A Stochastic Dynamic Methodology (StDM) for reservoir's water quality management: Validation of a multi-scale approach in a south European basin (Douro,Portugal)

Worldwide aquatic ecosystems have been impacted by broad-scale environmental pressures such as agriculture, point and non-point-source pollution and land-use changes overlapping in space and time, leading to the disruption of the structure and functioning of these systems. The present paper examined the applicability of a holistic Stochastic Dynamic Methodology (StDM) in predicting the tendencies of phytoplankton communities and physicochemical conditions in reservoirs as a response to the changes in the respective watershed soil use. The case of the Douro's basin (Portugal) was used to test the StDM performance in this multi-scale approach. The StDM is a sequential modelling process developed in order to predict the ecological status of changed ecosystems, from which management strategies can be designed. The data used in the dynamic model construction included true gradients of environmental changes and was sampled from 1995 to 2004. The dynamic model developed was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between the selected ecological components. The model validation was based on independent data, for all the state variables considered. Overall, the simulation results are encouraging since they seem to demonstrate the StDM reliability in capturing the dynamics of the studied reservoirs. The StDM model simulations were validated for the most part of the twenty-two components selected as ecological indicators, with a performance of 50% for the physicochemical variables, 75% for the phytoplankton variables, and 100% for the Carlson trophic state indices (TSI). This approach provides a useful starting point, as a contribution for the practical implementation of the European Water Framework Directive, allowing the development of a true integrated assessment tool for water quality management, both at the scale of the reservoir body and at the scale of the respective river watershed dynamics.     

Predicting the trends of vertebrate species richness as a response to wind farms installation in mountain ecosystems of northwest Portugal

The main objectives of this work were to examine the performance of a holistic stochastic dynamic methodology (StDM) in predicting the trends of the vertebrate species richness (amphibians, reptiles, birds and mammals) in response to changes induced by the ongoing wind farm installation in mountain areas of northwest Portugal. The StDM is a sequential modelling process developed in order to estimate the ecological status of changed ecosystems that have been damaged by anthropogenic disturbances. The performance of two complementary temporal approaches was tested, taking into account either annual or seasonal influences. The data used in the dynamic model construction included true gradients of environmental changes and was sampled from 2004 to 2006. The dynamic model developed was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between the selected ecological components, such as the species richness of each vertebrate group and the structural changes in habitat conditions. The results show the capacity of the model in capturing the dynamics of the studied system by predicting consistent trends for the global vertebrate species richness under complex and variable environmental scenarios. The average annual approach is considered sufficient for the aims of the most Environmental Impact Assessments while the seasonal approach is recommended for more detailed studies, namely regarding specific population, guilds or community dynamics.     

A stochastic dynamic methodology (SDM) to facilitate handling simple passerine indicators in the scope of the agri-environmental measures problematics

The present paper examined the applicability of a holistic stochastic dynamic methodology (SDM) in predicting the tendencies of simple ecological indicators as a response to the changes in agricultural hedgerow networks. Although considerable effort has been made to identify appropriate agri-environmental indicators, yet most of them are far too complex to be comprehensively measured and quantified by non-specialists. The ecological integrity of the typical hedgerows can be partly assessed by the observation of the occurrence of passerine indicators. Since the conventional measures’ regarding bird studies requires high-specialization levels, we proposed alternative simple, suitable and intuitive indicators capable of responding with comparable rigour to key changes in such agro-ecosystems. The dynamic model developed was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between conceptually isolated key-components of the studied hedgerows. The final model provided some basis to analyse the responses of simple passerine indicators to the agricultural scenarios that will characterize the region. Overall, the simulation results are encouraging since they seem to demonstrate the SDM reliability in capturing the habitat dynamics of the studied agro-ecosystems by predicting the behavioural pattern for simple measures, roughly associated with bird occurrence, habitat food resources and breeding conditions.     

