ReviewGround vegetation exceeds tree seedlings in early biomass production and carbon stock on an ash-fertilized cut-away peatland
Introduction
Peatlands cover about one-third of the land area in Finland and are thus the dominant features of the Finnish landscape. About 35%, i.e., 3.3 million hectares of the peatlands are still in natural condition and one-third of this area is protected. Over half of the original peatland area has been drained for forestry or agricultural purposes and less than one percent is utilized in the peat industry [1].
In their natural stage peatland ecosystems act as long-term sinks for atmospheric carbon which is stocked as peat in anaerobic conditions [2]. Drainage, vegetation removal and harvesting have, however, a crucial effect on carbon cycling in peatlands by disturbing severely the structure and function of the original bog ecosystem [3]. Peat harvesting is usually accomplished in about 20–50 years, but since the post-harvesting conditions are very harsh for plant establishment, cut-away areas may remain non-vegetated even for decades [4], [5], [6]. Coincidently, aerobic decomposition of the residual peat layer causes emissions of CO2 to seep into the atmosphere [7], [8]. Therefore, cut-away peatlands with no after-use act as a long-term source of atmospheric carbon [9], [10].
The after-use of cut-away peatlands is comprised of several alternatives, such as afforestation, agriculture, reed canary grass, Phalaris arundinacea L., cultivation, bird sanctuaries, berry production and habitat restoration [11]. Afforestation is one of the most popular options in Finland, Ireland and Sweden since it has both economical and aesthetic values [12], [13]. In addition to a high tree-growth rate, an important object of afforestation is to get the bare cut-away area covered by vigorous vegetation that restricts erosion and leaching of nutrients and fixes carbon into the ecosystem as soon as possible. Ash-fertilization, in particular, is found to increase significantly both the coverage and variety of ground vegetation and the quantities of birch seedlings on bare cut-away peatlands [6]. Although many studies have focused on the factors affecting the biomass production of tree stands on cut-away peatlands [14], [15], [16], [17], knowledge about the biomass dynamics of the ground vegetation in these areas is very scanty. In fact, changes in the ground vegetation biomass or CO2 fluxes have been studied only in restored cut-away areas [7], [18], [19], [20]. However, the high water-table level and anaerobic conditions of these rewetted cut-away peatlands make them differ completely from the afforested cut-away peatlands.
On afforested cut-away peatlands the decomposition rate of the residual peat layer and the productivity of the tree stands are regarded as the most important factors affecting the carbon balance [21]. Ground vegetation is readily disregarded in the present calculations of the climate impact of afforested cut-away peatlands [22] mainly due to the absence of exact studies. Still, the whole life cycle of the peatland including all the carbon emissions and sinks should be considered [23]. In fact, at the early stages of the afforestation vigorous ground vegetation may have a major role in carbon sequestration, quite comparable to that of tree seedlings. In this study we examined the biomass and carbon stock of ground vegetation and young tree seedlings on an ash-fertilized and afforested cut-away peatland.
Section snippets
Experimental field
The experimental field was established in 2000 in Finland (64° 44′ N, 25° 16′ E, 45 m a.s.l.) on a cut-away peatland, abandoned by the peat industry since 1996. The thickness of the residual peat layer, Sphagnum-Carex (H5), varied between 20 and 50 cm, and the soil below the peat was sandy till. Ditches of the trial area were cleaned in August 2000 but the surface of the area was left uncultivated prior to the establishment of the trial plots.
Three blocks were established on the experimental
Above-ground biomass and carbon stock
Fertilization increased the biomass of tree seedlings significantly (ANOVA F = 3.874, df = 5, p = 0.003) whereas the differences in the tree seedling biomass between the two afforestation methods (F = 1.938, df = 1, p = 0.167) or interaction between the afforestation and fertilization methods (F = 0.501, df = 5, p = 0.774) were statistically non-significant. Consequently, the data of the two afforestation treatments were combined and the results presented hereafter concern only the effects of fertilization. The
Discussion
The biomass of ground vegetation is frequently omitted when estimates are made of the biomass production and carbon balance on cut-away peatlands after afforestation. Our results, however, proved that the combined above-ground biomass of mosses and herbaceous plants and thus also the amount of C sequestered into the ecosystem was as much as two times the amount of the biomass of tree seedlings four growing seasons after fertilization. Surprisingly, the amount of mere ground vegetation biomass
Acknowledgements
Mr. J. Issakainen organized the field trials, Dr. A. Kauppi made competent comments on the manuscript and Mr. R. Gear revised the English text. The plant samples were prepared and analyzed in the laboratories of the Finnish Forest Research Institute (Metla) in Muhos and Vantaa. This study was a part of Metsähiisi – project, which was carried out in co-operation of Vapo Company and Metla. The National Technology Agency of Finland (Tekes) supported this work financially. We thank sincerely all
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2023, Science of the Total EnvironmentThe effect of oil shale ash and mixtures of wood ash and oil shale ash on the above- and belowground biomass formation of Silver birch and Scots pine seedlings on a cutaway peatland
2017, Ecological EngineeringCitation Excerpt :The Puhatu cutaway peatland has a high wood production potential because of the very fertile peat: the mean N cotent in the top layer peat was 3.0%. Huotari et al. (2009) considered that adequate peat N concentration for tree growth is 2.3%. An earlier study showed after fertilization with ashes that mixing oil shale ash with P-rich wood ash could be an alternative to stimulate the growth of trees in cutaway peatlands (Kikamägi et al., 2014).
Recycling of ash - For the good of the environment?
2015, Forest Ecology and ManagementCitation Excerpt :However, the review by Aronsson and Ekelund (2004) concluded that the biological effects of wood ash application on forest soil and aquatic ecosystems were ambiguous. Since then, experiments have matured and a considerable body of new results has been produced regarding ash fertilisation impacts on, e.g., heavy metal concentrations in berries and mushrooms (Moilanen et al., 2006), ground vegetation (Huotari et al., 2007, 2009, 2011), soil microbial processes (Rosenberg et al., 2010; Saarsalmi et al., 2010, 2012), greenhouse gas emissions (Maljanen et al., 2006a,b; Ernfors et al., 2010; Klemedtsson et al., 2010) and watercourses (Piirainen et al., 2013). Also, the new reports provide insight into the responses in peatland forests, which have received little attention in earlier papers (e.g., Augusto et al., 2008).
Profitability of short-rotation biomass production on downy birch stands on cut-away peatlands in northern Finland
2015, Biomass and BioenergyCitation Excerpt :Downy birch is an early successional tree species thriving on peatlands and in mineral soils with poor drainage. Dense downy birch stands can be established on cut-away peatlands by planting, seeding, or natural afforestation [2,22–26]. On account of the low concentrations of potassium and phosphorus in residual peat, however, improvement of soil nutrient status is usually a prerequisite for successful afforestation [2,23,25–27].