对“三北”工程区退化林修复策略的思考

自1978年“三北”工程启动以来;营建了大面积防护林、公益林;对筑牢我国北方生态安全屏障起到关键作用。“三北”工程早期营建的部分防护林出现老化、退化问题后;国家在“三北”工程区先后部署退化林修复相关的工程任务;目的是维护“三北”防护林体系完整性和生态功能的正常发挥。针对“三北”工程六期退化林修复亟需回答的复杂科学问题;本研究将“三北”工程区退化林限定为生长出现明显衰退、生态功能出现明显下降的人工林（含灌木）。退化林修复不仅要解决表征性林分退化;更要解决系统性土壤退化;发生系统性退化的根本原因是后期管护不到位;致使土壤和水分条件发生退化;而后期管护面临的最大限制性因素是水分。“三北”工程区幅员辽阔;退化成因的自然、灾害、生理、设计和人为因素叠加效应明显。首先;应根据自然禀赋特征进行退化林修复分区、分类、分级;确保精准施策;其次;考虑将过去以植被表征性为主的退化判定指标逐步升级为以植被功能性为主、结合表征性的判定退化指标。建议按退化程度的分级（轻度、中度、重度退化）;采取针对性的封育保护、补植补播和更新改造等修复策略。本研究提出提高林分全周期经营管护水平的管护制度建议;以期为“三北”工程退化林修复、制定相关技术规程和政策保障提供参考思路。     

退化森林生态系统人工针叶林恢复对鸟类群落的影响

2005-2006年夏季在河北塞罕坝地区运用固定样线法对退化森林生态系统人工针叶林恢复形成的40年生人工针叶林鸟类群落进行调查,并同自然恢复形成的天然落叶阔叶林和天然针阔混交林进行比较.共记录鸟类39种.分别隶属于8目17科.结果表明:人工针叶林恢复对退化森林生态系统鸟类群落具有重要影响;人工针叶林鸟类物种数为(4.14±0.60)种·hm-2,密度为(26.21±7.64)只·hm-2,均高于或显著高于(P=0.018)天然阔叶林,且密度与天然混交林无显著差异(P=0.902),人工针叶林中的沼泽山雀和黄眉柳莺的密度有了显著提高,分别从(2.78±0.67)只·hm-2和(1.21±0.45)只·hm-2增加到(13.57±5.58)只·hm.(P=0.027)和(5.95 4-1.56)只·hm-2(P=0.009,0.002),但人工针叶林鸟类群落物种多样性值(H')较小(0.98 4-0.10)、均匀度(J)显著较低(0.73 ±0.04)(P=0.003,0.045);在鸟类4个取食集团中,人工针叶林有2个取食集团的物种组成与自然恢复无显著差异,但密度却有较大的变化,人工针叶林可以显著提高食虫鸟的密度(P=0.041),但杂食鸟和食谷鸟密度均显著低于天然混交林(P=0.007,0.002).     

Removal of Acacia mangium overstorey increased growth of underplanted Anisoptera marginata (Dipterocarpaceae) on an Imperata cylindrica grassland site in South Kalimantan,Indonesia

Effect of removing Acacia mangium overstorey on the growth of underplanted Anisoptera marginata saplings was studied in a mixed tree plantation established on an Imperata cylindrica dominated grassland site in South-Kalimantan, Indonesia. At the time of overstorey removal the Acacia mangium trees were 80 months old (average height 21 m and DBH 20 cm) and the underplanted Anisoptera marginata saplings 68 months old (average height 4.2 m and DBH 3.1~cm), and the spacing of both species was 2 m × 4 m with such an arrangement that the saplings were located within the same lines as the nurse trees. Eight plots of 192 m² in size were randomly designated to overstorey removal (canopy gap) and no removal (closed canopy) treatments. Removal of Acacia mangium overstorey was carried out by girdling and later cutting down the dead trees. The Imperata grass did not show regrowth in canopy gaps. The mean annual increment for height and DBH of Anisoptera marginata within 22 months after the treatment were higher in canopy gaps (1.3 m a^-1 and 1.4 cm a^-1) than under closed canopy (0.7 m a^-1 and 0.7 cm a^-1). Results indicate good prospects for diversifying the composition of fast-growing forest plantations on grasslands and integrating slow-growing valuable species in plantation programs. Studies on other establishment methods, such as planting in gaps or lines, and further management practices as well as their effect on available light, moisture and nutrients are needed.     

