The growth and acclimation response of wild dipterocarp seedlings to environmental change caused by logging disturbance was examined in lowland dipterocarp forest in Central Kalimantan (Indonesian Borneo). The seedling microclimate was characterised in logged and unlogged forest using automated equipment and hemispherical photography. A system of analysis of hemispherical photographs was developed and calibrated against direct measurements of daily PPFD (photosynthetic photon flux density). Predictions from photographs were linearly related to measured irradiance over the range 1 - 60 % of above canopy totals. Predictions were repeatable and accurate (R<SUP>2</SUP>>0.95). Errors were large relative to absolute totals below 5 % of above canopy totals. Hemispherical photography and direct measurements using a shade band were used to estimate the proportion of above canopy diffuse irradiance (pDif) as 0.53 ± 0.03 (n = 4), with good agreement between the two methods. Apart from the obvious effects of increased irradiance, the microclimate of undisturbed and logged forest was influenced more by season and topography than by canopy opening. Wind speed varied with site elevation and season and had a strong influence on the degree of coupling between above and below canopy conditions. Low wind speed was an important feature which will tend to decouple seedling leaves from ambient conditions. The most important effect of logging on the seedling microclimate will be the effects of increased exposure of seedling leaves to direct sunlight, rather than relatively small changes in air temperature and humidity. It was hypothesised that low boundary layer conductance and high leaf temperatures during periods of the direct sunlight would be an important limitations to dipterocarp seedling regeneration in logging gaps. Logging increased patchiness and removed dipterocarp regeneration from the most disturbed areas. Abundant dipterocarp regeneration occurred in logged forest, but was unevenly distributed and lacking in the gaps where it is most required.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:643251 |
| Date | January 1997 |
| Creators | Clearwater, Michael J. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14532 |
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