Plot survey method was used in this study to investigate species composition at different microenvironments, as well as the distribution pattern of each species. The first step of survey was choosing sampled trees. Afterwards, I divided each sampled tree into different vertical zones, then set one or more plot(s) within each vertical zone. For each plot, I recorded all plant species appearing inside the plot and their abundance.
There were some considerations when choosing sampled trees. This study mainly focused on the effects of different microenvironments within trees, not the effects of large-scale environmental variables such as elevation or topography. Hence, I selected 24 sampled trees in similar environments. All of them were located in Fushan Botanic Garden and Water Source Reserve, and besides Hapen Creek (Figure 10). The geographic positions and altitudes of these sampled trees were similar. The altitudes of all sampled trees ranged from 600 m to 700 m. The sizes and architectures of trees were also under consideration. Only big canopy trees with heights over 14 m and diameters at breast height (DBH) over 50 cm were chosen (except for sampled tree T003). Besides, all the sampled trees did not incline too much. The inclination angles at breast height were all
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smaller than 20° (inclination angle is 0° if trunk is absolutely erect). To avoid the influences of some tree attributes that related to tree species, only evergreen broad-leaved tree species were chosen. All of the 24 sampled trees belong to Lauraceae except for T023, which belongs to Fagaceae. The detailed information of all sampled trees is shown in Appendix 1.
Figure 10. The locations of sampled trees
There were 24 sampled trees in total. All of them were located besides Hapen Creek.
Each sampled tree was divided into several vertical zones based on height above ground, and each vertical zone was 2 m high. Therefore, zone 1 was from the ground to 2 m high, zone 2 was from 2 to 4 m high, and so on (Figure 11). For those vertical zones
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higher than human height, I used doubled rope technique (DdRT) to climb up the tree and survey. The number of vertical zones that could be surveyed depended on accessibility of sampled trees. Therefore, only five vertical zones were surveyed for 18 sampled trees, and only six sampled trees had six vertical zones surveyed.
Within each vertical zone, one or two plot(s) was set to survey epiphytes species composition. When setting a plot, I chose a position where epiphytes species richness was high and the species composition was as representative as possible for that vertical zone.
Each plot was 40×50 cm surface area on trunk or a branch of the sampling tree, and it was further divided into 20 10×10 cm grids. When surveying a plot, all vascular plant species within the plot were recorded as well as the number of grids that each species occupied. The latter was an estimation of species abundance (Figure 12). For all species recorded in the plot, one individual was collected as a voucher which could be used for species identification. Considering accessibility, all of the plots were set on the trunk or erect main branches, not on those branches or twigs growing outward. Some positional variables of each plot were recorded, including the height of plot center, the inclination angle of plot surface, the aspect of the plot relative to the trunk and the dimeter of the growing substrate (the trunk or the branch) (Figure 13). The inclination angle was 0° if the plot was absolutely perpendicular to ground surface. The inclination angle was positive if the plot surface inclined toward the sky, and was negative if inclined toward
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the ground. The aspect of the plot was 0° if the plot set on the north face of the trunk, and ranged from 0° to 359°. These positional variables were used in further analyses.
Figure 11. Vertical zones of a sampled tree
Each vertical zone was 2 m high. Five to six vertical zones were surveyed for each sampled tree.
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Figure 12. A sampling plot used to survey epiphytes
Each plot was 40×50 cm, and it was divided into 20 grids which was 10×10 cm. All vascular plant species within the plot and the number of grids they occupied were recorded. For the case shown here, it is recorded that species A occupies seven grids and species B occupies three grids.
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Figure 13. Positional variables recorded for each plot
Four positional variables were recorded for each plot, including height, inclination angle, aspect and diameter of the growing substrate (the trunk or the branch). Height was the distance between plot center and the ground. Inclination angle was the angle difference between plot surface and vertical direction. Inclination angle was 0° if the plot was absolutely perpendicular to the ground. It was positive if the plot inclined toward the sky, while was negative if the plot inclined toward the ground. Aspect was the angle difference between the direction plot facing and the north direction, ranging from 0° to 359°.
There were some large bird’s-nest ferns growing on trees in the study area. They
actually belonged to two different species, Asplenium antiquum and Asplenium nidus, but sharing quite similar morphology. These bird’s-nest ferns may have some influences on
other epiphytes species, and the species compositions of the places below bird’s-nest ferns were usually different from other places based on observation. Hence, I avoided setting
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plots below bird’s-nest ferns if possible. However, in some vertical zones it was difficult to find a place not influenced by bird’s-nest ferns. For that case, I still set a plot below the bird’s-nest fern, but a special note was taken. There were nine plots below bird’s-nest
ferns in total.
All of the plot surveys in this study were done during January to April, 2018. In total, 24 sampled trees and 139 plots on them were surveyed. There were 52 vascular plant species recorded in these plots, and 39 of them were epiphytes. This study used a general definition of epiphytes, which includes true epiphytes, hemiepiphytes and facultative epiphytes, and life forms of recorded species were determined basically based on the epiphyte species list summarized by 徐嘉君 (2007). The information of all recorded species is shown in Appendix 2.
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