Forest Succession Patterns Research Articles

Unravelling the role of vegetation on the different trends between climatic and hydrologic drought in headwater catchments of Spain

The availability of water resources is a major challenge of the Mediterranean region. Intense land use transformation has impacted the headwaters of river basins that generate most of the water resources, reducing streamflow This study analyses the evolution of hydrological and climatic drought in headwater catchments of Spain and it explores the extent to which vegetation can reinforce trends in hydrological drought severity in comparison to the evolution of cFlimatic drought severity. We have used the Standardized Precipitation Evapotranspiration Index and Standardized Streamflow Index to examine hydrological and climatic drought, respectively, and examined the changes in the frequency, magnitude, and duration of climatic and hydrologic droughts over non-perturbed headwater catchments of Spain from 1961 to 2013. We quantified vegetation changes over time in the analysed catchments and we compared the changes in the climatic and hydrological droughts with changes in vegetation coverage using Pearson’s r correlations and linear regression model. The results show that the trends toward higher frequency, duration and severity of hydrological droughts are more marked than the observed trends in climatic droughts, which can be associated to the dominant increase in vegetation coverage and activity in the study domain. Finally, it is concluded that the spatial differences observed between the trends of climatic and hydrological droughts show some relationship with the patterns of forest succession observed in recent decades. Our results stress the relevance of land transformation processes on trends in water resources availability, particularly during periods of climatic droughts in which competence between vegetation water consumption and streamflow production is much more relevant.

Evaluating the Performance of a Forest Succession Model to Predict the Long-Term Dynamics of Tree Species in Mixed Boreal Forests Using Historical Data in Northern Ontario, Canada

Environmental concerns and economic pressures on forest ecosystems have led to the development of sustainable forest management practices. As a consequence, forest managers must evaluate the long-term effects of their management decisions on potential forest successional pathways. As changes in forest ecosystems occur very slowly, simulation models are logical and efficient tools to predict the patterns of forest growth and succession. However, as models are an imperfect representation of reality, it is desirable to evaluate them with historical long-term forest data. Using remeasured tree and stand data from three data sets from two ecoregions in northern Ontario, the succession gap model ZELIG-CFS was evaluated for mixed boreal forests composed of black spruce (Picea mariana [Mill.] B.S.P.), balsam fir (Abies balsamea [L.] Mill.), jack pine (Pinus banksiana L.), white spruce (Picea glauca [Moench] Voss), trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), northern white cedar (Thuja occidentalis L.), American larch (Larix laricina [Du Roi] K. Koch), and balsam poplar (Populus balsamefera L.). The comparison of observed and predicted basal areas and stand densities indicated that ZELIG-CFS predicted the dynamics of most species consistently for periods varying between 5 and 57 simulation years. The patterns of forest succession observed in this study support gap phase dynamics at the plot scale and shade-tolerance complementarity hypotheses at the regional scale.

Wildlife differentially affect tree and liana regeneration in a tropical forest: An 18‐year study of experimental terrestrial defaunation versus artificially abundant herbivores

