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Shade Cloth (shade + cloth)
Selected AbstractsLife-history traits of the edible stinkbug, Encosternum delegorguei (Hem., Tessaratomidae), a traditional food in southern AfricaJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2009C. M. Dzerefos Abstract Little is known of the life history of the edible stinkbug, Encosternum delegorguei, although it is an important food for people living in north-eastern South Africa and southern Zimbabwe. The present study aimed to establish key elements influencing long-term sustainable harvesting. Outdoor insectaries of two sizes were constructed to observe: daily activity, utilization of plants, copulation, oviposition, eclosion and survival from May 2006 to February 2007. The rest of the annual life cycle was observed in the field in March and April 2007 and identified as univoltine. In autumn (May) E. delegorguei entered reproductive diapause and aggregated within the escarpment mist-belt where it survived the winter on vapour condensation without feeding. Monthly dissections showed that abdominal fat content was highest in June. In spring (September) E. delegorguei fed on sap of the trees Combretum imberbe, Combretum molle, Peltophorum africanum, to a lesser degree on Dodonaea viscosa and the grass Pennisetum clandestinum. Copulation occurred in October and November. An overall total of 1752 E. delegorguei eggs were laid by 103 females and incubation time averaged 18.7 ± 9.0 days (range 7,37) at outdoor temperature ranging from 11°C to 25°C. The mean number of eggs in 64 egg masses was 27.4 ± 13.9 (range of 2,56 eggs). Shade cloth (68.8%) was the most commonly used substrate for depositing eggs followed by P. clandestinum (12.5%), C. imberbe (7.8%), P. africanum (6.3%), D. viscosa (1.6%), C. molle (1.6%) and C. erythrophyllum (1.6%). The parasitoid wasp, Anastatus sp. (Hymenoptera: Eupelmidae) infected 57% of the eggs deposited by captive females. Availability of food plants in combination with parasitoid threat may be a reason for seasonal migration between overwintering sites within the mist-belt and summer oviposition sites. Diminishing harvests could be attributed to fuelwood harvesting of food plants in the summer sites. [source] Effects of sunlight exposure and log size on pine engraver (Coleoptera: Curculionidae) reproduction in ponderosa pine slash in Northern Arizona, U.S.A.AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2009Christopher J. Hayes Abstract 1,Abiotic conditions within logs can affect pine engraver Ips pini (Say) reproductive success, and slash management techniques have been developed that exploit these relationships to reduce brood production. In the present study, we investigated the affect of sunlight exposure on phloem temperature and moisture in logs of two diameters and the subsequent effects on pine engraver reproduction. 2,Logs, 30 cm in length, with diameters of 10 and 15 cm, were cut, left in the field for natural colonization by I pini, and then placed in an open meadow and under shade cloth, providing 27% and 66% shade, until offspring beetles had left the logs. Phloem temperature and moisture were recorded over the duration of the experiment and, at the end of the field experiment, logs were dissected and galleries were measured to gauge beetle reproductive success. 3,As sunlight exposure increased, phloem temperatures increased and potentially lethal temperatures were often reached in the high-sunlight exposure but seldom in the low-sunlight. Smaller diameter logs had drier phloem than larger diameter logs. All logs dried with time but sunlight level did not affect desiccation rates. Ips pini preferred attacking larger logs and the bottom side of logs. Sunlight exposure had a significant effect on net reproductive success in smaller diameter logs, with very little net reproductive success in high-sunlight exposed logs, and the highest reproductive success was found in small diameter logs in the low-sunlight treatments. 4,Management implications of these results are discussed. [source] Responses of a California annual grassland to litter manipulationJOURNAL OF VEGETATION SCIENCE, Issue 5 2008Kathryn L. Amatangelo Abstract Question: What are the physical and chemical effects of plant litter on annual grassland community composition, above-ground net primary production (ANPP), and density? Location: California annual grassland. Methods: We manipulated litter and light levels independently and in concert. Litter removal and litter addition treatments tested both the physical and chemical impacts of litter's presence. We additionally simulated the effect of litter physical shading by using shade cloth, and added powdered litter to test for the chemical impacts of decomposing litter. Results: Increased whole litter and shading decreased grass germination and establishment, but not that of forbs or legumes. Species shifts occurred within all groups across treatments, including a transition from small-seeded to large-seeded grass and legume species with increased shading. ANPP was highest in control plots (473 ± 59 g/m2), and species richness was highest in litter removal plots. While the physical effects of litter via shading were significant, the chemical effects of adding powdered litter were negligible. Conclusions: This work suggests that over one growing season, the physical impacts of litter are more important than chemical impacts in shaping community structure and ANPP in annual grasslands. Changes in light availability with altered litter inputs drive shifts in species and functional group composition. Litter feedbacks to ANPP and species composition of local patches may help maintain diversity and stabilize ANPP in this grassland. [source] The influence of light environment on photosynthesis and basal methylbutenol emission from Pinus ponderosaPLANT CELL & ENVIRONMENT, Issue 12 2005DENNIS W. GRAY ABSTRACT Methylbutenol is a 5-carbon alcohol that is produced and emitted by several species of pine in western North America, and may have important impacts on the tropospheric chemistry of this region. In the present study the response