Plant Species Cover Research Articles

Examination of the Effects of Domestic Water Buffalo (Bubalus bubalis) Grazing on Wetland and Dry Grassland Habitats.

In nature conservation today, there is a global problem with the aggressive expansion of invasive plant species and the conservation of valuable grassland vegetation. Based on this, the following question has been formed: Is the domestic water buffalo (Bubalus bubalis) appropriate for managing various habitat types? How does grazing by water buffalo (Bubalus bubalis) affect on grassland vegetation? This study was carried out in four areas of Hungary. One of the sample areas was in the Mátra Mountains, on dry grassland areas where grazing had been applied for two, four and six years. The other sample areas were in the Zámolyi Basin, where wet fens with a high risk of Solidago gigantea and in a typic Pannonian dry grassland were investigated. In all areas, grazing was carried out with domestic water buffalo (Bubalus bubalis). During the study, we carried out a coenological survey, examining the change of cover of plant species, their feed values and the biomass of the grassland. According to the results, both the number and cover of economically important grasses (from 28% to 34.6%) and legumes (from 3.4% to 25.4%) increased in Mátra as well as the high proportion of shrubs (from 41.8% to 4.4%) shifted toward grassland species. In the areas of the Zámolyi Basin, invasive Solidago has been suppressed completely, the pasture has been converted completely (from 16% to 1%) and the dominant species has become Sesleria uliginosa. Thus, we have found that grazing with buffalo is suitable as a habitat management method in both dry grasslands and wet grasslands. Therefore, in addition to its effectiveness in the control of Solidago gigantea, grazing with buffalo is successful in both nature conservation and economic aspects of grassland vegetation.

Factors influencing the establishment of vascular plants at Sphagnum cultivation sites

Sphagnum cultivation is a type of paludiculture and a way to use formerly drained peatlands productively but under wet and therefore climate-friendly conditions. Where Sphagnum mosses are cultivated other plant species will also establish and possibly compete with the Sphagnum. The aim of this study was to determine which factors influence vascular plant cover as well as plant species numbers at Sphagnum cultivation sites and to derive recommendations for their management. Two cultivation sites were studied in northwest Germany. One of these was established directly after peat extraction while the other was rewetted seven years prior to establishment. Irrigation ditches for water management were installed at both sites. The cover of vascular plants and the number of plant species present were determined in systematically positioned plots. Six variables were tested for their influence on the assessed data by applying boosted regression tree models. The main factors influencing vascular plant cover at the two Sphagnum cultivation sites were the distance to an irrigation ditch (m), the site (location) and Sphagnum cover (%). The number of species per plot was influenced mainly by Sphagnum cover (%), the distance to an irrigation ditch (m) and the donor species used for initiating the cultivation sites. A sufficient supply of nutrient-poor water and optimal Sphagnum growth can reduce vascular plant cover and the number of plant species potentially present at a site. Insufficient water distribution and uneven Sphagnum establishment lead to inhomogeneous site conditions and thus to a higher number of plant species. The number and cover of plant species at a cultivation site are influenced by the vegetation of the sites’ surroundings and the selection of the donor site.

Soil-applied nitrogen uptake by young olive cultivars intercropped or not with Paspalum notatum

Nitrogen (N) applications can be made in orchards to meet the N demand of the olive tree (Olea europaea L.), which may differ between cultivars. But part of the N in the fertilizer may be taken up by ground cover plant species, which can be native, such as Paspalum notatum (P. notatum), derived from the Pampa biome in South America and present in olive orchards. The study aimed to evaluate the recovery and distribution of N fertilizer by olive cultivars, grown alone and intercropped with P. notatum. Young plants of olive cultivars 'Arbosana', 'Coratina' and 'Picual', with and without intercropping with P. notatum, were grown in pots with sandy soil for 16 months. Urea enriched with 10% excess atoms of 15N (0.32 g N vase−1) was applied. Dry matter production and total N and 15N values in soil and plant organs were evaluated. Photosynthetic and chlorophyll a fluorescence parameters were determined. Fertilizer-derived N (Ndff), soil-derived N (Ndfs) and fertilizer-derived N recovery were calculated. The highest values of recovery of applied N were observed in the organs of olive trees grown without the presence of P. notatum. Ndff applied to the soil surface was accumulated mainly in the leaves and roots of olive trees. The recovery of applied N in cultivars 'Arbosana', 'Picual' and 'Coratina' were low, not exceeding 15% of the N supplied. P. notatum showed a great ability to compete with olive trees for mineral forms of N available in the soil. This is because it decreased growth and N in organs of the olive cultivars.

