6,627 research outputs found
Coconut Phytophthora. Workshop proceedings, 26-30 October 1992, Manado, Indonesia
Ce séminaire sur le Phythophthora du cocotier avait pour but de réunir tous les acteurs d'un projet démarré en 1990 et de faire le point sur les études réalisées pour la connaissance et la lutte contre ce champignon. Ce projet a donné une grande priorité aux échanges d'informations et aux complémentarités entre les équipes de recherche européennes et tropicale
Floristic diversity and patch dynamics in hyper-disturbed tropical lowland rainforest fragments in north Queensland: no evidence for cyclone-disturbance and fragmentation driving species assemblages towards early-successional states
Tropical cyclones reshape the structure, composition and successional trajectories of forest ecosystems. Climate warming is expected to increase the intensity and impact of these storms while habitat fragmentation further modifies trajectories of response. Many studies over the past decade suggest that tropical forest fragments are locked into a future dominated by edge-favoured pioneer species, dramatic loss of late-successional, large-fruited species, and invasion by exotic weeds. However, this study shows that severely storm-damaged and fragmented tropical forests are remarkably resilient, with a capacity for rebuilding and maintaining plant species composition and diversity.
My study followed two severe tropical cyclone events, Cyclones Larry (2006) and Yasi (2011) in the Australian Wet Tropics. To date, no comparable investigation has measured the effects of successive severe tropical cyclone events on different forest habitats in lowland rainforest. My study investigated: 1) immediate effects of a second severe cyclone on the structural characteristics of different forest habitat types; 2) family and species-level responses to damage and short-term survival rates; 3) plant community and species-level assemblages across different forest habitats; and 4) life-history successional characteristics of species for different habitat types.
My results showed all trees sustained some level of damage (i.e. minor to severe) due to the effects of these two severe cyclone events. About 75% of trees had their main stem snapped compared to 11% of trees with major breakage of branches and less than 4% were uprooted. 10% of all trees sustained only minor damage including partial defoliation, twig-snapping and minor branches snapped. Snapping of tree trunks was higher in fragmented forest compared to continuous forest whereas snapping of major branches was significantly higher in continuous forest and edges. Trees resprouted within weeks of the cyclone and 96% of standing stems continued to show vigourous growth after eighteen months.
Although there was a dramatic loss of large canopy and emergent trees during Cyclone Larry five years earlier, 83% of all stems in my plots were identified as belonging to mid-late and late successional species, while only 13% of stems were early-mid successional species. These stems are mainly saplings (≤ 10-20cm DBH) which have survived successive severe cyclone events within the understorey 'vine tangles.' I found no evidence for proliferation of early successional or pioneer species in any of the habitat types, including fragmented forest sites, within the time-frame of this study. No evidence was found for elevated levels of exotic weed invasion following these events with these species comprising less than 1% of total assemblages. All forest habitat types showed an unexpected capacity for resistance and resilience following the combined effects of fragmentation and two severe tropical cyclones. My data suggest that forest habitat types influence successional life-history characteristics but are not driving species assemblages in fragmented forests towards proliferation of short-lived, edge-favoured generalists (i.e. pioneer species)
Population structure of palms in rainforests frequently impacted by cyclones
Tropical cyclones may act as important ecological drivers in northern Australia including north Queensland, as several cyclones impact this region each year between November and May. Extensive research has been conducted to investigate how the population structure of rainforest species respond to cyclonic disturbances. However, there have been few such studies on palms although they are important components of rainforests. Therefore, these study aimed to investigate how the population structure of Arenga australasica (H. Wendl. & Drude) S. T. Blake ex H. E. Moore, Calamus australis Mart., C. moti F. M. Bailey, Hydriastele wendlandiana (F. Muell.) H. Wendl. & Drude and Licuala ramsayi var. ramsayi (F. Muell.) H. Wendl. & Drude responded to a cyclone, as shown by size class reflecting mass recruitment after a periodic major disturbance (case study: Cyclone Larry). The field research was carried out in three study sites: Tam OShanter/Djiru National Park, Clump Mountain National Park and Kurrimine Beach Conservation Park located near Mission Beach and Kurrimine Beach, in north Queensland. Observations were made of life stage distribution, height and dbh distribution and wind resistance. We found that responses of the population structures of these rainforest palms varied following cyclonic disturbance by demonstrating higher densities of seedlings and juveniles, suggesting populations would be retained. More seedlings of C. australis and C. moti were found in gaps with higher canopy openness; oppositely, less seedlings of L. ramsayi were encountered under sites with lower sunlight
Ozark Gardens, November, 1965
Ozark Gardens was a regional gardening periodical with a focus on the Ozark region of the United States.https://ecommons.udayton.edu/imri_stokes_ozark/1001/thumbnail.jp
Innovative Foundation Alternative Inspired from Tree Roots
It is not easy to find a more efficient foundation system than the roots of a tree. Trees create a vast three-dimensional network of roots to support and anchor the critical above-ground trunks, leaves, and limbs. In this work, investigations are made for the feasibility of imitating such a technique and creating similar networks to support civil infrastructure, particularly those subjected to moment loads such as traffic signal posts. Some of the raised questions were: Is it feasible to have a shallow tree root-based foundation system to provide the same capacities as conventional foundation alternatives? If this is feasible: What would be the ideal depth of the Root Foundation System? How far should the roots extend to provide comparable support to a conventional deep foundation system? What diameter should the root bulb of the configuration be? How far should a vertical shaft extend into the ground?
