Fire temperature and residence time during dry season burning in a Sudanian savanna-woodland of West Africa with implication for seed germination

Prescribed fire is used in the Sudanian savanna-woodland of West Africa as a forest management tool. An experiment was carried out to assess the effects of season of burning, and different vertical probe positions on maximum fire temperature and temperature residence time above 60℃ which is considered lethal for plant tissues. Seasons of burning considered were： an early season fire set at the beginning of the dry season （beginning of December）, mid-season fire set at the peak of the dry season （mid-January）, and a late season fire at the end of the dry season （end of March）. The effects of these fires on the germination of buried seeds of three socio-economically valuable tree species were also examined. Results indicated significant differences in maximum fire temperature and residence time with respect to season of burning and vertical probe position （p 〈 0.001）. The highest and longest lasting temperatures were observed at 20 cm above ground during early fire and at the soil surface during mid-season and late fires. This, in turn, affected germination responses of seeds buried at different soil depths. Implications of these findings in the current management practices are discussed.

Future impacts of climate change on forest fire danger in northeastern China

Climate warming has a rapid and far-reaching impact on forest fire management in the boreal forests of China. Regional climate model outputs and the Canadian Forest Fire Weather Index （FWI） Sys- tem were used to analyze changes to fire danger and the fire season for future periods under IPCC Special Report on Emission Scenarios （SRES） A2 and B2, and the data will guide future fire management planning. We used regional climate in China （1961 1990） as our validation data, and the period （1991–2100） was modeled under SRES A2 and B2 through the weather simulated by the regional climate model system （PRECIS）. Meteorological data and fire danger were interpolated to 1 km 2 by using ANUSPLIN software. The average FWI value for future spring fire sea- sons under Scenarios A2 and B2 shows an increase over most of the region. Compared with the baseline, FWI averages of spring fire season will increase by 0.40, 0.26 and 1.32 under Scenario A2, and increase by 0.60, 1.54 and 2.56 under Scenario B2 in 2020s, 2050s and 2080s, respectively. FWI averages of autumn fire season also show an increase over most of the region. FWI values increase more for Scenario B2 than for Scenario A2 in the same periods, particularly during the 2050s and 2080s. Average future FWI values will increase under both scenarios for autumn fire season. The potential burned areas are expected to increase by 10% and 18% in spring for 2080s under Scenario A2 and B2, respectively. Fire season will be prolonged by 21 and 26 days under ScenariosA2 and B2 in 2080s respectively.

The impact of climate change on fire risk in Daxing'anling,China

Daxing’anling is a key region for forest fire prevention in China. Assessing changes in fire risk in the future under multiple climatic scenarios will contribute to our understanding of the influences of climate change for the region and provide a reference for applying adaptive measures for fire management. This study analyzed the changes in fire weather indices and the fire season under four climate scenarios (RCP2.6, RCP4.5, RCP6.0, RCP8.5) for 2021-2050 using data from five global climate models together with observation data. The results showed that the analog data could project the average state of the climate for a given period but were not effective for simulating extreme weather conditions. Compared with the baseline period (1971-2000), the period 2021-2050 was predicted to have an increase in average temperature of 2.02-2.65 °C and in annual precipitation 25.4-40.3 mm, while the fire weather index (FWI) was predicted to increase by 6.2-11.2% and seasonal severity rating (SSR) by 5.5-17.2%. The DMC (Duff moisture code), ISI (initial spread index), BUI (build-up index), FWI and SSR were predicted to increase significantly under scenarios RCP4.5, RCP6.0, and RCP8.5. Furthermore, days with high or higher fire danger rating were predicted to be prolonged by 3-6 days, with the change in the southern region being greater under scenarios RCP4.5, RCP6.0, and RCP8.5.

Distribution patterns of fire regime in the Pendjari Biosphere Reserve, West Africa

