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Early decay of Phragmites thatch: An outline of the problem
Aquatic Botany, 35 (1989) 129-132 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
129
Short Communication EARLY DECAY OF PHRAGMITES THE PROBLEM
THATCH: AN OUTLINE OF
S.M. HASLAM Botany School, University of Cambridge, Cambridge CB2 3EA (Gt. Britain) (Accepted for publication 2 November 1988) ABSTRACT
Haslam, S.M., 1989. Early decay of Phragmites thatch: an outline of the problem. Aquat. Bot., 35: 129-132. In Britain, Phragmites thatch is expected to last 50-80 years. Reports of breakdown within 410 years became significant by 1970, and caused concern by 1983. The complaints are associated with soft, weak reed. Moisture is said to alter breakdown.
INTRODUCTION Reeds (dead culms of Phragmites australis (Cav.) Trin. ex Steudel) are a traditional roofing material. In Britain, reed and straw (Triticum) thatch do not imply unacceptable poverty, and thatch is frequent in some rural areas. Most British reed comes from East Anglia, mainly from small, isolated marshes. The largest single producer is in Scotland (100 000 bundles year -1, Cator, 1986). Reed is imported from Hungary, France, The Netherlands and elsewhere (the 1985 imports of " B a m b o o Reeds and the like" were 7 602 576 kg, Cator, 1986). Reed thatch increased in the 1960s when the supply of thatching straw decreased, with the introduction of unsuitable short-stemmed wheats. Typically, in the past, reed was used near wetlands and straw in arable areas. Reed thatch should last 50-80 years (with repairs). Wind, temperature changes, light and water all act mainly on the outer layer, the butt (bases) of the culms. Rain remains outside, water movement being between one butt and the next. Moisture should seldom penetrate more than c. 5 cm (Brockett and Wright, 1986). Moisture is considered the primary (external) cause determining the rate of breakdown (P. Brockett, personal communication, 1983). Bosman ( 1985 ) describes the fungal decay of tissue, and the effect of ultra-violet light in degrading already-weakened tissue. Two qualities are needed for thatching reed. Thatchable reed must be easy to handle on the roof, being straight, fairly uniform in size, and of appropriate
0304-3770/89/$03.50
© 1989Elsevier Science Publishers B.V.
130 length (e.g. Haslam, 1972 ). Reed must be durable, and the Rural Development Commission considers strong reed durable. The two qualities vary independently. EARLYBREAKDOWN Reports of breakdown within 4-10 years became significant by 1970 and caused concern by 1983. Few roofs are affected at any one time, but in view of the cost of re-thatching, the problem is serious. Reed die-back has occurred in open waters in the Norfolk Broadland, as elsewhere, during this period. There has, however, been no die-back in the commercial reedbeds, and indeed no apparent decrease in vigour. The English Rural Development Commission links weak reed to early thatch breakdown. Weak reed is also linked to die-back on the continent (e.g. Sukopp and Markstein, 1981 ). THE NATUREOF THE PROBLEM (1) Has the problem always been present, but noted only when housing costs have risen and/or Phragmitesthatch increased? The number of early-decaying thatches has increased in the past two decades. (2) Is the problem caused by mismanagement by householders, or thatchers, or by inadequate conversion of roofs built for straw thatch? Mismanagement is recognizable and separate from the present problem. (3) Have virulent breakdown fungi etc. become more frequent? It seems more likely that reed type determines decay rather than vice versa. (4) Has air pollution damaged thatch in recent years? Air pollution is not the principal cause of early decay, as the affected roofs occur sporadically. One house had two roofs thatched the same year with different materials. Only one showed early decay. (5) In what way is decay influenced by the (micro) climate? Brockett and Wright (1986) state that roofs in the drier east of Britain last longer than those in the west, where they are also often of lower pitch. They find a difficult site (more common in the west) is a small valley surrounded by trees with a pond or stream. Longer, coarser reeds, which dry out more quickly, are recommended under these conditions. In contrast, they note thatch performing well in windy situations, even where water is present and rainfall heavy. Sunny dry roofs become brittle, and this second decay factor if of equal total importance although the relative importance varies depending on local conditions. (6) Is reed weaker because of variation within marshes, or because different marshes are now harvested? Reedbeds have varied in strength, e.g. some beds formerly cut in alternate years are now cut annually, because the dead reed no longer stands into its second year. Various traditionally harvested marshes are not now cut, and some beds were developed in recent decades. Reed strength does not vary consistently.
