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The use of biomass from forest harvesting residues or stumps for bioenergy has been increasing in the northern European region in the last decade. The present analysis is a regional review from Nordic and UK coniferous forests, focusing on the effects of whole-tree harvesting (WTH) or whole-tree thinning (WTT) and of WTH followed by stump removal (WTH + S) on the forest floor and mineral soil, and includes a wider array of chemistry data than other existing meta-analyses. All intensified treaments led to significant decreases of soil organic carbon (SOC) stock and total N stock in the forest floor (FF), but relative responses compared with stem-only harvesting were less consistent in the topsoil (TS) and no effects were detected in the subsoil (SS). Exchangeable P was reduced in the FF and TS both after WTT and WTH, but significant changes in exchangeable Ca, K, Mg and Zn depended on soil layer and treatment. WTH significantly lowered pH and base saturation (BS) in the FF, but without apparent changes in cation exchange capacity (CEC). The only significant WTH-effects in the SS were reductions in CEC and BS. Spruce- and pine-dominated stands had comparable negative relative responses in the FF for most elements measured except Mg and for pH. Relative responses to intensified harvesting scaled positively with growing season temperature and precipitation for most variables, most strongly in FF, less in the TS, but almost never in the SS, but were negative for P and Al. The greater reduction in FF and TS for soil organic carbon after intensive harvesting decreased with time and meta-regression models predicted an average duration of 20–30 years, while many other chemical parameters generally showed linear effects for 30–45 years after intensified harvesting. Exchangeable acidity (EA), BS and pH all showed the reversed effect with time, i.e. an initial increase and then gradual decrease over 24–45 years. The subsoil never showed a significant temporal effect. Our res

Floral resources are increasingly used in conservation biological control to support natural enemies of insect pests. However, the dietary value of floral resources in supporting predatory arthropods, including their effect on longevity and fecundity has not yet been systematically reviewed. To comprehensively evaluate this, the presented review summarizes published studies on the effect of various floral resources (flowers, pollen, and sugar solution (as a proxy for nectar)) on predatory arthropods. We identified 70 articles, including 628 trials, which measured predator longevity (3 4 7) and fecundity (2 8 1) when supplied with floral resources, as compared to a water only control. Across predator species, results showed that floral resources significantly increased predator longevity, especially whole flowers and sugar solution. Pollen could also prolong predator longevity but was less effective than sugar solution and flowers. The effect of flowers varied greatly among plant species, with those having open or exposed nectaries being more likely to prolong predator longevity, supposedly due to higher accessibility. Some predator species could oviposit on a diet consisting only of floral resources. The findings in the present study emphasize the value of floral resources on supporting predators. Predatory arthropods’ biological control services could be enhanced by choosing plants that favor them in conservation biological control programs.

Wheat is the most commonly grown cereal crop in Europe and in major parts of Europe the most yield limiting disease is Septoria tritici blotch (STB) caused by Zymoseptoria tritici. Currently, the control of the disease depends on cultivar resistance and substantial input of fungicides. The impact of using mixtures of elite cultivars as an alternative was investigated through a meta-analysis based on trial data from the Danish national cultivar testing. The cultivar testing includes a four-way cultivar mixture every year and in these trials STB severity and yield have been monitored at multiple locations between 1995 and 2017. Results from 19 years of cultivar testing trials provided a data set for 406 trials from which the effect of mixtures was evaluated. The meta-analysis revealed that cultivar mixtures reduced STB severity with 10.6% and increased yields with 1.4% across all trials. The effects were greatest in untreated trials where STB severity was reduced with 17% and yields increased with 2.4%. The mixtures did not only perform better than the average of their component cultivars grown as pure stand, they also performed better than the average of the four most grown cultivars in a given year. No relationship was found between disease pressure or location and the performance of the mixtures. The mixtures included in the cultivar testing were not designed to control STB and the results are therefore perceived as a baseline to the attainable disease control from mixtures. The use of cultivar mixtures is relevant for low input farming systems, but can also contribute to disease control in intensive farming systems. Cultivar mixtures have the potential to minimise dependency on fungicides as an important element in integrated pest management.

