68 research outputs found
The forest for the trees
No full textReview of 'Forests and Global Change'. D.A. Coomes, D.F.R.P Burslem & W.D. Simonson (editors), 2014, Cambridge University Press, UK
Aboveground biomass estimation in tropical forests at single tree level with ALS data
No full textIn this paper we present a study on the estimation of the aboveground biomass in tropical forests at single tree level using airborne laser scanning (ALS) data. Individual tree crowns (ITCs) are firstly detected using a method based on an adaptive window that change its size according to tree height. The diameter at breast height (DBH) and the aboveground biomass (AGB) of each ITC then are predicted using standard allometric models. Lastly, the AGB values are aggregated at plot level, and compared with field measured values. The results show that it is possible to accurately predict the aboveground biomass of tropical forests at single tree level using ALS dat
Differential responses to limiting resources among tree seedlings of lowland tropical rain forest in Singapore
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:D063341 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Silvics and wood properties of the common timber tree species on Kolombangara
No full textNatural forest management in the Solomon Islands is at an important stage of development. Undisturbed forest below the altitudinal limit for logging has mostly been logged at least once, and the remaining unlogged area is under concession. It is therefore inevitable that the focus of forest management will shift from exploitation of pristine forest to management of the large area of logged forest over the next few years. However, the research on which management prescriptions for Solomon Islands forests would be based has only just started, and there is an urgent need for the kind of information required to design appropriate management systems. This Manual collates the published and unpublished information currently available on the silvicultural behaviour and wood properties of the 12 most common timber tree species in Solomon Islands natural forests. Most of the silvics information has been obtained from a recent analysis of data obtained during monitoring of populations of all trees of these species >4.9cm diameter on permanent sample plots on Kolombangara, as part of the Kolombangara Ecological Survey (KES). The KES has been a research project of the Solomon Islands Forest Department since 1964 and the plots have been monitored 15 times over the 30 year interval. The total area of permanent sample plots was 13.9ha in the early phases of the project but has declined over time as plots have been lost to cyclone damage and logging, although nine plots (5.7ha) have been monitored over the full 30 years of the study. The silvics data presented include accounts of species distribution and the ecology and demography of seedlings drawn from previous phases of the KES. The Manual also presents updates of tree growth and mortality rates under natural forest conditions, new data on changes in median and maximum crown exposure with tree size, and population responses to cyclones. Sections on plantation experience and wood properties are included, drawn from other published sources. Thus this Manual brings together in one place a summary of the accumulated knowledge on the twelve species described, which are the main timber-producing species of the Western Solomons. It is hoped that a single reference source will be of value for planning natural forest management. Fuller details on methodology and analysis are not given here but can be found in the source documents on which this Manual is based
Responses to simulated drought and elevated nutrient supply among shade-tolerant tree seedlings of lowland tropical forest in Singapore
No full textBiotropica284 A636-648BTRO
The suitability of weed risk assessment as a conservation tool to identify invasive plant threats in East African rain-forests.
No full textWe tested the ability of an international Weed Risk Assessment (WRA) protocol to predict invasion status of 230 alien plant species introduced via a botanical garden to tropical rainforest in Tanzania. The reliability and accuracy of WRA in discriminating between invaders and non-invaders was independently assessed using field data on species demography and distribution. The WRA rejected 83% of known invaders, and accepted 74% of non-invaders. Only 1% of accepted species were known invaders at the site. WRA performance varied among different growth forms, and underestimated the risks arising from palm species. Among those species that had naturalised, the WRA was better at identifying invaders of open rather than forest habitats. The WRA score was significantly correlated with how widespread species had become at the site, suggesting some capacity to predict spatial spread at a landscape scale. Knowledge of propagule pressure and residence time did not increase explanatory power. These results indicate that the WRA was able to discriminate between invaders and non-invaders with accuracy comparable to similar assessments in temperate and sub-tropical regions. It could be made more effective by weighting traits important in tropical forests e.g. certain growth forms, shade tolerance etc. more heavily. Such a modified WRA could be used successfully elsewhere in the palaeotropics as a screening tool to identify the risk of invasion arising from plants introduced for agroforestry, horticulture or landscaping. Given the increasing pressures on tropical forests and importance of agroforestry to local economies, the WRA protocol represents a useful conservation tool
Area-based vs tree-centric approaches to mapping forest carbon in Southeast Asian forests from airborne laser scanning data
No full textTropical forests are a key component of the global carbon cycle, and mapping their carbon density is essential for understanding human influences on climate and for ecosystem-service-based payments for forest protection. Discrete-return airborne laser scanning (ALS) is increasingly recognised as a high-quality technology for mapping tropical forest carbon, because it generates 3D point clouds of forest structure from which aboveground carbon density (ACD) can be estimated. Area-based models are state of the art when it comes to estimating ACD from ALS data, but discard tree-level information contained within the ALS point cloud. This paper compares area-based and tree-centric models for estimating ACD in lowland old-growth forests in Sabah, Malaysia. These forests are challenging to map because of their immense height. We compare the performance of (a) an area-based model developed by Asner and Mascaro (2014), and used primarily in the neotropics hitherto, with (b) a tree-centric approach that uses a new algorithm (itcSegment) to locate trees within the ALS canopy height model, measures their heights and crown widths, and calculates biomass from these dimensions. We find that Asner and Mascaro’s model needed regional calibration, reflecting the distinctive structure of Southeast Asian forests. We also discover that forest basal area is closely related to canopy gap fraction measured by ALS, and use this finding to refine Asner and Mascaro’s model. Finally, we show that our tree-centric approach is less accurate at estimating ACD than the best-performing area-based model (RMSE 18% vs 13%). Tree-centric modelling is appealing because it is based on summing the biomass of individual trees, but until algorithms can detect understory trees reliably and estimate biomass from crown dimensions precisely, areas-based modelling will remain the method of choice
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