Basic and Applied Ecology

O_LIIncreasing biodiversity generally enhances productivity through selection and complementarity effects not only in natural but also in agricultural systems. However, explaining why diversity enhances productivity remains a central goal in agricultural science. C_LIO_LIIn a field experiment, we constructed monocultures, 2- and 4-species mixtures from eight crop species with and without fertilizer and both in temperate Switzerland and semi-arid Spain. We measured environmental factors and plant traits and related these in structural equation models to selection and complementarity effects to explain yield differences between monocultures and mixtures. C_LIO_LIIncreased crop diversity increased yield in Switzerland. This positive biodiversity effect was driven to almost same extents by selection and complementarity effects, which increased with plant height and C:N ratio, respectively. Also, ecological processes driving yield increases from monocultures to mixtures differed from those responsible for yield increases through the diversification of mixtures. C_LIO_LIWhile selection effects were mainly driven by one species, complementarity effects were linked to higher productivity per unit N. Yield increases due to mixture diversification were driven only by complementarity and were not mediated through the measured traits, suggesting that ecological processes beyond those measured in this study were responsible for positive diversity effects on yield beyond 2-species mixtures. C_LI

Land-use change and ecological invasion are two main drivers of biodiversity loss, and the restoration of semi-natural wet grasslands is needed to tackle invasive species and re-establish grassland biodiversity on former forest plantations. This study tested the effectiveness of two widely used management techniques (grazing by traditional Hungarian Grey cattle and mowing once a year in August) as a restoration method of wet meadows in a former forest plantation invaded by goldenrod species in Central Hungary. We compared the vegetation composition of grazed, mowed, and reference areas with semi-natural wet meadow vegetation based on plant biomass, species richness and cover of species groups of species origin, life span, growth form, and social behaviour types of Borhidi determining the grazing value and the nature conservation value of the grasslands. We found that grazing by Hungarian Grey cattle resulted in a vegetation that was more similar to the reference wet meadows than mowing once a year in late summer. Grazing was superior to mowing in terms of goldenrod control, total species richness and cover, as well as the abundance of natives, perennials, herbs, and legumes. However, in the grazed area, we detected more disturbance-tolerant and annual species than in the mowed area. Despite the improved vegetation condition in the grazed area, we identified substantial disparities between the grazed and reference areas after three years of grazing. Based on our results, we advise using continuous extensive grazing to restore and maintain semi-natural wet meadows.

AO_SCPLOWBSTRACTC_SCPLOWThe leaf economics spectrum (LES) is based on a suite of leaf traits related to plant functioning and ranges from resource-conservative to resource-acquisitive strategies. However, the relationships with root traits, and the associated belowground plant functioning such as N uptake, including nitrate (NO3-) and ammonium (NH4+), is still poorly known. Additionally, environmental variations occurring both in time and in space could uncouple LES from root traits. We explored, in subalpine grasslands, the relationships between leaf and root morphological traits for 3 dominant perennial grass species, and to what extent they contribute to the whole-plant economics spectrum. We also investigated the link between this spectrum and NO3- and NH4+ uptake rates, as well as the variations of uptake across four grasslands differing by the land-use history at peak biomass and in autumn. Although poorly correlated with leaf traits, root traits contributed to an economic spectrum at the whole plant level. Higher NH4+ and NO3- uptake abilities were associated with the resource-acquisitive strategy. Nonetheless, NH4+ and NO3- uptake within species varied between land-uses and with sampling time, suggesting that LES and plant traits are good, but still incomplete, descriptors of plant functioning. Although the NH4+: NO3- uptake ratio was different between plant species in our study, they all showed a preference for NH4+, and particularly the most conservative species. Soil environmental variations between grasslands and sampling times may also drive to some extent the NH4+ and NO3- uptake ability of species. Our results support the current efforts to build a more general framework including above- and below-ground processes when studying plant community functioning.

