Stockholms universitet

Kristoffer HylanderProfessor

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. Läs mer om mina forskningsprojekt, forskargruppen och nyheter på

Från 1 aug 2021 är jag prefekt på institutionen.



Jag undervisar på kursen "Biodiversitet - mönster och processer" som ges i början av höstterminen. 



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.


Mina nuvarande forskningsprojekt fokuserar på

1) Mikroklimat och extremväder - effekter på växters utbredning och tillväxt (både kärlväxter och mossor)

Med stöd från både Formas, Tryggers stiftelse och Bolin centret för klimatforskning (se länk) forskar jag på hur man kan anpassa skogsskötseln för både sydliga och nordliga arter givet klimatförändringar. Vi undersöker effekter av extremväder och utbredningsmönster för arter och samarbetar med forskare i Frankrike och Belgien.

Läs mer om projekten, personerna och nyheter från forskargruppen här! (på engelska).


2) Biodiversitet, ekosystemtjänser i Etiopiska skogs- och jordbrukslandskap

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

Jag leder ett nytt tvärvetenskapligt projekt finansierat av VR om vatten i landskapet, hur användningen, dess kvalité och dess associerade biodiversitet varierar beroende på markanvändning. Jag är dessutom mycket involverad i två projekt ledda av Ayco Tack som handlar om hur klimatet påverkar kaffeodling, dess sjukdomar och biodiversiteten i landskapet. Dessa projekt är finansierade av VR och Bolin Centre for Climate Research.

Läs mer om projekten, personerna och nyheter från forskargruppen här! (på engelska).





I urval från Stockholms universitets publikationsdatabas

  • Forest edge effects on moss growth are amplified by drought

    2023. Irena Adia Koelemeijer (et al.). Ecological Applications


    Forest fragmentation increases the amount of edges in the landscape. Differences in wind, radiation, and vegetation structure create edge-to-interior gradients in forest microclimate, and these gradients are likely to be more pronounced during droughts and heatwaves. Although the effects of climate extremes on edge influences have potentially strong and long-lasting impacts on forest understory biodiversity, they are not well understood and are not often considered in management and landscape planning. Here we used a novel method of retrospectively quantifying growth to assess biologically relevant edge influences likely caused by microclimate using Hylocomium splendens, a moss with annual segments. We examined how spatio-temporal variation in drought across 3 years and 46 sites in central Sweden, affected the depth and magnitude of edge influences. We also investigated whether edge effects during drought were influenced by differences in forest structure. Edge effects were almost twice as strong in the drought year compared to the non-drought years, but we did not find clear evidence that they penetrated deeper into the forest in the drought year. Edge influences were also greater in areas that had fewer days with rain during the drought year. Higher levels of forest canopy cover and tree height buffered the magnitude of edge influence in times of drought. Our results demonstrate that edge effects are amplified by drought, suggesting that fragmentation effects are aggravated when droughts become more frequent and severe. Our results suggest that dense edges and buffer zones with high canopy cover can be important ways to mitigate negative drought impacts in forest edges.

    Läs mer om Forest edge effects on moss growth are amplified by drought
  • Climate adaptation of biodiversity conservation in managed forest landscapes: [Adaptación Climática de la Conservación de la Biodiversidad en Paisajes Forestales Gestionados]

    2022. Kristoffer Hylander (et al.). Conservation Biology 36 (3)


    Conservation of biodiversity in managed forest landscapes needs to be complemented with new approaches given the threat from rapid climate change. Most frameworks for adaptation of biodiversity conservation to climate change include two major strategies. The first is the resistance strategy, which focuses on actions to increase the capacity of species and communities to resist change. The second is the transformation strategy and includes actions that ease the transformation of communities to a set of species that are well adapted to the novel environmental conditions. We suggest a number of concrete actions policy makers and managers can take. Under the resistance strategy, five tools are introduced, including: identifying and protecting forest climate refugia with cold-favored species; reducing the effects of drought by protecting the hydrological network; and actively removing competitors when they threaten cold-favored species. Under the transformation strategy, we suggest three tools, including: enhancing conditions for forest species favored by the new climate, but currently disfavored by forest management, by planting them at suitable sites outside their main range; and increasing connectivity across the landscape to enhance the expansion of warm-favored species to sites that have become suitable. Finally, we suggest applying a landscape perspective and simultaneously managing for both retreating and expanding species. The two different strategies (resistance and transformation) should be seen as complementary ways to maintain a rich biodiversity in future forest ecosystems. 

