This thesis examines the use of various osseous raw materials in craft activities in the Mälaren region during the Middle Ages. Places studied are: Birka, Sigtuna, Nyköping, Strängnäs and Uppsala. The aim is to capture both chronological and spatial changes in the use of osseous raw materials. Species and materials used reflect regional as well as international networks and how they change during time. The spatial distribution of waste from craft activities, its materiality and temporality mirror activities in different social contexts.  Quantitative and qualitative changes in the handling and exploitation of raw materials reflect varying and changing views of its value and how craft and exchange is affected by both a social and economic agency. In Birka, osseous waste material associated with craft was collected by Hjalmar Stolpe in the 1870s. An examination of the assemblage shows that imported material comprises a significant part of the collection. About a third of the waste consists of imported antler of red deer and reindeer. Red deer is particularly abundant (21%), signifying the importance of southern trading networks. The presence of whalebone can also be linked to south-western trading routes. The waste material collected during excavations in Sigtuna and representing the period c. 980-1300 has a different composition, reflecting different networks and perhaps different means of trade and production. As in Birka, elk antler constitutes the main bulk of the raw material used. Red deer antler is extremely limited, forming less than 1% of the material, appearing continuously though in small amounts from c. 1020-1300.  Reindeer antler is distinctly present in the oldest phase, c. 980-1000. This occurrence might represent a relic of the northern network manifested at Birka. An isotopic study indicates an origin in a forested biotope. After this initial phase the use of reindeer antler becomes as rare as that of red deer until the second half of the 12th century, indicating that the antler craft operated on a minor scale without any demand for long-distance trade in raw materials. A change occurs in the last quarter of the 12th century when large quantities of reindeer antler appear once more. Isotope signatures indicate an origin in more mountainous regions. This coincides with the introduction of another traded raw material of an arctic origin: walrus tusk. The craft had become more marked oriented. This is manifested in larger deposits of debris, a wider range of materials used, including bones from various domestic animals, but also the handling and exploitation of the material changes indicating a different view of production, trade and the value of raw materials than previous. This shift coincides with the introduction of minted silver. Western influences are evident both in the material culture and in the faunal assemblage. It is likely that a majority of the reindeer antler as well as the walrus tusk present in these later phases have a Norwegian origin. In the late 1100s and early 1200s craft in osseous material occur in other towns that emerge in the region but it seems to appear in new social contexts. Small assemblages of antler debris have been found in Uppsala, but the activities they represent lack the spatial continuity that exist in contemporary environments in Sigtuna and Strängnäs, indicating short lived occasional activities in a loosely regulated urban environment. Craft activities dependent purely on bone from domestic animals appear in the 1200s in Nyköping, Uppsala and Strängnäs. They represent craft activities in a new social context outside the private sphere of the local elite and instead subordinated other craft activities where domestic animals have been exploited on a large scale beyond the domestic household. Antler craft represents a social practise in the realms of the local elite with a continuity stretching back to the Iron Age. Monetization and an increasingly feudal society redefine social relations and practise. This can be seen in the occurrence of craft in new contexts in the late 1100s and 1200s, reflecting heterogeneity in social and economic functions in and between the towns in the region.

