Preindustrial reconstruction of a perhumid midboreal landscape, Anticosti Island, Quebec (original) (raw)
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Canadian Journal of Forest Research, 2015
The boreal forest ecosystem is one of the largest frontier forests of the world, providing many ecological services to society. Boreal forests are also economically important, but forest harvesting and management become increasingly difficult when one moves from south to north in boreal environments. An approach was thus developed to assess the suitability of land units for timber production in a sustainable forest management (SFM) context in the northern boreal forest of Quebec (Canada). This area includes all of Quebec's spruce -feather moss bioclimatic domain (closed forest), as well as the southern portion of the spruce-lichen bioclimatic domain (open woodland). Four criteria specific to the biophysical aspects of SFM were evaluated in 1114 land districts: physical environment, timber production capacity, forest vulnerability to fire (e.g., probability that it reaches maturity), and conservation of biodiversity. Indicators and acceptability cutoff values were determined for each selected criterion, and a sequential analysis was developed to evaluate if a land district has the potential to be sustainably managed. This analytical process led to the classification of land districts into three categories: slightly sensitive (SFM possible); moderately sensitive (SFM possible under certain conditions); and highly sensitive (SFM not possible). The results show that 354 land districts were highly sensitive, 62 due to physical constraints (7.5% of the area), 130 due to insufficient potential productivity (15.4% of the area), 92 due to insufficient potential productivity to account for the fire risk (13.8% of the area), and 70 due to an insufficient proportion of tall and dense forest habitats (7.7% of the areabiodiversity criterion). This work provides scientific background to proposing a northern limit for forest management activities in Quebec. The developed approach could be useful in other jurisdictions to address similar issues.
A dendroecological reconstruction of disturbance in an old-growth Fagus-Abies forest in Slovenia
Annals of Forest Science, 2007
The scarcity of large old-growth forests has made it challenging to quantify disturbance regimes in Central Europe. The objective of this study was to reconstruct the history of disturbance in an old-growth Fagus-Abies forest reserve in Slovenia using a dendroecological approach. We extracted cores from canopy trees blown down during a recent windthrow event and identified growth releases in the tree-ring series using boundary-line release criteria to infer past disturbances. A total of 216 release events were identified from 88 trees. Between 1790 and 1990, moderate, asynchronous release events were present in nearly every decade of the disturbance chronology, suggesting a history of frequent, low severity disturbance. However, there were also peaks in the chronology corresponding to synchronous release events in a large proportion of the trees, suggesting that less frequent, intermediate severity disturbance events played an important role in forest development. These events are likely caused from wind damage associated with local thunderstorms, which seem to occur at intervals between 20-80 years on the study site. Thus, in addition to the small-scale gap phase processes operating in the forest, the results indicate that periodic intermediate severity disturbance events are an important component of the disturbance regime in mountain forests of Central Europe. dendroecology / forest dynamics / Fagus sylvatica / Abies alba / forest development Résumé -Reconstruction dendroécologique des perturbations dans une hêtraie sapinière ancienne en Slovénie. Le faible nombre de forêts anciennes suffisamment étendues rend difficile la quantification des régimes de perturbation en Europe centrale. L'objectif de cette étude est de reconstituer l'histoire de ces perturbations dans une hêtraie-sapinière ancienne mise en réserve en Slovénie en utilisant une approche dendroécologique. Des carottes ont été extraites du tronc d'arbres dominants renversés lors d'un récent chablis. Les séries temporelles de cernes ont été analysées pour identifier des périodes de relâchement de contraintes de croissance et pour en déduire l'intensité des perturbations passées. Un total de 216 évènements de relâchement de contrainte a été identifié pour 88 arbres. Entre 1790 et 1990, des évènements d'intensité modérée et asynchrones ont été détectés dans les séries chronologiques au cours de pratiquement toutes les décennies. Cela suggère une fréquence élevée de perturbations de faible intensité. Cependant, des pics d'enregistrement d'évènements synchrones ont été identifiés dans la chronologie dans une proportion importante d'arbres. Cela suggère que des perturbations de sévérité intermédiaire ont joué un rôle important dans le développement de la forêt, malgré leur plus faible fréquence. Ces évènements ont probablement été causés par des chablis provoqués par des orages locaux violents, qui semblent se produire à des intervalles de 20 à 80 ans sur le site d'étude. Les résultats montrent ainsi qu'en sus de perturbations locales de faible intensité conduisant à la formation de petites trouées, les perturbations périodiques de sévérité intermédiaire constituent une composante importante du régime de perturbations dans les montagnes en Europe centrale. dendroécologie / dynamique forestière / Fagus sylvatica / Abies alba / développement forestier
Canadian Journal of Forest Research, 2008
Montane forests in the northeastern United States have experienced symptoms of declining vigor, such as branch dieback and increased mortality, over the last half-century. These declines have been attributed to the cumulative impacts of acid deposition, but reconstructing these declines from tree-ring records has proved difficult because of confounding factors that affect low-frequency growth patterns, including climate and natural growth trajectories following disturbance. We obtained tree-ring records of red spruce (Picea rubens Sarg.) and sugar maple (Acer saccharum L.) from three elevations on Bolton Mountain, Vermont, and applied traditional dendroclimatological analyses that revealed a profound declining growth-climate correlation since ca. 1970 for sugar maple but much less so for red spruce. We then applied a new multifaceted statistical approach that conservatively detrends tree-ring records by minimizing the influences of tree size, age, and canopy disturbances on radial growth. In contrast with the traditional analysis, this approach yielded chronologies that were consistently correlated with climate but with important exceptions. Low-elevation sugar maple suffered distinct episodes of slow growth, likely because of insect defoliators, and also a progressive decline since ca. 1988. Red spruce experienced subdecadal episodes of decline that may be related to freeze-thaw events known to injure foliage but showed no evidence of a progressive decline. This analysis was supported by a forest plot resurvey that indicated major declines in these species.
