Soil mycobiomes in native European aspen forests and hybrid aspen plantations have a similar fungal richness but different compositions, mainly driven by edaphic and floristic factors

BackgroundThe cultivation of short-rotation tree species on non-forest land is increasing due to the growing demand for woody biomass for the future bioeconomy and to mitigate climate change impacts. However, forest plantations are often seen as a trade-off between climate benefits and low biodiversity. The diversity and composition of soil fungal biota in plantations of hybrid aspen, one of the most planted tree species for short-rotation forestry in Northern Europe, are poorly studied.MethodsThe goal of this study was to obtain baseline knowledge about the soil fungal biota and the edaphic, floristic and management factors that drive fungal richness and communities in 18-year-old hybrid aspen plantations on former agricultural soils and compare the fungal biota with those of European aspen stands on native forest land in a 130-year chronosequence. Sites were categorized as hybrid aspen (17–18-year-old plantations) and native aspen stands of three age classes (8–29, 30–55, and 65-131-year-old stands). High-throughput sequencing was applied to soil samples to investigate fungal diversity and assemblages.ResultsNative aspen forests showed a higher ectomycorrhizal (EcM) fungal OTU richness than plantations, regardless of forest age. Short-distance type EcM genera dominated in both plantations and forests. The richness of saprotrophic fungi was similar between native forest and plantation sites and was highest in the middle-aged class (30–55-year-old stands) in the native aspen stands. The fungal communities of native forests and plantations were significantly different. Community composition varied more, and the natural forest sites were more diverse than the relatively homogeneous plantations. Soil pH was the best explanatory variable to describe soil fungal communities in hybrid aspen stands. Soil fungal community composition did not show any clear patterns between the age classes of native aspen stands.ConclusionWe conclude that edaphic factors are more important in describing fungal communities in both native aspen forest sites and hybrid aspen plantation sites than forest thinning, age, or former land use for plantations. Although first-generation hybrid aspen plantations and native forests are similar in overall fungal diversity, their taxonomic and functional composition is strikingly different. Therefore, hybrid aspen plantations can be used to reduce felling pressure on native forests; however, our knowledge is still insufficient to conclude that plantations could replace native aspen forests from the soil biodiversity perspective

Lehtpuupuistute majandamine

TäistekstKaasikute, maarjakase, haavikute, hübriidhaava, sanglepikute, hall-lepikute, tammikute, saarikute majandamine

Elevated atmospheric CO2 and humidity delay leaf fall in Betula pendula, but not in Alnus glutinosa or Populus tremula × tremuloides

Context: Anthropogenic activity has increased the level of atmospheric CO2, which is driving an increase of global temperatures and associated changes in precipitation patterns. At Northern latitudes, one of the likely consequences of global warming is increased precipitation and air humidity. Aims: In this work, the effects of both elevated atmospheric CO2 and increased air humidity on trees commonly growing in northern European forests were assessed. Methods: The work was carried out under field conditions by using Free Air Carbon dioxide Enrichment (FACE) and Free Air Humidity Manipulation (FAHM) systems. Leaf litter fall was measured over 4 years (FACE) or 5 years (FAHM) to determine the effects of FACE and FAHM on leaf phenology. Results: Increasing air humidity delayed leaf litter fall in Betula pendula, but not in Populus tremula × tremuloides. Similarly, under elevated atmospheric CO2, leaf litter fall was delayed in Betula pendula, but not in Alnus glutinosa. Increased CO2 appeared to interact with periods of low precipitation in summer and high ozone levels during these periods to effect leaf fall. Conclusions: This work shows that increased CO2 and humidity delay leaf fall, but this effect is species specific

