NorgePro: A spreadsheet program for the management of all-aged, mixed-species Norwegian forest stands
Espen Halvorsen1, Joseph Buongiorno2, Ole-Martin Bollandsås1
1Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.
2Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, USA.
Abstract
NorgePro is a spreadsheet program for Microsoft Excel to simulate the growth and management of all-aged forests stands of Norwegian spruce (Picea Abies), Scots pine (Pinus Sylvestris), birch (Betula spp.) and other hardwood trees in Norway.Its built-in growth models were calibrated on data from 7241field plots in Norway. Stands are described by the number of trees per unit area in each of 13 species specific size classes.
NorgePro allows managers to predict stand development by 5 year periods and for many decades from a specific initial state.Users can choose cutting regimes by specifying the interval between harvests (cutting cycle) and a target distribution of trees remaining after harvest. Tabulated and graphic results show diameter distributions, basal areas, volumes, income, net present values, biomass, carbon sequestration and indices of stand diversity by species and size.
This manual documents the program installation and activation, and provides suggestions for working with Excel. It offers an example comparing two different management regimes.
Keywords: Uneven-aged Management, Economics, Ecology, NorgePro, Simulation, Software, Growth model, Diversity.
Contents
Introduction
What is NorgePro?
Why simulate this type of stand?
How does NorgePro Work?
What is in this manual?
Getting Started
System Requirements
Installing NorgePro:
Using NorgePro
NorgePro Input
Saving and retrieving data
Running Simulations
Simulation output
Products worksheet
Basal area worksheet
Diversity worksheet
Volume by grade worksheet
Trees per ha worksheet
Biomass and carbon worksheet
Species BA
Class BA chart
Diversity chart
Volume chart
Biomass chart
Carbon chart
Acknowledgements
Literature cited
Glossary
Appendix 1: Example comparing two management regimes:
Appendix 2: Equations
Appendix 3: Definition of Diversity of Tree Species and Size
Introduction
NorgePro is a program intended to help forest managers predict the effects of management, or lack thereof, on stand growth, productivity, income, woodquality, diversity of species, and diversity of tree size, in Norwegian forests.
The NorgePro user’s manual documents background, instruction, and additional suggestions for using the NorgePro program. The manual explains how to install NorgePro on your computer and provides a description of the input data, as well as instructions for loading and saving these data, running simulations, and saving the results.
The manual gives examples of applications in simulating management regimes. If you are new to NorgePro, it will be useful to run these examples while reading the manual. Appendixes cover the growth equations, volume equations and log grade equations of NorgePro.
What is NorgePro?
NorgePro is a spreadsheet program that simulates the development of all-aged mixed species Norwegian spruce (Picea Abies) foreststands in Norway. With this program various management regimes can be considered, and their outcomes can be quickly predicted in terms of stand structure, species composition, economic returns, diversity indices, biomass and CO2 equivalence.
NorgePro is the latest of a series of similar programs developed for various species types in North America: SouthPro (Schulte et al., 1998), WestPro (Ralston et al., 2003), NorthPro (Liang et al. 2004a), CalPro (Liang et al. 2004b), WestProPlus (Liang et al. 2006).
Why simulate this type of stand?
Even-aged forest management emphasizing timber production has been the dominatingmanagement regime in Norway for 50–60 years. However, in the past few years more attention has been given touneven-aged forest management with selective cuttings.
Thisincreased interest is partly due to possible higher profits intimber production, but also to expected benefits for thebiodiversity of the forest ecosystem and to better recreational values of the forest landscape. Although even-aged managementregimes are expected to remain important in future,the options for alternative silvicultural treatmentswill increase in number and diversity (Lexerød & Eid, 2005).
How does NorgePro Work?
NorgePro predictions are based on a multi-species, site- and density-dependent matrix growth model for Norway (Bollandsås et al. 2008). The data used to estimate the model parameters came from 7241 permanent field plots of the Norwegian national forest inventory, measured at least twice between 1994 and 2005. The sample design, a 3 × 3 km grid, gave a representative sample of the Norwegian forest area. The northernmost county (Finnmark, above 70ºN latitude) which has few forests was excluded.
The model equations ofNorgePro predict growth, mortality, and the rate of ingrowth (recruitment) for Spruce, Pine, Birch and other Hardwoods as functions of stand basal area, site index, and individual tree size (See appendix2).
What is in this manual?
The next section explains how to install NorgePro on your computer.This is followed by a description of the data input, saving and loading the data, running simulations, and saving the results. Next, two examples of applications are given. The manual assumes familiarity with the basics of Microsoft Excel.