Pendjari Biosphere Reserve(PBR),a primary component of the W-Arly-Pendjari transboundary biosphere reserve,represents the largest intact wild ecosystem and pristine biodiversity spot in West Africa.This savannah ecosystem has long been affected by fire,which is the main ecological driver for the annual rhythm of life in the reserve.Understanding the fire distribution patterns will help to improve its management plan in the region.This study explores the fire regime in the PRB during 2001–2021 in terms of burned area,seasonality,fire frequency,and mean fire return interval(MFRI)by analysing moderate resolution imaging spectroradiometer(MODIS)burned area product.Results indicated that the fire season in the PBR extends from October to May with a peak in early dry season(November–December).The last two fire seasons(2019–2020 and 2020–2021)recorded the highest areas burned in the PBR out of the twenty fire seasons studied.During the twenty years period,8.2%of the reserve burned every 10–11 months and 11.5%burned annually.The largest part of the reserve burned every one to two years(63.1%),while 8.3%burned every two to four years,5.8%burned every four to ten years,and 1.9%burned every ten to twenty years.Only 1.3%of the entire area did not fire during the whole study period.Fire returned to a particular site every 1.39 a and the annual percentage of area burned in the PBR was 71.9%.The MFRI(MFRI<2.00 a)was low in grasslands,shrub savannah,tree savannah,woodland savannah,and rock vegetation.Fire regime must be maintained to preserve the integrity of the PBR.In this context,we suggest applying early fire in tree and woodland savannahs to lower grass height,and late dry season fires every two to three years in shrub savannah to limit the expansion of shrubs and bushes.We propose a laissez-faire system in areas in woodland savannah where the fire frequency is sufficient to allow tree growth.Our findings highlight the utility of remote sensing in defining the geographical and temporal patterns of fire in the PBR and could help to manage this important fire prone area.

Forest fire danger ratings in the 2040s for northeastern China

The average temperature of northeastern China is expected to increase 2.22 and 2.55℃ under two scenarios selected from the Intergovemmental Panel on Climate Change （IPCC）, i.e., A2 and B2, during the 2040s （2041-2050）, which will have an impact on fire activities in those areas. We calculated the output of regional climate models, using the Canadian Forest Fire Weather Index （FWI） on a scale of 50 km × 50 km. Meteorological data and fire weather index were interpolated to a scale of 1 km × 1 km by using ANUSPLIN software. The results show that the model of Providing Regional Climate for Impacts Studies （PRECIS） had the ability to provide good temperature and precipitation estimates of the study area in the baseline period, by simulation. In the 2040s the mean FWI values of the study area will increase during most of the fire seasons under both selected scenarios, compared with the baseline period. Under scenario B2 the peak fire season will appear in advance. The changes of FWI ratio （2×CO2/l ×CO2） show that the potential burned areas will increase 20% under scenario B2 and lightly increase under scenario A2 in 2040s. The days of high, very high and extreme fire danger classes will add 5 and 18 d under scenarios A2 and B2, respectively. It suggests adapting the climate change through improving fuel management and enhancing the fighting abilities.

Histological Study of the Liver Pigmentation of Chinese Fire-bellied Newt (Cynops orientalis) During Activity and Hibernation Periods

The pigmentation in the liver of Chinese fire-bellied newt(Cynops orientalis) was described during two periods of the annual cycle(summer activity and winter hibernation). A large number of melanin granules were gathered into clusters and distributed unevenly inside the pigment cells. Liver pigmentation(melanin content) was found unstable,varying during the annual cycle. During the hibernation period,pigmentation accumulation was shown to increase in the liver of the Chinese fire-bellied newt. Hepatocytes during the active period are approximately 14.64% larger than those in the hibernation period,while the nucleus is approximately 7.43% bigger during the active period when compared with that during the hibernation period. These findings indicate that variation in pigment distribution and hepatocyte morphology in Chinese fire-bellied newt liver may be an ecologically adaptive strategy to the adverse physiological conditions during hibernation.

气候变暖背景下内蒙古大兴安岭林区森林火灾发生日期的变化

By using Julian Date methods,this paper studied the changes of forest fire occurring date during 1980～2006 in Inner Mongolia Daxing’anling forest region,as well as discussed the changes of fire season and forest fire regime under global warming.The results indicated that Julian Date of fires changed obviously,i.e.the fires Julian Date in spring extended into summer markedly,and at the same time summer fires were mostly caused by lightning fires.The Julian Date of human-caused fires did not evidently change.In recent some years,the forest fires occurred in summer actually exceeded the sum of fires occurred in spring and autumn.Consequently,the fire seasons are not only in spring and autumn,so long as the litter has not been covered by snow,forest fires possibly take place.In the future,under a warmer climate,the authors’ suggestion for forest fire management departments is to adequately understand these forest fire regime changes and make adaptive policies,in order to reduce the damage induced by forest fires.

