The use of degradation gradients for the assessment and ecological interpretation of range condition

Multivariate procedures were used to subdivide the southern African climatic climax grasslands of the 700–800‐mm rainfall zone into relatively homogeneous grazing areas. A degradation gradient was constructed for each of these areas. This was done by means of centred PCA ordination, using static data representing compositional differences induced mainly by grazing. The first axis of these ordinations represented a gradient of degradation. The second and higher axes were combined in a single value, namely, the Euclidean distance from the first axis. The degradation gradients were then used as a basis for ordinating new sites into the old ordinations, assessing their condition in an objective and quantitative way. The Euclidean distances from the first axis were used to determine the appropriateness of the degradation gradients for the assessment of the condition of a particular site. Knowledge of species response to grazing, community dynamics and recovery potential obtained through the ordination and regression studies was used to interpret the condition assessments.     

An evaluation of veld condition assessment techniques in Highland Sourveld

An evaluation of six methods used to index veld condition showed that the majority provided indices that were insensitive to long‐term grazing impact. However, certain species were found to either increase or decrease in relative abundance with an increase in grazing intensity. A key species method is therefore suggested to be a potentially sensitive approach for indexing veld condition in relation to grazing management in the Highland Sourveld.     

Salinity ranges of some southern African fish species occurring in estuaries

The recorded salinity ranges of 96 fish species occurring in southern African estuaries are documented. Factors influencing the tolerance of fishes to low and high salinity regimes are discussed, with most species tolerant of low rather than high salinity conditions. This is important since most systems are subject to periodic freshwater flooding, especially during summer. The penetration of freshwater teleosts and elasmobranchs into estuaries is examined and the occurrence of marine fishes in rivers documented. Mortalities arising from salinity extremes in southern African estuaries are discussed, with temperature a key factor initiating such fish kills. Only eight fish species have been recorded spawning in estuaries although the fry of many species are attracted to estuarine waters. It is concluded that a small percentage of southern African fishes have succeeded in utilizing estuaries and this may be attributed to the paucity of strong osmoregulators     

A consideration of veld condition assessment techniques for commercial livestock production in South Africa

Abstract

A number of procedures have been developed for the evaluation of veld condition in a variety of vegetation types in South Africa. These include both agronomic and ecologically based methods, about which there still remain a great deal of controversy. However, the urgent need for methods which can be applied in practice has recently prompted the recommendation of specific methods for the vegetation types representative of the major livestock producing areas of South Africa.     

A comparison of five methods for assessing veld condition in the natal midlands

Abstract

Site rankings obtained from five methods of scoring veld condition in the highland sourveld and the moist tall grassveld of the Natal Midlands were correlated with rankings from methods of multivariate analysis. With few exceptions, all methods gave rankings which were strongly correlated with rankings from detrended correspondence analysis, thus indicating that they all provide a practical means of indexing the relative veld condition of sites with reasonable precision. The weighted quantitative climax and key species methods were superior to the other three methods in this respect. The key species method has the advantage of simplicity and speed, and should stimulate farmers to undertake routine monitoring of their veld in these two regions.     

中国南方草地现状与生产潜力

中国南方草地区为秦岭、淮河以南、青藏高原以东的广大地区 ,总面积约 2 70万 km2 ,分属淮河、长江、珠江 3大流域。南方草地多山 ,本文涉及的 12个南方省区中 ,山地与平原之比平均为 4 .85∶ 1,比全国平均比值高出 1倍。山地面积之大小与青藏高原距离的远近呈负相关。南方草地大体可以分为云贵高原区、华东区和华南区。笔者提出建立 3类系统耦合经济带 ,即西南岩溶山地系统耦合生态经济带、江淮平原丘陵系统耦合生态经济带和岭南沿海平原丘陵生态经济带。每一生态经济带内包含中心城市 ,农村生产基地和社会支持系统。据初步估算 ,这样的生态经济带蕴藏了巨大的经济潜力     

采用3种遗传标记技术对早熟禾属植物物种鉴定及系统学比较

采用3种不同的遗传标记技术对10种早熟禾属植物进行物种辅助鉴定，以形态学分类系统为基础对3种技术在早熟禾属种间亲缘关系研究中应用的可能性进行了比较和检验，结果表明：它们的共同特点是快速、简便和经济。POD、EST两种技术都可用于对早熟禾属物种的辅助鉴定，但POD技术在稳定性、酶带集中性和可操作性方面优于EST技术。RAPD技术无论是用于物种的鉴定还是种间亲缘关系的研究，其效果均好于前二者，而且它的系统聚类结果几乎与形态学分类结果完全一致。     

A comparative histochemical study of plant polyphenols in southern African grasses