Green roofs are considered key elements of the urban green infrastructure since they offer several environmental benefits, including habitat provision for arthropods. To achieve these benefits and ensure green roof success, an appropriate plant selection is an important step in the design of these infrastructures, especially where green roof technology is emerging like in South American cities. So far, decisions of using native or exotic plant species in green roofs had never been evaluated taking into account the plant potential to foster beneficial arthropods. By applying an integrative multicriteria decision framework that combined the habitat template hypothesis with the potential of plants to attract floral visitors and natural enemies, we obtained a ranked set of candidate native and exotic plant species. Among the best-ranked candidate species, we further compared the performance of six native and six exotic species in 30 experimental green roofs installed in Cordoba city, Argentina. To evaluate plant success, the occurrence and cover of each species were recorded one year after establishment under two management conditions: regular watering and weeding of spontaneous plants, and no management (15 roofs each). All selected species increased their vegetative cover one year after establishment. More interestingly, native plants had an advantage over exotic plant species as they exhibited a significantly higher occurrence and a slightly higher cover with no management than exotics. Native annuals were able to reseed the following season even in the absence of management, thus highlighting the relative importance of lifespan as a useful plant trait for future studies in green roof design. Given that green roofs are one of the possible solutions to ameliorate the negative effects of urban habitat loss on arthropod diversity, the development of an integrative multicriteria decision framework that takes into account the potential of native and exotic plant species for promoting beneficial arthropods would give a new twist in plant selection processes for green roofs.

O_LIBiodiverse vegetation that supports high rates of ecosystem functions can inherently express a messy appearance due to high numbers of local native plant species and their spatial distribution connected to niche complementarity. This messiness is assumed to lower peoples appreciation for vegetation in urban contexts. Since such vegetation and a positive relationship between people and biodiversity could contribute to mitigating biodiversity loss, this assumed low public appreciation warrants investigation. C_LIO_LIWe designed and constructed biodiverse flowerbeds using only local native plants, and with the intention to enhance planting productivity, resistance and resilience. To investigate the influence of messiness, we created flowerbeds in four high levels of species richness (8,12,16,20) shown to be relevant for ecosystem functioning, and three levels of order (no, semi, full). We tested public appreciation for the flowerbeds using a self-guided, on-site survey. C_LIO_LIWe found a positive mean rating for all flowerbeds, but no effect of species richness on the ratings. Increased order, however, had a strong negative effect: The odds of a fully ordered flowerbed receiving a negative rating were 88% higher than of a flowerbed with no order. Increasing designed order was correlated with decreasing plant biomass in the flowerbeds. C_LIO_LIThese findings challenge the assumption that the appearance of biodiverse plantings is too messy for public appreciation in urban contexts. Specifically, we demonstrate that introducing order and reducing messiness can compromise aesthetic appreciation for biodiverse vegetation, potentially by compromising productivity as indicated by lower biomass production in ordered plantings. C_LI Synthesis and applicationOur study shows that biodiverse vegetation can be appreciated in urban contexts. Flowerbeds can effectively serve both people as ornamentation and biodiversity as habitat when they are designed based on ecological principles Research highlightsO_LIWe designed and realized flowerbeds based on ecological principles. C_LIO_LIAll plantings received positive average ratings. C_LIO_LIIncreasing species richness in the flowerbeds did not affect participants aesthetic appreciation. C_LIO_LIIncreasing order in the design of the flowerbeds strongly lowered participants aesthetic appreciation. C_LIO_LIIncreasing order in the design was correlated to lower biomass productivity and more bare soil in the flowerbeds. C_LI

