Non-vascular Species Research Articles

Synergistic development of nonvascular species microalgae for bio-hydrogen production featured with nano titanium dioxide additive

With technological growth, renewable biofuel energy sources, extracted from organic materials and microalgae feedstock's rich energy substance, have the potential for future energy applications. Moreover, syngas production is limited due to microalgae processing. The prime aim of this research is to enhance the bio-hydrogen extraction by the source of sewage sludge and harvesting of microalgae from non-vascular species (Bryothyta) water with the integration of 0.05, 0.1, 0.15, and 2vol% of titanium dioxide (TiO2) nano additive. Influences of TiO2 concentration on synergistic specific microalgae growth are monitored concerning day and observed that the higher content (2vol%) of TiO2 own 0.87 microns/day, which involves hydrothermal gasification process configured with potassium hydroxide catalyst operating with 400, 500, 600, and 700 ⁰C gasification temperature under 60min time gap. Gasification temperature influencing molar fraction, bio-methane & and hydrogen yield, low heating value, hydrogen selectivity, and gasification efficiency is experimentally studied. With the importance KOH adopted hydrothermal gasifier functioned with higher gasification temperature of 700⁰C operated by 60min offered higher molar fractions of 62% in hydrogen & 17% in bio-methane, superior bio-methane & hydrogen yield of 9.1& 23mol/kg, reduced low heating value of 9.3 MJ/Nm3, higher hydrogen selectivity of 18.5, and superior gasification efficiency of 66%.

Establishing trace element concentrations for lichens and bryophytes in the ring of fire region of the Hudson Bay Lowlands, Ontario, Canada.

Peatlands dominate the landscape of the Hudson Bay Lowlands in Ontario, Canada. Recently, mineral deposits of chromium (Cr), nickel (Ni), and copper (Cu) were discovered in the region and anticipated future industrial mining operations have the potential to impact the environment. Lichens and bryophytes are considered excellent biomonitors and indicators of deposition, deriving their nutrients directly from the atmosphere. Trace element concentrations in lichens and bryophytes have not been reported in the Hudson Bay Lowlands. Here, we seek to determine the baseline trace element concentrations of six non-vascular species (Evernia mesomorpha, Bryoria spp., Cladonia stellaris, Cladonia stygia, Sphagnum fuscum, and Sphagnum capillifolium) common to the region, explore linear relationships of trace elements with iron (Fe) as a signature of particulates with geogenic origin, and calculate trace element enrichment factors. Thalli, foliage, and peat (0-30cm) were collected from 55 locations between 2013 and 2018 and analyzed for trace elements. Thalli and foliar concentrations are among the lowest reported in the broader literature and differ substantially from peat. Fe concentrations were significantly correlated (Pearson's r ≥ 0.8) with aluminum (Al), titanium (Ti), and vanadium (V) in all six species. Enrichment factors show some anthropogenic deposition effects non-vascular organism chemistry. Most trace element concentrations in lichens and bryophytes are indicative of long-range atmospheric transport of dust, but some is attributed to industry, with only minimal inclusions from the local area. Epiphytic lichens are well suited for ongoing atmospheric biomonitoring as industrialization commences.

Enumeration of Plant Species Inhabiting Oil Palm Trees (Elaeis-guineensis) at Zawlpui Plantation Site, Serchhip District, Mizoram

A survey of plant species inhabiting oil palm trees was conducted in Zawlpui area of Serchhip district, Mizoram. The study area is a tropical potent agriculture zone, wherein small-scale business of Elaeis guineensis plantation is carried out by several farmers mainly within the gentle sloppy terrain. Oil palm with a rough bark harbors immense inhabitation by a variety plants, that rooted mostly on the debris at leaf base. Species diversity on the plant stem supposedly encourage insects and termites to establish herewith, thus causing harming to the tree. The sample stands within 400 m–800 m altitude were picked randomly. A total of 50 palm tree were accounted and all associated plants on the stem above 30 cm from the ground are all recorded. Species that cannot be identified on the site were pressed and observed at Botany Research lab, Pachhunga University College. The survey documented 38 vascular plant species which include 4 epiphytes and 1 non-vascular species of lichen, 1 bryophyte and 4 fungal species at that time. Invasive Peperomia pellucida and epiphytic pteridophytes Nephrolepis biserrata was found in most of the stand sample; however, Peperomia population decreases with the increasing elevation. Dynamics of inhabitant species diversity also correlate to location of tree. The study also established that diversity of inhabiting species was comparatively high on parts of the stem facing sunlight.

