Using Tree-Rings to Reconstruct Fire History Information from Forested Areas

Summary

This work explains the most appropriate techniques and methods for conducting a fire history study from beginning site selection to final analysis of fire-climate relationship.

Abstract

Annual tree-ring patterns are a source of ecological and environmental information including the history of fires in forested areas. Tree-ring based fire histories include three fundamental phases: field collection, laboratory methods (preparation and dating), and data analysis. Here we provide step-by-step instructions and issues to consider, including the process for selecting the study area, sampling sites, plus how and which fire-scarred trees to sample. In addition, we describe fire-scar sample preparation and dating which are done in the laboratory. Finally, we describe basic analysis and relevant results, including examples from studies that have reconstructed fire history patterns. These studies allow us to understand the historical fire frequency, changes in those frequencies related to anthropogenic factors, and analyzes of how climate influences fire occurrence over time. The description of these methods and techniques should provide a greater understanding of fire history studies that will benefit researchers, educators, technicians, and students interested in this field. These detailed methods will allow new researchers to this field, a resource to start their own work and achieve greater success. This resource will provide a greater integration of tree-ring aspects within other studies and lead to a better understanding of natural processes with forested ecosystems.

Introduction

Forest fires, ignited by natural or anthropogenic causes, are considered one of the most common ecological disturbance factors that influence terrestrial ecosystems¹. For example, fire and more specifically fire regimes, influence plant species composition and structure². Fire is also a fundamental process linking biogeochemical cycles and climatic variability^3,4. In some areas, fire contributes to degradation and deforestation, while in other areas, fire is fundamental for regeneration and sustaining open forest structures^5,

Protocol

1. Sampling strategy

1. Determining the study area
   1. Generally, forest areas are extensive (hundreds or thousands of hectares), therefore, select a study area that will meet the objectives, which in this case, is to determine the fire history and its variability over time (Figure 1). Limit the study area only to the areas that contain fire-scarred trees which will be the sampling unit. Reconnaissance of the study area can often be facilitated using drones and video technologies, which provide views of the larger landscape, saving both time and money.
   2. Within a study area, identify potential sampling sites that....

Results

When a surface fire burns in a forest, the tree trunks of some trees are often damaged, causing injury that subsequently heals (Figure 7A). These scars form when the fire is intense enough or has a long enough residence time to penetrate the bark and kill part of the cambium. Historically, such fires occurred often enough to prevent the accumulation of fuels; therefore, most of these fires would not be able to reach the tree canopies. As a result, most mature trees survived and continued gro.......

Discussion

In forested ecosystems, fire is a key ecological process; therefore, reconstructing historical fire regimes is important toward understanding the frequency, seasonality, and variability of fires overtime. Changes to the historical fire regime can potentially lead to unintended consequences in regards to forest structure and health; therefore, such information is critical in forest management. This methodological approach focuses on the importance of selecting the study area and sites, collecting the best fire-scarre.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Belt Sander		Dewalt Dwp352vs-b3 3x21 PuLG	For sanding samples
Chain Saw Boots	Forestry Suppliers	There is no any specific characteristic	https://www.forestry-suppliers.com/Search.php?stext=Chain%20Saw%20Boots
Chain Saw Chaps	Forestry Suppliers	PGI 5-Ply Para-Aramid	https://www.forestry-suppliers.com/Search.php?stext=Chain%20Saw%20Chaps
Chainsaw	Stihl or Husqvarna for example	MS 660	Essential equipment for taking samples (Example: 18-24 inch bar)
Clinometer	Forestry Suppliers	Suunto PM5/360PC with Percent and Degree Scales	https://www.forestry-suppliers.com/Search.php?stext=Clinometer
COFECHA Software			https://www.ldeo.columbia.edu/tree-ring-laboratory/resources/software
Compass	Forestry Suppliers	Suunto MC2 Navigator Mirror Sighting	https://www.forestry-suppliers.com/Search.php?stext=compass
Dendroecological fieldwork program		Program where dating skills can be acquired or honed	http://dendrolab.indstate.edu/NADEF.htm
Diameter tape	Forestry Suppliers	Model 283D/10M Fabric or Steel.	https://www.forestry-suppliers.com/Search.php?stext=Diameter%20tape
Digital camera	CANON	EOS 90D DSLR	To take pictures of the site and the samples collected (https://www.canon.com.mx/productos/fotografia/camaras-eos-reflex)
Digital camera for microscope	OLYMPUS	DP27	https://www.olympus-ims.com/es/microscope/dp27/
Electrical tape or Plastic wrap to protect samples	uline.com		https://www.uline.com/Product/Detail/S-6140/Mini-Stretch-Wrap-Rolls/
FHAES Software			https://www.frames.gov/partner-sites/fhaes/fhaes-home/
Field format		There is no any specific characteristic	To collect information from each of the samples
Field notebook			To take notes on study site information
Gloves			For field protection
Hearing protection	Forestry Suppliers	There is no any specific characteristic	https://www.forestry-suppliers.com/Search.php?stext=Hearing%20protection
Large backpacks		There is no any specific characteristic	Strong backpack for transporting samples in the field
Safety Glasses	Forestry Suppliers	There is no any specific characteristic	https://www.forestry-suppliers.com/Search.php?stext=Safety%20Glasses
Sandpaper			From 40 to 1200 grit
Software CDendro/ CooRecorder		Tree-ring-measurements and dating can also be done using scanned images of the cross-sections	https://www.cybis.se/forfun/dendro/
Software Measure J2X		Version 4.2	ttp://www.voortech.dreamhosters.com/projectj2x/tringSubscribeV2.html
Stereomicroscope	OLYMPUS	SZX10	https://www.olympus-ims.com/en/microscope/szx10/
Topographic map, land cover map			Obtained from a public institution or generated in a first phase of research
Velmex equipment	Velmex, Inc.	0.001 mm precision	www.velmex.com
Wildland Fire Helmet	Forestry Suppliers	There is no any specific characteristic	https://www.forestry-suppliers.com/Search.php?stext=Wildland%20Fire%20Helmet