Volcanic fertilisation of tropical forest biomes

热带雨林生物群落是地球上最具多样性和生产力的生态系统之一，但预计也容易受到不断变化的气候和环境条件的影响。由于热带森林生物群落通常栖息在养分非常有限的土壤中，这些脆弱性加剧了。在大多数热带土壤中，磷（P）被认为是关键的限制养分，土壤磷浓度高的时期与森林的发展有关。最近的研究表明，火山活动可能在火山活动期间，在富含磷灰的大片热带森林中发挥作用。然而，这些落灰有一个复杂的时间影响土壤磷浓度和植被响应。这种关系需要进一步调查使用一些生物和地球化学示踪剂。其中最有潜力的是磷酸盐氧同位素，它可以通过古记录来区分土壤磷的来源。本研究项目将利用现代土壤和植物采样，结合Bulusan湖过去1,500年的古环境记录，重点研究东南亚菲律宾的龙脑香林。一系列标准的地球化学技术，包括iTrax微量元素绘图、火山灰鉴定和放射性碳年代学，将与更新颖的磷酸盐氧稳定同位素和古代DNA分析一起应用。这种组合代理方法旨在1.强有力地证明了火山灰沉积事件的时间和强度，2。确定这些事件在改变植物磷的可用性方面所起的作用，以及3.查明对森林植被的影响，包括其组成、结构和大量开花动态。只有彻底了解这些自然循环的磷添加，我们才能开始揭示真正的脆弱性，这些关键的生物群落在激烈的火山活动的地区，并预测他们如何发展和生存在不断变化的气候和人为的压力。

Tropical rainforest biomes are some of the most diverse and productive ecosystems on the planet, but are also projected to be vulnerable to changing climatic and environmental conditions. These susceptibilities are exacerbated as tropical forest biomes often inhabit very nutrient limited soils. In most tropical soils phosphorus (P) is considered the key limiting nutrient and periods of high soil P concentration are linked to enhanced forest development. Recent research has hinted at the role that volcanism may play in fertilizing large areas of tropical forest with P-rich ash during volcanic events. However, these ashfalls have a complex temporal impact on soil P concentration and vegetation response. This relationship needs further investigation using a number of biological and geochemical tracers. One with great potential is phosphate oxygen isotopes, which can distinguish between soil P sources through the palaeorecord.This studentship will focus on the Dipterocarp forest of the Philippines, Southeast Asia, utilising modern soil and plant sampling, coupled with the development of paleoenvironmental records from Bulusan Lake spanning the last 1,500 years. A range of standard geochemical techniques including iTrax trace element mapping, tephra identification and radiocarbon chronology will be applied alongside more novel, phosphate oxygen stable isotopes and ancient DNA analysis. This combined proxy approach aims to 1. robustly characterise the timing and intensity of volcanic ash deposition events, 2. identify the role these events have played in changing availability of P to plants, and 3. identify the resultant impact on forest vegetation, including its composition, structure and mass flowering dynamics. Only by gaining a thorough understanding of these natural cycles of P addition can we begin to reveal the true vulnerability of these critical biomes in areas of intense volcanic activity and predict how they may develop and survive under ever changing climatic and anthropogenic pressures.