The spatial pattern of soil-dwelling termites in primary and logged forest in Sabah, Malaysia

Abstract.  1. Primary and logged lowland dipterocarp forest sites were sampled for subterranean termites using soil pits located on a grid system in order to detect any patchiness in their distribution.
2. A spatial pattern in termite distributions was observed in the primary and logged sites, but the response differed between soil-feeding and non-soil-feeding termites.
3. Spatial analysis showed that soil-feeding termites were homogeneously distributed in the primary forest but significantly aggregated in the logged forest. This pattern was reversed for non-soil-feeding termites and may result from differences in resource provisioning between the two sites.
4. Gaps in termite distribution comprised a greater area than patches for both feeding groups and sites, but gaps dominated the logged site.
5. A significant association between soil-feeding and non-soil-feeding termite distributions occurred at both sites. This arose from an association between patches in the primary forest and between gaps in the logged forest.
6. Termite spatial pattern was optimally observed at a minimum extent of 64 m and lag of 2 m.
7. The spatially explicit SADIE (Spatial Analysis by Distances IndicEs) analyses were more successful than (non-spatially explicit) multivariate analysis (Canonical Correspondence Analysis) at detecting associations between termite spatial distributions and that of other biotic and abiotic variables.     

Bird diversity: a predictable function of satellite-derived estimates of seasonal variation in canopy light absorbance across the United States

Aim  To investigate the relationships between bird species richness derived from the North American Breeding Bird Survey and estimates of the average, minimum, and the seasonal variation in canopy light absorbance (the fraction of absorbed photosynthetically active radiation, fPAR) derived from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS).
Location  Continental USA.
Methods  We describe and apply a 'dynamic habitat index' (DHI), which incorporates three components based on monthly measures of canopy light absorbance through the year. The three components are the annual sum, the minimum, and the seasonal variation in monthly fPAR, acquired at a spatial resolution of 1 km, over a 6-year period (2000–05). The capacity of these three DHI components to predict bird species richness across 84 defined ecoregions was assessed using regression models.
Results  Total bird species richness showed the highest correlation with the composite DHI [ R ² = 0.88, P  < 0.001, standard error of estimate (SE) = 8 species], followed by canopy nesters ( R ² = 0.79, P  < 0.001, SE = 3 species) and grassland species ( R ² = 0.74, P  < 0.001, SE = 1 species). Overall, the seasonal variation in fPAR, compared with the annual average fPAR, and its spatial variation across the landscape, were the components that accounted for most ( R ² = 0.55–0.88) of the observed variation in bird species richness.
Main conclusions  The strong relationship between the DHI and observed avian biodiversity suggests that seasonal and interannual variation in remotely sensed fPAR can provide an effective tool for predicting patterns of avian species richness at regional and broader scales, across the conterminous USA.     

Long-term CO2 production from deeply weathered soils of a tropical rain forest: evidence for a potential positive feedback to climate warming

Currently, it is unknown what role tropical forest soils will play in the future global carbon cycle under higher temperatures. Many tropical forests grow on deeply weathered soils and although it is generally accepted that soil carbon decomposition increases with higher temperatures, it is not known whether subsurface carbon pools are particularly responsive to increasing soil temperatures. Carbon dioxide (CO₂) diffusing out of soils is an important flux in the global carbon. Although soil CO₂ efflux has been the subject of many studies in recent years, it remains difficult to deduct controls of this flux because of the different sources that produce CO₂ and because potential environmental controls like soil temperature and soil moisture often covary. Here, we report results of a 5‐year study in which we measured soil CO₂ production on two deeply weathered soil types at different depths in an old‐growth tropical wet forest in Costa Rica. Three sites were developed on old river terraces (old alluvium) and the other three were developed on old lava flows (residual). Annual soil CO₂ efflux varied between 2.8–3.6 μmol CO₂‐C m^?2 s^?1 (old alluvium) and 3.4–3.9 μmol CO₂‐C m^?2 s^?1 (residual). More than 75% of the CO₂ was produced in the upper 0.5 m (including litter layer) and less than 7% originated from the soil below 1 m depth. This low contribution was explained by the lack of water stress in this tropical wet forest which has resulted in very low root biomass below 2 m depth. In the top 0.5 m CO₂ production was positively correlated with both temperature and soil moisture; between 0.6 and 2 m depth CO₂ production correlated negatively with soil moisture in one soil and positively with photosynthetically active radiation in the other soil type. Below 2 m soil CO₂ production strongly increased with increasing temperature. In combination with reduced tree growth that has been shown for this ecosystem, this would be a strong positive feedback to ecosystem warming.     

