Microhabitat factors play an important role in regulating bryophyte species distribution and the development of bryophyte-dominated biological soil crusts (hereafter bryophyte crusts). We investigated the distribution and development of bryophytes in eight microhabitats in the water-wind erosion crisscross region of the Loess Pla-teau. We used the line intercept transects to explore and quantify the influencing pathways of microhabitat factors on bryophyte diversity and analyzed the influencing pathways of plant cover, slope aspect, and slope gradient by using structural equation model to quantify influencing coefficients. Our results showed that: 1) The Patrick, Shannon, Pielou, and Simpson indcies of bryophytes under plant canopy were 63.4%, 66.6%, 91.0%, and 68.3% lower than that without plant canopy, respectively, while the thickness, biomass, and chlorophyll content of bryophyte crusts were 0.5, 0.2, and 1.3 times higher than that without plant canopy, respectively. 2) The Patrick, Shannon, Pielou, and Simpson indexes of bryophytes on the north slope were 0.6, 0.9, 5.6, and 0.9 times higher than those on the south slope, while the thickness, biomass, and chlorophyll content of bryophyte crusts were 0.3, 0.3, and 0.6 times higher than those on the south slope, respectively. 3) As the slope increasing from 14° to 34°, the Patrick, Shannon, Pielou, and Simpson indexes of bryophyte were decreased by 59.8%, 84.1%, 57.3% and 68.0%, and the thickness, biomass, and chlorophyll content of bryophyte crusts were decreased by 15.2%, 25.0%, and 16.5%, respectively. 4) The importance of the three microhabitat factors on bryophyte diversity and the development of bryophyte crusts followed an order of plant canopy cover > slope aspect > slope gradient. The primary influencing pathway varied among the microhabitat factors. In conclusion, plant cover, slope aspect, and slope gradient significantly affected the distribution of bryophytes species and developmental level of bryophyte crusts through direct and indirect pathways. Therefore, full consideration should be given to microhabitat conditions when using bryophyte crusts to control desertification.
微生境因子对苔藓结皮的物种分布和发育有重要调控作用。为探明其作用途径和影响程度,以黄土高原水蚀风蚀交错区的苔藓结皮为研究对象,通过样线法调查了8种微生境中苔藓结皮的物种分布和发育特征,结合结构方程模型剖析了植物冠层覆盖、坡向和坡度对苔藓多样性和苔藓结皮发育的影响途径并量化了其影响系数。结果表明: 1)与无冠层相比,冠层覆盖使苔藓的Patrick、Shannon、Pielou和Simpson指数分别降低了63.4%、66.6%、91.0%和68.3%,但使苔藓结皮的厚度、生物量和叶绿素含量分别提高了0.5、0.2和1.3倍;2)北坡样地的4种苔藓物种多样性指数较南坡分别提高了0.6、0.9、5.6和0.9倍,而3种苔藓结皮发育指标分别提高了0.3、0.3和0.6倍;3)坡度从14°增加到34°,4种苔藓多样性指数分别降低了59.8%、84.1%、57.3%和68.0%,而3种苔藓结皮发育指标分别降低了15.2%、25.0%和16.5%;4)3种微生境因子对苔藓多样性和苔藓结皮发育的影响程度为冠层覆盖＞坡向＞坡度,其主要影响途径因微生境因子不同而存在差异。综上,植物冠层覆盖、坡度和坡向分异通过直接和间接途径显著影响了苔藓的物种分布和苔藓结皮发育,因此,在利用苔藓结皮进行荒漠化治理时应充分考虑微生境条件。.
Keywords: Loess Plateau of China; bryophyte crusts; plant canopy cover; slope aspect; slope gradient; species diversity.