    Läs mer om Climate adaptation of biodiversity conservation in managed forest landscapes
  • Changes in forest structure drive temperature preferences of boreal understorey plant communities

    2022. Ditte Marie Christiansen (et al.). Journal of Ecology 110 (3), 631-643

    1. The local climate in forest understories can deviate substantially from ambient conditions. Moreover, forest microclimates are often characterized by cyclic changes driven by management activities such as clear-cutting and subsequent planting. To understand how and why understorey plant communities change, both ambient climate change and temporal variation in forest structure have to be considered.
    2. We used inventories from 11,436 productive forest sites in Sweden repeated every 10th year 1993–2017 to examine how variation in forest structure influences changes in the average value of minimum and maximum temperature preferences of all species in a community, that is, community temperature indices (CTIs). We then evaluated to what extent these changes were driven by local extinctions and colonizations, respectively, and to what extent the difference in CTI value between two inventories was related to changes in forest density and in macroclimate. Lastly, we tested whether effects on CTI change by these two drivers were modified by topography, soil moisture and tree species composition.
    3. CTI values of the understorey plant communities increased after clear-cutting, and decreased during periods when the forest grew denser. During the period immediately after clear-cutting, changes were predominately driven by colonizations of species with a preference for higher temperatures. During the forest regeneration phase, both colonizations by species preferring lower temperatures and local extinctions of species preferring higher temperatures increased. The change in understorey CTI over 10-year periods was explained more by changes in forest density, than by changes in macroclimate. Soil moisture, topography and forest tree species composition modified to some extent the effects of changes in forest density and in macroclimate on understorey CTI values.
    4. Synthesis. Via stand manipulation, forest management impacts the effects of regional climate on understorey plant communities. This implies that forest management by creating denser stands locally even can counterbalance the effects of regional changes in climate. Consequently, interpretations of changes in the mean temperature preference of species in forest understorey communities should take forest management regimes into account.
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  • Unveiling the nature of a miniature world: a horizon scan of fundamental questions in bryology

    2022. Jairo Patiño (et al.). Journal of Bryology 44 (1), 1-34


    Introduction. Half a century since the creation of the International Association of Bryologists, we carried out a review to identify outstanding challenges and future perspectives in bryology. Specifically, we have identified 50 fundamental questions that are critical in advancing the discipline.

    Methods. We have adapted a deep-rooted methodology of horizon scanning to identify key research foci. An initial pool of 258 questions was prepared by a multidisciplinary and international working group of 32 bryologists. A series of online surveys completed by a broader community of researchers in bryology, followed by quality-control steps implemented by the working group, were used to create a list of top-priority questions. This final list was restricted to 50 questions with a broad conceptual scope and answerable through realistic research approaches.

    Key results. The top list of 50 fundamental questions was organised into four general topics: Bryophyte Biodiversity and Biogeography; Bryophyte Ecology, Physiology and Reproductive Biology; Bryophyte Conservation and Management; and Bryophyte Evolution and Systematics. These topics included 9, 19, 14 and 8 questions, respectively.

    Conclusions. Although many of the research challenges identified are not newly conceived, our horizon-scanning exercise has established a significant foundation for future bryological research. We suggest analytical and conceptual strategies and novel developments for potential use in advancing the research agenda for bryology.

