Treatment duration and time since disturbance affect vegetation development in a young ponderosa pine plantation

Abstract

The effect of early and delayed release treatments (designated as "Treat first 3 years" and "Treat second 3 years," respectively) on diameter, height, and foliar cover of ponderosa pine seedlings, and density, foliar cover, and height of competing vegetation was evaluated in a young northern California plantation. Manual grubbing created vegetation recovery times (the period of time from the last release treatment until the end of the study) that lasted 4 to 10 years. Duration and timing of the grubbing operations constituted the treatments. Development of species other than the planted pines was evaluated directly for density, cover, and height, and indirectly for effect on pine survival and growth. By 1995 greenleaf manzanita had higher values for density, cover, and height in the treatments allowing the longest recovery times. Survival of the ponderosa pines over all treatments after 1 growing season was 99 percent and after 10 seasons was 96 percent. Both release treatments resulted in greater conifer diameter, height, and foliar cover than in the control at the end of the study. Conifer values between the two release treatments did not differ significantly at the end of the study.