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Framework Report on the Development of the National Carbon Monitoring System

Contents

1. Executive Summary

2. Climate Change and Greenhouse Gas Mitigation

3. Developing the 1990 Baseline for Soils

4. A National Monitoring System For Soil Carbon

5 Development of Baseline 1990 Estimates for Forest and Scrub

7 An Information Management System for the CMS

8 International Review of the CMS Development

9 Response to the Review

10 Application of the Generalised Linear Model to Soils Data (Giltrap et al. 2001)

12 Potential Other End-User Requirements

13 Integration of the LCDB with the CMS (Stephens et al. 2001)

14 Improved Allometric Functions for Forest and Scrubland (Beets et al. 2001)

15 Forest Sampling Options for the CMS

16 Costs of a Proposed Structure

17 A Proposed Structure for the CMS

18 Concluding Remarks

20 APPENDICES

9 Response to the Review

9.1 Key issues to be addressed

A workshop was held in March 2000 involving key stakeholders and scientists. It addressed the key review issues so that over the following 18 months the science team was able to concentrate on responding to the recommendations of the review committee and producing an operational carbon monitoring system.

Immediate issues that were addressed included:

• the initial documentation of protocols, in particular QA/QC

• quantifying future soil carbon changes

• initiating work on the integration of the forest, scrub and soil components within the framework of the LCDB

• improving allometric relationships for individual tree species, biomass and hence vegetation carbon content.  

In the final year of the project the following components were completed:

• Definition of on-going research needs

• Final framework documentation and a presentation on the project

• Cost estimates for the operational system

• All specifications for the final working system

• Development of the reporting tools

• The unifying of the soil, forest and scrub components through the LCDB

• Improvement of allometric relationships

• Estimation of coarse woody debris and decay status in vegetation and its contribution to carbon budgets

• Consideration of sampling strategies, with an explicit component concentrating on new forest and regenerating scrub

• The testing of further sampling options

• The testing of soil estimates considering new variables, which include slope and aspect, and integrating the digital terrain model with the generalised linear model

• Consideration of the effect of land-use history on coefficients of change

• Consideration of a range of issues relating to further soil sampling requirements.

• Improvement of allometric relationships

• Estimation of coarse woody debris and decay status in vegetation and its contribution to carbon budgets

• Consideration of sampling strategies, with an explicit component concentrating on new forest and regenerating scrub

• The testing of further sampling options

• The testing of soil estimates considering new variables, which include slope and aspect, and integrating the digital terrain model with the generalised linear model

• Consideration of the effect of land-use history on coefficients of change

• Consideration of a range of issues relating to further soil sampling requirements.

9.2 On-going research needs (Allen 2001)

Rationale

Although the CMS can be implemented with the information and methodologies currently available, it can be improved.  There is a need to define and reduce current error estimates, to provide alternative methods to validate and verify the carbon estimates, and to meet other stakeholder needs in the most efficient and effective manner. The Research needs can be addressed through a combination of operational research within the CMS and underpinning research within the FRST portfolio. As a key stakeholder in environmental research, MfE’s underpinning needs for greenhouse gas reporting should be a priority for them.

LCDB related issues (Stephens et al. 2001)

The report of the international review panel (Theron et al 1999) recommended that every effort be made to develop a reliable base line as close to 1990 as possible. Sampling of aerial photography and satellite imagery could be used to quantify land-cover change between 1990 and 1996 to a known accuracy. These changes, when combined with the LCDB, could generate a 1990 picture of land cover. Thereafter, the soil CMS Generalised Linear Model (GLM) and an equivalent regression model of indigenous forest and scrub carbon could generate a 1990 carbon budget. There was also a requirement to reduce the over-estimation of bare ground from the LCDB and delineate arable cropping areas in the LCDB.

There are therefore two major tasks for future mapping research.  One is to define classes, or other measurements, that describe land cover/land use characteristics that are important to soil and vegetation CMS concerns, while recognising that, these must fit currently into the existing mapping framework (LCDB).  The second task is to develop methodologies for detecting and describing these classes of interest, using remote sensing imagery and any other relevant sources of information.  To meet the needs of this large‑area, frequent‑update-mapping exercise, these new methodologies must be highly automated, and the classes or measurements chosen must be amenable to automated discrimination. There are two generic needs for any land-use change detection method.  One is that the method should be as automated as possible, for objectivity and efficient operation over large areas.  The other need is for documentation accompanying the spatial database, specifying its purpose, limitations and accuracy, and defining its constituent classes or measurements with the methods used to obtain them.

