The δ13C changes in four plant species of the Loess Plateau over the last 70 years

The relative abundance of carbon isotope (δ¹³C) was measured in four C₃ species (Sophora viccifolia, Quercus liaotungensis, Ostryopsis davidiana and Zizyphus jujuba var. spinosa) of the Loess Plateau in China from the 1930’s to 2002. The results showed that the δ¹³C values in the four species varied from −25.05‰ to −29.75‰ with their a average at −27.04‰. A decrease in the δ¹³C value with time was found in all the four species, which indicating that the water use efficiencies (WUEs) of all the measured species declined during 70 years. However, the decrease in δ¹³C value differed among the four species with its significant decreases measured in two of the species, Sophora viciifolia and Quercus liaotungensis, its relatively significant decrease found in Ostryopsis davidiana, and its slight decrease appearing in Zizyphus jujuba var. spinosa. in the δ¹³C values in the four species decreased by 14.65 ‰, 14.46‰, 11.99‰ and 2.44‰, respectively. The different species were shown to have different sensitivities to climatic change, and Zizyphus jujuba var. spinosa was found to be the most drought-tolerant species of the four, which had a high WUE.     

Disturbance and the (surprising?) role of ecosystem engineering in explaining spatial patterns of non‐native plant establishment

Different conceptions of disturbance differ in the degree to which they appeal to mechanisms that are general and equivalent, or species‐, functional group‐, or interaction‐specific. Some concepts of disturbance, for example, predict that soil disturbances and herbivory have identical impacts on species richness via identical mechanisms (reduction in biomass and in competition). An alternative hypothesis is that the specific traits of disturbance agents (small mammals) and plants differentially affect the richness or abundance of different plant groups. We tested these hypotheses on a degu (Octodon degus) colony in central Chile. We ask whether native and non‐native forbs respond differently to degu bioturbation on runways versus herbivory on grazing lawns. We ask whether this can explain the increase in non‐native plants on degu colonies. We found that biopedturbation did not explain the locations of non‐native plants. We did not find direct evidence of grazing increasing non‐native herbs either, but a grazing effect appears to be mediated by grass, which is the dominant cover. Further, we provide supplementary evidence to support our interpretation that a key mechanism of non‐native spread is the formation of dry soil conditions on grazing lawns. Thus, ecosystem engineering (alteration of soil qualities) may be an outcome of disturbances, in which each interacts with specific plant traits, to create the observed pattern of non‐native spread in the colony. Based on these results, we propose to extend Jentsch and White (Ecology, 100, 2019, e02734) concept of combined pulse/ disturbance events to the long‐term process duality of ecosystem engineering/ disturbance.     

Fifty years of plant invasion dynamics in Slovakia along a 2,500 m altitudinal gradient

Knowledge on the main spatiotemporal trends in plant invasions of habitats is essential for a better understanding of the process of these invasions. The aim of this study was to determine the level of plant invasion, represented by relative richness and total cover of archaeophytes and neophytes, in 45 EUNIS habitat types along with spatiotemporal changes in invasion level with increasing altitude and time in Slovakia. In general, the most invaded habitats are those which are highly influenced by human activities. Generalized linear models and generalized linear mixed models were used to assess the associations between habitat-specific invasion level, altitude and time, respectively. There is a general decrease in the relative richness and total cover of archaeophytes and neophytes with increasing altitude in the invaded habitats. There is also an observable temporal trend in archaeophytes shifting from anthropogenic towards more natural habitats. Importantly, the relative neophyte richness has recently been increasing, predominantly in semi-natural and natural habitats, which brings about major concerns for nature conservation. This may be the manifestation of a lag phase in the dispersal of neophytes. However, accompanied with a significant increase in the relative richness of archaeophytes in some natural habitats, it may indicate more complex changes in the invaded habitats and be an early warning sign for ecological degradation of these habitats.     

