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61.
以镇赉县2004年和2014年森林资源规划设计调查成果为基础,分析森林资源的变化状况,结果表明:全县经营总面积由2004年的475 498 hm2减少到2014年的471 028 hm2;有林地面积由35 226.4 hm2减少到34 831.7 hm2;灌木林地面积由4 082.1 hm2增加到4 330.2 hm2。森林覆盖率为8.31%,较2004年(8.27%)提高了0.04%。活立木总蓄积量2 295 601 m3,较2004年(1 990 854 m3)提高了15.31%。针对森林资源现状提出了经营建议。  相似文献   
62.
利用ISSR分子标记技术对144份木棉(Bombax ceiba)种质资源遗传多样性进行分析。结果表明: 木棉种质资源具有较高的遗传多样性,采用筛选的26个ISSR引物共扩增出179个位点,多态性位点161个,多态性位点百分率为899%,有效等位基因数为16,Nei基因多样性指数为0350 5, Shannon信息多样性指数为0523 3,相似性系数为0238 6~0910 6。UPGMA聚类分析得出,木棉种质之间的亲缘关系与来源没有明显的相关性,对同一产地来说,绝大部分种质聚在一起,亲缘关系较近,同时不同产地之间多数木棉种质亲缘关系也较近。  相似文献   
63.
剖析森林旅游景区生物资源等要素的生态安全状态及其相应的景观感知,以及它们之间的传递关系,建立森林旅游景区生态安全与景观感知安全传递关系模型。通过对景区生态安全各要素的分析发现,在景区开发、游客干扰等人类活动的干扰下,我国一些森林旅游景区水体、土壤、空气、声音环境受到严重污染,动植物生长生存条件发生退化,并对游客的景观感知产生了显著的负面影响。对景区生态安全与景观感知安全的传递性分析表明,景观感知安全是人类活动对自然资源的影响转移到自身的一种反映,它对景区生态安全状态有一定的预知作用。在此基础上,结合景区生态安全与景观感知安全之间的传递关系,和对景区生态安全构念的分析,建立了包括生物生存环境安全和生物资源安全要素在内的森林旅游景区生态安全结构,及其与景观感知安全之间的传递关系模型。  相似文献   
64.
对2016-2017年引进的62个陆地棉新品种进行了形态特征、生物学特性和品质特性的鉴定及分析。结果表明:目前收集的新材料以中早熟棉为主,铃重以中等大小为主,衣分中等,悬殊较大,马克隆数值普遍偏大。  相似文献   
65.
甜菜抗褐斑病种质资源是甜菜种质资源中具有褐斑病抗性基因并且能稳定传递给子代的种质资源,是甜菜抗褐斑病育种工作的物质基础,也是农业可持续发展的战略资源。甜菜抗褐斑病种质资源研究的主要内容包括对甜菜品种的收集、鉴定与评价、保存、利用以及抗性遗传基因的克隆及利用。为了使人们更加清晰的了解甜菜抗褐斑病种质资源的研究状况。本文综述了甜菜抗褐斑病种质资源的收集、鉴定与评价、保存、利用及分子方面的研究,并对我国未来种质资源的研究作出展望。以期为以后甜菜抗褐斑病种质资源的研究提供方向。  相似文献   
66.
Water resources are critical for the existence and development of oases in endorheic basins. Thus, to enable sustainable development, it is fundamentally important to understand how to allocate and use these resources in a reasonable way. We therefore simulated and analyzed changes in water consumption pattern within the Dunhuang Oasis of China under three scenarios using a system dynamic model that corresponds to different water consumption pattern. This was done to assess the impacts of regional water resource planning (comprehensive planning of the rational use of water resource and protection of ecosystem services in the Dunhuang Basin) on water consumption pattern within the Dunhuang Oasis. The first of these, Scenario 1, is a baseline in which the status quo is maintained, while Scenario 2 incorporates the comprehensive effects of agricultural water-saving irrigation measures with an inter-basin water diversion project, and Scenario 3 focuses on ecological rehabilitation. In the baseline Scenario 1, the total water consumption within the Dunhuang Oasis increased progressively while agricultural water consumption remained extremely high and threatened overall ecological security. In contrast, Scenario 2 would decrease agricultural water consumption by almost 5.30×107 m3 following the implementation of water-saving practices. The additional water allocated from an inter-basin water diversion project would play an important role in alleviating ecological strain on the oasis. Finally, in Scenario 3, the total irrigated land must be decreased to 20.6×103 hm2 by 2025 assuming that water supply for ecosystem restoration would be at least 50% of the total consumption. Although water resource planning plays a very important role in alleviating the ecological water crisis within the oasis, it is necessary to consider the suitable scale of oasis with regard to current water consumption pattern.  相似文献   
67.
