Nutrient-rich Habitats Research Articles

Strong decline in grasshopper abundance over 20 years without major land-use changes: Is soil drying one of the drivers?

Strong declines in insect numbers have been described for different taxa and regions. These observations are of great concern such that broad scientific and public attention has been raised. Among other urgencies, the need for long-term insect data has been identified. Here, we present data on grasshopper (Caelifera) abundances recorded between 1992 and 2011 at over 600 sites in north-western Switzerland. While vegetation type, often semi-natural grasslands, had remained largely constant, total grasshopper abundance declined by around 50 % (while many other taxa showed much less decline). Numbers in July remained relatively stable until about 2003 but then declined similar to the declines seen in August–October already before. Greatest losses were observed for drier habitats and steeper slopes, suggesting that soil drying might be an important factor for the decline. Second, more nutrient-rich habitats suffered greater losses; possible reasons for this include small-scale vegetation changes in these habitats e.g. due to atmospheric nitrogen deposition, or isolation of sites. Other than abundance, species richness decreased much less, illustrating that important ecological changes may be strongly underestimated when only species lists are available. The strong declines at our sites, which often are in an agri-environmental scheme, is alarming. Apart from being yet another call to fight climate change, our results also point to the urgent need to reduce atmospheric nitrogen deposition and to continue extensive farming, but also to adapt it in preparation of expected effects of climate change, with the aim to favour a divers, ecologically robust insect community.

Eurasian watermilfoil (Myriophyllum spicatum) alters its root topology but conserves its root branching in response to freshwater cultural eutrophication

Cultural eutrophication is the main cause of the decline of submerged plants in freshwater ecosystems. While many studies have focused on the nutrient uptake by the roots of these plants, less attention has been given to the effects of eutrophication on root structure. We designed a mesocosm experiment with Eurasian watermilfoil (Myriophyllum spicatum), a submerged plant indigenous to the Eurasian continent. The responses of plant functional traits, including growth traits, morphological traits and root topological indices, to different nitrogen (N) and phosphorus (P) concentrations were elucidated. We found that high P concentrations suppressed all the morphological traits and reduced the root topological traits, whereas N concentrations had a comparatively minor effect. Although the root branching of M. spicatum did not change, its root topology became more dichotomous with fewer exterior root links being formed in nutrient-rich habitats, and the root form changed from deep and thin to shallow and dense with increasing P concentrations. The root nutrient absorption ability of M. spicatum may decrease with cultural eutrophication, and this change most likely reduces its anchoring ability and increases its sensitivity to dislodge from the sediment if disturbed by hydraulic forces.

Leaf phenotypic plasticity of European ash (Fraxinus excelsior) at its northern range in Dinaric Alps

The Dinaric Alps have been recognised on numerous occasions as a biodiversity hotspot. They host a variety of species with great importance in sustainable forestry operations and nature conservation. One such species is the European ash (Fraxinus excelsior L., Oleaceae), a broad-leaved, wind-pollinated and wind-dispersed forest tree. In this paper, we aimed to determine the morphological variability of the European ash populations of the northern Dinaric Alps. For this purpose, leaf samples from 10 individuals in seven populations were collected. Morphometric analysis of intra- and interpopulation variability was conducted using 19 morphological leaf traits. We determined great variability of trees within, and small variability among, populations. The variables that best discriminated studied populations were those relating to leaflet shape. Based on these variables, populations were grouped into two clusters. The first cluster encompassed individuals with acute leaflets, found in drier and rockier habitats, whereas the second cluster, defined by more rounded leaflets, was found in mesophilous and nutrient-rich habitats. However, this research revealed no influence of geographical or bioclimatic distances on morphological variability, which indicates that the rockiness and soil are most likely two predominant factors in shaping the phenotypic plasticity of European ash populations. These results are of great significance in the planning of future forest breeding programs, as populations from drier habitats are likely to persist and spread due to their adaptation to water scarcity, which will become more pronounced in the future.

Long-term shift towards shady and nutrient-rich habitats in Central European temperate forests.

