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  • 1.
    Bolmgren, Kjell
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. SLU Swedish University of Agricultural Sciences, Sweden.
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Are mismatches the norm? Timing of flowering, fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 5, p. 639-648Article in journal (Refereed)
    Abstract [en]

    The close morphological and temporal links between phases of plant growth and reproduction call for integrated studies incorporating several reproductive phases from flowering to recruitment, and associated plant-animal interactions. Phenological strategies, as well as plastic phenological response to climate change, incorporate complex interactions between developmental constraints, pollination and seed dispersal. Relationships between reproductive phenology and components of fitness were studied for two years in the north-temperate, self-incompatible, insect-pollinated, and bird-dispersed shrub Frangula alnus (Rhamnaceae). Fruit set, dispersal, germination and juvenile survival, as well as seed mass and juvenile size were measured in relation to flowering, fruiting and germination time. The results suggest that effects of flowering and fruiting time prevailed in subsequent phases, to some extent as far as to the juvenile phase, but effects of timing were complex and had partly opposing effects on different fitness components. Early flowers had higher fruit-set and experiments indicated that synchronous peak flowering increased fruit-set, but later flowers had higher seed mass. Peak fruiting was not associated with peak dispersal. Late fruits derived from late flowers promoted dispersal. Juvenile recruitment was enhanced by increasing seed size. We conclude that the phenology of flowering and fruiting in F. alnus comprises several features, each with different and sometimes counteracting effects on fitness components. From a general perspective, this result implies that we should not expect to find finely tuned matches in timing specifically between flowering and pollinators, and fruiting and seed dispersing birds.

  • 2.
    Eriksson, Ove
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bolmgren, Kjell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences, Sweden.
    Westin, Anna
    Lennartsson, Tommy
    Historic hay cutting dates from Sweden 1873-1951 and their implications for conservation management of species-rich meadows2015In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 184, p. 100-107Article in journal (Refereed)
    Abstract [en]

    Semi-natural hay meadows are species rich habitats, formed by a long history of management and they have experienced a drastic decline all over Europe. There is a vast literature on conservation and species diversity of semi-natural hay-meadows, but very limited information on historic timing of hay cutting. We analyzed data collected between 1873 and 1951 on hay cutting dates and phenology of six plant species from farms distributed across Sweden. The data set comprised 16,015 observations from 175 sites. Results show that date of start and end of hay cutting varied across Sweden. The start of hay cutting was generally delayed by 2.2 days per latitudinal degree and 1.5 days per 100 m altitude, while the end of hay cutting was generally delayed by 2.9 days per latitudinal degree and 2.5 days per 100 m altitude. The average hay cutting period was 18.5 +/- 6.6 days, and became slightly shorter northwards. Site-specific factors had a great impact on when hay cutting was performed, as indicated by a significant correlation between flowering (and leafing) phenology in other species and start date of hay cutting. Today, management for conservation is usually related to a calendar date (e.g. regulated in eligibility criteria and requirements for payment in agri-environment programs in EU). In order to mimic historic management that formed this habitat, management should instead account for latitude and altitude, between-year variation in timing of hay cutting, variation in both start and end dates of hay cutting and if possible local phenological conditions.

  • 3.
    Kullberg, Cecilia
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Fransson, Thord
    Hedlund, Johanna
    Stockholm University, Faculty of Science, Department of Zoology.
    Jonzen, Niclas
    Langvall, Ola
    Nilsson, Johan
    Bolmgren, Kjell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences SLU, Sweden.
    Change in spring arrival of migratory birds under an era of climate change, Swedish data from the last 140 years2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, p. S69-S77Article in journal (Refereed)
    Abstract [en]

    Many migratory bird species have advanced their spring arrival during the latest decades, most probably due to climate change. However, studies on migratory phenology in the period before recent global warming are scarce. We have analyzed a historical dataset (1873-1917) of spring arrival to southern and central Sweden of 14 migratory bird species. In addition, we have used relative differences between historical and present-day observations (1984-2013) to evaluate the effect of latitude and migratory strategy on day of arrival over time. There was a larger change in spring phenology in short-distance migrants than in long-distance migrants. Interestingly, the results further suggest that climate change has affected the phenology of short-distance migrants more in southern than in central Sweden. The results suggest that the much earlier calculated arrival to southern Sweden among short-distance migrants mirrors a change in location of wintering areas, hence, connecting migration phenology and wintering range shifts.

  • 4. Lindh, Magnus
    et al.
    Johansson, Jacob
    Bolmgren, Kjell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences, Sweden.
    Lundström, Niklas L. P.
    Brannström, Ake
    Jonzén, Niclas
    Constrained growth flips the direction of optimal phenological responses among annual plants2016In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 209, no 4, p. 1591-1599Article in journal (Refereed)
    Abstract [en]

    Phenological changes among plants due to climate change are well documented, but often hard to interpret. In order to assess the adaptive value of observed changes, we study how annual plants with and without growth constraints should optimize their flowering time when productivity and season length changes. We consider growth constraints that depend on the plant's vegetative mass: self-shading, costs for nonphotosynthetic structural tissue and sibling competition. We derive the optimal flowering time from a dynamic energy allocation model using optimal control theory. We prove that an immediate switch (bang-bang control) from vegetative to reproductive growth is optimal with constrained growth and constant mortality. Increasing mean productivity, while keeping season length constant and growth unconstrained, delayed the optimal flowering time. When growth was constrained and productivity was relatively high, the optimal flowering time advanced instead. When the growth season was extended equally at both ends, the optimal flowering time was advanced under constrained growth and delayed under unconstrained growth. Our results suggests that growth constraints are key factors to consider when interpreting phenological flowering responses. It can help to explain phenological patterns along productivity gradients, and links empirical observations made on calendar scales with life-history theory.

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