Flowering, fruiting, new growth and tree falls are among some of the interesting events that can be witnessed throughout the year. Depending on where you are, February in the forest might delight you with some of the following:
The many different epiphytes, mistletoes and vines in New Zealand means that there is always something interesting to find on tree trunks or in the canopy of our forests. Flowering, fruiting, new growth and tree falls are among some of the interesting events that can be witnessed throughout the year. Depending on where you are, February in the forest might delight you with some of the following: So make sure you get into your patch of forest in February to enjoy your local natural events!
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Two of the five Muehlenbeckia species in New Zealand are woody vines: pōhuehue (M. australis) and smalled-leaved pōhuehue (M. complexa). The other species predominantly creep along the ground, not reaching significant heights. These two vine species play an important role as "nature's band-aid*". Like many vines, they grow in open and disturbed places such as forest edges, young scrubland, landslide scars and cliff tops. Pōhuehue in particular can grow very densely in these high-light environments and effectively stabilise soil, buffer temperature and humidity, and capture energy in the area. These characteristics act like a "band-aid" by preventing further disturbance (e.g. further soil loss after a landslide) and creating conditions in which other species can establish. *Quote from ecologist Catherine Beard Muehlenbeckia species are often the only native species remaining in highly-modified landscapes and provide important habitat for diverse insect populations (QEII National Trust). They produce shiny black seeds within sweet white flesh that is thought to be a food source for insects and lizards. An interesting situation arises when pōhuehue establishes on the edges of restoration plantings or valuable crops and the ecological values of these species have to be weighed against the competitive nature of their dense growth form. The result is that these species are often treated as weeds and removed.
Welcome to the last epiphyte blog post for 2013. It has been a great year and we're going to finish it off with a photo post from the epiphyte treasure-trove that is the Pirongia Forest Park in western Waikato. Pirongia te Aroaro o Kahu Restoration Society care for this special maunga and you can read more about it on their website. This is the last post for the year - look out for more in January 2014 along with a revamped website. Happy holidays!
This was something I had never considered until reading this article by Koptur and colleagues. These researchers studied the epiphytic fern Pleopeltis crassinervata in cloud forest of Veracruz, Mexico. This species is related to our ngārara wehi (Pyrrosia eleagnifoia) and was found to employ bodyguards to keep nasty herbivores away! Pleopeltis crassinervata is one of many plants that produces nectar in glands outside of flowers (click here for more info). Nectaries on the leaves of this fern produce nectar that attracts ants. The ants then repay their host for this tasty meal with defence services against hungry caterpillars. Koptur et al. (2013) found that plants with healthy, functioning nectaries had fewer caterpillars browsing on their leaves and that the bodyguard ants were often responsible for attacking, removing or killing them. So that is how it is done in Mexico, now I wonder if any of New Zealand's epiphytes have similarly clever tactics?
This week I've been lucky enough to help with some PhD field work in Taranaki. It had nothing to do with epiphytes but I still took the opportunity to go a-hunting! Here are some of my favourite shots: A new article about facilitation cascades has been published by Christine Angelini and Brian Silliman from the University of Florida. It is such an interesting contribution to our understanding of epiphyte ecology that I'm going to dedicate four blogs to it. This week: application in New Zealand. The application of this model to the Tillandsia of Georgia worked really well, now I want to see if it will work for temperate New Zealand forests. The primary foundation species is the host tree because epiphyte species mostly rely on host trees for access to light. Let's say we have a tawa (Beilschmiedia tawa) host tree. The bare branches will support minimal flora and fauna communities but as it grows away from the shady forest floor it will become the first step in a facilitation cascade. Our secondary foundation species is often moss. Moss provides substrate and moisture that facilitates the arrival of invertebrates and other epiphytes such as orchids and ferns. It therefore increases both the diversity and abundance of plants and animals that can establish (type C cascade). But that isn't the end of the story! If a nest epiphyte species such as kahakaha (Collospermum hastatum) arrives on the moss, it will again significantly increase the diversity and abundance of flora and fauna communities (still type C). These large plants can host many plants and invertebrates as well as the occasional bird and reptile. If nest epiphytes do not establish the community will generally be smaller and less diverse. There are even species that depend on nest epiphytes, for example: tawhiri karo (Pittosporum cornifolium). Therefore we might consider nest epiphytes to be tertiary foundation species, adding another step to Angelini and Silliman's process: I suppose it all depends on your interpretation! If you consider the moss to be the foundation species it works more like the Georgia example but then the moss requires the host tree... what are your thoughts?
To finish, here is a photo illustrating the significant habitat that nest epiphytes can create for many other species. A new article about facilitation cascades has been published by Christine Angelini and Brian Silliman from the University of Florida. It is such an interesting contribution to our understanding of epiphyte ecology that I'm going to dedicate four blogs to it. This week: a model to explain the application. To understand and predict species assemblages and interactions in different facilitation cascades we can use the Foundation Species-Biodiversity model: According to this model, facilitation cascades can be described using three categories based on the difference that secondary foundation species make to the community: Type A: Secondary foundation species support more individuals of species that are already in the community (increased abundance) by providing functional traits that are similar to those of the foundation species. Type B: Secondary foundation species provide habitat for different individuals (increased diversity) by providing different functional traits than the foundation species. Type C: Secondary foundation species support more individuals of the existing species AND individuals of new species (increased abundance AND diversity) through the provision of a range of traits. Notes: some secondary species may not significantly increase either abundance or diversity, and facilitation cascades can switch if environmental conditions change. Examples of each facilitation cascade. Simplified from Angelini & Silliman: Type A: Foundation species: shoal grass Secondary foundation species: manatee grass Manatee grass facilitates an increase in the abundance of resident invertebrates and fish by providing more habitat of a similar nature. In other words, more of the same services. Type B: Foundation species: turtle grass Secondary foundation species: pen shells Pen shells facilitate increased diversity by providing places for fish to lay eggs. In other words, new and different services. Type C: Foundation species: mangroves Secondary foundation species: oysters Oysters facilitate both an increase in diversity and abundance. They provide more habitat for species that already inhabit mangrove roots but also provide habitat for species that are oyster-dependant. Next week: application of all of this theory to New Zealand epiphytes!
