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Environmentally cued germination may play an important role in promoting coexistence in Mediterranean annual plant systems if it causes niche differentiation across heterogeneous microsite conditions. In this study, we tested how microsite conditions experienced by seeds in the field and light conditions in the laboratory influenced germination in 12 common annual plant species occurring in the understorey of the York gum-jam woodlands in southwest Western Australia. Specifically, we hypothesized that if germination promotes spatial niche differentiation, then we should observe species-specific germination responses to light. In addition, we hypothesized that species’ laboratory germination response may depend on the microsite conditions experienced by seeds while buried. We tested the laboratory germination response of seeds under diurnally fluctuating light and complete darkness, which were collected from microsites spanning local-scale environmental gradients known to influence community structure in this system. We found that seeds of 6 out of the 12 focal species exhibited significant positive germination responses to light, but that the magnitude of these responses varied greatly with the relative light requirement for germination ranging from 0.51 to 0.86 for these species. In addition, germination increased significantly across a gradient of canopy cover for two species, but we found little evidence to suggest that species’ relative light requirement for germination varied depending on seed bank microsite conditions. Our results suggest that variability in light availability may promote coexistence in this system and that the microsite conditions seeds experience in the intra-growing season period can further nuance species germination behaviour.

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.

Root-associating arbuscular mycorrhizal (AM) fungi foster vegetation recovery in degraded habitats. AM fungi increase nutrient availability for host plants; therefore, their importance is expected to be higher when nutrient availability is low. However, little is known about how small-scale variation in nutrient availability influences plant and AM fungal communities in a stable ecosystem. We conducted a 2-year field study in the understorey of a boreonemoral forest where we examined plant and AM fungal communities at microsites (15 cm diameter) with intact vegetation cover and at disturbed microsites where vegetation was cleared away and soil was sterilized to remove soil biota. We manipulated soil nutrient content (increased with fertilizer, unchanged, or decreased with sucrose addition) and fungal activity (natural or suppressed by fungicide addition) at these microsites. After two vegetation seasons, manipulations with nutrient content resulted in significant, although moderate, differences in the content of soil nutrients (e.g. in soil phosphorus). Suppression of fungal activity resulted in lower richness, abundance and phylogenetic diversity of AM fungal community, independently of microsite type and soil fertility level. Plant species richness and diversity decreased when fungal activity was suppressed at disturbed but not in intact microsites. The correlation between plant and AM fungal communities was not influenced by microsite type or soil fertility. We conclude that small-scale variation in soil fertility and habitat integrity does not influence the interactions between plants and AM fungi. The richness, but not composition, of AM fungal communities recovered fast after small-scale disturbance and supported the recovery of species-rich vegetation.

Permanent landscape attributes such as topography (elevation [m]) and microtopography (local variation in elevation [cm]) can increase the risk of cold air drainage down-slopes and in microtopographic depressions, causing important temperature gradients that generate localized growing-season frosts. Since most studies on growing-season frosts are restricted to the northern parts of the boreal forest or to mountainous areas, their negative consequences on tree productivity at the boreal-temperate forest ecotone is often ignored. We quantified the intensity and probability of growing-season frosts at the boreal-temperate forest ecotone in regard to topographic and microtopographic landscape attributes, which were extracted from airborne LiDAR surveys. In situ air temperature was measured for two summers (2016–2017) with 252 temperature loggers installed in two 18-years-old spruce plantations established in both temperate and boreal mixedwood forests. Growing-season frosts were more intense and probable at the boreal mixedwood forest site compared to the temperate forest site. Still, at both sites, when growing-season frost occurred, air temperature could vary by 4 °C along the elevation gradient of 15 m, often reaching sub-zero values at low elevation while reaching above-freezing values at high elevation. The importance of microtopography on the risk of sub-zero temperatures increased where frost events were less likely to occur such as at the temperate forest and at high elevation. Considering that growing-season frosts can considerably reduce tree productivity, the effects of both topography and planting microsite should be considered when determining where to establish plantations in the landscape and to determine suitable frost-free planting microsites within a plantation.

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.

Plant litter decomposition is a key ecological process that is mostly studied at the forest floor. However, decomposition generally starts in the canopy. In this study, we evaluated the effect of litter composition and climate on the initial phase of decomposition in the soil and two contrasting types of canopy microsites along an elevational gradient (0–2200 m a.s.l.). To this end, we incubated standard material composed by green (fast decomposing) and rooibos (slow decomposing) tea bags for three months. Tea bags were placed in soil (buried at 5 cm) and in the canopy at ca. 5 m above the ground in “micro-wetlands” (tank bromeliads) and dry crown microsites (branches). Along the elevational gradient, green tea decomposed faster than rooibos tea in all microsites and forests. Mass loss for both tea types was lowest on branches at all sites, except for green tea in a wet forest where decomposition did not significantly differ among microsites. In wet forests, decomposition did not differ between bromeliads and soil, while in a dry forest, decomposition was faster in bromeliads. We found that the effects of climatic variables [monthly average temperature (TEMP) and total precipitation (PREC) for the incubation months] on decomposition differed between microsites. Along the elevational gradient, the mass loss in soil was positively correlated with TEMP but not with PREC, whereas on branches, mass loss was negatively correlated with TEMP and positively correlated with PREC. Unlike on branches, mass loss in bromeliads slightly decreased with PREC and increased with TEMP. Our study shows that microsite conditions interact with climate (TEMP and PREC) leading to differences in the general decomposition patterns in the forest canopy., CONACYT, Deutscher Akademischer Austauschdienst http://dx.doi.org/10.13039/501100001655, Heinz Neumüller Stiftung, Carl von Ossietzky Universität Oldenburg (3092)

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.