The Impact of Breeding Yellow-Legged Gulls on Vegetation Cover and Plant Composition of Grey Dune Habitats

The establishment of large populations of yellow-legged gull Larus michahellis in coastal and urban areas can lead to strong changes in vegetation cover and composition through creating physical disturbance in the vegetation and impacting the soil quality through defecation. In this study, we evaluated the effects of breeding yellow-legged gull populations on tall and short vegetation cover and plant species composition in old (occupied for 13 years) and new (occupied for 3 years) colony sites in grey dunes of the Algarve, southern Portugal. In each site, sampling plots were used to measure the percentage of vegetation cover in areas with and without breeding gulls. In the old colony site, the cover by tall vegetation was substantially reduced and the cover by short vegetation substantially increased in the areas where gulls are breeding in comparison with the adjacent areas. In the new colony sites, there were only minor differences. The increase in cover of short vegetation in the breeding area of the old colony site was mostly by nitrophilous species (Paronychia argentea and Malcolmia littorea) and should be explained by the decrease in vegetation cover of tall plant species and by feces deposition. Tall and slow-growing species Suaeda maritima and Helichrysum italicum covers were negatively affected. Our results showed that yellow-legged gulls affected vegetation cover and composition of grey dunes after 3 years of consecutive breeding, and this should be considered in the management of these habitats where breeding yellow-legged gulls are increasing.

Space resource utilization of dominant species integrates abundance‐ and functional‐based processes for better predictions of plant diversity dynamics

Sustainable ecosystem management relies on our ability to predict changes in plant diversity and to understand the underlying mechanisms. Empirical evidence demonstrates that abundance‐ and functional‐based processes simultaneously explain the loss of plant diversity in response to human activities. Recently, a novel indicator based on percent cover (CoverD) and maximum height (HeightD) of the dominant plant species – space resource utilization (SRUD) – has proven to give robust and better predictions of plant diversity dynamics than community biomass. Whether the superior predictive ability of SRUD is due to its capacity to simultaneously capture abundance‐ and functional‐based processes remains unknown. Here, we tested this hypothesis by quantifying mechanistic links between changes in SRUD and biodiversity in response to nutrients and herbivores. Furthermore, we assessed the relative contribution of dominant, intermediate and rare species to reduced density of individuals by combining null model analysis with field experiments. We found that SRUD successfully captured changes in ground‐level light availability and changes in the number of individuals to predict plant diversity dynamics, and each of CoverD and HeightD partly and independently contributed to both processes. Comparative results from null model analysis and field experiments confirmed that individual losses of dominant, intermediate and rare species followed non‐random processes. Specifically, compared with random loss process, rare species lost proportionally more individuals and thus disproportionately contributed to species loss, while dominant and intermediate species lost less. Our results demonstrate that SRUD captures both abundance‐ and functional‐based processes thus explaining why SRUD provides more accurate predictions of changes in species diversity. Given that rare species can play an important role in shaping community structure, resisting against invasion, impacting higher trophic levels and providing multiple ecosystem functions, reducing the SRU of dominant species could alleviate the risk of exclusion of rare species by mitigating abundance‐ and functional‐based competition processes.

