Litter dynamics in two Sierran mixed conifer forests. II. Nutrient release in decomposing leaf litter

The factors influencing leaf litter decomposition and nutrient release patterns were investigated for 3.6 years in two mixed conifer forests in the southern Sierra Nevada of California. The giant sequoia–fir forest was dominated by giant sequoia (Sequoiadendrongiganteum (Lindl.) Buchh.), white fir (Abiesconcolor Lindl. & Gord.), and sugar pine (Pinuslambertiana Dougl.). The fir–pine forest was dominated by white fir, sugar pine, and incense cedar (Calocedrusdecurrens (Torr.) Florin). Initial concentrations of nutrients and percent lignin, cellulose, and acid detergent fiber vary considerably in freshly abscised leaf litter of the studied species. Giant sequoia had the highest concentration of lignin (20.3%) and the lowest concentration of nitrogen (0.52%), while incense cedar had the lowest concentration of lignin (9.6%) and second lowest concentration of nitrogen (0.63%). Long-term (3.6 years) foliage decomposition rates were best correlated with initial lignin/N (r2 = 0.94, p < 0.05), lignin concentration (r2 = 0.92, p < 0.05), and acid detergent fiber concentration (r2 = 0.80, p < 0.05). Patterns of nutrient release were highly variable. Giant sequoia immobilized N and P, incense cedar immobilized N and to a lesser extent P, while sugar pine immobilized Ca. Strong linear or negative exponential relationships existed between initial concentrations of N, P, K, and Ca and percent original mass remaining of those nutrients after 3.6 years. This suggests efficient retention of these nutrients in the litter layer of these ecosystems. Nitrogen concentrations steadily increase in decomposing leaf litter, effectively reducing the C/N ratios from an initial range of 68–96 to 27–45 after 3.6 years.

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Litter dynamics in two Sierran mixed conifer forests. I. Litterfall and decomposition rates

Canadian Journal of Forest Research ◽

10.1139/x88-174 ◽

1988 ◽

Vol 18 (9) ◽

pp. 1127-1135 ◽

Cited By ~ 49

Author(s):

Thomas J. Stohlgren

Keyword(s):

Mass Loss ◽

Leaf Litter ◽

Litter Decomposition ◽

Woody Debris ◽

Leaf Litter Decomposition ◽

Decomposition Rates ◽

White Fir ◽

Mixed Conifer Forests ◽

Sugar Pine ◽

Giant Sequoia

Litterfall was measured for 4 years and leaf litter decomposition rates were studied for 3.6 years in two mixed conifer forests (giant sequoia–fir and fir–pine) in the southern Sierra Nevada of California. The giant sequoia–fir forest (GS site) was dominated by giant sequoia (Sequoiadendrongiganteum (Lindl.) Buchh.), white fir (Abiesconcolor Lindl. & Gord.), and sugar pine (Pinuslambertiana Dougl.). The fir–pine forest (FP site) was dominated by white fir, sugar pine, and incense cedar (Calocedrusdecurrens (Torr.) Florin). Litterfall, including large woody debris <15.2 cm in diameter, at the GS site averaged 6364 kg•ha−1•year−1 compared with 4355 kg•ha−1•year−1 at the FP site. Compared with other temperate coniferous forests, annual variability in litterfall (as computed by the ratio of the annual maximum/minimum litterfall) was extremely high for the GS site (5.8:1) and moderately high for the FP site (3.4:1). In the GS site, leaf litter decomposition after 3.6 years was slowest for giant sequoia (28.2% mass loss), followed by sugar pine (34.3%) and white fir (45.1%). In the FP site, mass loss was slowest for sugar pine (40.0%), followed by white fir (45.1%), while incense cedar showed the greatest mass loss (56.9%) after 3.6 years. High litterfall rates of large woody debris (i.e., 2.5–15.2 cm diameter) and slow rates of leaf litter decomposition in the giant sequoia–fir forest type may result in higher litter accumulation rates than in the fir–pine type. Leaf litter times to 95% decay for the GS and FP sites were 30 and 27 years, respectively, if the initial 0.7-year period (a short period of rapid mass decay) was ignored in the calculation. A mass balance approach for total litterfall (<15.2 cm diameter) decomposition yielded lower decay constants than did the litterbag study and therefore longer times to 95% decay (57 years for the GS site and 62 years for the FP site).