The divergent gap characteristics and spatial patterns of canopy gaps created by natural or artificial disturbances can exert a dominant influence on forest structure and composition. However, little research has been conducted on the effects of ice storm damage on canopy gaps in subtropical mature forests of South China. In this study, one semi-natural site was dominated by a broad-leaf forest and two managed sites were representative of plantations with coniferous forests. Based on airborne laser scanning data and field evidence across sites, statistical analyses were used to examine gap characteristics following ice storms of moderate severity. Generalized Ripley’s K-function analysis was applied to test gap spatial patterns at a range of scales, and spatial point pattern analysis was used to quantitate the relative importance of specific influences on patterns of gap occurrence. The results revealed that the average gap size was 75.7 m2 and that 12.2 gaps occurred per hectare. Most gaps were single-tree fall events. In addition to more gaps, the mean gap size was smaller and the shape was more complex in the semi-natural site than in two managed sites. Large differences in gap characteristics were observed among snapped, uprooted, snag, and artificial gap damage types. Gaps generally showed a clustered distribution at large scales (e.g. 70m), whereas spatial patterns varied with gap damage types at different sites. The occurrence of gaps was strongly related to slope and topographic position at the semi-natural site, whereas slope, stem density, and human accessibility (proximity to pathways) were the most important factors affecting gap occurrence at the managed sites. We suggest that gap-based silvicultural treatments and natural disturbances regimes conjoin, highlighting interactions with other factors such as microsite conditions, non-tree vegetation and more.

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.

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.

Biocrusts are globally distributed and important for sustaining critical ecosystem functions. Little is known about their continental drivers and how smaller-scale microsite differences might affect biocrusts along aridity gradients. This limits our ability to manage biocrusts effectively under drier climates. We collected data on biocrust cover, biotic (plants, litter, grazing intensity) and abiotic (soil texture, soil stability and integrity) attributes from four microsites (trees, shrubs, grasses, open) at 150 sites along an extensive aridity gradient in eastern Australia. At the sub-continental scale, average biocrust cover increased with declining litter cover, and crust cover became more variable with increasing aridity. Biocrust cover was greatest in open microsites and least under trees, and differences were related to the effects of soil texture, vegetation and grazing intensity, which either increased or declined with increasing aridity. Our study reveals that biotic and abiotic effects on biocrust cover vary at different spatial scales along an aridity gradient. Predicted increases in aridity in eastern Australia will likely enhance biocrust cover whereas microsite-level effects are likely to be driven by land management actions such as vegetation removal and overgrazing.

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.

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.

Litter decomposition in forests is affected by tree species composition which produces litters with specific characteristics and alters soil surface conditions and nutrient availability. The impact of such changes in soil microsite conditions on litter decomposition is however poorly elucidated. We studied the decomposition of sugar maple leaves in 22 plots varying from pure hardwoods to mixedwoods to conifer-dominated stands across four sites in the sugar maple bioclimatic domain in Quebec. Mass loss and nutrient release were assessed over a 2-year experiment. Proxies of moisture availability measured under the canopy were more valuable for explaining the variability in leaf litter decomposition rates than soil temperature, litter quality and general site measurements (e.g. air temperature, rainwater). Throughfall amounts and soil volumetric water content (VWC) explained 56% of the variability in mass loss constants. Sugar maple leaf litter under hardwoods also decomposed more rapidly than under conifer-dominated stands. Slower litter decomposition under conifer-dominated stands was again more largely controlled by the lower soil VWC than the more acidic forest floor created by the needles. This study highlights that proxies of moisture availability measured at the microsite level can be key variables to predict litter dynamics in forests.

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.

At the local (within site) scale, soil heterogeneity can influence ecosystem function. However, in former agricultural systems, soil heterogeneity can be low as a legacy of tillage (that is, via the process of soil homogenization). We investigated the relationship between soil homogenization and three ecosystem functional response variables—aboveground productivity, nitrogen retention (assessed via 15N tracer addition) and plant litter decomposition (assessed using litter bags)—during the first 2 years following a tallgrass prairie restoration in a former agricultural field. We compared plots with substrate heterogeneity (topsoil patches enriched with sand or woodchips) with homogeneous plots that contained the same overall ratios of the component materials. We also compared plots with topographic heterogeneity (pits and mounds) with flat plots. The ecosystem response variables varied significantly with soil homogenization, but the effect depended on the type of heterogeneity (sand vs. woodchips vs. microtopography), which was consistent with these sources of heterogeneity having variable effects on soil water and nutrient availability. Soil homogenization reduced aboveground productivity by 50% for the woodchip treatment, but it had the opposite effect for the topography treatment. Homogenization also reduced plant 15N retention for the woodchip treatment by 50%, but the rate of litter decomposition increased by 8%. Overall, variation in nitrogen retention and decomposition were associated with the treatment effects on aboveground productivity and the relative abundances of forbs and grasses. The latter results suggest that the influence of soil homogenization on ecosystem function may occur indirectly as a result of its effects on plant community assembly. Moreover, forb productivity and N retention along woodchip and mound edges differed from the means of the adjacent patches, which revealed that complementarity along microsite edges can contribute to soil heterogeneity effects on ecosystem function.

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.

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.

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

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.

