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Storage and Mineralization of Carbon and Nitrogen in Soils of a Frost-Boil Tundra Ecosystem in Siberia

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Storage and Mineralization of Carbon and Nitrogen in Soils of a Frost-Boil Tundra Ecosystem in Siberia Applied Soil Ecology 29 (2005) 173–183 www.elsevier.com/locate/apsoil Storage and mineralization of carbon and nitrogen in soils of a frost-boil tundra ecosystem in Siberia Christina Kaisera, Hildegard Meyera, Christina Biasia, Olga Rusalimovab, Pavel Barsukovb, Andreas Richtera,* aInstitute of Ecology and Conservation Biology, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria bInstitute of Soil Science and Agrochemistry, Russian Academy of Sciences, Siberian Branch, Str. Sovetskaya 18, Novosibirsk 630099, Russia Received 9 February 2004; received in revised form 22 October 2004; accepted 28 October 2004 Abstract This study examines the carbon and nitrogen stocks of soils and vegetation in different frost-boil tundra microsites (rims, troughs and bare soil patches) and aims at elucidating differences in controls of organic matter turnover. Troughs, the wettest microsite, stored the greatest part of soil C and N (23.9 and 1.7 kg mÀ2, respectively), while drier rims held only 50% and bare soil patches only about 17% of the C and N found in troughs. Both C and N mineralization rates were higher in rims compared to troughs, suggesting a higher turnover of organic matter in rims. On an areal basis N was predominantly mineralized in mineral horizons, while C mineralization was more or less equally distributed between organic and mineral horizons. Thus, atmospheric warming, which has a stronger effect on the upper soil layers, may increase C mineralization to a higher extent than N mineralization (mainly located in lower soil layers). This suggests that frost-boil tundra ecosystems may be (at least in the short- term) sources of CO2 to the atmosphere. Furthermore, the combined results of gross N mineralization and net N mineralization measurements showed a higher microbial sink strength for N in rims compared to troughs, suggesting that decomposition of organic material in rims is controlled mainly by N availability, while the main factor constraining decomposition in troughs may be unfavourable hydrothermal conditions. This may lead to differential responses of frost-boil tundra microsites to changing climatic conditions. # 2004 Elsevier B.V. All rights reserved. Keywords: Arctic soil; C and N storage; Global warming; Soil microbial biomass; Microrelief 1. Introduction Tundra soils exhibit the highest carbon densities of À2 * Corresponding author. Tel.: +43 1 4277 54252; all life-zones of the world (on average 21.8 kg C m ) fax: +43 1 4277 9542. and have been estimated to store approximately 14% E-mail address: [email protected] (A. Richter). of the world’s total soil carbon (Post et al., 1982). This 0929-1393/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apsoil.2004.10.005 174 C. Kaiser et al. / Applied Soil Ecology 29 (2005) 173–183 accumulation of organic material in arctic soils can be interesting system in which to study decomposition mainly explained by wet conditions, low temperatures processes. and low litter quality, that have constrained decom- The overall goals of this study were (1) to position of soil organic material more than net primary determine carbon and nitrogen stocks of soils and production (NPP) (Nadelhoffer et al., 1997; Hobbie vegetation in different frost boil tundra microsites in et al., 2000; Jonasson et al., 2001). The distribution of order to gain insight into historical differences in C and N stocks within different tundra ecosystems is organic matter turnover processes and (2) to elucidate highly variable, showing pronounced differences in whether differences in controls of organic matter organic matter turnover (Jonasson et al., 2001). Those turnover currently exist for different microtopographic arctic ecosystems that exhibit the highest accumula- positions. We hypothesised, that in wetter troughs, tion of organic matter and the highest soil to decomposition is mainly controlled by soil moisture, vegetation organic matter ratio are those with the while in drier rims the availability of N may be the wettest soils (Schlesinger, 1997; Hobbie et al., 2000; limiting factor for decomposition processes. Towards Shaver and Jonasson, 2001), demonstrating a strong these goals we measured gross and net N mineraliza- hydrological control on carbon exchange processes tion rates and estimated organic and inorganic N pools (Johnson et al., 1996). together with microbial, plant and soil C and N stocks. Predicted global warming, which is considered to be Based upon these data we discuss possible different more pronounced in high latitudes (IPCC, 2001)may responses to predicted climatic change. lead to enhanced soil respiration and C loss from tundra ecosystems. The potential of the N cycle to buffer such increased CO2 losses in tundra ecosystems is well 2. Methods studied. It is thought that higher soil temperatures may lead to enhanced soil N availability and subsequently to 2.1. Study site increased NPP in these N-limited ecosystems (Nadel- hoffer et al., 1992; Shaver et al., 1992; Schimel et al., We studied a frost-boil tundra ecosystem, also 1994; McKane et al., 1997; Jonasson et al., 1999, 2001). called spotted tundra in the Russian literature, at the However, not only NPP but also decomposition of Gydansky Peninsula in Siberia (N 69843.00,E organic material itself may be strongly N-limited in 74838.80; 74 m a.s.l.). The site was located in the tundra ecosystems (Moorhead and Reynolds, 1993). arctic bioclimate subzone D (CAVM Team, 2003), Therefore, the ability of microbial decomposer com- also called typical tundra subzone (Chernov and munities to successfully compete with plants for Matveyeva, 1997). nutrients may control the relationship between decom- The frost-boil tundra ecosystem consisted of position of soil organic matter and NPP (Fenchel et al., patches of bare soil (50–70 cm in diameter), 1998), and in turn be crucial for the carbon balance. It is surrounded by rims (5–15 cm high) and troughs thus essential to understand the specific limitation of (25–35 cm wide and 5–15 cm deep). It is thought that decompositionindifferent ecosystems.Evenwithinone this type of microrelief has developed by cryogenic tundra ecosystem, decomposition may be controlled by soil processes: cracks were first vegetated by mosses different factors, due to small-scale differences in and forbs, forming a soil with a peat horizon. In turn topography and hydrology. some of the cracks widened leading to troughs, while Frost-boil tundra has a three element structure: the turf eventually ‘‘creeped’’ onto the flat surface of patches of bare soil, surrounded by rims and troughs the ground, forming rims, adjacent to remaining that have developed due to cryogenic processes in the patches of bare soil (Chernov and Matveyeva, 1997). soil. The topographic differentiation into low-level The vegetation at our study site can be described as troughs, mid-level bare soil patches and high-level a nontussock sedge, dwarf-shrub, moss tundra (CAVM rims causes different hydrothermal conditions, such as Team, 2003). The shrub layer (15–20 cm) consisted of soil moisture and soil temperature, and different Betula nana, Salix glauca, S. lapponum, Vaccinium duration of snow cover within the three microsites vitis-idea, V. minus and Dryas punctata and the main (Chernov and Matveyeva, 1997), which makes it an graminoides were Carex arctisibirica, Arctagrostis Download English Version: https://daneshyari.com/en/article/9445218 Download Persian Version: https://daneshyari.com/article/9445218 Daneshyari.com.
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