基于TM影像的黄陵县土地利用变化动态监测

以1987年和2002年两期TM影像为信息源,应用计算机自动识别分类与GIS空间分析相结合的方法,提取了黄陵县不同时期的土地利用现状信息及其动态变化。结果表明:研究区森林覆盖率高,林地占区域土地总面积的70%以上;耕地面积较小,占地比例不到7%。1987年至2002年,耕地和草地面积明显减少,园地增加突出,林地、居民点及工矿用地略有增长,其中面积变化最大的是耕地,减少111.13 km2;变化率最大的是园地,达到329.44%。     

The joint action of fungicides in mixtures: comparison of two methods for synergy calculation

Two methods for evaluating the joint action of fungicides in mixtures were analysed. In order to obtain a relatively rapid answer on the type of interaction between fungicides in a mixture (additivity, synergism or antagonism), one can apply the Abbott formula to data on fungus survival. Tests with this method will not be accurate at high effective dose values. A more accurate determination of the joint action of fungicides can be made by the Wadley method, applied to data on effective doses. This involves more experimental work than the Abbott method. Optimization of mixing ratios of fungicides required a set of experimental data on effective doses with several mixing ratios.     

Impact of environmental factors on infestation of tea leaves byHelopeltis theivora, and associated changes in flavonoid flavor components and enzyme activities

Attack of tea plant (Camellia sinensis (L.) O. Kuntze) leaves by the tea mosquito bugHelopeltis theivora (Hemiptera: Miridae) was positively correlated to temperature and rainfall, and partially to humidity, as determined in 12 varieties during the period 2000–2002. The insect attack was severe during the months of May–September, which had high temperature and rainfall, and led to severe loss of biomass due to curling and drying up of the leaves. The biochemical response of these 12 varieties of tea to attack by the insect was determined with special reference to oxidative enzymes and flavonoid flavor components. Insect attack led to an increase in the activities of the oxidative enzymes peroxidase, ascorbate peroxidase and polyphenol oxidase. Activities of phenyl alanine ammonia lyase generally decreased as a result of insect attack, which was significant in the United Planters Association of South India (UPASI) varieties. A significant decrease in polyphenols was also obtained in UPASI varieties. HPLC analysis of catechins revealed a decrease in some of the catechins in the infected leaves. Analysis of theaflavins from infusion of healthy andHelopeltis-infested tea leaves revealed no changes. http://www.phytoparasitica.org posting Dec. 19, 2004.     

子午岭地区植被演替过程中土壤养分及酶活性特征研究

选择植被自然恢复不同年限的阳坡梁坡地作为研究对象,采用时空互代法研究子午岭地区植被恢复过程中土壤养分和酶活性的变化.结果表明,植被恢复140 a内,不同土层土壤有机质含量、全氮含量、蔗糖酶活性、脲酶活性、碱性磷酸酶活性和过氧化氢酶活性增加,且表土层(0～20 cm)土壤养分含量和酶活性高于下层土壤(20～40 cm).以裸露地为对照,土壤0～20 cm土层,有机质含量、全氮含量、蔗糖酶活性、脲酶活性、碱性磷酸酶活性和过氧化氢酶活性分别增加了23.8%～534.9%、9.3%～300.0%、213.6%～521.5%、40.4%～286.5%、22.7%～232.2%和3.2%～22.4%,土壤速效磷含量呈现波动变化, 过氧化氢酶活性变化幅度比其他三种酶低.土壤有机质含量与全氮、速效磷含量密切相关;土壤蔗糖酶与土壤有机质、全氮均为极显著的相关关系(0.930/0.918);土壤脲酶活性与全氮含量相关系数最高(0.804);土壤碱性磷酸酶活性与有机质、全氮含量都呈极显著相关(0.977/0.984);土壤过氧化氢酶活性与全氮含量极显著相关,相关系数达0.996.     

Enhancing pedotransfer functions with environmental data for estimating bulk density and effective cation exchange capacity in a data‐sparse situation

