Microsite Effects Research Articles

On the relevance of intraspecific trait variability—A synthesis of 56 dry grassland sites across Europe

The intraspecific plant trait variability (ITV) is key for many ecological processes, but large-scale analysis of co-occurring species are rare. Here we studied ITV of 14 plant traits for five co-occurring species across 56 European dry grassland sites – large parts of the species distribution ranges. We evaluated variation in ITV relative to between species trait variability (BTV) with a particular emphasis on how within versus between population variability contributes to ITV. We performed this analysis trait by trait (univariate) and by considering hypervolumes in the multi-variate trait space. We also tested whether climatic variables can be used to predict between population variation in traits.For the trait by trait analysis, for 9 out of 14 traits ITV exceeded BTV, which suggests an extraordinary large role of ITV. However, when considering all traits jointly the hypervolume occupied by ITV was only 23% of overall trait variability.We found comparatively small effects of within population variability in the uni- as well as in the multivariate analysis decreasing rapidly with increasing number of considered traits. The dominance of between population variability suggests that ITV is mainly driven by environmental effects rather than local biotic interactions and microsite effects. ITV of leaf chemical traits was related to precipitation and growing degree days until samplingITV can be substantial compared to BTV, in particular when considering single traits, such that ITV should be considered in trait-based research. Since the importance of ITV appears to decrease when considering multiple traits jointly, using species mean trait values is more appropriate for multi-variate trait analysis. Because ITV varied mainly between populations rather than within populations, and was related to climatic conditions, we suggest that ITV could be accounted for in future trait based research by including environmental covariates in hierarchical models of trait variation

An experimental test of the multi-scalar impacts of digging mammal reintroductions on invertebrate burrows

The decline of ecosystem engineers alters ecosystems, with impacts cascading through to other organisms. Through engineering and predation, digging mammals may affect burrowing invertebrate assemblages, leading to changes in invertebrate-driven soil engineering. Using a mammal reintroduction sanctuary in southern Australia, we tested how digging mammals alter invertebrate burrows (density and size of burrow entrances) and whether these impacts were scale-dependent. We examined the micro-site (pit-scale) effects of mammal foraging pits on invertebrate burrowing activity by comparing natural and artificial pits and bare-ground, and artificial pits of different dimensions within different microhabitat types. To test how mammals affected invertebrate burrows and soil physical and chemical properties at larger scales, we used an exclusion experiment (plot-scale) and surveys inside and outside a reintroduction reserve (landscape scale). Invertebrate burrows were more numerous in mammal pits than bare-ground and artificial pits, and larger in mammal pits than bare-ground. The density and size of invertebrate burrows depended on pit morphology, with burrow density greatest in narrow bilby pits and large burrows favoured by bettong pits. However, the influence of foraging pits on invertebrate burrows was scale-dependent: changes in invertebrate burrows were not detected at the plot or landscape scale. Only 4.5% of land surface area was occupied by pits and this might be insufficient to alter burrow or soil properties detectably in un-stratified surveys at larger scales. Digging mammals altered the small-scale (but not large-scale) distribution of invertebrate burrows, suggesting that their reintroduction provides an avenue through which to restore the heterogeneity of other organisms and functions in ecosystems.

Climate Regimes Override Micro-Site Effects on the Summer Temperature Signal of Scots Pine at Its Northern Distribution Limits.

