开林窗与封禁对华北落叶松林下植被多样性的影响

以木兰林管局典型的华北落叶松林为研究对象,对其采取开林窗、封禁等改造措施,采用样方法进行野外调查,通过丰富度、生态优势度、多样性、均匀度指数,分析不同经营措施下的生物多样性及样地的物种组成。结果表明:开林窗面积中等及较小的样地各生物多样性指数均呈上升趋势,且高于对照,而开林窗面积较大样地的Pielou均匀度指数成降低趋势;封育区的Simpson和Shannon-Wiener多样性指数与均匀度指数均大于对照区,而封育区的Margalef丰富度指数虽然呈上升趋势,但仍小于对照区;该实验区林下植被的优势物种为乌苏里苔草。     

Exploring the silvicultural and economic viability of gap cutting in Mediterranean softwood plantations

Gap cutting consists of the removal of all trees growing on a small surface,varying in size from 200 to 600 m 2.In Italy,gap cutting has been successfully tested for introducing the natural regeneration of native species into softwood plantations,thus accelerating the transition towards climax hardwood stands.Depending on plantation types and conditions,gap cutting should be started at an age between 70 and 80 years and the system should include at least 12 to 15 gaps,in order to produce enough wood to cover costs.Generally,natural regeneration is firmly established within 5-7 years from treatment.Gap cutting also offers superior results to selection thinning,the latter producing about 35% less value and incurring 25% to 30% more costs.As for all regeneration cuts,the success of gap cutting depends on wildlife control in order to prevent extensive damage to the regeneration.     

雷州半岛高桥红树林内带林窗特征分析——以湛江市廉江高桥红树林保护小区为例

对红树林林窗特征研究,是研究退化红树林生态系统恢复与重建、对次生红树林进行改造、科学管理红树林生态系统的基础。对雷州半岛廉江高桥红树林保护小区内带林窗特征进行了调查,分析林窗大小结构、形成方式、形成木特征等。调查发现:高桥红树林内带林窗主要以小面积林窗为主,分布在实际面积1～10 m2之间和扩展面积1～50 m2之间;林窗主要形成方式是枯死,其次是侧枝损坏;林窗形成木数量范围在1～6株之间,平均每个林窗有2.3株形成木;形成木种类是红海榄、桐花树、木榄、秋茄,各占总比例的5.4%,8.9%,60.7%,25.0%;形成木腐烂等级较高。     

林窗理论在山地型城市森林建设中的应用前景

从森林循环演替、森林特殊的生境、边缘效应、森林植被物种多样性及森林景观格局多样性等方面论述了林窗干扰作用,并讨论了林窗理论在山地型城市森林建设中森林动态管理、森林景观格局优化和林相改造等方面的应用前景。     

Extract from the Zooxanthellate Jellyfish Cotylorhiza tuberculata Modulates Gap Junction Intercellular Communication in Human Cell Cultures

On a global scale, jellyfish populations in coastal marine ecosystems exhibit increasing trends of abundance. High-density outbreaks may directly or indirectly affect human economical and recreational activities, as well as public health. As the interest in biology of marine jellyfish grows, a number of jellyfish metabolites with healthy potential, such as anticancer or antioxidant activities, is increasingly reported. In this study, the Mediterranean “fried egg jellyfish” Cotylorhiza tuberculata (Macri, 1778) has been targeted in the search forputative valuable bioactive compounds. A medusa extract was obtained, fractionated, characterized by HPLC, GC-MS and SDS-PAGE and assayed for its biological activity on breast cancer cells (MCF-7) and human epidermal keratinocytes (HEKa). The composition of the jellyfish extract included photosynthetic pigments, valuable ω-3 and ω-6 fatty acids, and polypeptides derived either from jellyfish tissues and their algal symbionts. Extract fractions showed antioxidant activity and the ability to affect cell viability and intercellular communication mediated by gap junctions (GJIC) differentially in MCF-7and HEKa cells. A significantly higher cytotoxicity and GJIC enhancement in MCF-7 compared to HEKa cells was recorded. A putative action mechanism for the anticancer bioactivity through the modulation of GJIC has been hypothesized and its nutraceutical and pharmaceutical potential was discussed.     