Hence, the main objective of this research is to identify and test the most effective Root Foundation System geometric configurations that can provide a similar capacity as a conventional foundation for traffic signal posts. Finite element model simulations on 54 different root-based foundation models show potential for replacing the conventional drilled shaft foundation for traffic signal posts. The conventional foundation was also modeled and produced a 0.528 mm deflection. Whereas some of the best performing root foundation models achieved 0.23 mm. By comparing the resulting deflection of the conventional foundation model to the deflection of the root foundation models, the best performing root foundation models were constructed from steel and physically tested. The root foundation models were then calibrated to predict the performance of root foundation models. Results show that the RFSs with half the length and diameter of conventional deep foundations (for traffic signal poles) were able to provide more than four times the lateral load capacity compared to the control sections. This shows that RFSs have excellent potential to replace the conventional deep foundation alternatives used to support traffic signal posts. The economic and environmental impacts due to the root-inspired foundation systems could be tremendous owing to the reductions in the material requirements
The Coconut Odyssey: the Bounteous Possibilities of the Tree of Life
Crop Production/Industries,
Diversity and Management of Phytophthora in Southeast Asia
Crop Production/Industries,
Ecological impacts of deforestation and forest degradation in the peat swamp forests of northwestern Borneo
Tropical peatlands have some of the highest carbon densities of any ecosystem and are under enormous development pressure. This dissertation aimed to provide better estimates of the scales and trends of ecological impacts from tropical peatland deforestation and degradation across more than 7,000 hectares of both intact and disturbed peatlands in northwestern Borneo. We combined direct field sampling and airborne Light Detection And Ranging (LiDAR) data to empirically quantify forest structures and aboveground live biomass across a largely intact tropical peat dome. The observed biomass density of 217.7 ± 28.3 Mg C hectare-1 was very high, exceeding many other tropical rainforests. The canopy trees were ~65m in height, comprising 81% of the aboveground biomass. Stem density was observed to increase across the 4m elevational gradient from the dome margin to interior with decreasing stem height, crown area and crown roughness. We also developed and implemented a multi-temporal, Landsat resolution change detection algorithm for identify disturbance events and assessing forest trends in aseasonal tropical peatlands. The final map product achieved more than 92% user’s and producer’s accuracy, revealing that after more than 25 years of management and disturbances, only 40% of the area was intact forest. Using a chronosequence approach, with a space for time substitution, we then examined the temporal dynamics of peatlands and their recovery from disturbance. We observed widespread arrested succession in previously logged peatlands consistent with hydrological limits on regeneration and degraded peat quality following canopy removal. We showed that clear-cutting, selective logging and drainage could lead to different modes of regeneration and found that statistics of the Enhanced Vegetation Index and LiDAR height metrics could serve as indicators of harvesting intensity, impacts, and regeneration stage. Long-term, continuous monitoring of the hydrology and ecology of peatland can provide key insights regarding best management practices, restoration, and conservation priorities for this unique and rapidly disappearing ecosystem
Moss: Flora of Maine
Moss: Flora of Maine
by Robert N. Miller
Gorham State Teachers College, Gorham, Maine, 1951.
Contents: What Are Mosses? / Moss Groups / Suggestions for Collecting, Mounting and Preservation of Moss Specimens / Over-All Pictures of the Capsules and Setae / Types of Leaves / Glossary / Outline Key to Some Maine Mosseshttps://digitalcommons.usm.maine.edu/me_collection/1129/thumbnail.jp
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