Intercropping drives plant phenotypic plasticity and changes in functional trait space

The relevance of intercropping, where two or more crop species are simultaneously grown on the same land space, is growing due to its potential for improving resource use and maintaining stable yields under variable weather conditions. However, the actual growth of intercropped species may differ resulting from the idiosyncratic effect of crop diversity, and with this, the realized benefits from intercrops are found to depend critically on the cultivar, species, management and environmental conditions. This study aimed to apply a trait-based approach, in which ecological niche spaces are defined through n-dimensional hypervolumes, to identify the contribution of species/cultivar, cultivation design (sole crop or intercrop) and management (low or high fertilization) to the trait diversity of four crop species, pea-barley and faba bean-wheat, when grown as sole crops and intercrops. Four traits were used as trait axes for the trait space analysis: canopy height, shoot biomass, tiller/node number, and grain yield. We found that trait spaces differed with crop species and cultivars, and whether they were grown as intercrops or sole crops. Trait spaces differed between high and low fertilization only for the cereals grown in the more productive site (i.e. Denmark). Species grown as intercrops had larger volumes than when grown as sole crops, as a result of trait plasticity. This response to intercropping was apparent in almost all the species grown in Sweden and Denmark, except for wheat in Denmark. The study demonstrated that individual species responded to intercropping compared to sole cropping through the plasticity of traits, which influenced the shape of the hypervolumes to divide up the trait space between the species. The findings are important in illustrating the plastic responses of arable crops, which are relevant for understanding the productivity of species grown in intercrops as compared to sole crops

Three-Dimensional Observation of Atmospheric Processes in Cities

To cope with weather and climate-induced impacts as well as with air pollution in cities, the German research programme “Urban Climate Under Change” ([UC]2) aims at developing, testing and validating a new urban climate model, which is able to cover the full range of temporal and spatial scales of urban atmospheric processes. The project “Three-dimensional Observation of Atmospheric Processes in Cities” (3DO), which forms the module B of the [UC]2 research programme, aims at acquisition of comprehensive, accurate three-dimensional observational data sets on weather, climate and air quality in the German cities of Berlin, Hamburg and Stuttgart. Data sets from long-term observations and intense observation periods allow for evaluation of the performance of a new urban climate model called PALM‑4U that is developed by the project “Model-based city planning and application in climate change” (MOSAIK), which forms the module A of the [UC]2 research programme. This article focuses on collaborative activities for compilation of existing and acquisition of new observational data within the 3DO project

Plant genetic diversity affects multiple trophic levels and trophic interactions

: Intraspecific genetic diversity is an important component of biodiversity. A substantial body of evidence has demonstrated positive effects of plant genetic diversity on plant performance. However, it has remained unclear whether plant genetic diversity generally increases plant performance by reducing the pressure of plant antagonists across trophic levels for different plant life forms, ecosystems and climatic zones. Here, we analyse 4702 effect sizes reported in 413 studies that consider effects of plant genetic diversity on trophic groups and their interactions. We found that that increasing plant genetic diversity decreased the performance of plant antagonists including invertebrate herbivores, weeds, plant-feeding nematodes and plant diseases, while increasing the performance of plants and natural enemies of herbivores. Structural equation modelling indicated that plant genetic diversity increased plant performance partly by reducing plant antagonist pressure. These results reveal that plant genetic diversity often influences multiple trophic levels in ways that enhance natural pest control in managed ecosystems and consumer control of plants in natural ecosystems for sustainable plant production

Connectedness of habitat fragments boosts conservation benefits for butterflies, but only in landscapes with little cropland

Context Global change pressures (GCPs) imperilspecies and associated ecosystem functions, but studies investigating interactions of landscape-scale pressures remain scarce. Loss of species-rich habitat and agricultural expansion are major threats for biodiversity, but if or how these factors interactively determine community-level shifts and conservation outcomes remains unclear. Objectives We tested whether matrix simplification (dominance of cropland) and reduced connectivity (i.e. landscape-scale habitat loss) either additively, synergistically or antagonistically cause community shifts in butterflies, a group of high conservation relevance. Methods We surveyed butterflies on 30 small calcareous grassland fragments (<1 ha) in Central Germany, representing independent gradients in grassland connectivity (an index combining grassland area and proximity), and matrix quality (landscape proportion of cropland). Using proportional odds logistic regression, we assessed whether connectivity and matrix quality interactively altered the distribution of Red List statuses, and assessed effects of local scale management (mowing, grazing, short-term abandonment). Results We found synergistic, conservation relevant effects: Connectivity boosted the proportion of redlisted species from 20 to 52% in crop land poor landscapes, but not in crop land rich landscapes, particularly driven by endangered and critically endangered species. Grazed sites had the lowest species richness, abundance, and proportions of conservation relevant butterflies. Implications Mitigation measures targeting one landscape-scale pressure only may be inefficient, particularly for red-listed species. Increasing habitat connectivity bolsters butterfly communities and potential pollination services, but only if accompanied by measures to soften the matrix. Hence, halting biodiversity losses needs better understanding and implementation of complex conservation measures at the landscape scale