Overview of restoration and management practices in the degraded landscapes of the Sahelian and dryland forests and woodlands of East and southern Africa§

The highest deforestation and forest degradation rates in Africa occur in the dry forests and woodlands where pressure for land is increasing, poverty is rampant, livelihood options are few and climate change effects are severe. This paper examines factors that cause land and forest degradation in the Sahel and dry forests and woodlands of eastern and southern Africa and highlights some successful restoration practices, technologies and approaches. In the Sahel, enclosures are used to protect young growing trees while in East Africa enclosures are implemented on degraded land as a mechanism for environmental rehabilitation with a clear biophysical impact. The choice of techniques for rehabilitating specific degraded areas depends first on the priorities and management objectives of stakeholders followed by the costs and benefits associated with available rehabilitation techniques and the economic, social, and environmental values of the land resources in their current and desired future states. In the Sahel, sustainable land management is considered to be an imperative for their sustainable development and the practices include soil and water conservation activities and structures. In all regions, natural forest rehabilitation has used both natural and assisted regeneration to promote the growth of especially indigenous species through coppice regrowth and root suckers rather than seeds. Assisted regeneration was especially prevalent in the Sahel where indigenous tree species have been identified to dominate the degraded sites during early stages of secondary forest succession. The success of any rehabilitation activities depends on community-based natural resources management. In addition, the forest policies and their related policies need to be enabling in order to address issues of concern, including (1) the full participation of communities, (2) clear land and tree tenure and (3) equitable benefit sharing.     

3种不同林型下蕨类多样性和林冠开阔度的关系

光照和水分对林下植物的分布具有重要作用,浅根系的地生蕨类植物对光照和水分比较敏感,可以作为林下生境变化的指针。研究选取热带雨林、喀斯特森林以及人工橡胶林3种不同的林型,研究林冠开阔度对地生蕨类生物多样性的影响。采用2.5 m×1 m的样方,每个样方10 m的间距比较地生蕨类生物多样性。结果显示,热带雨林和喀斯特森林具有类似的地生蕨类多样性(2.52±1.68,2.47±0.68),两者的多样性指数明显高于人工橡胶林(1.47±0.72,P<0.000 1)。但是热带雨林具有更多的个体总数(2 769)和更高的物种丰富度(3.29±0.04),而同样指标喀斯特森林(319,2.94±0.05)和人工橡胶林(175,2.39±0.09)则相对较低。另外,随着林冠开阔度增加,地生蕨类多样性和丰富度急剧降低。地生蕨类的分布状态取决于上层的林冠开阔度,光照对地生蕨类的生物多样性具有决定性的影响,相对较弱的地表根系缺乏足够的吸水能力,不足以应付强光照带来的蒸腾损失。因此绝大多数的地生蕨类植物在林下空地间采取了避退策略。由于相对较低的林冠开阔度,使得喀斯特森林保存了相对较高的林下生物多样性,它具有重要的生态价值而必须加以保护。     

昭通市退化草地修复技术研究

昭通市草地以山地草甸为主,草地生态系统脆弱,管理水平和建设能力不高,退化草地修复难度大。昭通市现有草地面积116 079.33 hm²,其中退化草地面积6 992.10 hm²,占全市草地总面积的6.02%。退化草地主要以轻度退化为主,面积4 221.00 hm²。草地退化的原因包括人为因素、有害生物侵入、生态环境脆弱和气候因素。文章给出近自然修复、人工促进修复、人工草地建植和综合修复等退化草地修复措施,并提出加快草种基地建设、规范草地管理、生态优先、因地制宜等草地修复策略。     

湘南典型残次阔叶林人工促进更新技术研究

于2003年在湖南省汝城县益将国有林场天然残次阔叶林内设置试验样地和对照样地各3个,采用林地清理、补植、补播等手段促进天然更新,并分别于2006年和2011年进行2次人工促进干预;同时,在6个样地内各设置3个样方,共计18个样方,分别于2003、2008、2013年冬,对幼树、幼苗、萌条的数量及地径进行统计,并对样方内胸径≥5 cm的立木进行每木调查。结果表明:种子补播保存率43%,幼苗补植保存率20%,平均保存率32%。树高≤30 cm且地径0.5 cm、31 cm≤树高≤50 cm且0.5 cm地径0.7 cm幼树的数量下降率分别是对照样地的17.5%、21.59%,树高≥51 cm且地径0.7 cm幼树的数量下降率是对照样地的121.66%。2008年单位面积蓄积量是对照样地的2.28倍,2013年达到3.80倍;经过10年更新,单位面积蓄积量是试验前的11.57倍,对照样地单位面积蓄积量仅是试验前的2.55倍;单位面积蓄积量是对照样地的4.54倍。人工促进天然更新所需的人工成本为1 860元/hm2,仅为同期人工营造杉木幼林所需人工成本5 310元/hm2的35%。     

