The biotic and abiotic changes associated with habitat fragmentation have been shown to have major consequences for plant recruitment and survivorship. However, few studies have quantified the growth of plants that persist in fragments. Over the course of a decade, we measured annual growth of 5200 individuals of the common understory herb Heliconia acuminata (Heliconiaceae) in an experimentall...

Interactions between plants can have strong effects on community structure and function. Variability in the morphological, developmental, physiological, and biochemical traits of plants can influence the outcome of plant interactions and thus have important ecological consequences. However, the ecological ramifications of trait variability in plants are poorly understood and have rarely been te...

Natural radioactivity levels in some selected medicinal plants commonly used in Ghana from the Centre for Scientific Research into Plant Medicine were investigated to determine the activity concentration and the annual committed effective dose due to naturally occurring radionuclides of (238)U, (232)Th and (40)K. The activity concentration was determined using gamma-ray spectrometry. The result...

Occupational exposures at nuclear power plants occur mostly during maintenance activities rather than during routine reactor operation. In this paper, statistical summaries of occupational exposures during routine maintenance activities for the years 1982-84 at nuclear power plants in Japan are presented, including comparison of the exposure levels by reactor type and by plant age. Average annu...

Replacement of perennial grasses with non-native annual grasses in California’s Central Valley grasslands and foothills has increased deep soil water availability. Yellow starthistle (Centaurea solstitialis), a deep-rooted invasive thistle, can use this water to invade annual grasslands. Native perennial bunchgrasses, such as Purple needlegrass (Nassella pulchra), also use deep soil water, so t...

and Applied Analysis 3 Combining 1.1 and 1.2 , we see that the Watkinson model of the annual plants is given by the difference equation N n 1 λN n 1 aN n γ λmN n , n 0, 1, 2, . . . . 1.3 In this model the density-independent mortality is not included and the growth of the population occurs only during the vegetative phase of the life cycle. Watkinson in 18 assumed that density-independent morta...

Trade-offs among traits are important for maintaining biodiversity, but the role of natural selection in their construction is not often known. It is possible that trade-offs reflect fundamental constraints, negative correlational selection, or directional selection operating on costly, redundant traits. In a Sonoran Desert community of winter annual plants, we have identified a trade-off betwe...