Use of Time Series LiDAR to Quantify Stand Biomass Response to Fertilization at Larger Spatial Scales in Coastal Douglas-fir Forests.
Abstract
Fertilization in coastal British Columbia public forests ranges from 6000 - 10000 ha annually with similar areas on private lands. In addition to wood production, fertilization could be a mitigation measure to increase C sequestration and a source of C offset credits. Models in combination with control and fertilized ground plot data, extrapolated to similar stand types, are currently the accepted methods for most C offset protocols. Carbon fluxes and plot C stocks have been studied since 2002 in an 83 ha research site in second-growth Douglas-fir planted in 1949 (DF49). LiDAR acquisitions were made in 2004, 2008, 2011 & 2016 over 524 ha of the DF49 site and surrounding forest, the latter with 7 stand types differing in % Douglas-fir, site index and planting year. In January 2007, 308 ha encompassing DF49 was aerially fertilized with 200 kg urea-N ha-1. The DF49 site was harvested in 2011. DF49 mean annual NEP post-fertilization (2007-10) was 35% (reconstruction model) or 64% (eddy covariance) greater than pre-fertilization (2002-06), however weather differed between periods, confounding the response. Sample trees in a second set of plots in adjacent unharvested fertilized and unfertilized control areas (DF49a) were felled and disks measured in 2011. Five year pre-fertilization volume increment was less in control (9.7m3ha-1yr-1) vs fertilized (10.0) plots, reflecting pre-existing plot differences, while post-fertilization, fertilized increment (12.2) was 30-40% greater than control (8.9). In 2010 at DF49 and 2013 at DF49a plots, all live, standing and down dead trees in each plot were cored to reconstruct year of death and yearly tree DBH's from plot DBH and height data for DF49 (2002, 2006, 2010) and DF49a (2011, 2017). Allometric equations were used to estimate tree and plot large tree aboveground biomass (LTAB) for LIDAR years. LiDAR metrics were extracted for 20mx20m cells centred on each plot for each LiDAR year and LTAB regression equations derived. Equations were applied for each LiDAR year to 53 paired LiDAR blocks (4 cells) selected on either side of the fertilization boundary. Preliminary results show no differences in paired block LTAB in 2004, 1.3-1.5% increase in LTAB for fertilized vs control in 2008 and 2011, and no differences in 2016. Comparisons among stand types and LTAB increments will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B33N2865T
- Keywords:
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- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0466 Modeling;
- BIOGEOSCIENCESDE: 0480 Remote sensing;
- BIOGEOSCIENCESDE: 1630 Impacts of global change;
- GLOBAL CHANGE