Ecological niche indicators have been scarcely adopted to assess the biological control of insect herbivores by their natural enemies. We hypothesize that plant diversification promotes the biocontrol services by narrowing the niches of herbivores and broadening the niches of natural enemies. In a large-scale experiment, we found that the abundance of natural enemies was increased by 38.1%, and the abundance of insect herbivores was decreased by 16.9% in peach orchards with plant diversification (treatment) compared to ones with monoculture (control). Stratified sampling indicated that the horizontal, vertical, temporal and three-dimensional niches of natural enemies were generally broader while these niches of herbivores were narrower. Additionally, diverse plants give rise to an increase in the temporal synchrony and spatial similarity of the herbivores and natural enemies in peach orchards. Our study reveals that plant diversification promotes the biocontrol services by shaping the niche of herbivores and natural enemies, and provides a new assessment method to understand the biodiversity-niche-ecosystem management interactions.

Intercropping has been proposed as a way to increase the diversity and production of agricultural land. To benefit from these properties, there is a need for more knowledge on how to combine species mixtures. Here trait plasticity could play an important role. The purpose of the present study is to evaluate the plasticity of plant traits important for light competition in a spring barley (Hordeum vulgare) and field pea (Pisum sativum) intercrop. Hereunder, the mechanisms behind as density effects, effect of changing neighbors and developmental differences between mixing treatments. In addition, the effect of trait plasticity on species complementarity is also assessed. A field trial consisting of two barley cultivars (Tamtam & Salome) and two pea cultivars (Ingrid & Audit) were setup in the spring of 2017 on the experimental farm of Copenhagen University in Tåstrup, Denmark. The trial consisted of a total of four different intercrop treatments and eight different monocrop treatments with three replicates. Four monocrops with a 100% density and four monocrops with a 50% density compared to the total density of the intercrop. During the trial traits important for light competition were measured. Plant height were measured eight time from the beginning of growth until maturity. Dry leaf area and dry leaf weight were measured two times. While internode length, tiller number (only for barley), node number, dry biomass (split up into leaves, stems and reproductive organs), number of reproductive organs, fresh leaf weight, fresh leaf area, leaf angle and chlorophyll concentration of leaves were measured once. Trait plasticity were observed for several of the measured traits across species and cultivars. The pea plants showed plastic responses on plant height, aboveground biomass and leaf morphology. For the barley plants height, leaf biomass, chlorophyll concentration and tiller number showed a plastic response. Barley and pea reacted differently to intercropping.

Increasing the biodiversity of cropped plants is a key leverage for agroecology, aiming to replace chemical inputs by ecological processes and regulations. Cultivar mixtures are a straightforward way to increase within-crop diversity, but they have so far been poorly used by farmers and they are not encouraged by advisory services. Based on the methodology developed by Kiær et al. (2009), we achieved a meta-analysis of cultivar mixtures in wheat. Among the 120 publications dedicated to wheat, we selected 32 studies to analyze various factors that may condition the success or failure of wheat mixtures by calculating overyielding, i.e. the difference in productivity of a variety mixture compared with the weighted mean of its component varieties in pure stand. The analysis highlighted a significant global overyielding of 3.5%, which reached 6.2% in condition of high disease pressures. Overyielding was not affected by seeding density or plot size. Under high disease pressure, overyielding increased by 3.2% point per added component variety. Overyielding was respectively 5.3% and 3.3% higher for mixtures heterogeneous in disease resistance or phenology than for homogeneous ones, and did not vary when considering height. Overyielding reached its highest values in the 1980s and 1990s, which reflects the predominance of disease-focused studies during this period. Our results confirm that cultivar mixtures are a potential way to increase yield relatively to pure varieties, especially under low pesticide cropping systems. Literature suggests that mixture practice is impeded by the lack of general rules that could help to mixing varieties. To design such rules it is needed to (1) achieve new experiments manipulating the heterogeneity in variety traits, (2) determine experimentally the ecological mechanisms underlying mixture performance and (3) develop new models allowing testing and analyzing these mechanisms.

