Linking community dynamics with ecosystem processes in tundra Conceptual, empirical and methodological approaches

In low-productive tundra systems, both small and large herbivores exert strong control over plant biomass and community composition. They may also modulate ecosystem process rates, including availability and cycling of nutrients and soil decomposition rates. However, evidence from different tundra systems is highly idiosyncratic, with reports of both deceleration and acceleration of ecosystem process rates in response to herbivore presence. Acceleration of process rates contradicts dynamics predicted by prevailing theories of herbivore-plant-soil interactions, which assume primacy of selective foraging and defection/urination in driving ecosystem process rates. In many tundra systems, such assumptions should therefore be re-evaluated. In my thesis, I used empirical (Chapters I and II) and conceptual (Chapters II and IV) approaches to address this research gap. I studied the effects of prominent activities small rodents and large ungulates - non-selective dwarf-shrub decimation and trampling, respectively - which up until now have barely been addressed in tundra. The dearth of research on spatially explicit interlinkages between small rodents, plants and soil may partially result from a lack of cost-efficient methods to estimate in situ rodent abundances. Therefore, I developed a novel method to study small rodent populations (Chapter III) that could augment current methods and allow addressing small rodent-plant-soil dynamics with small spatial grain and large extent. I provided both observational and experimental evidence that small rodents decimate poorly palatable dwarf-shrubs during their population peaks. An exceptionally strong vole and lemming peak resulted in severe plant decimation across a productivity gradient, as temporarily relaxed top-down control of predators allowed for strong herbivore-plant interactions in the productive tundra-forest ecotone (Chapter I). I showed, for the first time, that such decimation of dominant dwarf-shrubs can promote higher ecosystem process rates, indicated by increased community-level plant N content, increased soil inorganic N content and increased litter decomposition rates (Chapter II). In Chapter III, I assessed the ability of a near-infrared reflectance spectroscopy (NIRS) -based method to identify individual rodent fecal pellets to species. The model predictions were highly accurate especially with feces exposed to ambient weather. Moreover, I showed that a model based on feces from two regions predicted accurately samples from both regions, indicating feasibility of inter-regional or circumpolar calibrations. Ungulate trampling may contribute to tundra state-shifts towards accelerated process rates, yet little empirical knowledge and no conceptual synthesis exists of trampling effects on tundra soils. In Chapter IV, I review original papers on trampling effects on tundra soil structure, biota, microclimate and biogeochemistry, and present a conceptual model on ungulate trampling effects on tundra soils. Trampling may drive changes in process rates by e.g. compacting soil, altering soil fauna and microbiota, and by modulating plant-soil feedbacks. In tundra, trampling may accelerate process rates especially by reducing insulating bryophyte cover, which increases soil temperatures and promotes temperature-limited microbial activity and decomposition. I conclude that Arctic herbivores are likely to alter ecosystem process rates through both trophic and non-trophic activities, the latter being overlooked in prominent theories. Especially non-trophic or non-selective activities may be key to accelerated process rates. A realistic view on herbivore effect on tundra ecosystem function now and under a warming climate needs to build on a better understanding of small rodent and ungulate effects on soil, as well as an explicit consideration of all salient herbivore activities and their multiple roles.Pienet ja suuret kasvinsyöjät kontrolloivat voimakkaasti