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Pyrosilviculture: Combining prescribed fire with gap-based silviculture in mixed-conifer forests of the Sierra Nevada

Canadian Journal of Forest Research ◽

10.1139/cjfr-2020-0337 ◽

2020 ◽

Author(s):

Robert A. York ◽

Hunter Noble ◽

Lenya Quinn-Davidson ◽

John J. Battles

Keyword(s):

Sierra Nevada ◽

Prescribed Fire ◽

Fire Hazard ◽

Stand Age ◽

Conifer Forests ◽

Mixed Conifer ◽

Commercial Thinning ◽

Crown Scorch ◽

Mixed Conifer Forests ◽

Giant Sequoia

We used a prescribed fire study to demonstrate the concept of pyrosilviculture, defined here as a) using prescribed fire to meet management objectives or b) altering non-fire silvicultural treatments explicitly so that they can optimize the incorporation of prescribed fire in the future. The study included implementation of relatively hot prescribed burns in mixed-conifer forests that have been managed with gap-based silviculture. The fires burned through 12-, 22-, 32- and, 100-year old cohorts, thus enabling an analysis of stand age influences on fire effects. Mastication and pre-commercial thinning were assessed as pre-fire treatments in the 12-year-old stands. Post-burn mortality and crown scorch declined with stand age. There was a clear tradeoff between fuel consumption and high rates of tree damage and mortality in the 12-year-old stands. Masticated stands had higher levels of average crown scorch (78%) compared with pre-commercially thinned stands (52%). Mortality for all 12-year-old stands was high, as nearly half of the trees were dead one year after the fires. Giant sequoia and ponderosa pine had relatively high resistance to prescribed fire-related mortality. When applying the concept of pyrosilviculture, there could be opportunities to combine prescribed fire with regeneration harvests that create a variety of gap sizes in order to sustain both low fire hazard and to promote structural heterogeneity and sustainable age structures that may not be achieved with prescribed fires alone.

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Recent bark beetle outbreaks influence wildfire severity in mixed‐conifer forests of the Sierra Nevada, California, USA

Ecological Applications ◽

10.1002/eap.2287 ◽

2021 ◽

Author(s):

Rebecca B. Wayman ◽

Hugh D. Safford

Keyword(s):

Sierra Nevada ◽

Bark Beetle ◽

Conifer Forests ◽

Mixed Conifer ◽

Mixed Conifer Forests

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Characterizing the light environment in Sierra Nevada mixed-conifer forests using a spatially explicit light model

Canadian Journal of Forest Research ◽

10.1139/x04-013 ◽

2004 ◽

Vol 34 (6) ◽

pp. 1332-1342 ◽

Cited By ~ 26

Author(s):

Rolf Gersonde ◽

John J Battles ◽

Kevin L O'Hara

Keyword(s):

Leaf Area ◽

Sierra Nevada ◽

Forest Type ◽

Individual Species ◽

Spatially Explicit ◽

Conifer Forests ◽

Prediction Equations ◽

Mixed Conifer ◽

Sapwood Area ◽

Mixed Conifer Forests

The spatially explicit light model tRAYci was calibrated to conditions in multi-aged Sierra Nevada mixed-conifer forests. To reflect conditions that are important to growth and regeneration of this forest type, we sampled a variety of managed mature stands with multiple canopy layers and cohorts. Calibration of the light model included determining leaf area density for individual species with the use of leaf area sapwood area prediction equations. Prediction equations differed between species and could be improved using site index. The light model predicted point measurements from hemispherical photographs well over a range of 27%63% light. Simplifying the crown representation in the tRAYci model to average values for species and canopy strata resulted in little reduction in model performance and makes the model more useful to applications with lower sampling intensity. Vertical light profiles in managed mixed-conifer stands could be divided into homogeneous, sigmiodal, and continuous gradients, depending on stand structure and foliage distribution. Concentration of leaf area in the upper canopy concentrates light resources on dominant trees in continuous canopies. Irregular canopies of multiaged stands, however, provide more light resources to mid-size trees and could support growth of shade-intolerant species. Knowledge of the vertical distribution of light intensity in connection with stand structural information can guide regulation of irregular stand structures to meet forest management objectives.

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