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Environmental heterogeneity can interact with ecosystem processes to alter individual plant reproduction. A better understanding of the factors that contribute to variation in plant reproduction between and within populations will increase our ability to predict larger-scale plant persistence. Longleaf pine (Pinus palustris) savannas are mostly open, heterogeneous landscapes characterized by occasional patches of trees that create partially closed canopies. This creates a mosaic of microsite conditions that can alter plant reproduction. Frequent, low-intensity fires that occur during different seasons are also considered fundamental drivers of plant reproduction in this system. The effects of varying fire season on plant reproduction have produced mixed results, likely because fire season interacts with microsite conditions, such as canopy cover. We investigated fire season and canopy cover effects on reproduction of wiregrass (Aristida beyrichiana), a species whose reproduction can be fire stimulated. We established plots under open and partially closed canopies in three pine savanna management units burned during different seasons (i.e., early dry, mid-dry, and early wet). We recorded reproductive state and number of inflorescences produced by individuals occurring within plots and germinated seeds from reproducing individuals. We found that wiregrass burned during the early dry season had the lowest reproduction with few individuals flowering. When burned during the mid-dry season, probability of reproduction was the highest, but seed germination was low. Plants burned during the early wet season produced seeds with the highest probability of germination, especially under partial canopy. Our results indicate that wiregrass reproduction is affected by both small-scale environmental variation and large-scale ecosystem processes, with fires during the early wet season most likely to promote the production of viable seeds.

There are few side-by-side comparisons on how Kentucky bluegrass (Poa pratensis L.) invasion has affected plant diversity and carbon (C) and nitrogen (N) dynamics. Between 2013 and 2015, four plots (4.9 × 4.9 m) were annually located on a long-term (1916−2016), moderately stocked pasture at the Northern Great Plains Research Laboratory (USDA-ARS) near Mandan, North Dakota. All plots were located on loamy ecological with minimal microsite differences. Each site had areas that were visually observed to have the largest vegetative component dominated by either Kentucky bluegrass (KBG) or dominated by other species (CONT). Two 1/8 m2 quadrats were clipped by species, including detached plant material (litter), within each subplot between mid to late July 2013, 2014, and 2015. This period represents peak biomass production and offers the best opportunity to capture cool- and warm-season perennial species. In 2013, soil samples were taken at depths of 0−5, 5−10, and 10−20 cm within each plot and thatch samples were hand excavated after clipping. Carbon and N were determined on biomass, litter, thatch, and soil samples. KBG plots produced 28% more biomass annually than the CONT plots. In 2014 and 2015, species richness was 0.7−2.1 × greater in the CONT plots. Although N and C concentrations were similar between treatments for aboveground biomass, litter, and thatch when expressed on a g m−2 basis, N was 34% greater for aboveground biomass and 600% greater for litter in KBG plots. Soil organic C and total soil N at 0−5 cm were 26% and 22% greater in KBG plots, respectively. Our findings indicate that KBG plots had less diversity and greater aboveground and belowground N and C than CONT. More follow-on research is needed to understand how C and N stocks and dynamics influence Kentucky bluegrass invasion.

Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) is the vector of multiple arboviruses. To evaluate the association between environmental factors and the oviposition activity of Ae. aegypti in Argentina, data on the presence and abundance of eggs were collected using ovitraps, between September of 2018 and May of 2019, in the cities of Villa María, Río Cuarto and Salsipuedes (Córdoba province, Argentina). We analysed the relationships between oviposition and five environmental factors: Temperature, precipitation, vegetation cover, human population density and distance to sites with a potential high density of larval habitats, like cemeteries and trash dumps. Environmental factors' data were collected using satellite image products. The oviposition activity was randomly distributed in three cities. Using generalized linear mixed models, we show that the house where each ovitrap was placed was a source of variability in oviposition, suggesting the relevance of microsite factors and the importance of domestic control actions. Ae. aegypti oviposition was positively correlated with night-time temperature of the previous 3 weeks, and in a context-dependent manner, it was positively correlated with human population density, vegetation cover and precipitation. The consistency and magnitude of these relationships varied between cities, indicating that oviposition is related to a complex system of environmental variables.

Scatter-hoarding rodents store seeds throughout their home ranges in superficially buried caches which, unlike seeds larder-hoarded in burrows, are difficult to defend. Cached seeds are often pilfered by other scatter-hoarders and either re-cached, eaten or larder-hoarded. Such seed movements can influence seedling recruitment, because only seeds remaining in caches are likely to germinate. Although the importance of scatter-hoarding rodents in the dispersal of western juniper seeds has recently been revealed, the level of pilfering that occurs after initial burial is unknown. Seed traits, soil moisture, and substrate can influence pilfering processes, but less is known about how pilfering varies among caches placed in open versus canopy microsites, or how cache discovery and removal varies among different canopy-types, tree versus shrub. We compared the removal of artificial caches between open and canopy microsites and between tree and shrub canopies at two sites in northeastern California during late spring and fall. We also used trail cameras at one site to monitor artificial cache removal, identify potential pilferers, and illuminate microsite use by scatter-hoarders. Removal of artificial caches was faster in open microsites at both sites during both seasons, and more caches were removed from shrub than tree canopies. California kangaroo rats were the species observed most on cameras, foraging most often in open microsites, which could explain the observed pilfering patterns. This is the first study to document pilfering of western juniper seeds, providing further evidence of the importance of scatter-hoarding rodent foraging behavior in understanding seedling recruitment processes in juniper woodlands.

RESUMEN: El monitoreo a largo plazo es fundamental para comprender las respuestas a acciones de restauración en especies de lento crecimiento como la conífera nativa Pilgerodendron uviferum. Luego de incendios catastróficos, la mayoría de los árboles y semillas de esta especie fueron eliminados, restringiendo su recuperación natural. El objetivo de este estudio fue analizar las implicancias del monitoreo a corto y largo plazo en la interpretación de resultados en ensayos de restauración pasiva y activa de Pilgerodendron uviferum, posterior a incendios en la Isla de Chiloé. Durante 10 años se evaluó la producción de semillas, el reclutamiento natural, y la regeneración asistida mediante plantaciones de P. uviferum bajo diferentes condiciones de micrositio en bosque turbosos y luminosidad en bosque de mejor drenaje. La producción de semillas de P. uviferum fue irregular y abundante cada siete años (⁓200 semillas m-2). La regeneración natural luego de ocho años aumentó en un 80 %, principalmente en sustratos cubiertos con musgos y en asociación con Donatia fascicularis y Astelia pumilia. La abundancia de regeneración natural estuvo positivamente asociada a árboles semilleros de mayor edad, la altura y diámetro de las plantas fue favorecida por la protección arbustiva. En sitios turbosos, la plantación en camellones alcanzó mayores tasas de sobrevivencia (78 %) y en sitios con mejor drenaje, fue mayor bajo protección de dosel superior (100 %). Los resultados sugieren que especies de lento crecimiento como P. uviferum requieren de periodos prologados de monitoreo para interpretar adecuadamente los resultados de ensayos de restauración en bosques quemados.

Many tree recruitment studies in African savannas target individual factors that limit recruitment, yet recruitment of some species could be limited by an interplay of environmental filters. This study investigated the effects of land use and microsite availability on early seedling recruitment of Acacia tortilis in riverine woodlands in north-western Zimbabwe. The riverine woodlands were divided according to the level of human disturbance into protected and unprotected sites. Each site was further divided into riverine and off riverine microsites. In each microsite, we laid five main plots (100 × 50 m) and nine seedling subplots (5 × 5 m) nested in each main plot, making a total of 60 main plots and 180 subplots. We found higher seedling recruitment in unprotected than protected sites. Although seeder density was twice greater in protected than unprotected sites, seed bank density was lower in the former by a factor of 1.5. Tree cover and herbaceous biomass was 1.4 and 1.8 times greater in protected than unprotected sites, respectively but were negatively correlated with seedling density. Across all microsites, herbivory-related mortality was less than 40% while drought-related mortality was more than 60%. Put together, the results suggest that higher recruitment in unprotected sites was most likely facilitated by domestic ungulates through seed dispersal and grass suppression which enhanced the quality of regeneration sites. We conclude that encroachment of A. tortilis in communal grazing sites is not only important for its conservation but for a variety of goods and services derived from it.