The Sami people are the Natives of northern Scandinavia. The knowledge of the health and living conditions of the Swedish Sami is extremely limited which is in contrast to the large amount of detailed information on health and socioeconomic issues that is available for other circumpolar Natives. The encounter with the western society and the acculturation process has for many native populations had serious health consequences, causing a dramatic increase of lifestyle related diseases such as cancer, diabetes, stroke, obesity and hypertension as well as a dramatic increase of suicide and drug abuse. The overall objective of this thesis was to investigate the health conditions of the Sami population of Sweden using causes of death and incidences of cancer and cardiovascular diseases (CVD) as health indicators, and to evaluate their possible association with acculturative factors such as assimilation, integration, separation and marginalization. A Sami population was identified containing a total of 41 721 individuals. Specific cohorts were selected from this population for the different studies. A four times as large demographically matched non-Sami control population was used for comparisons. A study of causes of death, 1961-2000, showed small differences in overall mortality and life expectancy between the Sami and the non-Sami. However, Sami men showed significantly lower mortality risks for cancers but higher for external cause of injury and Sami women higher risks for diseases of the circulatory system (CVD) and of the respiratory system. An increased risk of dying from subarachnoid haemorrhage (SAH) was observed among both Sami men and women. The increased risk of dying from accidents among male reindeer herders is suggested to be caused by the increased socioeconomic pressure and the extensive use of terrain vehicles. It is concluded that commercial reindeer management is one of the most dangerous occupations in Sweden. In a study of the cancer risk among the reindeer herding Sami between 1961-1997, an overall lower risk to develop cancers, particularly prostate and malignant lymphoma was observed among the reindeer herding Sami. The risk for stomach cancer was significantly higher in relation to their non-Sami neighbours. The Sami and the non-Sami had similar risk factor-patterns for CVD. The main differences were related to working conditions and lifestyle factors of the reindeer herding Sami - the women showed a more unfavourable risk factor pattern than the men. Higher incidences of stroke were observed among Sami men and women compared to their non-Sami neighbours while the mortality rates of stroke were similar. The mortality ratio of AMI was increased for Sami women in spite of similar incidence ratios. A higher risk of SAH was observed among all groups of Sami. According to traditional socioeconomic risk factors, the differences in the levels of income and education observed between the Sami and the non-Sami, were poorely associated with the disparities of CVD. As has been shown, only minor differences in the health indicators were found between the Sami and their non-Sami neighbours. This is in clear contrast to several other native populations for which the health situation is largely unfavourable in comparison with that of the general population. The observed differences between the Sami and the non-Sami probably reflect differences in lifestyle, psychosocial and genetic factors. The relation between these factors and the acculturation process is dicussed, and it is suggested that separation or segregation of the reindeer herding Sami and the assimilation of the other Sami have influenced the health condition of the Sami, but with the largest impact probably prior to 1961 and the earliest start of follow-up for the studies in this thesis. Thus, the similarities in health between the Sami and the non-Sami 1961-2002, are probably a result of centuries of close interaction that has caused similarities in culture, attitudes and lifestyle, as well as equal accessibility to the health care services and the social security systems.

Human-caused ecological change negatively affects the sustainability of many wildlife populations but may be especially challenging for large carnivores and ungulates. Long-term physiological stress may be an important mechanism linking ecological change with impaired health and reduced population performance in these groups. The determination of hair cortisol concentration (HCC) has recently demonstrated potential as a biomarker of long-term stress in humans and domestic animals, and may also represent a practical technique for use in free-ranging wildlife. The objectives of this research program were to: 1) develop and apply an accurate and reliable method for measuring cortisol levels in hair collected opportunistically or remotely from free-ranging grizzly bears (Ursus arctos), polar bears (Ursus maritimus), and caribou (Rangifer tarandus sp.), and 2) to evaluate the utility of HCC as a biomarker of long-term stress (and thus potentially useful conservation tool) in these threatened species. An enzyme-immunoassay (EIA) based technique for measuring HCC in non-human primates was successfully modified for use with small quantities (5-100 mg) of hair representative of samples which may be obtained through opportunistic (e.g. hunting, research captures, archives) or remote (e.g. barb wire snagging) methods in each species. HCC was determined in 151 free-ranging grizzly bears from Alberta, Canada (mean 2.84 pg/mg, range 0.62-43.33 pg/mg); 185 free-ranging polar bears from southern Hudson Bay, Canada (mean 0.48 pg/mg range, 0.16-2.26 pg/mg); in 12 captive Alaskan caribou (R. t. granti) (mean 2.31 pg/mg, range, 1.57-3.86 pg/mg) and 12 captive reindeer (R .t. tarandus) (mean 2.88 pg/mg, range 2.21-3.40 pg/mg) injected either with adrenocorticotropic hormone (ACTH) or saline; and in 94 free-ranging caribou (R. t. groenlandicus) from West Greenland (mean 2.21 pg/mg, range 0.60-6.90 pg/mg). Factors influencing HCC in each species were then explored including: 1) technical considerations for the prudent use of HCC analysis and 2) potential relationships between HCC, biological traits, health, and prevailing environmental conditions. Evidence revealed in this study suggests that, with further research, this technique may show potential as a practical conservation tool for use in free-ranging grizzly bear, polar bear, and caribou populations.

