CAFRI Labs: Plot-level AGB Comparisons; Understory and Overstory

Lucas Johnson

Description

Our current FIA plot-level AGB calculations do not take into account separate scaling factors for stems sampled on microplots (DBH < 5in) and stems sampled on subplots (DBH >= 5in). Metrics derived from stems sampled on microplots (radius 6.8 feet) require a larger scaling factor than metrics derived from stems sampled on subplots (radius 24 feet).

This analysis aims to inform us of the impact of either 1) dropping understory AGB from the plot-level AGB calculation, or 2) proper scaling of understory AGB.

Calculations

Current: Understory (microplots only; DBH < 5in) and overstory (subplots; DBH >= 5in) AGB included, but all AGB scaled to Mg/Ha using (microplot + subplot sum) / [4 * (subplot area)] * 10000.
Overstory: Only overstory (subplots; DBH >= 5in) AGB included. Scaled to Mg/Ha using (subplot sum) / [4 * (subplot area)] * 10000.
Corrected: Understory (microplots only; DBH < 5in) and overstory (subplots: DBH >= 5in) AGB included. Understory AGB scaled to Mg/Ha using (microplot sum) / [4 * (microplot area)] * 10000 and overstory AGB scaled to Mg/Ha using (subplot sum) / [4 * (subplot area)] * 10000.

FIA plots included

Tiers 1 and 2 only
- Note: In some cases a tier 2 assignment did not hold constant for a given plot across the various calculations (2 became 6 and vice versa), and such plots were removed from the analysis.
Plots with any non-sampled subplots dropped
Plot centers within LiDAR coverage boundaries

Areas included

NYSGPO_WarrenWashingtonEssex_2015
NYSGPO_Cayuga_Oswego_2018
NYSGPO_AlleganySteuben_2016
USGS_3County2014

Results

NYSGPO_WarrenWashingtonEssex_2015

Calculation	Max	Mean	Median	SD
Current	300.0849	122.2852	129.8509	66.23040
Overstory	299.4383	121.4198	127.6852	66.11358
Corrected	307.4921	132.1998	137.4223	68.07132

NYSGPO_CayugaOswego_2018

Calculation	Max	Mean	Median	SD
Current	215.6985	66.27305	1.249731	76.32680
Overstory	213.8232	65.97316	1.249731	75.97292
Corrected	237.1829	69.70888	1.249731	80.51447

NYSGPO_AlleganySteuben2016

Calculation	Max	Mean	Median	SD
Current	227.0027	74.69407	53.37800	70.15954
Overstory	226.6727	74.20828	52.18493	69.96901
Corrected	230.7834	80.25963	62.49749	72.73425

USGS_3County2014

Calculation	Max	Mean	Median	SD
Current	349.1905	96.29956	92.94180	89.87556
Overstory	348.3439	96.00222	92.52331	89.70898
Corrected	358.8901	99.70615	96.50892	91.90828

Summary (All Areas Combined)

Calculation	Max	Mean	Median	SD
Current	349.1905	99.26969	102.1892	81.01323
Overstory	348.3439	98.76042	101.1290	80.80100
Corrected	358.8901	105.10427	111.8176	83.74072

Corrections

If you see mistakes or want to suggest changes, please create an issue on the source repository.

Citation

For attribution, please cite this work as

Johnson (2021, May 19). CAFRI Labs: Plot-level AGB Comparisons; Understory and Overstory. Retrieved from https://cafri-labs.github.io/acceptable-growing-stock/posts/plot-level-agb-comparisons-understory-and-overstory/

BibTeX citation

@misc{johnson2021plot-level,
  author = {Johnson, Lucas},
  title = {CAFRI Labs: Plot-level AGB Comparisons; Understory and Overstory},
  url = {https://cafri-labs.github.io/acceptable-growing-stock/posts/plot-level-agb-comparisons-understory-and-overstory/},
  year = {2021}
}