Profiles

Kristoffer Hylander

Kristoffer Hylander

Professor

Visa sidan på svenska
Works at Department of Ecology, Environment and Plant Sciences
Telephone 08-16 48 99
Email kristoffer.hylander@su.se
Visiting address Svante Arrhenius väg 20 A
Room N 418
Postal address Institutionen för ekologi miljö och botanik 106 91 Stockholm

About me

I am a landscape ecologist with an interest in patterns and determinants of species richness and composition in space and time in both natural and human modified landscapes. I have most experience from forest systems (boreal forest and montane tropical forests), but have also been studying tropical agricultural landscapes.

Teaching

Courses

I am director of studies in plant ecology at our department. I also teach on the basic ecology course (15 ect) for biologists and biology-geography students. I am also involved in several other courses, especially the master course "Biodiversity - patterns and processes" that is given in the autumn.

 

Master students

I supervise master students regularly. If you are a student: check my research projects and see if you get inspired to do a project on landscape ecology in Sweden or perhaps in Ethiopia. If you would like to do it in Ethiopia there is a posibility to apply for an MFS-grant.

Research

My current research is mostly focusing on

 

1) Variation in local climate and how that affects the performance and distribution of plants (both vascular plants and bryophytes)

Under this theme I do research through the Bolin centre for climate research at Stockholm University (see link). I have a Formas-financed project entitled "Adaptation to climate change for both northern and southern species".

Caroline Greiser is a PhD-student in this project with me as main supervisor and Johan Ehrlén, Miska Luoto and Eric Meineri as co-supervisors.

I am co-leader for RA7 (research area 7 about landscape and climate) in the Bolin centre for climate research at Stockholm University (see link). I supervise one PhD-student, Ditte Marie Christiansen, with support from the Bolin centre. She also study microclimate and plant distributions in a climate change and landuse context and have Johan Ehrlén, Eric Meineri and Heiner Körnich as co-supervisors.  

2) Biodiversity and Ecosystem services across Ethiopian agroecosystems

I have much involvement in Ethiopia since many years now.

My most recent project is entitled "Managing coffee to increase farmers' livelihood and biodiversity in Ethiopia". It is financed by VR/SIDA and we study fungal pathogens on coffee along a gradient from plantation coffee to forest coffee in SW Ethiopia.

Beyene Zewdie is a PhD-student in the project with me as main supervisor and Ayco Tack and Sileshi Nemomissa as co-supervisors.

I am also host for Maria Johansson, who is a postdoc with an own project on fire, biodiversity and carbon in Ethiopia.

Moreover I collaborate with Prof. Joern Fischer, Leuphana University, on a project on food security and biodiversity in Ethiopia

Publications

A selection from Stockholm University publication database
  • 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.

  • 2016. Ulrika Samnegård (et al.). Proceedings of the Royal Society of London. Biological Sciences 283 (1838)

    The expansion of pollinator-dependent crops, especially in the developing world, together with reports of worldwide 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 (restricted pesticide use, 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. Hendrik Haenke (et al.). Land use policy 59, 111-120

    After the severe droughts in the 1970s and 1980s, and subsequent debates about desertification, analyses of satellite images reveal that the West African Sahel has become greener again. In this paper we report a study on changes in tree cover and tree species composition in three village landscapes in northern Burkina Faso, based on a combination of methods: tree density change detection using aerial photos and satellite images, a tree species inventory including size class distribution analysis, and interviews with local farmers about woody vegetation changes. Our results show a decrease in tree cover in the 1970s followed by an increase since the mid-1980s, a pattern correlating with the temporal trends in rainfall as well as remotely sensed greening in the region. However, both the inventory and interview data shows that the species composition has changed substantially towards a higher dominance of drought-resistant and exotic species. This shift, occurring during a period of increasing annual precipitation, points to the complexity of current landscape changes and questions rain as the sole primary driver of the increase in tree cover. We propose that the observed changes in woody vegetation (densities, species composition and spatial distribution) are mediated by changes in land use, including intensification and promotion of drought tolerant and fast growing species. Our findings, which indicate a rather surprising trajectory of land cover change, highlight the importance of studies that integrate evidence of changes in tree density and species composition to complement our understanding of land use and vegetation change trajectories in the Sahel obtained from satellite images. We conclude that a better understanding of the social-ecological relations and emerging land use trajectories that produce new types of agroforestry parklands in the region is of crucial importance for designing suitable policies for climate change adaptation, biodiversity conservation and the sustainable delivery of ecosystem services that benefit local livelihoods in one of the world's poorest regions.

  • Article 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.

Show all publications by Kristoffer Hylander at Stockholm University

Last updated: August 15, 2018

Bookmark and share Tell a friend