森林火灾碳排放计量模型研究进展

森林火灾是森林生态系统重要的干扰因子,是导致植被和土壤碳储量减少的重要途径之一.森林火灾含碳气体排放对大气碳平衡及全球气候变化具有重要影响,科学有效地对其进行计量,对了解森林火灾在全球碳循环和碳平衡中的地位具有重要意义.本文从3个方面阐述森林火灾碳排放计量模型的研究进展： 森林火灾直接排放总碳和含碳气体计量方法;森林火灾碳排放计量模型的影响因子及计量参数;森林火灾碳排放计量中不确定性原因剖析.最后提出了提高碳排放计量定量化的3种路径选择： 利用高分辨率遥感数据、改进算法、提高森林火灾面积的估测精度、结合有效可燃物计量模型,提高估测可燃物载量的准确率;使用高分辨率遥感影像,并结合室内控制实验、野外试验与火烧迹地调查确定燃烧效率;通过大量室内燃烧实验和野外空中采样来确定排放因子和排放比.     

草地火行为研究

在松嫩平原采用野外放火的方法,研究了草地火速度、火强度、火烈度、火形态、火烧迹地形状及其与气象因子、可燃物、可燃物床特性的关系.结果表明,风速是影响草地头火速度最主要的因子.除风速外,晴天时相对湿度对头火速度影响较大,降水后大气温度对头火速度影响较大.头火速度＞侧翼火速度＞尾火速度.风速与火强度、火深度、火烧迹地形状呈现显著正相关.采用逐步回归方法建立了草地头火速度、火强度、火烧迹地形状的预测模型.     

森林可燃物及其管理的研究进展与展望

森林可燃物是森林生态系统的基本组成部分, 是影响林火发生及火烧强度的重要因素之一, 因此, 受到国内外学者的广泛关注。该文从以下4个方面综述了国内外可燃物研究的最新进展: 森林可燃物特性, 森林可燃物类型与火行为, 森林可燃物类型、载量的调查与制图, 森林可燃物管理。同时提出了我国森林可燃物今后的研究方向: 开展多尺度可燃物研究; 可燃物类型与火行为的研究; 把以试验观测为基础的静态研究与以空间技术和生态模型为基础的动态预测相结合, 研究可燃物处理效果; 全球气候变化背景下可燃物处理与碳收支。     

重度林火对大兴安岭土壤生境因子的影响

为探究重度林火对森林土壤生境因子的影响,以大兴安岭林区火烧迹地为研究对象,监测了火烧迹地和对照样地12个土壤生境因子在3年内的变化。结果表明:1年时间范围内重度林火减小了枯落物层厚度,降低土壤含水率、土壤容重、水稳性团聚体、有机质含量和微生物量碳,但提高了地表午间均温和土壤p H值,增加了土壤铵态氮、硝态氮、有效磷、代换性盐基的含量;而3年时间范围内重度林火导致有的土壤生境因子与对照样地差异越来越大,如枯落物层厚度、土壤有机质含量、土壤容重、水稳性团聚体和硝态氮含量,而有的土壤生境因子则表现出恢复的趋势,如土壤含水率、地表午间均温、土壤p H值、铵态氮含量、有效磷含量、代换性盐基含量和土壤微生物量碳。研究重度林火对各土壤生境因子的影响可为土壤生境质量的评价工作提供基础数据。     

兴安落叶松林火烧迹地土壤理化性质驱动因子

探索火烧迹地土壤理化性质的驱动因子是解释生态系统响应火干扰机制的重要组成部分。旨在分析兴安落叶松林火烧迹地土壤理化性质的决定因子，深入认识火干扰在北方森林生态系统所扮演的角色，为北方森林火烧迹地火后恢复、林业可持续发展提供科学支持和理论依据。以过火后1 a的兴安落叶松林火烧迹地为研究对象，设置了不同火烈度和立地条件的火烧迹地及对照研究样地共计35块。在每个研究样地记录了树种、胸径、存活状态等乔木数据，测量了坡向、坡位、坡度、海拔等地形数据，利用植被变化情况量化了火烈度。分别采集了0—5 cm和5—10 cm的土壤样品并测定其9种理化指标，对比了过火与未过火样地这些土壤理化指标的差异。然后，分析了各土壤理化指标与火烈度量化结果的关联趋势，比较了火烈度、地形和乔木因子对火烧迹地土壤理化性质的影响程度。与对照样地相比，火干扰提升了土壤理化指标观测值的离散程度，显著提高了0—5 cm土壤含水率(MC)(P<0.05)和5—10 cm土壤MC、总氮(TN)、总有机碳(TOC)含量(P<0.05)。土壤理化性质与火烈度有明显关联趋势的并不多，观察到0—5 cm土壤MC随火烈度指数的增加...     

