Profiles

Kristoffer Hylander

Kristoffer Hylander

Professor

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Arbetar vid Institutionen för ekologi miljö och botanik
Telefon 08-16 48 99
E-post kristoffer.hylander@su.se
Besöksadress Lilla Frescativägen 5
Rum N 418
Postadress Institutionen för ekologi miljö och botanik 106 91 Stockholm

Om mig

Jag kallar mig själv landskapsekolog och är intresserad av hur artrikedom och artsammansättning varierar i tid och rum. De flesta av mina studier är i brukade landskap - främst jobbar jag i skogslandskap i centrala Sverige och jordbrukslandskap i Etiopien. 

Undervisning

Kurser

Jag är studierektor i växtekologi på vår institution. Jag undervisar på den första grundkursen i ekologi (15 hp) på våren och på kursen "Biodiversitet - mönster och processer" som ges i mitten av hösten. 

 

Masterstudenter

Jag handleder regelbundet masterstudenter. Om du är en presumtiv sådan så titta på mina forskningsprojekt och publikationer och se om du blir intresserad av något. Det finns möjlighet att göra sitt exjobb både i Sverige och Etiopien (i det senare fallet kan man söka ett MFS-stipendium).

Forskning

Forskningsprojekt

1) Variation i lokalklimat och hur det påverkar växters utbredning och tillväxt (både kärlväxter och mossor)

Jag har ett Formas-finansierat projekt som handlar om hur man kan anpassa skogsskötseln för både sydliga och nordliga arter givet klimatförändringar. Caroline Greiser är doktorand i detta projekt med mig som huvudhandledare och Johan Ehrlén, Miska Luoto och Eric Meineri som biträdande handledare.

Jag är så kallad co-leader för RA7 (research area 7 om landskap och klimat) på Bolin centre på Stockholms universitetet (se länk). 

 

2) Biodiversitet och ekosystemtjänser i Etiopiska skogs- och jordbrukslandskap

Sen många år har jag en del av min forskning i Etiopien.

Mitt nuvarande viktigaste projekt är handlar om svampangrepp på kaffe och hur det varierar i en miljö- och brukningsgradient. Det är finansierat av VR/SIDA och Beyene Zewdie är doktorand i projektet med mig som huvudhandledare och Ayco Tack och Sileshi Nemomissa som biträdande handledare.

Jag är också värd för Maria Johansson, som är postdoc med ett eget projekt som handlar om eld, biodiversitet och kolinlagring i Etiopien.

Jag är också biträdande handledare till ett par doktorander på Addis Ababa universitet och samarbetar med Prof. Joern Fischer, Leuphana University, i ett projekt om mat och biodiversitet i västra Etiopien.

 

Publikationer

I urval från Stockholms universitets publikationsdatabas
  • 2017. Joern Fischer (et al.). Trends in Ecology & Evolution 32 (5), 335-345

    Given the serious limitations of production-oriented frameworks, we offer here a new conceptual framework for how to analyze the nexus of food security and biodiversity conservation. We introduce four archetypes of social-ecological system states corresponding to win-win (e.g., agroecology), win-lose (e.g., intensive agriculture), lose-win (e.g., fortress conservation), and lose-lose (e.g., degraded landscapes) outcomes for food security and biodiversity conservation. Each archetype is shaped by characteristic external drivers, exhibits characteristic internal social-ecological features, and has characteristic feedbacks that maintain it. This framework shifts the emphasis from focusing on production only to considering social-ecological dynamics, and enables comparison among landscapes. Moreover, examining drivers and feedbacks facilitates the analysis of possible transitions between system states (e.g., from a lose-lose outcome to a more preferred outcome).

