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Succession in boreal bryophyte communities – the role of microtopography and post-harvest bottlenecks by Martin Schmalholz Plants & Ecology Plant Ecology Department of Botany Stockholm University 2008/03 Succession in boreal bryophyte communities – the role of microtopography and post-harvest bottlenecks Licentiate thesis by Martin Schmalholz Supervisors: Kristoffer Hylander and Ove Eriksson Plants & Ecology Plant Ecology Department of Botany Stockholm University 2008/03 Plants & Ecology Plant Ecology Department of Botany Stockholm University S-106 91 Stockholm Sweden © Plant Ecology ISSN 1651-9248 Printed by Solna Printcenter Cover: Clear-cut covered with the grass species Deschampsia flexuosa, Lesjöfors, eastern Värmland. Summary Clear-cutting forestry can be considered to be the most important disturbance agent in the Fennoscandian boreal forest, where both effective fire and insect suppression have reduced the influence of natural disturbances considerably. Most conservational attention has been devoted to understand and mitigate the detrimental effects associated with the clear-cutting event. The first study of this thesis explores the successional trajectory of boreal bryophyte communities in search of other bottlenecks than the initial clear-cut disturbance. A bottleneck is here defined as a period with distinct retrogressive succession, where the ongoing reorganization process towards the mature forest community reverts due to decrease in abundance or local extinctions of mature forest species. Furthermore, we hypothesized that high grass cover following timber harvest, high litter cover during canopy closure and shortage of dead wood in the young forest would induce bottlenecks in three different bryophyte guilds. We did not find clear evidence of any bottleneck in species composition occurring during the recovery process for each of the three guilds. One reason for this pattern might be that the expected high values in needle cover during canopy closure and distinct decrease in dead wood in the young forest was not very pronounced. The retrogressive tendency found in the epilitic guild between 35-50 years after clear-cutting might be related to the infavorable light regime in the dense stands prior to first thinning. The epixylic guild displayed a gradual recovery during the first 50-60 years after clear-cutting. During the last 30 years of succession however, this guild was found to be constrained by the amount of large diameter logs (>25 cm) with sites with higher amount of woody debris displaying continued development and sites depleted of coarse woody debris displaying retrogressive tendencies. In the second study, we investigate the potential influence of microtopography on bryophyte post-harvest recovery. Microtopography, in this study expressed as boulder cover, was hypothesized to increase the initial clear-cutting resistance through providing sheltered microsites where drought-sensitive bryophytes may survive the clear-cut phase. We analyzed the importance of boulder cover on both initial resistance and the subsequent recovery rate for species density, composition and abundance change of single species. We found boulder-rich stand to have a higher density of closed-canopy species throughout the whole rotation cycle than compared to boulder-poor stands. We can not rule out the possibility that this result is due to the fact that boulders actually enhance the clear-cutting resistance by providing drough-sensitive species with “safe-sites” in which species can survive and from which subsequent recolonization can occur. Due to the absence of convergence over time in species 1 density, we belive that the effect of boulders may be in its effect on forest floor micro-sites and microclimatic heterogeneity. For species utilizing exposed substrates, recovery was not significantly affected by boulder cover, although the response surface for both composition and density suggest a higher resistance and a higher recovery rate. 2 Sammanfattning Denna avhandling omfattar två olika studierna som båda syftar till att utforska och undersöka återhämtningsprocessen hos mossamhällen i boreal kulturskog efter kalavverkning. I den första studien undersöktes förändringen i artsammansättning över tiden för tre olika mossguilder; mark-, block- och vedarter. Många studier har visat att skogskryptogamer påverkas negativt av kalavverkning, ett faktum som kan härledas till att många kryptogamer saknar effektiv vattenreglering och därigenom blir mer känsliga för de mer torra och varma mikroklimat som råder på hygget. Naturvårdsåtgärder på beståndsnivå inom skogsbruket har följaktligen nästan helt fokuserat på denna ”flaskhals” under rotationscykeln som det enda tillfälle då skyddsvärda och artrika kryptogamsamhällen slås ut eller decimeras. Ett normalt skogsbestånd genomgår i regel ett antal stadier som potentiellt kan tänka påverka mossamhället negativt. I den första studien i denna avhandling undersöktes mossuccessionen efter kalavverkning med avseende på förekomsten av ytterligare flaskhalsar utöver den initiala kalavverkningen. Vi var intresserade av att undersöka effekten av initialt hög grästäckning, hög täckningsgrad barrförna samt brist på död ved under ungskogsfasen. Vi fann inga distinkta flaskhalsar i mossuccessionen för de tre undersökta guilderna, vilket motiverar den nuvarande fokusen på kalhyggesfasen inom den skogliga naturvården. Mark- och vedguilden genomgick en gradvis förändring i artsammansättning över tiden medan blockarterna uppvisade en stor variation mellan bestånden. Sammansättningen av dödvedsarter var starkt korrelerat med mängden grov ved (>25 cm i diameter) under de sista 30 