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911.
Over the past decades, strong evidence has accumulated that low-frequency electromagnetic fields (EMFs) can be useful in treating human pathologies, such as bone fractures, soft tissue illnesses, and pain. Common strategies for the design of commercial therapeutic devices are to generate EMFs that simulate body endogenous EMFs, or EMFs that resonate with a particular biological process, such as the natural motions of ions. We recently came across a biologically active commercial EMF signal that seems to be different. The signal is generated by summing the fundamental frequencies and harmonics of several periodic base signals which remain proprietary to the company. When first examined in the time domain, the signal resembled electronic noise; however, when critically analyzed, the signal is not identical with noise. Rather, it is a highly complex waveform exhibiting a very wide range of values for the time derivative of the magnetic field density (dB/dt) and a beat frequency in the Extremely Low-Frequency range. In this paper, we speculate on the mechanism of action of this and similar signals. We consider it less likely that cells, or cell components, act like filters to extract and couple with individual signals that make up the complex EMF signal. Consequently, we favor the possibility that with the signal discussed here cells respond to the very complex signal and that the biological response can be modified by the presence of a beat in the signal, in this case a low-frequency beat. More generally, this would suggest the hypothesis that biological processes can be regulated by noise-like signals and that the effects of a noisy signal can be modified by the presence of signal repetition patterns, such as beats. Given the very small energy that signals like these can transduce into a biological system, biological effects can be expected only when the molecular processes involved are poised so that the available energy leads to molecular reactions that achieve the activation state for the reaction.  相似文献   
912.
Major Forest Types and the Evolution of Sustainable Forestry in China   总被引:1,自引:0,他引:1  
Dai L  Wang Y  Su D  Zhou L  Yu D  Lewis BJ  Qi L 《Environmental management》2011,48(6):1066-1078
In this article, we introduce China’s major forest types and discuss the historical development of forest management in China, including actions taken over the last decade toward achieving SMF. Major challenges are identified, and a strategy for SFM implementation in China is presented. China’s forests consist of a wide variety of types with distinctive distributional patterns shaped by complex topography and multiple climate regimes. How to manage this wide array of forest resources has challenged forest managers and policy-makers since the founding of the country. Excessive exploitation of China's forest resources from the 1950s to the late 1990s contributed to environmental problems and calamities, such as floods, soil erosion, and desertification. At the start of the new millennium, the Chinese government decided to shift its emphasis from timber production towards the achievement of sustainable forest management (SFM). With a series of endeavors such as the implementation of the “Six Key Forestry Projects” and the reform of forest tenure policies, and the adoption of a classification system for China's forests, a beginning has been made at reversing the trend of environmental degradation that occurred throughout the latter half of the last century. At the same time, huge challenges remain to be tackled for the development of forestry in China.  相似文献   
913.
We demonstrate the use of an expert-assisted spatial model to examine geographic factors influencing the poaching risk of a rare plant (American ginseng, Panax quinquefolius L.) in Shenandoah National Park, Virginia, USA. Following principles of the analytic hierarchy process (AHP), we identified a hierarchy of 11 geographic factors deemed important to poaching risk and requested law enforcement personnel of the National Park Service to rank those factors in a series of pair-wise comparisons. We used those comparisons to determine statistical weightings of each factor and combined them into a spatial model predicting poaching risk. We tested the model using 69 locations of previous poaching incidents recorded by law enforcement personnel. These locations occurred more frequently in areas predicted by the model to have a higher risk of poaching than random locations. The results of our study can be used to evaluate resource protection strategies and to target law enforcement activities.  相似文献   
914.
