Spatial dynamics of tree group and gap structure in an old-growth ponderosa pine-California black oak forest burned by repeated wildfires

Root minirhizotron tubes were installed at two sites around three different age classes of ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) to follow patterns of fine root (≤2 mm diameter) dynamics during a 4 year study. Both sites were old-growth forests until 1978, when one site was clear-cut and allowed to regenerate naturally. The other site had both intermediate-aged trees (50–60 years) and old-growth trees (>250 years old). Estimates of fine root standing crop were greatest around young trees and least around intermediate-aged trees. Root production was highly synchronized in all age classes, showing a single peak in late May – early June each year. Root production and mortality were proportional to standing root crop (biomass), suggesting that allocation to new root growth was proportional to root density regardless of tree age. The turnover index (mortality/maximum standing crop) varied from 0.62 to 0.89·year–1, indicating root life spans in excess of 1 year. It appears that young ponderosa pine stands have greater rates of fine root production than older stands but lose more fine roots each year through mortality. The results indicate that soil carbon may accumulate faster in younger than in older stands.

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Response of forest soil Acari to prescribed fire following stand structure manipulation in the southern Cascade RangeThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.

Canadian Journal of Forest Research ◽

10.1139/x07-241 ◽

2008 ◽

Vol 38 (5) ◽

pp. 956-968 ◽

Cited By ~ 13

Author(s):

Michael A. Camann ◽

Nancy E. Gillette ◽

Karen L. Lamoncha ◽

Sylvia R. Mori

Keyword(s):

Species Richness ◽

Forest Soil ◽

Prescribed Fire ◽

Ponderosa Pine ◽

Growth Characteristics ◽

Habitat Characteristics ◽

Organic Layer ◽

Old Growth ◽

Low Intensity ◽

Dominance Relationships

We studied responses of Acari, especially oribatid mites, to prescribed low-intensity fire in an east side pine site in the southern Cascade Range in California. We compared oribatid population and assemblage responses to prescribed fire in stands that had been selectively logged to enhance old growth characteristics, in logged stands to minimize old growth characteristics, and in undisturbed forest reference stands. Low-intensity prescribed fire altered habitat characteristics within the organic layer of forest soil. Acarine populations declined following prescribed fire, and oribatid losses accounted for two thirds of that decline. Individual oribatid species responded differently to prescribed fire, with a few populations increasing after fire but most declining. The prescribed fire also altered oribatid assemblages, reducing species richness and species diversity and modifying assemblage dominance relationships. We also identified several oribatid taxa that were potential indicator species of fire effects upon forest soil fauna. Finally, our results suggested that oribatid responses to fire were intensified by stand alteration and especially by removal of old growth structural characteristics. Decline in oribatid abundance, species richness and diversity, and loss of equilibrium dominance relationships was greatest in the low structural diversity plots.

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Prescribed-fire effects on fine-root and tree mortality in old-growth ponderosa pine

Canadian Journal of Forest Research ◽

10.1139/x91-086 ◽

1991 ◽

Vol 21 (5) ◽

pp. 626-634 ◽

Cited By ~ 141

Author(s):

D. Michael Swezy ◽

James K. Agee

Keyword(s):

Ponderosa Pine ◽

Tree Mortality ◽

Prescribed Burning ◽

Fine Root ◽

Soil Depth ◽

Fire Severity ◽

Dry Weight ◽

Prescribed Burn ◽

Old Growth ◽

Root Dry Weight

Old-growth Pinusponderosa Dougl. stands were surveyed at Crater Lake National Park to investigate potential accelerated mortality of large pines due to prescribed burning. Mortality of P. ponderosa greater than 22 cm diameter at breast height was higher in burned areas (19.5%) than in unburned areas (6.6%), and early-season burns had over 30% mortality. Mortality was associated with fire severity, as measured by scorch height and ground char, season of burning, and tree vigor. Pines of high, moderate, and low vigor were subjected to a prescribed burn in June; half of the trees had debris raked from tree bases as an additional treatment. Lethal heat loads (>60 °C) occurred in >75% of samples at the soil surface and at 5 cm soil depth, with duration exceeding 5 h. Burning reduced fine-root dry weight 50–75% 1 and 5 months after burning; raking and burning reduced fine-root dry weight more than burning alone after 1 month and had similar effects to burning after 5 months. A low-vigor tree that had been raked and burned died by the beginning of the fourth dry season after burning. Present fuel loads may be too high to burn during spring if old-growth P. ponderosa are to be protected.

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