åren, vilket indikerar att denna guild är starkt begränsad av mängden tillgängligt substrat under denna del av rotationscykeln. I studie två undersökte vi hur mikrotopografisk heterogenitet påverkar återhämtningen av mossamhället efter kalavverkning. Mikrotopografi i boreal skog beskriver markens ”knölighet”, dess grad av ojämnhet och styrs i hög utsträckning av mängden konvexa/konkava elements såsom block, lågor och gropar. I denna studie har vi dock valt att fokusera på betydelsen av block. I skuggan av stora stenblock kan mortaliteten i bottenskiktets mossamhälle i samband med kalavverkning tänkas vara mindre jämfört med mer exponerade partier. Dessa fläckar med överlevande individer från samhället innan störning brukar kallas refugier och har visat sig påverka återhämtningshastigheten i många ekosystem. Vi undersökte blockens betydelse med statistiska modeller samt med en tredimensionell visualiseringsgraf för markmossor samt arter på upphöjda substrat. De statistiska modellerna 3 gav få signifikanta samband medan de tredimensionella graferna emellertid antydde att blockighet var en viktig förklaringsvariabel för vissa arter i mossamhället. De tredimensionella graferna (responsytorna) antydde att mossor på upphöjda substrat har högre initiala överlevnad och en snabbare återhämtning. Dessa indikationer kunde emellertid inte bekräftas av våra statistiska modeller och bör därför tolkas med ett visst mått av försiktighet. För markmossorna verkar arttätheten vara konstant högre i blockrika skogar. Detta samband, som var signifikant, antyder dels en högre initial överlevnad samt en mer divers markmossflora i blockrika bestånd generellt. De är troligt att de blockrika skogarna erbjuder en större mängd mikrohabitat i sprickor och gropar mellan blocken och av den anledningen kan hysa fler arter generellt under rotationscykeln. 4 Introduction Disturbances are ubiquitous features of most natural and human influenced ecosystems, continuously remodeling the composition of plant communities and resetting secondary succession (Pickett et al. 1989, Johnson and Miyanishi 2007). Naturally occurring disturbances such as wildfires, insect outbreaks and storms usually vary in frequency, extent and intensity within landscapes resulting in a mosaic mixture of disturbed and unaffected habitats. Antropogenic disturbances, such as forestry practises, are on the other hand characterized by the low degree of spatial varition in both frequency and intensity. Although more uniform, the ecological responses to these homogenious disturbances will vary according to environmental heterogeneity and the species composition in the affected community. Succession in boreal forest understory communities is highly idiosyncratic with few generalities and many exceptions (Hart and Chen 2003). The majority of studies conducted on both post-fire and post-harvest succession are “snapshot”-studies, assessing the immediate effects on plant communities, usually vascular plants, neglecting other important groups such as bryophytes. Forestry and bryophytes in the boreal forest Forestry practices in the Fennoscandian countries have historically been intense and both fire and insect outbreaks have been successfully suppressed (Esseen 1997). Approximately 85% of the forest land in Sweden is today managed exclusively for extraction of timber and pulp (Anon. 2007). The disturbance regime prevailing in productive spruce dominated forest in Sweden is characterized by clear-cutting, ground preparation, pre-commercial thinning and one or two commercial thinning where stems are extracted for production of pulp or timber. Natural wildfires are scarce, only 0.01% of the forest area burns every year due to highly efficient fire suppression (Granström 2001). The transition from the natural fire-dominated disturbance regime to the silvicultural disturbance regime have resulted in a substantial loss of both within and among stand structural heterogeneity with old-growth forests surrounded by vast expanses of clear-cuts and young forests. At the same time, a growing awarness of the ongoing rapid decline in biodiversity have spurred the development of a more restrictive legislation. The new Forestry Act in Sweden from 1993 stipulates that equal importance should be given to timber extraction as to conservation (Anon.2006). The pronounced fragmentation of the boreal forest in Fennoscandia has lead forest ecologists and managers to realize that the quality of the matrix must be improved. Several studies have shown that young managed forests can support cryptogam species previously regarded as confined to old5 growth forest conditions (e.g. Rudolphi et al. in prep.).This result indicates that the capacity of managed “matrix” forest stands might actually support species previously imagined to be exclusive to old-growth conditions. Most research has been directed towards the standreplacing phase, assessing the impact of clear-cutting or the benefits of leaving living (i.e. “green-trees”) and/or dead trees during final felling operations. These adjusted management practices utilizes a coarse-grained approach to conservation and often aims at mimicking patterns or structures generated through natural disturbances. Bryophyte communities are known to have strong influence on the functioning of the boreal forest ecosystem, (Steijlen et al. 1995, De Luca et al. 2002). Apart from influencing nutrient and moisture levels, closedcanopy bryophyte communities are species rich (e.g. Berglund and Jonsson 2001) and provide important habitats for detrivorous invertebrates (Merrifield and Ingham 1998). Closed-canopy bryophytes are severely disrupted by clear-cutting disturbance (e.g. Hannerz and Hånell 1997, Jalonen and