Biodiversity world-wide has been under increasing anthropogenic pressure in the past century. The long-term response of biotic communities has been tackled primarily by focusing on species richness, community composition and functionality. Equally important are shifts between entire communities and habitat types, which remain an unexplored level of biodiversity change. We have resurveyed > 2000 vegetation plots in temperate forests in central Europe to capture changes over an average of five decades. The plots were assigned to eight broad forest habitat types using an algorithmic classification system. We analysed transitions between the habitat types and interpreted the trend in terms of changes in environmental conditions. We identified a directional shift along the combined gradients of canopy openness and soil nutrients. Nutrient-poor open-canopy forest habitats have declined strongly in favour of fertile closed-canopy habitats. However, the shift was not uniform across the whole gradients. We conclude that the shifts in habitat types represent a century-long successional trend with significant consequences for forest biodiversity. Open forest habitats should be urgently targeted for plant diversity restoration through the implementation of active management. The approach presented here can be applied to other habitat types and at different spatio-temporal scales.

Culturable Diversity of Thraustochytrids from Coastal Waters of Qingdao and Their Fatty Acids.

Thraustochytrids have gained significant attention in recent years because of their considerable ecological and biotechnological importance. Yet, the influence of seasons and habitats on their culturable diversity and lipid profile remains poorly described. In this study, a total of 58 thraustochytrid strains were isolated from the coastal waters of Qingdao, China. These strains were phylogenetically close to five thraustochytrid genera, namely Botryochytrium, Oblongichytrium, Schizochytrium, Thraustochytrium, and Sicyoidochytrium. Most of the isolated strains were classified into the genera Thraustochytrium and Oblongichytrium. Further diversity analysis revealed that samples collected from nutrient-rich habitats and during summer/fall yielded significantly higher culturable diversity of thraustochytrids than those from low-nutrient habitats and winter/spring. Moreover, sampling habitats and seasons significantly impacted the fatty acid profiles of the strains. Particularly, the Oblongichytrium sp. OC931 strain produced a significant amount (153.99 mg/L) of eicosapentaenoic acid (EPA), accounting for 9.12% of the total fatty acids, which was significantly higher than that of the previously reported Aurantiochytrium strains. Overall, the results of this study fill the gap in our current understanding of the culturable diversity of thraustochytrids in the coastal waters and the impact of the sampling habitats and seasons on their capacity for lipid accumulation.

Metabolome adaptation and oxidative stress response of common carp (Cyprinus carpio) to altered water pollution levels

Treated wastewater ponds (TWPs) serve as recipients and passive tertiary treatment mediators for recycled water. These nutrient-rich habitats are increasingly utilised in aquaculture, nevertheless multiple loads of various contaminants with adverse effects on aquatic fauna, including fish, have been recorded. In the present study, we investigated the effects of fish transfer in response to altered levels of pollution on liver metabolic profiles and tissue-specific oxidative stress biomarkers during short- and long-term exposure. In a field experiment, common carp (Cyprinus carpio) originating in severely polluted TWP were restocked after one year to a reference pond with a background pollutant concentration typical of the regional river. In contrast, fish that originated in the reference pond were restocked to TWP. Fish were sampled 0, 7, 14, 60, and 180 days after restocking and fish liver, kidney, intestine, and gill tissues were subjected to biomarker analysis. Pharmaceutically active compounds (PhACs) and metabolic profiles were determined in fish liver using liquid chromatography high-resolution mass spectrometry (LC-HRMS). Fish transferred from reference to polluted pond increased the antioxidant response and absorbed PhACs into metabolism within seven days. Fish liver metabolic profiles were shifted rapidly, but after 180 days to a lesser extent than profiles in fish already adapted in polluted water. Restocked fish from polluted to reference pond eliminated PhACs during the short phase within 14 days, and the highest antioxidant response accompanied the depuration process. Numerous elevated metabolic compounds persisted in such exposed fish for at least 60 days. The period of two weeks was suggested as sufficient for PhACs depuration, but more than two months after restocking is needed for fish to stabilise their metabolism. This study contributed to determining the safe handling with marketed fish commonly restocked to wastewaters and clarified that water pollution irreversibly altered fish metabolic profile.

Phenotypic plasticity and exotic plant invasions: Effects of soil nutrients, species nutrient requirements, and types of traits.

