黄土高原子午岭大披针苔草能量与养分特征

森林地表死可燃物是引起森林火灾的重要原因,掌握森林地表死可燃物载量的分布,对预防火灾和可燃物管理有重要意义.依据1 h、10 h和100 h分类标准,对呼中林区的不同林型内的地表死可燃物载量进行了对比分析.结果表明:樟子松林内死可燃物总载量最高,偃松林内的最低;对不同类型兴安落叶松林群落的地表死可燃物进行比较,发现笃斯越桔-兴安落叶松林内死可燃物总载量最高,而泥炭藓-杜香-兴安落叶松林的最低;此外,相关分析表明,兴安落叶松死可燃物总载量与平均胸径、平均树高、草本盖度、凋落物厚度呈显著的正相关,与坡向、腐殖质厚度等因子呈显著负相关;多元线性回归分析表明,用兴安落叶松林的凋落物厚度、草本盖度、平均树高因子可较好地估算地表死可燃物总载量,进而为森林可燃物的管理和指导森林防火提供科学的依据.     

An Invasive Grass Increases Live Fuel Proportion and Reduces Fire Spread in a Simulated Grassland

Fire is a globally important ecosystem process, and invasive grass species generally increase fire spread by increasing the fuel load and continuity of native grassland fuelbeds. We suggest that invasive grasses that are photosynthetically active, while the native plant community is dormant reduce fire spread by introducing high-moisture, live vegetation gaps in the fuelbed. We describe the invasion pattern of a high-moisture, cool-season grass, tall fescue (Schedonorus phoenix (Scop.) Holub), in tallgrass prairie, and use spatially explicit fire behavior models to simulate fire spread under several combinations of fuel load, invasion, and fire weather scenarios. Reduced fuel load and increased extent of tall fescue invasion reduced fire spread, but high wind speed and low relative humidity can partially mitigate these effects. We attribute reduced fire spread to asynchrony in the growing seasons of the exotic, cool-season grass, tall fescue, and the native, warm-season tallgrass prairie community in this model system. Reduced fire spread under low fuel load scenarios indicate that fuel load is an important factor in fire spread, especially in invaded fuel beds. These results present a novel connection between fire behavior and asynchronous phenology between invasive grasses and native plant communities in pyrogenic ecosystems.     

以地表死可燃物评估八达岭林场森林燃烧性

森林燃烧性是森林火险评估的基础,也是制定营林防火措施的依据.以北京市八达岭林场18种主要森林类型的地表死可燃物为研究对象,分别以死可燃物负荷量、含水率及综合属性为分析依据,结合国内外最新研究成果、林场实际情况和样地调查,分别讨论并对比不同森林类型的燃烧性,并划分等级.研究得出,以地表死可燃物综合属性为分析依据,研究不同森林类型的燃烧性更符合林场实际情况,并以综合属性为依据绘制林场燃烧性等级图,同时,死可燃物负荷量和含水率的分析,可以为营林防火措施的制定提供理论依据.     

Modelling surface fine fuel dynamics across climate gradients in eucalypt forests of south‐eastern Australia

An understanding of the effects of climate on fuel is required to predict future changes to fire. We explored the climatic determinants of variations in surface fine fuel parameters across forests (dry and wet sclerophyll plus rainforest) and grassy woodlands of south‐eastern Australia. Influences of vegetation type and climate on fuel were examined through statistical modelling for estimates of litterfall, decomposition and steady state fine litter fuel load obtained from published studies. Strong relationships were found between climate, vegetation type and all three litter parameters. Litterfall was positively related to mean annual rainfall and mean annual temperature across all vegetation types. Decomposition was both negatively and positively related to mean annual temperature at low and high levels of warm‐season rainfall respectively. Steady state surface fine fuel load was generally, negatively related to mean annual temperature but mean annual rainfall had divergent effects dependent on vegetation type: i.e. positive effect in low productivity dry sclerophyll forests and grassy woodlands versus negative effect in high productivity wet sclerophyll forests and rainforests. The species composition of the vegetation types may have influenced decomposition and steady state fuel load responses in interaction with climate: e.g. lower decomposition rates in the low productivity vegetation types that occupied drier environments may be partially due to the predominance of species with sclerophyllous leaves. The results indicate that uncertain and highly variable future trends in precipitation may have a crucial role in determining the magnitude and direction of change in surface fine fuel load across south‐eastern Australia.     

