Plant Species Mixtures Research Articles

Designing mixtures of varieties for multifunctional agriculture with the help of ecology. A review

Abstract - The study of natural ecosystems and experiments using mixtures of plant species demonstrates that both species and genetic diversity generally promote ecosystem functioning. Therefore, mixing crop varieties is a promising alternative practice to transform modern high-input agriculture that is associated with a drastic reduction of within-field crop genetic diversity and is widely recognized as unsustainable. Here, we review the effects of mixtures of varieties on ecosystem functioning, and their underlying ecological mechanisms, as studied in ecology and agronomy, and outline how this knowledge can help designing more efficient mixtures. We recommend the development of two complementary strategies to optimize variety mixtures by fostering the ecological mechanisms leading to a positive relationship between biodiversity and ecosystem functioning and its stability through time, i.e., sampling and complementarity effects. (1) In the “trait-blind” approach, the design of high-performance mixtures is based on estimations of the mixing abilities of varieties. While this approach is operational because it does not require detailed trait knowledge, it relies on heavy experimental designs to evaluate mixing ability. (2) The trait-based approach is particularly efficient to design mixtures of varieties to provide particular baskets of services but requires building databases of traits for crop varieties and documenting the relations between traits and services. The performance of mixtures requires eventually to be evaluated in real economic, social, and agronomic contexts. We conclude that the need of a multifunctional low-input agriculture strongly increases the attractiveness of mixtures but that new breeding approaches are required to create varieties with higher mixing abilities, to foster complementarity and selection effects through an increase in the variance of relevant traits and to explore new combinations of trait values.

An rbcL reference library to aid in the identification of plant species mixtures by DNA metabarcoding.

Premise of the study:DNA metabarcoding has broad-ranging applications in ecology, aerobiology, biosecurity, and forensics. A bioinformatics pipeline has recently been published for identification using a comprehensive database of ITS2, one of the common plant DNA barcoding markers. There is, however, no corresponding database for rbcL, the other primary marker used in plants.Methods:Using publicly available data, we compiled a reference library of rbcL sequences and trained databases for use with UTAX and RDP classifier algorithms. We used this reference library, along with the existing bioinformatics pipeline and ITS2 reference library, to identify species in an artificial mixture of nine species of pollen. We have made this database publicly available in multiple formats, to allow use with multiple bioinformatics pipelines, now and in the future.Results:Using the rbcL database, in addition to the ITS2 database, we succeeded in making species-level identifications for eight species and a family-level identification of the ninth species. This is an improvement on ITS2 sequence alone.Discussion:The reference library described here will assist with identification of plant species using rbcL. By making another gene region available for standard barcoding, this will increase the resolution and accuracy of identifications.

Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest

SummaryA major challenge of current ecological research is to determine the responses of plant and animal communities and ecosystem processes to future environmental conditions. Ecosystems respond to climate change in complex ways, and the outcome may significantly depend on biodiversity.We studied the relative effects of enhanced drought and of plant species mixture on soil biota and on litter decomposition in a Mediterranean oak forest. We experimentally reduced precipitation, accounting for seasonal precipitation variability, and created a single‐species litter (Quercus pubescens), a two‐species litter mixture (Q. pubescens+Acer monspessulanum) and a three‐species litter mixture (Q. pubescens+A. monspessulanum+Cotinus coggygria).In general, drier conditions affected decomposers negatively, directly by reducing fungal biomass and detritivorous mesofauna, and also indirectly by increasing the predation pressure on detritivorous mesofauna by predatory mesofauna. This is reflected under drier conditions in that Collembola abundance decreased more strongly than Acari abundance. One Collembola group (i.e. Neelipleona) even disappeared completely.Increased drought strongly decreased litter decomposition rates. Mixed litter with two and three plant species positively affected soil biota communities and led to a more efficient litter decomposition process, probably through a greater litter quality. Faster decomposition in mixed litter can thus compensate slower decomposition rates under drier condition.Synthesis. Our results highlight that, within our study system, drier climate strongly impacts on soil biodiversity and hence litter decomposition. Species‐rich litter may mitigate such a decline in decomposition rates. Diverse plant communities should hence be maintained to reduce shifts in ecosystem functioning under climate change.