Modelling the performance of bird surveys in non-standard weather conditions: General applications with special reference to mountain ecosystems

Although considerable effort has been made to identify the appropriate climatic conditions for bird surveys, considered as standard conditions, in many occasions these conditions are not fulfilled. These are for instance the case of environmental impact assessments (EIA), where the field work is, recurrently, carried out in variable and non-standard weather conditions or in the scope of general ecological monitoring (GEM) programs, where different taxa (birds and other animal groups) are sampled simultaneously with distinct methodological requirements. The present work examined the applicability of a stochastic dynamic methodology (StDM) for predicting the richness and diversity of passerine surveys in mountain habitats characterized by variable and, predominantly, non-standard weather conditions. The relative variations of these metrics are the underlying database of our StDM model, providing some basis to analyse the accuracy of bird surveys. This model focuses on the interactions between conceptually isolated key-components, such as the passerine richness and diversity, and the influence of the prevailing climatic conditions.The proposed model was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between the selected metrics versus climatic variables. Since this statistical analysis is static, the dataset recorded from the field included true gradients of weather conditions (ranging from standard to extreme conditions). The results of the StDM simulations revealed significant variations in the performance of passerine surveys in response to several combinations of non-standard weather conditions, which enable us to calculate the appropriated correction factors for discrete climatic scenarios. This could be used, in the future, to improve the quality of passerine diversity and richness estimates, namely in the scope of EIA studies when the climatic conditions are inevitably adverse for rigorous passerine surveys.     

Large‐scale assessment of regeneration and diversity in Mediterranean planted pine forests along ecological gradients

Aim There is increasing concern regarding sustainable management and restoration of planted forests, particularly in the Mediterranean Basin where pine species have been widely used. The aim of this study was to analyse the environmental and structural characteristics of Mediterranean planted pine forests in relation to natural pine forests. Specifically, we assessed recruitment and woody species richness along climatic, structural and perturbation gradients to aid in developing restoration guidelines. Location Continental Spain. Methods We conducted a multivariate comparison of ecological characteristics in planted and natural stands of main Iberian native pine species (Pinus halepensis, Pinus pinea, Pinus pinaster, Pinus nigra and Pinus sylvestris). We fitted species‐specific statistical models of recruitment and woody species richness and analysed the response of natural and planted stands along ecological gradients. Results Planted pine forests occurred on average on poorer soils and experienced higher anthropic disturbance rates (fire frequency and anthropic mortality) than natural pine forests. Planted pine forests had lower regeneration and diversity levels than natural pine forests, and these differences were more pronounced in mountain pine stands. The largest differences in recruitment – chiefly oak seedling abundance – and species richness between planted and natural stands occurred at low‐medium values of annual precipitation, stand tree density, distance to Quercus forests and fire frequency, whereas differences usually disappeared in the upper part of the gradients. Main conclusions Structural characteristics and patterns of recruitment and species richness differ in pine planted forests compared to natural pine ecosystems in the Mediterranean, especially for mountain pines. However, management options exist that would reduce differences between these forest types, where restoration towards more natural conditions is feasible. To increase recruitment and diversity, vertical and horizontal heterogeneity could be promoted by thinning in high‐density and homogeneous stands, while enrichment planting would be desirable in mesic and medium‐density planted forests.     

Restoring Fire to Long-Unburned Pinus palustris Ecosystems: Novel Fire Effects and Consequences for Long-Unburned Ecosystems

Biologically rich savannas and woodlands dominated by Pinus palustris once dominated the southeastern U.S. landscape. With European settlement, fire suppression, and landscape fragmentation, this ecosystem has been reduced in area by 97%. Half of remnant forests are not burned with sufficient frequency, leading to declines in plant and animal species richness. For these fire‐suppressed ecosystems a major regional conservation goal has been ecological restoration, primarily through the reinitiation of historic fire regimes. Unfortunately, fire reintroduction in long‐unburned Longleaf pine stands can have novel, undesirable effects. We review case studies of Longleaf pine ecosystem restoration, highlighting novel fire behavior, patterns of tree mortality, and unintended outcomes resulting from reintroduction of fire. Many of these pineland restoration efforts have resulted in excessive overstory pine mortality (often >50%) and produced substantial quantities of noxious smoke. The most compelling mechanisms of high tree mortality after reintroduction of fire are related to smoldering combustion of surface layers of organic matter (duff) around the bases of old pines. Development of effective methods to reduce fuels and competing vegetation while encouraging native vegetation is a restoration challenge common to fire‐prone ecosystems worldwide that will require understanding of the responses of altered ecosystems to the resumption of historically natural disturbances.     