Short‐term effects of the control of the invasive plant Asclepias syriaca: Secondary invasion of other neophytes instead of recovery of the native species

AbstractQuestionThis study aimed to assess the impact of the invasion of Asclepias syriaca, a perennial non‐native herbaceous species, on basic soil attributes and vegetation composition, and to study the effect of mechanical control, namely the cutting of Asclepias, on target and other plant species.LocationSandy region of Kiskunság National Park, Hungary, Central Europe.MethodsIn ten old‐fields, four 4 m × 4 m plots were established (n = 40), of which three were invaded by Asclepias, and one was uninvaded. The invaded plots were treated as: (1) all Asclepias shoots removed, (2) half of the Asclepias shoots removed, or (3) untreated. The treatment was conducted twice a year in summer during the period 2019–2021. Before the first treatment, soil and vegetation were sampled. Afterwards, vegetation monitoring was performed twice a year: the cover of each vascular plant species and the number of Asclepias shoots were recorded in each plot.ResultThere were no differences in the studied soil attributes between the uninvaded and invaded plots. However, there were differences in vegetation composition, namely, the cover of sand grassland specialists was higher in uninvaded plots. Short‐term cutting negatively affected Asclepias after two years. The cover of specialists did not change in response to treatments, but the cover of other neophyte plant species increased.ConclusionsBased on our results, the invasion of Asclepias changes the vegetation composition, but not the soil. Although short‐term mowing can reduce the cover of Asclepias, but the grassland specialist plants do not regenerate; instead, secondary invasion occurs. We conclude that more time or additional treatment is required for native plant recovery.

WATER USE EFFICIENCY AND YIELD OF BROCCOLI CULTIVATED UNDER NO-TILLAGE WITH DIFFERENT TYPES OF SOIL COVER STRAW AND IRRIGATION SYSTEMS

This study aimed to evaluate the water use efficiency and yield of broccoli, irrigated by surface and subsurface drip and cultivated with no-till vegetable system (NTVS), using different species of cover plants for straw formation. The experimental design was completely randomized, in a 4 x 2 factorial arrangement (4 soil covers and 2 types of drip irrigation: surface and subsurface). The treatments related to the cultivation system were: control treatment, cultivated under conventional tillage and uncovered soil (CT), and three treatments cultivated in NTVS varying the residual straw species used as soil cover, namely: straw from intercropping of Crotalaria ochroleuca and Brachiaria ruziziensis (NT1), straw from only C. ochroleuca (NT2) and straw from only B. ruziziensis (NT3). Treatments with NTVS obtained yield levels higher than or similar to that of the control treatment. NT1, with straw from the intercropping of C. ochroleuca and B. ruziziensis, stood out with a 27% increase in marketable yield of inflorescence (18.68 t ha-1) and higher water use efficiency (17.57 kg m-3), being 54% more efficient than the treatment with conventional tillage.

Patch and matrix characteristics determine the outcome of ecosystem engineering by mole rats in dry grasslands.

Burrowing mammals are important ecosystem engineers, especially in open ecosystems where they create patches that differ from the surrounding matrix in their structure or ecosystem functions. We evaluated the fine-scale effects of a subterranean ecosystem engineer, the Lesser blind mole rat on the vegetation composition of sandy dry grasslands in Hungary. In this model system we tested whether the characteristics of the patch (mound size) and the matrix (total vegetation cover in the undisturbed grassland) influence the structural and functional contrasts between the mounds and the undisturbed grasslands. We sampled the vegetation of 80 mounds and 80 undisturbed grassland plots in four sites, where we recorded the total vegetation cover, and the occurrence and cover of each vascular plant species. We used two proxies to characterise the patches (mounds) and the matrix (undisturbed grassland): we measured the perimeter of the mounds and estimated the total vegetation cover of the undisturbed grasslands. First, we compared the vegetation characteristics of the mounds and the surrounding grasslands with general linear models. Second, we characterised the contrasts between the mounds and the undisturbed grassland by relative response indices (RRIs) of the vegetation characteristics studied in the first step. Species composition of the vegetation of the mounds and undisturbed grasslands was well separated in three out of the four study sites. Mounds were characterised by lower vegetation cover, lower cover of perennial graminoids, and higher diversity, and evenness compared to undisturbed grasslands. The contrast in vegetation cover between mounds and undisturbed grasslands increased with decreasing patch size. Increasing vegetation cover in the matrix grasslands increased the contrasts between the mounds and undisturbed grasslands in terms of total cover, perennial graminoid cover, diversity, and evenness. Our results suggest that mole rat mounds provide improved establishment conditions for subordinate species, because they are larger than other types of natural gaps and are characterised by less intense belowground competition. The ecosystem engineering effect, i.e., the contrast between the patches and the matrix was the largest in the more closed grasslands.

