Non-vegetated Sites Research Articles

The effect of Zostera noltei recolonization on the sediment mercury vertical profiles of a recovering coastal lagoon

Mercury's extreme toxicity and persistence in the environment justifies a thorough evaluation of its dynamics in ecosystems. Aveiro Lagoon (Portugal) was for decades subject to mercury effluent discharges. A Nature-based Solution (NbS) involving Zostera noltei re-colonization is being tested as an active ecosystem restoration measure. To study the effect of Zostera noltei on the sediment contaminant biogeochemistry, seasonal (summer/winter) sediment, interstitial water and labile mercury vertical profiles were made in vegetated (Transplanted and Natural seagrass meadows) and non-vegetated sites (Bare-bottom area). While no significant differences (p > 0.05) were observed in the sedimentary phase, Zostera noltei presence reduced the reactive/labile mercury concentrations in the top sediment layers by up to 40% when compared to non-vegetated sediment, regardless of season. No differences were found between vegetated meadows, highlighting the fast recovery of the contaminant regulation ecosystem function provided by the plants after re-colonization and its potential for the rehabilitation of historically contaminated ecosystems.

Metabarcoding inventory of an arctic tundra soil ecosystem reveals highly heterogeneous communities at a small scale

Biodiversity surveys of Arctic soil ecosystems are limited. Here, we provide a sequence-based inventory of soil fauna from an Arctic tundra ecosystem near the Canadian High Arctic Research Station in Cambridge Bay, Nunavut. Invertebrate communities were extracted at a vegetated and non-vegetated site in three replicates and inventoried using 18S metabarcode sequencing. A total of 361 amplicon sequence variants (ASV) were identified and assigned to the closest matching taxonomic orders, most of which belonged to the Nematoda and Arthropoda. Vegetated soils showed no significantly higher ASV richness relative to non-vegetated soils although they contained a significantly higher diversity of arthropod taxa including insects, mites, and springtails. Most taxa were found only at a single location and even samples from the same site displayed distinct communities, suggesting that belowground species richness in Arctic tundra habitats is highly heterogeneous. Preserving soil biodiversity in a changing Arctic is essential for Inuit communities who rely on intact tundra ecosystems for their health and wellbeing.

Compositional stability of sediment microbial communities during a seagrass meadow decline

The presence of seagrass shapes surface sediments and forms a specific environment for diverse and abundant microbial communities. A severe decline of Cymodocea nodosa, a widespread seagrass species in the Mediterranean Sea, has been documented. To characterise and assess the changes in microbial community composition during the decline of a Cymodocea nodosa meadow, Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene was performed. Samples of surface sediments from two sites, one without any vegetation and one with a declining Cymodocea nodosa meadow, were collected at monthly intervals from July 2017 to October 2018. Microbial communities were stratified by sediment depth and differed between the vegetated and the nonvegetated site. Although the Cymodocea nodosa meadow declined to a point where almost no leaves were present, no clear temporal succession in the community was observed. Taxonomic analysis revealed a dominance of bacterial over archaeal sequences, with most archaeal reads classified as Nanoarchaeota, Thermoplasmatota, Crenarchaeota, and Asgardarchaeota. The bacterial community was mainly composed of Desulfobacterota, Gammaproteobacteria, Bacteroidota, Chloroflexi, Planctomycetota, and Campylobacterota. Our results show that sediment microbial communities are remarkably stable and may resist major disturbances such as seagrass meadow decline.

Metabarcoding of the phytotelmata of Pseudalcantarea grandis (Bromeliaceae) from an arid zone.

