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  • 1. Aarrestad, P. A.
    et al.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Masunga, G.
    Skarpe, C.
    Vegetation: Between Soils and Herbivores2014In: Elephants and Savanna Woodland Ecosystems: A Study from Chobe National Park, Botswana / [ed] Christina Skarpe, Johan T. du Toit and Stein R. Moe, Wiley-Blackwell, 2014, p. 61-88Chapter in book (Refereed)
    Abstract [en]

    The vegetation of the study area in Chobe National Park is influenced by a range of factors, including inundation by the Chobe River, soil moisture and fertility, and the impacts of different-size grazers and browsers. This chapter focuses on how the structure and species composition of the present vegetation in northern Chobe National Park is related to recent herbivory by elephants, as agents shaping the vegetation, and by mesoherbivores acting as controllers or responders, along with abiotic controllers such as soil type and distance to the river. In the study, a two-way indicator species analysis classified the vegetation data into four more or less distinct plant community groups (i) Baikiaea plurijuga-Combretum apiculatum woodland, (ii) Combretum mossambicense-Friesodielsia obovata wooded shrubland, (iii) Capparis tomentosa-Flueggea virosa shrubland and (iv) Cynodon dactylon-Heliotropium ovalifolium floodplain, named after the TWINSPAN indicator or preferential species with high cover, and the relative amount of shrubs and trees.

  • 2. Aarrestad, P. A.
    et al.
    Masunga, G. S.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Pitlagano, M. L.
    Marokane, W.
    Skarpe, C.
    Influence of soil, tree cover and large herbivores on field layer vegetation along a savanna landscape gradient in northern Botswana2011In: Journal of Arid Environments, ISSN 0140-1963, E-ISSN 1095-922X, Vol. 75, no 3, p. 290-297Article in journal (Refereed)
    Abstract [en]

    The response of the field layer vegetation to co-varying resource availability (soil nutrients, light) and resource loss (herbivory pressure) was investigated along a landscape gradient highly influenced by elephants and smaller ungulates at the Chobe River front in Botswana. TWINSPAN classification was used to identify plant communities. Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) were used to explore the vegetation-environment relationships. Four plant communities were described: Panicum maximum woodland, Tribulus terrestris woodland/shrubland, Chloris virgata shrubland and Cynodon dactylon floodplain. Plant height, species richness and diversity decreased with increasing resource availability and resource loss. The species composition was mainly explained by differences in soil resources, followed by variables related to light availability (woody cover) and herbivory, and by interactions between these variables. The vegetation structure and species richness, on the other hand, followed the general theories of vegetation responses to herbivory more closely than resource related theories. The results suggest a strong interaction between resource availability and herbivory in their influence on the composition, species richness and structure of the plant communities.

  • 3.
    Backéus, Ingvar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Var Sellingaffären kulmen på en sekellång botanisk konflikt?2018In: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 112, no 6, p. 380-393Article in journal (Refereed)
    Abstract [en]

    The 1950s saw a series of miscarriages of justice against public persons in Sweden. In one of these, the Royal Swedish Academy of Sciences tried to force Olof Selling from his professorship in paleobotany at the Swedish Museum of Natural History, on the basis of mental illness, but this failed after a long and public calamity. In his book Naturen inför rätta [Nature facing trial], Keith Wijkander (2017) claims that Selling was the victimof a century-long conflict between botanists in Uppsala and Stockholm,and places Selling in the Uppsala camp. We try to give a more balanced picture of the relationships between plant ecology in Uppsala and Stockholm during the early 20th century. R. Sernander, L.-G. Romell and G. E. Du Rietz are among the main actors. The fierce debates between the two camps make this an interesting period in Swedish botany.