Soil bulk density (BD) and effective cation exchange capacity (ECEC) are among the most important soil properties required for crop growth and environmental management. This study aimed to explore the combination of soil and environmental data in developing pedotransfer functions (PTFs) for BD and ECEC. Multiple linear regression (MLR) and random forest model (RFM) were employed in developing PTFs using three different data sets: soil data (PTF‐1), environmental data (PTF‐2) and the combination of soil and environmental data (PTF‐3). In developing the PTFs, three depth increments were also considered: all depth, topsoil (<0.40 m) and subsoil (>0.40 m). Results showed that PTF‐3 (R²; 0.29–0.69) outperformed both PTF‐1 (R²; 0.11–0.18) and PTF‐2 (R²; 0.22–0.59) in BD estimation. However, for ECEC estimation, PTF‐3 (R²; 0.61–0.86) performed comparably as PTF‐1 (R²; 0.58–0.76) with both PTFs out‐performing PTF‐2 (R²; 0.30–0.71). Also, grouping of data into different soil depth increments improves the estimation of BD with PTFs (especially PTF‐2 and PTF‐3) performing better at subsoils than topsoils. Generally, the most important predictors of BD are sand, silt, elevation, rainfall, temperature for estimation at topsoil while EVI, elevation, temperature and clay are the most important BD predictors in the subsoil. Also, clay, sand, pH, rainfall and SOC are the most important predictors of ECEC in the topsoil while pH, sand, clay, temperature and rainfall are the most important predictors of ECEC in the subsoil. Findings are important for overcoming the challenges of building national soil databases for large‐scale modelling in most data‐sparse countries, especially in the sub‐Saharan Africa (SSA).     

Canine transmissible venereal tumour: a review

Canine transmissible venereal tumour (CTVT) is a contagious venereal tumour of dogs, commonly observed in dogs that are in close contact with one another, or in stray and wild dogs that exhibit unrestrained sexual activity. CTVT represents a unique, naturally transmissible, contagious tumour, where the mutated tumour cell itself is the causative agent and perpetuates as a parasitic allograft in the host. Clinical history, signalment and cytological features are often obvious for establishing a diagnosis though biopsy and histological examination may be needed in atypical cases. Most cases are curable with three intravenous injections of vincristine sulphate at weekly intervals. The role of stray and wild dogs makes the disease difficult to control and necessitates sustained animal birth control in stray dogs along with prompt therapy of the affected dogs. This review captures the manifold developments in different areas embracing this fascinating tumour, including its biology, diagnosis and therapeutic alternatives.     

Computed Tomography of the Normal Bovine Tarsus

The objective of this study was to provide a detailed multiplanar computed tomographic (CT) anatomic reference for the bovine tarsus. The tarsal regions from twelve healthy adult cow cadavers were scanned in both soft and bone windows via a 16‐slice multidetector CT scanner. Tarsi were frozen at ?20^o C and sectioned to 10‐mm‐thick slices in transverse, dorsal and sagittal planes respecting the imaging protocol. The frozen sections were cleaned and then photographed. Anatomic structures were identified, labelled and compared with the corresponding CT images. The sagittal plane was indispensable for evaluation of bone contours, the dorsal plane was valuable in examination of the collateral ligaments, and both were beneficial for assessment of the tarsal joint articulations. CT images allowed excellent delineation between the cortex and medulla of bones, and the trabecular structure was clearly depicted. The tarsal soft tissues showed variable shades of grey, and the synovial fluid was the lowest attenuated structure. This study provided full assessment of the clinically relevant anatomic structures of the bovine tarsal joint. This technique may be of value when results from other diagnostic imaging techniques are indecisive. Images presented in this study should serve as a basic CT reference and assist in the interpretation of various bovine tarsal pathology.     

Fixed‐time Insemination in Pasture‐based Medium‐sized Dairy Operations of Northern Germany and an Attempt to Replace GnRH by hCG

A field study was conducted aimed at (i) evaluating the practicability of a fixed‐time insemination regime for medium‐sized dairy operations of north‐western Germany, representative for many regions of Central Europe and (ii) substituting hCG for GnRH as ovulation‐inducing agent at the end of a presynch or ovsynch protocol in an attempt to reduce the incidence of premature luteal regression. Cows of two herds synchronized by presynch and two herds synchronized by ovsynch protocol were randomly allotted to three subgroups; in one group ovulation was induced by the GnRH analog buserelin, in another by hCG, whereas a third group remained untreated. The synchronized groups were fixed‐time inseminated; the untreated group bred to observed oestrus. Relative to untreated herd mates, pregnancy rate in cows subjected to a presynch protocol with buserelin as ovulation‐inducing agent was 74%; for hCG it was 60%. In cows subjected to an ovsynch protocol, the corresponding relative pregnancy rates reached 138% in the case of buserelin and 95% in the case of hCG. Average service interval was shortened by 1 week in the presynch and delayed by 2 weeks in the ovsynch group. It may be concluded that fixed‐time insemination of cows synchronized via ovsynch protocol with buserelin as ovulation‐inducing agent is practicable and may help improve efficiency and reduce the work load involved with herd management in medium‐sized dairy operations. The substitution of hCG for buserelin was found to be not advisable.