  • 2017. Taye Jara, Kristoffer Hylander, Sileshi Nemomissa. Agriculture, Ecosystems & Environment 240, 92-100

    A recent trend in conservation biology is not only to focus on protected areas of natural vegetation but also on the management of agricultural landscapes, since these landscapes are considered to be-of vital importance for overall landscape biodiversity both through the opportunity for species to thrive there and as conduits for inter-patch dispersal. Since trees are considered to be key structures to enhance biodiversity in agricultural landscapes, we need to understand what factors regulate their occurrences. Farmers choices will decide the composition of land-uses and the associated densities and composition of trees. We compared tree density and tree species composition across eight different land use types replicated in ten agricultural landscapes in relatively humid climates of mid-altitudes (1500-2500 m asl) in Ethiopia. In each landscape five transects of 1 km divided into 50 plots of 20 x 20 m were surveyed for woody plants. Annual crop plots had a low tree density (of trees >10 cm DBH) (6 per ha), but since it generally was the most abundant land use type altogether, many tree species were still found there (4-29 per transect in the different landscapes). Most tree species had their highest relative occurrence in the perenial crops land-use type and among the different perenial crop types, plots with coffee were more species rich than plots with khat (Catha edulis) (a stimulant crop increasing in frequency); plots with Eucalyptus trees were intermediate. A few species were more associated with grazing areas and homegardens indicating that a combination of land-uses enhances the overall species diversity in these agricultural landscapes. However, if the trend of increasing areas of khat and Eucalyptus would lead to decreases in shade coffee there is a risk for severe erosion of tree density and species richness across these landscapes with cascading effects on associated biodiversity.

  • Ulrika Samnegård (et al.).

    The expansion of pollinator-dependent crops, especially in the developing world, together with reports of world-wide pollinator declines, raises concern of possible yield gaps. Farmers directly reliant on pollination services for food supply often live in regions where our knowledge of pollination services is poor. In a manipulative experiment replicated at 23 sites across an Ethiopian agricultural landscape, we found poor pollination services and severe pollen limitation in a common oil crop. With supplementary pollination, the yield increased on average by 91%. Despite the heterogeneous agricultural matrix, we found a low bee abundance, which may explain poor pollination services. The variation in pollen limitation was unrelated to surrounding forest cover, local bee richness and bee abundance. While practices that commonly increase pollinators (e.g. organic farming, flower strips) are an integral part of the landscape, these elements are apparently insufficient. Management to increase pollination services is therefore in need of urgent investigation.

  • 2016. Victor Johansson (et al.). Functional Ecology 30 (7), 1196-1204

    Understanding the complete dispersal process is important for making realistic predictions of species distributions, but mechanisms for diaspore release in wind-dispersed species are often unknown. However, diaspore release under conditions that increase the probability of longer dispersal distances and mechanisms that extend dispersal events in time may have evolutionary advantages. We quantified air humidity thresholds regulating spore release in the moss Brachythecium rutabulum. We also investigated the prevailing micrometeorological conditions when these thresholds occur in nature and how they affect dispersal distances up to 100m, using a mechanistic dispersal model. We show that moss spores were mainly released when the peristome teeth were opening, as relative air humidity (RH) decreased from high values to relatively low (mainly between 90% and 75% RH). This most often occurred in the morning, when wind speeds were relatively low. Surprisingly, the model predicted that an equally high proportion of the spores would travel distances beyond 100m (horizontally) when released in the wind conditions prevailing during events of RH decrease in the morning, that lead to peristome opening, as in the highest wind speeds. Moreover, a higher proportion of the spores reached high altitudes when released at the lower wind speeds during the morning compared to the higher speeds later in the day, indicating a possibility for extended dispersal distances when released in the morning. Dispersal in the morning is enhanced by a combination of a more unstable atmospheric surface layer that promotes vertical dispersal, and a lower wind speed that decreases the spore deposition probability onto the ground, compared to later in the day. Our study demonstrates an active spore release mechanism in response to diurnally changing air humidity. The mechanism may promote longer dispersal distances, because of enhanced vertical dispersal and because spores being released in the morning have more time to travel before the wind calms down at night. The mechanism also leads to a prolonged dispersal period over the season, which may be viewed as a risk spreading in time that ultimately also leads to a higher diversity of establishment conditions, dispersal distances and directions.