What determines probability of surviving predator attacks in bird migration?: the relative importance of vigilance and fuel load

Migrating birds must accumulate fuel during their journeys and this fuel load should incur an increased risk of predation. Migratory fuelling should increase individual mass-dependent predation risk for two reasons. First, acquisition costs are connected to the increased time a bird must spend foraging to accumulate the fuel loads and the reduced predator detection that accompanies foraging. Second, birds with large fuel loads have been shown to suffer from impaired predator evasion which makes them more vulnerable when actually attacked. Here, I investigate the relative importance of these two aspects of mass-dependent predation risk and I have used published data and a hypothetical situation for a foraging bird to investigate how much migratory fuelling in terms of escape performance and natural variation in predator detection contribute to individual risk during foraging. Results suggest that for birds foraging close to protective cover the negative impact of fuel load on flight performance is very small, whereas variation in time to predator detection is of great importance for a bird's survival. However, the importance of flight performance for predation risk increases as the distance to cover increases. Hence, variation in predator detection (and vigilance) probably influences individual survival much more than migratory fuel load and consequently, to understand risk management during migration studies that focus on vigilance and predator detection during fuelling are much needed.     

Fuels and landscape flammability in an Australian alpine environment

Factors governing landscape‐scale flammability are poorly understood, yet critical to managing fire regimes. Studies of the extent and severity of the 2003 Australian alpine fires revealed marked differences in flammability between major alpine plant communities, with the occurrence and severity of fire greater in heathland compared to grassland. To understand this spatial variation in landscape flammability, we documented variation in two physical properties of fuel – load and bulk density – at the life‐form and plant community scale. We measured the load (mass per unit area) and bulk density (mass per unit volume) of fine fuels (<6 mm) at 56 sites across the Bogong High Plains, southeastern Australia. Fine fuel load was positively correlated with shrub cover, and fine fuel bulk density was negatively correlated with shrub cover. Furthermore, fine fuel load and bulk density were accurately predicted using simple measures of canopy height and shrub cover. We also conducted a burning experiment on individual shrubs and snowgrass (Poa spp.) patches to assess comparative differences in flammability between these life‐forms. The burning experiment revealed that shrubs were more flammable than snowgrass as measured by a range of flammability variables. Consequently, our results indicate that treeless alpine landscapes of southeastern Australia are differentially flammable because of inherent life‐form differences in both fine fuel load and bulk density. If shrub cover increases in these alpine landscapes, as projected under climate change, then they are likely to become more flammable and may experience more frequent and/or severe fires.     

美国俄亥俄州南部两种不同间伐强度对森林可燃物载量和碳的影响(英文)

本研究的目的是测定两种不同间伐强度下(70%和50%),美国俄亥俄州南部橡树混交林森林可燃物(包括枯落物、木本、草本和倒木)碳储量和其燃烧后可能释放的碳量。研究结果表明枯落物和木本碳含量显著高于草本部分。在50%、70%间伐和对照中,森林枯落物分别占了总的橡树混交林可燃物碳储量的36.6%,50.9%和66.0%。粗木质残体分别占了58.4%,48.0%和32.6%。小的木本和草本在总的森林可燃物中占据很小比例。在50%、70%间伐和对照三种情况下,总的森林可燃物分别是54.07t/ha、41.98t/ha和20.73t/ha。如果对这些森林可燃物进行燃烧,50%、70%间伐和对照中,其森林可燃物将释放碳量分别为90.39t/ha、70.19t/ha和34.66t/ha。虽然它们之间没有产生显著的差异,但和对照进行比较,间伐后仍产生了较多的一、二级森林可燃物。在50%、70%间伐和对照中,分别产生了25.08t/ha、23.47t/ha和14.38t/ha一、二级的可燃物。计划用火在燃烧这些可燃物成分时,在50%、70%间伐和对照中,可能会分别释放41.93t/ha、39.24t/ha和23.55t/ha碳。此研究对使用计划用火来减少引起森林火灾的森林可燃物具有一定的意义。     

