Survival Rates show you what percentage of planted trees have survived since planting began. Terraware calculates Survival Rates for your Planting Sites based on initial plant densities — recorded as t0 data — and the live and dead plant counts recorded during Assigned Plot Observations. Survival Rates appear in the Observations pages at the Planting Site, Stratum, Substratum, and monitoring plot levels, and in the Plants Dashboard. Admins and Managers can access and manage Survival Rate settings.
What is t0 data?
T0 data is the initial plant density data used as the baseline for Survival Rate calculations. It represents the state of the Planting Site immediately after planting was completed — before any plants have died. The more accurately t0 data reflects actual post-planting conditions, the more meaningful your Survival Rates will be.
T0 data must be set for all permanent plots assigned to a Planting Site, and for all Strata if you choose to include temporary plots in your calculations. Survival Rates cannot be calculated until t0 data has been set.
Access Survival Rate settings
- Navigate to Observations for the Planting Site you want to configure.
- Click Survival Rate Settings. Note: This link is only available once at least one Observation with a status of Completed or Completed (Ended) exists for the Planting Site.
Set t0 data for permanent plots
For each permanent plot, you'll choose how to provide the initial plant density used for Survival Rate calculations. You have two options:
Option 1: Use an existing Observation
This is the recommended approach. Ideally, use the first Observation completed for the Planting Site, conducted right after planting was finished.
- In the Permanent Plots tab of the Survival Rate Settings page, find the plot you want to configure.
- Select Use Observation Data.
- Select the Observation to use as t0 data. Note: Only Observations that included this plot will appear in the selector.
- Review the t0 data that will be used and click Save.
Option 2: Enter plant densities manually
Use this option if no suitable Observation exists for a plot.
- Select Provide Plant Density per Species.
- For each Species listed, either enter a plant density manually or select Use Calculated Plant Density from Withdrawals to use the density calculated from your withdrawal records. Note: When new withdrawals are made to the Substratum containing the plot, the calculated density will update automatically and any newly planted Species will be added to the list.
- Click Save.
When t0 data has been set for a plot, you'll see t0 is set next to the plot in the Settings page. If a plot does not yet have t0 data set, you'll see Not set. When t0 data has been set for all permanent plots, you'll see t0 is set for Permanent Plots at the top of the Permanent Plots tab.
Note: If you change the t0 data for a plot after Survival Rates have already been calculated, Terraware will recalculate the rates based on the new data.
Include temporary plots in Survival Rate calculations
By default, Survival Rates are calculated using permanent plot data only. You can choose to include temporary plot data as well, which may produce Survival Rates that more closely reflect conditions across the whole Planting Site.
- In the Temporary Plots tab of the Survival Rate Settings page, check the box to include temporary plots in Survival Rate calculations.
- For each Stratum, provide plant densities per Species.
- Click Save.
To exclude temporary plots, uncheck the box. Survival Rates will be recalculated automatically whenever this setting is changed.
When t0 data has been set for all Strata, you'll see t0 is set next to each Stratum and t0 is set for Temporary Plots at the top of the Temporary Plots tab. If a Stratum does not yet have t0 data set, you'll see Not set next to it.
Note: If you include temporary plots, t0 data must be set for all Strata before Survival Rates can be calculated.
Survival Rate formulas
Permanent plots — using Observation data for t0:
- Plot Survival Rate = Live planted plants from the most recent Observation ÷ (Live + dead planted plants from the t0 Observation)
- Species Survival Rate = Live plants of that Species from the most recent Observation ÷ (Live + dead plants of that Species from the t0 Observation)
Permanent plots — using manually entered plant density for t0:
- Plot Survival Rate = Live planted plants from the most recent Observation ÷ (Sum of manually entered plant density by Species × 0.09 ha)
- Species Survival Rate = Live plants of that Species from the most recent Observation ÷ (Manually entered plant density for that Species × 0.09 ha)
Temporary plots:
- Plot Survival Rate = Live planted plants from the most recent Observation ÷ (Sum of manually entered plant density by Species × 0.09 ha)
- Species Survival Rate = Live plants of that Species from the most recent Observation ÷ (Manually entered plant density for that Species × 0.09 ha)
Note: Each monitoring plot is 0.09 hectares (30m × 30m). Survival Rate calculations do not include plants recorded as Existing and Can't Tell, or were added via the Other option during Observations.
When Survival Rates cannot be calculated
Terraware will display a "Cannot be calculated" message in the Survival Rate section of the Plants Dashboard if any of the following are true:
- Not all permanent plots have t0 data set (and temporary plots are not being used).
- Temporary plots are being used but not all Strata have t0 data set.
- The Planting Site geometry has changed and no subsequent Observation has been completed yet.
Note: Survival Rates are not calculated for Ad Hoc Plot Observations.