Alteration of Species Composition and Population Trends of Freshwater Turtles Following Invasion of Competitive and Predatory Alien Animals in Southern Kyoto, Japan

We examined the changes in the spatial distribution and trophic guild structure of the Georges Bank fish community associated with intense exploitation over the last 30 years. As heavily exploited species declined in abundance, their spatial ranges and degree of overlap with other species declined. The converse was true for weakly exploited species whose populations have increased. Despite dramatic alterations in species composition, the trophic guild structure was consistent over time. There are five major trophic guilds on Georges Bank across gradients from benthic to pelagic feeders and fish to invertebrate prey. Exploitation has strongly impacted the piscivores in this system and has modified species interactions through alterations in species composition.

Amplified by warming temperatures and drought, recent outbreaks of native bark beetles (Curculionidae: Scolytinae) have caused extensive tree mortality throughout Europe and North America. Despite their ubiquitous nature and important effects on ecosystems, forest recovery following such disturbances is poorly understood, particularly across regions with varying abiotic conditions and outbreak effects. To better understand post‐outbreak recovery across a topographically complex region, we synthesized data from 16 field studies spanning subalpine forests in the Southern Rocky Mountains, USA. From 1997 to 2019, these forests were heavily affected by outbreaks of three native bark beetle species ( Dendroctonus ponderosae , Dendroctonus rufipennis and Dryocoetes confusus ). We compared pre‐ and post‐outbreak forest conditions and developed region‐wide predictive maps of post‐outbreak (1) live basal areas, (2) juvenile densities and (3) height growth rates for the most abundant tree species – aspen ( Populus tremuloides ), Engelmann spruce ( Picea engelmannii ), lodgepole pine ( Pinus contorta ) and subalpine fir ( Abies lasiocarpa ). Beetle‐caused tree mortality reduced the average diameter of live trees by 28.4% (5.6 cm), and species dominance was altered on 27.8% of field plots with shifts away from pine and spruce. However, most plots (82.1%) were likely to recover towards pre‐outbreak tree densities without additional regeneration. Region‐wide maps indicated that fir and aspen, non‐host species for bark beetle species with the most severe effects (i.e. Dendroctonus spp.), will benefit from outbreaks through increased compositional dominance. After accounting for individual size, height growth for all conifer species was more rapid in sites with low winter precipitation, high winter temperatures and severe outbreaks. Synthesis . In subalpine forests of the US Rocky Mountains, recent bark beetle outbreaks have reduced tree size and altered species composition. While eventual recovery of the pre‐outbreak forest structure is likely in most places, changes in species composition may persist for decades. Still, forest communities following bark beetle outbreaks are widely variable due to differences in pre‐outbreak conditions, outbreak severity and abiotic gradients. This regional variability has critical implications for ecosystem services and susceptibility to future disturbances.

Phytoplankton, the primary producers in an aquatic ecosystem, also act as indicators of pollution by alterations in species composition and population structure. Study on plankton dynamics in relation to environment forms the base of any aquatic ecosystem management. So, a study on the variations in the plankton population influenced by abiotic factors was conducted in the Paleru Reservoir, India. A total of 48 plankton genera belonging to 9 classes were recorded. The Shannon-Wiener diversity index ranged from 1.098 to 2.615 with temporal variations. Plankton density showed significant (p ≤ 0.05) spatial variations with the highest density at the cage site irrespective of the season (4.126 × 105 ± 199 cells/litre, 2.814 × 105 ± 72.5 cells/litre and 3.197 × 105 ± 52.5 cells/litre during pre-monsoon, monsoon and post-monsoon, respectively). Seasonal analysis revealed significantly (p ≤ 0.05) high plankton density during pre-monsoon, followed by post-monsoon and monsoon respectively. The reservoir is moderately polluted as established from the diversity index and the Algal Genus Pollution Index except at the cage site where it receives a polluted status. The relationship of plankton distribution with the environment was established employing canonical correspondence analysis and correlation coefficient. Phosphate-P, nitrate-N, transparency, hardness, pH and dissolved oxygen are the major abiotic factors influencing the plankton distribution in Paleru. Even though Cyanophyceae dominated the plankton population, there was no plankton bloom-associated toxicity, indicating the health and dynamic nature of the reservoir. However, significantly high plankton density indicating a polluted status at the cage site reveals the influence of cage culture.

