11-year-old Betula alnoides plantations for density trial with five planting spacing treatments were investigated through stem analysis at Pingxiang City, Guangxi, to assess the effects of initial density on tree growth process. The results showed that the initial density had no remarkable effects on tree height growth and stem shape index, while there were significant differences in diameter at breast height (DBH), individual tree volume and stand volume among treatments of initial density, and the stand volume of treatment of 2 m×3 m was significantly higher than that of other treatments. The fast growing period of DBH trended to increase with the decrease of initial density, the DBH growth commenced to decrease since the sixth year after planted under the 1.5 m×2 m treatment, while it decreased mostly since the eighth year under other treatments, indicating that thinning should be conducted at the sixth year for 1.5 m×2 m treatment, and at the eighth year for 2 m×3 m and 3 m×3 m treatments, while for other treatments, it was delayed with the decrease of density. All the current and mean annual increment curves of tree height crossed when 5-6 years old, and did not reach quantity mature until 11 years old for all density treatments, while remarkable differences of the current annual increment of individual tree volume were seen among treatments. Taking factors such as growth performance, stand volume, and use efficiency of forest land, etc. into consideration, 2 m×3 m was determined as the most optimum planting density in the present study.

Betula alnoides Buch.-Ham. Ex D.Don is a fast-growing and precious tree species in tropical and warm subtropical regions. The wood borer damage has recently been one of key factors limiting the large-scale expansion of B. alnoides plantations. A trial including 26 provenances and 322 families were established at Shaoguan State-owned Forest Farm in northern Guangdong Province, which were suffered from heavy damage of wood borers within two years after planted. The growth performance and resistances to wood borers of B. alnoides were investigated for the purpose of early selection of germplasm. The results showed that there were significant differences among provenances in height and base diameter (PB. alnoides. Anoplophora chinensis (Förster) was the principal species of wood borer, which damaged trunk within the height of 20 cm above stem base. 1-5 larva of this species were found on each tree attacked, and the attack rate by A. chinensis was significantly and positively related to the diameter growth (P＜0.05). The attack rate showed no significant difference among provenances (P＞0.05), and the mean attack rates for one-year-old and two-year-old B. alnoides trees were 48.21% and 36.27%, respectively. Early selection of B. alnoides provenance was carried out based on its growth performance and the attack rate by the wood borers. These findings could be contributive to understand the occurrence of A. chinensis, protect from its damage, and provide evidences to select germplsm of B. alnoides with good growth performance and strong resistance to A. chinensis in northern Guangdong and surrounding areas with similar environment.

西南桦是我国热带、南亚热带地区的一个优良乡土阔叶树种,具有重要的生态和经济价值,目前推广面积已逾5万hm2,且仍呈良好的发展势头,已成为该地区造林面积最大的乡土阔叶树种。本文从生物学生态学特性,栽培技术,种质资源的收集、保存与应用以及人工林生态效益等方面回顾了我国以往西南桦的研究工作,评述了西南桦人工林大规模发展过程中出现的问题,并就其解决办法提出建议,据此提出了未来优先研究方向。

应用各种浓度蔗糖、蔗糖+硼酸培养基于系列温度下开展西南桦花粉萌发对比试验,研究了蔗糖、硼酸浓度对西南桦花粉离体萌发的影响,筛选出适合西南桦花粉萌发培养基的适宜组分和适宜培养温度,并应用4个单株的花粉对其萌发特征进行了初步研究。结果表明:蔗糖基本培养基上添加硼酸能够显著促进西南桦花粉萌发;西南桦花粉离体萌发的合适培养基为15%蔗糖+ 200 mg·kg-1硼酸,适宜培养温度为30 ℃;在此条件下培养3 h后花粉萌发率基本稳定,培养7 h后花粉管长度也趋于稳定。

从花序、单株、林分水平上对广西靖西县的一个土石山生态交错区内不同立地条件下西南桦的开花物候进行了观察和比较。结果表明:西南桦雌、雄花序开花持续时间为2 3 d,同一植株相同部位的雌花序较雄花序晚开花约14 d;其单株开花持续时间为4 28 d,开花同步性指数为0.160 0.259,绝大多数植株的冠层开花顺序依次为下层、中层和上层,土山和石山立地间单株开花持续时间和开花同步性均差异不显著 (P＞0.05);在林分水平上,西南桦开花持续时间为40 58 d,两种立地间差异不显著。