Ph.d.-afhandling. Københavns Universitet, 2001. / Haves kun i elektronisk udg.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Abstract Plant community composition and diversity are determined by the balance between rates of immigration and extinction. Processes of immigration to a local community, i.e. propagule availability and dispersal of propagules between and within habitats, set the upper limit for the pool of species potentially capable of coexisting in a community, while local biotic interactions, i.e., competition, facilitation, herbivory and interactions with below-ground ecosystem components, and environmental factors control colonisation and establishment, and determine the persistence and dynamics of already existing species. In this thesis, I studied (1) the interactions between propagule availability, biotic and environmental constraints on colonisation, and (2) the interdependence between biotic and environmental factors regulating community processes in already established resident vegetation. First, I found that both propagule availability and competition with adult plants limited the rates of colonisation and total community diversity in a relatively low-productive tundra ecosystem. Long-term exclusion of mammalian herbivores and alleviation of nutrient limitation by fertilization increased the intensity of competition with established vegetation, and diminished immigration rates. In addition, I also found that community openness to colonization depended on the initial community properties, i.e., the functional composition and the traits of dominant plants in resident vegetation, which mediate the effects of nutrient addition and biomass removal on immigration rates. Second, adult plants in the resident vegetation experienced an increased extent of neighbourhood competition and herbivory in nutrient enriched conditions and in naturally more fertile habitats. However, the effects were also species-specific. On a community level, release from heavy grazing favoured lichens over graminoids and increased species richness. Furthermore, I also showed that plant community composition was strongly linked with soil organic matter quality and microbial community composition, and that these vegetation-soil-microbe interactions varied along a gradient of soil pH. Overall, my results emphasise that propagule availability, biotic and environmental control over community processes are strongly interconnected in tundra ecosystems. Especially, my findings highlight the role of plant competition and herbivory and their dependence on soil nutrient availability in governing colonisation and resident community dynamics. My results also indicate that plant functional composition and traits of dominant plants are of great importance in channelling community responses to external alterations and dictating plant-soil interactions.

Abstract Grazing by reindeer (Rangifer tarandus L.) affects vegetation and soil microbial processes in tundra ecosystems. It is considered that grazing can induce two alternative vegetation states that differ in plant species composition and the rate of nutrient cycling. I hypothesised that these alternative vegetation states differ in ecosystem responses to climate warming. I tested the hypothesis using a factorial warming and fertilisation experiment on long-term lightly grazed (LG) and heavily grazed (HG) tundra. The reindeer grazing induced vegetation shift from dwarf shrubs to graminoids increased microbial activities for SOM decomposition. The grazer-induced shifts in vegetation and microbial activities in combination with the fertilisation via urine and faeces had important consequences on soil N availability and soil C quality that determined the ecosystem-level consequences of climate warming. Due to higher soil N