Microtopography and Plant-Cover Controls on Nitrogen Dynamics in Hummock Tundra Ecosystems in Siberia

Biasi, Christina; Wanek, Wolfgang; Rusalimova, Olga; Kaiser, Christina; Meyer, H.; Barsukov, Pavel; Richter, Andreas

doi:10.1657/1523-0430(2005)037[0435:mapcon]2.0.co;2

Cited by 36 publications

(46 citation statements)

References 63 publications

(67 reference statements)

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“…Likewise, frost heaving is an unlikely mechanism, as little topographic variation was evident in our mesocosms after the first winter. These processes could, however, be important in other systems where microtopography is plant derived (Fogel et al 2004, Biasi et al 2005, Bouma et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Formation of tussocks by sedges: effects of hydroperiod and nutrients

Lawrence¹,

Zedler²

2011

Ecological Applications

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Abstract. Tussock formation is a global phenomenon that enhances microtopography and increases biodiversity by adding structure to ecological communities, but little is known about tussock development in relation to environmental factors. To further efforts to restore wetland microtopography and associated functions, we investigated Carex stricta tussock size in relation to elevation (a proxy for water depth) at a range of sites in southern Wisconsin, USA, and tested the effect of five hydroperiods and N þ P addition (15 g N/m 2 þ 0.37 g P/m 2 ) on tussock formation during a three-year mesocosm experiment. Wet meadows dominated by C. stricta averaged 4.9 tussocks/m 2 , with a mean volume of 1160 cm 3 and height of 15 cm. Within sites, taller tussocks occurred at lower elevations, suggesting a structural adaptation to anoxic conditions. In our mesocosm experiment, C. stricta accelerated tussock formation when inundated, and it increased overall productivity with N þ P addition. Within two growing seasons, continuous inundation (þ18 cm) in the mesocosms led to tussocks that were nearly as tall as in our field survey (mean height in mesocosms, 10 6 1.3 cm; maximum, 17 cm). Plants grown with constant low water (À18 cm) only formed short mounds (mean height ¼ 2 6 0.4 cm). After three growing seasons, the volume of the largest tussocks (3274 6 376 cm 3 , grown with þ18 cm water depth and N þ P addition) was 12 times that of the smallest (275 6 38 cm 3 , grown with À18 cm water depth and no N þ P). Though tussock composition varied among hydroperiods, tussocks were predominantly organic (74-94% of dry mass) and composed of leaf bases (46-59%), fine roots (10-31%), and duff (5-13%). Only the plants subjected to high water levels produced the vertically oriented rhizomes and ascending shoot bases that were prevalent in field-collected tussocks. Under continuous or periodic inundation, tussocks achieved similar heights and accumulated similar levels of organic matter (range: 163-394 g C/m 2 ), and we conclude that these hydroperiods can accelerate tussock formation. Thus, C. stricta has high utility for restoring wetland microtopography and associated functions, including carbon accumulation.

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Section: Discussionmentioning

confidence: 99%

Formation of tussocks by sedges: effects of hydroperiod and nutrients

Lawrence¹,

Zedler²

2011

Ecological Applications

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“…Although the flow rate of mineralized N is smaller than the standing N stock in Arctic ecosystems (e.g., corresponding to only 0.2 % of the standing N stock in the case of Alaska; Shaver et al 1992), this flow N is precious because it is available to microbes and plants. Biasi et al (2005) evaluated gross N mineralization rates at ambient temperatures (1.0-6.2°C) in mineral soils of hummock tundra on the Taymyr Peninsula in central Siberia. Hummock tundra is a kind of patterned ground and consists of hummocks and interhummock areas.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of ammonia oxidation potentials and ammonia oxidizers in mineral soil under Salix polaris–moss vegetation in Ny-Ålesund, Svalbard

Hayashi

Shimomura²,

Morimoto

et al. 2015

Polar Biol

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Although nitrification is a unique and important process in the nitrogen cycle with respect to ammonium consumption and nitrate production, limited information on this process is available for high-Arctic soils. We elucidated the ammonia oxidation potentials (AOPs) and characteristics of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in mineral soils under climax vegetation, i.e., Salix polaris (polar willow)-moss vegetation, on a coastal hill in Ny-Å lesund, Svalbard. AOPs at 10°C were determined by incubation with sufficient substrate (2 mM ammonium). The ammonia monooxygenase subunit A (amoA) genes of AOB and AOA were analyzed by using quantitative polymerase chain reaction and pyrosequencing. AOPs ranged from 1.1 to 14.1 ng N g -1 dry soil h -1 -relatively low but of a similar order to the gross nitrification rates reported in another Svalbard study. AOP was positively correlated with thickness of the moss layer (P \ 0.01), soil water content, and ammonium nitrogen content (P \ 0.05). The population sizes of both AOB and AOA were not significantly related to AOP or edaphic factors. For AOB-amoA, six major operational taxonomic units (OTUs) were identified, all of which were classified into the Nitrosospira Mount Everest cluster. For AOAamoA, six major OTUs were also identified, five of which were grouped with sequences from cold environments within clade A of the Nitrososphaera cluster, i.e., species known to have low, or no, AOP. It is, therefore, possible that the AOPs measured at the study site were driven mainly by psychrotolerant AOB.

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“…Many studies have suggested that temperature (Oberbauer et al, 1991;Hobbie, 1996;Hartley et al, 1999;) and soil moisture (Johnson et al, 1996;Mueller et al, 1999) are major determinants of nutrient cycling rates in arctic soils, however there is increasing evidence that topographic patterns also play a role in controlling nutrient turnover (Walker et al, 2004;Mueller et al, 1999;Biasi et al, 2005). Topography is the primary determinant of soil moisture patterns across tundra landscapes, and therefore plays a major role in determining the distribution of vegetation types (Walker, 2000) and their cyanobacterial associations.…”

Section: Topography and Microtopographymentioning

confidence: 99%

“…In hummock-hollow tundra ecosystems mosses tend to dominate the hollows, which are expected to exhibit low growth rates, slow decomposition rates, relatively high C/N ratios and long nutrient turnover times (Hobbie, 1995;Biasi et al, 2005). In contrast hummocks can be dominated by graminoids and are expected to have higher growth rates, lower C/N ratios and more rapid nutrient turnover (Chapin et al, 1995;Hobbie, 1995;Biasi et al, 2005).…”

Section: Topography and Microtopographymentioning

confidence: 99%

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Nitrogen fixation by associative cyanobacteria in the Canadian Arctic.

Stewart¹

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Microtopography and Plant-Cover Controls on Nitrogen Dynamics in Hummock Tundra Ecosystems in Siberia

Cited by 36 publications

References 63 publications

Formation of tussocks by sedges: effects of hydroperiod and nutrients

Formation of tussocks by sedges: effects of hydroperiod and nutrients

Characteristics of ammonia oxidation potentials and ammonia oxidizers in mineral soil under Salix polaris–moss vegetation in Ny-Ålesund, Svalbard

Nitrogen fixation by associative cyanobacteria in the Canadian Arctic.

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