一年生云南松苗期生长动态规律研究

基于1a生云南松苗高和地径的定株、定期观测数据,采用Logistic方程对其生长过程进行拟合,根据其中参数分析生长动态规律。结果表明:(1)地径生长符合"S"型曲线,呈现"慢-快-慢"节律;苗高生长符合双"S"型曲线,呈现"慢-快-慢-快-慢"节律。(2)根据生长量变化规律,苗高生长过程可分为出苗期、速生期Ⅰ、过渡期、速生期Ⅱ和生长后期;地径生长过程可分为生长前期、速生期和生长后期。(3)苗高两个速生期为23～34d和89～150d,两个速生点时间为第28天和第120天;地径速生期为141～211d,速生点时间为第176天。(4)苗高、地径的累积生长量均在速生期最大,分别占理论上限值的58.37%和57.85%。(5)苗高、地径的生长表现出异速现象,150d之前苗木主要进行高生长、150d之后则以地径生长为主。     

重茬和品种差异对豫西夏大豆“症青”现象的影响

豫西地区夏大豆发生"症青"现象可导致大豆严重减产甚至绝收,但引发这种现象的原因尚不明确,防治手段也缺乏针对性。为了有效防治豫西夏大豆"症青"现象,采用裂区试验,研究了大豆重茬和品种差异对夏大豆"症青"现象的影响。结果表明,重茬地块大豆"症青"株率平均为31.70%,正茬地块大豆"症青"株率平均为1.01%,且两者差异达极显著水平。在重茬条件下,25个大豆品种均有一定程度的"症青"现象发生,"症青"株率变幅为8.6%～58.7%,品种间差异极显著。在正茬条件下,所有大豆品种的"症青"现象均较轻,56%的品种"症青"发生率不足1%,且品种间差异不显著。由此可见,重茬导致大豆"症青"现象发生或者加重,生产上应进行合理的轮作倒茬防治大豆"症青"发生,同时选择对"症青"现象抗性较好的大豆品种。     

陕甘山桃对根癌病的抗性评价

为评价陕甘山桃(Prunus davidiana var.potaninii Rehd)对根癌病的抗性,以实生钵苗为试材,采用人工接种的方法研究了其对根癌土壤杆菌(Agrobacterium tumefaciens Conn)和发根土壤杆菌(A.rhizogenes Conn)的抗性。结果表明:接种后60d,接种根癌土壤杆菌的陕甘山桃的株最大瘤径范围为0～10.1mm,平均瘤径2.7mm,接种发根土壤杆菌的株最大瘤径范围为0～11.6mm,平均瘤径3.0mm,根据抗性评价标准判定陕甘山桃群体高抗根癌土壤杆菌和高抗发根土壤杆菌。但陕甘山桃对根癌土壤杆菌和发根土壤杆菌的抗性存在广泛的的株间分离现象,均分离为免疫、高抗、中抗、低抗、感病和易感病6种类型,对根癌土壤杆菌免疫、高抗、中抗、低抗、感病和易感病型植株分别占群体总数的28%、33%、19%、13%、6%和1%,对发根土壤杆菌免疫、高抗、中抗、低抗、感病和易感病型植株分别占群体总数的16%、46%、15%、13%、8%和2%。陕甘山桃是优异的抗根癌病种质资源。     

北京山区主要针叶林可燃物空间连续性研究——可燃物水平连续性与树冠火蔓延

以北京市山区主要针叶林(侧柏林和油松林)为研究对象,通过对林分树冠可燃物的负荷量、结构、理化性质及火行为特征进行分析,建立了树冠可燃物水平连续性指数D和评估等级,并对侧柏林和油松林的可燃物水平连续性进行评估与分析。研究结果显示:可燃物负荷量对火蔓延速度的影响显著,随可燃物负荷量增大,火蔓延速度增加,增加幅度受到可燃物紧密度的影响;风速对火蔓延速度的影响十分明显,对可燃物水平连续性的影响程度大于坡度;相同风速下,油松林树冠火的蔓延速度大于侧柏林;侧柏林D的平均值为1.470(高度连续),油松林D的平均值为0.933(中度连续),侧柏林树冠火蔓延的危险性大于油松林,一旦发生火灾,侧柏林比油松林更容易形成大面积高强度树冠火;D的主要影响因素是针叶树种树冠负荷量及其空间分布,以及风速和坡度及其协同作用。     

