问题 问答题 论述题

如何根据群落的结构特征,合理安排农业生产?

答案

参考答案:

在配置农业生物垂直结构时,应注意到同一生境中各种生物个体间可能存在的各种相互关系和由此产生的各种群落总效应。农业生物间的互补作用是合理群落结构的基础。互补作用可能表现在对光、温、水、肥等自然资源的利用土,也可以表现在对资金、劳力、技术和交通等社会条件的要求上。互补作用还可能表现在对病虫害及不良环境的抗逆性上,以及营养价值、工业用途、经济用途、环境效益等方面。生态位不同的物种有希望构成理想的互补关系。因此,在生态位、株型、生育期、耐肥性、固氮能力、抗病虫等方面有差异的不同作物有可能构成合理的作物群落结构;食性不同、活动范围不同的畜禽品种,也有希望构成合理的动物群落结构。

在农业生产中的农、林、牧、渔以及各业内部的面积比例及其格局是农业生态系统的水平结构。控制农业生物群落的水平结构有两种基本方式:

(1)在不同的生境中因地制宜地选择合适的物种,宜农则农,宜林则林,宜牧则牧。

(2)在同一生境中配置最佳密度,并通过饲养、栽培手段控制密度的发展。各种农作物、果树、林木的种植密度、鱼塘的养殖密度、草场的放牧量等都对群落的水平结构及产量有重要影响。

在农业生产中,通过人为的栽培、饲养技术,调节作物和畜禽的组合匹配,使其机能节律与环境因素的变化节律最大限度地吻合和协调,是生产经营者与管理者所必须了解的。调节农业生物群落时间结构的主要方式是复种、套种、轮作和轮养、套养。如家畜中马对草料最挑剔,其次是牛,绵羊最耐粗食,据此合理轮牧,有利于提高牧草的利用率。根据作物害虫的繁殖行为、动态发展与环境因素的变化节律,及时预测、预报及采取相应的防治措施,也是提高作物产量的重要保证。

填空题
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Chicago, a city in the State of Illinois, is the second largest in the United States. It stretches for 29 miles along the southwest shore of Lake Michigan. Its splendid centre faces the lake behind a pleasant park. The Chicago River flows through the heart of the city. The city of Chicago, 713 miles west of New York and 1858 miles east of San Francisco, is located at the conjunction(连接) of the Great Lakes and the Mississippi River system and surrounded by the productive farmlands of the Midwest. This makes the city the crossroads of the nation and the “ bread basket” of the nation. From its beginning as a frontier fort(要塞) settlement in 1803, commerce(商业) has been the key to Chicago’s development, especially since the railroads and stockyards(牲畜围栏) were built in the 1840s and 1850s. Thousands of foreigners, attracted by the promise of steady jobs, have lived and worked there since the second half of the 19th century; thousands more come to visit its famous fairs, and millions of others cross it every day by road or railway. Chicago is the world’s biggest road and railway centre, and it should claim(要求得到身份或权利的承认) the world’s busiest airport.

66. If you go to New York from Chicago, you go _____ for _____ miles.

A. east…713   B. west…713   C. east…1858   D. west…1858

67. From the passage, we can see that there is _____.

A. a lake right in the middle of the city

B. the Mississippi River in the middle of the city

C. a park in the middle of the city

D. a lake 29 miles away from the city

68. Chicago is called the “ bread basket” of the nation because _____.

A. there is a river flowing through the city

B. it is located at the conjunction of the Great Lakes and the Mississippi River system

C. it is near the city of New York

D. there are rich farmlands around the city

69. _____ the city developed fastest.

A. Early in the 19th century

B. Around the middle of the 19th century

C. At the end of the 19th century

D. During the second half of the 19th century

70. Since the late 19th century thousands of people have kept coming to Chicago _____. Which of the following is wrong?

A. on business     B. for a visit

C. for better jobs   D. to claim the world’s biggest seaport