bluuebunny/crossref_metadata_2025 huggingface dataset:
Disease progression meta‐analysis model in Alzheimer's disease
Authors: Ito Kaori , Ahadieh Sima , Corrigan Brian , French Jonathan , Fullerton Terence , Tensfeldt Thomas ,   Alzheimer's Disease Working Group
Published: July 2009

Background

Various authors have evaluated disease progression in Alzheimer's disease (AD), using patient data from individual clinical studies or pooled data across various trials. We conducted a systematic review of public data sources from 1990 to 2008 for all available AChE inhibitor studies, as well as clinical studies that evaluated the rate of deterioration in AD patients. Unique to this analysis, we developed a model based on literature data to describe the longitudinal response in the Alzheimer's Disease Assessment Scale‐Cognitive (ADAS‐cog) (change from baseline) in mild to moderate severity AD patients. The model was used to estimate disease progression for both placebo‐treated patients and acetylcholinesterase (AChE)‐inhibitor treated patients, and factors that affected disease progression.

Methods

We collected 576 mean ADAS‐cog changes from baseline data points of 52 trials, representing data from approximately 19,972 patients and more than 84,000 individual observations. The model described the rate of disease progression, the evident placebo effect, and the symptomatic effect of AChE‐inhibitors. Baseline ADAS‐cog, Mini‐Mental State Examination score, age, and year of publication were tested as covariates.

Results

The disease progression in mild to moderate AD patients across all available and relevant literature sources was estimated as 5.5 points per year. An Emax‐type model best described the symptomatic drug effect of AChE inhibitors. The rate of disease progression (underlying disease progression) was no different between placebo and AChE‐inhibitors groups. Baseline ADAS‐cog is a significant covariate in disease progression. Baseline age was also tested as a covariate in the rate of disease progression, but the model was unable to describe any effects of age, likely because of the narrow distribution of mean age (literature‐level analysis). There was no significant impact of publication year in the model.

Conclusions

Baseline ADAS‐cog is a significant covariate affecting the rate of disease progression, and it describes or at least explains the different rates of deterioration evident in early or late stages of the disease. There was no significant impact of publication year in the model, suggesting that disease progression has not slowed in more recent trials.
Growth rates and age-size relationships of tropical wet forest trees in Costa Rica
Authors: Lieberman Diana , Lieberman Milton , Hartshorn Gary , Peralta Rodolfo
Published: July 2009

Diameter growth rates and age-size relationships are reported for 45 abundant tree species and one liana in tropical wet forest at La Selva, Costa Rica. Thirteen-year increments in each species were analysed using growth simulation, a stochastic technique which projects growth trajectories.

Median growth rates ranged from 0.35 mm yr-1(Anaxagorea crassipetala) to 13.41 mm yr-1) (Stryphnodendron excelsum). Maximum ranges ranged from 0.95 mm yr-1(Quararibea brac-teolosa) to 14.62 mm yr-1(Hernandia didymanthera). Minimum rates ranged from zero growth (Capparis pittieri, Colubrina spinosa, Doliocarpusspp.) to 7.45 mm yr-1(Stryphno dendron excelsum).

Projected lifespan (from 100 mm dbh to the maximum dbh for the species) varied from 52 years (Anaxagorea crassipetala, Guatteria inuncta) to 442 years (Carapa guianensis). The mean longevity among the 45 tree species studied is 190 years.

Four main patterns of growth behaviour are recognized, based upon longevity and growth rates: (1) understorey species have slow maximum growth rates and short lifespans; (2) shade-tolerant subcanopy trees live around twice as long as understorey trees and grow at approxi-mately the same maximum rates; (3) canopy and subcanopy trees that are shade-tolerant but respond opportunistically to increased light levels have long lifespans and fast maximum growth rates; (4) shade-intolerant canopy and subcanopy species are short-lived and have fast maximum growth rates. Understorey species intergrade with shade-tolerant subcanopy species in terms of growth behaviour; shade-tolerant subcanopy species with opportunistic, shade-tolerant species; and opportunistic, shade-tolerant with shade-intolerant species.

Intraspecific variation in growth rates is lower in short-lived trees (understorey species with uniformly slow growth and shade-intolerant species with uniformly rapid growth) than in the two long-lived groups. These patterns are discussed in the context of tree ecophysiology and forest light environments.
General flowering in the climax rain forests of South-east Asia
Authors: Appanah S.
Published: July 2009

The general flowering of lowland dipterocarp forests of South-east Asia is a unique phenomenon that occurs intermittently, sometimes many years apart, and may be widespread throughout the region or sporadic. During a general flowering a very large number of tree families, including the well-known Dipterocarpaceae, flower and fruit exceptionally heavily. The huge pulse of flowering is echoed by an apparent explosion in the number of pollinators, and this is further augmented by migration of pollinators from the forest fringes. The huge demand for pollinators seems to be solved among several dipterocarps through utilization of tiny, fast breeding, floral-feeding insects such as thrips and hoppers. Competition for pollinators is further reduced through development of sequential flowering among several groups of trees that share similar pollinators. The resulting massive general fruiting seems to contribute to a heightened level of faunal activity and numbers. This long-intervalled flowering and fruiting phenology which dominates these lowland dipterocarp forests may have partly contributed to the lowered animal biomass frequently alluded to when these forests are compared with neotropical forests.
Roosting site selection by Artibeus watsoni (Chiroptera: Phyllostomidae) on Anthurium ravenii (Araceae) in Costa Rica
Authors: Choe Jae C. , Timm Robert M.
Published: July 2009

