Patterns Of Forest Vegetation Research Articles

Response of soil microorganisms to soil fertility in the process of vegetation rehabilitation of degraded Pinus massoniana forest

AbstractThe rehabilitation of diverse and three‐dimensional forest vegetation patterns is crucial for preventing forest degradation and improving soil fertility. However, the relationship between soil microbial community and soil fertility was not clear. To accurately assess the capability of vegetation restoration measures on the real impact on degraded soil ecosystems. We selected three vegetation rehabilitation models of degraded Pinus massoniana forests in typical soil erosion areas in China as the research objects, with untreated bare land as the control. All three vegetation construction patterns increased the abundance and diversity of soil bacteria and fungi, thereby enhancing the stability of the soil ecosystem. Additionally, the vegetation rehabilitation models also altered the community structure of soil bacteria and fungi in the degraded P. massoniana forests. The pH and soil fertility index (IFI) were the main factors leading to variations in the community structure of the soil bacteria and fungi. Among them, the grass‐planting model showed a significantly greater improvement in the soil fertility of degraded P. massoniana forests than the shrub‐planting and arbor‐planting models. Furthermore, Ascomycota, Basidiomycota, and Glomeromycota exhibited the most significant response to IFI, indicating their potential as indicator microorganisms for soil fertility changes. The improvement in soil fertility in degraded P. massoniana forests was influenced primarily by the increase in urease activity (S‐UE) according to the vegetation rehabilitation models (84.20%, p = 0.000). In conclusion, the grass‐planting system effectively improved the soil ecosystem quality of degraded P. massoniana forests in southern erosion‐prone areas of China and was suitable for further application.

Frequent and strong cold-air pooling drives temperate forest composition.

Cold-air pooling is an important topoclimatic process that creates temperature inversions with the coldest air at the lowest elevations. Incomplete understanding of sub-canopy spatiotemporal cold-air pooling dynamics and associated ecological impacts hinders predictions and conservation actions related to climate change and cold-dependent species and functions. To determine if and how cold-air pooling influences forest composition, we characterized the frequency, strength, and temporal dynamics of cold-air pooling in the sub-canopy at local to regional scales in New England, USA. We established a network of 48 plots along elevational transects and continuously measured sub-canopy air temperatures for 6-10 months (depending on site). We then estimated overstory and understory community temperature preferences by surveying tree composition in each plot and combining these data with known species temperature preferences. We found that cold-air pooling was frequent (19-43% seasonal occurrences) and that sites with the most frequent inversions displayed inverted forest composition patterns across slopes with more cold-adapted species, namely conifers, at low instead of high elevations. We also observed both local and regional variability in cold-air pooling dynamics, revealing that while cold-air pooling is common, it is also spatially complex. Our study, which uniquely focused on broad spatial and temporal scales, has revealed some rarely reported cold-air pooling dynamics. For instance, we discovered frequent and strong temperature inversions that occurred across seasons and in some locations were most frequent during the daytime, likely affecting forest composition. Together, our results show that cold-air pooling is a fundamental ecological process that requires integration into modeling efforts predicting future forest vegetation patterns under climate change, as well as greater consideration for conservation strategies identifying potential climate refugia for cold-adapted species.

Reconstructing historical forest spatial patterns based on CA-AdaBoost-ANN model in northern Guangzhou, China

Influenced by natural and man-made factors—especially urbanization—regional forest landscapes and structures are in a dynamic process of constant change. It is of great significance to reconstruct the historical pattern of forest landscapes and construct maps of forest landscapes for long time series. Based on the investigation of Fengshui and carbon sequestration forests in northern Guangzhou city, this study combined with an artificial neural network (ANN) improved using the AdaBoost algorithm to create a cellular automaton (CA) to reconstruct species compositions and spatial distributions of historical forests. The model had the best effect at a 30 m spatial scale. At 30 m spatial scale, compared with the actual forest community’s spatial distribution, the overall accuracy of forest community distribution reconstructed by our retrospective model in 2000 was 89.17 %, the Lee Sallee index was 0.7972, and the landscape similarity index was 84.62 %. In 1990, the overall accuracy was 86.78 %, the Lee Sallee index was 0.7604, and the landscape similarity index was 80.84 %. This study provides an effective method for the reconstruction of forest vegetation patterns and the prediction of future scenarios.