一定体积的粳稻种子间隙吸水量的定量测试

为了简单快速地确定一定体积的水稻种子间隙的吸水量,本研究选用了中长粒型品种龙粳21和短圆粒型品种龙粳31作为研究对象,以量筒和量杯作为工具测量了一定体积的水稻种子间隙的吸水量。通过这种简单的测量方法得出长粒型的水稻品种龙粳21的种子体积与种子间隙吸水的体积之比为1:0.437,短圆粒型的水稻品种龙粳31的种子体积与种子间隙吸水的体积之比为1:0.3956。该研究可为浸种催芽时农药用量的确定提供依据。     

新疆城乡居民收入水平变化及其影响因素分析

根据新疆历年统计年鉴数据,从城乡居民收入变动、城乡居民可支配收入比、城乡居民收入差额变动、城乡居民恩格尔系数变动4个方面分析了新疆城乡居民收入水平变化情况,并分析了城乡居民收入差距的影响因素,指出自然地理条件、城乡隔离、教育投入差距和农村社会保障体系缺乏是导致新疆城乡居民收入差距扩大的主要因素。     

Yield gap and production constraints of mango (Mangifera indica) cropping systems in Tianyang County,China

Mango is an important cash crop in the tropics and subtropics. Determining the yield gap of mango and production constraints can potentially promote the sustainable development of the mango industry. In this study, boundary line analysis based on survey data from 103 smallholder farmers and a yield gap model were used to determine the yield gap and production constraints in mango plantations in the northern mountain, central valley and southern mountains regions of Tianyang County, Guangxi, China. The results indicated that the yield of mango in three representing regions of Tianyang County,Northern Mountains, Central Valley and Southern Mountains, was 18.3, 17.0 and 15.4 t ha~(–1) yr~(–1), with an explainable yield gap of 10.9, 6.1 and 14.8 t ha~(–1) yr~(–1), respectively. Fertilization management, including fertilizer N, P_2O_5 and K_2O application rates, and planting density were the main limiting factors of mango yield in all three regions. In addition, tree age influenced mango yield in the Northern Mountains(11.1%) and Central Valley(11.7%) regions. Irrigation time influenced mango yield in the Northern Mountains(9.9%) and Southern Mountains(12.2%). Based on a scenario analysis, the predicted yield would increase by up to 50%, and fertilizer N use would be reduced by as much as approximately 20%. An improved understanding of production constraints will aid in the development of management strategy measures to increase mango yield.     

Causes of maize density loss in farmers' fields in Northeast China

Increasing plant density is an effective and important way to reduce maize yield gaps in Northeast China. However, the fact is that a significant plant density gap exists between optimum plant density and actual plant density in farmers' fields.To quantify the density gap between planned planting density and final harvest plant density(HPD), we studied 60 farmers' fields on three types of soil for three crop seasons from 2015 to 2017 by measuring their plant-plant distance, actual seedlings density(ASD), final HPD and yield. We also explored the potential causes of density loss by digging the places where the seedlings were missing for two consecutive years in 2016–2017. Results show that the three-year average HPD in farmers' fields was 59 699 plants ha~(–1), which was significantly lower than the planned density, including both the machine setting density(MSD; 67 962 plants ha~(–1)) and theoretical plant density(TPD; 67 467 plants ha~(–1)). No significant difference was found in HPD between years and soil types. However, for MSD and TPD, the average value in 2015 was significantly higher than that in 2016 and 2017. No significant difference between soil types was observed. Furthermore,the results from 2016 till 2017 indicated that a lack of seeds in the soil, a failure to germinate due to low-quality seeds,and a lack of seedlings breaking out of the soil due to environmental problems explained approximately 60.88, 10.33 and 28.80% of density loss, respectively. According to our survey, 63% of farmers did not know their own TPD and HPD, and 54% of farmers did not know the density loss. Therefore, we argue that farmers' limited knowledge of density and density loss is an urgent problem that needs to be solved in maize production. These observations will be useful for determining best management practices for maize production and for providing helpful suggestions for machine improvement.