Artibeus watsoni (Chiroptera: Phyllostomidae) was found in Costa Rica to alter the shape of 11 species of broad-leafed plants in the families Araceae, Cyclanthaceae, Maran-taceae, Musaceae, and Palmae to form diurnal roost sites. The plant most commonly used for tent construction was Anthurium ravenii (Araceae). Bats create a tent on A. ravenii by severing the basal 2 to 5 lateral nerves at a distance of 5 to 10 mm from the midrib; the entire margin of the leaf then collapses downward to form a pyramid-shaped tent. The number of altered leaves per plant ranges from 1 to 4 with a mean of 2.1. A. watsoni appears to be selecting leaves of medium size and low within the plant. The size, shape, and location of leaves selected is consistent with the hypothesis that tent construction provides bats with roost sites that will be available to them for a long period of time and provides protection from both predators and the elements, thus conveying a selective advantage to the bats.
A preliminary investigation of small mammal biology in the Kora National Reserve, Kenya
Authors: Alibhai S. K. , Key G.
Published: July 2009

This study examined the ecological distribution and abundance of the small mammal fauna in the Kora National Reserve, Kenya. Over a period of eight weeks, 3300 trap-nights yielded 11 species and a total of 298 small mammals. All 11 species were trapped in the diverse nyika habitat, whereas in the riverine habitat five species were trapped and the rock outcrops had only two species. However, the catch per trap-night was the highest on the rock outcrops compared with the riverine and nyika habitats. The duration of prebaiting had a marked effect on both diversity and abundance. With one exception, males of all species were in breeding condition whereas females tended to be more erratic. The biology of small mammal species in Kora in the dry season is discussed.
Nutrient content of litterfall in coniferous forest plantations in central Java, Indonesia
Authors: Bruijnzeel L. A.
Published: July 2009

Production and nutrient content of small litterfall were studied for one year in four plantations ofAgathis dammararanging in age from 7 to 35 years old, in a 12-year-old stand ofPinus merkusiiand in an approximately three-year-old shrub community dominated byEupatoriumspecies. The densePinusplantation produced considerably more litter (10 t/ha/yr, with 5.5 t/ha as needles) than any of theAgathisstands (2.6–6.2 t/ha/yr; 2.3–3.5 t/ha as leaves) or nearby Lower Montane Rain Forest (6.8 t/ha/yr; 5.4 t/ha as leaves). Litterfall in theAgathisforests increased with stand age. The shrubs produced sizeable amounts of litter (3.4 t/ha/yr). The various species responded differently to a drought occurring during the study period.

Pine litter generally exhibited low nutrient concentrations (on average 9.2, 1.9, 2.5, 0.4 and 6.0 mg/g of calcium, magnesium, potassium, phosphorus and nitrogen respectively in needle litter), whilst concentrations in shrub litter were generally high (37.8, 4.9, 1.4, 1.05 and 21.5 mg/g for the same elements);Agathislitter usually showed nutrient concentrations that were intermediate between those for pine or shrub litterfall with only minor differences between stands. Comparison of the present findings with observations at other tropical sites suggests that nutrient content of litterfall in plantation forests may approach that of natural forests when the former become about 20 years old. Pine plantations may constitute an exception in this regard.
The murundus of the cerrado region of Central Brazil
Authors: de Araujo Neto M. Diniz , Furley P. A. , Haridasan M. , Johnson C. E.
Published: July 2009

Campos de murundus (earthmound fields) are common throughout the cerrado (savanna) in Brazil. They have a clearly defined distribution particularly where they are associated with ground water. There is a distinctive woody vegetation on the discrete mounds contrasting with surrounding grass-covered depressions.

After a reconnaissance ground and air-photograph survey of the nature and distribution of mounds within the Federal District, four one-hectare plots were chosen for detailed study within the ecological reserve of the University of Brasília. Measurements were made of the size, shape and frequency of mounds. Numbers varied from 26 to 61 ha-1 with a uniform distribution occupying 10–50% of the plots. Heights ranged from 0.05 to over 2 m. The generally semi-elliptical shape in ground plan had an average size of 7 by 5.5 m with no evidence of preferred orientation although water scouring from runoff partly influences the morphology. Volumes varied from 0.01 m3 to 141.5 m3. The soils of the murundus differed from those of surrounding depressions by being better drained, with bright colours and strong cohesive structures; they were more argillic with lower base saturation and pH values. Such sites favour colonization both by cerrado plants and by termites. A classification of the murundus is postulated. Although this paper does not consider the origins of murundus, they appear to relate more closely to drainage and differential erosion than to termite activity.
Chemical plant-soil relationships in tropical forests
Authors: Golley Frank B.
Published: July 2009

Plant and soil samples collected from four tropical forest areas were used to examine the correlation between the chemical abundances in soil and vegetation. On fertile soils in Panama and Colombia soil concentrations of copper, manganese, cobalt and zinc were correlated with plant concentrations. Calcium, caesium, iron, lead, magnesium, phosphorus, potassium, sodium and strontium-concentrations were not correlated. Factor analysis of plant chemistry at nine sites showed very little commonality between sites, even of vegetation belonging to the same plant association. A copper, manganese, cobalt, zinc factor was not recognized except in one case. A similar study of plant soil correlation in Colombia supported the conclusions from Panama; for most elements there was little evidence for significant correlation between plant and soil concentrations.

