| This research takes the Leymus chinensis meadow foraging ecosystem as research object in the Songnen meadow steppe. We carried through primary research of foraging behavior and diet selection of sheep and foraging strategies under foraging sequences in plots with different species richness through measure of grassland vegetation and observing and recording foraging behavior of herbivores. Aim of our research provides experiment data for theory of plant-herbivore mutualism and ecosystem stability and gives some information about grassland construction and management in the production practice.The main conclusions are as follows:(1) With the increase of species richness, intake mass of sheep increases accordingly. Data of intake mass is as follows: 1 species (954.1g), 4-6species (1079.9g) and >8 species (1162.2g). The difference among different species richness is significant (P =0.031). Intake mass of sheep in the afternoon is larger than that in the morning. Except that difference of intake mass of sheep between am and pm in plots with 4-6 species is nearly significant (P=0.076), in plots with 1, 2, >8 species this difference is significant (P=0.000, 0.030, 0.047). Preference of sheep foraging a specific plant is stable in the plots with 2 species. CV of preference index is only 31.5% at the most; in plots with 4-6 species richness preference index of sheep varies sharply and CV of that adds up to 45%, the largest is 78%; In plots with > 8 species CV of preference index of sheep foraging a specific plant is 107.7%.(2) With the increase of plant evenness, intake mass of sheep decreases. Intake mass of sheep appears regularity that it is high at low species evenness in plots with 2 species including L. chinensis-Chloris virgata and Phragmites communis-C. virgata. Difference of intake mass in plots with different species evenness is significant (P=0.008, 0.022). Intake mass of sheep in plots with L. chinensis and P. communis has no significant difference (P=0.059). The reason is that species evenness of two plots is almost same (0.9802, 0.9826). In plots with 4-6 species intake mass of sheep and species evenness is negative correlation significantly (r=-0.962, P=0.002). With the increase of species evenness, intake mass of sheep decreases gradually. While intake mass of sheep and species evenness hasn't obvious linear correlation in plots with >8 species richness (P=0.576).(3) With the increase of species richness, sheep can maintains longer time of intake mass peak. In plots with 1, 2, 4-6, > 8 species intake mass peak of sheep continues continual 4 (40min), 6 (60min), 6 (60min), 8 (80min) foraging sequences.(4) In foraging plots with 4-6, >8 species the number of plant species of sheep visiting decreases with lengthening of foraging sequences. Foraging sequences and the number of species of sheep visiting is quite significant negative correlation (r =-0.4792, P=0.000), isn't significant negative linear correlation (r =-0.1449, P=0.224), respectively.(5) With the increase of foraging plots, intake mass of sheep ascends gradually. Intake mass of sheep in 1000m~2 and 3000m~2 plots is larger significantly than that in 200m2 plots. It has no difference between 1000m~2 and 3000m2 plots. When foraging in 200m2 plot preferred species of sheep includes K. integrifolia and P. communis; when foraging in 1000m~2 plot they includes Kalimeris integrifolia and Artemisia scoparia; when foraging in 3000m~2 plot they includes Polygonum salinum, Taraxacum sinicum and Melilotus suaveolen.In natural grassland, species richness benefits improvement of intake mass of herbivores and species evenness could reduce it. Hence, grassland heterogeneity (species richness and species evenness) should be improved during foraging management in construction practice. In addition, foraging area should be proper. When foraging area is large, herbivores mainly choose preferred species and reduce usefulness of non-preferred and may induce access energy loss of sheep because of strong selectivity. When foraging area is small, intake mass of sheep is low and this doesn't benefit improvement of secondary production. In plots with 2, 4-6, >8 species intake mass peak of sheep continues continual 60, 60, 80min. This reveals foraging time should confine to 1-1.5h. Though intake mass of sheep may increase with increase of foraging time, energy loss of traveling when foraging will also increase. |