Vanha-Majamaa 2001). Ecological memory and resilience of bryophyte communities The concept of resilience has been utilized in various ecological contexts since it first was introduced by Holling in 1973. Resilience is currently beeing used in two quite different ways in the ecological litterature. The traditionally view of resilience describe the ability of a certain ecological system to cope with and reorganize after a disturbance and has been termed equilibrium or engineering resilience (Gunderson 2000). Ecological resilience, in contrast, acknowledges the possibility of several alternative stable states in ecosystems and describes the amount of disturbance that a system can absorb a state shift occurs. Due to the difficulties in quantifying ecological resilience, the more robust and easily interpretable concept of engineering resilience has historically been prefered. In this thesis I will stick to the traditional definition when discussing the recovery of bryophytes after clear-cutting. Resistance and recovery is usually considered to be two important components of engineering resilience describing the initial change in composition and species density and the subsequent rate of return (Halpern 1988). The recovery pattern of plant communities has traditionally been explained by distance to the nearest propagule sources, such as closest unaffected habitat (e.g. Glenn-Levin 1992, Fastie 1995). During the last two decades, ecologists have started to appreciate the importance of initial resistance, i.e. surviving species, during the reorganization of new communities (e.g. Franklin 1985). These patches have been termed refugia (e.g. Sedell 1990) and have been shown to be frequent in some lotic systems experiencing periodic flow disturbances (Matthaei et al. 2000). Several papers have found that refugia can affect recovery 6 rates through providing internal recolonization sources or through facilitating the establishment of incoming propagules that otherwise would fail to establish (Franklin et al. 1985, Gjerlöv et al. 2003, Panzer 2003). The importance of refugia have recently been incorporated into the concept of ecological memory that described the pattern of surviving species and structures necessary for recoloniation such as substrates, i.e. internal memory, as well as the distribution of potential dispersal sources in the adjacent unaffected part of the landscape, i.e. external memory, (Bengtsson et al. 2003). In the second paper we investigate the imporance of one aspect of internal memory, i.e. surviving species, during the recovery process. Aims with the thesis 1) Although the emphasis on clear-cutting effects might seem intuitive given the disruptive impact on forest bryophytes, additional bottlenecks might occur. The purpose with the first paper in this thesis was to provide data on bryophyte succession and assess to what extent post-harvest bottlenecks occur. More specifically, we wanted to understand the impact of the following three potentially hostile stand conditions; (1), high initial grass cover (2), high litter cover in young stands prior to thinning and (3),the decline in coarse woody debris in the young forest, on bryophyte communities recovery after a clear-cut disturbance. 2) The aim with the second study was to investigate the influence of microtopograhic structure on the bryophyte recovery process following clear-cutting. We used boulder cover as a proxy for microtopograhic structure. Since bryophytes are poikilohydric, i.e. lack the ability to regulate their own waterbalance, and are known to be negatively affected by clear-cutting, we hypothesized that they might be able to survive a clear-cutting phase in the shade of large boulders. Ultimately, the question that we wanted to explore in this study is to what extent microtopograhic structures can influence the resilience of bryophyte communities by mitigating the initial resistance and/or increasing the recovery potential. Methods Study 1 and 2 Study area The two studies included in this thesis were performed in the Bergslagen region of the three provinces Västmanland, Dalarna and Värmland during the summer and autumn 2007. The forest landscape in Bergslagen has been exploited for timber extraction since the beginning of 7 the 13th century due to the large charcoal demands by the mining industry. Stand regeneration by clear-cutting became the most common logging method earlier (>200 years ago) in this region than in other parts of Sweden (Nilsson 1996). The coniferous forest is dominated by Norway spruce, Picea abies. L, on mesic to moist soil and by Scots pine, Pinus sylvestris. L,on dry soils with nutrient poor soils and on peat producing wetlands. The yearly precipitation in the area lies between 800-1100 mm with increasing precipitation from east to west. The highest postglacial coastline is situated at ~170-180 m above sea level, usually well below the location of most study sites. Mean temperature for January is -7 and +14 degrees Celsius for July (Raab and Vedin 1999). Most of the forest land in this region is owned by the two large forest companies Bergvik Skog AB and Sveaskog. Stand selection and sampling design For practical reasons we chose to work with the two large landowners in the area (Bergvik Skog AB and Sveaskog). We used the well known chronosequence method to investigate the temporal pattern in bryophyte succession. In this method a sequence with stands of different ages is constructed and supposed to represent the successional trajectory of a hypothesized stand. This space-for time substitution will always introduce additional variation in the response variables that is not related to age, due for example to local stand conditions. This variation can be