2. 外语
  3. Exotic insect pests can produce both short-and long-term effects on forest ecosystems. Short-term effects include the disturbanc

Exotic insect pests can produce both short-and long-term effects on forest ecosystems. Short-term effects include the disturbanc

admin2021-03-28  127
问题     Exotic insect pests can produce both short-and long-term effects on forest ecosystems. Short-term effects include the disturbances directly associated with the action of the pest, which may cause the defoliation, loss of vigor, or death of trees. Long-term effects involve changes in tree species composition and the consequent alterations of forest structure, productivity, and nutrient uptake. Exotic pests are more efficient than most abiotic disturbances (e.g., fire or wind) at producing long-term changes in species composition. Pests often target specific tree species and, if they become established, they usually remain as permanent components of the ecosystem. Shifts in forest species composition ramify through the ecosystem in many ways because tree species have different, often unique properties.
The passage mentions which of the following as effects of exotic pests on forest ecosystems?
选项 A、Decreased vitality in trees
B、Defoliation of trees
C、Changes in forest structure
答案A,B,C
解析 A项对应短期影响。B项对应短期影响。C项对应长期影响。
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