Foliar chlorophyll content of ponderosa pine on black stain root disease sites after prescribed burning and subsoiling treatment combinations

A long term study involving underburning, subsoiling and subsoiling x underburning treatments along with untreated control plots were initiated in 2000 in the Lassen National Forest, California. The study site has active blackstain root disease. A tree within each of three randomly selected grid points among nine located within treatment plots was selected for foliar sampling. Each treatment was replicated four times in a randomized complete block design. Two branches per tree were obtained at mid crown from opposite sides of sampled trees by shooting with a 12 ga shotgun. Harvested needles were placed immediately in an ice chest and later analyzed for chlorophyll a and b content. Six years of needles were commonly retained, thus a short history of chlorophyll status is obtained for this species. Overall, needles from severely symptomatic trees (based on ground observations of gross needle color and appearance) had about 40% of fresh weight and needle length of non symptomatic or slightly symptomatic trees. Total chlorophyll content also declined with decline in needle fresh weight. Prescribed burn treatments also affected needle retention, with the burn treatment having the lowest average needle retention (25% for 2004) compared to the control (63% for 2004), indicating a long term treatment effect.