RMK lepinguline projekt 2016 - 2019: Kuusikute raieaja ja raieviiside mõju patogeenide levikule ja arvukusele ning puistu elurikkusele viljakates kasvukohatüüpides lõpparuande pikem versioon (LISA)

Käesolev uurimustöö on Eesti Maaülikooli ja Tartu Ülikooli kolme aastane lepinguline koostööprojekt. Iga osa koostasid või selle osa sisulist analüüsi juhtisid erinevad autorid, kes on nimetatud iga vastava aruande osa ees. Töö eesmärk on selgitada hariliku kuuse puistute majandamise (hooldus-, harvendus- ja sanitaarraie) mõju juuremädanike levikule ja kahjustusele ning seente ja epifüütide elurikkusele võrrelduna majandamata (raiumata) puistutega. Lepinguline töö jagunes järgmisteks osadeks: mullaseente elustik, lamapuidu seente elustik, seente elustik eluspuude puidus ja kändudes, samblike ja sammalde elustik, juurepessu antagonistid ning metsamajanduslik osa. Viimane sisaldab mädanike kahjude hinnanguid kuusikutes ja selle majanduslikke kalkulatsioone. Lepingulise koostööprojekti eesmärgid olid järgmised: 1. Hinnata erinevate metsamajandamise võtete, hooldusraiete korduse ning teostamise aja (puistu vanus ja aastaaeg) mõju patogeenide arvukusele, mullaelustikule ja epifüütidele viljakates kuuse-enamusega metsades. 2. Analüüsida teaduslikult kuusikute raieringi pikkuse mõju kuuse tüvepuidu sortimentide väljatulekule, tüvekahjustuste ulatusele ja elurikkusele. 3. Hinnata juuremädanikest tingitud majandusliku kahju suurust ja patogeenide arvukust viljakates kuusepuistutes (sh kändudes ja mullas) ning ühtlasi tuvastada potentsiaalseid juuremädanike antagoniste Eesti mulla- ja kliimatingimustes. 4. Koostada arvutusmudelid, mis võimaldavad erinevate sisendite (mädanike osakaal ja levik tüves, hooldusraiete aeg puistu vanusest ja vegetatsiooniperioodist lähtuvalt, mulla elurikkus) abil kirjeldada kuusikute kasvukäiku ja arvutada erinevaid tegureid arvestavad küpsusvanused, nt mahu- ja hinnaküpsus

Regional-scale in-depth analysis of soil fungal diversity reveals strong pH and plant species effects in Northern Europe

Soil microbiome has a pivotal role in ecosystem functioning, yet little is known about its build-up from local to regional scales. In a multi-year regional-scale survey involving 1251 plots and long-read third-generation sequencing, we found that soil pH has the strongest effect on the diversity of fungi and its multiple taxonomic and functional groups. The pH effects were typically unimodal, usually both direct and indirect through tree species, soil nutrients or mold abundance. Individual tree species, particularlyPinus sylvestris,Picea abies, andPopulus x wettsteinii, and overall ectomycorrhizal plant proportion had relatively stronger effects on the diversity of biotrophic fungi than saprotrophic fungi. We found strong temporal sampling and investigator biases for the abundance of molds, but generally all spatial, temporal and microclimatic effects were weak. Richness of fungi and several functional groups was highest in woodlands and around ruins of buildings but lowest in bogs, with marked group-specific trends. In contrast to our expectations, diversity of soil fungi tended to be higher in forest island habitats potentially due to the edge effect, but fungal richness declined with island distance and in response to forest fragmentation. Virgin forests supported somewhat higher fungal diversity than old non-pristine forests, but there were no differences in richness between natural and anthropogenic habitats such as parks and coppiced gardens. Diversity of most fungal groups suffered from management of seminatural woodlands and parks and thinning of forests, but especially for forests the results depended on fungal group and time since partial harvesting. We conclude that the positive effects of tree diversity on overall fungal richness represent a combined niche effect of soil properties and intimate associations

