One of the main questions in ecosystem restoration is where to obtain the seeds to re-establish plant communities. While the most commonly advocated approach is to use seeds from local sources, some ...experts argue against this because local populations may harbour little genetic variability for the restored populations to be able to adapt to and survive global change. Instead, they propose alternative strategies such as mixing seeds from various sources to increase genetic variability and adaptive potential, or using seeds from populations that have a similar climate as predicted for the target locality in the future. All these alternative seed-sourcing strategies have in common that they involve a transplanting of plant ecotypes, sometimes over large spatial scales. This is risky because plants from distant origins may be maladapted to the current local abiotic and biotic environment. In addition, introduction of non-local provenances will disrupt natural patterns of within-species biodiversity and will affect ecological networks, with unpredictable consequences. To balance the value of local adaptation with the need for future adaptation potential, we propose ‘regional admixture provenancing’ as a compromise strategy. Here seeds are sourced from multiple populations within the same region as the target locality and mixed prior to use. The mixing of seeds will increase the genetic diversity necessary for future adaptation, while restricting seed origins to a regional scale will maintain regional adaptation and reduce the risk of unintended effects on other biota. This approach is feasible in practice and has recently been implemented in Germany. We believe that it represents a compromise to reconcile opposing views on ecological restoration.
Vast amounts of cultivars of native plants are annually introduced into the semi-natural range of their wild relatives for re-vegetation and restoration. As cultivars are often selected towards ...enhanced biomass production and might transfer these traits into wild relatives by hybridization, it is suggested that cultivars and the wild × cultivar hybrids are competitively superior to their wild relatives. The release of such varieties may therefore result in unintended changes in native vegetation. In this study we examined for two species frequently used in re-vegetation (Plantago lanceolata and Lotus corniculatus) whether cultivars and artificially generated intra-specific wild × cultivar hybrids may produce a higher vegetative and generative biomass than their wilds. For that purpose a competition experiment was conducted for two growing seasons in a common garden. Every plant type was growing (a.) alone, (b.) in pairwise combination with a similar plant type and (c.) in pairwise interaction with a different plant type. When competing with wilds cultivars of both species showed larger biomass production than their wilds in the first year only and hybrids showed larger biomass production than their wild relatives in both study years. As biomass production is an important factor determining fitness and competitive ability, we conclude that cultivars and hybrids are competitively superior their wild relatives. However, cultivars of both species experienced large fitness reductions (nearly complete mortality in L. corniculatus) due to local climatic conditions. We conclude that cultivars are good competitors only as long as they are not subjected to stressful environmental factors. As hybrids seemed to inherit both the ability to cope with the local climatic conditions from their wild parents as well as the enhanced competitive strength from their cultivars, we regard them as strong competitors and assume that they are able to outperform their wilds at least over the short-term.
Native plants are increasingly used for revegetation and restoration. These plants are cultivated for several generations at plant nurseries and often they are of unknown provenance. Therefore, ...cultivated plants often differ from their wild progenitors in life‐history traits. Using germination behavior as example, we tested the assumption that cultivated plants have different life‐history traits than their uncultivated progenitors. Cultivated as well as wild individuals of Plantago lanceolata and Lotus corniculatus, two species frequently used in revegetation, were tested in a common garden experiment as well as in incubators for their germination behavior. We observed significantly faster and more abundant germination in cultivated varieties. Using artificial crossings, we found that also hybrids of cultivated varieties and wild relatives germinate faster and more abundant than the wilds. As wild plants acquire their life‐history traits by natural selection, we have to assume that they represent the optimal adaptation to the environmental conditions. If these traits are changed by cultivation or by hybridization between cultivated varieties and local populations, the long‐term survival probabilities of local populations may be altered. Therefore, the use of cultivated varieties of native plants should be avoided in revegetation.