The impacts caused on Chaco plant communities by the removal of woody species, together with the effects on the composition and functional structure of herbaceous plants, are still unknown. Therefore, this study aimed to assess the effects of anthropization on herb-subshrub communities in preserved and disturbed Chaco areas. Specifically, we examined differences and similarities in species diversity, composition and proportion of life forms in eight areas of Brazilian Chaco. Samples were taken from herb-subshrub communities using 800 1x1m² plots located in disturbed and preserved areas. Among 130 recorded species, 46 were exclusive to disturbed areas. The composition of species differed between preserved and disturbed areas (PERMANOVA; p = 0.001). PCoA ordination analysis showed greater aggregation of the plots in disturbed areas than in preserved areas. In preserved areas, an analysis of indicator species showed Hemicryptophytes species as the most representative life form. In disturbed areas, the proportion of life forms among indicator species was Hemicryptophytes, followed by Therophytes and Chamaephytes. Our study shows evidence that alterations in species composition, structure, and diversity, as well as sets of indicator species, occur in herb-subshrub communities. The removal of trees and bushes leads to a new configuration of this component in Chaco environments.

Logged forests are more prone to fire, shifts in species composition, and losses in biodiversity. In this work changes in the horizontal structure and species composition of a managed forest in the Tapajós National Forest, Eastern Amazon, Brazil, along 31 years (1981-2012) was evaluated. The disturbances included logging (1982), thinning of non-commercial species (1993/1994), and fire (1997). Data were obtained in 36 0.25-ha permanent plots split in 12 plots per each one of three harvesting treatments. In 1997, 16 plots were reached by an accidental superficial fire. The changes in species composition and diversity between the last measurement after logging and before fire (1995) and the last measurement (2012) were compared. PERMANOVA, considering the relationship between the NMDS axes and the treatment variable (logging / control + unburnt / burnt) differed in species composition, among treatments before fire (1995) and 15 years after fire (2012). The post-hoc test for PERMANOVA showed great similarity among logged forests before and after fire. The forest pre-disturbance conditions were important drivers in forest recovery, since logged forests under heavy thinning presented more losses in basal area and alterations in species composition. Therefore, stronger and more frequent disturbances can compromise the forest resilience.

Logged forests are more prone to fire, shifts in species composition, and losses in biodiversity. In this work changes in the horizontal structure and species composition of a managed forest in the Tapajós National Forest, Eastern Amazon, Brazil, along 31 years (1981-2012) was evaluated. The disturbances included logging (1982), thinning of non-commercial species (1993/1994), and fire (1997). Data were obtained in 36 0.25-ha permanent plots split in 12 plots per each one of three harvesting treatments. In 1997, 16 plots were reached by an accidental superficial fire. The changes in species composition and diversity between the last measurement after logging and before fire (1995) and the last measurement (2012) were compared. PERMANOVA, considering the relationship between the NMDS axes and the treatment variable (logging / control + unburnt / burnt) differed in species composition, among treatments before fire (1995) and 15 years after fire (2012). The post-hoc test for PERMANOVA showed great similarity among logged forests before and after fire. The forest pre-disturbance conditions were important drivers in forest recovery, since logged forests under heavy thinning presented more losses in basal area and alterations in species composition. Therefore, stronger and more frequent disturbances can compromise the forest resilience.

Precipitation change and biomass allocation in a temperate grassland: The role of intraspecific variation and species composition change

