Canopy Gap

Diversity and regeneration of woody species were investigated in two ecological niches viz. gap and intact vegetation in old-growth seasonally dry Shorea robusta (Gaertn. f.) forests in Nepal. We also related varieties of diversity measures and regeneration attributes to gap characteristics. Stem density of tree and shrub components is higher in the gap than in the intact vegetation. Seedling densities of S. robusta and Terminalia alata (B. Heyne ex Roth.) are higher in the gap than in the intact vegetation, while contrary result is observed for T. bellirica (Gaertn. ex Roxb.) and Syzigium cumini (L. Skeels) in term of seedling density. The complement of Simpson index, Evenness index, and species-individual ratio in the seedling layer are lower in the gap than the intact vegetation. Gap size can explain species richness and species establishment rate. Gaps created by multiple tree falls in different years have higher seedling density of S. robusta than gaps created by single and/or multiple tree falls in the same year. In conclusion, gaps maintain species diversity by increasing seedling density, and favor regeneration of Sal forests. In addition to gap size, other gap attributes also affect species diversity and regeneration.

 Effects of changing light conditions on the ecophysiological condition behind survival were examined on beech from two different populations. Plants were grown in a greenhouse under simulated understorey and canopy gap light conditions. Upon exposure to high light maximum photosynthesis of shade-acclimated leaves increased followed by a reduction over several days to between high- and low-light control rates. In the reciprocal transfer, the decrease in maximum photosynthesis was rapid during the first 2–3 days and then levelled off to values comparable to low-light controls. Seedlings from Sicily (Madonie) showed generally higher maximum photosynthetic rates than those from Abetone. Leaf conductance varied in the same direction as photosynthesis in high- to low-light seedlings but to a lesser degree. Leaves grown under low light and exposed to high light experienced photoinhibition. The Abetone population was more susceptible to photoinhibitory damage than the seedlings from Sicily. Exposure to high light of shade-acclimated seedlings resulted in intermediate chlorophyll concentrations between levels of the high-light and low-light seedlings. Carotenoid concentration was unaffected by treatments. Seedlings grew more in high light, but had a lower leaf area ratio. Light-limited seedlings showed a shift in carbon allocation to foliage. Leaves formed in the new light regime maintained the same anatomy that had been developed before transfer. Seedlings from Sicily had thicker leaves than those of seedlings from Abetone. Seedlings from Abetone were found to be more susceptible to changing light conditions than seedlings from Sicily. We conclude that small forest gaps may represent a favorable environment for photosynthesis and growth of beech regeneration as a result of the limited ability of seedlings to acclimate to sudden increases in high irradiance and because of the moderate levels of light stress in small gaps.

Better understanding of the functional biology of early angiosperms may clarify eco- logical factors surrounding their origin and early radiation. Phylogenetic studies identify Ambor- ella, Nymphaeales (water lilies), Austrobaileyales, and Chloranthaceae as extant lineages that branched before the radiation of core angiosperms. Among living plants, these lineages may rep- resent the best models for the ecology and physiology of early

We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains: Cache River, Arkansas (AR), Iatt Creek, Louisiana (LA), and the Coosawhatchie River, South Carolina (SC), USA. We used 5-min point counts to sample birds in each study area each spring from 1995 to 1998, and measured ground-surface elevations and a suite of other habitat variables to investigate bird distributions and community characteristics in relation to important environmental gradients. In both AR and SC, the average number of Neotropical migrant species detected was lowest in semipermanently flooded Nyssa aquatica Linnaeus habitats and greatest in the highest elevation floodplain zone. Melanerpes carolinus Linnaeus, Protonotaria citrea Boddaert, Quiscalus quiscula Linnaeus, and other species were more abundant in N. aquatica habitats, whereas Wilsonia citrina Boddaert, Oporornis formosus Wilson, Vireo griseus Boddaert, and others were more abundant in drier floodplain zones. In LA, there were no significant differences in community metrics or bird species abundances among forest types. Canonical correspondence analyses revealed that structural development of understory vegetation was the most important factor affecting bird distributions in all three study areas; however, potential causes of these structural gradients differed. In AR and SC, differences in habitat structure were related to the hydrologic gradient, as indexed by ground-surface elevation. In LA, structural variations were related mainly to the frequency of canopy gaps. Thus, bird communities in all three areas appeared to be organized primarily in response to repeated localized disturbance. Our results suggest that regular disturbance due to flooding plays an important role in structuring breeding bird communities in floodplains subject to prolonged inundation, whereas other agents of disturbance (e.g., canopy gaps) may be more important in headwater systems subject to only short-duration flooding. Management for avian community integrity in these systems should strive to maintain forest zonation and natural disturbance regimes.