Abstract Hunting and land use change modify native herbivore abundances and cause cascading effects in natural ecosystems. The outcomes for vegetation depend on changes to specific plant–animal interactions, such as seed dispersal or predation, or physical disturbances. We experimentally manipulated terrestrial wildlife populations in a primary lowland forest in Malaysia over an 18‐year period (1996–2014) to understand how artificially high or low animal densities affect tree and liana regeneration. Our study site retains a diverse wildlife community and artificially high densities of native wild pigs (Sus scrofa) that are sustained by crop raiding in distant oil palm plantations. We used fencing that excluded terrestrial animals >1 kg to experimentally simulate conditions similar to those in defaunated forests. These two treatments – abnormally high pig abundances and megafauna loss from hunting – represent common outcomes in disturbed Southeast Asian forests and are characteristic of many forests globally. We focused on trees and lianas because they are the two dominant woody life‐forms in tropical forests and crucial determinants of forest structure and function. We found that liana sapling abundances (30–100 cm height) increased by 86% in unfenced control plots with wildlife but were stable in exclosures. In contrast, tree abundances did not change in unfenced control plots but increased by 83% in exclosures without wildlife. Evidence of scaring on surviving stems suggested that these inverted outcomes were driven by selective use of tree saplings for wild pig nests. Lianas may also have greater tolerance to wildlife disturbances like nest building. By the end of the study, lianas comprised 38% of all saplings in unfenced controls but just 14% in exclosures. Synthesis and applications. We conclude that artificially abundant wildlife, such as crop‐raiding wild pigs, may shift tropical forest understories towards lianas while defaunation may shift it towards trees. These results highlight that ecological cascades from hunting or land use change can alter plant functional types and reshape to long‐term patterns of forest succession and change. Managing unnatural wild boar populations may be required to conserve native plant communities in both their native and exotic ranges.

Successional trajectories and rates of change in sub-tropical Quercus forests in west-central Mexico: evidences from a permanent plot network

Forest succession was studied in sub-tropical high-altitude, Quercus-dominated forest in west-central Mexico in order to address the following research questions: (1) How do successional trajectories progress in three contrasting floristic zones? (2) Which is the magnitude of successional rate of change at different time-scales? (3) What are the major environmental drivers contributing to the observed patterns of forest succession? Data was derived from 86 non-managed permanent plots, 500 m2 each, established along a 10 km floristic gradient, ranging from xeric to mesic sites. In portraying successional trajectories over time and to measure the magnitude of rate of change in three floristic zones, Detrended Correspondence Analysis (DCA) was developed. In order to represent the most significant environmental drivers on patterns of successional trajectories and successional rate of change, we used generalized linear models with gaussian error. Results showed that successional trajectories were not deterministic in each of the floristic zones over the different time-scales analysed; instead we observed four successional trajectories i) plots with an outstanding displacement between time periods, accompanied by an erratic migration over the DCA diagram; ii) plots with a moderate rate of change and uniform movement across the ordination space; iii) a small number of plots with slight change and; iv) few plots with no changes. Soil related variables such as pH, P, N, Mg and Mn, together with slope and catena, were predicted as important contributing factors related to successional processes.

Forty-Eight Years of Forest Succession: Tree Species Change across Four Forest Types in Mid-Missouri

In the central and eastern United States, many forest ecosystems have undergone recent shifts in composition and structure that may conflict with contemporary management objectives. Long-term forest inventory data were used to determine patterns of forest succession over a 48-year period for four forest types in mid-Missouri: bottomlands, dry ridge and slope, glade-like, and mesic slopes. All forest types increased in stand basal area and overstory quadratic mean diameter through time, with concomitant decreases in the number of midstory trees. Sugar maple (Acer saccharum Marshall) increased in importance value on dry ridge and slope and mesic slope forest types, largely due to the accumulation of trees in smaller diameter classes. White oak (Quercus alba L.) increased in overstory basal area in dry ridge and slope plots through the duration of the study, whereas black oak (Quercus velutina Lam.) and Shumard oak (Quercus shumardii Buckley) decreased in overstory density and basal area through time. Oak stems were nearly absent from the midstory across forest types in the recent sampling, suggesting future challenges for maintaining oak-dominated canopies following attrition of canopy trees through time on upland forest types. In glade-like plots, eastern redcedar (Juniperus virginiana L.) increased in both overstory density and basal area through time, and Shumard oak decreased in density. The importance value of chinkapin oak (Quercus muehlenbergii Engelm.) in the overstory decreased through time in glade-like plots, largely due to the increase in density of eastern redcedar rather than the loss of chinkapin oak from the overstory. The patterns of succession in this forest landscape of mid-Missouri suggest that forest management may be needed to address two common contemporary concerns: (1) the need for increasing oak advance reproduction and recruitment to maintain oak as a canopy species; and (2) reducing eastern redcedar encroachment for glade restoration and management.

