Even-aged Forest Research Articles

Circular distributions of fallen logs as an indicator of forest disturbance regimes

We present a retrospective method for studying forest disturbance regimes, and especially the role of windthrows, based on circular statistical models of directions of fallen logs. This approach was applied to fallen log data from three areas of pristine Picea abies-dominated boreal forests in northern Europe. The data consisted of 5 plots from each of the three areas, totaling 15 plots and covering an area of 24ha. The disturbance history of the plots, which varied from area to area, was known from previous detailed studies. We selected and fitted the most suitable circular model for each plot, based on goodness-of-fit and the Akaike information criterion. For uneven-aged forests, the symmetric von Mises distribution, was best fitted, while for the even-aged forest the sine-skewed wrapped Cauchy distribution was selected. The degree of concentration around the mean direction of fallen trees was strongest for the late-successional even-aged forest most exposed to windthrow, while an uneven-aged forest with drought-driven mortality had the lowest concentration and the greatest variance over the mean directions. For the third area, characterized by an uneven age structure and tree mortality driven by heart-rot fungi in old trees in interaction with wind, an intermediate between these two were derived. Our results suggested the utility of circular distributions of fallen logs and their statistical models for retrospective assessments of forest disturbance regimes.

Long-term and country scale projection of even-aged forest management: a case study for Fagus sylvatica in Croatia

Out of the 901,848 ha forests of the European beech (Fagus sylvatica L.) in Croatia, 383,473 ha are even-aged beech forests with irregular age-class structure. Potential forest management of the even-aged beech forests (including the conversion of coppice even-aged beech forests) was studied using a dynamic model system, in the context of long-term planning at the national level in Croatia. Three management policy scenarios were defined regarding the area control method, that is, planned area for annual regeneration felling was given as a function of (1) total forest area (conservative approach scenario–CAS), (2) area of stands older than 50 years (moderate approach scenario–MAS), and (3) area of stands older than 80 years (intensive approach scenario–IAS). Projections of future trends in the annual area of regeneration, age-class distribution, standing volume and annual felling, and thinning cut were obtained for each scenario. Management according to the Scenario 3 would lead to achievement of a best age-class balancing and more sustainable management in the next 50 years. The structure of the growing stock and the quality of harvested timber would also improve as a result of this approach. Intensive regeneration felling (4460 ha per year) and conversion of coppice forests (420 ha per year) is required to reach this goal.

Adaptation of a modelling strategy to predict the NPP of even-aged forest stands

The assessment of net forest production is important for both scientific and practical purposes. The current paper presents the application of a recently developed strategy to estimate the net primary productivity of an even-aged Mediterranean pine forest (Natural Park of San Rossore, Central Italy). The strategy is based on the use of two models, C-Fix and BIOME-BGC, whose outputs are combined with forest volume data in order to describe the actual status of the ecosystems examined. The accuracy of the simulation is tested against measurements of current annual increment (CAI) derived from a recent forest inventory of the Park. The results of this test indicate that the methodology must be modified to account for the even-aged nature of the study stands. The modification is performed by the analysis of dendrochronological and tree density data, which characterize the temporal volume and CAI evolution of representative forest stands. The modified methodology is capable of taking into account the effect of stand ageing and yielding nearly unbiased estimates of forest CAI.

Consequences of decreasing the number of cored trees per plot on chronology statistics and climate–growth relationships: a multispecies analysis in a temperate climate

Existing literature investigates the effect of the number of cored trees per plot (N) on chronology statistics. The present study sought to highlight (i) the effect of N on the reliability of both chronology and climate–growth relationships and (ii) its variability across five European tree species with differentiated ecophysiological patterns. Fifty-eight pure, even-aged forests were sampled across France. For each plot, dendroecological investigations were carried out using chronologies built from 28 to three trees. Chronology reliability was studied using the mean intertree correlation (rbt) and the expressed population signal (EPS), whereas the climate–growth relationships were evaluated through the bootstrapped correlation coefficients (BCC). The accuracy of the dendroecological investigations decreased with decreasing N: EPS and BCC approached zero, implying that the signal common to all trees weakened. Thus, most of the significant correlations became nonsignificant when the sample size decreased from 28 to three trees per plot. Differences were found between species. For a given sample size, the shade-intolerant species Quercus petraea and Pinus sylvestris displayed lower intertree differences in growth-index series (higher rbt) and higher EPS than the shade-tolerant species Abies alba, Fagus sylvatica, and Picea abies. These latter species also displayed a greater sensitivity to sample size decrease, with a stronger BCC weakening and a higher proportion of changes in correlation significance. The EPS threshold of 0.85 was reached for around six to 10 trees for shade-intolerant species versus 20–30 for the shade-tolerant ones and generally corresponded to a mean correlation precision of around 0.06. We finally propose a general method to estimate this precision.

