沙漠研究 22-1, 295 -298 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－Preliminary results on surface and soil characteristics of Brandt’s vole(Microtus brandti) habitat in Central Mongolia using satellite data
Marie SAWAMUKAI*1), Buho HOSHINO2), Sumiya GANZORIG2), Tsedendamba PUREVSUREN1),
Mitsuhiko ASAKAWA3) and Kenji KAWASHIMA1)
Abstract: Does Brandt’s vole (Microtus brandti) makes damage to the environment or provides management? To solve such
query, we analyzed land surface characteristics, the nitrogen content and soil hardness measurements at the Brandt’s vole colony, forexamining changes of land surface and soil by activity of Brandt’s vole. The soil hardness was lowest at colony (about 13 mm) andhighest at off colony area (about 25 mm). The soil became softer at the colony places. The nitrogen content was high on the mound,and showed high nutritive value of soil. The colonies were located at places with different altitude and slopes, but mostly at no shade(0.73~ 0.87). The soil mixing made by burrowing activity of Brandt’s voles might have a great impact on ecosystems of Mongolian
steppe. Soft soil on colony enriched in nitrogen presented good condition for such plants as Artemisia adamsii. As conclusion, we
considered that Brandt’s vole might indicate the degradation of pasture and play important role in ecosystem recovery.
Key Words: Brandt’s vole, Desertification, Land surface characteristic, Remote sensing, Soil hardness

1. Introduction
Until recently, burrowing rodents had been considered tobring pest damage to the pastureland and the cause of declineof grassland around the world (Zhong et al., 1985). The
impact of rodents in ecosystem of Mongolia is heavy; herders
are considering it as major cause of degradation of pastureland(Zhang and Zhoug, 1981). However, Brandt’s vole has
habitat to over a wide range in Mongolia, and modifying soil’s
physical properties through such as increasing above-groundbiomass, urinating and defecating. Their roles in ecologicaldiversity are now reconsidered (Yoshihara et al., 2010b).
This is said to be the “Keystone” species acting as an
ecosystem engineer. The Brandt’s vole prefers grassland
habitat with shorter plants, and easily expanding throughpastures that have been heavily grazed by livestock (Zhang etal., 2003). According to the researches (Batsaikhan et al.,2001) the Brandt’s vole dislikes steppes with tall grasses and its
expansion is usually in degraded pastures. The colonies ofBrandt’s vole are significantly changing vegetation, soil andlandscape of steppe in Mongolia. However, the influence of
the Brandt’s vole activity on the soil composition, surface soil
temperature and soil moisture at the landscape scale, remainedunclear. The goal of the present study is to clarify the effectof Brandt’s vole on the grassland by studying the differences insurface characteristics, plant and soil of each landscape. On

the basis of these evaluations, we hope to provide good
approaches to the management of Brandt’s vole in Mongolia.

2. Materials and Methods
2.1. Study site
The study sites (3) are locates 100 km south from
Ulaanbaatar in Mongolia. We set a plot with dimensions 100×100 m in the site 1 (47°25’54”N, 106°38’26”E) and made avegetation survey, soil sampling at off colony, new colony andold colony places, simultaneously. We set 2 additional plots(site 2: 47°40’37”N, 106°40’24”E, site 3: 47°35’32”N,106°38’21”E).
2.2. Satellite data
2.2.1. Normalized Difference Vegetation Index
The Normalized Difference Vegetation Index (NDVI) was
calculated using the satellite data from Landsat 5 Themaitic
Mapper (TM) (2010/07/31, pixel size 30 m, Path/Row: 131 /027). NDVI is expressed as follows:

NDVI =NIR − RED
NIR + RED

(1)

Where, NIR is near infrared reflectance and RED is visible redlight reflectance. This could be calculated from band 3(RED) and 4 (NIR) of the Landsat 5 Thematic Mapper (TM).

* Corresponding Author: sawamukai0818@gmail.com
582Bunkyodai-Midorimachi, Ebetsu, Hokkaido 068-8501, Japan
1) Graduate school of Dairy Science, Graduate School, RakunoGakuen University2) Department of Biosphere and Environ mental Sciences, Faculty of Environment Systems, RakunoGakuen University3) Department of Pathobiology / Wild Animal Medical Center, School of Veterinary Medicine, RakunoGakuen University

Table 1. The calibration constants of Landsat TM sensor.