Adaptive root foraging strategies along a boreal–temperate forest gradient

The tree root–mycorhizosphere plays a key role in resource uptake, but also in the adaptation of forests to changing environments. The adaptive foraging mechanisms of ectomycorrhizal (EcM) and fine roots of Picea abies, Pinus sylvestris and Betula pendula were evaluated along a gradient from temperate to subarctic boreal forest (38 sites between latitudes 48°N and 69°N) in Europe. Variables describing tree resource uptake structures and processes (absorptive fine root biomass and morphology, nitrogen (N) concentration in absorptive roots, extramatrical mycelium (EMM) biomass, community structure of root-associated EcM fungi, soil and rhizosphere bacteria) were used to analyse relationships between root system functional traits and climate, soil and stand characteristics. Absorptive fine root biomass per stand basal area increased significantly from temperate to boreal forests, coinciding with longer and thinner root tips with higher tissue density, smaller EMM biomass per root length and a shift in soil microbial community structure. The soil carbon (C) : N ratio was found to explain most of the variability in absorptive fine root and EMM biomass, root tissue density, N concentration and rhizosphere bacterial community structure. We suggest a concept of absorptive fine root foraging strategies involving both qualitative and quantitative changes in the root–mycorrhiza–bacteria continuum along climate and soil C : N gradients.Peer reviewe

Imijuuremorfoloogiat ja risosfääriprotsesse mõjutavad tegurid arukaasikutes

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Mineraaltoitainete, eelkõige lämmastiku kättesaadavus on peamine metsaökosüsteemi produktiivsust ja süsiniku salvestumist limiteeriv tegur. Doktoritöö põhieesmärk oli (I) analüüsida arukase (Betula pendula Roth.) imijuurte morfoloogilisi adaptatsioone ja risosfääriefekti erinevates kasvukohatingimustes; (II) välja selgitada puude vanuse mõju imijuurte morfoloogiale ja risosfääriefekti avaldumisele seoses puu mineraalse toitumusega. Kaasiku kasvukoht (jänesekapsa kasvukohatüüp, endine põllumaa ja rekultiveeritud karjäär) ning puu vanus avaldasid olulist mõju nii imijuurte morfoloogiale kui ka risosfääriefekti avaldumisele. Imijuurte eripind ja eripikkus olid suuremad väiksema lehelämmastiku, seega halvema lämmastikutoitumuse korral nii endistel põllumaadel kui ka metsamaal kasvavates kaasikutes. Kase imijuurte morfoloogia dünaamika oli sarnane nii happelisel metsamaal kui ka lubjakivirikkal karjääripuistangul kasvavate puistute vanuseridades, kusjuures muutused imijuurte morfoloogias toimusid kiiremini nooremas eas. Puu vanusega kahanesid imijuurte eripind ja eripikkus, samuti lehtede eripind ja lämmastikukontsentratsioon. Seega olid kiiret kasvu, kõrget efektiivsust ja füsioloogilist aktiivsust näitavad lehe- ja juureparameetrid suuremad nooremates puistutes ning võib järeldada, et lehtede ja imijuurte morfoloogia dünaamika puistu arengu vältel on kooskõlas. Mükoriisa seenpartneri mütseelitüüp (exploration type) mõjutas imijuurte morfoloogiat oluliselt. Risosfääriefekt oli seda suurem (risosfääribaktereid toetati seda enam), mida happelisem (bakteritele ebasoodsam) oli kasvukoha muld ja mida suurem oli imijuurte endi lämmastikusisaldus. Risosfääri hapestamine toimus, kui kasvukoha mulla pH(KCl)>5. Antud doktoritöös hinnati esmakordselt arukase ektomükoriissete imijuurte morfoloogiliste parameetrite varieeruvuse piire ning analüüsiti ektomükoriissete imijuurte morfoloogiliste adaptatsioonide funktsionaalset rolli erinevates kasvukohtades ja seoses puistute vanusega. Käesoleva töö tulemused aitavad püstitada uusi hüpoteese juurte ja risosfääri adaptatsioonimehhanismide edasiseks analüüsiks ja on kasutatavad erinevate keskkonnamõjude, sealhulgas muutuva maakasutuse tagajärgede prognoosimisel arukaasikutes.Limited nutrient acquisition from soil is a key process limiting productivity in boreal forest, and nutrition strategies change during stand development. The overall objective of the doctoral thesis was (i) to find and quantify the response of ectomycorrhizal (EcM) root morphology and rhizosphere effect of silver birch (Betula pendula) to different site conditions, (ii) to ascertain tree-age-related changes in EcM root morphology and rhizosphere effect in relation to nutrient status of silver birch. EcM morphology and rhizosphere effect were influenced by site properties, especially by previous land use (natural forest, forest on previous agricultural land, and forest in reclaimed opencast oil shale mine area) as well as tree age. High EcM root SRL and SRA can be considered as root N nutrition stress indicators for silver birch – both increased in case of low leaf N%. Ontogenetic changes in EcM root morphology were similar in natural forest and reclaimed oil shale mine area chronosequence despite the very different site conditions. Age-related changes in EcM root morphology occurred faster in younger age, before the age of 5–10 years. The functional balance between physiology and morphology of leaves and roots appeared during stand development in natural forest – the specific leaf area and specific EcM root area as well as leaf N decreased simultaneously with tree age, probably as a result of down-regulation of growth. Molecular analyses revealed 33 EcM fungal species among the dominant morphotypes in three age classes of natural forest chronosequence. The exploration type of EcM fungi affected EcM root morphology significantly. The rhizosphere effect was higher by lower pH and higher root N% on agricultural land. Rhizosphere acidification occurred in the studied stands when bulk soil pH(KCl) > 5. The results of the thesis pro¬vide a cognitive basis for formulating new hypotheses concerning fine root and rhizosphere processes under changing environmental conditions