Nine years of climber community dynamics in a Nigerian lowland rain forest 31 years after a ground fire

Successional studies in tropical forests have generally emphasized the tree component, ignoring the community dynamics of non-tree life-forms, and so there is a limited understanding of how the plant community as a whole is changing during succession within forests. Thus, this study examined the changes in climber community composition and structure in a regenerating secondary lowland rain forest at Ile-Ife that was ravaged by a ground fire 31 years ago using six sample plots. All individual climbers in each sample plot were identified, enumerated and their girths at breast height were measured. The girths were measured at 1.3 m height or just before the point of branching. Our data were compared with those of previous studies in the forest to determine the changes in floristics and structure of climber community over the years using Sorenson’s similarity index. The mortality and recruitment rates in the forest during the course of succession were determined. Climber species increased from 49 (2005) to 61 (2014). Climber density increased astronomically from 448–1152 ha^?1 (2005) to 1712–4492 ha^?1 but basal area only increased slightly from 0.37–1.10 m² ha^?1 (2005) to 0.40–1.14 m² ha^?1. The recruitment rate (8%) was higher than the mortality rate (5.8%). The similarity of the climber species composition calculated using the Sorenson similarity index showed that the similarity between the two periods of study was 0.53 (53%). This study concluded that during the study period, the climber community changed, and climber species abundance and structure increased.     

Responses of riparian plant communities and water quality after 8 years of passive ecological restoration using a BACI design

This study investigated the consequences of passive ecological restoration on a riparian habitat and on water quality. The restoration plan consists of excluding livestock by constructing fences along an entire stream 1 m from the stream bed, with the assumption that recovering riparian habitat will restore their ecological processes (e.g., filtration, soil stabilization). We measured responses of riparian plant communities and physico-chemical water quality. We presented data from an 8-year before-after control-impact design across a reference stream and a restored stream in a rural landscape in Normandy, France. Restoration appeared to modify plant communities. After 8 years of restoration, the restored stream had a complex riparian bank, similar to that of the reference stream, with an increase in the number of trees, a decrease in bare soil, and an increase in habitat heterogeneity. Despite this modification, water quality did not improve. The same low water quality in the reference stream demonstrated the need for a watershed-scale approach and for actions to improve agricultural practices before implementing restoration practices at a smaller scale. Nonetheless, the lack of improved water quality does not necessarily mean that the restoration failed. Other functions and services can be provided by excluding livestock.     

Erosion of insect diversity in response to 7000 years of relative sea-level rise on a small Mediterranean island

We have investigated the potential effects of global sea-level rise on Mediterranean coastal wetlands by studying the Coleoptera and pollen fossil remains in a 7000-year sedimentary record, which we obtained from a coastal marshy area on a small Mediterranean island (Cavallo, southern Corsica). Using beetle structural diversity and plant composition as recorded prior to marine and human influences as a ‘past analogue’, we reconstructed the impact of the Holocene relative sea-level rise on the coastal ecosystem. Our results show that beetle species richness and diversity were highest when freshwater was predominant, which was the case until about 6200 years ago. We also found that a major increase in salinity had occurred over the last 5300 years, experiencing a peak rate of increase at about 3700 years ago. These changes are clearly reflected in the fossil records of the following key taxa: halophilous beetles (Ochthebius sp., Pterostichus cursor), halophilous plants (Chenopodiaceae, Tamarix) and non-pollen palynomorphs (microforaminiferal linings). In particular, we note that the majority (60%) of wetland beetle fauna became locally extinct in response to the salinity changes, and these changes were exacerbated by the recent aggravation of human pressures on the island. The major part of this diversity loss occurred 3700 years ago, when the relative Mediterranean sea-level rose above ?1.5 ± 0.3 meters. These findings demonstrate the value of fossil beetle assemblage analysis as a diagnostic for the response of coastal wetland biodiversity to past salinity increases, and serve as a means of forecasting the effects of sea-level rise in the future. The conservation of inland freshwater bodies could ultimately prove essential to preserving freshwater insect diversity in threatened coastal environments.     