Analysis of plant-soil relationships on very infertile latosols with terra firme forest in the Amazon at San Carlos de Rio Negro, Venezuela and Manaus, Brazil revealed a soil effect on the statistical distributions of the elements in the plant biomass. This effect was strongest on the least fertile site at Manaus and was strongest for essential elements. The pattern of chemical distributions appears to be due to the fact that some species are capable of concentrating high levels of elements even under conditions of very low supply in the substrate.
Phenological changes in a Sumatran rain forest
Authors: Van Schaik C. P.
Published: July 2009

Phenological observations were made in a Sumatran rain forest during three years (1980–1982). Phenological changes followed a consistent seasonal pattern. The abundance of young leaves and the fall of leaf litter peaked between December and February (first dry season); flowers were most abundant between January and April (first dry and first wet sea son), and ripe fruits in July-August (the second dry season). The fruit of strangling fig trees showed peaks in April and October, both wet season months. Within the study area there was variation in both the phase and the amplitude of the phenological cycles. One year, 1981, displayed mast flowering and fruiting. The observations indicate that the conditions for production were better during the mast year, a finding that facilitates our understanding of the evolution of mast fruiting.
Soil–plant relations in a natural forest inviolate plot at Akure, Nigeria
Authors: Ola-Adams B. A. , Hall John B.
Published: July 2009

To up-date and extend knowledge of the Akure Strict Natural Reserve an assessment, block by block, of forest in the core of the Inviolate Plot was undertaken in 1974 and complemented with soil sampling. Principal components analysis indicated a gradient of soil reaction and available phosphorus through the core of the plot. Ordination (DECORANA) of floristic data revealed that a floristic trend paralleled the soil trend. In the vicinity of a drainage line, at the western end of the core, soils were lower in available phosphorus, more acid, sandier and texturally more uniform with depth. Typical trees of ferralsols were prominent on these soils but were replaced by species of ferric luvisols, especially members of the Sterculiaceae, on soils of superior nutrient status towards the eastern end. It is suggested that the soil gradients were not effects produced by the trees.

Comparison of a 1946 data set with the 1974 data supported the view that the forest had been structurally and floristically stable over the interval between assessments. This is considered justification of the original choice of the area as a Strict Natural Reserve representative of high forest in this part of Nigeria.
Invertebrates in the litter and soil at a range of altitudes on Gunung Silam, a small ultrabasic mountain in Sabah
Authors: Leakey R. J. G. , Proctor John
Published: July 2009

The numbers and biomass of litter and soil invertebrate fauna were investigated in six plots at altitudes of 280 m, 330 m, 480 m, 610 m, 790 m and 870 m on Gunung Silam, Sabah, East Malaysia. There were relatively high numbers and biomass in the lower plots, where the Oligochaeta were a high proportion of the total invertebrate biomass. The biomass of other invertebrate groups was low in the soil. There was a marked effect of altitude, particularly for the Oligochaeta above 610 m. The low biomass of the Oligochaeta in the higher plots suggested that the importance of this group may be diminished at relatively low altitudes on small mountains. However, several other soil faunal groups showed no evidence of an altitudinal effect, and it is suggested that the stunted forests near the summits of small mountains such as Gunung Silam may have a different litter and soil fauna from forests of a similar physiognomy at high elevations on large mountains.
Effects of fire regimes on lizards in the wet-dry tropics of Australia
Authors: Braithwaite Richard W.
Published: July 2009

A quantitative analysis of the effect of fire regime on the abundance of common lizard species and genera and the species richness of two lizard groups in Kakadu National Park (12° S) is presented. A surprising range of relationships between species abundance and components of fire regimes was revealed. Carlia amax, Heteronotia binoei and Carlia gracilis appear to be fire-sensitive, Diporiphora bilineata and Carlia triacantha are favoured by early hot fires, Cryptoblepharus plagiocephalus seems relatively unaffected, Carlia foliorum seems very tolerant of fires, while Ctenotus and Sphenomorphus spp. are favoured by low intensity, patchy fires with high intensity spots.

Lizard species experiencing the high-frequency fire regimes of the savannas and dry forests of the Australian wet-dry tropics are not able to select habitat at different stages of regeneration after fire but select habitat produced by fires of different types. The implication for management is that no one fire regime is optimal for the fauna as a whole. A range of fire regimes within a park should be maintained in order to retain the whole fauna.
Litterfall and productivity in a tropical rain forest, Southern Baakundu Forest Reserve, Cameroon
Authors: Songwe Nicholas C. , Fasehun F. E. , Okali D. U. U.
Published: July 2009

Litterfall was measured monthly in ten 1 m2traps in each of two 0.25 ha plots in the rain forest of Southern Bakundu Forest Reserve, Cameroon for 18 months from 1 July 1982 to 31 December 1983. Particular emphasis was placed on measuring species contributions and in relating litterfall to climatic factors; the litterfall data were also used in estimating leaf production. Annual litterfall ranged between 12.9 and 14.1 t ha−1and was partitioned to leaves (61–66%), branches (23–38%), fruits and flowers (8–12%) and ephiphytes (0.8%). Emergents and top canopy species likeDesbordesia glaucescens(evergreen) andCeiba pentandra(deciduous) contributed more litter than the numerically dominant lower storey species likeCola lepidotaandDiospyrosspp. Litter fell throughout the year but was greatest during the dry season (November to March); litterfall was thus strongly negatively correlated with environmental moisture variables and could be predicted from its linear regression on time of year, throughfall and relative humidity. By correcting the leaf fall data for leaf weight losses due to grazing and re-translocation, leaf production rates of 10.2 to 11.2 t ha−1yr−1were estimated for the forest.
Pioneer species distribution in treefall gaps in Neotropical rain forest; a gap definition and its consequences
Authors: Popma Jean , Bongers Frans , Martínez-Ramos Miguel , Veneklaas Erik
Published: July 2009

