火烧对黔中喀斯特山地马尾松林分的影响

采用样地比较法在黔中喀斯特山地上覆第四纪粘土的马尾松人工次生林内,研究了林火对马尾松林分的影响,结果表明过火马尾松林不同部位的受害率为树皮(95.51%)＞树枝(71.49%)＞树冠(62.95%),不同层片的植物死亡率为草本层(100.00%)＞灌木层(30.43%)＞乔木层(29.09%)。马尾松树皮受害率不因径级而变化、树枝和树冠受害率及植株死亡率随径级增高而降低,灌木层物种或全部死亡、或部分死亡、或全部存活,草本层物种或死亡、或萌生。过火马尾松林地生物量的潜在损失量(68.7755 t/hm²)＞直接损失量(12.1818 t/hm²)、直接损失率22.41%,直接损失量中乔木层(6.9382 t/hm²)＞枯物层(3.3441 t/hm²)＞灌木层(2.4964 t/hm²)＞草本层(0.8861 t/hm²),直接损失率中草本层或枯物层(100.00%)＞灌木层(33.36%)＞乔木层(23.59%)。过火马尾松林不同层片的Patrick指数、Gleason指数、Simpson指数和Hurlbert指数损失量为草本层＞灌木层＞乔木层、潜在损失量＞直接损失量,直接损失率中乔木层的相应值为14.29%、14.29%、17.85%、-11.29%,灌木层的相应值为26.76%、26.76%、37.63%、-18.53%,草本层为100.00%。     

Postfire response of North American boreal forest net primary productivity analyzed with satellite observations

Fire is a major disturbance in the boreal forest, and has been shown to release significant amounts of carbon (C) to the atmosphere through combustion. However, less is known about the effects on ecosystems following fire, which include reduced productivity and changes in decomposition in the decade immediately following the disturbance. In this study, we assessed the impact of fire on net primary productivity (NPP) in the North American boreal forest using a 17‐year record of satellite NDVI observations at 8‐ km spatial resolution together with a light‐use efficiency model. We identified 61 fire scars in the satellite observations using digitized fire burn perimeters from a database of large fires. We studied the postfire response of NPP by analyzing the most impacted pixel within each burned area. NPP decreased in the year following the fire by 60–260 g C m^?2 yr^?1 (30–80%). By comparing pre‐ and postfire observations, we estimated a mean NPP recovery period for boreal forests of about 9 years, with substantial variability among fires. We incorporated this behavior into a carbon cycle model simulation to demonstrate these effects on net ecosystem production. The disturbance resulted in a release of C to the atmosphere during the first 8 years, followed by a small, but long‐lived, sink lasting 150 years. Postfire net emissions were three times as large as from a model run without changing NPP. However, only small differences in the C cycle occurred between runs after 8 years due to the rapid recovery of NPP. We conclude by discussing the effects of fire on the long‐term continental trends in satellite NDVI observed across boreal North America during the 1980s and 1990s.     

1996—2005年北京城市生态质量动态

从生态要素、生态过程、生态功能和生态问题4个主题出发,构建了包含16个指标的北京城市生态质量评价指标体系,并分别采用熵权法、最差状态法和最佳状态法对指标进行赋权,通过加权平均法构建了北京城市生态要素指数（EEI）、生态过程指数（EPI）、生态功能指数（EFI）、生态问题指数（EDI）和综合生态质量指数（CEI）,用以评价1996—2005年北京城市生态质量动态变化.结果表明：研究期间,北京城市EEI无明显改善,持续维持在远离理想点的水平;EPI和EFI改善显著,由1996年的远离理想点到2005年接近于理想点的水平;EDI的年度波动较大,普遍远离理想点;CEI得到持续改善,但离理想点依然有一定距离.当人均国内生产总值（GDP）小于3 000美元时,EPI、EFI和CEI随GDP的增长而快速增大,改善显著,当人均GDP超过3 000美元后,EPI、EFI和CEI随GDP增长而增大的速度减慢;EEI和EDI受人均GDP的影响较小,主要受限于自然条件及全球和区域环境的变化.     

Simulation of forest net primary production and the effects of fire disturbance in Northeast China

 森林净初级生产力(NPP)是衡量陆地碳源/汇的重要参数, 准确地估算森林生态系统的NPP, 同时通过引入干扰因子以期更加完整地描述生态学过程及其响应是目前森林生态系统碳循环研究的重点。因此, 该研究基于北方生态系统生产力(BEPS)模型, 结合遥感数据和气象数据等模拟2003年东北林区NPP; 将BEPS模型模拟的结果作为整合陆地生态系统碳收支(InTEC)模型的参考年数据, 模拟东北林区1901–2008年的NPP, 并在InTEC模型中加入林火干扰数据, 模拟大兴安岭地区1966–2008年的森林NPP。结果显示: 在1901年, 东北林区NPP平均值仅为278.8 g C·m^–2·a^–1, 到了1950年, NPP平均值增加到338.5 g C·m^–2·a^–1, 2008年NPP平均值进一步增加到378.4 g C·m^–2·a^–1。其中长白山地区的NPP平均值始终最高, 大兴安岭次之, 小兴安岭始终最低。到了2008年, 大、小兴安岭和长白山地区的NPP平均值都有较大涨幅, 其中涨幅最高的是长白山地区, 达到200–300 g C·m^–2·a^–1; 东北三省中, 黑龙江和吉林的NPP平均值和总量都比较高, 辽宁相对较低, 但相比于1901年的涨幅最高, 达到70%; 重大火灾(100–1000 hm²)对NPP的影响不是很大, 而特大火灾(>1 000 hm²)的影响比较大, 使NPP下降幅度达到10%左右, 其他火灾年份, NPP增长迅速并保持在较高水平; 对火灾面积在100 000 hm²以上的4个年份的NPP进行分析, 发现NPP平均值都大幅度下降, 其中1987年下降幅度最大, 为11%以上。     