Influence of Edaphic Properties in Determining Forest Community Patterns of the Zabarwan Mountain Range in the Kashmir Himalayas

The significance of edaphic factors in describing forest vegetation patterns is becoming more well acknowledged, with significant implications for the description of biogeographical regions and biome classification, as well as abundance and growth patterns at regional levels. The current study examines the vegetation association in the Zabarwan mountain range of the Western Himalayas and its association with edaphic factors. To collect data on forest types, we employed a systematic random sampling strategy in 60 plots (0.1 ha) across five forest types. We investigated data using ordination and cluster analysis approaches after calculating the important value index (henceforth IVI) for each plant species and edaphic data from forests. In total, 76 plant species from 39 different families were found in the area. The Rosaceae family was the most numerous, followed by Fabaceae and Asteraceae. Scrub forest types have lower diversity indices, while broad-leaved forest types have greater diversity indices. Two-way cluster analyses classified the forest vegetation of the Zabarwan mountain range into two plant communities on the basis of indicator plant species. The ordination analysis (canonical correspondence analysis) indicated that vegetation association tended to be influenced differently by distinct levels of soil parameters. The soil pH and calcium content were the main factors influencing the species distribution in the different forest types. The phytosociological features (basal area) were higher in coniferous forest type (74.49 m2ha−1) compared to broad-leaved (58.63 m2ha−1) and scrub forest type (15.4 m2ha−1). Overall, the goal of this research is to gain a better understanding of the impact of soil elements on forest composition and associations in order to develop scientifically based management options for forest ecosystem protection in the Himalayan region.

Forest management effects on vegetation regeneration after a high severity wildfire: A case study in the southern Cascade range

Wildfires play a vital role in ecosystems and are one of the most significant natural processes that shape the northern Sierra Nevada and southern Cascade Mountain Ranges in northeastern California. At the same time, across the American West, a history of fire exclusion, timber salvage and harvest, and human-assisted reforestation has caused widespread changes in forest vegetation patterns over the past century. Federal agencies such as the National Park Service (NPS) and US Forest Service (USFS) have different missions and approaches to these land management activities, creating a mosaic of ecological conditions across managed landscapes both before and after wildfires. We studied vegetation recovery following a major fire that crossed jurisdictional boundaries to explore how management history (fire exclusion and timber harvest and salvage) and post-fire reforestation efforts may influence vegetation regeneration. Using both field-based data collection and remote sensing Normalized Difference Vegetation Index (NDVI) analyses, we assessed differences in vegetation communities found in the NPS and USFS portions of the footprint of the 2012 Reading Fire in northeastern California. We found that a legacy of timber harvest combined with fire exclusion was associated with denser shrub regeneration and minimal sapling recovery. In this context, areas that were reforested post-fire returned a relatively diverse and abundant suite of mixed-conifer tree species to the landscape. In areas with a history of fire exclusion that regenerated without human interference after the fire, saplings did establish on their own but were predominantly white fir (Abies concolor), a shade-tolerant species that is known to increase wildfire severity.

Climatic determinants of photosynthetic activity in humid subtropical forests under different forestry activities

Forests are key ecosystems providing a variety of contributions to societies that are based on the ecological processes occurring in them. Understanding the relationship between ecological processes and the climate system is essential to predict how they will respond to possible future climatic conditions and trajectories. In this study, the relationship between climate variables and vegetation dynamics was studied in different plots of preserved native forest, selectively logged forests, and pine plantations in an area of humid subtropical forest in Misiones, Argentina. Time series analysis via gaussian processes and multiple regressions with the moving average of explanatory variables combined with Bayesian model selection using the lowest Bayesian Information Index as selection criteria were used to determine the relationship between the Enhanced Vegetation Index (EVI) and meteorological variables including temperature, rainfall, global radiation, and potential evapotranspiration. Our results showed that EVI's variability is best explained by a combination of the moving average of temperature, global radiation, and the logarithm of potential evapotranspiration. The estimated EVI value is the minimum predicted value of each linear function of these variables, indicating that these ecosystems are conditioned by the most limiting meteorological variable for vegetation growth at each time among potential evapotranspiration, global radiation, and temperature, but not by a linear combination of these. The different ecosystems, in turn, responded differently to climatic variables. Both logged forests and pine plantations exhibited near-zero slopes with both global radiation and temperature, indicating they are close to temperature and radiation saturation points. Moreover, they presented a higher sensitivity to these variables than preserved forests that were more sensitive to atmospheric water demand. The proposed methodology allowed us to separate the external climatic influence in the forest photosynthetic activity from the internal vegetation processes. Moreover, the final model was capable to capture the multi-scale temporal patterns of forest vegetation.