Long-term effects of traditional and conservation-oriented forest management on the distribution of vertebrates in Mediterranean forests: a hierarchical hybrid modelling approach

Aim Recently, increasing attention has been devoted to the development of sustainable forestry practices aimed at finding a balance between the maintenance and enhancement of different forest resources. However, the long-term, large-scale effects of conservation-oriented forest management on vertebrates have been poorly studied. We tested the hypothesis that conservation-oriented forest management, being conceived to mimic the dynamics of a natural forest succession more closely than does traditional forestry, causes a less severe long-term impact on the distribution of forest vertebrates. Location Molise region, Central Italy. Methods We proposed a hybrid modelling framework based on the integration of a forest dynamic model (‘LANDIS-II’) with species distribution models (SDMs). The framework was applied on four forest specialist vertebrates (tiny salamander, slow worm, Eurasian nuthatch and Leisler's bat) and included three components: forest dynamic model (FDM), SDMs and spatial pattern analysis (SPA). FDM was used to simulate spatially explicit patterns of forest succession for the current time and for 2050, imposing three alternative forestry scenarios. The simulated forest succession patterns were analysed through SPA to calculate spatialized landscape metrics that were adopted as environmental predictors for SDMs. Landscape trajectories were calculated on current and future species distributions predicted with SDMs to evaluate the effect of alternative forestry practices on their extent and fragmentation. Results Forest management mainly affected the spatial configuration rather than the extent of the species potential distributions. Conservation-oriented forest management was more favourable than traditional forestry in increasing the extent and reducing the fragmentation of the studied species’ distributions. Main conclusions Conservation-oriented forest management, by mimicking the dynamics of a natural forest succession more closely than did traditional practices, favoured elements, such as forest unevenness, species richness, aggregation of patches and variability in their distances, which emerged as fundamental characteristics for preserving the long-term persistence of forest vertebrates.

Mapping Secondary Forest Succession on Abandoned Agricultural Land with LiDAR Point Clouds and Terrestrial Photography

Secondary forest succession on abandoned agricultural land has played a significant role in land cover changes in Europe over the past several decades. However, it is difficult to quantify over large areas. In this paper, we present a conceptual framework for mapping forest succession patterns using vegetation structure information derived from LiDAR data supported by national topographic vector data. This work was performed in the Szczawnica commune in the Polish Carpathians. Using object-based image analysis segments of no vegetation, and sparse/dense low/medium/high vegetation were distinguished and subsequently compared to the national topographic dataset to delineate agricultural land that is covered by vegetation, which indicates secondary succession on abandoned fields. The results showed that 18.7% of the arable land and 40.4% of grasslands, that is 31.0% of the agricultural land in the Szczawnica commune, may currently be experiencing secondary forest succession. The overall accuracy of the approach was assessed using georeferenced terrestrial photographs and was found to be 95.0%. The results of this study indicate that the proposed methodology can potentially be applied in large-scale mapping of secondary forest succession patterns on abandoned land in mountain areas.

Remote Sensing of Aboveground Biomass in Tropical Secondary Forests: A Review

Tropical landscapes are, in general, a mosaic of pasture, agriculture, and forest undergoing various stages of succession. Forest succession is comprised of continuous structural changes over time and results in increases in aboveground biomass (AGB). New remote sensing methods, including sensors, image processing, statistical methods, and uncertainty evaluations, are constantly being developed to estimate biophysical forest changes. We review 318 peer-reviewed studies related to the use of remotely sensed AGB estimations in tropical forest succession studies and summarize their geographic distribution, sensors and methods used, and their most frequent ecological inferences. Remotely sensed AGB is broadly used in forest management studies, conservation status evaluations, carbon source and sink investigations, and for studies of the relationships between environmental conditions and forest structure. Uncertainties in AGB estimations were found to be heterogeneous with biases related to sensor type, processing methodology, ground truthing availability, and forest characteristics. Remotely sensed AGB of successional forests is more reliable for the study of spatial patterns of forest succession and over large time scales than that of individual stands. Remote sensing of temporal patterns in biomass requires further study, in particular, as it is critical for understanding forest regrowth at scales useful for regional or global analyses.

