INGER ELISABETH MÅREN & VIGDIS VANDVIK Department of Biology & Bergen Museum, University of Bergen, Norway

Fire and Regeneration

Inger Elisabeth Måren INGER ELISABETH MÅREN & VIGDIS VANDVIK Department of Biology & Bergen Museum, University of Bergen, Norway

seed bank Frequency Results 25 0,0 0,2 0,4 0,6 0,8 1,0 vegetation Juncus bufonus Juncus conglemoratus 20 Salix caprea Senecio vulgaris The frequency of occur-

Study area Poa pratensis sampled rence of species registered -1 Digitalis purpurea 15 Taraxacum coll. Seed bank The islands of Lygra and Lu- Juncus effusus in the 130 sampled plots as Juncus filiformis viable seeds in the soil seed rekalven, situated at 60º 42' N, Sagina procumbens 10 LurekalvenLurekalven Veronica chamaedrys Myking Plantago major bank ( ) and the standing Norway and 5º 5' E, in the Lurefjorden LygraLygra Drosera rotundifolia vegetation ( ) found in the Sedum angglicum 5 fjord basin, Western Norway; Trifolium repens Calluna vulgaris heathland habitat man- characteristic oceanic climate Erica tetralix aged by traditional heather yr species of Mean no. Carex pilulifera 0 with small differences between Juncus squarrosus Agrostis canina burning at Lygra and Lu- 01234678910111224 Potentilla erecta Years since last fire Junae and January mean tem- Agrostis capillaris rekalven, Western Norway. Luzula multiflora A total of 75 taxa were iden- peratures (12ºC and 2ºC) a long Anthoxanthum odoratum Species richness was always higher in the vegetation in comparison to the corresponding Luzula pilosa growing season (220 days Galium saxatile tified. The 10 most com- seed banks. The species found were related largely to the localized vegetation, although Betula pubescens Molinia caerulea monly occurring species of some seedlings were more or less numerous than expected compared to the surrounding above 5ºC), abundant precipi- Hypericum pulchrum Carex panicea Seed bank and the seed bank constituted vegetation cover. tation (1600 mm/yr) evenly dis- Salix aurita Eriophorum ssp. standing vegetation 98 % of the germinated tributed throughout the year, Carex nigra a) b) Arctostaphylos uva-ursi seeds. The main component BergenBergen strong winds, seldom snow Polygala serpyllifolia of the seed bank; Calluna vul- 10 km Veronica officinalis Dantonia decumbens cover or periods of frost. Trientalis europaea garis, 48 % then Erica tetralix, 34 Campanula rotundifolia Lotus corniculatus %. The Sørenson’s index of Pinguicula vulgaris Dactylorhiza maculata similarity (Sørenson 1948) Pedicularis sylvatica Cerastium fontanum indicated a 68.4% concor- Trichophorum cespitosum Festuca vivipara dance between the species Juniperus communis Succisa pratensis composition of the seed Carex binervis Pinus sylvestris bank and the standing veg- Rumex acetosella BACKGROUND seeds/m2 Calluna Avenella flexuosa etation. Carex echinata Vaccinium vitis idaea Vaccinium myrtillus 5000 10000 15000 20000 25000 30000 Dormant seeds in the soil serve a dual function in plant populations. Vaccinium uliginosum Germitable Calluna seeds/m2 Chamaepericlymenum suecicum 5000 10000 15000 20000 25000 30000 Empetrum nigrum They are memories of populations and communities past, and at the Anemone nemorosa Sorbus aucuparia 01234678910111224 0 1 same time a potential for future persistence and survival. Hence, the Antennaria dioica Years since burning Wet heath (1) Festuca ovina c) d) longevity of seeds in the soil affects the resilience of plant communi- Salix repens Euphrasia micreantha Listera cordata Standing vegetation ties. Hieracium pilosella Oxalis acetosella Nardus stricta Narthecium ossifragum Heathlands are influenced by many factors leading to vegetation Vaccinium oxycoccus Hypochaeris radicans Leontodon autumnalis change. Burning and grazing have been the most commonly employed Lycopodium clavatum management practices in Western Scandinavia. Local seed availability Solidago virgaurea may be affected by e.g. seed-source density, seed production, dispersal a) strategy and predation, while microsite availability may be affected by Desc fle Gali sax Agro can 0 e.g. competition, disturbance, and grazing. In the open heathland Trie eur Vacc myr Agro cap 1. 2004 2003 Luzu pil

Fest viv Calluna % cover/m2 Litter landscape seed-sources may be sparse, and while the availability of Anem nem % cover/m2 vulgaris Calluna Vacc uli Cera fonCorn sue Pote ere Junc squ Oxal ace Luzu mul safe sites may be the major limitation in heavily grazed heathland Camp rot Bare soil 0 20406080

