Data on variables of fire behavior in a study carried out in the Caatinga Biome

The hypothesis is that the fire behavior varies with the type and quantity of combustible material in the different regions of the Caatinga. The objective of this work was (i) to evaluate the fire behavior of material from preserved areas of the Caatinga biome in different geographic regions of the hinterland of the Paraíba and (ii) to determine whether the type and amount of combustible material collected in each preserved area of Caatinga affect the fire intensity and spread. The combustible material was collected in the geographic regions of Cajazeiras, Catolé do Rocha, Itaporanga, Patos, Pombal, Princesa Isabel and Sousa in the hinterland of the Paraíba State, Brazil. The combustible material was collected in seven areas (one per region) of the Caatinga with at least 30 years of preservation with arboreal-shrubby vegetation and herbaceous layer in August 2018. Three plots of 20 x 20 m (400 m²) 200 meters apart from each other were marked per area. The combustible material wascollected with the aid of a template (1.0 m x 1.0 m), thrown randomly three times per plot totaling nine samples per area. The vegetation, up to 1.8 m high inside the template, was removed with a machete and pruning shears to facilitate the removal of superficial combustible material. The fire behavior variables observed during the burning of the material in each plot were: 1- propagation speed (PS); 2- burning duration (BD); 3- flame height (FH). These observations allowed to obtaining the following parameters: 1- fire intensity (I); 2- heat released per unit of area. The fire behavior response variables differed between regions. The propagation speed was higher in the material from the Cajazeiras region (0.0168 m s-1) than in the others and with the lowest value in Catolé do Rocha (0.0941 m s-1). The burning duration of the combustible material was longer for Catolé do Rocha (928.6 s) and shorter for Cajazeiras (203.0 s) and Princesa Isabel (271.3 s) materials. The flame height was greater in the combustible material from the Pombal (1.37 m) region, almost triple that of Catolé do Rocha, with the lowest value (0.53 m). An inverse pattern was observed for fire intensity, with a higher value in the material from the Catolé do Rocha region (9687.58 kJ m-1 s-2) than from the Cajazeiras, Princesa Isabel and Patos minor regions, 427.65 kJ m-1 s-1, 490.54 kJ m-1 s-1 and 667.97 kJ m-1 s-1 respectively. The fire behavior in materials from the Caatinga preserved areas of the hinterland of the Paraíba state, Brazil varied with the types and quantities of combustible material, with emphasis on the greater accumulation of fire in the Catolé do Rocha, Itaporanga and Pombal regions. The continuous deposition and the low moisture content of the combustible material on the forest floor prove that the areas evaluated are susceptible to high intensity fires.

本研究提出的假设为：卡廷加（Caatinga）生物群系不同区域内的可燃物类型与数量差异，会导致火灾行为发生变化。本研究的目标分为两项：（i）评估巴西帕拉伊巴（Paraíba）州内陆不同地理区域的卡廷加保护区内可燃物的火灾行为；（ii）明确各卡廷加保护区内采集的可燃物类型与数量，是否会对火灾强度与火灾蔓延产生影响。研究于2018年8月，在巴西帕拉伊巴州内陆的卡扎热拉斯（Cajazeiras）、卡托莱杜罗沙（Catolé do Rocha）、伊塔波兰加（Itaporanga）、帕托斯（Patos）、蓬巴尔（Pombal）、伊莎贝尔公主镇（Princesa Isabel）与苏萨（Sousa）共7个地理区域开展，每个区域设置1个保护区，该类保护区的乔灌植被与草本层已至少保留30年。每个区域内设置3块20×20米（即400平方米）的样地，样地之间间距为200米。研究借助1.0×1.0米的采样框开展可燃物采集：每块样地随机投掷采样框3次，每个区域共获得9份样品。使用砍刀与修枝剪移除采样框内高度不超过1.8米的植被，以方便采集地表可燃物。在每块样地的可燃物燃烧过程中，观测的火灾行为变量包括：1. 传播速度（propagation speed，PS）；2. 燃烧时长（burning duration，BD）；3. 火焰高度（flame height，FH）。基于上述观测结果，可计算得到以下参数：1. 火灾强度（fire intensity，I）；2. 单位面积释热量。研究结果显示，不同区域的火灾行为响应变量存在显著差异。卡扎热拉斯区域可燃物的传播速度（0.0168 m·s⁻¹）高于其余区域，而卡托莱杜罗沙区域的传播速度最低，为0.0941 m·s⁻¹。卡托莱杜罗沙区域的可燃物燃烧时长最长，达928.6 s，而卡扎热拉斯（203.0 s）与伊莎贝尔公主镇（271.3 s）区域的可燃物燃烧时长最短。蓬巴尔区域的可燃物火焰高度最高，达1.37 m，约为卡托莱杜罗沙区域的3倍，而卡托莱杜罗沙区域的火焰高度最低，仅为0.53 m。火灾强度则呈现相反的变化模式：卡托莱杜罗沙区域的可燃物火灾强度最高，达9687.58 kJ·m⁻¹·s⁻²，显著高于卡扎热拉斯、伊莎贝尔公主镇与帕托斯区域，这三个区域的火灾强度分别为427.65 kJ·m⁻¹·s⁻¹、490.54 kJ·m⁻¹·s⁻¹与667.97 kJ·m⁻¹·s⁻¹。本研究表明，巴西帕拉伊巴州内陆卡廷加保护区内的可燃物火灾行为，会随可燃物类型与数量的变化而产生差异，其中卡托莱杜罗沙、伊塔波兰加与蓬巴尔区域的可燃物积累量更高，火灾风险更为突出。地表可燃物的持续沉积与低含水率，证明本次评估的保护区均存在发生高强度火灾的潜在风险。