Compared to conventional, ecological intensive management promotes beneficial proteolytic soil microbial communities for agro-ecosystem functioning under climate change-induced rain regimes

Projected climate change and rainfall variability will affect soil microbial communities, biogeochemical cycling and agriculture. Nitrogen (N) is the most limiting nutrient in agroecosystems and its cycling and availability is highly dependent on microbial driven processes. In agroecosystems, hydrolysis of organic nitrogen (N) is an important step in controlling soil N availability. We analyzed the effect of management (ecological intensive vs. conventional intensive) on N-cycling processes and involved microbial communities under climate change-induced rain regimes. Terrestrial model ecosystems originating from agroecosystems across Europe were subjected to four different rain regimes for 263 days. Using structural equation modelling we identified direct impacts of rain regimes on N-cycling processes, whereas N-related microbial communities were more resistant. In addition to rain regimes, management indirectly affected N-cycling processes via modifications of N-related microbial community composition. Ecological intensive management promoted a beneficial N-related microbial community composition involved in N-cycling processes under climate change-induced rain regimes. Exploratory analyses identified phosphorus-associated litter properties as possible drivers for the observed management effects on N-related microbial community composition. This work provides novel insights into mechanisms controlling agro-ecosystem functioning under climate change

Natural variation in photosynthetic capacity, growth, and yield in 64 field-grown wheat genotypes

Increasing photosynthesis in wheat has been identified as an approach to enhance crop yield, with manipulation of key genes involved in electron transport and the Calvin cycle as one avenue currently being explored. However, natural variation in photosynthetic capacity is a currently unexploited genetic resource for potential crop improvement. Using gas-exchange analysis and protein analysis, the existing natural variation in photosynthetic capacity in a diverse panel of 64 elite wheat cultivars grown in the field was examined relative to growth traits, including biomass and harvest index. Significant variations in photosynthetic capacity, biomass, and yield were observed, although no consistent correlation was found between photosynthetic capacity of the flag leaf and grain yield when all cultivars were compared. The majority of the variation in photosynthesis could be explained by components related to maximum capacity and operational rates of CO2 assimilation, and to CO2 diffusion. Cluster analysis revealed that cultivars may have been bred unintentionally for desirable traits at the expense of photosynthetic capacity. These findings suggest that there is significant underutilized photosynthetic capacity among existing wheat varieties. Our observations are discussed in the context of exploiting existing natural variation in physiological processes for the improvement of photosynthesis in wheat. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology

MOLECULAR-CELL-D-20-01167_Revised Manuscript 12-2-2020

Supporting data for revised manuscript MOLECULAR-CELL-D-20-01167, Sadras et al

MOLECULAR-CELL-D-20-01167_Revised Manuscript 12-2-2020

Supporting data for revised manuscript MOLECULAR-CELL-D-20-01167, Sadras et al

MOLECULAR-CELL-D-20-01167_Supporting Data

Supporting data for MOLECULAR-CELL-D-20-01167, Sadras et al

Modelling heatwaves in viticultural regions of southeastern Australia

The production of quality wine grapes is sensitive to heatwaves, especially at key phenostages such as flowering and ripening. Climatological models of heatwaves with application in viticulture need to account for (a) a range of meteorological variables, (b) intensity, (c) duration and (d) timing of events. The meteorological variable most commonly associated with heatwaves is maximum temperature; however, high minimum temperatures associated with heatwaves are also relevant for viticulture. Intensity should be expressible as either exceeding a categorical threshold such as 35°C or a relative threshold such as the 90th percentile. In addition to the chance of heatwaves of a given intensity and duration for the growing season (September to April), viticulturists are interested in monthly and fortnightly windows to account for the timing of critical phenostages. The model presented here is an attempt to meet these four requirements. The model is stochastic and incorporates seasonality and daily persistence of temperature through a Markov process and implies that frequency (or the return period) of heatwaves decreases (increases) geometrically with each additional day of duration. The final model is expressed as a simple equation involving a single location-specific parameter, M, which relates to the maritime influence. The model was tested over the viticultural regions of southeastern Australia by comparison with observed data, and by assessing the physical and climatological meaning of parameter M. Cross-validated model estimates of annual frequency of heatwaves were in good agreement with observations. The parameter M proved robust and physically meaningful: it is location-specific, its isopleths have the qualitative impression of sea-breeze or maritime influence and it is quantitatively related to the skewness of the summertime maximum temperature distribution