Taiwania

Vegetation of Chamaecyparis montane cloud forest in Lalashan Forest Dynamics Plot To study how species composition and physiognomical structure of Chamaecyparis montane mixed cloud forest in Taiwan changes along main soil, topographical and microclimatic variables on a small scale, we established a 1-ha Lalashan Forest Dynamics Plot in northern Taiwan (24°43ʹ N, 121°26ʹ E, elevation 1758–1782 m a.s.l.). Plot is affected by prevailing NE wind direction related to winter monsoon, and by seasonal fog frequency with highest fog density in autumn and winter. We finished the first census of all woody species in August 2020, and collected environmental factors related to soil and topographical properties, measured microclimate and soil moisture within the plot. In total, we recorded 5220 individuals with diameter at breast height ≥ 1 cm. These belong to 65 species, 42 genera and 29 families, with a basal area of 69.1 m2 ha-1, and are dominated by Chamaecyparis obtusa var. formosana, Rhododendron formosanum and Quercus sessilifolia. Modified TWINSPAN classified vegetation into three types (ridge, east-facing slope and valley). Unconstrained ordination showed that the main gradients behind species composition changes are related to windwardness and convexity. Both east-facing slope type and valley type have relatively lower temperatures than ridge type, especially during summer. Convexity is related to soil moisture gradient (from dryer convex to wet concave sites). From soil properties, pH is negatively and phosphorus is positively related to topographical convexity. Collected data will serve as a baseline for future resurveys and monitoring changes within this montane cloud forest.

为探讨台湾山区云雾林中 Chamaecyparis montane 混交林物种组成及外貌结构随主要土壤、地形和微气候变量在小尺度上的变化规律，本研究在北台湾（北纬24°43'，东经121°26'，海拔1758-1782米）设立了1公顷的拉拉山森林动态样地。样地受冬季季风主导的东北风向影响，且受季节性雾的频率影响，秋季和冬季雾密度最高。我们于2020年8月完成了所有木质物种的首次普查，并收集了与土壤和地形属性相关的环境因素，在样地内测量了微气候和土壤湿度。总计记录了5220个胸径≥1厘米的个体，这些个体隶属于65个物种、42个属和29个科，基面积达到69.1平方米/公顷，主要物种为 Chamaecyparis obtusa var. formosana、Rhododendron formosanum 和 Quercus sessilifolia。经修改的TWINSPAN方法将植被划分为三种类型（脊地、东向坡和山谷）。无约束排序分析显示，物种组成变化背后的主要梯度与风向和凸度相关。东向坡型和山谷型相对于脊地型具有较低的温度，尤其在夏季。凸度与土壤湿度梯度（从干燥的凸地向湿润的凹地）相关。从土壤性质来看，pH值与地形凸度呈负相关，而磷含量与地形凸度呈正相关。收集到的数据将作为未来重新调查和监测此山地云雾林变化的基线。