Seedling establishment is a critical life history stage for savanna tree recruitment due to variability in resource availability. While tree–grass competition for water is recognized as an important driver of tree seedling mortality, the importance of sunlight exposure on tree seedling performance has received little attention in savanna ecosystems despite variable seedling light environments caused by heterogeneity in biomass of the grass canopy. We studied the seasonal sunlight micro-environment for two dominant East African tree species (Acacia = Vachellia) robusta (Burch) and A. tortilis (Forssk) under natural field conditions. In the Serengeti National Park, Tanzania, A. robusta trees occur in tall grasslands of the north (shady) and A. tortilis in the southern short grasslands (less shaded). We also designed a greenhouse experiment to quantify sunlight effects on seedling growth, architecture, and resource allocation traits. In the field, A. robusta seedlings were associated with lower understorey sunlight during the wet season compared to A. tortilis, with this trend switching during the dry season. In the greenhouse experiments, under low sunlight (25% radiation), A. robusta gained height faster than A. tortilis and self-shading among canopy leaves was evident in A. tortilis but not A. robusta. Biomass allocation to leaves, stems, and roots differed between species under different light environments suggesting phenotypic plasticity in response to variable light availability. Our study suggests that microsite light variability should be incorporated in models of the spatial and temporal variability of savanna tree recruitment.

Dryland ecosystems are increasing in geographic extent and contribute greatly to interannual variability in global carbon dynamics. Disentangling interactions among dominant primary producers, including plants and autotrophic microbes, can help partition their contributions to dryland C dynamics. We measured the δ13C signatures of biological soil crust cyanobacteria and dominant plant species (C3 and C4) across a regional scale in the southwestern USA to determine if biocrust cyanobacteria were coupled to plant productivity (using plant-derived C mixotrophically), or independent of plant activity (and therefore purely autotrophic). Cyanobacterial assemblages located next to all C3 plants and one C4 species had consistently more negative δ13C (by 2‰) than the cyanobacteria collected from plant interspaces or adjacent to two C4 Bouteloua grass species. The differences among cyanobacterial assemblages in δ13C could not be explained by cyanobacterial community composition, photosynthetic capacity, or any measured leaf or root characteristics (all slopes not different from zero). Thus, microsite differences in abiotic conditions near plants, rather than biotic interactions, remain a likely mechanism underlying the observed δ13C patterns to be tested experimentally.

Plants resist herbivores using both constitutive and induced defenses. Limited resources and biosynthesis costs of anti‐herbivore compounds may impose tradeoffs between these modalities, but the evidence is conflicting. We postulated that biological and ecological scale may influence potential tradeoffs and analyzed constitutive‐induced relationships from genotypic to interspecific levels. We focused on one system, conifer phloem monoterpenes that resist bark beetle attack, to minimize variation from feeding guild or phylogeny. We examined 45 half‐siblings in common gardens (n = 763), seven populations of five species with tree‐level data (n = 436) and 29 studies of nine species with population‐mean data in forests. All studies evaluated mature trees to correspond with beetle behavior in nature and employed common methods of induction and analysis. Rather than a global tradeoff between constitutive and induced defenses, relationships varied with level of biological organization. In common gardens, constitutive concentrations and inducibility (I–C) were inversely related across families and individuals. These relationships did not extend to forest populations, however, where constitutive concentrations and inducibility were positively related. Across populations and species, constitutive concentrations and inducibility were likewise positively related. There was no evidence for inducibility tradeoffs between monoterpene quantity and composition: trees showed no or positive relationships between constitutive concentrations and induced compositional changes. These results suggest environmental variability can supersede underlying physiological tradeoffs in some systems, allowing plants with greater resource pools to excel in multiple defense components. This is further supported by microsite effects on inducibility exceeding family effects in the common gardens, and by relationships between constitutive and absolute induced concentrations being positive at all levels. We present a general model for understanding how underlying physiological tradeoffs are variably manifested across scales. These results can contribute to the protection and resilience of agronomic and native ecosystems and help contextualize organismal‐level allocations to ecosystem‐level patterns across heterogeneous landscapes.

At a global scale, mean air or soil temperatures appear to be drivers of treeline position. However, at finer scales, seed availability and microsite conditions may limit the germination, establishment, and growth of tree seedlings—and therefore the position of treeline. Tree islands are features of many treelines, and they can alter microsite conditions by producing seed, providing shelter, and redistributing snow. Near Churchill, Manitoba, Canada, tree islands have higher seedling establishment than nearby forest and treeline sites and could be hot spots for treeline expansion. However, seedling establishment and tree recruitment events may be stochastic, making predictions based on the relationship between seedling counts and microsite conditions difficult. We asked whether current tree island seedling establishment can be predicted by (1) historical recruitment and/or (2) tree and snowpack characteristics. To answer these questions, we measured tree island tree characteristics and monitored seedling establishment and snowpack in five tree islands at latitudinal treeline near Churchill, Manitoba. We fit hierarchical, generalized linear mixed effect models to assess the influence of our hypothesized predictors. We found that tree recruitment in the past was strongly positively associated with current seedling density. Mean basal area and age of trees were also positively associated with seedling density, whereas tree density was negatively associated with seedling density. We found weak positive effects of snowpack snow water equivalent. Our results provide evidence for positive feedbacks within tree islands and suggest useful factors to include in models for predicting future treeline change.

Whether plant populations are limited by seed or microsite availability is a long-standing debate. However, since both can be important, increasing emphasis is placed on disentangling their relative importance and how they vary through space and time. Although uncommon, seed addition studies that include multiple levels of seed augmentation, and follow plants through to the adult stage, are critical to achieving this goal. Such data are also vital to understanding when biotic pressures, such as herbivory, influence plant abundance. In this study, we experimentally added seeds of a native thistle, Cirsium canescens, at four augmentation densities to plots at two long-term study sites and quantified densities of seedlings and reproductive adults over 9 years. Recruitment to both seedling and adult stages was strongly seed-limited at both sites; however, the relative strength of seed limitation decreased with plant age. Fitting alternative recruitment functions to our data indicated that post-dispersal mortality factors were important as well. Strong density-dependent mortality limited recruitment at one site, while density-independent limitation predominated at the other. Overall, our experimental seed addition demonstrates that the environment at these sites remains suitable for C. canescens survival to reproduction and that seed availability limits adult densities. The results thus provide support for the hypothesis that seed losses due to the invasive weevil, Rhinocyllus conicus, rather than shifting microsite conditions, are driving C. canescens population declines. Shifts in the importance of density-dependent recruitment limitation between sites highlights that alternate strategies may be necessary to recover plant populations at different locations.

Post‐fire restoration of foundation plant species, particularly non‐sprouting shrubs, is critically needed in arid and semi‐arid rangeland, but is hampered by low success. Expensive and labor‐intensive methods, including planting seedlings, can improve restoration success. Prioritizing where these more intensive methods are applied may improve restoration efficiency. Shrubs in arid and semi‐arid environments can create resource islands under their canopies that may remain after fire. Seedlings planted post‐fire in former canopy and between canopies (interspace) may have different survival and growth. We compared planting Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) seedlings post‐fire in former sagebrush canopy and interspace microsites at five locations. Four growing seasons after planting, seedling survival was 46 and 7% in canopy and interspace microsites, respectively. Sagebrush cover was 5.8 times greater in canopy compared to interspace microsites. Sagebrush survival and cover were likely greater because of less competition from herbaceous vegetation as well as benefiting from resource island effects in canopy microsites. Initially, post‐fire abundance of exotic annual grasses was less in canopy microsites, but by the third year post‐fire it was substantially greater in canopy microsites, indicating that resource availability to seedlings was greater, at least initially, in canopy microsites. These results suggest microsites with greater likelihood of success should be identified and then utilized to improve restoration success and efficiency. This is important as the need for restoration greatly exceeds resources available for restoration.