An innovative computer design for modeling forest landscape change in very large spatial extents with fine resolutions

Although forest landscape models (FLMs) have benefited greatly from ongoing advances of computer technology and software engineering, computing capacity remains a bottleneck in the design and development of FLMs. Computer memory overhead and run time efficiency are primary limiting factors when applying forest landscape models to simulate large landscapes with fine spatial resolutions and great vegetation detail. We introduce LANDIS PRO 6.0, a landscape model that simulates forest succession and disturbances on a wide range of spatial and temporal scales. LANDIS PRO 6.0 improves on existing forest landscape models with two new data structures and algorithms (hash table and run-length compression). The innovative computer design enables LANDIS PRO 6.0 to simulate very large (>10 8 ha) landscapes with a 30-m spatial resolution, which to our knowledge no other raster forest landscape models can do. We demonstrate model behavior and performance through application to five nested forest landscapes with varying sizes (from 1 million to 100 million 0.09-ha cells) in the southern Missouri Ozarks. The simulation results showed significant and variable effects of changing spatial extent on simulated forest succession patterns. Results highlighted the utility of a model like LANDIS PRO 6.0 that is capable of efficiently simulating large landscapes and scaling up forest landscape processes to a common regional scale of analysis. The programming methodology presented here may significantly advance the development of next generation of forest landscape models.

Patterns of forest succession and impacts of flood in the Upper Mississippi River floodplain ecosystem

The widespread loss of oak-hickory forests and the impacts of flood have been major issues of ecological interest concerning forest succession in the Upper Mississippi River (UMR) floodplain. The data analysis from two comprehensive field surveys indicated that Quercus was one of the dominant genera in the UMR floodplain ecosystem prior to the 1993 flood and constituted 14% of the total number of trees and 28% of the total basal area. During the post-flood recovery period through 2006, Quercus demonstrated slower recovery rates in both the number of trees (4%) and basal area (17%). In the same period, Carya recovered greatly from the 1993 flood in terms of the number of trees (11%) and basal area (2%), compared to its minor status before the flood. Further analyses suggested that different species responded to the 1993 flood with varying tolerance and different succession strategies. In this study, the relation of flood-caused mortality rates and DBH, f m ( d), can be expressed in negative exponential functions for each species. The results of this research also indicate that the growth functions are different for each species and might also be different between pre- and post-flood time periods. These functions indicate different survival strategies and emergent properties in responding to flood impacts. This research enhances our understanding of forest succession patterns in space and time in the UPR floodplain. And such understanding might be used to predict long-term impacts of floods on UMR floodplain forest dynamics in support of management and restoration.

Tree growth and competition in a post‐logging Quercus mongolica forest on Mt. Sobaek, South Korea

AbstractSecondary woodlands in South Korea cover most mountains from low to middle elevations. While general patterns of forest succession are well understood, little is known about mechanisms of stand recovery after disturbance. We examined the spatio‐temporal variations in establishment, growth, size inequality, and mode of competition among trees in a 50‐year‐old post‐logging Quercus mongolica‐dominated stand. We further compared the growth and stem allometry of single trees, presumably of seed origin, with multi‐stemmed trees resprouting from stumps. Q. mongolica formed the upper canopy 16–22 m tall, 88.3% of total stand basal area, and 36.2% of total stem density, with most trees established during the first post‐logging decade (51.2% were resprouts). During the first three decades, the Q. mongolica recruits grew exponentially, and disproportionately more in diameter than few older reserved trees left after the last cutting. This substantially decreased size inequality. The reverse trend was observed from 1994 to 2004: larger trees grow more, indicating an increasing asymmetry of competition for light. Neighborhood analysis revealed that when target trees had more or larger neighbors, their exponential phase of growth was reduced and maximum size was decreased. After the 50 years of stand development, more than 70% of Q. mongolica showed growth decline as a result of competitive stress, and mortality was about 30%, concentrated in smaller size classes. Compared to single stems, resprouts within clones do not seem to compete less asymmetric as might be expected based on studies of clonal herbaceous plants and physiological integration within genets. As Q. mongolica was also negatively affected by competition from woody species currently prevailing in the lower tree stratum (Tilia amurensis, Acer mono, Fraxinus rhynchophylla, Acer pseudosieboldianum), we predict the stand will become increasingly dominated by these more shade‐tolerant trees.

