Spatial and Seasonal Dynamics of Total Suspended Sediment, Total Dissolved Solids and Turbidity of a Lacustrine Reservoir in the Magoye Catchment, Southern Zambia

Dissolved and suspended sediment that form part of the Total Sediment Load (TSL) affects the quality of water making it unsuitable for selected aquatic invertebrates and livestock. The study aimed at determining spatial and seasonal dynamics in the concentration levels and distribution of selected physical parameters in a small lacustrine system whose main problem was punctuated by rapid deposition of clastic and none-clastic sediment. Water sampling was done during the rainy and cool-dry seasons across the reservoir using sampling bottles and DGPS. Laboratory analysis was done to determine variations in concentration levels of the parameters over time and space. Distributions of selected parameters across the reservoir were analysed using 3D Spatial Analysts Tool, Inverse Distance Weighted (IDW) in ArcGIS 10.2. Using paired T-Test at 0.05 level of significance, the study found statistically significant differences (p<0.001) in the concentration of TDS, TSS, and turbidity between the rainy season and cool-dry season. With exception of TDS, TSS and turbidity were higher in the rainy season than in the cool-dry season. Rainfall was the main control variable regarding seasonality influence on TDS, TSS, and turbidity. The study concluded that although lacustrine reservoirs may be closed systems, they still experience variations spatially and temporally in terms of concentration of TDS, TSS and turbidity. The study recommends implementation of integrated catchment-wide management of anthropogenic activities so as to minimize excess generation, transportation and deposition of sediment, which punctuate elevated levels of TDS, TSS and turbidity.

Cool-Dry Season Depression in Gas Exchange of Canopy Leaves and Water Flux of Tropical Trees at the Northern Limit of Asian Tropics

Trees on the northern boundary of Asian tropics experience hot-humid and cool-dry seasons, but little is known about their seasonal dynamics in canopy physiology. We used a canopy crane to reach the canopy of nine tropical tree species and measured canopy leaf gas exchange, water status, and trunk sap flux during the hot-humid and cool-dry seasons in Xishuangbanna, China. We found that most tree species exhibited significant reductions in maximum photosynthetic rate (Amax), stomatal conductance (gsmax), predawn and midday leaf water-potentials, and maximum sap flux density in the cool-dry season. Compared to the hot-humid season, Amax declined by 19 % − 60 %, and maximum water flux declined by -14% (an increase) to 42 %. The cool-dry season decline in Amax of four species can be partly explained by an increased stomatal limitation (decreased gsmax and intercellular CO2 concentrations). Therefore, a predicted increase in drought in this region may decrease the carbon sequestration and productivity of these forests. We did not find a tradeoff between performance (Amax in the hot-humid season) and persistence through the cool-dry season; species with higher Amax in the hot-humid season did not show higher percent seasonal declines in the cool-dry season. Amax was significantly and positively associated with the trunk spa flux for both seasons but the association was weak in the cool-dry season. Thus, our results suggest that some tradeoffs and trait associations are environment-dependent. Our results are important to understand carbon and water fluxes of seasonal tropical forests and their responses to environmental changes.

Respiração basal do solo sob três diferentes coberturas vegetais no Paraná

This study evaluated the soil basal respiration (SBR) of three forest types and seasons and their correlation with pedological attributes in the 0-5 cm land layer. Therefore, we selected two areas of commercial tree species in the central-southern Paraná region: one plot of Pinus taeda and one of Eucalyptus dunnii; and a control, a patch of native forest (Mixed Ombrophyllous Forest). We determined the SBR by the alkaline addition method, incubating the samples for seven days. We collected samples in the cool dry season (winter) and in the hot humid season (summer). Soil attributes were determined by a routine analysis (pH, K+, Ca2+, Mg2+, Al3+, P, Matéria Orgânica, areia grossa e areia fina, silte, argila e V%). We observed significant SBR differences only about summer and winter. SBR correlated significantly with organic matter. These results are similar to most of the literature. There was no difference between the forest types about the SBR, showing that even monoculture forests can present carbon fluxes statistically equal to those of an intermediate successional stage native forest. The specific edaphic fauna adapted to each ecosystem may explain the absence of this difference in relation to SBR.