Forest restoration is most efficient if it can take advantage of facilitative interactions between established vegetation and planted trees. However, positive and negative interactions have been identified in a number of plant communities. After centuries of anthropogenic fires, forest recovery has been extremely slow in southern bog forests previously dominated by the slow‐growing and vulnerable conifer Pilgerodendron uviferum on Chiloe Island, Chile. Today, the landscape is dominated by secondary shrublands with scattered patches of Sphagnum moss and limited natural tree regeneration. We hypothesized that the retention of secondary shrubs facilitates the early performance of P. uviferum restoration plantings by providing better microsite conditions. To test this hypothesis, we compared the response of seedlings planted on sites prepared at two levels of intervention: after shrubs had been removed or where shrubs were retained. Shrub retention showed a nurse‐plant effect on P. uviferum seedlings 4 years after planting, which resulted in reduced physiological stress (measured as Fv/Fm) for seedlings, as well as reduced browsing. Consequently, the seedlings growing in areas with shrub retention had larger height increment and higher vitality than those in areas where shrubs had been removed. Thus, the more open micro‐site conditions created by shrub removal resulted in generally poorer seedling performance, although seedling mortality—which was low overall (approximately 2–4%)—showed no significant difference between the two levels of intervention. These findings have direct implications for the restoration of slow‐growing conifers that can tolerate extreme wet conditions in highly degraded forests.

International audience; To investigate the movement and content of the acid soil Pi fractions at different distances from the green manure (GM) application site at a GM microsite, an incubation experiment was conducted. Stylosanthes GM (10 or 40 ton/ha) was applied with or without phosphate fertilizer (monocalcium phosphate, MCP) at a concentration of 44 kg/ha P, which was laid on the surface in soil cylinders. The GM/fertilizer and soil were incubated for 14 and 28 d. The results indicated the movement distance and content of the Pi fractions (Al-, Fe-, and Ca-associated Pi as well as occluded P) in the acid soil microsite were significantly increased after the addition of MCP; however, the movement distances of the Pi fractions were all less than 3 mm after incubation for 28 d. This information will improve the efficiency of combined P and GM use and decrease the environmental load due to P pollution caused by GM and phosphate fertilizer.

La vegetación no vascular está formada por líquenes, musgos, algas y cianobacterias tanto epífitas, como creciendo sobre el suelo. El objetivo de este trabajo fue estimar los cambios producidos por el fuego en la cobertura de briófitos y líquenes del suelo en parcelas de bosques de Polylepis australis (tabaquillo) en el Parque Nacional Quebrada del Condorito (PNQC) en el centro de Argentina. En un sector del Área Protegida incendiado en setiembre de 2015 se seleccionaron 40 parcelas de 30 x 30 m, 20 en bosques no quemados y 20 en bosques quemados. Quince meses después del siniestro, en cada parcela se seleccionaron al azar cinco cuadrados de 2 x 2 m para estimar cobertura en suelo diferenciando líquenes y briófitos. Además, se registraron la cobertura de plantas vasculares, suelo desnudo y mantillo. Como variables explicativas se midió la orientación y pendiente en cada cuadrado y en cada parcela. Además, se estimó la cobertura de bosque previo al incendio y la severidad del fuego. Los resultados muestran una muy baja superficie ocupada por líquenes y briófitos en el suelo afectado por el fuego a pesar de la recuperación de la vegetación vascular. La cobertura de líquenes y briófitos varían en función de características del micrositio tanto en parcelas quemadas como no quemadas. Se discute el posible impacto de la pérdida de esta cobertura en el ecosistema de bosque de Polylepis. The non vascular vegetation is formed by lichens, mosses, algae and cyanobacteria, both epiphytic and growing on soil. The aim of this work was to estimate the impact of fire on the coverage of bryophytes and soil lichens in forest plots of Polylepis australis (Tabaquillo) in Quebrada del Condorito National Park (PNQC), in central Argentina. In a sector of the Protected Area in Setember 2015, 40 plots of 30 x 30 m were selected, 20 in unburned and 20 in burned forests. Fifteen months after the incident, five quadrates of 2 x 2 m were randomly selected in each plot to estimate ground cover, differentiating lichens and bryophytes. In addition, the coverage of vascular plants, bare soil and mulch were recorded. As explanatory variables, orientation and slope of each square and plot measured. Furthermore, we estimated the forest cover before fire and fire severity. The results show a very low surface of the burned soli covered by lichens and bryophytes, despite the recovery of the vascular vegetation. Lichens and bryophytes coverage vary depending on the microsite characteristics, both in burned and unburned plots. Here, we discuss the possible impact of the loss of this coverage on forest ecosystem of Polylepis. Fil: Perazzo, Agostina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Ecología y Recursos Naturales Renovables; Argentina Fil: Rodriguez, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Ecología y Recursos Naturales Renovables; Argentina

Seedling recruitment following a masting event, where more fruits are produced in synchrony and intermittently compared with other species, plays a crucial role in determining species diversity and community structure. Such seedling recruitment can be superabundant, but followed by high mortality shortly thereafter. Differences in biotic factors such as seedling characteristics, competition, and herbivory, and microsite‐specific abiotic factors could determine seedling fate in space and time.In a subtropical forest in south China, for 2 years using censuses conducted every 1–2 months, we monitored 40 seed traps and 120, 1 m2 quadrats in five 1‐ha plots located from 1,400 to 1,850 m asl for the masting maple species, Acer campbellii subsp. sinense (Pax) P.C.DeJong. We measured biotic—conspecific and heterospecific seedling density, species richness, herbivory, seedling height, and leaf number—and abiotic—canopy openness, slope, and aspect—factors to assess drivers of seedling survival and evaluated A. campbellii subsp. sinense presence in the soil seed bank (SSB).The masting seed dispersal peak and seedling emergence peak occurred between October 2017 and January 2018, and May 2018, respectively. Of 688 selected seedlings, mortality was 92.7% within one year. No seeds were observed in the SSB. Seedling height and leaf number positively affected seedling survival, while seed placement as measured by aspect also showed effects on survival. Conspecific and heterospecific density and herbivory did not show any clear effect. Higher probabilities of seedling survival were found in areas with larger canopy openness (≥12% canopy gap size) and in steeper microsites (≥35°). Synthesis. Masting is mainly studied as a population‐level phenomenon from the fruiting tree perspective. Our study of individual seedling fate revealed that intrinsic biotic factors and seed placement were key drivers of survival. Although biotic determinants such as competition from conspecifics or heterospecifics or herbivory did not determine survival, their ubiquitous presence may be an underlying equalizer in community dynamics where seedlings that overcome biotic pressures, if placed at the right microsite, are at better odds at being recruited to the next life history stages., We monitored seed rain, soil seed bank, and seedling recruitment and survival for the masting maple species, Acer campbellii subsp., in a subtropical forest in South China. The masting seed dispersal peak and seedling emergence peak occurred between October 2017 and January 2018, and May 2018, respectively. Seedling mortality was 92.7% within 1 year, and we found no seeds in the SSB. Our study of individual seedling fate revealed that intrinsic biotic factors—seedling height and leaf number—and seed placement—aspect—were key drivers of survival.

Contribution of micromosaic structure of high mountain forests to ecological diversity of earthworms have been assessed. Intact forests of Arkhyz section of Teberda Nature Reserve were studied. The dominant types of forests have been recognized for the first time based on eco-coenotic classification. The ecological conditions of their functioning have been studied. Earthworm numbers have been studied in the recognized forest types. Diversity of earthworms was studied in soils under crowns, under fallen trees, and in mosses growing on rocks. 16 species of Lumbricidae have been found, with 4 of them being discovered for the first time. Full complexes of Lumbricidae were associated with biotopes of forest types of increased soil moisture content, low acidity, availability of nitrogen and pronounced litter. The largest abundance, diversity and biomass of Lumbricidae have been found in nitrophilous tallgrass gray alder forests. The lowest have been found in xeromesophytic pine forests with fir, spruce and birch. The most widespread dark coniferous forest with beech were inhabited by seven species of Lumbricidae, dominated by the epigeic species. There were few epi-endogeic and anecic species. The endogeic group of earthworms was represented by Crimea and Caucasus subendemic Dendrobaena schmidti. Diversity and biomass of earthworms in dark coniferous forests with beech were higher than in spruce-fir forests. During summer, dead fallen trees served as a microsite preferential for epigeic and endogeic species, while mosses growing on rocks were preferred by endogeic species.

