Stem Diameter Estimation from Aerial Photographs

Remote sensing techniques have proven successful for producing stem maps of forests in leaf-on condition from high-resolution imagery. This paper demonstrates how a mathematical model for the surface of a stem can be used to estimate the breast-height diameter of individual trees from aerial photographs to give information on basal area. The diameters are estimated by likelihood estimation from images of a forest in leaf-off condition where the stems and their shadows are visible. Applied to a homogeneous and monospecific oak ( Quercus robur L.) stand under standard silvicultural treatment in Denmark, the estimation was successful for 56 out of 60 trees. The root mean squared error on the diameter was 4.2 and 3.2 cm using three and five images, respectively. The key conclusion is that it is feasible to infer fairly accurate information about the diameters and three-dimensional positions of stems from aerial photographs.     

四川白河自然保护区连香树的空间分布与种群特征

以四川白河自然保护区连香树为研究对象,采用访问法、样线法和样方法相结合,调查连香树的空间分布位点、种群特征和干扰因素。调查结果表明:保护区有连香树365株,适宜面积约1 995.46 hm2;海拔1 900～2 200 m区域的连香树株数占总株数的89.53%,尤其是海拔2 000～2 100 m分布最为密集(占43.01%);径级分布为纺锤形,自然更新差,种群呈不稳定状态,胸径在12～32 cm之间的有238株(占65.20%)。连香树主要分布区与传统耕作区和放牧区的重叠性高,林地转化成耕地及放牧践踏是连香树种群数量和栖息地下降的主要原因;减少人为干扰、就地保护与监测、建立天然母树园、种子繁殖和扦插是保护连香树种群的有效措施。     

解决聚丙烯芯钢丝绳生产过程中钢丝“塌陷”（或间隙不均）及绳径超差问题

本文从生产制造角度来分析解决聚丙烯芯钢丝绳生产过程中易出现的钢丝塌陷、钢丝间隙不均及绳径超差等问题。与天然纤维芯相比，聚丙烯芯是一种合成纤维芯，除具有质轻、弹性好、不怕霉蛀等特性外，同时还具有较好的抗挤压性，因此，生产过程中，对聚丙烯芯直径公差的控制比对天然纤维芯直径公差的控制更为严格，如聚丙烯芯直径选择不当，易会出现股中钢丝塌陷(或钢丝间隙不均)、绳径超差等问题。笔者结合生产实际情况，从控制聚丙烯绳芯(股芯)直径公差入手，找出聚丙烯芯直径的计算值与其实测值之间合适的比例范围，对正确选择聚丙烯绳芯(股芯)直径大小，满足钢丝绳生产工艺要求，优化工艺参数，提高钢丝绳结构的稳定性和机台生产作业率有着重要的作用。     

牛卵母细胞体外成熟技术研究

从两方面探讨了牛卵母细胞的体外成熟培养效果,即对不同级别和不同卵巢卵泡直径的卵丘卵母细胞复合体（COCs）进行成熟培养,测定其成熟率。COCs级别不同,培养成熟率之间存在很大差异,A级COCs成熟率为63．81％,B级为47．81％,显著高于C级和D级（P〈0．01）。卵母细胞的成熟率与采集COCs时的卵泡直径关系密切。中等卵泡的卵母细胞的成熟率为61．82％,显著高于小卵泡和大卵泡（P〈0．01）。试验结果表明：A级和B级COCs是卵母细胞体外培养的主要资源;在卵母细胞体外培养过程中,宜选择卵泡发育水平基本正常的中等卵泡采集COCs,而不宜选择发育过大或过小的卵泡。     

Models for predicting tree and stand development on larch plantations in Hallormsstaður,Iceland

The aim was to model the growth of Siberian larch (Larix sibirica Ledeb.) and Russian larch (Larix sukaczewii Dyl., syn. L. sibirica var. sukaczewii) plantations in Hallormsstaeur, Iceland. The field inventory was carried out in eastern Iceland in June 2006. Models were constructed for predicting dominant height, total tree height and 5-year diameter increment. Several linear and non-linear forms of models were tested in preliminary analyses to find the equations that fitted the modelled characteristics best. Due to the spatially hierarchical correlation structure of the data (stands, plots and trees), the assumption of non-correlated error terms did not hold. Therefore, a random parameter modelling approach was adopted using mixed models when the estimates obtained for the random effects were statistically significant. The variance estimates for the random effects can be further used to calibrate the models. The models generated here performed well with independent test data and were consistent with the forest growth theory. They can be used to evaluate site quality and to estimate the growth and yield of larch stands in eastern Iceland in connection with forest planning.     

