Disturbance In Plant Communities Research Articles

Volcanogenic mercury and plant mutagenesis during the end-Permian mass extinction: Palaeoecological perturbation in northern Pangaea

The end-Permian extinction (EPE) (∼251.9 Ma) is considered the most severe biotic crisis in Earth’s history. Rapid climatic change and oceanic acidification triggered by Siberian Traps volcanism culminated in a widely documented mass extinction in the marine realm, but the event’s impact on terrestrial ecosystems, particularly plant communities, is less well understood. While the existence of a floral mass extinction at the Permian-Triassic Boundary (PTB) is still debated, there is mounting evidence for pervasive mutagenesis among various plant lineages, as expressed by the high incidence of aberrant spores and pollen grains. Previous studies have proposed a causal relationship between increased UV-B flux and plant mutagenesis across the PTB, yet the role of volcanically derived heavy metals as a contributing factor has received considerably less attention. Here we present the results of a high-resolution palynological, sedimentological, and geochemical analysis of a continuous and previously unstudied PTB section from the Norwegian Arctic. The study reveals an abrupt increase in the levels of heavy metals across the EPE negative carbon isotope excursion (CIE). Palynological analysis indicates disruption, and a phased transition of plant communities at the PTB, without a significant turnover in species or decrease in diversity. However, the abrupt appearance and elevated abundance of aberrant palynomorphs coincides with increased concentrations of As, Co, Hg, and Ni, which is interpreted as compelling evidence for heavy metal-induced stress and genetic disturbance in plant communities during the EPE. We hypothesise that biomagnification of these elements may have been a significant driver for the end-Permian biotic crisis. Our findings are correlated via biostratigraphy and chemostratigraphy with other circum-Arctic PTB sections described in the literature, demonstrating the isochroneity and facies independence of these widespread palaeoecological changes.

Isotopic evidence for a diet shift in a Pleistocene sub-adult mastodon from the Brazilian Pampa

ABSTRACT Palaeoecological studies on South American mastodons using stable isotopes from isolated teeth indicate variable diets, but represent only a short portion of the total lifetime of the studied individuals. Here is presented an analysis of the carbon (δ13C) and oxygen (δ18O) isotope ratios on three molariforms (m1, m2 and m3) from the jaw of a sub-adult mastodon found in southern Brazil, aimed at understanding its long-term feeding habits. The individual died at about ~26-30 years of age, and the isotopic signal recorded in each tooth spans up to ~3-5 years based on estimates of tooth development from enamel thickness, but apparently there were significant temporal gaps (>5 years) between the mineralisation of each tooth. The δ18O did not vary significantly between the teeth, but the more positive δ13C in the m1 indicates a diet with higher proportion (>30%) of C4 plants, whereas the m2 and m3 indicate considerably less (<20%) C4 plants ingested. This diet shift could have been the result of ontogenetic development, migration, or some disturbance in plant communities driven by environmental stresses. The results indicate that mastodons were able to change their diets at shorter timescales than can be addressed from the analysis of isolated teeth.

Natural and anthropogenic extensive destruction of the spruce forest community of the European part of Russia: main trends of biodiversity dynamics

We analyzed the main trends of the change in the species richness of plant communities after catastrophic natural (beetle outbreaks, windfalls) and anthropogenic (clear cutting) disturbances. We examined the dynamics of the structural diversity of species richness of herb-dwarf scrubs layer with different reforestation technologies after the death of spruce stands. The study of similarity and ordination of vegetation showed the proximity of the undamaged forest to the unharvested stand, and the difference of these plant communities from clear-cut. The main determining factor of species richness was the intensity of plant community disturbance after catastrophes. We analyzed the reforestation dynamics of plant communities after catastrophic disturbances. Clear cutting led to the formation of grassy communities with a sharp increase in the species and structural diversity of plant community.