Seasonal roosts of Red-lored Amazons in Ecuador provide information about population size and structure

ABSTRACT.   Data from roosts of Amazona parrots may be useful in creating demographic models, because these birds exhibit high roost fidelity and pairs are conspicuous in flight. However, few investigators have attempted to track changes in the number of pairs using such roosts. We studied Red-lored Amazons ( Amazona autumnalis ) at a communal roost in southwest Ecuador over a 1-yr period to understand better their population structure. Population size was estimated at 214 individuals. Counts revealed seasonal variation in numbers, but the occurrence of pairs and singles was seldom correlated. The number of paired individuals using the roost was lower during the breeding period. In contrast, the number of single birds at the roost nearly doubled during the breeding period. Overall, our data suggest that parental responsibilities during the nesting period explain fluctuations in the number of birds at the roost, and such fluctuations can be used to estimate the reproductive portion of the population. Protection of the small mangrove islands where the parrots roost would likely benefit a population that occupies a much larger area and would, at the same time, provide a useful tool for demographic studies of this poorly known neotropical parrot.     

Distribution, abundance, and conservation of Vinaceous Amazons (Amazona vinacea) in Argentina and Paraguay

ABSTRACT.   Vinaceous Amazons ( Amazona vinacea ) are endemic to the Atlantic forest of southeastern Brazil, eastern Paraguay, and the province of Misiones in Argentina. We searched for Vinaceous Amazons throughout the western part of its range in Argentina and Paraguay during 1639 days of fieldwork from 1997 to 2006. These parrots have disappeared from most areas where they were historically recorded in these countries, and are now limited to a few sites in northeastern Paraguay and central Misiones (Argentina). We estimate the minimum remaining populations at 220 individuals in Paraguay and 203 individuals in Argentina. Important sites for the species are (1) the farming area from San Pedro to Tobuna (Misiones, Argentina) and (2) the Itaipú reserves complex and Reserva Natural Privada Itabó (Paraguay). In our surveys, Vinaceous Amazons were absent from the largest tracts of forest in Misiones, and were most often observed feeding, roosting, and nesting in small forest remnants and in agricultural areas that included forest fragments and isolated trees. Threats to amazons in these areas include nest poaching, forest clearing, and being shot as a crop pest. We confirmed 40 Vinaceous Amazons kept as pets in 35 homes between San Pedro and Tobuna. Environmental education and law enforcement are urgently needed to reduce threats in populated areas, and subsistence farmers need technical and logistical support to slow or stop the conversion of forest into cropland. Finally, additional study is needed to determine this amazon's habitat preferences, nest site requirements, and demography in different habitats.     

Identifying forest‐obligate birds in tropical moist cloud forest of Andean Ecuador

ABSTRACT Large‐scale transformation of forested landscapes is a major factor in loss of biological diversity in the American tropics. Investigators examining the responses of species to deforestation rarely control for variation in the amount of forest relative to other habitats at the landscape‐level. Bellavista Reserve on the western slope of the Andes in Ecuador is located between similar‐sized areas of pristine, protected forest, and deforested landscapes. We used strip‐transect counts and mist netting to evaluate habitat use by passerine birds in a habitat mosaic consisting of abandoned pastures, forest edges, forest fragments, and large blocks of interior tropical montane cloud forest (TMCF). During 3600 net hours, we had 1476 captures, including 346 recaptures. Of 78 species captured in mist nets, 30 had sufficient counts for Poison Rate Regression (PRR) modeling (a statistical method for comparing counts). Twelve species (40%) had capture patterns indicative of an affinity for mature TMCF, and 6 species (20%) had significantly higher counts in degraded areas (forest edge, forest fragment, and regenerating pastures) than in interior TMCF. The remaining 40% showed no significant bias in detection among habitats. Combined with strip‐count data, our results suggest that about 38% of the 119 species sampled at the Bellavista Reserve occur primarily in mature TMCF, avoiding edges and early second‐growth forest. Populations of these species may be vulnerable to further loss, fragmentation, and degradation of TMCF and, as such, deserve additional study and a place on lists of species of conservation concern.     

