Climate change-induced vegetation change as a driver of increased subarctic biogenic volatile organic compound emissions

Emissions of biogenic volatile organic compounds (BVOCs) have been earlier shown to be highly temperature sensitive in subarctic ecosystems. As these ecosystems experience rapidly advancing pronounced climate warming, we aimed to investigate how warming affects the BVOC emissions in the long term (up to 13 treatment years). We also aimed to assess whether the increased litterfall resulting from the vegetation changes in the warming subarctic would affect the emissions. The study was conducted in a field experiment with factorial open-top chamber warming and annual litter addition treatments on subarctic heath in Abisko, northern Sweden. After 11 and 13 treatment years, BVOCs were sampled from plant communities in the experimental plots using a push–pull enclosure technique and collection into adsorbent cartridges during the growing season and analyzed with gas chromatography–mass spectrometry. Plant species coverage in the plots was analyzed by the point intercept method. Warming by 2 °C caused a 2-fold increase in monoterpene and 5-fold increase in sesquiterpene emissions, averaged over all measurements. When the momentary effect of temperature was diminished by standardization of emissions to a fixed temperature, warming still had a significant effect suggesting that emissions were also indirectly increased. This indirect increase appeared to result from increased plant coverage and changes in vegetation composition. The litter addition treatment also caused significant increases in the emission rates of some BVOC groups, especially when combined with warming. The combined treatment had both the largest vegetation changes and the highest BVOC emissions. The increased emissions under litter addition were probably a result of a changed vegetation composition due to alleviated nutrient limitation and stimulated microbial production of BVOCs. We suggest that the changes in the subarctic vegetation composition induced by climate warming will be the major factor indirectly affecting the BVOC emission potentials and composition

Age-related response of forest floor biogenic volatile organic compound fluxes to boreal forest succession after wildfires

The amplification of global warming in the Northern regions results in a higher probability of wildfires in boreal forests. On the forest floor, wildfires have long-term effects on vegetation composition as well as soil and its microbial communities. A large variety of biogenic volatile organic compounds (BVOCs) such as isoprene, monoterpenes, sesquiterpenes have been observed to be emitted from soil and understory vegetation of boreal forest floor. Ultimately, the fire-induced changes in the forest floor affect its BVOC fluxes, and the recovery of the forest floor determines the quantity and quality of BVOC fluxes. However, the effects of wildfires on forest floor BVOC fluxes are rarely studied. Here we conducted a study of the impacts of post-fire succession on forest floor BVOC fluxes along a 158-year fire chronosequence in boreal Scots pine stands near the northern timberline in north-eastern Finland throughout a growing season. We determined the forest floor BVOC fluxes and investigated how the environmental and ground vegetation characteristics, soil respiration rates, and soil microbial and fungal biomass are associated with the BVOC fluxes during the post-fire succession. The forest floor was a source of diverse BVOCs. Monoterpenes (MTs) were the largest group of emitted BVOCs. We observed forest age-related differences in the forest floor BVOC fluxes along the fire chronosequence. The forest floor BVOC fluxes decreased with the reduction in ground vegetation coverage resulted from wildfire, and the decreased fluxes were also connected to a decrease in microbial activity as a result of the loss of plant roots and soil organic matter. The increase in BVOC fluxes was associated with the recovery of aboveground plant coverage and soils. Our results suggested taking into consideration the implications of BVOC flux variations on the atmospheric chemistry and climate feedbacks.Peer reviewe

Metabolite Composition of Paper Birch Buds after Eleven Growing Seasons of Exposure to Elevated CO2 and O-3

Research Highlights: Long-term exposure of paper birch to elevated carbon dioxide (CO2) and ozone (O-3) modified metabolite content of over-wintering buds, but no evidence of reduced freezing tolerance was found.Background and Objectives: Atmospheric change may affect the metabolite composition of over-wintering buds and, in turn, impact growth onset and stress tolerance of perennial plant species in spring. Materials and Methods: Low molecular weight compounds of paper birch (Betula papyrifera) buds, including lipophilic, polar and phenolic compounds were analyzed, and freezing tolerance (FT) of the buds was determined prior to bud break after 11 growing seasons exposure of saplings to elevated concentrations of CO2 (target concentration 560 mu L L-1) and O-3 (target concentration 1.5 x ambient) at the Aspen FACE (Free-Air CO2 and O-3 Enrichment) facility. Results: The contents of lipophilic and phenolic compounds (but not polar compounds) were affected by elevated CO2 and elevated O-3 in an interactive manner. Elevated O-3 reduced the content of lipids and increased that of phenolic compounds under ambient CO2 by reallocating carbon from biosynthesis of terpenoids to that of phenolic acids. In comparison, elevated CO2 had only a minor effect on lipophilic and polar compounds, but it increased the content of phenolic compounds under ambient O-3 by increasing the content of phenolic acids, while the content of flavonols was reduced. Conclusions: Based on the freezing test and metabolite data, there was no evidence of altered FT in the over-wintering buds. The impacts of the alterations of bud metabolite contents on the growth and defense responses of birches during early growth in spring need to be uncovered in future experiments.</div

Secondary Organic Aerosol Formation from Healthy and Aphid-Stressed Scots Pine Emissions.

