Holarctic Marmots as a factor of Biodiversity.
Rumiantsev V.Yu;, Nikol'skii A.A. & Brandler O.V. eds.,
Abstracts, 3d Conference on Marmots (Cheboksary, Russia, 25-30 August 1997),
Moscow ABF 1997, 216p., 85 (Russian), 185-186 (English).


MARMOT'S IMPACT ON SOILS AND VEGETATION OF SOLONETZ COMPLEXES IN NORTHERN KAZAKHSTAN


V.Yu. Rumyantsev, M.S. Soldatov

Dept. of Geography, Moscow State University, Moscow, Russia


Marmots are the most active animals of mammals with digging activity which transform soil cover. The age of large marmot-created hillocks is comparable with that of ecosystems which cover them, and hillocks are old enough to form a speciflc soil profile. The moisture redistribution caused by marmot-created microrelief under the conditions of high soil salinity is typical for the Kazakhstan steppes, might play a very important role. But the publications devoted to biocenotic lmportance of marmots do not actually analyse these processes. In this report based on the data obtained in 1982-1989 we analysed some peculiarities of the steppe marmot' impact on soil and vegetation of Northern Kazakhstan steppes.

We tried the method of detaiIed description of a profile for a wall of ditch (20 m in length and 1.5 m in depth) which connected two neighboring hillocks and a hollow between them. Three more hillocks in different soils were studied: we made heelings of 30-50 sm in different parts of a hillock. From hilocks we sampled soils from all horizonts. Specific electric conductivity (EL) was determined for soils of two hlllocks. It reflected distribution of common salts in the profile. In soil samples of other hillocks the pNa (index of sodium ions activity) which indicated contents of very soluble salts under the condltions of chloride sodium salinity, and pH were determined. The dlstribution of indices of comparative soil moisture in a hillock profile was investigated by sampling from depth of 0-50 sm in 6 hillocks.

Summarizing the results we can say that in non-saline soils the profile combination of a hillock' central portion usually correlated with a zonal type of surrounding soil. In highly saline soils their very dlfferentiated profile was completely destroyed by marmots. In central positions of hillocks where carring of ground by marmots from the depth up to 5 m is the main factor of soil forming, there are a soil with typical collection of characteristics namely peculiar zoogenic solonchak.

The other forming factor is intensive surface run off from hillocks which disperses salts carried out to the surface by marmots in the area. On steep hillock slopes much moisture filters go through the soil, and the rest does down from hilloks and is absorbed around them, forming a zone of excessive humidification. Salts dissolved by athmospheric falls washed off from hillocks surface snd enter the soil in its periphery.

The partlcular results of moisture and salt mlgration depend on characteristics of hillocks (form, size, density) and natural conditions of the area. In solonetz dissalinization and formation of soils simllar to solods in a hillock periphery occure. Soil microcomplex of a hillook in this case covers solonchac-like soil in the centre, solod-like one on the periphery and a solonetz simllar but dissaliniziated around the hillock in the surrounding soil. Transitions between the belts are very smooth. In slightly saline zonal soils where underlying rocks are also saline, the catena will be nearly the same, but the belt around a hillock might be represented by more solonetzic zonal soil than that of a surrounding steppe because of the secondary salinization.

In the study area the human actlvity influences greatly upon the marmot. Hillock have been left and non-inihabited wlth animals. Left hillocks can be long above a hundred years distinquished in a relief and vegetation. The pecularity of their soils seems to be also preserved up to complete hillocks leveling and succession will be directed to the surrourding soils. 40 hillocks of different succession stages were investigated. We supposed that the general development of soil-geobotanic succession from the moment when marmots stop to use a hillock is well reflected in the soil and vegetation dynamics of its upper portion which is the youngest in its soil respect. Six main stages of such a succession have been identified.

The pioneer stages are represented with groupings of one year salt worts, among them Petrosimonia triandra and Bassia sedoides predominate. Soils are very saline: EL=2.3-5.0. Stage of Anabasis salsa is typical for hillocks built of very saline tertiary kaolinite clays (EL=5.0) and also those situated in terrases of large brackish lagoons. Stage of Artemisfa pauclflora is typical for hillocks left long ago. Soils are usually very saline (EL=2-2.5) and the deeper they are, their salinity is higher. Festuca sulcata and Artemisia nitrosa groupings cover the slopes of these hillocks. Their soils are less saline. Rather often there are seyged microhollows around such hillocks. Their soil profile is close to that of the meadow chestnut one, but from a depth of 30-35 sm they are saline.

Stage of Fectuca sulcata and Artemisia nitrosa is a community built of dominants typical for undisturbed areas. Salinity is low or mean (EL=0.5-2.3). In some hillocks soils are not saline up to a depth of 25-30 sm. Stipa capillata groupings are confined to a well distinguished pading which at the next stage appears on a hillock top. Its soils are not saline, however from a depth of 30 sm small quantity of salts is registred. At the stsge of collapsed hillock Stipa capillata and Stipa lessingiana can be met, but a dominant is Festuca sulcata. Soils are not saline. Around there is a distinguished ring of solonetzic soils on which Festuca sulcata and Artemisia nitrosa prevail.

In the landscapes where soil forming rocks have s1ighter salinity and higter carbonat contents, a demutation series has another character. At the pioneer stages ephemerals Eremopyron orientalis and Ceratocarpus arenarius predominate; Bassia sedoides and Petrosimonia triandra are rarely observed. Anabasis salsa and Artemisia pauciflora stages are absent. Pyrethrum kasachstanicum predominates instead or the latter, and induced soil carbonate content. Thus, a succession in hillocks left by the marmots, is greatly determined by soil - geomorphologic peculiarities of natural coplexes.

Thus marmots impact on ecosystems in two ways: on the one hand, it increases mosaic structure of an area, creates local salt concentrations which are dispersed in the area and raise its soionetzicity and carbonate content, on the other hand, it "ameliorates" solonetz. In solonetz the "tail" of comparatively excessive humidification around a hillock has 3-5 m width and more. When a hillocks density is high, such "tails" can join each other, then, dissalinisatlon covers much larger areas then central portions of hillocks.


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