Plantations are generally monocultures of economically important tree species, trees that are valued for their timber and rapid growth.  Compared to natural woodland, biodiversity is lower in monocultures. They are less resilient to extreme climatic events, attack by pests and/or disease and offer fewer ecosystems services.  Adding different trees into the mix of species can result in an increase in biomass (timber) production and resilience. Since the 1930’s, a ‘nursing mixture’ of Pines and Sitka Spruce has been used to establish Sitka forest in nutrient-poor soils (without the use of fertilisers or herbicides).  Quite how the pines benefited the growth of the Spruce was not known. One possible ‘mechanism’ is plant soil feedback [PSF], where plants change the nutrient make-up and/or the  bacterial and fungal community of the soil.  These changes then benefit the subsequent growth of seedlings / saplings.  Important in this respect are the fungi that can establish symbiotic / mycorrhizal associations with plant roots.  Ectomycorrhizae (ECM) exist mainly as an external coating on the roots, with some of the hyphae penetrating into the root tissue. Ectomycorrhizae are often associated with woody tree species, particularly conifers. There are a number of parts to a mycorrhizal association with trees: The Hartig net, this is the fungal hyphae that penetrate the roots of the tree, and make contact with the root cells, allowing for the exchange of carbon compounds, mineral nutrients, and water. The Mantle is the sheath of hyphae that covers the tree roots.  It is a more substantive structure than the Hartig net.  The fungal sheath probably offers some protection to the delicate root tips from pathogens and pests.   The Extra-radical hyphae. These grow out from the mantle into the soil. They may spread a significant distance from the actual roots, increasing the surface area for the absorption of water and minerals.  The Fruiting bodies.  These are the reproductive structures of the fungus and are visible above ground. Now some evidence is accumulating about how nursery mixtures / species have their effect.  Last year, researchers at Manchester University looked at the nursing effect of pine and silver birch on Sitka Spruce.   They collected soil from Cannock Chase, where these tree species co-existed.  The soil was sieved and some sand added and then placed in pots. Four groups of pots were created Pots with pine seedlings Pots with Spruce seedlings Pots with silver birch seedlings Pots with all three types of seedlings Pot Treatment Species grown in the conditioned soil Pine conditioned soil  Pine Spruce Birch Spruce conditioned soil  Pine Spruce Birch Birch conditioned soil  Pine  Spruce Birch Pine, Spruce & Birch conditioned soil  Pine Spruce Birch All the pots were placed in a greenhouse and the seedlings allowed to grow on for 34 weeks.  This allowed the growing seedlings to ‘condition’ the soil.  At the end of this time, the seedlings were removed and soil sieved and placed in fresh pots.   The four ‘types’ of ‘conditioned’ soil were then used to grow on newly germinated seeds of the three tree species.   One seedling was grown per pot, and the pots grown on for 24 weeks in the greenhouse again.   At the end of the 24 weeks, the seedlings from each pot were harvested and carefully examined.  For each, many features were recorded Root length Branching intensity Root tissue density Total root length dry weight /mass recorded Ectomycorrhizal colonisation (microscopic analysis) Specific leaf area VIII.Leaf dry matter Photosynthetic rate The soil was also subjected to detailed analysis (e.g : pH, nitrates, microbial enzymes etc). The results showed that  The Spruce seedlings grew best in the soil that had been previously ‘conditioned’ with Pine growing in it. The Spruce fared less well in the previously Spruce ‘conditioned’ soil The increased growth was associated with greater root colonisation by mycorrhizae. Longer term increased growth in the silver birch ‘conditioned’ soil might be associated with increased availability of soil nitrates It would seem that Pines facilitate the growth of the Spruce through the enhanced establishment of symbiotic, mycorrhizal connections.  These connections allow saplings to access vital mineral nutrients such as phosphate.  This study therefore goes some way to explaining the nursing effect of mixed species planting. Full details of this work may be accessed here :  https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.14848

