There are multiple pathogens around the world that are threatening particular tree species. In New Zealand we have thankfully come through a period of sudden decline in cabbage trees (ti kouka) but are currently very concerned about kauri dieback disease. In the Northern Hemisphere, European Ash trees are being lost as an invasive fungal pathogen effectively kills off large areas of forest. 

A recent study by Asko Lõhmus and Kadri Runnel from the University of Tartu in Estonia looks at the effect of European Ash dieback on the specialised and iconic lichen Lobaria pulmonaria.

Lobaria pulmonaria has many common names including tree lungwort, lung lichen, lung moss, lungwort lichen, oak lungs or oak lungwort. The use of "lung" reflects the fact that it looks somewhat like human lung tissue but also connects to the sensitivity of this species to air pollution. Lobaria pulmonaria populations around the world have been declining as a result of human activities and in Estonia the population is estimated to have been reduced by around 90% since the late 19th century. This species now faces the threat of host tree loss through Ash dieback.

Lõhmus and Runnel (2014) monitored lichens in a forest remnant affected by Ash dieback from 2009 to 2013. During this time the mortality of Ash trees reached almost 60%. They found that only 6% of trees that hosted reproductive lichen populations remained healthy and thus, the survival of Lobaria pulmoaria was concluded to be at risk. 

In forests with only one dominant host tree, epiphyte species will face local extinction if a species-specific pathogen affects those hosts. The authors therefore suggest that a crucial backup for epiphyte populations is the presence of different host tree species in the forest. In their study they found that large Populus and Ulmus trees, which are not affected by Ash dieback, were important refuges for epiphytic lichens. 

However, the problem in many of these European forests is that a mono-culture approach is practised by silviculture managers. The authors recommend a change in forestry management that preserves natural tree diversity in hopes of minimising biodiversity loss from dieback fungi and disease.

In New Zealand our native forests are no longer harvested (with the exception of some new, unfortunate allowances) so the natural tree diversity is in better shape. This means that we will have more host tree back ups in forests that are affected by species dieback. However, the variable characteristics of New Zealand tree species means that epiphytes with affinities for say, the bumpy bark of rewarewa, may be threatened if their 'favourite' host trees are lost. 

This issue highlights the complexity of ecosystems and their many related processes. It sure gives us plenty of reason to get out there and explore these natural environments; we need to understand what we have (through observation and scientific studies) so that we can notice change and minimise biodiversity loss.

Normally when searching for epiphyte news I do a google scholar search for papers published in 2013 or 2014. This time I entered 1940 and came up with this interesting piece from 1942 by George Simpson and John Scott Thomas. Amongst notes on a range of species are the following accounts of Metrosideros diffusa (white climbing rata) and Metrosideros robusta (northern rata). 

Metrosideros diffusa
The juvenile, whether terrestrial or climbing, pushes out wiry roots from closely-place nodes; adult flowering branches are shrubby divaricating laterals from the ascending stems. 

This is a very succinct description of the difference between the climbing, host-hugging juvenile and the cloud-shaped, highly-branched adult stems that form when they reach the sun.

Metrosideros robusta
Zotov (1939, p.275) disputes the theory of Kirk (1889, p.263) that the coalescence of the decending stems and lateral binders of this epiphyte imprisons and destroys forest trees. 

He states that he has not found evidence of strangulation, and he maintains that the "light demanding" host is destroyed by the intensity of shade thrown by the faster-growing epiphyte.

Other observers have suggested to us that root competition may be the destructive agent or a soil reaction set up by the closely matted fibrous roots. 

Kirk (loc. cit.) states that puriri (Vitex lucens), to increase its girth, bursts apart the stems of the epiphyte and, if this be accepted, shade can have but little effect on that species. 

A shade maximum is reached when the epiphyte slightly overreaches the crown of its host, yet the host lives through this crucial period and survives while the epiphyte develops large spreading branches with a high open crown affording a sufficiency of light, more than most trees offer to much of their foliage. 