Опыт оценки динамического состояния растительности на основе крупномасштабной карты современного растительного покрова (на примере территории «Левашовский лес», Санкт-Петербург)

The article is devoted to the vegetation mapping of the “Levashovskiy les”— a large forest-mire massif located in the northern part of St. Petersburg (Fig. 1). It continues a series of articles on the vegetation of existing and proposed specially protected natural areas of St. Petersburg (Volkova, Khramtsov, 2018). Large-scale map of modern vegetation (Fig. 2) is presented; the map legend includes 67 main numbers, the signs and numeric indexes at the numbers made it possible to show 93 mapping units (associations and their variants). Brief description of the main types of plant communities (spruce, pine, birch, aspen, gray alder and black alder forests; raised bogs, transitional mires and fens, floodplain and upland meadows) reveals the content of the legend. Vegetation cover is characterized by the dominance of secondary communities. The main anthropogenic impacts on modern vegetation are following: drainage reclamation, deforestation and former agricultural use, forest fires, gas pipelines, highways. Most of the forest communities are secondary ones; they have grown under the pressure of various anthropogenic factors and at different time. Nowadays an active process of natural regeneration of conife­rous (mainly spruce) trees goes in the forests. Plant community structure and species composition were taken into account as well as their dynamic state. To assess the degree of disturbance of plant communities and the potential for their restoration, the analysis of all mapped vegetation categories with respect to their position in the ranks of restorative successions was made. Then an assessment map “Dynamic state of plant communities” (Fig. 3) was compiled. The map shows following categories of dynamic types of communities: conventionally primary; relatively long-term secondary and stable long-term secondary (Sukachev, 1938; Isachenko, 1964; Karpenko, 1965; Gribova, Isachenko, 1972); short-term secondary that were divided into 3 categories representing different stages of restorative series. Present state of the vegetation cover of the “Levashovskiy les” can be determined by the ratio of the areas of conventionally primary and secondary communities. Areal analysis of dynamic categories of plant communities showed that only a bit more than 20 % of the territory is occupied by conventionally primary communities and about 60 % – by short-term secondary ones with good restorative potential. Without strong anthropogenic and natural disturbances, a significant part of the disturbed plant communities will be able to self-restore to their natural state. The establishment of a specially protected natural area as well as the regulation of conservation regime will support restoration process of nature ecosystems.

Important issues facing insect conservation in Australia: now and into the future

AbstractStudies of insect biodiversity and conservation in Australia have been severely limited by the many undescribed species and paucity of taxonomists and insect ecologists. In this review, I discuss important issues facing insect conservation, namely, key threatening processes, threats to habitats and ecological communities, the importance of maintaining insect interactions, the value of vegetation remnants in agricultural ecosystems and the importance of community participation, and provide recommendations for the conservation management of invertebrates and their habitats. Major threats to insect biodiversity continue from habitat loss through broadscale clearing of native vegetation, invasion by weeds, habitat fragmentation, loss of natural corridors and inappropriate fire regimes. Other threats include disturbance of plant communities on hilltops, creek embankments and in water courses, pesticide regimes, trampling and grazing by stock and feral animals, and exotic predators. Climate change affects those insects constrained by their thermal and moisture tolerances (climate envelopes), potentially influencing their distribution, development and reproduction, by disrupting diapause and aestivation or inducing torpor. Protected areas under State jurisdiction are at risk without Commonwealth protection and increasingly threatening those insects occurring only in national parks and other conservation areas. For effective conservation of mainland national parks, overarching national EPBC Act legislation is needed to protect parks for conservation of animal and plant diversity and natural landscapes. Retention of native vegetation as refuges for beneficial insects near farmlands is known to contribute to environmentally clean pest control. Information on conservation of beneficial insects and their dependence on native plants as habitats is needed by farmers to promote identification and protection of natural refuges for pollinators, parasitoids and predators and to support the case against indiscriminate tree clearing. Important community conservation activities are underway in several States and Territories, but to be effective, increased support and funding from appropriate agencies is required.

Importance of soil and plant community disturbance for establishment of Bromus tectorum in the Intermountain West, USA