Natural disturbances and the physiognomy of pine savannas: A phenomenological model

Abstract. Question: The decline of the Pinus palustris ecosystems has resulted from anthropogenic influences, such as conversion to pine plantation forestry, agriculture and land development, all of which are closely related to increases in human populations. Other effects, however, have arisen from alterations in disturbance regimes that maintain the structure and function of these ecosystems. How have alterations of the disturbance regime altered the physiognomy of ‘old‐growth’ stands, and what are the implications for ecosystem conservation and restoration? Methods: In contrast to models that emphasize close interactions among the vertically complex strata, we develop a conceptual phenomenological model for the physiognomic structure of Pinus palustris stands. We relate two natural disturbances (tropical storms and fire) that affect different stages of the life cycle to different aspects of the physiognomic structure. We then compare overstorey stand structure and ground cover composition of two old‐growth longleaf stands near the extremes of different composite disturbance regimes: the Wade Tract (frequent hurricanes and fire) and the Boyd Tract (infrequent hurricanes and long‐term fire exclusion). Results: We predict that tropical storms and fires have different effects on stand physiognomy. Tropical storms are periodic, and sometimes intense, whereas fires are more frequent and less intense. Hurricanes directly influence the overstorey via wind‐caused damage and mortality, and indirectly influence the herb layer by altering the spatial distribution of shading and litter accumulation. Fire exerts direct effects on juvenile stages and indirect effects on the herb layer via fine fuel consumption and selective mortality of potential competitors of P. palustris juveniles. These differences in effects of disturbances can result in widely different physiognomies for P. palustris stands. Finally, some global climate change scenarios have suggested that changes may occur in tropical storm and fire regimes, altering frequency and severity. Such changes may greatly affect pine stands, and ultimately entire pine savanna ecosystems. Conclusions: Our phenomenological model of disturbance regimes in Pinus palustris old‐growth produces very different physiognomies for different disturbances regimes that reflect natural process and human management actions. This model can be used to derive restoration strategies for pine savannas that are linked to reinstitution of important ecological processes rather than specific physiognomic states.     

Growth responses to climate and drought at the southernmost European limit of Mediterranean Pinus pinaster forests

Climate warming and increasing aridity may negatively impact forest productivity across southern Europe. A better understanding of growth responses to climate and drought in southernmost populations could provide insight on the vulnerability of those forests to aridification. Here we investigate growth responses to climate and drought in nine Pinus pinaster (maritime pine) stands situated in Andalusia, southern Europe. The effect of climatic variables (temperatures and precipitation) and drought on radial growth was studied using dendrochronology along biogeographic and ecological gradients. We analyzed old native stands with non-tapped and resin-tapped trees mixed, showing their usefulness in dendroclimatic studies. Our results indicate a high plasticity in the growth responses of maritime pine to climate and drought, suggesting that site aridity modulated these responses. The positive growth responses to spring precipitation and the negative responses to summer drought were stronger in the more xeric inland sites than in wet coastal ones, in particular from the 1980s onwards. The characterization of tree species’ responses to climate at the southern or dry limits in relation to site conditions allows improving conservation strategies in drought-prone forest ecosystems.     

Quantifying Disturbance in Terrestrial Communities: Abundance–Biomass Comparisons of Herpetofauna Closely Track Forest Succession

Herpetofauna are frequently cited as ideal indicators for environmental and restoration monitoring due to their importance to ecological functioning, dominance of vertebrate biomass, and sensitivity to environmental change. Despite this relevance, herpetofauna have yet to be fully integrated into comprehensive, community‐scale restoration monitoring methodologies. We tested the applicability of one such method, abundance–biomass comparisons (ABCs), to monitoring restoration success in a longleaf pine ecosystem currently undergoing restoration via prescribed burning. W statistics (a metric of environmental perturbation) for herpetofaunal assemblages in longleaf pine stands managed under varying fire intervals closely tracked forest succession from recently burned longleaf pine stands to those characterized by longer times since last burn and high levels of hardwood encroachment. Our results suggest that ABCs may be an applicable method for terrestrial restoration monitoring that encompasses entire faunal assemblages and allows for generality in restoration or disturbance response. We emphasize, however, that applications of this method and others need to take into account the specific ecological characteristics of study organisms and the natural history of study sites to avoid incorrect interpretations of disturbance response and inappropriate management recommendations.     