Land mapping

Even using multiple visual cues, some land uses will require knowledge of temporal dynamics for discrimination.  This may take the form of in‑depth knowledge of timing and rotation of farming practices in a certain region so that image acquisition can be carefully scheduled for critical periods when crops to be separated are at different stages of canopy development.  A second example could be a carefully timed image acquisition for direct spectral observation of soil pugging by cattle in wet conditions during the winter.  A multi‑temporal sequence of imagery can provide even further discriminating power, to track the flush and senescence cycles of different crops.

The uncertainty in measured forest and scrub carbon density far outweighs uncertainties in their mapped area (Stephens et al. 2001).  These uncertainties are related to the number of scrub (and forest) plots used in the analysis. More plots, especially of scrub, could reduce this uncertainty to a degree, but regression of carbon density on climate layers should also be researched.

Biomass calculations

Further work on allometric relationships will be required including seral vegetation types.

Mapping of land use and land-use change is a complex task, and is an area of active research in the international remote-sensing community.

Refining the scrub methodology

The methods used in the CMS for forests have been commonly applied to understanding spatial and temporal variability in forest biomass, while the methods proposed in the CMS for shrub-lands have not been widely used and have received little testing. Within the MfE carbon project the emphasis again remains on further testing and developing the CMS for forests.  Notwithstanding this, the international review panel called for explicit plans to account for the recruitment of new scrub areas (e.g., via pasture abandonment).  This is because of the recognition shrub-lands may receive in accounting for carbon sequestration as a consequence of changes in land use under the Kyoto Protocol.

Estimating and validating land-use effects on soil C (Wilde et al. 2001)

The soil CMS has been developed to allow the direction and likely magnitude of soil C changes from land-use changes at a scale of 1:250,000 to be assessed. It is based on the IPCC default methodology, and uses an efficient stratification of the land area by soil type and climate, with an additional factor (rainfall x slope) introduced to explain a significant fraction of the residual (within soil climate and land use categories) variance in soil C. This additional factor is a surrogate for the effects of soil erosion. Currently, major disturbance effects (e.g., erosion, drainage of organic soils) are not considered in the soil CMS.

The major land-use changes in New Zealand currently, and in the foreseeable future are: pasture-to-planted forest; low fertility pasture-to-scrub. A realistic time frame for directly monitoring soil C changes resulting from these land-use changes would require repeat sampling at, e.g., 20-year intervals, too long to be of practical use for international reporting. Furthermore, a direct monitoring approach involving more frequent (e.g., 5 years) remeasurement of soil C at fixed points is impractical for the soil CMS; monitoring the effects of key land-use changes on soil C at carefully selected benchmark sites can, however, be useful for testing and validating the soil CMS. Accordingly, soil C changes for key land-use changes predicted by the soil CMS will need to be validated by remeasuring soil C using paired (benchmark) sites, where soil C measurements were made at the time of the land-use change. Over the next 5 years, process-based models will increasingly be used to indicate the trajectories of these soil C changes over an appropriate time scale (e.g., 20 years), from which more accurate annual changes can be calculated.

Disturbance

As there will be a gap of several years between sampling any particular site, local periodic disturbance could occur without being detected. A method to predict disturbance would therefore be worthwhile. It is suggested the most critical disturbance agents on which to focus on in New Zealand from a carbon dynamics perspective are introduced herbivore impacts, land clearance, and the impacts of indigenous forestry.  Some research is already being undertaken on how these disturbances impact on carbon storage, and we suggest MfE may need to fund further research in this area related to their specific operational concerns.  There is also considerable other research on specific disturbance types that impact on forest structure.  Because much of New Zealand is tectonically active, some recent research efforts have focused on earthquake impacts on forests, both regionally and locally.

From a carbon storage perspective, the development of our understanding of the impacts of earthquakes in Westland forests may help explain any trajectories in forest carbon storage emerging from the CMS.

Verification

Verification is intended to help establish and improve the reliability of inventories.  Verification can be achieved in a number of ways.  These include:

• Comparisons with other independently compiled national- or regional-scale estimates.

• Comparisons with inventories from other countries, which allows cross-checking of the assumptions used, the completeness of the inventory, and the overall approach.

• Derivation of estimates using different methodologies.

With the small size and limited databases in New Zealand, on-going verification should occur to increase the international acceptance of our estimates.

Long-term ecological research (LTER) sites

The rationale for LTER sites is that to developing an understanding of such a wide range of ecosystem processes, and their interactions, at many locations is difficult.  In New Zealand there has been little support for such sites outside the scientific community  yet it must be more widely appreciated that such sites are essential for understanding the dynamics of ecosystems.  This is the case for understanding carbon dynamics.