High levels of glucose alter Physcomitrella patens metabolism and trigger a differential proteomic response.

Sugars act not only as substrates for plant metabolism, but also have a pivotal role in signaling pathways. Glucose signaling has been widely studied in the vascular plant Arabidopsis thaliana, but it has remained unexplored in non-vascular species such as Physcomitrella patens. To investigate P. patens response to high glucose treatment, we explored the dynamic changes in metabolism and protein population by applying a metabolomic fingerprint analysis (DIESI-MS), carbohydrate and chlorophyll quantification, Fv/Fm determination and label-free untargeted proteomics. Glucose feeding causes specific changes in P. patens metabolomic fingerprint, carbohydrate contents and protein accumulation, which is clearly different from those of osmotically induced responses. The maximal rate of PSII was not affected although chlorophyll decreased in both treatments. The biological process, cellular component, and molecular function gene ontology (GO) classifications of the differentially expressed proteins indicate the translation process is the most represented category in response to glucose, followed by photosynthesis, cellular response to oxidative stress and protein refolding. Importantly, although several proteins have high fold changes, these proteins have no predicted identity. The most significant discovery of our study at the proteome level is that high glucose increase abundance of proteins related to the translation process, which was not previously evidenced in non-vascular plants, indicating that regulation by glucose at the translational level is a partially conserved response in both plant lineages. To our knowledge, this is the first time that metabolome fingerprint and proteomic analyses are performed after a high sugar treatment in non-vascular plants. These findings unravel evolutionarily shared and differential responses between vascular and non-vascular plants.

First bryophyte records from Diego Ramírez Archipelago: Changing lenses in long-term socio-ecological research at the southernmost island of the Americas

Long-term socio-ecological research requires comprehensive assessments of biodiversity that overcome historical taxonomic biases, such as the strong focus on the vascular flora. This is particularly relevant at high latitudes where the richness of non-vascular plant species exceeds that of vascular species. Additionally, with respect to geographical regions, there is also a marked bias towards ecological and conservation research in the northern hemisphere. In contrast, few studies have investigated patterns of non-vascular species richness in relation to conservation priorities at sub-Antarctic latitudes, particularly in the sub-Antarctic Magellanic ecoregion. In this work, we contribute to overcome such taxonomic, geographical and ecoregional biases by moving outside these limits, and therefore “changing the lenses” that are commonly used to assess and conserve biodiversity. We implemented these new “biocultural lenses” by including, for the first time, bryophytes in the floristic inventory of the southernmost island of the American continent: Gonzalo Island (56°31’16.8’’S; 68°42’53.5’’W) in the Diego Ramirez Archipelago, Chile. The first bryological exploration of the Diego Ramirez archipelago, SW of Cape Horn, revealed a bryophyte flora composed of 14 species, eight liverworts and six mosses. This number of non-vascular plant species almost doubles the eight vascular plants present on the island. Consequently, with our study, we aim to fill a critical gap in the knowledge of the flora of the Diego Ramirez archipelago, and establish an integral floristic characterization for the long-term socioecological research and conservation of the southernmost archipelago of South America. Based on the field material collected, the new nomenclatural combination Chiloscyphus secundifolius (Hook. f. & Taylor) J.J. Engel is proposed. The moss flora comprises Amblystegium serpens, a widespread moss, yet hitherto unknown for sub-Antarctic Chile. The bryoflora of Diego Ramirez has its greatest affinities with that of the sub-Antarctic Magellanic ecoregion and Maritime Antarctica. None of the liverworts present on Gonzalo Island occurs on continental Antarctica; in contrast, four of the six mosses are shared between these two areas.

When facilitation meets clonal integration in forest canopies.

