sycamore stands, though the trees do provide abundant aphids and consequently are attractive to canopy feeding insectivorous birds. There would presumably be large changes in the characteristics of the leaf litter (both in chemistry and physical properties) within many woods that could conceivably affect invertebrate availability for ground feeding birds. • Ash trees themselves probably provide
rather few specific resources for birds. The biomass of insects provided by ash are not as high as oak for instance. Old ash trees, especially pollards, may contain large cavities, used for example by Stock Doves and owls. The seeds of ash are a major food of Bullfinches. The main effects of loss of ash, however, are likely to be through accumulation of dead wood and the structural changes that occur in woodland vegetation.
Phil Brown
Suffolk’s trees – going, going . . . ?
T
he Forestry Commission’s ‘Plant Health Conference’ at Ickworth on Monday 10 December was something of an eye-opener. Not due to its initial concentration on Chalara fraxinea (Ash dieback), but because of the range of pests and diseases reportedly battering Britain’s trees today. An accelerating problem Over the course of the twentieth century Britain’s trees only succumbed to five major pathogen outbreaks – with Dutch Elm featuring twice. Yet in the first decade of the new century this figure has already doubled. This frightening acceleration is attributed to a combination of lax biosecurity measures applied to the global plant trade (Britain apparently imports 70% of all of its plants) and climate change (most notably warmer winters). The list of threats is now a long one (see table):
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Tree species Ash Beech Conifers
Cypresses Elm Horse Chestnut Larch Oak
Plane trees Spruce Sweet Chestnut Willow Yew
THE HARRIER – December 2012
Threat Ash dieback fungus – Fraxinus excelsior Phytophthora kernoviae Dothistroma needle blight Pinewood Nemotode Pitch canker Pine Lappet Moth Asian Longhorn Beetle Phytophthora lateralis Dutch Elm Horse Chestnut Bleeding & Canker Leaf Miner Moth Phytophthora ramorum – pathogen Acute Oak Decline Oak Processionary Moth (Sudden Oak Death – potential threat) (Wilt disease – threat from US/China) Cerato cystis platoni Great Spruce Bark Beetle Sweet Chestnut Blight Asian Longhorn Beetle Phytophthora lateralis
