Recent Forest Research Articles

Historical ecology of Mediterranean forests: Land use legacies on current understorey plants differ with time since abandonment and former agricultural use

AbstractQuestionsLand use legacies in current forest understorey vegetation, thoroughly studied in temperate regions, were investigated in a Mediterranean context. We tested the effect of three historical variables on current forest plant communities and traits: forest temporal continuity (ancient: forested before 1860, recent: reforested after 1860, and very recent forest: reforested after 1958) and type of land use in 1860 and 1958 (forest, pasture or arable land).LocationThe Regional Natural Park of Luberon (southeastern France).MethodsWe used a comprehensive vegetation plot database (473 species in 1,429 plots). Species’ response to historical variables was tested with logistic regressions, and the relationship between plant traits and historical variables was analysed with RLQ and fourth‐corner analyses.ResultsAmong all studied species, 250 responded to forest temporal continuity, 208 to 1860 land use, and 246 to 1958 land use. Species associated with ancient forests were more frequently forest specialists or forest edge species, shade‐tolerant and perennials, while species associated with recent and very recent forests were more frequently annuals, anemochorous and heliophilous species. Species exhibited different traits and ecological preferences according to the type of land use prior to forest: therophytes were more frequent on former arable land while chamaephytes were more frequent on former pasture. Trait responses to 1860 and 1958 land uses were globally consistent.ConclusionsThe effect of forest temporal continuity and past land use on forest understorey communities was consistent with other studies in northern Europe or northern America, which suggests that the same ecological processes apply in temperate lowland and Mediterranean regions. This study highlights a succession of plant communities in the long term and different trajectories of succession according to the type of former agricultural use. The long‐term legacies of past land use in current forest plant communities highlight the importance to preserve ancient forests, where typical forest species can be maintained.

The potential of generalized additive modelling for the prediction of radial growth of Norway spruce from Central Germany

During the past decades managed forest ecosystems in Central Europe underwent vast changes, induced by extreme climate conditions and occasionally adverse forest management. Tree ring width patterns mirror these changes and thus have been widely examined as environmental archives and reliable empirical data sources in ‘tree growth modelling’. Dendrochronologists often suppose linear co-variation among the covariates, variable independence and homoscedasticity. Conventionally, these assumptions were achieved by eliminating biological age trends (detrending) and removing the autocorrelation from the time series (pre-whitening). Particularly detrending might be biased according to the scientific problem and sometimes inflexible age models. In this study, we tackle these issues and examine the suitability of a flexible Generalized Additive Model (GAM) on recently developed tree ring width time series of 30 Norway spruce stands (Picea abies [L.] H. Karst) from Central Germany.The model was established to simultaneously cope with the mentioned detrending issue, to unravel nonlinear climate-growth relationships and to predict mean ring width time series for spruce stands in the region. Particularly the latter was of primary interest, since recent forest planning relies on static yield tables that often underestimate the actual growth.The model reliably captured the empirical data, indicated by a small Generalized Cross Validation criterion (GCV = 0.045) and a deviance explained of 88.6 %. The flexible additive smoothers accounted for the social status of individual trees, captured low frequency variations of changing growth conditions adequately and displayed a rather flat biological age trend. The radial increment responded positively to summer season precipitation of the current and previous year. Positive temperature responses were found during the early vegetation period, whereas high summer season temperatures negatively affected the radial growth. The seasonal transition from spring to summer in June induced a shift in the climate response of the linear predictor, leading to a distinct negative effect of temperature and a no-role of precipitation on the linear predictor.Most important, utilizing the calibrated GAM for the purely climate-driven prediction of mean ring width time series from five independent spruce sites revealed proper coherencies. Herein, the mean ring width for sites located within the climatic-optimum for spruce growth were more exactly predicted than for sites with adverse spruce growth conditions. In addition, large mean ring widths were systematically underestimated, whereas small mean ring widths were precisely predicted. Overall, we strongly recommend GAMs as a powerful tool for the investigation of nonlinear climate-growth relationships and for the prediction of radial growth in managed forest ecosystems.