Few studies have explored how - within the same system - clonality and positive plant-plant interactions might interact to regulate plant community composition. Canopy-dwelling epiphytes in species-rich forests provide an ideal system for studying this because many epiphytic vascular plants undertake clonal growth and because vascular epiphytes colonize canopy habitats after the formation of nonvascular epiphyte (i.e. bryophyte and lichen) mats. We investigated how clonal integration of seven dominant vascular epiphytes influenced inter-specific interactions between vascular epiphytes and nonvascular epiphytes in a subtropical montane moist forest in southwest China. Both clonal integration and environmental buffering from nonvascular epiphytes increased survival and growth of vascular epiphytes. The benefits of clonal integration for vascular epiphytes were higher when nonvascular epiphytes were removed. Similarly, facilitation from nonvascular epiphytes played a more important role when clonal integration of vascular epiphytes was eliminated. Overall, clonal integration had greater benefits than inter-specific facilitation. This study provides novel evidence for interactive effects of clonality and facilitation between vascular and nonvascular species, and has implications for our understanding of a wide range of ecosystems where both high levels of clonality and facilitation are expected to occur.

How does the pedoenvironmental gradient shape non-vascular species assemblages and community structures in Maritime Antarctica?

The main terrestrial ecosystems dominated by lichens and mosses, which represent important ecological indicators of climatic changes in high polar latitudes, are found in the Antarctic continent. However, little is known about how environmental filtering shapes cryptogamic communities’ assemblages at fine-scale. In this study, we analysed changes in non-vascular species richness, species composition and plant coverage along a pedoenvironmental gradient in Maritime Antarctica. We hypothesized that pedoenvironmental filters (i.e. soil texture and chemistry properties) drive the non-vascular assembly community. We classified soils according to the World Reference Base for Soil Resources, selecting ten different pedoenvironments at fine-scale. The plant inventory data from 206 plots across these pedoenvironments was used to evaluate the main effect of plant coverage, soil texture and soil chemistry on non-vascular species richness and composition. The ecological value of the species was determined and the type of community it occurred in was characterized, then the associations of the species were classified in each pedoenvironment. Differences in species richness, species composition and plant coverage were detected along the pedoenvironmental gradient. However, plant coverage, soil chemistry, soil texture and soil variables did not affect species richness and species composition, with the exception of clay content that was particularly an important predictor of species composition. High pedoenvironmental filtering apparently has no effect on species richness but determined differences in species composition. Therefore, we assumed that pedoenvironmental filtering determined high beta diversity in this island from maritime Antarctica. This study reveals that fine scale heterogeneity contributes to specific species associations along a pedoenvironmental gradient; thus, pedoenvironmental filtering not only determines diversity pattern in non-vascular plants, but also type of communities.

Conservation of Thermospermine Synthase Activity in Vascular and Non-vascular Plants.

In plants, the only confirmed function for thermospermine is regulating xylem cells maturation. However, genes putatively encoding thermospermine synthases have been identified in the genomes of both vascular and non-vascular plants. Here, we verify the activity of the thermospermine synthase genes and the presence of thermospermine in vascular and non-vascular land plants as well as in the aquatic plant Chlamydomonas reinhardtii. In addition, we provide information about differential content of thermospermine in diverse organs at different developmental stages in some vascular species that suggest that, although the major role of thermospermine in vascular plants is likely to be xylem development, other potential roles in development and/or responses to stress conditions could be associated to such polyamine. In summary, our results in vascular and non-vascular species indicate that the capacity to synthesize thermospermine is conserved throughout the entire plant kingdom.

Physiognomic and Multivariate Phytosociological Analyses of a Subtropical Peat Bog Located on the Eastern Plateau in Southern Brazil

Subtropical peat bog vegetation in southern Brazil was examined using physiognomic and phytosociological approaches. The analysis included vascular (angiosperms, pteridophytes) and non-vascular species (bryophytes, mat-forming algae, lichens, macroscopic fungi). The breadth of this approach is novel among wetland studies in southern Brazil. The study examined the Banhado Amarelo peat bog (29°19′05″S, 50°08′18″W), which is located in the Brazilian highlands of Rio Grande do Sul (RS) state. Plant cover data extracted from 125 plots distributed among 13 physiognomically recognizable vegetation patches were analyzed using the Braun-Blanquet procedure. In total, 165 species were identified. Multivariate analysis distinguished four groups of patches. The distinctions among groups were particularly evident when all floristic elements were included, i.e., vascular + non-vascular species. When the peat soil in these 13 vegetation patches was analyzed, the proportional clay content of the soil was related to the distribution of patches. The integrated analysis of the Banhado Amarelo bog demonstrated the relevance of physiognomic studies to support phytosociological analyses and the importance of including all floristic elements and soil composition data in a comprehensive approach. These findings can be extended to other studies of subtropical bogs of southern Brazilian highlands that aim to conserve these important South American ecosystems.

