Weather and human impacts on forest fires: 100 years of fire history in two climatic regions of Switzerland

Understanding the factors driving past fire regimes is crucial in the context of global change as a basis for predicting future changes. In this study, we aimed to identify the impact of climate and human activities on fire occurrence in the most fire-prone regions of Switzerland. We considered forest fires, land use and meteorological data over the period 1904-2008 in the neighboring mountain cantons (states) of Valais and Ticino, which are characterized by distinct climatic regimes.The presence/absence of fire ignitions was analyzed using the Nesterov ignition index (as a proxy for fire weather), road density (for ignition sources), livestock density (for biomass removal), and change in forest area (for fire-prone abandoned agricultural areas).We found that fire weather played a key role in fire occurrence in both regions. Road and livestock densities had similar influences in the two cantons. However, while the increase in forest area was well correlated with fire occurrence in Ticino, no such correlation was evident in Valais, probably because land abandonment and forest cover change have been less extensive there. Our findings emphasize the non-linear nature of the relationships between fire occurrence and anthropogenic drivers, as we found thresholds above which road density was no longer correlated with fire occurrence. This implies that the projected future increase and spatial concentration of the human population may not result in a further increase in fire risk in intermediately to densely populated areas in both cantons.The driving factors behind fire activity differ slightly in the two cantons, in particular with increasing forest area enhancing fire occurrence in Ticino but not in Valais. These differences should be taken into account when assessing future fire risk, especially in Valais where the potential for an increase in the fire-prone area is still high. Fires are likely to become more frequent in a warmer climate, but future fire activity may develop differently in the two cantons. This should be taken into account when planning optimized fire prevention measures. This case study should help to better understand fire activity in highly populated regions where fire activity is still moderate but might markedly increase under a projected more fire-prone climate.     

Historic and current fire regimes in the Great Xing’an Mountains,northeastern China: Implications for long-term forest management

Understanding both historic and current fire regimes is indispensable to sustainable forest landscape management. In this paper, we use a spatially explicit landscape simulation model, LANDIS, to simulate historic and current fire regimes in the Great Xing’an Mountains, in northeastern China. We analyzed fire frequency, fire size, fire intensity, and spatial pattern of burnt patches. Our simulated results show that fire frequency under the current fire scenario is lower than under the historic fire scenario; total area burnt is larger with lower fire intensity under the historic fire scenario, and smaller with higher fire intensity under the current fire scenario. We also found most areas were burned by high intensity fires under the current fire scenario, but by low to moderate fires under the historic fire scenario. Burnt patches exhibit a different pattern between the two simulation scenarios. Large patches burnt by high intensity class fires dominate the landscape under the current fire scenario, and under historic fire scenario, patches burnt by low to moderate fire intensity fires have relatively larger size than those burnt by high intensity fires. Based on these simulated results, we suggest that prescribed burning or coarse woody debris reduction should be incorporated into forest management plans in this region, especially on north-facing slopes. Tree planting may be a better management option on these severely burned areas whereas prescribed burning after small area selective cutting, retaining dispersed seed trees, may be a sound forest management alternative in areas except for the severely burned patches.     

Spatial patterns of fire occurrence in Catalonia,NE, Spain

In this paper, we analyse spatial patterns of fire occurrence in Catalonia (NE Spain) during 1975–98. Fire scar maps, discriminated by means of 30–60 m resolution remote sensing imagery, have been used as a source of fire occurrence. We employ several visual or analytical approaches to interpret fire occurrence in this region, such as those of Minnich and Chou (1997), Ricotta et al. (2001) or Krummel et al. (1987). Crucial spatial patterns such as fire size distribution, fire frequency distribution, spots and residual vegetation islands are documented. In addition, several geographical layers were overlaid with burned area maps in order to determine interactions between fire occurrence and environmental parameters such as altitude, slope, solar radiation, and burned land cover. Assuming that fire occurrence is well determined by such a posteriori empirical factors we detect areas most prone to fire in this region and aim to enhance the local forest management and conservation plans.     

Activated carbon amendments to soil alters nitrification rates in Scots pine forests

The influence of charcoal on biotic processes in soils remains poorly understood. Charcoal is a natural product of wildfires that burned on a historic return interval of ∼100 years in Scots pine (Pinus sylvestris L.) forests of northern Sweden. Fire suppression and changes in forest stand management have resulted in a lack of charcoal production in these ecosystems. It is thought that charcoal may alter N mineralization and nitrification rates, however, previous studies have not been conclusive. Replicated field studies were conducted at three late-succession field sites in northern Sweden and supporting laboratory incubations were conducted using soil humus collected from these sites. We used activated carbon (AC), as a surrogate for natural-occurring fire-produced charcoal. Two rates of AC (0 and 2000 kg ha⁻¹), and glycine (0 and 100 kg N as glycine ha⁻¹) were applied in factorial combination to field microplots in a randomized complete block pattern. Net nitrification, N mineralization, and free phenol concentrations were measured using ionic and non-ionic resin capsules, respectively. These same treatments and also two rates of birch leaf litter (0 and 1000 kg ha⁻¹) were applied in a laboratory incubation and soils from this incubation were extracted with KCl and analyzed for NH₄⁺ and NO₃⁻. Nitrification rates increased with AC amendments in laboratory incubations, but this was not supported by field studies. Ammonification rates, as measured by NH₄⁺ accumulation on ionic resins, were increased considerably by glycine applications, but some NH₄⁺ was apparently lost to surface sorption to the AC. Phenolic accumulation on non-ionic resin capsules was significantly reduced by AC amendments. We conclude that charcoal exhibits important characteristics that affect regulating steps in the transformation and cycling of N.     