Background Bush clearing of encroached rangelands is crucial for restoration of herbaceous cover and diversity. Regeneration after bush clearing depends largely on the soil seed bank (SSB) size and composition. To assess the potential of the SSB to facilitate post-clearing herbaceous restoration, we examined the SSB density, composition and diversity and similarity between SSB and aboveground vegetation (AGV). Methods The study was conducted in semi-arid rangelands of Maseding and Kgomokgomo in North-West Province of South Africa. In each rangeland, all woody plants in three 1250 m2 plots were cut using saws and loppers, with the stumps treated with picloram. Paired observations were conducted in cleared and uncleared microsites. Soil samples were collected at three depths (0–10, 10–20 and 20–30 cm) in each microsite in April (pre-treatment), August, October and December 2016 and in April and August 2017. SSB was assessed using seedling emergence method, whereas pre- and post-clearing surveys of AGV were conducted in February 2016 and 2017, respectively. Results Cleared microsites had significantly (p < 0.01) higher seed bank densities (1872 and 693 seeds m-2 at Maseding and Kgomokgomo, respectively) relative to uncleared microsites in August 2017, with grasses accounting for higher densities than other plant functional groups in the upper 0–10 cm. Pioneer grasses (Aristida congesta subsp. barbicollis, Brachiaria eruciformis and Tragus berteronianus) and invasive forbs (Bidens pilosa and Schkuhria pinnata) dominated the SSB in cleared microsites at Maseding, whereas succulents (Portulaca spp.) and pioneer grasses (T. berteronianus and Urochloa mosambicensis) were abundant at Kgomokgomo in August 2017. SSB and AGV were dissimilar until December 2016; thereafter, similarity increased significantly (p < 0.05) in cleared microsites (Sørensen’s coefficient = 0.60 to 0.66 at Maseding and 0.43 to 0.52 at Kgomokgomo) compared to uncleared microsites. Species diversity was highest in August 2016 and April 2017 at Maseding, but it did not differ between two microsites (p > 0.05). At Kgomokgomo, SSB was more diverse in cleared than uncleared microsites in April and August 2017. Conclusion High seed bank densities in the upper soil layer in cleared microsites would promote passive restoration, but regeneration is likely to be initiated by early successional species. However, close monitoring and eradication of invasive forbs and succulents is necessary following bush clearing. The tendency of SSB resembling AGV over time in cleared microsites signifies that seed production from AGV is important for passive restoration following bush clearing.

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.

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.

The glacier retreat in the Antarctic Peninsula is opening new ice-free areas and providing an excellent opportunity to study successional processes. Antarctic terrestrial ecosystems have the particular characteristic of being dominated almost exclusively by lichens and mosses. The aim of the present study was to analyze the diversity, cover and composition of a lichen community on a deglaciated gradient on Potter Peninsula, King George Island (maritime Antarctica), and to investigate how microsite variables influence these patterns. Total lichen cover, species richness, and the frequency and cover of lichens species were measured in five 50 × 50 cm grids in 24 sites covering the whole Peninsula from the coast to the glacier front. Microsite conditions were also registered: slope, aspect, and proportion of different substrates (rocks, soil or bryophytes). We recorded a highly diverse and complex lichen community arranged in three assemblages of species. The lichen communities showed clear variations along the studied gradient, related to the distance to the glacier, the slope, the type of substrate, and the interaction between them. We consider that the patterns of these Antarctic lichen communities are dynamic and very heterogeneous, since they depend on macroclimatic variables but there is also a strong influence of microsite factors. 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 Fil: Passo, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Chiapella, Jorge Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad de Viena; Austria

Stand structural complexity enhancement is an increasingly popular management objective, especially on public lands. Complex stand structures are hypothesized to support a relatively high degree of native forest diversity and be more resistant and resilient to disturbances. Complex structures are characterized by the presence of deadwood and heterogeneity of tree-size classes and tree architecture. Relatively little is known about how discrete disturbance events affect structural complexity and compositional diversity in Quercus-dominated stands at fine spatial scales (i.e. neighborhoods). We established 20 0.05 ha fixed-radius plots on the Sipsey Wilderness of William B. Bankhead National Forest in northern Alabama to quantify woody plant species composition and structure. Trees were mapped on each plot to quantify overstory structural complexity and compositional diversity. We extracted two cores from all canopy Quercus spp. ≥ 5 cm diameter at breast height to quantify age, recruitment pulses, and reconstruct canopy disturbance history. Shannon species diversity in the sampled area was 1.75 for trees, 2.08 for saplings, and 1.69 for seedlings. Quercus alba had the greatest basal area, and Ostrya virginiana had the highest density. The stand exhibited a reverse J-shaped distribution with a q-factor of 1.72. The oldest Quercus dated to 1795, and the largest recruitment pulse occurred in the 1870s. The mean return interval for intermediate-severity disturbance was 38 years. Although we documented no relationships between disturbance frequency and compositional diversity at the neighborhood scale (0.05 ha), less frequent disturbance was associated with higher structural complexity (r2 = 0.258, p = 0.026) at the neighborhood scale. We suggest that localized disturbance increases species diversity and structural complexity, but these processes are manifest at the stand level and not at the neighborhood scale. We conclude that the spatial variability (i.e. size, shape, orientation, microsite conditions) is likely more influential on diversity and complexity than the temporal variation (frequency) of these processes at the neighborhood scale.