Tree growth at northern boreal treelines is generally limited by summer temperature, hence tree rings serve as natural archives of past climatic conditions. However, there is increasing evidence that a changing summer climate as well as certain micro-site conditions can lead to a weakening or loss of the summer temperature signal in trees growing in treeline environments. This phenomenon poses a challenge to all applications relying on stable temperature-growth relationships such as temperature reconstructions and dynamic vegetation models. We tested the effect of differing ecological and climatological conditions on the summer temperature signal of Scots pine at its northern distribution limits by analyzing twelve sites distributed along a 2200 km gradient from Finland to Western Siberia (Russia). Two frequently used proxies in dendroclimatology, ring width and maximum latewood density, were correlated with summer temperature for the period 1901–2013 separately for (i) dry vs. wet micro-sites and (ii) years with dry/warm vs. wet/cold climate regimes prevailing during the growing season. Differing climate regimes significantly affected the temperature signal of Scots pine at about half of our sites: While correlations were stronger in wet/cold than in dry/warm years at most sites located in Russia, differing climate regimes had only little effect at Finnish sites. Both tree-ring proxies were affected in a similar way. Interestingly, micro-site differences significantly affected absolute tree growth, but had only minor effects on the climatic signal at our sites. We conclude that, despite the treeline-proximal location, growth-limiting conditions seem to be exceeded in dry/warm years at most Russian sites, leading to a weakening or loss of the summer temperature signal in Scots pine here. With projected temperature increase, unstable summer temperature signals in Scots pine tree rings might become more frequent, possibly affecting dendroclimatological applications and related fields.

Publisher Correction: Carbon and oxygen isotopes in tree rings: climate signals and microsite effects

The manuscript number should not have been included in the title, the correct title reads “Carbon and oxygen isotopes in tree rings—climate signals and microsite effects”.

Physical dormancy alleviation and soil seed bank establishment in Cassia roxburghii is determined by soil microsite characteristics

Seeds with an impermeable coat, i.e. physical dormancy (PY) persist in the soil for a long-time until suitable environmental cues break dormancy and germination is synchronized with the growing season. However, the dormancy loss of seeds at different microsites has not been well characterized. In this study, the effect of microsite affecting dormancy loss in Cassia roxburghii was studied by artificially burying the seeds in an open site and under canopy and exhuming the seeds at 6 month intervals for two years. The soil temperatures of the two microsites at seed vicinity were determined using a data-logger. The results showed that fresh intact seeds did not absorb water, but mechanically scarifying the seeds resulted in water absorption and germination at a wide range of temperatures both in light and darkness. Thus, the seeds of C. roxburghii have PY. Throughout the study period, impermeable seeds buried in the open site broke dormancy in significantly higher number compared with seeds buried under canopy cover (P < 0.05), presumably due to the temperature variation between microsites. Open sites recorded temperatures above 60 °C during summer with diurnal temperature fluctuations close to 20 °C, whereas under canopy cover temperature remained close to 40 °C during summer and much lower during other seasons. These results suggest that the ability of C. roxburghii seeds to break dormancy and establish soil seed banks is affected by the microsite variation.

Visualizing Individual Tree Differences in Tree-Ring Studies

Averaging tree-ring measurements from multiple individuals is one of the most common procedures in dendrochronology. It serves to filter out noise from individual differences between trees, such as competition, height, and micro-site effects, which ideally results in a site chronology sensitive to regional scale factors such as climate. However, the climate sensitivity of individual trees can be modulated by factors like competition, height, and nitrogen deposition, calling attention to whether average chronologies adequately assess climatic growth-control. In this study, we demonstrate four simple but effective methods to visually assess differences between individual trees. Using individual tree climate-correlations we: (1) employed jitter plots with superimposed metadata to assess potential causes for these differences; (2) plotted the frequency distributions of climate correlations over time as heat maps; (3) mapped the spatial distribution of climate sensitivity over time to assess spatio-temporal dynamics; and (4) used t-distributed Stochastic Neighborhood Embedding (t-SNE) to assess which trees were generally more similar in terms of their tree-ring pattern and their correlation with climate variables. This suite of exploratory methods can indicate if individuals in tree-ring datasets respond differently to climate variability, and therefore, should not solely be explored with climate correlations of the mean population chronology.