Benefits of LTER sites:

• invaluable for monitoring a wide range of ecological response to anthropogenic (direct or indirect) changes.  They can provide experimental sites with documented land-use history and management.  From a carbon perspective, time-series data can be used to quantify the rates of sequestration along environmental gradients following disturbance and to contrast the impacts of various forms of land management.

• integrating long-term monitoring with short-term experimental work provides insights into why long-term changes occur, and allows for the development of robust process-based models by integrating research results obtained over multiple time scales.  For example, nutrient addition experiments are a useful way to test limitations on carbon sequestration rates under a range of conditions.

• long-term records are invaluable for validating model predictions over different time scales.  Changes in soil carbon with land-use change occur over years to decades, and recovery of soil carbon is even slower.  Models are required for multi-temporal predictions of soil carbon changes, but these are only as robust as the data on which they are based.

• Understanding of the causes of observed changes in ecosystems is essential for sound policy development.

• An LTER network could serve as a catalyst to bring together scientists, resource managers and policy agencies, who will need to be informed of existing and proposed networks and systems for resource management currently under development. Future research programmes could then be better tailored to meet both local, regional, and national needs.

• An LTER network, while serving as a tool to better understand systems, should be further networked with other monitoring activities. This is essential to maintain the relevance of research at each site, while also meeting as many overlapping needs as possible, e.g., relating to environmental indicators programme, resource accounting and biodiversity monitoring.

Remote sensing and modeling

It is not suggested that remote sensing could replace the need for plot-based monitoring. Current technology is not sufficiently advanced, but with further development it could act as a method for verification and validation of the CMS. Verification and validation of a particular carbon estimation methodology is important in an international context since each country’s efforts form only one piece of the requirements for the obligations under the Framework Convention on Climate Change.

Rather than duplicate the existing CMS in another country, or another country’s CMS within New Zealand, a commonly proposed strategy is to use a surrogate carbon estimation methodology on a selection of sites in several countries using remote sensing and modeling to derive the carbon figures.

There are three major remote sensing technologies that can be used as estimators for above-ground biomass, Light Detection and Ranging (LIDAR), Optical Remote Sensing and Radar Remote Sensing (SAR). The principle advantage of all these methods, when used in conjunction with a space-based platform, is that they provide a globally consistent biomass estimator, provided the models used properly consider all the relevant factors in the environment.

As more capable remote sensing instruments become available, it is expected that more complex models describing biomass could be developed, resulting in improvements in the accuracy of biomass estimation.  Also, gradual improvements in our understanding of the complex interaction between solar, laser or SAR illumination and the vegetation layer, will, in themselves, lead to models that more comprehensively describe vegetation from remote sensing data.  For these reasons, no one remote sensing technology can be seen to have a clear advantage as the “perfect” estimator of biomass, for as one instrument is launched with a better capability, advances are inevitably being carried out on another.  The best strategy would appear to be aware of the various technologies available from the literature, to note their strengths and weaknesses, and to be prepared, if necessary, to select the best features from one or more of these technologies.

Physiological process-based models

The use of process-based models, incorporating appropriate scaling procedures, provides a robust approach to estimating productivity by integrating across different scales ranging from leaves to stands. Such an approach is useful for estimating the effects of long-term perturbations to an ecosystem, such as the addition of nutrients or changing climate on the components of carbon balance and productivity. Outputs from the models can then be tested against long-term measurements of the change in carbon storage.

Progress to improve the capability of robust models to simulate changes in carbon storage at the ecosystem scale requires a rigorous approach based on physiological principles to investigate the processes of carbon input and loss at a range of scales from leaves to stands.

Research priorities to achieve this are:

• measurement of physiological properties for indigenous forest species and their distribution through canopies to model net carbon uptake

• determination of radiation-use efficiencies for forests with different water and nitrogen availabilities for use in modeling long-term productivity

• measurement of allometric relationships for tree components to determine ratios for allocation of carbon in relation to water and nutrient availability

• estimation of net carbon exchange for ecosystems, respiration from the soil surface and net carbon exchange for tree components to validate models; linking above- and below-ground processes of carbon uptake, loss and turnover in models.

Information system requirements (Dunningham & Gibb 2001)

The final work on the Information System for the CMS involved the compilation of information on a CD.

Included in the CD were :

• a copy of each CMS dataset provided as ArcView shape files

• A set of ArcView v3.2 projects containing maps of CMS data that can be browsed or colour printed

• A set of ArcView projects designed for using with CMS data

• A set of reports generated from the CMS data, which provide information required for reporting to IPCC and TBFRA 2000. They include:

Table 2 Reports from CMS Database

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