131 (7) Is softness of reed caused by genotypic or environmental characters? Different clones within an apparently uniform marsh differ in strength, indicating genotypic variation. Variations in strength occur too rapidly to be caused by replacement of clones, indicating environmental variation. Raghi-Atri and B o r n k a m m (1980) and Bornkamm and Raghi-Atri (1986), growing Phragmites in large pots with added nitrogen and phosphorus, found softer reed, and increased shoot nutrients, with these additions. No increased nutrient levels, however, occur in reeds from weaker reedbeds (S.M. Haslam, unpublished data, 1989). Many changes, in weather, reedbed habitat and management, and the use of the surrounding land, have occurred over the years, and the relevant factors have not been identified. (Air pollution can be excluded as the principal cause, because of the local variations in strength. ) (8) Is lowered strength within beds found in selected shoots or in the crop as a whole? Is it permanent? The strongest shoots are normally the first-year culms from the apex of the rhizome. In some beds the proportion of soft short shoots ("waste") has increased, e.g. from c. 5% to c. 30% in six years (D. Frencham, personal communication, 1984). In other beds, almost all shoots are weak. Shorter shoots grow from older rhizomes (Haslam, 1969), but the contrast between these and shoots from young rhizomes varies (Haslam, 1970a,b). Preliminary findings suggest that beds may increase as well as decrease in reed strength. CONCLUSIONS The early decay of Phragmites thatch is a complex problem. Research is in progress on the following points: (1) the characters which can be used to quantify potential durability and give a quality grading scheme; (2) the features of reedbed environment and reed plant which lead to reeds of good and bad durability; (3) defining the thatch environment so that reed of the correct durability is used to give an expected thatch life of more than 50 years. ACKNOWLEDGEMENTS I am most grateful to Mr P. Brockett, Rural Development Commission, for providing so much information. I would also like to thank Mrs H. Gillett and Miss Z. Whishaw sincerely for their help in durability research, the Scarfe, Mitchell and Nathan Trusts and the Broads Authority for partly funding the work, and the Botany School for facilities. J J~
132 REFERENCES Bosman, M.T.M., 1985. Some aspects of decay and weathering on the anatomical structure of the stem of Phragmites communis Trin. ex Steud. A W A Bull., No. 6: 165-170. Bornkamm, R. and Raghi-Atri, F., 1986. ~-ber die Wirkung unterschiedlicher Gaben von Stickstoff und Phosphor auf die Entwicklung von Phragmites australis(Cav.) Trin. ex Steudel. (On the effects of different nitrogen and phosphorus concentrations on the development of Phragmites australis (Cav.) Trin. ex Steudel.) Arch. Hydrobiol., 105: 423-441. Brockett, P. and Wright, A., 1986. The care and repair of thatched roofs. Society for the Protection of Ancient Buildings and Council of Small Industries in Rural Areas. Technical Pamphlet, No. 10, 12 pp. Cator, C.F., 1986. Draft report on the future of the reed and sedge growing industries. Unpublished report, British Reed Growers Association, 10 pp. Haslam, S.M., 1969. Stem types of Phragmites communis Trin. Ann. Bot., 33: 127-131. Haslam, S.M., 1970a. Variation of population type in Phragmites communis Trin. Ann. Bot., 34: 147-158. Haslam, S.M., 1970b. The development of the annual population in Phragmites communis Trin. Ann. Bot., 34" 571-591. Haslam, S.M., 1972. The Reed. Norfolk Reed Growers Association, 73 pp. Raghi-Atri, F. and Bornkamm, R., 1980. lJ-bet Halmfestigkeit von Schilf (Phragmites australis (Cav.) Trin. ex Steudel) bei unterschiedlicher Niihrstoffversorgung. (On the stiffness of stems of the reed plant (Phragmites australis (Cav.) Trin. ex Steudel) at different levels of nutrients added.) Arch. Hydrobiol., 90: 90-105. Sukopp, H. and Markstein, B., 1981. Veranderung von RShrichtstanden und Pflanzen als Indikatoren von Gewassernutzungen dargestellt am Beispiel der Havel in Berlin. Limnologica, 13: 459-471.