Inoculation of <Emphasis Type="Italic">Pinus halepensis</Emphasis> Mill. with selected ectomycorrhizal fungi improves seedling establishment 2 years after planting in a degraded gypsum soil

Vegetative inoculum of Amanita ovoidea (Bull.) Link and three isolates of Suillus collinitus (Fr.) Kuntze, as well as spore inoculum of Rhizopogon roseolus (Corda) Th. M. Fr. and S. collinitus, were evaluated for the production of Pinus halepensis Mill. in nursery and for the establishment of seedlings in a degraded gypsum soil. In nursery, most of the fungi significantly improved the height of seedlings and modified the accumulation of nutrients in needles. The percentage of ectomycorrhizas (ESR) per seedling ranged from 25 to 78%, depending on the fungi. One and 2 years after planting in the field, the survival of seedlings was significantly improved by inoculation with two isolates of S. collinitus and with spores of the same fungus. Inoculation with A. ovoidea had no significant effect on seedling survival, whilst R. roseolus caused a significant mortality of seedlings. Seedling height was significantly improved by inoculation with all fungi except R. roseolus and isolate CCMA-1 of S. collinitus. One year after planting, mycorrhization of control seedlings was negligible, and percentages of ESR were under 38% for the rest of treatments. In spring of the second year, seedlings in all treatments, including the control, became highly mycorrhizal (60–77% of ESR). Low ectomycorrhizal diversity (five morphotypes described) and seasonal variation on morphotype composition were detected 2 years after plantation. From a perspective of soil restoration management under limiting environmental conditions, nursery inoculation with selected fungi can be a key advantage for tree seedlings to surmount the initial transplant stress, assuring their establishment in the field. Our results emphasise the importance of selecting compatible fungal–host species combinations for nursery inoculation and sources of inoculum adapted to the environmental conditions of the transplantation site.     

Population genetic structure after 125 years of stocking in sea trout (<Emphasis Type="Italic">Salmo trutta</Emphasis> L.)

Stocking can be an effective management and conservation tool, but it also carries the danger of eroding natural population structure, introducing non-native strains and reducing genetic diversity. Sea trout, the anadromous form of the brown trout (Salmo trutta), is a highly targeted species that is often managed by stocking. Here, we assess the present-day population genetic structure of sea trout in a backdrop of 125 years of stocking in Northern Germany. The study area is characterized by short distances between the Baltic and North Sea river watersheds, historic use of fish from both watersheds for stocking, and the creation of a potential migration corridor between the Baltic and North Sea with the opening of the Kiel Canal 120 years ago. A survey of 24 river systems with 180 SNPs indicates that moderate but highly significant population genetic structure has persisted both within and between the Baltic and North Sea. This genetic structure is characterized by (i) heterogeneous patterns of admixture between the Baltic and North Sea that do not correlate with distance from the Kiel Canal and are therefore likely due to historic stocking practises, (ii) genetic isolation by distance in the Baltic Sea at a spatial scale of <?200 km that is consistent with the homing behaviour of sea trout, and (iii) at least one genetically distinct Baltic Sea river system. In light of these results, we recommend keeping fish of North Sea and Baltic Sea origin separate for stocking, and restricting Baltic Sea translocations to neighbouring river systems.     

Initial pedogenesis in a topsoil crust 3 years after construction of an artificial catchment in Brandenburg, NE Germany

