Figure 1. Permanent plot locations in the natural D.
pectinatum communities in the three national nature reserves of
Bawangling, Diaoluoshan and Jianfengling, Hainan Island, China.
Hainan Island is located at the northern edge of tropical Asia. The
topography is higher in the middle than around the edges of the island.
The average annual precipitation decreases from east to west, and the
annual average temperature decreases from south to north. The southwest
and west are affected by the ocean monsoon, and there are obvious wet
and dry seasons. More clouds and lower temperatures occur in the central
mountainous region than elsewhere on the island. The study was conducted
along three environmental axes (i.e., precipitation and temperature
gradients) in Bawangling, which is located in the southwestern part of
Hainan Island (18°53′-19°20′N, 108°58′-109°53′E), Diaoluoshan, which is
situated in the southeastern part of Hainan Island (18°43′-18°58′N,
109°43′-110°03′E), and Jianfengling, which is located in the
southwestern part of Hainan Island (18°23′-18°50′ N, 108°36′-109°05′E).
These areas are national nature reserves in China.
The total area of the Bawangling Nature Reserve is approximately 72,000
hm2. It has a tropical monsoon climate, the annual
mean temperature is 23.6 °C, and the annual mean precipitation is
between 1500 and 2000 mm. The total area of the Diaoluoshan Nature
Reserve is approximately 37,900 hm2. It has a marine
tropical monsoon climate. The annual mean temperature is 24.4 °C, and
the annual mean precipitation is between 1870 mm and 2760 mm. The total
area of the Jianfengling Nature Reserve is approximately 640
km2, and it has a monsoon climate typical of tropical
islands at low latitudes. The annual mean temperature is between 19.7 °C
and 25.2 °C, and the annual precipitation is between 1600 mm and 2600
mm.
The tropical mountain forests at the three sites are mainly distributed
on mountaintops at elevations above 800 m, and they are among the few
well-preserved forest types with tropical rainforest properties in
China. They constitute the northern boundary of the Southeast Asian
tropical rainforests and represent a forest type that transitions from
tropical rainforest to subtropical/warm temperate rainforest
(Ding et al. 2012). This unique setting
also allows these forests to play an irreplaceable role in research on
tropical and subtropical rainforest ecology
(Fang et al. 2004). They could also
provide an ideal place to explore the natural regeneration dynamics of
tropical forests. Hence, a total of sixty-eight permanent plots in the
natural D. pectinatum communities were investigated, and the
sampling information for the three sites is provided in Figure 1. Based
on field investigations, detailed coordinate, climate (data from
WorldClim-Global Climate Data (http://www.worldclim.org/ )) and
topography data for the three sites are shown in Table 1.
Table 1. Topographic and climatic characteristics across the
three study sites