  • 4. Hilmo, Olga
    et al.
    Ely-Aastrup, Hilde
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Holien, Håkon
    Population characteristics of old forest associated epiphytic lichens in Picea abies plantations in the boreal rainforest of Central Norway2011In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 41, no 9, p. 1743-1753Article in journal (Refereed)
    Abstract [en]

    The boreal rainforest in Central Norway is rich in rare and (or) red-listed epiphytic lichens but is subject to forest harvesting. Natural old Picea abies (L.) H. Karst. forests have been replaced increasingly by dense, even-aged plantations. This study aims at increasing our knowledge about populations of old forest associated lichens in P. abies plantations. In differently aged plantations, we measured occurrence of six lichen species and the population size and reproductive effort of :five lichen species. We found that the success of colonizing plantations differed because of species-specific constraints and needs, and that species occurrence depended on stand age and branch quality. A high number of reproducing thalli and small juvenile thalli of the cyanolichen Lobaria scrobiculata (Scop.) DC. and the pendulous lichen Ramalina thrausta (Ach.) Nyl. suggest effective recruitment within plantations. The populations of the cyanolichens Lobaria pulmonaria (L.) Hoffm. and Pseudocphellaria crocata (L.) Vain, were too small to be viable and demand special concern to survive in managed forests. The abundance of old forest associated lichens in a managed boreal rainforest could be promoted by a varied and heterogeneous branch structure, increased rotation periods (increase the value of plantations as propagule sources), small clearcuts and retention trees (shorten the distance between sources of propagules and target substrate), and maintaining Salix and Sorbus trees (important host trees for cyanolichens and thereby important dispersal sources).

  • 5.
    Hytteborn, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Svensson, Brita M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Kempe, Kerstin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Press, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Century-long tree population dynamics in a deciduous forest stand in central Sweden2017In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 28, no 5, p. 1057-1069Article in journal (Refereed)
    Abstract [en]

    Question: We quantify tree dynamics over a century of free development in a small broadleaved forest dominated by Fraxinus excelsior and Ulmus glabra. What are the internal and external factors driving the changes, and how predictable are they? What were the time scale and effects of the spread of Dutch elm disease (DED)? Location: Vårdsätra, eastern central Sweden.

    Methods: The survival, growth and recruitment of all trees (≥ 12 cm in girth) were monitored in 1912, 1967, 1988 and 2013 (more often for a part of the forest). Woody species in the field and shrub layers were surveyed in permanent plots in 1976 and 2012. We used transition matrix models to project changes in population sizes and species composition within the century and for 2050.

    Results: The results indicate that the forest was in a successional development during the first period. The species composition had stabilised by 1967, except for an expansion of Acer platanoides and the drastic effect of DED that struck the forest around 2000. It took only a decade to kill virtually all large elms in the forest, leading to strong decrease in stem density and basal area. The evidence for effects of DED is still weak, but there has been an increase in saplings, notably of Fraxinus, Prunus padus, Ulmus, and of shoots of Corylus avellana. Several species that are abundant in the vicinity and as seeds fail to establish (Picea abies, Betula spp., Quercus robur, Populus tremula). Projections for 2050 based on the third period (1988-2013) are probably unrealistic since also Fraxinus may disappear because of the recent arrival of the ash dieback.

    Conclusions: Slow dynamics in forests that could follow from climate change will locally probably be overruled by unforeseen catastrophes, such as invasions by forest pathogens. These initiate changes with long lag phases difficult to quantify. Still, a dense deciduous forest can resist invasion of colonist species and of regionally dominant conifers; the reason being unfavourable conditions for establishment rather than dispersal limitation

  • 6.
    Hytteborn, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Verwijst, Theo
    Small-scale disturbance and stand structure dynamics in an old-growth Picea abies forest over 54 yr in central Sweden2014In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 25, no 1, p. 100-112Article in journal (Refereed)
    Abstract [en]