Getting Started
System Requirements
You must have the following hardware and software to operate NorgePro:
- Computer with at least 128 megabytes of random access memory (RAM)
- Windows® 95 or newer
- Microsoft Excel 5.0 or newer
Installing NorgePro:
To install NorgePro download the xls-file to a known location.
To remove NorgePro, close NorgePro, select the file NorgePro and delete it
Using NorgePro
NorgePro Input
In the input data worksheet (figure 1) you enter the initial state of the stand you want to simulate. The state is defined by the number of trees per ha by species and size category. The target state, defined in the same way as the stand state, is the required state after each harvest.
The target stand state should be consistent with uneven-aged management principles, whereby substantial tree cover is left at all times.
After entering the input data, you immediately get a few summary statistics on the input data worksheet (Figure 1). On the right of the input data worksheet is a summary of the basal area and volume per ha of the initial and target state. Below the input data you get the total number of trees by species and diameter classes for the initial and target state.
At the bottom left of the sheet you are required to put in the year of the first harvest, length of the cutting cycle, simulation length, re-entry cost, interest rate (for the NPV calculations), site index, county, altitude and latitude of the simulated stand.See the glossary for the definition of terms. The year of first harvest, cutting cycle, and simulation length must be multiples of 5 years, the time unit used by the growth model.
At bottom middle you enter stumpage prices, by species and timber quality.
At bottom right there are two buttons. Pressing “Examples” gives you the choice of three different management regimes.
Example 1 cuts all the trees except those suggested bythe LivingForest standard(LivingForest, 2009),with a common initial distribution for an uneven aged stand, and a cutting cycle of 60 years.
Example 2 simulates a diameter limit cut, where all trees over 35 cm d.b.h. are cut,with a different starting stand than in example 1. The cutting cycle here is 5 years.
Example 3 gives another diameter limit cut, where all trees over 20 cm d.b.h. are cut.The starting stand is the same as example 2, but the cutting cycle is 15 years.
Figure 1: Input data worksheet.
Saving and retrieving data
After completing the Input Data worksheet, you can save this worksheet for later use. You should save your work frequently to avoid losing data. It is advisable to save the work in a particular folder with a descriptive name to facilitate locating the file in the future.
To run several simulations (e.g., to examine the effects of changing some of the parameters), you may find it efficient to work with previously saved input data. You retrieve the data by opening the stored worksheet as you would any other excel-file.
Running Simulations
After completing the Input Data worksheet or retrieving a previously saved one, you are ready to run a simulation. Clicking on the “start” button gives you the option to start the simulation immediately or to change the settings. The settings allow you to select what parts of the trees should be included in the biomass and carbon sequestration calculations. By default all parts of the trees are included.
Each NorgePro simulation produces the following worksheets and chartswhich show the development of various stand and harvest data over time:
- Products worksheet: The physical output and financial return from the harvests.
- Basal Area worksheet: The basal area by species and timber size.
- Diversity worksheet: Shannon’s indices of species and size diversity, and Gini index of size diversity.
- Volume by grade worksheet: The volume in stock by log grade.
- Trees per ha worksheet: The number of trees by species and diameter.
- Biomass and carbon worksheet: The biomass and CO2 equivalents of standing stock by species.
- Species BA chart: The stand basal area by species.
- Class BA chart: The stand basal area by timber class.
- Diversity chart: Shannon’s indices of species and size diversity, and Gini index of size diversity.
- Volume chart: The volume in stock by log grade.
- Biomass chart: The biomass by tree species.
- Carbon chart: The stored CO2 equivalents.
All the data in the output worksheets are protected and you cannot change them.To see how the results change with different assumptions, change the Input Data worksheet and rerun the simulation.
Upon running a simulation, NorgePro will replace any old tables and charts with new ones. For this reason, you should save the workbook with a separate name after each simulation if you want to keep it. To run a series of simulations, load the input data for the first management regime, run the simulation, save your outcome, and proceed to load and run the second management regime. You can then compare the economic return, various ecological criteria, and wood quality for different regimes. To that end, comparative charts and tables can be built with Excel from the NorgePro output worksheets.
Simulation output
The following results are for the simulation with initial condition and management specified by the input data in Figure 1 which correspond to the Example 2 storedin the program. This example applies a d.b.h limit cut of 20 cm to all species of trees, every 25 years.
Products worksheet
In the left part of the products worksheet (Figure 2) you will find the data for each year of harvest, the total basal area cut, the volume harvested by log grade, the gross income, the NPV of the current harvest, the total (cumulative) NPV of all harvests, and the initial stock value.