不同火烈度火烧迹地内油松叶功能性状的变化

叶功能性状对林火的响应是林火生态领域的研究热点之一,研究火后油松叶功能性状变化能够揭示油松为适应火环境形成的生长策略,为促进油松火后恢复提供参考。以山西省沁源县火烧迹地内油松为研究对象,选择当年生叶片分析叶功能性状在不同火烈度(未过火、轻度火烧、中度火烧)火烧迹地间的变化规律,并研究不同火烧迹地内叶经济谱的变化特征。结果表明: 除氮磷比外,叶功能性状在不同火烈度的火烧迹地间存在显著差异,其中,叶面积的差异最为明显,是最敏感的性状。随火烧迹地内火烈度的增加,叶面积、叶厚度、叶干物质含量、叶氮含量和叶磷含量升高,比叶面积、叶有机碳含量降低。部分叶功能性状间存在显著的相关关系,但其相关性在不同火烈度的火烧迹地间存在差异。叶经济谱沿着“未过火-轻度火烧-中度火烧”的火烧迹地环境总体向“快速投资-收益型”的资源权衡策略移动,低烈度火烧迹地内油松的生长恢复会加快。     

火烧强度和火后恢复时间对大兴安岭森林土壤有机碳含量的影响

在大兴安岭针叶林生态系统中,林火是驱动森林结构与功能变化的主要因子之一,对土壤碳循环过程产生了深刻影响.本研究在大兴安岭林区选择不同火烧强度(轻度、中度、重度)和火烧年份(1987-2012年)的火烧迹地开展野外调查,分土壤发生层(O层、A层、AB层、BC层、C层)采集样品,采用双因素方差分析和多重比较法,分析了火烧强度和火后恢复时间对森林土壤有机碳含量的影响.结果表明: 中度和重度火烧后,土壤O层有机碳含量呈逐年上升趋势;A、B层土壤有机碳含量在轻、中度火烧后呈逐年下降趋势,其随时间的变化情况为火后3年>火后5年>火后10年>火后10年以上,在重度火烧后的10年之内呈逐年上升趋势,但在火后10年以上又迅速下降;BC层有机碳含量变化无明显规律.     

黑龙江省大兴安岭林区火烧迹地森林更新及其影响因子

林火干扰是大兴安岭森林更新的影响因子之一,研究火烧迹地森林更新的影响因子(立地条件、火前植被、火干扰特征)对理解生态系统的结构、功能和火后演替轨迹具有重要意义。选取呼中及新林林业局55个代表性火烧样地,利用增强回归树分析法分析了火烧迹地森林更新的影响因素。结果表明:(1)立地条件是影响针、阔叶树更新苗密度的主要因素;海拔对针叶树更新苗密度的影响最大;坡度对阔叶树更新苗密度影响最大;(2)距上次火烧时间对针叶树更新苗比重影响最大,其次是林型;(3)中度林火干扰后森林更新状况好于轻度和重度火烧迹地。根据火烧迹地森林更新调查分析可知:林型影响火后演替模式,火前为针叶树或阔叶树纯林,火后易发生自我更新(火后树种更新组成与火前林型相同),而针阔混交林在火干扰影响下易于发生序列演替(火后初期以早期演替树种更新为主)。     