    QuestionsCan assumptions of the existence of spatially distinct patches (delineated structurally homogeneous parts of the forest, being either areas consisting of canopy trees or areas without canopy trees but in an early or later regenerative phase) and of directional development over time of the vegetation in such patches, as implied by current theory of storm gap dynamics, be verified by remapping previous study sites? LocationNatural, unmanaged boreo-nemoral spruce-dominated forest in eastern central Sweden. MethodsBy re-mapping three plots, ca, 50yr after the first inventory, we studied the structure and dynamics of gaps (patches without canopy tree cover) and major tree populations. The old and new maps allowed us to compare two independent assessments of the forest dynamics: one based on tree population changes and one on changes in gap area over time. ResultsThe current population structure could partly be described through the earlier-encountered structures of the different tree populations and consecutive processes of recruitment and mortality. However, the re-mapping exercise showed that spatially delineated patches did not develop directionally over time, nor was their development spatially discrete. ConclusionsPatch dynamics proceeds in such a way that the fate of a single patch may depend on the development of neighbouring patches. As gaps may partly close or merge into larger gaps, and as gap disappearance rate is a function of actual gap size, performance of an initially delimited patch is largely determined by developments in neighbouring patches and cannot be predicted from its momentary patch characteristics. Consequently, we propose an open matrix model' to describe the changes in a boreo-nemoral spruce forest, rather than a storm gap dynamics' model.

  • 7.
    Kaarlejärvi, Elina
    et al.
    Department of Ecology and Environmental Sciences, Umeå University.
    Baxter, Robert
    School of Biological and Biomedical Sciences, University of Durham.
    Hofgaard, Annika
    Norwegian Institute for Nature Research,Trondheim.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Khitun, Olga
    Department of Biological and Environmental Sciences, University of Gothenburg.
    Molau, Ulf
    Department of Biological and Environmental Sciences, University of Gothenburg.
    Sjögersten, Sofie
    School of Biosciences, University of Nottingham.
    Wookey, Philip
    Department of Geography, University of Sheffield.
    Olofsson, Johan
    Department of Ecology and Environmental Sciences, Umeå University.
    Effects of warming on shrub abundance and chemistry drive ecosystem-level changes in a forest-tundra ecotone2012In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 15, no 8, p. 1219-1233Article in journal (Refereed)
    Abstract [en]

    Tundra vegetation is responding rapidly to on-going climate warming. The changes in plant abundance and chemistry might have cascading effects on tundra food webs, but an integrated understanding of how the responses vary between habitats and across environmental gradients is lacking. We assessed responses in plant abundance and plant chemistry to warmer climate, both at species and community levels, in two different habitats. We used a long-term and multisite warming (OTC) experiment in the Scandinavian forest–tundra ecotone to investigate (i) changes in plant community composition and (ii) responses in foliar nitrogen, phosphorus, and carbon-based secondary compound concentrations in two dominant evergreen dwarf-shrubs (Empetrum hermaphroditum and Vaccinium vitis-idaea) and two deciduous shrubs (Vaccinium myrtillus and Betula nana). We found that initial plant community composition, and the functional traits of these plants, will determine the responsiveness of the community composition, and thus community traits, to experimental warming. Although changes in plant chemistry within species were minor, alterations in plant community composition drive changes in community-level nutrient concentrations. In view of projected climate change, our results suggest that plant abundance will increase in the future, but nutrient concentrations in the tundra field layer vegetation will decrease. These effects are large enough to have knock-on consequences for major ecosystem processes like herbivory and nutrient cycling. The reduced food quality could lead to weaker trophic cascades and weaker top down control of plant community biomass and composition in the future. However, the opposite effects in forest indicate that these changes might be obscured by advancing treeline forests.

