Early Plant Communities Research Articles

Survivorship dynamics of the flora of Devonian Angarida.

Devonian plants in Siberia present protracted pioneer succession. Research into the survivorship dynamics of early plant communities upon the palaeocontinent Angarida have demonstrated that transgression and volcanogenic nutrient influx were key to the survival of colonizing plants. Taxic proportions show that migrating taxa entered Angarida from the southwest, Kuznetsk and Minusinsk basins, dispersing across the continent in waves through central areas northwards. The patterns of dispersal are consistent throughout the Devonian. Increased nutrient load from the active pulses of the Viluy-Yakutsk Large Igneous Province, biogeomorphic ecosystem engineering and the increased biomass of Angaridan plants are assisted by Late Devonian transgression. These cumulative factors can be linked to the Late Devonian marine extinctions observed in Siberia.

Early ecosystem establishment using forest floor and peat cover soils in oil sands reclamation

ABSTRACT Early trends of plant community development provide the basis of ecosystem function and reclamation success of oil sand extraction sites. However, few studies have explicitly investigated species-level interactions with different cover soil types, placement depths, and time since reclamation during early plant community development in boreal forests. We investigated effectiveness of forest floor mineral mix (FMM) and peat mineral mix (PMM) cover soils and placement depths (10 and 20 cm) at four research sites 4 to 13 years after reclamation. Outcomes of this study indicate FMM had a more positive influence on woody plant densities, vegetation cover, and species richness than PMM. Species assemblage, composition, dominance, and types (successional stages, habitat types, competitive-stress tolerant-ruderal strategies) also showed FMM cover soil performed better than PMM. Greater vegetation cover and richness on deeper (20 cm) cover soil placements were evident. However, this effect of cover soil depth would likely decrease with time. Dominant and subdominant species on FMM were native and early to late successional, thus trajectory community development on FMM followed typical early succession of boreal forests (from ruderal and annual to perennial communities), while PMM was dominated by non-native and annual forbs which could slow succession and ecosystem recovery.

Growth of plants on the Late Weichselian ice-sheet during Greenland interstadial-1?

Unglaciated forelands and summits protruding from ice-sheets are commonly portrayed as areas where plants first establish at the end of glacial cycles. But is this prevailing view of ice-free refugia too simplistic? Here, we present findings suggesting that surface debris supported plant communities far beyond the rim of the Late Weichselian Ice-sheet during Greenland interstadial 1 (GI-1 or Bølling-Allerød interstadial). We base our interpretations upon findings from terrigenous sediments largely resembling ‘plant-trash’ deposits in North America (known to form as vegetation established on stagnant ice became buried along with glacial debris during the deglaciation). In our studied deposit, we found macrofossils (N = 10) overlapping with the deglaciation period of the area (9.5–10 cal kyr BP) as well as samples (N = 2) with ages ranging between 12.9 and 13.3 cal kyr BP. The latter ages indicate growth of at least graminoids during the GI-1 interstadial when the site was near the geographic center of the degrading ice-sheet. We suggest that exposure of englacial material during GI-1 created patches of supraglacial debris capable of supporting vascular plants three millennia before deglaciation. The composition and resilience of this early plant community remain uncertain. Yet, the younger group of macrofossils, in combination with pollen and ancient DNA analyses of inclusions, imply that shrubs (Salix sp., Betula sp. and Ericaceae sp) and even tree species (Larix) were present in the debris during the final deglaciation stage.

Multiple mechanisms of early plant community assembly with stochasticity driving the process.

Initial plant establishment is one of the most critical phases in ecosystem development, where an early suite of physical (environmental filtering), biological (seed limitation, species interactions) and stochastic factors may affect successional trajectories and rates. While functional traits are commonly used to study processes that influence plant community assembly in late successional communities, few studies have applied them to primary succession. The objective here was to determine the importance of these factors in shaping early plant community assembly on a glacial outwash plain, Skeiðarársandur, in SE Iceland using a trait based approach. We used data on vascular plant assemblages at two different spatial scales (community and neighborhood) sampled in 2005 and 2012, and compiled a dataset on seven functional traits linked to species dispersal abilities, establishment, and persistence for all species within these assemblages. Trait-based null model analyses were used to determine the processes that influenced plant community assembly from the regional species pool into local communities, and to determine if the importance of these processes in community assembly was dependent on local environment or changed with time. On the community scale, for most traits, random processes dominated the assembly from the regional species pool. However, in some communities, there was evidence of non-random assembly in relation to traits linked to species dispersal abilities, persistence, and establishment. On the neighborhood scale, assembly was mostly random. The relative importance of different processes varied spatially and temporally and the variation was linked to local soil conditions. While stochasticity dominated assembly patterns of our early successional communities, there was evidence of both seed limitation and environmental filtering. Our results indicated that as soil conditions improved, environmental constraints on assembly became weaker and the assembly became more dependent on species availability.