QuestionThe Cerrado is a global biodiversity hotspot, highly threatened by changes in land use. Alterations in species composition and the colonization of Cerrado grasslands by woody species can lead to long‐term changes in these communities. In this study, we investigated changes over 20 years in three grassland areas, in terms of species richness and diversity and growth‐form cover, as well as the effects of shrub and grass encroachment on species richness.LocationCerrado Brazilian savanna, moist grassland and dry shrub grassland. Areas under low and high anthropogenic pressure.MethodsPlant species composition and cover were sampled on seven occasions between the years 2000 and 2020, in permanent line‐transects. We compared plant cover, richness, diversity and growth‐form cover between the periods for each area. Next, we developed mixed‐effect linear models to test whether species richness in grasslands at the latest sampling event was altered by species representing 70% of the species cover at this time.ResultsGrasslands located in areas under higher anthropogenic pressure presented reduced richness and diversity, and cover concentrated on a few species of shrubs and large tussock grasses. Moist grassland undergoing encroachment by the native shrub Trembleya parviflora had lost over 50% of its diversity since encroachment. In the same area, a shrub grassland undergoing encroachment by native shrub Raulinoreitzia tremula, three native grass species and one exotic grass presented significantly reduced species richness. The moist grassland in an area under low anthropogenic pressure showed a reordering of the species cover over time, but a decrease in species richness.ConclusionWe observed changes in plant richness, diversity, cover, composition and growth‐form cover over a period of 20 years in grassland communities. We found, however, different trajectories in the three grassland areas sampled, mainly due to the encroachment of a few species, leading to floristic homogenization in grasslands located in areas under high anthropogenic pressure.

While some species rapidly decline, compromising vital ecosystem services, others are stable or even increasing in abundance. We studied shifts in species richness and abundance of moths over five decades in Central Sweden and examined whether and how changes were associated with phenotypic traits. We combined information from captures in a light trap in historical time (the 1970s) and contemporarily (2019) with provincial colonisation records. Both community species richness and the abundance of moths increased between the time periods. A large fraction (38%) of the 410 species were not present in both periods, 101 species had colonised the area (an estimated influx of about 2.5 new species per year), and 51 species had disappeared (an estimated local extinction rate of about 1.16 species per year). Abundance increased with an increasing number of host plants and with increasing colour pattern variation. The composition of the community shifted towards species characterised by smaller wingspan and larger ranges. The functional trait variability of the moth community was homogenised from the historical to the contemporary period, in line with reports from other species communities in modern landscapes. However, our finding of a concomitant increase in species richness and total abundance differs from the results of many recent studies of insect communities in other geographic regions.Implication for insect conservationWe conclude that the entire boreal moth fauna is undergoing a substantial biogeographical shift, changing to the moth species historically occurring at more southern latitudes. The alterations in species composition, overall abundance, and community-wide trait distribution described here may cascade up and down in the ecosystem because moths are important pollinators, herbivores, and prey.

Forests are dynamic in both structure and species composition, and these dynamics are strongly influenced by climate. However, the net effects of future tree species composition on net primary production (NPP) are not well understood. The objective of this work was to model the potential range shifts of tree species (DISTRIB Model) and predict their impacts on NPP (PnET-II Model) that will be associated with alterations in species composition. We selected four 200 x 200 km areas in Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-II model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m(2) per year. The effects of potential species redistributions on NPP were moderate (-12% to +8%) compared with the influence of future climatic changes (-60% to +25%). The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere.

Heavy infestations of a non-indigenous shrub, Amur honeysuckle (Lonicera maackii) are frequently linked to poor individual performance and reduced species diversity. We used chronosequence methods and analysis of forest strata to investigate potential impacts of L. maackii on 1) species richness, 2) density of sub-canopy recruitment layers, 3) indicator species affinity, and 4) within- and among-strata compositional similarities. We compared sites ranging from 12 to 26 years since initial invasion as well as non-invaded, control sites. When assessing non-invaded versus long-invaded sites, we found significantly (P ≤ 0.05) reduced densities in the herb (−57%), seedling (−58%), and sapling layers (−90%), and also reduced species richness in the seedling (−34%), and sapling (−58%), and herbaceous layers (−4%). Interestingly, the germinable seed bank density showed significant increases among non-invaded and long-invaded sites ( 78%), while the species richness of the seed bank demonstrated a marked decrease (−41%). Indicator species analysis found that most species had greater frequencies and abundances in non-invaded sites, and nearly all species had greater affinities for the non-invaded sites, especially in the seedling, sapling, and seed bank layers. Responses were species-specific in the herbaceous layer. Within-layer species similarity decreased with increased time of L. maackii occupancy in all sub-canopy strata. This pattern was also found with reductions in between-layer compositional similarity for the long-invaded (r = 0.16) versus the recently-invaded (r = 0.37) and non-invaded (r = 0.51) sites. Our data suggest that in many invaded sites, habitats are experiencing wholesale alterations in species composition, structure, and successional trajectory, and invasion may also change competitive interactions in forest understories as well as alter between-layer species linkages. These results validate the candidacy of L. maackii sites for increased removal and restoration efforts.