Recent anatomical studies have shown that tannin‐like substances (TLS) occur in the epidermal cells of a number of southern African tropical grasses, and the presence of condensed tannins in grasses has been confirmed by chemical analyses. A number of species from four of the five subfamilies of the Poaceae were compared for their responses to a range of histochemical tests which differ in their specificity for phenolic compounds. These included: ferrous sulphate, acidified vanillin, diazotized sulphanilic acid, Fast Blue‐BB, dimethoxybenzaldehyde and nitrous acid, Safranin and Fast Green. In addition, the radial diffusion test for protein precipitation was used. Comparative histochemical tests indicated that most taxa known to contain TLS showed comparable responses to the tests used here, with variations in intensity and hue of the coloured products formed. These qualitative differences suggest the presence of a number of different compounds including oligomeric procyanidins, oligomeric prodelphinidins, monomeric and/or dimeric flavan‐3‐ols and flavan‐3,4‐diols. The presence flavan‐4‐ols has been confirmed in the andropogonoid grasses by previous workers. Histochemical tests are adequate to identify the presence of condensed tannins and their precursors in plant tissue. However, they do not provide a means to identify those compounds which precipitate protein and function as digestibility‐reducing compounds in plant‐herbivore interactions.     

Patterns of plant selection by grazing cattle in two savanna grasslands: A plant's eye view

The amount of grazing experienced by individual tufts of the most abundant perennial grasses of two Transvaal savannas was monitored at regular intervals for two growing seasons. In general, Setaria incrassata and Themeda triandra were heavily grazed, Bothriochloa insculpla and Aristida bipartita were lightly grazed, and Heteropogon conlortus and Digitaria eriantha were intermediate. Tufts with a greater amount of moribund material were less heavily grazed. The smallest tufts of all species were the most lightly grazed, although the most heavily‐grazed tufts were on occasion intermediate in size rather than being the largest. A tuft had an increased likelihood of being heavily grazed if it had previously been heavily grazed, both within a growing season and for two successive growing seasons. A spatial pattern of grazing was evident, as individual species were less heavily grazed at different locations within the paddocks. The influence of species identity on the amount a tuft was grazed was not absolute but rather quantitative and conditional on the level of other variables. Tuft size and the amount a tuft had been previously grazed generally had a greater influence on the amount a tuft was grazed during an individual grazing event than species identity, location or moribund material. Species selection is possibly, in part, a consequence of selection for plant structure which optimizes intake.     

A comparison of retrobulbar and two peribulbar regional anesthetic techniques in dog cadavers

Objective

To compare injectate distribution and likelihood of regional anesthesia to the orbit following retrobulbar (RB) or peribulbar (PB) injections in dog cadavers.

A quantitative analysis of the marked asymmetry existing between some muscle partners in the pelvic girdle of southern African species of the genus Mabuya (Reptilia: Scincidae)

The pelvic girdle musculature of eleven of the eighteen southern African Mabuya species described by Branch (1988) was examined, using differences in mass to emphasize the marked asymmetry existing between partners of certain muscle pairs. The lighter muscles expressed as indices of their heavier partners gave a mean value of 0,38 (n= 27) with a range of 0,11 to 0,75. The mean value obtained for a symmetrical control pair was 0,95 (n = 27) with a range of 0,90 to 0,99. The arrangement of the asymmetric pairs was the same for all the species, irrespective of sex. The partners of a pair differed in size and the manner in which they originated on the pelvic girdle but showed agreement as far as their insertion on the head of the femur was concerned.     

拉萨河谷山地灌丛草地植物多样性监测方法的比较研究

生物多样性是西藏生态安全监测与评估的重要内容之一.在气候变暖和放牧干扰背景下沿海拔梯度探讨西藏拉萨河谷山地灌丛草地植物群落物种多样性的变化特征,对于该地区草地的保护与可持续利用具有重要意义.以拉萨市林周县白朗村沟域的山地灌丛草地为研究对象,采用常规样方法,重复样线法和Modified-Whittaker样地法3种方法进行系统调查,研究草地群落物种组成及其沿海拔梯度的变化特征.结果表明,1) 3种不同取样方法α多样性的物种丰富度均随海拔的升高呈先增加后降低的趋势,其中50 m样线法效果最好.2) 表征β多样性的Sorensen相似性指数和Bray-Curtis指数均随样地间海拔高差的增大而减小.3) 种-面积关系的截距c,斜率z随海拔的升高呈先增加后降低的趋势,与α,β多样性随海拔梯度的变化特征吻合一致.4) 依据种-面积关系研究结果,山地灌丛草地设置100 m²的样地可覆盖80%左右的植物物种.山地灌丛草地的α和β多样性指数沿海拔梯度均呈先增后减的变化特征,未来研究应注重植物多样性分布格局对山体气候梯度以及放牧干扰变化的响应和适应机制.     