Development of a stochastic dynamic model for ecological indicators’ prediction in changed Mediterranean agroecosystems of north-eastern Portugal

A holistic stochastic dynamic model was developed by focusing on the interactions between conceptually isolated key-components, such as local passerine guilds and changes in habitat conditions, in Mediterranean agroecosystems of the “Terra Quente Transmontana region” (north-eastern Portugal). The ecological integrity of the typical patchwork of this region, with respect to land use, can be partly assessed by the observation of the occurrence of passerine guilds. These important indicators and state variables are the underlying database of our model. This model aimed the prediction of the ecological changes which can be expected when olive orchards are being intensified. The model proposed was preceded by a conventional multivariate statistical procedure (stepwise multiple regression analysis) performed to discriminate the significant relationships between guild richness and environmental variables. Since this statistical analysis is static, the dataset recorded from the field included true gradients of habitat changes. The model parameters were estimated from the results of the stochastic treatment and from regional data regarding tendencies within the use of land. A period of 50 years was considered. The final model provided some basis to analyse the responses of passerine guilds to the environmental scenarios that will characterize the new agroecosystems of the region. The model simulations were incorporated into a Geographical Information System (GIS) approach. The results of the simulation revealed a structural drift within the different guild richness in response to the expected gradient of habitat changes. The possible local extinction of several species within the less well-represented guilds, such as the steppe passerine species, may be associated with a predictable reduction in ecological integrity of the typical agroecosystems. Therefore, a new structure of the passerine communities indicates that future agroecosystems will diverge from the initial or actual ecological state.     

Spatial segregation of pines and oaks under different fire regimes in the Sierra Madre Occidental

Surface fire can modify spatial patterns and self-thinning in pine-oak ecosystems. Spatial pattern analyses were used to compare pattern development and interspecific spatial interactions in trees and seedlings in five Madrean pine-oak stands with different recent fire histories. Interspecific and intraspecific patterns were compared in small (< 15 cm dbh) and large (< 15 cm dbh) diameter classes of the pines (Pinus durangensis, P. teocote, and P. leiophylla) and oaks (Quercus sideroxylla, Q. crassifolia, and Q. laeta) that collectively dominated the five stands. Numbers of juvenile trees in 2.5 × 2.5 m subplots were correlated with cumulative distances to adult trees. Small pine and oak trees were intraspecifically clustered at all scales, irrespective of fire regime. Large pines were strongly clustered only in stands with longer fire-free intervals, and patterns of large versus small pine trees were regular or random in frequent fire stands. These patterns were consistent with fire-induced mortality of maturing trees under frequent fire. Large and small pines were segregated from small oaks at short and long distances in one stand with a 32-year fire-free interval, implying that two or more dynamic factors had produced regular patterns at different scales. Such regular spatial patterns at short distances were not seen in other stands. Therefore, there was little evidence for direct competition between oaks and pines. The results reported here are consistent with studies from other pine-oak ecosystems showing that different fire regime and site factors interact to influence stand development processes and relative dominance of pines and oaks. In some stands, the continued absence of fire could foster increasing tree densities and an intensification of local neighborhood effects, producing segregation of pine and oak species at longer distances. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hazard ratings of pine forests to a pine wilt disease at two spatial scales (individual trees and stands) using self-organizing map and random forest

Pine wilt disease (PWD) caused by the pine wood nematode is the most serious global threat to pine forests. Hazard ratings of trees and forests to pest attacks provide important information to efficiently identify current or future hazardous conditions. However, in spite of the importance of hazard ratings for managing PWD, there are few studies on hazard ratings in this system. In this study, we evaluated the hazard ratings of pine trees and pine stands to PWD by considering environmental factors at the level of the stand and the individual tree. Our results showed that trees with larger diameter at breast height (DBH) showed a higher risk rate than those with smaller DBH, indicating that large trees have an increased probability of exposure to vector beetles because they are tall and have a large crown volume. We also found that reduced tree vigour could be related to susceptibility to PWD. In pine stands, geographical factors showed a high correlation with the occurrence of PWD. PWD occurrence was rare at high altitudes, but was more common on steep and south-facing slopes. These patterns were consistently observed in the results from 2 computational approaches: self-organizing map (SOM) and random forest models. The combination of SOM and random forest was effective to extract ecological information from the dataset. The SOM efficiently characterized relations among variables, and the random forest model was effective at predicting ecological variables, including the hazard rating of trees to disturbances.     

Holocene vegetation and fire dynamics in the supra-Mediterranean belt of the Gredos Range (central Iberian Peninsula)

Abstract

High-resolution pollen, macrofossil and charcoal data, combined with multivariate analysis, were used to reconstruct Holocene vegetation and fire dynamics at Manaderos. The studied mire is located in a highly valued location in the supra-Mediterranean belt of the Gredos Range (central Iberian Peninsula). The record started at 1260?calendar years (cal yrs) BP, according to eight radiocarbon dates, with the occurrence of an open Quercus pyrenaica forest and Pinus nigra stands. The palynological data show a dramatic change ～380?cal yrs BP, when the oak forest was progressively replaced by a maritime pine one. The interpretation of this record is related to an increase in agricultural and livestock activities and changes in the role of fire, thus Pyrenean oak canopy was consumed by fires providing openings for Pinus pinaster, better adapted to fire. The results are compared with other sequences from the Spanish Central System in order to better understand the past dynamics of the main forest constituents and to provide a critical view of the role of fire, anthropic dynamics and climatic events.     

