斯蒂芬森先生称，现在美国西部的夏季变得更长了，天气变得更热了。这使得树木的生命更脆弱，削弱了树木逃脱虫害和火灾的能力。
Mister Stephenson says summers are becoming longer and hotter in the western United States. This makes trees weaker and decreases their ability to survive insect attacks and forest fires.
这就意味着无论何种树木，即便是在遭遇极端气候灾害或者虫害的情况下，都至少有部分个体对灾害有抵抗能力。
That means that for most threatening conditions, for climate, insects, and pests, whatever, there will be at least some individual trees of any given species tree that are resistant.
此外，林地内的土壤元素含量在病害侵入前后也会发生一定的变化：受到轻度砍伐的林地内其P、K含量较高，有利于提高树木对病虫害的抵抗能力。
Furthermore, proportion of total N, available P, available K in soil are dissimilar after the disease invaded: Capacities of resistance on disease will be enhanced if infect trees are cut appropriate.
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