USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics Forest Management

Cone Fire Research
Variable Planting Densities - Effects of Seedling Growth and Competition Factors


There are many questions surrounding what proper seedling density should be utilized to achieve various management objectives. This research project hopes to help us better understand the differences and impacts of planting seedlings at variable densities in this forest type over time.

Study Area

This study is being conducted in the Cone fire-salvaged portion of the Blacks Mountain Experimental Forest (BMEF). The 10,300-acre BMEF was established in 1934. The forest of this area is generally of the inland ponderosa pine type. The fire regime of these forests generally is of the frequent, low-moderate severity type. (Click to view information about BMEF and BMERP)

Effects Data


Thirty 1-acre square plots were placed in the severely burned (salvaged) portion of BMEF. Five distinctive variable densities were utilized; 12-foot, 14-foot, 16-foot, 18-foot and 20-foot. There are a total of six randomly placed plots for each density located within the study area. All the plots were planted with one-year old container stock and to insure the proper density is maintained for each plot, a mortality survey is conducted for each of the first three years. Any seedling mortality found during the survey is replanted with the proper aged seedling. Periodic measurements over time will include: 1) Basal Diameter Growth, 2) Total Height, 3) Leader Length, 4) Height to Live-Crown Base, 5) Crown Width, 6) Diameter at Breast Height and 7) Understory Vegetation.


The first growth measurements were taken in Fall of 2008. Variability is high already due to animal damage, which tends to be clustered, and rocky soils.

At this early stage in the study there does not appear to be any effect of spacing on growth or mortality. The maximum heights of these trees, 4 years after planting, is about 5 feet with current annual height increments of about 1.2 to 1.6 feet per year if the trees are free from competing vegetation.

As we noticed in other areas of the cone fire, natural regeneration was very irregular and limited almost exclusively to Jeffrey Pine. We have almost no ponderosa pine naturals in these plantations. Areas near the boundary of the cone fire have some wind-dispersed seedlings and a few caches. However most of these can be found within a short distance of trees near the border of the burn or surviving trees. Since mortality in the Cone fire was very high, we have relatively little natural regeneration. The range in seedling establishment, some 6 years after the fire, is from zero per acre to around 20 per acre in areas adjacent to the boundary. Feel free to contact Martin Ritchie or Carl Skinner (Science Team Leaders) if you have any questions about this project.

Last Modified: Sep 12, 2013 07:22:04 PM