DYNAMICS OF FOREST ECOSYSTEM COMPONENTS IN THE BLACK SEA COAST OF THE CAUCASUS AGAINST THE BACKGROUND OF BOXWOOD DESTRUCTION AS A RESULT OF <i>CYDALIMA PERSPECTALIS</i> WALKER (LEPIDOPTERA, CRAMBIDAE) INVASION

The situation when the invasion of one species indirectly leads to ecosystem consequences of a larger scale is considered. The work was carried out in the relict ecosystem of Colchis, the flora and fauna of which was formed more than 15 million years ago. Disappearance of boxwood, the edifier of Colchian ecosystems, in the short term has not led to a significant change in soil characteristics. The succession of plant communities was expressed by an increase in vegetation cover of native plant species under the active introduction of alien species. The rates of seed regeneration of boxwood decreased, especially in the areas with low density of tree canopy. The study of the distribution of earthworms showed the general topical preferences of boxwood and most species of large soil oligochaetes that prefer shaded stations and moistened habitats.

More losses than gainsduring one century of plant biodiversity change in Germany.

Long-term analyses of biodiversity data highlight a 'biodiversity conservation paradox': biological communities show substantial species turnover over the past century1,2, but changes in species richness are marginal1,3-5. Most studies, however, have focused only on the incidence of species, and have not considered changes in local abundance. Here we asked whether analysing changes in the cover of plant species could reveal previously unrecognized patterns of biodiversity change and provide insights into the underlying mechanisms. We compiled and analysed a dataset of 7,738 permanent and semi-permanent vegetation plots from Germany that were surveyed between 2 and 54 times from 1927 to 2020, in total comprising 1,794 species of vascular plants. We found that decrements in cover, averaged across all species and plots, occurred more often than increments; that the number of species that decreased in cover was higher than the number of species that increased; and that decrements were more equally distributed among losers than were gains among winners. Null model simulations confirmed that these trends do not emerge by chance, but are the consequence of species-specific negative effects of environmental changes. In the long run, these trends might result in substantial losses of species at both local and regional scales. Summarizing the changes by decade shows that the inequality in the mean change in species cover of losers and winners diverged as early as the 1960s. We conclude that changes in species cover in communities represent an important but understudied dimension of biodiversity change that should more routinely be considered in time-series analyses.

Using superpixel- or pixel-based segmentation for efficient green roof digital image classification and rapid estimation of plant species cover

Green roofs are “nature-based solutions” that provide numerous ecosystem services in the context of urban green infrastructures. Plant species diversity and the associated vegetation communities, in strong interactions with green roof substrate, play a central role in the green infrastructure functioning. In order to better understand the influence of vegetation in relation with the co-benefits provided by green roofs as well as to select suitable species for these usually harsh environments, it is essential to be able to achieve accurate and long-term monitoring of plant communities. In this short communication, two free plugins recently developed for the open-source image analysis software Fiji (a distribution of the freely available ImageJ platform, initially dedicated to biological image analysis) were investigated for their capacity to rapidly and efficiently perform supervised machine-learning for the classification of green roof vegetation photographs, with the aim of estimating individual plant species abundance. Two simple methods are thus described using the Trainable Weka Pixel Segmentation (Arganda-Carreras et al., 2017) or the Trainable Superpixel Segmentation (Salinas Colina et al., 2018), which allowed for rapid, efficient and reproducible classification and estimation of multispecies colonized green roof regardless the color or shape similarities among species or ground cover materials. Finally, recommendations are made for the use of the Trainable Superpixel Segmentation which is particularly convenient for quick and efficient green roof image analysis.