Seasonal changes in the reproductive performance in local cows receiving artificial insemination in the Pursat province of Cambodia

Objective: The present study aimed to survey seasonal changes in reproductive performance of local cows receiving artificial insemination (AI) in the Pursat province of Cambodia, a tropical country, to investigate if ambient conditions affect the reproductive performance of cows as to better understand the major problems regarding cattle production.Methods: The number of cows receiving AI, resultant number of calving, and calving rate were analyzed for those receiving the first AI from 2016 to 2017. The year was divided into three seasons: cool/dry (from November to February), hot/dry (from March to June), and wet (from July to October), based on the maximal temperature and rainfall in Pursat, to analyze the relationship between ambient conditions and the reproductive performance of cows. Body condition scores (BCS) and feeding schemes were also analyzed in these seasons.Results: The number of cows receiving AI was significantly higher in the cool/dry season than the wet season. The number of calving and calving rate were significantly higher in cows receiving AI in the cool/dry season compared with the hot/dry and wet seasons. The cows showed higher BCSs in the cool/dry season compared to the hot/dry and wet seasons probably due to the seasonal changes in the feeding schemes: these cows grazed on wild grasses in the cool/dry season but fed with a limited amount of grasses and straw in the hot/dry and wet seasons.Conclusion: The present study suggests that the low number of cows receiving AI, low number of calving, and low calving rate could be mainly due to poor body condition as a result of the poor feeding schemes during the hot/dry and wet seasons. The improvement of body condition by the refinement of feeding schemes may contribute to an increase in the reproductive performance in cows during the hot/dry and wet seasons in Cambodia.

ANALYSIS OF THE IMPACT OF VEGETATION DISTRIBUTION, URBANIZATION, AND SOLAR RADIATION ON THE SEASONAL VARIATION OF THE URBAN HEAT ISLAND EFFECT IN CEBU CITY USING LANDSAT AND GLOBAL HORIZONTAL IRRADIANCE DATA

The Urban Heat Island (UHI) phenomenon is a manifestation of the abnormal amount of heat generated in urban areas and anthropogenic land surface modifications. While urbanization can improve material comfort and be a boon to the economy, the accompanying problems associated with urbanization like the UHI effect has implications on health, demand for water and energy, and impacts the microclimate. Land surface temperature (LST), the Normalized Difference Vegetation Index (NDVI), and the Normalized Difference Built-up Index (NDBI) were calculated from historical remotely-sensed Landsat data from 2013 to present. The global horizontal irradiance (GHI) was computed from the lidar-derived elevation model of Cebu City using the Geographical Resources Analysis Support System (GRASS). It is shown that annual variation in average temperatures in Cebu is generally less than 5 °C. Mean UHI temperatures in Cebu City do not show a clear trend over time, but categorizing data by season, namely the rainy season (June–November), the cool dry season (December–February), and the hot dry season (March–May), permits the emergence of a pattern. Surface temperatures for the cool dry season and hot dry season show a linearly increasing trend with R2 values of 0.916 and 0.514, respectively. This study further investigates the temporal change in the degree and extent of the UHI in Cebu City by analyzing LST maps. Regression analysis is done to determine how LST is affected by the distribution of vegetation (NDVI) and built-up (NDBI), and the seasonal variation in solar radiation through the GHI.

Distribution and fluctuations of backswimmers (Notonectidae) in a tropical shallow lake and predation on microcrustaceans

Notonectids are widely distributed in freshwaters and can prey on zooplankton in temperate lakes. However, its role in structuring the zooplankton community is unknown in tropical lakes. Thus, our objective was to study the notonectid Martarega uruguayensis in a Brazilian tropical shallow lake to evaluate its potential as a zooplankton predator. Its horizontal distribution was analized in the lake throughout one year in fortnightly samplings. Backswimmers were more abundant (mean density 162.9 ± 25.8 ind.m–2) in the cool-dry season, with a strong preference by the littoral zone (mean density 139.9 ± 17.5 ind.m–2). Laboratory experiments were undertaken with young and adult notonectid and the two most abundant cladocerans, Daphnia gessneri and Ceriodaphnia richardi, as prey. Predation by backswimmers in the laboratory showed that only juveniles fed on microcrustaceans (mean ingestion rate of 1.2 ± 0.2 Daphnia and 1.0 ± 0.2 Ceriodaphnia per predator per hour), without size selectivity. Adult insects probably have difficulties in detecting and manipulating small planktonic organisms. On the other hand, young instars might influence zooplankton community, especially in the littoral zone of the lake. This study does contribute to a better understanding of trophic interactions in tropical shallow lakes and is the first to investigate the predation of a notonectid on microcrustaceans from Lake Monte Alegre.