In just two decades, round goby Neogobius melanostomus (Pallas) has dispersed throughout most of the Baltic and the North American Great Lakes. It thrives in shallow sheltered areas, where it is impacting native fauna. In Denmark, researchers, governmental institutions and fishers have joined in an effort to establish a sustainable round goby fishery. To do so, basic information about the movement of round goby is essential, so the movements of 50 round gobies were tracked using acoustic telemetry. The results revealed that activity took place mainly at night and seasonal migrations were common. The most frequent migration behaviour observed was a seaward return migration during winter, which was further confirmed by a snorkel survey. Tracking data also revealed riverine upstream dispersal. The results demonstrate that the round goby can be mapped using telemetry, and it is suggested that fishing for round goby may improve efficiency by targeting seasonal migration corridors.  相似文献   
68.
针对莱芜水资源无客水、水资源空间分布不均匀、水资源年际年内变化大以及水资源监测技术、监测方法和设备落后的现状,莱芜适时启用水资源信息管理系统,实现对水量、水位等诸多信息实时监控,为莱芜水资源的综合开发利用、优化调度提供了重要的决策依据。  相似文献   
69.
  1. Amphidromy is the most prevalent type of diadromous migration. Despite this, the conservation and management of amphidromous species is exceptionally challenging because this life history type, with larval development in a pelagic habitat (usually marine) and adult development in fresh water, is poorly resolved.
  2. The chronological properties of otoliths, together with a spatial and temporal analysis of post‐larval migration traits and adult reproductive traits, were used to reconstruct the life history of a widespread, yet declining amphidromous galaxiid, Galaxias maculatus, and to explore relationships between marine and freshwater life phases.
  3. A wide range of post‐larval migration traits were observed over the peak migratory period. Post‐larvae were smaller and younger at inward migration late in the migration season (November) and were derived from winter spawning events. Earlier migrants (September) were larger, older and derived from autumn spawning events.
  4. Age estimates confirmed that G. maculatus is largely an annual species, but back‐calculated hatch dates showed that spawning times are more extensive than previously known.
  5. Growth reconstructions revealed that winter‐hatched larvae were faster growing during marine and freshwater life and attained sexual maturity at a younger age than autumn‐hatched fish. However, no differences in body size or reproductive investment were detected between autumn‐ and winter‐hatched larvae.
  6. The first 50 days of marine growth were inter‐dependent, indicating that early larval growth may be the critical link to understanding intra‐ and inter‐annual recruitment variations of inward migrating post‐larvae. Furthermore, growth after 60 days of larval life propagated through to adult freshwater development, highlighting linkages between late marine and adult freshwater life.
  7. This study highlights the value of studying the marine and freshwater life phases of amphidromous species in tandem. This interconnected understanding must ultimately be achieved for the conservation and management of species with this poorly understood life history type.
  相似文献   
70.
Striped marlin (Kajikia audax) is an epipelagic fish distributed in oceanic and coastal waters of the Pacific Ocean. This species is usually found in warm and coastal waters with high primary productivity. The main goal of this study was to describe the spatial segregation of striped marlin by average Eye‐Fork length (EFL) in the eastern Pacific Ocean (EPO) and its relationship with environmental variables using EFL data obtained from tuna purse‐seining and Generalized Additive Models (GAMs). The model suggested that larger individuals of striped marlin were more likely to be found in waters with high Chlorophyll‐a concentration (>2 mg/m3) and with temperatures lower than 25°C, within a region known as the “cold tongue” and the Humboldt current system, while smaller individuals were more likely to be found in warmer and low productive areas within a region known as the “warm pool of the EPO.” We observed that set type caused a large variation on average EFL of striped marlin; larger fish were captured in sets associated with floating objects (natural and manmade), while smaller fish were captured in sets associated with dolphins. Despite this, our findings suggest that striped marlin has a latitudinal gradient in average EFL; larger individuals occurred predominantly south of 10°N, while smaller ones occurred predominantly in coastal waters between 10°N and 20°N, thus demonstrating a spatial segregation of the species affected by its maturity stage.  相似文献   
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