Nachhaltiges Holzproduktionspotenzial im Schweizer Wald

Potential of sustainable wood production in Swiss forests In the Swiss National Forest Inventory (NFI), the data collected in the three inventories (NFI1 1983–1985, NFI2 1993–1995, NFI3 2004–2006) provide the basis not only for analysing the present state of the forest and how it has developed up to now, but also for assessing, with the help of models, how it might develop in future. The scenario model «Massimo 3», developed at the Swiss Federal Institut for Forest, Snow and Landscape Research, is an empirical and stochastic simulation model. It relies on data from the NFI and forecasts the development of the forest according to how it is managed. Six scenarios with different management regimes were defined according to the economic, silvicultural and ecological aspects considered. In three scenarios the growing stock is kept constant at the level of NFI3, but different management strategies are used (Scenario A: basis [business as usual], Scenario E: even-aged forests are transformed into uneven-aged forests, and Scenario F: near-natural percentages of conifers are promoted). In two scenarios forest management is partially abandoned for either ecological reasons (Scenario B: reservations, 10% of the forest area is left unmanaged) or for economic reasons (Scenario C: harvesting costs, 40% of the forest area is left unmanaged). Scenario D (rotation periods are shortened) was used to study the effects of augmenting the annual harvesting amount. A forecasting time period of 100 years was selected to assess the long-term effects of the scenarios. Scenarios A, D, and E show that the sustainable harvesting potential of merchantable wood lies in a relatively narrow range of 7.1 to 7.3 million m3/year, even though in Scenario D the growing stock is reduced from 360 m3/ha to 305 m3/ha. In Scenario F regeneration is systematically established with near-natural percentages of conifers, the long-term harvesting potential is slightly less: about 6.5 million m3/year of merchantable wood. If forest management is abandoned for economic reasons on as much as 40% of the forest area (Scenario C, harvesting costs), the impact on the wood reserves is very negative.

Individual tree detection based on variable and fixed window size local maxima filtering applied to IKONOS imagery for even-aged Eucalyptus plantation forests

Detection of individual trees remains a challenge for forest inventory efforts especially in homogeneous, even-aged plantation scenarios. Airborne imagery has mainly been used for detection of individual trees using local maxima filtering, as point spread function and signal-to-noise ratio are smaller than with satellite-borne imagery. This led to the development of a novel approach to local maxima filtering for tree detection in plantation forests in KwaZulu-Natal, South Africa, using satellite remote sensing imagery. Our approach is based on Gaussian smoothing for noise elimination and image classification, that is, natural break classification to determine the threshold for removing pixels of extremely bright and dark areas in the imagery. These pixels are assumed to belong to the background and hinder the search for tree peaks. A semivariogram technique was applied to determine variable window sizes for local maxima filtering within a plantation stand. A fixed window size for local maxima filtering was also applied using pre-determined tree spacing. Evaluation of the various approaches was based on aggregated assessment methods. The overall accuracy using a variable window size was 85%, root mean square error (RMSE) = 189 trees, whereas a fixed window size resulted in an accuracy of 80%, RMSE = 258 trees. The approach worked remarkably well in mature forest stands as compared to young forest stands. These results are encouraging for temperate–warm climate plantation forest companies, who deal with even-aged, broadleaf plantations and forest inventory practices that require assessment 1 year before harvesting.