Canadian Journal of Forest Research, 2012
In many northern forest ecosystems, the postfire transition from a closed-crown forest to open woodland is often observed but poorly understood. This paper looks at the effect of interactions between surficial deposit, climate, and fire cycle on postfire forest recovery within a large territory (190 000 km 2 ) of the boreal forest of eastern Canada. Postfire recovery was estimated using the time elapsed to move from the burnt stage to the regenerated stage and the young forest stage. The main objective was to determine if forests situated in dry regions (characterized by a high proportion of dry coarse surficial deposits, low precipitation, and short fire cycle) tend to reestablish more slowly after fire, obtaining a more open stand compared with wetter regions characterized by a longer fire cycle. To identify the best explanatory model for postfire recovery, multinomial logistic regressions with the Akaike information criterion were conducted using a combination of physicoclimatic factors. Our best model suggests that the most significant predictors of postfire recovery are time since fire (c 2 = 1370.06), surficial deposit type (c 2 = 651.95), the Canadian Drought Code (c 2 = 247.75), and the growing season precipitation (c 2 = 102.80). Fast recovery and dense forest regeneration are associated with subhydric till deposits only in the regions characterized by a long fire cycle (>500 years). Conversely, slow regeneration conducive to a sparse young forest was usually associated with regions characterized by a short fire cycle (<200 years) underlain by dry coarse deposits such as juxtaglacial but also mesic deposits in some cases. Our results also show that slow recovery and reduced forest regeneration are most likely to occur following fires that occurred in dry years, regardless of the deposit type and region.
Oecologia, 2002
We examined the size, age, and spatial structure of trees in an old Engelmann spruce (Picea engelmannii)-subalpine fir (Abies lasiocarpa) forest based on four stem-mapped, 0.25 ha plots. Dendrochronological techniques were used on basal discs of 1,190 trees to reconstruct age and growth pattern, including dates of rapid growth increases. There were no obvious age cohorts or other evidence of past major disturbance. The abundance of both subalpine fir and spruce decreased rapidly with age, especially beyond the ages of 150 years. Very old trees were present, but rare. The best evidence from treering width patterns for past disturbance was a period of release 100 years ago. However, few of the released trees grew into the canopy, which suggests a disturbance of low intensity. Patch dynamics and gap processes were not pronounced in the stand. Clumping was generally weak and only present at small spatial scales (<5 m) for live trees, and largely non-existent for dead trees; mortality was spatially random in this forest. Although spruce were sparse (5.1% of trees) in the forest relative to fir, which is consistent with predictions that fir will ultimately replace spruce in the absence of disturbance, coexistence seems more likely judging from the age structure and numbers of dead trees. In contrast to almost all spruce-fir forests studied previously, the stand we examined showed no record of major disturbances. Thus this stand falls at the limit of the range of dynamics-from disturbance-structured to near steady-state-encompassed in current thinking about forest ecosystems.
2007
The first re-measurement of a long-term permanent plot study of forest dynamics started in 1992.-Ecol. Bull. 52: 19-32. Suserup Skov (19.2 ha) is an old growth temperate forest dominated by beech Fagus sylvatica, pedunculate oak Quercus robur, ash Fraxinus excelsior, wych elm Ulmus glabra, and black alder Alnus glutinosa, admixed with lime Tilia platyphyllos and sycamore maple Acer pseudoplatanus. In 1992, a complete inventory of trees exceeding 3 cm in diameter at breast height (DBH, 1.3 m above forest floor) was carried out, as a starting point to study the longterm dynamics of the forest. In 2002 a first re-inventory was carried out including all trees ≥ 29 cm DBH in the whole forest, while trees with DBH > 3 cm were remeasured in three 1 ha plots. Based on the new inventory changes in the forest structure are analyzed and discussed in relation to ecological stability and forest management. A stem-position map based on the 2002 data was made to present an overview of the changes since 1992 and also as a practical tool for future research. The following conclusions were reached from the analysis of the results of the 1992 and 2002 inventories. 1) Between 1992 and 2002 Suserup Skov has been impacted by two important disturbances: an extreme storm and the Dutch elm disease. As an ecological system, the forest has proved relatively resistant. Although some changes have occurred in the diameter distribution, the forest ecosystem has not been pushed back into an early successional stage and no decline in the standing volume occurred. 2) The forest is still undergoing changes resulting from the cessation of livestock grazing around 1807 and the subsequent gradual cessation of management. Oak is retreating from the stand, while beech is losing some terrain to ash, lime and sycamore maple after a period of extensive dominance. On the wetter ground at the lake-shore, alder is still dominant, but ash is increasing. 3) The ecological disturbance caused by the 1999-storm has interacted with and speeded up the ongoing gradual long-term successional changes predicted in 1992. A fair number of large beech trees were blown over in the storm, whilst trees in smaller diameter classes were less affected and have shown vigorous growth. Especially sycamore maple, lime and (to some degree) ash have increased in importance, being capable of filling many of the gaps created where mature beeches have fallen.