中国自然生态系统修复研究文献综述

以中国自然生态系统为研究对象,对生态修复研究情况进行梳理,总结出相关研究的时间、主题分布特征,并对自然生态系统修复的技术、模式、类型、案例研究内容展开仔细分析。通过文献梳理,提出了对国内生态修复的展望。     

Reforestation and smallholder livelihoods in the humid tropics

Smallholder livelihoods and the restoration of tropical forests are intimately intertwined. To address the question of how reforestation affects livelihoods and how they in turn affect reforestation, a meta-synthesis was undertaken of 339 scientific publications identified from a systematic literature search. This study is focused on smallholders in the humid tropics, and uses the Sustainable Livelihoods Framework, which was developed by the UK Department for International Development as the framework for analysis. The links between reforestation and livelihoods are found to be diverse and highly interconnected. Reforestation is only one of a smallholder’s activities and typically forms part of a mosaic of land uses across a landscape. Therefore, reforestation should be designed, managed and evaluated under the perspective of a diverse livelihood portfolio, and not as a single activity isolated from other portfolio components, especially under current landscape approaches. It is important for reforestation to be a complementary rather than a competitive livelihood activity. Reforestation has great potential to address poverty, and to increase smallholder socio-ecological resilience and local social equity. However, reforestation outcomes are often suboptimal. Assessing smallholder capacity and the surrounding environment prior to reforestation, and addressing limiting local capacities and conditions in a timely manner, may enhance the likelihood of optimal benefits.     

Amazon forest on the edge of collapse in the Maranhão State,Brazil

The year 2019 in Brazil was marked by environmental setbacks, which catalyzed the increase of illegal deforestation and fire rates in the Brazilian Amazon. In the Amazon region of Maranhão state, original forest cover diminished from 25 % (24,700 km²) in 2016 to 24 % (23,967 km²) in 2019, and 6,038 km² of remaining forests were degraded by fires and/or illegal logging – processes related to high levels of violence against indigenous and rural communities. Almost half of all deforested areas in the region (36,060 km²) are considered a global restoration hotspot, however secondary vegetation remains unprotected and 8,294 km² were cleared between 2014 and 2018. Due to uncontrolled deforestation and fragmentation, Maranhão has no more forest core areas (outside protected areas) with the minimum size to ensure sustainable forest management practices for timber production. New policies at the state level must promote old-growth and secondary forest conservation and restoration. However, the trends point to the opposite direction: the Ecological-Economic Zoning (ZEE) allows the reduction of forest protection and the State Forest Policy reinforces federal legislation setbacks. The Amazon region of Maranhão state has forest aptitude, and forest and agroforestry product chains would bring social and environmental benefits, making them the best opportunity for sustainable economic development in the region. Therefore, the forest must be re-planted for the benefit of people and nature.     

中国森林生态恢复与重建生态效益评价研究进展

通过对国内森林生态恢复与重建生态效益评价指标构建和评价方法研究文献的综合分析发现:构建评价指标主要采用层次分析法,评价方法主要是以经济学为主的计量方法和以生态学为主的计量方法。经济学的评价方法侧重于森林恢复后的显性经济效益,生态学的评价方法侧重于森林所具有的生态功能。最后,指出基于经济学和生态学理论,运用数学模型加以修正的研究方法是其未来的方向。     

The Influence of Riparian Protection Measures on Residential Property Values: The Case of the Oregon Plan for Salmon and Watersheds

The Oregon Plan for Salmon and Watersheds encourages residential property owners to plant riparian buffers in an effort to reduce stream temperature and thus improve fish habitat. This study estimates the change in the value of streamside residential properties in response to planting a treed riparian buffer. A hedonic pricing analysis suggests that treed riparian buffers reduce the market value of stream-front residential property in the study area.     