内蒙古大兴安岭森林可燃物燃烧释放PM2.5中水溶性离子排放特性

研究森林可燃物燃烧释放的细颗粒物(PM_2.5)的排放因子对于揭示森林火灾对大气和生态系统的影响至关重要,而水溶性离子是细颗粒物的重要化学成分,对颗粒物的形成具有重要意义。利用自主设计的生物质燃烧系统,模拟内蒙古大兴安岭5种典型乔木(蒙古栎、白桦、兴安落叶松、黑桦、山杨)的3种组成部分(树干、树枝、树皮)及其地表死可燃物(凋落物层、半腐殖质层、腐殖质层)以及3种典型灌木(平榛、二色胡枝子、兴安杜鹃)树枝燃烧,采用ISC1100离子色谱分析仪测定2种燃烧状态(阴燃和明燃)下PM_2.5中水溶性离子(Na⁺、NH₄⁺、K⁺、Mg²⁺、Ca²⁺、F^-、Cl^-、NO₃^-、NO₂^-、SO₄^2-)的排放因子。结果表明:乔木所有组成部分及其地表死可燃物和灌木树枝燃烧所排放PM_2.5中检测到的水溶性离子,阴燃以K⁺、Cl^-和Na⁺为主要组分,明燃以K⁺、Cl^-和SO₄^2-为主要组分。不同燃烧状态下相同乔木树种及其地表死可燃物和相同灌木排放PM_2.5中检测到的水溶性离子总量均存在显著差异。灌木树枝在阴燃期间PM_2.5中水溶性无机离子的排放因子比明燃更高。乔木释放的PM_2.5中阳离子与阴离子的比率为1.26,地表死可燃物为1.12,灌木为2.0,表明颗粒物呈碱性。内蒙古大兴安岭的森林大火不会通过释放水溶性离子导致生态系统的酸化。     

大兴安岭火烧迹地恢复初期土壤微生物群落特征

对大兴安岭兴安落叶松2003年重度和中度火烧迹地以及未过火样地的土壤微生物群落进行了考察,旨在揭示火烧迹地恢复初期土壤微生物群落变化特征。研究结果表明火烧迹地土壤养分(全氮、全碳、土壤有机质、有效氮)和土壤水分与未过火对照样地存在显著差异;火烧迹地土壤微生物量碳氮、微生物代谢活性以及碳源利用能力均显著高于对照样地;但火烧迹地与对照样地土壤微生物群落结构指标土壤微生物量碳氮比(MBC/MBN)以及多样性指数没有显著差异。相关分析结果表明:土壤微生物量、代谢活性和碳源利用能力与土壤养分指标(全碳、全氮、速效氮、有机质)和土壤水分含量有显著相关性。主成分分析的结果表明火烧与否是火烧样地与对照样地土壤微生物对碳源利用能力差异的原因。所有样地土壤微生物群落真菌比例较高,可能与该地区土壤酸碱度有关(pH=4.12—4.68)。经过6a的恢复,重度和中度火烧迹地的土壤养分和水分、土壤微生物群落的生长、代谢、以及群落多样性仍存在差异,但均不显著,表明此时火烧程度对土壤微生物群落的影响已很微弱。     

黄土丘陵沟壑区地形变化对土壤微生物群落功能多样性的影响

研究黄土高原丘陵沟壑区破碎地形对土壤微生物功能多样性的影响,对于理解复杂地形区生态过程与系统功能的空间变化具有重要意义。选择陕西省安塞县陈家洼为研究区,依据坡面地形变化选择不同坡位土壤,采用Biolog微平板培养法探究地形变化对土壤微生物群落功能多样性的影响。实验发现,土壤微生物群落培养的平均颜色变化率(AWCD)增长曲线总的呈现出坡下部坡中部坡上部的规律,且坡下部AWCD值与坡中部、坡上部间差异显著(P0.05);坡下部土壤微生物群落功能多样性显著高于坡中部和坡上部,但不同土层深度(0—10 cm、10—20 cm)间无显著性差异(P0.05);对土壤微生物群落功能多样性差异贡献较大的碳源是糖类、羧酸类和多酚化合物类碳源;土壤含水率高低是不同坡位土壤微生物群落功能多样性差异显著的主要原因;微生物群落丰富度(H)和均一度(D)与土壤全氮含量正相关,优势度(U)反之,土壤全碳、全磷和p H对土壤微生物群落结构和功能多样性差异作用不显著。     