The survey was conducted on the growth of 10-year-old Manglietia glauc and their soil condition in different slope position from three sites: the original place Bào Yên of Lào Cai, Vietnam and the introduction places Baiyun and Shaoping in Pingxiang, Guangxi, China. It was found that the growth of M.glauc on different sites showed down slope>middle slope>upper slope. Comparing the down/upper slope with upper slope in different sites, the DBH, tree height and volume growth rose by 30.35%, 49.00%; 34.78%, 56.03%; 122.97%, 236.15% in Baiyun, 30.07%, 53.44%; 39.00%, 54.54%; 125.09%, 245.76% in Shaoping, and 19.75%, 35.08%; 11.08%, 27.49%; 56.58%, 119.21% in Bào Yên, respectively. Baiyun and Shaoping located in south subtropical zone, had higher effect on the growth of M. glauc than that in its original place Bào Yên located in north tropical zone. The effect of soil condition on M. glauc stands showed the same regularity. This implied that M. glauc is a soil sensitive species. Result of variance analysis showed that slope position on the growth of M. glauc reached a highly significant difference(PM. glauc was alike in the same climatic zones, but differed in the different climatic zones, the growth in the south subtropical zone was higher than that in the north tropical zone, the order of the growth linear gradient was the same as the trend of the effect on slope in different climatic zones. It is showed that the degree of effect on slope in M. glauc growth varied under different habitat condition.

目的 通过造林试验研究西南桦无性系早期生长对氮素施肥的响应，揭示西南桦幼林氮素需求规律及无性系间差异。 方法 以4个西南桦无性系作为试验材料，设置0、50、150、250、400、550、700 g·株⁻¹ 7个处理，开展氮素（尿素）施肥试验，调查保存率、生长（树高、胸径、枝下高和冠幅）、干形（径高比、树干通直度及主干分叉情况）等性状，分析这些性状在施肥处理间、无性系间的差异及二者的交互作用。 结果 造林后第5年，对于4个参试无性系而言，其保存率随施氮量的增加无明显变化规律，树高、胸径和冠幅整体上呈现“增加-稳定-减少”的变化趋势，径高比、树干通直度和主干分叉情况亦渐趋优良，但各施肥处理间差异并不显著（P>0.05）。各无性系间生长和干形均差异显著，无性系C3的各性状总体上表现最优，其保存率、树高、胸径、枝下高、冠幅、主干分叉及通直度比最差的无性系C2分别高34%、42%、32%、16%、25%、22% 和19%，氮肥和无性系的交互作用不显著。 结论 综上所述，施氮肥并不影响西南桦无性系造林后早期生长和干形质量，无性系间生长和干形差异显著，其中，无性系C3的生长和干形表现最佳。

目的 研究西南桦天然林物种组成和多样性特征，为西南桦天然林生物多样性保护及西南桦人工林近自然经营提供科学依据。 方法 在云南省德宏州瑞丽派罗山1958年皆伐后形成的天然次生林(PLS)和芒市桦桃岭刀耕火种1967年丢荒地形成的天然次生林(HTL)内分别设置总面积为10 000 m² 和5 000 m²的样地开展物种多样性调查。运用Simpson优势度指数、Shannon-Wiener多样性指数和Pielou均匀度指数，分析乔木层、灌木层和草本层物种组成和多样性，并对林分整体及重要值 > 5.00%的乔木层主要树种绘制径级分布图。 结果 PLS林分内无绝对优势种，树种润楠的重要值最大（14.76%），其次为西南桦（9.55%）；HTL林分，树种西南桦的重要值最大 (26.47%)，在林分内占据绝对优势。PLS林分各林层物种丰富度 (草本层除外)、Simpson优势度指数、Shannon-Wiener多样性指数和Pielou均匀度指数均高于HTL，但物种优势度低于HTL，物种分布更均匀。不同林层间Simpson优势度指数、Shannon-Wiener多样性指数和Pielou均匀度指数均以灌木层最高，而物种丰富度则乔木层最高。2种林分的径级结构均呈倒J形分布，重要值 > 5.00%的主要树种除西南桦分布在中大径级外，均集中分布在中小径级。 结论 PLS林分较HTL更接近演替后期，二者均属于稳定的群落类型。研究结果为西南桦天然林保护以及人工纯林近自然化改造和经营提供理论依据和技术参考。

以石英砂为基质,采用国际上通用的培养液配制方法,研究了酸、铝胁迫(各设5个处理)对马尾松种子萌发及芽苗生长过程的影响,结果表明:中强度的酸、铝胁迫对发芽势及种子萌发过程的影响不显著,而对芽苗根、茎长及根、茎、叶的干质量、鲜质量等生长指标具有明显的抑制作用;芽苗生长指标随pH值(5. 5～3. 0)的下降,先缓慢上升后下降,随铝离子浓度的增加呈下降趋势; pH值4. 5～5. 0时,芽苗生长最好;根受酸、铝胁迫影响最大,是反应最敏感的部位,茎、叶次之;根鲜、干质量占总量的比例随酸、铝胁迫的加剧先上升而后降低,茎、叶的鲜、干质量占总量的比例变化较小;当pH值低于4. 5,铝离子浓度达到50 mg·L-1时,即可对马尾松芽苗的生长产生明显的抑制作用。