A survey of the floristic composition of the Kambat Valley, District Dir Lower, Northern Pakistan

The composition and structure of the vegetation not only reflect the nature of basic phytosociological associations but also form a habitat for numerous organisms. This work aimed to study floristic composition. Five sites each considered as a stand in the research area were selected to analyze the vegetation. The data was collected through the quadrates method. In each stand 10 quadrates (10*10 m) for tree and shrub and a sub quadrate (1*1 m) for herb were taken for determining the Frequency, Density, and Cover of plant species. A total of 93 plant species were collected. Leading families of the area were Asteraceae (12) and Poaceae (10). The leading life form was Therophytes with the highest number of plant species (28) while Megaphenerophytes with only one species. In terms of leaf size, the area was dominated by Nanophylls. Stand wise constant species were Ailanthus altissima, Ficus palmate, and Populus nigra while the rare species were represented by Cynoglosum officinale, Artemisia vulgarus and Bellis perensis. Communities in each stand were developed based on the importance value index. These communities were Oxalis-Zanthoxylum-Platanus Community, Oxalis-Populus-Rosa Community, Dodonaea-Ficus-Ailanthus Community, Oxalis-Ficus-Ziziphus Community, and Ficus-Olea-Dodonaea. Due to the increase in population the demand for timber, and wood (fuel) has significantly increased and the natural vegetation of the area is under threat. Proper management is required for the conservation of vegetation in the area.

Warmer and Poorer: The Fate of Alpine Calcareous Grasslands in Central Apennines (Italy)

Global change threatens alpine biodiversity and its effects vary across habitat types and biogeographic regions. We explored vegetation changes over the last 20 years on two Mediterranean alpine calcareous grasslands in central Apennines (Italy): stripped grasslands (EUNIS code E4.436) with Sesleria juncifolia growing on steep slopes, and wind edge swards (EUNIS code E4.42) with Carex myosuroides. Based on a re-visitation of 25 vegetation plots of 4 × 4 m, we assessed changes in overall and endemic plant species cover and richness by nonparametric Kruskal–Wallis test. We explored changes in structure and ecology using growth forms and Landolt indicators for temperatures. We identified species’ contribution to temporal changes using the similarity percentage procedure (SIMPER). The results evidenced a significant decline in all species cover and richness on both plant communities with a significant decline in alpine and endemic species and in hemicryptophytes with rosette and scapose ones on stripped grasslands, as well as a decline in subalpine and suffruticose chamaephytes species on wind edge swards. Such biodiversity loss, so far observed only in the warmest and Southern Mediterranean summits of Europe, is likely attributable to the combined effect of higher temperatures; the increase in the vegetative period; and the decrease in water availability, which is particularly severe in calcareous regions. Our study suggested the vulnerability of the analyzed alpine ecosystems to global change and the importance of monitoring activities to better understand vegetation trends and adaptation strategies in subalpine, alpine, and nival ecosystems.

Analysis of the Natural and Cultural Dendroflora of the North-Western Zone of the Greater Caucasus