129
Short Communication EARLY DECAY OF PHRAGMITES THE PROBLEM
THATCH: AN OUTLINE OF
S.M. HASLAM Botany School, University of Cambridge, Cambridge CB2 3EA (Gt. Britain) (Accepted for publication 2 November 1988) ABSTRACT
Haslam, S.M., 1989. Early decay of Phragmites thatch: an outline of the problem. Aquat. Bot., 35: 129-132. In Britain, Phragmites thatch is expected to last 50-80 years. Reports of breakdown within 410 years became significant by 1970, and caused concern by 1983. The complaints are associated with soft, weak reed. Moisture is said to alter breakdown.
INTRODUCTION Reeds (dead culms of Phragmites australis (Cav.) Trin. ex Steudel) are a traditional roofing material. In Britain, reed and straw (Triticum) thatch do not imply unacceptable poverty, and thatch is frequent in some rural areas. Most British reed comes from East Anglia, mainly from small, isolated marshes. The largest single producer is in Scotland (100 000 bundles year -1, Cator, 1986). Reed is imported from Hungary, France, The Netherlands and elsewhere (the 1985 imports of " B a m b o o Reeds and the like" were 7 602 576 kg, Cator, 1986). Reed thatch increased in the 1960s when the supply of thatching straw decreased, with the introduction of unsuitable short-stemmed wheats. Typically, in the past, reed was used near wetlands and straw in arable areas. Reed thatch should last 50-80 years (with repairs). Wind, temperature changes, light and water all act mainly on the outer layer, the butt (bases) of the culms. Rain remains outside, water movement being between one butt and the next. Moisture should seldom penetrate more than c. 5 cm (Brockett and Wright, 1986). Moisture is considered the primary (external) cause determining the rate of breakdown (P. Brockett, personal communication, 1983). Bosman ( 1985 ) describes the fungal decay of tissue, and the effect of ultra-violet light in degrading already-weakened tissue. Two qualities are needed for thatching reed. Thatchable reed must be easy to handle on the roof, being straight, fairly uniform in size, and of appropriate
0304-3770/89/$03.50
© 1989Elsevier Science Publishers B.V.
130 length (e.g. Haslam, 1972 ). Reed must be durable, and the Rural Development Commission considers strong reed durable. The two qualities vary independently. EARLYBREAKDOWN Reports of breakdown within 4-10 years became significant by 1970 and caused concern by 1983. Few roofs are affected at any one time, but in view of the cost of re-thatching, the problem is serious. Reed die-back has occurred in open waters in the Norfolk Broadland, as elsewhere, during this period. There has, however, been no die-back in the commercial reedbeds, and indeed no apparent decrease in vigour. The English Rural Development Commission links weak reed to early thatch breakdown. Weak reed is also linked to die-back on the continent (e.g. Sukopp and Markstein, 1981 ). THE NATUREOF THE PROBLEM (1) Has the problem always been present, but noted only when housing costs have risen and/or Phragmitesthatch increased? The number of early-decaying thatches has increased in the past two decades. (2) Is the problem caused by mismanagement by householders, or thatchers, or by inadequate conversion of roofs built for straw thatch? Mismanagement is recognizable and separate from the present problem. (3) Have virulent breakdown fungi etc. become more frequent? It seems more likely that reed type determines decay rather than vice versa. (4) Has air pollution damaged thatch in recent years? Air pollution is not the principal cause of early decay, as the affected roofs occur sporadically. One house had two roofs thatched the same year with different materials. Only one showed early decay. (5) In what way is decay influenced by the (micro) climate? Brockett and Wright (1986) state that roofs in the drier east of Britain last longer than those in the west, where they are also often of lower pitch. They find a difficult site (more common in the west) is a small valley surrounded by trees with a pond or stream. Longer, coarser reeds, which dry out more quickly, are recommended under these conditions. In contrast, they note thatch performing well in windy situations, even where water is present and rainfall heavy. Sunny dry roofs become brittle, and this second decay factor if of equal total importance although the relative importance varies depending on local conditions. (6) Is reed weaker because of variation within marshes, or because different marshes are now harvested? Reedbeds have varied in strength, e.g. some beds formerly cut in alternate years are now cut annually, because the dead reed no longer stands into its second year. Various traditionally harvested marshes are not now cut, and some beds were developed in recent decades. Reed strength does not vary consistently.