The effect of fire on nutrients in a pine forest soil

The effect of a hot summer fire on soil nutrient contents in the upper 2 cm of Aleppo pine forest with a dense woody understory was studied from September 1985 to May 1986. In comparison with the adjacent unburned forest, total nitrogen decreased by 25% but available forms of nitrogen were much higher. In burned and unburned soils there was a similar trend to increase and decrease in NH ₄ ⁺ −N, However, while (NO ₂ ⁻ +NO ₃ ⁻ −N decreased in the unburned soil it rose rapidly in the burned ash soil. Total phosphorus increased by 300% after the fire but decreased again 2 months later. Also water-soluble P increased up to November and then decreased to the levels of the unburned soils. The same was true for electrical conductivity and pH, increasing immediately after the fire and then leveling off again. This increase in nutrient levels in the “ash soil” was reflected in the striking increase in shoot and root biomass and in the content of N, P, Mg, K, Ca, Zn and Fe in wheat and clover plants grown in pots in these soils. These nutrient levels were much higher in the wheat plants, which also produced 12 times more seeds in the “ash soil.” It seems that fire in these pine forests causes a short-term flush of the mineral elements in the upper “ash soil” layer which is reverted gradually via the herbaceous post-fire to the ecosystem.     

重度火烧迹地兴安落叶松(Larix gmelinii)根际土壤真菌群落研究

为探究内蒙古根河大兴安岭林区重度火烧迹地不同生长状态的兴安落叶松根际土壤真菌群落特征,选取火烧枯立木（BDW）、火烧存活木（BSW）、未火烧对照木（CK）,通过磷脂脂肪酸方法分析根际土壤真菌群落生物量变化,利用高通量测序技术对根际土壤真菌群落组成与功能进行分析,探讨影响根际土壤真菌群落的主要环境因子。结果表明：（1）相较于未火烧对照木,火烧枯立木与火烧存活木根际土壤真菌群落磷脂脂肪酸含量显著降低,真菌群落α多样性显著降低。β多样性分析与群落相似性分析结果显示,火烧枯立木、火烧存活木、未火烧对照木根际土壤真菌群落组成存在显著差异。（2）相较于未火烧对照木,火烧枯立木与火烧存活木根际土壤中担子菌门（Basidiomycota）真菌相对丰度显著下降,子囊菌门（Ascomycota）真菌相对丰度显著升高。子囊菌门（Ascomycota）内,火烧枯立木根际土壤中内生真菌相对丰度显著高于火烧存活木与未火烧对照木,而火烧存活木根际土壤中腐生-外生菌根复合型真菌相对丰度显著高于火烧枯立木与未火烧对照木。（3）根际土壤总磷、总钾含量是影响重度火烧迹地兴安落叶松根际土壤真菌群落优势菌门由担子菌门（Basidiomycota）转变为子囊菌门（Ascomycota）的主要环境因子,而根际土壤总碳、总氮、总磷含量则是造成火烧枯立木与火烧存活木根际土壤真菌群落组成与功能差异的主要环境因子。本研究有助于了解大兴安岭林区土壤真菌群落结构,对真菌群落多样性的维持与管理具有参考价值。     

Seven-Year Results of Thinning and Burning Restoration Treatments on Old Ponderosa Pines at the Gus Pearson Natural Area

Abstract We examined the 7‐year effects of three restoration treatments on leaf physiology and insect‐resistance characteristics of pre‐settlement age ponderosa pines (Pinus ponderosa Dougl. ex Laws.) at the Gus Pearson Natural Area (GPNA) in northern Arizona. Restoration treatments were: (1) thinned in 1993 to approximate pre‐Euro‐American settlement stand structure, (2) thinned plus prescribed burned in 1994 and 1998, and (3) untreated control. Tree physiological and insect‐resistance characteristics were measured in year 2000, 7 years after thinning, using the same procedures as an earlier study performed in 1996. Consistent with the 1996 results, pre‐dawn water potential in 2000 was consistently lower in the control than both thinned treatments. Both thinned treatments continued to have increased foliar nitrogen concentration in leaves 7 years after treatment. However lower leaf nitrogen concentration in the thinned and burned compared with the thinned treatment suggests lower nitrogen availability to trees in repeatedly burned plots. Analysis of leaf gas exchange characteristics and carbon isotope content (δ¹³C) suggests continued stimulation of photosynthesis by both thinning treatments. Differences among treatments in resin volume, a measure of bark beetle resistance, depended on season of measurement. Trees in both thinning treatments continued to have increased leaf toughness, a measure of resistance to insect folivores. Our results show that many beneficial effects of restoration treatments on carbon, water, and nitrogen relations and insect‐resistance characteristics of pre‐settlement ponderosa pines continue to be expressed 7 years after treatment at the GPNA.     