Xeric jack pine forests in northern boreal ecosystems are becoming more vulnerable with the increasing fire frequencies in this region. Understory vegetation is the most diverse aboveground component of this seemingly homogeneous system consisting of only jack pine in the overstory. Understanding the relationship between understory vegetation, fire severity, and resource availability is therefore necessary for managing these forests. In this study, we used spatial statistics to examine the relationship between understory vegetation and resource conditions as affected by two different pre-fire ages ( 60 years) and two fire severities (non-stand replacing fire, NRF, and stand replacing fire, SRF) in xeric jack pine forests in northern Alberta, Canada, four growing seasons post-fire. Using the same framework, we also tested the relationship between resource heterogeneity and species richness commonly known as the resource heterogeneity hypothesis. Spatial heterogeneity, that is, variability, scale of spatial dependency, and patchiness in plant functional groups (cover and richness), microsite conditions (forest floor and soil properties), and light availability were characterized using semivariograms, and their interrelationships were analyzed using spatial autoregressive models. Our findings indicated a stronger fire severity effect on the spatial properties of vegetation composition and microsite conditions than the pre-fire stand age effect. The spatial variability of microsite properties was greater in the NRF sites compared to the SRF sites, but varied in between pre-fire stand ages. Positive relationships were detected between species richness and variability of microsite properties in the NRF sites, whereas such relationships were negative in the SRF sites. Partial Mantel tests indicated a possible dependency of species richness on forest floor variability in the NRF and older sites, and on soil variability in the SRF and younger sites. Overall, findings from this study suggest that spatial heterogeneity in post-fire resource conditions influences the spatial assemblages of understory vegetation in xeric jack pine forests, and a change in fire severity might significantly alter the microsite variability and therefore the mechanisms that drive spatial patterns in understory vegetation.

Pinus sylvestris tree-ring delta C-13 and delta O-18 records from locally moist sites in central and northern Sweden contain consistently stronger climate signals than their dry site counterparts. ...

Seed dispersal and seedling establishment are essential for plant recolonization after disturbances, especially for plants that rely exclusively on sexual reproduction such as post-fire colonizer trees. Fire refugia may play a key role not only allowing trees to survive fire, but also functioning as seed sources after it. The estimation of seed dispersal and seedling establishment are essential for assessing plant recolonization ability, understanding landscape dynamics and determining which areas may not be able to recover due to lack of seed arrival. Here we study the post-fire recolonization ability of Austrocedrus chilensis (Cordilleran Cypress) from fire refugia in burned areas of northwest Patagonia, Argentina. We mapped all female trees, saplings and seedlings within and around fire refugia, recorded the reproductive capacity of female trees and characterized the microsite conditions for establishment. We used an inverse modelling approach and Approximate Bayesian Computation to estimate the seed dispersal kernel and the probability of seedling establishment. We found that the average dispersal distance of an A. chilensis seed was 88.52 m. The dispersal kernel was fat-tailed, meaning that A. chilensis has the capacity of producing accelerating expansions. Large woody debris, litter, and the protection of shrubs were the most important factors associated with the presence of recruits. We highlight the importance of fire refugia as seed sources for the recolonization of burned areas and thus the relevance of protecting these places to allow the persistence of fire-sensitive species. Fil: Landesmann, Jennifer Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina Fil: Morales, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Urbanisation is expanding at an unprecedented rate, affecting multiple taxa the world over. Ex situ conservation practices in urban areas (e.g. managed relocation) can help mitigate species extinction. However, systematic evaluations of ex situ practices and quantification of niche spaces, especially in urban areas, are largely lacking. Using epiphytic orchids as a study system, we translocated 13 propagated native species (2251 individuals) on 99 host trees across six urban sites. After 5 years, 12 of 13 species showed survival rates above 50% and 9 of 11 species exhibited positive growth. Generalised linear mixed models revealed that species and presence of humus corresponded to orchid survival, whereas the fork microsite and height from ground corresponded to orchid growth. Species-wise, the biophysical factors that were associated with survival and growth varied widely, with 7 of 11 species showing distinct interactions with more than one factor. Notably, the presence of humus and relative humidity influenced the survival of 4 of 11 species. This study suggests that managed relocation can serve as a viable conservation strategy for native orchids and possibly other epiphytes as well. We propose that species-specific niche requirements are identified and integrated into intervention actions.

Seed predation can cause substantial seed losses and influence plant population dynamics, but the impact depends on the extent to which populations are limited by seed availability or favorable microsites for recruitment. Harvester ants are the dominant post-dispersal seed predators in Australia’s tropical savannas, and their abundance and foraging efficiency, as well as the availability of seed and microsites, are affected by fire history. We undertook a predator-exclusion experiment to examine the interactive effects of fire history (no fire compared with annual burning over 5 years) and seed predation by ants on seedling establishment of the dominant savanna tree, Eucalyptus miniata, in northern Australia. Despite its large seed size, the rate of removal (~ 20–60%) was similar or higher than typically reported for eucalypts, although it was lower than that recorded for the smaller seeds of the co-occurring E. tetrodonta. Seed predation rates were twice as high in annually burnt compared to unburnt sites, but there was no significant difference in the proportion of seedlings that emerged from the initial seed available. Seedling emergence in both regimes was low, representing

Plants and biological soil crusts (biocrusts) are the key producers in drylands, but biocrusts seldom show net CO2 uptake. I hypothesized that biocrusts could augment CO2 fixation by incorporating plant-derived carbon. I collected biocrusts located at the base of Gutierrezia sarothrae (C3 forb), Bouteloua gracilis (C4 grass), and from bare interspaces between plants, and from a mesocosm experiment with live B. gracilis or dead B. gracilis roots. To trace carbon sources, I determined 13C values of the biocrust community, isolated cyanobacteria and lichen, and plant leaves because the photosynthetic pathway distinguishes the tissue 13C values. Biocrust communities and washed cyanobacteria and cyanolichen in G. sarothrae microsites were depleted by ~2‰ relative to other locations. Biocrust δ13C did not differ between the interspace and live or dead B. gracilis. Potential mechanisms for the trend in biocrust δ13C adjacent to C3 plants include differences in microsite conditions, biocrust communities, use of respired CO2 in the soil matrix for photosynthesis, or mixotrophic use of plant photosynthates. Further investigation of this observation may improve understanding of the degree to which the activities of dryland primary producers are coupled.