Evaluating the Impact of Future Global Climate Change and Bioeconomy Scenarios on Ecosystem Services Using a Strategic Forest Management Decision Support System

Sustainable Forest Management (SFM) has become an important pillar of modern forest management, and one way to evaluate the sustainability of forestry is to assess long-term supply of ecosystem services (ESs) indicators. The concept of sustainability also has come to include adapting to climate change and the associated dynamic timber markets. This study aims to: 1) incorporate several ESs indicators in a Forest Management Decision Support System (FMDSS) that can deal with climate change and dynamic timber markets; and 2) analyse the impact that intensified forest management, resulting from global change scenarios that represent different levels of climate change mitigation efforts, will have on forest ES indicators in the west of Ireland. A linear programming model that optimized Net Present Value (NPV) from mill-gate sales was previously developed in Remsoft Woodstock, a DSS framework used for strategic forest planning around the world. This Woodstock model was modified to include the effects of global scenarios that include climate change and dynamic timber prices. This model was further developed to include indicators for five ESs (carbon storage in the forest as well as in harvested wood products and carbon substitution, windthrow risk, biodiversity, water quality, and cultural values), to assess the impacts of these global scenarios on the forest landscape and the sustainability of forest management. The ES indicator values were mainly linked to forest age, forest type, and yield tables, and their inclusion in the FMDSS had almost no impact on total model run times. Intensified forest clearfelling, as a result of increasing timber prices associated with most global scenarios, led to increased phosphor emissions to waterbodies, and reductions in windthrow risk and carbon storage. The global scenarios only resulted in minor differences in the indicator values for biodiversity and cultural values. Besides the global scenarios, recent forest policy development and the poor soil conditions in the study area impacted on the results. The developed system, with its innovative method to incorporate climate change and associated market dynamics, could be applied to other forest landscapes in Ireland and Europe, or indeed by any forest company or organisation that uses Remsoft Woodstock.

Rickettsioses as Major Etiologies of Unrecognized Acute Febrile Illness, Sabah, East Malaysia.

Orientia tsutsugamushi, spotted fever group rickettsioses, and typhus group rickettsioses (TGR) are reemerging causes of acute febrile illness (AFI) in Southeast Asia. To further delineate extent, we enrolled patients >4 weeks of age with nonmalarial AFI in Sabah, Malaysia, during 2013-2015. We confirmed rickettsioses (past or acute, IgG titer >160) in 126/354 (36%) patients. We confirmed acute rickettsioses (paired 4-fold IgG titer rise to >160) in 38/145 (26%) patients: 23 O. tsutsugamushi, 9 spotted fever group, 4 TGR, 1 O. tsutsugamushi/spotted fever group, and 1 O. tsutsugamushi/TGR. PCR results were positive in 11/319 (3%) patients. Confirmed rickettsioses were more common in male adults; agricultural/plantation work and recent forest exposure were risk factors. Dizziness and acute hearing loss but not eschars were reported more often with acute rickettsioses. Only 2 patients were treated with doxycycline. Acute rickettsioses are common (>26%), underrecognized, and untreated etiologies of AFI in East Malaysia; empirical doxycycline treatment should be considered.

A relic of the past: current genetic patterns of the palaeoendemic tree Nothofagus macrocarpa were shaped by climatic oscillations in central Chile

