Growth of Douglas-fir （Pseudotsuga menziesii （Mirb.） Franco） in the Region of Yundola Training and Experimental Forest Range, Bulgaria

The aim of the article was to study the growth of Douglas-fir plantations in the region of the Training Experimental Forest Enterprise, Yundola （Central South Bulgaria）. The study sites were three Douglas-fir plantations, ranging between 50 and 55 years of age at altitudinal range between 1,400 m and 1,600 m above sea level （masl）. The mean height, diameter at breast height, site class, stem volume as well as the mechanical resistance （H/D ratio） of Douglas-fir were measured for each plantation. The results showed that Douglas-fir had the best height growth of the studied plantations on slope facing South at altitude 1,600 masl and Douglas-fir with age 55 years old reached a mean height of 32.4 m. The average diameter at breast height of the studied plantations reaches approximately 30 cm, which shows that they are suitable for large scale wood harvesting. The average stem volume of Douglas-fir in the observed plantations up to age of 55 is within the range of 400-600 m3/ha, with an average annual volume increment from 7 m3/ha to 12 m3/ha each year. The high index of mechanical resistance （H/D ratio） indicated a risk for abiotic damages, which implicated the need for the immediate implementation of felling.

悬铃木开花结实生物生态学特性研究 Ⅱ花芽分化随胸径变化的规律性

作者调查了悬铃木花芽分化随胸径变化的规律 .结果表明 ,胸径 5～ 10cm左右时开始结球 ,随着胸径的增大 ,花芽数量逐渐增多 ,2球花芽或果球数随胸径的增加更加明显 ,主导了花芽总数或雌雄球数随胸径的变化趋势 ;在胸径 15cm以下 ,1球雌雄球分化比率较大 ,2球次之 ,3球几乎没有分化 ;当胸径大于 15cm时 ,2球雌雄球数所占比例最大 ,1球次之 ,3球最小 ;在胸径达 30cm之前 ,叶芽数 /花芽数、雌花芽数 /雄花芽数、雌球数 /雄球数随着胸径的增大而变小 ,在胸径超过30cm情况下 ,其比率保持在较低的稳定水平 ;胸径接近 80cm的悬铃木分化出了更多的雌雄花芽 。

马尾松和杉木干基不同高度直径与胸径相关关系的研究

研究了马尾松和杉木离地面２０ｃｍ以下干基５个不同高度直径与胸径的相关关系，建立起精度达９８．６％的马尾松胸径与干基１０ｃｍ高处直径的数学模型和精度达９８．８％的杉木胸径与干基１５ｃｍ高处直径的数学模型。此两模型可用于被盗伐木的材积核实、森林资源采伐审计和马尾松割脂林木的胸径修正。

河南剌槐根径立木材积表编制的研究

利用河南山区、平原６２个县（市、区）收集的１１５４株刺槐样木，编制出了河南刺槐根径二元、一元立木材积表。用回归方法筛选出了刺槐根径与胸径关系的最佳数学模型（Ｄ１．３＝ａ０＋ａ１Ｄｒ＋ａ２Ｄ２ｒ）。并根据模型提出由立木积材表导算根径立木材积表的方法。