Conifer-angiosperm interactions: Physiological ecology and life history.

Worldwide, conifers are most successful on sites subject to chronic stresses that limit productivity (low temperatures, nutrient poverty, poor drainage). They are poorly represented in the lowland tropics but are often important in Montane tropical forests. Here I explore some functional differences between leaf and xylem traits of conifer and angiosperm trees and their implications for the distributions of these two groups on environmental gradients. Analysis of a global data set shows that compared with angiosperm trees, conifers tend to have longer-lived leaves with greater mass per area (LMA) and lower mass-based photosynthetic capacity. As leaf life span is thought to be the main determinant of nutrient retention time, the prominence of conifers on infertile soils worldwide is at least partly attributable to thrifty use of nutrients through long leaf life spans. Furthermore, because leaf life span correlates with litter decomposition rates, these leaf trait differences could potentially influence the competitive balance between conifers and angiosperms via positive feedbacks on nutrient cycling. Although scaling of leaf life span with LMA is similar in the two groups, angiosperms achieve slightly longer leaf life spans than conifers of similar photosynthetic capacity. This might be caused by less-efficient leaf display in conifers, resulting in the useful life span of leaves being curtailed by self-shading. Representatives of both lineages have narrower conduits in the temperate zone than in the lowland tropics/subtropics, reflecting selection for resistance to freeze-thaw embolism in cold climates. However, conduit diameters of conifers and angiosperm trees differ more in tropical and subtropical forests than at higher latitudes. This probably reflects mechanical constraints on maximum tracheid diameters in the homoxylous wood of conifers, preventing this group from producing the highly conductive wood typical of fast-growing angiosperm pioneers in tropical forests. This pattern might explain why coexistence of conifers and angiosperms is more common in temperate forests and on tropical mountains than in the lowland tropics. Impairment of angiosperm carbon gain by freeze-thaw embolism during cold weather may further narrow performance differences between the two lineages on temperate sites. Differences in canopy residence time probably deserve more attention as a determinant of conifer-angiosperm coexistence in many temperate forests, the longer life span of conifers compensating for infrequent recruitment

Brain Weight and Life-Span in Primate Species

In haplorhine primates (tarsiers, monkeys, apes, and humans), there is a significant correlation between brain weight and maximum life-span when the effect of body size is removed. There is also a significant correlation in haplorhine primates between brain weight and female age at first reproduction. For strepsirhine primates (lorises and lemurs), there are no significant correlations between brain weight and either life-span or female reproductive age when the effect of body size is removed. This lack of correlation in strepsirhine primates may be related to the fact that these primates are nocturnal and/or natives of the island of Madagascar, both of which conditions may reduce competition for resources and predation pressure. These findings suggest that in haplorhine primates the genetic systems controlling brain growth are linked to the systems governing the life cycle so that species with longer cycles have larger brains. When the effect of body weight is removed, leaf-eating haplorhines have significantly smaller brains and shorter lives than haplorhines with other diets. Harem-living haplorhines also have significantly smaller brains and shorter life-spans than troop-living haplorhines when the effect of body weight is removed. We also sought to test the rate-of-living hypothesis by determining whether primates with basal metabolic rates that are higher than would be expected for their body size have shorter maximum life-spans than would be expected for their body size. Metabolic rate is not correlated with life-span or female age at first reproduction when the effect of body size is removed

Effect Of Light Level On Growth And Shoot Development Of Five Species Of Tropical Saplings.

Saplings of Acacia mangium, Shorea roxburghii, Dyera costulata, Eusideroxylon zwageri and Cinnamomum iners were grown at 4%, 7%, 25%, 50% and 100% relative light intensities (RLIs) and their growth was monitored by rate of increment of height and diameter, rate of production of new leaves and leaf life span. Leaves were analysed for their content of nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), chlorine (Cl), sulphur (S), boron (B), manganese (Mn), copper (Cu) and zinc ( Zn). For each RLI, two samples of leaves were taken for analysis: young fully expanded leaves and old about-to-shed leaves. From these analyses, the fate of nutrients was determined. Acacia mangium and Cinnamomum iners were found to grow best at 100% RLI, Shorea roxburghii at 50% RLI and, Dyera costulata and Eusideroxylon zwageri at 25% RLI. Acacia mangium at 100% RLI had the highest weekly height and diameter increment of 16.15 cm and 0.77 cm respectively. This is 4 times higher than the second best growth species, Shorea roxburghii at 50% RLI and 21 times higher than the slowest growth species, Eusideroxylon zwageri at 25% RLI. Acacia mangium at 100% RLI had the highest mean leaf production rate per week on leaders and branches, of 1.70 and 1.60 leaves respectively. This is 3 times higher than the second best species, Shorea roxburghii at 50% RLI and 17 times higher than the slowest growing species, Eusideroxylon zwageri at 25% RLI. At 100% RLI, Acacia mangium had the shortest average leaf life span, of 130 days on leaders and 124 days on branches. In general, average leaf life span increased with reduction in RLI for all species. A fast-growing plant is associated with higher height increment, higher diameter increment, higher mean leaf production and shorter leaf life span. The level of NPK for these species in this study shared a similar range with major agricultural crops in Malaysia. The highest rate of NPK incorporation (g per week) was found in Acacia mangium, followed by Dyera costulata, and it was relatively low for other species. The levels of NPK were higher in young leaves than the old leaves for all species at all RLIs. Dyera costulata seems to withdraw more than 60% of NPK and Shorea roxburghii more than 60% of P from old leaves before they shed. All species did not withdraw Mn and Zn

