2.1 Study site
This study was conducted from July 2017 to October 2017 at six
study
sites, which extend from 28°4′ to 29°36′N latitude and from 106°28′ to
108°57′E longitude and are located in three typical karst districts of
southwestern China (Youyang (YY) in southeastern Chongqing; Yinjiang
(YJ) in northern Guizhou Province;
and
Beibei (BB) in northwestern Chongqing) (Fig. 1 and Table 1). The three
districts are separated by approximately 100~250 km and
are characterized by a typical subtropical monsoon climate, with mean
annual precipitation and evaporation of 1200 and 1177 mm, respectively,
and the average temperature ranges from 6.4 °C in the coldest month
(January) to 29.1 °C in the warmest month (July), with a mean annual
temperature of 18.5 °C.
The six
study
sites, which include two shrublands
(YY1 and YY2) and four woodlands (BB1, YJ1, YJ2 and YY3), where
elevation ranges
between
approximately 470-857 m asl, are located on a gentle slope of typical
karst mountains where the slope, aspect and inclination are basically
the same. The vegetation in these areas was strictly protected with the
same ways especially after 1998. The shrubland is dominated by
drought-tolerant plants, and the most common species
includeRhus chinensis Mill.,Rubus
coreanusMiq.,Rosa cymosa Tratt.,Berchemia
sinica Schneid., and Rubus lambertianus Ser. The dominant tree
species in woodland areas are Pinus massonianaL.,Ligustrum lucidum Ait., and Myrsine africana Linn. For
nomenclature of the species recorded, see the Flora of China (Wu et al.
2013).