BackgroundPseudalcantarea grandis (Schltdl.) Pinzón & Barfuss is a tank bromeliad that grows on cliffs in the southernmost portion of the Chihuahuan desert. Phytotelmata are water bodies formed by plants that function as micro-ecosystems where bacteria, algae, protists, insects, fungi, and some vertebrates can develop. We hypothesized that the bacterial diversity contained in the phytotelma formed in a bromeliad from an arid zone would differ in sites with and without surrounding vegetation. Our study aimed to characterize the bacterial composition and putative metabolic functions in P. grandis phytotelmata collected in vegetated and non-vegetated sites.MethodsWater from 10 individuals was sampled. Five individuals had abundant surrounding vegetation, and five had little or no vegetation. We extracted DNA and amplified seven hypervariable regions of the 16S gene (V2, V4, V8, V3–6, 7–9). Metabarcoding sequencing was performed on the Ion Torrent PGM platform. Taxonomic identity was assigned by the binning reads and coverage between hit and query from the reference database of at least 90%. Putative metabolic functions of the bacterial families were assigned mainly using the FAPROTAX database. The dominance patterns in each site were visualized with rank/abundance curves using the number of Operational Taxonomic Units (OTUs) per family. A percentage similarity analysis (SIMPER) was used to estimate dissimilarity between the sites. Relationships among bacterial families (identified by the dominance analysis and SIMPER), sites, and their respective putative functions were analyzed with shade plots.ResultsA total of 1.5 million useful bacterial sequences were obtained. Sequences were clustered into OTUs, and taxonomic assignment was conducted using BLAST in the Greengenes databases. Bacterial diversity was 23 phyla, 52 classes, 98 orders, 218 families, and 297 genera. Proteobacteria (37%), Actinobacteria (19%), and Firmicutes (15%) comprised the highest percentage (71%). There was a 68.3% similarity between the two sites at family level, with 149 families shared. Aerobic chemoheterotrophy and fermentation were the main metabolic functions in both sites, followed by ureolysis, nitrate reduction, aromatic compound degradation, and nitrogen fixation. The dominant bacteria shared most of the metabolic functions between sites. Some functions were recorded for one site only and were related to families with the lowest OTUs richness. Bacterial diversity in the P. grandis tanks included dominant phyla and families present at low percentage that could be considered part of a rare biosphere. A rare biosphere can form genetic reservoirs, the local abundance of which depends on external abiotic and biotic factors, while their interactions could favor micro-ecosystem resilience and resistance.

Infiltration capacity in urban areas undergoing frequent snow and freeze–thaw cycles: Implications on sustainable urban drainage systems

Sustainable Urban Drainage Systems (SuDS) promote environmental protection and climate resilience. SuDS implementation in cold climates faces concerns of impaired hydrological function due to infiltration-reducing frost. The goal of this research was to assess the seasonal variations in infiltration and how different surface covers prevalent in and near coastal cities respond to frequent rain-on-snow and freeze–thaw cycles. A total of 28 constant head infiltration measurements were conducted over a period of 28 months in Urridaholt in Gardabaer, Iceland (64° 4′18.46″ N, 21° 54′37.11″ W) in a grass swale, lupine, and barren terrains. All test locations exhibited infiltration-inhibiting frost in winter, whose severity increased with frequent snow and freeze–thaw cycles. The grass swale resisted structural deformations resulting from frost, which was attributed to the high near-surface porosity within the intertwined root layer and the high drainage capacity of the underlying soil. The sparsely vegetated lupine and the barren area experienced severe frost heaving and cracking, and soil structural collapse which led to bypass flow upon thawing. The non-vegetated site had 30 to 50 times lower infiltration during winter (19 mm h−1) compared to the grass swale and lupine field (630- and 890-mm h−1, respectively), and twenty times lower during summer and fall (45 mm h−1 vs. ∼ 1000 mm h−1). The study concludes that frequent warming and cooling renders soils particularly vulnerable to frost. Vegetation plays an instrumental role in maintaining the hydrological functions of SuDS in winter. Therefore, the greening of urban centers is an important step towards climate resiliency. Plant selection and SuDS design criteria need to account for cold climate hydrological performance. In that regard, plants that limit sunlight and fully shed their vegetation in winter, such as the invasive lupine, can potentially contribute to frost formation and increase runoff generation.

Soil water dynamics based on a contrastive experiment between vegetated and non-vegetated sites in a semiarid region in Northwest China