Rapid transgenerational effects in Knautia arvensis in response to plant community diversity

Summary Plant species persistence in natural communities requires coping with biotic and abiotic challenges. These challenges also depend on plant community composition and diversity. Over time, biodiversity effects have been shown to be strengthened via increasing species complementarity in mixtures. Little is known, however, whether differences in community diversity and composition induce rapid transgenerational phenotypic adaptive differentiation during community assembly. We expect altered plant–plant and other biotic interactions (mutualists or antagonists) in high vs. low diverse communities to affect immediate within‐ and between‐species trait differentiations due to competition for light and nutrients. Three years after the initiation of a large‐scale, long‐term biodiversity experiment in Jena, Germany, we tested for effects of varying experimental plant community diversity (1–60 plant species; one to four plant functional groups) and composition (with or without legumes and/or grasses) on phenotypic differentiation and variation of the tall herb Knautia arvensis. We measured reproduction at different diversity levels in the Jena Experiment (residents hereafter) and, in an additional common garden experiment without competition, recorded subsequent offspring performance (i.e. growth, reproductive success and susceptibility to powdery mildew) to test for differentiation in phenotypic expression and variability. We observed phenotypic differences among diversity levels with reduced fecundity of K. arvensis residents in more diverse communities. In the next generation grown under common garden conditions, offspring from high‐diversity plots showed reduced growth (i.e. height) and lower reproduction (i.e. fewer infructescences), but increased phenotypic trait variability (e.g. in leaf width and powdery mildew presence) and also tended to be less susceptible to powdery mildew infection. Community composition also affected Knautia parents and offspring. In the presence of legumes, resident plants produced more seeds (increased fecundity); however, germination rate of those seeds was reduced at an early seedling stage (reduced fertility). Synthesis. We conclude that rapid transgenerational effects of community diversity and composition on both mean and variation of phenotypic traits among offspring exist. In addition to heritable variation, environmentally induced epigenetic and/or maternal processes matter for early plant community assembly and may also determine future species coexistence and community stability.

Early plant community dynamics following overseeding for the rehabilitation of a Mediterranean silvopastoral system

The sowing of selected seeds is often applied as post-fire rehabilitation practice in Mediterranean silvopastoral systems. Often, the topography of these silvopastoral systems is sloppy and irregular, requiring low input and easy pasture rehabilitation practices, such as no tillage, low seed and fertilizer rates. In this paper, we studied the vegetation changes over 4 years, after a low-input overseeding (broadcasting) of non-native pasture species, within a post-fire rehabilitation program of a silvopastoral system in Sardinia (Italy). The main objective was to assess the effect of overseeding on the early plant community dynamics and on the relationship between topography, soil pH, and soil nitrogen content on the spatial and temporal dynamics of the grassland composition. Understorey vegetation was classified into nine “functional classes”, three corresponding to the oversown species (subclovers, burr medic and annual ryegrass) and six belonging to the native community, i.e. grasses, legumes, Cistus spp., spiny Carduaceae, spiny Rubus spp. and other forbs. The oversown species showed a rapid establishment, contributing from 30 up to 50% to the floristic composition of the oversown pasture. The overseeding reduced the abundance of post-fire invasive shrubs and spiny forbs by up to about 70% compared to the unsown pasture. The spatial patterns of the functional classes were only weakly influenced by nitrogen content, with a higher impact on introduced species in the first 2 years after overseeding, while the topographic variables had a desultory influence over the 4 years. Overseeding proved to be effective for the rehabilitation and improvement of semiarid Mediterranean grasslands without substantially constraining the ecological succession of floristic composition towards the native vegetation.

Microtopography Influences Early Successional Plant Communities on Experimental Coal Surface Mine Land Reclamation

AbstractSurface mining for coal represents one of the dominant forms of anthropogenic disturbance to forests of the eastern United States. Reclamation methods adopted under federal law in the 1970s have led to a state of arrested succession, failing to achieve pre‐disturbance conditions. New methods of reclamation have been proposed with the goal of returning mined land to its former forested state through the use of compaction reducing techniques that significantly increase fine‐scale heterogeneity. The Forestry Reclamation Approach creates topographic heterogeneity by loosely dumping overburden material into large piles to serve as a tree‐planting medium. We examined the effect of fine‐scale topographic relief, soil physical properties, and reclamation method on early plant community development on a mine site in eastern Ohio. We sampled plots at four microtopographic positions and three distances from the remaining forest edge in both experimentally and traditionally reclaimed areas of a surface mine. Multivariate analysis of variance (ANOVA) on distance matrices indicated significant differences in plant community composition among microtopographic positions and reclamation methods. Microtopographic positions also exhibited significant differences in measured soil properties significantly affecting plant community composition. Plots in the traditionally reclaimed areas had no woody plant colonization, indicating arrested succession common to sites reclaimed using traditional methods. Our results suggest that the creation of topographic heterogeneity at the time of reclamation markedly accelerates ecological succession and promotes enhanced plant community diversity. Expanded application of the methods used here could allow for a faster return to the former forested state of mined lands than traditional reclamation methods.