Multifunctional shade‐tree management in tropical agroforestry landscapes – a review

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87099/1/j.1365-2664.2010.01939.x.pd

Grain Yield Stability of Cereal-Legume Intercrops Is Greater Than Sole Crops in More Productive Conditions

The intercropping of two or more crop species on the same piece of land at a given time has been hypothesized to enhance crop yield stability. To address this hypothesis, we assessed the grain yield stability of various barley-pea and wheat-faba bean mixtures grown in seven experimental field trials (locations) across Europe during two years with contrasting weather (2017 and 2018). Three different yield stability measures were used, all based on the expected yield variability of the mixture components grown as sole crops, and the corresponding observed yield variability of the same components grown in 50:50 mixtures in a replacement design. Stability indices were calculated as ratios between the expected and observed variabilities, with values > 1 indicating greater stability of the intercrops. Mean grain yields tended to be higher in intercrops than sole crops. However, in contrast to our hypothesis, the observed (intercrop) yield stability was similar or lower than the expected (sole crop) stability in most locations except one. Furthermore, yield stability significantly increased with increasing mean yields when assessed across differentially productive locations. The results are relevant for the designing of intercropping systems as a means to increase yield stability and the resilience of cropping systems.This research was funded by the DIVERSify project, a grant from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 727284. MR was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—420661662. A.J.K. and A.C.N. are also supported by the strategic research programme funded by the Scottish Government’s Rural and Environment Science and Analytical Services Division.Peer reviewe

Improving insect conservation management through insect monitoring and stakeholder involvement

In recent years, the decline of insect biodiversity and the imminent loss of provided ecosystem functions and services has received public attention and raised the demand for political action. The complex, multi-causal contributors to insect decline require a broad interdisciplinary and cross-sectoral approach that addresses ecological and social aspects to find sustainable solutions. The project Diversity of Insects in Nature protected Areas (DINA) assesses insect communities in 21 nature reserves in Germany, and considers interactions with plant diversity, pesticide exposure, spatial and climatic factors. The nature reserves border on agricultural land, to investigate impacts on insect diversity. Part of the project is to obtain scientific data from Malaise traps and their surroundings, while another part involves relevant stakeholders to identify opportunities and obstacles to insect diversity conservation. Our results indicate a positive association between insect richness and biomass. Insect richness was negatively related to the number of stationary pesticides (soil and vegetation), pesticides measured in ethanol, the amount of area in agricultural production, and precipitation. Our qualitative survey along with stakeholder interviews show that there is general support for insect conservation, while at the same time the stakeholders expressed the need for more information and data on insect biodiversity, as well as flexible policy options. We conclude that conservation management for insects in protected areas should consider a wider landscape. Local targets of conservation management will have to integrate different stakeholder perspectives. Scientifically informed stakeholder dialogues can mediate conflicts of interests, knowledge, and values to develop mutual conservation scenarios

Functional identity versus species richness: herbivory resistance in plant communities

The resistance of a plant community against herbivore attack may depend on plant species richness, with monocultures often much more severely affected than mixtures of plant species. Here, we used a plant–herbivore system to study the effects of selective herbivory on consumption resistance and recovery after herbivory in 81 experimental grassland plots. Communities were established from seed in 2002 and contained 1, 2, 4, 8, 16 or 60 plant species of 1, 2, 3 or 4 functional groups. In 2004, pairs of enclosure cages (1 m tall, 0.5 m diameter) were set up on all 81 plots. One randomly selected cage of each pair was stocked with 10 male and 10 female nymphs of the meadow grasshopper, Chorthippus parallelus. The grasshoppers fed for 2 months, and the vegetation was monitored over 1 year. Consumption resistance and recovery of vegetation were calculated as proportional changes in vegetation biomass. Overall, grasshopper herbivory averaged 6.8%. Herbivory resistance and recovery were influenced by plant functional group identity, but independent of plant species richness and number of functional groups. However, herbivory induced shifts in vegetation composition that depended on plant species richness. Grasshopper herbivory led to increases in herb cover at the expense of grasses. Herb cover increased more strongly in species-rich mixtures. We conclude that selective herbivory changes the functional composition of plant communities and that compositional changes due to selective herbivory depend on plant species richness