Seed input and microsite suitability play a major role in tropical forest recovery. Understanding these can provide insights on passive restoration, especially in abandoned plantations near forests. This study assesses recovery of native species in abandoned tea plantations and identifies ecological and edaphic factors influencing seed input and seedling recruitment. We measured seed inputs from forest to plantation using 1 × 1 m plot along a transect at specific distances from the forest edge. The results showed that 54–63% of species reached plantations. Proximity to forest strongly influenced both seeds from seed bank and seedling establishment within the plantations. The plantations 25 m from forest recorded 37–59% of forest species while at 95 m only 11–14% of species were recorded. Seed input varied with elevation and seedling establishment at lower elevation strongly correlated with organic carbon and phosphorous whereas at higher elevation it was soil pH and electrical conductivity. Overall dispersal limitation and microsite conditions strongly influence seed colonization and establishment.

Climate change predictions include increased mean temperatures and increased frequency of heatwaves. Short-term responses to high air temperatures can allow animals to conserve water while maintaining a safe body temperature. For birds, cooling is often through evaporative water loss, which can be physiologically costly. Microsite use is an effective means of conserving water via reducing environmental heat load, so long as there are no negative trade-offs with other necessary functions, such as foraging. We examined behavioural responses to temperature in Cape rockjumpers, Chaetops frenatus (hereafter: ‘rockjumper’), an alpine specialist bird. We hypothesized that rockjumper behaviours would be temperature and microsite dependent. We collected data on rockjumper microsite use (sun, rock shade), behaviour (activity, foraging, preening, panting) and temperature (air, environmental). Rockjumpers made increased use of rock shade as air temperature increased. However, birds in rock shade foraged less. Depending on where their main food source is located, this suggests that when foraging demands are high, birds may need to remain in the sun despite risks of high thermal load, or else may suffer costs of lost foraging opportunities when using shade. The relationship between air temperature and heat dissipation behaviour (panting) was also mediated by microsite: birds showed significant increases in panting with increasing air temperature only when in the sun. The lack of increase in panting for birds in rock shade suggests that shade seeking may buffer physiological thermoregulatory costs (i.e. water expenditure). Individuals may therefore be able to mitigate some potential negative effects of high temperatures by making use of cooler microsites, although this could come at a cost to foraging.

Canopy openings due to harvesting practices constitute a disturbance that changes the environmental conditions of microsites. Its impact on the relative performance of the regeneration of different tree species could also be affected by site conditions and forest structure. The objective of this study was to determine how regeneration establishment of Nothofagus mixed forests is influenced by shelterwood silvicultural system. We focused on Lanin National Reserve (Neuquen, Argentina) where this silvicultural system has been applied since the late 1980s. The microsite scale analysis (one managed forest) showed that canopy cover was a key factor conditioning Nothofagus regeneration establishment, with older and larger individuals growing in less exposed microsites. Low understory dominance and leaf litter thickness were also associated with microsites with regeneration, while successful establishment (saplings taller than 2 m) showed positive correlation with soil moisture. Variations of these patterns were observed among species reflecting their specific eco-physiological requirements. On a stand scale (two managed forests along Lacar watershed) regeneration of N. dombeyi and N. alpina showed significant correlation with site and specific basal area, while N. obliqua was correlated with total basal area. Regeneration taller than 2 m was mainly correlated with site and altitude. At both, microsite and stand scale, the relative abundance of species changed between mature trees and regeneration. In particular, for N. alpina, an abundance decrease was observed on regeneration. Our results suggest that forest management systems should diversify silvicultural practices throughout the forest landscape, to provide at each site the micro-environmental conditions required by each species in order to maintain biodiversity and forest functions.

Productivity of forest ecosystems is constrained by site resource availability and utilisation at an individual tree level. A better understanding of nitrogen (N) nutrition addition to forest ecosystems is critical for maintaining optimal plantation productivity, given the influence of an environment gradient, genetics, and their interactions. We studied the aboveground growth response in a plantation setting of ten commercial P. radiata genotypes to N-fertilisation using three different N sources, and also assessed the effect of on-site environmental factors on this response. We compared, on equimolar basis, the effect of N-fertilisation with inorganic N (NH4NO3), organic N (L-arginine), and the two N sources combined (L-arginine:NO3−) to that of unfertilised trees on tree height, diameter, descriptors of microsite variability, and climate and seasonal information. After 2.5 years of fertilisation, genotype-specific variation in aboveground growth response to N sources were measured, and these were significantly influenced by field-scale heterogeneity. Across P. radiata genotypes, trees treated with inorganic N forms showed suppressed growth compared to unfertilised trees, while trees fertilised with organic N (either alone or in combination with inorganic N) were not significantly different than the untreated controls. We provide evidence of significant interactions between N source and genotype, N source and cover as well as genotype and microsite variability affecting temporal trends in tree volume. We conclude that the comprehension of field-scale variability in soil properties and associated environmental variables is essential for understanding genotype performance as they are crucial determinants of intraspecific variation in response to N-fertilisation.

This study investigated the effect of method of blending and spreading topsoil-waste rock (as dictated by waste dump position), rock addition, topsoil source and seed burial on seedling emergence from seeds broadcast onto mine restoration sites. Seed of 10 species were surface sown onto a waste rock dump plateau with six cover treatments spread by loose tipping; three topsoil source treatments (sand dunes, sandplains and stony hills) x two waste rock treatments (topsoil mixed and without waste rock). Emergence was greater on the waste dump plateau than slopes, where very few seedlings emerged. On the waste dump plateau, the addition of rock to topsoil increased seedling emergence >2.5-fold. Soil surface temperatures were cooler and water content at a depth of 2 cm was higher in topsoil mixed with rock than without rock. Higher seedling emergence with the addition of rock to topsoil was due to the creation of microsites where sub-soil moisture was retained for longer durations. Lack of emergence on waste dump slopes was attributed to relatively low surface roughness that reflected operational issues associated with different methods of spreading and mixing topsoil with rock on plateau versus on slopes.

Background Over the last century, fire exclusion has caused dramatic structural and compositional changes to southern New England forests, highlighting the need to reintroduce fires into the historically pyrogenic landscape to study the response. We investigated the effects of a single overstory thinning and midstory removal to create an open oak-hickory woodland structure, followed by repeated prescribed burns. We hypothesized that burning would create greater floristic diversity comprising fire-tolerant woody regeneration and shade-intolerant herbaceous flora. We followed shifts in plant structure, composition, and diversity over a 23-year period, using a before-after-control-impact design with data collected once prior to burning and twice after burn treatments had begun and with soil samples collected after nearly 20 years of burning. Results We observed a dense ingrowth of saplings on unburned plots that were largely absent from burned plots and a shift in midstory composition to favor mesic sweet birch (Betula lenta L.) in the unburned treatment, as opposed to the hickories (Carya Nutt. spp.) and oaks (Quercus L. spp.) that dominated the burned treatment. Burning resulted in a significantly greater density, richness, Shannon diversity, and evenness of understory vegetation (forbs, shrubs, tree seedlings). These four measures remained high on burned plots, despite a decrease in both floristic diversity and evenness on unburned plots and a reduction in unburned site-level richness. Understory composition varied significantly by year and burn treatment, with unburned plots largely characterized by shade-tolerant species while burned plots showed an enhanced abundance of heliophilic plants. Conclusions Our results suggest that periodic burning increases nutrient microsite heterogeneity and periodically maintains greater understory light, both of which in turn increase understory plant density and diversity and cause a shift in understory composition. This study shows that repeated prescribed burns in an open New England woodland have lasting structural and compositional effects capable of restoring pre-settlement, pyrogenic vegetation patterns.

