南亚热带典型人工林可燃物空间分布及潜在火行为研究

发布时间：2018-02-26 23:22

  本文关键词： 桂西南 负载量 马尾松人工林 调控措施 空间连续性　出处：《中南林业科技大学》2017年博士论文　论文类型：学位论文

【摘要】：本研究以广西南宁市典型人工林为研究对象,在对各林型内可燃物进行分类,采样调查、室内分析和模型预测的基础上,通过研究不同树种、灌木、草本、凋落物和腐殖质层等可燃物在空间上的分布规律和负载量特征,探讨不同林型单元内的可燃物属性、结构和潜在林火行为特征。在对马尾松纯林、马尾松-大叶栎混交林和大叶栎纯林可燃物负载量空间分布与树冠火行为关系分析的基础上,运用可燃物空间连续性指数评估模型,对不同林型可燃物垂直连续性和水平连续性进行计算,评估了针叶林和针阔混交林树冠火发生和蔓延的可能性,提出了阻滞树冠火转化和蔓延的调控措施。研究得出如下主要结论:(1)马尾松纯林枝叶负载量最高,松栎混交林居中,大叶栎纯林最低;马尾松纯林灌木层可燃物负载量也高于松栎混交林和大叶栎纯林;各类别可燃物中,冠层大枝占比最高,1000h枯枝占比最低;马尾松纯林中易燃可燃物负载量最高(16.29 t/hm2),其次是松栎混交林(15.64 t/hm2),大叶栎纯林最低(9.00 t/hm2),易燃可燃物是关键的引燃物,与森林火灾风险密切相关,马尾松林潜在树冠火风险最高,其次是松栎混交林,大叶栎纯林极难发生树冠火。(2)采用表面积加权算法的蔓延速度(MRE=5.43%)和火焰长度(MRE=14.27%)预测效果较好,采用负载量加权算法的反应强度(MRE=4.07%)和火线强度(MRE=16.29%)预测效果较好。(3)反应强度与可燃物负载量正相关,与含水率负相关;可燃物负载量、风速和坡度对于蔓延速度均有增益效果,但当可燃物负载量增大到一定量(高点)后,蔓延速度不再增加,三个林型可燃物负载量的(蔓延速度限制)高点分别为30～32t/hm2、40t/hm2和20t/hm2;风速对于蔓延速度贡献要大于坡度,同样风速下,马尾松林火蔓延速度最高,其次是松栎混交林,大叶栎林最低。(4)基于环境因子、可燃物性质和空间位置以及林火特征,将森林燃烧等级划为低、中、高三级,推算了不同燃烧等级下的火强度、可燃物消耗量和火焰高度。整体来看,马尾松在各等级燃烧条件下所释放能量密度均较高,发生树冠火后可燃物烧损量也最大,而大叶栎纯林无法形成树冠火,仅能在0～1m区间提供适宜的地表火燃烧条件,对森林生态系统影响最小。(5)基于Byram模型,根据平地无风条件下火焰燃烧状态、可燃物分层和冠层平均枝下高,建立了可燃物垂直连续性指数和水平连续性指数及等级。应用连续性评估模型对马尾松林和松栎混交林的可燃物空间连续性进行了定量评估,可燃物的垂直连续性高低决定地表火能否转化为树冠火,而水平连续性高低决定树冠火是否能大面积蔓延。结果表明,马尾松林可燃物整体垂直连续性指数和水平连续性指数较高,均达到了高度连续,松栎混交林可燃物整体垂直连续性为低等级连续,其水平连续性为高等级连续。(6)根据火焰高度分级和Byram模型,推导了可燃物连续性负载量阈值计算公式,分别计算了马尾松林和松栎混交林不同单元内0～3m区间可燃物垂直连续性负载量阈值,并以此为依据,制定了具体的可燃物调控措施,根据二次评估结果,筛选了不同林型的最佳调控方案(马尾松纯林采取方案一中的3m修枝高度,松栋混交林采取方案一中的3m修枝高度,亦可视具体情况调整为4m修枝高度),可兼顾森林生态系统稳定性维持、用材林目标树种生物量提高和森林潜在火灾风险控制多目标协同管理。
[Abstract]:In this study, Guangxi Nanning City, a typical plantation as the research object, in the combustible in each forest type classification, sampling survey, laboratory analysis and prediction model based on the study of different trees, shrubs, herbs, distribution of litter and humus layer and other combustible materials in space and the load characteristics. The attribute of combustibles in different forest types in the unit, structure and potential fire behavior characteristics. In the pure forest of Pinus massoniana, Pinus massoniana and Castanopsis fissa mixed forest and pure forest of castanopsisfissa fuel load based analysis of the relationship between the distribution and crown fire behavior, the use of combustible space continuity index evaluation model for different forest type of fuel vertical continuity and continuity are calculated, the assessment of possibility of coniferous forest and mixed forest crown fire occurrence and spread, and put forward the control measures into the block crown fire and spread application research. The main conclusions are as follows: (1) the highest load of branches of pure pine forest, pine and oak mixed forest center, Li Chunlin leaves the lowest; Pinus forest shrub layer is higher than the amount of fuel load and oak pine mixed forest of Castanopsis fissa plantations; various types of combustible materials, the highest proportion of big canopy, litter accounted for the lowest 1000h flammable materials; pure forest load was the highest (16.29 t/hm2), followed by pine oak mixed forest (15.64 t/hm2), castanopsisfissa pure forest is the lowest (9 t/hm2), is the key to the ignition of flammable combustible material, and is closely related to the risk of forest fires, the highest potential in masson pine forest crown fire risk, followed by Oak pine mixed forest, Castanopsis