You are not currently logged in.
Access your personal account or get JSTOR access through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Seasonal and Spatial Variation in the Light Environment in a Tropical Dipterocarp Forest and Gaps
James W. Raich
Vol. 21, No. 4 (Dec., 1989), pp. 299-302
Published by: Association for Tropical Biology and Conservation
Stable URL: http://www.jstor.org/stable/2388279
Page Count: 4
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
Incoming photosynthetically active radiation was continuously monitored for almost one year in closed-canopy dipterocarp forest and in two forest gaps. Mean weekly photosynthetic photon flux densities (PPFD) in the forest and in the small and large gap sites averaged 1.9, 8.3, and 37 percent respectively of the PPFD in the open. There was no apparent seasonality of PPFD in the open, but there was pronounced seasonal variation of PPFD in the forest and gap sites. Therefore, seedlings within forest gaps may be exposed to very different light regimes over the course of the year. Mean daily PPFD was highly correlated with canopy coverage in both short-term and long-term experiments. A short-term study indicated that light penetrating through canopy openings can increase the PPFD near ground level at least 20 m inside the forest from the nearest gap. Forest gaps are not discreet areas; they are environmental continua in both space and time.
Biotropica © 1989 Association for Tropical Biology and Conservation