Guankui Gao

Soil salinization is a major constraint on ecological restoration in arid regions. This study was conducted in the highly saline coal-mining area of Dananhu, Hami, Xinjiang, China. Using a spatial chronosequence approach, we compared soil salt distribution between unplanted bare land and plots planted for 1, 2, and 3 years, as well as ion composition in the roots, stems, and leaves of three halophyte species. The results showed that: (1) Soil salt contents were lower in planted plots than in unplanted bare land. Surface-soil salinity and the sodium adsorption ratio (SAR) differed among plots with different planting durations, with higher values in the 2-year plots than in the 1- and 3-year plots. (2) Na⁺, SO₄²⁻, and Cl⁻ were the dominant soil ions, and their relative proportions differed among plots, particularly in the surface soil. (3) The roots of Tamarix chinensis had a relatively high proportion of SO₄²⁻, whereas the leaves of Nitraria tangutorum had relatively high proportions of Na⁺ and Cl⁻. In contrast, the leaves of Phragmites australis had a relatively low proportion of Na⁺ and relatively high proportions of K⁺ and Ca²⁺. (4) Root Na⁺ contents in T. chinensis and P. australis were significantly positively correlated with SAR in the upper soil layer, whereas stem Na⁺ content in N. tangutorum was significantly negatively correlated with soil Cl⁻, Na⁺, and SAR. These findings highlight differences in soil ionic conditions and plant ion traits among plots with different planting durations.

Three different types of common halophytes (Haloxylon ammodendron, Tamarix chinensis, and Phragmites australis) in northwest China were used in this study. A field experiment approach was adopted, involving five solutions with different salt concentrations (0, 150, 200, 250, and 300 mmol·L⁻¹) for salt stress treatment. The changes in photosynthetic characteristics and physiological characteristics of three different types of halophytes and their relationship with biomass were measured and analyzed. The results showed that (1) with the increase in salt concentration, the plant height, stem diameter, and biomass of three halophytes showed a downward trend. (2) The chlorophyll a, chlorophyll b, and total chlorophyll contents of Haloxylon ammodendron and Tamarix chinensis first increased and then decreased with the increase in salt concentration. Phragmites australis showed a decreasing trend. The malondialdehyde content of three halophytes showed a clear increasing trend. (3) Under different salt concentrations, the diurnal changes in the net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency of three different types of halophytes all showed an “M” trend. The diurnal variation in intercellular carbon dioxide concentration showed a “W” trend. (4) With the increase in salt concentration, the daily average values of the net photosynthetic rate, transpiration rate, and stomatal conductance of three different types of halophytes showed a downward trend. The daily average value of intercellular carbon dioxide concentration showed a “V”-shaped trend of first decreasing and then increasing. The daily average value of water use efficiency showed a “single peak” trend of first increasing and then decreasing. Haloxylon ammodendron and Phragmites australis were mainly limited by stomata at a salt concentration of 0~200 mmol·L⁻¹ and were mainly limited by non-stomata at a salt concentration of 250~300 mmol·L⁻¹. Tamarix chinensis is mainly limited by stomata at a salt concentration of 0~250 mmol·L⁻¹ and is mainly limited by non-stomata at a salt concentration of 300 mmol·L⁻¹. Compared with Haloxylon ammodendron and Phragmites australis, Tamarix chinensis has better water use efficiency, salt tolerance, and adaptability. (5) Meteorological factors, growth morphological factors, physiological factors, photosynthetic factors, and salt concentration have higher explanatory degrees, which have significant effects on the biomass of halophytes. Among them, salt concentration and growth morphological factors have direct core driving effects on the biomass of three different types of halophytes, while meteorological factors, photosynthetic factors, and physiological factors have different effects due to the differences in and complexity of halophytes. This study can provide a theoretical basis for further revealing the adaptation mechanism of different halophytes to salt stress.

Long-term and extensive mineral mining in the Kuermutu mine section of the Two Rivers Nature Reserve in the Altai region has disrupted the ecological balance between soil and vegetation. To assess the effectiveness of various restoration measures in this abandoned mine area, we compared two restoration approaches—natural turf transplantation (NTT) and replanted economic crop grassland (ARGC)—against an unaltered control (original grassland). We employed 11 evaluation indices to conduct soil and vegetation surveys. We developed a comprehensive evaluation model using the Analytic Hierarchy Process (AHP) to assess restoration outcomes for each grassland type. Our findings indicate that both NTT and ARGC significantly improved ecological conditions, such as reducing soil fine particulate matter loss and restoring vegetation cover. This brought these areas closer to their original grassland state. The species composition and community structure of the NTT and ARGC vegetation communities improved relative to the original grassland. This was due to a noticeable increase in dominant species’ importance value. Vegetation cover averaged higher scores in NTT, while the average height was greater in ARGC. The soil water content and soil organic carbon (SOC) varied significantly with depth (p < 0.05), following a general ‘V’ pattern. NTT positively impacted soil moisture content (SMC) at the surface, whereas ARGC influenced SMC in deeper layers, with the 40–50 cm soil layer achieving 48.13% of the original grassland’s SMC. SOC levels were highest in the control (original grassland), followed by ARGC and NTT, with ARGC showing the greatest organic carbon content at 20–30 cm depths. A comprehensive AHP ecological-economic evaluation revealed that restoration effectiveness scores were 0.594 for NTT and 0.669 for ARGC, translating to 59.4% and 66.9%, respectively. ARGC restoration was found to be more effective than NTT. These results provide valuable insights into ecological restoration practices for abandoned mines in Xinjiang and can guide future effectiveness evaluations.