A comparison of three canopy interception models for a leafless mixed deciduous forest stand in the eastern United States

Canopy interception of incident precipitation is a critical component of the forest water balance during each of the four seasons. Models have been developed to predict precipitation interception from standard meteorological variables because of acknowledged difficulty in extrapolating direct measurements of interception loss from forest to forest. No known study has compared and validated canopy interception models for a leafless deciduous forest stand in the eastern United States. Interception measurements from an experimental plot in a leafless deciduous forest in northeastern Maryland (39°42'N, 75°5'W) for 11 rainstorms in winter and early spring 2004/05 were compared to predictions from three models. The Mulder model maintains a moist canopy between storms. The Gash model requires few input variables and is formulated for a sparse canopy. The WiMo model optimizes the canopy storage capacity for the maximum wind speed during each storm. All models showed marked underestimates and overestimates for individual storms when the measured ratio of interception to gross precipitation was far more or less, respectively, than the specified fraction of canopy cover. The models predicted the percentage of total gross precipitation (PG) intercepted to within the probable standard error (8.1%) of the measured value: the Mulder model overestimated the measured value by 0.1% of PG; the WiMo model underestimated by 0.6% of PG; and the Gash model underestimated by 1.1% of PG. The WiMo model’s advantage over the Gash model indicates that the canopy storage capacity increases logarithmically with the maximum wind speed. This study has demonstrated that dormant-season precipitation interception in a leafless deciduous forest may be satisfactorily predicted by existing canopy interception models.

Breeding distribution and population decline of globally threatened Grey-necked Picathartes Picathartes oreas in Mbam Minkom Mountain Forest, southern Cameroon

The Grey-necked Picathartes Picathartes oreas, considered 'Vulnerable', is an enigmatic ground-dwelling bird endemic to the central African equatorial rainforest and belongs to a family of only two species. Its distribution extends to the two Endemic Bird Areas within Cameroon (Guinea Congo forest biome and Cameroon mountain arc) and its population is thought to be in decline throughout its range due to increasing habitat fragmentation and disturbance. During March-April 2003 and June and October 2007 we surveyed Grey-necked Picathartes in the north-western region of the Mbam Minkom Mountain Forest. In January-March 2006 we surveyed the entire mountain range and found go breeding and 24 potential breeding sites, mostly located on the western slopes. From the complete survey, we estimated the population at 44 breeding individuals. Populations were highest in the north-west region but had apparently declined from 40 breeding individuals in 2003 to 20 in 2007. This region accounted for 41% of the entire population on the mountain range during the 2006 survey. The Mbam Minkom/Kala Important Bird Area was designated based on the presence of Grey-necked Picathartes but is under high pressure of imminent destruction from agricultural encroachment and illegal timber exploitation. These results have important implications for decision making in delimiting forest boundaries and core areas for protection in the development of management plans. We suggest possible remedial actions, appropriate repeatable methods for future monitoring and opportunities for community involvement in the management and conservation of the site.

The use of agricultural, open and forest habitats by juvenile Mauritius Kestrels Falco punctatus

Knowledge of tropical raptor habitat use is limited and yet a thorough understanding is vital when trying to conserve endangered species. We used a well studied, reintroduced population of the vulnerable Mauritius Kestrel Falco punctatus to investigate habitat preferences in a modified landscape. We constructed a high resolution digital habitat map and radiotracked 13 juvenile Kestrels to quantify habitat preferences. We distinguished seven habitat types in our study area and tracked Kestrels from 71 to 130 days old during which they dispersed from their natal territory and settled within a home-range after reaching independence. Mean home-range size was 0.95 km(2) characterized by a bimodal pattern of intensity around the natal site and post-independence home-range. Compositional analysis showed that home-ranges were located non-randomly with respect to habitat but there was no evidence to suggest differential use of habitats within home-ranges. Native and semi-invaded forest and grassland were consistently preferred, whereas agriculture was used significantly less than other habitats. No difference was found between the available length of edge dividing native forest and grassland within a home-range when compared to that available within a 2.35-km buffer around their nest-site, based on the maximum distance a juvenile was found to disperse. Repeating the analysis in three dimensions gave very similar results. Our results suggest that Mauritius Kestrels are not obligate forest dwellers as was once thought but can also exploit open habitats such as grassland. Kestrels may be using isolated mature trees within grassland as vantage points for hunting in the same way as they use the natural stratified forest structure. We suggest that the avoidance of agriculture is partly due to a lack of such vantage points. The conservation importance of forest degradation and agricultural encroachment is highlighted and comparisons with the habitat preferences of other tropical falcons are discussed.

Improving participatory varietal selection processes: participatory varietal selection and the role of informal seed diffusion mechanisms for upland rice in Ghana

This paper considers the process of Participatory Varietal Selection (PVS) and presents approaches and ideas based on PVS activities conducted on upland rice throughout Ghana between 1997 and 2003. In particular the role of informal seed systems in PVS is investigated and implications for PVS design are identified. PVS programmes were conducted in two main agroecological zones, Forest and Savannah, with 1,578 and 1,143 mm of annual rainfall, respectively, and between 40 and 100 varieties tested at each site. In the Savannah zone IR12979-24-1 was officially released and in the Forest zone IDSA 85 was widely accepted by farmers. Two surveys were conducted in an area of the Forest zone to study mechanisms of spread. Here small amounts (1-2 kg) of seed of selected varieties had been given to 94 farmers. In 2002, 37% of 2,289 farmers in communities surveyed had already grown a PVS variety and had obtained seed via informal mechanisms from other farmers, i.e. through gift, exchange or purchase. A modified approach for PVS is presented which enables important issues identified in the paper to be accommodated. These issues include: utilising existing seed spread mechanisms; facilitating formal release of acceptable varieties; assessing post-harvest traits, and; the need for PVS to be an ongoing and sustainable process.

