Forests dominated by Douglas‐fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old‐growth forest conservation. Despite the ...attention to their old‐growth characteristics, a tendency remains to view their disturbance ecology in relatively simple terms, emphasizing infrequent, stand‐replacing (SR) fire and an associated linear pathway toward development of those old‐growth characteristics. This study uses forest stand‐ and age‐structure data from 124 stands in the central western Cascades of Oregon to construct a conceptual model of stand development under the mixed‐severity fire regime that has operated extensively in this region. Hierarchical clustering of variables describing the age distributions of shade‐intolerant and shade‐tolerant species identified six groups, representing different influences of fire frequency and severity on stand development. Douglas‐fir trees >400 years old were found in 84% of stands, yet only 18% of these stands (15% overall) lack evidence of fire since the establishment of these old trees, whereas 73% of all stands show evidence of at least one non‐stand‐replacing (NSR) fire. Differences in fire frequency and severity have contributed to multiple development pathways and associated variation in contemporary stand structure and the successional roles of the major tree species. Shade‐intolerant species form a single cohort following SR fire, or up to four cohorts per stand in response to recurring NSR fires that left living trees at densities up to 45 trees/ha. Where the surviving trees persist at densities of 60–65 trees/ha, the postfire cohort is composed only of shade‐tolerant species. This study reveals that fire history and the development of old‐growth forests in this region are more complex than characterized in current stand‐development models, with important implications for maintaining existing old‐growth forests and restoring stands subject to timber management.
Tropical deforestation is a key contributor to species extinction and climate change, yet the extent of tropical forests and their rate of destruction and degradation through fragmentation remain ...poorly known. Madagascar's forests are among the most biologically rich and unique in the world but, in spite of longstanding concern about their destruction, past estimates of forest cover and deforestation have varied widely. Analysis of aerial photographs (c. 1953) and Landsat images (c. 1973, c. 1990 and c. 2000) indicates that forest cover decreased by almost 40% from the 1950s to c. 2000, with a reduction in ‘core forest’ > 1 km from a non-forest edge of almost 80%. This forest destruction and degradation threaten thousands of species with extinction. Country-wide coverage of high-resolution validated forest cover and deforestation data enables the precise monitoring of trends in habitat extent and fragmentation critical for assessment of species' conservation status.
The risks posed by forest destruction throughout the world are highly significant for all. Not only are forests a critical source of timber and non-timber forest products, but they provide ...environmental services that are the basis of life on Earth. However, only rarely do beneficiaries pay for the goods and services they experience, and there are severe consequences as a result for the poor and for the forests themselves. It has proved difficult to translate the theory of market-based approaches into practice. Based on extensive research and case studies of biodiversity conservation, watershed protected and carbon sequestration, this book demonstrates how payment systems can be established in practice, their effectiveness and their implications for the poor.
Moderate-severity disturbances appear to be common throughout much of North America, but they have received relatively little detailed study compared to catastrophic disturbances and small gap ...dynamics. In this study, we examined the immediate impact of moderate-intensity wind storms on stand structure, opening sizes, and light regimes in three hemlock-hardwood forests of northeastern Wisconsin. These were compared to three stands managed by single-tree and group selection, the predominant forest management system for northern hardwoods in the region. Wind storms removed an average of 41% of the stand basal area, compared to 27% removed by uneven-aged harvests, but both disturbances removed trees from a wide range of size classes. The removal of nearly half of the large trees by wind in two old-growth stands caused partial retrogression to mature forest structure, which has been hypothesized to be a major disturbance pathway in the region. Wind storms resulted in residual stand conditions that were much more heterogeneous than in managed stands. Gap sizes ranged from less than 10 m² up to 5000 m² in wind-disturbed stands, whereas the largest opening observed in managed stands was only 200 m² . Wind-disturbed stands had, on average, double the available solar radiation at the forest floor compared to managed stands. Solar radiation levels were also more heterogeneous in wind-disturbed stands, with six times more variability at small scales (0.1225 ha) and 15 times more variability at the whole-stand level. Modification of uneven-aged management regimes to include occasional harvests of variable intensity and spatial pattern may help avoid the decline in species diversity that tends to occur after many decades of conventional uneven-aged management. At the same time, a multi-cohort system with these properties would retain a high degree of average crown cover, promote structural heterogeneity typical of old-growth forests, and maintain dominance by late-successional species.
This volume is devoted to the derivation and application of simplified bioclimatic boundary conditions at vegetated land surfaces using natural selection of vegetation characteristics driven by ...productivity maximization. It investigates the internal control of forest growth by the vertical fluxes of light, CO2, water vapor, and heat within the canopy, as well as the external control offered by the balances of thermal energy and water. Through these means it seeks to determine how the physical characteristics and productivity of forest communities are related to the climates and soils in which they are found. Ecohydrology bridges the fields of hydrology and ecology and proposes new unifying principles derived from the concept of natural selection. It also has potential application in determining the response of vegetation to slow variations in climate and will provide fascinating reading for graduate-level students and research scientists working in ecohydrology, hydroclimatology, forest ecology, and surface water hydrology.