不同生境类型金莲花群落物种多样性比较

摘要：采用群落多样性指数中Shannon Wiener多样性指数、丰富度指数、Pielou均匀度指数及群落相似性指数中的Jaccard指数和Sorenson指数,对河北省承德接坝地区5种生境条件下金莲花(Trollius chinensis)群落进行比较。结果表明,林中空地、湿地、沟谷、荒坡及林下5种生境类型金莲花群落共包括36科、93属、182种,林中空地物种数最多,林下物种数最少。各群落的物种生态类型均表现为湿生植物多于旱生植物,反映了金莲花喜湿的特性。Shannon Wiener多样性指数表现为林中空地>沟谷>湿地>荒坡>林下,丰富度指数表现为林中空地>湿地>沟谷>荒坡>林下,均匀度指数表现为沟谷>林中空地>荒坡>湿地>林下。群落相似性比较表明,湿地和林中空地两种生境差异性最小,林下和沟谷差异性最大,群落相似性的比较结果与群落多样性的方差分析结果较为一致。土壤水分与光照是影响金莲花群落物种多样性及群落相似性的主要因子。     

A comparison of the potency of several Brucella allergens used to detect brucellosis in cattle

The potency of Brucella allergens prepared from a smooth Brucella abortus strain S-99, mucoid strain Leewarden, rough strain 45/20, and rough Brucella melitensis strain B-115 was assessed. The potency of these allergens was compared with that of a standard allergen prepared from smooth Brucella abortus S-99 that efficiently detected bovine brucellosis in other studies. Eight cattle experimentally inoculated with Brucella abortus 544 were tested with the allergens 4 and 10 weeks after infection, and again 8 months after infection. All the allergens effectively detected infection but there was a clear distinction in the mean skin reactions 48 and 72 h after injection of the allergens. The skin reactions provoked by the allergens prepared from smooth or mucoid strains of Brucella were most pronounced 48 h after injection. Skin reactions provoked by allergens prepared from rough strains of Brucella were strongest 72 h after injection. Allergens prepared from smooth or mucoid Brucella strains were more potent in detecting brucellosis than those prepared from rough strains of Brucella.Abbreviations Bruc/OCB Brucellergen OCB - cfu colony-forming units - CFT complement fixation test - ID-DLO Institute voor Dierhouderij en Diergezondheid-Dienst Landbouwkundig Onderzoek - ICFTU international complement fixation units - IU international units - LPS lipopolysaccharide - SAT serum agglutination test - SDTH skin delayed-type hypersensitivity     

盐渍条件下苜蓿和羊草生长与营养吸收的比较研究

通过室内模拟试验,研究了盐分对苜蓿和羊草生长与营养吸收的影响,结果表明,盐度处理对羊草植株生长的影响低于对苜蓿的影响,羊草较苜蓿更为耐盐。苜蓿的蒸散量和净光合速率（NPn),尤其是日最大净光合速率受盐分的影响比羊草显著。随土壤含盐量的增加,苜蓿和羊草植株N、P含量无明显变化,K含量迅速降低,而Na含量急剧增加。苜蓿与羊草相比,苜蓿则有相对较低的K特定吸收率（SAR）和高的Na特定吸收率（SAR）。     

A comparison of uniaxial and triaxial accelerometers for the assessment of physical activity in dogs

The present study compares the outputs of uniaxial accelerometer (UA) and triaxial accelerometer (TA) to determine whether UAs can be used instead of TAs in estimating physical activity (PA) in domestic dogs (N = 79). The PA of the dogs was measured simultaneously by a UA and a TA attached to regular collars under 3 different conditions: unstructured activity in the kennels (kennel activity); and 2 structured on-lead activities of different intensities on a designated pathway (walking and trotting). The study finds that UA consistently detected significantly more steps. Kennel activity showed the largest differences between the accelerometers, and trotting showed the least. Dogs in the heaviest body weight category showed the best correlation between the devices and the least differences between the accelerometers across the 3 activities. The limits of agreement were wide in all activities. Significantly higher agreements were associated with lower step counts in kennel activity and higher step counts in walking and trotting. The results show that these 2 types of accelerometers cannot be used interchangeably. Confounding factors, such as body weight, must be considered in future analysis of accelerometer outputs and selection of devices for different contexts. Optimal interpretation of objectively measured PA is paramount in supporting future dog fitness, health, and welfare studies.     

A comparison of grass and grass/legume pastures under irrigation in the Outeniqua area of the southern Cape

Two grass and five grass/legume pastures were evaluated over a period of two seasons at two seasonally set grazing pressures and under two grazing management systems, involving five and seven paddocks per flock and a seven‐day period of stay. Grazing capacity was most limiting during winter. Pastures with fescue as grass component had, overall, the highest grazing capacity, while white clover‐based pastures had the highest animal production. The legume content of the grass/legume pastures was markedly higher on the seven than on the five‐paddock system. Dry matter and animal production of white clover‐based pastures was favoured by a seven‐paddock system as opposed to a five‐paddock system, while mixtures containing lucerne and pure grass pastures were either not influenced by grazing management or promoted by a five‐camp system.