Contribution of plant species to the high N retention capacity of a subalpine meadow undergoing elevated N deposition and warming

While numerous studies have examined the effect of N deposition on ecosystem N retention, few have analyzed the involvement of plant species and climate warming in this process. We experimentally investigated the effects of increasing N deposition (Nexo) and climate warming on the fate of Nexo in a subalpine meadow and established the involvement of plant species. Using 15N tracer, we tracked Nexo sprayed on the vegetation in belowground and aboveground plant biomasses (AGB) and in bulk soil over three growing seasons. We assessed the Nexo absorption capacity of plant species and the contribution of Nexo to their AGB N pool. The meadow retained a large proportion of Nexo (≈65%, mostly in AGB) for depositions up to four times the background N rate. Nexo present in the meadow compartments in year 2 was still present in year 3, suggesting that the ecosystem was unsaturated after three years of high N input. Nexo retention resulted more from an increase in N concentration in plant tissues than from the increase in AGB. The species-specific Nexo absorption capacity was inversely related to their AGB N concentration. Nexo accounted for up to 40% of total AGB N depending on the species and the N treatments. The contribution of species to ecosystem Nexo retention more contingent on their AGB than on their relative cover in the community, ranked as follows: C. vulgaris (14.0%) > N. stricta (7.0%) > other Poaceae = C. caryophyllea (2.5%) > other Eudicotyledons (1.5%) > non-vascular species = P. erecta > Fabaceae (0.8–0.2%). Climate warming increased AGB and decreased tissue N concentration. No warming-Nexo interaction was observed. Thus, Pyrenean subalpine meadows that have not undergone a decline in plant species richness in recent decades paradoxically display a high potential to sequester atmospheric N deposition.

Epixylic vegetation abundance, diversity, and composition vary with coarse woody debris decay class and substrate species in boreal forest

Although the importance of coarse woody debris (CWD) to understory species diversity has been recognized, the combined effects of CWD decay and substrate species on abundance and species diversity of epixylic vegetation have received little attention. We sampled a wide range of CWD substrate species and decay classes, as well as forest floors in fire-origin boreal forest stands. Percent cover, species richness, and evenness of epixylic vegetation differed significantly with both CWD decay class and substrate species. Trends in cover, species richness, and evenness differed significantly between nonvascular and vascular taxa. Cover, species richness, and species evenness of nonvascular species were higher on CWD, whereas those of vascular plants were higher on the forest floor. Epixylic species composition also varied significantly with stand ages, overstory compositions, decay classes, substrate species, and their interactions. Our findings highlight strong interactive influences of decay class and substrate species on epixylic plant communities and suggest that conservation of epixylic diversity would require forest managers to maintain a diverse range of CWD decay classes and substrate species. Because stand development and overstory compositions influence CWD decay classes and substrate species, as well as colonization time and environmental conditions in the understory, our results indicate that managed boreal landscapes should consist of a mosaic of different successional stages and a broad suite of overstory types to support diverse understory plant communities.

Edge influence of low-impact seismic lines for oil exploration on upland forest vegetation in northern Alberta (Canada)

Low-impact seismic (LIS) techniques were developed to reduce the environmental footprint of oil exploration. Though relatively narrow (∼2–3m) and constructed with light-weight equipment, these lines cause forest fragmentation, and with their high density and potential edge influence extending into adjacent forest, their impact may be considerably underestimated. We assessed the effects of 3- to 4-year-old LIS lines in upland coniferous sub-boreal forests in northwestern Alberta (Canada) by investigating the distance of influence from the LIS line centre, through the edge and into the adjacent forest on vascular and non-vascular plant species diversity and cover and on several environmental factors. We also assessed whether cardinal orientation of the edge affects influence on plants and environmental factors. Edge orientation had no effect on extent of edge influence on plants or environmental variables, but distance from seismic line edge did. Species diversity of herbaceous plants was lowest from the seismic line edge up to 15m into the adjacent forest, when compared to mid- (25m) and far-interior (75m) forest. In contrast, cover was lower 5m from the seismic line edge in comparison to far-interior forest, but conditions on the seismic lines did not differ from the seismic line edge or any sampled distance up to 75m from the edge. Non-vascular species had lower diversity and cover on the seismic lines and along the edges in comparison to any distance away from the edge. There was no effect of distance from the seismic line edge on live woody plants, but deadwood was more frequently encountered near the seismic line edges in comparison to interior forest. Soil temperature was higher on the seismic lines and along the line edges whereas soil moisture on the seismic lines was about twice as high as at the edges and adjacent forest. Seismic lines and edges also received more light than the forest near the edge, but not more than the far-interior forest. With edge influence detectable up to 15m from edge 3 to 4years post-construction, long-term and regular monitoring of LIS lines is recommended, as active management and remedial reclamation actions might be required to bring the recovery of these disturbances on the right trajectory.

