森林粗木质残体的贮量和碳库及其影响因素

粗木质残体(CWD)是森林生态系统重要的组成要素,由于定量研究某特定区域CWD的贮量和碳量的工作量相当大,需要长期的研究才能获得可信的数据,因此有关全球森林生态系统CWD的贮量和碳量仍不太清楚.本文根据国内外研究结果综述全球不同森林中CWD的贮量和碳库情况.结果表明:温带针叶林CWD贮量最高(30～200 t·hm-2),而阔叶林最低(8～50 t·hm-2);全球森林CWD碳贮量范围大致为75～114或157 Pg.各森林CWD贮量值变化大,因林龄、CWD分解阶段和人类经营活动(如疏伐、皆伐和控制火烧)而异.今后需更广泛地开展森林CWD调查,以更深刻理解CWD与林分结构、树种特性及干扰的关系.此外,为了更准确地评价CWD在森林生态系统中的生态价值,建议在更大尺度上对全球各类森林的CWD贮量和碳库进行长期的研究.     

Gross N transformations were little affected by 4 years of simulated N and S depositions in an aspen-white spruce dominated boreal forest in Alberta, Canada

The effects of 4 years of simulated nitrogen (N) and sulfur (S) depositions on gross N transformations in a boreal forest soil in the Athabasca oil sands region (AOSR) in Alberta, Canada, were investigated using the ¹⁵N pool dilution method. Gross NH₄⁺ transformation rates in the organic layer tended to decline (P < 0.10, marginal statistical significance, same below) in the order of control (CK, i.e., no N or S addition), +N (30 kg N ha⁻¹ yr⁻¹), +S (30 kg S ha⁻¹ yr⁻¹), and +NS treatments, with an opposite trend in the mineral soil. Gross NH₄⁺ immobilization rates were generally higher than gross N mineralization rates across the treatments, suggesting that the studied soil still had potential for microbial immobilization of NH₄⁺, even after 4 years of elevated levels of simulated N and S depositions. For both soil layers, N addition tended to increase (P < 0.10) the gross nitrification and NO₃⁻ immobilization rates. In contrast, S addition reduced (P < 0.001) and increased (P < 0.001) gross nitrification as well as tended (P < 0.10) to reduce and increase gross NO₃⁻ immobilization rates in the organic and mineral soils, respectively. Gross nitrification and gross NO₃⁻ immobilization rates were tightly coupled in both soil layers. The combination of rapid NH₄⁺ cycling, negligible net nitrification rates and the small NO₃⁻ pool size after 4 years of elevated N and S depositions observed here suggest that the risk of NO₃⁻ leaching would be low in the studied boreal forest soil, consistent with N leaching measurements in other concurrent studies at the site that are reported elsewhere.     

洛伦茨曲线和基尼系数在林业上的应用

文章采用洛伦茨曲线和基尼系数的统计方法,对绥化市北林区一块样地的林木胸径分布情况进行统计分析,进而确定林木分化状况和分化程度,通过实践验证了洛伦次曲线和基尼系数的统计方法可正确反映林木分化程度,可用以正确指导和确定森林经营方案.     

现代生态园林景观建设要点浅析

生态园林景观建设是园林事业发展和进步的必然产物,是改善城市环境、以人为本的根本体现,针对当前园林景观建设中存在的问题及发展趋势,提出了在功能定位、设计理念等方面的解决意见。     

黑木相思株内木材基本材性变化与树龄关系的研究

对不同树龄和径向位置黑木相思木材的物理和主要力学性质测定研究表明:黑木相思株内边材、心材密度和主要力学性质随着树龄的增大而增大,径向和弦向的体积干缩率随着树龄的增大而减小;相同树龄黑木相思的边材密度和力学性能比心材小,干缩率比心材大.因此,在利用黑木相思时应对树龄、心边材径向位置加以特别考虑.     

子京和油丹的研究与保护

子京和油丹是我国海南省珍贵用材树种,有着重要的经济和科研价值,但天然林资源逐渐减少,均被列为国家二级濒危重点保护野生植物,急需加强对子京和油丹的保护、研究和开发利用.在进行子京和油丹天然资源调查和收集的基础上,文章从应用价值、生物学特性、分布生境、濒危现状、繁殖育苗、引种栽培和保护利用等方面进行了介绍和探讨,提出了子京...     