kasvillisuuden biomassaa ja yhteisörakennetta perustuotannoltaan alhaisissa tundraekosysteemeissä. Kasvinsyöjät vaikuttavat myös ekosysteemiprosesseihin ja niiden nopeuteen, kuten ravinteiden saatavuuteen ja kiertoon sekä orgaanisen aineksen hajotustoimintaan maaperässä. Tutkimustulokset tundralta viittaavat siihen, että kasvinsyöjät voivat sekä nopeuttaa että hidastaa ekosysteemiprosesseja; prosessien nopeutuminen on kuitenkin ristiriidassa vallitsevien, kasvinsyöjien kasvillisuus- ja ekosysteemivaikutuksia käsittelevien teorioiden kanssa. Prosessien hidastumista ennustavien teorioiden taustalla on oletus siitä, että valikoiva ravinnonkäyttö ja ulosteet/virtsa ovat kasvinsyöjien vaikutuksia välittävistä mekanismeista voimakkaimmat. Monilla tundra-alueilla nämä taustaoletukset on kuitenkin syytä kyseenalaistaa. Väitöskirjassani keskityin tähän tutkimusaukkoon käyttäen empiirisiä (luvut I ja II) ja käsitteellisiä (luvut II ja IV) lähestymistapoja. Tutkin sekä pienjyrsijöiden eivalikoivan varpujen katkomisen että suurten laiduntajien tallauksen (ns. ei-trofinen mekanismi) kasvillisuus- ja ekosysteemivaikutuksia, joita on tätä ennen tutkittu tundralla vain vähän. Kehitin lisäksi uuden, kustannustehokkaan menetelmän pienjyrsijäpopulaatioiden tutkimukseen (luku III): menetalmä voi mahdollistaa pienjyrsijöiden, kasvillisuuden ja maaperän in situ vuorovaikutusten tutkimisen ja parantaa jyrsijäpopulaatioiden seurannan maantieteellistä kattavuutta ja tarkkuutta. Väitöskirjani havainnollinen ja kokeellinen aineisto osoitti että pienjyrsijät katkovat ravintona heikkolaatuisia tai syömäkelvottomia varpuja populaatiohuippujensa aikana. Harvinaisen voimakas myyrä- ja sopulihuippu johti näiden varpujen hävitykseen maisematasolla ja halki tuottavuusgradientin, sillä petojen heikko ja viivästynyt saalistusvaste mahdollisti kasvinsyöjien voimakkaan vaikutuksen kasvillisuuteen myös tuottavassa puurajan ekotonissa (luku I). Osoitin ensimmäistä kertaa että tällainen dominanttien varpujen hävittäminen voi nopeuttaa ekosysteemiprosesseja, ts. johtaa kasviyhteisön korkeampaan typen pitoisuuteen, maaperän korkeampaan epäorgaanisen typen pitoisuuteen ja kohonneeseen karikkeen mikrobihengitykseen (luku II). Luvussa III osoitin että NIR-spektroskopian (NIRS) avulla pienjyrsijöiden yksittäiset papanat voi tunnistaa suvun ja lajin tarkkuudella. Kehittämäni malli tunnisti erityisen hyvin papanat, joita oli kokeellisesti altistettu sääoloille: tämä viittaa menetelmän soveltuvan maastosta kerättyihin papanoihin. Lisäksi osoitin että eri alueilta kerättyihin papanoihin perustuva malli tunnistaa papanat molemmilta alueilta: laajan alueellisen tai sirkumpolaarisen mallin kehittäminen voi siis olla mahdollista. Laiduntajien tallaus voi aiheuttaa ekosysteemitilan muutoksia ja ekosysteemiprosessien nopeutumista tundralla, mutta aiheesta on vain vähän empiiristä tietoa eikä yhtään käsitteellistä synteesiä. Luvussa IV tein kirjallisuuskatsauksen tallauksen vaikutuksista tundran maaperän rakenteeseen, eliöstöön, mikroilmastoon ja biogeokemiaan ja kehitin käsitemallin laiduntajien tallauksen maaperävaikutuksista. Tallaus voi vaikuttaa ekosysteemiprosesseihin tiivistämällä maata, muuttamalla maaperäeliöstön yhteisöjä ja muokkaamalla kasvi-maaperävuorovaikutuksia. Tallaus voi nopeuttaa ekosysteemiprosesseja etenkin ohentamalla eristävän sammalkerroksen paksuutta, mikä voi nostaa maaperän lämpötilaa ja johtaa lämpötilarajoitteisen mikrobitoiminnan nopeutumiseen. Johtopäätöksenäni esitän että arktiset kasvinsyöjät voivat muokata ekosysteemiprosesseja paitsi valikoivan ravinnonkäytön ja ulosteiden/virtsan kautta, myös tutkimieni ei-valikoivien ja ei-trofisten mekanismien välityksellä. Tällaiset eitrofiset tai ei-valikoivat mekanismit voivat olennaisesti vaikuttaa ekosysteemiprosessien nopeutumisen taustalla. Realistisen kuvan kasvinsyöjien vaikutuksesta tundran ekosysteemien toimintaan – nyt ja lämpenevässä ilmastossa – on siksi huomioitava myös ei-trofiset ja ei-valikoivat mekanismit, ja tunnistettava kasvinsyöjien moninaiset roolit osana tundran ekosysteemejä

