Search Results (17)

Pollarding, the practice of pruning tree branches at a specific height, has been crucial for managing open forests in Europe. This practice has supported the persistence of highly biodiverse open woodlands featuring ancient trees. Understanding historical management patterns is essential for interpreting past socioeconomic conditions and developing strategies to mimic traditional practices for biodiversity conservation. Current methods for reconstructing past management in pollarded forests often rely on techniques for large-scale forest disturbances, which may be suboptimal for detecting short-term perturbations like pollarding. To address this gap, we applied a random forest algorithm to detect pollarding events using tree-ring traits, reconstructing the multi-centennial management history of four deciduous oak dehesas in northern Spain. Our analysis revealed that short-term changes in latewood were the most reliable indicator of pollarding events. Pollarding typically reduced latewood production for about three years, with the most pronounced declines occurring toward the end of the pollarding effect period. Pollarding patterns underwent a major shift starting in the last third of the 20th century. Key historical decades of both high and low pollarding pressure were consistently observed across the studied dehesas. These findings enhance our understanding of these unique ecosystems and offer critical insights for their conservation. Full article

Forests are valuable for a wide variety of reasons, including biodiversity and carbon sequestration and storage. As such, in the U.S., various parties have proposed large-scale forest management efforts to enhance biodiversity conservation and carbon sequestration. Others, in contrast, argue that forests should not be harvested and have used legal action to prevent timber harvest on public lands. However, given that modern forests in the U.S. are reduced in extent compared to pre-settlement times, are subject to a reduced rate of natural disturbances but experience novel disturbances such as invasive pests and elevated fire risk, and are out of ecological balance due to past human activities, we suggest that active management is not only aligned with forest sustainability but necessary to conserve the maximum feasible range of forest biodiversity. In many areas of the U.S., species most in need of conservation depend on open canopy or early seral forest conditions, both of which can be created or maintained by forest harvest. We suggest that forest management for wood products simultaneously produces these needed conditions, whereas setting aside forests from management only benefits a subset of biodiversity. Although areas not subjected to forest harvest are important landscape components, active management is also needed to restore once-common forest types such as oak (Quercus spp.) woodland, mitigate invasive pests, reduce fire risk, and manage for species that need early seral or disturbed conditions, which are declining on the landscape. We document the current unbalanced conditions and the need for management with a focus on the eastern U.S. to demonstrate the issues. Full article

The southeastern United States was historically characterized by open forests featuring fire-adapted species before land-use change. We compared tree composition and densities of historical tree surveys (1802 to 1841) to contemporary tree surveys, with the application of a similarity metric, in the Coastal Plain ecological province of Mississippi, southeastern USA. We detected the boundary between historical pine and oak-pine open forests and differentiated historical and current forests. In the Coastal Plain, historical open forests converted from fire-tolerant longleaf pine (Pinus palustris) dominance, with pines comprising 88% of all trees, to loblolly (Pinus taeda) and slash (P. elliottii) pines within monocultures (45% of all trees). Wetland and successional tree species increased to 33% of all trees. Contemporary forests have greater tree densities, transitioning from closed woodlands (range of 168 to 268 trees ha⁻¹) to closed forests (336 trees ha⁻¹). In the ecotonal boundary of the northern Coastal Plain between historical pine and pine-oak woodlands, the pine component shifted over space from 88% to 34% of all trees due to a greater oak component. Fire-tolerant shortleaf pine and oak dominance converted to planted loblolly pine (52% of all trees), while successional tree species increased (20% of all trees). Historical tree densities represented woodlands (range of 144 to 204 trees ha⁻¹) but developed into closed forests (400 trees ha⁻¹). Historical Coastal Plain longleaf pine woodlands differed more from historical ecotonal oak-pine woodlands than contemporary forests differed from each other, demonstrating unique historical ecosystems and landscape-scale homogenization of ecosystems through forestation. Full article