The global ornamental plant trade is well-known as an important source of alien plants, but the unintentional dispersal of seeds as contaminants of this trade is rarely considered and largely understudied. We sampled the substrate of imported container-grown plants in several garden centres in Hungary to answer the following questions: (i) What species seeds are present in the substrate of imported garden plants and in what quantity? (ii) Do the substrates of plants imported from different countries contain seeds in different density and composition? (iii) Do characteristics of the host garden plants affect the number and diversity of seeds found in their substrate? We detected altogether 2,181 seeds of 80 taxa in the substrates. On average, 1 litre of substrate contained 36 seeds of five species. Most species were alien in Hungary and considered invasive in Europe. The majority of samples contained at least one seed of a species invasive in Europe. We found that the substrate of plants imported from different countries contained seeds in different number, diversity, and composition. Thus, the structure of the horticultural trade network can shape the alien flora of importing countries. Furthermore, the substrate of needle-leaved ornamental species contained more seeds than the substrate of broad-leaved ornamentals. Our findings demonstrate that the ornamental plant trade can disperse a large number of seeds of numerous species and introduce alien species into the importing countries. We conclude that this introduction pathway deserves greater attention in invasion biology and more studies of this phenomenon are urgently needed.

Studying the relationship between biodiversity patterns and processes in vegetation has been at the centre of interest in vegetation ecology for several decades. By studying the biomass of loess and alkaline grasslands along a water and salinity gradient, we aimed to analyse species diversity and CSR functional type patterns. We aimed to test the following hypotheses: i) The biomass and species richness scores and the species composition are significantly different between the sampled grassland community types. ii) The sampled communities are well separated based on the CSR strategy spectrum. iii) The amount of green biomass and litter are positively correlated with competitiveness and negatively with stress tolerance. The biomass and species richness scores and the species composition of the sampled communities along the sampled gradients were significantly different; the highest species richness, evenness and Shannon diversity values were found in loess grasslands. The highest level of litter accumulation was found in alkaline meadows. The communities were well separated in the ordinations but surprisingly, calculation of coordinates for CSR strategy types have not shown clear separation of the grassland community types. Based on the results we can conclude that the current CSR classification is too robust to delineate grassland communities in alkaline landscapes which are markedly different in composition. We point out that the CSR classification is based on the magnitude of stress, and it is not able to differentiate between the various forms of stress which might be responsible for the marked compositional differences. Therefore, developing an index focusing specifically on the functional characterisation of stressed communities and able to differentiate between different forms of stress (e.g., water and/or salinity stress) would be highly beneficial for future studies.

Sowing grass seeds generally supports the rapid development of a closed perennial vegetation, which makes the method universally suitable for fast and effective landscape-scale restoration of grasslands. However, sustaining the recovered grasslands, and increasing their diversity is a challenging task. Understanding the role of seed bank compositional changes and vegetation dynamics contributes to designating management regimes that support the establishment of target species and suppress weeds. Our aim was to reveal the effect of post-restoration management on the vegetation and seed bank dynamics in grasslands restored in one of the largest European landscape-scale restoration projects. Eight years after restoration we sampled the vegetation and seed bank in a total of 96 plots located in 12 recovered grasslands in the Great Hungarian Plain. In each recovered grassland stand we designated a mown (mown from Year 1 to Year 8) and an abandoned sample site (mown from Year 1 to Year 3 then abandoned from Year 4 to Year 8). Mown and abandoned sites showed divergent vegetation and seed bank development. Abandonment led to the decline of sown grasses and higher cover of weeds, especially in the alkaline grasslands. Our study confirmed that seed bank has a limited contribution to the maintenance of biodiversity in both grassland types. We found that five years of abandonment had a larger effect on the seed bank than on the vegetation. We stress that long-term management is crucial for controlling the emergence of the weeds from their dense seed bank in restored grasslands. Implications for practiceO_LISeed sowing of grass mixtures can be a feasible tool for restoring grasslands at large scales. However, the developed vegetation usually has low biodiversity and a high seed density of weeds is typical in the soil seed bank even several years after the restoration. Therefore, post-restoration management is necessary for suppressing weeds both aboveground and belowground. C_LIO_LIWe recommend to design the long-term management of the sites subjected to grassland restoration already in the planning phase of the restoration projects and ensure that the management plan is ecologically and economically feasible. C_LIO_LIWe recommend to complement the monitoring of vegetation with the analysis of soil seed bank for evaluating restoration success. C_LI

