Growth of Young Douglas-Fir Plantations Across a Gradient in Swiss Needle Cast Severity

Abstract

During the past decade, Swiss needle cast (SNC) damage has intensified in many Douglas-fir plantations in the Coast Range of Oregon, particularly along the immediate north coast. In plantations with severe symptoms, growth losses and reduced tree vigor are evident, but the magnitude of growth losses associated with varying intensities of damage is not known. A growth impact study was conducted in 1997 to quantify retrospectively the relationship between growth losses and visual symptoms in 10- to 30-yr-old Douglas-fir plantations in coastal northwestern Oregon, a population totaling 75,700 ha. A random sample of 70 Douglas-fir plantations was selected from the population and evaluated for Swiss needle cast severity. One 0.02 ha plot was destructively sampled in each plantation to reconstruct past height and basal area growth trends and to characterize foliage loss and distribution. The SNC “effect” was assessed by comparing growth of plantations with varying degrees of Swiss needle cast to growth of those that retained maximal amounts of foliage, after correcting for initial stand density, Douglas-fir growing stock, age, and site index. Of numerous possible SNC indices, mean needle retention (yr) explained the largest amount of variation in both basal area and top height growth. Prior to 1990, top height growth was similar across all plantations after correcting for site quality and plantation age; but, by 1992, top height growth losses appeared and were proportional to apparent foliage losses. In 1996, top height growth was reduced by up to 25% relative to plantations with little or no SNC. Basal area growth reductions began to appear around 1990, and in 1996 basal area growth of the most heavily damaged plantations was 35% less than the growth that would be expected in absence of SNC damage. The inferred volume growth loss for 1996 averaged 23% for the 75,700 ha target population, but this loss averaged as high as 52% for the most severely impacted plantations. West. J. Appl. For. 17(2):86ߝ95.

Using a climatic niche model to predict the direct and indirect impacts of climate change on the distribution of Douglas‐fir in New Zealand

“…As well as being correlated to pathogen abundance, needle retention has been found to be the most important determinant of reductions in tree volume (Maguire et al ., ). Consequently, our projections of foliage retention under current climate broadly agree with previous research describing how the disease spatially reduces Douglas‐fir volume within New Zealand.…”

Regional patterns of increasing Swiss needle cast impacts on Douglas‐fir growth with warming temperatures

“…The episodic behavior of SNC impact on stem growth was most pronounced in infected Douglas‐fir trees in Tillamook, Oregon, where SNC reduced growth by 100% in 1984, 1996, and 2004 (Black et al., ). Within the SNC impact zone of Oregon, reductions in volume growth of young Douglas‐fir by SNC were estimated to range between 23% and 50% (Maguire, Mainwaring, & Kanaskie, ; Maguire et al., ).…”

Tree‐ring stable isotopes record the impact of a foliar fungal pathogen onCO2assimilation and growth inDouglas‐fir

“…Maguire et al . ). In January 2012, we collected four increment cores (12 mm diameter) from each of six trees of similar age, diameter at breast height, height and crown width in both the fungicide‐treated stand and the untreated stand (Table ).…”