Архив метки: NDVI

THE USE OF MULTI-TEMPORAL HIGH-RESOLUTION SATELLITE IMAGES TO SOIL SALINITY ASSESSMENT IN THE SOLONETZIC COMPLEX (REPUBLIC OF KALMYKIA)

Arid Ecosystems

UDC 631.4

Prokopyeva K.O. THE USE OF MULTI-TEMPORAL HIGH-RESOLUTION SATELLITE IMAGES TO SOIL SALINITY ASSESSMENT IN THE SOLONETZIC COMPLEX (REPUBLIC OF KALMYKIA) // Arid Ecosystems. 2022. Vol. 28. № 4 (93). P. 61-74. | PDF

Remote assessment of soil salinity of natural solonetzic complexes, which are characterized by subsurface soil salinity, is a challenging task. Nevertheless, research in this area is promising, as salinity is a striking limiting factor affecting vegetation growth, and thus manifests itself on the spectral characteristics of the land surface. In this paper, an analysis of multi-temporal high-resolution satellite images compared with detailed ground data on soil salinity was carried out using the principal component method and multiple linear regression. Images from QuickBird (2007) and SuperView-1 (2021) satellites were used as remote sensing data with a spatial resolution of 2 m. Salinity was estimated by specific electrical conductivity (EC) in a water suspension of 1:5. Ground surveys were carried out in 2011 and 2021. It was found out that there were no significant changes in soil salinity in the key area during the 10-year period, but there were changes in vegetation conditions, which are reflected in the NDVI vegetation index maps. The principal components were calculated from multi-temporal high-resolution satellite images and it was concluded that the first three components explain almost 97% of the total image variability. Models based on multiple linear regression analysis describe well the soil salinity (R2 of the model is 0.68, 0.77, 0.83 for layers 0-30, 0-50, 0-100 cm, respectively). The constructed models based on remote sensing data have shown good agreement when tested with the control sample (R2 between predicted and measured EC values is 0.70, 0.87, 0.83 for layers 0-30, 0-50, 0-100 cm, respectively). The proposed models will be useful for estimation of salinity of soils of solonetzic complex of dry steppe from high resolution satellite images.

Keywords: QuickBird, SuperView-1, assessment of soil salinity, solonetzic complexes, Principal Components Analysis (PCA), NDVI, Caspian Lowland.

Acknowledgement. The author expresses gratitude for the help in the work of M.V. Konyushkova, I.P. Minkeev, A.F. Novikova, M.B. Shadrina, S.S. Ulanova, I.N. Semenkov, A.A. Kontoboitseva, Isinufen, N.M. Tserenov, U.Y. Ulumdjiev.

DOI: 10.24412/1993-3916-2022-4-61-74

EDN: PTOYDP

STABILITY OF PHYTOMASS DYNAMICS IN PROTECTED LOW MOUNTAIN-STEPPE LANDSCAPES AND PASTURES IN THE SOUTHERN URALS

Arid Ecosystems

UDC 911.2 (470.56)

Khoroshev A.V. STABILITY OF PHYTOMASS DYNAMICS IN PROTECTED LOW MOUNTAIN-STEPPE LANDSCAPES AND PASTURES IN THE SOUTHERN URALS // Arid ecosystems. 2022. V.28. № 3 (92). P. 3-13. | PDF

In the steppe zone, the high sensitivity of the vegetation cover to humidification contrasts raises the question of the dependence of the intraseasonal dynamics of phytomass on the spatial pattern of vegetation cover and relief in a landscape. We performed a case study in the Aituarskaya steppe (Orenburg region) to test the hypothesis about the inequality of the spatial factors of variability of functioning under the conditions of the reserve regime and pasture impact. Based on the frequency of occurrence of five gradations of deviations of the intraseasonal increments of the vegetation index NDVI from the mean values, the measure of instability of the types of dynamics of green phytomass (Shannon’s index) was calculated. The relationship between the types of dynamics and the types of natural boundaries, due to belonging to the relief forms with the characteristic types of phytocenoses, has been established. Areas of the most unstable phytoproductive functioning are characteristic of valleys with meadow steppes. The reserve regime stabilizes the dynamics of phytomass due to a higher subordination to landscape-scale climatic processes. On grazed areas, frequent changes in the variants of phytomass increments are more characteristic and dependence on local factors (e.g., stoniness, groundwater level) increases. In the pasture area, in some places, the dominant dynamics becomes with an intensive late spring accumulation of phytomass and a small decrease or renewal by the end of summer due to an increase in the proportion of non-palatable and grazing-resistant species.

Keywords: steppe, landscape, reserve, pasture, phytomass, NDVI, seasonal dynamics, stability, relief, Urals.