The Mediterranean-type forest of central Chile is considered a 'biodiversity hotspot' and a relic of a wider ancient distribution produced by past climatic oscillations. Nothofagus macrocarpa, commonly known as 'roble de Santiago', is a threatened palaeoendemic of this forest, poorly represented in the protected area system. This tree has been repeatedly misidentified as the sister species N. obliqua, which has affected its recognition and protection. Only a few populations of N. macrocarpa remain within a matrix of intensive land use that has been affected by recent forest fires. We tested the hypothesis that current populations of N. macrocarpa are a relic state of a previously widespread range, with the aim of contributing to its identification, its biogeographical history and the design of conservation measures using genetic information. We analysed remnant N. macrocarpa forests using nuclear (nDNA) and chloroplast DNA (cpDNA) sequences, conducted phylogenetic and phylogeographical analyses to reconstruct its biogeographical history, and assessed microsatellites [simple sequence repeats (SSRs)] to determine contemporary patters of diversity within and among all remnant populations. We also examined the degree of past, current and potential future isolation of N. macrocarpa populations using ecological niche models (ENMs). The species N. macrocarpa was confirmed by nDNA sequences, as previously suggested by chromosomal analysis. Small isolated populations of N. macrocarpa exhibited moderate to high genetic diversity according to SSRs. cpDNA analysis revealed a marked past latitudinal geographical structure, whereas analysis of SSRs did not find such current structure. ENM analyses revealed local expansion-contraction of the N. macrocarpa range during warmer periods, particularly in the northern and central ranges where basal-most cpDNA haplotypes were detected, and recent expansion to the south of the distribution. Genetic patterns confirm that N. macrocarpa is a distinct species and suggest a marked latitudinal relic structure in at least two evolutionarily significant units, despite contemporary among-population gene flow. This information must be considered when choosing individuals (seeds and/or propagules) for restoration purposes, to avoid the admixture of divergent genetic stocks.

Reviewing the Use of Resilience Concepts in Forest Sciences.

Resilience is a key concept to deal with an uncertain future in forestry. In recent years, it has received increasing attention from both research and practice. However, a common understanding of what resilience means in a forestry context and how to operationalise it is lacking. Here, we conducted a systematic review of the recent forest science literature on resilience in the forestry context, synthesizing how resilience is defined and assessed. Based on a detailed review of 255 studies, we analysed how the concepts of engineering resilience, ecological resilience and social-ecological resilience are used in forest sciences. A clear majority of the studies applied the concept of engineering resilience, quantifying resilience as the recovery time after a disturbance. The two most used indicators for engineering resilience were basal area increment and vegetation cover, whereas ecological resilience studies frequently focus on vegetation cover and tree density. In contrast, important social-ecological resilience indicators used in the literature are socioeconomic diversity and stock of natural resources. In the context of global change, we expected an increase in studies adopting the more holistic social-ecological resilience concept, but this was not the observed trend. Our analysis points to the nestedness of these three resilience concepts, suggesting that they are complementary rather than contradictory. It also means that the variety of resilience approaches does not need to be an obstacle for operationalisation of the concept. We provide guidance for choosing the most suitable resilience concept and indicators based on the management, disturbance and application context.

Effects of Past and Present-Day Landscape Structure on Forest Soil Microorganisms

Theory surrounding landscape ecology have been built on the species distribution of birds and plants, but increasing evidence now exists for below-ground organisms, whose dispersal may also be affected by above-ground landscape structures. Uncertainties remain for how communities of microorganisms respond to landscape structure over time, and whether some groups of microorganisms react more than others. Here, we investigated if fungal or bacterial diversity is driven by the amount of forest cover in the current or the past landscape. We tested the Habitat Amount Hypothesis (HAH) on ancient forests of the Cevennes national park, that experienced increased fragmentation 150 years ago, and are today surrounded by recent forests. As ancient forests are often more diverse in plant species, we hypothesized that the higher quantity of ancient forests in the landscape, the richer local fungal and bacterial communities would be. More precisely, we expected that ectomycorrhizal fungi, and pathotrophic fungi, often indicators of mature forests, would be also more sensitive to forest history and therefore to the quantity of ancient forests than bacteria and saprotrophic fungi. We sampled 40 soil cores per 0.5 ha, pooled in 8 composite samples per plot in 27 landscapes and sequenced ITS and 16S markers by Illumina-Mi seq. To identify functional groups of fungi, we relied on their taxonomy and the use of public databases. Our results partly follow the HAH, as fungal richness was positively related with the quantity of ancient forests in the landscape and not by the focal patch size. Ectomycorrhizal and pathotrophic fungi were positively affected by the ancient forest cover, and so were saprotrophic ones, but not bacteria. Local factors also shaped the communities such as soil composition and elevation, confirming classical patterns in soil microbial ecology. Interestingly, past landscape structure was better at explaining fungal community richness than contemporary landscape, suggesting a time lag in the response of communities to landscape modification and a potential extinction debt. Our results reveal the importance of below-ground communities in studies of landscape and historical ecology, with their structure and functions likely to be intimately linked with soil and landscape history.

