Fire persistence traits can be used to predict vegetation response to changing fire regimes at expansive landscape scales – an Australian example

Aim Building on a substantial literature addressing the fire responses of woody plants, particularly under mediterranean climates, we assess the extent to which fire persistence traits can be used to predict vegetation responses to fire regime changes in fire‐prone arid and savanna landscape settings. Location Australia, applying data from arid central to monsoonal northern regions (11–26° S, 129–138° E). Methods With reference to a substantial sub‐continental floristics dataset, we first assigned the fire response (obligate seeder, resprouter) and seedbank persistence (transient, dormant) of rapid and longer‐maturing (> 3 years) woody taxa. Using logistic regression, we then modelled the proportions of taxa possessing these traits as a function of mean annual rainfall (highly correlated with fire frequency) and terrain roughness (a measure of topographic variability) in 0.25° × 0.25° and 1° × 1° grid cells. Separate assessments were undertaken with datasets for 1264 sclerophyll and 236 rain forest taxa. Results This woody flora is characterized by taxa exhibiting mostly resprouting and dormant seedbank traits that promote site persistence. While numbers of obligate seeder and resprouter taxa were related positively to both rainfall and roughness, the relative abundance of both sclerophyll and rain forest obligate seeders decreased significantly with rainfall. The relative abundance of sclerophyll (especially long‐lived) obligate seeders alone increased with topographic roughness. The proportion of taxa with transient seedbanks increased with rainfall in resprouters generally, and in rain forest obligate seeders alone. Main conclusions We find that resprouters are favoured on more productive, fire‐prone sites, and obligate seeders are favoured in less productive, more fire‐protected settings. Seedbank persistence responses are more variable. These findings concur generally with theoretical constructs, and support comparable assessments in Australian and other fire‐prone systems ranging from mediterranean to boreal environments. Our observations illustrate that resprouting and obligate seeding syndromes, but not necessarily seedbank persistence, are useful predictors of vegetation responses to changing fire regime conditions at large landscape scales.     

Effects of a fire-retardant on oviposition habitat selection and larval development of the mosquito Culiseta longiareolata

1. Fire retardants are composed of fertilising salts that are commonly used for fighting wildfires. These chemicals have various effects on individual arthropod species and aquatic communities. 2. This study investigated the effects of four treatments of a prevalent fire retardant [FR CROS 134 (FR), applied at concentrations of 0, 3.8 × 10², 7.6 × 10² and 11.4 × 10² mg litre⁻¹] on oviposition habitat selection (OHS) by Culiseta longiareolata and Culex laticinctus mosquitoes in an outdoor mesocosm. Additionally, larval development of C. longiareolata was examined in response to this fire retardant. 3. The results demonstrate that OHS increased in both species, whereas survivorship (0–86.7%) and time to metamorphosis (5.4–23.1 days) of C. longiareolata were not affected by any of the treatments. However, cyanobacterial biomass increased and heterotrophic bacteria decreased in response to the addition of FR. 4. It was found that FR applications can have unintended consequences which can increase OHS by female mosquitoes. The growing use of fire retardants worldwide, and especially in Israel, justify evidence-based assessment and environmental management of their use. This study is a first critical step in filling the knowledge gap with respect to the impact of FR on aquatic ecosystems.     

油松人工林火烧迹地早期土壤入渗动态

土壤入渗是决定雨水或融水通过地表再分配给土壤的关键, 影响着森林生态水文过程。为研究北京油松(Pinus tabulaeformis)人工林火烧迹地早期土壤入渗特征及其结构性控制因素, 在火灾发生(2019年3月)的当年对火烧和对照样地的0-20 cm土壤进行为期8个月(5-12月)的采集, 测定分析土壤结构和入渗对火烧干扰的响应及随土壤深度和时间的变化, 并通过路径分析探讨火烧和土壤结构性质对土壤入渗的作用机制。结果表明: 1)土壤各结构指标(除小团聚体外)随土壤深度和时间变化总体具有浅层>深层和6-8月>其他月份的趋势。火烧改变了土壤结构原有的垂直分布特征和季节动态规律, 火烧后2个月土壤>5、2-5和1-2 mm团聚体含量和容重显著增加, 其余指标均显著减少。随土层加深和时间推移, 火烧的作用减弱, 但与土壤深度和时间变化具有明显的交互效应。2)土壤入渗特征随土壤深度变化缓慢, 但随时间变化显著, 表现为雨水较多且出现强降雨事件的8月土壤初渗速率、稳渗速率、入渗总量和饱和导水率最大。火烧后0-5 cm和6-9月的土壤入渗过程与对照相比差异较大, 各月土壤入渗特征均下降, 出现峰值时间提前1-2个月。3)火烧显著影响土壤结构性质, 而土壤入渗性主要受土壤结构性质的直接影响。在未受火烧干扰的情况下, 土壤的入渗性受到土壤团聚体、容重和持水量的正效应以及孔隙度的负效应, 有机质含量和初始含水率对入渗性的直接影响均不显著, 但有机质含量可以通过影响孔隙度或持水量间接影响入渗性。火烧后土壤初始含水率是唯一显著且直接影响入渗性的因素, 且初始含水率越高, 土壤入渗越慢。综上所述, 火烧会改变或解耦火烧迹地早期土壤结构对土壤入渗及其内部的作用程度及途径而间接影响土壤入渗。     

The effect of fire on an abstract forest ecosystem: An agent based study

Our model considers a new element in forest fire modeling, namely the dynamics of a forest animal, intimately linked to the trees. We show that animals and trees react differently to different types of fire. A high probability of fire initiation results in several small fires, which do not allow for a large fuel accumulation and thus the destruction of many trees by fire, but is found to be generally devastating to the animal population at the same time. On the other hand, a low fire initiation probability allows for the accumulation of higher quantities of fuel, which in turn results in larger fires, more devastating to the trees than to the animals. Thus, we suggest that optimal fire management should take into account the relation between fire initiation and its different effects on animals and trees. Further, wildfires are often considered as prime examples for power-law-like frequency distributions, yet there is no agreement on the mechanisms responsible for the observed patterns. Our model suggests that instead of a single unified distribution, a superposition of at least two different distributions can be detected and this suggests multiform mechanisms acting on different scales. None of the discovered distributions are compatible with the power-law hypothesis.