Seed and microsite limitations of large-seeded, zoochorous trees in tropical forest restoration plantations in northern Thailand

On deforested or degraded land, planting mixtures of native forest tree species facilitates establishment of incoming tree seedling species (species recruitment) by rapidly re-establishing canopy cover. However, delayed colonization of plantations by large-seeded, zoochorous (LSZ) tree species can affect the species composition, structure, and function of the developing forest. The objective of this study was to investigate whether microsites limit establishment (germination and early seedling survival) of LSZ tree species in three 13-year-old, seasonally dry, tropical forest restoration plantations in northern Thailand. We conducted a seed sowing experiment that combined five LSZ tree species with four microsite treatments in a split-plot design. All five tree species were previously absent from the understory of the plantations, despite seed sources being present in nearby natural forest. The four treatments simulated potential microsites that naturally-dispersed seeds may encounter. They included seed deposition on the surface of soil and on leaf litter, as well as seed burial beneath soil and beneath leaf litter. We fenced the experimental areas to prevent seed predation and focus on the environmental effects of microsites on the different stages of seedling establishment. Following seed sowing, we measured germination and seedling survival, mean height, and stem diameter over 26 months. The microsites treatments did not significantly affect germination and seedling survival, providing strong evidence that establishment of the tested species was not limited by the applied microsite environments. Furthermore, although there were significant differences in germination and survival among species, relatively high overall germination (37%) and 26-month seedling survival (58.5%), irrespective of microsite treatment, suggested that environmental conditions in the 13-year-old plantations generally met the requirements for germination and early seedling establishment. Microsite treatments also did not correlate with seedling height or stem diameter at 20 months, suggesting that initial germination microsites have no effect on seedling growth and robustness. Taken together, the results of this investigation support the hypothesis that seedlings of LSZ tree species are slow to colonize tropical forest restoration plantations because of seed limitations resulting from inadequate seed dispersal or low seed availability. The successful establishment of LSZ seedlings from sown seeds in this experiment suggests that direct seeding beneath the canopy of restoration plantations may be an effective way to offset seed dispersal limitations in restoration plantations. Furthermore, the absence of microsite treatment effects suggests broadcast sowing of seeds may be a simple way to recolonize closed-canopy restoration plantations with LSZ tree species.

Editor’s highlight for TSAF D-17-00396: carbon and oxygen isotopes in tree rings—climate signals and microsite effects

Isotopes are important proxies in tree rings but microsite differences are often not taken into account. Esper et al. (Trees 32:1–15, 2018) assessed microsite differences contributing to the understanding of local drivers. Carbon and oxygen isotopes are important proxies in tree ring archives that allow the reconstruction of the past climate as well as to retrospectively assess tree responses towards climatic drivers Esper et al. (Trees 32:1–15, 2018, this issue) took into account potential microsite differences as they not only chose a strong latitudinal gradient in Sweden (Kiruna, north of the polar circle vs. Stockholm) but also collected at both locations tree rings from Pinus sylvestris that grew directly at a lakeshore and trees up to 30 m upslope.

Animal generation of green leaf litter in an arid shrubland enhances decomposition by altering litter quality and location

Soil carbon (C) and nutrients are derived largely from decomposition of plant biomass. Animals that generate greenfall, or green leaf litter, influence C and nutrient cycling dynamics by altering the phenological condition, and therefore nutrient quality, of plant litter entering the soil, and transporting litter among microsites. Microsite effects on decomposition rates are particularly pronounced in arid and semi-arid ecosystems where vegetation cover is often patchy. We investigated differences in decomposition of greenfall and senesced litter of three common Chihuahuan Desert plants from which animals frequently generate greenfall. A litterbag study was used to quantify differences in mass, C, and nitrogen (N) losses between green and senesced leaves in shrub intercanopy and subcanopy microsites in desert shrublands. We found significant differences in nutrient concentration of green and senesced leaves, and that both litter condition (green or senesced) and microsite affected decomposition rate. For two of the three litter species, greenfall decomposed more rapidly than senesced litter; for all three species, litter decomposed more rapidly in intercanopy than subcanopy microsites. These results support the idea that creation and translocation of greenfall by animals are important mechanisms regulating decomposition speed and C and nutrient transfer from plant biomass into the soil.