K1K2

Landsat TM
607.761260.56

Table 2. Landscape characteristic of study area.
Altitude (m) Slope (°)
Site 1 1609±10.6 12.30±1.37
Site 2 1291±4.10 6.43±3.02
Site 3 1331±0.82 4.76±1.08

Aspect (°)
85.7±15.6
308.5±41.6
67.6±12.6

Shaded relief value
0.88±0.03
0.77±0.04
0.84±0.01

2.2.2. Land surface temperature
The Land surface temperature (LST) was calculated usingsame satellite data. LST is expressed as follows:
T=K2
 K1
+ 1
1n RCV2(2)Where, T is degrees Kelvin, CVR2 is the atmosphericallycorrected radiance, and K1 and K2 is calibration constants ofLandsat TM and the value of K1 and K2 are show in Table 1.
2.2.3. Landscape characteristic
Landscape characters of the Brandt’s vole habitat such as
the slope, altitude, aspect, and shaded relief value were studied
using ASTER GDEM (pixel size 30m, https://wist.echo.nasa.gov).
This data was calculated fromgeometric corrected ASTER spectral band 3N and 3B.
2.3. Field data
2.3.1. The soil hardnessThe measurement was made around each site (3 plots intotal), using Yamanakashiki device (Fujiwara ScientificCompany). We measured soil hardness at 5 cm, 10 cm and20 cm depth from the vertical position of soil profile.
2.3.2. Vegetation Survey
At each site 1×1m quadrates were set for the vegetation
survey (3 plots). This survey included measurement of theplant height, dry matter amount and coverage for each species
found inside the quadrate.
2.3.3. The soil and plant sampling
We measured the nitrogen content and carbon content ofsoil samples taken at 10 cm depth from surface. The
sampling was made three times at each plot (9 samples in 3plots). We also measured the nitrogen content and carbon
content of dominant plant (Stipa krylovii). We analyzed
carbon and nitrogen content of soil and plant, using N/Canalyzer (SUMIGRAPH, NC-22F).

3. Results and Discussion
3.1. The habitat of Brandt’s vole3.1.1. Landscape characteristic
The altitude, slope aspect and shaded relief values in eachsite was shown in Table 2. Colonies of Brandt’s vole at all
three sites located obviously at un-shaded, bright places.
Other landscape characteristics were highly varied.

Fig. 1. Normalized Difference Vegetation Index of study area in 31
July 2010. The (A) shows NDVI of study area near site 1; the(B) shows NDVI of study area near site 2; the (C) shows thezoomed image near site 2 to distinguish black circle.

3.1.2. Normalized Difference Vegetation Index
Figure 1 shows the NDVI image calculated from Landsat
5 spectral band 3 and band 4. The NDVI values of colonies
in site 1 ranged from 0.23 to 0.28 and mean was 0.25. The
NDVI values of colonies in site 2 ranged from 0.15 to 0.19 andmean was 0.17. But, the NDVI values at off colonies in site 1
ranged from 0.20 to 0.34 with a mean 0.27. The NDVI
values of off colonies in site 2 ranged from 0.13 to 0.19 andmean was 0.16. The habitat of Brandt’s vole appeared to behigh in the NDVI from Figure 1, however that values oncolony and off colony grounds were unclear at site 1 and 2.
Because, in regard to the colony size, a pixel size of satellite
image was too large. To make more detailed observation thehigher resolution satellite imagery is required.
3.1.3. Land surface temperature (LST)
Figure 2 shows LST calculated from Landsat 5 spectral
band 6. The LST values were lowest at the colony ofBrandt’s vole. LST of colonies in site 1 ranged from 23.4°Cto 30.7°C and mean was 31.8°C in site 1. LST of colonies insite 2 ranged from 32.4°C to 32.8°C and mean was 32.7°C.
But, the LST of off colonies in site 1 ranged from 29.4°C to32.8°C and mean was 31.8°C. The LST values in offcolonies in site 2 ranged from 31.9°C to 33.2°C and mean was
32.7°C. Because, in regard to the colony size, a pixel size of

Fig. 4. Plant coverage and Dry matter amount at each plot in site 1.
(a), (b), (c) were the measurement value of off colony; newcolony and old colony, respectively.

