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，结实量较大。     

祁连山水源林调整林分结构的数学模拟

通过实际调查和分析看出，祁连山林区林分直径结构存在着不合理的分布状态，林木分化比较严重，小径木株数所占比例较大。因此，调整林分直径结构，应将小径木及劣质木做为抚育采伐对象，杜绝以往抚育采伐中的“拔大毛”现象，并且通过Ｗｅｉｂｕｌｌ分布拟合，反映出弱度采伐中，只要尊重现实分布律，制定科学的抚育措施，就能使林分结构向合理方向发展。     

The effect of sucrose on the flower bud opening of ‘Madelon’ cut roses

Complete flower bud opening is characterised by an increase in the petal area, and by enhanced dry and fresh weights of the petals. The import of dry matter into the petals is used for osmotic, biosynthetic and respiratory demands. However, flowers of ‘Madelon’ cut roses frequently fail to open completely under postharvest conditions. An aqueous solution containing 45 mM sucrose induces proper flower bud opening, even when the cut roses have been exposed initially to a sucrose-free solution for 48 h. This points to a requirement for a supply of organic matter from source tissue to the flower as main sink. This conclusion is confirmed by the observation that complete flower bud opening can also be achieved without any addition of sucrose by a reduction in the number of participating petals. Replacing two-thirds part of the 45 mM sucrose by an isomolalic amount of KNO₃ does not affect the flower opening process, implying that a considerable amount of the added sucrose is claimed for osmoregulation. The role of added sucrose and the contribution of the endogenous storage pool in the process of flower bud opening is discussed.     

雨雪凝冻天气对不同密度马尾松天然中龄林的影响分析

分析了雨雪凝冻后贵州省都匀地区不同密度马尾松天然中龄林的生长状况,结果表明,不同密度马尾松天然林经雨雪凝冻后,损失量有显著差别,损失率为18%~34%,但在一定范围内,随密度的加大,受损量趋于平缓。林木损失为正态分布,即主要损失林木径阶处于平均径阶周围,随密度的增大,损失林木径阶主要为低于平均径阶之下的小径阶。     

基于光学三角形法与图像处理的立木胸径测量方法

为提高林木胸径测量精度,减少劳动负荷,结合光学三角形法、图像处理及最小二乘拟合法,研究一种新的立木胸径测量方法.通过理论分析制定算法,搭建测量系统,对5株不同径级的立木进行测量计算,实验结果表明,采用光学三角形法的测量算法计算的直径精度较高,误差一般小于22 mm,相对误差率小于5.5％.     

DISTRIBUTABLE PROFITS AND CAPITAL EXPENDITURE IN FORESTRY

Data on the effects of forests on water supplies under South African conditions are meagre but with local and overseas evidence the detrimental effects in the Natal uplands are deduced. The deductions are not highly reliable but in the greater part of the forestry zone there is only a small range within which afforestation can affect runoff.

Some popular misconceptions about the effects of forests are dispelled.

The effect of tree-planting on regional water supplies is discussed. It is concluded that afforestation can cause a marked decrease in local runoff. For the scale of future afforestation now considered likely, this effect, seen in relation to the growth of demand for water, is, however, so small that changes in dryland land management to increase runoff are not justified. Funds and energy would be better expended in securing additional water supplies from other sources which must, in any case, be found when existing supplies are no longer adequate.     

低压管道输水灌溉技术在土地整理工程中的应用

在土地整理工程中采用节水灌溉技术,对缓解项目区的用水矛盾意义重大。低压管道输水灌溉技术,以其节水、节地、节能等综合优势,被广泛地应用在土地整理项目中。介绍了低压管道灌溉技术的相关概念和主要内容,并以山西省阳高县大白登镇基本农田整理项目为例,详细介绍并分析了在土地整理项目中低压管道灌溉系统的规划设计方法以及相关水力计算。     

华北落叶松人工林直径分布规律及其动态的研究

以山西省现场调查的30块华北落叶松（Larix principis—rupprechtii Mayr）人工林临时标准地为材料,利用分布密度函数对林分的直径分布进行模拟和预测。检验结果表明：86．67％的服从分布,拟合效果良好,并据此建立起了a、b、c参数的预测模型。理论参数方程可用于华北落叶松人工林经营管理的实践中,为合理经营华北落叶松人工林提供了科学的理论依据。     

End-point diameter and total length coarse woody debris models for the United States

Coarse woody debris (CWD) may be defined as dead and down trees of a certain minimum size that are an important forest ecosystem component (e.g., wildlife habitat, carbon stocks, and fuels). Due to field efficiency concerns, some natural resource inventories only measure the attributes of CWD pieces at their point of intersection with a sampling transect (e.g., transect diameter) although measurements of large-end diameter, small-end diameter, and length are often required by natural resource managers. The goal of this study was to develop a system of empirical models that predict CWD dimensions (e.g., large-end diameter) based on CWD attributes measured at the point of intersection with a sample transect and ancillary data (e.g., ecological province). Results indicated that R-squared (R²) values exceeded 0.60 for most of this study's CWD large-end diameter and small-end diameter with only fair results for the length models. The mean residuals of numerous CWD models were within the measurement tolerance expected of actual field crews. Despite remaining unexplained variation, these CWD models may provide foresters with an alternative to the time-consuming activity of measuring all CWD dimensional attributes of interest during large-scale forest inventories.     

Stand-scale transpiration estimates in a Moso bamboo forest: (I) Applicability of sap flux measurements

The applicability of sap flux (F_d) measurements to bamboo forests has not been studied. This study was undertaken to establish an optimal and effective design for stand-scale transpiration (E) estimates in a Moso bamboo forest. To this aim, we validated F_d measurements in Moso bamboos in a cut bamboo experiment. In addition, we analyzed how sample sizes affect the reliability of E estimates calculated from F_d and conducting culm area (A_{S_b}). In the cut bamboo experiments, we found that F_d measurement using a 10 mm probe was a valid means of determining the water-use behavior of a Moso bamboo, although a specific correction was needed. Furthermore, we calculated E from stand A_{S_b} (A_{S_stand}) and mean stand F_d (J_S). Employing Monte Carlo analysis, we examined potential errors associated with sample size in E, A_{S_stand}, and J_S using an original dataset with A_{S_b} and F_d measured for 40 and 16 individuals, respectively. Consequently, we determined the optimal sample size for both A_{S_stand} and J_S estimates as 11. The optimal sample sizes for J_S were almost the same under different vapor pressure deficit and soil moisture conditions. The optimal sample size for J_S at the study site was less than that of a coniferous plantation in the same region probably owing to small individual-to-individual variations in sap flux in the Moso bamboo forest. Our study concludes that sap flux measurements are an applicable technique for assessing water use in Moso bamboo forests.