Associations with topographic units or soil types that vary in water availability are widespread in plant communities and are one of the main structuring aspects for local species distribution patterns, yet the underlying mechanisms are poorly understood. We hypothesized that differential seedling performance across habitats, particularly during the dry season, leads to habitat associations in ...

Reproductive tactics of some insects are affected by photoperiod because daylength is a reliable cue indicating seasonal change in environmental suitability. We tested the hypothesis that late-season (short-day) photoperiod affects the length of the oviposition cycle of the eastern lubber grasshopper, which is from a subtropical area with a winter dry season.We predicted that oviposition wouldo...

We study the attack rate, that is the total fraction of the population infected each year, for a disease with seasonally varying transmission rate. The attack rate is shown to be governed by both the reproductive number, reflecting the transmissibility of the disease, and the birth rate, which provides a source of new susceptibles. For the case of epidemics which have an annual period (like the...

Prior studies on the association between weather and psychological changes have produced mixed results. In part, this inconsistency may be because weather's psychological effects are moderated by two important factors: the season and time spent outside. In two correlational studies and an experiment manipulating participants' time outdoors (total N = 605), pleasant weather (higher temperature o...

Immune function can vary based on availability of resources, and most studies of such influences have focused on the co-investment of energy into immune and other physiological functions. When energy resources are limited, trade-offs exist, which can compromise immunity for other functions. As with energy, water limitation can also alter various physiological processes, yet water has received l...

*We examined the relationships between stem CO(2) efflux (E(s)), diameter growth, and nonstructural carbohydrate concentration in loblolly pine trees. Carbohydrate supply was altered via stem girdling during rapid stem growth in the spring and after growth had ceased in the autumn. We hypothesized that substrate type and availability control the seasonal variation and temperature sensitivity of...

Our concept of the ‘balance of TN : TP : SRSi-ratios’ attempts to determine whether the seasonal succession of phytoplankton communities is influenced by or responds to nutrient stoichiometry. Because the molar average of TN : TP : SRSi = 20 : 1 : 17 for 118 measurements (7 lakes, 3 inflows, all seasons) was close to the marine optimum stoichiometric ratio, we used the ratio TN : TP : SRSi = 16...

The dry subtropics are subject to a rapid expansion of crops and pastures over vast areas of natural woodlands and savannas. In this paper, we explored the effect of this transformation on vegetation productivity (magnitude, and seasonal and long-term variability) along aridity gradients which span from semiarid to subhumid conditions, considering exclusively those areas with summer rains (>66%...

Understanding global change impacts on the globally important carbon storage in alpine, Arctic and sub-Arctic soils requires knowledge of the mechanisms underlying the balance between plant primary productivity and decomposition. Given that nitrogen availability limits both processes, understanding the response of the soil nitrogen cycle to shifts in temperature and other global change factors ...

A total of 80 commercial broccoli samples were collected over a two-year period to determine seasonal variation in the levels of ascorbic acid (AA), vitamin C (the sum of AA and dehydroascorbic acid [DHAA]), the predominant flavonoids quercetin and kaempferol, and total phenolics at the consumer level. Levels of AA and vitamin C varied between 13.37–110.30 and 57.35–131.35 mg/100 g fresh weight...