Decline in Sitka Spruce on the South Wales Coalfield Edited by M.P. Coutts Forestry Commission ARCHIVE Technical Paper , FORESTRY COMMISSION TECHNICAL PAPER 9 Decline in Sitka Spruce on the South Wales Coalfield Edited by M.P. Coutts FORESTRY COMMISSION, EDINBURGH © Crown copyright 1995 First published 1995 ISBN 0-85538-332-1 FDC 174.7:181.3:425:453:(429) Acknowledgements The authors of these chapters acknowledge the help of Tony Price and Dave Thomas, who carried out, in all weathers, most of the field work on which the investigations were based. Substantial editorial help from Jenny Claridge is also gratefully acknowledged. KEYWORDS: Aphids, Conifers, Forest decline, Hydrology, Nutrition, Pathogens, Pollution, Water relations Enquiries relating to this publication should be addressed to: The Research Publications Officer The Forestry Commission, Research Division Alice Holt Lodge Wrecclesham, Farnham Surrey GU10 4LH CONTENTS Page Acknowledgements ii Preface iv Sum m ary v List of Contributors vi 1. History and symptoms of decline in Sitka spruce on the South Wales coalfield 1 M.P. Coutts and N.P. Danby 2. Atmospheric pollution in forests of the South Wales coalfield 5 M.P. Coutts, J.A. Winter and T.W. Ashenden 3. Water regimes of three soil types in forests on the South Wales coalfield 11 D.G. Pyatt 4. Stem analysis of healthy and declining Sitka spruce 29 M.P. Coutts and S. Corcoran 5. Correlations between tree growth, leaf chemistry and site factors in an area of declining Sitka spruce 35 M.P. Coutts, N.P. Danby and A. Burnand 6. The role of nutrition in the decline in Sitka spruce 47 J.C. Dutch 7. Afan peat: nitrogen content and nitrogen mineralisation 59 B.L. Williams 8. The relationship between metal content of the soil solution and tree growth at Afan Forest in South Wales 65 R.A. Skeffington and A.M. Graham 9. A tree-ring-based study of Sitka spruce growth in Afan Forest, South Wales: ring-width, wood density and chemical analysis 75 K.R. Briffa, T.M.L. Wigley, T.D. Davies, S.Landsberger, F.H. Schweingruber and S.fohansson 10. The green spruce aphid, spruce root aphids and tree growth in Afan Forest 95 C.Carter 11. Infection of Sitka spruce needles by endophytic fungi 105 M X Smith and N. Magan 12. Assessment of the role of physiological response to sulphur dioxide in Sitka spruce 111 PH. Freer-Smith and M.C. Dobson 13. C onclusions 119 M.P. Coutts Preface Problems concerning the poor growth of conifers in parts of South Wales have been recognised since the 1930s and several attempts have been made to find the underlying causes. Growth problems received more attention when some of the Sitka spruce which had been established on the Pennant Sandstone of the coalfield area between 1955 and 1975, and which had made acceptable growth for a number of years, was found to be in a condition of greatly reduced growth and poor crown health. In many cases the tops of the trees were bent. Conservator Wales asked Research Division to investigate this 'bent top', as the condition was called. Research was started in 1984 with the principal aim of gaining a greater understanding of the problem. It soon became clear that we were presented with a condition akin to certain examples of forest decline in Europe, with trees subject to a variety of stresses. A multidisciplinary approach was therefore needed and workers in a number of institutes were invited to help in a collaborative venture. The chapters in this Technical Paper describe the work carried out between 1984 and 1991. Summary This Technical Paper describes a collaborative effort to explain the reduced growth at time of canopy closure or later of Sitka spruce on parts of the South Wales coalfield. Stem analysis showed that growth had declined steeply over a period of about four years. Decline was associated with thin crowns and with bending of the tops of some of the trees. The climate is characterised by high rainfall and relatively warm winters, and late frosts are common. Atmospheric pollution by sulphur dioxide (S02) and nitrogen dioxide (N 02) was measured and found to be too low to cause direct damage to the trees, but large quantities of sulphur were found in the needles. Poor growth was found on all of the three main soil types (peaty ironpan, peaty gley and deep peat), but growth was generally poorest on the wetter sites. Detailed information on soil hydrology is presented. Mineral nutrition was found to have a bearing on the growth problem. The amount of readily mineralisable nitrogen was low in the peats, and concentrations of nitrogen and potassium in the foliage of the trees were positively correlated with growth. A fertiliser experiment in which NPK was applied to 20-year-old trees improved growth and reduced crown dieback. No clear-cut evidence was found for trace element deficiency or for toxic levels of heavy metals in the soil solution. Direct