大兴安岭呼中林区虫害与火干扰交互作用的长期模拟

虫害和林火是森林生态系统的两种主要干扰类型,各种干扰在大时空尺度上存在一定的交互作用.本文采用空间直观景观模型LANDIS模拟虫害和林火在300年内的交互作用.结果表明:虫害干扰降低了细可燃物载量,提高了模拟前期(0～100 a)和中期(100～200 a)的粗可燃物载量,降低了模拟前期和中期的林火频率,不同干扰预案模拟后期(200～300 a)火烧频率的结果比较接近;虫害干扰降低了模拟前期和后期的火烧强度,增加了模拟中期的火烧强度,提高了模拟中期的森林火险等级,降低了模拟前期和后期的火险等级.人类灭火可增加虫害的发生面积,因此建议森林管理部门采取适当的防虫措施,不可只注重灭火,可以采取可燃物去除和计划火烧等方式管理林火,促进森林生态系统的可持续发展.     

Optimal avian migration: A dynamic model of fuel stores and site use

Birds migrating between widely separated wintering and breeding grounds may choose among a number of potential stopover sites by using different itineraries. Our aim is to predict the optimal migration schedule in terms of (1) rates of fuel deposition, (2) departure fuel loads and (3) stopover site use, when only a handful of such sites are available. We assume that reproductive success depends on the date and fuel load at arrival on the breeding grounds. On migration, the birds face a trade-off between gaining fuel and avoiding predation. To allow the optimal decision at any given moment to depend on the fuel load and the location of the bird, as well as on unpredictability in conditions, we employed stochastic dynamic programming. This technique assumes that the birds know the probability distribution of conditions in all sites, but not the particular realization they will encounter. We examined the consequences of varying aspects of the model, like (1) the shape of the relationship between arrival date and fitness, (2) the presence of stochasticity in fuel deposition rates and wind conditions, and (3) the nature of predation (i.e. whether predation risk depends on the fuel load of the birds or their feeding intensity). Optimal fuel deposition rates are predicted to be constant if there are either only predation risks of maintaining stores or only risks of acquiring fuel stores. If only fuel acquisition is risky, fuel deposition rates can be below maximum, especially if there also is an intermediate best arrival time at the breeding ground. The fuel deposition rate at a site then depends not just on the site's quality but on the qualities of all visited sites. In contrast, rates of fuel deposition are not constant if both the acquisition and the maintenance of fuel stores carry risk. Optimal departure fuel loads are just enough to reach the next site if the environment is deterministic and are simply set by the energetic cost of covering the distance. As with time-minimizing models, more fuel than necessary to reach a site is only deposited under very restricted circumstances. Such overloads are more likely to be deposited if either fuel gains or expenditure are stochastic. The size of overloads is then determined by the variance in fuel gain at the target site and the worst possible conditions during flight. Site use is modified by differences in predation risk between sites and differences in fuel deposition rates. An expression derived to predict site use under time minimization provides a good approximation in state-dependent models. In some cases, the possibility of starvation may influence optimal decisions, even when the probability of starvation under the optimal policy is low. This effect of starvation has also been found in other contexts. This revised version was published online in July 2006 with corrections to the Cover Date.     