While many tree species occur across the Coastal Plain of the southeastern United States, longleaf pine (Pinus palustris C. Lawson) savannas and woodlands once dominated this region. To quantify longleaf pine’s past primacy and trends in the Coastal Plain, we combined seven studies consisting of 255,000 trees from land surveys, conducted between 1810 and 1860 with other descriptions of historical forests, including change to the present day. Our synthesis found support that Pinus palustris predominantly constituted 77% of historical Coastal Plain trees and upland oaks (Quercus) contributed another 8%. While Pinus still dominates these forests today (58% of all trees), most are now either planted loblolly (Pinus taeda L.) or slash (Pinus elliottii Engelm.) pines. Water oak (Quercus nigra L.), live oak (Quercus virginiana Mill.), sweetgum (Liquidambar styraciflua L.), and red maple (Acer rubrum L.) have increased their proportions compared to historical surveys; both longleaf pine and upland oaks have declined to ≤5% of all trees. Our work also supports previous estimates that longleaf pine originally dominated over 25–30 million ha of Coastal Plain forests. As late as the early 1900s, longleaf pine may still have covered 20 million ha, but declined to 7.1 million ha by 1935 and dropped to 4.9 million ha by 1955. Longleaf pine’s regression continued into the mid-1990s, reaching a low of about 1.3 million ha; since then, restoration efforts have produced a modest recovery to 2.3 million ha. Two centuries of overcutting, land clearing, turpentining for chemicals, fire exclusion followed by forest densification by fire-sensitive species, and other silvicultural influences, including widespread loblolly and slash pine plantations, have greatly diminished the Coastal Plain’s once extensive open longleaf pine forests. Full article

The wood mouse Apodemus sylvaticus is common in woodlands and open areas of the Western Palearctic. Despite extensive research, little is known about its population ecology in fields in the Mediterranean area, where the climate involves great seasonal changes in environmental features. Here, we investigated wood mice seasonal fluctuations in the number of captures and population structure by sampling long-fallow fields and woodlands, i.e., oak forest and conifer plantation, in a heterogeneous landscape of central Italy. Mice were live-trapped every two months for three years (23.814 trap-days). The number of captures, mice body weight, and proportion of adult, residents and breeding individuals were analyzed. Mice dynamics changed across seasons and habitats. In fields, we recorded more captures, more reproductive individuals, and fewer non-adults and resident individuals in the warmer months compared to the colder months; mice were heavier in warmer months. During the cold season, the captures and adult proportion in fields were lower than in resource-rich woodlands. Breeding and non-resident mice were more abundant in fields than in woodlands in warmer months. Overall, the seasonal demographic variations we recorded provide evidence that fields can represent a suboptimal habitat in Mediterranean heterogeneous landscapes, acting nonetheless as a source of food resources, cover, and mates for mice in spring–summer. Full article

Oak open woodlands (dehesas) have outstanding socioeconomic and ecological values, sustain traditional agro-silvo-pastoral uses, provide high-value ecosystem services, and constitute key biodiversity hotspots. Cerambyx cerdo and Cerambyx welensii are two large, oak-living, wood-boring, sympatric longhorn beetles (Coleoptera: Cerambycidae) that may reach pest status in SW Spain, contributing to oak decline. Understanding species-specific habitat requirements determining occupancy–abundance patterns is needed to develop management or control strategies. We conducted a large-scale, four-year study using 1650 feeding traps to ascertain longhorn abundance and species-specific habitat suitability in relation to 18 ecological variables, 9 biotic (oak species, forest mass, trunk diameter, tree density, basal area, forest cover, shrub cover, ground cover, oak renewal), and 9 abiotic (bedrock outcrops, altitude, ground slope, aspect, mean temperature: annual/July/January, annual precipitation, insolation). Results showed that longhorn abundance was sensitive to most ecological variables and to many interactions between them. Interestingly, interactions between ecological variables and longhorn species were widespread, signifying that responses were species-specific and therefore predictive Generalized Linear Mixed Models (GLMMs) were different between species. Our research contributes to the understanding of the ecological factors that shape longhorn species-specific occupancy–abundance patterns, delves into their sympatric relationship, and contributes toward improving sustainable forest practices that will mitigate longhorn impact in oak open forests. Full article

