Final Report: Measurement of El Niño Southern Oscillation (ENSO)-related Climate Conditions and Ecosystem Responses in Hawaiʻi
Dates
Publication Date
2017-12
Citation
Thomas Giambelluca, Yoshiyuki Miyazawa, Shelley Crausbay, Abby Frazier, and Mike Nullet, 2017-12, Measurement of ENSO-Related Climate Variables and Ecosystem Responses in Hawai‘i: .
Summary
Throughout the world, forests cover mountain slopes only up at a certain elevation. Above that level, trees become scattered. Higher up, no trees are found. The level where the forest ends, called the forest line or timberline, is higher in tropical areas than in colder regions, suggesting that cold climate conditions prevent forests from growing at higher elevations. On tropical island mountains, such as those in the Hawaiian Islands, the forest line is found at a lower elevation than we would expect based on the temperature. This leads us to suspect that some factor other than temperature, such as low rainfall, might be controlling the level of forest lines on these tropical islands. In this project, we sought to address this question [...]
Summary
Throughout the world, forests cover mountain slopes only up at a certain elevation. Above that level, trees become scattered. Higher up, no trees are found. The level where the forest ends, called the forest line or timberline, is higher in tropical areas than in colder regions, suggesting that cold climate conditions prevent forests from growing at higher elevations. On tropical island mountains, such as those in the Hawaiian Islands, the forest line is found at a lower elevation than we would expect based on the temperature. This leads us to suspect that some factor other than temperature, such as low rainfall, might be controlling the level of forest lines on these tropical islands. In this project, we sought to address this question by examining the characteristics of past droughts in a forest line study area on Haleakalā, Maui as well as, how the vegetation responded to those droughts. We directly observed the microclimate and plant responses in the study area during a period when we expected an El Niño drought to occur. In all droughts since 2000, except the one culminating in 2010, vegetation responded positively. Though, during the most severe drought, satellite imagery began to show significant browning of the vegetation. This research has shown that continuous monitoring of climate variables, including soil moisture, in this critically important area is vitally important for understanding both climate variability and its effects on the ecosystems below and above the forest line.