Mapping of invasive phragmites (common reed) in Gulf of Mexico coastal wetlands using multispectral imagery and small unmanned aerial systems

ABSTRACTIn coastal wetlands of the Gulf of Mexico, the invasive plant species Phragmites australis (common reed) rapidly alters the ecology of a site by shifting plant communities from heterogeneous mixtures of plant species to homogenous stands of Phragmites. Phragmites grows in very dense stands at an average height of 4.6 m and outcompetes native plants for resources. To restore affected wetlands, resource managers require an accurate map of Phragmites locations. Previous studies have used satellite and manned aircraft-based remote-sensing images to map Phragmites in relatively large areas at a coarse scale; however, low-altitude high-spatial-resolution pixel-based classification approaches would improve the mapping accuracy. This study explores the supervised classification methods to accurately map Phragmites in the coastal wetlands at the delta of the Pearl River in Louisiana and Mississippi, USA, using high-resolution (8 cm ground sample distance; GSD) multispectral imagery collected from a small unmanned aerial system platform at an altitude of 120 m. We create a map through pixel-based Support Vector Machines (SVM) classification using blue, green, red, red edge, and near-infrared spectral bands along with a digital surface model (DSM), vegetation indices, and morphological attribute profiles (MAPs) as features. This study also demonstrates the effects of different features and their usefulness in generating an accurate map of Phragmites locations. Accuracy assessment based on a) a subset of training/testing samples (to show classifier performance) and b) the entire ground reference (GR) map (to show the quality of mapping) is demonstrated. Kappa, overall accuracy (OA), class accuracies, and their confidence intervals (CIs) are reported. An OA of 91% and kappa of 63 is achieved. The results of this study indicate that features such as MAPs are very useful in accurately mapping invasive Phragmites compared with existing region-based approaches.

Nitrogen, Phosphor, and Potassium Level in Soil and Oil Palm Tree at various Composition of plant species mixtures grown

In productive oil palm plantation areas, poor vegetation is generally caused by low light intensity. This condition causes excessive erosion and decreases soil fertility. One of the efforts for soil and water conservation at oil palm plantations is through increased vegetation diversity. The changes of soil and plant nitrogen, phosporus, and potassium content, observed by planting two types of herbs under oil palm tree, with different compositions. Vegetation composition was set as: Arachis glabrata 100%; Stenotaprum secundatum 100%; Arachis glabrata 50% + Stenotaprum secundatum 50%; Arachis glabrata 75% + Stenotaprum secundatum 25%; Arachis glabrata 25% + Stenotaprum secundatum 75%. The shoot and root fresh/dry weight, nutrient content (nitrogen, phosphor, and potassium) of each cutting were measured at the end of the experiment. Ten of treatment plant were harvested and divided shoots and roots after washing out of soil. Biomass samples were dried at 70 °C for 48 h and weighed. The total N and its proportional concentration (N%) were analyzed with the micro- Kjeldahl method. Potasium analyzing with flamephotometry, and phosphor and from samples was determined by analyzing with spectrophotometry method. The results showed the highest shoot growth of A.glabarata if planting was mixed with S. secundatum, but the result was different with S.secundatum being superior if planted with monoculture system. Combination of interrow cultivation is more recommended for soil conservation and nutrient maintenance in palm oil trees were A. Glabarata 75% + S.secundatum 25%.

