Short‐term sequestration of slurry‐derived carbon and nitrogen in temperate grassland soil as assessed by 13C and 15N natural abundance measurements

Land application of animal wastes from intensive grassland farming has caused growing environmental problems during the last decade. This study aimed to elucidate the short‐term sequestration of slurry‐derived C and N in a temperate grassland soil (Southwest England) using natural abundance ¹³C and ¹⁵N stable isotope techniques. Slurry was collected from cows fed either on perennial ryegrass (C3) or maize (C4) silages. 50 m³ ha^—1 of each of the obtained C3 or C4 slurries (δ¹³C = —30.7 and —21.3‰, δ¹⁵N = +12.2 and + 13.8 ‰, respectively) were applied to a C₃ soil with δ¹³C and δ¹⁵N values of —30.0 ± 0.2‰ and + 4.9 ± 0.3‰, respectively. Triplicate soil samples were taken from 0—2, 2—7.5, and 7.5—15 cm soil depth 90 and 10 days before, at 2 and 12 h, as well as at 1, 2, 4, 7, and 14 days after slurry application and analyzed for total C, N, δ¹³C, and δ¹⁵N. No significant differences in soil C and N content were observed following slurry application using conventional C and N analysis techniques. However, natural abundance ¹³C and ¹⁵N isotope analysis allowed for a sensitive temporal quantification of the slurry‐derived C and N sequestration in the grassland soil. Our results showed that within 12 hours more than one‐third of the applied slurry C was found in the uppermost soil layer (0—2 cm), decreasing to 18% after 2 days, but subsequently increasing to 36% after 2 weeks. The tentative estimate of slurry‐derived N in the soil suggested a decrease from 50% 2 hours after slurry application to only 26% after 2 weeks, assuming that the increase in δ¹⁵N of the slurry plots compared to the control is proportional to the amount of slurry‐incorporated N. We conclude that the natural abundance tracer technique can provide a rapid new clue to the fate of slurry in agricultural C and N budgets, which is important for environmental impacts, farm waste management, and climate change studies.     

Status of Morelet's crocodile Crocodylus moreleti in Belize

An investigayion was made into the status of the Morelet's crocodile Crocodylus moreleti Dumeril & Dumeril in Belize, a Caribbean nation of Central America. Juvenile animals were found to be rather common in isolated areas, but very few adults were observed; we believe this to be an indication of over-exploitation. Certain aspects of the hide-hunting-dealing enterprise are also examined, and it is concluded that if C. moreleti is to survive in any numbers, a policy of protection should be instituted.     

Ammonium and nitrate in the rhizosphere of spring barley, hordeum vulgare L., and take-all disease

The incidence and severity of take-all disease, due to Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker, was observed on spring barley plants growing in soil in two glasshouse experiments. Soil amendments of NH⁺₄-N significantly increased the number of diseased plants and roots during the first month after germination in comparison with controls unamended with N (P < 0.05). No significant difference in the incidence of take-all disease was detected between more mature barley plants growing in soil amended with either NH⁺₄ or NO^?₃-N and unamended controls. The least take-all disease in 3 month-old barley plants was observed when N was supplied as foliar sprays of urea at 0.5 mg N kg^?1 soil (P < 0.01). There was no significant correlation between the degree of infection and the NH⁺₄-N to NO^?₃-N ratio in the rhizosphere soil     

Evaluation of the Effect of Orally Administered Acid Suppressants On Intragastric pH in Cats

Background

Acid suppressant drugs are a mainstay of treatment for cats with gastrointestinal erosion and ulceration. However, clinical studies have not been performed to compare the efficacy of commonly PO administered acid suppressants in cats.

Hypothesis/Objectives

To compare the effect of PO administered famotidine, fractionated omeprazole tablet (fOT), and omeprazole reformulated paste (ORP) on intragastric pH in cats. We hypothesized that both omeprazole formulations would be superior to famotidine and placebo.

Animals

Six healthy adult DSH colony cats.

Methods

Utilizing a randomized, 4‐way crossover design, cats received 0.88–1.26 mg/kg PO q12h fOT, ORP, famotidine, and placebo (lactose capsules). Intragastric pH monitoring was used to continuously record intragastric pH for 96 hours beginning on day 4 of treatment. Plasma omeprazole concentrations at steady state (day 7) were determined by high performance liquid chromatography (HPLC) with ultraviolet detection. Mean percentage time that intragastric pH was ≥3 and ≥4 were compared among groups using ANOVA with a posthoc Tukey‐Kramer test (α = 0.05).