Converse pathways of soil evolution caused by tree uprooting: A synthesis from three regions with varying soil formation processes

Post-disturbance pedogenetic pathways were characterized in three landscapes representing different degrees of weathering and leaching. Tree uprooting has been the main form of disturbance in all three landscapes. We hypothesized that the pedogenetic effect of trees due to uprooting is mainly governed by the regional degree of pedogenesis, which in turn affects soil and landscape evolution.The three regions were characterized by a chronosequence of treethrow pit-mound pairs, from fresh to almost leveled forms. Two sequences originated from the Czech Republic, one on Haplic Cambisols and one on Entic Podzols. The third and the oldest chronosequence, in Michigan, USA, was on Albic Podzols (dating back to 4080BCE). We analyzed 38 chemical and physical soil properties for 700 samples from 42 pit-mound pairs in these regions. Ordination and regression techniques allowed us to evaluate the effect of sample depth, microsite (pit, mound, and undisturbed control position), and age of the soils formed after uprooting.Depth was the most significant variable in all regions (p<0.001), followed by microsite location, and then age (time since disturbance). The significance of these variables decreased with increasing weathering and leaching intensity. The results suggest that intense pedogenesis, as at the Michigan site, decreases the polygenetic impacts of uprooting on soil development pathways. On Haplic Cambisols, disturbances increased the local variability of pedogenic processes by changing melanization and hydromorphic processes, as well as by mineral alteration. Conversely, on Albic Podzols, we found comparative chemical uniformity in post-uprooting pedogenesis between microsites, despite rapid podzolization in pits and slower podzolization on mounds. The general chemical convergence of pedogenesis in these landscapes towards vertically-dominated podzolization may limit divergence of pedogenic pathways after a disturbance. The formation and translocation of labile organic matter-sesquioxide complexes in the uppermost podzolic horizons in Entic Podzolś was a key threshold, in that it changed the pedochemical, ecological and biogeomorphic role of the treethrow features in the soil and landscape evolution. Although treethrow pits were accumulation sites for soil elements in Haplic Cambisols and Entic Podzols, they were microsites of intense leaching and elemental loss in Albic Podzols.

Enriched Topographic Microsites for Improved Native Grass and Forb Establishment in Reclamation

Low seed germination and seedling establishment are the greatest challenges for revegetation success. Topographic microsites are known to enhance seed germination and seedling establishment due to their unique soil properties and provision of shelter from elements and herbivores; soil amendments can supply organic matter and nutrients for plant establishment and growth when limited. We investigated the effect of three topographic microsites and six soil amendments and their additive effects on three disturbed grasslands in central and southern Alberta, Canada. Treatments were topographic microsites of mounds, pits, and flats, with and without amendments (erosion control blanket, hay, straw, manure, hydrogel, control) and were seeded with four native grasses and three native forb species. Seedling emergence and survival and soil temperature and water content were assessed over two seasons and plant cover over three seasons. The effect of microsites and amendments was not additive. The addition of erosion control blanket, hay, and straw to flat sites was just as productive as on topographic microsites. These amendments increased grass and forb emergence and buffered soil temperature. Mounds increased first year forb emergence and reduced over winter survival rates for grasses and forbs. Pits were not beneficial for revegetation. The effect of topographic microsites and amendments was influenced by site conditions.

Microsite and elevation zone effects on seed pilferage, germination, and seedling survival during early whitebark pine recruitment.