The role of specially protected natural monuments in the conservation of biological diversity is irreplaceable. Many reserves have been established in order to expand the network of specially protected natural areas of the Republic of Azerbaijan, to preserve biodiversity, and to use natural resources efficiently. Along with the State Nature Reserves, new parks and gardens have recently been built, with Eldar pine, acacia, alder, beech, etc. in the natural flora. Along with plants, trees and shrubs of the world flora (new species of catalpa, juniper, pine, cypress, etc.) were widely used. The research revealed that 81 species of natural flora and 36 species of alien flora were used in landscaping. Among the plants belonging to the alien flora, lilac catalpa, Kokatan tecoma, Japanese daisy, evergreen cypress plays a dominant role in the cultural flora on landscaping. The most commonly used species of local flora are oak, juniper, white acacia, sycamore, maple, hornbeam, ash, linden. The cultural dendroflora of Zagatala-Balakan region is represented by 44 taxa and 117 species of trees and shrubs of 91 genera; including 4 families, 7 genera and 16 species of gymnosperms; according to their life-stages: 42 species of trees, 51 species of shrubs, 5 species of lianas, 13 species of ornamental flowers, 1 species of cover plants; There are 80 species of natural flora and 37 species of alien flora.

Soil VOC emissions of a Mediterranean woodland are sensitive to shrub invasion.

Many belowground processes, such as soil respiration and soil-atmosphere VOC (volatile organic compounds) exchange, are closely linked to soil microbiological processes. However, little is known about how changes in plant species cover, i.e. after plant invasion, alter these soil processes. In particular, the response of soil VOC emissions to plant invasion is not well understood. We analysed soil VOC emissions and soil respiration of a Mediterranean cork oak (Quercus suber) ecosystem, comparing soil VOC emissions from a non-invaded Q. suber woodland to one invaded by the shrub Cistus ladanifer. Soil VOC emissions were determined under controlled conditions using online proton-transfer time-of-flight mass spectrometry. Net soil VOC emissions were measured by exposing soils with or without litter to different temperature and soil moisture conditions. Soil VOC emissions were sensitive to C. ladanifer invasion. Highest net emission rates were determined for oxygenated VOC (acetaldehyde, acetone, methanol, acetic acid), and high temperatures enhanced total VOC emissions. Invasion affected the relative contribution of various VOC. Methanol and acetaldehyde were emitted exclusively from litter and were associated with the non-invaded sites. In contrast, acetone emissions increased in response to shrub presence. Interestingly, low soil moisture enhanced the effect of shrub invasion on VOC emissions. Our results indicate that shrub invasion substantially influences important belowground processes in cork oak ecosystems, in particular soil VOC emissions. High soil moisture is suggested to diminish the invasion effect through a moisture-induced increase in microbial decomposition rates of soil VOC.

Ten‐year ecological responses to fuel treatments within semiarid Wyoming big sagebrush ecosystems

AbstractSagebrush ecosystems of western North America are threatened by invasive annual grasses and wildfires that can remove fire‐intolerant shrubs for decades. Fuel reduction treatments are used ostensibly to aid in fire suppression, conserve wildlife habitat, and restore historical fire regimes, but long‐term ecological impacts of these treatments are not clear. In 2006, we initiated fuel reduction treatments (prescribed fire, mowing, and herbicide applications [tebuthiuron and imazapic]) in six Artemisia tridentata ssp. wyomingensis communities. We evaluated long‐term effects of these fuel treatments on: (1) magnitude and longevity of fuel reduction; (2) Greater Sage‐grouse habitat characteristics; and (3) ecological resilience and resistance to invasive annual grasses. Responses were analyzed using repeated‐measures linear mixed models. Response variables included plant biomass, cover, density and height, distances between perennial plants, and exposed soil cover. Prescribed fire produced the greatest reduction in woody fuel over time. Mowing initially reduced woody biomass, which recovered by year 10. Tebuthiuron did not significantly reduce woody biomass compared to controls. All woody fuel treatments reduced sagebrush cover to below 15% (recommended minimum for Greater Sage‐grouse habitat), but only prescribed fire reduced cover to below controls. Median mowed sagebrush height remained above the recommended 30 cm. Cheatgrass (Bromus tectorum) cover increased to above the recommended maximum of 10% across all treatments and controls. Ecological resilience to woody fuel treatments was lowest with fire and greatest with mowing. Low resilience over the 10 posttreatment years was identified by: (1) poor perennial plant recovery posttreatment with sustained reductions in cover and density of some perennial plant species; (2) sustained reductions in lichen and moss cover; and (3) increases in cheatgrass cover. Although 10 years is insufficient to conclusively describe final ecological responses to fuel treatments, mowing woody fuels has the greatest potential to reduce woody fuel, minimize shrub mortality and soil disturbance, maintain lichens and mosses, and minimize long‐term negative impacts on Greater Sage‐grouse habitat. However, maintaining ecological resilience and resistance to invasion may be threatened by increases in cheatgrass cover, which are occurring regionally.

