荒漠草原向灌丛地转变过程中两种优势植物种子萌发及阈值特征

选取宁夏荒漠草原人为灌丛地转变过程中的两种优势种沙芦草（Agropyron mongolicum）和柠条锦鸡儿（Caragana korshinskii）为对象，利用不同浓度PEG条件下的种子萌发特性来探究其在干旱胁迫下植被更新萌发特征，结果表明：柠条锦鸡儿平均初始萌发时间早于沙芦草14 h，且柠条锦鸡儿吸水率低于沙芦草，分别为201.21%、293.43%；柠条锦鸡儿和沙芦草种子萌发率和萌发速率均随渗透势的升高呈先上升后下降趋势，且均在-0.02 MPa时萌发率最高，分别为28.67%、44.67%，在-1.2 MPa时最低，分别为6.67%、1.33%；两者萌发速率均在-0.02 MPa时达到最大，分别为12.84%、9.52%，且柠条锦鸡儿起始萌发天数少于沙芦草1-4 d；通过S型生长曲线和线性模型模拟种子萌发水势和萌发率关系，分析得出柠条锦鸡儿萌发水势阈值范围为-0.3--0.86 MPa、沙芦草为-0.3--0.65 MPa，灌木柠条锦鸡儿种子萌发水势阈值范围低于多年生禾草沙芦草。以上结果表明灌丛引入下的荒漠草原在未来干旱条件下，其灌丛柠条锦鸡儿种子在植被更新中较沙芦草更具萌发优势。

The seed germination characteristics and thresholds of two dominant plants in desert grassland-shrubland transition of the eastern Ningxia, China

Two dominate species in the desert steppe with anthropogenic introduced shrub (Caragana Korshinskii) in the eastern of Ningxia area, China, Agropyron mongolicum and Caragana korshinskii were selected to investigate the seed germination characteristics in soil drought gradients simulated by using different concentrations of PEG-6000, and to analyse the plant recruitment dynamics of the disturbed grassland under global precipitation pattern changed. The results showed that the averagely initial germination time of Caragana Korshinskii were earlier 14 h than that of Agropyron mongolicum and the water uptake of Caragana Korshinskii was lower than that of Agropyron mongolicum, which were 201.21% and 293.43%, respectively. The germination rates and speeds of them increased firstly and decreased gradually as the osmotic potential increased. The germination rates were the highest at -0.02 MPa, which were 28.67% and 44.67%, respectively, and the lowest were at -1.2 MPa, which were 6.67% and 1.33%. The highest germination speeds of Caragana korshinskii and Agropyron mongolicum were both at -0.02 MPa, which were 12.84%, 9.52%. The initial germination days of Caragana korshinskii were earlier 1-4 d than that of Agropyron mongolicum. The germination potential threshold range of Caragana korshinskii was from -0.3 to -0.86 MPa, while that of Agropyron mongolicum was from -0.3 to -0.65 MPa. Our results supported that Caragana korshinskii had more germination potentials than Agropyron mongolicum under soil drought acceleration resulted from the shrubs introduction into the desert steppe and climate changed. The study aimed to predict the plant recruitment dynamics of the desert grassland with anthropogenic shrub encroachment, providing the theoretical basis and reference for sustainability of desert steppe vegetation restoration.