中国主要生态地理区的林火动态特征分析

【目的】研究中国主要生态地理区的林火动态,为开展林火科学管理提供依据。【方法】基于中国生态地理区域系统的分类结果和森林火灾特点,把中国大陆植被区划分为寒温带湿润地区落叶针叶林区(R1)、中温带湿润地区森林区(R2)、中温带干旱地区荒漠针叶林区(R3)、中温带半干旱地区草原区(R4)、暖温带湿润/半湿润地区落叶阔叶林及人工植被区(R5)、中温带半干旱/干旱地区草原区(R6)、中北亚热带湿润地区阔叶林及人工植被区(R7)和热带南亚热带湿润地区阔叶林及人工植被区(R8)。根据2005—2012年卫星监测地面热点数据和林火统计数据,分析各生态地理区的林火空间与时间分布特征。【结果】野火主要分布在东部,其中分布在R8区域的野火占84.4%,分别在R1,R2,R3,R4,R5,R6和R7区域的野火分别占0.5%,3.8%,0.1%,2.7%,2.7%,0.1%和5.8%。根据林火发生时间分布确定各生态地理区的火险期,北方地区火灾主要发生在春秋季,而南方森林火灾主要发生在冬季和春季;各生态地理区的火险期分别为R1的3—10月、R2的4—5月和7—10月、R3的3—5月和8—10月、R4的3—6月和9—10月、R5的11—翌年5月、R6的12—翌年5月、R7的12—翌年5月和R8的11—翌年5月。虽然热带南亚热带湿润地区的火灾比较多,但比较容易控制,而寒温带湿润地区落叶针叶林区的火灾平均燃烧时间长。2005—2012年各生态地理区的林火发生次数和林火面积都表现出显著的波动性。人为干扰对林火动态的影响很大,特别在人口密度分布高的南方区域。热带南亚热带湿润地区阔叶林及人工植被区林火发生频度最高,年均发生森林火灾6 489次,火循环周期为4 547年;而寒温带湿润地区落叶针叶林区的火循环周期最短,林火发生频度为0.04次·(104hm2)-1,火循环周期为1 007年。中温带湿润地区森林区、中温带半干旱地区草原区的林火动态变化趋势与寒温带湿润地区落叶针叶林区相似。暖温带湿润/半湿润地区落叶阔叶林及人工植被区和中北亚热带湿润地区阔叶林及人工植被区火烧频度为0.28和0.25次·(104hm2)-1。【结论】中国的林火主要分布在东部区域。北方地区火灾主要发生在春季和秋季,南方地区火灾主要发生在冬季和春季。热带南亚热带湿润地区阔叶林、人工植被区林火发生频度最高,寒温带湿润地区落叶针叶林的火循环周期最短。建议根据林火动态变化和森林经营目的进行可燃物管理,维持林火动态在一个合理水平,实现森林资源的可持续利用。

未来情景下西南地区森林火险变化

采用区域气候模式输出的日值和加拿大森林火险天气指数系统,在50km×50km尺度下,分析IPCCSRESA2和B2情景下中国西南地区未来不同时段区域森林火险和森林火险期变化,为科学制定未来林火管理规划提供参考。气候情景数据使用区域气候模式系统(PRECIS)对中国区域1961—2100年SRESA2,B2情景下的气候模拟结果,计算研究区各格点森林火险天气指数(FWI),并利用ANUSPLIN软件把研究结果插值到1km×1km水平。结果表明:PRECIS模式对研究区的平均气温和月均降水均有较好的模拟能力,气温和降水空间分布形态及中心区域与观测数值基本一致。A2和B2情景下西南地区火险期(11月至翌年5月)内森林火险天气指数平均分别增加1.66和1.40。A2和B2情景下2041—2050年火险期FWI平均变率分别为1.22倍和1.24倍,表明A2和B2情景下西南地区的森林火烧面积在2041—2050年可能比基准时段增加22%和24%,并且在火险高的月份潜在的森林火烧面积增加更为明显。与基准时段相比,2种情景下都表现出低火险日数明显减少和极高火险日数显著增加的趋势。A2和B2情景下,2041—2050年高、很高和极高火险等级总日数分别增加17和13天。建议根据未来森林火险和火险期变化特点,加强早期预警、火灾监测和可燃物管理等,提高该区域适应气候变化的能力。

大兴安岭森林火险季节动态特征及其气候条件分析

森林火险季节是火环境中的一个重要因子，对于森林防火实际工作具有十分重要的意义．本文利用内 蒙古大兴安岭林区近３０年的林火资料和临近火点的气象资料，对比分析了该地区森林火险季节的时空分布 特征及其与气候条件的关系．结果表明：该地区多年平均森林火险季节长度大于２００ｄ，且２０世纪８０年代以 来呈增长趋势；南北林区火险季节指标差异明显，南部林区比北部林区进入火险季节的时间早而结束晚；森 林火险季节长度与全年无雪日数有关，起止日期与春季和秋季的日平均气温－５℃的日期相符合．

