Old Stands (old + stand)

Distribution by Scientific Domains

Selected Abstracts

Wind-throw mortality in the southern boreal forest: effects of species, diameter and stand age

Summary 1Patterns of tree mortality as influenced by species, diameter and stand age were assessed across a gradient in wind disturbance intensity in a southern boreal forest in Minnesota, USA. Few previous studies have addressed how wind impacts boreal forests where fire was historically the dominant type of disturbance. 2We surveyed 29 334 trees of nine species within a 236 000 ha blowdown in the Boundary Waters Canoe Area Wilderness (BWCAW), in forests that have never been logged and were not salvaged after the windstorm. Within the disturbed area, a range of disturbance severity from zero to complete canopy mortality was present, overlaying an existing mosaic of fire origin stands. For this study, we derived an index of wind disturbance intensity by standardizing the observed disturbance severity using common species with similar diameter at breast height (d.b.h.) distributions. We then used multiple logistic regression to assess patterns of tree mortality across gradients in tree size and wind intensity index, and for three stand ages. 3Probability of mortality was higher with increasing ln d.b.h. for all nine species, with two species (Abies balsamea and Picea mariana) showing much more dramatic shifts in mortality with d.b.h. than the others. As hypothesized, the species most susceptible to windthrow at all d.b.h. classes were early successional and shade intolerant (Pinus banksiana, Pinus resinosa, Populus tremuloides) and those least susceptible were generally shade tolerant (e.g. Thuja occidentalis, Acer rubrum), although the intolerant species Betula papyrifera also had low mortality. 4Mortality rates were higher in mature (c. 90 years old) stands than for old and very old (c. 126,200 years old) stands, probably because old stands had already gone through transition to a multi-aged stage of development. 5Synthesis. Quantification of canopy mortality patterns generally supports disturbance-mediated accelerated succession following wind disturbance in the southern boreal forest. This wind-induced weeding of the forest favoured Thuja occidentalis, Betula papyrifera and Acer rubrum trees of all sizes, along with small Abies balsamea and Picea mariana trees. Overall, the net impact of wind disturbance must concurrently consider species mortality probability, abundance and diameter distributions. [source]

The response of mammals to forest fire and timber harvest in the North American boreal forest

MAMMAL REVIEW, Issue 1 2005
ABSTRACT 1.,This paper reviews and compares the effects of forest fire and timber harvest on mammalian abundance and diversity, throughout successional time in the boreal forest of North America. 2.,Temporal trends in mammal abundance and diversity are generally similar for both harvested and burned stands, with some differences occurring in the initiation stage (0,10 years post disturbance). 3.,Small mammals and ungulates are most abundant immediately post disturbance, and decrease as stands age. Lynxes and hares utilize mid-successional stands, but are rare in young and old stands. Bats, arboreal sciurids and mustelids increase in abundance with stand age, and are most abundant in old growth. 4.,Substantial gaps in the data exist for carnivores; the response of these species to fire and harvest requires research, as predator,prey interactions can affect mammal community structure in both early and late successional stages. 5.,The lack of explicit treatment of in-stand forest structure post disturbance, in the reviewed literature made comparisons difficult. Where forest structure was considered, the presence of downed woody material, live residual trees and standing dead wood were shown to facilitate convergence of mammal communities to a pre-disturbance state for both disturbance types. 6.,Mammalian assemblages differed considerably between successional stages, emphasizing the importance of maintaining stands of each successional stage on the landscape when implementing forest management strategies. [source]

Ectomycorrhizal fungal succession in mixed temperate forests

Brendan D. Twieg
Summary ,,Ectomycorrhizal (ECM) fungal communities of Douglas-fir (Pseudotsuga menziesii) and paper birch (Betula papyrifera) were studied along a chronosequence of forest development after stand-replacing disturbance. Previous studies of ECM succession did not use molecular techniques for fungal identification or lacked replication, and none examined different host species. ,,Four age classes of mixed forests were sampled: 5-, 26-, 65-, and 100-yr-old, including wildfire-origin stands from all four classes and stands of clearcut origin from the youngest two classes. Morphotyping and DNA sequences were used to identify fungi on ECM root tips. ,,ECM fungal diversities were lower in 5-yr-old than in older stands on Douglas-fir, but were similar among age classes on paper birch. Host-specific fungi dominated in 5-yr-old stands, but host generalists were dominant in the oldest two age classes. ECM fungal community compositions were similar in 65- and 100-yr-old stands but differed among all other pairs of age classes. ,,Within the age range studied, site-level ECM fungal diversity reached a plateau by the 26-yr-old age class, while community composition stabilized by the 65-yr-old class. Simple categories such as ,early stage', ,multi stage', and ,late stage' were insufficient to describe fungal species' successional patterns. Rather, ECM fungal succession may be best described in the context of stand development. [source]

Litterfall of epiphytic macrolichens in Nothofagus forests of northern Patagonia, Argentina: Relation to stand age and precipitation

Abstract: The objective of this study was to analyse how stand age and precipitation influence abundance and diversity of epiphytic macrolichens in southern beech Nothofagus forests, estimated by lichen litter sampling. Five sites of Nothofagus dombeyi (Mirbel) Oersted were selected in Nahuel Huapi National Park, Argentina. At each site, lichen fragments from the forest floor were collected at 12.5 m2 plots in pairs of young and mature N. dombeyi forest. Additionally, two sites with multi-aged subalpine Nothofagus pumilio (Poepp. et Endl.) Krasser forest were investigated in a similar manner. Average litterfall biomass per stand varied from less than 1 kg ha,1 in a young low-precipitation stand to a maximum of 20 kg ha,1 in a mature high-precipitation stand. In places with higher precipitation, litterfall biomass in N. dombeyi forest was considerably higher in old stands as compared with young ones. In places with less than 2000 mm of precipitation, differences in biomass were less pronounced. Old humid stands contained about twice as many taxa in the litter as old low-precipitation stands and young stands in general. Mature stands in low-precipitation sites only contained 17% of the litter biomass as compared with mature stands in high-precipitation sites. Epiphytic lichen composition changed from predominating fruticose lichens (Usnea spp. and Protousnea spp.) in low-precipitation stands to Pseudocyphellaria spp., Nephroma spp. and other foliose lichens, in the high-precipitation stands. There were no clear differences in the proportion of fruticose and foliose lichens between young and old stands. Fruticose lichens dominated litter biomass in both N. pumilio sites. [source]