Resilience of understory vegetation after variable retention felling in boreal Norway spruce forests – A ten-year perspective

We studied the ten-year response of understory vegetation and lichens in mature boreal Norway spruce forests to five felling treatments in southern Finland. The stand level treatments represent a range in intensity of overstory removal: clear felling (CF) with site preparation and planting, retention felling (RF) (7% of stand volume retained) with site preparation and planting, gap felling with site preparation (GFs) (50% retained) and without planting, gap felling (GF) (50% retained) without site preparation or planting, and selection felling (SF) (67% retained) without site preparation or planting. Disc trenching was used for site preparation. Vegetation was sampled before and 1, 2, 3 and 10years after the treatments. Both species cover and number decreased significantly immediately after all treatments. The resistance of understory vegetation, defined as the amount of change in the community structure caused by the treatments, increased in the order CF<RF<GFs<SF<GF. The dynamics of vascular plants depended on the felling intensity. The dynamics of non-vascular species depended both on the felling intensity and site preparation. CF and RF caused almost similar effects on understory vegetation composition. Local extinctions of mosses and liverworts were caused especially by CF and RF. However, even with 67% retention, 18 bryophyte species were lost during the study period. Loss of bryophyte species was higher after SF than after GF treatments, suggesting that aggregated retention is better for maintaining bryophyte species in felling areas. The resilience of understory vegetation increased in the order CF<RF<GFs<GF<SF. The abundance of mosses, liverworts and dwarf shrubs had not recovered ten years after treatments. Herb species were the most resilient compared to other species groups. We conclude that in intensively managed forest landscapes, GF and SF can be recommended as alternatives to CF to better maintain understory diversity on the stand level. However, the aim with GF and SF treatments was to further harvest the stands. Subsequent removal of the residual stands may cause substantial changes in understory vegetation for the whole treatment area. To protect late-successional bryophytes in felling areas in mesic spruce forests, high levels of retention and minimizing soil disturbance would be required.

Interactive effects between plant functional types and soil factors on tundra species diversity and community composition.

Plant communities are coupled with abiotic factors, as species diversity and community composition both respond to and influence climate and soil characteristics. Interactions between vegetation and abiotic factors depend on plant functional types (PFT) as different growth forms will have differential responses to and effects on site characteristics. However, despite the importance of different PFT for community assembly and ecosystem functioning, research has mainly focused on vascular plants. Here, we established a set of observational plots in two contrasting habitats in northeastern Siberia in order to assess the relationship between species diversity and community composition with soil variables, as well as the relationship between vegetation cover and species diversity for two PFT (nonvascular and vascular). We found that nonvascular species diversity decreased with soil acidity and moisture and, to a lesser extent, with soil temperature and active layer thickness. In contrast, no such correlation was found for vascular species diversity. Differences in community composition were found mainly along soil acidity and moisture gradients. However, the proportion of variation in composition explained by the measured soil variables was much lower for nonvascular than for vascular species when considering the PFT separately. We also found different relationships between vegetation cover and species diversity according the PFT and habitat. In support of niche differentiation theory, species diversity and community composition were related to edaphic factors. The distinct relationships found for nonvascular and vascular species suggest the importance of considering multiple PFT when assessing species diversity and composition and their interaction with edaphic factors. Synthesis: Identifying vegetation responses to edaphic factors is a first step toward a better understanding of vegetation–soil feedbacks under climate change. Our results suggest that incorporating differential responses of PFT is important for predicting vegetation shifts, primary productivity, and in turn, ecosystem functioning in a changing climate.