Vegetation plays an active role in soil water dynamics and water balance in groundwater-soil-plant-atmosphere continuum systems. Therefore, we characterized soil water transport at depths of 0–4.0 m induced by root water uptake (RWU) at a groundwater-dependent Salix site during the whole growth stage and compared the results with those from a non-vegetated soil site, in the semiarid Ordos basin of China. The results showed that: during the whole experimental period, evapotranspiration at the vegetated site was more than twice evaporation at the bare site, indicating that the transpiration exceeded the evaporation and was the main output of soil water. For the bare site, the increase of soil water storage in the lysimeter was 97.9 mm in total, accounting for 27.5% of the precipitation, with 16.8% of rainfall as retention in the shallow vadose zone and 10.7% of rainfall as seepage below 150 cm depth. Conversely, in the vegetated site, rainfall-driven soil water was mainly consumed by vegetation, and the decrease of soil water storage was 254.4 mm in total, with no seepage being observed. Although the root system as the preferred channel improved the soil infiltration capacity, it did not mean that the deep soil water recharge increased. The infiltrated rainfwater could not offset the water consumption of the root system. An exponential normal composite RWU model obtained by the reverse method showed that the water deficit soil layers caused by RWU changed the soil water flow field and blocked soil water interchange. Consequently, deep soil water and groundwater could not be replenished by precipitation. Our results emphasize ascertaining the hydrodynamic processes of vegetation in semiarid regions and help to strike a balance between vegetation restoration and groundwater management.

Effect of the natural establishment of two plant species on microbial activity, on the composition of the fungal community, and on the mitigation of potentially toxic elements in an abandoned mine tailing

In Mexico, millions of tons of mining wastes are deposited in the open pit. Their content in potentially toxic elements (PTE) represents an environmental risk. In the tailings, pioneer plant communities are established, associated with a determined diversity of fungi; plants, and fungi are fundamental in the natural rehabilitation of mining wastes. The objective was to evaluate the impact of the natural establishment of two plant species on the microbial activity, on the composition of the fungal community, and on the mitigation of the effect of PTE in a contaminated mine tailing. In a tailing, we selected three sites: one non-vegetated; one vegetated by Reseda luteola, and one vegetated by Asphodelus fistulosus. In the substrates, we conducted a physical and chemical characterization; we evaluated the enzymatic activity, the mineralization of the carbon, and the concentration of PTE. We also determined the fungal diversity in the substrates and in the interior of the roots, and estimated the accumulation of carbon, nitrogen, phosphorus and PTE in plant tissues. The tailings had a high percentage of sand; the non-vegetated site presented the highest electric conductivity, and the plant cover reduced the concentration of PTE in the substrates. Plants increased the carbon content in tailings. The enzymatic activities of β-glucosidase and dehydrogenase, and the mineralization of carbon were highest at the site vegetated with A. fistulosus. Both plant species accumulated PTE in their tissues and exhibited potential in the phytoremediation of lead (Pb), cadmium (Cd), and copper (Cu). Fungal diversity was more elevated at the vegetated sites than in the bare substrate. Ascomycota prevailed in the substrates; the substrates and the plants shared some fungal taxa, but other taxa were specific. The plant coverage and the rhizosphere promoted the natural attenuation and a rehabilitation of the extreme conditions of the mining wastes, modulated by the plant species.

The Effectiveness of Riparian Hedgerows at Intercepting Drift from Aerial Pesticide Application.

The primary tool used currently for preventing pesticide drift from entering streams is a no-spray buffer zone. Riparian hedgerows may provide an additional option; however, quantitative information on their effectiveness is limited. To quantify the potential benefit of riparian hedgerows for drift reduction, aerial malathion {diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate} applications on blueberry ( L.) farms with fields adjacent to streams or ditches were monitored. Drift from fields with extensive dense woody riparian vegetation was compared with drift from fields with no dense woody riparian vegetation. Overall, total instream malathion deposition was 96.1% lower at vegetated sites compared with nonvegetated sites. Univariable models identified six variables that were significantly related to decreasing instream total malathion deposition: increasing bank canopy cover, increasing average site canopy cover, increasing canopy angle, increasing the distance between the field edge and vegetation edge, increasing the distance between the field edge and center of stream, and decreasing bank slope. For the variables most feasible for landowners to alter, the following increases could result, on average, in a 26% decrease in the total instream malathion deposition: bank canopy cover (7%), distance between field and vegetation (0.3 m), and distance between field and center of stream (0.9 m). No-spray buffer sizes needed for significant deposition reductions may be large, but for nonvegetated or minimally vegetated streams similar to those studied here, increasing bank canopy cover may give comparable advantages while allowing the use of the entire field area and conferring additional ecosystem benefits such as shading streams and improving habitat.