Novel frontier in wildlife monitoring: Identification of small rodent species from fecal pellets using near-infrared reflectance spectroscopy (NIRS)

Small rodents are prevalent and functionally important across the world's biomes, making their monitoring salient for ecosystem management, conservation, forestry, and agriculture. There is a growing need for cost-effective and noninvasive methods for large-scale, intensive sampling. Fecal pellet counts readily provide relative abundance indices, and given suitable analytical methods, feces could also allow for the determination of multiple ecological and physiological variables, including community composition. In this context, we developed calibration models for rodent taxonomic determination using fecal near-infrared reflectance spectroscopy (fNIRS). Our results demonstrate fNIRS as an accurate and robust method for predicting genus and species identity of five coexisting subarctic microtine rodent species. We show that sample exposure to weathering increases the method's accuracy, indicating its suitability for samples collected from the field. Diet was not a major determinant of species prediction accuracy in our samples, as diet exhibited large variation and overlap between species. fNIRS could also be applied across regions, as calibration models including samples from two regions provided a good prediction accuracy for both regions. We show fNIRS as a fast and cost-efficient high-throughput method for rodent taxonomic determination, with the potential for cross-regional calibrations and the use on field-collected samples. Importantly, appeal lies in the versatility of fNIRS. In addition to rodent population censuses, fNIRS can provide information on demography, fecal nutrients, stress hormones, and even disease. Given the development of such calibration models, fNIRS analytics could complement novel genetic methods and greatly support ecosystem- and interaction-based approaches to monitoring

Novel frontier in wildlife monitoring : Identification of small rodent species from fecal pellets using near-infrared reflectance spectroscopy (NIRS)

Small rodents are prevalent and functionally important across the world's biomes, making their monitoring salient for ecosystem management, conservation, forestry, and agriculture. There is a growing need for cost-effective and noninvasive methods for large-scale, intensive sampling. Fecal pellet counts readily provide relative abundance indices, and given suitable analytical methods, feces could also allow for the determination of multiple ecological and physiological variables, including community composition. In this context, we developed calibration models for rodent taxonomic determination using fecal near-infrared reflectance spectroscopy (fNIRS). Our results demonstrate fNIRS as an accurate and robust method for predicting genus and species identity of five coexisting subarctic microtine rodent species. We show that sample exposure to weathering increases the method's accuracy, indicating its suitability for samples collected from the field. Diet was not a major determinant of species prediction accuracy in our samples, as diet exhibited large variation and overlap between species. fNIRS could also be applied across regions, as calibration models including samples from two regions provided a good prediction accuracy for both regions. We show fNIRS as a fast and cost-efficient high-throughput method for rodent taxonomic determination, with the potential for cross-regional calibrations and the use on field-collected samples. Importantly, appeal lies in the versatility of fNIRS. In addition to rodent population censuses, fNIRS can provide information on demography, fecal nutrients, stress hormones, and even disease. Given the development of such calibration models, fNIRS analytics could complement novel genetic methods and greatly support ecosystem- and interaction-based approaches to monitoring.Peer reviewe