In recent decades, restoring abandoned wood pastures are being rediscovered as an effective way to preserve biodiversity. Their restoration include the control of invasive plant species. In our study, we compared the vegetation composition of wet meadow patches uninvaded and invaded by giant and Canadian goldenrod in a wood pasture located in Somogyfajsz, Hungary. We sampled the vegetation of the wet meadows of the pasture in 16 pairs of 1 x 1 m invaded and uninvaded quadrats in June 2020. We studied the effect of goldenrod invasion on nature conservation value in terms of species diversity, origin of species, and Social Behaviour Types, and forage quality and quantity. The study revealed that goldenrod invasion had negative effects on species richness and community-level biomass in wet meadows, leading to a significant reduction in species diversity and total cover. Goldenrod invasion also impacted the richness and cover of both native and exotic species, with a decrease in richness but not cover, highlighting the competitive ability of goldenrods and their potential to alter vegetation composition.

Widespread campaigns on forest restoration and various tree planting actions lower the awareness of the importance of grasslands for carbon sequestration or biodiversity conservation. Even lower attention is given to the conservation of biodiversity and ecosystem functioning in remnants of ancient, so called old-growth grasslands. Old-growth grasslands in general harbour high biodiversity and even small patches of these can act as important refuges for many plant and animal species in urbanised or agriculture driven landscapes. Spontaneous succession of grassland is frequently viewed as a cost-effective tool for grassland restoration, but its applicability is strongly dependent on many local to landscape-scale factors and the recovery often slow. Thus, for the assessment of the effectiveness of spontaneous succession as a restoration tool, it is essential to compare the species diversity and functional attributes of old-growth and secondary grasslands. We studied the taxonomic and functional diversity in thirteen loess steppic grasslands (8 old-growth and 5 secondary) using differently sized plots ranging from 0.01 to 100m2. Our results indicated that there are remarkable differences in taxonomic and functional diversity between old-growth grasslands and secondary ones. We also point out that during secondary succession there is a likely functional saturation of the species assembly in the first few decades of recovery, and while patterns and structure of secondary grasslands became quite similar to those of old-growth grasslands, the species richness and diversity remains still much lower. Old-growth grasslands support considerable plant diversity, and species composition is slow to recover if destroyed for agricultural land use. This underlines the priority of protecting existing old-growth grassland remnants over restoration actions and the recovery of secondary grasslands.

The growing global horticultural trade is having a steadily increasing impact on the rate at which alien species are introduced into new areas, partly because horticultural trade also entails the unintentional dispersal of many contaminant species. Although there are reports about noteworthy occurrences of alien plant species in garden centres, this phenomenon has hardly been studied systematically. To bridge this knowledge gap, we conducted systematic field surveys in 12 garden centres in Hungary to assess their alien flora. We hypothesised that (i) the number of alien species inhabiting a garden centre is positively correlated with its size, (ii) relative to their size, garden centres host a disproportionately large proportion of the local alien flora, and (iii) alien species inhabiting garden centres differ from the regional alien flora in their traits. We recorded altogether 93,788 individuals of 67 introduced species, seven of which have not yet been reported from the country. There was considerable variability in the number of species and individuals found in each garden centre, but there was no correlation between the size of the garden centres and the number of species they host. Despite their relatively small size, the studied garden centres hosted a considerable proportion of the local alien flora, indicating that they strongly accumulate alien species and that they can act as invasion hubs for several alien species. Alien species inhabiting garden centres differed from the regional alien flora in some of their trait values, indicating that the species that are most successful at establishing populations inside garden centres are both good dispersers and possess an effective resource-acquisitive strategy. We conclude that established alien plant populations in garden centres may induce local invasions, and in the meantime, individuals and seeds inside the containers of ornamental plants are regularly transported to distant areas by the customers. Therefore, plant species dispersed as contaminants of horticultural stock need to be better considered in invasion biology to reduce the threat they may present.