Growth and Yield of Hybrid Castor (Ricinus communis L.) under Different Spacing during Rabi Season in Tamil Nadu

A field experiment was conducted at Tapioca and Castor Research Station, Yethapur, Salem district, Tamil Nadu during the year 2012 – 2014. The following treatments were imposed and replicated thrice in split plot design. In main plot, different hybrids viz., YRCH 1(M1 ), GCH 4 (M2 ), DCH 519 (M3 ) and DCH 177 (M4 ) and in sub plot, different spacing viz., 90 x 90 cm (S1 ), 120 x 90 cm (S2 ) and 120 x 120 cm (S3 ) were evaluated during rabi season under irrigated condition. The results revealed that, castor crop grown well during Rabi season under irrigated condition. It is mainly due to the reason that, in Rabi sown crop there is no incidence of Botrytis gray mold disease and also cool dry season promotes seed setting in castor which results higher seed yield was obtained. Hybrids performed better in wider spacing because, they produce more number of spikes and effective spike length in castor. This is mainly due to in wider spacing, there is lesser competition between the plants. In the nutshell, hybrid YRCH 1 with a spacing of 120 x 120 cm recorded 19 per cent higher seed yield (2572 kg ha-1) than closer spacing of 90 x 90 cm (2157 kg ha-1) under irrigated condition

Trematode infections of the freshwater snail Biomphalaria pfeifferi from a south-east Nigerian community with emphasis on cercariae of Schistosoma

Knowledge of trematode infections in Biomphalaria pfeifferi from south-eastern Nigeria is scarce, due to the absence of Schistosoma mansoni infection in the region. Therefore, the present study sought to describe trematode infections in B. pfeifferi from the River Uzuru in the Nigeria Cement Factory area, Nkalagu, south-eastern Nigeria. Four hundred and sixty snails were checked for trematode infections, and mice were exposed to the Schistosoma cercariae shed from the snails. Adult worms were harvested from the mice 13 weeks post-infection, while sections of the liver and spleen were examined. Primary school children living in the area were screened for S. mansoni infection and assessed for activities involving water contact. The edges of the river were also searched for burrows and rodents. The five cercaria morphotypes found were armatae xiphidiocercariae, echinocercariae, Schistosoma cercariae, cystophorous cercariae and cercariaeum cercariae. The overall prevalence and mean intensity of trematode infections were 39.78% and 195.46, with the prevalence and mean intensity of most cercaria morphotypes higher in the hot–dry than in the cool–dry season. The infected mice showed S. mansoni-like characteristics but the stool samples of the schoolchildren were negative for S. mansoni eggs. Water-contact activities in the River Uzuru were minimal. Burrows were seen at the river edges but no Schistosoma eggs were recovered from captured rats. This is the first report of Schistosoma cercariae and other cercaria morphotypes in B. pfeifferi from south-eastern Nigeria. Additional molecular investigations are needed to identify correctly these Schistosoma cercariae, due to their public health implication.

Dispersal and germination syndromes of tree seeds in a seasonal evergreen monsoon rainforest on Hainan Island, China

This paper examines the dispersal–germination strategy of seeds of 66 native tree species from a seasonal evergreen monsoon rainforest on Hainan Island, China, and assesses correlations among seed germination and phylogeny, dispersal mode and dispersal season. Seeds of 15, 7, 25 and 19 species were dispersed during the warm dry (March–May), rainy (June–September), late rainy (October–November) and cool dry (December–February) seasons, respectively. Berries (16 species), drupes (14 species) and capsules (12 species) were common and represented about 64% of the species. Zoochory was the most common dispersal mode (69.7%) followed by anemochory (16.7%) and autochory (13.6%). More than 65% of species had dormant seeds. Based on germination speed and synchrony, six patterns were recognized: rapid and synchronous germination (13 species), intermediate and synchronous germination (3 species), intermediate and intermediately synchronous germination (24 species), intermediate and asynchronous germination (2 species), slow and intermediately synchronous germination (5 species), and slow and asynchronous germination (19 species). One-way ANOVAs revealed that the variance in germination percentages among species was largely dependent upon phylogeny. The mean and median length of germination (MLG) were largely dependent upon phylogeny, dispersal mode and dispersal season. Anemochorous seeds germinated faster than autochorous and zoochorous seeds. Seeds dispersed in the late dry or early rainy season (March–May) tended to germinate quickly, whereas those dispersed towards the end of the rainy season and into the cool dry season are likely to have a much longer length of dormancy. Correlation analyses indicated that larger seeds germinated faster and had higher germination percentages.