Study site
The study site was located at the
Xishuangbanna Tropical Botanical
Garden (21°54′ N, 101°46′ E) in the Mengla County, Yunnan Province,
China. The zonal vegetations here are tropical rain forests and monsoon
forests, which is not only a critical region for China’s tropical rain
forests, but also the northern limit for tropical rain forests in
Southeast Asia. The Xishuangbanna region is an important part of the
Indo-Burma global biodiversity hotspots, and harbor over 5000 vascular
plant species, which account for 16% of vascular species across China
(Cao et al. 2006). The rain forests here not only possess
biodiversity that is important both nationally and globally, but also
revealed one of the highest forest productivity across China (Fenget al. 1999) as a result of high energy and water availability.
Climate in this region is controlled by northern tropical monsoon, with
a mean annual temperature of 21.5 °C, and mean temperature in June and
January of 25.5 °C and 14.8 °C, respectively. Annual precipitation
averaged 1557 mm, of which 1335 mm (87%) occurred in the wet season
(May to October), while precipitation during the dry season (November to
the next April) accounts for only 13% of annal total. Relative humidity
averaged around 80 %, and frost was never recorded in this region.
The dataset
The dataset was provided by the Xishuangbanna National Forest Scientific
Observation and Research Station, available at the Chinese Ecosystem
Research Network (CERN) (http: //www.cnern.org.cn/). The data we
downloaded included: 1) repeated measurements of 10 permanent plots (50
m × 50 m) in the rain forests of Xishuangbanna, including different
forest types from secondary to primary forests (Table 1); 2) allometric
equations to estimate tree biomass for each forest type (Table S1). 3)
Soil variables, including ten soil variables (soil organic carbon, pH,
moisture, nitrogen, phosphorous and kalium concentrations, etc.)
measured at three locations in each plot in the year of 2010. These 10
plots were established in 2004, each consist of 25 subplots (10 m × 10
m), which were investigated annually from 2004 to 2010. In each subplot
by each year, tree species name and diameter at breast height (DBH, 1.3
m) for all individuals with a DBH ≥1.0 cm were recorded.
To examine the effect of grain size on the relative importance of
diversity vs. stand factors on ecosystem functions and stability, we
split each 0.25 ha plot into subplots with different sizes: i.e. 400
m2, 800 m2 and 1200
m2. As a result, we obtained 61, 30, 20, and 10
(sub)plots with an area of 400, 800, 1200 and 2500 m2,
respectively.