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 Svante Arrhenius väg 20 A
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 mosaiklandskap 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).

 

Ställföreträdande prefekt - BIG

Sedan Augusti 2018 är jag ställföreträdande prefekt på BIG. Prefekt är Ann-Kristin Östlund Farrants.

Forskning

Forskningsprojekt

1) Mikroklimat och extremväder - effekter på 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). Jag handleder en doktorand Ditte Marie Christiansen med finansiering från Bolin centret. Hon studerar också mikroklimat och växters utbredning och har Johan Ehrlén, Eric Meineri och Heiner Körnich som biträdande handledare.

Den torra sommaren 2018 minns vi alla. I ett projekt finansierat av Formas kommer doktorand Irena Koelemeijer att studera effekterna av extrem torka på växter (kärlväxter, mossor och lavar) i nyckelbiotoper i barrskogar i Sverige. Hon har Johan Ehlrén, Mari Jönsson (SLU), Pieter DeFrenne (Dept. of Environment, Ghent University) som biträdande handledare. 

 

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. Även dokorand Biruk Ayalew jobbar i detta studiesystem med Ayco Tack som huvudhandledare och mig som biträdande handledare. Hans fokus är mer på klimatets påverkan på dessa samspel.

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

Jag samarbetar med Prof. Joern Fischer, Leuphana University, i ett projekt om mat och biodiversitet i västra Etiopien.

 

Publikationer

I urval från Stockholms universitets publikationsdatabas
  • 2020. Caroline Greiser (et al.). Ecography

    The role of climate in determining range margins is often studied using species distribution models (SDMs), which are easily applied but have well-known limitations, e.g. due to their correlative nature and colonization and extinction time lags. Transplant experiments can give more direct information on environmental effects, but often cover small spatial and temporal scales. We simultaneously applied a SDM using high-resolution spatial predictors and an integral projection (demographic) model based on a transplant experiment at 58 sites to examine the effects of microclimate, light and soil conditions on the distribution and performance of a forest herb, Lathyrus vernus, at its cold range margin in central Sweden. In the SDM, occurrences were strongly associated with warmer climates. In contrast, only weak effects of climate were detected in the transplant experiment, whereas effects of soil conditions and light dominated. The higher contribution of climate in the SDM is likely a result from its correlation with soil quality, forest type and potentially historic land use, which were unaccounted for in the model. Predicted habitat suitability and population growth rate, yielded by the two approaches, were not correlated across the transplant sites. We argue that the ranking of site habitat suitability is probably more reliable in the transplant experiment than in the SDM because predictors in the former better describe understory conditions, but that ranking might vary among years, e.g. due to differences in climate. Our results suggest that L. vernus is limited by soil and light rather than directly by climate at its northern range edge, where conifers dominate forests and create suboptimal conditions of soil and canopy-penetrating light. A general implication of our study is that to better understand how climate change influences range dynamics, we should not only strive to improve existing approaches but also to use multiple approaches in concert.

  • 2020. Caroline Greiser (et al.). Global Change Biology

    Climate warming is likely to shift the range margins of species poleward, but fine-scale temperature differences near the ground (microclimates) may modify these range shifts. For example, cold-adapted species may survive in microrefugia when the climate gets warmer. However, it is still largely unknown to what extent cold microclimates govern the local persistence of populations at their warm range margin. We located 99 microrefugia, defined as sites with edge populations of 12 widespread boreal forest understory species (vascular plants, mosses, liverworts and lichens) in an area of ca. 24,000 km(2) along the species' southern range margin in central Sweden. Within each population, a logger measured temperature eight times per day during one full year. Using univariate and multivariate analyses, we examined the differences of the populations' microclimates with the mean and range of microclimates in the landscape, and identified the typical climate, vegetation and topographic features of these habitats. Comparison sites were drawn from another logger data set (n = 110), and from high-resolution microclimate maps. The microrefugia were mainly places characterized by lower summer and autumn maximum temperatures, late snow melt dates and high climate stability. Microrefugia also had higher forest basal area and lower solar radiation in spring and autumn than the landscape average. Although there were common trends across northern species in how microrefugia differed from the landscape average, there were also interspecific differences and some species contributed more than others to the overall results. Our findings provide biologically meaningful criteria to locate and spatially predict potential climate microrefugia in the boreal forest. This opens up the opportunity to protect valuable sites, and adapt forest management, for example, by keeping old-growth forests at topographically shaded sites. These measures may help to mitigate the loss of genetic and species diversity caused by rear-edge contractions in a warmer climate.