Xie X  Wang Q  Dai L  Su D  Wang X  Qi G  Ye Y 《Environmental management》2011,48(6):1095-1106
The maintenance of a timely, reliable and accurate spatial database on current forest ecosystem conditions and changes is essential to characterize and assess forest resources and support sustainable forest management. Information for such a database can be obtained only through a continuous forest inventory. The National Forest Continuous Inventory (NFCI) is the first level of China’s three-tiered inventory system. The NFCI is administered by the State Forestry Administration; data are acquired by five inventory institutions around the country. Several important components of the database include land type, forest classification and ageclass/ age-group. The NFCI database in China is constructed based on 5-year inventory periods, resulting in some of the data not being timely when reports are issued. To address this problem, a forest growth simulation model has been developed to update the database for years between the periodic inventories. In order to aid in forest plan design and management, a three-dimensional virtual reality system of forest landscapes for selected units in the database (compartment or sub-compartment) has also been developed based on Virtual Reality Modeling Language. In addition, a transparent internet publishing system for a spatial database based on open source WebGIS (UMN Map Server) has been designed and utilized to enhance public understanding and encourage free participation of interested parties in the development, implementation, and planning of sustainable forest management.  相似文献   
915.
Recently Prévot-Julliard and colleagues presented a concept paper on biological conservation strategies using exotic species as a case study. They emphasized the difficulty of integrating conservation into a broad picture that accounts for public perception as well as scientific knowledge. We support this general call for better integration of society in conservation research, but we believe that the original framework might misguide conservation practices if wrongly interpreted. Our objective is to complement their paper and correct a few misleading points, by showing that (1) for regions of high endemicity “reservation” may be the best conservation practice, and does not prevent public participation, (2) aiming for broad societal agreement is valuable, but in some cases risky, and always complex, and (3) calling a harmful invasive species harmful shouldn’t be an issue. The Australian context provides us with many cases of the labeling of exotic species as harmful or not, using inputs from scientists, industry, and the public. Integration of social and scientific points of view can only improve conservation on the ground if it allows managers to use the ecological, economic and social impacts of exotic species to prioritize conservation actions in an operative way.  相似文献   
916.
Forest certification is a mechanism involving the regulation of trade of forest products in order to protect forest resources and improve forest management. Although China had a late start in adopting this process, the country has made good progress in recent years. As of July 31, 2009, 17 forest management enterprises and more than one million hectares of forests in China have been certified by the Forest Stewardship Council (FSC). Several major factors affect forest certification in China. The first set is institutional in nature. Forest management in China is based on centralized national plans and therefore lacks flexibility. A second factor is public awareness. The importance and value of forest certification are not widely understood and thus consumers do not make informed choices regarding certified forest products. The third major factor is the cost of certification. Together these factors have constrained the development of China’s forest certification efforts. However, the process does have great potential. According to preliminary calculations, if 50% of China’s commercial forests were certified, the economic cost of forest certification would range from US$0.66–86.63 million while the economic benefits for the forestry business sector could exceed US$0.66–86.63 million while the economic benefits for the forestry business sector could exceed US150 million. With continuing progress in forest management practices and the development of international trade in forest products, it becomes important to improve the forest certification process in China. This can be achieved by improving the forest management system, constructing and perfecting market access mechanisms for certificated forest products, and increasing public awareness of environmental protection, forest certification, and their interrelationship.  相似文献   
917.
The management of wild mushroom is interdisciplinary in nature, whereby the biophysical considerations have to be incorporated into the context of a wide range of social, economic and political concerns. However, to date, little documentation exists illustrating an interdisciplinary approach to management of wild mushrooms. Moreover, the empirical case studies necessary for developing applicable and practical methods are even more rare. This paper adopted an interdisciplinary approach combining participatory methods to improve the habitat management of Thelephora ganbajun, an endemic and one of the most economically valuable mushroom species in Southwest China. The paper documents an empirical case of how an interdisciplinary approach facilitated the development of a scientific basis for policy and management practice, and built the local capacity to create, adopt and sustain the new rules and techniques of mushroom management. With this integrative perspective, a sustainable management strategy was developed, which was found not only technically feasible for farmers, but also acceptable to the government from an ecological and policy-related perspective. More importantly, this approach has greatly contributed to raising the income of farmers. The paper highlights how the integration of biophysical and socioeconomic factors and different knowledge systems provided a holistic perspective to problem diagnosis and resolution, which helped to cope with conventional scientific dilemmas. Finally, it concludes that the success of this interdisciplinary approach is significant in the context of policy decentralization and reform for incorporating indigenous knowledge and local participation in forest management.  相似文献   
918.