Falco sparverius (American Kestrel), an obligate cavity-nesting bird species, has experienced declines in much of its range for decades. Among possible causes for the decline are loss of suitable habitat and availability of nesting cavities. The species seems to benefit from nest boxes installed at locations assumed to meet all other habitat requirements. Nest boxes mounted on billboard posts and the backs of road signs—especially along 4-lane highways—are becoming more commonplace because of the perceived cover associated with these landscapes. Based on monitoring American Kestrel occupancy of nest boxes (n = 37) from 2015 to 2017 in southeastern Ohio, we were able to create a database of occupied versus unoccupied sites, as well as documenting the presence/absence of Sturnus vulgaris (European Starling), an apparent competitor for nesting cavities. Using this database, we conducted a GIS-based analysis of land cover across multiple scales for each site, with the objective of identifying a suite of landscape-cover features that might enable deployment of nest boxes in the region with greater usage by American Kestrels. Using principal components analysis coupled with k-means clustering, we identified 2 landscape niche clusters, which differed significantly along the PC1 axis (P < 0.001). One cluster was occupied by American Kestrels and European Starlings, the other was occupied by European Starlings only. The American Kestrel-occupied cluster had 10–40% herbaceous and

Establishment of trees in subalpine meadows is a potential indicator of ecological effects of climate change. Tree establishment is a multi-year process including cone and seed production, germination, establishment, and growth, with each demographic step possibly sensitive to different climate limitations. While most studies have focused on one or a few steps, this study follows a cohort of individually marked saplings for 27 years beginning as seeds in two meadows on Hurricane Ridge, Olympic National Park. These meadows are examples of a south-facing tall sedge community type rather than the north-facing heath-shrub type where establishment has usually been observed. Results showed that mortality was high for the first few years, but number of saplings stabilized after the first decade. Seedling mortality during germination and establishment was directly related to weather that resulted in high air and soil temperatures and drought, while mortality of established saplings was indirectly related to weather through effects on growth. Growth was enhanced by longer growing season and warmer minimum temperatures; growth over three years and sapling height were predictive of mortality. Most sapling survival occurred in lichen (primarily Trapeliopsis granulosa) and Vaccinium deliciosum plant communities. Many saplings are growing at very low rates compared with the rate predicted from adult trees. It is also apparent that while microsite within meadow (e.g., relative snow depth) is important in determining sapling success, the landscape position of meadows (e.g., north versus south aspect) exerts a higher-level control over whether a subalpine meadow is likely to disappear with warming climate.

Understanding microsite preferences of species at the sapling stage is crucial for successful forest restoration, as efforts can be concentrated onto the most promising sites, and invaded sites can be manipulated toward more suitable conditions for target species. The Hawaiian Lowland Wet Forest is a highly endemic and endangered ecosystem that has received limited attention in terms of research on recruitment dynamics. Our study combined density records and sapling-based measurements within a forest reserve, an invaded forest, a traditional restoration project and a novel restoration project. We recorded substrate type, soil depth, surface roughness, and light availability for 382 saplings of the four native tree species Metrosideros polymorpha, Myrsine lessertiana, Pipturus albidus, and Psychotria hawaiiensis, and 146 spots where the target species were absent. The invaded forest had the lowest native sapling density, lower light availability, and lower surface roughness than the remaining management units. The novel restoration project had more moss/nurselog sites and higher light availability than the remaining management units. The traditional restoration project was mainly characterized by rocky substrate. Metrosideros and Pipturus showed significantly higher light demand than Myrsine and Psychotria. Pipturus was associated with rough microsites and Metrosideros with moss/nurselog substrates. Our findings suggest that restoration strategies considering manipulation of the canopy light environment and microsite preferences of target species can better facilitate native recruitment into heavily invaded forests.

Environmental conditions and seedling quality interact to produce complex patterns of seedling survival and growth. Root growth potential (RGP) is one metric of seedling quality that can be rapidly measured prior to planting, but the correlation of RGP and seedling performance is not consistent across studies. Site factors including microsite objects that cast shade and competing vegetation can also influence seedling performance. We examined the effects of RGP, presence/absence of a microsite object, and competition cover on the survival and growth of three native conifers to the Inland Northwest, USA, over 5 years. We found that RGP had no effect on the survival or growth of western larch (Larix occidentalis), Douglas fir (Pseudotsuga menziesii var. glauca), and grand fir (Abies grandis) at a mesic north aspect site and a xeric south aspect site. Comparatively, the presence of a microsite increased the odds of survival by 37% for western larch and 158% for grand fir, while the absence of forb cover increased the odds of survival of western larch by 72% and of grand fir by 26%. Douglas fir was less sensitive to microsites and competition. The strong effects of neighborhood conditions around seedlings help inform silvicultural practices to enhance the establishment of western larch and grand fir, including planting seedlings near shading objects and competition control, while these practices may not be as important for Douglas fir.

Spatial heterogeneity of soil properties plays a major role in regulating ecosystem structure and functioning. In general, soil resources accumulate beneath woody plant-covered patches more than in the open interspace, mak ing them function as fertility islands. Whilst wildfire is a common disturbance, little information is available on the role of particular plant species in maintaining soil fertility underneath in areas that are subjected to recurrent fires. This is an important issue given that land abandonment, together with a warmer and drier climate, is in creasing fire danger in regions such as the Mediterranean. We determined whether increasing fire frequency, producing changes from a Quercus ilex L., woodland to a shrubland, modifies the effect of woody plant canopy on soil fertility. Additionally, the effect of fire history on species-specific leaf and litter nutrient concentration was assessed. Areas affected by none, one, two or three fires were selected. Within each area, soil fertility was measured underneath Cistus ladanifer L., Retama sphaerocarpa L., Phillyrea angustifolia L. and Quercus ilex canopies and in open interspace. Unburned soils located underneath P. angustifolia and Q. ilex canopies were significantly more fertile than in open interspaces. The microsite effect on soil fertility was fire frequency dependent. As fire frequency increased, the plant canopy microsite effect decreased for soil organic matter (SOM), cation exchange capacity (CEC), total C, P, Ca, K and Mg, labile phosphate, arylsulfatase and acid phosphatase activities. Total N, ammonium, nitrate and β-glucosidase activity decreased with increasing fire frequency, but their spatial variabil ity was maintained along all fire frequency scenarios. Fire frequency decreased foliar N concentration but in creased P concentration in some species, leading to a decrease in their N:P ratio. Our findings suggest that soil fertility heterogeneity will be reduced with increasing fire frequency. This could compromise the recovery of soil and ecosystem functioning.

International audience; Aims: Understanding limitations to plant recruitment is a key element in devising effective restoration of semi-arid ecosystems: only when these limitations are identified can management interventions be effectively targeted. This study investigated demographic, seed and microsite limitations to establishing native plant species in a semi-arid, post-mining restoration context.Methods: We assessed ex situ and in situ germination and in situ emergence for eight key tree, shrub and annual herb species. We sowed non-treated seeds and seeds that were pre-treated to overcome dormancy, at differing densities and across diverse microsites to assess the roles of dormancy, seed density and microsite type as limiting factors for seedling recruitment.Results: We found that dormancy loss, in situ germination and in situ emergence limited one or more species, and we were able to improve emergence of one species by seed addition and targeted manipulation of microsites.Conclusions: The study has resulted in management implications including the importance of understanding methods to overcome dormancy to maximise germination; identifying key and species-specific demographic transitions; the importance of species-specific testing of seed sowing density; and the potential for increasing emergence by sowing seeds in furrows rather than broadcasting across rises and furrows, or on flat, unripped soil.

Enrichment plantings into secondary forest are an important option in restoring species diversity and ecosystem services. However, little attention has been given to environmental requirements for species performance. This study evaluated the effects of lightgaps and topographic position on the growth and survival of four native tree species (Pouteria caimito, Garcinia macrophylla, Dipteryx odorata and Cynometra bauhiniaefolia) planted into a 26-year old secondary forest originating from abandoned pastures in the central Amazon Basin. Artificial lightgaps and control plots under closed canopy were uniformly distributed on plateaus and bottomlands near water bodies. Seedlings were planted randomly into the plots and monitored for 28 months. Seedling survival rate was high (93%) and did not differ among species. Overall, lightgaps produced a 38% increase in seedling height relative to the controls. Although the four species naturally occur in mature forest, two of the four grew significantly more in lightgaps than in closed canopy secondary forest. Overall, bottomlands facilitated greater seedling growth in height (38%) relative to plateaus, but only one species exhibited a significant increase. This study shows the importance of the environmental variability generated with canopy openings along the topographic gradient, suggesting that both the selection of species and microsite conditions of planting sites have to be considered important criteria in the recovery of degraded areas. RESUMO O plantio de enriquecimento em florestas secundárias é uma opção para restaurar a diversidade de espécies e os serviços ecossistêmicos. No entanto, pouca atenção tem sido dada aos requerimentos ambientais para o melhor desempenho das espécies. Este estudo avaliou os efeitos de clareiras e posição topográfica sobre o crescimento e sobrevivência de quatro espécies arbóreas nativas (Pouteria caimito, Garcinia macrophylla, Dipteryx odorata and Cynometra bauhiniaefolia) plantadas em florestas secundárias oriundas de pastagens abandonadas há 26 anos na Amazônia central. Clareiras artificiais e parcelas de controle sob dossel fechado foram distribuídos uniformemente em platôs e baixios. Mudas foram plantadas aleatoriamente nas parcelas e monitoradas por 28 meses. A taxa de sobrevivência das plântulas foi alta (93%) e não houve diferenças entre as espécies. Entre todas as espécies, houve um incremento de 38% na altura das plântulas em comparação com os controles. Embora as quatro espécies ocorram naturalmente em florestas maduras, duas das quatro cresceram significativamente mais em clareiras do que sob dossel fechado. Entre todas as espécies, plântulas tiveram um maior crescimento em altura (38%) nos baixios que nos platôs, mas apenas uma espécie apresentou um aumento significativo. Este estudo mostra a importância da variabilidade ambiental gerada com aberturas do dossel ao longo do gradiente topográfico, sugerindo que, tanto a seleção de espécies como as condições microambientais deveriam ser considerados como critérios importantes na recuperação de áreas degradadas.

