Establishment and growth of oak (Quercus alba, Quercus prinus) seedlings in burned and fire-excluded upland forests on the Cumberland Plateau

Recurrent problems with regeneration of oaks (Quercus spp.) have been documented across a wide range of ecosystems. In oak-dominated forests of the central and Appalachian hardwood regions of the United States, a lack of competitive oak regeneration has been tied, in part, to fire suppression in these landscapes, and managers throughout the region are using prescribed fire to address this concern. To examine fire effects on oak regeneration, researchers have generally relied on inventories or population studies of existing seedlings. These studies are valuable but do not permit examination of the role of fire in enhancing the establishment and growth of new oak seedlings stemming from oak mast events. In this study, white (Quercus alba) and chestnut oak (Quercus prinus) acorn mast crops serendipitously occurred in year three (fall 2005) of a landscape-scale prescribed fire experiment. We examined establishment, survival, height and diameter of new seedlings on sites on the Cumberland Plateau in eastern Kentucky. Treatments were fire exclusion, a single prescribed fire (1x-burn; 2003), and repeated prescribed fire (3x-burn; 2003, 2004, and after acorn drop in 2006), all conducted in late spring. Initial densities of newly established chestnut and white oak seedlings were statistically similar across treatments (P = 0.42), despite fires on the 3x-burn site having occurred after acorns were on the ground. Oak seedling density was significantly predicted by oak basal area on all sites (R² = 0.12–0.46), except for chestnut oak on fire-excluded sites (R² = 0.04). Litter depth was less on 3x-burn sites compared to 1x-burn and fire-excluded sites, whereas canopy openness was greater on both burn treatments compared to fire-excluded sites. Seedling mortality was generally higher on fire-excluded sites compared to burn sites, especially for white oak. Oak seedling mortality in the first two growing seasons was significantly predicted by initial litter depth and open sky, with greater litter depth and lower percent open sky leading to higher mortality. In the third growing season none of the measured variables predicted chestnut oak seedling survival; for white oak, percent open sky remained a significant predictor of mortality. Initially, seedlings on the fire-excluded sites had similar height but smaller diameter; after three growing seasons there were few differences in seedling height or diameter among treatments. Our findings suggest a potential role for prescribed fire in establishing forest floor and light conditions that may enhance the success of new oak germinants, although different responses among species may suggest the need to target management for individual oak species.     

营养师的一个新武器——益生木质纤维

<正>日粮纤维是家畜饲料的重要组成部分。益生木质纤维素(eubiotic lignocellulose)由新鲜木材制成,是一种相对较新的饲料原料,试验证明它是一种非常有价值的饲用纤维原料,对动物营养有众多的益处。日粮纤维是单胃动物消化调节的必需物质。高淀粉日粮易于快速发酵,通常在消化过程的早期就几乎被完全发酵,到达大肠时极少或已无物可发酵。在日粮中添加纤维能够使发酵进程后移至结肠,并且促进有益菌的增殖。益生菌所产生的挥发性脂肪酸能够提高肠道的健     

Compressive Strength of Wheat Endosperm: Comparison of Endosperm Bricks to the Single Kernel Characterization System

The three major classes of endosperm texture (grain hardness) of soft and hard common, and durum wheat represent and define one of the leading determinants of the milling and end‐use quality of wheat. Although these three genetic classes are directly related to the Hardness locus and puroindoline gene function, much less is known about the kernel‐to‐kernel variation within pure varietal grain lots. Measurement of this variation is of considerable interest. The objective of this research was to compare kernel texture as determined by compression failure testing using endosperm bricks with results of whole‐kernel hardness obtained with the Single Kernel Characterization System 4100 hardness index (SKCS HI). In general terms, the variation obtained with the SKCS HI was of similar magnitude to that obtained using failure strain and failure energy of endosperm brick compression. Objective comparisons included frequency distribution plots, normalized frequency distribution plots, ANOVA model R², and coefficients of variation. Results indicated that compression testing and SKCS HI similarly captured the main features of texture classes but also reflected notable differences in texture properties among and within soft, hard, and durum classes. Neither brick compression testing nor the SKCS HI may be reasonably expected to correctly classify all individual kernels as to genetic texture class. However, modest improvements in correct classification rate or, more importantly, better classification related to end‐use quality may still be achievable.     

