with longer measurement cycles. To investigate this we exposed leaves of red oak (Quercus rubra L.) to temperature regimes of 35,45 °C for periods of 20,60 min. Isoprene emission increased during the first 10 min of high temperature exposure and then decreased over the next 10 min until it reached steady state. This phenomenon was common at temperatures above 35 °C but was not noticeable at temperatures below that. The response was reversible within 30 min by lowering leaf temperature to 30 °C. Because there is no storage of isoprene inside the leaf, this behaviour indicates regulation of isoprene synthesis in the leaf. We demonstrated that the variability in isoprene decline results from regulation and explains the variability in the temperature response. This is consistent with our theory that isoprene protects leaves from damage caused by rapid temperature fluctuations. [source] Effects of invasive alien kahili ginger (Hedychium gardnerianum) on native plant species regeneration in a Hawaiian rainforestAPPLIED VEGETATION SCIENCE, Issue 1 2010V. Minden Abstract Questions: Does the invasive alien Hedychium gardnerianum (1) replace native understory species, (2) suppress natural regeneration of native plant species, (3) increase the invasiveness of other non-native plants and (4) are native forests are able to recover after removal of H. gardnerianum. Location: A mature rainforest in Hawai'i Volcanoes National Park on the island of Hawai'i (about 1200 m a.s.l.; precipitation approximately 2770 mm yr,1). Study sites included natural plots without effects of alien plants, ginger plots with a H. gardnerianum -dominated herb layer and cleared plots treated with herbicide to remove alien plants. Methods: Counting mature trees, saplings and seedlings of native and alien plant species. Using non-parametric H -tests to compare impact of H. gardnerianum on the structure of different sites. Results: Results confirmed the hypothesis that H. gardnerianum has negative effects on natural forest dynamics. Lower numbers of native tree seedlings and saplings were found on ginger-dominated plots. Furthermore, H. gardnerianum did not show negative effects on the invasive alien tree species Psidium cattleianum. Conclusions: This study reveals that where dominance of H. gardnerianum persists, regeneration of the forest by native species will be inhibited. Furthermore, these areas might experience invasion by P. cattleianum, resulting in displacement of native canopy species in the future, leading to a change in forest structure and loss of other species dependent on natural rainforest, such as endemic birds. However, if H. gardnerianum is removed the native Hawaiian forest is likely to regenerate and regain its natural structure. [source] | ||||||||||