High-phenotypic plasticity has long been considered as a characteristic promoting exotic plant invasions. However, the results of the studies testing this hypothesis are still inconsistent. Overlooking the effects of species resource requirements and environmental resource availability may be the main reasons for the ambiguous conclusions. Here, we compared phenotypic plasticity between five noxious invasive species with different nutrient requirements (evaluated using the soil nutrient status of their natural distribution ranges) and their phylogenetically related natives under five nutrient levels. We found that species with high-nutrient requirements showed greater plasticity of total biomass than species with low-nutrient requirements, regardless of their status (invasive or native). Invasives with high-nutrient requirements had greater growth plasticity than their related natives, which may contribute to their invasiveness under high-nutrient environments. However, compared with the related natives, a higher growth plasticity may not help exotic species with low-nutrient requirements to invade nutrient-rich habitats, and exotic species with high-nutrient requirements to invade nutrient-limited habitats. In contrast, invasives with low-nutrient requirements exhibited lower growth plasticity than their related natives, contributing to their invasiveness under nutrient-limited habitats. Functional traits showed growth-related plasticity in only 10 cases (3.8%), and there was no functional trait whose plastic response to soil nutrients was beneficial to exotic plant invasions. Our study indicates that low-growth plasticity could also promote exotic plant invasions, high plasticity may not necessarily lead to invasiveness. We must test the adaptive significance of plasticity of functional traits when studying its biological roles.

No effects of waterproof marking on the behaviour and growth of Physa acuta Draparnaud, 1805 (Gastropoda: Hygrophila: Physidae) in the laboratory

Physa acuta Draparnaud, 1805 is one of the most common freshwater gastropod species, with worldwide distribution. It is an effective periphyton grazer and a potential keystone species in shallow-water systems, where it can boost macrophyte well-being and thus help maintain high water clarity even in nutrient-rich habitats. P. acuta also has been extensively studied in ecotoxicological and behavioural investigations. Such investigations may require observations on individual snails. A method to distinguish individual snails in small-scale experiments is marking their shells with paint dots. However, such marking must not influence snail behaviour (nutritional, reproductive, respiratory, etc.) or growth to avoid confounding effects. Earlier investigations point to no or very limited effects of marking on aquatic and terrestrial snail survival, behaviour, and growth. We tested whether marking could affect the behaviour (as snail activity) and growth of P. acuta using a waterproof, oil-based, non-toxic, fine-point car-body paint marker. Snails were divided into a “marked” and an “unmarked” (control) group of ten snails each in an eight-day experiment. The marking had no effect on the snail activity or growth. The snails survived the experiment and produced egg clutches well beyond the eight-day period. The marking persisted without fading during and beyond the experimental period. Our results support earlier findings that the use of oil-based, non-toxic markers can assist in carrying out reliable observations on individual snails, including the small-bodied P. acuta. Combinations of two dots of different colours allow simultaneous observations on a high number of replicate individuals.

Differences in growth-economics of fast vs. slow growing grass species in response to temperature and nitrogen limitation individually, and in combination

BackgroundFast growing invasive alien species are highly efficient with little investment in their tissues. They often outcompete slower growing species with severe consequences for diversity and community composition. The plant economics trait-based approach provides a theoretical framework, allowing the classification of plants with different performance characteristics. However, in multifaceted background, this approach needs testing. The evaluation and prediction of plant performance outcomes in ecologically relevant settings is among the most pressing topics to understand and predict ecosystem functioning, especially in a quickly changing environment. Temperature and nutrient availability are major components of the global environmental change and this study examines the response of growth economic traits, photosynthesis and respiration to such changes for an invasive fast-growing (Bromus hordaceus) and a slow-growing perennial (Bromus erectus) grass species.ResultsThe fully controlled growth chamber experiment simulated temperature—and changes in nitrogen availability individually and in combination. We therefore provide maximum control and monitoring of growth responses allowing general growth trait response patterns to be tested. Under optimal nitrogen availability the slow growing B. erectus was better able to handle the lower temperatures (7 °C) whilst both species had problems at higher temperatures (30 °C). Stresses produced by a combination of heat and nutrient availability were identified to be less limiting for the slow growing species but the combination of chilling with low nutrient availability was most detrimental to both species.ConclusionsFor the fast-growing invader B. hordeaceus a reduction of nitrogen availability in combination with a temperature increase, leads to limited growth performance in comparison to the slow-growing perennial species B.erectus and this may explain why nutrient-rich habitats often experience more invasion than resource-poor habitats.