The study examined the effects of leaf traits, soil microsite, and microclimate characteristics on litter decomposition of the dominant species in two functional groups (FG), deciduous and evergreen, in shrublands in NW Patagonia, Argentina. Leaf traits considered were nutrient concentration (C, N, P, C/N, and N/P) and physical characteristics (area, strength, specific leaf area, and dry matter content). Soil microsite characteristics measured were pH, C, N, P, C/N and water retention capacity, while soil microclimate characteristics recorded were soil and air, temperature and moisture, and solar radiation. Five evergreen and five deciduous woody shrub species were selected. During 1 year, litter and microsite properties were measured below canopy: (i) senescent leaf chemical and physical properties, and the quantity as well as field decomposition of litter and (ii) soil chemistry, and soil and air physical properties. The factors controlling litter decomposition were different for each FG. In deciduous species, C/N ratio had a negative effect on decomposition. In evergreen species, decomposition was affected negatively by leaf carbon and dry matter content. Litter decomposition depended exclusively on the inherent senescent leaves traits. The common decomposition pattern between species of both FG could be attributed to similar leaf traits and the correlation between variables that control decomposition in both groups. Plant nutrient inputs associated with the litter decomposition process did not explain the soil nutrient content. These results suggest that other organic matter sources (roots, branches, and fruits) are more important than leaves on soil fertility. Fil: de Paz, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Gobbi, Miriam E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Raffaele, Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Buamscha, G.. Lanin Iman; Estados Unidos

Successful sexual reproduction may be more important for regeneration of clonal species in high-latitude and -altitude areas than has been previously suggested. We investigated the potential of Vaccinium myrtillus, V. vitis-idaea and Empetrum nigrum ssp. hermaphroditum (E. hermaphroditum) for sexual reproduction at three sites in the forest–tundra ecotone in Finnish Lapland. We studied whether the potential differs between plant communities, whether disturbance enhances germination, and whether seedling emergence is limited by seed availability. We established a field experiment with disturbance and sowing treatments, and monitored seed and seedling numbers and survival rates for two years. The number of mature seeds of V. myrtillus was higher in plants from the tundra heath than in those from the coniferous and mountain birch forests. The number of mature seeds and seedlings emerging from the seed bank of E. hermaphroditum tended also to be higher in the tundra heath. Disturbance marginally increased the seedling emergence of V. myrtillus and E. hermaphroditum, whereas sowing generally increased the seedling numbers. The seedling number of V. myrtillus was lower in the tundra heath and that of E. hermaphroditum was lower in the coniferous forest than at the other sites. Seedling survival was equal for all plant species at all sites. We conclude that the capacity for sexual reproduction varies among plant communities, and seed availability is a stronger constraint than microsite availability for the studied species. Once the crucial early phase of seedling establishment is overcome, seedling survival enables successful recruitment of V. myrtillus, V. vitis-idaea and E. hermaphroditum in the subarctic area.

Understanding the factors limiting population growth is crucial for species management and conservation. We assessed the effects of seed and microsite limitation, along with climate variables, on Helianthemum squamatum, a gypsum soil specialist, in two sites in central Spain. We evaluated the effects of experimental seed addition and soil crust disturbance on H. squamatum vital rates (survival, growth and reproduction) across four years. We used this information to build integral projection models (IPMs) for each combination of management (seed addition or soil disturbance), site and year. We examined differences in population growth rate (λ) due to management using life table response experiments. Soil crust disturbance increased survival of mid to large size individuals and germination. Contributions to λ of positive individual growth (progression) and negative individual growth (retrogression) due to managements varied among years and sites. Soil crust disturbance increased λ in the site with the highest plant density, and seed addition had a moderate positive effect on λ in the site with lowest plant density. Population growth rate (λ) decreased by half in the driest year. Differences in management effects between sites may represent a shift from seed to microsite limitation at increasing densities. This shift underscores the importance of considering what factors limit population growth when selecting a management strategy.

The extent to which small shifts among local topographic microsites could mitigate the effects of larger-scale climate change in arctic–alpine systems including mountain top organisms is largely unknown. This study is among the first to evaluate the relative contribution of microsite and altitude as a proxy for climate change on saxicolous lichen communities. We registered 107 lichen species in 54 boulders ranging from 900 to 2700 m.a.s.l. and in a large array of microsites in central Argentina. Communities ordinated along NMS multivariate analysis axes 1, 2 and 3 presented a cumulative R2 of 80%. The three axes were explained by altitude with axis 1 only being explained by altitude. Axis 2 was also explained by slope and aspect whereas axis 3 was explained by the interaction of altitude with aspect indicating that aspect was important only at lower altitudes but not at the mountain top. Lichen cover and richness were similar throughout the altitudinal gradient. We interpret that under a climate warming scenario, lower altitude species occupying pole ward facing slopes will have to migrate upwards while at the mountain top—for most communities-there still is scope for microsite segregation to compensate climate change. 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 Fil: Renison, Daniel. 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 Fil: Filippini, Edith Raquel. 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 Fil: Estrabou, Cecilia. 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