Earthworms as Ecosystem Engineers and the Most Important Detritivors in Forest Soils

Earthworms are considered as soil engineers because of their effects on soil properties and their influence on the availability of resources for other organisms, including microorganisms and plants. However, the links between their impacts on the soil environment and the resulting modification of natural selection pressures on engineer as well as on other organisms have received little attention. Earthworms are known to have a positive influence on the soil fabric and on the decomposition and mineralization of litter by breaking down organic matter and producing large amounts of fasces, thereby mixing litter with the mineral soil. Therefore, they play an important part in changes from one humus from to another according to forest succession patterns. Consequently, they are also expected to be good bio-indicators for forest site quality and are thus useful when planning forest production improvement. Earthworm's populations are as indicator that in exploited regions is destruction indicator and reclamation plans is nature return indicator. In this study we summarized the current knowledge in relation to earthworm's ecology in forest soils as ecosystem engineers.

Mercury Contamination of Biota from Acadia National Park, Maine: A Review

We reviewed literature reporting both total and methylmercury from biota from Acadia National Park, Maine, USA. Our review of existing data indicates that 1) mercury contamination is widespread throughout the Park's various aquatic ecosystems; 2) mercury pollution likely represents a moderate to high risk to biota inhabiting the Park; and 3) biota at all trophic levels possess elevated concentrations of both total and methylmercury. Watershed fire history and the resulting post-fire forest succession patterns are an important landscape attribute governing mercury cycling at Acadia National Park. Therefore, park service personnel should consider these factors when planning and implementing Hg biomonitoring efforts. Additional baseline funding from the National Park Service for Hg research and biomonitoring will likely be required in order to further evaluate the spatial and temporal patterns of mercury contamination in the park's biota.

Modeling the Influence of Dynamic Zoning of Forest Harvesting on Ecological Succession in a Northern Hardwoods Landscape

Dynamic zoning (systematic alteration in the spatial and temporal allocation of even-aged forest management practices) has been proposed as a means to change the spatial pattern of timber harvest across a landscape to maximize forest interior habitat while holding timber harvest levels constant. Simulation studies have established that dynamic zoning strategies produce larger tracts of interior, closed canopy forest, thus increasing the value of these landscapes for interior-dependent wildlife. We used the simulation model LANDIS to examine how the implementation of a dynamic zoning strategy would change trajectories of ecological succession in the Great Divide Ranger District of the Chequamegon-Nicolet National Forest in northern Wisconsin over 500 years. The components of dynamic zoning strategies (number of zones in a scenario and the length of the hiatus between successive entries into zones) and their interaction had highly significant impacts on patterns of forest succession. Dynamic zoning scenarios with more zones and shorter hiatus lengths increased the average amount of the forest dominated by early successional aspen (Populus sp.). Dynamic zoning scenarios with two zones produced more late successional mature northern hardwoods than scenarios with four zones. Dynamic zoning scenarios with very short (30 years) or very long (120 years) hiatus lengths resulted in more late successional mature northern hardwoods than scenarios with intermediate hiatus lengths (60 and 90 years). However, none of the dynamic scenarios produced as much late successional mature northern hardwoods as the static alternative. Furthermore, the amounts of all habitat types in all dynamic zoning scenarios fluctuated greatly in time and space relative to static alternatives, which could negatively impact wildlife species that require a stable amount of habitat above some minimum critical threshold. Indeed, implementing dynamic zoning scenarios of different designs would have both positive and negative effects on wildlife species and for other objectives of forest management.