Plant-plant competition is ubiquitous in nature. However, studying below ground behaviour of roots has always posed certain difficulties. Pea (Pisum sativum L.) has become a sort of model species for ecological studies about how plant roots respond to neighbouring plant roots and barriers in soil. However, published results point in several different directions. This has sometimes been interpreted as pea having sophisticated context dependent responses that can change in complex ways depending on its surroundings. To explore this further, here, we combine the result of five new experiments with published results to examine 18 unique experiments from 7 different studies for a total of 254 replicates. We used a Bayesian hierarchical meta-analysis approach to estimating the likely effect size from the available data, as well as quantify heterogeneity among different experiments, studies and cultivars. The posterior distributions show that, at the coarsest possible scale of total root production, it is unlikely that P. sativum root growth is influenced by either neighbours or barriers to root growth imposed by the walls of pots that vary in volume. We suggest that further work should consider repeating experiments that reported finer scale root plasticity in pea at the rhizosphere scale, and also consider alternative model species for the study of plant root responses to external cues.

For the effective control of an invasive species, gathering as much information as possible on its ecology, establishment and persistence in the subjected communities is of utmost importance. We aimed to review the current distribution and characteristics of Sporobolus cryptandrus (sand dropseed), an invasive C4 grass species of North American origin recently discovered in Hungary. We aimed to provide information on (i) its current distribution paying special attention to its invasion in Eurasia; (ii) the characteristics of the invaded habitats in Central Europe; (iii) seed bank formation and germination characteristics, crucial factors in early establishment; and (iv) the effects of its increasing cover on vegetation composition. Finally, we aimed to (v) point out further research directions that could enable us to understand the invasion success of this potential invasive species. Field surveys uncovered large stands of the species in Central and Eastern Hungary with most of the locations in the former, especially the Kiskunsag region. The species invaded disturbed stands of dry and open sand grasslands, closed dune slack grasslands and it also penetrates into natural open sand grasslands from neighbouring disturbed habitats. Increasing cover of Sporobolus cryptandrus caused a decline in species richness and abundance of subordinate species both in the vegetation and seed banks, but a low density of Sporobolus cryptandrus can even have a weak positive effect on these characteristics. Viable seeds of Sporobolus were detected from all soil layers (2.5 cm layers measured from the surface to 10 cm in depth), which indicates that the species is able to form a persistent seed bank (1,114 to 3,077 seeds/m2 with increasing scores towards higher abundance of the species in vegetation). Germination of Sporobolus cryptandrus was negatively affected by both litter cover and 1 cm deep soil burial. To sum up, Sporobolus cryptandrus can be considered as a transformer invasive species, whose spread forms a high risk for dry sand and steppe grasslands in Eurasia. We can conclude that for the effective suppression of the species it is necessary: (i) to clarify the origin of the detected populations; (ii) to assess its competitive ability including its potential allelopathic effects; (iii) to assess its seed bank formation potential in habitats with different abiotic conditions; and (iv) to assess the possibility of its suppression by natural enemies and management techniques such as mowing or livestock grazing.

Spontaneous plant communities have undergone considerable constraints due to human-mediated changes. Understanding how plant communities are shifting in response to land management and climate changes is necessary to predict future ecosystem functioning and improve the resilience of managed ecosystems, such as agroecosystems. Using Mediterranean weed communities as models of managed plant communities in a climate change hotspot, we quantified to which extent they have shifted from the 1980s to the 2020s in response to climate and management changes in vineyards. In four decades, the annual range of temperatures (i.e. the difference between the warmest months and the coldest months mean temperatures) increased by 1.2{degrees}C and the summer temperatures by 2{degrees}C. Weed management diversified over time with the adoption of mowing that replaced the chemical weeding of inter-rows. Current weed communities were 41% more abundant, 24% more diverse and with a less even distribution of abundance across species than the 1980s communities at the vineyard level. Modern communities were composed of more annual species (57% of annual species in the 1980s versus 80% in the 2020s) with lower lateral spreadability and seed mass and were composed of fewer C4 species. They had higher community-weighted specific leaf area, higher leaf dry matter content and lower leaf area than 1980s weed communities. At the community level, the onset of flowering was earlier and the duration of flowering was longer in the 2020s. Climate change induced more stress-tolerant communities in the 2020s while the diversification of weed management practices over time filtered less competitive communities. This study shows that plant communities are adapting to climate change and that land management is a strong lever for action to model more diverse and functional plant communities in the future.