Understanding Willow Transcriptional Response in the Context of Oil Sands Tailings Reclamation.

One of the reclamation objectives for treated oil sands tailings (OST) is to establish boreal forest communities that can integrate with the surrounding area. Hence, selection of appropriate soil reclamation cover designs and plant species for revegetation are important aspects of tailings landform reclamation and closure. Research and monitoring of the long term and immediate impacts of capped OST on the growth and survival of native boreal plant species are currently underway. However, plant responses to OST-associated toxicity are not well known at the molecular level. Using RNA sequencing, we examined the effects of three types of OST on the willow transcriptome under different capping strategies. The transcriptomic data showed that some genes respond universally and others in a specific manner to different types of OST. Among the dominant and shared upregulated genes, we found some encoding protein detoxification (PD), Cytochrome P450 (CYPs), glutathione S-transferase regulatory process (GST), UDP-glycosyltransferase (UGT), and ABC transporter and regulatory process associated proteins. Moreover, genes encoding several stress-responsive transcription factors (bZIP, BHLH, ERF, MYB, NAC, WRKY) were upregulated with OST-exposure, while high numbers of transcripts related to photosynthetic activity and chloroplast structure and function were downregulated. Overall, the expression of 40 genes was found consistent across all tailings types and capping strategies. The qPCR analysis of a subset of these shared genes suggested that they could reliably distinguish plants exposed to different OST associated stress. Our results indicated that it is possible to develop OST stress exposure biosensors merely based on changes in the level of expression of a relatively small set of genes. The outcomes of this study will further guide optimization of OST capping and revegetation technology by using knowledge based plant stress adaptation strategies.

Responses of a tidal freshwater marsh plant community to chronic and pulsed saline intrusion

Abstract Climate change causes both chronic and pulsed environmental changes to ecosystems. In estuaries, tidal freshwater marshes experience both extended and episodic periods of elevated salinities due to sea level rise, reduced river discharge during drought and storm surge, but most research has focused on extended (press) perturbations. Over a 4‐year period, we added diluted seawater to replicated plots in a tidal freshwater marsh in Georgia, USA to raise porewater salinities from freshwater to oligohaline. We assessed the ecosystem effects of press (continuous) and pulse (2 months per year) changes in salinity by measuring the responses of dominant angiosperms, benthic microalgae and dominant macro‐invertebrates (fiddler crabs). We transplanted angiosperms typical of oligohaline and mesohaline conditions into plots as bioindicators (phytometers) to assess potential for vegetation changes over longer time periods. In the press treatment, the cover of all common plant species decreased. Ludwigia repens almost disappeared within the first month; Polygonum hydropiperoides nearly disappeared within the first growing season; Pontederia cordata and Zizaniopsis miliacea declined over the 4 years but did not completely disappear. The decline in the four most dominant plant species decreased total above‐ground plant biomass, leading to an increase in light penetration and increased densities of benthic diatoms and cyanobacteria. The density of fiddler crab burrows was not significantly affected by the treatments, but was positively related to above‐ground plant biomass across all replicates. Transplant experiments indicated that plants typical of higher salinity conditions (e.g. Schoenoplectus sp.) performed well under conditions prevalent in the press plots. In the pulse treatment, only L. repens declined, and there was no effect on community‐level above‐ground biomass or other community variables. Synthesis. Our results indicate that tidal freshwater marsh plant and animal communities are vulnerable to extended periods of salinization but resilient to short saline pulses. Although saline pulses did not impair most ecosystem functions, the decline in a single species (L. repens) in the pulse treatment was associated with reduced marsh accretion and no elevation gain—factors which must be positive for wetland survival in an era of rising seas. Thus, periodic salinization may threaten the long‐term persistence of freshwater wetlands even before dramatic changes in community structure occurs.