availability, warming increased plant productivity (GEP) on HG but not on LG tundra, where N limitation prevented the warming-increased plant production. The varying effects of warming on GEP at different grazing intensities determined the effects of warming on ecosystem net C sink, which was unaffected by warming on HG but decreased on LG tundra. Reindeer grazing reduced the soil C quality, as soils under LG stored a higher proportion of carbohydrates vulnerable to microbial decomposition than soils under HG. According to laboratory soil incubations, the grazer-induced reduction in soil C quality mitigated the responses of soil microbial activity to prolonged warming. Warming caused a stronger decrease in concentrations of phenolics, an important means of plant defence against biotic and abiotic stresses, in Empetrum nigrum ssp. hermaphroditum under HG than LG. Grazing history by reindeer, with the associated vegetation shift from dwarf shrubs to graminoids, can significantly alter the ecosystem-level consequences of climate warming. Overall, this thesis highlights that the effects of reindeer grazing on soil properties, soil N availability and C quality, are important determinants of the ecosystem responses to climate warming. Therefore, future research on climate warming should take into account herbivores and aim towards a more holistic approach that includes both aboveground and belowground components of the ecosystem. / Tiivistelmä Tundralla porolaidunnus vaikuttaa kasvillisuuteen ja maaperän mikrobien toimintaan. Porolaidunnus voi aikaansaada kaksi vaihtoehtoista kasvillisuuden tilaa, jotka eroavat toisistaan paitsi kasvilajiston myös ravinnekierron suhteen. Esitin hypoteesin, jonka mukaan ilmaston lämpenemisen vaikutukset eroavat tundratyypeillä, jotka edustavat vaihtoehtoisia kasvillisuustiloja. Testasin hypoteesia faktoriaalisen lämmitys- ja lannoituskokeen avulla tundra-alueilla, joilla poron laidunnuspaine on ollut pitkäaikaisesti joko kevyttä tai voimakasta. Poron aiheuttama kasvillisuusmuutos varpuvaltaisesta heinävaltaiseksi lisäsi maaperän mikrobien hajotusaktiivisuutta. Poron aiheuttamat erot kasvillisuudessa ja mikrobiaktiivisuuksissa yhdessä virtsan ja papanoiden lannoittavan vaikutuksen kanssa muuttivat maaperän typen saatavuutta sekä hiilen laatua. Erot maaperän ominaisuuksissa puolestaan ohjasivat ilmaston lämpenemisen ekosysteemitason vaikutuksia. Lämmitys kasvatti ekosysteemituotantoa ravinteikkaalla voimakkaasti laidunnetulla tundralla mutta ei kevyesti laidunnetulla tundralla, joka oli typpirajoitteinen. Lämmityksen erilaiset vaikutukset ekosysteemituotantoon eri laidunpaineissa määrittivät lämmityksen vaikutuksen ekosysteemin hiilinieluun, joka pysyi muuttumattomana voimakkaasti laidunnetulla tundralla mutta pieneni kevyesti laidunnetulla tundralla. Porolaidunnus alensi maaperän hiilen laatua, ja kevyesti laidunnetulla tundralla maaperässä oli enemmän mikrobien hajotukselle alttiita hiilihydraatteja kuin voimakkaasti laidunnetulla tundralla. Laboratoriossa suoritetun inkubaatiokokeen perusteella maaperän hiilen alhaisempi laatu lievensi mikrobien hajotusaktiivisuuden vastetta pitkäaikaiseen lämmitykseen. Lämmitys vähensi pohjanvariksenmarjan fenoliyhdisteiden, jotka ovat tärkeä osa kasvien puolustusta bioottisia ja abioottisia stressitekijöitä vastaan, pitoisuuksia enemmän voimakkaasti kuin kevyesti laidunnetulla tundralla. Poron laidunnushistoria yhdessä kasvillisuusmuutoksen kanssa voi merkittävästi vaikuttaa ilmaston lämpenemisen ekosysteemitason seurauksiin. Tämän väitöstyön tulokset osoittavat, että poron vaikutukset maaperän typpeen ja hiileen määrittävät lämpenemisen vaikutukset ekosysteemissä. Tulevaisuudessa ilmastonmuutostutkimuksen pitäisikin kokonaisvaltaisemmin huomioida sekä herbivorian että ekosysteemin eri osien merkitys.