Human-driven disturbances change the vegetation characteristics of temperate forest stands: A case study from Pir Panchal mountain range in Kashmir Himalaya

Globally, biodiversity-rich forest ecosystems are facing higher risk of climate and land-use changes. Therefore, understanding the role of anthropogenic factors in affecting forest community composition and vegetation patterns assume urgent research priority and are prerequisites for conservation and sustainable management of forest ecosystems. We used a systematic random sampling method to obtain data on floristic diversity within four forest compartments of Pir Panchal Range in Kashmir Himalaya. We characterized the comparative disturbance levels based on a visual assessment within and around each of the forest compartment. The importance value indices along with environmental data of the sampled compartments were obtained and analyzed using hierarchical cluster analysis and ordination techniques. Floristically, in all the compartments, we found 74 species distributed among 33 families and 4 life forms. The species number per hectare showed a declining trend with an increase in disturbance level. Plant community diversity indices were positively correlated with decreasing levels of anthropogenic disturbances. The phytosociological features such as tree basal area and density were negatively correlated with increasing levels of anthropogenic disturbance. Our study, using standard statistical methods, has empirically characterized the intensity of anthropogenic impacts in each forest compartment, and analyzed the relationship between these impacts and the forest vegetation patterns. Our results will help in a better understanding of the role of anthropogenic factors in affecting forest community composition, which in turn will foster the sustainable forest management and biodiversity conservation in this Himalayan region.

Effects of Spatial Pattern of Forest Vegetation on Urban Cooling in a Compact Megacity

Urban forests can be an effective contributor to mitigate the urban heat island (UHI) effect. Understanding the factors that influence the cooling intensity of forest vegetation is essential for creating a more effective urban greenspace network to better counteract the urban warming. The aim of this study was to quantify the effects of spatial patterns of forest vegetation on urban cooling, in the Shanghai metropolitan area of China, using correlation analyses and regression models. Cooling intensity values were calculated based on the land surface temperature (LST) derived from remote sensing imagery and spatial patterns of forest vegetation were quantified by eight landscape metrics, using standard and moving-window approaches. The results suggested that 90 m × 90 m was the optimal spatial scale for studying the cooling effect of forest vegetation in Shanghai’s urban area. It also indicated that woodland performed better than grassland in urban cooling and the size, shape, and spatial distribution of woodland patches had significant impacts on the urban thermal environment. Specifically, the increase of size and the degree of compactness of the patch shape can effectively reduce the LST within the woodland. Areas with a higher percentage of vegetation coverage experienced a greater cooling effect. Moreover, when given a fixed amount of vegetation covers, aggregated distribution provided a stronger cooling effect than fragmented distribution and increasing overall shape complexity of woodlands can enhance the cooling effect on surrounding urban areas. This study provides insights for urban planners and landscape designers to create forest adaptive planning strategies to effectively alleviate the UHI effect.

