Changes in wildfire severity from maritime pine woodland to contiguous forest types in the mountains of northwestern Portugal

Large and severe wildfires are now widespread in the Mediterranean Basin. Fire severity is important to ecosystem properties and processes and to forest management but it has been neglected by wildland fire research in Europe. In this study, we compare fire severity between maritime pine (PS) woodland and other forest (OF) types, identify other variables influent on fire severity, and describe its variation. We sampled contiguous, paired stands of PS and OF cover types – including deciduous and evergreen broadleaves and short-needled mountain conifers – that burned under very high to extreme fire danger in northwestern Portugal. Data on stand characteristics and fire severity metrics were collected in plots along transects perpendicular to the PS–OF boundary. Fire severity was rated in separate for the tree canopy, understorey vegetation and forest floor layers, and then an average (composite) fire severity rating was calculated. Fire intensity inferred from stem char height (adjusted for the effects of other factors) was highest in PS, followed by deciduous broadleaved woodland and short-needled conifer forest. With a few exceptions, all fire severity ratings were significantly different between PS and OF at all sites. Most fire severity metrics and ratings were correlated. The distance for fire severity minimization did not differ between OF types (median = 21 m). Variation in composite fire severity was accounted for by a classification tree (R² = 0.44) based on cover type (contributing with 51% to the overall explanation), stand variables, aspect, distance to the PS–OF edge and fire spread pattern. Except for a more immediate decline in deciduous broadleaves, fire severity rating was not affected by OF type and tended to decrease in more mature stands and moister aspects. The fire severity moderation from PS to OF was compounded by a dominant pattern of down slope fire propagation into moister topographical positions, exacerbating the fuel effect implicit in the cover type change. The results are consistent with fire hazard and fire incidence studies and support conventional knowledge that advocates the expansion of broadleaved deciduous or evergreen forest as a means to achieve more fire-resilient ecosystems and landscapes.     

论集体林区林地产权制度变迁的路径

林地产权制度改革是实现林业可持续发展的需要。文中在分析集体林区林地产权制度缺陷的基础上,提出了林地产权制度变迁的路径。     

论我国林地保护制度

林地保护制度是森林法确立的一项法律制度。结合林地保护与管理实践,研究林地保护制度,探讨林地保护制度的理论问题,提出进一步完善林地保护制度的建议。     

How rare is too rare to harvest?: Management challenges posed by timber species occurring at low densities in the Brazilian Amazon

Tropical forests are characterized by diverse assemblages of plant and animal species compared to temperate forests. Corollary to this general rule is that most tree species, whether valued for timber or not, occur at low densities (<1 adult tree ha⁻¹) or may be locally rare. In the Brazilian Amazon, many of the most highly valued timber species occur at extremely low densities yet are intensively harvested with little regard for impacts on population structures and dynamics. These include big-leaf mahogany (Swietenia macrophylla), ipê (Tabebuia serratifolia and Tabebuia impetiginosa), jatobá (Hymenaea courbaril), and freijó cinza (Cordia goeldiana). Brazilian forest regulations prohibit harvests of species that meet the legal definition of rare – fewer than three trees per 100 ha – but treat all species populations exceeding this density threshold equally. In this paper we simulate logging impacts on a group of timber species occurring at low densities that are widely distributed across eastern and southern Amazonia, based on field data collected at four research sites since 1997, asking: under current Brazilian forest legislation, what are the prospects for second harvests on 30-year cutting cycles given observed population structures, growth, and mortality rates? Ecologically ‘rare’ species constitute majorities in commercial species assemblages in all but one of the seven large-scale inventories we analyzed from sites spanning the Amazon (range 49–100% of total commercial species). Although densities of only six of 37 study species populations met the Brazilian legal definition of a rare species, timber stocks of five of the six timber species declined substantially at all sites between first and second harvests in simulations based on legally allowable harvest intensities. Reducing species-level harvest intensity by increasing minimum felling diameters or increasing seed tree retention levels improved prospects for second harvests of those populations with a relatively high proportion of submerchantable stems, but did not dramatically improve projections for populations with relatively flat diameter distributions. We argue that restrictions on logging very low-density timber tree populations, such as the current Brazilian standard, provide inadequate minimum protection for vulnerable species. Population declines, even if reduced-impact logging (RIL) is eventually adopted uniformly, can be anticipated for a large pool of high-value timber species unless harvest intensities are adapted to timber species population ecology, and silvicultural treatments are adopted to remedy poor natural stocking in logged stands.     