Acknowledgements. Expressing gratitude to D.E. Sharova, O.M. Podgorny, I.V. Volovinsky, G.M. Leonova for participation in field research and arrangement of remote materials and to reviewers for constructive comments.

Financing. The study was carried out with the financial support of the Russian Foundation for Basic Research, project No. 20-05-00464 «Spatial structure as a factor of stability of landscape functioning», 2020-2022.

DOI: 10.24412/1993-3916-2022-3-3-13

CHARACTERISTICS OF THE SPRING-SUMMER DROUGHTS DURING THE DRY AND WET PERIODS IN THE SOUTH OF EUROPEAN RUSSIA

Arid Ecosystems

Zolotokrylin A.N., Titkova T.B., Cherenkova E.A. CHARACTERISTICS OF THE SPRING-SUMMER DROUGHTS DURING THE DRY AND WET PERIODS IN THE SOUTH OF EUROPEAN RUSSIA // Arid ecosystems. 2020. V. 26. № 4 (85). P. 76-83. | PDF

Distribution patterns of spring and summer droughts characteristics during high and low annual humidification periods are studied in twelve federal subjects of the South of European Russia for the period 1901-2018. During this time, four periods of different humidification conditions (alternate more humid, dry, humid and again dry periods) with variable durations are observed through data on anomalies of the aridity index in seven regions: Kursk, Belgorod, Voronezh, Saratov, Volgograd, Rostov Oblasts and the Republic of Kalmykia. The draining period was noted in Samara and Astrakhan Oblasts from the beginning of 20th century until its middle. Then the draining period changed to more humid. The most frequent change of periods with different humidification conditions was observed in Stavropol Krai, where five alternate periods were distinguished. It was found that the frequency of spring and summer droughts is consistent with the long-period humidification conditions. According to data of the Standardized Precipitation Index (SPI), it increases during the dry period by an average of 1.5 times while the intensity of droughts rises insignificantly. The increased humidification conditions observed in every above-mentioned federal subject in the second half of the 20th century changed to drier conditions in the beginning of the 21st century. The spreading of drier conditions began from east regions. The development of the dry period of humidification in the 21st century is confirmed by a distribution of a negative NDVI trend throughout the territory. While the aridization trends are not statistically significant in the regions of the South of European Russia in more than a century, there are prolonged interdecadal periods of aridizational strengthening and weakening, which are characterized by significant differences in frequency and intensity of spring and summer droughts.

Keywords: humidification periods, aridization, aridity index, droughts, SPI, NDVI.

DOI: 10.24411/1993-3916-2020-10121

ASSESSMENT OF SPATIAL – TEMPORAL VARIABILITY OF ARID ECOSYSTEMS IN THE REPUBLIC OF BURYATIA

Arid Ecosystems

Garmaev E.Zh.,  Ayurzhanaev A.A.,  Tsydypov B.Z.,  Alymbaeva Zh.B.,  Sodnomov B.V., Andreev S.G.,  Zharnikova M.A.,  Batomunkuev V.S.,  Mandakh N., Salikhov T.K.,  Tulohonov А.К.  ASSESSMENT  OF  SPATIAL – TEMPORAL VARIABILITY OF ARID ECOSYSTEMS IN THE REPUBLIC OF BURYATIA // Arid ecosystems. 2020. V. 26. № 2 (83). P. 34-42. | PDF

Climate change and human activity on the territory of the Republic of Buryatia intensify the processes of desertification and land degradation. Zoning of the territory of Buryatia was carried out according to the aridity index using ENVIREM high spatial resolution climatic data. Based on the correlation analysis of the time series of the NDVI AVHRR vegetation index, meteorological series of the NCEP / NCAR reanalysis and field studies, a quantitative assessment of the long-term changes in vegetation cover in arid and humid zones was carried out. Maps of the spatial distribution of linear trends of NDVI and precipitation for 1982-2015 with the separation of wet (1982-1999) and dry periods (2000-2015) were obtained. During the wet period, positive NDVI trends are observed for almost the entire territory of the Republic, while the dry period is characterized by a significant increase in the negative trends of the vegetation index. The positive correlation between the Selyaninov hydrothermal coefficient and NDVI is observed for intermountain steppificated hollows, negative for forest landscapes. The dynamics of NDVI of steppe vegetation largely depends on precipitation, the dynamics of NDVI of forests — on temperature. Reforestation, post-pyrogenic succession, shrubbing of abandoned fields, etc., cause the increase of NDVI. Negative NDVI trends are typical for steppe ecosystems under conditions of decreasing precipitation, and for forest vegetation prone to cuttings and fires.

Keywords: Buryatia, arid zones, vegetation, NDVI, Selyaninov hydrothermal coefficient, precipitation, trend, reanalysis, dendrochronology.

DOI: 10.24411/1993-3916-2020-10093