Estimation of Evapotranspiration Using a Nonparametric Approach Under All Sky: Accuracy Evaluation and Error Analysis

Accurate estimation of regional evapotranspiration (ET) or latent heat flux (latent energy, LE) remains a challenge. On the basis of a nonparametric approach, this study proposed an all-sky algorithm based on moderate-resolution imaging spectroradiometer (MODIS) products and datasets of China Meteorological Administration Land Data Assimilation System (CLDAS). Eddy covariance observations from three nonvegetated sites (desert, Gobi, and village) and three vegetated sites (orchard, vegetable, and wetland) over an arid/semiarid region were used as references to validate the new algorithm. Results showed that the spatial and temporal patterns of LE coincided with desert–oasis ecosystems. Comparison of the retrieved and reference values yielded the following results: R 2 = 0.19–0.63, bias = −129–56 W/m2, relative error (RE) = 5%–29%, and root-mean-square error (RMSE) = 95–150 W/m2. Remote-sensing-retrieved LE (RSLE) exhibited relatively good accuracy and poor agreement with ground observations at the nonvegetated sites (RE: 5%–23%, R2: 0.19–0.40), whereas contradicting scenario occurred at the vegetated sites (RE: 24%–29%, R2: 0.46–0.63). In the arid nonvegetated region, the ET error might have been caused by net radiation, soil heat flux, land surface temperature, and air temperature. In the vegetated region, the errors of MODIS and CLDAS products were not the dominant error sources of RSLE. The validation supported the applicability of the proposed algorithm in the arid/semiarid region.

Influence of urban vegetation on air pollution and noise exposure – A case study in Gothenburg, Sweden

Air pollution levels (NO2, PAHs, O3) were investigated, before (BLE) and after (ALE) leaf emergence, in the urban landscape of Gothenburg, Sweden. The aims were to study the 1) spatial and temporal variation in pollution levels between urban green areas, 2) effect of urban vegetation on air pollution levels at the same distance from a major emission source (traffic route), 3) improvement of urban air quality in urban parks compared to adjacent sites near traffic, 4) correlation between air pollution and noise in a park. O3 varied little over the urban landscape. NO2 varied strongly and was higher in situations strongly influenced by traffic. Four PAH variables were included: total PAH, total particle-bound PAH, the quantitatively important gaseous phenanthrene and the highly toxic particle-bound benzo(a)pyrene. The variation of PAHs was similar to NO2, but for certain PAHs the difference between highly and less polluted sites was larger than for NO2. At a vegetated site, NO2 and particulate PAH levels were lower than at a non-vegetated site at a certain distance from a busy traffic route. This effect was significantly larger ALE compared to BLE for NO2, indicating green leaf area to be highly significant factor for air quality improvement. For particulate PAHs, the effect was similar BLE and ALE, indicating that tree bark and branches also could be an important factor in reducing air pollution. Parks represented considerably cleaner local environments (park effect), which is likely to be a consequence of both a dilution (distance effect) and deposition. Noise and air pollution (NO2 and PAH) levels were strongly correlated. Comparison of noise levels BLE and ALE also showed that the presence of leaves significantly reduced noise levels. Our results are evidence that urban green spaces are beneficial for urban environmental quality, which is important to consider in urban planning.

Two energy balance closure approaches: applications and comparisons over an oasis-desert ecotone

Studies of energy balance that rely on eddy covariance (EC) are always challenged by energy balance closure, which is mainly caused by the underestimations of latent heat flux (LE) and sensible heat flux (Hs). The Bowen ratio (BR) and energy balance residual (ER) approaches are two widely-used methods to correct the LE. A comprehensive comparison of those two approaches in different land-use types is essential to accurately correcting the LE and thus improving the EC experiments. In this study, two energy balance approaches (i.e., BR and ER) were compared to correct the LE measured at six EC sites (i.e., three vegetated, one mixed and two non-vegetated sites) in an oasis-desert ecotone of the Heihe River Basin, China. The influences of meteorological factors on those two approaches were also quantitatively assessed. Our results demonstrated that the average energy closure ratio ((LE+Hs)/(Rn–Gs); where Rn is the surface net radiation and Gs is the surface soil heat flux) was approximately close to 1.0 at wetland, maize and village sites, but far from 1.0 at orchard, Gobi and desert sites, indicating a significant energy imbalance at those three latter sites. After the corrections of BR and ER approaches that took into account of soil heat storage, the corrected LE was considerably larger than the EC-measured LE at five of six EC sites with an exception at Gobi site. The BR and ER approaches yielded approximately similar corrected LE at vegetated and mixed sites, but they generated dissimilar results at non-vegetated sites, especially at non-vegetated sites with low relative humidity, strong wind, and large surface-air temperature difference. Our findings provide insight into the applicability of BR and ER approaches to correcting EC-based LE measurements in different land-use types. We recommend that the BR-corrected and ER-corrected LE could be seriously reconsidered as validation references in dry and windy areas.