福建柏人工林调查研究

研究表明我省大部分山地适宜福建柏生长，除少数Ｉ类立地条件下福建柏林分生长量次于杉木外，其余地类的林分生长量均超过杉木；就福建柏林分而言，人工林比天然林生长好，混交林比纯林生长好。     

Regeneration dynamics and sylvigenesis in the moist deciduous forests of southwest India

Sustained management of natural forest depends on their ability to regenerate. The pace at which older trees are replaced by younger ones is important in this respect. This study was conducted to assess the demographic details of natural regeneration dynamics of south Indian moist deciduous forests. The status of natural regeneration has been assessed in eight localities of varying levels of disturbance in Thrissur Forest Division of Kerala State of southwest India. Enumeration of trees and their regeneration were analyzed at three levels of organization; whole-stand, stratum, and species.The trees of the forest were grouped into upper, middle and lower vertical strata. Species richness was highest in the middle stratum. Upper stratum species were commercially important. The mean basal area for the Forest Division was 12.83 m²/ha. and average number of trees per hectare (>=20 cm dbh) was 150. Regeneration of the upper stratum species was higher at about 10% gap in the canopy.The growing stock of established seedlings and saplings (height > 100 cm and dbh <=10cm) was very low compared to unestablished seedlings (height <=100 cm). Owing to very low survival probability in the sapling stage (dbh >=1 cm to <=10 cm), a low numbers of poles (dbh >=10 cm to <=20 cm) in the upper stratum was observed. Presence of fire, grazing, browsing and over expoitation by humans are the major constraints of natural regeneration recognized in these forests.     

吴起县不同退耕还林模式生态效益研究

对陕西省吴起县城周边地区进行样地植被和土壤调查,研究退耕还林过程中人工植被恢复区与自然植被恢复区的生态效益.结果表明,通过退耕还林可使植被得以恢复,达到控制水土流失的目的.在自然植被恢复区,植物群落主要以草本群落为主,偶见一些灌木群落.在人工植被恢复区,乔、灌、草3种植被群落均有分布,在生物多样性方面差异不大.人工植被恢复区草本群落的各多样性指标略高于自然植被恢复区.在生物量方面,人工恢复区明显高于自然恢复区.由此可见,人工恢复区植被恢复程度优于自然恢复区,在退耕还林过程中进行适当的人工干预有助于提高植被的生态效益.     

我国人工林天然更新研究进展

森林天然更新是生态系统中森林资源再生产的一个重要生物学过程, 对森林群落的重构起着至关重要的作用。文中总结了我国人工林天然更新的现状及主要影响因子, 归纳了天然更新的研究方法及相关指标, 在此基础上对人工林天然更新的研究进行了概述和展望, 以期为我国人工林的健康可持续经营提供科学依据。     

中国西南山区天然林退化分区

The mountain region of Southwest China is not only one of the two key regions that China’s natural forests distributed, but also has lots of degraded natural forests. Its natural forests are essential to keep regional ecosystems safe and biodiversity conservation. The forests geographical zoning plays an important role in regional forests management. Based on plants geographical division and some special topic zonings published, according to zonal climax forest types, land features and drivers of degradation, this paper used the DIVA-GIS and ArcMap, divided the degraded natural forests in mountain areas of Southwest China into five zones, namely tropical rain and monsoon forests of low-mountain in South Yunnan, evergreen broad-leaf and Pinus massoniana forests over limestone in Guizhou-Yunnan, evergreen broad-leaf and Pinus yunnanensis forests of plateau in Central Yunnan, evergreen broad-leaf and Cryptomeria-Metasequoia-Cunninghamia forests of low-mountain around Sichuan Basin, dark coniferous forests over valley and mountains in Sichuan-Yunnan. Introduced the degradation state and main reasons of natural forests of each zone. Zoning of the degraded natural forests at regional level will contribute to the ecological restoration of the degraded natural forests in mountains of Southwest China.     