We examined the influence of small-scale gap disturbances on stand development and tree species coexistence in an old-growth Fagus sylvatica–Abies alba forest in the Dinaric Mountains of Bosnia–Herzegovina. The structure and composition of tree regeneration in gaps were compared to the forest as a whole, and the influence of gap size on the density and composition of regeneration was assessed. Transition probabilities were also calculated from gapfillers in different life stages to examine canopy replacement patterns. The structure and composition of tree regeneration were similar between gaps and the forest as a whole, and there was no relationship between overall regeneration density and gap size, indicating most individuals established prior to gap formation. Likewise, there was no strong evidence of gap-size partitioning for shade tolerant F. sylvatica and A. alba, although less tolerant Acer pseudoplatanus only recruited to taller life stages in larger gaps. Transition probabilities calculated from the seedling and sapling data suggest that most gaps will be captured by F. sylvatica, while probabilities based on pole-sized gapmakers indicate both A. alba and F. sylvatica will be maintained in the canopy. We suggest that gaps primarily play a role in reorganizing advance regeneration, and that coexistence of shade tolerant F. sylvatica and A. alba is more likely related to their differential ability to tolerate shaded understory conditions, particularly during larger life stages, rather than gap-size partitioning.

Tree regeneration is severely hampered in the fragmented afromontane forests of northern Ethiopia. We explored how trees regenerate in remnant forests along the gradient from open field, forest edge to closed sites and canopy gaps inside the forest. We investigated the effects of seed sowing, litter removal, and weeding on the regeneration success along this gradient. Regeneration success was investigated for four indigenous tree species, and measured in terms of seedling establishment, growth, and survival. Species performed differently according to site conditions. Within the forest, local canopy openings facilitated seed germination (Ekebergia), seedling growth (all species except Olea), or survival (Ekebergia and Olea), suggesting that all species benefited from local high light conditions in the forest. Outside the forest, germination (all species) and growth rates (Juniperus and Olea) were lower in the open field, most probably due to water stress in the dry season. Outer edge conditions favored growth for three of the four species. Natural seed germination was, however, zero at any site for Juniperus and Olea and low for Ekebergia and Prunus in the open field. Soil scarification influenced germination positively, while weeding did not have a positive effect. These results suggest that simple measures may improve seedling establishment, and that, for some species, forest edges are particularly useful for growth and survival after succesful establishment. Together with erecting fences, needed to protect seedlings against grazing, seed sowing, planting seedling, and soil scarification may contribute to maintain and restore church forests in the fragmented landscapes of northern Ethiopia.

Beavers strongly modify their environment by not only building dams and creating ponds, which slow the water flow, but also by selective cutting and removing of trees, which change the spatial structure of the forest. We aimed to test the hypothesis that beaver activity promotes new foraging sites for insectivorous bats. The beaver’s influence can be especially significant on aerial hawkers that prefer moderate structural clutter, like the Pipistrellus species (by creating new canopy gaps), and on water-surface foragers, like Myotis daubentonii (by creating ponds with smooth water surface). The study was conducted on small streams in forest areas of northern Poland, which were colonized by the European beaver (Castor fiber). Bat activity was recorded with a Pettersson D-980 ultrasound detector on line transects. The number of bat passes was significantly higher in the stream sections modified by beavers (flooded and subjected to intensive tree cutting) than in the unmodified sections (for Pipistrellus nathusii, Pipistrellus pipistrellus, Pipistrellus pygmaeus, Nyctalus noctula, and all species lumped together). Contrary to our expectations, the activity of the Myotis species was significantly lower on the transect with the largest beaver ponds, possibly due to the blanket of duckweed (Lemnaceae), which is known to produce clutter echoes, thereby reducing prey detection by echolocating M. daubentonii.

