The Ecological Regulating Effect Of Achnatherum Inebrians- Epichloe Gansuensis Symbiont On Biodiversity And Diseases

In this study, we investigated ecological consequences of a toxic grass in six overgrazed grasslands formed in recent decades in northwest China. Achnatherum inebrians, locally known as drunken horse grass, is becoming widely distributed in degenerated grassland in northwest China. Its toxicity is due to it being host to a seed-transmitted fungal endophyte of Epichloe gansuensis. The main findings are:1. Compared with overgrazed area without A inebrians, there were more seeds produced by forage grasses and other edible plant species in area with A inebrians. In Xiahe,25 of 31 plant species that were surveyed in this study had more inflorescence number or plant number in area with A inebrians than area without A inebrians (P< 0.05); In Guinan,9 of 12 plant species that were surveyed in this study had more inflorescence number or plant number in area with A inebrians than area without A inebrians (P< 0.05); In Alxa, all of 5 plant species that were surveyed in this study had more inflorescence number or plant number in area with A inebrians than area without A inebrians (P< 0.05). Compared with overgrazed area without A inebrians, almost all of the arthropods had more abundance and diversity in area with A inebrians.2. The result showed that:1. this grass was heavy infected by powdery mildew (Blumeria graminis), rust (Puccinia stipae-sibiricae), ergot (Claviceps purpurea) and stem smut (Ustilago hypodytes) in six sites; 2. mycoparasitism rate of Ampelomyces quisqualis and Sphaerellopsis filum were very high on the diseased leaf of A inebrians. The only found mycophagous arthropod, Aleocharinae was only found in soil block under tussock of A inebrians; 3. disease level of most plants was significantly higher in A inebrians-out than A inebrians-in treatment in overgrazed grassland fenced by one year. Therefore, we point out that the presence of susceptible A inebrians can control the level of grassland disease by providing enough food for natural enemy of fungal disease when the disease is going to out of control after the grassland fenced. Therefore, toxic A inebrians is not only like a fence to protect the grassland, but also susceptible A inebrians could be a key species to control the happening of plants disease in overgrazed grassland at a certain area.3. A inebrians can readily establish in bare soil where was made by burrowing animals, zokor (Myospalax baileyi) and pika (Ochotona curesezoniae) and then expand. A inebrians, typically regarded as an unwanted toxic invader, should be viewed as beneficial for grasslands as their presence maintains necessary plant seed resource, abundance and biodiversity of arthropod and provide a foundation stone to reconstruction and restoration of grassland ecosystem with help of burrowing animals which are frequently regarded as pests.4. After compared with tall fescue and rye grass, it can be found that drunken horse grass is very similar with them. They are three representatives in fungal endophyte symbiosis, they have similar tiller number and plant height. Compared with those two grass, drunken horse grass can produce much more seeds, our result shoewed that one plant of wild drunken horse grass can produce almost 5800 seeds. It is well known to us that tall fescue and ryegrass are common turfgrasses and widely planted in green belt in city, as a native species, drunken hourse grass widely distributes in northwest China, it could be a potential cool-season grass species to use as environmental and city greening.