不同修剪措施对成龄‘绿岭’核桃抗腐烂病能力及树势的影响

为探索早实核桃成龄树的最佳修剪方法,以10年生早实核桃‘绿岭’为试材,测定了重回缩、拉枝、既重回缩又拉枝和放任生长4种不同修剪方式下核桃树体腐烂病的发病率、病情指数、叶片的氮、磷、钾含量、叶片叶绿素含量和根系活力。结果表明:重回缩、拉枝、既重回缩又拉枝和放任生长4种修剪方式的腐烂病发病率分别为1.77%、1.50%、1.30%和1.87%,以放任生长处理的最高,既重回缩又拉枝处理最低;4种修剪方式的病情指数分别为0.27、0.27、0.20和0.32;叶片全氮含量分别为2.68%、2.29%、2.69%和2.09%,以重回缩和既重回缩又拉枝处理的最高,放任生长的最低;叶片叶绿素a的含量分别为2.52、2.61、2.90和2.11 mg·g-1;根系活力分别为201.53、224.29、246.69和179.08μg·g-1h-1。     

重回缩与拉枝对成龄‘绿岭’核桃新梢数量、产量和根系活力的影响

为了确定早实核桃成龄树的适宜修剪方法,以10a生早实核桃‘绿岭’为试材,研究了重回缩、拉枝、既重回缩又拉枝和放任生长4种不同修剪方式的核桃树单株新梢发生数量、产量和根系活力。结果表明:在果实成熟期,重回缩、拉枝、既重回缩又拉枝和放任生长4种修剪方式的‘绿岭’核桃每株新梢发生数量分别为32.33条、22.67条、26.67条和12.67条,重回缩处理的新梢发生数量最多;单果重分别为11.16g、10.53g、12.22g和11.58g,既重回缩又拉枝处理的单果重最高;每667m2地产量分别为129.36kg、154.44kg、155.32kg和97.24kg,既重回缩又拉枝处理的产量最高,其次为拉枝;生长季末期,4种修剪方式的根系活力分别为193.22μg/(g·h)、181.53μg/(g·h)、231.65μg/(g·h)和150.60μg/(g·h),既重回缩又拉枝处理的根系活力最高。     

不同修剪方式对成龄‘绿岭’核桃光合作用的影响

为了确立早实核桃成龄树的适宜修剪方法,以10年生早实核桃‘绿岭’为试材,研究了处理1（重回缩）、处理2（拉枝）、处理3（既重回缩又拉枝）和对照 CK（不修剪）4种不同修剪方式对果实成熟期‘绿岭’核桃树冠内膛微域相对空气湿度、温度、照度、叶片净光合速率、蒸腾速率、气孔导度、细胞间隙 CO2浓度和叶绿素含量的影响。结果表明：8月中旬中午12：00,4种修剪方式的树冠内膛微域相对空气湿度和细胞间隙 CO2浓度以处理3的最低,分别为33.60％和233.00μmol/ mol;树冠内膛温度和最大光强均以处理3最高,分别为40.43℃和86800 lx;处理3的叶片最大净光合速率和蒸腾速率也最大,分别为8.22和3.33μmol/（m2·s）;气孔导度分别为0.19,0.21,0.24和0.16 mmol/（m2·s）;叶绿素 a 含量分别为2.41,2.52,2.79和1.17 mg/ g,其中处理3显著高于处理1和 CK。     

干旱胁迫对不同种源沙柳苗木水势和水分利用效率的影响

通过人工模拟方式对5个种源沙柳苗木进行干旱胁迫处理,研究干旱处理不同阶段苗木小枝水势日变化、叶片相对含水量、水分饱和亏缺、保水力及水分利用效率。结果表明:干旱胁迫下5个种源的沙柳苗木小枝水势和叶片相对含水量均下降,而水分利用效率在轻度干旱时呈上升趋势,随干旱胁迫的加剧而下降。干旱处理15天后,民勤种源的沙柳日平均小枝水势下降幅度最大为0.77 MPa,然后依次为达拉特旗0.57 MPa、盐池0.36 MPa、榆林0.25 MPa和乌审旗0.12 MPa,其中民勤种源的苗木在充分供水和干旱胁迫下小枝水势差异达到显著。干旱处理18天后叶片相对含水量分别下降:民勤1.68%、盐池7.03%、达拉特旗7.25%,榆林9.35%和乌审旗11.07%,水分饱和亏缺民勤<盐池<达拉特旗<榆林<乌审旗。结果表明,民勤种源的沙柳抗旱的能力较强,而盐池和达拉特旗沙柳苗木在受到水分胁迫时水分利用效率下降幅度较小,即水分胁迫对苗木干物质的积累影响较小,因此具有更高的经济价值。     

不同修剪方法对核桃幼树生长量的影响

为增强树势,提高抗性,以早实核桃"薄壳早"、"客龙早"、"珍珠核桃"、"川香"、"辽宁1号"和晚实核桃"清香"为试材,研究了不同修剪方法对不同品种核桃幼树生长量的影响。结果表明:(1)核桃幼树通过修剪以后,萌芽数量随修剪强度的增强而减少,但萌芽成枝力随修剪强度的增强而增强。(2)新梢伸长生长与粗生长均表现为重剪﹥中剪﹥轻剪﹥对照,且呈正相关,在6个核桃品种中,"薄壳早"的生长量最大。(3)叶片长度均表现为重剪﹥中剪﹥轻剪﹥对照,"薄壳早"和"客龙早"叶片长度增长明显。(4)核桃秋季栽植后,于次年春季及时修剪定干,修剪以重剪为主、中剪为辅,定干高度为30 cm~50 cm。     