  • 2019. Pieter De Frenne (et al.). Nature Ecology & Evolution 3 (5), 744-749

    Macroclimate warming is often assumed to occur within forests despite the potential for tree cover to modify microclimates. Here, using paired measurements, we compared the temperatures under the canopy versus in the open at 98 sites across 5 continents. We show that forests function as a thermal insulator, cooling the understory when ambient temperatures are hot and warming the understory when ambient temperatures are cold. The understory versus open temperature offset is magnified as temperatures become more extreme and is of greater magnitude than the warming of land temperatures over the past century. Tree canopies may thus reduce the severity of warming impacts on forest biodiversity and functioning.

  • 2018. Caroline Greiser (et al.). Agricultural and Forest Meteorology 250-251, 147-158

    The majority of microclimate studies have been done in topographically complex landscapes to quantify and predict how near-ground temperatures vary as a function of terrain properties. However, in forests understory temperatures can be strongly influenced also by vegetation. We quantified the relative influence of vegetation features and physiography (topography and moisture-related variables) on understory temperatures in managed boreal forests in central Sweden. We used a multivariate regression approach to relate near-ground temperature of 203 loggers over the snow-free seasons in an area of ∼16,000 km2 to remotely sensed and on-site measured variables of forest structure and physiography. We produced climate grids of monthly minimum and maximum temperatures at 25 m resolution by using only remotely sensed and mapped predictors. The quality and predictions of the models containing only remotely sensed predictors (MAP models) were compared with the models containing also on-site measured predictors (OS models). Our data suggest that during the warm season, where landscape microclimate variability is largest, canopy cover and basal area were the most important microclimatic drivers for both minimum and maximum temperatures, while physiographic drivers (mainly elevation) dominated maximum temperatures during autumn and early winter. The MAP models were able to reproduce findings from the OS models but tended to underestimate high and overestimate low temperatures. Including important microclimatic drivers, particularly soil moisture, that are yet lacking in a mapped form should improve the microclimate maps. Because of the dynamic nature of managed forests, continuous updates of mapped forest structure parameters are needed to accurately predict temperatures. Our results suggest that forest management (e.g. stand size, structure and composition) and conservation may play a key role in amplifying or impeding the effects of climate-forcing factors on near-ground temperature and may locally modify the impact of global warming.

  • 2018. Niklas Lonnell, Kristoffer Hylander. Journal of Biogeography 45 (4), 885-894

    Aim: Dispersal range is a key factor for understanding species' persistence in dynamic landscapes. However, dispersal, especially over long distances, is inherently difficult to study. Making use of a unique system of anthropogenically disturbed, geographically isolated mires, we assessed dispersal ranges for a group of plants restricted to wet calcareous conditions via empirical studies of colonization patterns. We hypothesized that more species would have colonized the less isolated mires and that colonization frequencies would be related to traits influencing propagule pressure. Location: Sweden. Taxon: Calcicolous vascular plants and bryophytes. Methods: The study system consisted of 52 acidic mires that had acquired a high pH through active liming by the Swedish government during the past two decades. These conditions killed off mat-forming peat mosses, rendering the mires open to colonization by other species. In each mire, we recorded the presence of rich fen plant species typically found in high pH wet soils throughout the country. We used citizen science-collected records of occurrences of obligate-rich fen species surrounding each mire to examine the likely dispersal distances that were involved in creating the colonization patterns. Results: A lower proportion of vascular plants than bryophytes from their respective species pools colonized the limed mires (27% vs. 67%, p = .001). The number of colonized rich fen species per site was 0-6 for vascular plants and 10-31 for bryophytes, and was positively related to potential diaspore sources >20km from the mires (p = .026 and p = .012, respectively). The proportion of colonized mires was positively related to the species' regional frequency, but not with their diaspores' terminal velocity. Main conclusions: Many bryophyte species can effectively disperse over long distances (tens of kilometres) and variation among species in total diaspore production seems to be an important regulator of colonization across landscapes, for both vascular plants and bryophytes, in communities that are open to colonization.

