草甸草原天然打草场植物群落对刈割干扰的响应

为了研究刈割干扰下天然打草场植物群落呈现出的消长状态,试验对呼伦贝尔草甸草原天然打草场不同植物群落物种组成、数量特征、物种多样性、生物量等指标进行了定量分析。结果表明:在刈割干扰下,羊草+杂草类群落中物种总数略低于贝加尔针茅+羊草群落;羊草+杂类草群落的密度和盖度均显著高于贝加尔针茅+羊草群落(P0.05);羊草+杂类草群落的Shannon-Wiener多样性指数和Pielou均匀度指数均显著高于贝加尔针茅+羊草群落(P0.05);羊草+杂类草群落的现存量和枯落物量均显著高于贝加尔针茅+羊草群落(P0.05)。说明刈割干扰对羊草+杂类草群落的影响小于对贝加尔针茅+羊草群落的影响。     

围栏封育对呼伦贝尔草甸草原群落特征的影响

以呼伦贝尔草甸草原为研究对象,利用围栏封育样地内外连续4年的植被调查资料,对比分析了围栏内外的植被组成和群落特征,结果表明:围栏封育措施提高了草甸草原植被的地上生物量、盖度、高度及密度,其均显著高于相应年份围栏外(P0.05);围栏内外植物群落组成没有发生明显变化;围栏封育使围栏内羊草、贝加尔针茅优势种的优势地位明显增加。     

呼伦贝尔不同草地类型土壤微生物量及土壤酶活性研究

以呼伦贝尔5种不同草地类型(线叶菊草原、贝加尔针茅草原、羊草草原、大针茅草原、克氏针茅草原)为研究对象,分析了不同草地类型土壤理化性状、土壤微生物数量、土壤微生物量、土壤酶活性的变化特征及其相互关系。研究表明,各类菌群数量分布在5种草地中均为细菌>放线菌>真菌,但不同菌群数量及区系组成在各草地类型间均存在显著差异(P<0.05)。细菌数量在5种草地中依次为:羊草>贝加尔针茅>克氏针茅>线叶菊>大针茅,真菌数量依次为:线叶菊>克氏针茅>羊草>贝加尔针茅>大针茅,放线菌数量依次为:克氏针茅>羊草>线叶菊>贝加尔针茅>大针茅。土壤微生物量碳、氮(SMBC、SMBN)在不同草地类型间差异显著(P<0.05),线叶菊草原土壤微生物量碳、氮均显著高于其他草地类型(P<0.05),其中大针茅草原、羊草草原土壤微生物量碳、氮均较低。研究还表明,各草地类型土壤酶活性的垂直分布均表现为表层土壤(0~10cm)酶活性大于下层土壤(10~20cm)酶活性,不同草地类型间土壤酶活性亦存在显著差异(P<0.05),线叶菊草原土壤过氧化氢酶和转化酶活性均显著高于贝加尔针茅草原和大针茅草原;土壤脲酶活性以克氏针茅草原最高,且与线叶菊草原、贝加尔针茅草原和大针茅草原差异显著;而土壤磷酸酶活性则为羊草草原显著高于其他样地。相关分析结果表明,不同草地类型土壤微生物数量、土壤微生物量、土壤酶活性、土壤理化性状之间均存在相关性,从回归分析得出的2个方程可知,土壤微生物量碳随着土壤含水量、细菌数量的增加而增加,随着土壤磷酸酶活性的增加而降低;土壤微生物量氮则随着土壤过氧化氢酶活性的增加而增加,而随着土壤磷酸酶活性与土壤容重的增加而降低。     