不同烈度林火对油松林潜在地表火行为的影响

油松是我国华北地区代表性树种之一,含有丰富油脂,容易引发大面积高烈度森林火灾。阐明不同烈度林火对油松林地表可燃物负荷量和潜在地表火行为的影响,对于油松林林火管理具有重要意义。以辽河源自然保护区2014年不同烈度林火干扰后油松林分为研究对象,根据不同烈度(重度、中度、轻度)和对照(未过火)分别设置3块20 m×20 m样地,共12块样地,调查地表可燃物和林分结构指标,结合室内实验,利用BehavePlus 5.0软件进行潜在火行为模拟,探讨不同烈度林火5年后油松林地表可燃物负荷量和潜在地表火行为特点,并分析影响潜在地表火行为的主要因素。研究结果表明：(1)不同烈度林火之间,细小可燃物负荷量和地表可燃物总负荷量均不存在显著性差异(P>0.05)。(2)不同烈度林火后,在不同风速和可燃物含水率条件下,油松林潜在地表火蔓延速度、火线强度不存在显著性差异(P>0.05),单位面积发热量、火焰高度、反应强度存在显著性差异(P<0.05)。(3)不同烈度林火后油松林潜在地表火行为主要受油松更新幼苗基径、灌木负荷量、油松平均冠幅、上层枯叶负荷量、油松更新幼苗密度的影响。研究结果表明不...     

Seasonal differences in energy requirements of Garden Warblers Sylvia borin migrating across the Sahara desert

The Sahara desert acts as an ecological barrier for billions of passerine birds on their way to and from their African wintering areas. The Garden Warbler Sylvia borin is one of the most common migrants involved. We used body mass of this species from Greece in autumn and spring to simulate the desert crossing and to assess how body mass relates to fuel requirement. The flight range estimates were adjusted to the seasonal extent of the desert, 2200 km in autumn and about 2800 km in spring. In autumn, with an average fuel load of about 100% of body mass without fuel, birds were not able to cross the desert in still air, but northerly winds prevail during September and with the average wind assistance only one in 14 was predicted to fail to make the crossing. Body mass data from spring, after the desert crossing, was used to estimate departure body mass from south of the desert. The average wind assistance in spring is close to zero and departure body mass of the average bird arriving at Antikythira, a small Greek island, under such conditions was estimated to be 34.6 g, which corresponded to a fuel load of 116%. Calculations based on 1% body mass loss per hour of flight showed slightly larger body mass loss than that calculated from flight range estimates. The results suggest that passerine birds about to cross the eastern part of the Sahara desert need to attain a larger fuel load in spring than in autumn.     

Alternative fuel properties of tall oil fatty acid methyl ester-diesel fuel blends

In this experimental work, tall oil methyl ester-diesel fuel blends as alternative fuels for diesel engines were studied. Tall oil methyl ester was produced by reacting tall oil fatty acids with methyl alcohol under optimum conditions. The blends of tall oil methyl ester-diesel fuel were tested in a direct injection diesel engine at full load condition. The effects of the new fuel blends on the engine performance and exhaust emission were tested. It was observed that the engine torque and power output with tall oil methyl ester-diesel fuel blends increased up to 6.1% and 5.9%, respectively. It was also seen that CO emissions decreased to 38.9% and NO(x) emissions increased up to 30% with the new fuel blends. The smoke opacity did not vary significantly.     