Temporal stability and patterns of runoff and runon with different cover crops in an olive orchard (SW Andalusia, Spain)

Conventional tillage (CT) and cover crops (CC) trigger different runoff (Q) and runon (Qin) magnitudes and patterns in woody crops. The spatial and temporal stability of these patterns is not well known yet. In this study, we run the uncalibrated DR2-2013© SAGA v1.1 model (0.5×0.5m of cell size) to simulate time to ponding (Tp), runoff duration (TQ), initial runoff per raster cell (q0), Qsim and Qin in six olive plots (480m2 per plot) during two years (108 rainfall events and 648 simulations). Two plots were managed with a mixture of plant species (CC-I), two with one single plant species (CC-II) and two with CT. Runoff yield from each plot was collected (Qobs) in gauging-stations during 27 time-integrated samples and used for modelling validation (162 control points). On average, Qobs was 9% higher under CT than under CC-I, and 8% higher than under CC-II. Topsoil saturation was simulated for the entire plots during 29 events (test-period), and Qsim appeared in another 51 and 52 events in the plots with CC and CT. Tp with CT was 2.3 times higher (59s) than the average duration with CC and the topsoil became saturated 3.3 times faster in the inter-rows than below the trees. Values of q0 with CC were 2.3% lower than with CT and total Qsim with CC was 2% higher than with CT. However, the differences of Qsim between the different treatments were not statistically significant. The mean observed and simulated runoff coefficients were of 11 and 14%, with median values of 7 and 10%. Qsim correlated well with Qobs (Pearson ca. 0.861), and Qsim was overestimated ca. 10%. The model performed better when rainfall depth and intensity were high, and the range of variability of both Qsim and Qobs was similar. The average, best and worst Nash–Sutcliffe coefficients were 0.665, 0.791 (P6) and 0.512 (P3) and thus model simulations were satisfactory. The four plots with CC presented on average a worse performance (Kling–Gupta coefficient=0.607) than the two plots with CT (KGE=0.769). The lowest spatial variability of q0, Qobs, Qsim and actual available water (Waa, the sum of Qin and stored water in the soil surface) were found in the plots with CC. CT triggered higher spatial variability of runoff and higher temporal variability of runon than CC.

Enriching plant diversity in grasslands by large-scale experimental sward disturbance and seed addition along gradients of land-use intensity

Aims The relationship between biodiversity and ecosystem functioning is among the most active areas of ecological research. Furthermore, enhancing the diversity of degraded ecosystems is a major goal in applied restoration ecology. In grasslands, many species may be locally absent due to dispersal or microsite limitation and may therefore profit from mechanical disturbance of the resident vegetation. We established a seed addition and disturbance experiment across several grassland sites of different land use to test whether plant diversity can be increased in these grasslands. Additionally, the experiment will allow us testing the consequences of increased plant diversity for ecosystem processes and for the diversity of other taxa in real-world ecosystems. Here we present details of the experimental design and report results from the first vegetation survey one year after disturbance and seed addition. Moreover, we tested whether the effects of seed addition and disturbance varied among grassland depending on their land use or pre-disturbance plant diversity. Methods A full-factorial experiment was installed in 73 grasslands in three regions across Germany. Grasslands were under regular agricultural use, but varied in the type and the intensity of management, thereby representing the range of management typical for large parts of Central Europe. The disturbance treatment consisted of disturbing the top 10 cm of the sward using a rotavator or rotary harrow. Seed addition consisted of sowing a high-diversity seed mixture of regional plant species. These species were all regionally present, but often locally absent, depending on the resident vegetation composition and richness of each grassland. Important findings One year after sward disturbance it had significantly increased cover of bare soil, seedling species richness and numbers of seedlings. Seed addition had increased plant species richness, but only in combination with sward disturbance. The increase in species richness, when both seed addition and disturbance was applied, was higher at high land-use intensity and low resident diversity. Thus, we show that at least the early recruitment of many species is possible also at high land-use intensity, indicating the potential to restore and enhance biodiversity of species-poor agricultural grasslands. Our newly established experiment provides a unique platform for broad-scale research on the land-use dependence of future trajectories of vegetation diversity and composition and their effects on ecosystem functioning.