Tree recruitment is a spatially structured process that may undergo change over time because of variation in postdispersal processes. We examined seed pilferage, seed germination, and seedling survival in whitebark pine to determine whether 1) microsite type alters the initial spatial pattern of seed caches, 2) higher abiotic stress (i.e. higher elevations) exacerbates spatial distribution changes, and 3) these postdispersal processes are spatially clustered. At two study areas, we created a seed distribution pattern by burying seed caches in microsite types frequently used by whitebark pine's avian seed disperser (Clark's nutcracker) in upper subalpine forest and at treeline, the latter characterized by high abiotic environmental stress. We monitored caches for two years for pilferage, germination, and seedling survival. Odds of pilferage (both study areas), germination (northern study area), and survival (southern study area) were higher at treeline relative to subalpine forest. At the southern study area, we found higher odds of 1) pilferage near rocks and trees relative to no object in subalpine forest, 2) germination near rocks relative to trees within both elevation zones, and 3) seedling survival near rocks and trees relative to no object at treeline. No microsite effects were detected at the northern study area. Findings indicated that the microsite distribution of seed caches changes with seed/seedling stage. Higher odds of seedling survival near rocks and trees were observed at treeline, suggesting abiotic stress may limit safe site availability, thereby shifting the spatial distribution toward protective microsites. Higher odds of pilferage at treeline, however, suggest rodents may limit treeline recruitment. Further, odds of pilferage were higher near rocks and trees relative to no object in subalpine forest but did not differ among microsites at treeline, suggesting pilferage can modulate the spatial structure of regeneration, a finding supported by limited clustering of postdispersal processes.

Sobrevivencia y crecimiento de plántulas reforestadas de Podocarpus glomeratus (Podocarpaceae) en diferentes altitudes y micrositios en ecosistemas de pastizales de los Andes bolivianos después de cuatro años

La altitud y el micrositio son factores clave para el establecimiento de las plantas en ecosistemas de montana. En este estudio evaluamos como la sobrevivencia y el crecimiento de plantulas de Podocarpus glomeratus, una conifera nativa vulnerable a la extincion, varia a traves de ambos factores. Plantamos 150 plantulas de la especie, repartidas en 15 parcelas a lo largo de un gradiente altitudinal con cinco altitudes (2700, 3000, 3300, 3600 y 3900 m s.n.m) y tres repeticiones por altitud (parcelas anidadas) en ecosistemas de pastizales de la comunidad de Pajchanti (Cochabamba, Bolivia). La sobrevivencia, crecimiento y los componentes del micrositio alrededor de cada plantula (porcentaje de cobertura de pastos, arbustos, piedras, musgos, hierbas y porcentaje de pendiente) se evaluaron tres veces durante cuatro anos. La influencia de la altitud sobre la sobrevivencia final o el crecimiento acumulado de cada plantula fueron analizados con modelos lineales generalizados mixtos (MLGM) y pruebas de Tukey (incluyendo a las parcelas repetidas como factor aleatorio). Asimismo, la influencia de cada uno de los componentes del micrositio sobre la sobrevivencia o el crecimiento de cada plantula fueron analizados por separado para cada altitud, tambien con MLGM, para que los efectos de esas variables no se confundan debido a su correlacion. La sobrevivencia de las plantulas fue mayor en la altitud intermedia y menor en ambos extremos altitudinales. Sin embargo, el crecimiento fue mayor en el rango de la altitud inferior y la intermedia (2700 a 3300 m s.n.m) y menor en altitudes mayores. Los componentes del micrositio no influyeron en la sobrevivencia. Sin embargo, la cobertura de arbustos incremento el crecimiento en la altitud inferior, la cobertura de piedras redujo el crecimiento en la altitud intermedia, y mayor porcentaje de pendiente y cobertura de piedras incrementaron el crecimiento a 3590 m s.n.m. La reforestacion de P. glomeratus en ecosistemas de pastizales deberia realizarse entre 2700 y 3300 m s.n.m. Sin embargo, las piedras, arbustos y pendiente, dependiendo su porcentaje de cobertura en el micrositio e interacciones con la altitud, incrementan o reducen el establecimiento de las plantulas, por lo que deben manejarse en futuras reforestaciones.

Litter decomposition of woody species in shrublands of NW Patagonia: how much do functional groups and microsite conditions influence decomposition?

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.