Changes in selected physical water quality characteristics after thinning in a forested watershed

Climate change is a natural phenomenon with far-reaching impacts. Due to global warming, forest vegetation patterns in the Mediterranean region can be affected and the extent of forested areas can be altered. The purpose of this study was to investigate the impact of slightly decreased forest density on physical water quality parameters by employing 18% thinning with a paired watershed methodology in a broadleaf forest ecosystem. After a 70-month monitoring period that started in December 2005, calibration equations were established between control and treatment watersheds for streamwater parameters including pH, color, turbidity, electrical conductivity (EC), suspended sediment concentration (SSC), water and air temperatures. After 18% standing timber volume was harvested from the treatment watershed, streamwater was also sampled for the same parameters in both watersheds during the 46-month treatment period between January 2012 and October 2015. Changes in the mean monthly values of streamwater parameters were determined as the differences between measured and estimated values derived from the calibration equations. Results showed that 18% forest thinning caused 7.3 μS cm−1 increase in the overall average monthly EC, 2.8 NTU in turbidity, 15.1 mg L−1 in SSC, 0.3 °C increase in the air temperature, and 1.2 °C in the maximum air temperature, whereas it caused 0.5 °C decrease in overall average monthly minimum temperature and 1.3C.P·U in overall mean monthly color. In contrast, forest harvest did not have significant impact on overall average monthly pH and streamwater temperature values. Results of 18% forest harvest indicated that even a small decrease in the forest cover can significantly affect selected physical water quality parameters and hence aquatic life in the forested watersheds.

Low-latitude vegetation and climate dynamics at the Paleocene-Eocene transition – A study based on multiple proxies from the Jathang section in northeastern India

We present a multi-proxy study of an upper Paleocene-lower Eocene succession from the paleo-equatorial region. The study is carried out on a coal-bearing, shallow-marine succession exposed at Jathang, east Khasi hills, Meghalaya, northeastern India. The succession was deposited in a low-energy, coastal marsh-bay complex. Dinoflagellate cyst biostratigraphy yields a late Paleocene to early Eocene age for the section. The deposits of the lower part of the succession represent a transgressive systems tract (TST) defined by seven parasequences, each starting with bay sediments deposited during transgression, followed by a shallowing-upward bay fill-marsh deposit. In the vertical succession, each parasequence acquires an increasingly marine character, culminating in a maximum flooding surface at the Paleocene-Eocene boundary. It is followed by four shallowing upward parasequences deposited in a highstand systems tract (HST). Enhanced chemical weathering and high terrestrial supply are testified by raised SiO2 and Al2O3 contents and high percentages of terrestrial palynomorphs. The pollen flora recovered from the Jathang section was used for quantitative paleoclimate and vegetation reconstructions. The Coexistence Approach was applied based on Nearest Living Relatives (NLRs) of sixty fossil species recorded at different stratigraphic levels. Seven climate variables were determined for the fossil assemblages, and, as a measure of the seasonality of climate, the number of dry months was estimated. Our study shows that during the Paleocene there existed warm, seasonally dry tropical climate conditions with mean annual temperature at ca. 24–26 °C and mean annual precipitation at ca. 700–1800 mm, and with a dry season of 5–6 months. Particularly warm and wet, perhumid climate conditions with 26–27 °C and 2200–3200 mm mean annual precipitation with a dry period of 2–3 months were reconstructed for the latest Paleocene-earliest Eocene interval. The study shows a distinct vegetational turnover from palm-dominated, seasonally dry tropical forest during the Paleocene to highly diversified dicotyledonous megathermal rainforest during the latest Paleocene-early Eocene. The present study demonstrates that the reduced duration of the dry period during the latest Paleocene-earliest Eocene, due to a more active hydrological cycle, played a major role in determining the climate and shaping the vegetation cover in the paleo-equatorial region. There is evidence from our data that seasonality of rainfall is the determining factor for the tropical forest vegetation pattern of the equatorial region rather than mean annual rainfall condition. As the main trigger for the observed step-wise changes of the hydrology along the studied succession, the fast northward movement of the Indian Plate is inferred.