割草地群落特征与土壤化学性质对利用年限的响应

对呼伦贝尔不同利用年限的贝加尔针茅(Stipa baicalensis)+日阴菅(Carexpe pediformis)和羊草(Ley-mus chinensis)+杂类草两种类型的割草地群落特征、植物营养成分及土壤营养成分进行了比较分析。结果表明,多年刈割使群落盖度降低,贝加尔针茅株丛破碎化、小型化,羊草退化;多年刈割的贝加尔针茅+日阴菅样地群落Mar-garlef丰富度指数、Shannon-Wiener多样性指数均高于同类型围封3年的样地,羊草+杂类草割草利用多年的样地Margarlef丰富度指数高于利用5年的样地。随刈割年限的增加,蔷薇科、菊科、毛茛科等一年生植物随之增加,地上生物量、枯落物现存量随着刈割年限的增加而降低;多年刈割使土壤有机质、全氮、速效氮的含量降低。     

典型草原区植物群落结构特征动态监测

1999～2002年在内蒙古锡林郭勒盟白音锡勒牧场典型草原区海流特,监测主要植物群落结构特征.结果表明,随时间推移,试验区主要群落的优势植物大针茅、羊草相对高度、相对盖度、相对密度和相对生物量呈降低趋势,退化指示植物冷蒿、狼毒相对高度、相对盖度、相对密度、相对生物量呈增加趋势;试验区群落物种丰富度指数、多样性指数和均匀性指数随时间推移均呈降低趋势;围栏在试验区草地植物群落特征的保持方面很有效,但围栏内植物群落特征随时间推移仍呈退化趋势.     

松嫩平原主要草地群落放牧退化演替阶段的划分

本文采用聚类分析和主分量分析的方法对松嫩平原主要草地群落；贝加尔针茅－羊草群落，贝加尔针茅群落，贝加尔针茅－线叶菊群落、羊草群落和羊草－杂类草群落和羊草－杂类草群落的放牧经演替阶段进行划分，结果表明，每个群落的放牧退化演替过程的可划分为四个阶段，即：轻牧、中牧、重牧和过牧。随着放牧压梯度的变化，群落主要植物种的优势地位明显的替代变化，这与其生态生物学特性和动物的采集行为密切相关。     

典型草原区植物群落结构特征动态监测

1999-2002年在内蒙古锡林郭勒盟白音锡勒牧场典型草原区海流特,监测主要植物群落结构特征。结果表明,随时间推移,试验区主要群落的优势植物大针茅、羊草相对高度、相对盖度、相对密度和相对生物量呈降低趋势,退化指示植物冷蒿、狼毒相对高度、相对盖度、相对密度、相对生物量呈增加趋势;试验区群落物种丰富度指数、多样性指数和均匀性指数随时间推移均呈降低趋势;围栏在试验区草地植物群落特征的保持方面很有效,但围栏内植物群落特征随时间推移仍呈退化趋势。     

松嫩平原主要草原群落放牧干扰梯度对植物多样性的影响

松嫩草原五个主要群落类型放牧干扰梯度对植物样性影响的研究结果表明,在放牧过程通过牧畜的啃食、践踏作用干扰草原环境,使群落物种组成发生变化,优势地位发生更替,导致植物多样性变化。随着放牧干扰强度的增大,群落丰富度随之下降。多样性指标在中牧或重牧阶段出现峰值,主要缘于群落均匀度的增加。β多样性研究结果表明,羊草群落和羊草－杂类草群落植物多样性的耐牧性较差,而贝加尔针茅－羊草群落、贝加尔针茅－杂类草群落     

放牧对草甸草原植物群落结构及多样性的影响

在贝加尔针茅—羊草草甸草原的同一草地地境上,按放牧退化程度,将其划分为轻度退化区、中度退化区及重度退化区,并测定每一样地内植物群落特征及多样性指标。结果表明,随着放牧强度的增加,群落地上总生物量与中旱生植物的生物量变化保持一致,均呈降低趋势;中生植物先呈增加趋势,后下降;旱生植物呈增加趋势;群落优势种贝加尔针茅Stipa baicalensis和羊草Leymus chinensis呈降低趋势;物种丰富度指数先增加,而后降低;多样性指数和均匀度指数均呈增加趋势,优势度指数则相反。     

种植星星草改良碱斑地的研究

黑龙江省松嫩平原,地处温带大陆性季风地区,植被为温带草甸草原。构成草原的主要草类常见的有羊草、贝加尔针茅草、线叶菊杂类草等。其中以羊草分布较广,面积较大,且草质肥美,营养价值     

Dominance in domestic dogs revisited: Useful habit and useful construct?