An attempt was made to evaluate the consequences of applying a strict definition (Brokaw 1982a) to the delimitation of forest gaps in the field. The northernmost Neotropical rain forest, at Los Tuxtlas, Mexico, was searched for young (1–2 years old) single-event gaps that would meet the criteria of the definition. In 60 ha of rain forest, only 12 such gaps containing pioneer species could be found. Thirty-three pioneer species (shrubs and trees) were used as indicator species for gap conditions. Gap size, measured as projected canopy opening (sensu Brokaw 1982a), underestimated from 44 to 515% the size of the area colonized by pioneer species. On average the size of the colonized area was 3.4 times larger than the size of the projected canopy opening. The majority of the pioneer species showed a relative preference for gap borders, an area generally not included in the projected canopy opening. Pioneer plant abundance and density, and species richness and density, did not differ significantly between gap centres and gap borders. Floristical variation was not related to gap size or location in the gap. These findings can be explained if gap environment (to which pioneer plants respond) is seen as the result of many interacting factors, of which size of the canopy opening is only one. It is concluded that the definition for delimiting gaps in the field as proposed by Brokaw (1982a) cannot be regarded a generally applicable definition, and that its value as a comparative standard is doubtful.
Internal heterogeneity of gaps and species richness in Costa Rican tropical wet forest
Authors: Brandani Aldo , Hartshorn Gary S. , Orians Gordon H.
Published: July 2009

In Costa Rican tropical wet forest the distribution of seedlings of most tree species colonizing 51 tree-fall gaps is clumped, probably because of differences in the proximity of gaps to fruiting trees. Different gap zones (root, bole and crown) are more similar to one another, in terms of their species composition, than they are to other zones in the same gap. This nonrandom pattern is established soon after gap formation, indicating that mortality of young seedlings is both high and related to gap zones. Some tree species are strongly positively associated with one of the gap zones, whereas others are associated with the age of the gap at the time the census was taken or the species of tree whose fall caused the gap. Root zones are dominated by fewer species than are bole or crown zones. Results are consistent with the assumption that an initial random distribution of seedlings is quickly changed to a strongly non-random pattern by selective mortality of seedlings of different tree species in the different gap zones. The internal heterogeneity of gaps is probably one of the factors helping to maintain the high tree species richness characteristic of tropical wet forests.
Jamaican limestone forests: floristics, structure and environment of three examples along a rainfall gradient
Authors: Kelly D. L. , Tanner E. V. J. , Kapos V. , Dickinson T. A. , Goodfriend G. A. , Fairbairn P.
Published: July 2009

We describe forests from three areas of Jamaica, all on White Limestone but with markedly different rainfall regimes. The areas are Hog House Hill in the north-east with lower montane rain forest at c. 450 m altitude with a rainfall of c. 4000 mm yr−1; Broom Hall in the centre of the island with evergreen seasonal forest at c. 670 m altitude and with a rainfall of c. 1600 mm yr−1and a marked dry season; and Round Hill near the south coast with dry semi-evergreen forest at c. 300 m altitude with an irregularly distributed rainfall of c. 1000 mm yr−1. Species lists were made from c. 180 ha at Hog House Hill, c. 5 ha at Broom Hall and c. 50 ha at Round Hill, and detailed inventories made of five sample sites of c. 1000 m2, two at Hog House Hill, one at Broom Hall and two at Round Hill.

At Hog House Hill we listed 280 vascular plant species, including 118 species of trees and larger shrubs; at Broom Hall 247 and 135; at Round Hill 129 and 81. Species-area and species-individuals curves confirm that Broom Hall was richer in tree species than Hog House Hill. The wetter forests contain high proportions of species endemic to Jamaica: 40% of the total flora at Hog House Hill and 36% at Broom Hall. Canopy height decreased from c. 26–28 m at Hog House Hill to c. 13–24 m at Broom Hall to c. 8–15 m at Round Hill. Predominant leaf size decreased from mesophyll at Hog House Hill to notophyll at Broom Hall to microphyll at Round Hill.

Compared with forests on other Caribbean islands, the Jamaican forests appear to be as species-rich as any, but lower in stature than natural forest in Trinidad and Dominica. Continental Neotropical forests are both more species-rich and taller.
Dormancy, germination and seedling growth of two Kalaharian perennials of the genus Harpagophytum (Pedaliaceae)
Authors: Ernst W. H. O. , Tietema T. , Veenendaal E. M. , Masene R.
Published: July 2009

Dormancy and germination ecology of two Harpagophytum species (Pedaliaceae) from an open Acacia savanna in Botswana were investigated. The maintenance of dormancy is governed partly by the seed coat but mainly by the endosperm and the embryo itself, as demonstrated by removal of the endosperm. Dissemination of the seed from the fruit can be delayed for several years without affecting the viability of the embryo, due to very low respiration rates.

