Quarterly reports and results
By the end of 2009, the first year of the China RCC being fully operational, trees in all of the plots were censused. In 2009 through to 2010, leaf litter collection and sorting had commenced in some, but not all plots. Poor weather has delayed the set up of leaf litter traps and dendrometer bands, but overall the project is on target.
Twelve plots have been set up in China. Topographic maps for nine of the plots are presented below (fig 3), illustrating the difficult terrain at the China RCC.
Figure 3 Topographic maps of research plots 1, 2, 3, 4, 5, 6, 8, 9, 10 in China
More than 10,000 trees have now been tagged and censused. Data entry from the more recently measured plots is ongoing. Initial analyses of plots 1 and 3, compared with primary forest (from previous investigations) show that the highest number of species was found in secondary forest (fig 4). This was an unexpected result.
In the second quarter of 2010 the trees for dendrometer installation were identified, and installation begun. Despite heavy rain slowing field work, wood density was assessed for 42 trees, and leaf litter collection and sorting continued. Data from the first census of all the plots was prepared for publication.
Figure 4 Number of tree species in primary, secondary and plantation forest
From October to December 2010 the team in China have been busy, having conducted surveys for coarse and fine woody debris in all 12 plots. This involves recording details (species, location, decay status, size) of all dead wood greater than 10 cm diameter when walking along transects (100 m; 6 per 1 ha plot); dead wood smaller than 10 cm diameter is recorded from 1 m sections of the transect. Similar surveys are conducted within 20x20m subplots (9 per ha), which include standing dead wood as well as fallen. Dead wood inventoried along the transects is taken back to the lab to be dried and weighed. These surveys tell us how much carbon is contained within dead wood within the forest. Climate Champions have been helping with these surveys, as well as with leaf litter collection and sorting and with checking, installing and measuring dendrometer bands.
As large quantities of data are collected by volunteers, each of whom normally stay no longer than two weeks, it is essential to monitor the quality of data collected, and understand where errors might exist. Four 1-ha plots were randomly selected, and in which 20 randomly selected quadrats of 20 x 20 m were chosen. All trees with DBH >= 10 mm were re-measured, including species identification, DBH and coordinate measurement. The criteria of correct measurement are that the error for DBH is within 2 mm, and that for coordinate is within 50 cm.
Percentage of measurements that were incorrect were 0.98%, 1% and 2.1% for species identification, DBH and coordinate respectively, after removing the maxima of 11.9%, 7.6% and 7.6%.
Data were tracked back and it was found that the maximum errors were in data collected by an elderly local helper with poor eyesight, who had problems reading instruments in the dark forest on very cloudy days.
In the first quarter of 2011 leaf collection has begun, to initiate leaf litter decomposition experiments. This involves collecting 30-40 kg of fresh leaves from two tree species. These will then be dried, and placed in bags with varying mesh size, to understand the contribution of small-medium sized soil fauna to the decomposition process. Work has also begun to measure soil respiration, for which 144 PVC collars have been placed in the soil. A machine that quantifies carbon dioxide will then be used at regular intervals to see how much carbon dioxide is released from the soils in different plots. Measurement of dendrometer bands and collection of leaf litter from the traps has continued.
Soil respiration monitoring has commenced at the China RCC in the second quarter of 2011. Between April and June there have been monthly measurements of carbon dioxide coming out of the soil (respiration of soil-dwelling organisms) at 12 points in each of the 12 plots, at two hour intervals throughout the day, one day a month. In four plots there are extended 24 hour measurements, so that the patterns of respiration throughout the day can be compared. Leaf litter collection and sorting has continued, and several thousand bags of leaf litter have been prepared for the leaf litter decay experiment, which will assess how quickly different types of leaf litter break down on the soil, in different habitats. In May, the centre hosted a one week workshop of the China Biodiversity – Ecosystem Function group, a collaboration between Chinese and German scientists.
Despite unexpectedly hot weather in the third quarter of 2011, the team in China managed to collect over 800 soil samples throughout the plots, which will be used to analyse the amount of carbon stored in the soil and fine roots. They also continued to measure dendrometer bands, collect leaf litter and measure soil respiration. Soil samples will be analysed in the next quarter, during which surveys of dead trees and woody debris in the plots will enable estimates of carbon stored in dead wood. The team are analysing data and preparing papers for publication, which will allow scientists around the world to benefit from the knowledge gained on this programme. They have also involved NGO stakeholders, through a visit to the site from representatives of 9 NGOs in September.