Aeromonas veronii and Plesiomonas shigelloides (Gammaproteobacteria) isolated from Glossogobius aureus (Gobiidae) in Lake Sampaloc, Laguna, Philippines

Bacterial infections are high-risk factors in fisheries, with reports of high mortality among diseased fish stocks posing a threat to both capture and aquaculture fisheries in inland waters. Diseases-causing bacteria in fishes may lead to decreased yield and economic loss to fishers, whose livelihood primarily depends on landed catch. Lake fisheries are most affected by such disruptive changes because of limitations in water turnover aggravated by wastewater inputs. In this study, we isolated and characterized gut bacteria from landed catch of the gobiid Glossogobius aureus from Lake Sampaloc, a small but commercially important aquaculture area in Luzon. Isolated axenic gut bacteria were identified through Gram stain reaction, microscopy, API biochemical tests, and 16s rRNA gene sequencing. From these, we identified two species with known fish pathogenicity, namely Aeromonas veronii and Plesiomonas shigelloides which are known to thrive in disrupted and nutrient-rich habitats and cause visible damage to fish health. Interestingly, our samples have shown no such visible signs of the disease. It is therefore important for future researches to determine what conservation and management practices in small inland waters like lakes will limit potential environmental stressors that may trigger susceptibility of both capture and farmed fish species to infection. Ultimately, rehabilitation of inland water aquaculture areas such as Lake Sampaloc is essential not only to fish conservation but also to public health and local food security.

Assessment of the habitat conditions of a rare and endangered inland saline wetland community with Bolboschoenus maritimus (L.) Palla dominance in Southeastern Europe: the effects of physical–chemical water and soil properties

Continental inland saline wetlands are among the most endangered habitats in Europe. In the Danube-Tisza-Danube canal network (Serbia, Southeastern Europe), which is one of the largest canal networks on the continent, the rare and endangered inland saline wetland Bolboschoenus maritimus community (BMC) has been found at only two locations. Two vegetation types of the community have been identified: (i) with Bolboschoenus maritimus and Marsilea quadrifolia (BMC-M) dominance and (ii) with Bolboschoenus maritimus and Butomus umbellatus (BMC-B) dominance. The aim of the study was to compare the habitats of the ascertained vegetation types in terms of 55 water and soil properties that influence their development, floristic composition and differentiation. The main properties influencing the community development and differentiation were water alkalinity, chemical oxygen demand, CO32−, water pH, soil conductivity, K+ and Ca2+ content in the soil. Both vegetation types grow in non-saline, slightly alkaline, nutrient-rich habitats with eutrophic water. When compared to BMC-B, BMC-M was found on heavy clay soils with higher conductivity, CaCO3, humus, nutrients, macroelements, and Na+ content, in shallower water with higher suspended solids and oxygen content, lower contents of nutrients, dissolved salts, HCO3−, macroelements, conductivity, and alkalinity. The study provides new data on the BMC distribution in this part of Europe and the first detailed information on its habitat conditions. Thirty-one species from the European Red List of Threatened Species were found in the stands. These results may be useful when deciding on the appropriate preservation measures aimed to rehabilitate other wetland habitats and biodiversity.

Ecology, threats and conservation status of Carex buekii (Cyperaceae) in Central Europe