Fig. 2. The LST of study area in 31 July 2010. The (A) shows LSTof study area near site 1; the (B) shows LST of study area near site
2; black circle: colony of Brandt’s vole.

The soil hardness (mm)305cm

2010cm1020cm
0abcFig. 3. The soil hardness of each plot in site 1. (a), (b), (c) were themeasurement value of off colony; new colony and old colony,respectively.

satellite image was also too large, so we need to use more highresolution satellite imagery to observation LST of habitat ofBrandt’s vole.
3.2. The effect of Brandt’s vole3.2.1. Soil hardness
The soil hardness was lowest at colony (about 13 mm),highest at off colony area (about 25 mm) (Fig. 3). The soilbecame softer after colony habitation. Thus, we can consider
that Brandt’s vole digging activity has been softening the soil
around its colony ground and that Brandt’s vole provided goodcondition for the plant growth, especially for those species that
prefer soft soil.
3.2.2. Vegetation Survey
The plant coverage was low at off colony and new colony(22.9% and 21.5%) and highest at old colony area (69.3%)(Fig. 4 (A)). Dry matter amount was lowest at off colony(105.2 g/m2) and highest at old colony area (160.6 g/m2) (Fig.
4 (B)). Brandt’s vole activity supposedly has increased aFig. 5. Carbon and nitrogen content and their ratio of soil in site 1.
(a),(b), (c) were the value of off colony, new colony and oldcolony, respectively.

compartment (Artemisia adamsii) on colony ground.
Because, livestock don’t like to eat Artemisia adamsi, and also
the colony soil provided better condition for the plant grow.
3.2.3. Comparative studies of carbon and nitrogen of soil
and plant in the area of on colony and off colony
The soil carbon content was lowest at off colony (5.57%),
highest at old colony (7.63%) (Fig. 5 (A)). The soil nitrogencontent was lowest at off colony (0.23%), highest at old colony(0.28%) (Fig. 5 (B)). The soil C/N ratio was lowest at offcolony (24.6), highest at old colony (27.3) (Fig. 5 (C)). Thus,
we considered that the increase of both carbon and nitrogencontent of soil is due to colonial activity of Brandt’s vole.
The intake of organic matter to soil can be explained by thelarge amount of vole’s urine and feces.
The carbon and nitrogen content was studied in Stipa
krylovii (Sk), which is a main dominant species in community
and may also serve as an indicator species of healthy
undegraded grassland, because in degraded pastures the Sk ismostly eaten by livestock. The carbon content of Sk waslowest at old colony (61.1%) (Fig. 6 (A)). The nitrogencontent of Sk was highest at old colony (2.69%) (Fig. 6 (B)).

manager.
To understand the mechanism, further detailed studies arenecessary. We will increase plot numbers to get more dataand samples necessary for the thorough future analysis.

AcknowledgementThis work was supported by Grant-in-Aid for Scientific
Research (S) (No.) 21221011 (Project leader: Prof. Y.
Shimada) from JSPS of Ministry of Education, Culture, Sports,Science and Technology.
References

Fig. 6. Carbon and nitrogen content and their ratio of soil in site 1.
(a), (b), (c) were the value of off colony, new colony and oldcolony, respectively.

The C/N ratio of Sk was lowest at old colony (22.7) (Fig. 6(C)). We suggest that reserves of nitrogen were becamemuch more accumulated at the old colony.

4. Conclusion
Our preliminary research has revealed that Brandt’s vole
activity softens soil at colony places, increases the nitrogencontent of soil, and increased the aboveground biomass
amount based on field measurement. However, the satellite
imagery that was used in present study did not revealed clear
differences between NDVI and LST at colony and off colony
places. Because, the pixel size of satellite image was larger
than of colony size (5×5 m). The higher resolution forsatellite imagery (30×30 m) is needed for thorough observation.
Also, more data is required for the detailed analysis andinterpretation of the ecosystem role of the Brandt’s vole inMongolia. Thus, it is necessary to evaluate the correlation.
So far, the rodent not only consuming the plants in large
volumes and harms pastures, but also its activity makes
environment more better for various plant species. The
Brandt’s vole can be rightly called grassland ecosystem

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