Permanent Sample Plot
- Permanent Sample Plots (PSPs) provide a unique long-term re-measurement dataset that is used to develop growth-and-yield models that support timber supply analysis and sustainable forest management decisions.
- Due to increased interest in modelling forest recovery after disturbances, PSPs with natural damage (insects, disease, windthrow, fire, snow, or animal) may be protected and re-measured.
- The authoritative source for PSP location is the BC Data Catalogue Growth and Yield Samples - Active Status layer.
In the 1920s, the B.C. government began installing permanent growth-and-yield (GY) plots for research purposes. Increasing interest in GY data led to the creation of a Growth-and-Yield program in 1961 that established Permanent Sample Plots (PSPs) across the province. The original goals of this program were to,
- Check assumptions in yield projections made from Temporary Sample Plots,
- Produce data necessary to develop and calibrate GY models, and
- Provide ground-control data for a variety of purposes.
The Forest Productivity Council (FPC) was created in 1986 to develop a provincial PSP strategy, a system to rank plot value, protocols, and program management tools. FAIB still uses the FPC’s matrix and ranking systems to prioritize plots for protection and re-measurement. The objective of the matrix is to ensure that plots are located on a wide range of ecosystem types (matrix cells are a unique combination of BEC zones, tree species, stand density, site index, stand age, and any previous treatments). The objective of the ranking system is to ensure that the most valuable plot per matrix cell is protected. Using this system for prioritizing highest value plots, FAIB is currently managing 2,600 plots.
PSPs are one component of a larger coordinated ground-sampling effort that provides information needed to make management decisions. PSPs provide long-term re-measurement data in natural stands that have no influence from harvesting. To understand natural forest dynamics PSPs now include plots with partial damage. The other plot type that requires no influence from harvesting are the Experimental Plots (EPs) that address a range of research questions (Please contact Keith Thomas. There are also many ground plots that are not protected from harvesting. The Provincial Monitoring Plots (CMI, YSM and NFI plots) are not protected because their goal is to monitor change on the landscape, including harvest. Vegetation Resource Inventory (VRI) temporary plots are also not protected because they are a one-time measurement to validate photo interpretation.
Uses of PSP data
The primary use of the PSP dataset is to support growth-and-yield model development and validation. GY models estimate current timber supply and predict future forest conditions. The PSP dataset and GY models together support the Minister’s Mandate letter, and many business applications.
Secondary uses of the PSP dataset are to support public sector, private sector and academia in addressing topics such as carbon accounting, wildlife habitat assessment, forest health, climate change effects, forest dynamics, tree mortality, forest regeneration, and validation of imagery based inventories. The ability to use the PSP dataset to address these secondary issues has changed over time. For example, historically the program focused on healthy stands but the importance of understand forest dynamics in damaged stands has led to the incorporation of damaged stands into the program. Currently, the program maintains and re-measures damaged stands.
To access the PSP dataset please contact Rene de Jong to set-up a data sharing agreement. Things to keep in mind when using the PSP data:
- The plots included in the PSP database can have different sizes, shapes, diameter cut-off limits, and sub-plot sizes because standards changed over time.
- Measurements of partially damaged stands started in 1994.
- Plots are subjectively located to cover a wide range of ecosystem and stand types.
- Individual tree mortality and damage is measured within each plot, but plot-level catastrophic mortality has not been captured in the past.
Conflict with Harvesting
The Forest Analysis and Inventory Branch (FAIB) and the Office of the Chief Forester (see memo below) request that all harvest and other land-use plans consult the BC Data Catalogue Growth and Yield Samples - Active Status layer to ensure no active PSPs are in the development area.
- Protection is required,
- Release is granted after a final re-measurement, or
- Release is granted without a final re-measurement.
Recently, several protected plots have been harvested without consultation with FAIB. Many of these have been in beetle damaged stands. Historically their plots would have been released from the program, but due to increased interest in modelling forest recovery after natural disturbance, PSP with natural damage may now be protected (insects, disease, windthrow, fire, snow, or animal damage). It is therefore necessary to contact FAIB even in salvage harvesting situations.
Future of PSPs
A 10-Year (2019-2029) Strategic Plan for Permanent Sample Plots has recently been completed and is available [here] (post July 2018) .
The priorities for the PSP program are:
- Maintaining a robust and effective long-term repeat measurement program,
- Protecting plots by providing guidance and updated location information,
- Ensuring effective database management,
- Loading un-entered PSP data, and
- Annually assessing re-measurement criteria.
- Providing data to the many users identified above.