北京西山油松林可燃物调控的影响评价

森林可燃物调控及其影响评价研究是可燃物管理的基础,对减少火灾的发生具有重要的意义。在北京西山实验林场,选取华北地区典型针叶林-油松林(Pinus tabulaeformis),设立4块20m×20m样地,通过对林分可燃物分布特征的调查和分析,制定以修枝、割灌为主的调控措施,对比研究调控与未调控林分林下植被多样性和优势灌木的光合生理特性。研究结果表明:(1)不同油松林可燃物垂直分布特征表现为0—3m层可燃物负荷量最大(平均为1053.94 g/m2),且可燃物种类最多,随着高度的增加可燃物的负荷量均呈现减少的趋势。(2)调控林分林下优势灌木(主要为孩儿拳头和黑枣)最大净光合速率、光饱和点、光补偿点、暗呼吸速率均比对照增加;而表观量子效率则减小。(3)不同的可燃物调控措施改变了林下植被多样性;不同调控措施的草本层物种丰富度、物种多样性、物种优势度以及物种均匀度均高于对照林分。由此可见,森林可燃物调控措施对林下植被多样性和优势物种的光合生理特性均有影响。研究结果可为森林可燃物管理提供科学依据。     

Optimal stopover decisions of migrating birds under variable stopover quality: model predictions and the field data

Dataset on departure fuel loads, stopover length and fuel deposition rate of the European robins Erithacus rubecula during their migration in the Baltic area is presented. We test these empirical data against the predictions of an optimal migration model assuming that robins minimize time spent on migration, and that fuel deposition rate varies stochastically. The latter assumption sets this model apart from the alternative ones and makes it more realistic. In particular, it is applicable in frequently observed situations when fuel deposition rate is negative. Our model assumes stochastic variation of the fuel deposition rate at sites along the migratory rout and thus is applicable when negative values of fuel deposition rate are recorded. The model predicts the relationship between fuel deposition rate and departure fuel load rather well. The agreement between the observed and the predicted values of optimal stopover duration is much poorer. Predictions of optimal migration theory are known to be dependent on the form of flight equation chosen. Our model fits the data best when the costs of transport are low. This supports the idea that transport costs of fuel stores may be low, especially when fuel stores are modest.     

A Temporally Explicit Production Efficiency Model for Fuel Load Allocation in Southern Africa

Abstract We present a regional fuel load model (1 km² spatial resolution) applied in the southern African savanna region. The model is based on a patch-scale production efficiency model (PEM) scaled up to the regional level using empirical relationships between patch-scale behavior and multi-source remote sensing data (spatio-temporal variability of vegetation and climatic variables). The model requires the spatial distribution of woody vegetation cover, which is used to determine separate respiration rates for tree and grass. Net primary production, grass and tree leaf death, and herbivory are also taken into account in this mechanistic modeling approach. The fuel load model has been calibrated and validated from independent measurements taken from savanna vegetation in Africa southward from the equator. A sensitivity analysis on the effect of climate variables (incoming radiation, air temperature, and precipitation) has been conducted to demonstrate the strong role that water availability has in determining productivity and subsequent fuel load over the southern African region. The model performance has been tested in four different areas representative of a regional increasing rainfall gradient—Etosha National Park, Namibia, Mongu and Kasama, Zambia, as well as in Kruger National Park, South Africa. Within each area, we analyze model output from three different magnitudes of canopy coverage (<5, 30, and 50%). We find that fuel load ranges predicted by the model are globally in agreement with field measurements for the same year. High rainfall sustains green herbaceous production late in the dry season and delays tree leaf litter production. Effect of water on production varies across the rainfall gradient with delayed start of green material production in more arid regions.     

Optimal migration strategies in animals that run: a range equation and its consequences

Optimal migration theory depends to a large extent on the range equation, that is, a function relating potential distance moved to fuel load. Such range equations derived from aerodynamic principles exist for birds. I derive an analogous range equation for animals that run based on biomechanical principles. The range for animals that run isY∞ ln(1+f), where f is the relative fuel load at departure and relates the mass at departure (m) to the lean mass (m₀) as m=(1+f) m₀. Predictions pertaining to migration decisions, such as optimal stopover duration, fuel load and detours around barriers, can thereby be made for animals other than birds. I hope this paper will stimulate further experimental tests regarding migration decisions in suitable animal systems.     