Open woodlands dominated by shortleaf pine (Pinus echinata Mill.) and oak are historically an important component of the landscape across the southeastern United States. These ecosystems support numerous wildlife species, many of which have declined in recent years as the amount and condition of their habitat have declined. Land managers and private landowners need guidance on how to efficiently and accurately quantify the condition and wildlife habitat value of the pine stands that they manage. Here we provide a set of rapid assessment metrics, based on NatureServe’s ecological integrity assessment (EIA) method, to (a) identify exemplary tracts that provide the best habitat for key wildlife species, and (b) monitor restoration efforts to assess progress toward the improved quality of existing tracts. To ensure an ecologically appropriate scaling of metrics, we distinguished six types of shortleaf pine–oak woodland: A.—Interior Highlands shortleaf pine–oak (including A.1—shortleaf pine–oak forest and woodlands; A.2—shortleaf pine–bluestem woodlands); B—montane longleaf pine–shortleaf pine woodlands; C—southern Appalachian pine–oak woodlands; D—West Gulf coastal plain shortleaf pine–oak woodlands; and E—southeast coastal plain and Piedmont shortleaf pine–oak woodlands. We relied on a narrative conceptual model and peer review-based indicator selection to identify a core set of 15 stand-level metrics (two were optional). Individual assessment points (thresholds) and ratings (Excellent, Good, Fair, and Poor) were developed that were sensitive to the distinct attributes of each of the five shortleaf pine–oak and Appalachian pine–oak types. Values for the metrics can all be collected using rapid field methods, such as using basal area prisms and ocular (visual) estimates of cover. Protocols for the consistent application of these EIA methods are provided. A case study is presented from the Cherokee National Forest in Tennessee. These methods provide improved and rapid EIA metrics for all shortleaf pine–oak ecosystems in the southeastern US to help guide conservation-minded landowners in assessing the biodiversity and priority wildlife values of shortleaf pine–oak and southern Appalachian pine–oak ecosystems. Full article

At the landscape scale, the Mediterranean region is a mosaic of habitats occupied by plants and animals with different resilience to fire. One of these habitats, the pine plantation, is characterized by its structural simplification and susceptibility to fire. Despite its high flammability, few studies have compared the response of animal communities between pine plantations and other autochthonous woodlands. For five years after a large fire in southwestern Europe, we surveyed reptiles in two natural habitats (oak forest, scrubland) and a pine plantation managed with salvage logging, a post-fire practice which consists of the complete harvesting and removal of death burnt trees. Reptile abundance and species composition were examined to assess differences in the reptile community between these habitats. Differences between burnt and unburnt transects were limited to the first year after the fire, while, over the entire five-year period, differences in species composition and abundance were due to vegetation type instead of fire. The pine logged area showed a delay in the recovery of vegetation and also in the appearance of many reptile species after the fire. At the reptile species level, we found evidence of both positive responses to fire (for lizards with high heliothermic activity) and negative ones (for specialist snake species). Overall, our results confirm the resilience of the reptile community to fire. The mosaic of habitats in the Mediterranean region and the openness caused by fire can increase the reptile biodiversity (landscape- plus pyro-diversity effects), but some practices such as salvage logging coupled with fire regime shifts (larger and more frequent fires) can compromise the conservation of the biodiversity in fire-prone regions. Full article

Phytophthora root rot caused by the pathogen Phytophthora cinnamomi is one of the main causes of oak mortality in Mediterranean open woodlands, the so-called dehesas. Disease control is challenging; therefore, new alternative measures are needed. This study focused on searching for natural biocontrol agents with the aim of developing integrated pest management (IPM) strategies in dehesas as a part of adaptive forest management (AFM) strategies. Native Trichoderma spp. were selectively isolated from healthy trees growing in damaged areas by P. cinnamomi root rot, using Rose Bengal selective medium. All Trichoderma (n = 95) isolates were evaluated against P. cinnamomi by mycelial growth inhibition (MGI). Forty-three isolates presented an MGI higher than 60%. Twenty-one isolates belonging to the highest categories of MGI were molecularly identified as T. gamsii, T. viridarium, T. hamatum, T. olivascens, T. virens, T. paraviridescens, T. linzhiense, T. hirsutum, T. samuelsii, and T. harzianum. Amongst the identified strains, 10 outstanding Trichoderma isolates were tested for mycoparasitism, showing values on a scale ranging from 3 to 4. As far as we know, this is the first report referring to the antagonistic activity of native Trichoderma spp. over P. cinnamomi strains cohabiting in the same infected dehesas. The analysis of the tree health status and MGI suggest that the presence of Trichoderma spp. might diminish or even avoid the development of P. cinnamomi, protecting trees from the worst effects of P. cinnamomi root rot. Full article

