Abstract
The desiccation of the Aral Sea due to water withdrawal from contributing rivers has resulted in an unprecedented change in the region’s climate, from maritime to hot dry desert. Afforestation has been implemented on the desiccated seafloor—the Aralkum Desert—for stabilizing the exposed substrate. However, studies on the long-term status of the afforested sites are limited. Here, we examined C and N isotopic signatures in Haloxylon aphyllum plantations, as indicators of time-integrated plant response to the prevalent water and salinity constraints, in northern Aralkum, Kazakhstan. Foliar 13C composition analysis in a chronosequence of H. aphyllum plantation sites (aged 1–27 years) on the sandy substrate revealed a significant trend towards higher water-use efficiency in older plantations, possibly in response to declining water availability. A lack of correlation between plant 13C signature and soil electrical conductivity suggests no history of salt stress despite the saline environment. Furthermore, 15N enrichment in plant tissue in the water-limited Aralkum ecosystem indicates the relative openness of N cycling. There was an increase in species richness and self-propagation at the plot scale, indicating successful afforestation effort. Coupled with other approaches, isotope discrimination might elucidate mechanisms underlying stress tolerance in H. aphyllum, which could support the afforestation efforts.
Highlights
The desiccation of the Aral Sea due to withdrawal of water from the contributing rivers has resulted in a significant change in the region’s climate, from maritime to dry hot desert, with irreversible consequences for the regional ecosystems and local livelihoods [1,2,3]
Black and white saksaul species (Haloxylon spp.), native to the central Asian deserts, have been the pioneering species in the afforestation efforts dating to the late 1980s and more recent decades
Including H. aphyllum, eight plant species belonging to five families were identified in the afforested sites (Table 1), which corresponded to the species richness observed in the later successional stages (20–30 years) in naturally vegetated sandy areas in northern Aralkum [6]
Summary
The desiccation of the Aral Sea due to withdrawal of water from the contributing rivers has resulted in a significant change in the region’s climate, from maritime to dry hot desert, with irreversible consequences for the regional ecosystems and local livelihoods [1,2,3]. Soil salinity is found to be the ratio of water loss to biomass gain), because a decrease in water availability induces stomatal correlated with δ13C because salinity-induced water stress, due to a lower water potential of saline closure thereby enhancing the WUE [9]. Natural abundance of 15N in plants and soils can be used as water uptake by the roots [13], reduces stomatal conductance and increases intrinsic an indicator of N cycling in an ecosystem [14], but the interpretation of 15N signatures is more complex. N isotopic signatures as indicators of plant vigor in response to the prevalent examining the range of C and N signatures in plant communities of Haloxylon-based afforestation water and in Aralkum. Chronosequence sites, and (iii) interpreting the observed variations in relation to the plant water status
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