Magnetic cues and time of season affect fuel deposition in migratory thrush nightingales (Luscinia luscinia)

Bird migration requires high energy expenditure, and long-distance migrants accumulate fat for use as fuel during stopovers throughout their journey. Recent studies have shown that long-distance migratory birds, besides accumulating fat for use as fuel, also show adaptive phenotypic flexibility in several organs during migration. The migratory routes of many songbirds include stretches of sea and desert where fuelling is not possible. Large fuel loads increase flight costs and predation risk, therefore extensive fuelling should occur only immediately prior to crossing inhospitable zones. However, despite their crucial importance for the survival of migratory birds, both strategic refuelling decisions and variation in phenotypic flexibility during migration are not well understood. First-year thrush nightingales (Luscinia luscinia) caught in the early phase of the onset of autumn migration in southeast Sweden and exposed to a magnetic treatment simulating a migratory flight to northern Egypt increased more in fuel load than control birds. By contrast, birds trapped during the late phase of the onset of autumn migration accumulated a high fuel load irrespective of magnetic treatment. Furthermore, early birds increased less in flight-muscle size than birds trapped later in autumn. We suggest that the relative importance of endogenous and environmental factors in individual birds is affected by the time of season and by geographical area. When approaching a barrier, environmental cues may act irrespective of the endogenous time programme.     

Microbial fuel cells meet with external resistance

The influence of external load on the composition of the anodic biofilm microbial community and biomass yield was investigated in a microbial fuel cell fed with glucose and domestic wastewater was used as source of electrogens. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rRNA gene fragments revealed distinct differences in anodic bacterial communities formed at the anode of each MFC operated under a different external load. These results implied that in an MFC, electrogenic bacteria were enriched under higher current densities, i.e., low external load, and were able to sustain better current and effluent quality. The influence of the external resistance applied to the MFCs during formation of the bacterial communities from sewage wastewater was shown to have no significant effect on power performance of the MFCs nor to have a significant influence on their anodic activity with both glucose and brewery wastewater as fuel. As expected, current generation, COD removal and the biomass yield were all directly influenced by the external load. Significantly, when operated under lower external load, the biomass yield in the MFC was less than that in conventional anaerobic digestion (i.e., control).     

Combustion characteristics and NO formation for biomass blends in a 35-ton-per-hour travelling grate utility boiler

Measurements were taken for a 35-ton-per-hour biomass-fired travelling grate boiler. Local mean concentrations of O₂, CO, SO₂ and NO gas species and gas temperatures were determined in the region above the grate. For a 28-ton-per-hour load, the mass ratios of biomass fly ash and boiler slag were 42% and 58%, the boiler efficiency was 81.56%, and the concentrations of NO_x and SO₂ at 6% O₂ were 257 and 84 mg/m³. For an 18-ton-per-hour load, the fuel burning zone was nearer to the inlet than it was for the 28-ton-per-hour load, and the contents of CO and NO in the fuel burning zone above the grate were lower.     

Restoration rocks: integrating abiotic and biotic habitat restoration to conserve threatened species and reduce fire fuel load

With rapid urban expansion, biodiversity conservation and human asset protection often require different regimes for managing wildfire risk. We conducted a controlled, replicated experiment to optimise habitat restoration for the threatened Australian pink-tailed worm-lizard, Aprasia parapulchella while reducing fire fuel load in a rapidly developing urban area. We used dense addition of natural rock (30 % cover) and native grass revegetation (Themeda triandra and Poa sieberiana) to restore critical habitat elements. Combinations of fire and herbicide (Glyphosate) were used to reduce fuel load and invasive exotic species. Rock restoration combined with herbicide application met the widest range of restoration goals: it reduced fire fuel load, increased ant occurrence (the primary prey of A. parapulchella) in the short-term and increased the growth and survival of native grasses. Lizards colonised the restored habitat within a year of treatment. Our study documents an innovative way by which conflicts between biodiversity conservation and human asset protection can be overcome.