Migration tracking reveals geographic variation in the vulnerability of a Nearctic-Neotropical migrant bird

We compared the vulnerability of a Nearctic-Neotropical migrant (Swainson’s Thrush, Catharus ustulatus) for three geographically-defined breeding populations in California by linking breeding and wintering regions, estimating migration distances, and quantifying relative forest loss. Using data from light-level geolocator and GPS tags, we found that breeding birds from the relatively robust coastal population in the San Francisco Bay area wintered predominantly in western Mexico (n = 18), whereas the far rarer breeding birds from two inland populations that occur near one another in the Sierra Nevada and southern Cascades mountain ranges migrated to farther wintering destinations, with birds from the Lassen region (n = 5) predominantly going to Central America and birds from the Tahoe region (n = 7) predominantly to South America. Landscape-level relative forest loss was greater in the breeding and wintering regions of the two Cascade-Sierra populations than those of coastal birds. Longer migration distances and greater exposure to recent forest loss suggest greater current vulnerability of Cascade-Sierra birds. Our results demonstrate that for some species, quantifying migration distances and destinations across relatively small distances among breeding populations (in this case, 140–250 km apart) can identify dramatically different vulnerabilities that need to be considered in conservation planning.

Mapping Forest Disturbances between 1987–2016 Using All Available Time Series Landsat TM/ETM+ Imagery: Developing a Reliable Methodology for Georgia, United States

Forest resources have a high economic value in the State of Georgia (USA) and the landscape is frequently disturbed as a part of forest management activities, such as plantation forest management activities. Thus, tracking the stand-clearing disturbance history in a spatially referenced manner might be pivotal in discussions of forest resource sustainability within the State. The two major objectives of this research are (i) to develop and test a reliable methodology for statewide tracking of forest disturbances in Georgia, (ii) to consider and discuss the use and implications of the information derived from the forest disturbance map. Two primary disturbance detection methods, a threshold algorithm and a statistical boundary method, were combined to develop a robust estimation of recent forest disturbance history. The developed model was used to create a forest disturbance record for the years 1987–2016, through the use of all available Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM+) data. The final product was a raster database, where each pixel was assigned a value corresponding to the last disturbance year. The overall accuracy of the forest disturbance map was 87%, and it indicated that 4,503,253 ha, equivalent to 29.2% of the total land area in Georgia, experienced disturbances between 1987 and 2016. The estimated disturbed area in each year was highly variable and ranged between 84,651 ha (±36,354 ha) to 211,780 ha (±49,504 ha). By combining the use of the disturbance map along with the 2016 database from the National Land Cover Database (NLCD), we also analyzed the regional variation in the disturbance history. This analysis indicated that disturbed forests in urban areas were more likely to be converted to other land-uses. The forest disturbance record created in this research provides the necessary spatial data and address forest resource sustainability in Georgia. Additionally, the methodology used has application in the analysis of other resources, such as the estimation of the aboveground forest biomass.

Direct estimates of metapopulation capacity from dispersal show high interannual variability, but little effect of recent forest encroachment on network persistence

CONTEXT: Habitat loss and isolation are leading threats for biodiversity. Alpine habitat throughout the world is being lost and fragmented by forest encroachment. Previous analysis of forest encroachment from 1952 to 1993 in a population network along Jumpingpound Ridge, Alberta, Canada showed a 78% loss in meadow area, resulting in an estimated 41% reduction in dispersal of the alpine butterfly Parnassius smintheus. OBJECTIVES: Here, we pursue three questions. First, has forest encroachment continued since 1993? Second, if so, has it affected butterfly dispersal? And third, have any changes altered estimates of metapopulation persistence of this species? METHODS: The area of each meadow and distance between each pair of meadows were determined in GIS using aerial photographs taken in 1952, 1993, 1999, 2008, and 2012. Mark-recapture (1995–2015) and landscape data were used to estimate annual butterfly dispersal and network persistence. RESULTS: Alpine meadows along Jumpingpound Ridge continued to be fragmented by encroaching forest showing a decrease in area and increase in the amount of forest between them. Annual dispersal parameters varied over the study, but the only consistent response to forest encroachment was an increase in male dispersal distance within meadow habitat. Estimates of metapopulation capacity also varied greatly among years due to variability in dispersal. The network was predicted to persist based on nearly all estimates. CONCLUSIONS: Metapopulation capacity is a potentially powerful tool for conservation, but interannual variability in dispersal hampers its utility under realistic conditions and could result in erroneous conclusions regarding metapopulation persistence. The 7 km long network of 18 subpopulations of Parnassius smintheus along the Jumpingpound Ridge and Cox Hill is currently at little risk of extinction due to forest encroachment.

