Moisture status during a strong El Niño explains a tropical montane cloud forest’s upper limit

• Published in: Oecologia 2014-05, Vol.175 (1), p.273-284
• Main Authors: Crausbay, Shelley D, Frazier, Abby G, Giambelluca, Thomas W, Longman, Ryan J, Hotchkiss, Sara C
• Format: Article
• Language: English
• Subjects: Analysis; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; climate; Climate change; Climate models; Climate variability; Cloud forests; COMMUNITY ECOLOGY; Community ecology - Original research; Community structure; Drought; Droughts; Ecology; Ecosystem; Ecosystems; Ecotones; El Nino; El Nino-Southern Oscillation; Forestry; Fundamental and applied biological sciences. Psychology; General aspects; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Global temperature changes; habitats; Hawaii; Humidity; Hydrology/Water Resources; Life Sciences; Metrosideros polymorpha; Microclimate; Microclimates; Models, Theoretical; Montane environments; Mountain ecology; Mountain ecosystems; Physiological aspects; Physiology; Plant Sciences; prediction; Rain; Rain and rainfall; Rainfall; Relative humidity; Species composition; species diversity; Taxa; Temperature; Trees - physiology; tropical montane cloud forests; Vegetation
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-014-2888-8

Growing evidence suggests short-duration climate events may drive community structure and composition more directly than long-term climate means, particularly at ecotones where taxa are close to their physiological limits. Here we use an empirical habitat model to evaluate the role of microclimate during a strong El Niño in structuring a tropical montane cloud forest’s upper limit and composition in Hawai‘i. We interpolate climate surfaces, derived from a high-density network of climate stations, to permanent vegetation plots. Climatic predictor variables include (1) total rainfall, (2) mean relative humidity, and (3) mean temperature representing non-El Niño periods and a strong El Niño drought. Habitat models explained species composition within the cloud forest with non-El Niño rainfall; however, the ecotone at the cloud forest’s upper limit was modeled with relative humidity during a strong El Niño drought and secondarily with non-El Niño rainfall. This forest ecotone may be particularly responsive to strong, short-duration climate variability because taxa here, particularly the isohydric dominant Metrosideros polymorpha, are near their physiological limits. Overall, this study demonstrates moisture’s overarching influence on a tropical montane ecosystem, and suggests that short-term climate events affecting moisture status are particularly relevant at tropical ecotones. This study further suggests that predicting the consequences of climate change here, and perhaps in other tropical montane settings, will rely on the skill and certainty around future climate models of regional rainfall, relative humidity, and El Niño.