O_LIPlants take up nutrients from the soil while investing in absorptive root surface or mycorrhizal partners. Root hairs - a major structure for nutrient uptake and cheap to build - increase the absorptive root surface. As such they are an important component of plant resource economics but largely neglected in root economic concepts so far. C_LIO_LIThis is mainly due to data scarcity, which we set out to overcome by measuring root-hair traits on 82 European grassland species in a greenhouse experiment. Using fluorescence and light microscopy, root-hair length and incidence was measured along with mycorrhizal colonization. C_LIO_LIWe found a phylogenetically conserved trade-off between plant investment into root hairs and mycorrhiza. A similar trade-off between root-hair incidence and mycorrhiza occurred at the intraspecific level, while patterns were heterogeneous among species. Plant species with high colonization rates showed the highest variability in root-hair incidence. C_LIO_LIWe conclude that plants vary along a gradient ranging from investment into root hairs as part of a "do-it-yourself" strategy to collaboration with mycorrhizal fungi while showing intraspecific variation in root-hair incidence. These findings demonstrate that root hairs play a fundamental role in fine-root trait variation and need to be considered when studying belowground plant economic strategies. C_LI

Understanding how human land-uses impact on local communities is required to implement management and conservational policies and practices. Tree plantations have become one of the fastest-growing land uses in recent decades and their impact on biodiversity was evaluated mainly at the taxonomic level. Our aim was to analyze the effects of changes in environmental drivers along the 12 years eucalypt plantations chronosequence on alfa, beta, taxonomic and functional diversity of understory plant communities. We selected nine plantation ages with three replicates per age and three protected grasslands as reference habitat. At each replicate, we established three plots to measure plant species cover and environmental variables, which are expected to change with plantation age. Results showed that species richness and all diversity indices significantly declined with increasing plantation age. Canopy cover, soil pH, and leaf litter were the most important drivers that explained the decline in taxonomic and functional diversity of plants through the forest plantation. Based on the Path analyses results, canopy cover had an indirect relationship with plant functional diversity mediated by leaf litter, soil pH and plant species richness. The results of the association between functional traits and environmental variables have revealed that high dispersal potential, annual, barochorous, and zoochorous plant species were the functional traits more affected by the eucalypt plantations. Given that leaf litter was negatively associated with all diversity facets, we recommend reducing their accumulation within eucalypt plantation to enhance biodiversity conservation and the provision of pampean grassland ecosystem functions.

Invasive plant species often exhibit greater growth and lower anti-herbivory defense than native plant species. However, it remains unclear how nutrient enrichment of invaded habitats may interact with competition from resident native plants to affect growth and defense of invasive plants. In a greenhouse experiment, we grew five congeneric pairs of invasive and native plant species under two levels of nutrient availability (low vs. high) that were fully crossed with simulated herbivory (clipping vs. no-clipping) and competition (alone vs. competition). Invasive plants produced more gibberellic acid, and grew larger than native species. Nutrient enrichment caused a greater increase in total biomass of invasive plants than of native plants, especially in the absence of competition or without simulated herbivory treatment. Nutrient enrichment decreased leaf flavonoid contents of invasive plants under both simulated herbivory conditions, but increased flavonoid of native plants under simulated herbivory condition. Nutrient enrichment only decreased tannins production of invasive species under competition. For native species, it enhanced their tannins production under competition, but decreased the chemicals when growing alone. The results indicate that the higher biomass production and lower flavonoids production in response to nutrient addition may lead to competitive advantage of invasive species than native species.

