石漠化干旱环境中石生藓类水分吸收特征及其结构适应性

The saxicolous moss′s features of absorbing water and its structural adaptability in the heterogeneous environment with rock desertification

苔藓是荒漠植被演替过程中常见的先锋植物,同时也是极端恶劣环境的开拓者。比较石漠化地区常见的穗枝赤齿藓(Erythrodontium julaceum(Schwaegr.)Par.)、反叶扭口藓(Barbula fallax Hedw.)和真藓(Bryum argenteum Hedw.)对干旱环境的适应性,为石漠化环境的恢复和治理提供理论依据。结果表明:最大持水能力和保水率穗枝赤齿藓和反叶扭口藓均大于真藓。3种苔藓的吸水过程包括外吸水和内吸水,吸水动力学曲线均表现为S型饱和曲线,但吸水特征存在较大差异;穗枝赤齿藓和反叶扭口藓的饱和吸水量相差甚微,但远大于真藓,前两者约为后者的2.5倍;最大总、内、外吸水速度穗枝赤齿藓分别为真藓的3.41、2.52倍和3.02倍,反叶扭口藓分别是真藓的2.79、2.52倍和3.55倍。茎的解剖学结构显示真藓和反叶扭口藓有明显的中轴,属内导水型藓类,而穗枝赤齿藓无中轴,属外导水型;但严格的内导水型植物是不存在的,不少植物属于混合导水型,这与环境水分高低有关。因此,中轴的有无并不是导致吸水能力强弱的决定性因素,还与苔藓所处的环境状况、生长型、毛细管系统类型和茎叶结构密切相关。

Bryophytes are a class of pioneer plants at desert vegetation succession and even in extremely dry environments.In this study,a theoretical foundation for the interest of recovering and administering the environments of rock-desertification ecology was provided by compared with the adaptability to habitat heterogeneity in rocky desertification environments among Erythrodontium julaceum,Barbula fallax and Bryum argenteum.The results show that,firstly,E.julaceum and B.fallax are more than B.argenteum in the capacity of holding maximal water and also in the rate of preserving natural water.Secondly,the water-uptaking processes of the three mosses are outer water uptake and inner water uptake.Although the three species had the same dynamic curve of the S type saturated water content,they had considerably different dynamic properties.Little difference was found in the amount of water saturated by E.julaceum and B.fallax.However,the amount of saturated water in E.julaceum and B.fallax were about 2.5 times of that in the silver B.Argenteum.The amount of saturated water and the maximal rates of water uptake,inner as well as outer water uptake in E.julaceum were 3.41,2.52 and 3.02 times than those of B.argenteum,respectively.Similar results were also found in B.fallax.Furthermore,the stem cross-section structure of three mosses showed that B.argenteum and B.fallax had the obvious conducting strand and belonged to endohydric mosses.In contrast,E.julaceum owned no conducting strand and belonged to the part of the ectohydric.Strictly,the structure of endohydric and ectohydric in mosses is not the decisive factor of water absorption capability,which has close relationship with many aspects including growth form,type of capillary system and microstructure of stem and leaf positive correlations.