Variation in plant community composition and vegetation carbon pools a decade following a severe fire season in interior Alaska

AbstractQuestionsHow does fire severity, measured as depth of burn of ground layer fuels, control the regeneration of understorey species across black spruce‐dominated stands varying in pre‐fire organic layer depths? Are successional shifts from evergreen to deciduous understorey vegetation more likely to occur with greater depth of burn? Does a shift in understorey vegetation community towards more deciduous species influence carbon accumulation in vegetation biomass?LocationNorthern boreal forest, interior Alaska.MethodsWe sampled 32 stands in interior Alaska that burned in 2003 and 2004 in which depth of burn had been recorded soon after fire. In 2014 we characterized tree density, understorey vegetation composition, above‐ and below‐ground vegetation carbon pools, and a suite of environmental variables. We used ANOVA and multivariate redundancy analysis models to analyse the dominant controls on vegetation composition and carbon pools.ResultsFire severity was a strong control on post‐fire tree and non‐vascular species composition. Ten years post‐fire, sites that experienced deeper burning of organic layers had a higher abundance of deciduous tree species, fire‐adapted mosses, forbs and graminoids, and lower abundances of evergreen shrubs and Sphagnum mosses. Environmental variables (elevation, soil bulk density and mineral soil pH, moisture and temperature) served as important controls on tree and vascular understorey species composition. We found no evidence that carbon pools associated with recovering vegetation biomass were influenced by landscape position, fire severity or environmental variables.ConclusionsBoth fire frequency and depth of burn are projected to increase with a warmer climate in interior Alaska. These shifts in fire regime are expected to favour the regeneration of deciduous species over conifers, which have the potential to regulate successional pathways and large‐scale trends in albedo, which both ultimately could influence ecosystem–climate feedbacks and dampen future fire cycles. Our results show that understorey species composition is controlled by fire severity, suggesting that more severe burning causes a decline in the self‐replacement of conifer communities across a range of hydrologic settings. Overall, our results suggest a loss of resilience in black spruce forests in the face of a changing fire regime. However, we found no evidence that fire severity influences vegetation carbon pools 10 yrs post‐fire, suggesting that there is less landscape variation in biomass carbon pools than in vegetation composition and succession during early post‐fire succession.

Understory species and functional diversity in a chronosequence of jack pine and red pine stands in the south-central boreal forest

Dominant tree species and anthropogenic disturbances influence understory taxonomic diversity (TD) and species traits (functional diversity, FD) in managed forests. We compared understory TD and FD in managed jack pine (Pinus banksiana Lamb.) stands and red pine (Pinus resinosa Ait.) plantations. Understory herbs, grasses, shrubs, and nonvascular species were assessed in 1 m2 quadrats on two perpendicular line transects. Data were analyzed using generalised least squares regression, and multivariate fourth corner and RLQ analyses. Although there were few differences in understory species communities, red pine plantations appeared to impose weak environmental filters on TD in ways that were absent from the jack pine stands. Taxonomic diversity declined with age in red pine but not in jack pine, and may have been affected by the accumulation of litter cover in red pine stands. Although vegetation cover was lower in red pine than in jack pine, species richness on a percent cover basis was greater, and saturated at high cover levels in jack pine. Functional richness and evenness were unaffected by overstory species, but high litter cover favoured higher values of functional divergence. These results imply that there was a high level of functional redundancy among species for the suite of traits that we analyzed.

Trends in NDVI and Tundra Community Composition in the Arctic of NE Alaska Between 1984 and 2009

As Arctic ecosystems experience increases in surface air temperatures, plot-level analyses of tundra vegetation composition suggest that there are important changes occurring in tundra communities that are typified by increases in shrubs and declines in non-vascular species. At the same time analyses of NDVI indicate that the Arctic tundra is greening. Few studies have combined plot-level trends in species composition and cover with remote sensing measurements to understand the linkages between tundra vegetation dynamics and NDVI over time. This study reports on trends in species composition for field plots in the Arctic National Wildlife Refuge in NE Alaska from 1984 to 2009 and links these trends to the trends in NDVI at fine and coarse scales. Over this time frame there were few changes in plant community composition. None of the five tundra types that were measured had increases in total vegetative cover, and deciduous shrub cover did not show the large increases reported elsewhere. Surface-(plot) measured NDVI was positively correlated to deciduous and evergreen shrub composition suggesting that these functional groups had a strong influence on NDVI values. Modeled values of NDVI, derived from measures of deciduous and evergreen shrub composition over time, decreased slightly for tussock tundra but did not change for other tundra types. This result suggests that surface NDVI did not change over time on these tundra types. Fine-scale (30-m pixels) Landsat NDVI also did not show any changes for the pixels located at the permanent plots (1992–2009). However, coarse-scale (8-km pixels) AVHRR NDVI across the study area did increase (1988–2007). Furthermore, aggregate values of Landsat pixels matching the same area as AVHRR pixels also did not show significant changes over time. Although Landsat NDVI was consistent with surface-measured NDVI, AVHRR NDVI was not. AVHRR NDVI values showed increases that were in neither the field nor Landsat data. This result suggests that AVHRR may be demonstrating increasing trends in NDVI that are not occurring on the ground in some Arctic tundra ecosystems. These results highlight the need to combine remote sensing with on-the-ground measurements of plant community composition and NDVI in the analysis of the responses of Arctic tundra ecosystems to climate change.