Cyanobacteria and green algae present in biological soil crusts are able to colonize mineral substrates even under extreme environmental conditions. As pioneer organisms, they play a key role during the first phases of habitat colonization. A characteristic crust was sampled 3 years after installation of the artificial water catchment “Chicken creek”, thus representing an early successional stage of ecosystem development. Mean annual rainfall and temperature were 559 mm and 9.3°C, respectively. We combined scanning electron microscopy (SEM/EDX) and infrared (FTIR) microscopy to study the contact zone of algal and cyanobacterial mucilage with soil minerals in an undisturbed biological soil crust and in the subjacent sandy substrate. The crust was characterized by an approximately 50 μm thick surface layer, where microorganisms resided and where mineral deposition was trapped, and by an approximately 2.5 mm thick lower crust where mineral particles were stabilized by organo-mineral structures. SEM/EDX microscopy was used to determine the spatial distribution of elements, organic compounds and minerals were identified using FTIR microscopy and X-ray diffraction (XRD). The concentration of organic carbon in the crust was about twice as much as in the parent material. Depletion of Fe, Al and Mn in the lower crust and in the subjacent 5 mm compared to the geological substrate was observed. This could be interpreted as the initial phase of podzolization. Existence of bridging structures between mineral particles of the lower crust, containing phyllosilicates, Fe compounds and organic matter (OM), may indicate the formation of organo-mineral associations. pH decreased from 8.1 in the original substrate to 5.1 on the crust surface 3 years after construction, pointing to rapid weathering of carbonates. Weathering of silicates could not be detected.     

Dynamics of a small re-introduced population of wild dogs over 25 years: Allee effects and the implications of sociality for endangered species’ recovery

We analysed 25 years (1980–2004) of demographic data on a small re-introduced population of endangered African wild dogs (Lycaon pictus) in Hluhluwe-iMfolozi Park (HiP), South Africa, to describe population and pack dynamics. As small populations of cooperative breeders may be particularly prone to Allee effects, this extensive data set was used to test the prediction that, if Allee effects occur, aspects of reproductive success, individual survival and population growth should increase with pack and population size. The results suggest that behavioural aspects of wild dogs rather than ecological factors (i.e. competitors, prey and rainfall) primarily have been limiting the HiP wild dog population, particularly a low probability of finding suitable mates upon dispersal at low pack number (i.e. a mate-finding Allee effect). Wild dogs in HiP were not subject to component Allee effects at the pack level, most likely due to low interspecific competition and high prey availability. This suggests that aspects of the environment can mediate the strength of Allee effects. There was also no demographic Allee effect in the HiP wild dog population, as the population growth rate was significantly negatively related to population size, despite no apparent ecological resource limitation. Such negative density dependence at low numbers indicates that behavioural studies of the causal mechanisms potentially generating Allee effects in small populations can provide a key to understanding their dynamics. This study demonstrates how aspects of a species’ social behaviour can influence the vulnerability of small populations to extinction and illustrates the profound implications of sociality for endangered species’ recovery. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Lack of genetic differentiation among four sympatric southeast African intertidal limpets (Siphonariidae): phenotypic plasticity in a single species?

Specimens of four sympatric intertidal limpet species (Siphonariadayi, S. tenuicostulata, S. anneae and S. nigerrima) were collectedfrom four localities on the east coast of South Africa and southernMozambique. Their phylogenetic relationships were investigatedusing sequences of the mitochondrial COI gene and the intron-containingnuclear ATPSß gene. Two closely related lineages wererecovered, which grouped specimens on the basis of geographyrather than morphology. One lineage was associated with thesubtropical coastline of South Africa's east coast and the otherwith the tropical coastline of northeastern South Africa andsouthern Mozambique. This genetic discontinuity coincides witha biogeographic boundary located in the vicinity of Cape StLucia. Combined genetic diversity of the four species was lowerthan that of three other southern African congeners, and fellwithin the range determined for single southern African marinemollusc species. We suggest that the four limpet species arein fact different morphotypes of a single species. (Received 6 October 2006; accepted 29 March 2007)     

Biodiversity and ecosystem services−A case study for the assessment of multiple species and functional diversity levels in a cultural landscape