Since the late 1800s, pinyon–juniper woodland across the western U.S. has increased in density and areal extent and encroached into former grassland areas. The San Carlos Apache Tribe wants to gain qualitative and quantitative information on the historical conditions of their tribal woodlands to use as a baseline for restoration efforts. At the San Carlos Apache Reservation, in east-central Arizona, large swaths of woodlands containing varying mixtures of juniper (Juniperus spp.), pinyon (Pinus spp.) and evergreen oak (Quercus spp.) are culturally important to the Tribe and are a focus for restoration. To determine changes in canopy cover, we developed image analysis techniques to monitor tree and large shrub cover using 1935 and 2017 aerial imagery and compared results over the 82-year interval. Results showed a substantial increase in the canopy cover of the former savannas, and encroachment (mostly juniper) into the former grasslands of Big Prairie. The Tribe is currently engaged in converting juniper woodland back into an open savanna, more characteristic of assumed pre-reservation conditions for that area. Our analysis shows areas on Bee Flat that, under the Tribe’s active restoration efforts, have returned woodland canopy cover to levels roughly analogous to that measured in 1935. Full article

Research Highlights: The regeneration of Quercus species is usually very difficult in many oak woodlands transformed by livestock farming. Some studies have reported that shrubs can facilitate regeneration. However, the strength of interaction may vary depending on, among other factors, the shrub species and the stress tolerance of the oak species. Moreover, further studies are necessary to clarify the relative importance of the two facilitation mechanisms in the same community. Background and Objectives: Cytisus multiflorus (L’Her.) Sweet is a predominant shrub species in the Mediterranean grazed open-oak-woodlands found in the central west of the Iberian Peninsula (bioclimatic limit) and is present with Quercus pyrenaica Willd and Quercus ilex subsp. ballota Samp trees. Thus, we assessed the effect of these native shrubs and acorn size, and the effect of excluding large herbivores, on the seedling emergence of two contrasting co-occurring Quercus species under a bioclimatic limit. Materials and Methods: A manipulative field experiment was carried out considering four treatments as a combination of shrubs (shrub/no-shrub) and fence (fenced/open) factors. A total of twenty plots, five replicates for each treatment were available. In each plot, 20 acorns were sown: 10 acorns (5 small and 5 large) for each Quercus species. Acorn emergence was recorded during the first four years following the sowing. Results: Seedling emergence took place mostly in the spring of the first year after sowing. The presence of shrub was the main significant factor and incremented the emergence of both Q. ilex and Q. pyrenaica. The effect of the fence depended on the Quercus species considered, improving only the emergence of Q. pyrenaica. A negative effect with the small acorns was detected but only for Q. pyrenaica. In all treatments, Q. ilex emerged more than Q. pyrenaica. Conclusions: C. multiflorus had a clear facilitative effect on the seedling emergence of Q. ilex and Q. pyrenaica, which was much greater than the physical effect that acorn size and excluding large herbivores had. As such, this native shrub may have a key role in oak regeneration in Mediterranean grazed areas. Furthermore, in these areas of contact between marcescent and sclerophyllous Quercus species, Q. ilex currently emerges more than Q. pyrenaica. This could be indicative of a shift towards more xeric climatic conditions, which could lead to a change in the dominant tree species in the future. However, this change could be modulated by the effects of native shrub and large herbivores. Full article