Tree species diversity and utilities in a contracting lowland hillside rainforest fragment in Central Vietnam

BackgroundWithin the highly bio-diverse ‘Northern Vietnam Lowland Rain Forests Ecoregion’ only small, and mostly highly modified forestlands persist within vast exotic-species plantations. The aim of this study was to elucidate vegetation patterns of a secondary hillside rainforest remnant (elevation 120–330 m, 76 ha) as an outcome of natural processes, and anthropogenic processes linked to changing forest values.MethodsIn the rainforest remnant tree species and various bio-physical parameters (relating to soils and terrain) were surveyed on forty 20 m × 20 m sized plots. The forest's vegetation patterns and tree diversity were analysed using dendrograms, canonical correspondence analysis, and other statistical tools.ResultsForest tree species richness was high (172 in the survey, 94 per hectare), including many endemic species (>16%; some recently described). Vegetation patterns and diversity were largely explained by topography, with colline/sub-montane species present mainly along hillside ridges, and lowland/humid-tropical species predominant on lower slopes. Scarcity of high-value timber species reflected past logging, whereas abundance of light-demanding species, and species valued for fruits, provided evidence of human-aided forest restoration and ‘enrichment’ in terms of useful trees. Exhaustion of sought-after forest products, and decreasing appreciation of non-wood products concurred with further encroachment of exotic plantations in between 2010 and 2015. Regeneration of rare tree species was reduced probably due to forest isolation.ConclusionsDespite long-term anthropogenic influences, remnant forests in the lowlands of Vietnam can harbor high plant biodiversity, including many endangered species. Various successive future changes (vanishing species, generalist dominance, and associated forest structural-qualitative changes) are, however, expected to occur in small forest fragments. Lowland forest biodiversity can only be maintained if forest fragments maintain a certain size and/or are connected via corridors to larger forest networks. Preservation of the forests may be fostered using new economic incentive schemes.

Mapping forest vegetation patterns in an Atlantic–Mediterranean transitional area by integration of ordination and geostatistical techniques

Mapping forest vegetation patterns in an Atlantic–Mediterranean transitional area by integration of ordination and geostatistical techniques

Forest fires within a temperate landscape: A decadal and millennial perspective from a sandstone region in Central Europe

In Europe, fire is considered an integral part of forest dynamics only in the Mediterranean and in Fenno-Scandinavia. In Central Europe, the ecological role of fire is largely neglected and deemed unimportant. To fill this knowledge gap, we studied ancient and recent fires in temperate coniferous forests of a sandstone landscape. We used palaeoecological and contemporary forestry data to reveal wildfire events in the present-day landscape and in the distant past. Using linear regression and the ENFA method, we identified the factors influencing fire occurrences in the landscape on two time scales. Analyses of soil charcoal concentrations correspond with contemporary forestry data. The main driving factors affecting the incidence of fires were topographic features, namely the heat load index and presence of rocks. Additional important factors were forest composition features, especially the abundance of Pinus sylvestris. Even though the landscape is populated and attractive to tourists, present-day anthropogenic factors, surprisingly, have only marginal effects. Fires have been occurring in similar fire-prone habitats at least since the Subatlantic period, regardless of whether they were caused by humans or lightning. Our results therefore show that fire affects long-term forest vegetation development also in temperate forests of Central Europe. This has far reaching consequences for forest management because, contrary to prevailing beliefs, fire must be considered a natural driver of forest vegetation patterns even in this temperate region.

산림식생유형에 따른 조류 종다양성 분석

For this paper, a study targeting 9 forest patches in Dangjin to suggest for the wild birds, was conducted. The correlation between the emergence of wild birds and the forest vegetation was analyzed, and the patterns of forest vegetation for the improvement of species diversity were suggested by classifying wild birds and foraging guild by the type of forest vegetation. As for the characteristics of the wild birds emerged, more species and bigger population appeared in the vegetation type of mixed stand forest where the natural deciduous broadleaf trees and evergreen needleleaf trees coexisted in the large scale vegetation area. Thus, it was known that the advent of summer migratory birds and resident birds were affected the most by forest patches and vegetation types. As for foraging guild, the larger the forest paches the more the species and the population of the wild birds inhabiting in shrubs and bushes.