Puude kasv ja seda mõjutavad tegurid noortes hübriidhaavaistandikes

Lühikese raieringiga metsandus (SRF) on uudne metsakasvatuslik meetod hemiboreaalsesse metsavööndisse kuuluvas Eestis. Eesti kliimas SRF jaoks sobilik puuliik peab olema noores eas kiirekasvuline ning samas külmakindel. Teiste maade kogemuse põhjal on meie regioonis üheks kõige kiiremakasvuliseks lehtpuuks hübriidhaab – hariliku haava (Populus tremula L.) ja Ameerika haava (P. tremuloides Michx.) kunstlikul teel saadud ristand, mis ületab heteroosi tõttu kasvukiiruse ning biomassiproduktsiooni poolest tunduvalt oma lähteliike. Hübriidhaavaistandike kasvatamise peamiseks eesmärgiks on toota 25-aastase raieringiga paberipuitu (jämedamatest tüvedest haavapalki). Eestis on alates 1999. aastast rajatud endistele põllumajandusmaadele üle 700 ha hübriidhaavaistandikke, hübriidhaaba on katseliselt istutatud ka ammendatud põlevkivikarjääri metsastamiseks. Arvestades eeltoodut, püstitati käesoleva doktoritöö eesmärgid: 1) hinnata puude kasvu ja produktsiooni noortes hübriidhaavaistandikes; 2) uurida endiste põllumuldade keemiliste ja füüsikaliste omaduste mõju hübriidhaabade kasvukiirusele ja toitainete omastamisele; 3) määrata maapealse lehtedeta biomassi produktsioon, allokatsioon, peamiste toitainete sisaldus ja kalorsus noortes hübriidhaavakultuurides; 4) uurida hübriidhaava sobivust ammendatud põlevkivikarjääride metsastamiseks; 5) täiendada olemasolevaid teadmisi taim-muld suhetest SRF istandikes ja anda praktilisi soovitusi kasvukoha valikuks hübriidhaavaistandike rajamiseks. Püstitatud küsimustele vastuste leidmiseks rajati 58 püsiproovitükist (á 0,1 ha) koosnev katsealade võrgustik 26 hübriidhaavakultuuris. Katsealadel mõõdeti puude takseertunnused, määrati puulehtede peamiste toitainete sisaldused, võeti mudelpuud biomassi produktsiooni ja omaduste analüüsimiseks ning teostati põhjalik mulla füüsikaliste ja keemiliste omaduste analüüs. Saadud tulemuste põhjal võib järeldada, et hübriidhaab on Eesti kliima- ja mullatingimustes noores eas kiirekasvuline ja suure produktsioonivõimega lehtpuu. Kümneaastases hübriidhaavaistandikus võib puude keskmine kõrgus ulatuda 13 m-ni ja tagavara olla kuni 87 tm ha–1. Endistel põllumajandusmaadel on puude kasv noores eas seotud eelkõige mulla hüdrofüüsikaliste omadustega, eelnevalt väetatud muldade toitainevarud on olnud enamasti piisavad. Hübriidhaavale sobilikud mullad on ülaosas kergema lõimisega parasniisked või gleistunud leetunud, näivleetunud ja leetjad mullad. Mulla eripinna ja lasuvustiheduse põhjal kaudselt määratavat taimede poolt omastatava vee varu mullas võib pidada heaks indikaatoriks kasvukoha valikul, seejuures on olulised ka alumiste mullakihtide omadused. Kiireks kasvuks piisav omastatava vee varu 75 cm mullakihis on üle 150 mm. Hübriidhaabade biomassi allokatsioon, kuivaineühiku toitainesisaldus ja kütteväärtus on sarnased teiste kiirekasvuliste lehtpuude vastavate näitajatega. Energiapuidu tootmisel peaks tüve sihtdiameeter olema vähemalt 4 cm, mis tagab suurema puidu osakaalu biomassis. Hübriidhaab suudab kasvada karjääripuistangu ekstreemsetes tingimustes, kuid seal ei avaldu noores eas tema suur kasvupotentsiaal, puud kasvavad kiiremini taastatud huumuskattega karjäärialal.The current study was supported by the Estonian Science Foundation grant No. 6064. Publication of this dissertation is supported by the Estonian University of Life Sciences and by the Doctoral School of Earth Sciences and Ecology created under the auspices of European Social Fund

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

Impact of deadwood decomposition on soil organic carbon sequestration in Estonian and Polish forests

