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| Titel |
Reindeer grazing in subarctic boreal forest – influences on the soil carbon dynamics |
| VerfasserIn |
Kajar Köster, Frank Berninger, Egle Köster, Jukka Pumpanen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113081
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| Publikation (Nr.) |
 EGU/EGU2015-13278.pdf |
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| Zusammenfassung |
| Reindeer (Rangifer tarandus L.) are the most important large mammalian herbivores in the
northern ecosystems , which have many effects on plant diversity, soil nutrient cycling and
soil organic matter decomposition. Changes caused by reindeer in vegetation have indirect
effects on physical features of the soil e.g. soil microclimate, root biomass and also on soil C
dynamics. Earlier, the role of reindeer grazing in ground vegetation dynamics and in
soil carbon (C) dynamics has been mostly investigated in open tundra heaths. The
objectives of this study were to examine if and how the reindeer grazing (and the
possible temperature changes in soil caused by heavy grazing) is affecting the soil C
dynamics (CO2 efflux from the soil, C storage in soil, microbial biomass in the
soil).
In a field experiment in Finnish Lapland, in Värriö Strict Nature Reserve (67Ë 46’ N, 29Ë
35’ E) we have assessed the changes occurring in above- and belowground biomasses, and
soil C dynamics (CO2 efflux, soil C content, soil microbial biomass C) among areas grazed
and ungrazed by reindeer. Our study areas are located in the northern boreal subarctic
coniferous forest at the zone of the last intact forest landscapes in Fennoscandia,
where large areas of relatively undisturbed subarctic Scots pine (Pinus sylvestris
L.) forests can still be found. The sample plots located in the Värriö Strict Nature
Reserve (10 sample plots in total established in year 2013) are situated along the
borderline between Finland and Russia, where the ungrazed area was excluded from the
reindeer grazing already in 1918, to prevent the Finnish reindeer from going to
the Russian side and there are not many reindeer on Russian side of the area. To
characterize the stands we have established circular sample plots on areas with a
radius of 11.28 m, where different tree characteristics were measured (diameter at
1.3 m, height, height of a tree, crown height, crown diameter, stand age, etc.). On
every sample plot, four 0.5 x 0.5 m ground vegetation squares were established for
species composition and recovery measurements. The squares were photographed
for ground vegetation coverage analyses and definition of species composition.
Ground vegetation biomass was determined from 4 sample squares (0.2 x 0.2 m)
located systematically inside the circular sample plots (close to the ground vegetation
squares).
For soil C content measurements 5 soil cores (150 mm in length and 50 mm in diameter)
were taken from every sample plot in Värriö and in Sodankylä. The soil cores were divided
according to the morphological soil horizons; to litter and organic layer (F-horizon) and
humus layer (O-horizon). The layers in mineral soil were divided to eluvial (A-horizon) and
illuvial (B-horizon), and sieved. All roots were separated for root biomass calculations. The
soil C content was measured with an elemental analyser (varioMAX CN elemental
analyser, Elementar Analysensysteme GmbH, Germany). The soil respiration rates
were measured only in Värriö study areas. In order to determine the CO2 efflux
from soil to atmosphere, manual chamber measurements with a diffusion type CO2
probe (GMP343), were performed on 6 collars at each sample plot from June till
September (five times per collar) at measuring intervals of two weeks. Soil microbial
biomass was measured from five soil samples (soil from lower humus layer) per
sample plot in Värriö. To determine the soil microbial C biomass (Cmic) and soil
microbial N biomass (Nmic) chloroform fumigation direct extraction method was
used.
The average soil temperatures during the growing season (from June till September) were
similar in all sample plots in Värriö, ranging from 10.9 to 11.5 Ë C. There were also no
differences between daily average temperatures or soil moisture between grazed and
ungrazed areas. There was no statistically significant effect of reindeer grazing on soil C
content, although it was mainly higher in grazed area compared to the ungrazed area. Also
there was no significant differences in the soil CO2 efflux between the grazed and ungrazed
area. This means that although the soil CO2 efflux was mostly lower in the ungrazed area,
reindeer herding had no significant influence on the soil CO2 efflux. The CO2 effluxes were
lowest in June. In July and August, the CO2 effluxes were more than two times higher
compared to June.
The microbial biomass C (Cmic) measured from humus horizon was lower in the grazed
areas compared to the ungrazed areas, but the difference was not statistically significant.
However, the microbial biomass N (Nmic) was significantly lower (p > 0.05) in the grazed
areas compared to the ungrazed areas.
We found also that grazing decreased significantly the biomass and cover of lichens in the
coniferous forests. In Sodankylä the biomass of lichens was decreased around 74% due to
grazing. In Värriö the decrease was even bigger, there the amount of lichen biomass was
decreased more than 90% due to reindeer grazing. Ttal above ground biomass was higher in
the area where no reindeer grazing had occurred. Moreover, the tree biomass was higher in
the area with no grazing and tree regeneration was heavily affected by grazing, as we had
much less tree regeneration in the grazed areas compared to the ungrazed areas. |
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