A lot of research work now focuses on the resilience of woodlands and forests in the light of climate change, that is their ability to cope with conditions like drier, hotter summers and/or  warmer/wetter winters. It has generally been assumed that trees at the limit of their range in dry regions would be most affected by climate change (with rising temperatures and less water).  However, a major study of some six million tree annual ring samples, (involving 120+ species) coupled with analysis of historical climate data has shown that trees in drier regions show a certain resilience to drought.  Trees seemingly become less sensitive to drought as they approach the edge of their range.  Trees in wetter climates are less resilient when they experience drier conditions or drought.  It seems probable that many species in wetter woodland and forest ecosystems will face significant challenges if the climate does move to a drier and warmer state. Assisted migration may be needed.  One idea is to ‘exploit’ the genetic diversity found at the edge of a species range.  The slow natural migration of trees may not be able to keep pace with the speed of climate change. Full details of this study by the University of California can be found here : Drought sensitivity in mesic forests heightens their vulnerability to climate change The effects of climate change have become very clear in recent times.  This last year witnessed:- Record breaking wild fires in Canada, with the smoke extending across to the East coast of the States. [caption id="attachment_40597" align="aligncenter" width="675"] Canadian forest fire[/caption] Heat waves in parts of America , for example, Phoenix (Arizona) suffers the best part of a month with temperatures of 43oC. Parts of the North Atlantic Ocean saw unprecedented temperatures The global temperature in July was 1.5oC above the pre-industrial average, September saw temperatures 1.8oC above the pre-industrial average. Parts of Chile and Argentina saw a ‘heatwave’ in the middle of their winter. It is clear that ‘unchartered waters’ lie ahead.

We purchased Knox Wood in August 2023, part of Boltonmuir Wood, an old woodland site on fairly boggy ground in East Lothian. Our five acres are split 50% almost pure birch (Silver and Downy) regenerating [about 20 years old] and 50% mature Scots Pine that is well thinned over mixed natural regeneration.  All of the site has previously been used for commercial forestry so there is plenty of natural regeneration from Sitka Spruce, Douglas Fir, Western Hemlock, Silver Fir and Larch. Some oak, rowan, hawthorn and beech regeneration is also present. Roe deer use the site but are not having much impact on the trees, just ticks to be aware of.   Plenty of mosses, ferns and bracken that indicate acidic soil conditions. Our plan is to improve the site for biodiversity and use some birch for green wood working.  So far we have been taking out non-native conifer regen, leaving a few that are suitable for bird nesting and to provide a bit of evergreen shelter. A few Rhododendrons to eliminate as well, easy enough using the lever and mulch technique. We will create some standing deadwood and add to the fairly good level of deadwood from previous birch thinning that is now well rotten.  We will add a few native species, such as Aspen and maybe more Willows for weaving.   Also hoping to grow some edible fungi on site, there are wild mushrooms and I am sure plenty of people already roam around there collecting them.  As Alien Spoons, I teach green wood working so will thin out the birch for spoon carving, shrink pots, bowls and other treen.  Maybe make some besoms and other products with it as well.    [caption id="attachment_41045" align="aligncenter" width="675"] Birch regenerating[/caption]  

The diet of bees has changed over the years.   In the past, bees were able to forage and collect pollen and nectar from a variety of plants.  With the spread of highly mechanised agriculture, increasing urbanisation and road network - now their options are somewhat limited.  Large fields of monocultures, for example, of oil seed rape are now common. Whilst oil seed rape is a good source for foraging bees and bumblebees, they need to collect nectar and pollen from a variety of sources so that they get a range of nutrients, such as the essential amino acids.  Without these particular amino acids, the growth and development of bees is affected, as is their resistance to disease and their ability to raise the brood.  It is important that our pollinators are able to find a range of plants / pollen to provide all their nutrients. Whilst wild flowers [aka weeds], like dandelions, ragworts, and clovers are a lifeline for bees and bumblebees, recent research at the University of East Anglia has shown that woodlands can offer important habitats for bees, isuch as the leaf canopy.  The research team studied 15 woodland sites in agricultural areas across Norfolk (in Spring).  Within the woodlands, they looked at the bee activity in  the understorey  the woodland edge  and at different levels in the tree canopy.   They found that bees were active high up in the sunlit tree canopy, and their activity was particularly high near flowering sycamore trees.  Red tailed bumblebees (Bombus lapidarius) were busier in the canopies than elsewhere.  The understorey and woodland edges were also significant contributors to bee activity.  This study emphasises the importance of woodland habitats for the wild bee community.  