fissa plantations can hardly occur crown fire. (2) using surface area weighted algorithm (MRE=5.43%) and the rate of spread of flame length (MRE=14.27%) better prediction effect by reactive load intensity weighted algorithm (MRE=4.07%) and fire intensity (MRE=16.29 %) better forecasting effect. (3) the reaction intensity and fuel load of positive correlation, negative correlation with water content; fuel load, wind speed and slope for the spread has gain effect, but when the fuel load increased to a certain amount (high), the spread rate no longer increased three Lin type fuel load (spread speed limit) high were 30 ~ 32t/hm2,40t/hm2 and 20t/hm2; the wind speed for spreading speed is bigger than the slope under the same wind velocity, masson pine forest fire spread fastest, followed by the oak pine mixed forest, Castanopsis fissa forest was the lowest. (4) based on the environmental factor, the combustible material and space the location and characteristics of forest fire, forest fire will be classified as low grade, grade, grade, fire intensity under different combustion calculated, fuel consumption and flame height. Overall, Masson conditions in the energy released in the combustion of each grade were density The high occurrence of crown fire after the fuel consumption is the largest, and the pure forest of Castanopsis fissa cannot form a crown fire, only in the interval from 0 to 1m provide a suitable surface fire combustion conditions, with minimal impact on forest ecosystem. (5) based on the Byram model, according to the ground without wind flame burning state, combustible layered and canopy height under branch, established fuel vertical continuity index and horizontal continuity index and the rating. Combustible space application continuity evaluation model of Masson pine forest and pine oak mixed forest continuity were assessed quantitatively, fuel vertical continuity decides the surface fire can be transformed into crown fire. While the level of continuity determines whether a large area of crown fire spread. The results showed that the Masson pine forest combustible overall vertical continuity index and horizontal continuity index was higher, reached the height of continuous, pine and oak mixed forest combustibles The overall vertical continuity for the low level continuously, its level of continuity for high grade continuous. (6) according to the classification of flame height and Byram model, deduces the combustible continuous load threshold formula, forest and pine oak mixed forest of Pinus massoniana in different units is 0 ~ 3M between fuel vertical continuity load threshold respectively. The calculation, and on this basis, developed a combustible specific control measures, according to the two assessment results, the optimum control scheme of different forest types (pure pine forest program one 3m in the height of pruning, pine mixed forest, take a program of 3M pruning height, depending on the particular circumstances of adjustment is also 4m), can take into account the pruning height to maintain the stability of forest ecosystem, forest tree biomass and improve target timber forest fire risk control potential multi-objective collaborative management.

【学位授予单位】：中南林业科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S762
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本文编号：1540131