Effects induced by living mulch on rhizosphere interactions in organic artichoke: The cultivar's adaptive strategy

AbstractThe plant root apparatus and the surrounding micro-environment is strongly influenced by specific abiotic and biotic conditions which occur in the plant rhizosphere system. The hypothesis of the reported research was that, in an organically managed horticultural system, the use of living mulch (LM) promotes the arbuscular mycorrhizal fungi (AMF) colonization among neighboring roots, because of the coexistence of different plants roots in confined soil spaces. This effect determines nutrient uptake optimization, although roots belong to different plant species. In the reported 2-yr field experiment (2012–2013), two Italian artichoke cultivars [Cynara cardunculusL. var.scolymus(L.),Jesinocv. andMazzaferratacv.] were intercropped with a LM mixture of plant species and compared with a no LM control. Every year, the effect of LM on artichoke root morphology and AMF colonization was evaluated by scanning electron microscopy, in order to assess abiotic and biotic rhizosphere interactions, as affected by artichoke cultivars. Also the artichoke yield, the soil available phosphorus (P) and rhizosphere P were determined. Results showed that the LM did not reduce yield of both the artichoke cultivars, when compared with the no LM ones. Furthermore, LM has: (i) induced structural changes in artichoke roots by proliferation of root hairs resulting in an increase of effective absorbing surface; (ii) promoted the rhizosphere mycorrhizal infection which improved P uptake. The modified rhizosphere interactions were found to be cultivar-dependent, being recorded only inJesinoartichoke.

Perturbation Experiments in Community Plant Species during Recovery from Agricultural Abandonment in a Semi-Arid Region of Central-Western Spain

Background: Can high diversity mixtures of later succession plant species be able to suppress early successional (arable weed) species than low diversity species mixtures? Can the removal of plant functional groups have important consequences on the sys-tem stability? Location: The study area was located at 850 m a.s.l., fifteen kilometers (15 km) to the west of Salamanca city, Spain, in a dehesa-like woodland. Methods: The field experiment was installed in Spring 1996 (May). The plots represented former agricultural lands cropped with (a rotation of) monocultures and abandoned right at the beginning of the experiment after the last crop was harvested in 1995. Before in-stalling plots, the fields were harrowed and equalized. The treatments (NC-natural colonization, LD-low diversity seed mixture and HD-high diversity seed mixture) were randomly allocated to the plots in each block. The experiment was organised accord-ing to a block design with five replicate blocks. Within each block, four plots measur-ing 10 × 10 m were marked out and each of the three treatments was randomly as-signed to one plot. All plots were separated by 2 m walkways. Results: The competitive ability of the sown species in different mixtures in LD, valued on the basis of their performance in HD, is a good predictor of their ability to suppress the weed crops spe-cies. This was also corroborated by the high relationship between the efficiency of the sown species in both treatments of species mixture (R2 = 0.51, F (1, 33) = 34.56, P

Strategic use of native species on environmental gradients increases diversity and biomass relative to switchgrass monocultures

Switchgrass (Panicum virgatum) monocultures are a leading feedstock choice for producing cellulosic biofuels. However, in natural stands, switchgrass is only dominant in a narrow ecological niche of the Tallgrass Prairie. This suggests that strategically selected monocultures or binary mixtures of species, adapted to particular ecological niches, might outyield switchgrass monocultures while increasing biodiversity at the field and landscape scales. To test this hypothesis, we planted monocultures of switchgrass and three alternative species at each of three landscape positions (shoulderslope, midslope, and footslope). Alternative species were also mixed with switchgrass such that they composed 33 or 67% of the total number of plants in each plot. Alternative species at each position included a C3 grass, a C4 grass, and a forb. Biomass data were collected in autumn during each of the two consecutive years following the establishment year. At the shoulderslope, the highest-yielding treatments were those containing little bluestem (Schizachyrium scoparium; 12.0Mgha−1) and those dominated by switchgrass (10.4Mgha−1). At the midslope and footslope, there were interactions of year×treatment (p<0.05). In general, the highest-yielding treatments at the midslope were those containing big bluestem (Andropogon gerardii; 16.4Mgha−1). At the footslope in 2013, the prairie cordgrass (Spartina pectinata) monoculture and treatments with at least 67% of the plants being cup plant (Silphium perfoliatum) produced the most biomass (24.3Mgha−1; p<0.05) but there were few yield differences at the footslope in 2014. This research demonstrated that biomass yield of two- and three-year-old stands of monocultures or binary mixtures of native plant species with switchgrass, when appropriately matched to their natural landscape positions, produced biomass in equal or greater amounts than switchgrass monocultures.