Germination can be enhanced slightly by high temperatures under natural conditions, and by gibberellic acid or removal of the endosperm under laboratory conditions. Relative growth rates for both Harpagophytum species are lower than for subtropical grasses and legumes, due to a strong investment in root and tuber biomass. Germination and seedling growth is discussed in relation to the drought avoidance syndrome and the animal disperser syndrome.
Crepuscular biting activity of mosquitoes at Peradeniya, Sri Lanka
Authors: Amerasinghe F. P.
Published: July 2009

Thirty-four spedes of mosquitoes (Diptera: Culicidae) were collected at a series of human-bait catches designed to study evening crepuscular biting activity using the Nielsen crep unit, at a site at Peradeniya, Sri Lanka. Crepuscular biting profiles of seven species (Armigeres subalbatus, Aedes albopictus, Culex pseudovishnui, Cx. gelidus, Cx. fuscocephala, Cx. tritaeniorhynchus and Mansonia uniformis) were obtained. Modal periods for the onset of biting were analysed in six species: Cx. pseudovishnui, Cx. fuscocephala, Cx. gelidus, Cx. tritaeniorhynchus, Cx. quinquefasciatus and Ma. uniformis. Successions in the biting peaks and in modal onset of biting were seen in these species. Analysis of biting in Ar. subalbatus and Cx. pseudovishnui under high (clear sky) and low (cloud-overcast sky) light intensities showed earlier biting in both species under the latter conditions. The value of the Nielsen crep unit in making latitudinal comparisons is illustrated in Ma. uniformis, for which parallel data are available from Africa.
Litterfall in an Australian population of Mimosa pigra, an invasive tropical shrub
Authors: Lonsdale W. M.
Published: July 2009

An investigation of seasonal changes in litterfall in a dense stand of the invasive tropical shrub Mimosa pigra was carried out in northern Australia between October 1984 and December 1986. Total annual litterfall averaged 758 g m−2, close to the value predicted for the latitude and altitude of the site. Leaf litter formed 56.6% of this total, woody material 22.7%, and reproductive material 20.7%. Total litterfall was strongly seasonal, at a maximum in the late wet season or early dry season, and at a minimum late in the dry season. A broadly similar pattern was shown by the various components of the litter, except for woody litterfall, which followed no strong seasonal trend. Variation in the amount of available soil moisture, as calculated from a simple water balance model, accounted for much of the variation in the components of litterfall.

The proportion of all initiated flower heads which produce seeds was estimated to be between 2.1 and 4.5%. The mean annual seed fall was 9103 m−2, nearly two orders of magnitude higher than most native shrub populations, and it is argued that this is partly a result of the absence of natural enemies in the introduced range.
Effects of isolation on the water status of forest patches in the Brazilian Amazon
Authors: Kapos Valerie
Published: July 2009

Patterns of edge-related environmental changes and plant water relations were investigated in the isolated forest reserves of the INPA-WWF Minimum Critical Size of Eco-systems project near Manaus, Brazil early in the wet season.

Air temperature was elevated and humidity reduced in the understorey within 40 m of the reserve margins, and air temperature and vapour pressure deficit (VPD) were higher in the interiors of 1 ha reserves than in 100 ha reserves. There was increased photosynthetically active radiation penetration to understorey level up to 40 m into a 100 ha reserve.

Soil moisture was depleted in the outer 20 m of both small and large reserves, and surface soil water potentials fell below – 1.5 MPa at the margin of a 1 ha reserve.

Studies of leaf relative water contents (RWCs) in understorey shrubs revealed no appreciable saturation deficits, though RWCs were sometimes lower at the reserve margins. Studies of leaf conductances revealed no evidence of restriction of water loss in these plants, and conductances of plants near the edges were significantly higher and higher for longer.

The implications of these results for reserve design and for local and regional water budgets, as well as the possible role of water stress in increased tree mortality in isolated reserves are discussed.

Padrōes de mudanças ambientais e hídricos de plantas relacionados a bordas de matas isoladas foram investigadas no início da estação seca nas reservas de floresta do Projeto Dinâmica Biológica de Fragmentos Florestais do INPA-WWF, proximo de Manaus, Brasil.

No sub-bosque, até 40 m da borda da mata, a temperatura ambiental estava elevada e a umidade reduzida, e a temperatura do ar e o DPV estavam maiores nas reservas de 1 ha do que nas reservas de 100 ha. A penetração de radiaçao fotosintéticamente ativa no sub-bosque estava aumentada até 40 m da borda em reservas de 100 ha.

A umidade do solo baixou consideravelmente nos 20 m periféricos de reservas grandes a pequenas, e o potencial hídrico na superficie do solo baixou para menos de −1.5 MPa na margem de uma reserva de 1 ha.

Estudos do teor relativo de água (TRA) em folhas de arbustos de sub-bosque nӑo revelaram deficits de saturação apreciaveis apesar de que TRAs foram menores nas bordas das reservas. Estudos da conductancia foliar não revelaram evidência de restrições de perdas hídricas nessas plantas, e as conductancias de plantas próximas a bordas foram significativamente maiores durante um período mais longo.