The annual grass Bromus tectorum has invaded millions of hectares in western North America and has transformed former perennial grass and shrub-dominated communities into annual grasslands. Fire plays a key role in the maintenance of B. tectorum on the landscape but the type of disturbance responsible for initial invasion is less well understood. We conducted an experiment in a perennial shrub/grass/forb community in eastern Idaho, USA to examine the roles of plant community and soil disturbance on B. tectorum emergence and establishment prior to state-changing fires. Our experiment consisted of a plant community disturbance treatment where we (1) removed the shrub component, (2) removed the grass/forb component, or (3) removed all shrubs, grasses, and forbs. We followed this treatment with seeding of B. tectorum onto the soil surface that was (1) intact, or (2) disturbed. Each experimental plot had an associated control with no plant community disturbance but was seeded in the same manner. The experiment was replicated 20 times in two sites (high and low aboveground biomass). We measured emergence by counting seedlings in late spring and establishment by counting, removing, and weighing B. tectorum individuals in mid-summer. We also examined the influence of plant community disturbance on the soil environment by measuring extractable NH4 + and NO3 – four times each summer. Soil disturbance greatly influenced the number of B. tectorum individuals that emerged each spring. Plant community disturbance, specifically disturbance of the grass/forb component, increased N availability in the late growing season and biomass of B. tectorum the following summer. We conclude that soil disturbance and plant community disturbance interact to promote the initial invasion of B. tectorum in Intermountain West valley ecosystems. Copyright A. Joshua Leffler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. NeoBiota 30: 111–125 (2016) doi: 10.3897/neobiota.30.7119 http://neobiota.pensoft.net RESEARCH ARTICLE Advancing research on alien species and biological invasions A peer-reviewed open-access journal

Determination of the Degree of Pasture Factor Digression in the Communities of Environment Contact Sites (Some Methodological Approaches)

This paper is concerning the problem of determining of the character of disturbance of plant communities under the influence of the pasture factors. There are methodological approaches for determining of the degrees of the digression of the plant communities based on qualitative and quantitative parameters of the structure of cenoses for different natural zones. However, there are no approaches and techniques for comprehensive (multifactor) assessment of the character of responses of vegetation to particular anthropogenic influences given the high contrast of the physico-geographical conditions of the territory. The paper discusses some results of preliminary comprehensive assessment of the disturbance of plant communities of the environment contact sites of the Baikal region as an example.

FORAGES AND PASTURES SYMPOSIUM: Improving soil health and productivity on grasslands using managed grazing of livestock.

Beyond grazing, managed grasslands provide ecological services that may offer economic incentives for multifunctional use. Increasing biodiversity of plant communities may maximize net primary production by optimizing utilization of available light, water, and nutrient resources; enhance production stability in response to climatic stress; reduce invasion of exotic species; increase soil OM; reduce nutrient leaching or loading in surface runoff; and provide wildlife habitat. Strategically managed grazing may increase biodiversity of cool-season pastures by creating disturbance in plant communities through herbivory, treading, nutrient cycling, and plant seed dispersal. Soil OM will increase carbon and nutrient sequestration and water-holding capacity of soils and is greater in grazed pastures than nongrazed grasslands or land used for row crop or hay production. However, results of studies evaluating the effects of different grazing management systems on soil OM are limited and inconsistent. Although roots and organic residues of pasture forages create soil macropores that reduce soil compaction, grazing has increased soil bulk density or penetration resistance regardless of stocking rates or systems. But the effects of the duration of grazing and rest periods on soil compaction need further evaluation. Because vegetative cover dissipates the energy of falling raindrops and plant stems and tillers reduce the rate of surface water flow, managing grazing to maintain adequate vegetative cover will minimize the effects of treading on water infiltration in both upland and riparian locations. Through increased diversity of the plant community with alterations of habitat structure, grazing systems can be developed that enhance habitat for wildlife and insect pollinators. Although grazing management may enhance the ecological services provided by grasslands, environmental responses are controlled by variations in climate, soil, landscape position, and plant community resulting in considerable spatial and temporal variation in the responses. Furthermore, a single grazing management system may not maximize livestock productivity and each of the potential ecological services provided by grasslands. Therefore, production and ecological goals must be integrated to identify the optimal grazing management system.

Coastline Dune Vegetation Dynamics: Evidence of No Stability

Coastal dune ecosystems are subjected to severe stress and disturbance factors that are particularly high in the beach-foredune environment and generally decrease with distance from the coast. The present study aimed to link plant species composition of coastal foredunes with the physical dynamical processes of the coastline in central Italy. A random hierarchical sampling design, based on two spatial scales (quadrant and parcel), was applied to estimate the variation in plant community composition. Permutational multivariate analysis of variance (PERMA- NOVA) revealed an approximately similar amount of variation with respect to both the coastal dynamic class and the parcel level. In addition, principal coordinate analyses showed that three taxa - Ammophila arenaria, Elymus farctus and Otanthus maritimus subsp. maritimus - were mainly linked to the coastal dynamics: A. arenaria increases its abundance where erosion of the shoreline is very high, while E. farctus and O. maritimus are more abundant in the prograding coast. Finally, similarity percentages analysis (SIMPER) highlighted that where the erosive process- es were strongest, the number of the species contributing to the total similarity was the highest. This is likely to indicate instability and a strong disturbance of plant communities that results in an unstable equilibrium. These findings have important implications for management and conservation actions.