The period between seed germination and successful seedling establishment is considered the most vulnerable phase for plant development. To better predict recruitment patterns within plant communities, it is essential to identify the abiotic constrains and biotic interactions that allow for the colonization of substrates by plant species. We evaluated which combination of factors are associated with successful survival and development of seedlings of the seagrass Posidonia oceanica in order to identify the most important microsite features acting together on recruitment success. Our results show that P. oceanica seedlings are rather specific in their environmental requirements during their first 18 months of life, when their development and survival are favored in microsites of consolidated substratum (solid rock, and to a lesser extent P. oceanica matte) covered by macroalgae (mainly crustose algae) and located in sheltered locations (with energy flux values not exceeding 7 × 105 kg s−2 m s−1). After this phase, their probability of surviving becomes more independent from external conditions., Support to L. Pereda-Briones was provided by a PhD Fellowship from the Balearic Islands Government and the European Social Fund. Funds for this work were provided by the Ministry of Science and Innovation (RESIGRASS project, n° ref.: CGL2014-58829-C2-2-R) to FT and JT.

Small forest fragments are often the most abundant type of semi-natural habitat in intensive agricultural landscapes. Wild pollinators can use these forest patches as nesting or foraging habitat. However, the importance of small forest fragments as pollinator habitat has been neglected so far. We evaluated the role of these forest patches as pollinator habitat, focusing on the effect of nesting and foraging resources, both at a local and at a landscape scale. Pollinators were sampled with pan traps in 78 forest patches, spread over five study regions in Northwestern Europe. We evaluated effect of forest and landscape characteristics on bee and hoverfly species richness, diversity and activity-abundance. We showed that the bee community is influenced by both microsite conditions and landscape characteristics. Species richness and activity-abundance were higher when suitable nesting resources, such as sloped terrain and bare soil were available. This suggests that forest edges are important in providing nesting sites, but that most species forage in different habitats. Hoverfly species richness was higher in old forest fragments. This relation was mainly caused by the presence of forest specialist hoverflies in old forest fragments. Small forest fragments in agricultural landscapes can harbour a diverse pollinator community. Increasing the amount of nesting habitat, such as bare soil and sloped terrains is expected to have beneficial effects on the bee community, whereas older forest fragments should be conserved to sustain a rich hoverfly community.

Ploughing disturbance and inversion of soil sequences result in erosion and leaching of suspended solids and nutrients in northern boreal forests. Here, we assessed microsite soil physical-chemical properties at two cut-off spruce (Picea abies L. Karst.) sites 12, 14 and 16 years and microsite morphology with LiDAR DEMs 25 years after ploughings. The sites, one treated with (Marttiini) shoulder ploughing (SP) and the other with tilt ploughing (TP), contained the following microsites: trench, tilt (TP) or shoulder (SP), and untreated soil between the disturbance tracks. Using the classification and regression tree (CART), 90% of the microsites were correctly explained with apparent soil electrical conductivity (σa) and dielectric permittivity (DP). CART of soil chemistry explained 74.7% of microsites with the most important variates being C, Mg, Na, Mn, Ca, Ba, Al, Fe and N. Concentration of the elements in trench were significantly (p = 0) lower than in untreated microsites such that decrease for Al (49%), Ca (46%), S (51%), C (67%), and N (57%) at TP-site, as well as Al (31%), Ca (34%), K (30%), Mg (56%), Na (32%), P (22%), S (32%) and N (37%) at SP-site were observed, respectively. Ploughings had negative impact on the soil properties, such that the artificial regeneration with spruce had failed. Micromorphology still remains after 25 years and losses in soil nutrient supply will continue during consecutive snowmelt events implying that soil inversion does not sustain soil quality in Lapland.

Larix chinensis Beissn forms a subalpine timberline on Taibai mountain, Shaanxi, China. Seed emergence and survival of seedlings were studied by seed sowing experiments across an altitudinal gradient (3150–3400 m a.s.l). Three main factors were considered: seed addition, shrub shadowing and disturbance. In three different habitats (from low altitude to high: the Abies fargesii forest, the Larix chinensis forest and the shrub meadow), seeds emergence was examined and the seedling number and growth in every plot were recorded continuously over 4 years. Kruskal-Wallis ANOVA was used to analyze the relationship between seedling emergence/recruitment and the explanatory variables in every stand. The results showed that seed addition in disturbed plots always caused significantly increased seedling emergence and recruitment in the A. fargesii forest and the L. chinensis forest, but not in undisturbed plots under the canopy of forests. It demonstrated that recruitment of L. chinensis was limited by seed and microsite availability under closed forest, and litter is one of the factors leading to microsite limitation. However, in the shrub meadow, no treatments improved recruitment, indicating that the shrub meadow was not suitable for seedling establishment because of more intense light and lower temperature. In the L. chinensis forest and the A. fargesii forest, more recruited seedlings indicated that these two forests are safer for L. chinensis seedling establishment, though seeds limitation and the litter obstacle had seriously constrained the regeneration of L. chinensis.

The results of study of the population ontogenetic structure of the main forest-forming species (Pinus sylvestris, Quercus robur, Acer platanoides, Betula pendula, Populus tremula) of the Left Bank Polissia of Ukraine are presented. The study covered plant communities, which are the most common and typical in the region. They are represented by four formations of forest vegetation, viz. Pineta sylvestris, Querceta roboris, Betuleta pendulae, Populeta tremulae, and belonged to 24 syntaxes in the rank of association groups and up to 42 syn-taxons in the rank of associations. The study was based on the use of geobotanical and population-ontogenetic approaches and methods. It was established that in the forests of the region, the most part of main forest-forming species populations have left-sided ontogenetic spectrum. Invasive populations are the predominant category. Only in the populations of the species involved in the formation of the second and especially the first tier of stands reveals the centred and bimodal spectra. In these species, the frequency of normal population occurrence increased, but their proportion was within 6.7–13.6%. No regressive populations were found in the main forest-forming species of the region. It was fixed that the ontogenetic spectra of the most of populations of the studied species were incomplete due to the absence of plants of some ontogenetic states. It was noted that the individual extinction of the young generation before they reached the generative ontogenetic state, was the clear evidence of significant disturbance in the region forests of the generation variability in forest-forming species. The limited representation of windfall microsite complexes in the composition of the forest plant communities of the Left-Bank Polissia of Ukraine as well as gaps enough in size to ensure successful undergrowth development and formation of a continuous flow of generations is one of the consequences of long-term man-made impact on these forests. Keywords: forest phytocoenosis, forest-forming tree species, population analysis, population structure, ontogenetic spectrum, Polissia of Ukraine

Teak (Tectona grandis Linn. f.), one of the most-valued tree species in the world, is slow-growing with a long period until it can be harvested; therefore, ensuring that only high-quality seedlings or clones are selected for planting is critical. The main objective was to determine performance and repeatability of selected clones in terms of growth and survival rates in different micro-environments. A 2-year clonal trial using 41 clones and a local seedling of teak as a control were grown at 4 microsites differing in spacing, soil fertility and alley crops to assess tree height, diameter and survival rate that was evaluated in Purwakarta, West Java, Indonesia using a randomized complete block design with four replicates of each clone at each microsite. Teak growth was influenced by clone (p

