主要研究 今天

A year after two consecutive major hurricanes hit Puerto Rico in 2017, 硝酸盐含量, 必需的植物营养素, 河流和流域的水位空前高涨. This high amount of nitrate may have important climate change implications that could harm forest recovery and threaten ecosystems along Puerto Rico’s coastline by escalating algal blooms and dead zones.

These are findings from 主要研究 researchers reported at the 2018 fall meeting of the American Geophysical Union (AGU) in Washington, D.C.， 12月. 10.

“硝酸盐对植物生长很重要, 但在这种情况下，你可能会有太多的好东西,” 威廉·麦克道尔，香港大学教授 联合国大学环境科学. “我们看到的硝酸盐含量异常高. 在过去的三十年里, 我们注意到飓风过后硝酸盐含量升高, 但在这些接连不断的大风暴之后, 汽车的轮子掉了下来. We saw an increase in the nitrate levels that still has not fully recovered.”

研究ers used aquatic sensors in streams in the tropical Luquillo Mountains of Puerto Rico to obtain readings every 15 minutes to follow weekly stream chemistry after both Hurricane Irma in August 2017 and Hurricane Maria in September 2017. They compared this new data to weekly stream chemistry results compiled over the last 35 years — the longest record of tropical stream chemistry in the world. 正如过去飓风所预料的那样, 每次风暴过后的几个月里，硝酸盐浓度都会上升, 在四个月左右达到顶峰.

“在飓风厄玛和玛丽亚之后, 硝酸盐的基本水平似乎出现了一个“新常态”.”

但研究结果显示，与过去的飓风不同, the increase was still evident nine months after Hurricane Maria and did not return to previous base levels. 基础指数仍然较高, 每次下雨，硝酸盐含量就会飙升, 即使是在小暴雨之后, likely reflecting major biotic processes (leaf and tree decomposition and vegetation regrowth) that control nitrate fluxes.

“在飓风厄玛和玛丽亚之后, 硝酸盐的基本水平似乎出现了一个“新常态”,麦克道尔说. “If this continues and the mountain streams transport these higher 硝酸盐含量 to the ocean, 它可能会破坏沿海生态系统, 可能危及珊瑚和其他海洋生物.”

森林生产力也值得关注. Based on previous studies and observations at the Luquillo study site, the historical frequency of major hurricane direct hits on the island was estimated to be every 50 to 60 years. 但最近的记录显示，现在这种情况每10年发生一次. 随着风暴频率和强度的增加, much greater export of nitrate to nitrogen-limited coastal waters can be expected than previously estimated, which could deplete the standing stocks of nitrate in the forest and have uncertain effects on forest productivity and regrowth.

This research is based on work supported by the National Science Foundation (NSF) and New Hampshire Agricultural Experiment Station and was conducted at the NSF Long-Term Ecological 研究 and the National Critical Zone Observatory site in the Luquillo Mountains. ​

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