兴安落叶松老龄林分幼苗天然更新及微生境特点

对落叶松老龄林幼苗天然更新及微生境研究采用样线法,沿样线设置样方,调查样方内幼苗数、测定环境变量。结果表明,原始老龄林各环境变量中地表层的作用最突出,光照的作用最小,灌木层居中。一般,枯落物、根系盘结层和苔藓的作用较大,其中枯落物对苔藓的发育有抑制作用。抑制兴安落叶松更新的主要因素：在丛桦落叶松林中主要是草本植物、赤杨落叶松林为苔藓厚度、杜香落叶松林为苔藓厚度和根系盘结层厚度。     

Forests,people and environment: some African perspectives§

Forests in Africa support the livelihoods of millions of people through provision of timber and non-timber forest products, food and nutrition, energy and payment of environmental services. However, mismanagement of forests has resulted in deforestation and forest degradation, thereby contributing to the increased emission of carbon dioxide into the atmosphere. This special issue highlights some of the research outcomes presented at a pre-congress workshop organised by the African Forest Forum and partners at the 2015 World Forestry Congress. In this issue, the main drivers of land degradation are highlighted vis-à-vis population growth, agricultural expansion, climate variability, drought and energy needs. Promising traditional management practices are identified including age-old farmer-managed natural regeneration and exclosures. In addition, research presented indicates that age-old systems such as native non-browse shrubs in Ethiopia are important in that they facilitate regeneration of late-successional tree species. Furthermore, opportunities for using forests to mitigate climate change are highlighted with a case study on the economics associated with carbon markets. The issue also highlights the methodological challenges of quantifying carbon in African forests. The effect of climate change on threatened forest species and biodiversity in general is discussed, and the associated human disturbances impacting on the population structure of a threatened species, e.g. Afzelia africana in West Africa, is presented. The important role of non-timber forest products in income generation for the rural communities and the associated challenges of commercialisation is emphasised with examples from two important tree species: shea (Vitellaria paradoxa) and baobab (Adansonia digitata). Finally, the issue covers a people-centred approach in tree planting and management where studies demonstrated that there are still problems of poor participation of local communities due to poor implementation of enabling policies, lack of involvement in initial planning and subsequent lack of clear benefit-sharing mechanisms.     

高黎贡山国家级自然保护区火烧迹地的自然恢复与更新

采用样方、样线调查法,对保护区与边缘地区同等条件的火烧迹地分别与其未过火林地进行对比,分析了不同火烧迹地天然更新情况。结果认为,在火后恢复初期,乔木层平均高和平均胸径比火烧前增加;灌木层灾后重新郁闭的片层,盖度、平均高低于未烧林地,生活力较强;野生动物物种丰富度降低。     

Secondary forest regeneration under fast-growing forest plantations on degraded Imperata cylindrica grasslands

Natural regeneration of native tree species in the understoreys of fast-growing plantation tree species (Acacia mangium, Gmelina arborea and Paraserianthes falcataria) and in adjacent natural riverine forest and non-cultivated grassland areas were studied on Imperata cylindrica grassland sites in Riam Kiwa plantation area, South Kalimantan, Indonesia. Seedling and sapling densities as well as species composition and richness were assessed in a total of 35 ha by a systematic line plot survey.Floristic composition was similar in A. mangium and P. falcataria stands which differed distinctly from G. arborea stands and Imperata grassland area. Riverine forest was characterized by later successional species. In A. mangium and P. falcataria stands, a total of 63 species from 24 families were recorded. Seedling stock consisted merely of pioneer and secondary species, but also several fairly commonly occurring primary forest species. Euphorbiaceae was the most common family representing 42% of sapling and 29% of seedling densities. The most abundant regeneration occurred in A. mangium stands (4,706 seedling/sapling ha^-1), followed by P. falcataria (2,242 ha^-1) and G. arborea (554 ha^-1). Seedling recruitment was significantly lower in plots dominated by grass vegetation than those dominated by no vegetation or shrub vegetation. Breast height diameter and basal area of canopy trees as well as coverage and height of ground vegetation did not explain seedling/sapling density. Results show that plantation establishment with suitable fast-growing tree species facilitates recruitment of a variety of native tree species. This provides potential for rapid restoration of forest ecosystem and for further development of the mixed stands of fast-growing exotics and naturally regenerated native species.     

退化生态系统植被恢复理论与技术探讨

植被恢复是退化生态系统恢复与重建的首要工作。在回顾国内外植被恢复研究进展的基础上, 提出了植被恢复的理论基础, 总结了植被恢复技术措施, 包括植被恢复目标的确定、植被恢复的步骤与途径及其采用的技术方法, 最后探讨了植被恢复研究尚存在的问题。