A dynamic model of patterns of deforestation and their effect on the ability of the Brazilian Amazonia to provide ecosystem services

This paper presents a dynamic systems model that shows how different land use patterns degrade the value of ecosystem services provided by the Brazilian Amazonia. The model consists of four sectors: (1) deforestation drivers; (2) land use/cover; (3) ecosystem services; and (4) ecosystem valuation. The deforestation drivers sector models the economic and social incentives that small farmers and large pasture investors have for clearing the forest. The land use/cover sector shows how these different groups clear land, and further shows how patterns of forest succession and associated biomass differ by primary land use type. Different land use patterns greatly impact the quality and economic value of ecosystem services. These impacts are dealt with in the ecosystem services sector, which models the region's hydrological cycle, the nutrient cycle, carbon sequestration capacity, and species diversity. Calculations are made in the ecosystem valuation sector according to a reference monetary value for these ecosystem services. The model calculates the change in these values according to the land use practices that occur over time. Findings show that over a 100-year simulation, forest area remains about 44% of original area with pasture and abandoned pasture becoming the dominant land cover. The value of ecosystem services declines from $1431 to $658 and $781 ha −1 year −1 for agriculture and pasture, respectively. These findings are compared to annual revenue derived from different land use practices for which land was cleared in the Brazilian Amazonia. In the context of these findings, the authors discuss how an explicit monetary valuation of ecosystem services could create positive incentives for land stewardship and conservation.

BELOW-GROUND PROCESSES IN GAP MODELS FOR SIMULATING FOREST RESPONSE TO GLOBAL CHANGE

Gap models have a rich history of being used to simulate individual tree interactions that impact species diversity and patterns of forest succession. Questions arise, however, as to whether these same models can be used to study the response of forest structure and composition under a changing climate. In contrast to many process-based models, gap models have traditionally been based on rather descriptive representations of species-specific growth processes. Opportunities now exist to expand upon these simple empirical relationships with more mechanistic descriptions of growth, the response of growth to environmental variables, and competition among species for avail- able light, water, and nutrient resources. In this paper, we focus on several areas of below-ground research with the potential to improve the utility of gap models for predicting forest composition in response to a changing climate. Specific areas for model improvement include (1) improved descriptions of the soil environment for seed germination and subsequent seedling establishment, (2) multi-layer representations of soil water and nutrient availability, (3) more accurate information on biomass allocation to roots and root distribution within the soil profile, (4) improved treatment of inter- and intra-specific competition for available soil resources, (5) increased consideration of spatial processes as related to land-surface hydrology, and (6) improved attention to above- and below-ground interactions. This list is meant to stimulate discussion and provide guidance for future field research and model development. As an example of how increased attention to below- ground processes could help address intra-specific competition for water among trees of differing size classes, the gap model LINKAGES was modified to include a sub-model of multi-layered soil hydrology. It was then used to examine the impact of root distribution within soils on the simulated drought response of seedlings, saplings, and mature trees. An annual simulation of soil water con- tent for a deciduous forest in eastern Tennessee showed that seedlings whose roots were restricted to the upper 20-cm of the soil experienced far more 'drought days' than did saplings and larger

