龙脑香热带雨林附生苔藓沿宿主垂直梯度的微生境偏好及其指示作用

Habitat preferences of epiphytic bryophytes along the vertical gradient and their indicator functions in a tropical dipterocarp rain forest

该研究首次借助林冠塔吊调查了西双版纳国家级自然保护区龙脑香热带雨林样地内69棵树13个垂直高度上的附生苔藓植物,结果表明:目标样树上共记录到隶属于25科60属的90种附生苔藓,其中细鳞苔科物种数最多,占比达25.6%。13个垂直高度上共划分出三种生态类型:喜阳苔藓(散生巨树上>45 m 的区域),喜阴苔藓(乔木树干上<15 m的区域),广布苔藓(广泛分布于宿主各个垂直高度上,生态位宽),并筛选出对微生境有特殊偏好的17种苔藓指示种(IndVal≥0.7, P <0.05)。随宿主垂直高度的升高,扇型和交织型的苔藓占比降低,悬垂型苔藓占比先升高后降低,细平铺型和粗平铺型的苔藓占比升高。大气湿度、水汽压、胸径以及树皮粗糙度对附生苔藓生活型的分布偏好具有显著影响。总之,沿宿主垂直高度上的附生苔藓对微环境变化在生活型和形态结构上有着不同的响应方式,而同一种生态型的苔藓群落有相似的适应机制。因此,在森林林冠生境变化的监测和管理中,对微生境具有明显偏好的附生苔藓物种可作为有效的指示材料。

Epiphytic bryophytes play significant roles in maintaining water and nutrient cycles in the forest ecosystem. However, diversity and distribution patterns of epiphytic bryophytes in forest canopies are understudied because of the limitations of canopy investigation techniques. Epiphytic bryophytes and their life-forms were investigated from 69 trees in thirteen vertical segments using a canopy crane in a tropical dipterocarp rain forest in Xishuangbanna National Nature Reserve. Canonical correlation analysis (CCA) and the species indicator method were applied to analyze the microhabitat preferences of the epiphytic bryophytes and to find indicators along the vertical gradient of the hosts. The main results were as follows: In the study area 90 species, belonging to 60 genera and 25 families, were recorded. Lejeuneaceae was the most species-rich family, representing 25.6% of all bryophyte species recorded. Three special ecological types were extracted from the thirteen vertical segments, including sun-loving bryophytes (>45 m on tree trunks in the forest canopies of emergent trees), shade-loving bryophytes (<15 m on tree trunks) and generalist bryophytes (usually distributed in various host heights with a broad niche width). Seventeen bryophyte species (IndVal≥0.7, P <0.05) were selected as indicators for specific vertical segments. With the increase in the height sampled, the proportion of species with fan and weft life-forms decreased, the proportion of pendant life-forms increased first and then decreased, while the proportion of smooth mat and rough mat life-forms increased. The relative humidity, vapor pressure, diameter at breast height (DBH) and bark roughness had significant influences on the distribution preferences of epiphyte life forms. In conclusion, epiphytic bryophytes show different life-form compositions and morphological structures in response to changes in the micro-environment along the vertical gradient of hosts, while bryophytes assembled in the same micro-habitat usually have similar adaptation mechanisms. The epiphytic species with obvious preferences for specific microhabitats can be used as indicators during the monitoring and management of habitat changes in the forest canopy.