In the last decade, the validity and relevance of the dominance model was regularly put into question regarding relationships between canids like dogs and wolves, and consequently, human–dog relationships as well. The concept underlying this model, scientifically defined as an intervening variable reflecting status difference between individuals, is applicable when formal status signals symbolize the long-term relationship between individuals, resulting in a formalized dominance hierarchy. This article reviews the basics underlying the concept of dominance and reflects on the value and importance of some new quantitative studies on the applicability of the concept of dominance in domestic dogs. The conclusions are, first, that formal dominance is present in the domestic dog, expressed by context-independent unidirectional formal status signals. Consequently, formal dominance (e.g., submission) plays an important role in assessing status in dog–dog relationships. Second, that nonverbal status–related communication in humans resembles that in dogs to a considerable degree, and hence dogs may be well able to interpret this human status–related nonverbal communication from their perspective. Dominance is therefore also likely to play a role in human–dog relationships. Hence, the dominance concept might be useful to explain the development of certain problems in dog–dog and dog–human relationships. However, enforcing a dominant status by a human may entail considerable risks and should therefore be avoided.     

云南马龙县山地草甸植物优势度及优势植物光合特征研究

以云南马龙县退化山地草甸为研究对象,对其草地群落数量特征及优势植物的光合特性进行了研究。结果表明:8个不同种群的净光合速率(Pn)依次为:白茅>西南委陵菜>火绒草>矮生胡枝子>白健秆>西南杭子梢>丝叶球柱草>山苦荬;CO2固定能力的强弱顺序与Pn相同;群落数量特征与净光合速率(Pn)成正相关,其显著性水平依次为:相对干重(r=0.959 1)>重要值(r=0.869 9)>相对盖度(r=0.829 5)>相对频度(r=0.755 1)>相对密度(r=0.585 4)>相对高度(r=0.283 5)。     

Genomic estimation of additive and dominance effects and impact of accounting for dominance on accuracy of genomic evaluation in sheep populations

The objectives of this study were to estimate the additive and dominance variance component of several weight and ultrasound scanned body composition traits in purebred and combined cross‐bred sheep populations based on single nucleotide polymorphism (SNP) marker genotypes and then to investigate the effect of fitting additive and dominance effects on accuracy of genomic evaluation. Additive and dominance variance components were estimated in a mixed model equation based on “average information restricted maximum likelihood” using additive and dominance (co)variances between animals calculated from 48,599 SNP marker genotypes. Genomic prediction was based on genomic best linear unbiased prediction (GBLUP), and the accuracy of prediction was assessed based on a random 10‐fold cross‐validation. Across different weight and scanned body composition traits, dominance variance ranged from 0.0% to 7.3% of the phenotypic variance in the purebred population and from 7.1% to 19.2% in the combined cross‐bred population. In the combined cross‐bred population, the range of dominance variance decreased to 3.1% and 9.9% after accounting for heterosis effects. Accounting for dominance effects significantly improved the likelihood of the fitting model in the combined cross‐bred population. This study showed a substantial dominance genetic variance for weight and ultrasound scanned body composition traits particularly in cross‐bred population; however, improvement in the accuracy of genomic breeding values was small and statistically not significant. Dominance variance estimates in combined cross‐bred population could be overestimated if heterosis is not fitted in the model.     