Optimum forest program when the carbon sequestration service of a forest has value

This paper develops an optimum forest program for even-aged and multi-age forest management when the carbon sequestration service of a forest has value. It is shown that for even-aged forest management, the optimum rotation might be longer or shorter than when the carbon sequestration service is not considered. For multi-age forest management, it is shown that the optimum steady state is characterized by the optimum rotation for an even-aged forest. The optimum rotation is affected by how to evaluate the carbon release after harvesting, which is a central concern for the issue of “harvested wood products” in the United Nations Framework Convention on Climate Change.

Evoluzione della copertura forestale nella Foresta della Lama (Parco Nazionale delle Foreste Casentinesi) dal Piano di assestamento di Siemoni e Seeland del 1837 a oggi

Abstract: Forest estates with a long history of forest management plans are quite rare in Italy. In such cases, the analysis of historical documents combined with the use of GIS technology, can provide useful information on the evolution of forest cover and silvicultural and management techniques. Based on two unpublished documents by Karl Siemon and Anton Seeland dating back to 1837 and 1850, an archive of historical maps for the Lama Forest (Foreste Casentinesi, Monte Falterona and Campigna National Park) was created using GIS techniques. This archive outlines the evolution of the Lama Forest over the last 170 years. Particular attention was given to silver fir plantations, which have strongly characterized silviculture and local economics in the Foreste Casentinesi area. The results of our analysis show that changes in different historical periods have been caused both by silvicultural interventions prescribed by the management plans and by external causes such as changes in forest property or war periods, which have markedly influenced forest area and stand characteristics. Furthermore, our analysis confirms that the work of Karl Siemon and Anton Seeland, carried out between 1835 and 1837, is the oldest forest management plan for an Italian forest. It is interesting to note that the aim of the plan, i.e., a regulated (or “normal”) even-aged forest, and the way the plan was laid out, typical of classic forest management originated in Germany at the end of the XVIIIth century, served as model for the forest management plans drawn out by the Florence Forestry School almost until the end of the XXth century.

A tree-growth model to optimize silviculture

In this paper, we present the description of a simplified model of the dynamic of a monospecific even-aged forest. The model studied is a tree-growth model based on a system of two ordinary differential equations concerning the tree basal area and the number of trees. The analytical study of this model permits us to predict the behavior of the system solutions. We try to highlight the influence of economic parameters and growth parameters on the system solutions, in the framework of the optimization of silviculture.

Changes in humus forms and soil N pathways along a 130-year-old pure beech forest chronosequence

We investigated changes in humus morphology and soil potential net N mineralization pathways along a pure beech even-aged forest chronosequence, composed of four stages (15, 65, 95, and 130 years old) on Luvisol. To quantify the respective contributions of bacteria and fungi to soil N processes, we used acetylene and a fungicide (captan). We analyzed the data in order to highlight correlation patterns between soil N cycling and humus morphology. We sampled the OL layer (unmodified leaf fragments), the FH layer (mixture of coarse plant fragments with fine organic matter) and the A layer. Within the organic layers, N mineralization was two times higher in mature stands than in younger ones. Nitrification decreased sharply within the OL and the A layers along the chronosequence but was stable in the FH layer. The relative contributions to ammonification by bacteria and fungi remained constant along the chronosequence in both the OL and the A layers. In the FH layer, fungal contribution to ammonium production increased along the chronosequence. Nitrification was mainly autotrophic. We observed strong correlations between morphological and soil N variables. Our results suggest that pure beech forest maturation promotes soil ammonium production; its efficiency is probably controlled by fungal activity. They also suggest the potential use of selected macro-morphological variables as indicators of both soil N mineralization rates and the nature of N pathways.

Hipsometric relationship modeling using data sampled in tree scaling and inventory plots

This work evaluated eight hypsometric models to represent tree height-diameter relationship, using data obtained from the scaling of 118 trees and 25 inventory plots. Residue graphic analysis and percent deviation mean criteria, qui-square test precision, residual standard error between real and estimated heights and the graybill f test were adopted. The identity of the hypsometric models was also verified by applying the F(Ho) test on the plot data grouped to the scaling data. It was concluded that better accuracy can be obtained by using the model prodan, with h and d1,3 data measured in 10 trees by plots grouped into these scaling data measurements of even-aged forest stands.