The right part of the products worksheet shows the average annual cut and the average stock in terms of basal area and volume by log grade. It also displays the average species diversity and size diversity over the whole simulation period.
The results show that with these particular starting parameters and a 25-year cutting cycle, the average yield over 200 years would be 5,8 m3/ha/yr, for a NPV of 131581 NOK/ha. This is the return from the land and the initial trees, under this management.
Figure 2: Products worksheet, showing production and economics of a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Basal area worksheet
The Basal area worksheet (Figure 3) shows for each simulated year, the total stand basal area, the stand basal area by tree species, by log grade (Prime, Second, Pulpwood), and basal area for three timber size categories: small timber for trees from 50 to 250 mm in diameter at breast height (d.b.h.), medium timber from 250 to 350 mm d.b.h., and large timber from 350 mm d.b.h. and larger. Underlined numbers show the year of harvest and the basal areas just after harvest.The row marked “average” shows the average basal area over the whole simulation period.
Figure 3: Basal area worksheet for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Diversity worksheet
The diversity worksheet (Figure 4) shows Shannon equitability indices (that is Shannon indices relative to their maximum theoretical value) for species and size diversity. The Gini index of size diversity is also reported for each simulated period. The indices aredefined in Appendix 3.The underlined data show the year of harvest and the values of the diversity indices just after harvest. The average of the diversity indices over all periods is in the first row.
Figure 4: Diversity worksheet, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Volume by grade worksheet
The volume by grade worksheet (Figure 5) shows the volume in stock by log grade (prime, second, and pulpwood). The log grade equations used by NorgePro appear in appendix 2. The underlined numbers represent the year of harvest and the volume per hectare just after harvest.The first row shows the average volume over the whole simulation period.
Figure 5: Volume by grade worksheet, for a 20 cm d.b.h. limit management regime, with a25 year cutting cycle.
Trees per ha worksheet
This worksheet (Figure 6) shows the number of trees per hectare, by species and diameter class for each year of the simulation. Scrolling to the right reveals the tree distribution of the other species, the size distribution for all species, and the total number of trees of all species and sizes in each period. The underlined numbers are the year of harvest and the number of trees per hectare after the harvest.
Figure 6: Trees per ha worksheet, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Biomass and carbon worksheet
This worksheet (Figure 7) shows the biomass and CO2 equivalents stored in the stand of trees, in total and by species.CO2equivalents are the mass of CO2that would result from the carbon stored in the trees. The output is the summed mass of the tree parts selected in the settings menu at the start the simulation (by default every part of the tree is accounted for). The biomass and CO2 equations are in appendix 2. The underlined numbers represent the year of harvest and the biomass and CO2stored in the remaining stock just after harvest. The top row gives the averages over the entire simulation period.
Figure 7: Biomass and carbon worksheet, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Species BA
This chart (Figure 8) shows the development of basal area by species throughout the simulation period. The sharp decreases in total basal area are due to the periodic harvests. This particular example suggests that in both the long and short run we would not get much pine with this management, but we would sustain all the other species.
Figure 8: Stand basal area by species chart, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Class BA chart
This chart (Figure 9) shows the evolution of the stand basal area by timber quality; prime sawtimber, second sawtimber, and pulpwood. This particular example suggests that, the total basal area would increase over the period from 50 to 200 years, but there would be a reduction in timber quality as the basal area of prime and second sawtimber would decrease relative to the basal area of pulpwood.
Figure 9: Stand basal area by timber class chart, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Diversity chart
The diversity chart (Figure 10) displays the evolution of Shannon’s indices and of the Gini index over time. In this particular example there would be an improvement in species diversity over the simulation period as the index value increases. The size diversity would decrease sharply after each harvest but remain fairly constant on average.
Figure 10: Diversity chart, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Volume chart
The volume chart (Figure 11) shows the development of volume in stock by log grade throughout the simulation period. As in the basal area charts this shows how the stand grows, but the volume chart might be more interesting from a harvesting point of view. This example confirms a decrease in timber quality as the volume of pulpwood increases over time while the volume of prime and second sawtimber decreases.
Figure 11: Stand volume by log grade chart, for a 20 cm d.b.h. limit management regime, with a 25 year cutting cycle.
Biomass chart
This chart (Figure 12) shows the stand biomass, in tons, in total and by species, given the settings selected at the start of the simulation. This particular example suggests that the management being investigated would lead, after the first harvest, to an increase in the total biomass due mostly to hardwoods, while the biomass of spruce would decline.