Climate and plant litter diversity are major determinants of carbon (C) and nitrogen (N) cycling rates during decomposition. Yet, how these processes will be modified with combined changes in climate and biodiversity is poorly understood. With a multisite field experiment, we studied the interactive effects of reinforced and prolonged summer drought (using rainout shelters) and tree species mixing on leaf litter decomposition in beech forests in the French Alps. Forests included monospecific stands of Fagus sylvatica, Abies alba and Quercus pubescens and two-species mixtures composed of beech and one of the other species. We hypothesized (1) slower C and N release during decomposition in response to experimentally prolonged summer drought, but (2) less so in mixed compared to monospecific tree stands, due to indirect canopy effects and direct litter mixing effects. Litter lost 35% of initial C and 15% of N on average across all sites and litter types over 30 months of decomposition. The experimentally prolonged summer drought led to weakly slower C loss but had no effect on N loss. Tree species mixing did not alter drought effects on decomposition but had non-additive effects on C and N loss, which were dominated by direct litter mixing rather than indirect plot-specific tree species composition effects. Our data suggest relatively small effects of reinforced and prolonged summer drought on decomposition, possibly because process rates are generally slow during summer and because microsite variability is larger than the effects of rainfall exclusion. The dominant contribution of litter mixing to the overall effect of plot-specific tree species mixtures on decomposition supports the importance of microsite conditions for C and N dynamics during decomposition, which should be accounted for more explicitly in climate and biodiversity change predictions.

In Low Arctic tundra, thermal erosion of ice‐rich permafrost soils (thermokarst) has increased in frequency since the 1980s. Retrogressive thaw slumps (RTS) are thermokarst disturbances forming large open depressions on hillslopes through soil wasting and vegetation displacement. Tall (>0.5 m) deciduous shrubs have been observed in RTS a decade after disturbance. RTS may provide conditions suitable for seedling recruitment, which may contribute to Arctic shrub expansion. We quantified in situ seedling abundance, and size and viability of soil seedbanks in greenhouse trials for two RTS chronosequences near lakes on Alaska's North Slope. We hypothesized recent RTS provide microsites for greater recruitment than mature RTS or undisturbed tundra. We also hypothesized soil seedbanks demonstrate quantity–quality trade‐offs; younger seedbanks contain smaller numbers of mostly viable seed that decrease in viability as seed accumulates over time. We found five times as many seedlings in younger RTS as in older RTS, including birch and willow, and no seedlings in undisturbed tundra. Higher seedling counts were associated with bare soil, warmer soils, higher soil available nitrogen, and less plant cover. Seedbank viability was unrelated to size. Older seedbanks were larger at one chronosequence, with no difference in percent germination. At the other chronosequence, germination was lower from older seedbanks but seedbank size was not different. Seedbank germination was positively associated with in situ seedling abundance at one RTS chronosequence, suggesting postdisturbance revegetation from seedbanks. Thermal erosion may be important for recruitment in tundra by providing bare microsites that are warmer, more nutrient‐rich, and less vegetated than in undisturbed ground. Differences between two chronosequences in seedbank size, viability, and species composition suggest disturbance interacts with local conditions to form seedbanks. RTS may act as seedling nurseries to benefit many Arctic species as climate changes, particularly those that do not produce persistent seed.

Among four species of Clusiaceae (sensu lato) occurring in a mosaic of different types of tropical vegetation, Kielmeyera coriacea Mart. & Zucc. and Calophyllum brasiliense Camb. were C3-species with similar performance at micro-sites of contrasting water supply, Clusia criuva Cambess—although potentially a C3/CAM intermediate species—performed C3-photosynthesis, while Clusia arrudea Planchon & Triana ex Engl. performed C3-photosynthesis or CAM-cycling depending on site characteristics and dry or wet season. Depending on individual species, C3-photosynthesis proves to be a suitable option at a variety of environmental conditions, while CAM-cycling appears to be an escape under more severe stress. In this ecophysiological field work, we investigated possible microhabitat-dependent expression of modes of photosynthesis among species of Clusiaceae (sensu lato) in a mosaic of tropical vegetation. The study site was in the Serra de Sao Jose (21°08’S, 44°17′W; in the municipality of Tiradentes, state of Minas Gerais, SE-Brazil). The mosaic of tropical vegetation types was made up of rupestrian grasslands, cerrado, small rock outcrops, and riverine and gallery forest alongside a small river. Four species were measured, namely C. criuva Camb., C. arrudea Planchon & Triana ex Engl., K. coriacea Mart. & Zucc., and C. brasiliense Camb. K. coriacea and C. brasiliense performed C3-photosynthesis with midday depressions and reversible acute photoinhibition in response to varying environmental conditions related to habitat types and wet and dry seasons, respectively. The C3/CAM intermediate C. criuva also performed C3-photosynthesis with midday depression and acute photoinhibition. It appeared not to be stressed enough to switch to its intrinsic CAM option. In contrast, while C. arrudea under favourable conditions in the gallery forest and the wet season also performed C3-photosynthesis, under drier conditions, it used CAM-cycling. For particular species, realization of CAM-options is a possibility of acclimation. Other species contemporarily may rely on different alternatives such as plastic performance of C3-photoynthesis. At the microsite level, overlapping functional diversity of species and diversity of habitats contributes to the complexity of this vegetation type.

Tree growth of Nothofagus betuloides forests south of 50°S is affected by local temperature and precipitation together with large-scale high-latitude climate patterns, but also significant influences from the Tropical Pacific were found. The characterization of past climate dynamics in southern South America is difficult due to the shortness of instrumental data. However, abundant forests in the southernmost part of the continent makes it an ideal place to assess the dendroclimatological potential for developing high-resolution climate proxy time series to extend the observations back in time. Whereas the majority of dendroclimatological studies have focused on latitudes north of 50°S, we present six new Magellan’s beech (Nothofagus betuloides (Mirb.) Oerst.) tree-ring width (TRW) chronologies, spanning between 202 and 500 years, developed from southernmost Patagonia (> 50°S), Chile. The climate signal in the trees was analyzed using local station data, regional sea surface temperature (SST) and large-scale atmospheric indices: the Southern Oscillation Index (SOI) and the southern annual mode (SAM). The correlations between individual site chronologies and observed summer temperatures and precipitation varied, reflecting diverse microsite conditions and local scale geographic patterns. An influence of southern Pacific SST was evident at two of the northern sites. Although the associations with SOI and SAM were weak, the influence of regional sea level pressure on tree growth in the region was evident.

Proper management of woods infested by bark beetle – clearing infested trees to prevent spread of bark beetle, or leaving them to preserve biodiversity – is a hotly debated topic. Differences in temperature regime between differentially managed areas are often-used arguments in these discussions. Results from the field measurements are confusing. Therefore, here we review previous studies and report our results of using thermal sensors in the field to determine the factors that might affect the differences in temperature reported in previous papers. Our results indicate that the variability recorded in one particular habitat, dry forest, is associated with the specific characteristics of the locality of each microsite/sensor. We conclude that it is important to consider not only the temperatures recorded but also describe microsites in detail in terms of vegetation structure, sunshine or numbers of trees per unit area.

The effective sustainable management of introduced woody species requires understanding of the mechanisms which affect successful colonization in different forest habitats. We studied the spontaneous spread of the alien species – Northern red oak (Quercus rubra) in the Scots pine (Pinus sylvestris) forest located in Poland. We analysed the impacts of seed source distance, presence of and distance from linear structures (public and forest roads) in the landscape, as well as microhabitat diversity, on the distribution of juvenile red oaks. We also studied the effects of types of acorn deposition sites (under shrubs, within clumps of Vaccinium myrtillus, in the open), and ways of seed burial (in moss wefts, in rodent corridors) by animal seed hoarders on seed germination and seedling growth. Field data were collected in six transect lines divided into 3300 plots (1 m2 each). We found that Q. rubra efficiently colonizes Scots pine monoculture. Results of spatially explicit hierarchical generalized linear models showed that distance from acorn sources and occurrence of sparse shrub layers are the most important predictors of Q. rubra ecological success, defined as establishment of juvenile specimens. The presence of roads – potential migration corridors for avian and mammalian acorn consumers/dispersers – favoured non-random red oak spread. The “nurse effect” of native understory components on red oak seed germination and seedling growth was indicated by higher numbers of juvenile specimens as well as by higher proportions of germinated seeds noted under shrubs than in open areas (without shrubs) or within clumps of V. myrtillus. All red oaks developed from seeds buried in compact moss wefts or in spacious caches and corridors created by rodents in the moss layer, which indicated a positive “burial effect”. We conclude that microhabitats make the Scots pine forests very suitable for Q. rubra invasion. Because of the wide distribution of numerous red oak stands in European temperate forests and the presence of numerous oak seed dispersers, the continuous colonization of widespread Scots pine monocultures by Q. rubra must be expected.

