Digital Phytoindication of Soil Salinity in Dry Steppes (Republic of Kalmykia)

• Published in: Arid ecosystems Vol. 11; no. 2; pp. 173 - 185
• Main Authors: Prokopyeva, K. O., Konyushkova, M. V., Novikova, N. M., Sobolev, I. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-04-2021; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Boreholes; Depth; Ecology; Festuca valesiaca; Flowers & plants; Grasses; Halophytes; Herbivores; Identification; Kochia prostrata; Life Sciences; Plant communities; Plant populations; Plant species; Regression analysis; Saline soils; Salinity; Salinity effects; Soil; Soil salinity; Soil testing; Species; Steppes; Systematic Study of Arid Territories; Tanacetum; significance; CART and Random Forest algorithms; communication models; indication accuracy; plant species and communities; indicators of salinization depth and degree; validity; machine learning; soil salinization; phytoindication
• ISSN: 2079-0961; 2079-0988
• DOI: 10.1134/S207909612102013X

Soil and geobotanical studies were carried out in a landscape district within the Northern Sarpa lowland of the Caspian Depression in a zone of light-chestnut soil. The collected data made it possible to assess the variation of soil-salinity values typical for dry-steppe plant species and communities in the Republic of Kalmykia and to produce digital models for a geobotanical indication of soil salinity. Geobotanical plots, soil test pits, and boreholes up to 2 m deep were established along a 64-m transect at 1 m intervals. The pNa salinity index was measured in aqueous suspensions of soil samples (1 : 5). As a result, it became possible to determine the salinity at depths of 0–30, 0–50, and 0–100 cm for 12 plant species and 7 plant communities registered on the transect and to distinguish three plant groups based on their tolerance to soil salinity. The first group includes species confined to nonsaline soils (salt concentrations vary within a narrow range). Plants belonging to the second group tolerate a broad range of salinity values and prefer nonsaline soils. The third group consists of salt loving species (halophytes) confined to saline and highly saline soils. Of the seven plant communities registered on the transect, two occur on nonsaline (down to a depth of 2 m) soils (
Stipa lessingiana
+
Festuca valesiaca
+
Artemisia lerchiana
and
Stipa lessingiana
+
Festuca valesiaca
+
Tanacetum achilleifolium
); two others tend to occur in soils that are not saline to a depth of 50 cm (
Festuca
valesiaca
+
Artemisia lerchiana
+
Tanacetum achilleifolium
and
Artemisia lerchiana
+
Tanacetum
achilleifolium
+
Artemisia pauciflora
); and three communities occur only on soils that are saline from a depth of  25–50 cm (
Kochia prostrata
+
Artemisia pauciflora
,
Artemisia pauciflora
, and
Poa bulbosa
+
Anabasis
aphylla
). The Classification and Regression Tree (CART) method makes it possible to predict the soil salinity based on the occurrence of plant species identified as predictors. The prediction accuracy is 80% for the 0- to 30-cm layer, 81% for the 0- to 50-cm layer, and 64% for the 0- to 100-cm layer. The following plants have been identified as important (rank > 60) predictors:
Kochia prostrata
,
Tanacetum achilleifolium
,
Artemisia austriaca
, and
Festuca valesiaca
. Other species feature low prediction importance (validity) values and therefore cannot be used as predictors.