Understanding functional traits that capture species response to grazing is crucial for uncovering mechanisms underlying the grazing-induced alterations in vegetation composition. Currently, the majority of studies ignore the effects of life form on the response of above- and below-ground traits to grazing. In this study we quantified i) whether below-ground traits exhibit similar response to overgrazing as do above-ground traits; and ii) whether the response of above- and below-ground traits to overgrazing varied with life form (annual versus perennial species). To testify the generality of these two questions, we compared common grassland species between an undisturbed and an over grazed meadow at each of four elevations ranging from 3000m to 3600m on the Qinghai Tibetan Plateau. We found both above-ground and below-ground traits exhibited similar resource conservation vs. resource acquisition trade-off for responding to overgrazing. Moreover, perennial species but not annual species determine the response of above- and below-ground traits to overgrazing. This work bridges the gap in the literature for the influence of land-use (in the absence and presence of overgrazing) and life forms (annual and perennial species) on species-specific response at both above-, and below-ground level.

O_LIDrainage canals are ubiquitous components of agricultural landscapes worldwide. Although canals have greatly contributed to biodiversity loss by desiccating wetlands, they have recently attracted conservation attention due to their potential to function as refugia for native wetland-dependent species in intensively managed landscapes. However, their conservation role in complex landscapes comprising a mosaic of agricultural and desiccated semi-natural habitats, on which canals still pose a heavy burden, is unknown. Improved understanding of drainage canals and related biodiversity in these landscapes could help unlock their potential and support synergistic land management for nature conservation and water management. C_LIO_LIWe applied a multitaxon approach, including plants, butterflies, true bugs, spiders and birds, to (1) assess the conservation value of drainage canals in a heavily drained European lowland region, (2) to test landscape-level and local canal parameters for aiding prioritization among canal types, and (3) to propose a reconciliation-based management framework that suits the interest of all stakeholders. C_LIO_LIWe found that drainage canals concentrate more species across most taxa than adjacent semi-natural habitats, owing to the micro-environmental heterogeneity and the comparatively low management intensity in the canals. The species-concentrating capacity is particularly high in canals that traverse semi-natural habitats, although agricultural canals also support remarkable species diversity. However, agricultural canals are important dispersal corridors for invasive plants, which may negatively affect native species. Canal size has little effect on biodiversity but habitat stress is an important determinant. The higher the stress (due to sandiness and salinity), the higher is the added value of canals to landscape-wide biodiversity. C_LI Synthesis and applicationsWe provide evidence that drainage canals can harbour surprisingly high levels of biodiversity and should therefore be recognized as important novel ecosystems with high conservation value, even within semi-natural habitats. Canals have previously been considered detrimental to nature conservation due to their association with loss of wetlands. However, by reducing water loss with reversible obstructions, controlling invasive species and applying specific conservation measures, they may be turned into conservation allies without compromising long-term interests of water management and agricultural land use.

Nitrogen is often a limiting factor for plant growth, and its availability is a major determinant of level of competition. In clonal plants, patterns of nitrogen translocation between ramets may be part of plant nitrogen economics, and, as such, may also be related to the typical availability of nitrogen. In nutrient-poor habitats, extensive nutrient sharing balancing resource availability may be important, whereas nutrient sharing between established ramets may not be beneficial in productive habitats. I tested the proposed nutrient sharing strategies on nitrogen translocation in six stoloniferous species that occur in habitats of varying productivity. Mother and daughter ramets of each species were grown either in a homogeneous nutrient-poor treatment or in a "nutrient-poor to nutrient-rich" treatment. I traced the translocation of nitrogen in both directions using stable isotope labelling when the daughter ramets were one month old. Surprisingly, I found no effect of nutrient treatment on nitrogen translocation. Instead, each species translocated nitrogen either acropetally, basipetally, or equally in both directions. There was no relationship between the direction of translocation and the productivity of the species habitats. However, net translocation seemed to be related to the relative size of daughters across species, and within Veronica officinalis. The results suggest that the relative size of plant parts is an important determinant of the strength of the sink for nitrogen they form, and that the growth habit of a species can affect its nitrogen translocation. Under certain conditions, such internally induced source-sink relationships may dominate over external nitrogen heterogeneity. I speculate that growth habit, together with nitrogen translocation patterns, may be part of adaptive growth strategies.