Carbon sequestration in fly ash dumps: Comparative assessment of three plant association

The aim of the present study was to measure in-situ fly ash (FA) CO2 flux from naturally vegetated and non-vegetated sites of FA dumps for identifying potential plant species for carbon sequestration by using an automated soil CO2 flux system. The FA CO2 flux was found to be higher in vegetated site than non-vegetated site due to higher root density and respiration. The presence of organic carbon, microbial activity and root biomass are important indicators for sequestration of atmospheric CO2 in naturally vegetated site of FA dumps because of the fresh FA dumps are supposed to be initially free of organic carbon. Furthermore, in the naturally vegetated site, the FA CO2 efflux rates were least in Saccharum spontaneum (lower by 84.29%) and Prosopis juliflora (lower by 92.09%) association as compared to Typha latifolia association. Thus, the field results proved that S. spontaneum and P. juliflora associations are potentially suitable for sequestering atmospheric CO2 in the fresh FA deposited sites.

Field assessment of the effectiveness of organic amendments for aided phytostabilization of a Pb–Zn contaminated mine soil

A field trial was carried out to assess the effectiveness of organic amendments (COW: cow slurry; POULTRY: poultry manure; PAPER: paper mill sludge mixed with poultry manure) for the aided phytostabilization of vegetated and non-vegetated sites of an abandoned Pb/Zn contaminated mine. A native ecotype of Festuca rubra L. was used for colonizing the initially non-vegetated sites. Two and six months after amendment application, soil Pb and Zn availability (CaCl2-extractability) decreased. COW and POULTRY treatments resulted in highest reduction in Pb extractability in non-vegetated sites. In vegetated sites, COW-treated plots showed the highest decrease in metal extractability at 6months. All amendments, especially POULTRY, led to higher F. rubra biomass and vegetation cover in vegetated and initially non-vegetated sites, respectively. Two months after soil treatment, soil basal and substrate-induced respiration peaked in vegetated sites. Based on a root elongation bioassay with Lactuca sativa L., beneficial effects of soil amendments were also observed in terms of soil phytotoxicity. The problem of high variability (spatial, temporal and environmental) of vegetated and non-vegetated mine soils for an effective aided phytostabilization is discussed.

Effect of Sulfate Availability on the Isotopic Signature of Reduced Sulfurous Compounds in the Sediments of a Subtropical Estuary

We examined spatial patterns of sulfate utility and δ 34S signatures of sulfur species in sediments of a northern Taiwan subtropical estuary in December 2007. Results distinguished a sulfide-concentrated and freshwater-dominated site (called HR) in the upper estuary from two sulfate-concentrated and brackish-water-dominated sites (GR and GM) in the lower estuary. At the HR site, sulfide plays a crucial role in sulfur cycling. The δ 34S signature of sulfur species suggests two source pools: one with depleted 34S as seen in pyrite-S (−8.9‰), elemental sulfur (elemental-S, −8.6 ‰), and organic sulfur (organic-S, −7.5‰), and the other with enriched 34S as seen in acid-volatile sulfur (AVS, 6.9 ‰). These signatures greatly differed from those predicted in an environment in which sulfate (+21‰) is extremely limited, suggesting the relative importance of this isotopically light source. The two sites in the lower estuary were further differentiated: a mangrove-vegetated site (GM) had high elemental-S and pyrite-S concentrations, while a non-vegetated site (GR) had higher AVS and organic-S concentrations. These discrepancies may reflect the importance of mangrove vegetation in mediating sulfur speciation in estuarine sediments. At the GR and GM sites, the δ 34S signature became enriched with increasing depth because of sulfate limitation. δ 34S values of sulfur species in the deeper layer of the non-vegetated site varied with 34S enrichment, with remarkable enhancement to a value of 17.8‰ in AVS at a depth of 50 cm. Signatures of organic-S (9.8 ‰) and pyrite-S (−1.1 ‰) were also enriched. Such small fractionation, particularly in AVS, is likely to be associated with a sulfate deficiency in this lower estuarine area.