The Calan-Hertfordshire Extrasolar Planet Search

The detailed study of the exoplanetary systems HD189733 and HD209458 has given rise to a wealth of exciting information on the physics of exoplanetary atmospheres. To further our understanding of the make-up and processes within these atmospheres we require a larger sample of bright transiting planets. We have began a project to detect more bright transiting planets in the southern hemisphere by utilising precision radial-velocity measurements. We have observed a constrained sample of bright, inactive and metal-rich stars using the HARPS instrument and here we present the current status of this project, along with our first discoveries which include a brown dwarf/extreme-Jovian exoplanet found in the brown dwarf desert region around the star HD191760 and improved orbits for three other exoplanetary systems HD48265, HD143361 and HD154672. Finally, we briefly discuss the future of this project and the current prospects we have for discovering more bright transiting planets.Comment: 4 pages, 2 figures, to appear in the conference proceedings "New Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets" Shanghai 200

Ilmastonmuutos ja vesihuolto - varautuminen ja terveysvaikutukset

Ilmastonmuutos vaikuttaa monin tavoin myös Suomessa säähän ja ilmastoon, esimerkkeinä lämpötilan nouseminen, sateisuuden lisääntyminen, muutokset sään vuodenaikaisvaihtelussa ja äärevien sääilmiöiden yleistyminen. Sään tiedetään vaikuttavan monin tavoin vesihuoltoon. Monet ennustetuista muutoksista voivatkin aiheuttaa ongelmia talousveden valmistuksessa käytettävän raakaveden laadussa tai vedenjakelussa, ja siten lisätä juomaveteen liittyviä terveysriskejä. Suomessa on toistaiseksi kiinnitetty vain vähän huomiota vesihuollon kautta välittyviin ilmastonmuutoksen terveysriskeihin. Ilmastopaneelin rahoittamassa hankkeessa ”Ilmastonmuutos ja vesihuolto: varautuminen ja terveysvaikutukset” (2017 –2019) pyrittiin muodostamaan kokonaiskuva ilmastonmuutoksen merkityksestä vesihuollolle Suomessa. Kokonaiskuvan muodostamisessa hyödynnettiin koti- ja ulkomaista kirjallisuutta. Hankkeeseen sisältyi myös vesihuoltolaitoksille suunnattu kyselytutkimus, jonka avulla pyrittiin selvittämään muun muassa sitä, millaisia ongelmia sää aiheuttaa vesihuollolle tällä hetkellä, millaisena ongelmana ilmastonmuutos nähdään, ja miten muutokseen on varauduttu. Lisäksi hankkeessa arvioitiin ekonometrisesti vesihuoltoon liittyvien terveyshaittojen ja toisaalta niihin varautumisen aiheuttamia kustannuksia. Ilmastonmuutoksen hillintätoimet ovat tärkeä osa ilmastonmuutoksen ja vesihuollon kokonaisuutta ja kustannuksia, mutta niitä ei ole käsitelty tässä raportissa. Muuttuva ilmasto vaikuttaa myös raakaveden saatavuuteen sekä jätevesihuoltoon, mutta jätevesihuolto on rajattu tämän hankkeen ulkopuolelle ja saatavuutta on käsitelty vain kyselyaineistoon liittyen. Hankkeen tuottamat tiedot edistävät osaltaan sopeutumista ilmastonmuutokseen vesisektorilla.nonPeerReviewe

An insulin hypersecretion phenotype precedes pancreatic β cell failure in MODY3 patient-specific cells

MODY3 is a monogenic hereditary form of diabetes caused by mutations in the transcription factor HNF1A. The patients progressively develop hyperglycemia due to perturbed insulin secretion, but the pathogenesis is unknown. Using patient-specific hiPSCs, we recapitulate the insulin secretion sensitivity to the membrane depolarizing agent sulfonylurea commonly observed in MODY3 patients. Unexpectedly, MODY3 patient-specific HNF1A+/R272C β cells hypersecrete insulin both in vitro and in vivo after transplantation into mice. Consistently, we identified a trend of increased birth weight in human HNF1A mutation carriers compared with healthy siblings. Reduced expression of potassium channels, specifically the KATP channel, in MODY3 β cells, increased calcium signaling, and rescue of the insulin hypersecretion phenotype by pharmacological targeting ATP-sensitive potassium channels or low-voltage-activated calcium channels suggest that more efficient membrane depolarization underlies the hypersecretion of insulin in MODY3 β cells. Our findings identify a pathogenic mechanism leading to β cell failure in MODY3.Peer reviewe

