Variability of plant species diversity during the natural restoration of the subalpine birch forest in the Central Great Caucasus

Abstract

Pall. shrubs occurring only on the northern slopes at 2100-2900 m a.s.l. (Dolukhanov, 2010). These birch-dominated forests are widespread in the subalpine belt of the Kazbegi district of Georgia (Nakhustrishvili et al., 2006).Currently, birch forests have significantly decreased in the temperate zone worldwide. They are represented as treelines only in four regions (Dolukhanov, 2010): Mount Etna (Sicily) -Betula aetnensis Raf., the Caucasus -B. litwinowii, the Himalayan range -B. utilis D. Don and B. ermanii Cham., and mount Fujiyama (Japan) -B. ermanii. The deciduous subalpine birch forests of the Central Greater Caucasus Mountains in the Kazbegi district of Georgia are represented by a combined species composition where B. litwinowii is a dominant treeline species. The main plant species associations in a birch forest habitat are represented by Betula raddeana Trautv.,

Separating reflectance signatures of shrub species – a case study in the Central Greater Caucasus

“…However, some studies report that B. litwinowii and tall herb communities with V. lobelianum grow in close proximity (Walter ; Nakhutsrishvili et al. ; Togonidze & Akhalkatsi ). The separation of the reflectance signal extracted from the vegetation relevés was thus considerably lower than the separation achieved with the simulated data.…”

“…This can be explained by the fact that the data were selected from a database that did not include vegetation relev es from pastures with dominant V. lobelianum stands. However, some studies report that B. litwinowii and tall herb communities with V. lobelianum grow in close proximity (Walter 1974;Nakhutsrishvili et al 2006;Togonidze & Akhalkatsi 2015). The separation of the reflectance signal extracted from the vegetation relev es was thus considerably lower than the separation achieved with the simulated data.…”

Analysing Betula litwinowii encroachment and reforestation in the Kazbegi region, Greater Caucasus, Georgia

“…In total, the mean annual precipitation is 806 mm. The average annual temperature is of 4.9°C, where Jul is warmest (average temperature 14.3°C) and Jan is coldest, with an average temperature of −5.2°C (Lichtenegger, Bedoschwili, Hübl, & Scharfetter, ; Togonidze & Akhalkatsi, ).…”

“…In the sub‐alpine belt (1,800–1,900 to 2,400–2,500 m a.s.l.) shrub woods and crook‐stem forests, mainly formed of B. litwinowi, and to a lesser extent of Salix caprea and Sorbus caucasica, are very common on north‐exposed slopes (Nakhutsrishvili, ; Togonidze & Akhalkatsi, ). Additionally, sub‐alpine grasslands and tall herbaceous vegetation, often used as meadows or pastures, occur (Tephnadze et al., ).…”

“…Consequently, the timber line of the Central Greater Caucasus has been lowered by up to 200 m (Dolukhanov, ). Recent investigations in the Kazbegi district revealed that forest vegetation has been recovering as a result of natural reforestation (Togonidze & Akhalkatsi, ). However, these were qualitative observations and no quantitative data were provided.…”