Recent dynamics of pine and oak forests in Mexico

Temperate forests worldwide are dominated by two families, Pinaceae and Fagaceae. In the last decades, temperate forests are experiencing rapid changes and, in some regions, a directional increase in Fagaceae abundance at the expense of Pinaceae has been detected. Here, we analyze the recent forest dynamics of Pinaceae and Fagaceae in Mexican forests to assess whether there is a directional change in the relative abundance of these two families and identify the environmental factors that are determining their recent growth dynamics. We take advantage of repeated surveys data from the Mexican National Forest and Soil Inventory, obtained in 2004–2007 and 2009–2014. Our results show that, at present, there is no overall directional trend in the changes of the relative abundance of Pinaceae and Fagaceae in the temperate forests of Mexico, which likely reflects a complex mixture of forest dynamics, locally dominated by different types of disturbance or successional dynamics. At the same time, however, we find evidence that the growth of Fagaceae species is responding more favorably than that of Pinaceae to currently rising temperatures in Mexico. Although these results need to be confirmed by longer-term studies, the resulting changes in composition could potentially have strong impacts on forest ecosystem function in the midterm.

Light availability and land‐use history drive biodiversity and functional changes in forest herb layer communities

Abstract A central challenge of today's ecological research is predicting how ecosystems will develop under future global change. Accurate predictions are complicated by (a) simultaneous effects of different drivers, such as climate change, nitrogen deposition and management changes; and (b) legacy effects from previous land use. We tested whether herb layer biodiversity (i.e. richness, Shannon diversity and evenness) and functional (i.e. herb cover, specific leaf area [SLA] and plant height) responses to environmental change drivers depended on land‐use history. We used resurvey data from 192 plots across nineteen European temperate forest regions, with large spatial variability in environmental change factors. We tested for interactions between land‐use history, distinguishing ancient and recent (i.e. post‐agricultural) forests and four drivers: temperature, nitrogen deposition, and aridity at the regional scale and light dynamics at the plot‐scale. Land‐use history significantly modulated global change effects on the functional signature of the herb layer (i.e. cover, SLA and plant height). Light availability was the main environmental driver of change interacting with land‐use history. We found greater herb cover and plant height decreases and SLA increases with decreasing light availability in ancient than in recent forests. Furthermore, we found greater decreases in herb cover with increased nitrogen deposition in ancient forests, whereas warming had the strongest decreasing effect on the herb cover in recent forests. Interactive effects between land‐use history and global change on biodiversity were not found, but species evenness increased more in ancient than in recent forests. Synthesis. Our results demonstrate that land‐use history should not be overlooked when predicting forest herb layer responses to global change. Moreover, we found that herb layer composition in semi‐natural deciduous forests is mainly controlled by local canopy characteristics, regulating light levels at the forest floor, and much less by environmental changes at the regional scale (here: warming, nitrogen deposition and aridity). The observed disconnect between biodiversity and functional herb layer responses to environmental changes demonstrates the importance of assessing both types of responses to increase our understanding of the possible impact of global change on the herb layer.