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  • Forest microclimates and climate change

    2021. Pieter De Frenne (et al.). Global Change Biology 27 (11), 2279-2297


    Forest microclimates contrast strongly with the climate outside forests. To fully understand and better predict how forests' biodiversity and functions relate to climate and climate change, microclimates need to be integrated into ecological research. Despite the potentially broad impact of microclimates on the response of forest ecosystems to global change, our understanding of how microclimates within and below tree canopies modulate biotic responses to global change at the species, community and ecosystem level is still limited. Here, we review how spatial and temporal variation in forest microclimates result from an interplay of forest features, local water balance, topography and landscape composition. We first stress and exemplify the importance of considering forest microclimates to understand variation in biodiversity and ecosystem functions across forest landscapes. Next, we explain how macroclimate warming (of the free atmosphere) can affect microclimates, and vice versa, via interactions with land-use changes across different biomes. Finally, we perform a priority ranking of future research avenues at the interface of microclimate ecology and global change biology, with a specific focus on three key themes: (1) disentangling the abiotic and biotic drivers and feedbacks of forest microclimates; (2) global and regional mapping and predictions of forest microclimates; and (3) the impacts of microclimate on forest biodiversity and ecosystem functioning in the face of climate change. The availability of microclimatic data will significantly increase in the coming decades, characterizing climate variability at unprecedented spatial and temporal scales relevant to biological processes in forests. This will revolutionize our understanding of the dynamics, drivers and implications of forest microclimates on biodiversity and ecological functions, and the impacts of global changes. In order to support the sustainable use of forests and to secure their biodiversity and ecosystem services for future generations, microclimates cannot be ignored.

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  • Temporal dynamics and biocontrol potential of a hyperparasite on coffee leaf rust across a landscape in Arabica coffee's native range

    2021. Beyene Zewdie (et al.). Agriculture, Ecosystems & Environment 311


    Agroforestry systems can provide habitats for a rich biodiversity including multitrophic interactions, which presents opportunities to develop natural pest control. Shade coffee systems in several coffee growing areas of the world host such unique habitats where pests and their natural enemies interact. One of the major global challenges for coffee production, coffee leaf rust caused by the fungal pathogen Hemileia vastatrix is attacked by the fungal hyperparasite, Lecanicillium lecanii. However, we lack insights in the dynamics and biocontrol potential of the hyperparasite on coffee leaf rust from landscapes in Arabica coffee's native range. To understand the temporal dynamics across landscapes and environmental drivers of the rust and hyperparasite, and the potential for biocontrol of the rust by the hyperparasite, we studied the rust and hyperparasite during the dry and wet seasons for three consecutive years at 60 sites across a gradient of coffee management in southwestern Ethiopia. We found that coffee leaf rust was more severe during the dry season, whereas the hyperparasite was more severe during the wet season in two out of three years. The rust growth rate from the wet to the dry season transition was negatively related to the hyperparasite index during the wet season, implying a potential top-down control. Coffee leaf rust was generally more severe at lower altitudes in the dry season, whereas the hyperparasite was more severe at high altitude. The rust incidence increased with management intensity, while the hyperparasite was more common under less intensive management. This study could be interesting in that it represents a landscape where Arabica coffee originated and the rust and hyperparasite might have a long co-evolutionary history. Our findings highlight the potential of the hyperparasite to suppress the rust's growth rate from the wet to dry season transition when the rust severity could otherwise be at its peak. We show that less intensively managed landscapes with dense shade levels are likely to increase hyperparasite abundance and result in an improved top-down control of the rust. However, more detailed knowledge is needed on the interaction of these species to assess its importance for reducing rust induced yield losses or the risk of rust outbreaks.

    Läs mer om Temporal dynamics and biocontrol potential of a hyperparasite on coffee leaf rust across a landscape in Arabica coffee's native range
  • Hiding from the climate

    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.

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  • Global buffering of temperatures under forest canopies

    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.

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  • Calcicolous plants colonize limed mires after long-distance dispersal

    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.

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  • Reframing the Food-Biodiversity Challenge

    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).

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  • Waiving the extinction debt

    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.

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  • Fine-grain, large-domain climate models based on climate station and comprehensive topographic information improve microrefugia detection

    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.

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  • The mechanisms causing extinction debts

    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.

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Visa alla publikationer av Kristoffer Hylander vid Stockholms universitet