Fire effects on ecosystem nitrogen cycling in a Californian bishop pine forest

Fire can cause severe nitrogen (N) losses from grassland, chaparral, and temperate and boreal forest ecosystems. Paradoxically, soil ammonium levels are markedly increased by fire, resulting in high rates of primary production in re-establishing plant communities. In a manipulative experiment, we examined the influence of wild-fire ash residues on soil, microbial and plant N pools in a recently burned Californian bishop pine (Pinus muricata D. Don) forest. Ash stimulated post-fire primary production and ecosystem N retention through direct N inputs from ash to soils, as well as indirect ash effects on soil N availability to plants. These results suggest that redistribution of surface ash after fire by wind or water may cause substantial heterogeneity in soil N availability to plants, and could be an important mechanism contributing to vegetation patchiness in fire-prone ecosystems. In addition, we investigated the impact of fire on ecosystem N cycling by comparing ¹⁵N natural abundance values from recently burned and nearby unburned P. muricata forest communities. At the burned site, ¹⁵N natural abundance in recolonising species was similar to that in bulk soil organic matter. By contrast, there was a marked ¹⁵N depletion in the same species relative to the total soil N pool at the unburned site. These results suggest that plant uptake of nitrate (which tends to be strongly depleted in ¹⁵N because of fractionation during nitrification) is low in recently burned forest communities but could be an important component of eco- system N cycling in mature conifer stands. Received: 29 June 1999 / Accepted: 24 October 1999     

Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence

Tropical montane cloud forests (TMCFs) harbour high levels of biodiversity and large carbon stocks. Their location at high elevations make them especially sensitive to climate change, because a warming climate is enhancing upslope species migration, but human disturbance (especially fire) may in many cases be pushing the treeline downslope. TMCFs are increasingly being affected by fire, and the long‐term effects of fire are still unknown. Here, we present a 28‐year chronosequence to assess the effects of fire and recovery pathways of burned TMCFs, with a detailed analysis of carbon stocks, forest structure and diversity. We assessed rates of change of carbon (C) stock pools, forest structure and tree‐size distribution pathways and tested several hypotheses regarding metabolic scaling theory (MST), C recovery and biodiversity. We found four different C stock recovery pathways depending on the selected C pool and time since last fire, with a recovery of total C stocks but not of aboveground C stocks. In terms of forest structure, there was an increase in the number of small stems in the burned forests up to 5–9 years after fire because of regeneration patterns, but no differences on larger trees between burned and unburned plots in the long term. In support of MST, after fire, forest structure appears to approximate steady‐state size distribution in less than 30 years. However, our results also provide new evidence that the species recovery of TMCF after fire is idiosyncratic and follows multiple pathways. While fire increased species richness, it also enhanced species dissimilarity with geographical distance. This is the first study to report a long‐term chronosequence of recovery pathways to fire suggesting faster recovery rates than previously reported, but at the expense of biodiversity and aboveground C stocks.     