Redbud woodlands conservation status in Afghanistan: Implications for sustaining vulnerable ecosystems under multiple drivers of change

Afghan redbud (Cercis griffithii Boiss.) woodlands near Kabul, Afghanistan face continued impacts from multiple drivers of change, including urban expansion, grazing, illegal cutting, and the implementation of forest policies. In this study, we collected ecological and social data from three sites to assess stand characteristics, as well as community perceptions on the drivers of change impacting them. A survey of community perceptions revealed that while only 24% of respondents perceived that natural regeneration was occurring on redbud forests, only 25% perceived that the forests were declining in status. Respondents perceived that Afghan redbud stands were exposed to multiple proximate and underlying drivers of change, although these perceptions differed across the three sites. Ecological surveys of stand conditions indicated that although all three study sites were exposed to the pressures of urbanization, the intensity of wood collection differed among the sites. Differences in contextual factors, such as the availability of effective traditional institutions, socio-demographic characteristics of residents, and the availability of alternative sources of fuel seem to explain the differences in fuelwood collection among the sites. Following the collapse of the Taliban regime, the heaviest cutting was associated with stands where unauthorized construction of new houses by repatriated populations from Pakistan and Iran was most prevalent, while impacts were lower where alternative fuel sources were available and local institutions were effective. Given the challenges entailed in the enforcement of recent forest protection policies in Afghanistan, our findings suggest that a promising starting point for the sustainable management of Afghan redbud forests is the initiation of a community-based natural resource management approach that addresses local socio-economic concerns while engaging local communities in the decision-making process. Conservation programs in conflict-impacted environments should consider local government capacity and stakeholder motivations to propose practical alternatives to strict forest protection policies. Training local policing authorities to differentiate between destructive and sustainable natural resource management practices and educating local populations on sustainable use could catalyze improved environmental engagement.

Soil moisture and a legacy of prehistoric human activities have contributed to the extraordinary plant species diversity of grasslands in the White Carpathians

The factors that determine the unique species richness and composition of some temperate grasslands are poorly known. Uniqueness of the extraordinarily species-rich grasslands in the White Carpathian mountain range (Czech Republic, Slovakia), with many disjunct occurrences of species, have been previously attributed to intermittently wet deep soils, which facilitate the co-occurrence of steppe and wet-grassland species, and Holocene continuity of open land, resulted in large species pools. Based on a detailed investigation of 23 well-preserved regularly mown grasslands differing in their vegetation composition and species richness, we tested the relative importance of the hypothetical determinants of compositional variability within semi-dry grasslands. For the first time we included measurements of seasonal moisture at different soil depths and landscape differences in the intensity of the effect of prehistoric humans. Soil moisture was measured using the frequency-domain reflectometry based Profile Probe PR2 sensor at depths of 10, 20, 30, 40 and 60 cm in the soil, repeatedly every four weeks from April to November. Soil samples were taken from the same depths in order to determine soil basicity and nutrient content. As a proxy of the intensity of the effect of prehistoric human activities, mean distances between sampled localities and the five nearest Neolithic or Aeneolithic settlements were used. The species richness was best explained by mean soil moisture, which increased towards the most species-rich grasslands, whereas the distance from prehistoric settlements had no effect. Basicity, moisture and the distance from prehistoric settlements had significant conditional effects on species composition. There was a high frequency of species of intermittently wet soils, thermophilous oak forests and forest fringes in the most valuable grasslands, which are located mostly in the south-western part of the area where the soils were moister and closer to prehistoric settlements, but the seasonal variation in moisture was not high. We conclude that coexistence of species from different habitats is dependent on regular management and high soil moisture throughout the growing season. Due to intermediate moisture conditions that are tolerated by multiple ecological groups of species, many species may locally coexist and form a species-rich grassland community of unique species composition. In addition, prehistoric human activities contributed to landscape openness and helped maintain a forest-steppe species pool during the Holocene forest optimum. Our results indicate that although this historical determinant shapes predominantly the species composition pattern, the extraordinarily species-rich spots are determined rather by abiotic factors, such as intermediate moisture and biotic interactions resulting from the type and duration of management practices.

Design and Implementation of an Automatic Forest Fire Extinguisher Using Sprinklers

Objectives/methods: Recent forest fires have damaged many acres of forest, not only do they harm the forest, but they are also a major threat to plant and animal life. It is more difficult to extinguish such fires. Rather than regretting injuries, it is better to take care. This study provides a one-time solution for an automatic fire extinguisher that requires a sprinkler to drowse the fire. Findings/application: Sensors used are a smoke detector, a digital humidity and temperature (DHT), and a buzzer warning. There is a centrifugal pump which gives the necessary pressure to the water. When a forest fire is in operation, the smoke detector detects the smoke, the relay turns on the pump, and the sprinkler begins to turn 360 degrees and drowses the fire.Keywords: Recent Forest Fires, Sprinkler, Injuries, Automatic fire extinguisher

¿Es sustentable el aprovechamiento de tierra de hoja en bosques de encino?

