Epiphytes and wind in a changing world

附生植物是热带森林的关键元素，热带森林被称为生物多样性的摇篮。附生植物本身高度多样化，为许多依赖生物提供栖息地和食物，并在生态系统的水和养分循环中发挥关键作用。它们在结构上依赖于它们的寄主，生长在陆地植被和大气的交界面，与大气紧密耦合，因此更容易受到任何气候制度变化的影响。因此，令人惊讶的是，人们对风如何影响附生植物知之甚少。拟议中的项目将生物多样性研究与物理学联系起来，旨在了解风对附生植物对其宿主的重要依附的影响。这一点变得更加重要，因为它们的自然栖息地热带森林因土地利用变化而变得支离破碎，使它们进一步暴露，从而加剧了气候变化的负面影响，例如强风暴事件的加剧。在这个项目中，我想确定附生植物-宿主系统中的瓶颈，即风是否能够将附生植物从它们的基质中移除，或者基质是否首先失效。为此，我设计了四个子项目（SP）来研究系统的不同方面。在飓风带的几个国家进行的一项描述性研究（SP4）将确定风暴后有基质和没有基质的附生植物从其宿主中移出的百分比。虽然在文献中有关于附生植物被吹走的轶事陈述，但没有定量研究确定实际的瓶颈。这部分将与当地同事合作完成。尽管附生植物附着在底物上很重要，但人们对它们维持这种附着的能力一无所知。子项目1和子项目2是与奥尔登堡大学物理研究所的风能研究人员合作设计的。通过在风洞中进行的一系列实验，测量风应力作用在附生植物上的力（SP1）和使附生植物与底物分离所需的力（SP2）。如果风不能将附生植物从其基质上剥离，那么整个系统的破坏将严重威胁附生植物群落的生存。sp1和sp2的试验将辅以附生根（SP3）的力学特性研究。为此，将测量它们的固有拉伸和附着强度，并量化根毛对基体的渗透深度。最后，将通过实验研究模拟恒定风压下附生植物根系生长是否表现出表型可塑性。这些子项目结合起来将确定附生植物-寄主系统的瓶颈，并评估土地利用和气候变化对热带植物多样性的一个关键因素的影响。

Epiphytes are a key element of tropical forests that are known as a cradle of biodiversity. Highly diverse themselves, epiphytes provide habitat and food for many dependent organisms and play a key role in the water and nutrient cycling of the ecosystem. Structurally depend on their host and growing at the interface between terrestrial vegetation and the atmosphere, they are tightly coupled to the atmosphere and hence much more affected to changes in any climate regime. Therefore, it is surprising how little is known about how wind affects epiphytes. The proposed project links biodiversity research with physics aiming to understand the effect of wind on the epiphytes` vital attachment to their host. This becomes even more important as their natural habitat, the tropical forests, are fragmented by land-use change, exposing them further, which potentiates the negative effects of climate change, e.g. intensification of strong storm events. With this project I want to identify the bottleneck in the epiphyte-host system, i.e. if wind is able to dislodge epiphytes from their substrate or if the substrate fails first. To do so I designed four subprojects (SP) that study different aspects of the system. A descriptive study (SP4) in several countries in the hurricane belt will identify the percentage of epiphytes dislodged from their host with and without the substrate after a storm. Although there are anecdotal statements in the literature that epiphytes were blown off, there is no quantitative study that identifies the actual bottleneck. This part will be done in cooperation with local colleagues. Despite the importance for epiphytes to stay attached to their substrate nothing is known about their ability to maintain this attachment. Subprojects 1 and 2 are designed as a collaboration with the wind researchers from the physics institute of Oldenburg University. With a series of experiments in the wind tunnel the force acting on epiphytes under wind stress will be measured (SP1) and the force necessary to detach epiphytes from their substrate (SP2). If wind is unable to strip epiphytes from their substrate only the destruction of the entire system can threaten epiphyte community survival severely. The experiments of SP 1 and 2 will be complemented by the investigation of the mechanical properties of the epiphyte roots (SP3). To this end, their innate tensile and their attachment strength will be measured and the penetration depth of the root hairs into the substrate quantified. Lastly, it will be experimentally investigated if epiphytes show phenotypic plasticity by enhanced root growth due to a simulated constant wind pressure. In combination the subprojects will identify the bottleneck in the epiphyte-host system and allow an assessment of the consequences of land-use and climate change for a key element of tropical plant diversity.