Carex buekii is a tall sedge, forming large stands in wetlands, particularly in river floodplains across Central Europe and thus on many sites determining the typical appearance of riverine habitats. Our paper aims at increasing the knowledge on ecology of C. buekii and its role in the wetlands. Field data were collected in Poland, the Czech Republic, Slovakia, Hungary, and Italy. Carex buekii usually occurs in nutrient rich habitats, but is also capable of colonising relatively nutrient-poor ones; it grows on both acidic and alkaline soils (pH 3.3–7.4) with diverse concentrations of assimilable elements (Ca, Mg, P, K). One of the most important ecological characteristics of C. buekii is its relationship to the floodplains of watercourses. It seems to be dependent on, or at least very tolerant to regular disturbances by streaming, floods and transport of sediments. Carex buekii usually forms relatively uniform stands of its own association, Caricetum buekii. The species most frequently accompanying C. buekii are Urtica dioica, Calystegia sepium, Galium aparine, Rubus caesius, Phalaris arundinacea, and Cirsium arvense. The sedge also occurs in the understorey of forests with e.g. Alnus glutinosa, Salix fragilis, Padus avium, and Quercus robur. Carex buekii is able to colonise man-made or man-changed habitats such as railway embankments and roadsides or regulated river banks. Taking into account the IUCN Red List Criteria we propose to regard C. buekii as a least-concern (LC).

Inland salt areas of Southeast Serbia: ecological preferences of certain representatives of flora

Simultaneous monitoring of vegetation and soil of inland salt areas of Southeastern Serbia was performed in order to assess the univariate response of species along the environmental gradients. Five habitat types were recognized by classification analysis based on physicochemical characteristics of soil. Ecological preferences of 9 species recognized as diagnostic of established habitats were estimated by Huisman-Olff-Fresco models. Carex distans, Cynod on dactylon and Plantago coronopus are diagnostic species of habitat type I which is characterized by electrical conductivity lower than 500 μScm−1, slightly alkaline reaction and low concentration of nutrients. Habitats of type II with alkaline soil, where concentration of available potassium (53 mg K2O/100 g soil) and phosphorus (19 mg P2O5/100 g soil) is high and electrical conductivity is in range of 608 to 860 μScm−1, are suitable for Carex divisa, Juncus compressus and Limonium gmelinii. Puccinellia festuciformis shows affinities to habitats of type III, characterized by electrical conductivity of 1200–2800 μScm−1 and low water and nutrient content. Presence of Camphorosma monspeliaca on habitats (type IV) indicates high concentration of OH− ions, salts (>3000 μScm−1) and chlorides in soil. Puccinellia distans shows affinities to strongly saline, alkaline and nutrient rich habitats (type V) with fluctuating water regime during the vegetation season. Information on objectively assessed ecological preferences of plant species represents a suitable foundation for defining local or regional indicator systems, calibration of existing ecological indices and realization of procedures with the goal of conservation and enhancement of threatened ecosystems such as inland salt areas.

Middle Jurassic terebratulide brachiopods from the Jordan Valley (northwestern Jordan)

ABSTRACT The Middle Jurassic terebratulide brachiopods from the Jordan Valley, northwestern Jordan, are herein revised and systematically described and new taxa are added to the faunal list. A new genus and species Jordanithyris ardainensis gen. et sp. nov., is introduced from the upper Bathonian (Hamam Formation) and lower Callovian (Mughanniyya Formation) of the Arda section. In the upper Bathonian Hamam Formation (consisting of limestone, dolomite, alternating sandstone, and marlstone beds), Ptyctothyris quillyensis occurs. The assemblage Arabatia bihinensis, Ectyphoria sinaiensis, Ptyctothyris quillyensis, Dorsoplicathyris dorsoplicata, and Tubithyris jurayfahiensis is recorded in the lower Callovian limestone beds with marlstone interbeds of the Mughanniyya Formation. Brachiopods of the Jordanian Hamam and Mughanniyya formations can be correlated with the fauna of the Aroussiah Formation in Sinai and the Zohar and Matmor formations in southern Israel. The sedimentary environment is interpreted as the protected shallow inner shelf, and nutrient rich habitat resulting in high faunal diversity. The high degree of endemism of this fauna is yet another confirmation of the representative pronounced Middle Jurassic endemism along the southern Tethyan margin of the Ethiopian Province.

