Empirical and theoretical evidence suggests that facilitation between plants, when it occurs, is more likely during periods of abiotic stress, while competition predominates under more moderate conditions. Therefore, one might expect the relative importance of competition vs. facilitation to vary seasonally in ecosystems characterized by pronounced dry (abiotically stressful) and wet (benign) s...

The Brazilian cerrado presents strong climate seasonality. During the dry season, plants may be exposed to stressful situations, such as a soil surface water deficit, that stimulate their chemical defenses. However, the seasonality effect on the production of allelopathic compounds of cerrado plant species is poorly understood. In this study, the phytotoxic activities of common native cerrado p...

We evaluated changes of different soil nitrogen forms (total N, available ammonium and nitrate, total N in microbial biomass, and soil N mineralization) after conversion of semideciduous dry tropical forest in 5- and 18-year-old pastures (YP and OP, resp.) in the western Llanos of Venezuela. This evaluation was made at early rainy season, at end rainy season, and during dry season. With few exc...

Rockland pine forests of south Florida dominated by Pinus elliottii var. densa characteristically have poor soil development in relation to neighboring hardwood hammocks. This has led to the hypothesis that Everglades hammock trees are more reliant on soil moisture derived from local precipitation whereas pineland plants must depend more on groundwater linked to broader regional hydrologic patt...

Moth species trapped using the sex pheromone of Stenoma catenifer (LaSalle) as a lure, were registered at 2 commercial avocado orchards (one consisting of “Hass” and other of “Criollo”) and in wild “Criollo” avocado trees in southern Mexico. Traps were maintained for 1 mo in two seasons (dry and wet) on avocado trees under these 3 production conditions, changing the baits each season. Weekly ob...

In the wet-dry tropics, animal species face the major challenges of acquiring food, water or shelter during an extended dry season. Although large and conspicuous animals such as ungulates and waterfowl migrate to wetter areas during this time, little is known of how smaller and more cryptic animal species with less mobility meet these challenges. We fenced off the entire entrance of a gorge in...

Deuterium-labeled water was used to study the effect of the Tapajós Throughfall Exclusion Experiment (TTEE) on soil moisture movement and on depth of water uptake by trees of Coussarea racemosa, Sclerolobium chrysophyllum, and Eschweilera pedicellata. The TTEE simulates an extended dry season in an eastern Amazonian rainforest, a plausible scenario if the El Niño phenomenon changes with climate...

The study was designed to determine diurnal and seasonal changes in basic physiologic responses of donkeys adapted to the tropical Savannah. The rectal temperature (RT), respiratory rate (RR) and heart rate (HR) of six male Nubian pack donkeys, and the dry-bulb temperature (DBT), relative humidity and heat index of the experimental site were concurrently recorded hourly, from 06:00 h to 18:00 h...

Surveys were conducted in malaria-endemic villages in the southern province of Attapeu, Lao PDR during various seasons over a 3-year period. All-night mosquito landing collections, blood surveys and a case-control study were conducted. Plasmodium falciparum was the predominant species, and slide positivity rates were higher during the transition/dry season compared with the wet season. Anophele...

In mud houses in Wakara, Upper Volta, dichlorvos dispensers installed at the rate of one dispenser per approximately 500 cubic feet (14 m(3)) produced 70% or higher average kills of adult Aëdes aegypti, exposed overnight in screen wire cages suspended at levels of 6 feet (1.8 m) and 2 feet (0.6 m), for approximately three months during the wet season and four months during the dry season. Avera...