斑块面积对干燥-复水条件下藓类植物生理活性的影响

干扰会导致生物结皮斑块破碎并退化。为明确生物结皮斑块破碎诱发生物结皮退化机理,以黄土丘陵区土生对齿藓(Didymodon vinealis)结皮为研究对象,研究了干燥-复水条件下,单株和直径1 cm、2 cm、3 cm、4 cm、5 cm的藓结皮斑块内土生对齿藓的干燥速率、渗透调节物质、丙二醛和光合色素含量等的变化,以期揭示干扰后生物结皮退化的生物学机理。结果表明(1)除单株外,干燥速率随斑块面积减小而增加,直径1 cm斑块内藓的干燥速率是直径5 cm的2倍。(2)反复干燥-复水25天后,直径小于5 cm的斑块内藓的可溶性糖、可溶性蛋白和叶绿素含量低于直径5 cm斑块内藓的含量,丙二醛含量随斑块面积变化无明显规律。(3)干燥速率与斑块面积、可溶性糖、可溶性蛋白及叶绿素含量均呈极显著负相关。以上结果表明,藓结皮斑块面积通过影响斑块内藓类植物干燥速率进而影响其渗透调节和光合作用能力。藓结皮斑块面积减小,藓类植物干燥速率增大,生理活性降低,是藓结皮斑块破碎诱发其退化的原因。研究从藓类植物生理的角度,阐明了干扰后藓类植物衰亡的生理学原因,为生物结皮的保护和管理提供了科学依据。

Effects of patch sizes of moss dominated biocrusts on the physiological activity of mosses under repeated de-rehydration conditions

Disturbance usually causes fragmentation and degradation of biological soil crusts (biocrusts). To clarify the mechanism of biocrust degradation caused by disturbance-induced fragmentation, we selected the moss (Didymodon vinealis) dominated biocrusts (moss crusts hereafter) from the hilly-gully region of the Loess Plateau as the object of study. The dehydration rates and contents of osmoregulatory substances, malondialdehyde and photosynthetic pigment in the individual mosses and mosses of the moss crust patches with different sizes, which measured in the diameters of 1 cm, 2 cm, 3 cm, 4 cm, and 5 cm, were measured under 25 rounds repeated de-rehydration conditions, so as to reveal the biological mechanism of biocrusts degradation after disturbance. The results showed that (1) the dehydration rate of mosses increased with the decrease of patch sizes of moss crusts. The dehydration rate of mosses in the patch with diameter of 1 cm was twice of that with diameter of 5 cm. (2) The contents of soluble sugars, soluble proteins, and chlorophyll of mosses in the patches with diameter less than 5 cm were lower than those with diameter of 5 cm patches, and the content of malondialdehyde had no significant change with different moss crust patches sizes after 25 days of repeated de-rehydration. (3) Dehydration rate of mosses was extremely significantly negatively correlated to sizes of moss crust patches, the contents of soluble sugars, soluble proteins, and chlorophyll. The results of the study showed that the sizes of moss crust patches affected the dehydration rate of mosses in the patches and then affected their osmotic regulation and photosynthetic capacity. The dehydration rate of mosses increased as the size of moss crust patches decreased, which damaged to physiological activities of mosses and might be the cause of degeneration induced by fragmentation of moss crust patches. This study explains the physiological causes of mosses degradation after disturbance from the perspective of mosses physiology, which provides scientific basis for the protection and management of biocrusts.