Urban forests provide valuable ecosystem services, but their long-term viability is often threatened by low tree recruitment due to seed and/or microsite limitation. Distinguishing between these two causes of low recruitment has important management implications, but has been little studied in urban environments. We tested for seed and microsite limitation in an urban forested park in Seattle, Washington, USA by adding conifer tree seeds and seedlings to experimental plots in which we manipulated microsite conditions by removing invasive ivy (Hedera spp.) and adding deadwood. We found that natural seed production was low, and adding seeds increased the number of observed seedlings. Furthermore, adding deadwood increased seedling survival, whereas removing Hedera did not have strong effects. Seed limitation is frequently addressed through management actions such as sowing seeds and transplanting seedlings, and our results suggest that such actions address a critical barrier to tree recruitment in urban forests. However, we also observed strong microsite limitation. At our study site, microsite limitation can be addressed primarily by adding deadwood and retaining coarse woody debris on site. Addressing microsite limitation may be a critical component of successful management efforts to improve tree recruitment in urban forests, and should not be overlooked. Furthermore, our study highlights the need for active monitoring and data analysis alongside management, since the most apparent threat (widespread cover of an invasive plant in this case) may not be the primary limit on suitable microsite conditions.

Studies of perennial plants generally search for a seed size vs. seed number trade-off. Surprisingly, the fact that perennials may replace an investment in large seeds by the allocation to vegetative propagation has not yet been investigated as an additional pathway enabling species coexistence. We focused on the mechanisms of coexistence in Carex elata and C. elongata, two co-occurring clonal sedges dominant in European swamp alder forests. We asked the following questions: i) Is the number of germinated seeds a better predictor of species coexistence than the total number of seeds? ii) What recruitment conditions and competition rules determine vegetative sprouting to be an alternative to large, competitively superior seeds? We measured several species functional traits related to the colonisation and fitness of perennials. To examine the competitive hierarchy between species and microsite species preferences, we analysed the effects of environmental factors and plant densities on fitness-related traits using Structural Equation Modelling (SEM). Then, using a series of spatially explicit simulations partly parameterised based on the field measurement, we evaluated the importance of seed and ramet propagation and recruitment conditions for long-term species coexistence. SEM indicated a competitive hierarchy and a large overlap in microsite preferences between species. As a response to our initial questions we found that: i) Only differences in the numbers of germinated seeds, allowed the two species to coexist. If we consider only differences in the total number of seeds, the superior competitor (Carex elata) outcompeted the inferior competitor (C. elongata) in all scenarios. This is because the former produced about three-times as many seeds as the latter. ii) We show that vegetative sprouting represents an additional pathway for the seed size-number trade-off when the competitive superiority of species is attributed to vegetative propagation. This is another way that a species deals with the omnipresent seeds of other species. Taken together, our study demonstrates that differences in seed performance, coupled with differences in vegetative propagation related to competitive ability, are an additional mechanism allowing the coexistence of perennial plants.

Root fungal relationships in forest understory may be affected by tree harvesting. Deschampsia flexuosa forms a mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi functioning in nutrient uptake, and a more loose association with dark septate endophytic (DSE) fungi. We asked how harvesting affects fungal colonisations and whether DSE is more prone to change than AM. Deschampsia flexuosa plants were sampled close to a control or a cut tree after top-canopy harvesting in a primary successional site. Colonisations were studied using light microscopy. Shoot N%, vegetation cover and soil nutrients were determined. Tree harvesting did not affect vegetation and soil parameters, except potassium (K+) increasing near cut trees. AM colonisation did not change, while DSE increased. Shoot N% increased with increasing DSE near cut trees. Hyaline septate (HSE) hyphae and soil K+ and magnesium (Mg2+) were positively correlated near control trees. Lichen cover and HSE correlated negatively. DSE colonisation increased but AM did not change after harvesting. Positive correlation of DSE with shoot N% near cut trees may suggest a role for DSE in favouring plant nitrogen uptake after disturbance in an open microsite. HSE may play a role in K+ and Mg2+ uptake.

Bogs comprise various niches that are ideal habitats for diatoms. Even though diatoms are widely used bioindicators in many aquatic ecosystems, little is known about their within-site distribution and versatility in bogs. The abundance of bogs in hemiboreal region offers a good opportunity to study the variability of diatom assemblages in different bog habitats and factors influencing it. This study aims to describe the diatom assemblages (1) in the most common bog ecotopes and (2) along the microtopography, and (3) to evaluate the extent to which abiotic environmental parameters (i.e. water table, electric conductivity, pH, moisture and shading) affect the diatom assemblages. According to our results, the most widespread and abundant species are typical bog-inhabiting acidophilic taxa, such as Eunotia paludosa, Kobayasiella parasubtillissima and E. bilunaris. Multivariate analyses showed that some patterns in different microhabitats and ecotopes can be distinguished according to diatom assemblages. In this study, the diatom assemblages were affected by moisture, shading and pH. The study demonstrates the potential usefulness of diatom assemblages as bioindicators to provide additional information about the microsite conditions in bogs.

Studies on lianas conducted within temperate forest stands have provided scant information on host trees, microsites, past disturbances, and liana size classes. Studies focussing on East Asia are also lacking, although this information is important for a comprehensive understanding of temperate liana ecology. The aim of this study was to compare the liana community structure of a 6-ha plot in the Ogawa Forest Reserve, an old-growth temperate forest of Japan, with that of other temperate forests. We also examined the relative importance of past disturbances, host trees, and microsite characteristics on specific liana distribution, especially variations among climbing types and liana size classes. The diameter at breast height, species name, and the locations of all liana stems were recorded. The most dominant liana species was Wisteria floribunda, contributing 85 % to the total basal area of the liana community. The liana community structure at the study site was similar to that of other temperate forests in terms of flora at genus level, basal area, and climbing types. Occurrences of stem twiners and root climbers were negatively correlated with tree size gradients, as reported for other temperate forests. Each liana species significantly aggregated at a 25-m scale, on average, whereas there were no exclusive distribution patterns among liana species. Most liana species were dependent on past disturbances, with host tree sizes also influencing liana distribution, and microsite characteristics being less important. Further studies in temperate East Asia will contribute to a comprehensive understanding of liana communities in temperate forests.