Fire-scars and polymodal age-structure provide evidence of fire-events in an Aleppo pine population in southern France

Aleppo pine (Pinus halepensis Mill.) is adapted to fire, the most important disturbance in Mediterranean ecosystems. This species is known to be sensitive to fire and is usually killed when burned, but has a powerful regenerative capacity following burning. Sometimes, however, pines survive within burned areas, suggesting a certain potential for recording fire events in terms of age-structure and eventually scars. In the present study, fire scars on Aleppo pine trunks were used to construct a 150-year fire record in a burned forest in southern France. Four fires were detected with a mean fire return interval of 27 years: minimum 13 years and maximum 45 years. The age structure of the Aleppo pine population was analyzed on the basis of dated fire-scars in order to test the role of fire in creating the polymodal structure of the pine population. Results show the presence of multiple “cohorts” (subpopulations) of Aleppo pine. There appear to have been several pulses of tree recruitment, with the two largest cohorts corresponding to regeneration after the 1919 and 2000 fires. Other fires were recognized based on fire scars but these were not associated with obvious post-fire pine recruitment. Regeneration success is likely to depend on fire severity and on the length of fire-free intervals. Fire history and associated age-structure can thus be reconstructed using Aleppo pine stands.     

A multi-scale looping approach to predict spatially dynamic patterns of functional species richness in changing landscapes

Land-use/land-cover (LU/LC) change is one of the main drivers of global biodiversity change. However, the lack of detailed data on species’ local distributions is frequently a major constraint to identify effective indicators of impact and to prescribe effective conservation and management measures. Here we aim to describe and demonstrate the applicability of a novel looping approach to predict spatially dynamic ecological responses to LU/LC changes. The methodology integrates statistical downscaling, multi-model inference, stochastic-dynamic modelling and simulations, and spatial projections under a common and interactive framework. We illustrate the approach with a study of passerine foraging groups and their potential indicator role under LU/LC change scenarios. Based on the coarse occurrence data from published atlases, this approach allowed transposing species richness to fine resolutions in order to assess regional ecological integrity by up scaling the local responses of those indicators again at the landscape level. Overall, our proposed framework was able to provide realistic patterns of passerine foraging responses to LU/LC changes, highlighting the usefulness of existing databases for model-based research in addressing complex emergent problems across scales. Comparative analysis between simulations and independent field data showed a promising model performance, with consistent projections of the local passerine functional composition for a significant number of point-counts tested. Our approach represents a contribution for more universal applications in the scope of conservation and landscape planning, especially when fine resolution data is difficult to obtain due to resources constraints.     

Effects of Chronic Human Activities on Invasion of Longleaf Pine Forests by Sand Pine

Chronic human activities may result in new and permanent successional trajectories in certain ecosystems. The invasion of longleaf pine ecosystems by sand pine in the Florida Panhandle is one such change in the landscape. This study examined the spatial pattern of sand pine expansion and explored the natural and anthropogenic disturbances that fostered this invasion. Aerial photographs (1949, 1994) and Geographic Information Systems analyses confirmed sand pine expansion at Eglin Air Force Base. In 1949, there were 8,982 ha of sand pine in the southern portion of the study area near riparian and coastal lowland forests. By 1994, sand pine had expanded further upland and inland, for a total of 17,147 ha in the study area. Sand pine age data showed that this expansion had started by 1920 but increased rapidly in the 1940s. Historical accounts and structural data from stands suggest that land-use activities associated with the extraction of turpentine promoted the invasion by sand pine. Fires were suppressed in longleaf pine forests to protect turpentine trees, resulting in increased vegetation cover and decreased regeneration of longleaf pine. In addition, stands were typically harvested after turpentining, and there was little or no advanced regeneration of longleaf pine. Sand pine age histograms showed that the onset of high establishment rates (1940s) coincided with changes in land ownership and widespread fire suppression. Sand pine is likely to persist in these ecosystems due to its abundant regeneration. Received 17 March 1999; accepted 28 January 2000.     