Its fascinating that our understanding of the effect that Northern rata has on its hosts has not advanced a whole lot since 1942. It is still considered that this hemiepiphyte does not strangle its host but either out-lives or maybe shades it out. Interesting that Kirk talked about puriri bursting these Northern rata stems apart - what a sight that would be!

In pre-European times Māori in New Zealand depended on the land for food, medicine and materials. They were wonderfully clever and the New Zealand Landcare Research Māori Plant Use database tells us that some epiphyte, mistletoe and vine species were important resources:

Astelia solandri was used for fibre in weaving to give different colours. The fruits were eaten and the 'down' from the base of the leaves was suggested by one author to be good for pillows!

Ripogonum scandens had many uses: a treatment for rheumatism and skin diseases; a food source in the berries and young shoots; a coarse weaving material; a building material and in fishing.

The sweet chewy berries of Peraxilla tetrapetala were chewed like gum, the flavour was described as "pleasant enough while it lasted"

The strong smell of Microsorum scandens was used as a perfume and in scented oils.

Leaves of Rubus species have been used to relieve coughs, congestions and also as a laxative. The fruit were eaten and the vines were used for catch fish.

There are likely to be many other uses for many other species that aren't recorded in books or databases. I have heard a story of the water from the base of nest epiphytes being used as an anaesthetic for face tattooing. These traditional uses can help us understand this interesting guild and appreciate them for more than just their beauty.

Studying the flora and fauna of a forest canopy is exciting, adventurous and often ground-breaking work. But it can also be back-breaking and technically challenging to access and spend time in the heights of the forest canopy. The beginnings of forest canopy access were both humble and bizarre. There are accounts of researchers hiring local people to climb for them, cutting down the study tree, shooting off branches or even training monkeys to collect samples for them! 

Modern researchers/adventurers have many more options and for some it seems that the sky really is the limit with some pretty amazing canopy access methods at their fingertips. Lets have a look at the different approaches people take to exploring the canopy:

If you're lucky you might get involved in a canopy project that has some serious tools/toys. Balloons, inflatable platforms, towers, cranes and walkways are all used in the tropics to get up close and personal with canopy flora and fauna. They allow relatively quick access to the same sites for monitoring, sampling and observations and can be very useful for long-term studies.

The disadvantages of the cranes, walkways and towers are (1) that your sample area is fixed and (2) that the construction of these structures causes damage to the surrounding forest. The main downside of using balloons is the dependence on suitable weather conditions. 

As for the inflatable platform... it is 400 square metres and was put in place by helicopter. Moving past "wow that is awesome!", I think it would share some of the disadvantages of both the balloons (weather dependent for installation) and the large structures (fixed study area). These large-scale methods are also expensive but some operators can offset costs through eco-tourism.

A slightly more humble method of canopy access that is available to many more people is tree climbing. Taking on the appearance of an aborist or rock climber, tree climbing involves donning harness, helmet and various nifty climbing tools to pull (with your arms) or push (with your legs) yourself into the tree tops using a system of ropes. Once in the canopy, various methods can be employed to move around branches and undertake surveys etc. 

The advantage of tree climbing is that it costs a lot less than the above approaches and as long as you can walk to your study tree you can usually climb it with very little impact on the forest. The downside is that it can be time intensive to set up ropes and then climb up, especially if the tree is very tall. It is also hard explore the outer canopy because the branches are too thin.

Every canopy explorer starts in the same, wonderful place: on the ground with a pair of binoculars. This can be an awesome, low cost, low risk, easy way to access the canopy. I have very good memories of lying on the forest floor for long periods of time, gazing up into the forest ceiling through some binocs, wondering about the plants and animals in the sunny tree top ecosystems. So if you're interested in the forest canopy and you haven't done so already, get out there with some binoculars and see what you can discover.

I recently went out to Pukemokemoke Bush Reserve to hunt for Metrosideros albiflora. I didn't find this large-leaved climbing rata but I found quite a few other vine species that belong to the Waikato region. Here are photos of a few of them: