There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline.
对于为什么树线以上的树木会突然停止生长，至今还没有一个公认的解释。
2
Some experts reacted with scepticism that the population would really hit the upper end of the predicted spectrum of growth and reach 15 billion so quickly.
一些专家对此持怀疑态度，他们不相信人口真的会如此之快地达到增长范围的预期上限——150亿。
3
Industrial service providers and business partners can define constraints on resources for initial resource allocation and determine the upper limit for potential growth in future.