Herbivore Effects on Ecosystem Process Rates in a Low-Productive System

Mammalian herbivores shape the structure and function of many nutrient-limited or low-productive terrestrial ecosystems through modification of plant communities and plant–soil feedbacks. In the tundra biome, mammalian herbivores may both accelerate and decelerate plant biomass growth, microbial activity and nutrient cycling, that is, ecosystem process rates. Selective foraging and associated declines of palatable species are known to be major drivers of plant–soil feedbacks. However, declines in dominant plants of low palatability often linked with high herbivore densities may also modify ecosystem process rates, yet have received little attention. We present data from an island experiment with a 10-year vole density manipulation, to test the hypothesis that herbivores accelerate process rates by decreasing the relative abundance of poorly palatable plants to palatable ones. We measured plant species abundances and community composition, nitrogen contents of green plant tissues and multiple soil and litter variables under high and low vole density. Corroborating our hypothesis, periodic high vole density increased ecosystem process rates in low-productive tundra. High vole density was associated with both increasing relative abundance of palatable forbs over unpalatable evergreen dwarf shrubs and higher plant N content both at species and at community level. Changes in plant community composition, in turn, explained variation in microbial activity in litter and soil inorganic nutrient availability. We propose a new conceptual model with two distinct vole–plant–soil feedback pathways. Voles may drive local plant–soil feedbacks that either increase or decrease ecosystem process rates, in turn promoting heterogeneity in vegetation and soils across tundra landscapes.</p

Levels of C-peptide, body mass index and age, and their usefulness in classification of diabetes in relation to autoimmunity, in adults with newly diagnosed diabetes in Kronoberg, Sweden

Objective: C-peptide is a main outcome measure in treatment trials of diabetes. C-peptide also has a role in the classification of diabetes, which is often difficult in adults and this is also increasingly recognised in adolescents and elders. Aim: We aimed to describe the levels of C-peptide in relation to age and body mass index (BMI) in a large population-based cohort of adults with newly diagnosed diabetes and compare the capabilities of C-peptide, age and BMI to discriminate between autoimmune and non-autoimmune diabetes. Subjects and methods: Blood samples from 1180 patients were analysed regarding islet cell antibody, glutamic acid decarboxylase antibody and fasting C-peptide (FCP). Receiver operating characteristics (ROC) curves were analysed to check the ability of age, BMI and C-peptide to discriminate between autoantibody-positive (Ab(+)) and -negative (Ab(-)) diabetes. Results: Mean FCP was 0.73 +/- 0.5 (range 0.13-1.80) nmol/l in the Ab(+) and 1.42 +/- 0.9 (range 0.13-8.30) nmol/l in the Ab(-). FCP was 0.02 nmol/l higher per year increase in age at diagnosis of diabetes. Mean BMI was 26.0 +/- 4.8 (range 18.0-39.0) kg/m(2) in the Ab(+) and 28.9 +/- 5.3 (range 15.5-62.6) kg/m(2) in the Ab(-). FCP increased with age also within each BMI group. The highest area under the curve (AUC) in the ROC analysis was found for C-peptide, followed by age and BMI (0.78, 0.68 and 0.66 respectively). Conclusions: At diagnosis of diabetes, C-peptide was superior to age and BMI in discriminating between autoimmune and non-autoimmune diabetes. C-peptide increased significantly with BMI and age, latter also within each BMI group. Most of the adults had normal or high levels of C-peptide at presentation of diabetes among the autoimmune patients