风险决策模型在农户决策研究中的应用：庆阳农户养兔及种草行为分析

运用二阶随机优势分布模型和目标值—平均绝对偏差法（ＴａｒｇｅｔＭＯＴＡＤ模型）实证地研究了市场的波动对西北黄土高原地区农户养兔及种草行为的影响，利用庆阳等地的农户调查资料对所提出的研究假设进行了检验。研究结果表明，当地以传统生产方式为主的小农户具有很强的回避风险的意识。他们的决策目标并非收益的最大化。造成西北黄土高原地区农户毛兔养殖积极性下降的原因是，不规范的兔毛市场交易行为导致的农户兔毛生产收益的不确定性。政府应制定有关的政策法规来规范兔毛收购行为，并加强对农户兔毛质量控制和分级技术的推广，使农户在市场交易中增强维护自身利益的能力     

南非克鲁格斯多普禁猎区珠鸡的社群组织

1982年3月至1984年2月,在南非豪登省的克鲁格斯多普禁猎区(Krugersdorp Game Reserve),通过翼标观察对珠鸡(Numida meleagris)的社群组织进行了研究.珠鸡必须以社群的方式才能在野外存活,而集群(7-10只珠鸡)并非随机组成.地位最高的雄鸟(雄鸟A)是群体日常活动的核心,例如决定觅食方向等.地位较高的雄鸟(雄鸟A和B)密切协作以驱赶闯入者.在繁殖期,繁殖雌鸟与高地位雄鸟的结合更为紧密.尽管雄鸟中存在明显的等级差异,但群内争斗频率很低,这些争斗只是在维系群体稳定时才发生.雌性成鸟始终位于优势雄鸟和亚成体之间,以免受天敌伤害.但优势雄鸟与其配偶暂时离开群体进行繁殖时,次优势雄鸟(雄鸟B)成为集群中心,其余个体聚集在其周围以保持集群的稳定.大多数成鸟都协助抚育优势雄鸟的雏鸟.珠鸡的集群具有监视天敌的作用,以保障其在地表植被有限的环境中觅食并在冬季最大限度地获得食物.     

Control and Ecology of the Black-Backed Jackal Canis Mesomelas in the Transvaal

Benthic oxygen demand was measured by dark and light bottle technique at two beaches in the Swartkops estuary, near Port Elizabeth. Respiration of nematodes was measured by polarographic micro-rcspirometer technique. Secondary production was 82 g C/m²/y in sandy areas and 863 g C/m²/y in muddy areas rich in the prawn Callianassa kraussi. Meiofauna production was 1,72 g C/m²/y in sand and 0,24 g C/m²/y in mud. The meiofauna] contribution to secondary production was 2,1% and 0,03% for these two areas respectively. The largest proportion of secondary production was due to micro-organisms: 92% in sand and 73,5% in mud. Macrofauna accounted for 5,75% and 24,4%. It is concluded that meiofauna in these exposed sand and mud flat areas is not quantitatively important, but the qualitative importance may be considerable.     

Impact of fitting dominance and additive effects on accuracy of genomic prediction of breeding values in layers

Most genomic prediction studies fit only additive effects in models to estimate genomic breeding values (GEBV). However, if dominance genetic effects are an important source of variation for complex traits, accounting for them may improve the accuracy of GEBV. We investigated the effect of fitting dominance and additive effects on the accuracy of GEBV for eight egg production and quality traits in a purebred line of brown layers using pedigree or genomic information (42K single‐nucleotide polymorphism (SNP) panel). Phenotypes were corrected for the effect of hatch date. Additive and dominance genetic variances were estimated using genomic‐based [genomic best linear unbiased prediction (GBLUP)‐REML and BayesC] and pedigree‐based (PBLUP‐REML) methods. Breeding values were predicted using a model that included both additive and dominance effects and a model that included only additive effects. The reference population consisted of approximately 1800 animals hatched between 2004 and 2009, while approximately 300 young animals hatched in 2010 were used for validation. Accuracy of prediction was computed as the correlation between phenotypes and estimated breeding values of the validation animals divided by the square root of the estimate of heritability in the whole population. The proportion of dominance variance to total phenotypic variance ranged from 0.03 to 0.22 with PBLUP‐REML across traits, from 0 to 0.03 with GBLUP‐REML and from 0.01 to 0.05 with BayesC. Accuracies of GEBV ranged from 0.28 to 0.60 across traits. Inclusion of dominance effects did not improve the accuracy of GEBV, and differences in their accuracies between genomic‐based methods were small (0.01–0.05), with GBLUP‐REML yielding higher prediction accuracies than BayesC for egg production, egg colour and yolk weight, while BayesC yielded higher accuracies than GBLUP‐REML for the other traits. In conclusion, fitting dominance effects did not impact accuracy of genomic prediction of breeding values in this population.     