城市森林火灾隐患及其管理

人为纵火、林区吸烟、施工用火、闪电、林区建筑物以及不合理的城市森林规划等是城市森林火灾发生的重要隐患,常常导致城市森林火灾的发生,给城市居民的生命和财产造成了巨大的损失。加强对城市森林火灾发生原因的研究,合理规划城市森林布局和结构,加强对火灾隐患的管理,减少城市森林火灾的发生,是维护城市生态可持续发展的必然要求。       

Long-term impact of prescribed burning on the nutrient status and fuel loads of rehabilitated bauxite mines in Western Australia

Alcoa World Alumina Australia has been rehabilitating bauxite mines in the jarrah (Eucalyptus marginata) forest of Western Australia for more than 35 years. It is a requirement of Alcoa’s completion criteria that rehabilitated areas can be incorporated into the prescribed burning program implemented in the surrounding forest. Rehabilitated areas may be more susceptible to nutrient losses following burning because of their relatively young age and reliance on N fixation from a legume understorey. The objective of this study was to assess the impact that prescribed burning has on the nutrient pools within rehabilitated ecosystems 5 and 8 years after fire, and compare these responses to unburnt rehabilitated areas and the unmined forest. The nutrient status of sites established in previous studies were assessed five (burnt and unburnt forest, 1989 and 1992 rehabilitation) and 8 (spring, autumn and unburnt 1981/1982 rehabilitation) years after burning. Soil, litter and understorey samples were collected and analysed for nutrient content. Burning 1981/1982 rehabilitation in either season 8 years earlier had no long-term negative effect on the nutrient status of the rehabilitation compared to the unburnt controls. Spring burning increased the nitrogen status of the rehabilitated areas by 52 kg ha⁻¹ compared with the unburnt control. Sites rehabilitated in 1989 and burnt 5 years ago showed similar post-fire recovery of nitrogen status to that of the burnt native forest sites (77–85%), while 1992 rehabilitation sites had only recovered 52% of the of the nitrogen of the unburnt sites. Therefore, the impact of burning on nitrogen status was greatest in the 5-year-old rehabilitation and least in the 12–13-year-old sites. Phosphorus was less affected by burning than nitrogen largely because the majority of P is bound in the soil in the jarrah forest. It is recommended that rehabilitated sites are burnt under low intensity in spring when they are 12–15-year-old to ensure rapid post-fire recovery of nutrients.     

Fine root decomposition in tropical dry evergreen and dry deciduous forests in Thailand

Dry evergreen forest (DEF) and dry deciduous dipterocarp forest (DDF) are major forest types extensively distributed in northeastern Thailand, exhibiting different nutrient cycling properties. This study aims to improve our understanding on the pattern of mass loss and nitrogen release from two categories of roots (fine, <2 mm and small, 2–5 mm) of Hopea ferrea at DEF and fine roots of mixed trees and dwarf bamboo (Arundinaria pusilla) at DDF sites. Decomposition experiment was performed for more than 12 months using buried litter bag technique. Initial chemistry was significantly different among the four root litters; fine root of H. ferrea exhibited a low ratios of C:N and acid-insoluble:N. The fine root of dwarf bamboo was characterized by high contents of total carbohydrate and ash. Decomposition rate constants (year⁻¹) of ash-free weight remaining were 1.27 and 0.55 for fine and small roots of H. ferrea, and 0.73 and 0.66 for fine root of mixed trees and dwarf bamboo, respectively. At the end of the experiment, the N concentration in fine and small roots of H. ferrea increased to 1.5 times the initial concentration. Whereas, N mass of dwarf bamboo decreased during the experiment. This suggests a different pattern of root decomposition and N release in two forest ecosystems. Generally, the fine root decomposition was faster in the DEF than in the DDF. The role of initial litter chemistry was more pronounced than the climatic seasonality on the belowground decomposition pattern in our study.     