Perdas de solo e água por erosão hídrica em floresta equiânea em Um Latossolo Vermelho-Amarelo

Water erosion contributes significantly in soil degradation, and vegetation cover is one of the important factors that influence the intensity of this erosion on the soil. To this end, this study aimed to evaluate soil and water losses by water erosion under natural rainfall in eucalyptus even-aged forest, relating them to limit-values of tolerance in a Red-Yellow Dystrophic Latosol. A standard plot was installed within the forest. From this collection, soil and water collections were carried out, after each erosive rainfall. The estimated soil loss presented and average value of 0.2566 ton ha-1 in the study period (six months). The estimated water loss was of 8.36 mm in the study period. The low values show the sustainability of the studied forest, within the context of erosion, when compared to the soil loss tolerance limit, and to other research findings in native forest and bare soil.

Avifauna e struttura nella pineta Ragabo (Linguaglossa, CT)

Structural analysis of a forest ecosystem may allow to assess the spatial heterogeneity and temporal dynamics of the vegetation, the factors related to tree recruitment and the dynamics of canopy gaps, as well as to define the niche of wildlife. The study of the ecosystem response to different silvicultural treatments may also provide hints of the bio-ecological functionality and forest ecosystem stability. In this work, we analyzed the most representative structural types within the Ragabo pine wood (monoplane forest and multilayered forest), and their relationships with the specific composition of the local breeding bird community. The results show the strong sensitivity of birds to environmental changes and their large selectivity in the choice of habitats. In particular uneven-aged forests remain particularly suited to maintain over time a bird community richer and more stable than the even-aged forests.

Short term response of small mammals and forest birds to silvicultural practices differing in tree retention in irregular boreal forests

The effects of logging on wildlife have been evaluated mainly in landscapes dominated by even-aged forest stands, leaving the impacts of harvesting on wildlife in irregularly structured stands less documented. We assessed the response of small mammals and birds to 4 silvicultural treatments with different levels of tree retention (from < 10% to 73%) in old-growth boreal forests of eastern Canada, where approximately 70% of stands have irregular structure. The experimental design controlled for local variation in the abundance of forest birds and small mammals by pairing each experimental harvested stand with an uncut stand. We found that species richness of small mammals and birds did not vary according to tree retention. Moss cover and vertical cover influenced small mammal community composition, whereas forest bird assemblages responded to conifer basal area, vertical cover, and snag availability. Species associated with silvicultural practices entailing retention levels > 55% included those that prefer closed canopy, such as the brown creeper (Certhia americana), ruby-crowned kinglet (Regulus calendula), and red-backed vole (Myodes gapperi). Our study demonstrates that silvicultural practices with retention levels > 55% are the most suitable for mitigating the impact of logging on animal communities in old-growth irregularly structured stands.

A stand dynamic model for red pine plantations with different initial densities

A stand dynamic model was developed to predict the growth response in even-aged forest plantations of different initial planting densities. The model is based on the integration of three subcomponents: height growth, self-thinning, and diameter increment. The integrated model uses the height of dominant trees to simulate stand response to site quality and internal growth potential. An extended self-thinning submodel is used to simulate mortality in stands due to crowding and inter-tree competition. A diameter increment submodel is used to link the height growth and self-thinning submodels. The height growth submodel is based on an application of the “Pipe Model” theory. The three-parameter self-thinning submodel is developed from an extended self-thinning law that captures self-thinning in stands before they attain full stocking. The diameter increment model is based on the assumption that diameter increment is related to height growth and available growing space described by stand density. The integrated model is applied to data collected from a 45-year-old red pine (Pinus resinosa Ait.) plantation subsectioned with different initial planting densities. For the data used, only two parameters were required to capture 99% of measured variation in height growth. Additional data from sites with different planting intensities are required to formulate a more generalized height growth model. The slope of the linear self-thinning limit for red pine is approximately −1.5. Model predictions are consistent with field measurements.