The tropical dry forests (TDFs) occur in regions which, historically, have had climatic and soil characteristics suitable for human occupancy and development of various kinds of infrastructure including agriculture. As a consequence, these forests have suffered from high level of biotic disturbance including gradual and abrupt land-use changes causing fragmentation and replacement of biotic communities. The forests have been converted to other ecosystem types, such as savanna, treeless grassland and cultivated land. These changes have resulted in marked alteration in species composition, diversity, soil characteristics and ecosystem functioning and also in the invasion by exotic species. In this chapter we describe the general effects of biotic disturbance, decrease in the forested area and susceptibility to climate change, changes in species composition and diversity, fragmentation and edge effect, recruitment pattern of saplings and juveniles, impact of village ecosystems, savannization and changes in soil properties with emphasis on soil microbial biomass and microbial processes.

The contribution of microarthropod activity to litter decomposition varies widely but can be substantial. Oribatid mites are the most diverse and abundant of the microarthropod groups in forest litter. This experiment was designed to examine the effect of litter type and complexity on the diversity and species composition of oribatid mites, and to test whether alterations in species composition due to litter type affected litter decomposition. In an array of plots on a mixed-hardwood site in the mountains of North Carolina, I exposed microarthropod assemblages to a range of litter types: yellow birch, sugar maple, red oak and two mixed litters. Over several years, the litter types selected oribatid mite assemblages of different species composition. By comparing the decomposition of consecutive cohorts of litter, it was possible to detect differences in decomposition accompanying the shifts in the assemblage. A comparison of the mass loss rates between the two litter cohorts over eighteen months reveals similar trajectories for four litter types. In the oak litter, however, the second cohort disappeared significantly faster than the first. In both years, the litters came from the same trees and were nearly identical in initial carbon and nitrogen contents. Since the response was specific to oak litter, it is unlikely that differences in environmental factors are responsible for the faster mass loss of oak. A significant increase of endophagous oribatid mites, those that burrow into plant material, in the second cohort of oak may account for its accelerated decomposition. The woody petioles and thick leaf-planes of oak leaves provide microhabitats for burrowing mites. Endophage activity can accelerate the litter decomposition both through direct comminution of leaf material and by facilitating microbial growth. Because of their low population growth rates, oribatid populations that are reduced by disturbance are slow to recover and by disrupting these non-resilient populations, disturbance may have long-term repercussions for decomposition.

River regulation intensity matters: Riverbank vegetation is characterized by more typical riverbank plant species with increasing distance from weirs

The native vegetation conversion into exotic pastures has been some of the most common land changes in the Brazilian Cerrado, causing biodiversity declines. However, our understanding of how biodiversity communities are responding to this activity is still limited for many biological groups. In this study, we evaluated the effects of Cerrado vegetation conversion into exotic pastures on flower chafer beetle assemblages. We sampled flower chafer beetles using aerial fruit baited-traps, every two weeks from October to December 2013, in five sites of Brazilian Cerrado (sensu stricto) and in five sites of exotic pastures (Urochloa spp.) in Aquidauana, Mato Grosso do Sul, Brazil. A total 311 individuals from three genera and seven species were sampled. The species richness and abundance of flower chafer beetles were higher in Cerrado remnants. Species composition was similar between Cerrado remnants and exotic pastures in position, but was different in dispersion. Our results demonstrate that Cerrado conversion into exotic pastures reduces the abundance and species richness of flower chafer beetles, causing the alteration in species composition in terms of dispersion. Although these beetles can be ‘guests’ in exotic pasture sites, using them as ecological corridors, exotic pastures establishment negatively impacts flower chafer beetle assemblages in the Brazilian Cerrado.