One barrier to predicting biogenic secondary organic aerosol (SOA) formation in a changing climate can be attributed to the complex nature of plant volatile emissions. Plant volatile emissions are dynamic over space and time, and change in response to environmental stressors. This study investigated SOA production from emissions of healthy and aphid-stressed Scots pine saplings via dark ozonolysis and photooxidation chemistry. Laboratory experiments using a batch reaction chamber were used to investigate SOA production from different plant volatile mixtures. The volatile mixture from healthy plants included monoterpenes, aromatics, and a small amount of sesquiterpenes. The biggest change in the volatile mixture for aphid-stressed plants was a large increase (from 1.4 to 7.9 ppb) in sesquiterpenes-particularly acyclic sesquiterpenes, such as the farnesene isomers. Acyclic sesquiterpenes had different effects on SOA production depending on the chemical mechanism. Farnesenes suppressed SOA formation from ozonolysis with a 9.7-14.6% SOA mass yield from healthy plant emissions and a 6.9-10.4% SOA mass yield from aphid-stressed plant emissions. Ozonolysis of volatile mixtures containing more farnesenes promoted fragmentation reactions, which produced higher volatility oxidation products. In contrast, plant volatile mixtures containing more farnesenes did not appreciably change SOA production from photooxidation. SOA mass yields ranged from 10.8 to 23.2% from healthy plant emissions and 17.8-26.8% for aphid-stressed plant emissions. This study highlights the potential importance of acyclic terpene chemistry in a future climate regime with an increased presence of plant stress volatiles

Wildfire effects on BVOC emissions from boreal forest floor on permafrost soil in Siberia

One of the effects of climate change on boreal forest will be more frequent forest wildfires and permafrost thawing. These will increase the availability of soil organic matter (SOM) for microorganisms, change the ground vegetation composition and ultimately affect the emissions of biogenic volatile organic compounds (BVOCs), which impact atmospheric chemistry and climate. BVOC emissions from boreal forest floor have been little characterized in southern boreal region, and even less so in permafrost soil, which underlies most of the northern boreal region. Here, we report the long-term effects of wildfire on forest floor BVOC emission rates along a wildfire chronosequence in a Larix gmelinii forest in central Siberia. We determined forest floor BVOC emissions from forests exposed to wildfire 1, 23 and > 100 years ago. We studied how forest wildfires and the subsequent succession of ground vegetation, as well as changes in the availability of SOM along with the deepened and recovered active layer, influence BVOC emission rates. The forest floor acted as source of a large number of BVOCs in all forest age classes. Monoterpenes were the most abundant BVOC group in all age classes. The total BVOC emission rates measured from the 23- and >100-year-old areas were ca. 2.6 times higher than the emissions from the 1-year-old area. Lower emissions were related to a decrease in plant coverage and microbial decomposition of SOM after wildfire. Our results showed that forest wildfires play an important indirect role in regulating the amount and composition of BVOC emissions from post-fire originated boreal forest floor. This could have a substantial effect on BVOC emissions if the frequency of forest wildfires increases in the future as a result of climate warming. (C) 2019 Elsevier B.V. All rights reserved.Peer reviewe