Seed dormancy and germination of Ficus lundellii and tropical forest restoration

We investigated seed dormancy and germination in Ficus lundellii Standl. (Moraceae), a native species of Mexico's Los Tuxtlas tropical rain forest. In an 8-h photoperiod at an alternating diurnal (16/8 h) temperature of 20/30 degrees C, germination was essentially complete (96%) within 28 days, whereas in darkness, all seeds remained dormant. Neither potassium nitrate (0.05-0.2%) applied continuously nor gibberellic acid applied either continuously (10-200 ppm) or as a 24 hour pretreatment (2000 ppm) induced germination in the dark. Germination in the light was not reduced by a 24-h hydrochloric acid (0.1-1%) pretreatment, but it was reduced both by a 24-h pretreatment with either H2O2 (0. 1-5 M) or 5% HCl, or by more than 5 days of storage at 40 degrees C (4.5% seed water content). In a study with a 2-dimensional temperature gradient plate, seeds germinated fully and rapidly in the light at a constant temperature of 30 degrees C, and fully but less rapidly in the light at alternating temperatures with low amplitudes (< 12 degrees C) about the optimal constant temperature. The base, optimal and ceiling temperatures for rate of germination were estimated as 13.8, 30.1 and 41.1 degrees C, respectively. In all temperature regimes, light was essential for the germination of F lundellii seeds.

Gold mining in Ghana's forest reserves: a report on the current debate

This paper examines the debate surrounding a recent decision made by the Ghanaian government to permit gold exploration - and potentially, mining - in 'protected' forest reserves. In 2001, four mining companies were awarded mineral exploration concessions in forested regions of the country, and have since put forward applications to mine for gold. Notwithstanding the sharp divide in opinion on the issue, the continued uncertainty surrounding the implications of the proposed activities makes further research on the ground imperative in the short term. Work aiming to elicit indigenous perspectives on the projects, as well as research that facilitates dialogue between and/or among stakeholder parties, should be prioritized.

Intra- and interspecific variations in vacuolar flavonoids among Ficus species from the Budongo Forest, Uganda

Leaves of 14 species of Ficus growing in the Budongo Forest, Uganda, were analysed for vacuolar flavonoids. Three to six accessions were studied for each species to see whether there was intraspecific chemical variation. Thirty-nine phenolic compounds were identified or characterised, including 14 flavonol O-glycosides, six flavone O-glycosides and 15 flavone C-glycosides. In some species the flavonoid glycosides were acylated. Ficus thonningii contained in addition four stilbenes including glycosides. Most of the species could be distinguished from each other on the basis of their flavonoid profiles, apart from Ficus sansibarica and Ficus saussureana, which showed a very strong intraspecific variation. However, on the whole flavonoid profiles were sufficiently distinct to help in future identifications.

A data forest: multi-dimensional visualization

As Terabyte datasets become the norm, the focus has shifted away from our ability to produce and store ever larger amounts of data, onto its utilization. It is becoming increasingly difficult to gain meaningful insights into the data produced. Also many forms of the data we are currently producing cannot easily fit into traditional visualization methods. This paper presents a new and novel visualization technique based on the concept of a Data Forest. Our Data Forest has been designed to be used with vir tual reality (VR) as its presentation method. VR is a natural medium for investigating large datasets. Our approach can easily be adapted to be used in a variety of different ways, from a stand alone single user environment to large multi-user collaborative environments. A test application is presented using multi-dimensional data to demonstrate the concepts involved.

Data forest: a collaborative version

As we increase our ability to produce and store ever larger amounts of data, it is becoming increasingly difficult to understand what the data is trying to tell us. Not all the data we are currently producing can easily fit into traditional visualization methods. This paper presents a new and novel visualization technique based on the concept of a Data Forest. Our Data Forest has been developed to be utilised by virtual reality (VR) systems. VR is a natural information medium. This approach can easily be adapted to be used in collaborative environments. A test application has been developed to demonstrate the concepts involved and a collaborative version tested.

Recent patterns of change in vegetation structure and tree composition of British broadleaved woodland: evidence from large-scale surveys

Evidence is presented of widespread changes in structure and species composition between the 1980s and 2003–2004 from surveys of 249 British broadleaved woodlands. Structural components examined include canopy cover, vertical vegetation profiles, field-layer cover and deadwood abundance. Woods were located in 13 geographical localities and the patterns of change were examined for each locality as well as across all woods. Changes were not uniform throughout the localities; overall, there were significant decreases in canopy cover and increases in sub-canopy (2–10 m) cover. Changes in 0.5–2 m vegetation cover showed strong geographic patterns, increasing in western localities, but declining or showing no change in eastern localities. There were significant increases in canopy ash Fraxinus excelsior and decreases in oak Quercus robur/petraea. Shrub layer ash and honeysuckle Lonicera periclymenum increased while birch Betula spp. hawthorn Crataegus monogyna and hazel Corylus avellana declined. Within the field layer, both bracken Pteridium aquilinum and herbs increased. Overall, deadwood generally increased. Changes were consistent with reductions in active woodland management and changes in grazing and browsing pressure. These findings have important implications for sustainable active management of British broadleaved woodlands to meet silvicultural and biodiversity objectives.