Introduction to HSBC Climate Partnership Research
Earthwatch co-ordinates HSBC Climate Partnership volunteers and local scientists to conduct research projects on climate change and disturbed forests at five global sites
Background
The Earth's climate is changing due to human activities such as burning fossil fuels and tropical deforestation. However, beyond a clear global warming trend, great uncertainties remain in how climate change will progress, and how such changes will affect ecosystems. Forests are of particular interest as they are the natural vegetation of over two thirds of the Earth's land surface, and provide important ecosystem services such as clean air and water, carbon sequestration and soil protection. Very little of the Earth's forests remain undisturbed by humans; activities such as logging alter forest composition, while fragmented areas that remain may function differently to intact areas. Such disturbances in forests can alter their responses to climate. This is most clear in the tropics, where harvesting opens the forest canopy and increases susceptibility to drought and fire. In other regions, disturbance-climate interactions are less well understood, but may nevertheless be important determinants of forest dynamics, carbon balance, and biodiversity.
Aims
The aim of the programme is to quantify how anthropogenic disturbances and climate interact to affect forest composition, dynamics and carbon cycling. To this effect, Earthwatch has established five Regional Climate Centres (RCCs) in forests around the world (figure 1). Parallel climate change research projects are run at the RCCs with local partner research organisations, creating a global study of the relationship between disturbance, climate, and forests, as part of the HSBC Climate Partnership (HCP). Also within the partnership is the Smithsonian Tropical Research Institute (STRI), whose research organisation the Centre for Tropical Forest Sciences (CTFS) have an existing network of forest research plots in undamaged tropical forests. The goal of the programme is to monitor changes in forest structure and composition over a five year period (commencing in 2008 and completing in 2012) in areas of forest that have been subjected to different forms and intensities of human disturbance, and to relate these changes to climatic variables. This will allow better understanding of the role that different types of disturbed forests play in the global carbon cycle, and how forests can be managed to reduce negative impacts of climate change.
Specific objectives are to understand long term ecological trends and carbon cycling within the forests by investigating how species composition, tree size and density vary over time and with climate, and by quantifying dead wood within forests. Short term dynamics will be investigated by measuring tree growth and leaf litter fall over a timescale of months.
Figure 1 Locations of Regional Climate Centres and local partners
To hear about the need for this research from some of the scientists involved, and to understand more about the relationships between Earthwatch and their partners and the role that volunteers have within the project, you can watch this video.
Methods
Research is carried out in a series of 1 ha permanent plots in the five RCCs in Brazil, China, India, the UK and the USA. 10-12 plots are established at each RCC, selected to represent forest areas with a gradient of human disturbance. The nature of the disturbance is specific to each area, reflecting past human activity in the region. For example, in Brazil the plots follow a gradient of selective logging (initial, intermediate, advanced) within primary (untouched forest), whereas in the UK the plots are in secondary forest fragments of different sizes.
The data collection methods follow those of the Centre for Tropical Forest Science (CTFS), a research centre within the Smithsonian Tropical Research Institute. In using the well-established methods from this project, Earthwatch ensures that reliable, standard methods are used by the entire project. Specific methodologies are outlined below.
Forest structure is analysed by tagging, identifying the species, mapping and measuring diameter of all stems with diameter at breast height (DBH) greater than 5 cm in each plot. A visual example of this is in figure 2. Tree height is estimated visually or with clinometers, an instrument frequently used in forestry for measuring tree height. This is repeated every 3-5 years to show long-term dynamics.
Figure 2 Tree distribution in unlogged mature forest in the US RCC.
Coarse woody debris (CWD), dead wood above 10 cm diameter, is quantified by walking along pre-determined straight lines (transects) in each plot and recording details (size, species) of any CWD on the line. CWD includes fallen dead trunks and branches. This is repeated every 3-5 years.
Dendrometers are used to measure stem diameter of a number of trees in each plot (Fig 3). Trees to which dendrometers are fixed are selected so that a number of species are represented, with a range of stem diameters / ages of each species. Stem diameters are measured every 1-3 months according to growth rates in the different regions.
Figure 3 Dendrometer attached to tree at Wytham Wood. A steel spring keeps the band tightly attached to the stem and expands with tree growth, allowing incremental growth to be measured every 1-3 months.
Litter traps are placed throughout the plots. A litter trap is a catching device, a 1 sq m frame with a fine mesh net, used to intercept material that falls from trees. Litter is dried and sorted into fractions: leaves, stems and flowers, fruits and seeds and identified to species. This is done every 2-4 weeks according to season and location. Thus, time of year that flowering, fruiting and leaf fall occur is recorded and can be related to climatic variables. The quantity of material reaching the ground is used in understanding carbon dynamics.
Climate is monitored by automatic stations and electronic sensors, then related back to other variables measured. Automatic weather stations collect continuous meteorological data (precipitation, min/max temperature, wind speed). Electronic sensors monitor soil temperature.