Effects of El Nino drought on tree mortality and growth across forest types at different elevations in Borneo

FOREST ECOLOGY AND MANAGEMENT

卷:490

Article

Miyamoto, Kazuki¹  Aiba, Shin-ichiro²  Aoyagi, Ryota^1,3  Nilus, Reuben⁴ 

[1] Forest Res & Management Org, Forestry & Forest Prod Res Inst FFPRI, Dept Forest Vegetat, Tsukuba, Ibaraki 3058687, Japan

[2] Hokkaido Univ, Fac Environm Earth Sci, Sapporo, Hokkaido 0600810, Japan

[3] Japan Soc Promot Sci, Chiyoda Ku, Tokyo 1020083, Japan

[4] Forest Res Ctr, Sabah Forestry Dept, Sandakan 90715, Sabah, Malaysia

关键词: El Nino;    Drought;    Heath forest;    Mixed dipterocarp forest;    Isolated forest;    Sabah;   

DOI  :  10.1016/j.foreco.2021.119096

来源: Elsevier

【 摘 要 】

The 2015-2016 El Nino drought had a strong impact on tropical forest tree dynamics in Borneo. To assess the effects of the drought on trees growing in different environments, we examined differences in tree mortality and growth before and during the drought at two elevations (ca. 500 m vs. 1000 m a.s.l.) and among forest types (mainly heath forest on sandy soils and mixed dipterocarp forest) in Sabah, Borneo. We hypothesized that the effects of the drought on trees would be greater at low elevation than at high elevation, and in mixed dipterocarp forest than in heath forest, since tree species in heath forest are likely to adapt to stressful conditions. Tree mortality in heath and mixed dipterocarp forests was higher during the drought than before the drought. In addition, tree mortality was markedly higher at low elevation than at high elevation in both forest types. There was no significant interaction between drought and elevation, indicating that the drought and elevation independently affected tree mortality. Contrary to our expectation, at low elevation, heath forest trees showed comparable or higher mortality than mixed dipterocarp forest trees. Moreover, diameter and basal area growth rates were higher during the drought than before, particularly at low elevation, probably owing to the improved light conditions for surviving trees after the death of surrounding trees. Species-level wood density did not significantly affect tree mortality in our sites. Species mean stem growth rates before the drought negatively affected tree mortality, suggesting that species with higher tree mortality had reduced stem growth prior to the severe drought period. Our results show that the El Nino-induced drought increased mortality and growth of heath forest trees on sandy soils as well as in mixed dipterocarp forest trees. The results also suggest that markedly high tree mortality at low elevation was caused by the additive effect of drought and elevation.

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