damage to needles, with subsequent crown dieback, was caused by the green spruce aphid and by two needle fungi, Lophodermium piceae and Rhizosphaera kalkhoffii. As with most instances of forest decline which have been recorded in Europe and elsewhere, several factors and their interactions are involved. However, when nutritional problems have been corrected, the trees are better able to cope with othei adverse conditions; there is scope for improving tree health and growth on the coalfield by the application of fertilisers. List of Contributors T.W. Ashenden Institute of Terrestrial Ecology, Bangor Research Unit, University College of North Wales, Bangor, Givynedd LL57 2 UP, UK K.R. Briffa Climatic Research Unit, University of East Anglia, Norivich NR4 7T], UK A.C. Burnand Forestry Commission Northern Research Station, Roslin, Midlothian EH25 9SY, UK C. Carter Forestry Commission Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey GU10 4LN, UK S. Corcoran Forestry Commission Research Office, Cefn Gethiniog, Talybont-on-Usk, Brecon, Powys LD3 7YN, UK M.P. Coutts Forestry Commission Northern Research Station, Roslin, Midlothian EHz25 9SY, UK N.P. Danby Forestry Commission Research Office, Cefn Gethiniog, Talybont-on-Usk, Brecon, Poivys LD3 7YN, UK T.D. Davies School of Environmental Sciences, University of East Anglia, Norivich NR4 7TJ, UK M.C. Dobson Forestry Commission Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey GU10 4LH, UK J.C. Dutch Forestry Commission Northern Research Station, Roslin, Midlothian EH25 9SY, UK P.H. Freer-Smith Forestry Commission Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey GU10 4LH, UK A.M. Graham National Power and Technology and Environmental Centre, Leatherhead, Surrey KT22 7SE, UK S.Johansson Department of Nuclear Physics, Lund Institute of Technology, Solvegatan 14, S-223 62 Lund, Sweden S. Landsberger Department of Nuclear Engineering, University of Illinois at Urbana- Champaign, Urbana, IL 61801-2984, USA N. Magan Biotechnology Centre, Cranfield Institute of Technology, Cranfield, Bedford MK43 OAL, UK D.G. Pyatt Forestry Commission Northern Research Station, Roslin, Midlothian EH25 9SY, UK F.H. Schweingruber Institute Forest, Snow and Landscape Research, Zurcherstrasse 11, CH- 8903 Birmensdorf Switzerland R.A. Skeffington National Power and Technology and Environmental Centre, Leatherhead, Surrey K22 7SE, UK M.K. Smith Biotechnology Centre, Cranfield Institute of Technology, Cranfield, Bedford MK43 OAL, UK T.M.L. Wigley Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK B.L. Williams Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB9 2QJ, UK J.A. Winter Department of Science, The Polytechnic of Wales, Pontypridd, Mid Glamorgan CF37 1DL, UK Front cover Main picture: Sitka spruce in decline on the South Wales coalfield showing yellowing of foliage and dieback of branches. Inset: twig from a declining tree with unexplained browning of needles. Chapter 1 History and symptoms of decline in Sitka spruce on the South Wales coalfield M.P. Coutts and N.P. Danby History found that the growth of Sitka spruce was correlated with concentrations of phosphorus Poor growth of trees in the coalfield area of and nitrogen in the needles. However, they South Wales has been recognised for many years. concluded that other factors must also be Day and Sanzen-Baker (1938) investigated poor involved in poor growth. Broad and Mayhead growth of established crops on freely drained (1973) made estimates of yield class for Sitka soils on some of the valley slopes. They spruce and other species on freely drained attributed the slow growth of conifers mainly to upland brown earths and intergrade soils in five the poor soils on the Pennant Sandstone. The forest blocks. The yield class of Sitka spruce area was known to be polluted by sulphur ranged from 12 to 17 with the poorest growth in dioxide (SOz) but growth was good on the better the more polluted areas. soils in polluted areas and it was considered that pollution was much less important than soil Mayhead et al. (1974) investigated stands more fertility. Sitka spruce (Picea sitchensis Bong. Carr.) than 20 years old on the better drained soils suffered from defoliation by the green spruce (upland brown earth, intergrade and ironpan) of aphid (Elatobium abietinum Walker), and young the coalfield and found that on some sites Sitka plantations were often damaged by early and spruce achieved only yield class 8-10. They late frosts, although these types of damage are found that owing to establishment problems, common elsewhere in Britain. some areas had been repeatedly beaten up resulting in lower crop ages than would be In 1968 an investigation called the Pennant Project expected from the original planting dates, and was started by the Forestry Commission's this gave a pessimistic assessment of yield class Ecologist, J.M.B.