Se investigó si el esquema actual con el que se realiza el aprovechamiento de tierra de hoja es sustentable. Con este fin se evaluó la producción de hojarasca en un bosque de encino con aprovechamiento de tierra de hoja bajo tres condiciones: sin aprovechamiento (C1), aprovechamiento en los últimos dos años (C2) y aprovechamiento de más de dos años (C3). Se estimó la cantidad anual de nutrientes (N, P, K, Ca, Mg y S) que regresa al piso forestal mediante la caída de hojarasca. Se emplearon trampas de hojarasca de 0.5 m2 de área. La producción de hojarasca fue mayor en C2 y C3 [(9.36 ± 0.64; 10.04 ± 1.92) Mg ha-1 año-1, respectivamente], en comparación con C1 [(6.74 ± 0.45) Mg ha-1 año-1]. La cantidad de nutrientes que regresa al piso forestal es 40% mayor en los sitios bajo aprovechamiento que en los sitios sin aprovechamiento. Los resultados sugieren que el aprovechamiento de tierra de hoja estimula la producción de hojarasca. Sin embargo, aun cuando pueda haber un proceso de estimulación en la producción, se debe tener cuidado con el tiempo que se deja descansar un área bajo aprovechamiento, ya que, de acuerdo con los resultados de este estudio, se requieren 14 años de descanso para aprovechar en forma sustentable un mismo sitio; es decir, un tiempo al menos dos veces y media mayor al que se da actualmente. Un esquema sustentable implica que el tiempo entre dos fechas de aprovechamiento es igual al tiempo requerido para formar la capa orgánica retirada.

The role of land cover change in Arctic-Boreal greening and browning trends

Many studies have used time series of satellite-derived vegetation indices to identify so-called greening and browning trends across the northern high-latitudes and to suggest that the productivity of Arctic-Boreal ecosystems is changing in response to climate forcing at local and continental scales. However, disturbances that alter land cover are prevalent in Arctic-Boreal ecosystems, and changes in Arctic-Boreal land cover, which complicate interpretation of trends in vegetation indices, have mostly been ignored in previous studies. Here we use a new land cover change dataset derived from Landsat imagery to explore the extent to which land cover and land cover change influence trends in the normalized difference vegetation index (NDVI) over a large (3.76 M km2) area of NASA’s Arctic Boreal Vulnerability Experiment, which spans much of northwestern Canada and Alaska. Between 1984 and 2012, 21.2% of the study domain experienced land cover change and 42.7% had significant NDVI trends. Land cover change occurred in 27.6% of locations with significant NDVI trends during this period and resulted in greening and browning rates 48%–128% higher than in areas of stable land cover. While the majority of land cover change areas experienced significant NDVI trends, more than half of areas with stable land cover did not. Further, the extent and magnitude of browning and greening trends varied substantially as a function of land cover class and land cover change type. Forest disturbance from fire and timber harvest drove over one third of statistically significant NDVI trends and created complex mosaics of recent forest loss (as browning) and post-disturbance recovery (as greening) at both landscape and continental scale. Our results demonstrate the importance of land cover changes in highly disturbed high-latitude ecosystems for interpreting trends of NDVI and productivity across multiple spatial scales.

Distribution of soil properties along forest-grassland interfaces: Influence of permanent environmental factors or land-use after-effects?

