Quarterly reports and results
The first year, 2008, saw all plots established, and trees were mapped in five of them. Leaf litter collection was started, as were phenological observations of trees and dendrometer fitting. Light penetration measures and canopy observations showed that logged areas of forest had dramatically reduced canopy heights compared to intact forests.
In 2009, leaf litter collectors were placed in all plots, and by the end of 2009 there was at least one season of data for all plots (fig 2). Litterfall is highest in autumn in all plots; total litterfall appears to be greater in control, intact plots than in logged plots. Microclimate sensors were installed, and coarse woody debris measured in five of the plots. Trees in all eight 1 ha plots were tagged and censused, as well as trees in nine ha of the 16 ha CTFS-style plot. Observations of leaf phenology and ground vegetation regeneration continued.
By the second quarter of 2010 all of the Earthwatch plots had been censused, as had 11 ha of the CTFS-protocol plot. Dendrometer bands were installed within the censused plots. Aboveground carbon balances were calculated for each plot using above ground biomass of trees, standing dead wood, coarse woody debris, tree growth and litter fall data. It was decided to conduct annual tree morality surveys, as the five year censusing is too coarse a timescale for this aspect of the carbon budget.
In the 4th quarter of 2010 a further 1 ha of the CTFS plot has been stem-mapped, leaving just two to go. In these last two plots subgridding has begun, and should be finished around February. Two full cycles of leaf litter collection are now complete, and data up to November 2010 confirms previous patterns in the data, that there is higher leaf fall (measured in grams of litter per square meter) in the control plots than the logged plots.
Figure 2 litterfall in the 8 plots from 2007 to 2009. C, control, L logged; I, intermediate, M, Mature.
From the dendrometers installed, estimates of tree biomass across whole plots were extrapolated. By comparing the results from 2008 and 2009, it was found that tree biomass increase, in tonnes per ha, were almost twice as high in logged than in control, intact forest plots (fig 3).
Figure 3 Tree growth in 2009. C, control, L, logged; I, intermediated, M, Mature.
In the first quarter of 2011, more of the CTFS plot was censused – 97% of it is now complete, and the final 3% should be complete in the coming quarter. Measurements of all dendrometer bands will start in the coming quarter, with a subset to be measured on a weekly basis. This provides a more detailed picture of how tree growth responds to local weather – results from last year show how tree growth slowed during periods of drought (at days 180, 220 and 250 in the figure below).
Between April and June 2011, the Climate Champions continued to help with mapping the 16 ha plot – it’s nearly finished, and is due to be completed in Autumn 2011. A new initiative has been started: soil respiration is being measured in the logged and unlogged plots, to see how much carbon dioxide is produced in the two types of plots. Also in this quarter, the team held a very successful one day climate workshop for local politicians and policy makers showing them the exciting climate change research going on so near to them.
Despite the challenges of an unusually rainy August and September, strong winds from hurricane Irene and a minor earthquake, the North American team finished mapping the 16 ha forest plot in this quarter! A total of 33,488 trees in 84 species have been mapped and measured; congratulations to all involved. During this period leaf litter traps, dendrometer bands measurements have continued. Awareness of the programme has been increased through a poster presentation at a NASA carbon cycling workshop, and an educational video about recent findings of accelerated local forest growth was filmed, for the Smithsonian Astrophysical Observatory. Data analysis continues, to feed into papers for publication in peer-reviewed journals.
Invasive plants and deer
In the first quarter of the experiment, October to December 2008, materials to construct the deer exclusion cages were obtained. The following quarter saw cages constructed with the assistance of Climate Champions, and the location of other plots decided.
In the spring and summer of 2009 baseline data for all the plots was collected. This included plant community composition, soil moisture, soil compaction, light availability, leaf area index, insect abundance and small mammal activity. Hand weeding was completed in the "no-weeds" plots, and one cage was repaired after it was damaged by a falling tree.
Over October to December 2009 data were checked for quality control purposes. In the plots, quantification of course woody debris began, and hand weeding continued. A film explaining the study was made on site, which will be available on this and other websites once completed.
In the second quarter of 2010 volunteers removed invasive plants around deer exclusion plots.
Between July and September 2010 Climate champions assisted with the identification, measurement and tagging of trees and shrubs less than 2m tall in approximately 80 1m2 plots. This contributed to the study of forest regeneration that John Parker is conducting in parallel with his study into the effects of exotic species and deer herbivory. Climate Champions also assisted with collecting deer scat for genetic analysis. DNA is extracted from the scat; from this, individual deer can be identified, as well as the plant species that they are eating.
Despite the project having run for only a year, there are already interesting results coming out from the data. Preliminary results show that there is increased soil compaction in the logged plots, which also have a lower insect diversity and non-native plant species are more abundant and diverse than in non-logged plots. Contrary to popular belief, it was found that in the plots from which deer were excluded, cover of exotic plant species increased 50% in comparison to plots to which deer had access. In 2011 data from the sapling plots, which Climate Champions helped census in the 3rd Quarter of 2010, will be analysed, focussing first of all on forest regeneration.
Figure legend: Exotic plant cover increases when deer are excluded, but remains constant when deer are present. Deer therefore play an important role in controlling exotic invasive plants in this ecosystem.