We know that forests are important to all life on the planet.  They have often been referred to as the ‘lungs of the earth’, a reference to the fact that they produce vast quantities of oxygen - which is essential for respiration for so many forms of life.  They also take up carbon dioxide and ‘fix’ it into complex organic molecules - from starches, to cellulose and lignin.  Thus, the carbon is locked away for months, years or even millennia.  The equatorial forests of Brazil and Sumatra are species rich, incredibly diverse, but deforestation and the expansion of agriculture are threats to many biodiverse, forested areas across the world. As so many forests and woodlands have been felled, there is now a movement to plant millions and millions of trees (across the world) in an attempt to mitigate climate change and in the UK to increase our percentage tree cover from a pretty low base.  Sadly, twentieth century forestry in the U.K was largely based on monocultures (for timber production). The trees planted were large stands or plantations of conifers - using Scots Pine, Larch and Spruce. These plantations not only lacked biodiversity, but were / are susceptible to wide scale pest infestation and extreme weather events.   Woodlands and forests that have a diverse range of tree species are not only healthier but show greater growth and carbon fixation. They are more resilient.  The diversity of trees ensures the each species accesses slightly different resources from the environment  - from soil minerals, water and light.  Diversity means that trees of the same species are less likely to be clustered together so pest and pathogen outbreaks are less common or less severe.  One area that has undergone an extensive and diverse planting regime is Norbury Park Estate (near Stafford).  Since 2009, over 100 different tree species have been planted, and the woodlands can now produce 1500 tonnes of new wood each year, and harvest 5000 tonnes of carbon dioxide from the air.  Not only can diverse woodlands / forests fix carbon, supply harvestable timber but they also offer areas for rest and relaxation. Whilst it is not possible to plant an 'instant' forest or woodland, it is possible to plant a range of tree and shrub species that will in time grow and mature to form a diverse and species-rich area.  As Charles Darwin said many years ago “more living beings can be supported on the same area the more they diverge in structure, habits, and constitution” [On the Origin of Species by means of Natural Selection, 1859] Managing woodlands for wildlife - see here.   N.B.  Opens a PDF.    

When you look at a small person (also known as a baby) you know that they will grow bigger in every dimension.  Trees don't grow like that. A tree's branch will stay at the same height however tall the tree grows: by contrast a child's arm rises to a higher level as he or she grows taller. The reason for this is that trees only grow in areas called meristems where they form new cells. Cells are created by cell division (mitosis) within the meristems, and these cells then expand and specialise.  These growth areas are found at the tops of the trees, and the tips of branches; these are "apical meristems".  Growth also happens in the apical meristems at the ends / tips of the tree's roots. Read more...

Tilhill UPM manage many large private forestry estates and produce an excellent annual report on the state of the market both for the land itself and forestry products.  Some time back, I  went to the presentation of Tilhill's 2011 Forest Market Report which was surprisingly upbeat.  The main message was that land values are strongly up, forest product prices are strongly up and volumes of land sold, measured by value, are at historically high levels.  Property values have increased about 15% in the year to the end of September 2011, according to Crispin Golding of Tilhill UPM, mainly because:  there is increased demand for land from investors who are tax-driven or who are looking for safe havens for cash, or both; timber prices have gone up principally because of high oil prices and the devaluation of the pound (making UK timber forestry output more competitive with foreign countries including the Baltic States who are enormous timber exporters). Read more...

On 16th October 1987, the Great Storm took away many mature trees from the landscape of southeast England, a great swathe of destruction was wreaked on our woodland and parkland trees.  Many trees and overlarge coppice still lie where they fell, the coppice more often than not growing up again but from a much larger base.  The mature trees have been gradually rotting. All the resources locked up in the wood being released and taken up by bacteria, fungi, invertebrates and so to higher organisms.  It was a major ecological disturbance,  that in some ways has been of considerable benefit to wildlife. Read more...

About 70% of Britain's commercial tree plantations are Sitka Spruce.  The Forestry Commission have been planting sitka since as far back as the 1930s both because it is able to survive in inhospitable peaty conditions and because sitka grows fast and produces good quality timber.  Botanically called Picea sitchensis, sitka spruce is most easily identified by the "three p's": it has a pointed crown, its leaves (needles) are on pegs and it has pendant cones. Read more...

Are you the owner of an ancient woodland in the High Weald of Sussex and Kent? If so read on... The High Weald AONB (Area of Outstanding Natural Beauty), the Woodland Trust and the Forestry Commission are jointly funding a Plantations on Ancient Woodland Sites (PAWS) Project focusing on returning ancient woodland plantations to native, broadleaved tree cover. The AONB contains some 7% of England’s Read more...