Shade and leaf retention: an aspect of effective Coffee Leaf Rust management

Coffee Leaf Rust (CLR) has been reported in over 50 coffee growing countries causing significant economic losses in Arabica coffee. The aim of this study was to determine the effect of shade on leaf life span in relation to severity of coffee leaf rust. To achieve this objective, three shade levels (shaded, partial shade, unshaded) were applied in three agro-ecological zones (AEZ) i.e. Upper-Midland (UM) I, II and III. Each treatment was replicated 4 times in 7 farms in each AEZ. All the farms had similar agronomic management levels. Infected leaves were counted per tree and disease severity was scored every month, between January and September, 2014 which is the peak period for CLR. Yields per plot were estimated using the method of Cilas and Descroix, 2004. The results showed that shaded trees retained the infected leaves 8 weeks longer than the unshaded in all the agro-ecological zones. Similarly, yield estimate from the shaded coffee (1521kg/ha clean coffee) was significantly higher than the unshaded (1050kg/ha clean coffee). Although leaves remain longer on shaded trees, allowing more time for the disease to develop and progress, severity level of shaded trees remains lower (12.8%) than unshaded (19.0%), suggesting the expression of regulation mechanism under the control of shade. Moreover, full shade generated by dense canopy, such as the one from mango or avocado tree best manages CLR across all the tested three agro-ecological zones

Eco control of agro pests using imaging, modelling & natural predators

Caterpillars in their various forms: size, shape, and colour cause significant harm to crops and humans. This paper offers a solution for the detection and control of caterpillars through the use of a sustainable pest control system that does not require the application of chemical pesticides, which damage human health and destroy the naturally beneficial insects within the environment. The proposed system is capable of controlling 80% of the population of caterpillars in less than 65 days by deploying a controlled number of larval parasitoid wasps (Cotesia Flavipes, Cameron) into the crop environment. This is made possible by using a continuous time model of the interaction between the caterpillar and the Cotesia Flavipes (Cameron) wasps using a set of simultaneous, non-linear, ordinary differential equations incorporating natural death rates based on the Weibull probability distribution function. A negative binomial distribution is used to model the efficiency and the probability that the wasp will find and parasitize a host larva. The caterpillar is presented in all its life-cycle stages of: egg, larva, pupa and adult and the Cotesia Flavipes (Cameron) wasp is present as an adult larval parasitoid. Biological control modelling is used to estimate the quantity of the Cotesia Flavipes (Cameron) wasps that should be introduced into the caterpillar infested environment to suppress its population density to an economically acceptable level within a prescribed number of days. Keywords

Effects of aqueous extracts of basil, Ocimum basilicum L., Sodom's apple, Calotropis procera Ait and Coriander Coriandrum sativum L. on leaf miner, Liriomyza spp., on okra crop : PS7TH432 Others

The Hymenopterous parasitoids, Hemiptarsemus varicornis (Girault) and Opius dissitus (Muesebeck) are associated with the leaf miner, Liriomyza spp., populations in Central Sudan. The effects of Liriomyza trifolii (Burgess) and Liriomyza sativae (Blanchard) reared on common bean, Phaseolus vulgaris, on the development and efficiency of their two parasitoids were studied at constant conditions of temperature, relative humidity and photoperiod. No significant differences were found between parasitism percentage of H. varicornis or O. dissitus on L. trifolii or L. sativae. However, significant differences were found with respect to adult (male and female) life span as well as the number of adult parasitoids emerged of H. varicornis and O. dissitus. The life span of H. varicornis was shorter than that of O. dissitus, but more adults of the later emerged from the pupae than those of H. varicornis which might have accounted for their almost equal parasitism percentages. Also, no significant differences were recorded with regard to the development of H. varicornis on L. sativae reared on four of its host plants. However, parasitism percentage was significantly higher on gourd (Cucurbita moschata) followed by zucchini (cucurbita pepo), haricot bean (Phaseolus vulgaris) and tomato (Lycopersicon esulentium), respectively. (Résumé d'auteur

A comparative study on the life cycles of the leaf miners Liriomyza trifolii (Burgess) and Liriomyza sativae (Blanchard) (Agromyzidae: Diptera)

The life cycles of the leaf miners, Liriomyza trifolii (Burgess) and Liriomyza sativae (Blanchard), were studied in a growth chamber (Temp, 25 ± 1°C; R.H. 75 ± 5%; L/D 12 hL/12 hD and 3000 - 4000 LUX) at CIRAD, Montpellier, France. The host plant used was haricot bean, (Phaseolus vulgaris). The egg incubation period of both species lasted for two days. Highly significant differences (P<0.01) were recorded between the number of feeding punctures caused by L. trifolii and L. sativae. Differences between the larval periods and number of emerging adults were not significant. Upon hatching, during 1996, the number of larvae of L. trifolii was significantly higher than that of L. sativae, but the total life span of L. sativae was significantly longer than that of L. trifolii. (Texte intégral

A morphogenetic crop model for sugar-beet (Beta vulgaris L.)

This paper is the instructions for the proceeding of the International Symposium on Crop. Sugar beet crop models have rarely taken into account the morphogenetic process generating plant architecture despite the fact that plant architectural plasticity plays a key role during growth, especially under stress conditions. The objective of this paper is to develop this approach by applying the GreenLab model of plant growth to sugar beet and to study the potential advantages for applicative purposes. Experiments were conducted with husbandry practices in 2006. The study of sugar beet development, mostly phytomer appearance, organ expansion and leaf senescence, allowed us to define a morphogenetic model of sugar beet growth based on GreenLab. It simulates organogenesis, biomass production and biomass partitioning. The functional parameters controlling source-sink relationships during plant growth were estimated from organ and compartment dry masses, measured at seven different times, for samples of plants. The fitting results are good, which shows that the introduced framework is adapted to analyse source-sink dynamics and shoot-root allocation throughout the season. However, this approach still needs to be fully validated, particularly among seasons

Krymsk®1 (VVA-1), A dwarfing rootstock suitable for high density plum orchards in the Netherlands

Krymsk®:1 (Prunus tomentosa × Prunus cerasifera) was selected by Gennady Eremin at the Krymsk Breeding Station in Russia in 1966. Since 1994, it has been tested as a rootstock for several plum cultivars in The Netherlands. Graft compatibility was good for scion cultivars ‘Avalon’, ‘Excalibur’, ‘Jubileum’, ‘Opal’, and ‘Victoria’. Growth and production efficiency of plum on Krymsk®:1 was compared with that of plum on St. Julien A and, depending on the cultivar, also with Ferlenain, Otesani 8 and Pixy. With all cultivars, trees on rootstock Krymsk®:1 were by far the least vigorous, most precocious, and most production efficient. The production efficiency of ‘Avalon’ and ‘Excalibur’ on Krymsk®:1 grown for 10 years was 0.41 and 0.26 kg/cm² trunk cross sectional area, respectively, 3.4 and 4.3 times higher on Krymsk®:1 than on St. Julien A. With ‘Opal’ the production efficiency calculated over the first 5 years after planting was 2 to 3 times higher than on St. Julien A, but this difference became non significant after 7 years of cultivation. This was due to the much higher increase in production per tree during the 5th and 6th leaf of the trees on St. Julien A than on Krymsk®:1. Fruit size of ‘Opal’, ‘Avalon’ and ‘Excalibur’ was similar for trees grown on Krymsk®:1 and St. Julien A. With ‘Victoria’ fruit size was significantly larger (5 g) with Krymsk®:1 than with St. Julien A. Krymsk®:1 also increased the percentage of first pick by 15%, the sugar content by 9%, enhanced the development of fruit overcolour and reduced the percentage of fruits with gummosis in ‘Victoria’ plums. Dutch fruit growers show great interest in Krymsk®:1 as a rootstock for plum, as this rootstock makes high density plum orchards feasible. Growers switching to trees on Krymsk®1 have to take more care of their trees, especially in the first years after planting. Pruning, irrigation, and fertilization of the trees need much more attention in order to keep the trees vigorous and ensure good production levels. From 2002 to spring 2008, 120,000 plum trees on Krymsk®1 have been planted in The Netherlands and planting densities have increased from 830 up to 2,285 trees/ha. The main cultivar planted is ‘Victoria’

Unravelling the Impact of Temporal and Geographical Locality in Content Caching Systems

To assess the performance of caching systems, the definition of a proper process describing the content requests generated by users is required. Starting from the analysis of traces of YouTube video requests collected inside operational networks, we identify the characteristics of real traffic that need to be represented and those that instead can be safely neglected. Based on our observations, we introduce a simple, parsimonious traffic model, named Shot Noise Model (SNM), that allows us to capture temporal and geographical locality of content popularity. The SNM is sufficiently simple to be effectively employed in both analytical and scalable simulative studies of caching systems. We demonstrate this by analytically characterizing the performance of the LRU caching policy under the SNM, for both a single cache and a network of caches. With respect to the standard Independent Reference Model (IRM), some paradigmatic shifts, concerning the impact of various traffic characteristics on cache performance, clearly emerge from our results.Comment: 14 pages, 11 Figures, 2 Appendice