Legacy microsite effect on the survival of bitterbrush outplantings after prescribed fire: capitalizing on spatial variability to improve restoration

AbstractRestoration of shrubs in arid and semi‐arid rangelands is hampered by low success rates. Planting shrub seedlings is a method used to improve success in these rangelands; however, it is expensive and labor intensive. The efficiency of shrub restoration could be improved by identifying microsites where shrub survival is greater. Bitterbrush (Purshia tridentata Pursh DC) is an important shrub to wildlife that has declined because of conifer encroachment, excessive defoliation, wildfires, and low recruitment. We investigated planting bitterbrush seedlings in western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroached shrublands after prescribed fire was used to control trees. Bitterbrush seedlings were planted in under (canopy) and between (interspace) former juniper canopies at five blocks and evaluated for three growing seasons. Bitterbrush survival was greater than 50% in the former canopy, but only 5% in the interspace microsite by the third growing season. Growth of bitterbrush was also greater in the former canopy compared with the interspace, potentially due to markedly less perennial vegetation in this microsite. Exotic annual grasses and annual forbs became prevalent in the former canopy in the second and third growing season, suggesting that soil resource availability was greater in this microsite. These results suggest that restoration success will vary by specific locations within a burned landscape and that this variability can be used to improve restoration efficiency. In this situation, bitterbrush restoration can be improved by planting seedlings in former canopy compared with interspace microsites.

Initial Transplant Size and Microsite Influence Transplant Survivorship and Growth of a Threatened Dune Thistle

Identifying optimal transplant size and microsite requirements are critical challenges facing restoration practitioners, and refining this information may lead to more cost effective decisions. In this study, we evaluate the effects of transplant size and microsite on restoration success of the federal threatened <i>Cirsium pitcheri</i> (Pitcher’s thistle), a monocarpic perennial restricted to shoreline sand dunes of the Great Lakes in the United States, using a ten-year dataset. Using general and generalized mixed linear models, we determined how microsite variables influenced first-year-transplant survival and subsequent growth. Our data show a higher probability of first-year survival associated with larger transplants. We also found greater plant growth at higher elevations while plants on steeper slopes are smaller the year after they are transplanted. These results have implications for restoration success, which may be maximized by regulating transplant size and selecting habitat.

Microsite and grazing intensity drive infiltration in a semiarid woodland

AbstractHuman activities such as vegetation removal and overgrazing that result in changes in land cover have substantial impacts on ecosystem processes, including the infiltration of water. Different land cover types (microsites) vary in their capacity to conduct water, but the extent to which infiltration is affected by different herbivores or microsites is largely unknown. We examined the effects of grazing and microsite on infiltration in two extensive woodland communities in semiarid eastern Australia that vary in current condition. Poor condition sites had lower steady‐state infiltration under ponding than either average or good condition sites, and this effect was consistent across the two communities. Ponded infiltration and sorptivity beneath grasses, shrubs or trees were about twice that on bare soil, and this corresponded to greater indices of macroporosity. Structural equation modelling showed that shrubs, trees, and grasses had strong positive effects on sorptivity and steady‐state infiltration under ponding, whereas grazing had generally negative effects. The suppressive effects of grazing on soil hydrological processes were mainly due to cattle grazing. The positive effects of grasses, shrubs, and trees on hydrology were twice as strong as the negative effects of grazing. Our results also suggest that prolonged overgrazing that leads to reductions in grass cover is likely to have a synergistic reduction in hydrological function in these woodlands by reducing the cover of highly conductive patches and by reducing the extent of macropores.