Effects of burning season and frequency on saw palmetto (Serenoa repens) flowering and fruiting

Medicinal use of saw palmetto (Serenoa repens) fruits in treating benign prostatic hypertrophy has driven a recent sharp increase in fruit harvesting. At the same time, saw palmetto often is considered a keystone species, serving as habitat or a food source for several hundred mammal, bird, reptile, amphibian and insect species. Due to harvesting pressure on this ecologically important, non-cultivated species, land management practices that produce environmentally sustainable harvests are needed. As part of research focusing on use of controlled burning as a management tool, we investigated effects of burning season and frequency on saw palmetto flowering and fruiting in 32 pine flatwoods sites in central and southwest Florida from 1997 to 1999. The study was conducted as two repeated measures experiments, each involving 16 sites. Each experiment included two among-subjects factors – burning season and past burning frequency – and one within-subjects factor – year – with four replications of each treatment combination. For both experiments, growing season (i.e., April–July) burns had high flowering levels the first year after burning (mean proportion of saw palmettos flowering = 0.49, n = 16 sites), but decreased the second year after burning (mean proportion flowering = 0.15, n = 16 sites), while winter (i.e., November–February) burns had intermediate levels of flowering during both the first and second years after burning (mean proportions flowering = 0.21 and 0.28 for first and second years after burning, n = 16 sites). Although most flowering occurred during April and May, flowering occurred 2–5 months after winter burns, but did not occur until 9–12 months after growing season burns. During the 1997–1998 experiment, fruit infection by the fungus Colletotrichum gloeosporioides caused a fruiting failure in all sites. During the 1998–1999 experiment, fruit yields were higher in growing season burns only in infrequently burned (i.e., burned less often than every 5 years) sites, and only in 1998 (mean fruit yields = 325 kg/ha and 0.25 kg/ha for growing season, infrequently burned sites and winter, infrequently burned sites; n = 4 sites in each group). Frequently burned (i.e., burned every 2–3 years) sites generally had low fruit yields (mean fruit yields = 163 kg/ha and 242 kg/ha for frequently burned sites in 1998 and 1999; n = 8 sites). Although controlled burning can be an effective management tool in producing economically sustainable saw palmetto fruit harvests, land managers also must consider ecological needs of other plant and animal species when planning environmentally sustainable burning regimes.     

内蒙古大兴安岭林区发展非公有制林业探讨

发展非公有制林业对我国生态建设、林业产业发展具有重要意义.针对内蒙古大兴安岭林区的现实,提出国有林区发展非公有制林业必须解放思想、科学规划,遵守国家法律,建立相应的服务体系,遵守相关原则.     

西双版纳生物多样性保护战略研究

西双版纳具有珍贵的热带雨林,生物多样性丰富,素有野生动植物宝库之称。作者通过 论述自然地理特征,剖析了其生境复杂性;通过系统研究主要植被类型及珍稀物种,阐明了 该区生物多样性的主要成分和价值;通过对生物多样性保护现状的评价,揭示了保护实践中 潜在的危机和问题。本文通过借鉴现代保护生物学理论和国内外的创新经验,提出了该区生 物多样性保护的4条首要战略,以期建立良性互动机制,促进生物多样性保护与利用的有机 结合,有效提高当地民众生活水平,以相对减少林区居民对于资源过分依赖性。     

安源林地资源管理现状及发展对策

分析了安源林地资源概况及开发利用现状,针对当前安源林地保护管理中存在的问题及原因,提出了林地资源保护管理工作的发展对策。     

上海城市森林规划实施研究

实施上海城市森林规划需要在制度安排、产业支撑、政策支持、法律保障等方面展开系统研究。只有通过一系列创新,才能化解上海城市森林规划实施面临的林地、资金和农民等难点,才能建设永久林地,确立长效管理,实现持续发展。     

集体林区林地产权制度改革途径研究

林地产权制度改革是实现林业可持续发展的需要。本文在分析集体林区林地产权制度缺陷的基础上,提出了林地产权制度改革途径。     

火烧迹地次生林天然更新株数模型的建立

作者根据火烧迹地天然更新情况,通过数量化方法的计算,对白桦、杨树两种树种建立天然更新株数模型进行了详细叙述。     

小规模林地合作经营趋势与国外经验借鉴

林权制度改革实际上是家庭承包经营责任制在林业领域的延伸。家庭承包经营责任制带来了林地小规模经营。分析了家庭承包经营责任制下的林农分化情况, 阐述了小规模林地合作经营的趋势及当前的农民合作经济组织形式。在借鉴国外小规模林地合作经营做法的基础上, 提出了我国小规模林地合作经营的路径:健全法制、依法治林、促进林业合作经营, 鼓励组建林业合作组织, 加强对林业合作组织的规范化管理、完善内部管理制度, 对农民进行合作经济组织基本知识培训, 促进跨区域、全国性合作组织的成立。