On Dryopteris site type forests in Estonia

Abstract Fern-rich forest communities are presented in Estonia in mesic or moderately humid nutrient-rich habitats, in areas of drained mire forests, on floodplains and lower parts of talus slopes of the North-Estonian limestone escarpment (klint). In the recent official forest typology only one site type has been distinguished and labelled by the ferns: the Dryopteris site type in the scope of boreo-nemoral forests. The aims of the current study were (i) to clarify whether distinguishing between two fern-rich forest site types, one among the full-drained forests group and another in the boreo-nemoral forests group, is reasonable, and if so, then (ii) what the main characteristics of both considered forest site types are, (iii) what the main environmental factors determining the structure of these communities are, and (iv) what the mutual relationship between those forests and other fern-rich forest communities is. Our results asserted a distinct difference between the full-drained and undrained Dryopteris site type forests distinguished by the former scholars. The undrained boreo-nemoral fern-rich stands have developed in the same place in harmony with habitat conditions, while drained forests have significantly changed. It seems that despite some vagueness due to long-lasting post-drainage succession, it is nevertheless justified to recognise the fern-rich drained stands in Estonian forest typology as representing an autonomous forest site type in the group of full-drained forests. To avoid confusion in nomenclature, in the future, the undrained fern-rich boreo-nemoral forests site type could be named according to the most conspicuous indicator species as the Athyrium (filix-femina) site type and fern-rich stands on full-drained peat soils as the Dryopteris (expansa) site type.

Fear of the dark: decline in plant diversity and invasion of alien species due to increased tree canopy density and eutrophication in lowland woodlands

The abandonment of traditional forest management and the conversion of lowland woodlands from coppices to high forests may lead to a reduction in plant diversity. We studied long-term changes in semi-natural lowland woodland vegetation in the Czech Republic (Central Europe) by resampling 29 vegetation plots (releves) first sampled in the 1950s. The results indicated a shift to shady plant communities (i.e. loss of heliophilous species and expansion of shade-tolerant species), caused by an increase in the tree and shrub layer canopy due to the expansion of deciduous tree species. At the same time, species richness (alpha diversity) had declined significantly, though we noted no signs of homogenisation in the vegetation cover. Species typical of nutrient-rich habitats and alien and/or invasive species had expanded. We confirmed the shift in vegetation composition, which was probably caused by changes in lowland woodland forest management (decline in coppicing), eutrophication (deposition of atmospheric nitrogen, agricultural runoff) and disturbance effects of game, especially wild boar (Sus scrofa).

Nitrogen starvation induces distinct photosynthetic responses and recovery dynamics in diatoms and prasinophytes.

Nitrogen stress is an important control on the growth of phytoplankton and varying responses to this common condition among taxa may affect their relative success within phytoplankton communities. We analyzed photosynthetic responses to nitrogen (N) stress in two classes of phytoplankton that often dominate their respective size ranges, diatoms and prasinophytes, selecting species of distinct niches within each class. Changes in photosynthetic structures appeared similar within each class during N stress, but photophysiological and growth responses were more species- or niche-specific. In the coastal diatom Thalassiosira pseudonana and the oceanic diatom T. weissflogii, N starvation induced large declines in photosynthetic pigments and Photosystem II (PSII) quantity and activity as well as increases in the effective absorption cross-section of PSII photochemistry (σʹPSII). These diatoms also increased photoprotection through energy-dependent non-photochemical quenching (NPQ) during N starvation. Resupply of N in diatoms caused rapid recovery of growth and relaxation of NPQ, while recovery of PSII photochemistry was slower. In contrast, the prasinophytes Micromonas sp., an Arctic Ocean species, and Ostreococcus tauri, a temperate coastal eutrophile, showed little change in photosynthetic pigments and structures and a decline or no change, respectively, in σʹPSII with N starvation. Growth and PSII function recovered quickly in Micromonas sp. after resupply of N while O. tauri failed to recover N-replete levels of electron transfer from PSII and growth, possibly due to their distinct photoprotective strategies. O. tauri induced energy-dependent NPQ for photoprotection that may suit its variable and nutrient-rich habitat. Micromonas sp. relies upon both energy-dependent NPQ and a sustained, energy-independent NPQ mechanism. A strategy in Micromonas sp. that permits photoprotection with little change in photosynthetic structures is consistent with its Arctic niche, where low temperatures and thus low biosynthetic rates create higher opportunity costs to rebuild photosynthetic structures.

Lifestyles in transition: evolution and natural history of the genus Lactobacillus.