  • 8.
    Lokken, Jorn Olav
    et al.
    Norwegian Inst Nat Res, POB 5685, NO-7485 Trondheim, Norway;Norwegian Univ Sci & Technol, Dept Biol, Trondheim, Norway.
    Hofgaard, Annika
    Norwegian Inst Nat Res, POB 5685, NO-7485 Trondheim, Norway.
    Dalen, Linda
    Norwegian Environm Agcy, Trondheim, Norway.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Grazing and warming effects on shrub growth and plant species composition in subalpine dry tundra: An experimental approach2019In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 30, no 4, p. 698-708Article in journal (Refereed)
    Abstract [en]

    Questions

    Vegetation in the forest–tundra ecotone faces changes in both climate and land‐use. While climate warming is an important driver of vegetation growth and composition, herbivory may have opposing effects. In the present study, we experimentally test how removal of sheep herbivory affects the vegetation in an alpine forest–tundra ecotone, and how responses are manifested at higher temperatures.

    Location

    Dovre Mountains, Central Norway.

    Methods

    Shrub growth (height and cover) and ground layer composition were analysed each third year over an 18‐year period in a nested, three‐factorial experiment (ambient temperature and herbivory; ambient temperature and no herbivory; increased temperature and no herbivory). Fencing and open‐top‐chambers were used as expedients. Treatment effects and interactions over time were analysed using linear mixed effects models and ordination.

    Results

    Shrub height and cover increased over time due to reduced herbivory, but without additional warming effect. Lichen cover declined in all treatments over time, but more rapidly and earlier under warming treatment (significant after three years). Contrary to expectations, there was no statistically significant increase in woody species due to warming, although evergreen woody species displayed a trend shift after six years, comprising a sharp decline towards year twelve. Litter accumulated in all treatments, but at higher rates under warming (significant after nine years).

    Conclusions

    Our results disclose removal of sheep herbivory as a prominent driver of shrub growth, with warming as a subordinate driver in the studied alpine vegetation. The warming‐driven increased litter abundance may, however, be caused by the decrease of wind inside chambers and the subsequent absence of wind‐driven removal of litter. This chamber effect and the displayed timing differences in vegetation responses call for the critical use of short‐term experimental data in predictions of long‐term consequences of environmental change.

  • 9. Moe, S. R.
    et al.
    Rutina, L.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Du Toit, J. T.
    Impala as Controllers of Elephant-Driven Change within a Savanna Ecosystem2014In: Elephants and Savanna Woodland Ecosystems: A Study from Chobe National Park, Botswana / [ed] Christina Skarpe, Johan T. du Toit and Stein R. Moe, Wiley-Blackwell, 2014, p. 154-171Chapter in book (Refereed)
    Abstract [en]

    To understand ecosystem structure and dynamics we need more knowledge of how common species affect ecosystem dynamics. In this context, impala are especially interesting in the Chobe ecosystem, where they are now common but were much less so just a few decades ago. The chapter uses the Chobe ecosystem as a case-study to explore the possibility that the recovery of the elephant population has created habitat that favours impala. The authors hypothesise that, following changes in plant structure and species composition along the Chobe river caused by increasing numbers of elephant, the impala population grew substantially and is currently preventing the shrubland from reverting to its previous woodland state. The conceptual framework used in the chapter is that of Pickett et al., in which elephants function as agents responsible for the change in state. Species other than impala can also play a role in seedling predation in African Savannas.

  • 10.
    Pedrotti, E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ingmar, T.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Turunen, P.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Granath, Gustaf
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Fine-scale dynamics and community stability in boreal peatlands: revisiting a fen and a bog in Sweden after 50 years2014In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 5, no 10, p. 133-Article in journal (Refereed)
    Abstract [en]

