Monitoring climate change

 

A number of forest monitoring networks exist in the UK for which Forest Research is either the national co-ordinator or is a key contributor. These networks are being used partly to monitor how climate change may be affecting the nation’s woodlands.

Monitoring networks

• Carbon flux network (CFN)
• Intensive forest health monitoring EU/ICP-Forests Level II network (L-II)
• Permanent mensuration sample plot network (PSP)
• Forest condition monitoring EU/ICP-Forests Level I network (L-I)
• UK forest condition survey network (FCS)
• National inventory of woodlands and trees (NIWT)
• Environmental Change Network (ECN).

Long-term carbon flux network (CFN)

Four long-term carbon flux-monitoring sites have been established in woodland in the UK these are detailed as follows:

Straits Enclosure (Forest Research, Alice Holt): 90 ha stand of GYC 6 oak planted during the 1930s on a surface water gley soil in Hampshire. The flux station was established in 1998, and has operated continually. The entire stand is due to be thinned in 2004-5.

Harwood (University of Edinburgh): Two flux systems were established in 2000 in a 4000 ha Sitka spruce forest in Northumberland of varying planting year and yield class on a peaty gley soil. One continuous system is sited in a 30-year old stand, with a second roving system used to assess carbon fluxes in a chronosequence investigating the effects of stand age on carbon balance.

Griffin (University of Edinburgh): Sitka spruce plantation (GYC 14) planted in 1981 on a peaty gley soil in Perthshire. The flux station was established in 1996 and has operated continuously, apart from a break in 2002-3. The forest has recently been thinned.

Pang catchment (CEH Wallingford): Mixed broadleaf woodland dominated by oak and located in Berkshire. The flux station has recently been established as part of the NERC funded LOCAR project.

These four sites only represent two species – oak and Sitka spruce. As a result of their limited species and geographical coverage, their contribution is limited. All are partners within the EU FP6 CarboEurope IP. Their most valuable contribution is in providing data for the parameterisation and validation of stand level process models of carbon and water exchange. An additional function is in monitoring inter-annual variability in carbon exchange, and enabling this to be related to climate.

Intensive forest health monitoring EU/ICP-Forests Level II network (L-II)

The network for intensive monitoring on permanent observation plots was established in 1994. Currently there are approximately 900 plots across Europe, although the intensity of measurements varies from plot to plot. In the UK, ten sites were established in 1995 (oak, Sitka spruce and Scots pine), with a further ten added in 2002 (beech and Norway spruce) to represent more species and regions within the UK

Stand height, diameter and volume increment, foliar chemistry, soil chemistry, crown condition and ground vegetation are assessed at all sites, while litter, air quality, meteorology and soil water chemistry are assessed at a proportion of the sites.

Permanent mensuration sample plot network (PSP)

The first permanent mensuration sample plots were established before 1920, with the aim of providing data on which to base yield models for forest management and production forecasting. On the whole PSPs have been established in single species, even-aged stands, and thus are not fully representative of all current forestry practice in the UK.There are currently 509 active plots, representing primarily the major commercial species planted in the UK.

Forest condition monitoring EU/ICP-Forests Level I network (L-I)

The L-I Forest Condition Survey is a Europe-wide assessment of spatial and temporal variation in forest condition using crown density or transparency as the principal indicator. Surveys of crown density have been carried out on an annual basis since 1986 at between 1700 plots (in 1988) and 6000 plots (in 2000) across Europe.

In the UK, there are approximately 90 L-I plots covering five tree species (oak, beech, Scots pine, Sitka spruce, Norway spruce). The protocol requires a minimum plot size of 0.25 ha (although this is not always realised), with the crown density of 24 ‘internal’ plot trees assessed across the four aspects (N, S, E, W). The plots have been established on a 16 × 16 km transnational grid across Europe, enabling pan-European assessments of forest condition to be made.

UK forest condition survey network (FCS)

The FCS was instigated in 1984 prior to the establishment of the L-I network and provides greater spatial representation and more detailed measurements than strictly required for the EU L-I network. As such, the L-I network forms a subset of the FCS network. The same five tree species are assessed (59 beech, 55 Norway spruce, 86 oak, 81 Scots pine, 66 Sitka spruce and 3 mixed broadleaf).

More variables are measured in FCS than are strictly required under the EU L-I protocol. The supplementary measurements include annual assessments of dbh and a single assessment of top height recorded on establishment.

Supplementary tree quality measures assessed on an annual basis -

• Crown form/branch pattern
• Discoloration
• Degree of canopy closure
• Needle retention
• Mechanical damage
• Flowering
• Fruiting
• Insect and pathogen damage.

National inventory of woodlands and trees (NIWT)

This inventory, otherwise known as the Census of Woodland, is carried out every 10-15 years. The most recent survey is based on a combination of analysis of the 1:25000 OS map and, primarily, interpretation of aerial photography. The NIWT considered woods of more than 2 ha area, although a separate survey of small woods and linear features was also conducted as part of the assessment, but in less detail. A wide range of attributes are recorded, many of which could be interpreted in terms of a changing climate.

Environmental Change Network (ECN)

The UK Environmental Change Network (ECN) is one of the UK's long-term, integrated environmental monitoring and research programme. ECN gathers information about the pressures on and responses to environmental change in physical, chemical and biological systems. It is supported by a consortium of fourteen sponsoring organisations and eight research organisations. Forest Research is the responsible for a site managed as productive forest (broad-leaved and coniferous) and located at Alice Holt Forest, Hampshire UK.

ECN's objectives are:

• To establish and maintain a selected network of sites within the UK from which to obtain comparable long-term datasets through the monitoring of a range of variables identified as being of major environmental importance
• To provide for the integration and analysis of these data, so as to identify natural and man-induced environmental changes and improve understanding of the causes of change
• To distinguish short-term fluctuations from long-term trends, and predict future changes
• To provide, for research purposes, a range of representative sites with good instrumentation and reliable environmental information.