Biodiversity goals are becoming increasingly important in stream restoration. Typical models of stream restoration are based on the assumption that if habitat is restored then species will return and ecological processes will re-establish. However, a range of constraints at different scales can affect restoration success. Much of the research in stream restoration ecology has focused on habitat constraints, namely the in-stream and riparian conditions required to restore biota. Dispersal constraints are also integral to determining the timescales, trajectory and potential endpoints of a restored ecosystem. Dispersal is both a means of organism recolonization of restored sites and a vital ecological process that maintains viable populations. We review knowledge of dispersal pathways and explore the factors influencing stream invertebrate dispersal. From empirical and modeling studies of restoration in warm-temperate zones of New Zealand, we make predictions about the timescales of stream ecological restoration under differing levels of dispersal constraints. This process of constraints identification and timescale prediction is proposed as a practical step for resource managers to prioritize and appropriately monitor restoration sites and highlights that in some instances, natural recolonization and achievement of biodiversity goals may not occur.  相似文献   
919.
Roads function as prime habitats and corridors for invasive plant species. Yet despite the diversity of road types, there is little research on the influence of these types on the spread of invaders. Common ragweed (Ambrosia artemisiifolia), a plant producing large amounts of allergenic pollen, was selected as a species model for examining the impact of road type on the spread of invasive plants. We examined this relationship in an agricultural region of Quebec, Canada. We mapped plant distribution along different road types, and constructed a model of species presence. Common ragweed was found in almost all sampling sites located along regional (97%) and local paved (81%) roads. However, verges of unpaved local roads were rarely (13%) colonized by the plant. A model (53% of variance explained), constructed with only four variables (paved regional roads, paved local roads, recently mown road verges, forest cover), correctly predicted (success rate: 89%) the spatial distribution of common ragweed. Results support the hypothesis that attributes associated with paved roads strongly favour the spread of an opportunistic invasive plant species. Specifically, larger verges and greater disturbance associated with higher traffic volume create propitious conditions for common ragweed. To date, emphasis has been placed on controlling the plant in agricultural fields, even though roadsides are probably a much larger seed source. Strategies for controlling the weed along roads have only focused on major highways, even though the considerable populations along local roads also contribute to the production of pollen. Management prioritizations developed to control common ragweed are thus questionable.  相似文献   
920.
Exploitation of certain resources within a protected area on a sustainable basis could contribute to higher living standards of rural people, particularly those in poor countries, and decrease conflicts between these populations and park authorities. This article presents data from a case study of Kopaonik National Park (NP), Serbia, which is a park with natural resources, most notably bilberries, which have always been relied on by local people. Vaccinium myrtillus traditionally has been collected for decades in Kopaonik NP and used by local people. However, little is known about the socioeconomic and ecological relations that affect the collection and use of this species. The aim of the present study was to understand how local people collect bilberries in Kopaonik NP and what their attitudes toward the park are. Household questionnaire data were used to examine how local people collect bilberries and how to improve the relations between local people and NP authorities. The survey questionnaire included 52 households from 7 local communities, and we applied a purposive sampling strategy. In addition, expert interviews were conducted, and from these data we obtained a broader understanding of the relation between local people and NP authorities. The results indicate that in Kopaonik NP, there is a conflict between pickers and NP authorities. Sustainable management should be directed toward the protection of bilberries. Education of local people is a key element in the sustainable collection and protection of natural resources.  相似文献   
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