Timber harvests may facilitate ant invasions of forested landscapes, fostering interactions between non-native and native ants. Harvests that include removal of low-value woody biomass as forest bioenergy feedstock may reduce residual coarse woody debris, thereby altering food and cover resources for ant species. We manipulated: (1) volume and distribution of coarse woody debris in stand-scale treatments ranging from intensive coarse woody debris removal to no coarse woody debris removal; and (2) coarse woody debris availability at microsite locations within stand-scale treatments, including piles of hardwood stems, piles of conifer stems, and no pile locations in North Carolina, USA and windrows (i.e., long, linear piles of harvest residues) and no windrows in Georgia, USA, in recently clearcut pine plantations (n = 4 per state). We captured ants in regenerating stands and tested treatment- and location-level effects on non-native and native ant relative abundances. Invasive ants represented 19% of ant taxa richness, but comprised 94% of total ant captures. Red imported fire ant (Solenopsis invicta Buren, hereafter “RIFA”) dominated the ant community in young plantations. RIFA avoided windrows, but its relative abundance did not differ among stand-scale treatments. Coarse woody debris retention in stand-scale treatments and at microsite locations favored non-RIFA ants, including Asian needle ant (Brachyponera chinensis Emery) and several native ant species. Dual invasions of RIFA and Asian needle ant in young plantations of the eastern United States may commonly occur because the two species may not compete for resources on the forest floor. Reduction of coarse woody debris via intensified woody biomass harvesting may negatively affect non-RIFA ant species and promote RIFA colonization, thereby indirectly increasing deleterious effects of RIFA on other wildlife.

In mountain ecosystems, plants are sensitive to climate changes, and an entire range of species distribution can be observed in a small area. Therefore, mountains are of great interest for climate-growth relationship analysis. In this study, the Siberian spruce’s (Picea obovata Ledeb.) radial growth and its climatic response were investigated in the Western Sayan Mountains, near the Sayano-Shushenskoe Reservoir. Sampling was performed at three sites along an elevational gradient: at the lower border of the species range, in the middle, and at the treeline. Divergence of growth trends between individual trees was observed at each site, with microsite landscape-soil conditions as the most probable driver of this phenomenon. Cluster analysis of individual tree-ring width series based on inter-serial correlation was carried out, resulting in two sub-set chronologies being developed for each site. These chronologies appear to have substantial differences in their climatic responses, mainly during the cold season. This response was not constant due to regional climatic change and the local influence of the nearby Sayano-Shushenskoe Reservoir. The main response of spruce to growing season conditions has a typical elevational pattern expected in mountains: impact of temperature shifts with elevation from positive to negative, and impact of precipitation shifts in the opposite direction. Chronologies of trees, growing under more severe micro-conditions, are very sensitive to temperature during September-April and to precipitation during October-December, and they record both inter-annual and long-term climatic variation. Consequently, it would be interesting to test if they indicate the Siberian High anticyclone, which is the main driver of these climatic factors.

Prescribed burnings have been generally used for fuel reduction in Mediterranean forest ecosystems and in fire-prone areas. It is usually held that prescribed fire may alter microsite conditions, but very little is known about the impact of prescribed burning on Mediterranean pine species’ natural regeneration. In this study, we aim to know the effect of prescribed burning, soil preparation (scalping) and seed protection on the initial recruitment of Spanish black pine (Pinus nigra Arn. ssp salzmannii), maritime pine (Pinus pinaster Ait.) and Aleppo pine (Pinus halepensis M.) in the Cuenca Mountains (central-eastern Spain) after a 1 year of experiments. Our results indicated that the seed emergence rate was higher in the scalped plots for Maritime pine and Aleppo pine. In the case of Spanish black pine, differences comparing treatments for the emergence rate were weaker. Scalped and protected plots showed the highest seedling survival rate for Aleppo pine and Spanish black pine whereas protected and control plots perform better in the case of Maritime pine. Thus, seed protection is a crucial factor for ensuring seedling survival after the first growing season. By considering our results about early pine species recruitment, prescribed burning must be carefully planned when the natural regeneration of Spanish black pine, maritime pine and Aleppo pine is the aim.

Soil scarification is widely used in boreal forestry to promote the growth and survival of seedlings. The aim of the study was to describe and analyze the impact of disc trenching on soil temperature and water content dynamics during the first six growing seasons after clearcutting. The site is a sub-xeric, coarse textured, coniferous field experiment, near Hagfors, central Sweden. Soil temperature and water content were measured hourly both 20 and 45 cm below the original surface of the mineral soil in three types of microsites created by disc trenching (furrows, ridges, and between-furrow areas) and an undisturbed control microsite outside the disc-trenched area. Pinus sylvestris L. seedlings were planted in the furrows and the control area before the measurements. The soil temperature and water content data were analyzed using linear mixed-effect models. Numbers of days exceeding critical thresholds of soil temperature and water content for seedling growth at each microsite were also calculated. Disc trenching increased soil temperature in the topsoil ( In conclusion, soil temperature and water regimes were more favorable for the seedlings in the furrows than in the control area for at least six growing seasons. We recommend planting soon after disc trenching to maximize benefits from the improved soil temperature conditions in the furrows.

Prescribed fires are used as a fuel reduction tool, but heat alter microsite conditions affecting the natural regeneration of Mediterranean pine forests. Our study tested the hypothesis that implementing prescription before or after pine seed release may influence the composition of tree communities by changing the regeneration patterns of Pinus pinaster Aiton across a climatic gradient in the eastern Iberian Peninsula. We ran a seed-sowing experiment to analyse the recruitment patterns of this pine species in prescribed-burned stands, in two different biogeographical seed provenances from wetter and drier areas than the local seeding site. Survival of seedlings was through one year, until the end of the first drought and winter period, respectively. >5400 seeds were sown during the study distributed in sixty plots (30 burned, 30 unburned) per site and treatment, with 10 seeding units per plot. General linear models (GLMs) and ANOVA analyses indicated higher performance for the Drier seed provenance in burned areas, whereas a similar performance was recorded in the control area. Control areas showed higher germination and success rates for plant establishment throughout the study period. Total germination and survival after one year were slightly higher, respectively, at northern sites due to massive mortality during summer in the southern stands. At the burned sites, the mean germination time was significantly longer in those seeds sown before fire passage than those sown after fire. Total germination and successful establishment were significantly higher in the individuals sown before the passage of the fire than in those sown after fire. Most of the mortality occurred in summer for the southern stand, while winter was the most constraining period at the northern sites. The understanding of the dynamics in this species' establishment can help managers to perform a better management planning according to the species' ecology.

Wind disturbance generates heterogeneous microsite structures, including downed logs, windthrow mounds, and pits. While these structures can provide opportunities for regeneration of certain tree species, the long-term influence of microsites and microsite heterogeneity on forest development has not been quantified. We used long-term measurements of a formerly old-growth Tsuga canadensis – Pinus strobus forest severely damaged by a category 3 hurricane in 1938 to quantify the impact of microsite conditions on overstory composition and structure. We asked (i) “What are the patterns in live-tree size, growth, and mortality five and seven decades after disturbance?” and (ii) “What roles do microsite heterogeneity and the presence of disturbance-generated microsites play in long-term forest development following disturbance?” We compared live-tree (>2 cm DBH) development and survival to microsite heterogeneity at the 100 m2 scale. Microsite diversity was positively related to overstory species diversity and stem density and negatively related to average tree size. We propose that plots with higher microsite diversity may have experienced more severe local disturbance, which allowed more species and individuals to establish and created varied niches that allowed these individuals to coexist and generate greater stand-level diversity. These persistent relationships highlight how microsite conditions affect forest development after severe disturbances.