Erosion control blankets, organic amendments and site variability influenced the initial plant community at a limestone quarry in the Canadian Rocky Mountains

Abstract. Season of seeding and soil amendment with manure mix, wood shavings and erosion control blankets were evaluated over two growing seasons to determine their effect on soil properties and native grass establishment at a Canadian limestone quarry and lime processing plant. A season (fall, spring) of soil amending and seeding did not significantly affect revegetation or soil properties. Site characteristics such as slope, aspect, initial soil nutrients and surrounding plant communities influenced early plant community development and overall effects of soil treatments. Erosion control blankets resulted in the highest seeded plant cover and the lowest non-seeded plant cover despite not significantly changing soil chemical properties. Total nitrogen and carbon significantly increased establishment of seeded grasses and non-seeded species. Increased nitrogen and carbon in the constructed soils were best achieved through addition of manure. Wood shavings did not favour establishment of vegetation and resulted in similar, and in some cases less, vegetation than the controls. Assisted revegetation increased plant cover from < 6 to 50% and reduced cover of non-seeded species. Amendments that modified both chemical and physical soil conditions were best to increase vegetation establishment in the harsh conditions of the quarry.

Early development of plant community in a created mitigation wetland as affected by introduced hydrologic design elements

The goal of this study was to investigate early plant community development in two sites (i.e., higher and lower elevation sites—LC1 and LC2, respectively) of the Loudoun County (LC) mitigation wetland created in the Virginia Piedmont. The effects of hydrologic design elements incorporated during the construction (i.e., disking-induced microtopography—MT and site level elevation difference) on vegetative and hydrologic attributes (e.g., species richness, biodiversity, plant cover, floristic quality assessment index, wetland indicator status, soil moisture content, and water table depths) were investigated. The study was conducted at the end of two growing seasons in 2008 and 2009 (i.e., second and third growing seasons). Drought conditions that persisted into the second growing season resulted in the abundance of a seeded cover grass, Lolium multiflorum (Italian ryegrass), intentionally planted during initial seeding for erosion control. L. multiflorum was subsequently phased out and replaced by facultative wet and obligate wetland species by the third growing season when above-average precipitation occurred, leading to a decrease in total percent cover. Prevalence index changed in both LC1 and LC2, dropping from overall facultative status in 2008 to obligate status in 2009 when obligate species such as Bidens cernua, Carex frankii, and Juncus effusus thrived and expanded with the change of hydrologic regime in 2009. Microtopographic treatment (i.e., disked or undisked) positively influenced vegetation development for LC1 site in 2008, but the positive influence was not consistent for LC2, which experienced an additional month of standing water conditions in the same year, nor for either site in 2009 when above-average precipitation occurred. The site differences in elevation, and thus hydrologic regime, seemed to overwhelm the effects on vegetation of disking-induced microtopography in each site when precipitation was at or above average range. Although shown on short spatial and temporal scales in this study, incorporation of micro- and macrotopographic design elements in creating a mitigation wetland can be beneficial to the early development of diverse vegetation communities wetland under varying climate conditions.

Post-eruption Legacy Effects and Their Implications for Long-Term Recovery of the Vegetation on Kasatochi Island, Alaska

We studied the vegetation of Kasatochi Island, central Aleutian Islands, to provide a general field assessment regarding the survival of plants, lichens, and fungi following a destructive volcanic eruption that occurred in 2008. Plant community data were analyzed using multivariate methods to explore the relationship between pre- and post-eruption plant cover; 5 major vegetation types were identified: Honckenya peploides beach, Festuca rubra cliff shelf, Lupinus nootkatensis–Festuca rubra meadow, Leymus mollis bluff ridge (and beach), and Aleuria aurantia lower slope barrens. Our study provided a very unusual glimpse into the early stages of plant primary succession on a remote island where most of the vegetation was destroyed. Plants that apparently survived the eruption dominated early plant communities. Not surprisingly, the most diverse post-eruption community most closely resembled a widespread pre-eruption type. Microhabitats where early plant communities were found were distinct and apparently crucial in determining plant survival. Comparison with volcanic events in related boreal regions indicated some post-eruption pattern similarities.