Exploring the “nutrient hot spot” hypothesis at trees used by bats

Abstract Temperate bat species are well-known predators of nocturnal insects; however, their role in forest nutrient cycling is unclear. We tested the “nutrient hot spot” hypothesis, which suggests that colonial bats should create nutrient peaks in and around their roosts via guano deposits. We measured the mass and nitrogen content of guano deposited outside of roosts occupied by maternal colonies of 2 tree-roosting species, Myotis septentrionalis and M. sodalis. We assessed whether these measures were related to date, species, and bat abundance using least-squares regression. We then compared the expected amount of nitrogen deposited over a maternity season to the expected annual amount of nitrogen mineralized by a forest. Mass of guano deposited increased with bat abundance and corresponded to periods of parturition and lactation. Nitrogen mineralization near a large roost of bats can be 380% of that due to decay of leaf litter. Such nutrient peaks could influence patterns of forest vegetation by impac...

Simulated effects of forest management alternatives on landscape structure and habitat suitability in the Midwestern United States

Understanding the cumulative effects and resource trade-offs associated with forest management requires the ability to predict, analyze, and communicate information about how forest landscapes (1000s to >100,000 ha in extent) respond to silviculture and other disturbances. We applied a spatially explicit landscape simulation model, LANDIS, and compared the outcomes of seven forest management alternatives including intensive and extensive even-aged and uneven-aged management, singly and in combination, as well as no harvest. We also simulated concomitant effects of wildfire and windthrow. We compared outcomes in terms of spatial patterns of forest vegetation by age/size class, edge density, core area, volume of coarse wood debris, timber harvest, standing crop, and tree species composition over a 200-year simulation horizon. We also used habitat suitability models to assess habitat quality for four species with diverse habitat requirements: ovenbird ( Seiurus aurocapilla), prairie warbler ( Dendroica discolor), hooded warbler ( Wilsonia citrina), and gray squirrel ( Sciurus carolinensis). Management alternatives with similar levels of disturbance had similar landscape composition but different landscape patterns. The no-harvest scenario resulted in a tree size class distribution that was similar to scenarios that harvested 5% of the landscape per decade; this suggests that gap phase replacement of senescent trees in combination with wind and fire disturbance may produce a disturbance regime similar to that associated with a 200-year timber rotation. Greater harvest levels (10% per decade) resulted in more uniform structure of small or large patches, for uneven- or even-aged management, respectively, than lesser levels of harvest (5% or no harvest); apparently reducing the effects of natural disturbances. Consequently, the even-aged management at the 10% level had the greatest core area and least amount of edge. Habitat suitability was greater, on average, for species dependent on characteristics of mature forests (ovenbird, gray squirrel) than those dependent on disturbance (prairie warbler, hooded warbler) and habitat suitability for disturbance dependent species was more sensitive to the management alternatives. The approach was data-rich and provided opportunities to contrast the large-scale, long-term consequences for management practices from many different perspectives.

Structure and development of expanding western juniper woodlands as influenced by two topographic variables

Juniper and pinon woodlands have been expanding throughout the Intermountain West, USA since the late 1800s. Although causal factors attributed to woodland expansion have been documented, data are lacking that describe the influence of topographic features on rates of development and structural attributes of expanding woodlands. Our primary objective was to determine the relationship between stand-level developmental and structural attributes of four expanding western juniper ( Juniperus occidentalis) woodlands with two topographic features commonly important to forest vegetation patterns, site exposure (an index of insolation exposure based on slope and aspect) and elevation. To accomplish this we measured tree density and age across four western juniper woodlands in Oregon and Idaho. Site exposure and elevation were consistently correlated with spatial and temporal components of woodland development and structure. Holding slope constant, a shift from a north to south aspect resulted in a 4.9 trees/ha/year decrease in tree establishment at a similar elevation. A 200 m rise in elevation was associated with a 1.8 trees/ha/year increase in tree establishment with similar exposure. A 100 m rise in elevation was associated with a 5-year decrease in the time required for a stand to reach dominance and a 22% increase in dominant tree density among stands with similar site exposure. Although significant, site exposure and elevation only explained a portion of the process of woodland dynamics. However, our data suggest exposure and elevation are contributing variables influencing woodland expansion across landscapes, resulting in spatial and temporal heterogeneity in stand structure and development. Models of woodland expansion incorporating landscape topographic features may be practical for identifying windows of opportunity for less costly restoration.

