land Article The Effect of Grazing on the Temperature Regime of the Alas Soils of Central Yakutia Victor Makarov * , Grigory Savvinov , Lyudmila Gavrilieva and Anna Gololobova Scientific Research Institute of Applied Ecology of the North, M.K. Ammosov North-Eastern Federal University, 43 Lenin Prospekt, 677980 Yakutsk, Russia; [email protected] (G.S.); [email protected] (L.G.); [email protected] (A.G.) * Correspondence: [email protected]; Tel.: +7-4112-33-68-51 Received: 7 September 2020; Accepted: 22 September 2020; Published: 1 October 2020 Abstract: There are numerous studies on the effect of grazing on the physical and chemical parameters of soils. However, the impact of grazing on the temperature regime of the alas soils in Central Yakutia is still poorly understood. This paper presents the results of long-term observations of the state of the soil-and-plant cover of thermokarst basins—i.e., alases—located in the Lena-Amga interfluve and actively used as pastureland. Observations of the process of the self-restoration of grass cover and changes in the temperature regime of alas soils were carried out on different variants (with isolation from grazing and without isolation). A significant increase in the average height of the grass stand and its foliage projective cover was observed with a gradual reduction in the number of species when isolated from grazing. Changes in the structure of the alas vegetation cover influence the microclimate of the soil. As a result of livestock grazing, the mean annual soil temperature rises and the amount and depth of the penetration of active temperatures increase. The most severe changes in the temperature regime occur in years with an abnormally high cover of snow. The soil warming observed during grazing undoubtedly has a favorable effect on soil organisms. However, in conditions of climate warming, grazing, especially overgrazing, can disrupt the permafrost regime and thereby provoke or intensify thermokarst phenomena. Keywords: soil temperature; climate change; alas soils; grazing 1. Introduction A significant part of the hay and pasture lands of the Republic Sakha (Yakutia) is made up of alas meadows. In the Leno-Amga interfluve, they occupy up to 50% of the natural feeding ground area. The alas landscapes, widespread in Central Yakutia, led to the establishment and further development of the northernmost cattle-breeding culture there. The ancestors of the modern Yakuts in the 13th and 14th centuries brought horses and cattle with them when entering the Middle Lena basin. They organized hayfield and pasture farming and, for many centuries, made certain changes not only in economic life but also in the ecological and geographical appearance of the region, according to historians [1]. Dispersed population distribution over vast areas of the Lena-Amga interfluve was typical for this region until the 1920s. Therefore, the anthropogenic pressure on thermokarst landscapes was minimal. The expansion of livestock farms and the local concentration of livestock were the main reasons for the intensification of degradation processes [2–10], which began in the 1920–1940s and coincided with the Soviet period of collectivization in the last century. Environmental mistakes in nature management were exacerbated by numerous unjustified organizational and economic decisions. For example, the enlargement of agricultural enterprises and the creation of large rural agglomerations in Central Yakutia happened without taking into account the environmental characteristics of taiga–alas ecosystems. According to Roman V. Desyatkin [6], Land 2020, 9, 365; doi:10.3390/land9100365 www.mdpi.com/journal/land Land 2020, 9, 365 2 of 15 the excessive enlargement of settlements was accompanied by a sharp reduction in forest areas, the mainLand 2020 environment-forming, 9, x FOR PEER REVIEW factor in the conditions of an arid climate. 2 of 15 In the post-Soviet period, after the collapse of planned farms, private livestock became tied to pastureDesyatkin and [6], hayfields the excessive near enlargement the communities. of settlements Thus, was unsystematic accompanied grazing by a sharp from reduction early spring in to late autumnforest areas, for the 145–165 main environment-forming days led to the complete factor in degradation the conditions of of pastures an arid climate. within a 3–5 km radius around settlements.In the post-Soviet Vegetation period, after under the suchcollapse conditions of planned is farms, severely private disturbed livestock and became represented tied to by low-productivitypasture and hayfields species. near The the soil communities. surface of pastures Thus, unsystematic is often exposed; grazing the from foliage early projectivespring to late cover of autumn for 145–165 days led to the complete degradation of pastures within a 3–5 km radius the plants does not exceed 40–50% [5]. around settlements. Vegetation under such conditions is severely disturbed