minimized if strict selection criteria are used when choosing among objects to include. When choosing among forest stands the following five criteria’s were used; 1. slightly poor to moderate productivity (i.e. site index G22-G28 according to Hägglund and Lundmark 1999), 2. mesic moisture conditions (i.e. dry and wet sites omitted), 3. tree species composition dominated by Norway spruce (>50 % basal area) and less than 15 % deciduous trees, 4. regeneration after traditional clear cutting and 5. low to intermediate cover of boulders (paper 1 only). A field visit of each stands was also conducted in order to assess the suitability. Approximately 1/3 of all stands were excluded from further data collection. Data was collected using 0.1 ha, sample plot (50x20m). We chose this plot size since we wished to include as many species as possible from the stand species pool. Each plot was divided into ten 10x10 m subplots, enabling frequency counts between 1-10 to be obtained for each occurring species. The plots were located in a representative part at least 25 m from the stand edge. 8 Data collection We collected data belonging to three categories: 1. general stand variables, i.e. stem basal area and canopy cover, 2; predictor variables; grass-and littercover and CWD-surface area (study 1) and boulder cover (study 2), 3; response variables; species composition, density and abundance (cover and frequency) (study 1 and 2). Each subplot was inventoried for all bryophyte species. Samples of bryophytes that could not be identified in field were collected for later identification using a light microscope. To ensure effective data collection the following taxa were treated as one taxon l: Dicranum fuscescens/flexicaule, Plagiothecium laetum/curvifolium, Chiloschyphus pallescens/polyanthus, Cephalozia lunulifolia/affinis and Bryum sp. The nomenclature follows Hallingbäck et al. (2006). In study 1 we classified species in three groups depending on main habitat preference; 1. epigeeics, i.e. forest floor living species, 2. epilitics, rock and boulder living species and 3. epixylics, i.e. dead wood living species. In study 2, we chose to omit obligate epilitic species, since they are affected by boulder cover as a substrate, and obligate epiphytes. When analyzing the impact of microtopography on species composition we classified species into one of the two groups, epigeeics or species on exposed substrates. The latter group comprises both obligate epixylics and facultative epiphytes, utilizing tree-bases as a substrate. For species density, species that were considered to be favored or at least indifferent to clear-cutting were omitted. Statistical analysis Due to the exploratory approach in the first study we chose to work with robust nonparametric methods not depending on particular model assumptions such as linearity or normally distributed variables. To investigate the general patterns in species composition over time density and species abundance within the three bryophyte guilds, we performed locally weighted scatterplot smoothing (LOWESS)-regressions with a narrow window-width (f=0.5). We used the site scores of a two-dimensional non-metric multidimensional scaling (NMDS) ordination (using Bray-Curtis distance measure for frequency values) as a measure of species composition. The three selected guilds were; epigeeic, epilitics, and epixylics. These were chosen since we hypothesized they would display different degree of susceptibility to the three potenially hostile stand conditions. Finally, Spearman correlations were performed in order to test hypothesis about bottlenecks during certain critical age intervals. All statistical analyses were performed in R 2.4.0 (R development Core Team 2007). 9 In study 2 we chose to visualize our data with three-dimensional response surface. This approach facilitated our understanding of the potential interaction between the two predictors of interest, i.e. stand age and boulder cover and was used as a compliment to our statistical models. Furthermore, Generalized Additive Models (GAM) was used to evaluate if and how boulders affect our response variables. As predictors in the models we used the logarithm of boulder cover and a smooth function of stand age. The product of the logarithm of boulder cover and the logarithm of stand age was included as a third predictor to be able to detect possible interaction effects. Site ordination scores from a one-dimensional NMDS-analysis were used for species composition using relative Sørensen dissimilarity index on frequency data in the statistical program PCord (McCune and Mefford 1999). Results and discussion Study 1 We found no clear evidence of any bottleneck in species composition during the post-harvest recovery of the forest floor guild. Neither grass nor litter cover was found to disrupt the compositional recovery in the epigeic or epilitic guild as we hypothesized. The forest floor guild, mainly composed of long-lived pleurocarps, was more or less recovered 40-45 years after clear-cutting. The three most dominant species within this guild, i.e. Hylocomium splendens, Pleurozium schreberi and Dicranum majus, all displayed clearly non-monotonic recovery pattern with P.schreberi and D.majus having distinct peaks in the young forest, i.e. during the first 50 years. H. splendens instead showed a gradual increase during the first 3040 years followed by a period with haltered recovery between 40 and 60 years after clear cutting and thereafter increasing again. This dynamic change in abundance is an interesting finding since they occur after maximum bryophyte cover was attained, implying competitive interactions as an important structuring factor in this guild. In the epilitic