Background: In forests subject to stand-replacing disturbances, conventional models of succession typically overlook early-seral stages as a simple re-organization/establishment period. These models ...treat structural development in essentially 'relay floristic' terms, with structural complexity (three-dimensional heterogeneity) developing primarily in old-growth stages, only after a closedcanopy 'self-thinning' phase and subsequent canopy gap formation. However, is it possible that early-successional forests can sometimes exhibit spatial complexity similar to that in old-growth forests — i.e. akin to an 'initial floristic' model of structural development? Hypothesis: Based on empirical observations, we present a hypothesis regarding an important alternative pathway in which protracted or sparse forest establishment and interspecific competition thin out tree densities early on — thereby precluding overstorey canopy closure or a traditionally defined self-thinning phase. Although historically viewed as an impediment to stand development, we suggest this process may actually advance certain forms of structural complexity. These young stands can exhibit qualities typically attributed only to old forests, including: (1) canopy gaps associated with clumped and widely spaced tree stems; (2) vertically heterogeneous canopies including under- and midstories, albeit lower stature; (3) co-existence of shade-tolerant and intolerant species; and (4) abundant dead wood. Moreover, some of these qualities may persist through succession, meaning that a significant portion of eventual old-growth spatial pattern may already be determined in this early stage. Implications: The relative frequency of this open-canopy pathway, and the degree to which precocious complexity supports functional complexity analogous to that of old forests, are largely unknown due to the paucity of naturally regenerating forests in many regions. Nevertheless, recognition of this potential is important for the understanding and management of early-successional forests.
The even-aged northern hardwood forests of the Upper Great Lakes Region are undergoing an ecological transition during which structural and biotic complexity is increasing. Early-successional aspen (
...Populus
spp.) and birch (
Betula papyrifera
) are senescing at an accelerating rate and are being replaced by middle-successional species including northern red oak (
Quercus rubra
), red maple (
Acer rubrum
), and white pine (
Pinus strobus
). Canopy structural complexity may increase due to forest age, canopy disturbances, and changing species diversity. More structurally complex canopies may enhance carbon (C) sequestration in old forests. We hypothesize that these biotic and structural alterations will result in increased structural complexity of the maturing canopy with implications for forest C uptake.
At the University of Michigan Biological Station (UMBS), we combined a decade of observations of net primary productivity (NPP), leaf area index (LAI), site index, canopy tree-species diversity, and stand age with canopy structure measurements made with portable canopy lidar (PCL) in 30 forested plots. We then evaluated the relative impact of stand characteristics on productivity through succession using data collected over a nine-year period. We found that effects of canopy structural complexity on wood NPP (NPP
W
) were similar in magnitude to the effects of total leaf area and site quality. Furthermore, our results suggest that the effect of stand age on NPP
W
is mediated primarily through its effect on canopy structural complexity. Stand-level diversity of canopy-tree species was not significantly related to either canopy structure or NPP
W
. We conclude that increasing canopy structural complexity provides a mechanism for the potential maintenance of productivity in aging forests.
Climate change induces multiple abiotic and biotic risks to forests and forestry. Risks in different spatial and temporal scales must be considered to ensure preconditions for sustainable ...multifunctional management of forests for different ecosystem services. For this purpose, the present review article summarizes the most recent findings on major abiotic and biotic risks to boreal forests in Finland under the current and changing climate, with the focus on windstorms, heavy snow loading, drought and forest fires and major insect pests and pathogens of trees. In general, the forest growth is projected to increase mainly in northern Finland. In the south, the growing conditions may become suboptimal, particularly for Norway spruce. Although the wind climate does not change remarkably, wind damage risk will increase especially in the south, because of the shortening of the soil frost period. The risk of snow damage is anticipated to increase in the north and decrease in the south. Increasing drought in summer will boost the risk of large‐scale forest fires. Also, the warmer climate increases the risk of bark beetle outbreaks and the wood decay by Heterobasidion root rot in coniferous forests. The probability of detrimental cascading events, such as those caused by a large‐scale wind damage followed by a widespread bark beetle outbreak, will increase remarkably in the future. Therefore, the simultaneous consideration of the biotic and abiotic risks is essential.
In Finland, projected climate change acts to increase forest growth by the mid‐21st century, particularly in the northern parts of the country. Nonetheless, in the south, the growing conditions may become suboptimal for Norway spruce due to drought and excessively high temperatures. Biotic damages, mainly caused by Spruce bark beetles and Heterobasidions, are anticipated to increase in southern Finland. Abiotic disturbances due to windstorms, drought and forest fires will be exacerbated especially in the south with snow damages in the north. Climate change likewise increases detrimental cascading events, for example, large‐scale wind damages followed by a widespread bark beetle outbreak.