Compared to enrichment planting techniques, direct seeding may represent a viable low-cost method to ensure the conservation and recovery of forest ecosystems. However, it is necessary to identify the environmental factors that affect seed germination and seedling establishment in order to improve the success of this technique. It has been suggested that the establishment of Oreomunnea mexicana (Juglandaceae), a threatened tropical montane cloud forest tree species, is associated with microsites of high soil moisture. We assessed seedling emergence in O. mexicana through direct seeding in a secondary forest and characterized the microenvironmental conditions of the sowing microsite. We also assessed the effect of seed hydration on seedling emergence and evaluated the effect of soil moisture content and seed hydration in O. mexicana seed germination and seedling emergence under laboratory conditions. Seedling emergence was lower in the field than in the laboratory (37 vs. 42 %, respectively). At microsite level, seedling emergence correlated positively with soil moisture content but negatively with vegetation cover. After 11 months, 52 % of the emerged seedlings still survived. Under laboratory conditions, seedling emergence did not differ significantly between hydrated and non-hydrated seeds (43.2 ± 0.52 vs. 40.3 ± 0.51 %, respectively), but did between high and low soil moisture contents (80 ± 0.18 vs. 3.5 ± 0.085 %, respectively). With appropriate soil moisture and vegetation cover conditions, O. mexicana seed introduction into secondary forest is a reliable technique. However, the method could be improved by protecting the seedlings from physical damage.

In Abies alba Mill. stands and mixed stands of A. alba and Picea abies L. (H. Karst), microsites neighbouring the trunks of adult trees were more conducive to A. alba regeneration. Although at the stand level, the effect of Fagus sylvatica L. was positive; the local effect of the adult F. sylvatica neighbourhood was insignificant. Hence, forming mixed stands with a fine-grained mosaic of admixed species might better facilitate natural regeneration of A. alba than monospecific stands. The establishment of natural regeneration in Abies alba Mill. stands is a slow, spatially heterogeneous and stochastic process. Recent studies based on inventory data indicate that A. alba more readily regenerates in mixed stands than in monospecific stands. The objective was to examine how this positive association evidenced at the stand level operates on the scale of microsites with contrasting local species composition and stand density. In 8 monospecific and 22 mixed stands with Fagus sylvatica L. or Picea abies L. (H. Karst), microsites with a contrasting density of A. alba seedlings were selected and compared in terms of local species composition, stand density, canopy characteristics and topsoil properties. In A. alba stands, seedling density was positively associated with the proximity of adult trees. In mixed stands of A. alba and P. abies, adult trees of both species exerted a positive effect on A. alba regeneration, but the P. abies neighbourhood influenced regeneration occurrence more strongly than the A. abies neighbourhood. In mixtures with F. sylvatica, however, the effect of local stand density and local species composition was not evidenced at all. Although at the stand level, P. abies and F. sylvatica exert a positive effect on A. alba regeneration, on the microsite scale, their influences differ. In stands with a dominance of A. alba, the hampered seedling establishment in gaps may be considered an inhibitive effect that facilitates the emergence of other species.

Feces of wildlife species are commonly used indicators for species’ presence or relative abundance. These might however be biased due to inconspicuousness, due to rapid decay and disappearance, or due to high site-dependent variance in decay dynamics. Mapping of indirect signs is a frequently applied approach to study habitat use or distribution of grouse species. However, only a few studies addressed avian dropping decay up to now, and no study focused on dropping decay of European grouse species. Consequently, we conducted field surveys and greenhouse trials, studying time spans over which capercaillie (Tetrao urogallus) droppings persist and factors influencing the decay rates (i.e., habitat type, small mammal access, and precipitation regime). In the field survey, after an exposure of 98 days, only 6% of droppings (n = 156) decayed completely and most droppings remained nearly unchanged. The decay rate was influenced by microsite conditions (i.e., vegetation and location), with lowest decay rates in areas with little ground vegetation or on tree stubs. Destruents were not found to play a major role in affecting decay rate. The greenhouse trial revealed the impact of precipitation on the decay rate of droppings (n = 400): under high-amount and high-intensity precipitation regime droppings decayed faster compared to low-amount and low-intensity precipitation. The slow decay rate, and resulting long time period that they can be detected, therefore means that capercaillie droppings are a valid proxy for species’ occurrence.

Andropogon gayanus Kunth. is a large African tussock grass invading Australia’s tropical savannas. Invasion results in more intense fires which increases the mortality rate of adult woody plants. Invasion may also affect community structure by altering the recruitment potential of woody plants. We investigated the effects of A. gayanus invasion on ground-level microclimate, and the carbon assimilation potential and recruitment potential of two Eucalyptus species. We compared microclimatic variables from the early wet-season and into the mid-dry season to coincide with the period of growth of A. gayanus. We assessed Eucalyptus recruitment by monitoring seedling establishment, growth and survival of experimentally sown seed, and estimating seedling density resulting from natural recruitment. A. gayanus invasion was associated with increased grass canopy height, biomass and cover. Following invasion, the understorey microclimate had significantly reduced levels of photon flux density, increased air temperatures and vapour pressure deficit. The conditions were less favourable for woody seedling with aboveground biomass of seedlings reduced by 26% in invaded plots. We estimated that invasion reduced daily carbon assimilation of woody seedlings by ~30% and reduced survivorship of Eucalyptus seedlings. Therefore, A. gayanus invasion reduces recruitment potential, contributing to the transformation of savanna to a grassland ecosystem.