ERROR PROPAGATION IN A FOREST SUCCESSION MODEL:THE ROLE OF FINE-SCALE HETEROGENEITY IN LIGHT

A central challenge in ecology is understanding the emergence of broad-scale community and ecosystem patterns as the result of interactions among individuals. We identify the role of fine-scale light heterogeneity in controlling broad-scale community behavior in SORTIE, an empirically derived, stochastic forest simulation model. SORTIE employs a very detailed measure of local light based on a 216-point sample around every tree. We test the importance of this fine-scale description of local light by reformulating SORTIE with less detail in this algorithm. Predicted forests are compared at several scales from total tree biomass (coarse grained) and patterns of forest succession to the local spatial pattern of light availability at the forest floor (fine grained). SORTIE is surprisingly insensitive to the amount of detail used in the calculation of the local resource, light. In all simulations, 48- and 16-point samples accurately reproduce the local light environment and thus predict forest development without appreciable error. A one-point sample of light significantly alters the estimates of the local light environment, but the emergent forest dynamics are insensitive to these alterations. The robustness of the forest model to the altered light environment stems from two very different mechanisms. First, the alterations of the light environment have very short correlation lengths in time and space. This allows fine-scale averaging to occur on the landscape. Second, the functional relationships among light availability, growth rate, and mortality risk in several key species tend to prevent the altered light environment from affecting individual tree performance. These results demonstrate that emergent forest dynamics in SORTIE do not require detailed local light estimation to capture the interaction between local resource heterogeneity and the functional responses of trees. In addition, we have shown that comparing model predictions at several scales provides a strong methodology to identify relevant detail and understand scaling in this model of a forest.

Henry David Thoreau's science inThe Dispersion of Seeds

Summary A major manuscript by nineteenth-century American writer-naturalist Henry David Thoreau was published for the first time in 1993. The Dispersion of Seeds is a study of ecological dynamics in forests in and around Concord, Massachusetts. Drafted by Thoreau just before his premature death in 1862, it emphasizes plant-animal mutualism in the dispersion of oak seed, as a fundamental factor in forest succession patterns. If Thoreau had lived to publish this study, it is likely that his pioneering role in the history of ecology would be considerably enhanced. This paper explores dimensions of Thoreau's science that are revealed for the first time in this new publication.

Large‐Scale Patterns of Forest Succession as Determined by Remote Sensing

The spatial pattern of and the transition rates between forest ecological states were inferred for °260 000 pixel—sized (3600 m2) landscape units using stallite remote sensing. Transition rates were estimated from 1973 to 1983 Landsat images of the study area, classified into ecological states associated with forest succession. The effects of classification error on transition rate estimates were modeled and error adjustments made. Classification of the 1973 and 1983 Landsat images of the 900 km2 study region required a relatively small set of ground—observed and photo—interpreted plots in 1983, with a total area of just 1.62 km2. An innovative technique for correcting multiyear Landsat images for between—image differences in atmospheric effects and sensor calibration, permitted classification of the 1973 Landsat image using 1983 ground observations. Given current Landsat data, and ground observations in one year, this technique would permit monitoring of forest succession and dynamics for nearly a 20—yr period. Results of applying these techniques to a forest ecosystem showed that during the 10—yr observation period it was patchy and dynamic. For both a wilderness and a nonwilderness area in the study region, sizeable values of transition rates were observed and over half of the landscape units were observed to change state: however, a Markov analysis, using the observed transition probabilities, suggests that at the regional level neither the wilderness nor the nonwilderness areal proportions of ecological states are undergoing rapid change.

Time Series and Postglacial Forest Ecology

AbstractForest ecology suffers from a lack of long-term community records. Preserved pollen data are richer in such information than is generally realized. By applying suitable statistical techniques to pollen records, one can learn much about competition, succession, and population dynamics in past tree communities. In this study, preserved pollen records from Everitt Lake, Nova Scotia, are analyzed as time series. Time domain studies reveal the post-fire responses of individual tree taxa. Correlograms yield models of past forest succession patterns. The models explain some effects of changing fire frequency, thus suggesting mechanisms by which fire, competition, and climate combine to produce long-term forest composition changes. Frequency domain studies suggest relationships between disturbance cycles, stand composition, and forest mosaics. Fire frequencies are seen to be highest where fire-dependent species abound and most regular where tree stands have uniform, not mixed, composition.