The plural of anecdote is not data: Rigorously testing a boreal forest chronosequence

"Forests appear stable because the ecologists who study them die." The chronosequence, with its space-for-time substitution, is a widely-employed workaround for a difficult problem: many interesting ecosystem processes occur at much longer time scales than researchers can afford to spend studying them. But their use is problematic, particularly for vegetation succession but also for biogeochemical cycling: having sites of different ages is only a necessary, and not a sufficient, condition. How do we test the validity and representativeness of a chronosequence, particularly given ecosystem variability in time and space? Here we use data from an intensively-studied group of stands in northern Manitoba, Canada, to assess the spatial and temporal variability of carbon fluxes in this boreal forest, and examine the suitability of a chronosequence study design for making larger-scale (in space and time) generalizations. This ecosystem is well suited for examining this question, being floristically simple, frequently disturbed by wildfire, and thus generally composed of even-aged forests of known origin. A number of techniques can be brought to bear: re-visiting chronosequence sites after a significant period converts single-point measurements into data vectors; measurements that integrate fluxes over longer time periods (e.g., tree ring cores) provide a similar capability, extending our observation window; replication of the chronosequence stands extends the spatial domain; process modeling may indicate site selection errors. We can also examine data at local, regional and global scales to ask, for any particular pool or flux, if replication in time or space is more useful. For example, global soil respiration studies indicate that spatial and interannual variability are of roughly equal magnitude; in contrast, boreal tree ring data suggest that carbon sequestration is more variable year-to-year than it is site-to-site, after controlling for forest age and soil drainage. Different sampling strategies may thus be appropriate for each flux; historical records such as databases of wildfire occurrence also help constrain this problem. We conclude that while unreplicated chronosequences provide anecdotes, not data, extending measurements in space and time lets us quantifiably assess their performance.

The plural of anecdote is not data: Rigorously testing a boreal forest chronosequence

Abstract"Forests appear stable because the ecologists who study them die." The chronosequence, with its space-for-time substitution, is a widely-employed workaround for a difficult problem: many interesting ecosystem processes occur at much longer time scales than researchers can afford to spend studying them. But their use is problematic, particularly for vegetation succession but also for biogeochemical cycling: having sites of different ages is only a necessary, and not a sufficient, condition. How do we test the validity and representativeness of a chronosequence, particularly given ecosystem variability in time and space? Here we use data from an intensively-studied group of stands in northern Manitoba, Canada, to assess the spatial and temporal variability of carbon fluxes in this boreal forest, and examine the suitability of a chronosequence study design for making larger-scale (in space and time) generalizations. This ecosystem is well suited for examining this question, being floristically simple, frequently disturbed by wildfire, and thus generally composed of even-aged forests of known origin. A number of techniques can be brought to bear: re-visiting chronosequence sites after a significant period converts single-point measurements into data vectors; measurements that integrate fluxes over longer time periods (e.g., tree ring cores) provide a similar capability, extending our observation window; replication of the chronosequence stands extends the spatial domain; process modeling may indicate site selection errors. We can also examine data at local, regional and global scales to ask, for any particular pool or flux, if replication in time or space is more useful. For example, global soil respiration studies indicate that spatial and interannual variability are of roughly equal magnitude; in contrast, boreal tree ring data suggest that carbon sequestration is more variable year-to-year than it is site-to-site, after controlling for forest age and soil drainage. Different sampling strategies may thus be appropriate for each flux; historical records such as databases of wildfire occurrence also help constrain this problem. We conclude that while unreplicated chronosequences provide anecdotes, not data, extending measurements in space and time lets us quantifiably assess their performance.

Wie erfolgreich war das Dauerwaldkonzept bislang: eine historische Analyse | Continuous cover forests – a success? A historical analysis

Since the beginning of the 19th century, differe nt methods of natural regeneration and single-tree orientated systems of management existed in southern Germany and in Switzerland. In the early 1920s, Alfred Möller from Eberswalde created the term “continuous cover forest” (perpetual forest, Dauerwald), which was introduced in the practice of forestry and was controversially discussed by forestry experts. Considerably differing opinions on how to manage this type of forest and on its economical and ecological yield (output) were expressed. During the 1930s, the maxim of perpetual forests temporarily reached the status of a forest economic doctrine in the state forests but it was finally suspended because of additional need of timber in times of war and striving after economic independence. In the aftermath of war, renowned experts of forest science and practice in West and East Germany sought economical concepts of managing the overexploited forests in order to re-establish profit-yielding forests. These efforts led to the founding of the ANW, a forestry panel which turned down the principle of even-aged forests while stressing the importance of sustainability. This can be seen as an equivalent of the traditional principle of continuous cover forests during the 1920s and 1930s. However, after an enthusiastic start, the ANW sank almost into insignificance until the 1980s when the increasing perception of ecology loss re-directed attention towards its ideas. The demands from the ecologically orientated part of our society brought the idea of continuous forests back into current and future discussions in Germany and in other European countries.