Low‐productivity forests are often the last remaining pristine forests in managed forest landscapes and typically overrepresented among protected forests. However, the provisioning of individual and ...multiple ecosystem services (ES‐multifunctionality) by these forests remains poorly assessed, making it difficult to evaluate their importance in forest conservation and management.
Here, using nationwide data on ES from over 2,000 forest plots, we test whether levels of ES‐multifunctionality and individual ES differ between low‐productivity forested mires and rocky outcrops in relation to the levels of productive forests, and as a function of forest age, tree species richness and climate. We defined ES‐multifunctionality using different threshold values of the maximum levels (low, medium and high) and weighted these according to land‐use objectives (equal weight of all services, greater weight to cultural and supporting ES or greater weight to production).
We show that the ES‐multifunctionality of forested mires is consistently lower than those of productive forests. However, the ES‐multifunctionality increased with forest age in forested mires but not in productive forests. The ES‐multifunctionality of forested rocky outcrops, on the other hand, was higher or equivalent to that of productive forests under equal weight and supporting land‐use objectives, respectively. Our findings highlight that forested rocky outcrops can supply multiple ES, especially older forested stands with mixtures of coniferous and deciduous trees. Generally, we found no evidence for strong trade‐offs between the ES studied and our results highlight the importance of forest age for increasing the ES‐multifunctionality of low‐productivity forests.
Synthesis and applications. Low‐productivity forests should not be exempt of forestry or protected purely based on low productivity or low land‐use conflict if the goal is to conserve multiple ecosystem services (ES). Inclusion grounds for protecting low‐productivity forests should instead carefully consider the site type (dry vs. wet), forest age and tree species richness. To maintain higher ES‐multifunctionality in low‐productivity forests, older or deciduous trees should also not be harvested. This will require changes in current conservation or management policies of low‐productivity forests of some countries.
Svensk sammanfattning
Skogar med låg produktivitet (impediment) är ofta de sista återstående orörda skogarna i det brukade skogslandskapet och överrepresenterade bland skyddade skogar. Vilka enskilda ekosystemtjänster (ET) och sammanvägda ekosystemtjänster (ET‐multifunktionalitet) som tillhandahålls av dessa skogar är dåligt undersökt, vilket gör det svårt att utvärdera deras betydelse för skoglig naturvård.
Här använder vi rikstäckande data om ET från över 2000 skogliga provytor för att testa om nivåerna av ET‐multifunktionalitet och enskilda ET skiljer sig mellan lågproduktiva skogliga myrimpediment och bergimpediment i förhållande till produktiva skogar, och som en funktion av skogens ålder, antalet trädarter och klimat. Vi definierade ET‐multifunktionalitet med hjälp av olika tröskelvärden för maximala nivåer (låga, medelhöga och höga) och viktade dessa enligt tre olika scenarier för markanvändning (lika vikt för alla tjänster, större vikt till kulturella och stödjande tjänster, eller större vikt för försörjande produktionsinriktade tjänster).
Resultaten visar att ET‐multifunktionaliteten hos skogliga myrimpediment var konsekvent lägre än för produktiva skogar. ET‐multifunktionaliteten ökade emellertid med skogens ålder hos myrimpediment, men inte på motsvarande sätt i de produktiva skogarna. ET‐multifunktionaliteten för de skogliga bergimpedimenten var högre eller motsvarande den för produktiva skogar när alla ET viktades lika eller när stödjande och kulturella tjänster viktades upp. Våra resultat visar att skogliga bergimpediment kan förse flera ET, särskilt äldre bergimpediment med en blandning av barr‐ och lövträd. Generellt sett hittade vi inga bevis för starka avvägningar (konflikter eller synergier) mellan de studerade ET och våra resultat belyser vikten av skogens ålder för att öka ET‐multifunktionaliteten i lågproduktiva skogar.
Syntes och tillämpningar. Skogar med låg produktivitet (impediment) bör inte undantas från skogsbruk eller skyddas enbart baserat på låg produktivitet eller låg markanvändningskonflikt om målet är att bevara flera ekosystemtjänster (ET). En grund för att skydda lågproduktiva skogar bör istället noga överväga markförhållanden (berg kontra myr), skogens ålder och antalet trädslag. För att upprätthålla högre ET‐multifunktionalitet i skogar med låg produktivitet bör äldre träd och lövträd inte avverkas. Detta kräver förändringar i nuvarande skötsel och policy för skogliga impediment i vissa länder.
Low‐productivity forests should not be exempt of forestry or protected purely based on low productivity or low land‐use conflict if the goal is to conserve multiple ecosystem services (ES). Inclusion grounds for protecting low‐productivity forests should instead carefully consider the site type (dry vs. wet), forest age and tree species richness. To maintain higher ES‐multifunctionality in low‐productivity forests, older or deciduous trees should also not be harvested. This will require changes in current conservation or management policies of low‐productivity forests of some countries.
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