Lactobacillus species are found in nutrient-rich habitats associated with food, feed, plants, animals and humans. Due to their economic importance, the metabolism, genetics and phylogeny of lactobacilli have been extensively studied. However, past research primarily examined lactobacilli in experimental settings abstracted from any natural history, and the ecological context in which these bacteria exist and evolve has received less attention. In this review, we synthesize phylogenetic, genomic and metabolic metadata of the Lactobacillus genus with findings from fine-scale phylogenetic and functional analyses of representative species to elucidate the evolution and natural history of its members. The available evidence indicates a high level of niche conservatism within the well-supported phylogenetic groups within the genus, with lifestyles ranging from free-living to strictly symbiotic. The findings are consistent with a model in which host-adapted Lactobacillus lineages evolved from free-living ancestors, with present-day species displaying substantial variations in terms of the reliance on environmental niches and the degree of host specificity. This model can provide a framework for the elucidation of the natural and evolutionary history of Lactobacillus species and valuable information to improve the use of this important genus in industrial and therapeutic applications.

Nutrient enrichment increases plant biomass and exotic plant proportional cover independent of warming in freshwater wetland communities

Anthropogenic environmental change can increase exotic species performance and reduce native biodiversity. Nutrient enrichment may favor exotic plants with higher growth rates. Warming may increase the performance of exotic species from warmer native ranges and/or decrease the performance of locally adapted native species. However, community level impacts of nutrient enrichment and warming may depend on their combined effects on individual species and species interactions. We conducted a factorial 11-month field experiment that manipulated 1) plant origin: native, exotic (species from warmer and nutrient rich habitats), or native-&-exotic; 2) nutrients: ambient or high; and 3) temperature: ambient, +1 °C, or +2 °C. Elevated nutrients increased biomass and exotic plant proportional cover. Exotic diversity was higher with elevated nutrients. Native and exotic biomass responses to elevated nutrients were smaller in native-&-exotic treatments. Elevated nutrients increased the relative abundance of two exotic and decreased one exotic and three native species in native-&-exotic treatments. The predicted exotic to native biomass ratio was higher than the observed ratio, indicating that native plants reduced the potential growth of exotic plants in native-&-exotic treatments. Warming had no effect on plant biomass or diversity. These results suggest that nutrient enrichment increases the performance of some exotic plants and that it is critical to consider native and exotic plant interactions when assessing anthropogenic factor and exotic plant effects on native plant communities.

Pattern and dynamics of biomass stock in old growth forests: The role of habitat and tree size

Forest ecosystems play a fundamental role in the global carbon cycle. However, how stand-level changes in tree age and structure influence biomass stock and dynamics in old-growth forests is a question that remains unclear.In this study, we quantified the aboveground biomass (AGB) standing stock, the coarse woody productivity (CWP), and the change in biomass over ten years (2004–2014) in a 25 ha unmanaged broad-leaved Korean pine mixed forest in northeastern China. In addition, we quantified how AGB stock and change (tree growth, recruitment and mortality) estimations are influenced by the variation in habitat heterogeneity, tree size structure and subplot size.Our analysis indicated that Changbai forest had AGB of 265.4 Mg ha−1 in 2004, and gained1.36 Mg ha−1 y−1 between 2004 and 2014. Despite recruitment having better performance in nutrient rich habitat, we found that there is a directional tree growth trend independent of habitat heterogeneity for available nutrients in this old growth forest. The observed increases in AGB stock (∼70%) are mainly attributed to the growth of intermediate size trees (30–70 cm DBH), indicating that this forest is still reaching its mature stage. Meanwhile, we indicated that biomass loss due to mortality reduces living biomass, not increment, may be the primary factor to affect forest biomass dynamics in this area.Also, spatial variation in forest dynamics is large for small sizes (i.e. coefficient of variation in 20 × 20 m subplots is 53.2%), and more than 90 percent of the inherent variability of these coefficients was predicted by a simple model including plot size. Our result provides a mean by which to estimate within-plot variability at a local scale before inferring any directional change in forest dynamics at a regional scale, and information about the variability of forest structure and dynamics are fundamental to design effective sampling strategies in future study.