湿地松,火炬松木材密度变异和优树选择的研究

研究了影响湿地松、火炬松木材密度变异的主要因素；探讨了对木材密度进行综合选择的选优方法，选出湿地松，火炬松优良单株７３株。     

Species richness and biomass of understory vegetation in a Eucalyptus globulus Labill. coppice as affected by slash management

The aim of this study was to assess the effect of different slash management practices on understory biodiversity and biomass in Eucalyptus globulus coppices in Central Portugal. The experiment consisted of four treatments: (a) removal of slash (R), (b) broadcast over the soil (S), (c) as in S but concentrating woody residues between tree rows (W) and (d) incorporation of slash into soil by harrowing (I). Understory vegetation was surveyed during 1–6, 9, and 10 years, the proportion of soil cover by plant species estimated, and diversity and equitability indexes determined. Above ground understory biomass was sampled in years 2–6, 9, and 10. The highest number of species in most years occurred in plots where slash was removed. Differences between treatments in the proportion of plant soil cover were never significant, whereas differences in diversity index were only occasionally significant and apparently related to the number of species. Thus, differences in the equitability index were not significant. Understory biomass did not decrease during the rotation period, and was usually highest in R and I, and lowest in S, but not significantly different. At the end of the rotation period, understory biodiversity indices and biomass were apparently independent of slash treatment.     

高产脂湿地松引种评价及优树选择

为了选择高产脂、高产材的湿地松优良品系,对从美国引进的10个湿地松高产脂品系的生长与产脂性状进行了综合分析评定,结果表明品系间生长指标及产脂量表现差异显著,其中表现最优的品系是204和215。另外,还从湿地松高产脂试验林中选择出生长与产脂均佳的15株优树,其单株材积比林分平均单株材积大20%以上,单株产脂量比林分平均值大200%左右。     

Fallow enrichment with pada (Macaranga denticulata (Bl.) Muell. Arg.) trees in rotational shifting cultivation in northern Thailand

Shifting cultivators in Thailand widely attribute the maintainance of crop productivity to pada (Macaranga denticulata (Bl.) Muell. Arg.), rotation cycles having become much shorter than the customary 10–20 years. This paper examines the use of pada in a 7-year rotation on an acid soil with low available soil P (2–4 mg kg^–1 by Bray II). Dense pada patches in 7-year-old fallow averaged 43 tons ha^–1 of above ground biomass, 20% more than sparse patches. The biomass in dense pada contained disproportionately more P, K, Ca and Mg (34%, 92%, 80% and 107% more, respectively) than in sparse pada patches. Slashing and burning 7-year-old fallow with dense pada produced a subsequent rice yield that was three time that with sparse pada. Rice grown after dense pada had been slashed and burned after three years yielded less than one third of that after a full 7-year rotation. It is, as yet, unclear how rice yield in dense pada patches is enhanced in the full 7-year rotation. Nutrient concentrations in the mature rice were generally either the same or higher in the sparse than dense pada patches. In dense pada patches rice accumulated twice to four times as much nutrients as in sparse pada patches, and a much larger fraction of the nutrients was stored in the fallow. Uptake of nutrients in the sparse pada patches may have been limited by some factor that either governs availability of the nutrients released by burning or depressing rice growth and so its nutrient demand.This revised version was published online in November 2005 with corrections to the Cover Date.     

森林采伐迹地清理方式对迹地土壤理化性质的影响

采伐剩余物迹地清理是森林作业的重要组成部分之一。本文通过在黑龙江省带岭林业局野外迹地取样和实验室分析 ,对森林采伐剩余物迹地清理方式对迹地土壤的影响进行了初步研究。结果表明 ,迹地清理方式对作业迹地土壤理化特性产生一定程度的影响 ,进而影响森林采伐后的迹地天然更新与苗木生长质量。研究结果还表明 ,火烧和堆积方法对迹地土壤物理特性影响不十分显著 ,但对土壤的化学特性影响十分显著 ,尤其是火烧迹地土壤养分流失程度差异比较显著     

Does harvest residue management influence biomass and nutrient accumulation in understory vegetation of Eucalyptus globulus Labill. plantations in a Mediterranean environment?