重特大火灾对南京市火灾发生影响规律的时间序列研究

本文采用时间序列法分析中国江苏省南京市每月火灾发生次数受该时间段内江苏省特大火灾以及南京市重特大火灾的影响规律。在对原始数据依次进行了异常点剔除、季节调整后,运用时间序列干涉模型对调整后的数据序列进行滞后分析,分析结果表明通常重特大火灾的影响可持续三个月。

3种南方防火树种理化性质的试验研究

以火力楠、木荷、油茶3种防火树种为研究对象,对各季节3种防火树种树枝、树皮、树叶的含水率、燃点、热值、灰分含量、粗脂肪含量、木质素含量、粗纤维含量等理化性质进行测定分析,以评估不同树种在不同季节的燃烧性。结果表明:各季节3种防火树种树枝、树皮、树叶的含水率、燃点、灰分含量和木质素含量总体为木荷>油茶>火力楠;热值春季为油茶>木荷>火力楠,秋冬两季为火力楠>油茶>木荷;粗脂肪含量各季节均为火力楠>油茶>木荷;粗纤维含量各季节均为油茶>火力楠>木荷。研究结果为3种防火树种的防火效能分析提供数据支持。

季节调整分析在城市火灾发生规律研究中的应用

利用样本周期图法定量分析了城市火灾序列的周期性,并实例分析得出了北京市火灾时间序列具有12个月和48个月的周期性。然后采用季节调整法,将火灾时间序列中的季节因子和不规则因子提取出来,得出了经季节调整后的时间序列,从而得到了北京市火灾发生受季节因素影响的大小和城市火灾时间序列的基本发展趋势,大大提高了火灾数据之间的可比性。同时结论可为消防管理部门有针对性地采取消防监督管理措施和科学地安排消防执勤战备提供有力指导。

燃气直燃机的使用对季节调峰的作用

分析了月用气量的组成 ,引入了 5个参数描述燃气管网的运行状态。研究了当城市的天然气消耗结构变化时直燃机的使用对季节调峰的影响。计算了直燃机的使用带来的经济效益。

煤炭与太阳能互补发电系统四季典型日变辐照聚光集热性能研究

光煤互补发电系统能将300℃以下的中低温太阳热能与传统燃煤电站相结合,用以替代回热抽汽加热给水,从而增加汽轮机出功。对传统的单轴跟踪槽式太阳能集热器用于光煤互补电站的热力性能进行了分析,并对其损失分布进行了研究。针对损失分布特性,提出了一种倾斜跟踪轴的槽式太阳能聚光集热器,并对该聚光集热器用于光煤互补电站后四季典型日的余弦损失、集热效率、太阳能瞬时功率、年均性能等进行了分析。结果表明,当跟踪轴倾斜角为15°时,年均余弦损失将从17.0%下降到9.8%,从而使年均集热效率从52.3%提升到59.5%,年均太阳能净发电效率从19.1%提升到21.7%,太阳能年发电量从17.2GW?h增加到19.6GW?h。

Seasonal fires shape the germinable soil seed bank community in eastern Mediterranean woodlands

We explored if and how seasonal fires interact with microhabitat type(i.e.under Pistacia shrub,under Cistus shrub or a canopy gap)to influence the composition of the germinable soil seed bank(GSSB)community in a typical eastern Mediterranean woodland.We conducted a field experiment,involving prescribed spring and autumn burns,and thereafter quantified the seed germination patterns using soil samples collected from both burned and adjacent unburned control plots.Soil temperature was significantly higher during autumn burns,while being more variable during spring burns.Fire caused overall reductions in GSSB density,richness and diversity.The reductions in GSSB richness and diversity were significantly stronger under Pistacia and Cistus shrubs located within plots subjected to autumn burns,and these patterns were mainly evident among annuals.GSSB density of dwarf shrubs was higher in samples collected from burned plots,and this pattern was more pronounced in samples collected under Pistacia and Cistus shrubs.Together with the appearance of unique species,seasonal fires led to significant changes in the composition of the GSSB community.Our results illustrate that seasonal fires interact with spatial heterogeneity to influence the composition of the GSSB community mostly via differential effects on the germination densities of annuals and dwarf shrubs.These findings imply that the increase in the frequency of seasonal fires,which has occurred in the eastern Mediterranean basin during the last few decades,may translate into a shift in eco-evolutionary selection pressures,operating on plants inhabiting this unique ecosystem.

