This article throws light upon the three main formations of vegetation of cold arid zone. The formations are: 1. Sub-Tropical Semi Desert 2. Alpine Steppe 3. Steppe of Artemisia.
Formation # 1. Sub-Tropical Semi Desert:
(i) On steep rocky slopes Olea cuspidata, Rosa webbiana, Pistacia sp., Halophyllurn griffithianum and Matthiola odoratissima are the chief species,
(ii) On screen fans Artemisia maritima, Salsola spp., Rumex hastatus, H. griffithianum can be noticed,
(iii) The dry river bends with sandy loamy terrace are chiefly occupied by Capparis spinosa, Salsola kali, Peganum harmala, Calotropis procera,
(iv) Bunchy woody grasses and shrub grow on permeable soils and moving sand. The grasses help in checking the sand drift. Some of the common species are Capparis spinosa, Matthiola odoratissima, Zygophyllum spp. and Ephedra spp.,
(v) Vegetation on the water courses is limited in distribution because of enormous changes in water content. The common species are Tamarix gallica var. pallesii, Populus spp., Ficus palmata, Rosa moschata, Rumex sp. and Saccharum spontaneum.
Formation # 2. Alpine Steppe:
(i) In water courses:
Here all the vegetation is concentrated along natural or artificial water courses. The growing trees and shrubs are Rubus spp., Populus spp., Salix spp., Retula japonica, Clematis spp., Tamarix spp., Myricaria spp., and Hippophae rhamnoides etc. which can be seen in contrast to the open landscape around.
(ii) In swampy valleys:
They are often put to cultivation. The vegetation is confined to stream beds and in high land valleys, thorny scrubs are common. The common species listed are Carex spp., Taraxacum spp., Triglochin spp., Hippuris vulagris and Ranunculus aquatilis, Potamogeton spp., near stream flows. Saline soils which are the former lake basins are occupied by halophytic vegetation Salsola kali, Triglochin spp., Glaux maritima, Chenopodium spp.,
(iii) Sand dunes are occupied by Sophora vicifolia, Oxytropis sericopetala, Onosma spp.
A more pronounced alpine vegetation exists on the steep rocks and ranges of high lands. The species listed are Gentiana waltonii, Selaginella Aveus and Didissandra lanuginosa.
Formation # 3. Steppe of Artemisia:
(i) Rocky terrain and gullies which occasionally carry water are vegetated by Juniperus spp., Rasa webbiana, Clutea arborescens, Prunus spp., Berberis spp., and Sophora spp.,
(ii) The und water vegetation is the-steppe type and becomes conspicuous during July. Several species of Populus, Salix and Lonicera along with Ribes, Rosa give a peculiar look,
(iii) The heath vegetation on the rocks includes Ephedra intermedia, Quercus spp., Juniperus spp., Eremurus spp., and Astragalus spp., Other succulent vegetation of the ground forms a dense cover with species like Scutellaria prostrata, Hedysarum falconeri etc.
(iv) The grassy steppes of Artemisia are rich in humus content especially where the Artemisia steppes do not abruptly change into humid coniferous forests (N aspect 300 m in and S aspect very high). The characteristic species are Leontopodium spp., Thymus serpyllum, Nepeta spp., Koeleria gracilis, Stipa spp., Dianthus spp., Gentiana spp., and Scorzonera spp.