Fungerar kretsloppen om vi använder mera biobränslen?

• Biobränslen kan i praktiken betraktas som koldioxidneutrala. • Vid uttag av biobränslen bör blad och barr lämnas kvar för att minska näringsförlusterna. • Återföring av vedaska krävs förmodligen för omfattande utnyttjande av biobränslen från skog. • Upprätthållandet av kretsloppen för viktiga grundämnen är inte vad som kommer att sätta gränserna för hur mycket biobränslen som kan utnyttjas. Det är andra faktorer såsom upprätthållande av biodiversitet, landskapsbild, risk för näringsläckage samt ekonomi

Ratkaisuja ja kehitysehdotuksia maatalouden ympäristöhaasteisiin MATO-tutkimusohjelman perusteella

Maatalouden ympäristövaikutusten tutkimusohjelmassa (MATO) 2016–2020 koottiin yhteen maa- ja metsätalousministeriön ja ympäristöministeriön rahoittamat maatalouden ympäristöasioihin liittyvät tutkimushankkeet viiden vuoden ajan. Tutkimusohjelman tavoitteena oli (1) edistää maatalouden ympäristötavoitteiden toteutumista, (2) luoda pohjaa tulevan rahoituskauden 2021–2026 ympäristötoimenpiteiden suunnittelulle, (3) tuottaa ratkaisuja ongelmiin, jotka vaikeuttavat ympäristötavoitteiden toteutumista, sekä (4) tuottaa tietoa maaseutuohjelman vaikuttavuuden arvioinnin tueksi. Näiden tavoitteiden taustalla oli maaseutuohjelman viisi ympäristötavoitetta: (1) vesien ravinnekuormitus vähenee ja vesistöjen tila paranee, (2) maaperän kasvukunto paranee, (3) luonnon monimuotoisuus lisääntyy, (4) kasvihuonekaasupäästöt vähenevät ja ilmastonmuutoksen hillintä tehostuu sekä (5) ilmastonmuutokseen sopeutuminen tehostuu. Synteesi ohjelmassa rahoitettujen 25 tutkimushankkeen tärkeimmistä tuloksista koottiin viiden eri hankkeita yhdistäneen teeman alle: (1) Maatalouden ympäristötoimenpiteiden vaikutus ympäristön tilaan, (2) Maaperä ja ravinnetaseet, (3) Kiertotalous: hiilen ja ravinteiden kierto sekä energiatehokkuus osana kestävää maataloutta, (4) Maatalouden moninaiset ekosysteemipalvelut ja (5) Työkaluja parempaan maatalousympäristön tilan hoitoon. Kussakin synteesiluvussa esitetään yhteenveto siitä, miten teeman hankkeet tuottivat sovelluskelpoista, päätöksenteossa tarvittavaa tietoa ja mitkä ovat aihepiirin tärkeimmät jatkotutkimustarpeet

Carbon and nitrogen pools and mineralization rates in boreal forest soil after stump harvesting

The use of forest-derived biomass has steadily increased in Finland and Sweden during the past decades leading to more intensive forest management practices in the region, such as whole-tree harvesting, both above- and belowground. Stump harvesting results in a direct removal of stump and coarse-root carbon (C) from the stand and can cause extensive soil disturbance, which has been suggested to increase C mineralization. In this study, the effects of stump harvesting on soil C and nitrogen (N) mineralization, and soil surface disturbance were studied in two different clear-felled Norway spruce (Picea abies) sites in Central Finland. The treatments were whole-tree harvesting (WTH, removal of stems and logging residues), and WTH and stump harvesting (WTH + S). Both sites, Honkola (2 stands) and Haukilahti (6 stands) were mounded. In both treatments, soil samples were taken from different soil layers down to a total depth of 20 cm in the mineral soil from (i) mounds, (ii) undisturbed soil and (iii) pits. The sampling was performed 11-12 years after treatments. Soil C and N mineralization rates were determined in laboratory incubation experiments. In addition, total C and N pools (g m(2)) were estimated for each disturbance class and soil layer. Soil C and N pools had a tendency to be lower following stump harvesting, but no statistically significant treatment effect was detected. Stump harvesting increased soil mixing as indicated by a significant decrease in C concentration in the mound disturbance class. There was no significant effect of stump harvesting on soil C mineralization rates. A combination of mineralization rates and soil pool data showed that field C mineralization (g CO2-C m(-2) yr(-1)) did not significantly differ between stands where stumps were removed or were retained. Further, stump harvesting did not seem to have any stimulating effect on soil CO2 efflux 11-12 years after treatment. (C) 2016 Elsevier B.V. All rights reserved.Peer reviewe