The attenuation of current‐ and wave‐driven flow within submerged multispecific vegetative canopies

AbstractHistorically, submerged vegetative canopies have either been reported as or modeled after unispecific examples—communities comprised of only a single vegetative species or element type. Field surveys of a shallow Florida Bay seagrass meadow highlighted a more diverse benthic landscape. Although dominated by Thalassia testudinum, the communities were distinctly multispecific, composed of a mixture of both plant and algal species. Strap‐like seagrass elements defined the upper portion of these canopies (the upperstory) while broad‐bodied algal species were found concentrated close to the bed (the understory). To predict the hydrodynamic implications of this dual‐story canopy structure, we derived a new canopy flow attenuation model, formulated to account for vertical canopy heterogeneities like those seen at our field site. The model was validated through a series of laboratory experiments: multispecific canopy mimics were installed in a current‐wave flume and exposed to a range of unidirectional and oscillatory flows. Mean and fluctuating velocity was measured above and within each canopy to determine vegetation‐induced flow attenuation. Velocities near the bed were markedly reduced through the addition of understory elements, results that were consistent with model predictions. These findings suggest that accurate prediction of flow‐regulated processes like sediment transport and propagule dissemination depends on a thorough accounting of community composition. These properties are also expected to change in response to seasonal variability and episodic environmental stresses.

The influence of boreal tree species mixtures on ecosystem carbon storage and fluxes

Plant species mixtures are often seen as being able to achieve higher productivity and carbon (C) sequestration than their single-species counterparts, but it is unclear whether this is true in natural forests. Here, we investigated whether naturally-regenerated mixtures of common North American boreal tree species were more productive and stored more C than single-species stands. We also examined how closely the different C pools and fluxes were interrelated and whether these relationships varied with species composition. Single- and mixed-species stands of trembling aspen, black spruce and jack pine on mesic sites were selected in two regions of the Canadian boreal forest to assess aboveground and belowground productivity and C storage. Although previous studies conducted in these stands found synergistic effects of tree species mixtures on specific C pools and fluxes, such as higher organic layer C stocks and higher fine root productivity in some mixtures, no effects were detected on combined C pools or fluxes at the ecosystem level in the current study. Aspen abundance was linked with higher aboveground tree productivity, higher aboveground living biomass and higher soil heterotrophic respiration, indicating that aspen acts as a key driver of ecosystem C storage and fluxes in these natural forest ecosystems, more so than species richness. However, our results do not rule out the possibility of increased productivity and C storage in mixed stands under environmental conditions or stand developmental stages that are different from the ones studied here. Furthermore, when the entire forest ecosystem is considered (not only tree parts), synergistic effects of tree species mixtures may be more difficult to observe because the beneficial effect of species mixing on one specific C pool may be counterbalanced by a negative effect on another pool.

Complementarity and selection effects in early and mid‐successional plant communities are differentially affected by plant–soil feedback

Summary Many studies that provided evidence for a positive relationship between plant diversity and productivity have proposed that this effect may be explained by complementarity among species in resources utilization, or selection of particularly productive species in high‐diversity plant communities. Recent studies have related the higher productivity in diverse plant communities to suppression of pathogenic soil biota. If soil biota plays a role in diversity–productivity relationships, the question remains about how they may influence complementarity and selection effects. Here we examine how complementarity and selection effects may depend on soil biota using a plant–soil feedback approach. We used monocultures and mixtures of early successional plant species, which are known to have mostly negative plant–soil feedback effects, and mid‐successional plant species, which generally have neutral plant–soil feedback. We found that plant–soil feedback effects differed between monocultures and mixed plant communities, as well as between early and mid‐successional plants. This resulted in a significant interaction effect between diversity and successional stage. In monocultures, plant–soil feedback tended to be negative for early and positive for mid‐successional plant species. Interestingly, the community feedback responses of the mixed communities were opposite, being positive for early and negative for mid‐successional community. Plant–soil feedback differentially affected complementarity and selection effects of early and mid‐successional plant communities: it enhanced complementarity effects of early and decreased selection effects of mid‐successional species. Synthesis. Soil biota that drive plant–soil feedback effects can influence the diversity–productivity relationship not only through decreased biomass production in monocultures compared to mixtures, but also through influencing complementarity and selection effects among species in mixed plant communities. Our results reveal that biodiversity–productivity relationships depend on plant–soil feedback interactions, which depend on the successional position of the plant. We propose that including successional position and trait‐based analyses of plant–soil feedback in diversity‐functioning studies will enhance understanding consequences of biodiversity loss for productivity and other ecosystem processes.