Abiotic factors modulate post-drought growth resilience of Scots pine plantations and rear-edge Scots pine and oak forests

The proportion of planted forests in the Mediterranean Basin is one of the largest in the world. These plantations are dominated by pine species and present a series of characteristics such as low elevation, high competition or small tree size that make them more vulnerable to droughts. However, quantitative assessments of their post-drought growth resilience in accordance with species, site factors and tree characteristics are lacking. In this study we sampled 164 trees at four forest sites located in the drought-prone Sierra Nevada, southeastern Spain. We compared growth responsiveness to drought in rear-edge planted vs. relic natural Scots pine (Pinus sylvestris) and coexisting Pyrenean oak (Quercus pyrenaica) stands. Our objective was to characterize and compare the different growth responses to drought between species and sites and the effect of the main physiographic factors (altitude, aspect, and slope) on these responses since the influence of these factors on post-drought resistance and resilience has received little attention to date. Our results reveal that the planted pine sites with the lowest mean growth rates displayed greater resistance during drought, and that higher altitude was associated with improved resistance and/or resilience for all species and sites. Natural pine and Pyrenean oak stands were better adapted to the dry climatic conditions of the Mediterranean region where the study was undertaken, displaying greater resistance and/or resilience and lower influence of drought on growth in comparison to stands of planted pines. These results suggest that promoting the conservation of high-elevation pine plantations and enhancing the regeneration of natural pine and oak may improve the resistance and resilience of these drought-prone forest ecosystems.     

An estimation of Scots pine (Pinus sylvestris L.) ecosystem productivity on reclaimed post-mining sites in Poland (central Europe) using of allometric equations

The work presents determination of the productivity of post-mining ecosystems (PME) derived from the aboveground biomass and annual biomass increment of Scots pine (Pinus sylvestris L.) stands. Single tree biomass assessment data from 42 cut trees were used in developing local allometric equations which may be used as an index during post-mining reforestation projects. The total biomass of pine ecosystems was determined from dendrometric measurements of sample plots with the use of elaborated equations. Forest floor vegetation was determined using the harvest method. Control plots were set up in the vicinity of the mining-sites at a managed forest on natural pine sites (NPS). Results confirm wide ecological amplitude of pine and indicate a high PME productivity on all substrates (2.79-4.34 Mg ha⁻¹ yr⁻¹).     

Evaluating the dendroclimatological potential of central Appalachian Table Mountain pine (Pinus pungens LAMB.)

Table Mountain pine (Pinus pungens Lamb.) is an Appalachian endemic that occurs in a patchy distribution from Georgia to Pennsylvania on xeric, fire-prone sites. Beginning in the 1990s, Table Mountain pine first showed usefulness in reconstructing fire regimes in these xeric Appalachian forests. The next step in Table Mountain pine research, the relationships between fire occurrence and climate variables, cannot happen until the dendrochronological potential of the species has been proven. This research investigates the annual ring structure and formation, relationship between climate and growth, and dendrochronological dating between trees in the same stands to prove the species’ effectiveness in climate reconstructions. Table Mountain pine cores and cross-sections were collected from four sites in the Virginia Appalachian Mountains. Results indicate that the species is sensitive to climate (monthly precipitation and temperature, PDSI and PHDI). Climate analyses revealed that Table Mountain pine growth is reduced when the previous year's September is drier than normal, the current year’s February is wetter than average, and the winter is colder than average. Results of these climate analyses illustrate a regional climate signal in Table Mountain pine stands; however, results from individual sites provided more significant details on the influence of climate on the species.     

Simulating the impacts of southern pine beetle and fire on the dynamics of xerophytic pine landscapes in the southern Appalachians

Question: Can fire be used to maintain Yellow pine (Pinus subgenus Diploxylon) stands disturbed by periodic outbreaks of southern pine beetle? Location: Southern Appalachian Mountains, USA. Methods: We used LANDIS to model vegetation disturbance and succession on four grids representative of xeric landscapes in the southern Appalachians. Forest dynamics of each landscape were simulated under three disturbance scenarios: southern pine beetle, fire, and southern pine beetle and fire, as well as a no disturbance scenario. We compared trends in the abundance of pine and hardwood functional types as well as individual species. Results: Yellow pine abundance and open woodland conditions were best maintained by a combination of fire and southern pine beetle disturbance on both low elevation sites as well as mid‐elevation ridges & peaks. On mid‐elevation SE‐W facing slopes, pine woodlands were best maintained by fire alone. Conclusions: Our simulations suggest that fire can help maintain open pine woodlands in stands affected by southern pine beetle outbreaks.