Effects Of Grassland Caterpillar On The Vegetation Of Kobresia Pygmaea Alpine Grassland Under The Interference Of Grazing

The experiment was to study the large-scale grazing livestock(yak) and the grassland caterpillar(mainly insect herbivores), by the method of artificial field control(caterpillar presence and absence) and field controlled grazing(grazing and non-grazing) in Qinghai Province Yushu Tibetan Autonomous Prefecture Chengduo County Jane Xiang Qin alpine meadow(Qinghai University, Tsinghua University in Sanjiangyuan grassland ecological field observation station). The effects of grassland caterpillar of alpine meadow grassland caterpillar quantity and population density and grassland vegetation community(ground biomass, vegetation coverage, community height and plant diversity) and under the interference of yak grassland caterpillar of alpine meadow small Song hastily vegetation communities(ground biomass, vegetation coverage, community height and plant diversity) effects of was carried out. The main results are as follows:1、Grassland caterpillar population dynamic variation is first increased and then decreased in experimental observations during the period from June 5 to July 10, every day the number of grassland caterpillar increase averagely about 2.04 only / m2, July 10, after the grassland caterpillar population density per day reduced on average only about 428 / m2. The study area after June 5, temperature and precipitation were the rapid increase, and in mid July after the temperature and precipitation respectively at the beginning of slowly decreasing, which may is one of the main reasons for the grassland caterpillar population density first increased and then decreased.2、Grassland caterpillar on small humilis vegetation to total biomass has little effect(P > 0.05), Cyperaceae plants biomass significantly reduced(P < 0.05), miscellaneous grass biomass increased significantly(P < 0.05), the influence of biomass of grasses and legumes not significant(P > 0.05). Cyperaceae is dominant species in the study area in Alpine Kobresia pygmaea meadow, grassland caterpillar to Cyperaceae plants is the main source of food, of grassland caterpillar selective grazing reduced the ability of competition in the community, thus making forbs plant biomass increased.3、Grassland caterpillar impact on small Song hastily vegetation coverage was not significant(P > 0.05), grassland caterpillar remove experimental plots of average vegetation coverage is 95% and the control plots the average coverage was 91.7%. Effect of height on grassland vegetation of Alpine Grassland Caterpillar significantly(P<0.05). The community average heights of the experimental plot and control experimental plot were 3.83 cm and 2.68 cm, respectively. The stem and leaf of the main plants in the grassland caterpillar affected the height of the community; the effect on the plant tillering and branching was not very large, so the vegetation coverage changed little.4、Grassland caterpillars on small humilis to vegetation diversity effect significantly, experimental plots of the Simpson index, Shannon Wiener index and Pielou index were significantly lower than remove test area(P < 0.05). Selective foraging of herbivores can increase the competitive ability of the forage grass species and reduce the competitive ability of the forage grass species, which makes the ecological niche of the plant species change, which influences the plant diversity.5、The variation law of the monthly dynamic of grassland caterpillar population under grazing disturbance was first increased and then decreased. Grazing area growth trend is higher than that in the control area, in the experimental observation period from June 5th to July 10 th, the number of grassland caterpillars in the grazing area increased by 2.93 /m2(average daily average of about 2.04 /m2). The number of grassland caterpillar population in grazing area was lower than that in control area, and the grazing area was reduced by about 4.28 /m2 per day after July 10th(average daily average of about 5.76 /m2).6、The variation law of the monthly dynamic of grassland caterpillar population under grazing disturbance was first increased and then decreased. Grazing area growth trend is higher than that in the control area, in the experimental observation period from June 5th to July 10 th, the number of grassland caterpillars in the grazing area increased by 2.93 /m2(average daily average of about 2.04 /m2). The number of grassland caterpillar population in grazing area was lower than that in control area, and the grazing area was reduced by about 4.28 /m2 per day after July 10th(average daily average of about 5.76 /m2).7 、 Grazing grassland caterpillar on small humilis to vegetation diversity effect significantly, in four diversity index(richness, Simpson index, Shannon Wiener index and Pielou index) were different(P < 0.05) were significantly less than CK(P < 0.05). The small humilis main plant vegetation species importance value also has the effect of grassland caterpillar grazing. The selective foraging of the two kinds of herbivores changes the competition and the relationship between plant species, which makes the ecological niche of plant species change, and then influences the diversity of plant species.