Multi-scale ecological filters shape the crayfish microbiome

A general and practical understanding of the processes that drive microbiome assembly and structure are paramount to understanding organismal biology, health, and evolution. In this study of stream-dwelling crayfish, we conceptualized colonization of microbial symbionts as a series of ecological filters that operate at the environment, host, and host microsite levels, and identified key ecological processes at each level. A survey of Cambarus sciotensis in western Virginia, USA, showed that the local environment and host microsites interact to create complex patterns of microbial diversity and composition. An in situ experiment confirmed a prevailing effect of host microsite on microbial composition, and also showed that an ectosymbiotic worm (Annelida; Branchiobdellida) which feeds on biofilms and other symbionts had significant effects on microbial composition of the host carapace, but not gills. Bacterial communities of the carapace were taxonomically rich and even, and correlated with microbial communities of the ambient environment. Conversely, communities on gills were less diverse and dominated by two taxa with potential functional significance: Comamonadaceae and Chitinophagaceae. The bacterial communities of the gills appear to be tightly coupled to host biology, and those of the carapace are mostly determined by environmental context. Our work provides the first characterization of the crayfish microbiome and shows how multi-scale and experimental studies of symbiont community assembly provide valuable insights into how the animal microbiome is structured under conditions of natural complexity. Furthermore, this study demonstrates that metazoan symbiont taxa, i.e., the branchiobdellidans, can alter microbiome assembly and structure.

Warmer seed environments increase germination fractions in Australian winter annual plant species

AbstractClimate can influence plant demographic processes and life stages in different ways, but such details are often ignored in analyses that focus on adult life stages and annual climate averages. In particular, the effects of climate on seeds may be hugely important under climate change. Climate is known to influence seed survival and germination, which in turn can strongly affect population persistence and community dynamics. We investigated climate and other environmental effects on seed viability and germination probabilities of six winter annual plant species persisting in small, isolated habitat fragments in the Mediterranean‐climate region of southwestern Australia. Seeds were collected from southern (cool) and northern (warm) bushland remnants and factorially placed into each location to assess the effects of natural dormancy alleviation via after‐ripening. Seeds were then exposed to cool and warm germination treatments (representing average germination conditions in the two remnants). For five of the six species, seeds from warm maternal populations had higher germination probabilities (or germinated more seeds sooner). Regardless of maternal population, germination probabilities were higher (or germination was more rapid) for seeds that were after‐ripened in the warm remnant for almost all species. For all species, germination was higher (or more rapid) under the warmer germination temperatures. We also found strong microsite effects on seed viability for some species. In the absence of adaptation in dormancy regulation and germination physiology, our results indicate that most of the winter annual species studied will germinate higher fractions of seeds under future climate conditions due to the cumulative effects of warmer maternal, after‐ripening, and germination environments. The fate of isolated populations under climate change may therefore depend strongly on postgermination survival and reproduction to prevent seed bank depletion.

Using facilitation microsites as a restoration tool for conversion of degraded grasslands to Nothofagus forests in Southern Patagonia

In Southern Patagonia, introduction of exotic grasses after forest fires strongly restricts restoration of Nothofagus spp forests. The use of polycarbonate shelters to shield Nothofagus seedlings has been not enough for getting restoration success. Selection of natural facilitation microsites (i.e. logs, rocks, pioneer plants) for seedling outplanting may improve early performance of Nothofagus pumilio (Poepp. et. Endl.) Krasse (N. pumilio), by reducing the incidence of limiting factors such as soil water and light stress. In 2012, seedlings of N. pumilio shielded with polycarnonate shelters were planted close to log piles, nurse plants of native shrubs, and open areas to evaluate the effect of natural facilitation microsites on early performance of the species. After three growing seasons, soil measurements, seedlings survival, stem diameter and height of plants, electronic transport rate, stomatal conductance, and the chlorophyll index were evaluated to explore leaf photochemistry and any possible limitation to photosynthesis associated to microsite conditions. Seedling survival was significantly lower in open sites in comparison to the other microsite conditions. Seedling height was highest both under nurse plants and log piles microsites. Stomatal conductance was higher for seedlings in nurse plant microsites despite the fact that the soil water content was similar across all conditions. Soil penetration resistance and electron transport rate were higher, but chlorophyll index was lower, in open sites when compared to the other microsites. Our results show that the use of facilitation microsites such as pioneer nurse shrubs and logs for N. pumilio reforestation or restoration plans in degraded grassland areas in Southern Patagonia should be considered even when plants are protected with polyethylene shelters.