Results

The mean percentage time ± SD that intragastric pH was ≥3 was 68.4 ± 35.0% for fOT, 73.9 ± 23.2% for ORP, 42.8 ± 18.6% for famotidine, and 16.0 ± 14.2% for placebo. Mean ± SD plasma omeprazole concentrations were similar in cats receiving fOT compared to those receiving ORP and in a range associated with acid suppression reported in other studies.

Conclusions and Clinical Importance

These results suggest that both omeprazole formulations provide superior acid suppression in cats compared to famotidine or placebo. Fractionated enteric‐coated OT is an effective acid suppressant despite disruption of the enteric coating.     

Use of principal components,factor analysis and varimax rotation to describe variability in wood of Eucalyptus deglupta blume

The variation in twenty-four parameters measrued on small wood samples of Eucalyptus deglupta has been described adequately by four principal components. The interpretation of these components and determination of the relative importance of variables within components were aided by techniques of factor analysis and varimax rotation.     

越南石灰岩喀斯特生态系统的保育:挑战与机遇

石灰岩喀斯特地貌在东南亚地区的经济活动中具重要的地位,其生物多样性保育与文化遗产价值更是弥足珍贵.越南的喀斯特地区正好是当中的写照,区内观光景点林立,亦有不少世界遗产地区、植物多样性的全球中心及多个具有国际保育重要价值的地点.尽管喀斯特生态系统在越南的保护区系统内占一定数量,可是一连串活动如采矿、土地开垦、基建发展,都对水文或栖息地做成严重干扰;另外野生动物的偷猎及非法砍伐等各种消耗森林资源的活动,都日益威胁整个喀斯特生态系统.因此,喀斯特地区已成为野生动植物保护国际(FFI)的重点保育对象.下文将会略谈越南喀斯特生态系统现正面临的威胁,继而介绍现时FFI在四个主题领域上利用的若干保育手法:(1)景观地貌层面上的管理;(2)社区参与保育;(3)生态旅游及保育关系(4)从文化着手的保育方法.     

Leaf water relations and stomatal behavior of four allopatric Eucalyptus species planted in Mediterranean southwestern Australia

In 1986, four allopatric Eucalyptus species (E. camaldulensis Dehnh, E. saligna Smith, E. leucoxylon F. Muell and E. platypus Hook.) were planted together in a 480-mm rainfall zone, in 8-m wide contour belts as part of a plan to minimize waterlogging and secondary salinization. Throughout 1997, 1998 and 1999, there was significant inter-specific variation in predawn leaf water potential (Psi(pd)); however, maximum stomatal conductance (g(sm)) only differed significantly between species in mid to late summer. Relationships between g(sm) and Psi(pd) were significant and showed that stomata of E. camaldulensis were significantly more sensitive to Psi(pd), and presumably soil water potential, than stomata of E. leucoxylon or E. platypus. When applied to the Psi(pd) data, these relationships predicted that g(sm), and by inference transpiration, varied much less between species than Psi(pd). Diurnal measurements throughout the season confirmed this prediction, and showed that E. camaldulensis and E. saligna avoided drought by gaining access to deeper water, whereas E. leucoxylon and E. platypus maintained greater g(sm) at a given water stress than E. camaldulensis or E. saligna. Osmotic potentials measured after rehydration and water release curves of the leaves indicated that different mechanisms accounted for the apparent drought tolerance of E. leucoxylon and E. platypus. In summer, E. leucoxylon reduced osmotic potential at full and zero turgor by similar amounts compared with winter. In summer, E. platypus had a significantly lower bulk elastic modulus and relative water content at turgor loss point than E. camaldulensis, E. saligna or E. leucoxylon. This elastic adjustment resulted in a larger difference between osmotic potential at full and zero turgor in summer than in winter. The inherently low osmotic potential in E. leucoxylon and elastic adjustment in E. platypus resulted in turgor loss at a similar and significantly lower water potential than in E. camaldulensis or E. saligna. These results have implications for species selection for planting to manage groundwater recharge in areas prone to waterlogging and secondary salinization.