guild, species composition displayed a small retrogressive tendency around 30-50 years after clear-cutting. Since the majority of species in this group are drought-resistant and thriving in semi-shaded light conditions, e.g. Racomitrium microcarpon, Paraleucobryum longifolium and Hedwigia ciliata, we believe these species to be disfavored by the very shady conditions prevailing in Norway spruce stands prior to first thinning. The recovery process in the epixylic guild did not seem to be severly affected by the extreme low values of CWD during the first 60 years. The gradual change away from the initial clear-cut composition might be explained by the development of a favorable microclimate during canopy closure. Instead we found that the area large logs (>25 cm in diameter) was strongly correlated with species composition during 10 the last 30 years of recovery. Stands with low amounts of large logs exhibited retrogressive tendencies becomming more similar in composition to the clear-cut stands. The response in abundance of the species within this guild differed, with some species showing slow recovery followed by a strong decline during the last 30 years of succession, e.g. Blepharostoma trichophyllum, and some species displaying fast recovery, e.g. Tetraphis pelludia and Ptilidium pulchellum. In addition to micro-site limitations it is possible that some species of liverworts can be negatively affected by the changed microclimate in the newly thinned stands between 45-55 years or by a second thinning around 65-75 years. Study2 The general response of the forest floor guild was somewhat different between the two measure responses, i.e. species composition and density. We found the forest floor guild to have a higher density of closed-canopy species confined to mature forests throughout the whole rotation cycle in boulder-rich stands. This implies that boulders might affect the resistance to clear-cut disturbance by enhancing the initial survival and perhaps by having higher forest floor micro-sites and microclimatic heterogeneity. The recovery of Hylocomium splendens was found to be significantly affected by boulder cover. According to the response surface the recovery rate but not the initial resistance was higher in the boulder-rich forests. One possible reason for this faster recovery might be a higher establishment success on the microclimatically more heterogeneous forest floor of the boulder-rich sites. Dicranum majus seems to recover equally well independent of boulders during the first half of the rotation cycle. On the other hand boulders affected the late seral trajectory, in that boulder poor forests supported much denser populations of D.majus compared to boulder-rich stands. The effect of boulder cover on the recovery of species utilizing exposed substrates was not statistically significant, although the response surface for both composition and density suggest a higher resistance and a higher recovery rate. The same pattern was evident for Barbilophozia attenuata at least during the first half of the cycle. During the later part boulders seems to have a negative influence on the recovery of this species. Conclusion and future ideas The two major goals with this thesis were to describe the post-harvest bryophyte succession in boreal forests and to investigate the impact of microtopographic structure and three potentially hostile stand conditions. Our results suggest that bryophyte succession is a gradual process for both epigeeic species and epixylic species and perhaps partly non-monotonic for 11 epilitic species. Our three-dimentional response surface indicates that microtopographic structure might be important, although we need a larger data set before solid conclusions can be drawn. Some management practices, especially thinning, that were not considered in these studies, might also introduce additional variation in our response variables. In moderately productive spruce-dominated stands in south-central Sweden, thinning is usually carried out at two occasions reducing stem densities with as much as 30-35%. It is possible that the canopy break-up during thinning could induce compositional changes in the bryophyte community through alterations in microclimatic parameters. Species relying on a stable moist and shaded microclimate might be negatively affected and species depending on semi-shaded conditions might increase. It is perhaps also possible that the field layer response due to the increased light levels could affect the composition of the forest floor guild. Recent studies indicate that bryophyte recolonization might be depending on the regional propagule source rather than a local source, from a nearby stand (e.g. Hylander unpublished). In southern and south-central Sweden the landscape is in many places dominated by clear-cuts and young forest. Thus, one interesting objective for the future is to evaluate the influence stand age distribution on a landscape scale for the local post-harvest recovery. It is possible that landscape structure is important for species that commonly reproduces sexually and that disperese by spores. Acknowledgement I would like to thank Kristoffer and Ove for excellent supervision during my first two years, Juha Loenberg for helping me with fieldwork and Börje Pettersson and Rune Andersson at the forest companies Bergvik Skog AB and Sveaskog for providing me with stand data. 12 References Anonymous. 2006. Skogsvårdslagen-Handbok, (The Swedish Forestry Act-a handbook guide. Skogsstyrelsen. Skogsstyrelsens Förlag, Jönköping. Anonymous. 