中国温带阔叶红松林不同演替系列土壤有机碳矿化特征

土壤有机碳矿化与陆地生态系统碳循环和全球气候变化关系密切,为准确评估中国温带小兴安岭阔叶红松林不同演替系列土壤有机碳矿化特征及变化规律。以年代序列法代替群落次生演替过程,采用室内恒温培养(碱液吸收法)测定阔叶红松林不同演替系列(中生演替系列、湿生演替系列、旱生演替系列)6种群落类型土壤有机碳矿化量和矿化速率。3个演替系列土壤有机碳含量均表现出一致的剖面变化特征,随着土层深度的加深有机碳矿化量逐渐降少。且不同演替系列土层间有机碳矿化量不同,中生演替系列原始阔叶红松林土壤有机碳累计矿化量最大,其次为旱生演替系列,湿生演替系列最小。3个演替系列土壤有机碳矿化速率随时间变化呈现基本一致的趋势,即培养前期快速下降、后期逐渐趋于平稳。3个演替系列6种群落类型土壤有机碳矿化差异显著,表现为原始阔叶红松林白桦次生林云冷杉红松林红松枫桦次生林蒙古栎红松林蒙古栎、黑桦次生林。阔叶红松林不同演替系列土壤有机矿化采用非线性指数拟合效果较好。阔叶红松林不同演替系列土壤有机碳矿化与土壤全氮、凋落物量显著正相关,与土壤含水率、容重、土壤酸碱度显著负相关。不同演替系列群落的演替历史、土壤质地和养分状况等生态因子是导致阔叶红松林不同演替系列土壤有机碳矿化差异的原因。     

Restoring Fire to Long-Unburned Pinus palustris Ecosystems: Novel Fire Effects and Consequences for Long-Unburned Ecosystems

Biologically rich savannas and woodlands dominated by Pinus palustris once dominated the southeastern U.S. landscape. With European settlement, fire suppression, and landscape fragmentation, this ecosystem has been reduced in area by 97%. Half of remnant forests are not burned with sufficient frequency, leading to declines in plant and animal species richness. For these fire‐suppressed ecosystems a major regional conservation goal has been ecological restoration, primarily through the reinitiation of historic fire regimes. Unfortunately, fire reintroduction in long‐unburned Longleaf pine stands can have novel, undesirable effects. We review case studies of Longleaf pine ecosystem restoration, highlighting novel fire behavior, patterns of tree mortality, and unintended outcomes resulting from reintroduction of fire. Many of these pineland restoration efforts have resulted in excessive overstory pine mortality (often >50%) and produced substantial quantities of noxious smoke. The most compelling mechanisms of high tree mortality after reintroduction of fire are related to smoldering combustion of surface layers of organic matter (duff) around the bases of old pines. Development of effective methods to reduce fuels and competing vegetation while encouraging native vegetation is a restoration challenge common to fire‐prone ecosystems worldwide that will require understanding of the responses of altered ecosystems to the resumption of historically natural disturbances.     

帽儿山地区不同土地利用方式下土壤-微生物-矿化碳氮化学计量特征

土地利用方式的变化导致土壤碳氮含量及其化学计量关系的变化,然而土壤微生物化学计量及其驱动的碳氮矿化过程如何响应这种变化仍不明确。以帽儿山地区天然落叶阔叶林、人工红松林、草地和农田4种不同土地利用类型为对象,测定其土壤有机碳(C_(soil))、全氮(N_(soil))、微生物生物量碳和氮(C_(mic)和N_(mic))、土壤碳和氮矿化速率(C_(min)和N_(min)),旨在比较不同土地利用方式对土壤、微生物碳氮化学计量特征及矿化速率的影响,探索土壤-微生物-矿化之间碳氮化学计量特征的相关性,揭示微生物对土壤碳氮化学计量变化的响应和调控机制。结果显示:C_(soil)、N_(soil)、C_(mic)、N_(mic)和C_(min)均呈现天然落叶阔叶林人工红松林草地农田,而天然落叶阔叶林和草地的N_(min)显著高于人工红松林和农田。土地利用方式显著影响土壤和微生物碳氮比(C∶N_(soil)和C∶N_(mic)),均呈现农田最高。不同土地利用方式的数据综合分析发现:碳氮矿化速率比与C∶N_(mic)呈负相关,而和微生物与土壤碳氮化学计量不平衡性(C∶N_(imb))显著正相关。单位微生物生物量的碳矿化速率(qCO_2)随着C∶N_(mic)的增加而降低,而单位微生物生物量的氮矿化速率(qAN)随着C∶N_(mic)的增加而增加。C∶N_(imb)与qCO_2正相关,与qAN负相关。以上结果表明,微生物会通过改变自身碳氮化学计量、调整碳氮之间相对矿化速率,以适应土地利用变化导致的土壤碳氮及其化学计量的变异性,以满足自身生长和代谢的碳氮需求平衡。