  • 2018. Maria U. Johansson (et al.). Global Change Biology 24 (7), 2952-2964

    Species are often controlled by biotic factors such as competition at the warm edge of their distribution range. Disturbances at the treeline, disrupting competitive dominance, may thus enable alpine species to utilize lower altitudes. We searched for evidence for range expansion in grazed, fire-managed Ethiopian subalpine Erica heathlands across a 25-year chronosequence. We examined vascular plant composition in 48 plots (5x5m) across an altitudinal range of 3,465-3,711m.a.s.l. and analyzed how community composition changed in relation to increasing competition over time (using a Shade index based on Erica shrub height and cover) and altitude. Species habitats and altitudinal ranges were derived from literature. Time since fire explained more variation (r(2)=.41) in species composition than altitude did (r(2)=.32) in an NMDS analysis. Community-weighted altitudinal optima for species in a plot decreased strongly with increasing shade (GLM, Standardized Regression Coefficient SRC=-.41, p=.003), but increased only weakly with altitude (SRC=.26, p=.054). In other words, young stands were dominated by species with higher altitudinal optima than old stands. Forest species richness increased with Log Shade index (SRC=.12, p=.008), but was unaffected by altitude (SRC=-.07, p=.13). However, richness of alpine and heathland species was not highest in plots with lowest Shade index, but displayed a unimodal pattern with an initial increase, followed by a decrease when shading increased (altitude was not significant). Our results indicate that disturbance from the traditional patch burning increases the available habitat for less competitive high-altitude plants and prevents tree line ascent. Therefore, maintaining, but regulating, the traditional land use increases the Afro-alpine flora's resilience to global warming. However, this system is threatened by a new REDD+ program attempting to increase carbon storage via fire suppression. This study highlights the importance of understanding traditional management regimes for biodiversity conservation in cultural landscapes in an era of global change.

  • 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. Kristoffer Hylander, Sileshi Nemomissa. Diversity & distributions 23 (8), 888-897

    AimLocal extinction after habitat modifications is often delayed, leading to an extinction debt. Our first aim was to develop a conceptual model for natural and human-mediated habitat improvements after a disturbance that may waive part of the predicted extinction debt. Second, we wanted to test this model on the distribution of epiphytic plants on trees that had been isolated in the agricultural matrix after forest clearing, around which coffee subsequently had been planted with a possible improvement of the microclimate. LocationBonga, Southern Nations, Nationalities and Peoples Region (SNNPR), Ethiopia. MethodsWe studied 50 trees that had been isolated for periods ranging from a few years to half a century after clearing. The trees were now located in the agricultural landscape at different distances from intact Afromontane forests. Fourteen trees in the forests were used as references. Each tree was inventoried for all vascular epiphytic plants, mosses and liverworts. ResultsTime since clearance had a direct negative effect on number of forest specialist species via delayed extinctions and the detected large extinction debt of both bryophytes and vascular plants continued to be paid over several decades. However, time since clearance had an indirect positive effect on number of forest indicator species via the reappearance of shade from coffee planted surrounding the trees, even if the waiving effect on the extinction debt was rather small. Additionally, trees at further distances from the forest edge had fewer forest-associated species. Main conclusionsOur results show that the ability of agroecological landscapes to foster forest biodiversity may be overestimated if meta-community processes over time and space are not taken into account. However, the possibility of initiating counteracting processes that modify the level of expected local extinctions should be evaluated more often to find ways of improving conditions for biodiversity in human-modified landscapes.

  • 2017. Eric Meineri, Kristoffer Hylander. Ecography 40 (8), 1003-1013

    Large-domain species distribution models (SDMs) fail to identify microrefugia, as they are based on climate estimates that are either too coarse or that ignore relevant topographic climate-forcing factors. Climate station data are considered inadequate to produce such estimates, a viewpoint we challenge here. Using climate stations and topographic data, we developed three sets of large-domain (450 000 km(2)), fine-grain (50m) temperature grids accounting for different levels of topographic complexity. Using these fine-grain grids and the Worldclim data, we fitted SDMs for 78 alpine species over Sweden, and assessed over-versus underestimations of local extinction and area of microrefugia by comparing modelled distributions at species' rear edges. Accounting for well-known topographic climate-forcing factors improved our ability to model fine-scale climate, despite using only climate station data. This approach captured the effect of cool air pooling, distance to sea, and relative humidity on local-scale temperature, but the effect of solar radiation could not be accurately accounted for. Predicted extinction rate decreased with increasing spatial resolution of the climate models and with increasing number of topographic climate-forcing factors accounted for. About half of the microrefugia detected in the most topographically complete models were not detected in the coarser SDMs and in the models calibrated from climate variables extracted from elevation only. Although major limitations remain, climate station data can potentially be used to produce fine-grain topoclimate grids, opening up the opportunity to model local-scale ecological processes over large domains. Accounting for the topographic complexity encountered within landscapes permits the detection of microrefugia that would otherwise remain undetected. Topographic heterogeneity is likely to have a massive impact on species persistence, and should be included in studies on the effects of climate change.

  • 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
  • 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: 2 mars 2020

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