2007. Skogsstatistisk årsbok (2007)-Swedish statistical Yearbook of Forestry (2007). Skogsstyrelsen (Swedish Forest Agency). Jönköping. Bengtsson, J., Angelstam, P., Elmqvist, T., Emanuelsson, U., Folke, C., Ihse, M., Moberg, F. and Nyström, M. 2003. Reserves, Resilience and Dynamic Landscapes. AMBIO 32: 389-396. Berglund, H. and Jonsson, BG. 2001. Predictability of plant and fungal species richness of old-growth boreal forest islands. Journal of Vegetation Science 12: 857-866. 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Nematodes and other aquatic invertebrates of Eurhynchium oreganum of Marys Peak, Oregon coast range. The Bryologist.101: 505-511. Nilsson, NE. 1996. Editor in Skogen, 2th edition. Sveriges National Atlas (SNS). Panzer, R. 2003. Importance of In Situ Survival, Recolonization and Habitat Gaps in the Postfire Recovery of Fire -Sensitive Prairie Insect Species. Natural Areas Journal 23: 14-21. Pickett, S.T.A., Kolasa, J., Armesto, J.J. and Collins, L. 1989. The ecological concept of disturbance and its expression at various hierarchial levels. Oikos 54:129-136. Raab, B. and Vedin, H. 1999. Editors in Klimat, sjöar och vattendrag. Svensk National Atlas (SNS) R Developmental Core Team. 2007. R: A language and environment for computing. In. R Foundations for Statistical Computing, Vienna, Austria. Rudolphi, J., Gustafsson, L. and Berglund T. Old-growth forest and lichens in young boreal production forests. In prep. Sedell, J.R., Reeves, G.H., Hauer, F.H., Stanford, J.A. and Hawkins, C.P. 1990. Role of 14 Refugia in Recovery from disturbance: Modern Fragmented and Disconnected River Systems. Environmental Management 14:711-724. Steiljen, I., Nilsson, MC. and Zackrisson, O. 1995. Seed regeneration of Scots pine in boreal forests stands dominated by lichen and feather moss. Canadian Journal of Forest Research 25:713-723. 15 Serien Plants & Ecology (ISSN 1651-9248) har tidigare haft namnen "Meddelanden från Växtekologiska avdelningen, Botaniska institutionen, Stockholms Universitet" nummer 1978:1 – 1993:1 samt "Växtekologi". (ISSN 1400-9501) nummer 1994:1 – 2003:3. Följande publikationer ingår i utgivningen: 1978:1 Liljelund, Lars-Erik: Kompendium i matematik för ekologer. 1978:2 Carlsson, Lars: Vegetationen på Littejåkkadeltat vid Sitasjaure, Lule Lappmark. 1978:3 Tapper, Per-Göran: Den maritima lövskogen i Stockholms skärgård. 1978:4: Forsse, Erik: Vegetationskartans användbarhet vid detaljplanering av fritidsbebyggelse. 1978:5 Bråvander, Lars-Gunnar och Engelmark, Thorbjörn: Botaniska studier vid Porjusselets och St. Lulevattens stränder i samband med regleringen 1974. 1979:1 Engström, Peter: Tillväxt, sulfatupptag och omsättning av cellmaterial hos pelagiska saltvattensbakterier. 1979:2 Eriksson, Sonja: Vegetationsutvecklingen i Husby-Långhundra de senaste tvåhundra åren. 1979:3 Bråvander, Lars-Gunnar: Vegetation och flora i övre Teusadalen och vid Autaoch Sitjasjaure; Norra Lule Lappmark. En översiktlig inventering med anledning av områdets exploatering för vattenkraftsändamål i Ritsemprojektet. 1979:4 Liljelund, Lars-Erik, Emanuelsson, Urban, Florgård, C. och Hofman-Bang, Vilhelm: Kunskapsöversikt och forskningsbehov rörande mekanisk påverkan på mark och vegetation. 1979:5 Reinhard, Ylva: Avloppsinfiltration - ett försök till konsekvensbeskrivning. 1980:1 Telenius, Anders och Torstensson, Peter: Populationsstudie på Spergularia marina och Spergularia media. I Frödimorfism och reproduktion. 1980:2 Hilding, Tuija: Populationsstudier på Spergularia marina och Spergularia media. II Resursallokering och mortalitet. 1980:3 Eriksson, Ove: Reproduktion och vegetativ spridning hos Potentilla anserina L. 1981:1 Eriksson, Torsten: Aspekter på färgvariation hos Dactylorhiza sambucina. 1983:1 Blom, Göran: Undersökningar av lertäkter i Färentuna, Ekerö kommun. 16 1984:1 Jerling, Ingemar: Kalkning som motåtgärd till försurningen och dess effekter på blåbär, Vaccinium myrtillus. 1986:1 Svanberg, Kerstin: En studie av grusbräckans (Saxifraga tridactylites) demografi. 1986:2 Nyberg, Hans: Förändringar i träd- och buskskiktets sammansättning i ädellövskogen på Tullgarnsnäset 1960-1983. 1987:1 Edenholm, Krister: Undersökningar av vegetationspåverkan av vildsvinsbök i Tullgarnsområdet. 1987:2 Nilsson, Thomas: Variation i fröstorlek och tillväxthastighet inom släktet Veronica. 1988:1 Ehrlén, Johan: Fröproduktion hos vårärt (Lathyrus vernus L.). - Begränsningar och reglering. 1988:2 Dinnétz, Patrik: Local variation in degree of gynodioecy and protogyny in Plantago maritima. 1988:3 Blom, Göran och Wincent, Helena: Effekter of kalkning på ängsvegetation. 1989:1 Eriksson, Pia: Täthetsreglering i Littoralvegetation. 1989:2 Kalvas, Arja: Jämförande studier av Fucus-populationer från Östersjön och västkusten. 1990:1 Kiviniemi, Katariina: Groddplantsetablering och spridning hos smultron, Fragaria vesca. 1990:2 Idestam-Almquist, Jerker: Transplantationsförsök med Borstnate. 1992:1 Malm, Torleif: Allokemisk påverkan från mucus hos åtta bruna makroalger på epifytiska alger. 1992:2 Pontis, Cristina: Om groddknoppar och tandrötter. Funderingar kring en klonal växt: Dentaria bulbifera. 1992:3 Agartz, Susanne: Optimal utkorsning hos Primula farinosa. 1992:4 Berglund, Anita: Ekologiska effekter av en parasitsvamp - Uromyces lineolatus på Glaux maritima (Strandkrypa). 1992:5 Ehn, Maria: Distribution and tetrasporophytes in populations of Chondrus crispus Stackhouse (Gigartinaceae, Rhodophyta) on the west coast of Sweden. 1992:6 Peterson, Torbjörn: Mollusc herbivory. 1993:1 Klásterská-Hedenberg, Martina: The influence of pH, N:P ratio and zooplankton on the phytoplanctic composition in hypertrophic ponds in the Trebon-region, Czech Republic. 1994:1 Fröborg, Heléne: Pollination and seed set in Vaccinium and Andromeda. 17 1994:2 Eriksson, Åsa: Makrofossilanalys av förekomst och populationsdynamik hos Najas flexilis i Sörmland. 