- Effects from climate change, adaptations and
greenhouse gas reduction at 2050

Abstract:

A major issue of our today's research is to help meeting the challenges of future food security. One task is to assess and develop crop management strategies adapted to predicted future climatic conditions. Yet, both the variability of environmental conditions and the uncertainty of climate projections as well as the orchestra of multiple plant responses and their interaction with the environment make it difficult to predict plant behavior in the field. Recent studies have demonstrated the usefulness of classical crop models as a tool to investigate crop productivity under predicted climate conditions. These models use data on plant architecture only to a limited extent as they usually follow a systems approach by focusing on processes for predicting dry matter production. However, plant architecture is a major determinant of the crops’ resource use efficiency. Moreover, plants show time dependent structural changes as they grow and develop, and these processes are affected by various environmental factors and stresses. Virtual plant models consider both the three-dimensional plant architecture and concepts of plant physiology. Here, we outline the way in which virtual plant modelling can further improve our understanding on the impact of climate change on food production. Greenhouse and growth chamber experiments may serve as data sources for model parameterization, in particular of response functions with respect to environmental stimuli. Data from field experiments in free air carbon enrichment (FACE) facilities, such as those obtained in the new Geisenheim FACE for special crops, may be used to evaluate virtual plant models with respect to future climatic conditions. A combination of field data and virtual plant model simulations may then allow us to assess the specific role of plant architecture in resource use efficiency and help to develop advanced strategies for future crop production.

Abstract:

Global warming is currently a much discussed topic with as yet largely unexplored consequences for agro-ecosystems. Little is known about the warming effect on the bacterial microbiota inhabiting the plant surface (phyllosphere), which can have a strong impact on plant growth and health, as well as on plant diseases and colonization by human pathogens. The aim of this study was to investigate the effect of moderate surface warming on the diversity and composition of the bacterial leaf microbiota of the herbaceous plant Galium album. Leaves were collected from four control and four surface warmed (+2°C) plots located at the field site of the Environmental Monitoring and Climate Impact Research Station Linden in Germany over a 6-year period. Warming had no effect on the concentration of total number of cells attached to the leaf surface as counted by Sybr Green I staining after detachment, but changes in the diversity and phylogenetic composition of the bacterial leaf microbiota analyzed by bacterial 16S rRNA gene Illumina amplicon sequencing were observed. The bacterial phyllosphere microbiota were dominated by Proteobacteria, Bacteroidetes, and Actinobacteria. Warming caused a significant higher relative abundance of members of the Gammaproteobacteria, Actinobacteria, and Firmicutes, and a lower relative abundance of members of the Alphaproteobacteria and Bacteroidetes. Plant beneficial bacteria like Sphingomonas spp. and Rhizobium spp. occurred in significantly lower relative abundance in leaf samples of warmed plots. In contrast, several members of the Enterobacteriaceae, especially Enterobacter and Erwinia, and other potential plant or human pathogenic genera such as Acinetobacter and insect-associated Buchnera and Wolbachia spp. occurred in higher relative abundances in the phyllosphere samples from warmed plots. This study showed for the first time the long-term impact of moderate (+2°C) surface warming on the phyllosphere microbiota on plants. A reduction of beneficial bacteria and an enhancement of potential pathogenic bacteria in the phyllosphere of plants may indicate that this aspect of the ecosystem which has been largely neglected up till now, can be a potential risk for pathogen transmission in agro-ecosystems in the near future.

Abstract:

Soil respiration of terrestrial ecosystems, a major component in the global carbon cycle is affected by elevated atmospheric CO2 concentrations. However, seasonal differences of feedback effects of elevated CO2 have rarely been studied. At the Gießen Free-Air CO2 Enrichment (GiFACE) site, the effects of +20% above ambient CO2 concentration have been investigated since 1998 in a temperate grassland ecosystem. We defined five distinct annual seasons, with respect to management practices and phenological cycles. For a period of 3 years (2008–2010), weekly measurements of soil respiration were carried out with a survey chamber on vegetation-free subplots. The results revealed a pronounced and repeated increase of soil respiration under elevated CO2 during late autumn and winter dormancy. Increased CO2 losses during the autumn season (September–October) were 15.7% higher and during the winter season (November–March) were 17.4% higher compared to respiration from ambient CO2 plots. However, during spring time and summer, which are characterized by strong above- and below-ground plant growth, no significant change in soil respiration was observed at the GiFACE site under elevated CO2. This suggests (1) that soil respiration measurements, carried out only during the growing season under elevated CO2 may underestimate the true soil-respiratory CO2 loss (i.e. overestimate the C sequestered), and (2) that additional C assimilated by plants during the growing season and transferred below-ground will quickly be lost via enhanced heterotrophic respiration outside the main growing season.