Abstract

Grasslands and grassy woodlands worldwide have experienced declines in extent and condition, with substantial changes to their ground-layer biodiversity. In Australia, this decline has coincided with the extinction of many digging mammals that may have once created regeneration niches for native ground layer plants. These digging mammals are widely recognised as ‘ecosystem engineers’, due to their influence on biopedturbation and resultant soil functions. Yet there is uncertainty as to the benefits of digging in restoring grassland diversity with current levels of modification and the presence of exotic plants. We investigated the effect of digging by the reintroduced eastern bettong (Bettongia gaimardi) on seedling germination in a temperate grassy woodland in south-eastern Australia. We marked fresh bettong foraging pits and undisturbed control plots in dense and open grassland. We added seeds of seven native forb species and monitored germination and establishment over 2 years. We found significantly more seedlings in bettong pits than controls, particularly in dense grassland. This effect persisted beyond 1 year, suggesting that pits may have increased seedling survival in dry conditions. Surprisingly, native species displayed a stronger positive response to pits than exotic species, particularly in a wet year. There was an initial reduction in exotic species, but this was followed by their increase in 1-year-old pits, suggesting that the disturbance created by digging could eventually lead to an increase in weed abundance. Our results demonstrate that while bettong pits provide a germination niche for native forbs, reintroducing digging animals will not necessarily result in the desired restoration outcomes. Ongoing persistence of exotic species is to be expected, and seed addition may be required for species that are seed-limited.

中文翻译：

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重新引入的生态系统工程师为本地植物物种提供了萌发利基

摘要

世界范围内的草原和草林地的面积和状况都在下降，其底层生物多样性发生了巨大变化。在澳大利亚，这种下降与许多挖过的哺乳动物的灭绝相吻合，这些哺乳动物曾经曾经为本地的地层植物创造了再生壁ches。这些挖掘哺乳动物因其对生物扰动和由此产生的土壤功能的影响而被广泛认为是“生态系统工程师”。然而，在目前的改良水平和外来植物的存在下，挖掘在恢复草地多样性方面的好处尚不确定。我们调查了重新引入的东部bettong（Bettongia gaimardi）的挖掘效果）在澳大利亚东南部的温带草木林中发芽。我们在茂密和开阔的草原上标记了新鲜的bettong觅食坑和不受干扰的控制地。我们添加了7种本地Forb物种的种子，并在2年内监测了萌发和建立。我们发现bettong矿坑中的幼苗明显多于对照，尤其是在茂密的草原上。该效果持续超过1年，表明在干燥条件下，小坑可能增加了幼苗的存活。出人意料的是，与外来物种相比，本地物种对坑的阳性反应更强，尤其是在雨季。外来物种最初有所减少，但随后增加了1岁的小坑，这表明挖掘造成的干扰最终可能导致杂草丰度增加。我们的结果表明，虽然bettong坑为本地的福布斯提供了发芽的利基，但重新引入挖掘的动物并不一定会导致所需的恢复结果。预计外来物种将持续存在，并且对于种子有限的物种可能需要添加种子。