The effect of harvest residue management options on biomass and nutrient accumulation in understory vegetation, as well as the contribution of understory to nutrient cycling, were assessed during the early rotation stage of a Eucalyptus globulus Labill. plantation in Central Portugal. The effects of residue management options on early tree growth were also evaluated. Treatments established at the time of plantation and replicated four times in a simple completely randomised design included removal of harvest residues (R), incorporation of residues into the soil by harrowing (I) and maintenance of residues on the soil surface (S). Understory biomass was sampled in the spring between 2002 and 2006, and every 2 months between March 2006 and March 2007. The latter samples were stratified into biomass, standing dead mass and litter for net above ground primary production (NAPP) assessment. Samples were oven dried, weighed and analysed for nutrient contents. Results showed that understory standing biomass strongly increased from the first to the third year and that quantities of nutrients accumulated in ground vegetation followed similar patterns between the three treatments. Nutrient accumulation in ground vegetation was greater than in tree biomass until at least the second spring after plantation. Bimonthly sampling revealed treatment R to have the largest amounts of standing biomass, standing dead mass, litter and nutrient immobilisation, while treatment S exhibited the lowest values. NAPP (4th–5th year) was 639, 511 and 362 g m⁻² year⁻¹, respectively in R, I and S, corresponding the standing biomass increase to 277, 183 and 143 g m⁻² year⁻¹. These values are comparable to those observed for litter fall in similar stands (age and tree density) in the same area. The contribution of ground vegetation to nutrient accumulation in the system was unaffected by harvest residue management methods, but further research is necessary in order to establish whether slash management options influence long term tree growth and vegetation dynamics.     

Oleoresin yield of Pinus elliottii in a subtropical climate: Seasonal variation and effect of auxin and salicylic acid-based stimulant paste

The extraction of induced oleoresin from Pinus elliottii through bark streaking supplies products to the food, pharmaceutical and chemical industries. Resin flow is a typical defense response in conifers and is controled by various environmental factors. Although many studies have focused on oleoresin production in temperate forests, particularly in response to bark beetle attacks, relatively little is known about the physiological regulation of sustainable resin exudation in subtropical planted forests, in which commercial exploitation of this product is favored by the absence of significant pest insect populations. Therefore, the annual oleoresin yield of approximately 2660, 28-year-old trees from different sites was monitored for two consecutive years in southern Brazil. Plain wounding and wounding followed by application of a commercial resin stimulant paste containing the ethylene precursor 2-chloroethylphosphonic acid (CEPA) were used as reference treatments. Different concentrations of auxin, paraquat, yeast extract, and salicylic acid (isolated or in combination with CEPA) were also tested. Higher resin yields were associated with spring and summer, whereas winter had lower but significant yields. Auxin and salicylic acid stimulated the production of oleoresin relative to commercial paste in at least one concentration. Replacement of CEPA with auxin or salicylic acid yielded equivalent oleoresin production, indicating a comparable or complementary effect of these molecules in the process, as well as having implications for new stimulant paste formulations.     

The influence of fire severity,serotiny, and post-fire management on Pinus pinaster Ait. recruitment in three burnt areas in Galicia (NW Spain)

The effect of fire severity and post-fire management on Pinus pinaster recruitment was evaluated in three burnt areas in Galicia (NW Spain) exhibiting different levels of serotiny. Three sites were sampled, each of which had two of the following levels of fire severity: combusted crown, scorched crown and unaffected crown. Viable seed rain was closed related to the canopy cone bank and stand serotiny level. Soil burn severity also favoured seed dispersal. Relative germination success increased with soil burn severity whereas initial and final seedling density depended on both the canopy cone bank and soil burn severity. A positive influence of fire severity on the final/initial seedling density and final density/total seed dispersal ratios was also observed.     

湿地松制造中密度纤维板工艺的研究

以湿地松（Ｐｉｎｕｓｅｌｉｏｔｉ）为原料制造中密度纤维板工艺的研究,采用正交试验方法,分析了施胶量、板坯含水率、热压温度及热压时间对中密度纤维板物理力学性能的影响。试验结果表明：板坯含水率及热压时间对试验板质量影响较大,热压温度及施胶量的影响较小。采用适宜的工艺,即板坯含水率在１０％、热压温度１６５℃、热压时间５ｍｉｎ,施胶量可以降至８％～９％,试验板的各项物理力学性能可以达到国标特级品的要求。     

造林密度对湿地松人工林木材性质的影响效应

湿地松4种初植密度（900、1350、1800、2700株/hm^2)林分间树高、胸径、材积、蓄积量和单位面积上1-2级优势木数理等因子存在着显著的差异。初植密度对其人工林木材管胞解剖特征、化学成份含量、干缩性状和木材力学性能有一定的影响，但没有达到显著的程度。稀植的林分木材纵向干缩大、差异干缩大。1800、1350株/hm^2的林分，其木材管胞长、长宽比大、微纤丝角小，干缩特性适中，力学强度较高，适于培养建筑结构用材。1800株/hm^2林分单位蓄积量大，管胞长、长宽比大、纤丝角小，纤维纱与综纤维素含量高，木素含量低，适于培育纸浆材。