Sandbox3 - Revision history

Peder at 10:44, 8 March 2016

2016-03-08T10:44:35Z

Peder: /* About time periods, time points and treatment years */

2016-03-08T10:43:38Z

About time periods, time points and treatment years

Peder: /* Understanding how growth is calculated */

2016-03-08T10:43:28Z

Understanding how growth is calculated

Peder: /* CAI gross */

2016-03-08T10:43:00Z

CAI gross

Peder: /* CAI net */

2016-03-08T10:41:54Z

CAI net

Peder: /* Basis calculation steps */

2016-03-08T10:40:30Z

Basis calculation steps

Peder: /* Change variable= */

2016-03-08T10:40:14Z

Change variable=

Peder: /* Yield variable= */

2016-03-08T10:40:02Z

Yield variable=

Peder: /* State, yield and change variables */

2016-03-08T10:39:51Z

State, yield and change variables

Peder: /* State, yield and change variables */

2016-03-08T10:38:54Z

State, yield and change variables

@@ Line 39: / Line 39: @@
 Growth and mortality [[#change|change]] refers to how a forest stand is changing from one time point to the next. Growth is reported as gross growth and net growth. Gross growth includes mortality, net growth does not.
-==CAI net==
+====CAI net====
 The current annual '''net''' volume growth is the same as the volume change from one time (after harvest) to the next (before harvest). Mortilty is not included. CAI net is calculated as:<br>
@@ Line 49: / Line 49: @@
 ''a'' = number of years
-==CAI gross==
+====CAI gross====
 The current annual '''gross''' volume growth includes mortality and is calculated as CAI net but with mortality added:<br>

@@ Line 1: / Line 1: @@
 ==About time periods, time points and treatment years==
 Heureka’s is using a discrete time period model, typically using five-year time intervals. The term time period is somewhat misleading, because a “time period” may refer to a time point or a period, depending on context. For example, if you use StandWise to project the growth of a stand, the “time period” is actually better interpreted as a time index marking the beginning of a period. For a case with many stands in PlanWise or RegWise on the other hand, the time index marks the midpoint of a time period. The motivation for this is that although all stands scheduled for harvest in the first period have been assigned the same treatment year (year 2.5) in the model, they should harvested simultaneously, but the harvest activities would be spread out evenly over the five-year period.
 ==Period year and treatment year==

@@ Line 36: / Line 36: @@
 ==Understanding how growth is calculated==
 Growth and mortality [[#change|change]] refers to how a forest stand is changing from one time point to the next. Growth is reported as gross growth and net growth. Gross growth includes mortality, net growth does not.
 ==CAI net==

@@ Line 50: / Line 50: @@
 ==CAI gross==
-The current annual '''gross''' volume growth is calculated as:<br>
+The current annual '''gross''' volume growth includes mortality and is calculated as CAI net but with mortality added:<br>
 <math>G_{t+a} = \displaystyle \frac{V_{t+a}- V_a + H_t + M_t}{a} </math>

@@ Line 40: / Line 40: @@
 ==CAI net==
-The current annual '''net''' volume growth is calculated as:<br>
+The current annual '''net''' volume growth is the same as the volume change from one time (after harvest) to the next (before harvest). Mortilty is not included. CAI net is calculated as:<br>
 <math>G_{t+a} = \displaystyle \frac{V_{t+a}- V_a + H_t}{a} </math>
@@ Line 48: / Line 48: @@
 ''H<sub>t</sub>'' = Volume harvested at time t, and <br>
 ''a'' = number of years
 ==CAI gross==

@@ Line 22: / Line 22: @@
 A third type of variable describes '''change''' of a stand, for example growth and mortality. Growth and mortality that are reported in a certain time period t, represents the growth and mortality that has occurred after harvesting in the previous period (t -1) to the current period year.
-==Basis calculation steps==
+==Basic calculation steps==
 As a Heureka user, it is important that you have a fundamental understanding of how a prognosis is done. The following principal steps are performed when making a prognosis from one time point (t) to another (t+1).
 .	Calculate state variables for the stand at time t from tree-level data, for example stand volume and mean diameter. This is the Before-value.
@@ Line 31: / Line 31: @@
 .	Let t = t +1. Update the tree list for this period and repeat from step 1.
-==Subtract half a period’s harvest volume to obtain
+==Subtract half a period’s harvest volume to obtain==
 If you want to create for example a graph of how the standing stock (the total volume) of a large forest holding develops over time according to a simulation in PlanWise, and you have used period midpoints (the default in a TPG-simulation), you should subtract half the period’s harvest volume from the Before-value. The reason is that the Before-value has been adjusted for a half a period’s growth and mortality, but not for half a periods harvesting. In reality, in a case with many stands, some of the stands will be harvested early in the period, other stands in the middle of the period, and other stand at the end of the period. But in the model, all harvesting takes place in the middle of the period. Extracting half a periods harvesting is a simple way to at least approximately adjust for this error.

@@ Line 19: / Line 19: @@
 A '''yield''' variable refers to some output from an activity, such as the harvest volume.
-===Change variable====
+====Change variable====
 A third type of variable describes '''change''' of a stand, for example growth and mortality. Growth and mortality that are reported in a certain time period t, represents the growth and mortality that has occurred after harvesting in the previous period (t -1) to the current period year.

@@ Line 16: / Line 16: @@
 ====State variable====
 A '''state''' variable refers to a description variable for a stand at a certain time, for example the mean age or the volume.
-===Yield variable====
+====Yield variable====
 A '''yield''' variable refers to some output from an activity, such as the harvest volume.
 ===Change variable====
 A third type of variable describes '''change''' of a stand, for example growth and mortality. Growth and mortality that are reported in a certain time period t, represents the growth and mortality that has occurred after harvesting in the previous period (t -1) to the current period year.

@@ Line 14: / Line 14: @@
 ==State, yield and change variables==
-*A '''state''' variable refers to a description variable for a stand at a certain time, for example the mean age or the volume.
+====State variable====
-*A '''yield''' variable refers to some output from an activity, such as the harvest volume.
+A '''state''' variable refers to a description variable for a stand at a certain time, for example the mean age or the volume.
-*A third type of variable describes '''change''' of a stand, for example growth and mortality. Growth and mortality that are reported in a certain time period t, represents the growth and mortality that has occurred after harvesting in the previous period (t -1) to the current period year.
+===Yield variable====
 ==Basis calculation steps==