Key message: The deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests. In warmer conditions (Poland), the deadwood decomposition process had a higher rate than in cooler Estonian forests. Soil organic matter fractions analysis can be used to assess the stability and turnover of organic carbon between deadwood and soil in different experimental localities. Context: Deadwood is an important element of properly functioning forest ecosystem and plays a very important role in the maintenance of biodiversity, soil fertility, and carbon sequestration. Aims: The main aim was to estimate how decomposition of deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests. Methods: The investigation was carried out in six forests in Poland (51° N) and Estonia (58° N). The study localities differ in their mean annual air temperature (of 2 °C) and the length of the growing season (of 1 month). The deadwood logs of Norway spruce (Picea abies (L.) Karst.), common aspen (Populus tremula L.), and silver birch (Betula pendula Roth) were included in the research. Logs in three stages of decomposition (III–V) were selected for the analysis. Results: There were differences in the stock of soil organic carbon in two experimental localities. There was a higher soil carbon content under logs and in their direct vicinity in Polish forests compared to those in the cooler climate of Estonia. Considerable differences in the amount of soil organic matter were found. The light fraction constituted the greatest quantitative component of organic matter of soils associated with deadwood. Conclusion: A higher carbon content in surface soil horizons as an effect of deadwood decomposition was determined for the Polish (temperate) forests. More decomposed deadwood affected soil organic matter stabilization more strongly than less decayed deadwood. This relationship was clearer in Polish forests. Higher temperatures and longer growing periods primarily influenced the increase of soil organic matter free light fraction concentrations directly under and in close proximity to logs of the studied species. The slower release of deadwood decomposition products was noted in Estonian (hemiboreal) forests. The soil organic matter mineral fraction increased under aspen and spruce logs at advanced decomposition in Poland

The Value of Hybrid Aspen Coppice Investment under Different Discount Rate, Price and Management Scenarios: A Case Study of Estonia

Hybrid aspen is one of the most promising tree species for short-rotation forestry in Northern Europe. After the clearcutting of hybrid aspen plantation, the next generation arises from root and stump sprouts. The economic feasibility of different management strategies of hybrid aspen coppice stands has not yet been comprehensively evaluated in Northern Europe. We compared the land expectation values (LEVs) of hybrid aspen coppice stands managed according to four scenarios: three early thinning methods (corridor, cross-corridor and single-tree) followed by conventional management and intensive bioenergy production (repeated harvests in 5-year rotations) over a 25-year period in hemiboreal Estonia. We considered the historic price volatility of aspen wood assortments under various discount rates (1–20%). We found that the 25-year rotation with different early thinning methods was more profitable than short bioenergy cycles in the case of low discount rates (<5%). The LEV of short coppice cycles for only bioenergy production became more profitable in comparison with those by thinning methods, when higher discount rates (>10%) were applied. Hybrid aspen coppice stands can be managed profitably, but more risks are taken when the management strategy focuses only on bioenergy production

Diversity of lichens and bryophytes in hybrid aspen plantations in Estonia depends on landscape structure

Importance of single-species forest plantations in sustaining biodiversity could be bigger than expected. We described the diversity of lichens and bryophytes in 15 midterm (16â 17-year-old) hybrid aspen (Populus tremula Ă P. tremuloides) plantations in Estonia. Species richness and composition data were linked with environmental and landscape-scale variables. Altogether, 44 lichen and 37 bryophyte species were recorded from plantations; richnesses of bryophytes and lichens were positively correlated. Lichen species composition was significantly affected by landscape-scale parameters (distance to the nearest present forest, distance to the nearest forest continuously occurring in the same place since 1930s, and forest area in the study plot vicinity in 1930s). Bryophyte species composition was affected mainly by light conditions and forest area in 1930s. Among lichens, functional group of sexual crustose species dominated in midterm plantations; appearance of asexual lichens of different growth forms is expected during next years. Our results indicate importance of long-term availability of good-quality forests as sources of propagules. Short-rotation hybrid aspen plantations can provide temporary habitats for forest species and thus in part contribute to preserving landscape-scale biodiversity, if they are close to possible colonisation sources. Green-tree retension in plantations will probably raise the biodiversity value of those short-term communities.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

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