Microbial immobilisation and turnover of N labelled substrates in two arable soils under field and laboratory conditions

Microbial biomass N dynamics were studied under field and laboratory conditions in soils of high yield (HY) and low yield (LY) areas in an agricultural field. The objective of the study was to determine the size and activity of soil microbial biomass in the soils of the different yield areas and to compare these data obtained under field and laboratory conditions. Soils were amended with ¹⁵N labelled mustard (Sinapis alba) residues (both experiments) and labelled nitrate (laboratory only) at 30 μg N g⁻¹ dry soil. Soil microbial biomass (SMB) N, mineral N (N_min) and total N content was monitored both in the field and in the laboratory. N₂O efflux was additionally measured in laboratory treatments. Isotope ratios were determined for SMB in both experiments, for all other parameters only in the laboratory treatments. In the laboratory less amounts of added substrate N were immobilised by the SMB in HY soils compared to LY soils, whereas in the field immobilisation of added N by SMB was higher in HY soils initially and slightly lower after 40 days of incubation. Calculated turnover times in the laboratory nitrate, laboratory mustard and field mustard amendments were 0.18, 0.27 and 0.74 years (HY) and 0.22, 0.61 and 1.01 years (LY), respectively. The turnover times of added substrate N always showed the trend to be faster in HY soils compared to LY soils. A faster turnover of nutrients in the HY soils may involve a better nutrient supply of the plants, which coincides with the higher agricultural yield observed in these areas.     

自动测量胸径和树高便携设备的研制与测量精度分析

胸径和树高测量是评价立地质量和林木生长状况的重要依据,该文以图像自动识别原理、摄影测量原理、相似三角形几何原理和三角函数原理为理论基础,研制了可测量胸径和树高的多功能便携式微型超站仪,该设备集成电荷藕合器件图像传感器、倾角传感器、激光测距传感器、中央处理器、存储器、液晶显示屏,测量时可获取测站点到待测点的倾角和距离2个参数值,并记录存储测量时的图像信息,通过仪器的嵌入式操作程序,实现胸径的自动测量、树高测量、任意处直径自动测量、基本测量等4项基本功能。通过试验验证,215株立木的单次胸径测量的平均绝对误差为0.369 cm,平均相对误差为2.08%。101株立木的单次树高测量的平均相对误差为1.44%。胸径测量精度达到97.92%,树高测量精度达到98.56%,符合国家森林资源连续清查中的测量精度要求。该设备为森林资源调查提供了参考。     

水分淋洗下菜园土壤各形态锌的迁移转化特征

采用室内模拟降雨淋溶土柱的方法，研究了经过1年降雨的淋溶后，菜园土壤垂直方向上各形态锌的迁移转化规律。结果表明：锌的大多数形态很难随水分运动发生迁移，～年的降雨至多能使占总量0．57％的水溶态锌发生淋溶损失。水分淋洗和施磷锌平均能使分别占总量3％和4％的难溶态RES—Zn和OX-Zn向易被植物利用的EX—Zn、CABS—Zn和OM—Zn形态转化。随施锌量的增加，土壤锌的有效性指数增加30％～78％．有效锌总量增加3．12～10．07mg／kg。当施磷50mg／kg时，土壤Zn的有效性指数增加3％～28％，有效锌总量增加0．04～0．28mg／kg，磷锌在土壤中表现为协同作用。     

Soil nutrient supply and biomass production in a mixed forest on a skeleton‐rich soil and an adjacent beech forest

In the natural forest communities of Central Europe, beech (Fagus sylvatica L.) predominates in the tree layer over a wide range of soil conditions. An exception with respect to the dominance of beech are skeleton‐rich soils such as screes where up to 10 broad‐leaved trees co‐exist. In such a Tilia‐Fagus‐Fraxinus‐Acer‐Ulmus forest and an adjacent mono‐specific beech forest we compared (1) soil nutrient pools and net nitrogen mineralization rates, (2) leaf nutrient levels, and (3) leaf litter production and stem increment rates in order to evaluate the relationship between soil conditions and tree species composition. In the mixed forest only a small quantity of fine earth was present (35 g l^—1) which was distributed in patches between basalt stones; whereas a significantly higher (P < 0.05) soil quantity (182 g l^—1) was found in the beech forest. In the soil patches of the mixed forest C and N concentrations and also concentrations of exchangeable nutrients (K, Ca, Mg) were significantly higher than in the beech forest. Net N mineralization rates on soil dry weight basis in the mixed forest exceeded those in the beech forest by a factor of 2.6. Due to differences in fine earth and stone contents, the volume related soil K pool and the N mineralization rate were lower in the mixed forest (52 kg N ha^—1 yr^—1, 0—10 cm depth) than in the beech forest (105 kg N ha^—1 yr^—1). The leaf N and K concentrations of the beech trees did not differ significantly between the stands, which suggests that plant nutrition was not impaired. In the mixed forest leaf litter fall (11 %) and the increment rate of stem basal area (52 %) were lower than in the beech forest. Thus, compared with the adjacent beech forest, the mixed forest stand was characterized by a low volume of patchy distributed nutrient‐rich soil, a lower volume related K pool and N mineralization rate, and low rates of stem increment. Together with other factors such as water availability these patterns may contribute to an explanation of the diverse tree species composition on Central European screes.