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Radiation Interception (radiation + interception)
Selected AbstractsA test of the relationship between seasonal rainfall and saguaro cacti branching patternsECOGRAPHY, Issue 4 2003Taly Dawn Drezner Reproductive output, as well as photosynthetically active radiation interception and CO2 uptake, increase as saguaro cacti Carnegiea gigantea (Engelm.) Britt. and Rose branch, and branching increases with increasing moisture. The Sonoran Desert experiences distinct summer and winter precipitation regimes that vary in both geography and scale. Many aspects of saguaro ecology are known to depend on the summer rains, which has resulted in an emphasis on summer rains in the literature. Similarly, branching studies have been limited geographically to areas that receive relatively high amounts of summer rainfall. These studies, therefore, attribute branching patterns to the summer (or possibly annual) rains, and conclusions reflect the summer precipitation bias. Environmental variability in space was explored in the present study to investigate saguaro branching patterns. I collected height and branching data in thirty saguaro populations across their American range. Stepwise regression was used to determine which climate, vegetation and soil variables best predict branching. Contrary to the literature, this study found that winter precipitation, particularly from January to April, was the best predictor of branching, not summer or annual rain. Surprisingly, the relationship between the summer monsoons (July and August precipitation) and branching was negative. This is likely due to the fact that summer and winter rainfall patterns are geographically distinct. Winter precipitation appears to play a key role in branching, and thus in seed production. This suggests that saguaros benefit from moisture during the winter, possibly utilizing cold-season rains for increasing their reproductive output through branching, and challenging the view that the summer rains dominate virtually every aspect of the saguaro life-cycle, and creating a more balanced view of saguaro ecology. [source] Shade Effects on Phaseolus vulgaris L. Intercropped with Zea mays L. under Well-Watered ConditionsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2004M. Tsubo Abstract Field experiments were carried out under unstressed conditions of soil water during two summer crop growing seasons (1998,99 and 1999,2000 seasons) in a South African semi-arid region (Bloemfontein, Free State, South Africa). The aim of this study was to investigate shade effects on beans intercropped with maize in terms of plant mass and radiation use. The experimental treatments were two cropping systems (no shading/sole cropping and shading/intercropping) and two row orientations (north,south and east,west). At the top of bean canopies shaded by maize, incident radiation was reduced by up to 90 %. Shading reduced total dry matter of beans by 67 % at the end of the growing season, resulting in yield losses. The dry matter partitioning into leaf and stem (the ratios of leaf and stem to total biomass) was about 50 % higher in intercropping than sole cropping. In contrast, intercropped beans had 40 % lower dry matter partitioning into pod (the ratio of pod to total biomass). Fraction of radiation intercepted by sole-cropped beans steeply increased until canopy closure (0.9) and then slowly decreased, while fraction of radiation intercepted by intercropped beans remained constant between 0.0 and 0.2 throughout the growing seasons. However, intercropped beans had 77 % higher radiation use efficiency (RUE) than sole-cropped beans. In contrast, for maize, no effect of intercropping (shading) was found on growth, partitioning, yield, radiation interception or RUE. Consequently, lower bean yield losses can be attained in association with late shading rather than early shading. This can be controlled by growing crops with different temporal and spatial treatments. As regards row treatment, no effect of row direction was found on growth, partitioning, yield, radiation interception or RUE. [source] Regional climate modulates the canopy mosaic of favourable and risky microclimates for insectsJOURNAL OF ANIMAL ECOLOGY, Issue 3 2007SYLVAIN PINCEBOURDE Summary 1,One major gap in our ability to predict the impacts of climate change is a quantitative analysis of temperatures experienced by organisms under natural conditions. We developed a framework to describe and quantify the impacts of local climate on the mosaic of microclimates and physiological states of insects within tree canopies. This approach was applied to a leaf mining moth feeding on apple leaf tissues. 2,Canopy geometry was explicitly considered by mapping the 3D position and orientation of more than 26 000 leaves in an apple tree. Four published models for canopy radiation interception, energy budget of leaves and mines, body temperature and developmental rate of the leaf miner were integrated. Model predictions were compared with actual microclimate temperatures. The biophysical model accurately predicted temperature within mines at different positions within the tree crown. 3,Field temperature measurements indicated that leaf and mine temperature patterns differ according to the regional climatic conditions (cloudy or sunny) and depending on their location within the canopy. Mines in the sun can be warmer than those in the shade by several degrees and the heterogeneity of mine temperature was incremented by 120%, compared with that of leaf temperature. 4.,The integrated model was used to explore the impact of both warm and exceptionally hot climatic conditions recorded during a heat wave on the microclimate heterogeneity at canopy scale. During warm conditions, larvae in sunlight-exposed mines experienced nearly optimal growth conditions compared with those within shaded mines. The developmental rate was increased by almost 50% in the sunny microhabitat compared with the shaded location. Larvae, however, experienced optimal temperatures for their development inside shaded mines during extreme climatic conditions, whereas larvae in exposed mines were overheating, leading to major risks of mortality. 5,Tree canopies act as both magnifiers and reducers of the climatic regime experienced in open air outside canopies. Favourable and risky spots within the canopy do change as a function of the climatic conditions at the regional scale. The shifting nature of the mosaic of suitable and risky habitats may explain the observed uniform distribution of leaf miners within tree canopies. [source] Crop traits and the tolerance of wheat and barley to foliar diseaseANNALS OF APPLIED BIOLOGY, Issue 2 2009I.J. Bingham Abstract The relationship between yield loss and disease severity can differ widely between crops. This has given rise to the concept of disease tolerance, with some crops exhibiting a smaller yield loss under a given severity of disease than others. Genetic improvement to minimise yield loss under disease is an attractive goal, as it exerts little or no selection pressure on pathogen populations, and could form a useful component of durable disease management programmes. However, progress towards this end requires a thorough understanding of the phenotypic traits that influence the response of yield to disease, their genetic control and the possible trade-offs involved with other desirable agronomic characteristics. This paper examines the candidate crop traits that may confer tolerance of foliar disease in wheat and barley and reviews evidence of genetic variation in their expression. In wheat grown under the relatively low light conditions of North-West Europe, post-anthesis source (assimilate supply) and grain sink capacity (capacity for dry matter accumulation) appear to be closely balanced. Traits associated with maintaining post-anthesis radiation interception and radiation use efficiency in spite of disease may confer tolerance. The most promising traits include a larger flag leaf and compensatory increases in photosynthetic rate in non-infected parts of leaves. In barley, yield is often more strongly sink limited, and early-season disease management is required to protect the formation of potential grain sites. A wider range of potential traits may influence tolerance including compensatory adjustments in leaf growth and morphology, and differences in the sensitivity of tiller and spikelet mortality to photoassimilate supply. Different methods for quantifying tolerance are suggested depending on the trait of interest. [source] | ||||||||||