Constant Final Yield

Constant final yield is an empirical generalization concerning the total biomass production of plant stands growing at different densities after a period of growth. Total standing biomass initially increases in proportion to density, levels off, and then remains constant as density increases further. We review the empirical basis for and mathematical formulations of this pattern, and we clarify the relationship of constant final yield to density-dependent mortality (self-thinning). There are several mechanisms that can explain the pattern, and it has a clear evolutionary basis. Constant final yield is a key to understanding population- and community-level phenomena. Establishing whether or not a plant community is at or close to constant final yield is important for understanding and predicting its behavior. It represents the maximum biomass for a genotype in an environment after a period of growth and, as such, can serve as a baseline for the measurement of disturbance in plant communities.

The definition of a new plant diversity index “H′dune” for assessing human damage on coastal dunes—Derived from the Shannon index of entropy H′

Abstract The presented paper shows that the common usage of H′ is not an appropriate index of plant diversity for studying disturbance in plant communities. H′ is strongly dependent on evenness, whereas species richness and species density are not adequately incorporated. Therefore, the common usage of H′ is only a measure for relative diversity in respect to the maximum possible diversity for each community. Furthermore, using the abundance of species relative to the total abundance of all species will result in the loss of information on species density (plant cover) when H′ is calculated and comparisons between disturbed and undisturbed communities become difficult. Instead it could be shown that the newly introduced index H ′ dune , which uses the species abundance (as coverage percentage) relative to the constant sampling area for calculation, will more clearly detect changes in species richness and composition. Sample size (plot size) is always constant and information on species density (coverage) is also incorporated in the index. H ′ dune is used to compare different coastal dunes along the southern Baltic Sea coast of Germany and Poland which differ in the degree of disturbance from recreational activities. The two main changes observed were damages because of trampling and a change in species composition, because of increasing nutrient levels. Two methods to detect different types and levels of anthropogenic disturbance and stress from recreational activities on coastal dunes are presented.

Influence of disturbance by mowing on the vegetation of old-fields in the Bohemian Karst

Successional stages of the xeric series of old-fields in the Bohemian Karst have been studied from the point of view of disturbance of plant communities by different intensities of mowing. Changes of biomass, diversity and population structure have been examined. The communities of younger successional stages are relatively more disturbed but they are able to reestablish themselves rather quickly. The communities of the older stages are characterized by a slower rate of recovery. The stability of younger stages may be understood as resilience and stability of older stages as resistance.

Risk analysis of hazardous materials in oil shale

A future oil shale industry will be a massive solids-handling industry generating large amounts of hazardous materials. A risk analysis was performed on a hypothetical oil shale industry to aid in the formulation and management of research. The analysis considered occupational, public, and ecosystem risks for a steady-state one million barrels per day (160 cubic dekameters per day) industry. The risks for designated groups of the occupational workforce were statistically described by accident and injury rates for fatalities, accidents with days lost from work, and accidents with no days lost from work. Workforce diseases analyzed were cancers, silicosis, pneumoconiosis, chronic bronchitis, chronic airway obstruction, and high-frequency hearing loss. The miners represented the group with the largest fatality and the most serious accident rate. Lung disease from inhalation exposure to dust about the nuisance dust threshold limit value presented the most significant risk for future concerns. Public health inhalation risks were estimated for life-time cancer risks from As, Cd, Cr, Ni, polycyclic aromatic hydrocarbons, and radiation to be less than 10 −7 occurrences per person per year. An air pollution surrogate, sulfate, as a measure of all air pollution exposure, yielded a result of 10 −5 deaths per person per year with large uncertainties. Public health risks associated with oil shale solid waste were considered for leachates. Ecosystem risks considered impact on designator species, plant damage from sulfates, and disturbance in plant communities. The simple analysis approach indicated that the potential impact on the semi-arid, high-altitude ecosystem was minimal from air pollutants and land disturbances, but of potential concern for aquatic systems under extreme conditions. The methodology and treatment of uncertainties are oriented towards establishing research implications.