Gap Fraction, leaf pigment contents (content of chlorophylls a and b (${\mathrm{C}}_{ab}$) and carotenoids content (Car)), Leaf Mass per Area (LMA), and Equivalent Water Thickness (EWT) are considered relevant indicators of forests’ health status, influencing many biological and physical processes. Various methods exist to estimate these variables, often relying on the extensive use of Radiation Transfer Models (RTMs). While 3D RTMs are more realistic to model open canopies, their complexity leads to important computation times that limit the number of simulations that can be considered; 1D RTMs, although less realistic, are also less computationally expensive. We investigated the possibility to approximate the outputs of a 3D RTM (DART) from a 1D RTM (PROSAIL) to generate in very short time numerous extensive Look-Up Tables (LUTs). The intrinsic error of the approximation model was evaluated through comparison with DART reference values. The model was then used to generate LUTs used to estimate Gap Fraction, ${\mathrm{C}}_{ab}$, Car, EWT, and LMA of Blue Oak-dominant stands in a woodland savanna from AVIRIS-C data. Performances of the approximation model for estimation purposes compared to DART were evaluated using Wilmott’s index of agreement ($d_r$), and estimation accuracy was measured with coefficients of determination ($R^2$) and Root Mean Squared Error (RMSE). The low approximation error of the proposed model demonstrated that the model could be considered for canopy covers as low as 30%. Gap Fraction estimations presented similar performances with either DART or the approximation ($d_r$ 0.78 and 0.77, respectively), while ${\mathrm{C}}_{ab}$ and Car showed improved performances ($d_r$ increasing from 0.65 to 0.77 and 0.34 to 0.65, respectively). No satisfying estimation methods were found for LMA and EWT using either models, probably due to the high sensitivity of the scene’s reflectance to Gap Fraction and soil modeling at such low LAI. Overall, estimations using the approximated reflectances presented either similar or improved accuracy. Our findings show that it is possible to approximate DART reflectances from PROSAIL using a minimal number of DART outputs for calibration purposes, drastically reducing computation times to generate reflectance databases: 300,000 entries could be generated in 1.5 h, compared to the 12,666 total CPU hours necessary to generate the 21,840 calibration entries with DART. Full article

The scientific debate over how to make visible the connections between the standard System of National Accounts (SNA) and its ongoing satellite Environmental Economic Ecosystem Accounting–Experimental Ecosystem Accounting (SEEA–EEA) is a challenge that is still pending. The literature on environmental accounting of agroforestry and silvopastoral landscapes rarely values the multiple ecosystem services of an area, an economic unit (e.g., farm), or a vegetation type (e.g., holm oak—Quercus ilex L.—open woodland). Generally, the literature presents the market value of the products consumed directly or a correction of the latter that reduces their exchange values in order to approximate them to their resource rents. In our previous publications, we have applied and compared our Agroforestry Accounting System (AAS) with the System of National Accounts (SNA), and we refined the latter to avoid the lag between income generation and its accounting in the period in which the product is extracted. These previous publications did not develop experimental applications of the SEEA–EEA with comparisons to the SNA and it being integrated into the AAS. The main novelty of this article is that, for the first time, we present detailed applications and comparisons of our developments of the refined SEEA–EEA and refined SNA with a simplified version of the AAS. The accounting frameworks applied take the production and capital accounts in the process of being updated by the United Nations Statistics Division (UNSD) at the scale of the holm oak open woodlands of Andalusia into account. In this study, we compare three environmental accounting approaches for ecosystem services and environmental income measurements at basic and social prices: our slightly refined standard System of National Accounts (rSNA); our refined, updated and ongoing satellite System of Environmental Economic Accounting–Experimental Ecosystem Accounting (rSEEA–EEA); and our simplified Agroforestry Accounting System (sAAS). We tested them for 15 economic activities in 1408 thousand hectares of the predominantly mixed holm oak open woodland (HOW) land use tiles in the region of Andalusia, Spain. We considered the government institutional sector to be the collective owner of public economic activities, which we incorporated in the rSNA and the sAAS approaches. We discuss consistencies in environmental incomes identified from the results of the three ecosystem accounting frameworks applied to the HOW. The discrepancies in the measurement of ecosystem services of the government institutional sector between the rSEEA–EEA and the sAAS were due to the omission in the former of the government manufactured costs incurred in the supply of freely consumed public final products. The most notable finding of our comparison is that the ecosystem services and the environmental income results for individual market products offered the same values, whichever the ecosystem accounting framework applied. This was not the case with the ecosystem services of public products without market prices, due to the fact that the rSNA estimates these products at production cost and the rSEEA–EEA did not consider the government manufactured production costs and ordinary manufactured net operating margin of government final public product consumption. We also found that, according to modeling of the scheduled management of future biological resources of the HOW, the environmental income shows biological sustainability of the individual nature-based total product consumption. Full article