The expansion of large-scale plantations has a major impact on landscapes in the Tropics and Subtropics. Crops like soy bean, oil palm and rubber have led to drastic changes in land cover over the past decades, thereby altering ecosystem functions and services (ESS). Associated shifts in ESS such as climate regulation, erosion and water cycles, biodiversity as well as soil fertility or the provisioning of raw materials have been assessed through several models and software solutions (InVEST, ARIES, MIMES). However, suitable methods for the integration of a range of biodiversity assessments in agricultural landscapes are scarce.With this study, we introduce a methodology for incorporating multiple levels of species diversity into models to allow an integrated evaluation of ESS. We collected data sets from both published and unpublished sources on the distribution of vascular plants, selected pollinator groups, ground beetles, ungulates as well as amphibians, mammals, reptiles and birds in rubber-dominated landscapes, with a focus on our study sites in Southwest China and Thailand. Based on this information, we developed a common classification scheme that enables the integration of different facets of biodiversity (species diversity and functional diversity) to complement an interdisciplinary ESS assessment.Species diversity data were normalized against the most divers habitats reported (using habitat scores) to assess the impact of rubber cultivation on multiple levels of biodiversity. This resulted in a comparable matrix of different land use types and their suitability as habitat for the respective species groups allowing the aggregation of very diverse indicators. The findings were applied to two alternative land use scenarios in southern China to highlight the potential effects of land use and management decisions on species and functional diversity. Our results highlighted that the conservation oriented scenario did score higher for habitat suitability in both total species (+5%) as well as IUCN Red List species (+6%) assessments compared to the current state or business as usual scenarios (-2% and −3% compared to current state).The process presented here allows for an application within established ESS software programs, in our case InVEST, using aggregated indices while additionally providing enhanced opportunities for comparable, spatially explicit assessments of the expected impact of the analyzed scenarios on specific species groups.     

Estimation of soil-to-plant transfer factors of radiocesium in 99 wild plant species grown in arable lands 1 year after the Fukushima 1 Nuclear Power Plant accident

One year after the deposition of radionuclides from the Fukushima 1 Nuclear Power Plant (A formal name is Fukushima Daiichi Nuclear Power Station) in March 2011, radiocesium (¹³⁴Cs, ¹³⁷Cs) concentrations ([Cs]) were comprehensively investigated in the wild plants of 99 species most of which were annual or summer green perennial herbs and started to grow from April 2012 at the heavily contaminated fields of paddy (three study sites) and upland (one study site) in Fukushima Prefecture. The survey was conducted three times (April, July and October) in the year. In each site, soils (soil cores of 5-cm depth) and plants (aerial shoots) were collected for determination of [Cs] on a dry weight basis, and then the transfer factor (TF) of radiocesium from soil to plant ([Cs]_plant/[Cs]_soil) was estimated in each species. The [Cs] values of both soils and plants largely varied. However, some species exhibited relatively high TF values (more than 0.4) (e.g., Athyrium yokoscense, Dryopteris tokyoensis, and Cyperus brevifolius), while others exhibited almost negligible values (less than 0.01) (e.g., Salix miyabeana, Humulus scandens, and Elymus tsukushiensis). In addition, judging from the 11 species grown in both paddy and upland fields, TF values were generally higher in the paddy fields. The estimation of phytoextraction efficiency of soil radiocesium by weed communities in the paddy fields suggests that the weed community is not a practical candidate for phytoremediation technique.     

An assessment of plant growth and N<Subscript>2</Subscript> fixation in soybean genotypes grown in uninoculated soils collected from different locations in Ethiopia