Decision support for integrated landscape evaluation and restoration planning

The historical patterns of Inland Northwest United States forests have been dramatically altered by a little more than two centuries of human settlement and land use. Spatial patterns of forest structural conditions, tree species composition, snags and down wood, and temporal variation in these patterns, have been altered to such an extent that the natural ebb and flow of terrestrial habitats and their linkages has been disrupted. Closely coupled with these changes, fire and other disturbance processes in most dry and many mesic forest types have also shifted, with a bias for increased severity and extent. Here, in the context of planning restoration of some semblance of historical vegetation pattern–disturbance process interactions, we briefly revisit why it is theoretically sound to estimate the range and variation in historical forest spatial patterns. We call these estimates of range and variation, reference conditions or reference variation (RV), and discuss how forest managers might use them when evaluating current landscape patterns to identify changes that may have important ecological implications. We term such evaluations, departure analyses, and we describe how departure analysis is implemented in a decision support system (DSS) for integrated landscape evaluation and restoration planning. The initial phase of the DSS uses logic-based modeling to evaluate existing patterns of forest vegetation in subwatersheds of one ecoregion against a corresponding envelope of historical reference conditions for the same region, thereby highlighting key departures. The secondary planning phase uses results from the analysis phase in a decision model to prioritize watersheds for possible management actions related to landscape restoration and maintenance. We conclude from our example that there are at least two advantages to a decision-support approach that treats evaluation and planning as distinct but integrated phases: (1) the overall decision process is rendered conceptually simpler and (2) practical considerations of efficacy and feasibility of management actions can be easily accommodated.

Differences in forest composition in two boreal forest ecoregions of Quebec

Abstract. In order to describe and compare the post‐fire succession patterns of the two ecological regions (mixed‐wood and coniferous ecoregions) of northwestern Quebec, 260 forest stands were sampled with the point‐centred plot method. The mixed‐wood ecological region belongs to the Abies balsamea‐Betula papyrifera bioclimatic domain whereas the coniferous ecological region belongs to the Picea mariana‐moss bioclimatic domain. In each plot, tree composition was described, surficial deposits and drainage were recorded, and fire history was reconstructed using standard dendro‐ecological methods. Ordination techniques (Correspondence Analysis and Canonical Correspondence Analysis) were used to describe the successional patterns of forest vegetation and to correlate them with the explanatory variables. The results showed the importance of surficial deposits, the time since fire and the ecoregion in explaining the variation of stand composition. Abies balsamea tends to increase in importance with an increase in time since fire, and this trend is more pronounced in the mixed‐wood region. Even when controlling both for surficial deposits and time since fire, differences in successional trends were observed between the two ecoregions. As all the species are present in both ecoregions and as they are all observed further north, our results suggest that both the landscape configuration and fire regime parameters such as fire size and fire intensity are important factors involved in these differences.

Nitrogen mineralization and nitrification in upland and peatland forest soils in two Canadian Shield catchments

Net mineralization and nitrification in surface forest soils were measured in upland forest stands and valley peatlands using in situ soil incubations at two headwater catchments of Harp Lake, Ontario from July 1995 to October 1996. No difference in either net N mineralization or nitrification was observed between the two adjacent catchments despite differences in catchment N export. Annual rates of net N mineralization in surface 10 cm were higher in forest soils of the deciduous (11.5 ± 3.1 g/m2; mean ± SE) and conifer-mixed (conifer-hardwoods) (13.9 ± 2.3 g/m2) stands than in peatland soils (1.6 ± 0.6 g/m2). Mean annual nitrification rates were higher in deciduous soils (6.6 ± 0.7 g N/m2) than in mixed stands (1.9 ± 0.6 g N/m2) and peatland soils (0.1 ± 0.2 g N/m2). Annual net N mineralization and nitrification were correlated with variations in soil C and N content and moisture associated with different forest stands. Frequent winter incubations indicate that net mineralization and nitrification under snow cover in upland surface soils can contribute as much as 49 and 23% of the annual net production, respectively. The importance of forest vegetation patterns, winter N transformations, and dissolved organic N pools to total N and NO3- cycling and leaching in these catchments is discussed.