Abstract During the past few decades in Finland, the growth of wolf (Canis lupus) and wild forest reindeer (Rangifer tarandus fennicus lönnb.) populations has created modern human-wildlife conflicts, of which the wolf conflict has expanded from a local to the EU level. The conflicts have emerged between local people and species but also between different stakeholders concerning methods of management and especially concerning the role of hunting in wolf management. The aim of this thesis is to make such conflicts more transparent and understandable. This thesis also provides suggestions regarding the governance of the conflicts. Wolf conflict data is based on a semi-structured questionnaire distributed among interest groups and open hearings among local people throughout Finland during 2004. The data of the wild forest reindeer conflict is based on a questionnaire answered by farmers in the Suomenselkä area. Methodologically, qualitative as well as quantitative tools are used. The scientific approach of this thesis is animal geography. The conflict in wild forest reindeer management is predicted by biology of species, by damages occurring in farming though also social predictors can be found. However, the conflict is solvable in nature. The wolf conflict is an example of one of the multifaceted human-wildlife conflicts where complex socioeconomical challenges are connected to each other at a local level. The specific biological abilities, the negative image of wolves and fear among people are of concern in this matter. In the society the conflict appears mostly trough stakeholders’ contradictory goals. However, the predictors of conflict between stakeholders became better understood through spatial and cultural contexts. Especially hunting developed by local elements and conservation having a non-local background, have clashed with the wolf being the major bone of contention. The wolf conflict can be defined as insolvable by nature, where the understanding of this is the key of management and mitigation processes. Because no final solution is in sight, despite constant management efforts, adaptive and learning processes are needed. / Tiivistelmä Susi on palannut Suomen eri maakuntiin 1990-luvun aikana ja muodostanut kehittyvän populaation. Sen kannan hoito on muuttunut ristiriitaiseksi kannan kasvun myötä. Konflikti siirtyi 2000-luvun alussa erilaisten intressiryhmien ja myös hallinnollisten tasojen väliseksi kamppailuksi ulottuen Suomen valtion ja EU:n väliseksi. Myös metsäpeura on palannut Suomen luontoon viime vuosikymmenien aikana. Sen kannan hoidossa koettiin ristiriitoja 1990-luvulla lähinnä sen viljelylle aiheuttamien vahinkojen vuoksi. Molemmille lajeille laadittiin 2000-luvun puolivälissä hoitosuunnitelmat, joiden tarkoituksena oli linjata näiden kannan hoitoa ja suojelua. Tämä tutkimus perustuu hoitosuunnitelmien valmistelua varten kerättyyn aineistoon, jossa pääpaino on susikonfliktissa. Metsäpeurakonfliktin roolina on tarjota vertailupohja. Tutkimusotteen voidaan määritellä kuuluvaksi eläinmaantieteen alaan, jossa tarkastellaan ihmisen ja eläinlajin välistä vuorovaikutusta pääasiassa paikallisesta ja sosioekonomisesta kontekstista. Työssä myös verrataan suomalaista susikonfliktia Yellowstonen kansallispuiston suden palautusohjelman toteutuksesta seuranneeseen kamppailuun. Siitä johdetussa teoriassa konflikti kytketään luonnonsuojelun ja sen käytön aate- ja arvopohjaan. Tutkimuksessa käytetyssä aineistossa on sekä laadullisia että määrällisiä osioita, jotka esitellään neljässä erillisessä artikkelissa. Susikonflikti on esimerkki moniulotteisesta luonnonsuojelun ja -hoidon konfliktista, johon kytkeytyy niin historia, lajin biologia, ihmisen paikallisesti kehittyneet traditiot ja kulttuuriset piirteet kuin institutionaaliset rakenteet mukaan lukien EU-jäsenyys. Tästä kokonaisuudesta on rakentunut paikallisten tahojen ja sen ulkopuolisen kokemusmaailman välinen kamppailu, jossa erilaisista intressiryhmistä ovat aktiivisimpina näkyneet metsästäjä- ja luonnonsuojelutahot. Sekä metsästykseen että lajien suojeluun liittyy useita paradoksaalisia piirteitä, jotka tekevät lajien ja suojelun kentän jännitteelliseksi. Metsäpeurakannan hoidossa esiintyneet konfliktit ovat hallittavissa, koska metsäpeuraan liittyy merkittävästi hyödyn tunne, sen ja ihmisen välille ei muodostu paikallisesti ekologista kilpailutilannetta ja myös sen aiheuttamat vahingot ovat hallittavissa. Susi kantaa mukanaan historiallista ja emotionaalista painolastia, eikä siihen liity paikallisesta näkökulmasta hyödyn tunnetta vaan lähinnä haastava asetelma. Nykyisellä suomalaisen maaseudun elinkeinorakenteella ja luonnon käytön kulttuurilla susikonfliktin hoidossa joudutaan sietämään jatkossakin ratkaisemattomia kysymyksiä. Susikonfliktin hallinnassa onkin keskeistä jatkuvasti avoin, sopeutuva ja oppiva toimintapolitiikka.

