Ponderosa pine initial spacing study at Challenge Experimental Forest

This data publication includes original tree data collected as a guide to investigate the effect of initial tree spacing, brush competition, and the interaction of these two factors on growth and development of a ponderosa pine (Pinus ponderosa Laws.) plantation at the Challenge Experimental Forest in northern California. Data span over 60 years with height and diameter at breast height (if tree height reached 1.37 meters) being measured every year from 1968 to 1975, every two years from 1975 to 1985, every four years from 1985 to 2002, and every five years after that up through 2022. Other measurements recorded during these same years include tree condition codes, height to live crown, crown width (1970-2002), and volume measurements for some trees (1977-1993).
The purpose of the original study was to determine the relationship between initial spacing and growth of ponderosa pine and how this relationship was affected by the normal influx of understory vegetation. Since establishment, many authors have used partial or full data to address some specific contemporary questions such as carbon sequestration, overstory-understory interactions, and appropriate stand density for healthy and resilient forests.
These data have been fully and partially used in various publications (listed as cross-references below) to address scientific and management questions. This study has also been a popular show piece for visiting land managers and other interested parties.