火干扰对兴安落叶松林土壤轻组有机碳的影响

该研究基于土壤轻组有机碳在土壤碳循环中的重要作用,以大兴安岭林区兴安落叶松林土壤为研究对象,分析了火干扰后不同年份高强度火烧对土壤轻组有机碳的影响。用比重分离法对兴安落叶松林火干扰后3年(2008年)、火干扰5年(2006年)和火干扰后9年(2002年)样地及各对照样地的土壤样品进行测定。结果表明:不同年限火干扰后土壤轻组有机碳存在显著差异(P<0.05):火干扰后3年土壤轻组有机碳增加11.99%,而火干扰后5年土壤轻组有机碳含量减少了8.77%,火干扰后9年土壤轻组有机碳含量减少了6.27%,减少程度随着时间的推移有所下降。研究结果表明,土壤轻组有机碳与土壤含水率并无显著性关系;火干扰后3年和5年样地轻组有机碳与pH值呈显著性负相关,火干扰后轻组有机碳与土壤温度具有显著性负相关(P<0.05)。火干扰后短期内土壤轻组有机碳表现出更加明显的季节动态性。该研究为进一步了解火干扰对北方森林土壤碳循环、碳平衡的影响机理以及火干扰后森林生态系统的碳效应提供基础数据。

暖季型草坪草优良选系和品种抗盐性的初步评价

以叶片枯黄率为指标,通过水培法对5属12种50份暖季型草坪草优良选系和品种进行了抗盐性评价,为选育抗盐优质草坪草新品种提供试验依据。结果表明,供试草种间的抗盐性变异很大,总的变异系数达到60%,其中,结缕草属和狗牙根属变异系数分别为52%和29%,而结缕草和中华结缕草是变异最大的种,变异系数分别为56%和52%。总的来讲,抗盐性最强的多为细叶结缕草和沟叶结缕草植物,海雀稗‘Adalayd’、钝叶草‘S004’及部分结缕草、中华结缕草植物的抗盐性也较强,部分结缕草属其他材料和狗牙根属植物的抗盐性中等或较弱,而假俭草的抗盐性最弱。结缕草属中抗盐性比‘马尼拉’强的有7份材料,比‘兰引3号’强的有12份材料,而狗牙根属中除‘C158’、‘南京’狗牙根和‘C610’外,多数材料的抗盐性比对照品种‘Tifgreen’和‘Tifdwarf’强。抗盐性最强的3份选系(品种)为细叶结缕草‘Z160’、沟叶结缕草‘Diamond’和‘Z075’。

基于差分自回归移动平均模型的城市火灾趋势预测

以火灾统计数据中的火灾发生起数为研究对象,利用时间序列分析中的差分自回归移动平均模型对城市火灾进行预测。以北京市2000～2006年火灾数据为例,建立了乘积季节模型,进而预测了北京市2007年月火灾发生起数,并与实际值相比较,发现该模型预测结果较为准确,可用于对火灾作短期预测,预测结果可为消防部门的决策提供科学依据。

热带次生林、旱稻种植地和火烧迹地土壤节肢动物群落结构特征及季节变化

通过模拟刀耕火种过程 ,对刀耕火种前后的次生林、旱稻地 (第 2年 )和火烧迹地 (火烧后直接撂荒地第 2年 )土壤节肢动物群落结构特征及季节变化进行了调查研究。结果显示 :3块样地土壤节肢动物群落的优势类群组成相同 ,均为蜱螨目、膜翅目和弹尾目 ,但不同生境样地中各优势类群所占群落总数的比例不同 ,并且 3样地常见和稀有类群的组成差异较大 ;土壤节肢动物类群数、个体数和 DG多样性指数表现为次生林高于其它 2块样地 ,而旱稻地和火烧迹地则无较大差异 ,但一些类群在旱稻地、火烧迹地的数量分布与次生林具有差异 ,且在土壤层的表现较为突出 ;3块样地土壤节肢动物群落具有较好相似性 ,其中旱稻地与火烧迹地达到极相似水平 (D、DS>0 .9)。3种不同类型生境土壤节肢动物群落在类群数、个体数和多样性指数的季节变化总体呈现出雨量少的干季或雨季初末期高于雨量最大的雨季中期 ,与当地降雨量和气温变化有密切关系 ,同时各样地土壤节肢动物群落因生境条件不同及人为活动干扰强弱而形成各自的季节消长特点。研究表明刀耕火种后的旱稻种植对土壤节肢动物群落的恢复和发展在一定限制条件 (面积、周围次生林和坡度 )下无破坏性影响 ,但植被改变。