A Study of Fenpropathrin Residues in Tomatoes and Green Beans Grown in Greenhouses in Spain

The reduction in residue levels of fenpropathrin with time after treatment of tomatoes and green beans, grown in two types of commercial greenhouse in Almería, Spain, was investigated. Extracted residues were quantified by GC-ECD and their composition verified using GC-MS. Recovery of fenpropathrin from samples spiked with differing amounts of the compound were assessed. For statistical purposes, the loss of fenpropathrin with time was considered to follow a pseudo-first order reaction. The plant species and the season had a significant affect on rates of loss of fenpropathrin but the effect of the type of greenhouse and of the applied dose were not significant. © 1997 SCI.     

Implications of feeding frequency,prey size and condition,and intraspecific competition for the commercial aquaculture of the nudibranch Berghia stephanieae

Marine ornamental aquaculture is a growing industry. Although most species are cultured for aesthetic purposes, there is increasing interest in organisms that provide functional services. Nudibranchs provide an example in which they act as biological controls by consuming aquaria pests. Berghia stephanieae is a commercially relevant nudibranch that feeds on Exaiptasia anemones, which overgrow sessile invertebrates. However, information pertaining to B. stephanieae feeding habits remains unaddressed. Therefore, this study investigated the following: (a) the effect of feeding frequency on fecundity, (b) optimum prey size, (c) the ability to feed on prey fragments, and (d) the influence of intraspecific competition. Distinct feeding frequencies were tested and embryos produced were quantified; growth of nudibranchs offered different anemone sizes was measured; whole and fragmented anemones were offered, with preference recorded; and growth and mortality of juvenile nudibranchs were recorded in the absence and presence of adult conspecifics. Results show that feeding daily produced the highest number of embryos. Juveniles fed on medium-sized anemones showed the highest growth rate. Smaller juveniles were unable to feed on whole anemones and preferred fragmented anemones. Juvenile growth and survival decreased in the presence of adults. To maximize production, breeders must feed broodstock daily, provide medium-sized anemones or fragments, and segregate juveniles from adults.     

A comparison of catch rates of artificial lures from an automated handline fishery at Shetland,UK

Automated handlining (jig fishing) has recently been trialled in waters around Shetland, UK. Although different types and colours of artificial lures are commercially available there is a paucity of information available on the effects of either lure design or lure colour on resulting catches. We compared the catch rates of (1) five colours of rubber eel tube lures; and (2) five different designs of artificial lure commonly used in handline fisheries. Lure colour did not significantly affect catches of pollack (Pollachius pollachius), saithe (Pollachius virens), cod (Gadus morhua), ling (Molva molva) or tusk (Brosme brosme). Cod showed a preference for lower hooks on the six hooks per reel set-up when lures were black and pollack showed a preference for lower hooks when the lures were blue. There were no significant differences in catches of saithe, cod, ling or tusk between the five lure types. However, catches of pollack on a novel ‘sonar’ lure were lower than on other lures. No evidence of a preference for any hook position on the reels was found with any of the lure types.     

Impact of heat stress on pod-based yield components in field pea (Pisum sativum L.)

Elevated temperatures associated with climate change result in crops being exposed to frequent spells of heat stress. Heat stress results in reduced yield in field pea (Pisum sativum L.); it is therefore important to identify cultivars with improved pod and seed retention under heat to mitigate this loss. Objectives were to investigate the effect of heat stress on phenology, yield and pod-based yield components. Sixteen pea cultivars were evaluated at normal and late (hot) seeding dates in the field in Arizona 2012 and in growth chambers with two temperature regimes (24/18°C and 35/18°C day/night temperature for 7 days) during reproductive development. We measured variation in the pattern of pod retention at four-node positions on plants, seed retention by ovule position (stylar, medial and basal) within pods and screened cultivars for pod retention, seed retention and yield. Heat stress reduced seed yield by accelerating the crop lifecycle and reducing pod number and seed size. Heat stress had the most damaging effect on younger reproductive growth (flowers and pods developed later), resulting in ovary abortion from developing flowers. Heat also accelerated seed abortion in all ovule positions within pods. Two high-yielding cultivars under control temperature, “Naparnyk” and “CDC Meadow”, maintained high yield in heat, and “MFR043” had the lowest yield. Cultivars “40-10” and “Naparnyk” retained the most ovules and seeds per pod, and “MFR043” aborted seeds when exposed to heat. In half of the cultivars, ovules at the basal peduncle end of pods were likely to abort while ovules at the medial and stylar end positions developed into seeds. For seven of the field cultivars, ovules at the medial pod position also produced mature seeds. Cultivars “40-10”, “Naparnyk” and “CDC Meadow” had greater pod and ovule retention or maintained high yield under heat stress, and were identified as heat-tolerant cultivars. Our results allow for a better understanding of pod-based yield components in field pea under heat stress and developing heat-tolerant cultivars.