  • Artikel Microrefugia
    2015. Kristoffer Hylander (et al.). Ambio 44, s60-S68

    Microrefugia are sites that support populations of species when their ranges contract during unfavorable climate episodes. Here, we review and discuss two aspects relevant for microrefugia. First, distributions of different species are influenced by different climatic variables. Second, climatic variables differ in the degree of local decoupling from the regional climate. Based on this, we suggest that only species limited by climatic conditions decoupled from the regional climate can benefit from microrefugia. We argue that this restriction has received little attention in spite of its importance for microrefugia as a mechanism for species resilience (the survival of unfavorable episodes and subsequent range expansion). Presence of microrefugia will depend on both the responses of individual species to local climatic variation and how climate-forcing factors shape the correlation between local and regional climate across space and time.

  • 2015. Nicole J. Fenton, Kristoffer Hylander, Emma J. Pharo. Routledge Handbook of Forest Ecology, 239-249
  • 2015. Ulrika Samnegård (et al.). Agriculture, Ecosystems & Environment 211, 185-194

    A comprehensive understanding of how spatial variation across landscapes regulates local abundances and species richness also needs to consider possible temporal changes in such relationships. In many tropical areas, the contrast between dry and rainy season is pronounced and the types and distributions of the main floral resources differ (herbs vs trees). This shift in resources could result in different pollinator abundances, species richness and trait compositions between seasons, as well as in how these components are spatially distributed. We compared the bee species composition between dry and rainy season in an agricultural mosaic landscape in southwestern Ethiopia, and analyzed it in relation to forest cover. We sampled bees for 67 days in the dry season and 86 days in the rainy season with pan and vane traps in 28 homegardens covering a gradient from low to high tree cover in the surrounding area. We found a clear shift in species composition between seasons, with more small bee species and more below-ground nesting bees in the rainy season compared to the dry season. The distribution of height at which the bees were foraging shifted between seasons with a higher proportion of the bees foraging at tree level in the dry season. Bee abundance and richness were generally positively affected by higher forest cover surrounding the homegardens, but there were no clear interaction effects between seasons, in contrast to our hypothesis. The clear turnover in species composition between seasons and the positive effect of forest cover show that mechanisms acting both at spatial and temporal scales are important in regulating local bee communities.

  • 2015. Eric Meineri, C. Johan Dahlberg, Kristoffer Hylander. Ecological Modelling 313, 127-136

    Landscape physiography affects temperature, soil moisture and solar radiation. In turn, these variables are thought to determine how species are distributed across landscapes. Systems involving direct and indirect associations between variables can be described using path models. However, studies applying these to species distribution modelling are rare. Bayesian Networks are path models designed to represent associations across observed variables. Here, we demonstrate the use of Bayesian Networks to disentangle the direct and indirect associations between landscape physiography, soil moisture, solar radiation, temperature and the distribution patterns of four plants at their northern range limit in Sweden. Fine scale variations in maximum temperatures were associated with variations in elevation, distance to coast and solar radiation. In contrast, fine scale variations in minimum temperature were associated with distance to coast, cold air drainage and soil moisture. These associations between landscape physiography and minimum and maximum temperature were predicted, furthermore, to be associated with growing season length, growing degree day and ultimately species distributions. All species were indirectly associated with aspect through their responses to either solar radiation or temperature. The models demonstrated strong indirect associations between landscape physiography and species distributions. The models suggested that local variation in light can be as important as temperature for species distributions. Disentangling the direct and indirect associations between landscape physiography, environmental variables and species distribution can provide new and important insights into how landscape components are linked to species distributions.

  • 2013. Kristoffer Hylander, Johan Ehrlen. Trends in Ecology & Evolution 28 (6), 341-346

    Extinction debts can result from many types of habitat changes involving mechanisms other than metapopulation processes. This is a fact that most recent literature on extinction debts pays little attention to. We argue that extinction debts can arise because (i) individuals survive in resistant life-cycle stages long after habitat quality change, (ii) stochastic extinctions of populations that have become small are not immediate, and (iii) metapopulations survive long after that connectivity has decreased if colonization-extinction dynamics is slow. A failure to distinguish between these different mechanisms and to simultaneously consider both the size of the extinction debt and the relaxation time hampers our understanding of how extinction debts arise and our ability to prevent ultimate extinctions.

Visa alla publikationer av Kristoffer Hylander vid Stockholms universitet

Senast uppdaterad: 20 juni 2017

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