Changes in Brazil’s Forest Code can erode the potential of riparian buffers to supply watershed services

In Brazil, the Forest Code requires landholders to maintain fixed-width buffers of native vegetation along watercourses – legally called Areas of Permanent Preservation (APPs). In 2012, agricultural activities started to be partially allowed in APPs, but only if best management practices on soil and water conservation are adopted and if a narrow buffer strip with native vegetation is restored adjacently to the watercourse. In this paper, we present a modeling framework to investigate the capacity of legal compliant APPs to supply watershed services (erosion control and stream bank stabilization) in a 2,200 ha watershed in São Paulo State, Brazil. Our results suggest that the narrower the riparian buffer the lower the control of soil erosion dynamic within APPs, and that riparian buffers smaller than 8 m can act as a source of sediments to streams. The adoption of best management practices can contribute to controlling soil erosion within APPs but the presence of native forests in the first 15 m is necessary to guarantee equivalent protection to streams when compared to APPs completely covered by forests. Moreover, we observed that forest restoration within APPs helped to reduce the average soil loss of the watershed by only 20 %, compared to a reduction of 55 % when best practices are implemented in all watershed agricultural areas. We conclude that (i) the reduced requirements for APP restoration may contribute to stream sedimentation, which will likely affect the supply of watershed services by stream ecosystems; (ii) the implementation of best management practices in APPs will not have the same effect as native forests to reduce stream sedimentation; and (iii) the adoption of best management practices in all agricultural production areas – and not only within APPs as required by law – is the best strategy to promote the supply of watershed services to society.     

A Unifying Framework and Comparison of Algorithms for Non-negative Matrix Factorisation

Non-negative matrix factorisation (NMF) is an increasingly popular unsupervised learning method. However, parameter estimation in the NMF model is a difficult high-dimensional optimisation problem. We consider algorithms of the alternating least squares type. Solutions to the least squares problem fall in two categories. The first category is iterative algorithms, which include algorithms such as the majorise–minimise (MM) algorithm, coordinate descent, gradient descent and the Févotte-Cemgil expectation–maximisation (FC-EM) algorithm. We introduce a new family of iterative updates based on a generalisation of the FC-EM algorithm. The coordinate descent, gradient descent and FC-EM algorithms are special cases of this new EM family of iterative procedures. Curiously, we show that the MM algorithm is never a member of our general EM algorithm. The second category is based on cone projection. We describe and prove a cone projection algorithm tailored to the non-negative least square problem. We compare the algorithms on a test case and on the problem of identifying mutational signatures in human cancer. We generally find that cone projection is an attractive choice. Furthermore, in the cancer application, we find that a mix-and-match strategy performs better than running each algorithm in isolation.     

吉林长白山国家级自然保护区风灾区植被恢复情况调查

长白山国家级自然保护区风灾区形成于1986年,风灾面积11386hm2,由于大面积森林被摧毁,以及毗临中朝边境线,成为全国重点火险区之一;通过对20多年来风灾区植被自然及人工恢复情况实地调查,全面掌握了保护区风灾区生态环境的现状,客观分析了影响恢复的各项因素,提出了加快恢复的有关措施。     

A note on finite sample breakdown points of projection based multivariate location and scatter statistics

In this note, general results of finite sample breakdown point are obtained for two classes of projection based location and scatter statistics: the Stahel-Donoho statistics and the Maronna-Yohai statistics. It is shown that these projection based location and scatter statistics can achieve the maximum breakdown point of affine equivariant multivariate location and scatter statistics. General relationships between the finite sample breakdown point of these statistics and the uniform finite sample breakdown point of the sample median and a modified sample median absolute deviation are formally established. Received: May 1999     

笔绘唐卡损伤原因分析及维护与修复

笔绘唐卡的维护和修复是为长期保存作品而使用的重要技术。其关键在于能够对画面水渍、烟熏、霉斑、白粉层和颜料龟裂剥落、画面扭曲变形等问题分别进行清洁、填补、移植和整形,以达到防止损害现象进一步恶化,使唐卡的寿命得以延长。同时,为了减少先天性因素的损害,画师在作品尚未诞生前,对基底材料和颜料的选择及处理、调色与上色技术的运用等问题应予以重视。