An exciting new article about facilitation cascades has been published by Christine Angelini and Brian Silliman from the University of Florida. It is such an interesting contribution to our understanding of epiphyte ecology that I'm going to dedicate four blogs to it. This week: an epiphyte study. Angelini & Silliman (In Press) conducted a range of experiments in Southern USA to investigate the relationships between Southern live oak trees (Quercus virginiana) and Spanish moss (Tillandsia usneiodes) a common epiphyte that is infact in the bromeliad, not moss, family. I'll briefly run through some of the interesting things that they discovered. Oak-Tillandisa-insect facilitation cascade:
Key evidence: Tillandsia relies on oak trees to provide conditions that it can establish and survive in. In this part of the world the conditions on the ground are hot and dry and very unfavourable for Tillandsia. Within an oak tree, clumps of Tillandsia (called festoons) increase the structure, or physical space, available for insect habitat as well as stabilising temperature and humidity. This increases not only the abundance of invertebrates already present in the tree, but also in the number of species, the different types of feeding guilds (e.g. decomposers, herbivores), and the life stages (e.g. juveniles, adults). These invertebrates cannot survive on the tree without the epiphytic Tillandsia. One example of the Tillandsia providing for invertebrates also happens to be my favourite part of this study: The researchers found that Tillandsia acts as a nursery by protecting juvenile crickets from spider predation. This experiment involved releasing baby crickets onto A) a branch with no epiphytes and B) a branch with Tillandsia, then letting the spiders loose! After 12 hours they counted live crickets and inspected dead crickets to find that the branch with Tillandsia had a 95 % cricket survival rate while the bare branch had only 60 % and all dead crickets had spider wounds... can't argue with that! To sum up this epiphyte example of facilitation cascades: "secondary foundation species can complement and magnify the facilitative effects of primary foundation species. In attracting novel species, life stages, and feeding guilds, secondary foundation species can increase the number and complexity of species interactions that occur and likely increase the diversity of ecosystem services that the associated community can provide (e.g. pollination, nutrient cycling, pest control) to affect overall ecosystem functioning." Angelini & Silliman (In Press). Next week: a model to understand the roles that different species play in facilitation cascades.
A great new article about facilitation cascades has been published by Christine Angelini and Brian Silliman from the University of Florida. It is such an interesting contribution to our understanding of epiphyte ecology that I'm going to dedicate a few blogs to it. This week: the theory. A facilitation cascade describes the order of species arrival in a given environment AND the interactions between these species. The example I’ll use does not involve epiphytes but is adapted from one of the original articles on this idea by Andrew Altieri, Brian Silliman, and Mark Bertness (2007). Facilitation cascade theory applies when harsh environmental conditions are improved by the arrival of a foundation species. An example is the establishment of seagrass on rocky coastlines which stabilises rocks, softens the impact of breaking waves, and provides shade. The foundation species provides habitat for a secondary foundation species. Seagrass provides stable substrate for the establishment of mussels that cannot successfully establish on bare rocks. The combination of foundation and secondary foundation species provides the necessary conditions for many other species to establish and interact. In a coastal system the seagrass and mussels provide substrate and refuge for a diverse and abundant community that includes barnacles, snails and amphipods. The key concepts here are that the seagrass does not require the presence of other species to establish but the mussels need the seagrass, and the other species need BOTH the mussels and seagrass. The positive interactions between these species occur in a hierarchical order and, unlike successional theory, the foundation species is not replaced by subsequent species. Next week: an example of a facilitation cascade in the canopy!
Nalini Nadkarni couldn’t have said it better, but how do we communicate what we know as scientists to the rest of the general community? Nalini has come up with a many different angles to present the ideas of canopy ecology, biodiversity and conservation. She developed the tree top Barbie as a pop icon ambassador to promote women in science, and to appeal to budding young canopy scientists. She has introduced science into prisons, and encouraged artists and musicians to portray the forest canopy in their work. She even managed to get a rap artist to write a song about preserving the tree canopy!
As scientists, we talk to each other, but we all already agree that biodiversity and conservation is crucial to the continued functioning of forest ecosystems. We need to talk to the wider community, and tell them why we should all save the forests we love. Take 18 minutes out of your Friday to watch the video below, and let your mind wander about all the possibilities! http://www.youtube.com/watch?v=rN7VcY1f-1Q |
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Catherine KirbyI work with NZ's native vascular epiphytes at the University of Waikato. I completed an MSc on epiphyte ecology and the shrub epiphyte Griselinia lucida and have recently published the Field Guide to NZ's Epiphytes, Vines & Mistletoes. Categories
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