Our study investigated the effects of fire frequency on the tree and grass components of Cumberland Plain Woodland, an endangered grassy eucalypt woodland in eastern Australia. We located three sites within each of three fire frequency classes (high, moderate, low) based on fire history and a similar time since last fire. For trees, we asked whether fire frequency affected density, eucalypt population structure, basal area and spatial patterning. For grasses, we tested for fire frequency effects on total abundance and the abundance of two common species. Density of trees was not significantly affected by fire frequency for juveniles, saplings or adult trees and neither was basal area per hectare. Features of a recruitment bottleneck model were present for eucalypts. There was a large pool of suppressed juveniles making up more than half the population at each fire frequency. Saplings were the smallest group and were susceptible to fire‐induced stem mortality, with particularly low numbers relative to juveniles and small trees where fire was frequent or intense. Despite this difference in sapling mortality, numbers of small trees did not differ with fire frequency. Saplings could transition to small trees in equal numbers if they did so more quickly at high than at lower fire frequencies, and if recruitment of saplings into the tree layer was controlled independently of fire frequency. The size hierarchy of small to medium eucalypt trees was homogeneous over eight of the nine sites, spatial patterning of adult trees was random tending to regular, and mean tree size decreased with density at all sites. These features of eucalypt population structure are indicative of possible resource competition which could regulate tree recruitment. Total grass cover index was high across all fire frequencies, with Themeda triandra dominating at high and moderate fire frequencies and Microlaena stipoides at low fire frequency.

中文翻译：

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草地林地的火灾频率效应：树木和草

我们的研究调查了火灾频率对澳大利亚东部濒临灭绝的桉树林地坎伯兰平原林地的树木和草地成分的影响。我们根据火灾历史和自上次火灾以来的相似时间，在三个火灾频率等级（高、中、低）中的每一个中定位了三个地点。对于树木，我们询问火灾频率是否影响密度、桉树种群结构、基底面积和空间格局。对于草，我们测试了火灾频率对两种常见物种总丰度和丰度的影响。树木的密度不受幼苗、树苗或成年树木的火灾频率的显着影响，每公顷的基面积也不受火灾频率的影响。桉树存在招聘瓶颈模型的特征。在每个火灾频率下，都有大量被压制的青少年，占人口的一半以上。树苗是最小的群体，容易遭受火灾引起的茎死亡，相对于火灾频繁或激烈的幼苗和小树而言，树苗的数量特别少。尽管树苗死亡率存在这种差异，但小树的数量与火灾频率没有差异。如果树苗在高火灾频率下比在低火灾频率下更快地转变为相同数量的小树，并且如果树苗向树层的补充不受火灾频率的控制。九个地点中的八个中小型桉树的大小等级是同质的，成年树的空间格局随机趋于规则，并且所有地点的平均树木大小都随着密度而减小。桉树种群结构的这些特征表明可能的资源竞争可以调节树木的补充。在所有火灾频率中，总草覆盖指数都很高，其中 Themeda triandra 在高和中等火灾频率下占主导地位，而 Microlaena stipoides 在低火灾频率下占主导地位。