Timing and intensity of precommercial thinning in Pinus sylvestris stands

The effects of timing and intensity of precommercial thinning were studied in three Scots pine artificially regenerated stands on Vaccinium forest sites in southern Finland. A two-level factorial design (3×3) was used in each stand: thinning at dominant height of 3, 6 and 9 m to 1000, 1600 and 2200 stems ha^?1. The effects of the treatments were analysed after a period of 23–25 yrs when the dominant height was 14–15 m. Early thinning resulted in the highest standing volume and amount of merchantable wood, and also in slightly accelerated height development. Thinning to 1000 stems ha^?1 caused a considerable production loss, but there were no differences between the densities of 1600 and 2200 stems ha^?1. Branches became thicker after early thinning, but the differences between the treatments were negligible for crop trees. Crown ratio was lowest as the result of early or moderate thinning (2200 stems ha^?1).     

整地措施及苗木类型对麻疯树生长的影响研究

麻疯树耐旱、耐瘠薄,广泛分布于海拔1 500 m以下的干热河谷地区,不仅是干热河谷地区的水土保持树种,也是开发利用前景较好的能源植物。受立地条件及栽培管理措施的影响,双柏县麻疯树座果率低、单株产量小,产量极不稳定。2006～2011年在双柏县大沙坝进行不同整地措施和苗木类型造林试验,结果表明,科学整地、科学选择苗木及合理密植可促进麻疯树速生、丰产和稳产。     

Variation in sapwood thickness of Picea abies in Estonia depending on the tree age

Variation of sapwood thickness in terms of a linear measurement and a growth ring count with reference to the age was studied in dominant and suppressed Norway spruce trees. In the trees of both dominance classes the sapwood thickness increased in absolute terms, while its relative portion decreased with the age of the trees growing. Great differences were found in sapwood thickness between dominant and suppressed trees in linear measurements but not in the number of sapwood rings or the rate of the heartwood formation. The number of sapwood growth rings reached 40 in old trees. The index of vigour differed considerably in dominant and suppressed trees.     

Canopy density in stands of Picea abies and Pinus sylvestris after different thinning methods

Altogether 82 plots (261 estimations) of Picea abies (L.) Karst, and 193 plots (360 estimations) of Pinus sylvestris (L.) stands were estimated by a vertical tube. The “crown free projection”, CFP, of stands thinned in three methods with different thinning grades was measured: unthinned, heavily and very heavily thinned, heavily thinned delayed first thinning, extra heavily thinned and thinned from the top. Basal area (m²ha^?1) density (stems ha^?1) and diameter sum (m ha^?1) were plotted against CFP. Basal area was the best practical measure of stand in this study. Generally Scots pine stands have higher CFP and the curves are steeper than in Norway spruce stands. Depending on the grade of thinning, heavily and very heavily thinned spruce stands, delayed first thinning included, have CFP values of 10–15% and stands thinned from the top, 20–40%, compared with 30–80% and 30–60% respectively in pine stands. Extra heavily thinned stands have the highest CFP, 20–80% in spruce and 50–90% in pine stands. The CFP levels after thinning are too high in pine stands for avoidance of sucker and sprout production of aspen and birch. In dense Norway spruce stands thinned from the top or heavily and very heavily thinned, the CFP values are low enough (≤30%) to diminish the production of suckers.     

Rooting Success of Cuttings from Young Picea abies in Transition to Flowering Competent Phase

Abstract

Abundant flowering occurred in a central Swedish trial with 10-yr-old Picea abies L. (Karst.) cuttings, taken on 4-yr-old seedlings. Large deviations in cone-set between clones were assumed to reflect different stages in transition from juvenile to flowering competent phase. Rooting success and first-yr growth performance (leader length, leader origin and plagiotropic growth) were studied on cuttings originating from the upper and lower parts of the crown in 15 clones with heavy cone-set and 15 clones without cones. Twigs from the lower part of the crown had a significantly higher rooting percentage. Cone-set did not have an effect on any of the variables analysed. The results suggest that flowering ability and rooting capacity are independent age-related processes, implying that selection for high rooting capacity in clonal forestry does not reduce flowering competence. The results will have a great impact on breeding of P. abies, since both early flowering and high rooting ability are important traits for reducing the turnover time of the breeding cycle.