Osskyn at 08:16, 26 November 2024

2024-11-26T08:16:10Z

Peder at 16:32, 27 May 2015

2015-05-27T16:32:37Z

Peder at 12:36, 7 April 2014

2014-04-07T12:36:13Z

Peder at 11:56, 4 April 2014

2014-04-04T11:56:25Z

Peder at 08:13, 4 April 2014

2014-04-04T08:13:09Z

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Peder: Peder Wikström moved page Version 2.0.0 to Upcoming: Version 2.0.0

2014-01-17T16:10:33Z

Peder Wikström moved page Version 2.0.0 to Upcoming: Version 2.0.0

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 ==Summary==

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 ====Changed default choice for growth model====
-The default choice of using a whole stand growth model for calibrating the single-tree calculations is inactivated when creating a new project. This parameter is found in control table Production Model as "Growth Model Whole-Stand", and has been changed to "None", meaning that Björn Elfving's single-tree functions are used alone, without calibrating them with the stand-level growth model. The reason is not more accurate growth predictions per se, the differences between the models are rather small, but the single-tree growth functions used alone gives a more smooth transitions from young stand phase to the established phase, at least in a numerous cases tried.
+The default choice of using a whole stand growth model for calibrating the single-tree calculations is inactivated when creating a new project. This parameter is found in control table Production Model as "Growth Model Whole-Stand", and has been changed to "None", meaning that Björn Elfving's single-tree functions are used alone, without calibrating them with the stand-level growth model. The reason is not more accurate growth predictions per se, the differences between the models are rather small, but the single-tree growth functions used alone gives a smoother transition from the young stand phase to the established phase, at least in numerous cases tried.
 The default function choice for calculating tree diameters for sapling trees (parameter "Sapling Diameter Model" in control table Production Model) has also been changed, from "NystromSoderberg" to "Elfving", for the same reason.
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 ==== New mortality model ====
-A new mortality model is available and used as default model in new project. For existing projects (created in previous program version), we recommend that you select this model instead. The model is called "Elfving" and is selected in control table Production Model. With the old model, mortality in non-dense stands have been calculated with a somewhat "primitive" model (Göte Bengtsson 1978), with a fixed mortality precentage for each species. The new model is a single-tree model based on a large set of NFI-data (Rikskogstaxeringens data). The new model also replaces the single-tree mortality model by Fridman & Ståhl which has used until now to distribute mortlaity to trees. The latter is in it basic form a stochastic model, while the new one is determinstic, and therefore better suited for Heureka. <feedDate>2014-04-04</feedDate>
+A new mortality model is available and used as default model in new project. For existing projects (created in previous program version), we recommend that you select this model instead. The model is called "Elfving" and is selected in control table Production Model. With the old model, mortality in non-dense stands have been calculated with a somewhat "primitive" model (Göte Bengtsson 1978), with a fixed mortality precentage for each species. The new model is a single-tree model based on a large set of NFI-data (Rikskogstaxeringens data). The new model also replaces the single-tree mortality model by Fridman & Ståhl which has been used until now to distribute mortality to trees. The latter is in it basic form a stochastic model, while the new one is determinstic, and therefore better suited for Heureka. <feedDate>2014-04-04</feedDate>
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 For an established stand, Heureka calculates the mean age (variable "ForestData.MeanAge excl overstorey") as the basal area weighted mean age of the trees. For a young stand, the variable is calculated as a weighted arithmetic mean age, where the calculated probabilities for crop trees (beräknade huvudstamssannolkheter) are used as weights. In established stands (mean height ≥ 7 m), tree ages are by default calibrated so that the calculated mean age and the mean age imported (for example from the stand register) are the same. This calibration has not been applied for young stands. The reason for this is that the imported mean age for young stands has not been used if a mean height has been available. In that case, the mean age has been based on the calculated sapling ages, which in turn depend on tree heights and site index. This have resulted in a more model-driven than data-driven approach, which is probably good since data for young stands are often reported as very uncertain. If relying too much on the age/height relation in young stands, there is a risk that the calculated growth for young stands with a large height/age ratio is overestimated. In stands where there have been a few years of large height growth, these few years constitute a large part of the total age of the stand and will affect growth much more in relative terms than is the case for an older stand. As a drawback, the ages for young stands calculated in Heureka have often differed from the mean ages in the stand register. Several measures has been taken to handle this, and some more will be available later this year in version 2.1.
 *One change is that by default, mean heights for young stands are ignored when simulating tree list. When simulating tree lists from stand register data, you will find a new check box "Let system automatically calculate tree heights for young stands". The corresponding function is available when entering data manually, in the sapling simulator dialog you can choose "Calculate from age" (see Figure 2a and 2b). Using this option (which is default) will result in more robust height/age-relations in young stands, and smaller differences between stand register age and age calculated by Heureka.
-*Sapling ages can now be calibrated so that the mean arithmetic age of main saplings should be close the entered mean age of the stand. The use of this calibration is activate in control table ProductionModel, parameter Calibrate Age Young Stand, which is set to True in new projects. You should change this parameter when you open old projects. Before this calibration, the program projects the growth for the number of years that differs between the mean age calculated by the model (as a function of tree heights), and the entered mean age.
+*Sapling ages can now be calibrated so that the mean arithmetic age of main saplings should be close to the entered mean age of the stand. The use of this calibration is activated in control table ProductionModel, parameter Calibrate Age Young Stand, which is set to True in new projects. You should change this parameter when you open old projects. Before this calibration, the program projects the growth for the number of years that differs between the mean age calculated by the model (as a function of tree heights), and the entered mean age.
 *Another improvement is that the start up of a young stand has been refined to better match the usage of five-year period lengths. When not using this function (by unchecking the check box), tree heights will be calibrated so that the mean height for each species is as close as possible to the entered mean height.

Version 2.0.0 - Revision history

Osskyn at 08:16, 26 November 2024

Peder at 16:32, 27 May 2015

Peder at 12:36, 7 April 2014

Peder at 11:56, 4 April 2014

Peder at 08:13, 4 April 2014

Peder: Peder Wikström moved page Version 2.0.0 to Upcoming: Version 2.0.0