Documenting the terrestrial invertebrate fauna of Barrow Island, Western Australia

An intensive survey of terrestrial invertebrates was undertaken on Barrow Island, off the north-west coast of Western Australia, over a 5-year period from 2005 to 2009. The study was conducted as part of an environmental impact assessment for a liquefied natural gas (LNG) development on the island, with the aim of providing baseline information on invertebrates as a component of a future detection program in support of the island's quarantine system. The study used a standardised methodology for sampling a variety of undisturbed native vegetation communities, in addition to disturbed sites (vegetated and non-vegetated sites) across the island. Pre-eminent invertebrate taxonomists from Australia and overseas were engaged to assist with the identification of the various invertebrate orders collected. A total of 1873 species and morphospecies from 27 invertebrate orders were collected, 292 of which represented named species. A total of 321 families of invertebrates were represented in the collections. Samples taken during the same month in two consecutive years exhibited almost the same degree of difference as samples taken during the same year in the wet and the dry season. For ants, the fauna had greater affinity with the adjacent Pilbara than the Carnarvon basin Bioregion. In terms of sampling rigour and taxonomic coverage, this work represents one of the most intensive and comprehensive terrestrial invertebrate surveys presently undertaken in Australia.

Influence of flooding and vegetation on carbon, nitrogen, and phosphorus dynamics in the pore water of a Spartina alterniflora salt marsh

Four sites were selected in a salt marsh in the Bahía Blanca Estuary (Argentina): (1) low marsh (flooded by the tide twice daily) vegetated by S. alterniflora; (2) non-vegetated low marsh; (3) high marsh (flooded only in spring tides) vegetated by S. alterniflora; (4) non-vegetated high marsh. The pH and Eh were measured in sediments, while dissolved nutrients (ammonium, nitrate, nitrite and phosphate) and particulate organic matter (POM) were determined in pore water. pH (6.2-8.7) was only affected by vegetation in low areas. Eh (from −300 to 250 mV) was lower at low sites than at high ones; in the latter, the values were higher in the non-vegetated sediments. The POM concentration was greater in the high marsh than in the low marsh, with no effect of vegetation. Ammonium was the most abundant nitrogen nutrient species in pore water, except in the non-vegetated high marsh where nitrate concentration was higher. All nitrogen nutrients were affected by both flooding and vegetation. Phosphate was always present in pore water at all sites throughout the year and its concentration varied within narrow limits, with no effect of flooding and greater values always at non-vegetated sites. Our results showed that the variability of the pore water composition within the marsh is greater than the temporal variation, meaning that both tidal flooding and vegetation are important in the dynamics of nutrients and organic matter in the sediment pore water.

Microbial community structure and nutrient availability in oil sands reclaimed boreal soils

Alberta has one of the largest oil reserves in the world, some of which is extracted by surface mining representing a large scale disturbance to forest soils. We examined ecosystem function in reclaimed soils by measuring microbial community structure with phospholipid fatty acid (PLFA) analysis and nutrient availability with plant root simulator (PRS™) probes. Samples were taken from three slope positions, at three sites, on three dates (June and August 2005, and August 2006), and non-metric multi-dimensional scaling ordination was used to examine trends in the data. Repeated measures ANOVA was used to examine trends over time in key response variables identified by ordination. Ordination results revealed distinct differences between the spring and summer microbial community structure across sites, although large site differences were also found between fall measurements in the two consecutive years. Total microbial biomass (TMB) and the fungal to bacterial ratio (FBR) emerged as key response variables for microbial community structure, and repeated measures ANOVA indicated significant site differences for these parameters. Soil nutrient availability was predominantly affected by site, but was also greatly affected by season and by year of sampling. The key response variables for nutrient availability were NH 4 + and NO 3 −, which also varied significantly by site and season, with high NH 4 + availability in the spring on vegetated/fertilized sites and high NO 3 − availability year round on the non-vegetated site. Slope position had an inconsistent effect on the measured parameters which may indicate that these reclaimed soils are not characterized by near surface lateral flow. Seasonal fluctuations in nitrogen and boron availability, reflected in microbial community PLFA profiles, point at possible mechanistic linkages between the functioning of microbial communities and soil mineral nutrient availability.