Soil properties of North Iberian wet heathlands in relation to climate, management and plant community

Background and aimsHeathlands are a broad vegetation type characterized by the dominance of evergreen shrub species that thrive on nutrient-poor soils, thus sensitive to small changes in soil conditions. Here we aimed to identify soil gradients related to climate, management and main species in wet heathlands.MethodsSoil nutrient levels, organic matter and acidity were studied at two soil depths on ninety plots from 18 sites in Erica mackayana wet heaths of NW Iberian Peninsula, in relation to presence and cover of structural plant species (shrubs and graminoids) at two scales: plot and site (landscape) scale.ResultsWe identified one main soil gradient explained by soil organic matter (SOM), the effective cation exchange complex (eCEC), available phosphorus (P), and Aluminium-Calcium ratio (Al:Ca). Cattle density had a positive correlation with the main gradient in the surface layer, all other climate and management factors were unrelated to soil conditions. Molinia caerulea had a positive relation with SOM, eCEC, basic cations and low Al:Ca ratio. Erica cinerea showed the opposite reaction at both scales. Ulex gallii showed a negative correlation with C:N ratio at the plot scale and deeper layer.ConclusionSOM accumulation, low nutrient levels and Al toxicity explain the uniqueness of E. mackayana heathland vegetation and soils. Main indicator species react to soil conditions at plot and landscape scales. Cattle density correlated positively with soil nutrient levels, but density of wild ponies is unrelated to soil conditions. Large herbivores, especially ponies, are needed for conservation management of these heathlands.

Post-Fire Habitat Heterogeneity Leads to Black Spruce–Kalmia L. Shrub Savannah Alternate State

Many nutrient-poor coarse-textured Kalmia L.–black spruce forest sites in eastern Canada turn to ericaceous heath dominated by Kalmia angustifolia L. after clearcutting and fire. While the mechanisms of post-fire forest and heath formation have been well documented, the origin of shrub savanna vegetation has received limited attention. This study demonstrates the significance of post-fire island regeneration of black spruce in Kalmia heath to the origin of shrub savannah alternate state. The study was conducted in Three Brooks, 10 km west of Grand Falls-Windsor, Newfoundland (48°51′ N; 55°37′ E). Black spruce forest in the site was clearcut, then a wildfire burned the area, and the site was subsequently planted with black spruce. Plant species cover, black spruce growth (stem density, stem height, basal diameter, and yearly volume increment), and foliar nutrients of planted spruce and soil properties (pH, humus and Ae horizon depth, and nutrients) in tree islands were compared with adjacent Kalmia heath. Black spruce islands had significantly lower cover of Kalmia and higher stem density of black spruce compared to Kalmia heath (7100 stems/ha in islands vs. 1920 stems/ha in heath). Height, basal diameter, and yearly volume increment of black spruce were more than three times higher in spruce islands than in Kalmia heath. Foliar nutrients of black spruce growing in Kalmia heath had significantly lower N and Mg (33 and 38%, respectively) but had significantly higher Mn and Zn (46 and 33%, respectively) than in black spruce islands. Black spruce growth inhibition in Kalmia heath is attributed to soil nutrient imbalance due to Kalmia evidenced by reduced concentrations of N and Mg and increased concentrations of Al, Fe, and other inorganic ions in the foliage. These results suggest that post-fire black spruce islands in severely burned patches provide “safe sites” for spruce regeneration, whereas Kalmia heath developing in non-severe burn area inhibits spruce regeneration and creates shrub savannah community as an alternate vegetation state.