Soil Bacterial and Archaeal Communities and Their Potential to Perform N-Cycling Processes in Soils of Boreal Forests Growing on Well-Drained Peat

Funding Information: This study was supported by the Estonian Forest Management Centre, the Estonian Research Council grants PRG548, PRG916, and PRG352, WaterJPI-JC-2018_13 project, and Centres of Excellence Environ and EcolChange.Peer reviewedPublisher PD

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

Eesti hall-lepikud bioenergiaressursina : SA Keskkonnainvesteeringute Keskuse lepingu nr. 11-10-8/196 KIK metsanduse programmi 2010.a. projekt nr. 27 tulemuste kokkuvõte

Järjest suurenev nõudlus energiapuidu järele muudab aktuaalsemaks kiirekasvuliste puude kasvatamise ja majandamise Eestis. Üheks kiirekasvulisemaks ning vastupidavamaks puuliigiks meie looduses on hall lepp (Alnus incana (L.) Moench) ning ta on perspektiivne puuliik ka lühikese raieringiga metsanduse (energiametsanduse) seisukohalt. Hetkel on Eestis kasvavate hall-lepikute tagavara 31 miljonit m3 (Aastaraamat Mets 2010) ja see ressurss on tugevalt alamajandatud. Kuid kahanev fossiilsete kütuste varu maailmas ja suurenev nõudlus bioenergia järele lubavad oletada, et lähitulevikus hakatakse Eestis hall-lepikuid senisest rohkem majandama. Biomassi, sealhulgas puidu kasutamine energia tootmiseks võimaldab oluliselt vähendada CO2 emissiooni ja seeläbi leevendada ka võimalikke kliimamuutusi. Euroopa Liit on seadnud aastaks 2020 energia sektorile eesmärgiks suurendada taastuvenergia kasutamist 20%-ni (Directive 2009/28/EC). Sellest tulenevalt võib lähitulevikus oodata intensiivsemat ja ulatuslikumat hall-lepikute majandamist, mis aga eeldab paremaid teadmisi nende puistute kasvukäigust, produktsioonivõimest, aga ka majandamise mõjust keskkonnale, eelkõige lämmastikuringele. Kuigi Eestis on uuritud hall-lepikute biomassi ja kasvudünaamikat viimasel kümnendil üsna intensiivselt (Uri et al. 2002, 2009, 2010), pärinevad esimesed ning seni ainukesed Eestis koostatud hall-lepikute kasvukäigutabelid aastast 1930 (Raukas 1930). Samas peaks metsade jätkusuutlik ning looduslähedane majandamine põhinema adekvaatsetel teadusuuringutel ning nende põhjal koostatud puistute kasvumudelitel. Käesolevas projektis on püütud katta mõningaid olulisi seni uurimata hall-lepikute kasvatamise ning majandamisega seotud aspekte Eestis

Maaelu Edendamise Sihtasutuse projekt : lõpparuanne 30.11.2007

Vastavalt Maaelu Edendamise Sihtasutuse ja Eesti Maaülikooli vahel sõlmitud töövõtulepingule uuring peab: 1) Andma võrdleva ülevaate Eestis viljelemiseks sobivatest ning soovituslikest energiakultuuride liikidest ja sortidest (sh geneetiliselt muundatud) vastavalt kasutuseesmärgile; 2) Analüüsima energiakulutuuride viljelemiseks vajaminevat tehnikat ja agrotehnoloogia olemasolu kohta ning täiendavast vajadusest või olemasoleva kohendamisvajadusest potentsiaalset tootmismahtu silmas pidades; 3) Analüüsima ja kirjeldama eri energiakultuuride viljelemise mõju mulla viljakusomadustele; 4) Andma hinnangu eri energiakultuuride sobivuse ja kasvatamise võimaluste kohta piirkonniti tulenevalt EL ühise põllumajanduspoliitika jõustuvatest ristvastavusnõuetest; 5) Analüüsima energiakultuuride kasvatamist piiravaid ja soodustavaid tegureid (sh keskkonnakaitselisi nõudeid); 6) Analüüsima oodatavaid keskkonnamõjusid; 7) Andma soovitused energiakultuuride laialdasema viljelemise korraldamiseks Eestis. Viiakse läbi varemkogutud erinevate puuliikide erinevate biomassifraktsioonide kalorsuse uuringud. Tulemuseks peab olema analüüs, mis annab ülevaate, milliseid kultuure konkreetsetes oludes on võimalik ja otstarbekas viljelda, milliseid keskkonnakaitselisi ja agrotehnoloogilisi nõudeid (sh ristvastavusnõudeid) tuleb viljelemisel arvestada, toob välja energiakultuuride kasvatamist piiravad ja soodustavad tegurid ning esitab vajadusel ettepanekud ametliku korralduse (õigusaktid, fiskaalinstrumendid jms) muutmiseks, et soodustada energiakultuuride viljelemist soovitataval määral

