广西喀斯特次生林地表碳库和养分库特征及季节动态

以自然保护区原生林为对照,调查了广西喀斯特区处于同一次生演替序列中的灌丛、藤刺灌丛、乔灌丛3个群落的地表凋落物存量,同时对凋落物层和土壤表层(0-5 cm)的有机碳,全氮、磷、钾等养分元素的含量、贮量状态及其雨季前后的变化进行了研究.结果表明:地表凋落物存量及有机碳、全氮贮量随演替阶段上升均呈增高趋势;除全磷外,土壤的有机碳和养分元素含量与凋落物层贮量相关性显著(p<0.05);雨季期间,凋落物迅速分解,地表凋落物的分解量要大于当季凋落量,并且次生林的凋落物分解与养分释放量显著高于原生林;雨季后,各群落有机碳和养分的凋落物层贮量以及土壤含量均有所降低.其中凋落物层贮量下降显著的是藤刺灌丛与乔灌丛.土壤养分含量则在灌丛与原生林阶段下降更为明显.在从灌丛向顶级群落演替的进程中,森林的自养能力可能存在一个先增高再降低的过程.     

Sex‐dependent responses of perch to changes in water clarity and temperature

Rising temperatures and decreasing water transparency of lakes have strong wide ranging effects on fish. Fish responses to various changes in the environment are usually species‐dependent, but responses may also vary within species. In general, large individuals are considered to be more sensitive to environmental variation due to higher energy demand, than smaller individuals. Similarly, large individuals require more food to maintain bodily functions and are thus more sensitive to resource and food scarcity. These size‐specific responses to environmental gradients are also sex‐dependent in species that exhibit sexual size dimorphism (SSD). We studied in enclosures with short‐term experiments how rising temperatures and decreasing water transparency regulate the feeding rates of female and male European perch (Perca fluviatilis L.). To explore experimental results, we calculated perch SSD in nine lakes with varying environmental conditions using previously collected field data. The results of the experiments revealed that the combined effect of water transparency and temperature on the feeding rate of fish is gender‐dependent: feeding rate of females decreased more than that of males. The experimental results were also supported by field data that revealed a negative relation between water transparency and the magnitude of SSD in perch. Our results suggest that rising temperatures and decreasing water transparency may potentially decrease fish size in a sex‐dependent manner. As female size is one of the main demographic traits determining the reproductive success of a fish population, changing environments may have unexpected and far‐reaching consequences on fish population dynamics.     

长期免耕和秸秆覆盖下黄土高原旱作土壤不同粒级复合体中酸解有机氮含量及分配比例变化

【目的】探明不同保护性耕作措施对黄土高原旱作土壤不同粒级复合体中有机氮含量与分配的影响,可对评价耕作措施的效果提供科学依据。【方法】基于黄土高原旱区14年的长期定位试验,采用Bremner法, 对传统耕作(T)、免耕(NT)、秸秆覆盖(TS)及免耕+秸秆覆盖(NTS)四种耕作措施条件下不同土壤粒级复合体中的有机氮含量和分配进行了研究。【结果】保护性耕作方式均增加了2~10 μm粒级土壤复合体的比例,增幅为20.0%~31.7%;降低了0~2 μm粒级土壤复合体在土壤中所占的比例,降幅为27.6%~31.0%。在所有耕作措施下,耕层土壤中不同粒级复合体所占的比例为10~50 μm＞2~10 μm＞0~2 μm＞50~100 μm＞100 μm。保护性耕作方式均明显提高了耕层0~2 μm粒级土壤复合体中氨基糖氮的含量,增幅在46.9%~107.1%,降低了单位质量0~2 μm粒级土壤复合体中的NH+4-N含量,降幅在14.8%~27.0%;明显提高了耕层单位质量2~10 μm粒级土壤复合体中酸解总氮、氨基酸氮和氨基糖氮的含量,增幅分别为8.2%~14.3%、16.2%~31.5%和154.9%~184.3%;降低了单位质量2~10 μm粒级土壤复合体中NH+ 4-N的含量,降幅为28.7%~46.6%。传统耕作(T)条件下,与各粒级土壤复合体相结合的有机氮量顺序为10~50 μm＞0~2 μm＞2~10 μm＞50~100 μm＞100 μm以上,而保护性耕作条件下,与各粒级土壤复合体相结合的有机氮量顺序为10~50 μm＞2~10 μm＞0~2 μm＞50~100 μm＞100 μm以上;与传统耕作相比,保护性耕作措施显著地增加了耕层土壤中酸解总氮、氨基酸氮、氨基糖氮的含量,增幅分别为6.6%~20.4%、89.0%~113.0%和11.9%~31.6%,降低了NH+4-N的含量。【结论】与传统耕作(T)处理相比,保护性耕作(NT、TS、NTS)措施明显提高了土壤2~10 μm粒级复合体的比例,降低了0~2 μm粒级复合体的比例;增加了耕层土壤中酸解氮总氮、氨基糖态氮和氨基酸态氮的含量,降低了NH+ 4-N的含量。土壤中以氨基酸态氮占优势地位,其它形态的有机氮无明显分布规律。     

Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types

The chemical composition of green leaves and leaf litters of sweet chestnut (Castanea sativa), oak (Quercus robur) and beech (Fagus sylvatica) were determined for 26 sites grouped into high fertility (HF) and low fertility (LF) soils according to base saturation and N-mineralization potentials. Measurements were made of total carbon, acid detergent fibre (ADF), Klason lignin, holo-cellulose, sugar constituents of hemicellulose and phenylpropanoid derivatives of lignin, and nutrient concentrations (N, Ca, P, Mg, K and Mn). Leaf and litter constituents varied within and between species according to soil groups, but beech showed contrasting responses to oak and chestnut. Beech leaves had lower ADF, lignin and cellulose on HF soils than LF soils, whereas oak and chestnut leaves had higher ADF, lignin and cellulose on HF than the LF soils. Conversely, the same constituents in beech leaf litter were higher on HF soils than LF soils, but lower in oak and chestnut leaf litter on HF soils than LF soils. The phenylpropanoid derivatives of lignin and sugar constituents of hemicellulose also showed similar variations in relation to soil groups with contrasting patterns for in leaves and litters. Re-absorption of N from leaves before litter fall was negatively correlated with soil N mineralization potential for beech (highest on LF soils) but showed an unexpected, positive relationship for oak and chestnut (highest on HF soils). These intra-specific differences of leaf and litter chemistry in relation to soil fertility status are unprecedented and largely unexplained. The observed patterns reflect phenotypic responses to soil type that result in continuum of litter quality, within and between tree species, that have been shown in related studies to significantly influence litter decomposition rates.     

马铃薯脱毒小薯密度试验及其田间实用性探讨

本文研究了马铃薯脱毒小薯５个不同粒度水平和３个密度水平下的生产能力和种薯的投入产出情况．通过试验，分析和比较了不同处理的主要经济性状的表现．综合评价了不同处理的利用价值，筛选了可用于生产的较好的粒度和密度水平。试验结果表明：０．５～１０．ｇ的脱毒小薯是田间生产较好的粒度水平，合理的种植密度为９０００株／亩。     

Effective population size and inbreeding depression on litter size in rabbits. A case study

The purpose of this study is to use demographic and litter size data on four Spanish maternal lines of rabbits (A, V, H and LP), as a case study, in order to: (i) estimate the effective population size of the lines, as a measure of the rate of increase of inbreeding, and (ii) study whether the inbreeding effect on litter size traits depends on the pattern of its accumulation over time. The lines are being selected for litter size at weaning and are kept closed at the same selection nucleus under the same selection and management programme. The study considered 47 794 l and a pedigree of 14 622 animals. Some practices in mating and selection management allow an increase of the inbreeding coefficient lower than 0.01 per generation in these lines of around 25 males and 125 females. Their effective population size (Ne) was around 57.3, showing that the effect of selection, increasing the inbreeding, was counterbalanced by the management practices, intended to reduce the rate of inbreeding increase. The inbreeding of each individual was broken down into three components: old, intermediate and new inbreeding. The coefficients of regression of the old, intermediate and new inbreeding on total born (TB), number born alive (NBA) and number weaned (NW) per litter showed a decreasing trend from positive to negative values. Regression coefficients significantly different from zero were those for the old inbreeding on TB (6.79 ± 2.37) and NBA (5.92 ± 2.37). The contrast between the coefficients of regression between the old and new inbreeding were significant for the three litter size traits: 7.57 ± 1.72 for TB; 6.66 ± 1.73 for NBA and 5.13 ± 1.67 for NW. These results have been interpreted as the combined action of purging unfavourable genes and artificial selection favoured by the inbreeding throughout the generations of selection.     

塔克拉玛干沙漠腹地纵向沙垅表面沙物质粒度特征

本文对塔克拉玛干沙漠腹地纵向沙垅表面沙粒、丘间地沙粒进行了粒度分析。结果表明,沙垅以极细沙为主,平均粒径３．０６Φ,沙粒从沙垅迎风侧到背风侧逐渐变细。沙丘沙比丘间地沙分选好,沙垅背风侧比迎风侧分选好。沙粒属极负偏,偏度－０．２２,丘间地沙比沙丘沙更趋向负偏。峰度１．３８,属尖峰态。粒径与偏度和峰度成正相关,分选和偏度成良好负相关。沙丘沙以单峰态为主,累积频率曲线为２～３段式,丘间地以双峰态为主,累积频率曲线为３～４段。大尺度地形对沙粒段式没有影响,对各段组分含量相对大小有影响。     

波尔山羊杂交后代体尺、体重与肉用性能的相关性研究

本文利用 SPSS数据处理软件 (10 .0版 )统计分析了 2 3只 (约 8～ 9月龄 )波尔山羊与唐山奶山羊杂交后代公羊的体尺、体重和肉用性能。结果表明 :(1)波尔山羊与唐山奶山羊杂交 F1 代体尺、体重与肉用性能指标的变异程度大于 F2 代 ,其中宰前重、胴体重、净肉重和胸宽四项指标变异程度在 F1 和 F2 代中都很大 ;(2 )杂交 F1 代、F2 代各项指标 t检验结果 ,除胸宽外其余指标差异显著或极显著 ;(3 )波尔山羊杂交后代中胸宽与各项指标间相关不显著 ,宰前重、胴体重、净肉重与体尺指标相关显著或不显著。     

细小泥沙粒径对迷宫流道灌水器堵塞的影响

为探明细小泥沙粒径对迷宫流道灌水器抗堵塞性能的影响,该文以内镶片式斜齿形迷宫流道灌水器为研究对象,应用类短周期堵塞测验方法对8种粒径小于0.1 mm的泥沙颗粒进行浑水测试。在此基础上,分析了泥沙粒径和含沙量对灌水器堵塞的影响,探讨引起灌水器发生堵塞时的敏感粒径范围与含沙量水平。试验结果表明:对于粒径小于0.1 mm的细小颗粒,含沙量是引起灌水器堵塞的主要原因,当浑水含沙量水平大于1.25 g/L时,影响尤其显著,呈正相关关系;粒径对堵塞的影响并不是单调的递增或递减,堵塞发生的敏感粒径范围在0.03～0.04 mm之间。试验结果有助于进一步提高含沙水源滴灌的应用水平。     

Maximum prey size estimation of longtooth grouper,Epinephelus bruneus,using morphological features,and predation experiments on juvenile cannibalism

In fish culture, cannibalism, which induces critical damage, is separated into two types: type I, which occurs in early larval stages when size heterogeneity is low; and type II, which starts in later larval and/or early juvenile stages following type I when size heterogeneity is high. In type II, the cannibal's maximum prey size is limited by its gape size relative to the prey fish body size. Ratios of prey to cannibal body size changes are associated with allometric factors and feeding behaviour with growth. In a previous study on grouper, the maximal prey size was estimated morphologically (i.e., the relationship between gape size and body height). This method is very simple and useful; however, it does not consider allometric factors and feeding behaviour changes; therefore, it probably causes a large estimation error. To overcome this, we present a new method for estimating maximal prey size to determine the size ranges for size grading of longtooth grouper, Epinephelus bruneus, juveniles using predation experiments. It is shown that grouper type II cannibalism is affected by two factors; in early juvenile stages by morphology and in later (TL over 50 mm) by prey size selectivity.