Phosphorus and iron erosion from non-vegetated sites in a post-mining landscape, Lusatia, Germany: Impact on aborning mining lakes

Abstract Particulate phosphorus (P) can be transported via soil erosion in overland flow to waters, where it provides a long-term source of P for aquatic biota, and can accelerate freshwater eutrophication. Hence, knowledge of P sources is important for good environmental management. However, data on P, and related Fe, losses from various structures of a post-mining landscape are lacking. A year-long monitoring, and ten short rainfall simulations on plot scale, at ridges and rills and a combination of them, revealed high erosion from bare lignite mining dumps at Schlabendorf-North, Lusatia, Germany. The mean annual soil erosion rate from the year-long monitoring site was 18 × 106 kg km− 2 yr− 1, corresponding to 0.034 g m− 2 min− 1. The erosion rates were lowest at rill plots (1.9–4.4 g m− 2 min− 1), intermediate at ridge plots (14.3–37.1 g m− 2 min− 1), and highest at a combined rill and ridge plot (48.7–63.4 g m− 2 min− 1). These differences in extent were due to small scale differences in morphology and extreme water repellency. The hydrophobicity leads to very low infiltration, thus generating surface runoff even at low rainfall intensities. Loss rates of P and Fe, as deduced from the year-long erosion rate, were 470–650 kg km− 2 yr− 1, and 37.9 × 103–71 × 103 kg km− 2 yr− 1 respectively. However, these P inputs from lignite mining dump erosion, consisting of P-poor (17–90 μg g− 1) tertiary spoil materials, into aborning mining lakes, are negligible since they are accompanied by high Fe inputs, which favour an efficient P co-precipitation in the water column.

Effects of topography and management history on natural forest recovery in abandoned forest after clear-cutting in Miyazaki, Japan

We investigated factors limiting the recovery of natural forest in former large-scale conifer plantations abandoned after clear-cutting in southwestern Japan. We analyzed forest recovery status (“recovered” sites covered by evergreen broad-leaved trees, and “unrecovered” sites covered by pioneer community or nonvegetated sites) using aerial photographs and field survey. We applied logistic regression analyses to evaluate the effects of topography, construction of harvesting roads, distance from remnant forest, stand condition before clear-cutting, and prior land-use history on forest recovery. Human factors, i.e., land use and clear-cutting age, were found to affect to forest recovery more than environmental factors such as topography. Harvesting roads had the strongest negative impact on forest recovery. Forest recovery after clear-cutting of young sugi plantations also took longer than after clear-cutting of old sugi plantations or evergreen broad-leaved forests. Furthermore, areas formerly utilized as meadows recovered less successfully than those that had been managed as coppices. The influences of these factors were thought to be promoted by the advance reproduction as the regeneration sources for forest recovery. The influence of stand age before logging suggested an effect of thinning, which might alter the abundance of advanced reproduction in the understory. However, distance from remnant forest appeared to be less important. An influence of topography was also detected, but this could be partly explained by the existence of advance reproduction in the understory in certain topographic positions. Thus, our analysis suggests that regeneration sources originating from advanced reproduction in plantations play a significant role for the recovery of natural forest after clear-cutting.

The Effects of Habitat on Dispersal Patterns of an Invasive Thistle, Cynara Cardunculus

Dispersal of offspring is a critical step in the spread of invasive species, yet dispersal patterns are seldom well studied, inhibiting effective management and ecological understanding of invasions. Dispersal patterns can be affected by characteristics of the parent plant and by climatic or site characteristics, including community vegetation structure, but these factors have not been studied in the context of plant invasion processes. Cynara cardunculus (L.) is a polycarpic perennial thistle invasive in coastal grasslands in California that produces large numbers of wind-dispersed seeds. This study quantified and compared C. cardunculus dispersal patterns in an exotic grassland (vegetated site) and an agricultural field (non-vegetated site). Seed size variation in C. cardunculus was also quantified within inflorescences, between inflorescences, and between years of production, and compared across dispersal distances. Results indicate that dispersal distance increased dramatically from less than 20 m in the vegetated site to more than 40 m in the non-vegetated site. Plants producing fewer seeds produced heavier seeds and dispersal distance decreased over time, but seed size was not related to dispersal distance, which may serve to spread the risk to seeds or seedlings across the environment. C. cardunculus has great potential for dispersal in open areas such as agricultural fields or disturbed sites, but may be limited in highly structured natural communities. Management of C. cardunculus and other wind-dispersed plant invasions may be improved by prioritizing populations with open or disturbed areas downwind and minimizing the removal of vegetation during dispersal.