Arthropod Assemblages Associated with Wild and Cultivated Indigenous Proteas in the Grabouw area, Cape Floristic Region

Control of arthropod pests on indigenous flower crops often has particular challenges. Here we investigate the arthropod species associated with indigenous cultivated Protea species and cultivars in the Cape Floristic Region (CFR), South Africa. Arthropod individuals were collected from various commercial varieties of protea as well as from wild protea plants. Arthropod individuals were recorded directly on plants in the field (for disturbance-sensitive species), as well as from specific plant parts carefully enclosed in plastic bags and taken to the laboratory. Of the arthropod morphospecies recorded, 95.9 % were insects, and the rest mostly mites. A total of 37 % of the individuals could be identified to species level, along with 33 new species records of arthropods on protea plants. Taxonomically, Coleoptera, Lepidoptera, Hymenoptera and Diptera were the most abundant and speciose groups. Structurally complex plants and mixed stands of plant species harboured the most arthropod species. Morphospecies were sorted into guilds, as determined by previous studies. In general, guild structure reflected the complexity of structure of individual plants as well as the mixture of plant species and cultivars, with apparently strong natural enemy activity on complex plants and mixed groups. The free-living, flower visitor guild was the most abundant, with largely beetles contributing to this guild. Endophages were about equal in abundance across all cultivars but less on those with simple structures. From rank abundance curves, a total of 30 % of the arthropod species were categorized as abundant, with the rest (70 %) being rare. Most species were generalists on the various proteas, with some being species or cultivar specialists. A total of 7.26 % species recorded were major pests affecting commercial production of proteas in the CFR. This protea agroecosystem, being composed of plant types being grown in their general native area, resulted in about 93%of the arthropod species being restricted to the Proteaceae, with only 5.6%associated with other South African crops. Even though some of this arthropod assemblage is adverse for protea farming in theCFR, these commercial fields are nevertheless playing a role in biodiversity conservation in the fynbos. The wild proteas supported only intermediate arthropod abundance, suggesting strong, and probably complex, natural regulatory processes at work.

GREEN MANURES IN 'KENT' MANGO ORCHARD

Continuous and intensive use of the soils of the Lower-Middle Sao Francisco River Valley (Vale do Submedio Sao Francisco) through the growing of mango trees in irrigated systems has caused soil degradation and consequently threatened the quality and sustainability of this agribusiness activity in the region. The predominant soil cover in this region has a sandy texture and low organic matter content and water retention capability, which are further compromised by high temperatures and insolation which cause serious restrictions to agricultural productivity when associated with inadequate irrigation management. The aim of this paper was to study crop systems (green manures) used as cover crops and green manure in the establishment of a ?Kent? mango tree orchard by means of quantification and mineral composition of the plant matter resulting from each one of the formative prunings. The leguminous plants used in the intercropped plant mixture were: Calopogonium mucunoide Desv., Crotalaria juncea L., Crotalaria spectabilis Roth., Canavalia ensiformes DC., Cajanus cajan L., Dolichos lablab L., Mucuna aterrina L., and Mucuna conchinchinensis L. The mixture also included non-leguminous species, such as: Sesamum indium L., Chysantemum peruviamum maius, Ricinus communis L., Penissetum americanum L. and Sorghum vulgare Pers. Three plants per plot in four replications were used for evaluations. The mean value of fresh matter production resulting from each one of the four prunings of establishment of the orchard showed that the intercropped plant species mixture with 75% leguminous plants and 25% non-leguminous plants increased plant vigor. Increases were 16.6, 19.7, 45.1 and 23.9% at pruning 1, 2, 3 and 4, respectively, when compared to the treatment of spontaneous vegetation without soil turnover. Significant differences were observed between the treatments in relation to total content of nitrogen, phosphorus, potassium, calcium, and magnesium in the leaves and accumul ated branches at the end of the formative prunings of the plants. The use of intercropped plant species mixtures allows the orchard establishment period to be shortened, which makes it possible to advance the time for beginning management of flower induction and production of mango trees of the Kent cultivar.

