Environmental aspects of the black saxaul forests’ distribution in the cold semi-deserts of central asia

Abstract

Haloxylon aphyllum Minkw. (Black Saxaul) is the main brush-forest-forming species in Kazakhstan. While the latter is a rain-fed shrub principally distributed on sand dunes, the former is a phreatophyte, which uses groundwater as water source. Accordingly, Black Saxaul is mainly distributed on the current and ancient alluvial river terraces. Saxaul played and still plays an important role as fodder plant and fuel wood for herders. The Black Saxaul (Haloxylon aphyllum Minkw.) is the principal arboreal taxon of the continental deserts (Turanian Desert) of Central Asia between the Caspian Sea in the West and the Zhungarian Basin in the East. Due to over-grazing and over-exploitation for fuel, the once-dominant Saxaul vegetation has considerably retreated. The degradation process of the older Saxaul stands reduces the trees’ biomass. Annual productivity of the Saxaul communities largely depends on the overall vegetation density that reflects specific environmental conditions at particular locations and the determinant local hydrology regime. The potentially negative effect of the ongoing climate change-related regional aridizafication on the shrub-forest communities has not yet been demonstrably proven. On the contrary, the increased seasonal winter-spring rainfall rates meteorologically documented from SE Central Asia over the past 50 years seem to contribute to a better sustainability and rejuvenation of the local Saxaul vegetation The patterned changes in the plants’ growth parameters at different sites suggest differences in the local geomorphic, atmospheric and hydrological conditions. The investigated and geomorphologically specific settings of the Ili Delta area, including alluvial plains, riverine terraces and sand dune fields, indicate an increased revitalization rate of the Saxaul stands if not-affected by human actions (mainly firewood-use and pastoralist activities). In spite of the fact that the study sites in the present Ili delta have more favorable pedogenic–hydrological conditions for the pristine Saxaul forest expansion, negative anthropogenic effects reduce significantly the ability of woodlands for their natural revitalization and sustainment. Resilience to seasonal dryness and the plants’ capability to sustain from deep-located ground-water reservoirs apart of limited seasonal rains are the principal aspects for vegetation survival. Results from the Ili Delta field monitoring sites provide new insights on the natural reproductive potential of the Black Saxaul shrub-forests in natural and culturally disturbed places of the winter-cold semi-deserts of Central Asia with strongly continental climate regime. © SGEM2017. All Rights Reserved.