As impliçõtes desses resultados para o planejamento de reservas e para o balanço hídrico local e regional, assim como as possiveis funçoes de ‘stress’ hídrico na alta mortalidade de árvores em reservas isoladas são discutidas.
A study of the ecological history, vegetation and conservation management of Ile aux Aigrettes, Mauritius
Authors: Parnell John A. N. , Cronk Q. , Jackson P. Wyse , Strahm W.
Published: July 2009

Much of the unique native vegetation of Mauritius has been destroyed. Coastal ebony (Diospyros egrettarum I.B.K. Richardson) forest forms an extreme type of Mauritian lowland forest which no longer exists on mainland Mauritius and only survives on one offshore islet, Ile aux Aigrettes. Undisturbed D. egrettarum forest is resistant to invasion by exotic plants, which have now invaded most relict patches of native lowland vegetation in Mauritius. Human disturbance however, has allowed many exotics (particularly Flacourtia indica (Burm. fil.) Merrill) to invade and form new vegetation types. Much of the disturbance was caused by illegal woodcutting up to 1985, prompted by an acute fuelwood shortage in Mauritius. On the basis of 132 4 X 4 m quadrats, we recognize 10 types of natural, semi-natural and exotic vegeta-tion. The conservation of the remaining natural ebony woodland vegetation requires the total cessation of woodcutting and the eradication of Tabebuia pallida (Lindl.) Miers (potentially the most damaging exotic species).
Environmental factors affecting physiognomic and floristic variation in an area of cerrado in central Brazil
Authors: Oliveira-Filho Ary Teixeira De , Shepherd George John , Martins Fernando Roberto , Stubblebine William Henry
Published: July 2009

Cerrado is a species-rich savanna-like vegetation that covers a large area in central Brazil. Soil, and particularly soil fertility, is considered to be the major factor determining the wide and diverse physiognomic-floristic gradients encountered within cerrado vegetation. To describe the vegetational variations within a cerrado in southern Mato Grosso state (15° 21'S, 55° 49'W), a 1 ha transect was located to pass through an interfluvial cerrado and climb a steep talus slope. The vegetational and environmental variations are described by means of field classification, direct gradient analysis and reciprocal averaging ordination. The effects of differences in ground water regime in the interfluvial cerrado and differences in inclination with associated rockiness in the talus cerrado are related to the vegetational variations. As the soils are very similar in texture and in the majority of chemical properties, the role of the above environmental factors was more easily distinguished. In the interfluvial cerrado, the vegetation variations are probably related to the seasonal fluctuation in water table level.
Length-mass relationships among an assemblage of tropical snakes in Costa Rica
Authors: Guyer Craig , Donnelly Maureen A.
Published: July 2009

Length-mass relationships within an assemblage of tropical snakes are used to describe morphological groups. We report patterns of body size based on length and mass measurements of 603 individual snakes of 27 species captured at La Selva, Costa Rica from March 1982 through August 1984. This assemblage of snakes is composed of at least four morphological groups each of which consists of species with similar habitat preferences. These groups are heavy-bodied terrestrial forms, light-bodied arboreal forms, long-tailed leaf-litter forms, and forms of unextreme relative mass and tail length. This tropical snake assemblage is more diverse in species richness and morphological diversity than a temperate assemblage.
Assessment of permanence and stability in the territories of Kirk's dikdik (Rhynchotragus kirki) in Tanzania
Authors: Amubode Felix O. , Boshe John I.
Published: July 2009

The permanence and stability of 20 territories of the dikdik Rhynchotragus kirki, were studied at Arusha National Park Tanzania. Response criteria included the structure, size and vegetation attributes of territories, density of dikdik, and spatial distances between neighbouring territories. Fourteen of the territories studied were spatially fixed and stable while six were unstable. Two of the unstable territories were completely abandoned. Mean territory size was 0.11 and 0.13 ha during the rainy and dry seasons, respectively. 14.2% of circular territories and 42.9% of elliptical and kidney-shaped territories were stable. The figure of 55 dikdik km−2 sighted during morning censuses was lower than that for evening censuses by 13.5%. Spatial distance between territories ranged from 4.5 m to 100 m, an indication that population density might be a function of the size of suitable habitat. Although shrub canopy cover within stable territories decreased by 44.6% between 1982 and 1987, and some territories were realigned with changes in rainfall pattern, pair-bond was maintained by dikdik in 70% of the territories studied.
Phenology, seed dispersal, and recruitment inCecropia peltata(Moraceae) in Costa Rican tropical dry forest
Authors: Fleming Theodore H. , Williams Charles F.
Published: July 2009

We studied the seed dispersal ecology of the Neotropical pioneer treeCecropia peltataL. (Moraceae) in tropical dry forest by documenting its (1) fruiting phenology, (2) rates of visitation by vertebrate frugivores, and (3) rate of recruitment of juveniles in different habitats at Santa Rosa National Park in northwestern Costa Rica.

At Santa Rosa,C. peltatais a common but patchily-distributed plant. Fruiting in females is seasonal, and fruit availability peaks in June through August (the early wet season). Females bear a few ripe fruit per day over a 4–5 month, fruiting period. At least 28 vertebrate species (15 diurnal and 13 nocturnal species) eatCecropiafruit; equal numbers of ripe fruit are removed during the night and day. Owing to their more gentle treatment of seeds in the gut, birds and bats probably are more effective dispersal agents than monkeys. The recruitment rate of juveniles into already established populations was about 0.8 ha−1y−1compared with a rate of 176 ha−1y−1during the colonization of a cleared roadside.
Nitrogen and phosphorus fertilization of Jamaican montane forest trees
Authors: Tanner E. V. J. , Kapos V. , Freskos S. , Healey J. R. , Theobald A. M.
Published: July 2009

Plots in the Jamaican montane forest were fertilized with nitrogen or with phosphorus to test the hypothesis that growth of trees in this natural forest is limited by the supply of N and P from the soil.