No Evidence of Complementary Water Use along a Plant Species Richness Gradient in Temperate Experimental Grasslands

Niche complementarity in resource use has been proposed as a key mechanism to explain the positive effects of increasing plant species richness on ecosystem processes, in particular on primary productivity. Since hardly any information is available for niche complementarity in water use, we tested the effects of plant diversity on spatial and temporal complementarity in water uptake in experimental grasslands by using stable water isotopes. We hypothesized that water uptake from deeper soil depths increases in more diverse compared to low diverse plant species mixtures. We labeled soil water in 8 cm (with 18O) and 28 cm depth (with ²H) three times during the 2011 growing season in 40 temperate grassland communities of varying species richness (2, 4, 8 and 16 species) and functional group number and composition (legumes, grasses, tall herbs, small herbs). Stable isotope analyses of xylem and soil water allowed identifying the preferential depth of water uptake. Higher enrichment in 18O of xylem water than in ²H suggested that the main water uptake was in the upper soil layer. Furthermore, our results revealed no differences in root water uptake among communities with different species richness, different number of functional groups or with time. Thus, our results do not support the hypothesis of increased complementarity in water use in more diverse than in less diverse communities of temperate grassland species.

The impact of grassland management on biogeochemical cycles involving carbon, nitrogen and phosphorus

Grassland introduction into intensively managed agricultural landscapes may enhance soil organic matter (SOM) content and ecosystem services. However, the magnitude of this effect depends on grassland management practices, and their influence on the soil system. The aim of this paper is to highlight these impacts and their consequences for SOM dynamics and element cycling. We focused in particular on the effect of different grassland management practices in terms of grazing regime, fertilization, and species choice. While carbon, nitrogen and phosphorus cycles are more strongly coupled under grassland as compared to permanent cropping, uncoupling of elemental cycles may occur through management intensification. Grazing regime, fertilization and species choice affect elemental coupling and SOM turnover via organic matter input and rhizosphere activity to different extent, thereby resulting in contrasting SOM storage. Grazing may be more beneficial for SOM contents compared to mowing up to a certain animal density depending on soil type and pedoclimatic context. SOM storage may be increased in some cases through specific fertilizer additions, whereas in others no change was observed. Species choice, e.g. high diversity or introduction of legumes, influence element budgets and soil nutrient availability through plant physiological constraints as well as intra-or interspecific interactions. The effect of different plant species mixtures on soil parameters has rarely been elucidated. We conclude that the impact of grassland management practices on SOM of different soil types and the resulting ecosystem services, such as C and nutrient storage need further research in contrasting pedoclimatic contexts. More studies on the controls of belowground biogeochemical cycling of elements are necessary in order to fully understand and manage belowground processes via aboveground plant communities.

Choosing an optimal land-use pattern for restoring eco-environments in a semiarid region of the Chinese Loess Plateau