Algal Response to Removal of the Invasive CordgrassSpartina densiflorain a Salt Marsh at Humboldt Bay, California, USA

There are few published studies examining the effects of invasive vascular plants on cooccurring nonvascular species, despite the fact that photoautotrophic algae and cyanobacteria exist at the base of the marine food web. This study tested whether the removal of the invasive dense-flowered cordgrass (Spartina densiflora Brogn.) resulted in an increase in biomass of micro- and macroalgae in a salt marsh located in northern California. The site was sampled over a two-year time period, and percent cover of benthic algae was measured using a point-intercept technique in treated and control areas. Treatment consisted of selective mechanical removal of S. densiflora. The functional groups green filamentous and green sheet algae as well as diatoms and cyanobacteria were found. Growth peaks in algal biomass were significantly lower in the control compared to the treated areas. In addition, successional trends were observed in treated plots; green filamentous algae and diatoms were first to colonize, followed by cyanobacteria during the second year's growth. Our results suggest that the presence of S. densiflora lowers both algal biomass and functional group diversity in an invaded salt marsh, with implications for resulting trophic cascades.

Is rewetting enough to recover Sphagnum and associated peat-accumulating species in traditionally exploited bogs?

When restoring ecosystems, the simple removal of stresses causing degradation may seem preferable over other more costly and time consuming approaches. However, some restoration techniques can be implemented at reasonable cost and with increased efficiency in certain cases. We examined the successional trajectories of vegetation within abandoned block-cut peatlands in a major peat-producing region of Eastern Canada to evaluate whether the use of rewetting as a restoration technique can assist in the recovery of a typical bog plant community dominated by Sphagnum compared to spontaneous recolonization alone. We surveyed a total of 55 trenches in 6 peatlands twice, ~25 and ~35 years after the cessation of peat extraction. Canonical ordinations evidenced a generalized process of afforestation during the decade studied, partially driven by agricultural drainage in the surrounding landscape. Plant communities were dominated by ericaceous shrubs that hampered the spontaneous recovery of a Sphagnum-dominated system typical of bogs in the short and medium-term. Three of the six peatlands surveyed were partially restored by blocking drainage ditches. There, we surveyed plant composition in rewetted (28) and non-rewetted (26) trenches and observed that rewetting mitigated the increase in tree dominance, decreased the dominance by ericaceous shrubs, and favored the spread of non-vascular species with a wet habitat preference (notably Sphagnum species from the Cuspidata section). We conclude that the use of low intervention restoration techniques in block-cut bogs, such as the blockage of former drainage ditches, can re-orient undesired vegetation trajectories driven by spontaneous recolonization alone.

Are richness patterns of common and rare species equally well explained by environmental variables?

We investigated relationships between richness patterns of rare and common grassland species and environmental factors, focussing on comparing the degree to which the richness patterns of rare and common species are determined by simple environmental variables. Using data collected in the Machair grassland of the Outer Hebrides of Scotland, we fitted spatial regression models using a suite of grazing, soil physicochemical and microtopographic covariates, to nested sub-assemblages of vascular and non-vascular species ranked according to rarity. As expected, we found that common species drive richness patterns, but rare vascular species had significantly stronger affinity for high richness areas. After correcting for the prevalence of individual species distributions, we found differences between common and rare species in 1) the amount of variation explained: richness patterns of common species were better summarised by simple environmental variables, 2) the associations of environmental variables with richness showed systematic trends between common and rare species with coefficient sign reversal for several factors, and 3) richness associations with rare environments: richness patterns of rare vascular species significantly matched rare environments but those of non-vascular species did not. Richness patterns of rare species, at least in this system, may be intrinsically less predictable than those of common species.