Once a year from 1983 to 1986, urea was added to one plot (at 150 kg N ha−1 y−1) and triple superphosphate was added to another (at 50 kg P ha−1 y−1). In each of these plots and in two control plots, foliage of four common tree species was collected immediately before each fertilizer addition. Trunk growth was measured in 105 individuals.

Foliar N concentrations were not significantly higher in trees fertilized with N compared to control trees. In Dendropanax cf. pendulus and Hedyosmum arborescens fertilization with N resulted in lower P concentrations but only after the third year of fertilization, possibly due to dilution by increased leaf production. Mean trunk diameter growth was significantly higher in the N-fertilized trees than in controls.

Mean foliar P concentrations were higher in Podocarpus urbanii and Clethra occidentalis following fertilization with P, but only after two years of fertilization. Trunk diameter growth was greater in the P fertilized plot.

Thus growth in some Jamaican montane forest trees was limited by the natural supplies of N and of P.
Survival and growth of juvenile Virola surinamensis in Panama: effects of herbivory and canopy closure
Authors: Howe Henry F.
Published: July 2009

Effects of mammalian herbivory and seasonal drought were studied for Virola surinamensis (Myristicaceae) juveniles on Barro Colorado Island, Panama. Seedlings were planted at three months of age and the juveniles were monitored for two years; Treatments included: intact plants protected from mammals by cages, defoliated plants similarly protected, and unprotected plants, each planted in treefall gaps, on gap edges, and in the shaded understorey.

Juveniles planted in treefall gaps survived seasonal drought far better than those planted on gap edges or in shaded understorey. Two years after establishment, juveniles protected from mammalian herbivory showed a 78% survival in gaps (mean 6.8% skylight), 50% survival on gap edges (mean 3.0% skylight), and 33% survival in shaded understorey (1.4% skylight). This advantage was due to accelerated growth in gaps. Juveniles in gaps increased 616% in height, 1075% in leaf number, and 1800% in total leaf area. Comparable numbers in edges were 247%, 378% and 690%; in understorey 33%, 222% and 289%. Accelerated growth in gaps permitted yearlings to survive drought that killed suppressed yearlings in understorey. Mean light differentials as small as 0.6% and 0.3% skylight significantly influenced survival on edges and in shaded understorey, respectively.

Mammalian herbivory killed juveniles directly, and defoliation by mammals strongly accentuated drought mortality by suppressing root development. Natural defoliation was not attributable to gap conditions. Demographic projections from experimental data suggest that mammalian herbivory kills at least 48% of the juveniles of this species over two years, and contributes to the death of 32% more that actually die of drought stress. These projections suggest that 14% of the juveniles of this species die of drought mortality, independent of herbivory, during the first two years. Herbivory most strongly affects plants < 0.5 m in height, and is a continuing source of mortality among suppressed juveniles in the understorey. Steep slopes and large seed size each enhanced juvenile growth and survival in the intermediate conditions of gap edges, but not under the extreme conditions of gaps or shaded understorey.

The context of establishment determines the ‘shade tolerance’ of this conspicuous canopy tree. Without serious mammalian herbivory or extreme dry seasons, V. surinamensis can easily recruit as a shade tolerant plant in the understorey. Under present conditions on Barro Colorado Island, it cannot. Persistence involves both the chances of arrival in different microhabitats, and survival therein. Projections that include both the forest area represented by gaps, gap edges, and understorey and the experimental results from this study indicate that juvenile V. surinamensis can survive for two years in gaps, edges, and understorey, but that the higher proportions of vigorous individuals survive in edges, gaps and understorey, respectively.
Root proliferation in recent and weathered sandy soils from Veracruz, Mexico
Authors: Kellman Martin
Published: July 2009

Field observations and laboratory experiments on unweathered and weathered dune sand beneath a tropical deciduous forest in Veracruz, Mexico were used to test the hypothesis that temporary nutrient adsorption by more weathered soil facilitates more effective nutrient recycling through the stimulation of a superficial fine root system. An analysis of soil solution composition in the field indicated that K, P andwere being more effectively retained in weathered sand topsoil than in recent sand but, in a leaching experiment, onlywas more effectively adsorbed by this soil. Fine roots in weathered sand were more concentrated superficially than in recent sand, and a bioassay with seedlings ofCedrela odoratashowed more fine root proliferation in this medium than in recent sand. In combination, these data suggest that weathering of sand in this area promotes an increased nitrate adsorption capacity which may stimulate greater root proliferation in topsoils and lead to the entrainment of other nutrients in a more concentrated topsoil-vegetation cycle. If these results can be applied to the larger domain of tropical soils generally, they suggest that nitrate adsorption may play an important role in stimulating effective nutrient recycling by forests occupying weathered soils.
Trophic structure of bat communities in the understorey of lowland dipterocarp rain forest in Malaysia
Authors: Francis Charles M.
Published: July 2009

