We investigated long-term changes, from 1979 to 2015, in the abundance of Protea roupelliae subsp. roupelliae trees growing in a montane grassland of the uKhahlamba-Drakensberg mountains. The study involved counting the numbers of adults and juveniles (saplings and seedlings) in six groves on three occasions over 36 years, documenting the fire-return intervals and the seasons when fires occurred in each grove, and measuring the fuel loads of the grass swards in five of the groves. Only in one grove did adults persist in their original numbers, but not the juveniles. Adults and juveniles declined in three groves, and in two groves both adults and juveniles died. Neither mean fire-return interval nor its variation, or seasonal distributions of fire could account for the transition from tree persistence to extirpation among the six groves after 36 years. Instead, the only plausible explanation for the persistence of Protea trees in one grove was that its grass sward produced a significantly lower mean, but higher variation in fuel load (biomass), compared with groves where Protea tree abundances either declined or were extirpated. As such, the recruitment bottleneck imposed on seedling establishment by the grass sward is an obvious avenue for future research.

我们调查了从1979年到2015年长期存在的Protea roupelliae亚种的变化。菊科uKhahlamba-Drakensberg山的山地草原上生长的树木。这项研究涉及在36年中的3次中，对6个树丛中的成年和少年（幼树和幼苗）的数量进行计数，记录回火间隔和每个树丛中发生火灾的季节，并测量草皮的燃料负荷。在五个树林中。只有在一个树林中，成年人才能保持其原始数量，而未成年人则保持不变。在三个树林中，成年和未成年动物的数量下降了，在两个树林中，成年和未成年者都死亡了。在36年之后，这六个树林中，平均回火间隔或其变化或火的季节分布都无法解释从树木的持久性到灭绝的过渡。相反，对于持续存在的唯一合理的解释普罗蒂亚与普罗梯亚木丰度下降或被淘汰的树丛相比，一个树丛中的树木的草皮产生的平均值低得多，但燃料负荷（生物量）的变化却更大。这样一来，草皮草对种苗建立的限制就成为今后研究的明显途径。