1994:3 Klee, Irene: Effekter av kvävetillförsel på 6 vanliga arter i gran- och tallskog. 1995:1 Holm, Martin: Beståndshistorik - vad 492 träd på Fagerön i Uppland kan berätta. 1995:2 Löfgren, Anders: Distribution patterns and population structure of an economically important Amazon palm, Jessenia bataua (Mart.) Burret ssp. bataua in Bolivia. 1995:3 Norberg, Ylva: Morphological variation in the reduced, free floating Fucus vesiculosus, in the Baltic Proper. 1995:4 Hylander, Kristoffer & Hylander, Eva: Mount Zuquala - an upland forest of Ethiopia. Floristic inventory and analysis of the state of conservation. 1996:1 Eriksson, Åsa: Plant species composition and diversity in semi-natural grasslands with special emphasis on effects of mycorrhiza. 1996:2 Kalvas, Arja: Morphological variation and reproduction in Fucus vesiculosus L. populations. 1996:3 Andersson, Regina: Fågelspridda frukter kemiska och morfologiska egenskaper i relation till fåglarnas val av frukter. 1996:4 Lindgren, Åsa: Restpopulationer, nykolonisation och diversitet hos växter i naturbetesmarker i sörmländsk skogsbygd. 1996:5 Kiviniemi, Katariina: The ecological and evolutionary significance of the early life cycle stages in plants, with special emphasis on seed dispersal. 1996:7 Franzén, Daniel: Fältskiktsförändringar i ädellövskog på Fagerön, Uppland, beroende på igenväxning av gran och skogsavverkning. 1997:1 Wicksell, Maria: Flowering synchronization in the Ericaceae and the Empetraceae. 1997:2 Bolmgren, Kjell: A study of asynchrony in phenology - with a little help from Frangula alnus. 1997:3 Kiviniemi, Katariina: A study of seed dispersal and recruitment of plants in a fragmented habitat. 1997:4 Jakobsson, Anna: Fecundity and abundance - a comparative study of grassland species. 1997:5 Löfgren, Per: Population dynamics and the influence of disturbance in the Carline Thistle, Carlina vulgaris. 1998:1 Mattsson, Birgitta: The stress concept, exemplified by low salinity and other stress factors in aquatic systems. 18 1998:2 Forsslund, Annika & Koffman, Anna: Species diversity of lichens on decaying wood - A comparison between old-growth and managed forest. 1998:3 Eriksson, Åsa: Recruitment processes, site history and abundance patterns of plants in semi-natural grasslands. 1998:4 Fröborg, Heléne: Biotic interactions in the recruitment phase of forest field layer plants. 1998:5 Löfgren, Anders: Spatial and temporal structure of genetic variation in plants. 1998:6 Holmén Bränn, Kristina: Limitations of recruitment in Trifolium repens. 1999:1 Mattsson, Birgitta: Salinity effects on different life cycle stages in Baltic and North Sea Fucus vesiculosus L. 1999:2 Johannessen, Åse: Factors influencing vascular epiphyte composition in a lower montane rain forest in Ecuador. An inventory with aspects of altitudinal distribution, moisture, dispersal and pollination. 1999:3 Fröborg, Heléne: Seedling recruitment in forest field layer plants: seed production, herbivory and local species dynamics. 1999:4 Franzén, Daniel: Processes determining plant species richness at different scales examplified by grassland studies. 1999:5 Malm, Torleif: Factors regulating distribution patterns of fucoid seaweeds. A comparison between marine tidal and brackish atidal environments. 1999:6 Iversen, Therese: Flowering dynamics of the tropical tree Jacquinia nervosa. 1999:7 Isæus, Martin: Structuring factors for Fucus vesiculosus L. in Stockholm south archipelago - a GIS application. 1999:8 Lannek, Joakim: Förändringar i vegetation och flora på öar i Norrtälje skärgård. 2000:1 Jakobsson, Anna: Explaining differences in geographic range size, with focus on dispersal and speciation. 2000:2 Jakobsson, Anna: Comparative studies of colonisation ability and abundance in semi-natural grassland and deciduous forest. 2000:3 Franzén, Daniel: Aspects of pattern, process and function of species richness in Swedish seminatural grasslands. 2000:4 Öster, Mathias: The effects of habitat fragmentation on reproduction and population structure in Ranunculus bulbosus. 2001:1 Lindborg, Regina: Projecting extinction risks in plants in a conservation context. 2001:2 Lindgren, Åsa: Herbivory effects at different levels of plant organisation; the individual and the community. 19 2001:3 Lindborg, Regina: Forecasting the fate of plant species exposed to land use change. 2001:4 Bertilsson, Maria: Effects of habitat fragmentation on fitness components. 2001:5 Ryberg, Britta: Sustainability aspects on Oleoresin extraction from Dipterocarpus alatus. 2001:6 Dahlgren, Stefan: Undersökning av fem havsvikar i Bergkvara skärgård, östra egentliga Östersjön. 2001:7 Moen, Jon; Angerbjörn, Anders; Dinnetz, Patrik & Eriksson Ove: Biodiversitet i fjällen ovan trädgränsen: Bakgrund och kunskapsläge. 2001:8 Vanhoenacker, Didrik: To be short or long. Floral and inflorescence traits of Bird`s eye primrose Primula farinose, and interactions with pollinators and a seed predator. 2001:9 Wikström, Sofia: Plant invasions: are they possible to predict? 2001:10 von Zeipel, Hugo: Metapopulations and plant fitness in a titrophic system – seed predation and population structure in Actaea spicata L. vary with population size. 2001:11 Forsén, Britt: Survival of Hordelymus europaéus and Bromus benekenii in a deciduous forest under influence of forest management. 2001:12 Hedin, Elisabeth: Bedömningsgrunder för restaurering av lövängsrester i Norrtälje kommun. 2002:1 Dahlgren, Stefan & Kautsky, Lena: Distribution and recent changes in benthic macrovegetation in the Baltic Sea basins. – A literature review. 2002:2 Wikström, Sofia: Invasion history of Fucus evanescens C. Ag. in the Baltic Sea region and effects on the native biota. 