Coppicing improves the growth response of short-rotation hybrid aspen to elevated atmospheric humidity

Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens' northern range, climate models predict an increase in precipitation and, consequently, in atmospheric humidity. Our aim was to clarify the long-term effect of elevated air humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. x P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p < 0.001): negative in 4 years, positive also in 4 years and non-significant in 3 years. Mean basal area of humidified (11.6 +/- 0.8 cm(2)) and control trees (15.0 +/- 1.0 cm(2)) differed significantly (p = 0.035) at the end of the first but not the second rotation period (9.3 +/- 0.9 cm(2) and 9.3 +/- 1.2 cm(2), respectively). Average growth differences levelled out already in the beginning of the second rotation, suggesting that some root-level acclimation must have taken place. The annual size-growth relationships (SGR) indicated a more size-symmetric growth in humidified (SGR = 1.00 +/- 0.05) and a size-asymmetric growth (SGR = 1.12 +/- 0.04) in control stands, implying a greater role of root-competition in humidified stands. In humidified stands, the growth of re-sprouting trees was more strongly determined by parent tree size, indicating a stronger carry-over of size hierarchy. The tree height diversity fluctuated more in control stands, where mortality was higher, especially after dry years. To summarise, short- and long-term responses of hybrid aspen to elevated air humidity varied, emphasizing the importance of long-term climate manipulations with trees. Generally, hybrid aspen short-rotation coppice forests showed promising acclimation capacity with future more humid climate predicted for northern latitudes

The Composition, Physicochemical Properties, Antioxidant Activity, and Sensory Properties of Estonian Honeys

Thirty honey samples from different regions of Estonia were investigated to determine the chemical compositions, physicochemical properties, bioactive compounds, and sensory characteristics of typical honeys from a northern climate. The physicochemical parameters, such as electrical conductivity, moisture content, free acidity, hydroxymethylfurfural, diastase, and invertase activity were measured. The color was measured and expressed by L*-, a*-, and b*-coordinates. Sensory parameters were determined by using “fruity”, “floral”, “berry-like”, “herbal”, “woody”, “spicy”, “sweet”, and “animal-like” as the main odor and flavor attributes. The total polyphenol and flavonoid contents were in the range of 26.2–88.7 mg gallic acid equivalents (GAE) per 100 g and 1.9–6.4 mg quercetin equivalents (QE) per 100 g, respectively. The identified polyphenols showed the highest intensities of caffeic acid, coumaric acid, and abscisic acid and its derivatives. The protocatechuic acid intensity was highest in honeys containing traces of honeydew elements and of cinnamic acid and myricetin in heather honey. The water-soluble antioxidant values were 37.8–311.2 mg ascorbic acid equivalents (AAE) per 100 g and the lipid soluble antioxidant values were 14.4–60.7 mg Trolox equivalents (TE) per 100 g. The major amino acid in the analyzed honeys was proline, with variable values depending on the honey’s botanical source. Correlations were calculated based on the results obtained. It was revealed that the typical Estonian honey has floral, berry-like, sweet, and rather mild sensory characteristics. Most of the honeys lacked stronger spicy, woody, and animal-like attributes. The typical color of Estonian honey is quite light