Alice Springs Herbarium, Department of Land and Resource Management, Northern Territory Government, Alice Springs, NT, Australia.
School of Agriculture and Food Science, University of Queensland, Brisbane, QLD, Australia.
Ann Bot. 2018 Jan 25;121(1):119-128. doi: 10.1093/aob/mcx136.
Plant species with fire-triggered germination are common in many fire-prone ecosystems. For such plants, fire timing in relation to the timing of reproduction may strongly influence post-fire population regeneration if: (a) flowering occurs infrequently (e.g. plants are mast seeders); and (b) seed survival rates are low and input from the current year's flowering therefore contributes a large proportion of the viable dormant seedbank. The role of fire timing in relation to masting as a driver of post-fire recruitment has rarely been examined directly, so this study tested the hypothesis that fires shortly after masting trigger increased recruitment of the obligate-seeding arid zone spinifex, Triodia pungens R. Br., an iteroparous masting grass with smoke-cued germination.
Phenological monitoring of T. pungens was conducted over 5 years, while a longitudinal seedbank study assessed the influence of seeding events on soil-stored seedbank dynamics. Concurrently, a fire experiment with randomized blocking was undertaken to test whether T. pungens hummocks burnt shortly after masting have greater post-fire recruitment than hummocks burnt when there has not been recent input of seeds.
Triodia pungens flowered in all years, though most flowerings were characterized by high rates of flower abortion. A mast flowering with high seed set in 2012 triggered approx. 200-fold increases in seedbank densities, and seedbank densities remained elevated for 24 months after this event. The fire experiment showed significantly higher recruitment around hummocks burnt 6 months after the 2012 mast event than around hummocks that were burnt but prevented from masting by having inflorescences clipped.
Fires shortly after masting trigger mass recruitment in T. pungens because such fires synchronize an appropriate germination cue (smoke) with periods when seedbank densities are elevated. Interactions between natural fire regimes, seedbank dynamics and fire management prescriptions must be considered carefully when managing fire-sensitive masting plants such as T. pungens.
在许多易发生火灾的生态系统中，具有火触发萌发特性的植物物种很常见。对于此类植物，如果：(a) 开花频率较低（例如，植物为结实大年）；并且(b) 种子存活率低，并且当年开花的种子输入对有活力的休眠种子库贡献很大。火发生时间与结实大年作为火灾后繁殖驱动力的关系很少被直接研究，因此本研究检验了以下假设：在结实大年之后发生的火灾会触发强制性结实的干旱区针茅草 Triodia pungens R. Br. 的繁殖增加，这是一种具有烟雾触发萌发特性的多次结实的禾本科植物。
对 T. pungens 进行了 5 年的物候监测，同时进行了纵向种子库研究，以评估结实事件对土壤中储存的种子库动态的影响。同时，进行了具有随机分组的火灾实验，以检验在最近没有种子输入的情况下燃烧与在结实大年之后燃烧相比，T. pungens 丘是否具有更高的火灾后繁殖能力。
T. pungens 每年都开花，尽管大多数开花都伴随着高比例的花败育。2012 年，一次结实大年伴随着高种子结实率，引发了种子库密度约 200 倍的增加，并且在该事件发生后 24 个月，种子库密度仍然保持在较高水平。火灾实验表明，在 2012 年结实大年之后 6 个月燃烧的丘周围，繁殖能力明显高于被修剪了花序而阻止结实的丘周围。
在结实大年之后发生的火灾会触发 T. pungens 的大量繁殖，因为这种火灾将适当的萌发信号（烟雾）与种子库密度较高的时期同步。在管理 T. pungens 等对火灾敏感的结实大年植物时，必须仔细考虑自然火灾发生模式、种子库动态和火灾管理方案之间的相互作用。