The woodlands blog has previously reported on the damage being wreaked by bark beetles.  These beetles may be small (less than a centimetre in length) but their effects on the western forests of North America has been immense. Some areas have lost 90% of their conifers.   Outbreaks of these beetles have been increasing in size and severity.  Indeed, across Europe, the eurasian bark beetle (Its typographus) has killed millions of conifers. Whilst bark is broadly protective, it can also offer a home to certain insects.  Bark beetles lay their eggs just below the bark so that when the larvae hatch, they can feed on the nutrient-rich living tissue of the cambium and phloem. Consequently, the tree's transport systems begin to fail.  The beetles may also introduce disease-causing fungi and bacteria. Ageing stands of trees coupled with warmer winters, which help the overwintering stage of the insect, have contributed to the spread of bark beetles. .  Conifers, by their nature, are not defenceless.  When a pine tree is cut / wounded, it produces a pale yellow and sticky fluid - RESIN to seal the cut or wound [see above image]. This material helps prevent the entry of pests or pathogens, and can stem water loss. The resin may trap insect invaders as  witnessed by those trapped in time capsules of amber.  Resin is rich in terpenes, these are used in the building of many complex organic molecules and contribute to the make-up of the volatile oils, produced by many plants.  Terpenes are made from units of isoprene, which has the formula C5H8. So the basic formula of a terpene is (C5H8)n, where n is the number of isoprene units that have been joined together.  Terpenes are also readily available in coniferous oils, which contribute to the unique smell of a pine forest or a burning log. [caption id="attachment_40973" align="alignleft" width="300"] Old and dying tree[/caption] These ‘chemical defences’ should trap, poison or deter an insect invader, such as the bark beetle.  But it would seem that bark beetles ‘don’t mind’ these defences. Research suggests that the eurasian bark beetle might have an ally.  Certain fungi (from the genus - Grosmannia) are found in association with these beetles. When the  Grosmannia fungi infect spruce trees they alter the chemical profile the trees, so that infected trees produce different volatile chemicals - ie they smell different.  The bark beetles are able to detect these differences and exploit this ‘breach’ of the trees natural defences.  The unique chemical profile of infected trees and the pheromones produced by the beetles probably help explain the swarming behaviour of the bark beetles.  A heavy beetle infestation results in the death of a tree. However, there is a possible positive in this rather sad tale.  At present, traps for bark beetles rely solely on using pheromones but if the pheromones can be combined with the chemicals produced by the fungi then it opens the door to more effective beetle traps.  

A recent article in the New Scientist suggests that staking newly planted trees may be pointless for trees that are planted in gardens and parks.  James Wong argues that stakes are often not needed because trees have a natural tendency to grow straight and vertical. Indeed, staking may cause damage because the tie that connects the post and the tree can cut into the tree.  Also the tie-up to the stake creates a weak point where a sapling can snap in high winds. Even if it doesn’t snap, it develops an unnaturally thick trunk at that point to stop it from breaking. Despite this, you might still want to use a stake in a garden or park for reasons unrelated to the growth of the tree - to avoid it being run over by a lawn mower or accidentally walked into. For forestry planting, using stakes is a very different matter. Stakes are easy to spot and help forestry contractors to find their new trees for weeding and for “beating up” - the odd phrase used by foresters to refer to replanting where trees have died. Using stakes can also help make the trees grow straight which is important for producing top-quality timber. However, the most important function of tree stakes in most new woodland planting is to keep tree guards vertical and securely in position. Most stakes for tree planting use treated softwood and are sawn, but there is a case for using longer-lasting sweet chestnut pales made by splitting. Such stakes are readily and cheaply available from suppliers in East Sussex and Kent. These stakes are strong and easier to bang into hard, stony ground. As well as being long-lasting, sweet chestnut does not need treating so for those using biodegradable tree guards and wanting to “leave no trace”, these may be the best stakes for new planting. Using untreated stakes like this avoids putting extra chemicals into the environment. Another option, often used for new planting of hedgerow trees, is using bamboo canes to hold the saplings and their guards, usually very light spiral guards. Canes as stakes have the added advantage that they are light and easy to transport: when you are planting any new trees there is lots of material to move around the site - guards, young trees, stakes and spades. getting ready for some serious planting