Deciduous trees affect small-scale floristic diversity and tree regeneration in conifer forests

Abstract

There is a growing interest in the effects of deciduous trees on biodiversity, soil processes and long-term productivity in boreal, conifer-dominated forests. This study investigated whether individual birch trees allowed to grow to maturity in the coniferous forest can have a local effect on floristic richness and regeneration of tree saplings. The ground vegetation was compared in 2?m radius plots around the stem under the canopies of matched conifer–deciduous trees in a mature, conifer-dominated forest, and included in the analysis variables that could potentially mediate the tree effect (soil pH, cover of lichens, bryophytes, leaf and needle litter). The field layer vegetation was more species rich under birch (Betula pendula and B. pubescens) than under conifers (Picea abies and Pinus sylvestris), and several vascular plant species (including saplings of tree species) occurred more often under birch than under conifers. However, when the effect of the number of subordinate trees was taken into account the difference between birch and pine was not significant. The number of tree regenerations (saplings) was lowest under pines, but did not differ between spruce and birch. There were no effects of the canopy species on soil pH or on cover of lichens and bryophytes. The difference in diversity may be caused by the different effects of leaf and needle litter, and it is also likely that canopy structure has an influence via interception and throughfall and by affecting the light and microclimate.     

光皮桦生长量分析及与杉木混交技术研究

以光皮桦(Betula luminifera)为基础,研究光皮桦与杉木之间进行混交的可行性。运用数理统计的方法从树高、胸径和材积等方面阐述二者混交的优点和可能性,并且通过南平市郊教学林场的试验得到证实。     

秦岭华山松红桦混交林与纯林生长调查

通过研究,17a生华山松混交林,树高、胸径和材积的总生长量均比同期纯林要大,树高、胸径的连年生长量下降趋势比纯林慢,材积连年生长量上升比纯林快.8a生华山松仅树高定期生长量比纯林大,胸径与材积定期生长量不及纯林.混交林的叶量、叶面积及单位重量的叶绿素含量均比纯林高.华山松营养根呈簇状疏散分布,无明显主根,根系分布浅而细根密集,根系总长度比纯林大20％以上,种间根系无互相排斥现象.     

德宏州西南桦人工林的生物多样性分析

生物多样性的保持是人工林发展过程中一个倍受关注的焦点问题,本研究选择德宏州的西南桦人工林作为研究对象,在样地调查的基础上,统计分析西南桦人工林的生物多样性状况。结果表明,调查的10块典型样地中,植物种类44－124种。西南桦人工林的群落结构包括单层纯林、单优多层多种林、混交林和林农作物间作等不同类别,并在人工林内记录到部分国家级和省级保护植物种类。通过与德宏州铜壁关自然保护区的天然西南桦林和同处云南热区的西双版纳普文试验林场西南桦人工林相对比,表明德宏州营建的西南桦人工林显现出较好的生物多样性恢复能力。     

东北白桦遗传效应分析与优异群体选择

[目的]系统分析了东北白桦家系子代树高、胸径和冠幅3个性状的变异程度和生长规律,筛选并推荐优异群体。[方法]以张广才岭和老爷岭自然分布的东北白桦为研究对象,采取固定标准地连续定位测定和临时标准地随机调查点面相结合的方法,系统分析了林分树高和胸径的生长动态规律,综合评价了数量性状的遗传效应。[结果]将东北白桦适生地域的立地条件划分4个立地级,各立地级的生长进程大致经历速生期、均稳生长期和缓慢生长期3个阶段,且不同立地级和不同生长阶段的林分生长量存在较大差异,但生长动态规律却趋于一致。群体间树高、胸径、东西冠幅和南北冠幅的变异幅度较大,差异极显著;家系遗传能力强,遗传增益较大,家系遗传力分别为0.558 2、0.762 3、0.652 3和0.721 9,遗传增益分别为8.09%、17.67%、14.56%和17.53%。[结论]综合各项评价指标,确定MES(帽儿山)群体为优异群体,群体内个体间的变异较小,生长稳定,且生长势强健,遗传效应明显。     

枫桦树枝和树根木质部非结构性碳水化合物的地区差异

以中国伏牛山脉木札岭和小兴安岭帽儿山2个区域的散孔材树种枫桦(Betula costata)为对象,研究落叶后树枝和树根木质部中非结构性碳水化合物(NSC)含量的地域差异。结果表明,帽儿山枫桦树根和树枝的可溶性糖与淀粉含量均>木札岭;2个区域枫桦树根的可溶性糖与淀粉含量均>树枝。枫桦非结构性碳水化合物的地区差异以及组织差异是树木在休眠期应对环境变化特别是温度变化的结果。     

荷斯坦牛抗热应激候选基因S441的检测

本试验以S441为奶牛假定抗热应激候选基因。在核心母牛场湖南省奶牛原种场测定不同世代的种母牛213头,在核心公牛场湖南省种公牛站,以及北京、上海、南京、安徽等地测定种公牛46头,共检测出具有S441基因的母牛27头,检出率为12．7％（27／213）,公牛15头,检出率为32．6％（15／46）。在湖南省奶牛原种场,有、无抗热应激候选基因的母牛在热应激期间的产奶量分别为1736．75kg和1528．63kg,产奶量下降率分别为3．51％和22．56％,产奶量差异不显著（P〉0．05）,但产奶量下降率差异显著（P〈0．05）,基本肯定该基因为抗热应激候选基因。     

环境温度对阔叶慈姑发育的影响

研究表明,环境温度为影响阔叶慈姑发育的主导因素.在相同的栽培条件下,植株经过8周的5～15℃低温环境处理,可于春季里分化花芽,当绽蕊后,部分植株能够结出果实.没有经低温处理的阔叶慈姑始终未见花芽分化,依然保持着营养生长状态.     

Distribution of ectomycorrhizas and ectomycorrhizal fungal inoculum with soil depth in a birch forest

The distributions of ectomycorrhizas and ectomycorrhizal fungal inoculum with soil depth (0–45 cm) were determined in a 40-year-oldBetula platyphylla var.japonica forest. Mycorrhizal and non-mycorrhizal fine roots were measured in each soil core sample that was collected at soil depths of 0–5, 5–10, 10–15, 15–20, 20–25, 30–35, and 40–45 cm. The ectomycorrhizas were mainly distributed (>50%) in the top soil (0–5 cm) of organic forest floor horizons. Below 5 cm the quantity of ectomycorrhizas decreased sharply. The percentage of fine roots which were ectomycorrhizal gradually declined with the depth of soil. The ectomycorrhizal fungal inoculum was evaluated by a bioassay method, measuring the lengths of the entire root system and of the ectomycorrhizal roots of birch seedlings planted in each soil sample. The soil samples were collected from 0–5, 10–15, 20–25, 30–35, and 40–45 cm depths of the soil profile. Ectomycorrhizal formation on birch seedling roots in the bioassay was high in both the soil depth intervals 0–5 cm and 10–15 cm, while the amount was lower in the soil depth interval from 20–45 cm. The results of these investigations show that the amount of the ectomycorrhizas in soil, and the ectomycorrhizal fungal inoculum potential as determined by bioassay, are not always consistent with each other.     

白桦组培再生系统的研究(Ⅱ)——影响因素及培养程序

在“白桦（Ｂｅｔｕｌａｐｌａｔｙｐｈｙｌａｓｕｋｓ）组培再生系统的研究（Ⅰ）”的基础上,以展叶顶芽、休眠腋芽和种子为最初外植体,通过初始培养获得无菌苗后,选取无菌苗的不同部位作外植体,如：茎节、嫩枝、愈伤组织等,经过诱导培养、分化培养及生根培养,形成再生植株。研究了培养基、激素种类及浓度、无性系、外植体类型、蔗糖浓度对诱导及生根的影响,提出白桦组培的最佳条件及程序。最佳无性系的一个外植体,经三次继代培养增殖达３０００株,最佳培养基上的生根率达９５％以上,Ⅰ、Ⅱ级苗的移栽成活率达９０％。