Biomass production and nitrogen balance of naturally afforested silver birch (Betula pendula Roth.) stand in Estonia

Silver birch ( Roth.) is one of the main pioneer tree species occupying large areas of abandoned agricultural lands under natural succession in Estonia. We estimated aboveground biomass (AGB) dynamics during 17 growing seasons, and analysed soil nitrogen (N) and carbon (C) dynamics for 10 year period in a silver birch stand growing on former arable land. Main N fluxes were estimated and nitrogen budget for 10-year-old stand was compiled. The leafless AGB and stem mass of the stand at the age of 17-years were 94 and 76 Mg ha respectively. The current annual increment (CAI) of stemwood fluctuated, peaking at 10 Mg ha yr at the age of 15 years; the mean annual increment (MAI) fluctuated at around 4â5 Mg ha. The annual leaf mass of the stand stabilised at around 3 Mg ha yr. The stand density decreased from 11600 to 2700 trees ha in the 8- and 17-year-old stand, respectively. The largest fluxes in N budget were net nitrogen mineralization and gaseous N-N emission. The estimated fluxes of NO and N were 0.12 and 83 kg ha yr, respectively; N leaching was negligible. Nitrogen retranslocation from senescing leaves was approximately 45 kg ha, N was mainly retranslocated into stembark. The N content in the upper 0â10 cm soil layer increased significantly (145 kg ha) from 2004 to 2014; soil C content remained stable. Both the woody biomass dynamics and the N cycling of the stand witness the potential for bioenergetics of such ecosystems.Betula pendulaâ1â1â1â1â1â1â1222â1â1â1â

Morphological Variation in Absorptive Roots in Downy Birch (<i>Betula pubescens</i>) and Norway Spruce (<i>Picea abies</i>) Forests Growing on Drained Peat Soils

Peatland drainage based on ditch systems is a widely used forestry management practice in the boreal and hemiboreal forests to improve tree growth. This study investigated the morphological variation in absorptive roots (first- and second-order roots) across the distance gradient from the ditch with four sampling plots (5, 15, 40, and 80 m) in six drained peatland forests dominated by Downy birch and Norway spruce. The dominating tree species had a significant effect on the variation in absorptive root morphological traits. The absorptive roots of birch were thinner with a higher specific root area and length (SRA and SRL), higher branching intensity (BI), and lower root tissue density (RTD) than spruce. The distance from the ditch affected the absorptive root morphological traits (especially SRA and RTD), but this effect was not dependent on tree species and was directionally consistent between birch and spruce. With increased distance from the ditch (from plot 5 to plot 80), the mean SRA increased by about 10% in birch and 5% in spruce; by contrast, the mean RTD decreased by about 10% in both tree species, indicating a potential shift in nutrient foraging. However, soil physical and chemical properties were not dependent on the distance from the ditch. We found a species-specific response in absorptive root morphological traits to soil properties such as peat depth, pH, and temperature. Our results should be considered when evaluating the importance of morphological changes in absorptive roots when trees acclimate to a changing climate