ACTA PHYTOGEOGRAPHICA SUECICA 74 EDIDIT SVENSKA V AXTGEOGRAFISKA SALLSKAPET lngvar Backeus Aboveground production and growth dynamics of vascular bog plants in Central Sweden UPPSALA 1985 ACTA PHYTOGEOGRAPHICA SUECICA 74 EDIDIT SVENSKA V AXTGEOGRAFISKA SALLSKAPET lngvar Backeus Aboveground production and growth dynamics of vascular bog plants in Central Sweden Almqvist Wiksell International, Stockholm & UPPSALA 1985 Doctoral thesis at Uppsala University 1985 ISBN 91-7210-074-5 (paperback) ISBN 91-7210-474-0 (cloth) ISSN 0084-5914 Backeus, I. 1985: Abovegroundproduction and growth dynamics of vascular bog plants in Cen­ tral Sweden. Acta Phytogeogr. Suec. 74, 98 pp. ISBN 91-7210-074-5; ISBN 91-7210-740-0. Aboveground primary production and biomass of the field layer plants were studied on an om­ brotrophic mire in the central Swedish uplands. The study was made on the population level, and results on the population ecology of certain species were also obtained. The study included Andromeda polifolia, Betula nana, Calluna vulgaris, Drosera anglica, D. rotundifolia, Empet­ rum nigrum s.str., Eriophorum vaginatum, Rhynchospora alba, Rubus chamaemorus, Scheuchzeria palustris, Trichophorum caespitosum, Vaccinium microcarpum, V. oxycoccos and V. uliginosum. Production and biomass per unit area of each species and of modules (leaves, inflorescences, etc.) of certain species were determined from figures on mean individual weight and mean density. Aboveground biomass of vascular plants was estimated at 2700 kg· ha·1 on hummocks, 682 kg· ha·1 in 'lawns' and 310-390 kg· ha·1 in two kinds of 'carpets' (Cuspidatetum dusenietosum and C. tenelletosum Fransson, respectively). Total aboveground production of vascular plants was 830, 610, 360 and 340 kg · ha·1 • year·1, respectively. Growth in some species was followed throughout the growing season through repeated har­ vesting. Seasonal variation in weight of individual leaves was similarly followed in evergreen species. Length growth of shoots of six species and length growth of leaves in two monocots were followed through direct measurements. Length growth rate of B. nana and Calluna shoots and of Scheuchzeria leaves was shown to be closely dependent on temperature, while growth of E. vaginatum leaves was not. Two peaks in production were found: (1) during shoot formation in June and (2) in August when perennial leaves were becoming winter-hardened and wood increment in Calluna and An­ dromeda (remarkably late) took place. Seasonal changes in biomass were comparatively small because of evergreenness in the dominant species. Survivorship ofleaves of certain species was studied. Flowering was poor and seedlings absent in most species. Instead plants were propagated vegetatively, and different means for such pro­ pagation are discussed. The interactions between the field and bottom layer plants are also dis­ cussed, notably how the former avoid being overgrown by mosses. Ingvar Backeus, Institute of Ecological Botany, Box 559, S-751 22 Uppsala, Sweden © Ingvar Backeus 1985 Svenska Vaxtgeografiska Sallskapet Box 559, 75 1 22 Uppsala Editor: Erik Sjogren Technical editor: Gunnel Sjors Phototypesetting: Textgruppen i Uppsala AB Printed in Sweden 1985 by Borgstroms Tryckeri AB, Motala Contents Th e study area 7 Topography and geology 7 Climate and weather 7 Temperature 7, Precipitation 11 Vegetation 12 Description of the sampling areas 15 Phenological development 17 Methods of collecting and presenting the phenological data 17 Results and discussion 17 Production and dy namics of individual species 20 Methods 20 Andromeda polifolia 21 Betula nana 26 Calluna vulgaris 28 Carex limosa 33 Carex pauciflora 33 Drosera anglica 33 Drosera rotundifolia 34 Empetrum nigrum 35 Eriophorum vaginatum 39 Rhynchospora alba 48 Rubus chamaemorus 51 Scheuchzeria palustris 56 Trichophorum caespitosum 60 Vaccinium microcarpum 62 Vaccinium oxycoccos 63 Vaccinium uliginosum 64 Field layer density, biomass and production 68 Discussion on methods 68 Density 72 Mean total aboveground biomass and production 72 The seasonal course of the total aboveground production and changes in the total aboveground biomass 77 The seasonal course of production 77, Seasonal changes in biomass 77 Variations between years in production 80 The dependence on environmental variables of length growth in stems and leaves 81 4 lngvar Backeus Th e bog environment and the behaviour of plants 84 Rate of production 84 Flowering and reproduction 85 Vegetative propagation 86 Moss overgrowth 87 Grime's C-, S- and R-selection 88 Age structure of modules 89 Interdependence of ramets 90 Concluding remarks 91 References 92 Introduction Works in production ecology, e.g.within the Inter­ possible to draw more general conclusions about the national Biological Programme, have often been response of plants to the particular environment ecosystem-oriented. Great efforts have been made that was studied. to obtain figures on the total biomass and produc­ The aim of my investigation has been to find out tion in various ecosystems. The