How does prescribed fire shape bird and plant communities in a temperate dry forest ecosystem?

To mitigate the impact of severe wildfire on human society and the environment, prescribed fire is widely used in forest ecosystems to reduce fuel loads and limit fire spread. To avoid detrimental effects on conservation values, it is imperative to understand how prescribed fire affects taxa having a range of different adaptations to disturbance. Such studies will have greatest benefit if they extend beyond short-term impacts of burning. We used a field study to examine the effects of prescribed fire on birds and plants across a 36-year post-fire chronosequence in a temperate dry forest ecosystem in south-eastern Australia, and by making comparison with long-unburnt reference sites (79 years since wildfire). We modelled changes in the relative abundance of 22 bird species and the cover of 39 plant species, and examined how individual species, functional groups, species richness and community composition differed between sites with different fire history. For most individual bird and plant species modelled, relative abundance or cover at sites subject to prescribed fire did not change significantly with time since fire or differ from that of long-unburnt vegetation. When bird species were pooled into functional groups, time since prescribed fire had strong effects on birds that forage in the lower-midstorey, facultative-resprouting shrubs and obligate-seeding shrubs. Species richness for both taxa did not differ between sites subject to prescribed fire and those in long-unburnt vegetation. Bird communities varied significantly between the youngest (0-3 years) and oldest (79 years) post-fire age-classes, driven by species associated with understorey vegetation. Plant community composition showed little evidence of a post-fire successional trajectory. The prevalence of bird species with broad habitat and dietary niches and plant regeneration through resprouting, make bird and plant communities in these forests relatively resilient to small and patchy prescribed fires they have experienced to date. Application of prescribed fire will be most compatible with maintaining biodiversity by taking a landscape approach that: 1) plans for a geographic spread of stands with a range of between-prescribed-fire intervals to ensure provision of suitable habitat for all taxa, and 2) avoids burning in moist gullies to maintain their value as fire refuges.

为缓解严重野火对人类社会与自然环境的影响，计划火烧（prescribed fire）已被广泛应用于森林生态系统，以降低燃料负荷并抑制火势蔓延。为避免对保护价值造成不利影响，亟需明确计划火烧如何影响那些对干扰具有各类不同适应策略的类群。此类研究若能超越火烧的短期影响，将发挥最大效益。
本研究依托澳大利亚东南部温带干旱森林生态系统内一处跨度达36年的火烧后时间序列样地（chronosequence），并以未受火烧长达79年的长期未烧对照样地作为参照，通过野外调查探究计划火烧对鸟类与植物的影响。我们对22种鸟类的相对多度以及39种植物的盖度进行建模，同时分析不同火烧历史样地间的单个物种、功能群、物种丰富度及群落组成的差异。
针对绝大多数建模的鸟类与植物物种，计划火烧样地内的相对多度或盖度并未随火烧后时间推移发生显著变化，也与长期未烧植被的对应指标无显著差异。当将鸟类按功能群合并分析时，火烧后时间对中下层觅食的鸟类、兼性萌蘖灌木以及专性播种灌木类群具有显著影响。两类群的物种丰富度在计划火烧样地与长期未烧样地间均无显著差异。
鸟类群落在最年轻（0-3年）与最年老（79年）的火烧后年龄组间存在显著差异，这一差异由与下层植被相关的鸟类物种驱动。植物群落组成几乎未表现出火烧后演替轨迹。具备宽泛栖息地与食物生态位的鸟类物种，以及通过萌蘖实现更新的植物物种占比偏高，使得该森林中的鸟类与植物群落对迄今经历的小规模、斑块状计划火烧具有较强的恢复力。
采用景观尺度的管理策略，可使计划火烧与生物多样性保护更具兼容性：1）规划火烧间隔各异的林分在地理上的分布范围，确保为所有类群提供适宜栖息地；2）避免在潮湿沟壑中开展火烧，以维持其作为火灾避难所的生态价值。