Carbon stocks of soil and vegetation on Danubian floodplains

Abstract

Riparian forests are assumed to play a crucial role in the global carbon cycle. However, little data are available on C stocks of floodplains in comparison to other terrestrial ecosystems. In this study, we quantified the C stocks of aboveground biomass and soils of riparian vegetation types at 76 sampling sites in the Donau‐Auen National Park in Austria. Based on our results and a remotely sensed vegetation map, we estimated total C stocks. Carbon stocks in soils (up to 354 t ha–1 within 1 m below surface) were huge compared to other terrestrial ecosystems. As expected, soils of different vegetation types showed different texture with a higher percentage of sandy soils at the softwood sites, while loamy soils prevailed at hardwood sites. Total C stocks of vegetation types were significantly different, but reflect differences in woody plant biomass rather than in soil C stocks. Mature hardwood and cottonwood forests proved to have significantly higher total C stocks (474 and 403 t ha–1, respectively) than young reforestations (217 t ha–1) and meadows (212 t ha–1). The C pools of softwood forests (356 t ha–1) ranged between those of hardwood/cottonwood forests and of reforestations/meadows. Our study proves the relevance of floodplains as possible C sinks, which should be increasingly taken into account for river management. Furthermore, we conclude that plant‐species distribution does not indicate the conditions of sedimentation and soil C sequestration over the time span of interest for the development of soil C stocks.

Heterogeneity of soil carbon pools and fluxes in a channelized and a restored floodplain section (Thur River, Switzerland)

“…On one hand, this ensures the provision of a large diversity of habitats. On the other hand, the complex interplay of organic matter input and hot spots of both mineralisation and incomplete degradation strongly affects the potential of floodplains to store carbon, an ecosystem service of great current interest (Cierjacks et al, 2010). River widening combined with hydrological reconnection with former floodplains (from the time before channelization) as in the example presented here, is likely to be a successful recipe to achieve this goal, at least for a river characterised by pulse flooding.…”

Carbon storage and soil organic matter stabilisation in near-natural, restored and embanked Swiss floodplains

“…soil layers containing high proportions of soil organic matter (SOM), sedimentation/erosion events lead to i) the inheritance of organic matter brought by sedimentation (Bechtold and Naiman, 2009), and/or ii) the erosion of humic layers (Hoffmann et al, 2009), and/or iii) the burying of humic layers under new sediments (Blazejewski et al, 2009;Cierjacks et al, 2010). SOM accumulation also depends on in situ soil pedogenesis between floods, as well as the elevation from the riverbed, especially along a primary forest succession from pioneer tree species to old-growth uneven-aged forest (Van Cleve et al, 1993).…”

“…Focusing more specifically on soil organic carbon, the major component of soil organic matter, its storage in alluvial soils may vary as a function of several variables. For instance, the frequency of flooding (Bernal and Mitsch, 2008) and the concomitant deposition of carbon-rich sediments usually lead to an increase in soil organic carbon stocks (Cierjacks et al, 2011;Wohl et al, 2012), either in the humic layer or in the underlying organic matter layers enriched within the profile (Blazejewski et al, 2009;Cierjacks et al, 2010) thus preserving autochthonous organic material (Zehetner et al, 2009). Moreover, vegetation directly influences soil carbon accumulation and consequently soil development by aboveground and belowground inputs (Giese et al, 2000) leading to high spatial heterogeneity in terms of vertical and horizontal SOM distribution (Blazejewski et al, 2009;Drouin et al, 2011).…”

“…Only some research has highlighted the necessity to include carbon storage in the framework of river restoration (Ballantine and Schneider, 2009;Cabezas and Comin, 2010;Cierjacks et al, 2010).…”

Impact of flood deposits on earthworm communities in alder forests from a subalpine floodplain (Kandersteg, Switzerland)

“…As mentioned by Cierjacks et al [38], a large variability of soil properties within one vegetation type may be observed. These authors concluded that there is no clear correlation between vegetation type and soil properties.…”