2.3. Vegetation measurements
All plots were sampled in July, August, September, and October
in 2008. Plant species richness, the individual number, height, and
cover of each species were assessed within ten quadrats
(0.25 0.25 m) arranged evenly along each of two 20 m cater-246 H. Zhu et al. / Agriculture, Ecosystems and Environment 212 (2015) 245–252
corner transects in each plot. Structural heterogeneity was
estimated as the coefficient of variation (CV) of plant height.
Aboveground plant biomass was measured by collecting plant
materials from five randomly located 0.5 0.5 m quadrats per plot.
Plant samples were clipped to 1 cm above the soil surface with
pruning shears. Plants samples were air forced oven-dried for 48 h
at 80
C, and weighed. Some vegetation attributes, such as plant
species richness, plant cover, plant height, plant structural
heterogeneity, and plant biomass in this study were calculated
in our previous paper (Zhu et al., 2012), and here we did not show
these results. Plant diversity (Shannon–Wiener index) was
calculated as H = S
s
1
ðPi lnPi
Þ, where Pi is the proportion of
individuals represented by species i, and s is the number of plant
species