不同灌水量对早实核桃水分利用的影响

为科学指导早实核桃水分管理,以8年生早实核桃‘绿岭’为试材,每次分别进行0,15,30,45和60kg/株5个水平的灌水处理,以常规管理园片的灌水量600 kg/(株·次)为对照,研究了不同处理对树干液流、水分利用效率、产量及果实品质的影响。结果表明:0~60kg/(株·次)5个处理及对照的4—9月平均土壤含水量分别为17.16%,18.11%,19.21%,20.30%,21.12%和21.88%;晴天各处理液流速率日变化曲线随着土壤含水量的减小由单峰变为双峰,且主峰的波峰变窄;瞬时最大液流速率及日平均液流速率均以60 kg/(株·次)或对照最大;各处理蒸腾速率、光合速率日变化均呈单峰曲线,水分利用效率日变化为双峰曲线,日平均水分利用效率以30kg/(株·次)最高,为1.54mmol/mol;随着土壤水分的减少,叶片水势日变化曲线由"V"型变为"W"型,日平均叶片水势以对照最高,为-1.23MPa;坚果品质随着土壤含水量的增大得以一定程度的提高,产量随着土壤含水量的增加先增大后减小,两者之间呈‘抛物线’状相关。早实核桃‘绿岭’的最适土壤含水量范围为20.01%~21.96%。     

不同树形油茶无性系发枝及光合特性研究

研究了不同树形油茶无性系的发枝和光合特性及对修剪处理的响应。结果表明:供试油茶无性系的树形指数介于0.72 1.33之间,树形指数大小顺序为长林175号长林40号长林53号长林4号长林46号,长林175号、长林40号无性系树形直立,长林4号和长林46号无性系树形开张,长林53号无性系居中。与树冠下层和内层相比,树冠上层的新梢发枝量、新梢长度、新叶比、叶片净光合速率(Pn)和叶片水分利用效率(WUE)较高,且随着树形指数增大,新梢长度、新叶比、叶片净光合速率(Pn)和叶片水分利用效率(WUE)总体上表现出先升高后下降的趋势,树冠不同部位的新梢发枝量、新叶比差异逐渐变大,新梢长度的差异减小,树形指数居中的长林53号无性系新梢长度、新叶比和叶片净光合速率(Pn)最高。油茶无性系冠层反射率(Re)的日变化表现出先下降后上升的趋势,冠层截获率(In)则表现出先升高后下降趋势,树形直立的长林175号无性系冠层反射率(Re)最高,冠层截获率(In)较低,树形开张的长林4号无性系冠层反射率(Re)较低,冠层截获率(In)较高。修剪处理显著降低了树形直立的油茶无性系新梢发枝量,并提高了树形开张的无性系新梢发枝量和树冠内层新梢长度;修剪处理还降低了冠层截获率(In),显著提高了冠层内部叶片的净光合速率(Pn)和水分利用效率(WUE)。研究结果为油茶栽培、修剪管理以及优良油茶资源的发掘利用提供了技术依据。     

火烧对幼树净光合速率和叶绿素荧光参数的影响

以水曲柳、核桃楸和蒙古栎3种幼树为研究对象,研究3种火烧处理对幼树新生叶的净光合速率、蒸腾速率、水分利用效率和荧光参数的影响.结果如下:1)对水曲柳、核桃楸和蒙古栎进行3种火烧处理T1、T2、T3(分别为:叶片被火烧、枝被火烧、茎被火烧)后,除了蒙古栎的T3处理新生叶净光合速率显著降低外,其他处理新生叶的净光合速率都显著提高.2)蒙古栎的T1、T2处理新生叶的水分利用效率显著降低,水曲柳的T1处理新生叶水分利用效率显著提高,核桃楸的3种处理新生叶的水分利用效率无明显变化.3)蒙古栎的T1、T2处理新生叶的蒸腾速率显著提高,水曲柳和核桃楸的3种处理新生叶的蒸腾速率无明显变化.4) 火烧后3种幼树新生叶的荧光参数的变化没有一定规律.研究表明火烧处理对幼树新生叶的净光合速率和叶绿素荧光参数产生不同的影响,这与幼树被火烧的部位和幼树本身抗火特性等因素有关.对一些树种进行适当的火烧会促进树木的生长.     

薄壳红杂交榛修剪反应规律研究

薄壳红杂交榛具有果个大、果壳薄、抗寒力强的特点.一些山区栽培量较多,但存在因整形修剪不当而造成树形紊乱、结实不多等问题.通过对1年生枝不同程度的短截、长放与拉枝,对多年生枝放任与回缩试验观察,结果表明,1年生枝中截、重截比长放、拉枝在萌芽率、成枝率、雌花芽数和雌花芽率方面明显多,长放、拉枝其萌芽率、成枝率、雌花芽量等方...     

北京4种常见园林植物的水分分级管理

用盆栽和蒸散皿分别对大叶黄杨、金叶女贞、铺地柏3种灌木和草地早熟禾进行控水试验,测定土壤干旱胁迫过程中植物的蒸腾速率,观测外貌变化,据此将4种灌草植物的水分管理分为特级、一级和二级.特级为充分供水,植物生长旺盛,灌木和草坪的土壤水势分别为-0.24～-0.08 MPa和-0.07～-0.02 MPa;一级为轻度缺水,植物蒸腾减弱,但生长正常,外观未见明显的干旱胁迫症状,灌木和草坪的土壤水势分别为-0.48～-0.24 MPa和-0.18～-0.07 MPa;二级为中度缺水,植物出现短暂萎蔫,但对观赏效果影响不大,灌木和草坪的土壤水势分别为-1.41～-0.48 MPa和-0.78～-0.18 MPa.植物水分分级管理有利于提高水分利用效率,节约水资源.     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.