科尔沁沙地南缘主要固沙植物旱季水分来源

探讨固沙植物水分来源以及物种间水分利用关系对揭示植物共存机理和固沙植被稳定机制具有重要意义.本研究选取科尔沁沙地南缘两种典型生境(固定沙丘和丘间低地)共12种固沙植物,通过测定植物水、同期降水、地下水和土壤水的稳定同位素比率(δD和δ¹⁸O),利用IsoSource模型计算植物对不同深度土壤水的利用比例,初步阐明半干旱沙区主要固沙植物旱季水分来源以及物种间的水分利用关系.结果表明:两种生境中不同生活型固沙植物水δD和δ¹⁸O差异显著,但丘间低地乔木和灌木差异不显著.在丘间低地从乔木到草本水分来源逐渐变浅,乔木和灌木主要利用50～150 cm或30～50 cm土壤水,半灌木主要利用10～30 cm土壤水,草本主要利用0～10 cm土壤水;固定沙丘灌木主要利用0～30 cm土壤水,半灌木则主要利用50 cm附近土壤水.表明旱季固定沙丘植物比丘间低地植物更依赖0～50 cm土壤水.固沙植物水分来源与植物生活型、根系分布范围有关,其中根系分布范围影响可能更大.

Water sources of dominant sand-binding plants in dry season in southern Horqin Sandy Land,China

It’s important to explore the water sources of sand-binding plants and their relationship to reveal the mechanism underling species coexistence and vegetation stability. In the present study, 12 sand-binding species in two typical habitats (fixed dune and dune slack) in southern Horqin Sandy Land were selected. The δD and δ¹⁸O values of plant water, rain water, ground water and soil water were determined, and the percentages of soil water at different depths used by plants were calculated with the IsoSource model. Our results showed that the δD and δ¹⁸O values of stem water were significantly different among various life forms in both habitats except for those of trees and shrubs in dune slack. From trees to grass, the depth of soil water contributed to main water source of plant became shallower in dune slack: trees and shrubs mainly used soil water in 50-150 cm or 30-50 cm layer, subshrubs mainly used soil water in 10-30 cm layer while grass relied on soil water of 0-10 cm layer. Shrubs mainly used soil water of 0-30 cm layer and subshrubs mainly used soil water around 50 cm at fixed dune. This study indicated that in dry season plants at fixed dune are more dependent on soil water of 0-50 cm layer compared with those in dune slack. The water sources of sand-binding plants are correlated with plant life form and root distribution range, and the later might play a more important role.