Abstract Air temperatures in high-latitude regions are anticipated to rise by several degrees by the end of the century and result in substantial northward shifts of species. These changes will likely affect the source and sink dynamics of greenhouse gases and possibly lead to a net carbon release from high-latitude soils to the atmosphere. However, regional differences in carbon cycling depend highly on the vegetation community composition, which may be controlled by the abundance of herbivores. I investigated whether mammalian herbivores, mainly reindeer and rodents, alter ecosystem carbon storage through their impacts on vegetation and on dominant plant functional traits. I combined observations of recent changes in ecosystem carbon with experimental field manipulations of both herbivory and climate change and measured carbon storage in vegetation and soil, the uptake and release of carbon dioxide, microbial activity and compared these to plant community composition. Results of my PhD thesis show that under ambient conditions, the impacts of herbivory on both above- and belowground carbon storage ranged from positive to negative. Herbivory altered dominant plant functional traits and these were fairly good predictors of the changes in soil carbon. When combined with experimental warming, herbivory continued to exert control on the dominant plant functional traits but the strong effects of warming on ecosystem carbon storage mostly concealed the impact of herbivory. Interestingly, herbivory–nutrient interactions that were not linked to dominant functional traits determined the consequences of warming on soil carbon. Taken together, I show clear and site-specific impacts of herbivores on vegetation and ecosystem carbon storage and the processes that govern them. Therefore, I suggest that an improved understanding of the role of herbivory in the global carbon cycle could improve estimations of global carbon–climate feedbacks. / Tiivistelmä Vuosisadan loppuun mennessä arktisten alueiden lämpötilan odotetaan nousevan usealla asteella ja johtavan lajien siirtymiseen yhä pohjoisemmaksi. Nämä muutokset todennäköisesti muuttavat pohjoisten ekosysteemien kykyä vapauttaa ja sitoa ilmakehän hiiltä ja saattavat johtaa siihen, että yhä enemmän hiiltä vapautuu tundramailta ilmakehään. Kuitenkin paikallisesti hiilenkierto on riippuvainen kasviyhteisöstä ja erityisesti kasvien funktionaalisista ominaisuuksista. Väitöskirjassani tutkin, voivatko herbivorit, pääasiassa porot sekä jyrsijät, muokata hiilenkiertoa muuttamalla kasvillisuutta. Tutkimuksissani seurasin kuinka alueen laidunnushistoria on muokannut hiilivarastoja ja hiilenkiertoa tällä hetkellä ja pyrin arvioimaan herbivorien vaikutusta lämpenevässä ilmastossa kokeiden avulla, joissa manipuloidaan sekä herbivoriaa että lämpötilaa tai ravinteiden saatavuutta. Tulokseni perustuvat arvioihin hiilen varastoista, hiilidioksidin vapautumisesta ja sitoutumisesta sekä mikrobien aktiivisuudesta, joita vertaan kasviyhteisöön. Tulokseni osoittavat, että herbivoria voi joko lisätä tai vähentää ekosysteemin hiilivarastoja sekä maan päällä että maan alla. Muutokset hiilivarastoissa selittyivät varsin hyvin herbivorien tuottamilla kasvillisuusmuutoksilla ja valtalajien funktionaalisilla ominaisuuksilla. Herbivoria muokkasi kasviyhteisöä myös kokeellisen lämmityksen yhteydessä, mutta lämmityksen välittömät vaikutukset hiilivarastoihin peittivät suureksi osaksi alleen herbivorian vaikutukset. Kuitenkin herbivorian ja lannoituksen kasvillisuusmuutoksista riippumattomat yhdysvaikutukset määrittivät lämpenemisen seuraukset maan hiileen. Kaiken kaikkiaan, tutkimukseni osoittaa, että herbivorit voivat paikkakohtaisesti muokata kasvillisuutta, ekosysteemin hiilivarastoja sekä hiilenkierron prosesseja. Näiden tulosten myötä ehdotan, että parempi ymmärrys herbivorian vaikutuksista maailmanlaajuisesti voisi parantaa nykyisiä ennusteita siitä, kuinka ilmaston lämpeneminen muuttaa hiilenkiertoa.