There is growing consensus regarding the implementation of a new statistical framework for environmental-economic accounting to improve ecosystem related policies. As the standard System of National Accounts (SNA) fails to measure the economic contribution of ecosystems to the total income of individuals, governments recognize the need to expand the standard SNA through the ongoing System of Environmental Economic Accounting (SEEA). Based on the authors’ own data, this study focuses on linking 15 economic activities and 12 ecosystem services for a holm oak (Quercus ilex L.) open woodlands (HOW) ecosystem type in Andalusia, Spain. We emphasize that overcoming the challenges of multiple use is preferable to measuring single ecosystem products for improving habitat conservation policies. The objectives of this paper are to measure and compare the environmental assets, ecosystem services, and incomes at basic and social prices by applying a refined version of the standard System of National Accounts (rSNA) and the authors’ Agroforestry Accounting System (AAS), respectively, to HOW. Considering intermediate products and consumptions of HOW farmer and government activities, we find that the rSNA ecosystem services and environmental incomes at basic prices are 123.3 €/ha and −28.0 €/ha, respectively, while those of the AAS at social prices are 442.2 €/ha and 250.8 €/ha. Given advances in non-market valuation techniques, we show that an expanded definition of economic activities can be applied to measure the contribution to total income of managed natural areas taking into account the multiple uses of the ecosystem type. However, HOW sustainability continues to be a challenging issue that requires ecological threshold indicators to be identified, not only because of the economic implications but also because they provide vital information on which to base policy implementation. Full article

This paper investigates the reliability of free and open-source algorithms used in the geographical object-based image classification (GEOBIA) of very high resolution (VHR) imagery surveyed by unmanned aerial vehicles (UAVs). UAV surveys were carried out in a cork oak woodland located in central Portugal at two different periods of the year (spring and summer). Segmentation and classification algorithms were implemented in the Orfeo ToolBox (OTB) configured in the QGIS environment for the GEOBIA process. Image segmentation was carried out using the Large-Scale Mean-Shift (LSMS) algorithm, while classification was performed by the means of two supervised classifiers, random forest (RF) and support vector machines (SVM), both of which are based on a machine learning approach. The original, informative content of the surveyed imagery, consisting of three radiometric bands (red, green, and NIR), was combined to obtain the normalized difference vegetation index (NDVI) and the digital surface model (DSM). The adopted methodology resulted in a classification with higher accuracy that is suitable for a structurally complex Mediterranean forest ecosystem such as cork oak woodlands, which are characterized by the presence of shrubs and herbs in the understory as well as tree shadows. To improve segmentation, which significantly affects the subsequent classification phase, several tests were performed using different values of the range radius and minimum region size parameters. Moreover, the consistent selection of training polygons proved to be critical to improving the results of both the RF and SVM classifiers. For both spring and summer imagery, the validation of the obtained results shows a very high accuracy level for both the SVM and RF classifiers, with kappa coefficient values ranging from 0.928 to 0.973 for RF and from 0.847 to 0.935 for SVM. Furthermore, the land cover class with the highest accuracy for both classifiers and for both flights was cork oak, which occupies the largest part of the study area. This study shows the reliability of fixed-wing UAV imagery for forest monitoring. The study also evidences the importance of planning UAV flights at solar noon to significantly reduce the shadows of trees in the obtained imagery, which is critical for classifying open forest ecosystems such as cork oak woodlands. Full article