Distributions of tree species along point bars of 10 rivers in the south‐eastern US Coastal Plain

Aim To determine the degree to which rivers within the south‐eastern US Coastal Plain show a predictable spatial distribution of floodplain tree species along each point bar of river bends in relation to elevation and/or soil texture, as seen on the Bogue Chitto River, Louisiana, USA. Also, to understand spatial patterns of tree species on land created during river‐bend migration, and to interpret which physical characteristics of rivers predict this pattern of vegetation. Location The south‐eastern US Coastal Plain. Methods Ten randomly selected rivers within a portion of the region were studied. At each of 10 river bends per river, a census of trees and shrubs was taken and elevation and soil texture were measured at upstream, mid‐ and downstream locations along the forest–point bar margin. To identify physical characteristics of rivers that are predictive of patterns of tree species along point bars, aerial photographs, hydrographs and field data were analysed. Results Tree species composition varied predictably among the three point bar locations, corresponding to an elevation gradient on each bar, on seven of 10 rivers. Species occupying a given point bar location on one river usually occupied the same location on other rivers, in accordance with species‐elevation associations identified in past studies of floodplain forests. Multivariate analysis of river characteristics suggested that rivers failing to show the expected pattern were those with relatively low stream energy and geomorphic dynamics and/or those with hydrological regimes altered by upstream dams. Main conclusions A distinct pattern of streamside forest community structure is related to fluvial geomorphic processes characterizing many rivers within the south‐eastern US Coastal Plain. Characteristics of rivers required to promote the predicted pattern of tree species include a single, meandering channel with point bars; an intermediate level of stream energy; a natural hydrological regime; and location in a biome where a large number of tree species are capable of colonizing point bars.     

Effects of light history on primary productivity in a phytoplankton community dominated by the toxic cyanobacterium Cylindrospermopsis raciborskii

1. The effects of instantaneous irradiance and short‐term light history on primary production were determined for samples from a subtropical water reservoir dominated by the toxic cyanobacterium Cylindrospermopsis raciborskii. ¹⁴C‐bicarbonate uptake incubations were conducted on water samples from the reservoir, for irradiance (photosynthetically active radiation) ranging from 0 to 1654 μmol quanta m⁻² s⁻¹. Prior to the ¹⁴C incubations, cells were pre‐treated at irradiance levels ranging from 0 to 1006 μmol quanta m⁻² s⁻¹. 2. The average irradiance experienced by cells during the 2–2.5 h pre‐treatment incubations affected the productivity–irradiance (P–I) parameters: exposure to high light in pre‐treatment conditions caused a substantial decrease in maximum rate of primary production P_max and the photoinhibition parameter β when compared to cells pre‐treated in the dark. 3. While the data collected in this study were not sufficient to develop a full dynamic model of C. raciborskii productivity, P_max and β were modelled as a function of pre‐treatment irradiance, and these models were applied to predict the rate of primary production as a function of both instantaneous and historical irradiance. The results indicated that while cells with a history of exposure to high irradiance will be the most productive in high irradiance, production rates will be highest overall for dark‐acclimated cells in moderate irradiance. 4. Our results may explain why optically‐deep mixing favours C. raciborskii. If the mixing depth z_m exceeds the euphotic depth z_eu, cells will be dark‐acclimated, which will increase their rate of production when they are circulated through the euphotic zone. These results also predict that production rates will be higher during morning hours than for the same irradiance in the afternoon, which is consistent with other phytoplankton studies. 5. Since the rate of production of C. raciborskii‐dominated systems cannot be described by a single P–I curve, accurate estimates of production rates will require measurements over the daily light cycle.     

Vascular Epiphyte Communities in the Inner-Crown of Hyeronima alchorneoides and Lecythis ampla at La Selva Biological Station, Costa Rica

The community composition and percent cover of vascular epiphytes were examined in relation to photosynthetic photon flux density (PFD), temperature, vapor pressure, and tree characteristics in the inner-crown of two emergent tree species, Hyeronima alchorneoides and Lecythis ampla, at La Selva Biological Station, Costa Rica. A total of 53 species were found in a total sampled branch area of 32 m² in eight trees—four trees per species. Community composition varied both among individuals of the same tree species and between tree species. However, percent cover patterns of vascular epiphytes were significantly different between the two tree species; Hyeronima had a significantly greater percent cover of epiphytes than Lecythis . The higher percent light transmittance as well as lower humidity in Lecythis are likely causes of its lower percent cover of epiphytes.