青藏高原东部针叶林下8种藓类植物的持水和保水能力比较研究

Change of water holding and conservation capacity of eight species of bryophytes under subalpine coniferous forests in Eastern Tibetan Plateau

青藏高原东部针叶林下8种藓类植物5个生境的自然含水率以及2种室内环境下持水变化的实验表明,供试藓类植物在原始林下的自然含水率最高,5种生境中金发藓自然含水率最低,提灯藓自然含水率最高;藓类持水能力与保水能力呈负相关关系;持水能力随时间变化逐渐降低,在相同的环境条件下失水过程和失水速率变化趋势相似,但种间差异明显,与藓类本身对水分的适应能力、环境条件变化,以及藓类失水过程中生理生态适应与环境变化的协同进化机制相关;经过失水—饱和—再失水过程的藓类持水能力均明显降低,可能与第一次失水过程中植物细胞受到伤害后未能恢复有关。塔藓、山羽藓和金发藓的持水与保水特征暗示,它们可能是森林采伐破坏后迹地地表微环境变化的潜在指示者。

The eight mosses,including Thuidium lepidoziaceum,Rhytidium rugosum,Dicranum a-ssamicum,Mnium sp.,Rhytidiadelphus triquetrus,Actinotiuidium hookeri,Polytrichum alpinum,Entodon concinnus and Hylocomium splendens,are all common in subalpine coniferous forest in the Eastern Tibetan Plateau.The objective is to compare and detect their differences in water ho-lding capacity under5different habitats and desiccation process of two environmental condi-tions.Water contents in5different habitats were determined.Their changes of water retention capacity under two kinds of indoor environments were measured.The results indicated that water contents of all bryophytes were higher under virgin forest than under other four habitats.In eight species,P.alpinum has the lowest natural water content,while Mnium sp.has the highest under all five different habitats.There existed negative correlation between water holding and water retention capacities,and their water holding capacities tend to decrease temporally,an indication of the same tendency both in the process and the ratio of moisture loss under the same environment.However,there existed significant difference in retention capacity of different species,which was probably resulted from different adaptabilities to moisture stress and habitats change,and discrepancy of the mechanisms of physiological habituation and co-evolution to the environment changes of different species.The results also imply that water holding capacity in all eight species decreases significantly after a desiccation-hydration-redesiccation process.This is probably related to that cell damage induced by first time water stress in the desiccation process.All the parameters of water holding and retention capacities of eight species under different habitats showed that H.splendens,A.hookeri and P.alpinum are potential biological indicators on forest-floor environmental change resulted from forest depletion.