California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor.
根据周二发表的一项研究，自上世纪30年代以来，加州已经失去了一半的大树，气候变化似乎是主要因素。
The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.
新的研究发现，在超过46000平方英里的加州森林中，直径超过2英尺的树木数量减少了50%。从雾蒙蒙的北海岸到内华达山脉，再到洛杉矶上空的圣加布里埃尔，没有一个地区幸免。在塞拉高地，大树的数量下降了55%以上；在南加州部分地区，下降了近75%。
Many factors contributed to the decline, said Patrick McIntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources.
该研究的主要作者、生态学家帕特里克·麦金太尔说，多种因素导致了这种下降。伐木工人以大树为目标，住房开发陷入困境，声势浩大的山火控制使得加利福尼亚州的森林里挤满了小树，它们与大树争夺资源。
But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, McIntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.
但是，通过将20年代和30年代对加利福尼亚森林的研究与2001年和2010年之间的另一项研究进行比较，麦金太尔和他的同事记录了一种广泛的大树死亡现象，这种现象甚至在保护森林免受砍伐或开发的荒地中也很明显。
The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taking into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt.
在树木缺水最严重的地区，大树的损失最大。研究人员通过计算机模型计算缺水量，该模型计算了树木获得的水分与它们需要的水分的对比，并考虑了降雨、气温、土壤湿度和融雪时间等因素。
Since the 1930s, McIntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.
麦金太尔说，自30年代以来，该州缺水量上升的最大因素是气温上升，导致树木向空气中流失更多水分，以及更早的融雪，减少了旱季树木的供水。
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