work input in this the distribution of production in time and space kind of investigation is considerable also when only (within a plant and within the site) of all field layer moderate resolution is accepted and time-consum­ plants (including Betula nana) on an ombrotrophic ing harvesting, sorting and weighing are necessary. mire. The amount of work and numerous methodo­ It is also possible to make production ecological logical problems made it necessary to exclude the studies on the population level. By working out suit­ bottom layer and the rhizosphere as well as decom­ able techniques for all or the more important spe­ position at this stage. This limitation of course has cies, figures on total production can be obtained caused gaps in my results that will have to be filled also by such an approach, which is attempted in this before a reasonably good understanding of the pro­ treatise. duction on the bog can be obtained. The aim is somewhat different than in an The ombrotrophic mire is an extreme environ­ ecosystem-oriented study, even though populations ment. There is no input of nutrients except through of organisms are often used as a basis also in the lat­ precipitation. There are several reasons for this ter type of investigation. Other variables are choice of study object, besides the obvious fact that measured and information on density, age struc­ ombrotrophic mires constitute important ecosys­ ture, growth rhythm and growth rate is obtained. tems in Scandinavia and are interesting per se: In contrast to animals, higher plants do not have The vegetation is poor in species and all species a definite size. The size instead varies with the en­ are fairly well distributed within the community. vironment, both the abiotic and the biotic. The indi­ Such a simple system makes it easier to work out vidual 'modules' of the plant, leaves, flowers, etc. methods, and the low number of species makes it usually vary much less (cf. Harper 1978). The study possible to study all species. of these metapopulations (White 1979) refines the Few environmental factors vary within one site. production ecological methodology and increases The water level varies in space in an obvious and our knowledge of the survival potential of the indi­ easily understandable way and lack of water is rare vidual. for the field layer plants. The chemistry of the sub­ Population ecologists usually work with only one strate is very uniform. In time, temperature is an im­ or a few, similar or contrasting, species. Examples portant variable factor and in space (and time) the that will be discussed later are found in Fetcher overgrowth by mosses. & Shaver (1983), Flower-Ellis (1971), Karlsson (1982), The ombrotrophic bog is an unusually well-de­ Noble et al. (1979), Robertson Woolhouse fined ecosystem and this was also a reason for my & (1984a,b), Sarukhan Harper (1973) and Schmid choice. Within a restricted area this ecosystem re­ & (1984). The response of these species to environ­ curs from site to site with very little variation. In a mental factors in different environments is studied. larger area, e.g. Europe or Holarctis, the variation It has been less common to study the response to en­ is certainly greater but still moderate and usually vironmental factors of all the different populations successive. Comparisons with investigations from in a community. Evidently the work on each species other places are therefore easy to make. cannot be very intense in such a study and has to fo­ As a mire ecologist I should also explain why I cus on the main points, but nevertheless it might be have chosen to study production. The mire plants Acta Phytogeogr. Suec. 74 6 lngvar Backeus form their substrate themselves through production I have had the opportunity to carry out the field and decomposition. Information on total produc­ work on a bog that was previously thoroughly inves­ tion and decomposition must therefore be essential tigated ecologically, the 'Special Area' of the Skatt­ for a better understanding of the mechanisms be­ losberg Stormosse (Sjors 1948). Sjors described in hind the rise of the mire surface and its differentia­ detail the vegetation and the distribution of plants tion into hydromorphological structures, of the re­ and mineral elements in this area. This made it poss­ lations between these structures and of their se­ ible for me to concentrate from the beginning on quence in time. Production and production proces­ production studies without lengthy data collections ses are therefore central problems in mire ecology. concerning the vegetation and environment. Here it must again be emphasized that my investiga­ The field work was carried out in 1980, 1981 and tion is still in its beginning. The aboveground parts 1982, thus giving figures from three successive of the vascular plants contribute very little to the growing periods. peat formation. Peat is mainly formed by mosses Nomenclature for vascular plants follows Moore and below ground parts of vascular plants and a lot (1982), except for Empetrum nigrum v.