Chronosequence predictions are robust in a Neotropical secondary forest,but plots miss the mark |
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| Authors: | Justin M Becknell Stephen Porder Steven Hancock Robin L Chazdon Michelle A Hofton James B Blair James R Kellner |
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| Affiliation: | 1. Environmental Studies Program, Colby College, Waterville, ME, USA;2. Institute at Brown for Environment and Society, Brown University, Providence, RI, USA;3. Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA;4. Department of Geographical Sciences, University of Maryland, College Park, MD, USA;5. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA;6. NASA Goddard Space Flight Center, Greenbelt, MD, USA |
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| Abstract: | Tropical secondary forests (TSF) are a global carbon sink of 1.6 Pg C/year. However, TSF carbon uptake is estimated using chronosequence studies that assume differently aged forests can be used to predict change in aboveground biomass density (AGBD) over time. We tested this assumption using two airborne lidar datasets separated by 11.5 years over a Neotropical landscape. Using data from 1998, we predicted canopy height and AGBD within 1.1 and 10.3% of observations in 2009, with higher accuracy for forest height than AGBD and for older TSFs in comparison to younger ones. This result indicates that the space‐for‐time assumption is robust at the landscape‐scale. However, since lidar measurements of secondary tropical forest are rare, we used the 1998 lidar dataset to test how well plot‐based studies quantify the mean TSF height and biomass in a landscape. We found that the sample area required to produce estimates of height or AGBD close to the landscape mean is larger than the typical area sampled in secondary forest chronosequence studies. For example, estimating AGBD within 10% of the landscape mean requires more than thirty 0.1 ha plots per age class, and more total area for larger plots. We conclude that under‐sampling in ground‐based studies may introduce error into estimations of the TSF carbon sink, and that this error can be reduced by more extensive use of lidar measurements. |
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| Keywords: | biomass La Selva Land Vegetation and Ice Sensor secondary succession tropical forest waveform lidar |
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