Reindeer can have strong effects on the plant species composition and functioning of tundra ecosystems, and often promote a transition towards a graminoid-dominated vegetation type. As a result, they influence many ecological processes, such as nutrient dynamics, soil biotic composition and functioning, and carbon storage. Several studies suggest that the effect of reindeer on vegetation may follow predictable patterns and could induce an alternative stable vegetation state. However, little empirical data on the long-term stability of reindeer effects on vegetation exist, as it is inherently challenging to study these ecological processes experimentally on a sufficiently long timescale. The main objective of this thesis was therefore to gain a better understanding of the long-term ecological processes following reindeer-induced vegetation shifts. In order to gain a more mechanistic insight in what initially drives this transition, I used a field-based grazing simulation experiment in which I separated defoliation, trampling, moss removal and the addition of feces. This allowed me to test the relative contribution of reindeer-related activities to initiating the shift from moss and heath- dominated tundra towards a graminoid-dominated vegetation state. Additionally, I studied the long-term ecological stability following such a vegetation shift. I did this by addressing historical milking grounds (HMGs): sites where high reindeer concentrations associated with historical traditional reindeer herding practices induced a vegetation transition from shrubs towards graminoids several centuries earlier, but which were abandoned a century ago. Studying HMGs allowed me to address: 1. The potential stability of reindeer-induced vegetation shifts; 2. The ecological mechanisms contributing to the long-term stability of these vegetation shifts; and 3. How such long-lasting vegetation changes influence soil carbon- and nutrient cycling. I found that trampling by reindeer is an important mechanism by which reindeer cause vegetation change. Addressing HMGs further revealed that this vegetation change can be hightly persistent, as the studied HMGs showed only a low encroachment at the surrounding borders in the last 50 years. The vegetation in the core areas of all studied HMGs had remained strikingly stable, and were hardly invaded by surrounding shrubs. Interestingly, soil nutrient concentrations and microbial activities were still different from the surrounding area as well, and even comparable to actively grazed areas. Even after many centuries of changed vegetation composition and soil processes, there was no difference in total carbon sequestration. This suggests that the environmental conditions for microbial decomposition were more important than vegetation composition for the soil carbon stocks, in our study site. After studying the contemporary habitat use of HMGs by reindeer and other herbivores, investigating the potential plant-soil feedbacks mechanisms and detailed soil analyses, I concluded that several ecological mechanisms contribute to the long-term stability of HMGs: first, the altered soil biotic and abiotic conditions appear to have a stronger advantage for HMG vegetation than for the surrounding tundra vegetation. Furthermore, I found a clear browsing preference of small rodents on single shrubs proliferating in HMGs, causing a strong limitation on shrub expansion. Moreover, the dense established sward of graminoids likely poses a strong direct competition for space and nutrients, hindering seedling establishment. Finally, I conclude that HMGs are highly stable on relevant ecological timescales, and propose how the concepts of historical contingency and ASS can be applied to understand stability of these reindeer-induced vegetation transitions.