Bat communities in the understorey of primary lowland dipterocarp forest in peninsular Malaysia and Sabah were sampled with mist nets and harp traps to estimate their trophic structure. Overall, 4 of 26 species (15%) at one site, and 6 of 33 species (18%) at the other site were frugivores, while the remainder were insectivores. In terms of individuals, 7–12% of all captures were frugivores. However, the true proportion of frugivores at both sites was probably closer to 1%, because the sampling procedures were strongly biased towards frugivores. In contrast, previously published studies indicate that frugivores comprise 34–48% of species, and up to 80% of individuals in bat communities in the understorey of Neotropical forest. These results support the hypothesis, developed from studies of bird communities, that the under-storey of Malaysian dipterocarp forest supports relatively few obligate frugivores, at least in non-masting years. However, further data are required on bats in the canopy, and on the foraging ranges of bats to compare the absolute densities of bats in Malaysian and Neotropical forests.
Mineral nutrient flow from an inselberg in south-western Nigeria
Authors: Isichei Augustine O. , Morton Alan J. , Ekeleme Friday
Published: July 2009

In a study carried out to find out if inselbergs enrich their surroundings with nutrients via drainage, amounts of total nitrogen, nitrate-nitrogen and potassium in rainfall, drainage from bare rock patches and vegetation mats on an inselberg in south-western Nigeria were measured over one year. 43.3 kg ha−1total nitrogen, 4.8 kg ha−1nitrate-nitrogen and 10.7 kg ha−1potassium were recorded in rainfall for the year of study. The amount of total nitrogen in drainage from bare rock was 79% of that in rainfall whilst that in drainage from vegetation mats was 29% of the rainfall amount. The respective values for nitrate-nitrogen were 57% and 13%; for potassium they were 90% and 38%.

It was assumed that the loss of nutrients as water drains through vegetation mats and over bare patches was due to absorption by plants and soil in the mats and lichens in the bare patches. It was therefore concluded that there was no net enrichment of rainwater with nutrrients as it flows over inselberg slopes. There is, however, a funelling of water along with contained nutrients from the inselberg to the surrounding areas. This funnelling is additional to the nutrients and rainfall incident on these surrounding areas and may account for the vegetation around inselbergs being more lush than vegetation in the same area but further away from the inselbergs.

A simple modelling approach was used to assess potential nutrient outflow from inselbergs. The model shows that discharge of nutrients from the edges of inselbergs increases linearly with inselberg diameter. The model further shows that if nutrient funnelling only affects an area near to the edge of the inselberg then nutrient addition is several times higher than would be expected from rainfall deposition alone.
A case study of a plant-animal relationship: Cola lizae and lowland gorillas in the Lopé Reserve, Gabon
Authors: Tutin Caroline E. G. , Williamson Elizabeth A. , Rogers M. Elizabeth , Fernandez Michel
Published: July 2009

The frails of Cola lizae, an endemic tree with a limited geographical distribution, have been a major food source for lowland gorillas in the Lopé Reserve during part of each year over a six-year period. Faecal analysis indicated that 11,000-18,000 Cola seeds km-2 were deposited by gorillas during the 4-month season in 1989. Gorillas are the only important dispersers of this species: other primates consume the succulent mesocarp, but do not swallow the large seed; elephants do not eat Cola fruits. Observations of Cola seeds in gorilla faeces showed a very high germination rate and, despite initial high mortality, 18% of seedlings still survived six months after deposition. Survival of seedlings was significantly better in faeces left at nest-sites than in other areas of the forest: 40% of seedlings were viable at nest-sites six months after deposition. This suggests that the open areas of forest, preferred by gorillas as nest-sites, are advantageous to the propagation of this species.
Leaf litter production by lianes and trees in a sub-tropical Australian rain forest
Authors: Hegarty Elwyn E.
Published: July 2009

Leaf litter production by lianes (=lianas) and trees was compared in an evergreen rain forest in subtropical Australia. Several successional stages were represented at the main site. Lianes contributed 2.2% of total basal area (69.6 m2 ha-1) of this site, but 24% of leaf litterfall (5.9–6.5 tha-1 y-2 over two years. Minor year-to-year variation in litterfall was attributed to incidence of severe storms, and drought. Lianes were responsible for about 17% of leaf litterfall in spring, 21% in the summerpeak, and 40% in autumn, more lianes than trees being deciduous. Leaf litter production by 23 individual species of liane, in relation to their basal area within the main site, was, on average, 15 times as great as that by 34 tree species, but declined more steeply between the species-groups of early and later succession. Tendrillar lianes, unlike twiners and scramblers, were confined to the ‘early’ successional group, and their foliage was spread across canopy surfaces, maximizing light interception. It was concluded that this contributed to greater production of leaf litter, per unit basal area, by tendrillar than by other climbers, and to the successional decline in leaf litterfall from lianes.
Comparative effects of Acacia albida and Kigelia africana trees on soil characteristics in Zambezi riverine woodlands
Authors: Dunham Kevin M.
Published: July 2009

Soil nutrient concentrations under Acacia albida and Kigelia africana trees growing in Zambezi riverine woodlands were compared with soils in the open, beyond tree canopies. Concentrations of N, C, P and K were higher under tree canopies. Concentrations of Ca and Mg were unchanged. Soils were slightly more acid under A. albida trees relative to open soil, but were less acid under K. africana. Soil P concentration was higher under K. africana than under A. albida. Otherwise, the two species had similar effects on soil fertility. Despite previous claims, A. albida is probably no more efficient at increasing soil fertility than other savanna trees.