and represented by low-productivityAccording to many species. researchers The soil [surface9–17], theof pastur physical–hydrologicales is often exposed; andthe foliage agrochemical projective properties cover of the soilof the are plants changed does by no overgrazing,t exceed 40–50% along [5]. with the degradation of vegetation, including the compaction of the sodAccording horizon toto criticalmany researchers limits, a sharp [9–17], decrease the physical–hydrological in the water permeability, and agrochemical the desiccation properties of the root-inhabitedof the soil soilare changed layer, an by increase overgrazing, in alkalinity along wi andth salinity,the degradation and a decrease of vegetation, in humus including and nutrients. the The ecompactionffect of grazing of the on sod the horizon temperature to critical regime limits of, alasa sharp soils decrease in Central in Yakutiathe water remains permeability, poorly the studied to date.desiccation It is known of the that root-inhabited the thermophysical soil layer, an properties increase in of alkalinity the soil changeand salinity, during and the a decrease compaction in of the soilhumus under and the nutrients. influence The of effect domestic of grazing animals. on Besidesthe temperature this, the regime penetration of alas of soils direct in sunlightCentral into the upperYakutia layers remains of alaspoorly soils studied is enhanced to date. It with is known the active that the grazing thermophysical of grass properties for livestock, of the especially soil change during the compaction of the soil under the influence of domestic animals. Besides this, the in exposed sites. In this context, the aim of this study is to determine the effect of grazing on the penetration of direct sunlight into the upper layers of alas soils is enhanced with the active grazing temperatureof grass regimefor livestock, of alas especially soils. in exposed sites. In this context, the aim of this study is to determine the effect of grazing on the temperature regime of alas soils. 2. Materials and Methods 2. Materials and Methods A typical thermokarst alas of Nyagaatta (N 62◦10043,4”; E 132◦00019,3”) in the middle part of the Lena-AmgaA typical interfluve thermokarst was selected alas of Nyagaatta for research. (N 62°10 It is located′43,4″; E 132°00 near the′19,3 village″) in the of middle Bere and part is of used the as a pastureLena-Amga all year roundinterfluve (Figure was selected1). for research. It is located near the village of Bere and is used as a pasture all year round (Figure 1). FigureFigure 1. ( a1.– cLocation) Location of the of study the study area. area. Land 2020, 9, 365 3 of 15 Land 2020, 9, x FOR PEER REVIEW 3 of 15 TheThe weather weather conditions conditions of theof the observed observed years years are representedare represented by theby datathe data of the of weather the weather station “Churapcha”station “Churapcha” (N 61◦59 0(N05”; 61°59 E 132′05″◦;26 E 0132°2615”), which′15″), which is located is located 28 km 28 southwestkm southwest of theof the object object of of our researchourLand research (Figure 2020, 9, x(Figure 2FOR). The PEER 2). climatic REVIEW The climatic characteristics characteristics of the researchof the research area based area based on the on materials the materials3 of of 15 the of last 10 yearsthe last of 10 observations years of observations have the following have the following indicators: indicators: the average the annualaverage air annual temperature air temperature is 8.7 ◦ C, − theis absolute −8.7 °C,The maximumthe weather absolute conditions is maximum+37.4 ◦ofC, the is and +37.4observed the °C, absolute andyears the minimumare absolute represented isminimum 55.2by the◦C. isdata On−55.2 average,of °C.the Onweather 281average, mm of − precipitation281station mm of “Churapcha” falls precipitation per year, (N andfalls 61°59 2 /per3′05 of″ ;year, theE 132°26 annual and′ 152/3″ amount), ofwhich the fallsisannual located in April–October. amount 28 km southwestfalls in The April–October. of average the object maximum of The snowaverageour thickness research maximum is (Figure 0.37 snow m. 2). The Thethickness territory climatic is characteristics is0.37 located m. The in an ofterritory the area research of is continuous located area based in permafrost. an on areathe materialsof Thecontinuous seasonalof the last 10 years of observations have the following indicators: the average annual air temperature thawingpermafrost. of soil The begins seasonal in early thawing May andof soil reaches begins from in early 1.5 toMay 3.0 and m by reaches the end from of September. 1.5 to 3.0 m by the is −8.7 °C, the absolute maximum is +37.4 °C, and the absolute minimum is −55.2 °C. On average, end of September. 281 mm of precipitation falls per year, and 2/3 of the annual amount falls in April–October. The average maximum snow thickness is 0.37 m. The territory is located in an area of continuous permafrost.