Hydroponisen rehuntuotannon mahdollisuudet Suomessa

Hydroponisella rehuntuotannolla tarkoitetaan siementen idätystä ja versotusta niin, että iduista ja versoista syntyy kokonaisuudessaan eläimille syötettävä rehumassa tai –matto. Hydrorehu-hankkeessa selvitettiin hydroponisen rehuntuotannon mahdollisuuksia Pohjois-Savon ja Etelä-Pohjanmaan olosuhteissa vuosina 2017–2018. Hankkeessa kokeiltiin ja kehitettiin hydroponista rehuntuotantoa Itä-Suomen yliopiston kasvatuskaapeissa sekä kuudella kotieläintilalla Pohjois-Savossa ja Etelä-Pohjanmaalla tarkoitusta varten vuokratussa siirrettävässä kasvatusdemokontissa. Kasvatuskokeissa optimaaliseksi kasvatuslämpötilaksi osoittautui +21 °C. Viljoilla ja herneellä riittävä kasvatusaika kasvatuskontissa oli 7 vrk, kun siemenet esikäsiteltiin vedellä ja liotettiin 4–12 h. Lisäksi havaittiin, että kasteluveden määrä on aina säädettävä kullekin siemenerälle ja kasvatussysteemille erikseen ja että suhteellisen edulliset kasveille tarkoitetut LED-valot soveltuivat hyvin hydroponiseen versonkasvatukseen. Homeet lisääntyivät kasvustoissa nopeasti, mikäli kasvatushuoneen lämpötila nousee korkeaksi ja kosteus on korkea. Optimaalinen tilanne kasvun kannalta on, kun kosteus on 50–60% ja huoneistossa on riittävä ilman vaihto. Kasvatuksessa kokeiltiin eri lajeja ja lajikkeita. Ohra, kaura ja härkäpapu kasvoivat huonosti ja kasvustoissa oli homeita. Vehnä ja herne kasvoivat hyvin. Tuoresatoa saatiin sekä vehnästä että herneestä keskimäärin 4,5 kg käytettyä siemenkiloa kohti, vaihtelu satomäärissä oli kohtalaisen suurta. Salmonellaa ei löydetty ja Escherichia coli –bakteerin pitoisuudet olivat kahta versorehunäytettä lukuun ottamatta hyvällä tasolla ja kahdella versorehunäytteellä tulokset sijoittuivat luokkaan, jota pidetään elintarvikekäytössä hyväksyttävänä rajana. Alkuperäiseen siemenmateriaaliin verrattuna versorehu sisälsi enemmän raakavalkuaista, NDF-kuitua sekä kivennäis- ja hivenaineita, mutta vähemmän solunsisällyshiilihydraatteja. Puhdas kasvusto maittoi eläimille pääasiassa hyvin. Havaittiin, että rehu tulee syöttää nopeasti, sillä se ei kestä varastointia.Ulkomailla tehtyjen tutkimusten mukaan hydroponinen viljely on hyvin harvoin nähty taloudellisesti kannattavana rehuntuotantomuotona. Hydrorehu-hankkeen demokasvatuksissa havaittiin, että työkustannukset, energiakustannukset, siemenkustannukset sekä haasteet rehun laadussa tuovat uhkia sekä kustannuksia hydroponisen rehun tuottoon. Mahdollisuudet kasvatuksessa voivat olla esimerkiksi virikerehun tuotannossa tai pieneläinten ja hyönteisten rehuntuotannossa. Sato tuotetaan ympäristöystävällisesti, sillä rehun tuotannossa ei tarvitse käyttää kemiallisia lannoitteita eikä kasvinsuojeluaineita tai muita kemikaaleja, mikäli siemen on hyvälaatuista. Lisätutkimuksia hydroponisesti tuotettujen rehujen merkityksestä kotieläinten hyvinvointiin tarvitaan, jotta saadaan selville hydroponisen tuotannon todellinen kannattavuu

Unravelling the functions of biogenic volatiles in boreal and temperate forest ecosystems

Living trees are the main source of biogenic volatile organic compounds (BVOCs) in forest ecosystems, but substantial emissions originate from leaf and wood litter, the rhizosphere and from microorganisms. This review focuses on temperate and boreal forest ecosystems and the roles of BVOCs in ecosystem function, from the leaf to the forest canopy and from the forest soil to the atmosphere level. Moreover, emphasis is given to the question of how BVOCs will help forests adapt to environmental stress, particularly biotic stress related to climate change. Trees use their vascular system and emissions of BVOCs in internal communication, but emitted BVOCs have extended the communication to tree population and whole community levels and beyond. Future forestry practices should consider the importance of BVOCs in attraction and repulsion of attacking bark beetles, but also take an advantage of herbivore-induced BVOCs to improve the efficiency of natural enemies of herbivores. BVOCs are extensively involved in ecosystem services provided by forests including the positive effects on human health. BVOCs have a key role in ozone formation but also in ozone quenching. Oxidation products form secondary organic aerosols that disperse sunlight deeper into the forest canopy, and affect cloud formation and ultimately the climate. We also discuss the technical side of reliable BVOC sampling of forest trees for future interdisciplinary studies that should bridge the gaps between the forest sciences, health sciences, chemical ecology, conservation biology, tree physiology and atmospheric science