Pinus heldreichii H. Christ. is a tertiary relict and endemic to the western Balkans and southern part of Apennine peninsula. It is an Oro-Mediterranean species occurring at altitudes between 1200 and 2000 m and primarily on calcareous soils. P. heldreichii forests are of key importance for nature conservation, protection against gravitational natural hazards, landscape conservation and recreation. However, these forests are currently highly fragmented and require the elaboration of guidelines for sustainable management and conservation that should be based on scientific knowledge. Ectomycorrhizal (ECM) fungi are important for successful regeneration, establishment and growth of P. heldreichii. The aim of this study was to investigate ECM and other fungal communities associated with fine roots of P. heldreichii at two different sites in Ku?i Mountains, south-eastern Montenegro. Roots and soil were sampled from 70 trees. Soil was subjected to chemical analyses, fine roots were morphotyped and selected root morphotypes were Sanger sequenced using ITS rDNA as a marker. Sequencing resulted in 431 high-quality sequences representing 147 different fungal species including a large number of ECM species. The most common species were ECM fungi Lactarius sanguifluus (5.1%), Wilcoxina rehmii (4.2%) and Amphinema sp. KK28 (3.2%). Climatic factors were similar between the sites, but site size, inclination, elevation, tree age (old growth versus young trees), and some soil characteristics differed. The results demonstrate relatively high fungal diversity and site-specific effects on abundance and composition of fungal communities in fine roots of P. heldreichii growing in high-altitude marginal habitats.     

Photosynthetic characteristics and biomass distribution of the dominant vascular plant species in a high Arctic tundra ecosystem,Ny-Ålesund,Svalbard: implications for their role in ecosystem carbon gain

Studies on terrestrial ecosystems in the high Arctic region have focused on the response of these ecosystems to global environmental change and their carbon sequestration capacity in relation to ecosystem function. We report here our study of the photosynthetic characteristics and biomass distribution of the dominant vascular plant species, Salix polaris, Dryas octopetala and Saxifraga oppositifolia, in the high Arctic tundra ecosystem at Ny-Alesund, Svalbard (78.5 degrees N, 11.5 degrees E). We also estimated net primary production (NPP) along both the successional gradient created by the proglacial chronosequence and the topographical gradient. The light-saturated photosynthesis rate (A (max)) differed among the species, with approximately 124.1 nmol CO(2) g(-1)leaf s(-1) for Sal. polaris, 57.8 for D. octopetala and 24.4 for Sax. oppositifolia, and was highly correlated with the leaf nitrogen (N) content for all three species. The photosynthetic N use efficiency was the highest in Sal. polaris and lowest in Sax. oppositifolia. Distributions of Sal. polaris and D. octopetala were restricted to the area where soil nutrient availability was high, while Sax. oppositifolia was able to establish at the front of a glacier, where nutrient availability is low, but tended to be dominated by other vascular plants in high nutrient areas. The NPP reflected the photosynthetic capacity and biomass distribution in that it increased with the successional status; the contribution of Sal. polaris reached as high as 12-fold that of Sax. oppositifolia.     

Is it getting hot in here? Adjustment of hydraulic parameters in six boreal and temperate tree species after 5 years of warming

Global temperatures (T) are rising, and for many plant species, their physiological response to this change has not been well characterized. In particular, how hydraulic parameters may change has only been examined experimentally for a few species. To address this, we measured characteristics of the hydraulic architecture of six species growing in ambient T and ambient +3.4 °C T plots in two experimentally warmed forest sites in Minnesota. These sites are at the temperate–boreal ecotone, and we measured three species from each forest type. We hypothesized that relative to boreal species, temperate species near their northern range border would increase xylem conduit diameters when grown under elevated T. We also predicted a continuum of responses among wood types, with conduit diameter increases correlating with increases in the complexity of wood structure. Finally, we predicted that increases in conduit diameter and specific hydraulic conductivity would positively affect photosynthetic rates and growth. Our results generally supported our hypotheses, and conduit diameter increased under elevated T across all species, although this pattern was driven predominantly by three species. Two of these species were temperate angiosperms, but one was a boreal conifer, contrary to predictions. We observed positive relationships between the change in specific hydraulic conductivity and both photosynthetic rate (P = 0.080) and growth (P = 0.012). Our results indicate that species differ in their ability to adjust hydraulically to increases in T. Specifically, species with more complex xylem anatomy, particularly those individuals growing near the cooler edge of their range, appeared to be better able to increase conduit diameters and specific hydraulic conductivity, which permitted increases in photosynthesis and growth. Our data support results that indicate individual's ability to physiologically adjust is related to their location within their species range, and highlight that some wood types may adjust more easily than others.