Afforestation influences soil organic carbon (SOC) stocks in terms of magnitude, direction (gain, loss or no change) and duration. Due to data shortage at regional or national scales, global datasets have commonly been evaluated by meta-analysis to address the effects of land use changes on SOC. Here, we present a meta-analysis of relative change in SOC within the Northern European region, which has not been well represented in previous syntheses. Effect sizes were reported as log response ratios (RR) for each pair of agricultural (control) and afforested plots. To quantify effects of afforestation on SOC stocks in forest floors and mineral soils (0-10 cm and 0-20/30 cm), we tested the influence of different former land use classes, such as croplands and grasslands, forest age and forest type on SOC stock changes. Secondly, we investigated the influence of study design, since SOC stock estimates from control/afforested plots have an implicit spatial dependency according to the experimental approach used. This has not been accounted for in meta-analyses of afforested soils before. In addition, changes in SOC stocks (in 0-10 cm) were expressed on equivalent soil mass and fixed depth to estimate possible differences in effect size related to these two SOC accounting methods. We found an overall positive effect of afforestation on SOC accumulation with age, supported by the oldest age classes (>30 years). This effect was enhanced when the forest floor was included in the total SOC stock, in particular for coniferous forests. Afforestation on former grasslands had a negative (RR= -0.06, for both soil depths) non-significant (p> 0.05) effect on SOC stocks. In croplands, effects depended on the soil layer and were significantly positive (RR= 0.14, p< 0.05) in 0-10 cm, while negative and nonsignificant (RR= -0.01, p>0.05) in the 0-20/30 cm layer. This suggests that cropland to forest conversion increases SOC stocks in top-soils within a decadal time scale. R

Northern Europe supports large soil organic carbon (SOC) pools and has been subjected to high frequency of land-use changes during the past decades. However, this region has not been well represented in previous large-scale syntheses of land-use change effects on SOC, especially regarding effects of afforestation. Therefore, we conducted a meta-analysis of SOC stock change following afforestation in Northern Europe. Response ratios were calculated for forest floors and mineral soils (0–10 cm and 0–20/30 cm layers) based on paired control (former land use) and afforested plots. We analyzed the influence of forest age, former land-use, forest type, and soil textural class. Three major improvements were incorporated in the meta-analysis: analysis of major interaction groups, evaluation of the influence of nonindependence between samples according to study design, and mass correction. Former land use was a major factor contributing to changes in SOC after afforestation. In former croplands, SOC change differed between soil layers and was significantly positive (20%) in the 0–10 cm layer. Afforestation of former grasslands had a small negative (nonsignificant) effect indicating limited SOC change following this land-use change within the region. Forest floors enhanced the positive effects of afforestation on SOC, especially with conifers. Meta-estimates calculated for the periods <30 years and >30 years since afforestation revealed a shift from initial loss to later gain of SOC. The interaction group analysis indicated that meta-estimates in former land-use, forest type, and soil textural class alone were either offset or enhanced when confounding effects among variable classes were considered. Furthermore, effect sizes were slightly overestimated if sample dependence was not accounted for and if no mass correction was performed. We conclude that significant SOC sequestration in Northern Europe occurs after afforestation of croplands and not grasslands, and changes

Afforestation influences soil organic carbon (SOC) stocks in terms of magnitude, direction (gain, loss or no change) and duration. Due to data shortage at regional or national scales, global datasets have commonly been evaluated by meta-analysis to address the effects of land use changes on SOC. Here, we present a meta-analysis of relative change in SOC within the Northern European region, which has not been well represented in previous syntheses. Effect sizes were reported as log response ratios (RR) for each pair of agricultural (control) and afforested plots. To quantify effects of afforestation on SOC stocks in forest floors and mineral soils (0-10 cm and 0-20/30 cm), we tested the influence of different former land use classes, such as croplands and grasslands, forest age and forest type on SOC stock changes. Secondly, we investigated the influence of study design, since SOC stock estimates from control/afforested plots have an implicit spatial dependency according to the experimental approach used. This has not been accounted for in meta-analyses of afforested soils before. In addition, changes in SOC stocks (in 0-10 cm) were expressed on equivalent soil mass and fixed depth to estimate possible differences in effect size related to these two SOC accounting methods. We found an overall positive effect of afforestation on SOC accumulation with age, supported by the oldest age classes (>30 years). This effect was enhanced when the forest floor was included in the total SOC stock, in particular for coniferous forests. Afforestation on former grasslands had a negative (RR= -0.06, for both soil depths) non-significant (p> 0.05) effect on SOC stocks. In croplands, effects depended on the soil layer and were significantly positive (RR= 0.14, p< 0.05) in 0-10 cm, while negative and nonsignificant (RR= -0.01, p>0.05) in the 0-20/30 cm layer. This suggests that cropland to forest conversion increases SOC stocks in top-soils within a decadal time scale. R