The timing of seedling emergence may strongly affect fitness in competitive environments. Therefore, selection should favour mechanisms that allow sensing neighbours prior to emergence. We tested ...whether or not germination is affected by density and identity of neighbouring seeds or seedlings of desert perennial plants. Based on theory, we predicted that germination fractions are independent of neighbouring seeds, that germination is accelerated in dense interspecific neighbourhoods, and neighbour effects are caused by seedlings, not by seeds. We examined germination fraction and timing of four naturally coexisting sandy desert perennial species in low versus high seed densities in both intra- and interspecific neighbourhoods, and with and without removal of newly emerged seedlings. Neighbours accelerated germination independent of density and this pattern was apparently caused by the presence of early emerging seedlings. Germination fractions were lower in high seed densities even when neighbours did not germinate, indicating that seeds were able to sense each other prior to emergence. Early germination may be adaptive because fast emerging seedlings may gain a competitive edge over slow emerging ones. However, since seeds that did not germinate died, delayed germination may only be advantageous for mother plants when sib competition is intense. Another key finding was a competitive hierarchy with late successional species germinating faster and inhibiting germination of pioneer species. This indicates that successional processes may be directed as early as during germination.
•We analyzed plant species richness in green spaces with a multivariable approach.•Species groups were affected most by different combinations of driving factors.•Green space size was most relevant ...factor driving vascular plant species richness.•Patch shape and distance to the urban edge were of minor relevance.•Urban green spaces larger than 6ha should be given priority in being conserved.
Many studies have shown high vascular plant species richness in urban areas and, especially, in its green spaces. However, little is known about the factors driving the numbers and proportions of different species groups. The aim of our study was to test for the effects of patch size, patch shape, and distance to the urban edge as well as the combined effects of these factors on the numbers and proportions of total, native, non-native, endangered, ornamental, and nitrophilous vascular plant species. We conducted vascular plant surveys in 32 urban green spaces in the city of Hannover, Germany. We detected positive correlations between patch size and total, native, non-native, endangered, ornamental, and nitrophilous vascular plant species numbers and the proportion of endangered species by Spearman's rank correlations and linear regressions. A more compact patch shape, calculated by the shape index, affected the proportion of native, non-native, and ornamental species positively. Testing combined effects of factors with multiple linear regressions underlined the importance of patch size in combination with distance to the urban edge, and in combination with distance and patch shape. We conclude that in the context of recent urbanization processes, it is most important to create and conserve large urban green spaces (>6ha) in order to maintain vascular plant species richness. As species groups were affected most by different combinations of driving factors, our study highlights the importance of using multivariable approaches for detecting effects more precisely.
•Cultivated varieties considerably differed in life-history traits from their wild relatives.•Wild plant species coped better with local climatic conditions than their cultivated ...varieties.•Wild×cultivar hybrids showed heterosis effects for survival and generative biomass production.•The use of cultivated varieties of native plants should be avoided in re-vegetation.
Cultivated varieties may have life-history traits which are very different to those of their wild progenitors. Changes in life-history traits due to cultivation may not be desirable for plant material used for re-vegetation, as these plants may be adapted to constant human care and lack the finely tuned trade-off that allows wild plants to cope with the often harsh and heterogeneous environmental conditions outside of nurseries. Research is needed to identify differences in life-history traits between cultivated varieties used in re-vegetation and restoration and their wild relatives. If such traits are changed by cultivation, it is necessary to examine if they will persist also at the re-vegetation site and may be transferred to wild relatives by hybridization as that may reduce their survival or lead to undesirable changes on local ecosystems.
In this study we examined whether cultivated varieties of Plantago lanceolata and Lotus corniculatus, two species frequently used in re-vegetation and restoration projects, differ from their wild relatives in morphology or flower phenology and whether differences could be transferred into wild relatives by hybridization. We tested if cultivated varieties are bred for high vegetative and generative yield in greenhouse studies. In common garden experiments we studied if the detected enhanced biomass production is persistent under the climatic conditions of the wild plant's natural habitat in Central Europe. Additionally, we tested if hybrids show effects of outbreeding depression or heterosis.
The cultivated varieties of both species grew very vigorously and showed a more erect growth pattern than their wild relatives. The cultivated varieties seem to be selected toward high vegetative and generative yield. However, if exposed to local climatic conditions, cultivated varieties suffered a fitness loss with a complete mortality for the L. corniculatus cultivar and a reduced vegetative biomass production for P. lanceolata cultivars. On the other hand, we detected heterosis effects in hybrids for survival and generative biomass production in L. corniculatus and number of leaves in P. lanceolata. As it remains possible that the use of cultivated varieties may result in strongly competitive genotypes or reduced local adaptation of wild plant populations (via hybridization), large-scale use of cultivated varieties of native plants should be avoided in re-vegetation and restoration.
Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short ...life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear.
We used a trait‐based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large‐scale rainfall gradient.
Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large‐scale rainfall gradient.
Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals.
This study builds towards a better understanding of grazing response strategies of winter annual plants in drylands. Using a trait‐based approach, we showed that annuals exhibit both grazing escape and tolerance. Our findings indicate that annuals with pronounced escape traits are convergently favoured by drought and grazing, suggesting that they will increase under global change, decreasing forage production.
Urban green spaces provide habitat for numerous plant and animal species. However, currently we have little knowledge on which determinants drive the species richness within and across taxonomic ...groups. In this paper we investigate the determinants of total, native, and endangered species richness for vascular plants, birds, and mammals within and across taxonomic groups. We examined a stratified random sample of 32 urban green spaces in Hannover, Germany. Species inventories for plants and birds were generated on the basis of line transect surveys. Mammals were surveyed by means of point counts using camera traps. Using a principal component analysis and multiple regression models, we tested 10 explanatory variables for species-area effects, distance effects, and the effects of habitat structure of green spaces on species richness. When analyzing single explanatory variables, we determined that the species richness of all groups was significantly positively correlated to patch area, number of habitat types, and a short distance to the nearest green space. Testing combined effects of variables showed that patch area in combination with habitat heterogeneity was most important for plants (total, native, and endangered), birds (total and native), and overall species richness. This emphasizes the importance of the species-area effect and the effects of habitat structure on species richness in urban green spaces. We conclude that, in the context of urban planning, it is important to conserve large green spaces that include a high diversity of habitats to maintain high species richness.
Surface run-off and erosion are the major contributors to soil degradation worldwide. These processes are especially severe in regions with sparse vegetation cover. A 2-year experiment was set up ...along an aridity gradient in Al-Khalil, Palestine, to quantify soil loss and water loss from arable fields and to test for the mitigating effect of native perennial filter strips in arable fields. Three useful native plant species were chosen as intercrops: Majorana syriaca, Salvia fruticosa and Salvia hierosolymitana. The water and soil losses were experimentally measured in all the treatments. The results showed that considerable amounts of water (223–288 m3) and soil (3.2–5.6 ton ha−1) are lost from the fields. However, both total run-off and erosion were strongly reduced when the annual crop was intercropped with strips of native perennial plants (NPPs). The filter strips reduced the run-off by 34–89% and soil loss by 45–94%. This effect was more pronounced at the drier part of the studied sites and during the drier season. Our study implies that using filter strips of NPPs is a beneficial strategy for reducing run-off and soil erosion in the semi-arid regions of east Mediterranean.
•We introduced an intercropping practice for reducing land degradation in the arid–semi-arid regions.•The surface run-off and soil erosion could be reduced by strips of useful native perennial plants (NPPs).•The efficiency of the intercropping system is consistent under different amounts of annual precipitation.•The efficiency of the intercropping system does not depend on the intercrop species.
Microbiotic crusts are a common and widespread feature of arid and semi-arid landscapes. Their effect on vascular plant success has been discussed controversially. However, only very few field ...studies have yet tried to experimentally investigate the effect of microbiotic crusts on vascular plant establishment. In this study we investigate the influence of cyanobacteria dominated microbiotic soil surface crust on vascular plants in a desert sand dune area by using a series of manipulative experiments. Crusts were disturbed and removed and density response to these treatments was monitored during the two following years. Emergence densities of vascular plants were considerably higher when crusts were removed and destroyed. This effect was particularly pronounced when the disturbances were applied before the main seed dispersal period. By experimentally preventing seed dispersal into disturbed areas we could show that undisturbed crusts reduce the probability for seeds to come to rest. This indicates that soil surface roughness is a major determinant for the establishment of vascular plants in the study area. We conclude that small-scale and well-timed disturbances of microbiotic crusts in arid lands may increase vascular plant establishment probabilities. A potential feedback process of long-term vegetation dynamics is suggested: disturbance of microbiotic crusts results in higher numbers of emerging plants, which in turn represent a rough seed-trapping element leading to a further increase in densities in consecutive years.
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