of methylbutenol basal emission rate (measured at a constant light intensity of 1500 µmol m,2 s,1 and temperature of 30 °C) to the light and temperature conditions of the growth environment was examined, using field-grown plants shielded with shade cloth of various densities. Methylbutenol basal emission rates increased linearly with the temperature of the growth environment but did not respond to the shading of foliage during growth and development. Both photosynthesis and basal methylbutenol emission rate declined in older needles; however, these declines appear to result from parallel but independent processes and not from basal MBO emission rate directly tracking photosynthetic rates. Older needles did not occupy cooler microenvironments within the canopy; and thus differing thermal microenvironment could not explain the reduced MBO emission in older needles. [source] Acclimation of tropical tree seedlings to excessive light in simulated tree-fall gapsPLANT CELL & ENVIRONMENT, Issue 12 2001G. H. Krause Abstract Acclimation to periodic high-light stress was studied in tree seedlings from a neotropical forest. Seedlings of several pioneer and late-succession species were cultivated under simulated tree-fall gap conditions; they were placed under frames covered with shade cloth with apertures of different widths that permitted defined periods of daily leaf exposure to direct sunlight. During direct sun exposure, all plants exhibited a marked reversible decline in potential photosystem II (PSII) efficiency, determined by means of the ratio of variable to maximum Chl a fluorescence (Fv/Fm). The decline in Fv/Fm under full sunlight was much stronger in late-succession than in pioneer species. For each gap size, all species exhibited a similar degree of de-epoxidation of violaxanthin in direct sunlight and similar pool sizes of xanthophyll cycle pigments. Pool sizes increased with increasing gap size. Pioneer plants possessed high levels of , -carotene that also increased with gap size, whereas , -carotene decreased. In contrast to late-succession plants, pioneer plants were capable of adjusting their Chl a/b ratio to a high value in wide gaps. The content of extractable UV-B-absorbing compounds was highest in the plants acclimated to large gaps and did not depend on the successional status of the plants. The results demonstrate a better performance of pioneer species under high-light conditions as compared with late-succession plants, manifested by reduced photoinhibition of PSII in pioneer species. This was not related to increased pool size and turnover of xanthophyll cycle pigments, nor to higher contents of UV-B-absorbing substances. High , -carotene levels and increased Chl a/b ratios, i.e. reduced size of the Chl a and b binding antennae, may contribute to photoprotection in pioneer species. [source] The effect of modified roofing on the milk yield and reproductive performance of heat-stressed dairy cows under hot-humid conditionsANIMAL SCIENCE JOURNAL, Issue 5 2010Sriapa KHONGDEE ABSTRACT The objective was to measure the effects of cooling techniques (shade cloth vs. normal roof) on performance and physiology of 16 Friesian crossbred cows (87.5% Holstein Friesian × 12.5% Brahman) located at Sakol Nakhon Livestock Research and Testing Station, Department of Livestock Development, Ministry of Agriculture and Cooperatives (Sakol Nakhon, Thailand). They were divided randomly into two groups of eight. The two groups were used to evaluate the effects of modified roofing (normal roof fitted with woven polypropylene shade cloth) on the subjects' milk yield and reproductive performance under hot humid conditions. Results indicated that the modified roofing offered a more efficient way to minimize heat stress than the normal roof. The difference was sufficient to enable the cows to have a significantly lower mean rectal temperature and respiration rate (38.56°C, 61.97 breaths/min) than that of the cows housed under normal roofing (39.86°C; 85.16 breaths/min). The cows housed under modified roofing produced more milk (P < 0.05) but did not differ significantly in reproductive performance from the cows housed under normal roofing. [source] Shade facilitates an invasive stem succulent in a chenopod shrubland in South AustraliaAUSTRAL ECOLOGY, Issue 5 2003TANJA I. LENZ Abstract The invasive stem succulent Orbea variegata (L) Haw. (Asclepiadaceae) tends to be more abundant underneath shrubs than in open areas in chenopod shrublands near Whyalla, South Australia. To assess the role of facilitation in the life cycle of O. variegata, we investigated the effect of chenopod shrubs on different life stages of the species by experimentally manipulating temperature, light, soil moisture and nutrient levels. Experimental results suggest that the reduction in light and temperature under shrubs, but not increased nutrient levels, are the main facilitative mechanisms for O. variegata. Temperatures above 30°C, which are more likely to occur on the soil surface of open areas than under shrubs, inhibited seed germination. Seedling survival at low watering frequency and the growth of established ramets were increased by 75,80% shade cloth. Ramets growing in full light contained a high concentration of anthocyanin pigments. One of the functions of these pigments is to absorb excess radiation, suggesting that O. variegata experiences radiation stress in full light. In the field O. variegata performed considerably better under Atriplex vesicaria Heward ex Benth. (Chenopodiaceae) or under 75,80% shade cloth than in full light. Monthly irrigation of 20 mm did not reduce this positive effect of the A. vesicaria canopy on O. variegata, suggesting that O. variegata is inhibited by high light intensities or temperatures, independent of water availability. In conclusion, whereas shrub canopies do not seem to be required for the establishment or survival of O. variegata, shrubs improve adult growth and can improve establishment. The possibility of exotic plants being facilitated by other plants has to be taken into account when assessing the probability and rate of invasion. [source] | |||||||||||||