2002:3 Janson, Emma: The effect of fragment size and isolation on the abundance of Viola tricolor in semi-natural grasslands. 2002:4 Bertilsson, Maria: Population persistance and individual fitness in Vicia pisiformis: the effects of habitat quality, population size and isolation. 2002:5 Hedman, Irja: Hävdhistorik och artrikedom av kärlväxter i ängs- och hagmarker på Singö, Fogdö och norra Väddö. 2002:6 Karlsson, Ann: Analys av florans förändring under de senaste hundra åren, ett successionsförlopp i Norrtälje kommuns skärgård. 2002:7 Isæus, Martin: Factors affecting the large and small scale distribution of fucoids in the Baltic Sea. 2003:1 Anagrius, Malin: Plant distribution patterns in an urban environment, Södermalm, Stockholm. 20 2003:2 Persson, Christin: Artantal och abundans av lavar på askstammar – jämförelse mellan betade och igenvuxna lövängsrester. 2003:3 Isæus, Martin: Wave impact on macroalgal communities. 2003:4 Jansson-Ask, Kristina: Betydelsen av pollen, resurser och ljustillgång för reproduktiv framgång hos Storrams, Polygonatum multiflorum. 2003:5 Sundblad, Göran: Using GIS to simulate and examine effects of wave exposure on submerged macrophyte vegetation. 2004:1 Strindell, Magnus: Abundansförändringar hos kärlväxter i ädellövskog – en jämförelse av skötselåtgärder. 2004:2 Dahlgren, Johan P: Are metapopulation dynamics important for aquatic plants? 2004:3 Wahlstrand, Anna: Predicting the occurrence of Zostera marina in bays in the Stockholm archipelago,northern Baltic proper. 2004:4 Råberg, Sonja: Competition from filamentous algae on Fucus vesiculosus – negative effects and the implications on biodiversity of associated flora and fauna. 2004:5 Smaaland, John: Effects of phosphorous load by water run-off on submersed plant communities in shallow bays in the Stockholm archipelago. 2004:6 Ramula Satu: Covariation among life history traits: implications for plant population dynamics. 2004:7 Ramula, Satu: Population viability analysis for plants: Optimizing work effort and the precision of estimates. 2004:8 Niklasson, Camilla: Effects of nutrient content and polybrominated phenols on the reproduction of Idotea baltica and Gammarus ssp. 2004:9 Lönnberg, Karin: Flowering phenology and distribution in fleshy fruited plants. 2004:10 Almlöf, Anette: Miljöfaktorers inverkan på bladmossor i Fagersjöskogen, Farsta, Stockholm. 2005:1 Hult, Anna: Factors affecting plant species composition on shores - A study made in the Stockholm archipelago, Sweden. 2005:2 Vanhoenacker, Didrik: The evolutionary pollination ecology of Primula farinosa. 2005:3 von Zeipel, Hugo: The plant-animal interactions of Actea spicata in relation to spatial context. 2005:4 Arvanitis, Leena T.: Butterfly seed predation. 2005:5 Öster, Mathias: Landscape effects on plant species diversity – a case study of Antennaria dioica. 2005:6 Boalt, Elin: Ecosystem effects of large grazing herbivores: the role of nitrogen. 21 2005:7 Ohlson, Helena: The influence of landscape history, connectivity and area on species diversity in semi-natural grasslands. 2005:8 Schmalholz, Martin: Patterns of variation in abundance and fecundity in the endangered grassland annual Euphrasia rostkovia ssp. Fennica. 2005:9 Knutsson, Linda: Do ants select for larger seeds in Melampyrum nemorosum? 2006:1 Forslund, Helena: A comparison of resistance to herbivory between one exotic and one native population of the brown alga Fucus evanescens. 2006:2 Nordqvist, Johanna: Effects of Ceratophyllum demersum L. on lake phytoplankton composition. 2006:3 Lönnberg, Karin: Recruitment patterns, community assembly, and the evolution of seed size. 2006:4 Mellbrand, Kajsa: Food webs across the waterline - Effects of marine subsidies on coastal predators and ecosystems. 2006:5 Enskog, Maria: Effects of eutrophication and marine subsidies on terrestrial invertebrates and plants. 2006:6 Dahlgren, Johan: Responses of forest herbs to the environment. 2006:7 Aggemyr, Elsa: The influence of landscape, field size and shape on plant species diversity in grazed former arable fields. 2006:8 Hedlund, Kristina: Flodkräftor (Astacus astacus) i Bornsjön, en omnivors påverkan på växter och snäckor. 2007:1 Eriksson, Ove: Naturbetesmarkernas växter- ekologi, artrikedom och bevarandebiologi. 2007:2 Schmalholz, Martin: The occurrence and ecological role of refugia at different spatial scales in a dynamic world. 2007:3 Vikström, Lina: Effects of local and regional variables on the flora in the former semi-natural grasslands on Wäsby Golf club’s course. 2007:4 Hansen, Joakim: The role of submersed angiosperms and charophytes for aquatic fauna communities. 2007:5 Johansson, Lena: Population dynamics of Gentianella campestris, effects of grassland management, soil conditions and the history of the landscape 2007:6 von Euler, Tove: Sex related colour polymorphism in Antennaria dioica. 2007:7 Mellbrand, Kajsa: Bechcombers, landlubbers and able seemen: Effects of marine subsidies on the roles of arthropod predators in coastal food webs. 22 2007:8 Hansen, Joakim: Distribution patterns of macroinvertebrates in vegetated, shallow, soft-bottom bays of the Baltic Sea. 2007:9 Axemar, Hanna: An experimental study of plant habitat choices by macroinvertebrates in brackish soft-bottom bays. 2007:10 Johnson, Samuel: The response of bryophytes to wildfire- to what extent do they survive in-situ? 2007:11 Kolb, Gundula: The effects of cormorants on population dynamics and food web structure on their nesting islands. 2007:12 Honkakangas, Jessica: Spring succession on shallow rocky shores in northern Baltic proper. 2008:1 Gunnarsson, Karl: Påverkas Fucus radicans utbredning av Idotea baltica? 2008:2 Fjäder, Mathilda: Anlagda våtmarker i odlingslandskap- Hur påverkas kärlväxternas diversitet? 23