Abstract
Ecological conservation and restoration have increasingly captured attention worldwide due to the degradation of ecosystems. As one of the most ecologically fragile areas, the Tarim River Basin, of Xinjiang, China, encountered serious decline of desert riparian forests. The Chinese government has implemented the “Ecological Water Conveyance Project” (EWCP) since 2000, protecting and restoring the dominant natural species of the desert riparian forests, i.e., Populus euphratica Oliv. The regenerative effect after the water conveyance was noteworthy. For the purpose of clarifying the mechanism of P. euphratica forest regeneration to find a better prescription for the ecological restoration works in the Tarim River Basin, we investigated the relationship between the distribution of P. euphratica and soil salinity. Experimentally evaluated the effects of surface soil salinity on P. euphratica seed germination and the influence of river flooding on the salinity of surface soils. The results showed that (1) P. euphratica trees mainly spread along the river channel within 2 km; with increasing vertical distance to the channel, the number of trees declined significantly; (2) where the salinity of the surface soil is high, there are less living P. euphratica trees; (3) the germination of P. euphratica seeds decreases with increased soil conductivity; when the soil conductivity was higher than 7 ms/cm, the germination of P. euphratica seeds was severely curtailed. (4) Flooding regimes were a pre-condition of P. euphratica restoration; they had profound effects on improving the germination of the seeds via ameliorating water conditions and reducing salinity. Our results point out that the most efficient ecological prescription for restoring and protecting desert riparian forests is to induce flooding twice yearly during June to August with 10- to 15-day durations each time. Such a plan (especially in the Tarim River Basin) should prioritize the protection of seedlings.
Highlights
Www.nature.com/scientificreports mitigate ecological degradation, e.g. the “Reforestation of Fragmented Forests Project” in Kianjavato, Madagascar[15], the “Megadiversity Atlantic Forest Biome Restoration Project” in Iracemápolis, Brazil[16] and the “Comprehensive Management” in the Tarim River Basin[17]
This paper manipulated the interactions between the hydrologic regime and salinity level through investigations into the relationships between P. euphratica distributions and surface soil salinity and experiments of seed germination and river flooding
As revealed by the research carried out in the lower reaches of the Tarim River, we answered the scientific questions regarding,(1) how soil salinity affects the distribution of P. euphratica, and (2) further investigated the role that river flooding plays in the process of P. euphratica restoration
Summary
Www.nature.com/scientificreports mitigate ecological degradation, e.g. the “Reforestation of Fragmented Forests Project” in Kianjavato, Madagascar[15], the “Megadiversity Atlantic Forest Biome Restoration Project” in Iracemápolis, Brazil[16] and the “Comprehensive Management” in the Tarim River Basin[17]. With great adaptive abilities (such as its tolerance to drought and salinity), P. euphratica is the major tree and keystone species that constitutes the desert riparian forest and forms a natural eco-barrier or so-called “green corridor.” It protects the development of oases, stabilizes river channels, maintains the ecological balance of river basins, and fertilizes forest soil[25,26,27]. Our previous research has revealed the minimum groundwater depths for different ages of P. euphratica trees in detail[24] All these studies mainly focused on the effects of the water conditions on P. euphratica trees following the procedure of the river flow diversion and extremely severe water shortage in the lower reaches of the Tarim River. Our objectives are to reveal the mechanism of P. euphratica forest regeneration in the lower reaches of the Tarim River and explore the efficient ecological water delivery modes and effects of flooding on ecological restoration to guide the operation of the EWCP efficiently
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