A Model for Social Networks

Social networks are organized into communities with dense internal connections, giving rise to high values of the clustering coefficient. In addition, these networks have been observed to be assortative, i.e. highly connected vertices tend to connect to other highly connected vertices, and have broad degree distributions. We present a model for an undirected growing network which reproduces these characteristics, with the aim of producing efficiently very large networks to be used as platforms for studying sociodynamic phenomena. The communities arise from a mixture of random attachment and implicit preferential attachment. The structural properties of the model are studied analytically and numerically, using the $k$-clique method for quantifying the communities.Comment: 15 pages (Latex), 6 figures (Postscript

N2O Release from agro-biofuel production negates global warming reduction by replacing fossil fuels

The relationship, on a global basis, between the amount of N fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and the total emission of nitrous oxide (N2O), has been re-examined, using known global atmospheric removal rates and concentration growth of N2O as a proxy for overall emissions. For both the pre-industrial period and in recent times, after taking into account the large-scale changes in synthetic N fertiliser production, we find an overall conversion factor of 3–5 % from newly fixed N to N2O–N. We assume the same factor to be valid for biofuel production systems. It is covered only in part by the default conversion factor for ‘direct’ emissions from agricultural crop lands (1 %) estimated by IPCC (2006), and the default factors for the ‘indirect’ emissions (following volalilization/deposition and leaching/runoff of N: 0.35–0.45 %) cited therein. However, as we show in the paper, when additional emissions included in the IPCC methodology, e.g. those from livestock production, are included, the total may not be inconsistent with that given by our “top-down” method. When the extra N2O emission from biofuel production is calculated in “CO2-equivalent” global warming terms, and compared with the quasi-cooling effect of ‘saving’ emissions of fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), depending on N fertilizer uptake efficiency by the plants, can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species, have more favourable climate impacts. This analysis only considers the conversion of biomass to biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment

Modeling persistence of coarse woody debris residuals in boreal forests as an ecological property

There is a trade-off between leaving coarse woody debris (CWD) in the stand, providing desirable ecosystem services, and harvesting it. To consider this trade-off, forest management needs to model describing the decomposition of CWD. When a trunk is lying on the ground, it can be attacked by microorganisms faster than when it is still standing. Current decomposition models fail to account for these local differences in processes, which may give rise to errors in the estimation of stand C balance. We extended the Q decomposition model to represent the influences of tree species and the local position of the wood. We utilized data from two studies on long-term deadwood decomposition in forests. We first calibrated the model on the whole dataset, and then divided the data into different CWD decomposition classes, and then allowed some of the parameters to vary between different CWD decomposition classes. The calibrations were performed within a Bayesian framework, which allowed for a statistically sound comparison of the calibration results. The difference between the remaining C mass predicted by the two versions of the model, one considering one single calibration for all decomposition classes and one specific to decomposition classes, depended on the CWD class but was in general substantial. Some classes, when modeled with a specific parameterization, resulted in C stocks after 50 yr 1-5 times less than that predicted by the single parameterization model. Logs decayed faster than snags, and birch wood much faster than pine and spruce wood, with little difference between the two conifers. Russian spruce wood decomposed somewhat faster than Finnish spruce wood. Incorporating our calibration, describing specifically the processes driving the wood decay locally, into a C balance model of forests may change model estimates substantially