林火对大兴安岭典型植被土壤理化性质的影响

以大兴安岭地区西部呼中国家级自然保护区2008年受火烧干扰的林分为研究对象,对2个典型林型落叶松林和白桦林不同火烧强度的土壤理化性质进行了分析。结果表明:2个林型在不同火烧强度的作用下,其土壤含水率、土壤密度、pH值、有机质及营养元素质量分数等理化性质表现出显著的差异性。     

Tree-ring: a suitable implement for spatial and temporal fire distribution analysis in savanna woodland and dry forest

Based on 120 stem discs collected during3 months of fieldwork along a 12 km route,the history of fires in the Wari Maro Forest(09 1000 N–02 1000E) over the past century in savanna woodland and dry forest was reconstituted.Three major ecological areas are characterized:one highly burnt zone located between two relative less burnt areas.By analyzing tree rings,246 fire scars were identified.The scars were caused by 51 fire years,occurring at a mean interval of 2.23 years.From 1890 to1965,only 6 years with fires were recorded from sampled trees.Since 1966,no year has passed without fire.The fire frequency point scale reached 14 years.This was the case of Burkea africana,which has been identified as a species tolerant to fire and could be planted to create a natural firewall.In contrast,Anogeissus leiocarpa is highly sensitive to fire,and in a dry forest ecosystem that burns seasonally,it requires a special conservation plan.Two new concepts are described:the rebarking of trees after fire and Mean Kilometer Fire Interval.The first concept was tested with Daniellia oliveri(Rolfe) Hutch & Dalz trees,and the second concept was used to evaluate spatial fire distribution.We demonstrate that savanna woodland and dry forest were subject to a degradation process caused by destructive fires related to vegetation cover clearance and illegal logging.     

不同时间尺度下吉林省森林火灾发生规律

对吉林省1969—2013年间发生的森林火灾情况进行分析,结果显示,受森林防火条例有效实施的影响,1984年后林火发生次数显著降低并趋于稳定;春、秋两季为林火高发季节,且在进行森林防火资源的调配过程中,火灾次数较多的4月和5月应以控制火源为主要目的,受害森林面积较大的9月应以强化扑火能力为工作重点;此外,月初林火发生概率相对较高,应针对该时间段提高防火警惕;林火的发生主要集中在8:00—16:00,需重点部署防火工作,而且2:00左右受害森林面积相对较大,火灾扑救能力应需加强。     

梨火疫病菌在中国的潜在分布及入侵风险分析

 【目的】细菌性梨火疫病最早发生在北美洲，随着水果贸易等人为因素向世界其它地区传播。对当地的生物多样性和经济带来了极其严重的威胁，亟需对其在中国的适生区进行预测。【方法】苹果开花期的温度和降水量是影响梨火疫病菌适生分布的关键气候因子，本研究根据这一生物学特性及生态环境因子，应用地理信息系统分析得出了梨火疫病在中国两个苹果优势产区的潜在定殖区域。【结果】用该方法对梨火疫病在欧洲的发生情况的预测结果与其历史分布记录相符，使用相同的空间建模方法对梨火疫病在渤海湾和黄土高原两个苹果优势栽培产区的潜在定殖区域进行风险评估，结果表明这两大苹果产区中优先扶持的县大多处于梨火疫病发生的高风险范围。【结论】梨火疫病在中国的大部分地区适生，在有适宜寄主分布的地区，就可能严重发生。     

黑龙江省大兴安岭林区森林气象火险指数的适用性研究

基于1996～2005年黑龙江省大兴安岭林区的气象数据及林火数据,比较研究了3种常用的气象火险指数（KBDI、FFDI和NMCI）在大兴安岭林区的适用性。结果表明,FFDI适用于日和月尺度的大兴安岭林区森林火险预报,而NMCI更适于年尺度的大兴安岭林区潜在森林火险评价,但3种气象火险指数与发生林火的相关系数均不高,需要进一步修正其初始条件或选择更合适的参数,以达到更好的预报效果。     

火干扰对天然红松林结构和演替过程的影响

1990—1992年期间对小兴安岭凉水林场天然红松林土壤中木炭、火烧木疤痕和林分组成进行了调查。探讨火干扰对森林形成和演替的生态作用。在不同火干扰年代的林分中,抽样挖掘木炭,测量木炭块的大小和分布深度,记录各林分结构特征和红松更新状况,并根据树木火疤园盘确定火干扰年代。选择了50 hm~2火干扰林分,对火烧疤痕木进行详细调查,并在其中设置样地,调查各样地林分组成和红松径阶结构。结果表明:Ⅰ.不同火干扰年代的林分。土壤中的木炭平均深度与火干扰发生的时间关系密切。Ⅱ.根据50 hm~2火干扰林分中火烧木疤痕的调查,绘制了火行为动态图。火烧方向和火干扰程度与立地条件关系密切。Ⅲ.火干扰并未完全破坏森林,导致林分中不同地点上林分组成和红松径阶结构的差异明显。在火干扰后,整个林分的水平结构是一个由不同树种组成和不同红松径阶结构的树木群团构成的镶嵌体,各树木群团的演替趋势不同。在火干扰较重的地点,阳性阔叶林占优势,在阔叶树下更新着大量的红松小树。在火干扰较轻的地点,耐阴性阔叶树种占优势,并有少量大径阶红松。火干扰轻微的地点,大径阶的红松占优势。