Response of Douglas-fir leaf area index and litterfall dynamics to Swiss needle cast in north coastal Oregon, USA

Weiskittel, Aaron R.; Maguire, Douglas A.

doi:10.1051/forest:2006096

Cited by 9 publications

(2 citation statements)

References 55 publications

(66 reference statements)

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“…SLA differed depending on the crown position for both Scots pine and Norway spruce, with lower SLA values higher up in the crown. This agrees with previous studies with similar results (Hager and Sterba 1985;Marshall and Monserud 2003;Weiskittel and Maguire 2007). SLA was also tested against DBH and height of the measured trees, but no significant correlation was found for either of the species.…”

Section: Discussionsupporting

confidence: 91%

Comparing direct and indirect leaf area measurements for Scots pine and Norway spruce plantations in Sweden

Goude¹,

Nilsson²,

Holmström³

2019

Eur J Forest Res

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The area of foliage absorbing solar radiation is often expressed as leaf area index (LAI). In this study, specific leaf area (SLA), leaf area at tree level (LA) and LAI at stand level were measured on eight experimental plots of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris), together with tree and stand measurements from biomass harvest. Both projected area and half total surface area were measured, and a model of the relationship between the units was constructed. SLA was larger for pine (61.62 cm 2 g −1) compared to spruce (50.2 cm 2 g −1) and showed a trend of decreasing higher up in the crown. Leaf area was significantly higher for Norway spruce compared to Scots pine on both tree and stand level. Models were constructed using diameter at breast height, tree height and stand basal area to estimate LA. The models were general site-independent models that can be used for easy estimations of single tree leaf area. Indirect measurement of LAI (LAIe) was shown to underestimate LAI with on average 30-73% depending on species and measurement technique. Using the extensive data collected, conversion models were constructed for estimating LAI from LAIe together with basal area, stem number and stand height. These species-specific conversion models will allow for more accurate estimations of LAI that can be used in mechanistic models of forest growth and for future estimates of LAI from remote sensing data.

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Section: Discussionsupporting

confidence: 91%

Comparing direct and indirect leaf area measurements for Scots pine and Norway spruce plantations in Sweden

Goude¹,

Nilsson²,

Holmström³

2019

Eur J Forest Res

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“…Because western hemlock is shade tolerant, it can persist and grow below the main canopy. In SNC-impacted stands that have suffered significant Douglas-fir foliar loss (foliage retention (FR) ≤1.5 years), leaf area index of Douglas-fir has declined up to 31 per cent relative to healthy stands (initial Douglas-fir FR ≥3.5 years) (Weiskittel and Maguire, 2007). This degree of Douglas-fir foliar loss in mixed stands would be expected to evoke compensatory growth in western hemlock for two reasons: (1) greater light penetration through the upper Douglas-fir canopy enhances light availability to subordinate species and (2) loss of foliage results in diminished height growth (Garber et al, 2007) and reduced crown expansion of Douglas-fir (Weiskittel, 2003), thereby lowering its ability to compete with non-susceptible species.…”

Section: Forestryani Nternational Journal Of Forest Researchmentioning

confidence: 99%

Western hemlock growth response to increasing intensity of Swiss needle cast on Douglas-fir: changes in the dynamics of mixed-species stands

Zhao

Maguire²,

Mainwaring

et al. 2014

Forestry: An International Journal of Forest Research

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Western hemlock (Tsuga heterophylla (Raf.) Sarg.) is a major commercial tree species in western Oregon and Washington and is often associated with coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var menziesii) and other species in coniferous forests of the Coast Ranges and Cascade Mountains. Growth of Douglas-fir in many coastal forests has been negatively affected by Swiss needle cast (SNC), a foliar disease caused by the ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr. and characterized by premature foliage loss on severely infected Douglas-fir trees. The effect of SNC on stand dynamics in mixed Douglas-fir-western hemlock stands was tested by constructing a diameter increment model for western hemlock that quantified its growth response to varying SNC severity in Douglas-fir. Diameter increment of western hemlock in any given growth period increased with increasing initial SNC severity as measured by Douglas-fir foliage retention (FR), here defined as the number of annual needle cohorts held by the tree. Furthermore, a decline in Douglas-fir FR during the growth period was associated with an additional increase in diameter increment of western hemlock trees. Assuming no change in FR over the growth period, western hemlock trees in stands with severely impacted Douglas-fir (initial FR ≤1.5 years) averaged 79 per cent greater diameter growth than that in relatively healthy stands (initial Douglas-fir FR ≥3.5 years). The implied annual diameter growth response of a western hemlock with initial diameter at breast height of 10, 20, 30 or 40 cm was 0.29, 0.52, 0.65 and 0.68 cm year 21 , respectively. Compensatory growth by western hemlock in mixed-species stands alters stand dynamics by allowing this species to surpass the growth of Douglas-fir experiencing severe SNC.

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A hybrid model for intensively managed Douglas-fir plantations in the Pacific Northwest, USA

2009

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Recent advances in traditional forest growth models have been achieved by linking growth predictions to key ecophysiological processes in a hybrid approach that combines the strengths of both empirical and process-based models. A hybrid model was constructed for intensively managed Douglas-fir plantations in the Pacific Northwest, USA, by embedding components representing fundamental physiological processes and detailed tree allometrics into an empirical growth model for projecting individual tree and stand development. The simulated processes operated at a variety of scales ranging from individual branches to trees and stands. The canopy structure submodel improved predictions of leaf area index at the stand level when compared to allometric and other empirical approaches (reducing mean square error by 30-42%). In addition, the hybrid model achieved accuracy in short-term volume growth prediction comparable to an empirical model. Biases in 4-year stand growth predictions from the hybrid model were similar to those from the empirical model under thinning, fertilization, and the combination of these treatments; however, volume growth predictions in unmanaged plantations averaged approximately 36% less bias. These improvements were attributed to detailed information on crown structure (i.e. size, location, and foliage mass of primary branches), simple representation of key physiological processes, and improved site characterization. Soil moisture, temperature, and nitrogen mineralization predicted by the hybrid model also agreed closely with observed values from several previous studies. Overall, the model framework will be helpful for future analyses as it can lend insight into the influence of weather and site edaphic factors on growth, help identify mechanisms of response to silvicultural treatments, and facilitate the design of sound management regimes for Douglas-fir plantations across the Pacific Northwest region.

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Response of Douglas-fir leaf area index and litterfall dynamics to Swiss needle cast in north coastal Oregon, USA

Cited by 9 publications

References 55 publications

Comparing direct and indirect leaf area measurements for Scots pine and Norway spruce plantations in Sweden

Comparing direct and indirect leaf area measurements for Scots pine and Norway spruce plantations in Sweden

Western hemlock growth response to increasing intensity of Swiss needle cast on Douglas-fir: changes in the dynamics of mixed-species stands

A hybrid model for intensively managed Douglas-fir plantations in the Pacific Northwest, USA

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