One of the biggest concerns about global climate change impacts relates to how forests and other ecosystems will be affected. Along with increasing concentrations of carbon dioxide in the atmosphere and warming temperatures, rainfall, cloud cover, storm frequency, and other aspects of climate will also change. These shifts are likely to have effects on plants, such as changing the amount of water they use or how fast they grow. In this project, we investigated the connections between environmental conditions (such as temperature, rainfall, solar radiation, humidity, wind speed, soil moisture) and plant water use and growth rates of two forest ecosystems in Hawai‘i. Based on those connections, we sought to project how a specific set of possible future climate changes will affect water use and growth of these forests. The forests chosen for study represent relatively undisturbed native forest and a forest that has been invaded by the non-native tree strawberry guava. As a result of this study, we have found that more water is used at the non-native forest site, and growth characteristics of the two sites are different. Projections of changes that will be caused by future climate change show that both forests will use more water and will grow more slowly. It appears that both of these effects will be greater for the non-native site, i.e., the water use will increase more for the non-native forest and the growth will be reduced more there. Our findings are important because future increases in forest water use caused by climate change could reduce the availability of groundwater resources and streamflow. Reduced growth rates could affect forest health and stability, which could further curtail the ecosystem services they provide.
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As climate changes in Hawai`i over the next 100 years, shifts in temperature, rainfall, clouds, the amount of CO2 in the air, and other variables will impact Hawaiian forests. These effects may include changes in growth rates and water use by forest vegetation. Many native forests in Hawai‘i are being invaded by non-native species, with devastating effects on the native ecosystems and possible negative consequences for water supply and water quality. With climate change, current and future efforts to slow the spread of non-native species, preserve Hawai`i’s native ecosystems, and maintain healthy stream flow and groundwater recharge rates will be affected by climate-related changes in vegetation. Therefore, it is important to gain a better understanding of how the changing climate will affect both native and non-native species, to allow for more effective natural resource management. In this study, researchers will make use of existing scientific results and datasets on how climate variations affect native and non-native forest species, gather new data of this type, and combine that information with estimates of the expected changes in temperature, rainfall, and other variables to simulate the effects of future climate change on Hawai`i’s native and non-native forests.