Vero off 0 20406080 Moli cae Hier pil Anth odo Tric ces Care nig Erio ang Dant dec LOI areas, seed limitation may become the most important limiting factor Juni com Euph mi 2002 Erio vag Nart oss pH 01234678910111224 Vacc oxy Care pan Sorb auc 0 1 Vacc vit Hype pul 2001 Care pil as grazing pressure decreases. A proper understanding of how heath- Poly ser Ante dio Graminoids Years since burning Wet heath (1) Herbs Dact mac 1980 Arct uva Lotu cor 1995 lands respond to disturbance must take account of seed production-, 1998 Pedi syl dispersal-, seed bank- and germinability dynamics. In cyclic vegetation 2 PCA axis Eric tet 2 PCA axis 1997 (a) Calluna vulgaris showed significantly higher germination rates the two first years following 2000 Lichen fire. Fire might cause changed chemical properties of the soil; charcoal particles deposited 1996 types such as heathlands, seed banks are particularly important so that 1992 1994 on the surface may absorb germination inhibitors and allelophathic chemicals, and smoke the species can survive locally with time. 1993 and ash may act as germination cues. Hence, increased germination rate immediately after Heath height a fire may be explained by fire-related chemical and physical changes taking effect. We have Call vul started a project to investigate this further. (b) Significantly more seedlings emerged from -1.0 -1.0 0.4 We investigated the relationship between standing vegetation and soil -1.0 -0.8 PCA axis 1 1.0 -0.8PCA axis 1 0.8 north facing wet heath. (c) Increase of Calluna cover in the standing vegetation over the seed bank in burnt heath of varying age (recently burnt – 30 years since course of the post-fire succession. d) There is significantly higher coverage ofCalluna vulgaris in last fire), using a chronosequence approach. An indirect seedling b) the south facing moderately moist sites. Junc squ emergence technique was used to analyse the soil seed samples. Conclusions

Care nig Main aims were; (1) to investigate the soil seed bank/ standing vegeta- Call vul Estimates of seed bank density and composition are dependent on the methods applied. The tion relationships over a post fire succession in northern European large, persistent soil seed stores of Calluna vulgaris, Erica tetralix, Agrostis spp. and Juncus spp., all

Tric ces known to have long-lived seeds, indicate that oure methods were suitable for the detection heathlands. (2) does similarity between seed bank and vegetation Moli cae Junc con Poa hum Aven fle of the persistent reservoir of readily germinable seeds in this system. Lotu cor Poly ser 0.4 1980 imply importance of seed banking in restoration? (3) how do seed bank Sedu ang Betu pub 2003 1992 2004 Gali sax Sene vul 2002 Camp rot Digi pur Junc buf and vegetation densities and species richness vary over the course of Hype pul Vero off Junc eff Ping vul 1996 The high similarity supports the thesis that in frequently disturbed communities vegetation Arct uva Pedi syl Care pil Eric tet 1995 Vero cha Dros rot 2001 succession? (4) how does the key species Calluna vulgaris respond to 2000 and seed bank composition should be similar. This correspondence exists because distur- Anth odo 1993 Agro can 1997 bance limits community composition to early successional species with more persistent seed fire, both in the way of seed germatability and regrowth in the vegeta- Pote ere 1998 Agro cap tion? 1994 banks for colonization instead of later successional species that colonize by invasion. The -0.6 PCA axis 2 (13.4%) 2 axis PCA -0.6 0.8 -0.6 PCA axis 2 (13.4%) PCA axis -0.6 soil seed bank is often used to assess the restoration potential of a site, in particular in frag- -0.6 PCA axis 1(57.2%) 1.2 -1.0 PCA axis 1 (57.2%) 1.5 mented landscapes where the probability of influx of viable seeds is extremely limited. The size and the quality of the viable seed bank may both be determinants of successful heathland management and restoration on successional sites. PCA ordination diagrams of environmental variables and years of the chronosequence, and species of the standing vegetation (a) and soil seed bank (b) over the post-fire succession From a management point of view, prescribed burning is successful in many aspects as it is (n=130). The compositional change from the pre-fire census (marked 1980) to recently burnt not labour intensive or time consuming and at low cost. These findings emphasize the need (marked 2004) is drawn as a trajectory. Trends in various environmental variables are indi- for continued management measures in order to maintain northern heathlands. Our study cated. During the first 24 years after fire the heathland vegetation progresses from open shows that burning by rotation creates heterogeneity which in turn contributes to a de- ground via species rich graminoid and herbaceous dominated vegetation to Calluna- pendable seed bank for revegetation of bared ground after disturbance in these coastal dominated heath. The post-fire succession is less clearly reflected in the seed bank, as it is areas. Heathland management is dependent on some form of disturbance regime, and the dominated mainly by a few very abundant species, such as Calluna vulgaris, Erica tetralix, Juncus squar- response of the vegetation will thus partly depend on the composition, density and spatial rosus and Carex pilulifera. distribution of the seed bank.