Seasonal variations in sexual behavior, testosterone, testicular size and semen characteristics, as affected by social dominance, of tropical hair rams (Ovis aries)

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behavior and testosterone concentration (T4) in dominant and subordinate Pelibuey rams. Six groups of three animals were evaluated every 2 weeks over a 12 month period. Dominant (D), medium (M) and subordinate (S) animals in each group were identified through a food competition test every 15 days. All rams ejaculated and produced semen throughout the year. A linear hierarchy was clearly established and maintained during the year. S rams had lower levels (P < 0.05) of semen volume, sperm concentration and testicular volume than D rams, regardless of season. Scrotal circumference was not influenced (P > 0.05) by their social position. D rams were more affected by the photoperiod, decreasing (P < 0.05) reaction times, increasing (P < 0.05) T₄ and producing more (P < 0.05) sperm per ejaculation than S rams during short days (14.65 ± 1.22 vs 26.92 ± 1.65 s; 8.68 ± 0.44 vs 7.37 ± 0.40 ng/mL and 3.37 ± 0.17 vs 2.04 ± 0.16 sperm/10⁹, respectively). Semen volume and sperm concentration were significantly (P < 0.05) greater during short days in all rams, regardless of their social status, with the exception of sperm concentration in D rams where no variation was found. M rams displayed variable values in the range between the D and S rams. It was concluded that the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year and that seasonal variation within the variables affected the social ranks differently.     

Estimation of additive and non-additive genetic effects for fertility and reproduction traits in North American Holstein cattle using genomic information

Non-additive genetic effects are usually ignored in animal breeding programs due to data structure (e.g., incomplete pedigree), computational limitations and over-parameterization of the models. However, non-additive genetic effects may play an important role in the expression of complex traits in livestock species, such as fertility and reproduction traits. In this study, components of genetic variance for additive and non-additive genetic effects were estimated for a variety of fertility and reproduction traits in Holstein cattle using pedigree and genomic relationship matrices. Four linear models were used: (a) an additive genetic model; (b) a model including both additive and epistatic (additive by additive) genetic effects; (c) a model including both additive and dominance effects; and (d) a full model including additive, epistatic and dominance genetic effects. Nine fertility and reproduction traits were analysed, and models were run separately for heifers (N = 5,825) and cows (N = 6,090). For some traits, a larger proportion of phenotypic variance was explained by non-additive genetic effects compared with additive effects, indicating that epistasis, dominance or a combination thereof is of great importance. Epistatic genetic effects contributed more to the total phenotypic variance than dominance genetic effects. Although these models varied considerably in the partitioning of the components of genetic variance, the models including a non-additive genetic effect did not show a clear advantage over the additive model based on the Akaike information criterion. The partitioning of variance components resulted in a re-ranking of cows based solely on the cows’ additive genetic effects between models, indicating that adjusting for non-additive genetic effects could affect selection decisions made in dairy cattle breeding programs. These results suggest that non-additive genetic effects play an important role in some fertility and reproduction traits in Holstein cattle.     

莫莫格湿地干-湿界面优势植物种群动态分析

莫莫格湿地从高河漫滩底端到顶端选取有代表性的植物群落片断作为固定观测样带,并设置6个观测样方,生长季5月、7月、9月3次观测结果表明,小叶章优势种群5月份密度最高达1154-1594株/平方米,7月种群数量下降,9月有所升高;踏头苔草优势种群5-7月份密度在3 414-7 193株/平方米,9月份种群数量大幅度下降;土壤相对含水量低地段小叶章种群相对优势度大,土壤相对含水量高地段踏头苔草种群相对优势度大,局部地段生长季内有相对优势度相互替代过程,莫莫格湿地干-湿界面上小叶章和踏头苔草两个种群可以共存。