The natural environments in the semiarid regions of the Chinese Loess Plateau (CLP) are fragile due to the serious soil erosion and the weak ecological services of the plants. To ascertain and then evaluate a sustainable land-use pattern in these regions, we selected six typical land-use patterns (i.e., a farmland, a natural grassland, a homogeneous shrubland (S), a mix of shrubland and cultivated grassland (S–Alf), a mix of shrubland and orchard (S–O) and a mix of shrubland and grassland (S–G)) on the plateau and then measured the soil water, related soil properties and plant root indices to a depth of 1800cm. We also measured the aboveground net primary productivities (ANPPs). The mean soil water content (SWC) within the 0–1800cm profile was significantly highest (15.2%) in farmland, followed by grassland (11.4%) and S–Alf (8.0%). The available water (AW), the ratio between AW and AW capacity, and the thickness of the dried soil layers also demonstrated that farmland had the best conditions of soil water, followed by grassland and shrubland. The aboveground biomasses of grassland in both non-growing (140gm−2) and growing (370gm−2) seasons were significantly higher than those of shrublands. The ANPPs of the grassland (2.0gm−2d−1) demonstrated a similar trend. The patterns of land use (including the mixtures of different plant species) greatly affected the patterns of vertical distribution and quantities of soil water within the 1800-cm profile. The data for the soil–water regime and the ANPP further indicated that grassland would be an optimal use of the land for these semiarid regions. This information should be useful to the ecological scientists and policy makers for developing strategies for the sustainable management of vegetation on the CLP and possibly other water-limited regions around the world.

Remote sensing and GIS analysis for mapping spatio-temporal changes of erosion and deposition of two Mediterranean river deltas: The case of the Axios and Aliakmonas rivers, Greece

Wetlands are among Earth's most dynamic, diverse and varied habitats as the balance between land and water surfaces provide shelter to a unique mixture of plant and animal species. This study explores the changes in two Mediterranean wetland delta environments formed by the Axios and Aliakmonas rivers located in Greece, over a 25-year period (1984–2009). Direct photo-interpretation of four Landsat TM images acquired during the study period was performed. Furthermore, a sophisticated, semi-automatic image classification method based on support vector machines (SVMs) was developed to streamline the mapping process. Deposition and erosion magnitudes at different temporal scales during the study period were quantified using both approaches based on coastline surface area changes. Analysis using both methods was conducted in a geographical information systems (GIS) environment.Direct photo-interpretation, which formed our reference dataset, showed noticeable changes in the coastline deltas of both study areas, with erosion occurring mostly in the earlier periods (1990–2003) in both river deltas followed by deposition in more recent years (2003–2009), but at different magnitudes. Spatial patterns of coastline changes predicted from the SVMs showed similar trends. In absolute terms SVMs predictions of sediment erosion and deposition in the studied area were different in the order of 5–20% in comparison to photo-interpretation, evidencing the potential capability of this method in coastline changes monitoring. One of the main contributions of our work lies to the use of the SVMs classifier in coastal mapping of changes, since to our knowledge use of this technique has been under-explored in this application domain. Furthermore, this study provides important contribution to the understanding of Mediterranean river delta dynamics and their behaviours, and corroborates the usefulness of EO technology and GIS as an effective tool in policy decision making and successful landscape management. The latter is of considerable scientific and practical value to the wider community of interested users, given the continued open access to observations from this satellite radiometer globally.

Plant performance in living wall systems in the Scandinavian climate

Living walls (LW) are a way to increase urban green infrastructure. Previous research has mainly focused on microclimatic cooling effect or the technical functioning of LW, while the development of autochthonous plant species and visual plant aspects for LWs have largely been neglected. In this study we focused on the possibility of establishing LWs by seeding, which is not used very often despite obvious advantages such as low costs, low maintenance requirements, and a high species diversity potential.Within a three-year field study in a temperate oceanic climate, we established a meadow-LW by sowing seed mixtures of >30 species on textile mats without soil substrate. After a pre-growing period with horizontal mats in the greenhouse, we placed the greened mats vertically on experimental walls exposed to the North, South, East, and West. We documented species coverage and visibility over time, growth height, and maintenance steps. After cutting, the vegetation recovered within a few weeks and we recommend one complete cut in summer and removing dead plant material after the frost period.From April to October, we observed an increasing growth height and vegetation coverage reaching >100%, followed by a decline till December. Differences of plant species composition and development between different expositions and study years were observed especially after the cold winter of 2017/2018.This study was able to demonstrate that seeded meadow-LWs can be easily established. The use of autochthonous plant species mixtures can create new biodiverse habitats, are aesthetically attractive and increase human wellbeing.