    Multi-decadal studies of community and ecosystemdynamics are rare; however, this time frame is most relevant for assessing the impact of anthropogenic influences and climate change on ecosystems. For this reason, we investigated changes in vegetation and microtopography over 52 years in two contrasting mire ecosystems, one ombrotrophic (bog) and one minerotrophic (fen), representing different successional stages and contrasting hydrological settings. In both peatlands, floristic composition was recorded in the same permanent plots (n = 55-56, 0.25 m(2)) in both 1960 and 2012 and microtopography was mapped over a large area (ca. 2500 m(2)) that encompassed these same plots. We quantified and compared the community-level changes and internal spatial dynamics, tested associations between pH/microtopography and community/species change, and examined how the area and location of hummock microforms had changed over time. The bog exhibited little site level change in vegetation, where few species changed significantly in cover and plot frequency. However, detailed analyses revealed some large within-plot changes over time in the bog, illustrating that bogs can be highly dynamic systems at a fine scale. In contrast, the rich fen experienced a clear directional change; specifically, bryophyte abundance decreased by 70% and brown mosses were almost extinct. Although pH had decreased over time at the rich fen, this decrease at the plot-level was not associated with the decline of brown moss abundance. The microtopographic structure did not change substantially at the bog where similar to 70% was covered by lawn/hummocks; however, in the rich fen hummocks expanded (from 10% to 16% cover) and moved or expanded down slope. Our study suggests, that at the site-level, the bog ecosystem was more resistant to environmental changes over time compared to the rich fen, as evidenced by shifts in vegetation and microtopography. The contrasting scales of vegetation dynamics observed within a bog (i.e., within-plot changes vs. site-level) indicate that plant-environment feedbacks contribute to the peatland level stability. While in rich fens, internal feedbacks may be weaker and the ecosystem's vegetation and microtopographic structure are vulnerable to shifting hydrological fluxes.

  • 11. Skarpe, C.
    et al.
    Bergström, R.
    Makhabu, S.
    Rooke, T.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Danell, K.
    Plant-Herbivore Interactions2014In: Elephants and Savanna Woodland Ecosystems: A Study from Chobe National Park, Botswana / [ed] C. Skarpe, J. T. du Toit and S. R. Moe, Wiley-Blackwell, 2014, p. 189-206Chapter in book (Refereed)
    Abstract [en]

    To a casual observer, the importance of large herbivores for ecosystem structure and dynamics can seem more obvious in African savannas than in many other ecosystems because of their high abundance, diversity and species richness of ungulates. African savannas have also had a long uninterrupted history of mammalian herbivory, leading to the evolution of plant traits adapted to herbivory and to reciprocal traits in herbivores. In nutrient-poor savannas such as those on Kalahari sand in the Chobe National Park, Botswana, elephants, Loxodonta africana, are a main agent creating spatial and temporal variation in the vegetation and ecosystems. Within this framework, elephants and smaller herbivores interact with individual plants and plant populations, exploiting and modifying heterogeneity at many scales. Intermittent grazing in systems of migratory or highly mobile herbivores provides food plants with a recovery period, and could be one reason for the 'success' and abundance of many migratory herbivore species.

  • 12. Skarpe, C.
    et al.
    Hytteborn, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Moe, S. R.
    Aarrestad, P. A.
    Historical Changes of Vegetation in the Chobe Area2014In: Elephants and Savanna Woodland Ecosystems: A Study from Chobe National Park, Botswana / [ed] Christina Skarpe, Johan T. du Toit and Stein R. Moe, Wiley-Blackwell, 2014, p. 43-60Chapter in book (Refereed)
    Abstract [en]

    Elephants are the main agent shaping the vegetation (substrate), whereas soil properties and, at a larger scale, climate constitute major controllers of elephants' activities and of their effects on vegetation. However, elephants have not been the only agents of change in the Chobe ecosystem and its vegetation during the 150 or more turbulent years covered by this chapter. There have been others. The chapter discusses the vegetation dynamics that took place concurrently with the fall and rise of the elephant population following the ivory hunt in the end of the 20th century, and explains the relative importance of elephants, smaller herbivores and direct human impact through logging, burning and livestock grazing in causing these changes. The fall and rise of the Chobe elephant population during the last 150 or so years, has affected the vegetation on the relatively nutrient rich alluvium differently from that on the nutrient-deficient sand.

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