As the world’s biodiversity is increasingly threatened by destruction and/or climate change, rare species reintroductions may be necessary to conserve species threatened with extinction. When ecological processes change or a species’ range is heavily fragmented, it may be difficult to determine microsite characteristics needed for a successful reintroduction. In such cases, experimental reintroductions can be used to learn more about the species’ reproductive niche while establishing new self-sustaining populations. We reintroduced the Florida endangered species, Tephrosia angustissima var. corallicola, to examine native microsite requirements and feasibility of reintroduction into nearby suitable habitat. We transplanted Tephrosia into three microsites with varying light and substrate and characterized their wet and dry season soil moisture, soil bulk density, and light conditions. We monitored transplant and recruited seedling growth, reproduction, and survival and seedling germination in each microsite for 6 years. The microsite supporting greatest survival changed across developmental stages and time. Although no original transplants survived to 2009, the reintroduced population persists in 2015 through recruitment. Highest recruit growth, flowering, and survival occurred in shady, dry microsites. Recruits germinated more in the wettest microsite, reproduced most in the driest, and persisted longest in the wettest. Recruits germinated in shadier locations than where adults were planted. Although assessing whether a reintroduction is self-sustaining will require decades of monitoring, this experimental reintroduction elucidated the necessity for heterogeneous microsites at recipient sites and the efficacy of planting reproductive individuals for rapid next generation recruitment. Determining appropriate microsites for species requiring human assisted migration may also benefit from these techniques.

This paper examines the effect of landscape heterogeneity on pine establishment and survival at both juvenile and mature stages. A field survey of seedlings (juvenile stage) was carried out in two sites (Shaharia and Nahal HaHamisha) close to planted forests of Pinus halepensis in the dry mediterranean region of Israel. Seedling establishment rate at the microsite level was determined by comparing to the proportions of actual land-cover categories—bare ground, rock, shrub, and tree, using a spectral classification of aerial photographs. The dynamics of tree colonization at one of the sites (Shaharia) during the last 30 years were examined using aerial photographs, GIS tools and generalized linear models, to assess the effects of distance from planted forest, aspect, slope, and land cover on the density of pine trees, was conducted. Shrub cover was significantly favorable for both juvenile and mature pines at both sites, while the opposite was true for bare ground. Trees had a negative effect at one site. Rock had a positive effect on juveniles in both sites and a negative effect on mature pine distribution, reflecting its facilitative effect in the early stage and constraints for the late stage. A combined land-cover category of shrub+rock in one site, undetectable from aerial photographs, had the strongest effect of both covers on pine establishment. Proximity to the planted forest significantly increased pine density. Facilitation mechanisms provide the necessary mitigation of stresses imposed by irradiance, moisture shortage, and competition from neighboring vegetation on seedling establishment and survival. These mechanisms, combined with the spatial aspect of seed dispersal from planted forests, are the key to understanding the multiple–scale dynamics of pine expansion.

Presented Models describe the current growth rate. These models are good tools for growth prediction in the near future and will be compareable with further models; they will demonstrate the Norway spruce growth changes considering the climate change. Tree growth depends on genetic, climatic, microsite conditions and stand structure variations. A new evaluation method was carried out for studying mutual tree competition based on the social area of each trees. Nine Norway spruce (Picea abies (L.) Karst.) stands were investigated. The objectives of this study were to quantify each individual tree basal area increment during the years 2008–2012 with respect to the social area of the individual trees, competition indexes and the dendrometric characteristics of the trees. The social area of the trees in the investigated plots varied from 0.06 to 43.04 m2 where correlation coefficient (R 2) with each individual basal area increment was significantly high. Distance characteristics [e.g. minimum weighted distance (D i min) and maximum weighted distance (D i max)] provided a correlation coefficient (with individual tree basal area increments) varying from 0.69 to 0.84. Values of the R 2 between individual basal area increments and nearest trees dependent (NTD6) competition indexes varied from 0.41 to 0.66, while for distance-dependent competition indexes it varied from 0.59 to 0.78. To facilitate 5-year individual basal area increment inventories (I g5), linear models were used to develop the new specific functions. Individual tree growth models based on the distance measurement components and their combinations resulted in very high estimation accuracy. Therefore, the best model to determining basal area increment is the proven linear model using a social tree area, stem diameter at the breast height and crown length as input variables.

Restoring natural forests after field abandonment is a land management objective that fosters the recovery of forest biodiversity. We performed seeding and transplanting of native tree species 40 years after the abandonment of an arable field that became dominated by a dwarf bamboo (Pleioblastus chino (Franch. et Sav.) Makino) and by kudzu (Pueraria lobata (Willd.) Ohwi). By permutation tests, the removal of competing vegetation (gap creation) significantly increased the survival of three seeded species of Fagaceae and of eight transplanted species. In contrast, intact vegetation prevented most individuals of all species from surviving for 1 year after planting. The lack of natural recruitment of Fagaceae in the nonseeded subplots indicated that seed limitation was a cause of the slow afforestation. Although litter accumulation in gaps at the time of seeding slightly increased survival for late-germinating Quercus myrsinifolia Blume and Castanopsis sieboldii (Makino) Hatus. ex T. Yamaz. et Mashiba, the effect was not consistent among plots and was not statistically significant. Our results suggest that for successful afforestation using native trees in abandoned fields, it will be necessary to remove competitive native species to avoid severe limitations on microsite availability and that simultaneous tree establishment by seeding or transplanting should be implemented to accelerate the establishment of native tree species.