内蒙古草原三种植物群落中狭翅雏蝗造成的牧草损失(英文)

狭翅雏蝗Chorthippus dubius是我国北方草原的重要蝗种之一,在大发生年对牧草的威胁很大。它对牧草的损失至今尚无较准确的定量估算。本文通过测定不同发育阶段狭翅雏蝗的取食率、掉落毁损率,结合野外自然种群数据,对内蒙古草原三种植物群落中狭翅雏蝗造成的牧草损失进行了估测,并对三种草场蝗虫的经济阈值进行了计算。主要研究结果如下: 1.狭翅雏蝗对羊草、冷蒿、大针茅的取食率相似;取食率与虫体体重存在显著的线性相关。 2.狭翅雏蝗每个个体在一生中平均造成牧草损失487.55—784.4mg(干重),每日消耗与浪费的牧草为7.64—11.45mg。 3.狭翅雏蝗种群造成的牧草损失在冷蒿群落、羊草-大针茅-羊草群落、羊草-大针茅群落分别为1.52,1.65,0.76g/m,占地上初级生产量的2.96％、1.18％、0.42％,表现为越退化的草场,狭翅雏蝗对牧草的压力越大。其累积损失量的季节程式可以刚logisuc方程拟合。 4.狭翅雏蝗的经济阈值在羊草、羊草+大针茅+冰草、冷蒿草原分别为每平方米18.5、19.4、11.8头四龄为主个体。

FORAGE LOSSES CAUSED BY GRASSHOPPER CHORTHIPPUS DUBIUS (ZUB. ) ON GRASSLAND IN INNER MONGOLIA OF CHINA

To quantitatively assess the losses of forage. we conducted experiments to determine the average amount of forage destroyed (forage consumed plus forage cut-off and dropped to the ground) per day by the grasshopper, Chorthippus dubius (Zub. ), at its different life stages in laboratory and then extrapolated estimates cf losses caused by the field grasshopper population from these results and the population densities of this grasshopper. The main results are as follows:1.Ch. dubius is a late-occurring species of grasshoppers in Inner Mongolian grassland. It occurred from June to October. The duration for each instar and the longevity of the adult under natural conditions ranged from 9. 09-9. 81 (days) and 17. 65-19. 44(days) respectively.2. Both consumption and forage defoliation rates by Ch. dubius increase with its developemnt. The consumption rates had significantly linear relationships with the grasshopper's body weights.3. Average losses caused by one grasshopper in its whole lifespan were 487. 55-784. 4 mg (dry weight) and the average amount of forage consumed and wasted per day was 7. 64-11. 45 mg.4. Total losses caused by Ch. dubius population in 1990 ranged from 0. 762-1. 647 g/m2 in the three types of vegetation, and the largest value was found in restorative type. The seasonal courses of cumulative forage losses would fit logistic equations in the three vegetation types.5. Population densities (18. 5. 194. ,11. 8/m2. 4th instar nymph predominantly) were suggested as the levels at which control should be initiated on the three types of pastures respectively.