Soil properties vary spatially according to land use; both because land users have selected specific soil properties for specific land uses, and land uses modify the soil properties. However, permanent environment factors and land-use effects are unlikely to display the exact same spatial patterns. Study of the spatial and historical patterns of distribution of soil properties could help to separate between these two causes. In this aim, we studied 22 forest-grassland interfaces with controlled historical configurations in northeast France. In each land use (forest and grassland), three distances to the edge (edge, periphery and core) and two land-use histories (ancient and recent) were studied.Along forest-grassland interfaces, forests were usually located slightly upslope of grasslands, and mainly because this non-random topographic position the topsoil texture was significantly more silty in forests, and clayey in grasslands. After statistically controlling for the effects of topography and soil texture, we observed two main gradients of variation in soil properties according to the distance-to-edge (acidity in forest and nutrient content in grassland). In forest, pH and Ca dropped from the edges to the peripheries (15 m distance), while in grassland, C, N, P and Na sharply increased from the edges to the cores (25 m distance). These results demonstrate, through the edge effect, the strong influence of the land use on a part of soil properties. Furthermore, less than two centuries after grassland afforestation or deforestation, we observed that soil properties in recent forests and recent grasslands were respectively closer to their current land use than to their former land use. These results demonstrate a rapid change in soil properties after land-use change. However, recent forests and recent grasslands kept a legacy of soil texture from their former land use, respectively. Recent grasslands also kept a lower soil density, N and Na content compared to ancient grasslands.Hence, this study of forest-grassland interfaces show strong and short-scale relationships between land use and soil properties and suggest that they express both original choices of land users for specific soil properties and land-use after-effects. The non-random topographic position of the forest-grassland interfaces indicates a conscious choice of this positioning by the land users, for agronomic reasons. Beyond that, land use, through vegetation composition and management practices, also has a strong impact on soil properties. The fact that land-use changes affect most soil properties after only a few decades confirms the existence of land-use effects over time.

Recent Forest Cover Loss in the Core Zones of the Monarch Butterfly Biosphere Reserve in Mexico

The Monarch Butterfly Biosphere Reserve (MBBR) in central Mexico was established in 2000 to protect monarch butterfly (Danaus plexippus) overwintering colonies and contribute to the conservation of the monarch migratory phenomenon. Since it was decreed, the MBBR has faced deforestation pressures (forest cover loss) due to illegal logging and climatic factors. Here we report deforestation trends from 2012 to 2018 in the core zones of the MBBR where most monarch overwintering colonies perch. We used aerial ortho-photographs and satellite images complemented with field validation for temporal comparisons. During this period, 163.44 ha of forest cover were affected; 125.44 ha due to natural factors (rain and wind), 25.86 ha due to large-scale illegal logging, and 12.14 ha due to small-scale illegal logging. The core zone of the MBBR located in the State of Michoacan showed the highest deforestation values with 94.07 ha lost due to climatic factors, and 32.63 ha lost due to large-scale illegal logging. Over all illegal logging significantly decreased in the core zones of the MBBR due to an effective shared conservation effort including local communities, NGOs, academic institutions, governmental agencies, and philanthropists. Our study also showed a significant decrease of approximately 98% in large-scale illegal logging in the core zones of the MBBR compared to previous years from 2001 to 2012 (Vidal et al., 2013). Deforestation due to climatic factors remained similar (120 to 130 ha) between both studies. The decrease of deforestation during the period studied suggests that factors elsewhere rather than deforestation in the monarch butterfly’s winter habitat have strongly contributed to the dramatic population declines observed in recent years of monarch overwintering colonies since 2010.

The economy of selective cutting in recent mixed stands during restoration of temperate deciduous forest

ABSTRACTForest cover is increasing in many regions due to spontaneous reforestation on abandoned pastures and fields. The resulting recent forests may need management to improve ecosystem quality, and this could possibly be combined with timber production in specific cases. Temperate deciduous (TD) trees have declined steeply during the past millennium, but some now increase in the recent forests, often mixed with Norway spruce. Removing spruce may benefit these trees and for example oak regeneration, flowering plants and pollination. The total area of forest suitable for restoration in Norway and Sweden is >100,000 ha. We evaluate the cost of selective cutting based on 26 field trials, 13 in each country, and sales from the initial cutting on average just barely compensate for the costs. By resurveying plots from a parallel project in Sweden, we found that about half of the cut volume had regrown after 16 years, and a second thinning may be needed in the near future. Coarse woody debris (CWD) had increased by 78%, indicating increasingly natural conditions. We conclude that selective cutting in recent forests may be part of a strategy to reach restoration and sustainability goals, but that long-term incentives for landowners need to be developed.