红火蚁对我国一些生物潜在影响的初步分析

通过分析国际上对红火蚁影响生境中其他生物的研究成果,认为红火蚁主要通过以下3种方式危害其他生物:(1)攻击、捕食刚孵化的地栖性卵生动物个体,或者以群体力量捕食昆虫幼虫、成虫等;(2)竞争有限的食物资源,导致其他物种因为缺乏足够食物供给而种群数量减少甚至灭绝;(3)通过叮咬而使得某些动物存活率降低,改变生境,甚至弃巢外逃,或者因为受攻击活动量加大而增加被捕食的几率。同时初步分析在《国家重点保护野生动物名录》中列举的379种野生动物名录中,有22种鸟类(占9.6%)、1种两栖类(占14%)、所有的18种爬行类(占100%)可能因为红火蚁的入侵导致种群数量下降甚至灭绝。     

Effects of Hardwood Reduction Techniques on Longleaf Pine Sandhill Vegetation in Northwest Florida

We tested whether the intensity of hardwood midstory reduction causes commensurate improvements of herbaceous groundcover in fire‐suppressed Pinus palustris (longleaf pine) sandhills. Using a complete randomized block design, we compared the effects of three hardwood reduction techniques (spring burning, application of the ULW^® form of the herbicide hexazinone, chainsaw felling/girdling) and a no‐treatment control on plant species richness, and on life form and common species densities at Eglin Air Force Base, Florida, U.S.A., from 1995 to 1998. ULW^® and felling/girdling plots were burned for fuel reduction two years after initial treatment application. We also sampled the same variables in frequently‐burned reference sandhills to establish targets for restoration. Spring burns achieved partial topkill of oaks (17.6–41.1% from 1995 to 1998) compared to reductions of 69.1–94% accomplished by ULW^® and of 93.2–67.8% by felling/girdling treatments. We predicted that plant species richness and densities of herbaceous groundcover life forms would increase according to the percent hardwood reductions. Predictions were not supported by treatment effects for species richness because positive responses to fire best explained increases in plant richness, whereas ULW^® effects accounted for the largest initial decreases. Legumes, non‐legume forbs, and graminoids did not respond to treatments as predicted by the hypothesis. Again, positive responses to fire dominated the results, which was supported by greater herbaceous densities observed in reference plots. Overall, we found that the least effective and least expensive hardwood midstory reduction method, fire, resulted in the greatest groundcover improvements as measured by species richness and herbaceous groundcover plant densities.     

Coming to terms with Ox‐eye Daisy (Leucanthemum vulgare) in Kosciuszko National Park,New South Wales

Australia's mountain vegetation is under pressure from a range of threats, not least being weed invasion. Can a program to control the introduced Ox‐eye Daisy succeed and what can be learned to assist management of this weed in other natural areas?     

Using Dominance-Diversity Curves to Assess Completion Criteria After Bauxite Mining Rehabilitation in Western Australia

Abstract Dominance‐diversity curves have been previously constructed for a range of ecosystems around the world to illustrate the dominance of particular species and show how their relative abundances compare between communities separated in time or space. We investigate the usefulness of dominance‐diversity curves in rehabilitated areas to compare the floristic composition and abundance of “undisturbed” areas with disturbed areas, using bauxite mining rehabilitation in Western Australia as an example. Rehabilitated pits (11–13 years old) subjected to prescribed fire in autumn and spring were compared with unburned rehabilitated areas and the native jarrah (Eucalyptus marginata) forest. Dominance diversity curves were constructed by ranking the log of the species density values from highest to lowest. Species were categorized according to a variety of functional responses: life form (trees, shrubs, subshrubs, and annuals), fire response syndrome (seeder or resprouter), nitrogen fixing capability, and origin (native or adventive). Exponential functions showed extremely good fits for all sites (r² = 0.939–0.995). Dominance diversity graphs showed that after burning of rehabilitated areas, sites exhibited a more similar dominance‐diversity curve than before burning. This was emphasized in a classification (UPGMA) of the regression equations from the dominance‐diversity curves that showed that sites burned in spring were more similar to the native forest than sites burned in autumn. There was no significant segregation of the nitrogen‐fixing and species origin categories, although the life form and fire response groupings showed significant segregation along the dominance‐diversity curve. Resprouters tended to be over‐represented in the lower quartiles and under‐represented in the upper quartiles of post‐burn sites. It is suggested that using dominance‐diversity curves in the monitoring of rehabilitated areas may be a useful approach because it provides an easily interpretable visual representation of both species richness and abundance relationships and may be further utilized to emphasize categories of plants that are over‐ or under‐represented in rehabilitated areas. This will assist in the post‐rehabilitation management of these sites.     

Pattern,prediction and parsimony in continental‐scale synthesis of pyromes: a reply to Gosper et al.

We (Murphy et al., 2013; Clarke et al., 2015) have recently developed a framework to understand the spatial distribution of fire regimes and plant fire‐response traits at large spatial scales. We integrated a range of data sources to create a continental‐scale overview of Australian pyromes from which to infer pyrogeographic drivers. Gosper et al. (in press) have criticized our approach, based on our misclassification of a vegetation type (eucalypt woodland), with distinct fire regime, in the Coolgardie bioregion of Western Australia. We argue that the intention of our integrative approach was to develop and refine conceptual models of Australian pyrogeography, not to produce a predictive map of fire regimes, and certainly not to guide local‐scale fire management. Like all models, continental‐scale syntheses of pyromes are imperfect, yet they still represent powerful tools for understanding the drivers of the spatial distribution of fire regimes.