Ecological study of Gigantochloa manggong , one of the endemic bamboo species at Java was done in the secondary tropical forest of Meru Betiri National Park, East Java, Indonesia. Distribution was limited in eastern part of the national park. In general, G. manggong grows well in lowland secondary forest patches at altitudes 5 - 50 m on the clay loam soil. Absence of large trees caused canopy gaps which made bamboo grows well and spread. There were several associate species such as Callamus sp., Erioglussum rubiginosum, Voacanga grandifolia, Pleomelesp., and Ficus sp. Throughout the field observation, its sexual reproduction was not found. However, vegetative reproduction by developing new culms was found in all of the quadrats. Bamboo harvesting in Sukamade forest by villagers was the threats of G. manggong population at the wild habitat. Furthermore, our study showed that the range of the species distribution has contracted substantially from that recorded in 1987, and this has le...

Understory plants could can act as indicators of temperate forest sustainability, health and conservation status due to their importance in ecosystem function. Harvesting impacts on understory plant diversity depends on their intensity. Variable retention has been proposed to mitigate the harmful effects of timber harvesting, but its effectiveness remains unknown in southern Patagonian Nothofagus pumilio forests. The objectives of this study were to: (i) define a baseline of understory plant diversity in old-growth forests along a site quality gradient and under canopy gaps; (ii) evaluate stands with three different variable retention treatments compared to old-growth forests; and (iii) assess temporal changes during 4 years after harvesting (YAH). A 61 ha N. pumilio forest was selected. Understory plant (Dicotyledonae, Monocotyledonae and Pteridophyta) richness, cover (including woody debris and bare forest floor) and aboveground dry biomass were characterized in summer for 5 years. Before harvesting, baseline samples were conducted along a site quality gradient and outside/inside canopy gaps. Analyzed treatments include a control of old-growth forest (OGF) and three different harvesting treatments with variable retention: (i) dispersed retention (DR) of 30 m2 ha−1 (20–30% retention); (ii) aggregated retention (AR) with one aggregate per hectare and clear-cuts (28% retention); and (iii) combined dispersed and aggregated retention (DAR) with one aggregate per hectare and dispersed retention of 10–15 m2 ha−1 (40–50% retention). Data analyses included parametric and permutational ANOVAs, multivariate classification and ordinations.Before harvesting, 31 plant species were found, where richness, cover and biomass were directly related to site quality. The presence of canopy gaps did not have a significant impact on the measured variables. After harvesting, 20 new species appeared from adjacent associated environments (two from N. antarctica forests and 18 from grasslands and peatlands). At the stand level, understory values were higher in AR > DR > DAR > OGF. Most (81–95%) plant richness at baseline conditions was conserved in all treatments, where inside the aggregates understory remained similar to OGF. Combination of aggregated and dispersed retention (DAR) better limited exotic species introduction and protected sensitive species, improving conservation in harvested stands. Changes in understory variables were observed after the first YAH in all treatments; greater changes were observed in the harvested areas than in aggregates. Changes stabilized at the fourth YAH. As a conclusion, the location of retention aggregates should be selected to preserve species understory diversity of more speciose and diverse habitats or particularly uncommon stands. Implementation of different kinds (patterns and levels) of retention for improvement of biodiversity conservation in harvested forests should be included in timber and forest management planning.► Understory plant diversity before harvesting was directly related to site quality. ► Variable retention impacts over plant diversity by species incorporation and loss. ► Understory remains similar to old-growth forests inside aggregates. ► Combination of retention patterns improves conservation in harvested stands. ► Temporal changes occur in understory diversity of harvested and old-growth forests.

To explore the importance of light availability for seedling growth in low light environments, we examined light-dependent growth, biomass allocation and mortality of tree seedlings growing in sites with 0.2-6.5% full sun, the range of light commonly encountered in the understory of closed canopy, lowland tropical forests. We transplanted seedlings of the canopy tree species, Dipteryx panamensis, Virola koschnyii, and Brosimum alicastrum into second-growth forest and native tree plantations at La Selva Biological Station, Costa ...

ABSTRACT. The capacity of rainforests to recover from logging disturbance is difficult to model due to the compounding interactions between long-term disturbance effects, natural dynamics, site characteristics and tree species regeneration strategies. The aim of this study was to develop a quantitative model using over three decades of data from stands subjected to various levels of disturbance ranging from natural, through increasing intensities of tree removal to intensive logging. Data for trees≥ 10 cm diameter at 1.3 m above the ground ( ...