Development of vegetation patterns in early primary succession

Question: We investigated colonisation filters in early plant community development on a glacial outwash plain. We asked if these were related to seed limitation or to a lack of safe sites, if topographical heterogeneity affected species patchiness and how species life cycles influence successional trajectories. Location: An outwash plain (Skeiðarársandur) in southeast Iceland. Methods: We identified surface heterogeneity at two different scales, ca. 10–15 cm (larger stones and established plants) and ca. 50 m (shallow depressions representing dry river beds) at two study sites. We quantified species cover, flowering plant density, seed production, seed rain, seed bank density, seedling emergence and seedling survival from June 2005 to June 2007 for the whole plant community, and measured seed production for five species. Results: Mean vegetation cover was <2.5% at the sites. Low emergence rates and high seedling mortality were the two main recruitment filters. Only 1.4% of seedlings emerging in 2005 survived into the 2007 growing season. Topographical heterogeneity had little effect on plant colonisation. High annual variation was recorded, and the two study sites (ca. 2 km apart) differed in their colonisation success. Of the five species, establishment of Cerastium alpinum and Silene uniflora was most limited by lack of seeds, whereas establishment of Luzula spicata, Poa glauca and Rumex acetosella was most limited by safe sites. Conclusions: We conclude that colonisation processes and patterns in early primary succession on Skeiðarársandur were largely influenced by stochastic factors.

Phytoliths in woody plants from the Miombo woodlands of Mozambique

There are no descriptions of phytoliths produced by plants from the 'Zambezian' zone, where Miombo woodlands are the dominant element of the largest single phytochorion in sub-Saharan Africa. The preservation of phytoliths in fossil records of Africa makes phytoliths a tool to study early plant communities. Paleo-ethnobotanical interpretation of phytoliths relies on the comparison of ancient types with morphotypes extracted from living reference collections. Phytoliths were extracted from plant samples representing 41 families, 77 genera and 90 species through sonic cleaning, dry ashing and acid treatment; and phytoliths thus extracted were quantified. For each species, an average of 216 phytoliths were counted. The percentage of each morphotype identified per species was calculated, and types were described according to the descriptors from the International Code for Phytolith Nomenclature. Phytolith assemblages were subject to discriminant analysis, cluster analysis and principal component analysis. Phytoliths were grouped into 57 morphotypes (two were articulated forms and 55 were discrete shapes), and provide a reference collection of phytolith assemblages produced by Miombo woody species. Common and unique morphotypes are described and taxonomic and grouping variables are looked into from a statistical perspective. The first quantitative taxonomy of phytoliths from Miombos is presented here, including new types and constituting the most extensive phytolith key for any African ecoregion. Evidence is presented that local woody species are hypervariable silica producers and their phytolith morphotypes are highly polymorphic. The taxonomic significance of these phytoliths is largely poor, but there are important exceptions that include the morphotypes produced by members from >10 families and orders. The typical phytolithic signal that would allow scientists to identify ancient woodlands of 'Zambezian' affiliation comprises only half of the original number of phytoliths originally produced and might favour the more resilient blocky, cylindroid, globular and tabular forms.

Soil Fungal Communities Underneath Willow Canopies on a Primary Successional Glacier Forefront: rDNA Sequence Results Can Be Affected by Primer Selection and Chimeric Data

Soil fungal communities underneath willow canopies that had established on the forefront of a receding glacier were analyzed by cloning the polymerase chain reaction (PCR)-amplified partial small subunit (18S) of the ribosomal (rRNA) genes. Congruence between two sets of fungus-specific primers targeting the same gene region was analyzed by comparisons of inferred neighbor-joining topologies. The importance of chimeric sequences was evaluated by Chimera Check (Ribosomal Database Project) and by data reanalyses after omission of potentially chimeric regions at the 5'- and 3'-ends of the cloned amplicons. Diverse communities of fungi representing Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota were detected. Ectomycorrhizal fungi comprised a major component in the early plant communities in primary successional ecosystems, as both primer sets frequently detected basidiomycetes (Russulaceae and Thelephoraceae) forming mycorrhizal symbioses. Various ascomycetes (Ophiostomatales, Pezizales, and Sordariales) of uncertain function dominated the clone libraries amplified from the willow canopy soil with one set of primers, whereas the clone libraries of the amplicons generated with the second primer set were dominated by basidiomycetes. Accordingly, primer bias is an important factor in fungal community analyses using DNA extracted from environmental samples. A large proportion (>30%) of the cloned sequences were concluded to be chimeric based on their changing positions in inferred phylogenies after omission of possibly chimeric data. Many chimeric sequences were positioned basal to existing classes of fungi, suggesting that PCR artifacts may cause frequent discovery of new, higher level taxa (order, class) in direct PCR analyses. Longer extension times during the PCR amplification and a smaller number of PCR cycles are necessary precautions to allow collection of reliable environmental sequence data.