Role of Agricultural Management in the Provision of Ecosystem Services in Warm Climate Vineyards: Functional Prediction of Genes Involved in Nutrient Cycling and Carbon Sequestration

(1) Background: Maintaining soil fertility and crop productivity using natural microbial diversity could be a feasible approach for achieving sustainable development in agriculture. In this study, we compared soils from vineyards under organic and conventional management by predicting functional profiles through metagenomic analysis based on the 16S rRNA gene. (2) Methods: The structure, diversity and predictive functions of soil bacteria related to the biogeochemical cycle of the soil were analyzed, including oxidative and hydrolytic C-cycling enzymes, N-cycling enzymes and P-cycling enzymes. The inter-row spontaneous vegetation in the organic vineyards was also characterized. (3) Results: A clear effect of the farming system (organic vs. conventional) and cover management (herbicides plus tillage, mowing only and mowing plus tillage) on bacterial beta diversity and predicted functions was evidenced. While conventional viticulture increased the potential capacity of the soil to regulate the cycling of inorganic forms of N, organic viticulture in general enhanced those functions involving organic N, P and C substrates. Although the soil bacterial community responded differently to contrasting soil management strategies, nutrient cycling and carbon sequestration functions remained preserved, suggesting a high bacterial functional redundancy in the soil in any case. However, most of the predicted bacterial functions related to soil organic matter turnover were enhanced by organic management. (4) Conclusions: We posit the potential for organic viticulture to adequately address climate change adaptation in the context of sustainable agriculture.

Density-Dependent Effects of Simultaneous Root and Floral Herbivory on Plant Fitness and Defense

Plants are attacked by multiple herbivores, and depend on a precise regulation of responses to cope with a wide range of antagonists. Simultaneous herbivory can occur in different plant compartments, which may pose a serious threat to plant growth and reproduction. In particular, plants often face co-occurring root and floral herbivory, but few studies have focused on such interactions. Here, we investigated in the field the combined density-dependent effects of root-chewing cebrionid beetle larvae and flower-chewing pierid caterpillars on the fitness and defense of a semiarid Brassicaceae herb. We found that the fitness impact of both herbivore groups was independent and density-dependent. Increasing root herbivore density non-significantly reduced plant fitness, while the relationship between increasing floral herbivore density and the reduction they caused in both seed number and seedling emergence was non-linear. The plant defensive response was non-additive with regard to the different densities of root and floral herbivores; high floral herbivore density provoked compensatory investment in reproduction, and this tolerance response was combined with aboveground chemical defense induction when also root herbivore density was high. Plants may thus prioritize specific trait combinations in response to varying combined below- and aboveground herbivore densities to minimize negative impacts on fitness.

Host Gall Size and Temperature Influence Voltinism in an Exotic Parasitoid

Insect phenology is highly temperature-dependent. Higher temperatures can lead to earlier emergence and lengthening of the active period, which enable many insect groups to complete more generations. Studies on the effects of climate change on insect populations are providing concerning evidence supporting this relationship. These kind of shifts in phenology and voltinism also occur in agricultural and forest insect pests and their natural enemies, with potential implications for biological control. The consequences derived from changing temperature regimes on tritrophic interactions remain poorly studied, particularly in gall-inducing insects and their parasitoids. Here we detail the occurrence of bivoltinism in the exotic parasitoid Torymus sinensis, previously categorized as univoltine, a widely introduced species to fight against the invasive Asian chestnut gall wasp Dryocosmus kuriphilus wherever this pest spread. This plasticity in voltinism has been observed in the southernmost European distribution of D. kuriphilus, and appears to be mediated by both temperature and gall traits, namely size or the number of gall chambers. Bivoltinism was most common at annual mean temperatures around 13.5°C and in galls with more chambers. Through this work, we intend to unravel the factors behind this phenomenon and discern the possible consequences on host-parasitoid interactions.

Invasive earthworms erode soil biodiversity: A meta-analysis

Biological invasions pose a serious threat to biodiversity and ecosystem functioning across ecosystems. Invasions by ecosystem engineers, in particular, have been shown to have dramatic effects in recipient ecosystems. For instance, invasion by earthworms, a below-ground invertebrate ecosystem engineer, in previously earthworm-free ecosystems alters the physico-chemical characteristics of the soil. Studies have shown that such alterations in the soil can have far-reaching impacts on soil organisms, which form a major portion of terrestrial biodiversity. Here, we present the first quantitative synthesis of earthworm invasion effects on soil micro-organisms and soil invertebrates based on 430 observations from 30 independent studies. Our meta-analysis shows a significant decline of the diversity and density of soil invertebrates in response to earthworm invasion with anecic and endogeic earthworms causing the strongest effects. Earthworm invasion effects on soil micro-organisms were context-dependent, such as depending on functional group richness of invasive earthworms and soil depth. Microbial biomass and diversity increased in mineral soil layers, with a weak negative effect in organic soil layers, indicating that the mixing of soil layers by earthworms (bioturbation) may homogenize microbial communities across soil layers. Our meta-analysis provides a compelling evidence for negative effects of a common invasive below-ground ecosystem engineer on below-ground biodiversity of recipient ecosystems, which could potentially alter the ecosystem functions and services linked to soil biota.