1. Many plants are simultaneously attacked by arthropod herbivores and phytopathogens. These may affect each other directly and indirectly, enhancing or reducing the amount of plant resources they each consume. Ultimately, this may reduce or enhance plant performance relative to what should be expected from the added impacts of herbivore and pathogen when they attack alone. 2. Previous studies have suggested synergistic and antagonistic impacts on plant performance from certain combinations of arthropods and pathogens, for example, synergistic impacts from necrotrophic pathogens together with wounding arthropods because of facilitated infection and antagonistic impacts from induction of pathogen resistance by sucking herbivores. 3. We compiled published studies on the impact of plant–herbivore–pathogen interactions on plant performance and used meta-analysis to search for consistent patterns of impacts among plant, herbivore and pathogen characteristics and experimental conditions, and to test the suggested hypotheses on synergistic or antagonistic impacts. 4. None of the hypotheses based on proximate interactions between arthropods and pathogens were supported by our analysis; in contrast, the patterns we found were related to plant traits and experimental conditions. 5. Our results suggest that immediate loss of resources from interactions between arthropod herbivores and pathogens is generally moderated by compensation to an extent where there are no interactive effects on plant performance. However, as interactive impacts also differed among environments and parasite manipulation methods, this suggests that the ability of plants to compensate such losses may depend on environmental conditions and probably also overall infection load.

Hybridization and its possible impacts is a subject of increased attention in connection with the risk of unintended gene flow from cultivated (including genetically modified) plants to wild relatives. Whether such gene flow by hybridization is likely to take place depends among other things on the persistence of the hybrids in a natural environment over time. To evaluate this, we studied an experimental hybridizing population of wild and cultivated chicories Wichorium intybus) relative to a previous study on the same population 2 years earlier. We compared the genetic composition, morphology and fitness traits of plants from 2004 to the plants in the same plot in 2002. The majority of the plants in 2004 was more morphologically and genetically intermediate than in 2002. This indicates that no selection towards being wild-like or cultivar-like was present over the period of 2 years. Furthermore, no distinct fitness differences existed between the plants of 2004, probably due to most of the plants being intermediate. No hybridization barriers appeared to be present between wild and cultivated chicories beyond the F, generation, since F-2 hybrids and backcrosses were in abundance; in fact, hybrids of probably fourth or fifth generation were present. In conclusion, all results indicate that no barriers exist to the temporal persistence of chicory hybrids in a natural environment.

Crop species are known to hybridize spontaneously with wild relatives, but few studies have characterized the performance of hybrids at various genealogies, life stages and environments. A group of cultivar-like individuals and potential hybrids were observed in a roadside population of wild chicory plants in Denmark. Seeds were collected from all reproductive plants and grown in a common garden experiment, and their morphological and genetic compositions were analysed. Intermediate plants were identified as hybrids and comprised various backcross and F(n) combinations. A genotypic hybrid index (HI), spanning from wild-like to cultivar-like, was highly correlated to a morphological index. Plant survival, growth and reproduction were evaluated and compared to the genotypic HI. Overall, cultivar-like and intermediate plants grew larger than wild-like plants, flowered longer, and produced more flowers and seeds. The common garden included a nutrient gradient. At higher nutrient levels, intermediate and cultivar-like plants produced more flowers and seeds than wild-like plants, whereas this effect was less pronounced at lower nutrient levels. During winter, small rodents consumed roots of cultivar-like and intermediate plants preferentially. Thus, cultivated and wild chicory are able to hybridize spontaneously, producing hybrid offspring of several generations that may reproduce more effectively than their wild parent, but herbivory and poor environmental conditions may negatively affect their fitness.