2.2. Experimental design and grazing treatments
To test the interactive effects of large herbivore species and
plant diversity of pre-grazing on insect community, three plant
diversity levels and three single grazer species were selected. In
this study, 9 blocks (each for 0.3 ha in size) with flat topography
and similar soil type were established. The nine blocks investigated
were classified into three plant diversity levels: low (4–5 species),
intermediate (8–9 species), and high (15–17 species) based on
vegetation investigation of pre-grazing, with three blocks (three
replicates) for each plant diversity level. Each block for each plant
diversity level was one plant community, and the plant community
composition (species, and individual number of each plant species)
that was similar with other blocks in same plant diversity level, and
was different from the blocks in other plant diversity levels.
Detailed descriptions of experimental plant diversity treatments of
pre-grazing can be found in Zhu et al. (2012). Grazing treatments
were nested within the block of each plant diversity treatment, and
no grazing and three single grazing treatments with one grazer in
each grazed plot were used. That is, each block was composed of
four plots (each for 0.05 ha in size) enclosed with barbwire.
Neighboring plots within each block were separated by 18–20 m.
The four grazing treatments were assigned randomly to the four
plots in each of the nine blocks as follows: (1) no livestock grazing
(control); (2) grazing by cattle (a hybrid of native and yellow
breed), and two cattle (221 5.5 kg) per plot (= 7.14 sheep ha
1
);
(3) grazing by goats (Liaoning Cashmere breed), and eight goats
(34 1.6 kg) per plot (= 7.08 sheep ha
1
); (4) grazing by sheep
(small-tail Han breed), and eight sheep (33 1.6 kg) per plot
(= 7.21 sheep ha
1
).
Intermediate grazing intensity (50–65% of the available forage
was removed) was used in all grazed plots. The similar grazing
pressure (sheep unit per hectare) among cattle, goats, and sheep
was gained by calculating the intake and body weight of each
individual of the three grazers. The plots were grazed by livestock
from the second week of July in 2007 and 2008 when new growth
ensured sufficient forage for grazing. Grazing was conducted twice
per day: from 06:00 to 08:00 AM and from 16:00 to 18:00 PM
during their normal grazing time and was terminated when about
60% of the available forage was removed (about 10–15 d within
each month). Large herbivores were not allowed to graze the plots
that were visibly wet or following measurable rain (10 mm).
Vegetation and insects were assessed after 1.5 years of grazing
treatments
2.2. Experimental design and grazing treatmentsTo test the interactive effects of large herbivore species andplant diversity of pre-grazing on insect community, three plantdiversity levels and three single grazer species were selected. Inthis study, 9 blocks (each for 0.3 ha in size) with flat topographyand similar soil type were established. The nine blocks investigatedwere classified into three plant diversity levels: low (4–5 species),intermediate (8–9 species), and high (15–17 species) based onvegetation investigation of pre-grazing, with three blocks (threereplicates) for each plant diversity level. Each block for each plantdiversity level was one plant community, and the plant communitycomposition (species, and individual number of each plant species)that was similar with other blocks in same plant diversity level, andwas different from the blocks in other plant diversity levels.Detailed descriptions of experimental plant diversity treatments ofpre-grazing can be found in Zhu et al. (2012). Grazing treatmentswere nested within the block of each plant diversity treatment, andno grazing and three single grazing treatments with one grazer ineach grazed plot were used. That is, each block was composed offour plots (each for 0.05 ha in size) enclosed with barbwire.Neighboring plots within each block were separated by 18–20 m.The four grazing treatments were assigned randomly to the fourplots in each of the nine blocks as follows: (1) no livestock grazing
(control); (2) grazing by cattle (a hybrid of native and yellow
breed), and two cattle (221 5.5 kg) per plot (= 7.14 sheep ha
1
);
(3) grazing by goats (Liaoning Cashmere breed), and eight goats
(34 1.6 kg) per plot (= 7.08 sheep ha
1
); (4) grazing by sheep
(small-tail Han breed), and eight sheep (33 1.6 kg) per plot
(= 7.21 sheep ha
1
).
Intermediate grazing intensity (50–65% of the available forage
was removed) was used in all grazed plots. The similar grazing
pressure (sheep unit per hectare) among cattle, goats, and sheep
was gained by calculating the intake and body weight of each
individual of the three grazers. The plots were grazed by livestock
from the second week of July in 2007 and 2008 when new growth
ensured sufficient forage for grazing. Grazing was conducted twice
per day: from 06:00 to 08:00 AM and from 16:00 to 18:00 PM
during their normal grazing time and was terminated when about
60% of the available forage was removed (about 10–15 d within
each month). Large herbivores were not allowed to graze the plots
that were visibly wet or following measurable rain (10 mm).
Vegetation and insects were assessed after 1.5 years of grazing
treatments
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