131 (7) Is softness of reed caused by genotypic or environmental characters? Different clones within an apparently uniform marsh differ in strength, indicating genotypic variation. Variations in strength occur too rapidly to be caused by replacement of clones, indicating environmental variation. Raghi-Atri and B o r n k a m m (1980) and Bornkamm and Raghi-Atri (1986), growing Phragmites in large pots with added nitrogen and phosphorus, found softer reed, and increased shoot nutrients, with these additions. No increased nutrient levels, however, occur in reeds from weaker reedbeds (S.M. Haslam, unpublished data, 1989). Many changes, in weather, reedbed habitat and management, and the use of the surrounding land, have occurred over the years, and the relevant factors have not been identified. (Air pollution can be excluded as the principal cause, because of the local variations in strength. ) (8) Is lowered strength within beds found in selected shoots or in the crop as a whole? Is it permanent? The strongest shoots are normally the first-year culms from the apex of the rhizome. In some beds the proportion of soft short shoots ("waste") has increased, e.g. from c. 5% to c. 30% in six years (D. Frencham, personal communication, 1984). In other beds, almost all shoots are weak. Shorter shoots grow from older rhizomes (Haslam, 1969), but the contrast between these and shoots from young rhizomes varies (Haslam, 1970a,b). Preliminary findings suggest that beds may increase as well as decrease in reed strength. CONCLUSIONS The early decay of Phragmites thatch is a complex problem. Research is in progress on the following points: (1) the characters which can be used to quantify potential durability and give a quality grading scheme; (2) the features of reedbed environment and reed plant which lead to reeds of good and bad durability; (3) defining the thatch environment so that reed of the correct durability is used to give an expected thatch life of more than 50 years. ACKNOWLEDGEMENTS I am most grateful to Mr P. Brockett, Rural Development Commission, for providing so much information. I would also like to thank Mrs H. Gillett and Miss Z. Whishaw sincerely for their help in durability research, the Scarfe, Mitchell and Nathan Trusts and the Broads Authority for partly funding the work, and the Botany School for facilities. J J~
132 REFERENCES Bosman, M.T.M., 1985. Some aspects of decay and weathering on the anatomical structure of the stem of Phragmites communis Trin. ex Steud. A W A Bull., No. 6: 165-170. Bornkamm, R. and Raghi-Atri, F., 1986. ~-ber die Wirkung unterschiedlicher Gaben von Stickstoff und Phosphor auf die Entwicklung von Phragmites australis(Cav.) Trin. ex Steudel. (On the effects of different nitrogen and phosphorus concentrations on the development of Phragmites australis (Cav.) Trin. ex Steudel.) Arch. Hydrobiol., 105: 423-441. Brockett, P. and Wright, A., 1986. The care and repair of thatched roofs. Society for the Protection of Ancient Buildings and Council of Small Industries in Rural Areas. Technical Pamphlet, No. 10, 12 pp. Cator, C.F., 1986. Draft report on the future of the reed and sedge growing industries. Unpublished report, British Reed Growers Association, 10 pp. Haslam, S.M., 1969. Stem types of Phragmites communis Trin. Ann. Bot., 33: 127-131. Haslam, S.M., 1970a. Variation of population type in Phragmites communis Trin. Ann. Bot., 34: 147-158. Haslam, S.M., 1970b. The development of the annual population in Phragmites communis Trin. Ann. Bot., 34" 571-591. Haslam, S.M., 1972. The Reed. Norfolk Reed Growers Association, 73 pp. Raghi-Atri, F. and Bornkamm, R., 1980. lJ-bet Halmfestigkeit von Schilf (Phragmites australis (Cav.) Trin. ex Steudel) bei unterschiedlicher Niihrstoffversorgung. (On the stiffness of stems of the reed plant (Phragmites australis (Cav.) Trin. ex Steudel) at different levels of nutrients added.) Arch. Hydrobiol., 90: 90-105. Sukopp, H. and Markstein, B., 1981. Veranderung von RShrichtstanden und Pflanzen als Indikatoren von Gewassernutzungen dargestellt am Beispiel der Havel in Berlin. Limnologica, 13: 459-471.