Relationships of culm surface area to other culm dimensions for bamboo, Phyllostachys pubescens

We determine the relationships of culm surface area to other culm dimensions for one of the largest bamboo species, Phyllostachys pubescens Mazel ex Houzeau de Lehaie. A total number of 150 sample culms were collected from a stand of P. pubescens in Mt. Toshima, Kumamoto Prefecture, western Japan. The culm surface area for each sample was calculated, and then the relationships of the culm surface area to basal area and product of diameter at breast height (dbh) and culm height were analyzed. The relationship between culm surface area and basal area could be described successfully by the power equation, whereas there was a linear relationship of culm surface area to product of dbh and height. Although the regression equations determined here would be useful in estimating culm surface area of P. pubescens, it is necessary to select an appropriate equation depending on the purpose and available time and labor.     

血管紧张素Ⅱ对牛肉品质的影响

取屠宰后5头杂交牛(鲁西黄牛×西门塔尔)的背最长肌,置于2~4℃贮藏7 d,注射样品重10%的血管紧张素Ⅱ,观察在成熟过程中血管紧张素Ⅱ对牛肉剪切力、肌原纤维小片化指数(MFI)、凋亡酶活力,以及肌纤维直径变化的影响。结果显示:贮藏期间对照组和处理组样品剪切力均显著下降(P<0.05),MFI值逐渐增大,caspase-3、6、9酶活力宰后迅速激活随后其活力逐渐下降;血管紧张素Ⅱ注射处理显著降低了牛肉的剪切力值和肌纤维直径(P<0.05),而对MFI值及caspase-3、6、9活力无显著影响。因此,caspase-3、6、9对牛肉嫩度的影响可能仅发生在宰后初期极短的一段时间内;肌细胞宰后生理和活体状况下不太一致,血管紧张素Ⅱ注射降低了牛肉剪切力可能由于它能显著防止肌纤维的收缩。     

应用“林分结构复原法”评价经营措施及更新效果研究

介绍了林分调查的一种方法：“林分结构复原法”,即根据林分的现时直径分布和直径生长量,应用林分表法进行径阶转移的原理,推算n年前的直径分布,并根据直径与其他林分因子的关系,再现林分在前n年时的林分结构,从而为评价采伐的合理性以及鉴定超采、盗伐提供可靠数据。     

适于FVS的长白落叶松树皮因子

为估算长白落叶松的去皮直径及树皮厚度等,利用小兴安岭南部68株长白落叶松解析木与生物量数据,对带皮胸径与去皮胸径之间、树干材积与木材材积之间、树皮厚度与相对树高之间、树皮因子与树高之间等相关模型进行了研究.结果表明,长白落叶松胸径处去皮直径的最优模型为D1B=0.922DOB(R2=0.99),胸径处树皮因子和树皮调整...     

A shifting algorithm to simulate thinnings from below and above

Thinning is a silvicultural practice to improve tree growth and health. Thinning from below for the even-aged silviculture and thinning from above for the uneven-aged silviculture are the two mainly applied thinning practices. In forest management simulations, algorithms that describe which individual trees to be removed from a forest have developed in five growth simulators (Söderbergh and Ledermann, 2003). We have developed a shifting algorithm that determines the proportion of trees to be thinned from different diameter classes to complement the individual tree selection algorithms. Sampled (or mapped) tree diameters are grouped into diameter classes. Given the target thinning volume, the algorithm automatically computes the thinning rate in each of the diameter classes using the three-parameter Weibull distribution. The thinning rate is obtained by shifting the location parameter of an estimated Weibull distribution either to the right or to the left for thinnings from below and above, respectively. A modified bisection method is used to search for the new location parameter that yields the desired thinning volume. The proposed algorithm is demonstrated in examples by using experimental forest datasets. A stand-alone program called Weibull_thinning is downloadable at http://www.it.abo.fi/suswood/weibull_thinning/.