Nitrogen dynamics across silvicultural canopy gaps in young forests of western Oregon

Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. The effect of gap creation on available nitrogen (N) is of concern to managers because N is often a limiting nutrient in Pacific Northwest forests. We investigated patterns of N availability in the forest floor and upper mineral soil (0–10 cm) across 6–8-year-old silvicultural canopy gaps in three 50–70-year-old Douglas-fir forests spanning a wide range of soil N capital in the Coast Range and Cascade Mountains of western Oregon. We used extractable ammonium (NH 4 +) and nitrate (NO 3 −) pools, net N mineralization and nitrification rates, and NH 4 + and NO 3 − ion exchange resin (IER) concentrations to quantify N availability along north-south transects run through the centers of 0.4 and 0.1 ha gaps. In addition, we measured several factors known to influence N availability, including litterfall, moisture, temperature, and decomposition rates. In general, gap-forest differences in N availability were more pronounced in the mineral soil than in the forest floor. Mineral soil extractable NH 4 + and NO 3 − pools, net N mineralization and nitrification rates, and NH 4 + and NO 3 − IER concentrations were all significantly elevated in gaps relative to adjacent forest, and in several cases exhibited significantly greater spatial variability in gaps than forest. Nitrogen availability along the edges of gaps more often resembled levels in the adjacent forest than in gap centers. For the majority of response variables, there were no significant differences between northern and southern transect positions, nor between 0.4 and 0.1 ha gaps. Forest floor and mineral soil gravimetric percent moisture and temperature showed few differences along transects, while litterfall carbon (C) inputs and litterfall C:N ratios in gaps were significantly lower than in the adjacent forest. Reciprocal transfer incubations of mineral soil samples between gap and forest positions revealed that soil originating from gaps had greater net nitrification rates than forest samples, regardless of incubation environment. Overall, our results suggest that increased N availability in 6–8-year-old silvicultural gaps in young western Oregon forests may be due more to the quality and quantity of litterfall inputs resulting from early-seral species colonizing gaps than by changes in temperature and moisture conditions caused by gap creation.

Effects of planting spacing and site quality on 25-year growth and mortality relationships of Douglas-fir ( Pseudotsuga menziesii var. menziesii)

Growth and mortality of coast Douglas-fir ( Pseudotsuga menziesii var. menziesii) were studied for 25 years after planting seedlings at 1–6-m spacings on a site of moderate quality in the western Cascade Mountains of Washington. Responses were compared to those from two other studies representing high and low site qualities. Third-year height did not differ among spacings ( P = 0.80), providing no evidence that close spacing stimulated early growth. Piecewise regression identified the onset of competition-induced mortality when stand density index (SDI [Reineke, L.H. 1933. Perfecting a stand density index for even-aged forests. Journal of Agricultural Research 46, 627–638]) exceeded 52% (S.E. = 4.6) of the species’ maximum or when average crown ratio (CR) declined below 52% (S.E. = 0.9). For a range of SDI values, CR averaged 2–7% points greater at the high-quality site than at the moderate-quality site. In a regression analysis of combined data from the moderate- and high-quality sites, relative values of average stem diameter and stand volume (% of maximum values observed per site) 23–25 years after planting increased and decreased with planting spacing, respectively ( R 2 = 0.97 and 0.91, respectively). Intersection of these relationships at 3-m spacing indicated a point of equivalent relative development of tree size and stand yield. For a range of site qualities, stands planted at 3-m spacing: (1) maintained tree vigor (CR ≥ 50%) and stability (average height:dbh ratio <90), (2) experienced little or no competition-induced mortality through age 25 years, and (3) allocated 25-year growth equitably to development of tree size and stand yield, thereby providing a desirable starting point for subsequent management.