Mechanistic Modelling of Soil–Plant–Atmosphere Systems

Process-based modeling to assess the nutrient removal efficiency of two endangered hydrophytes: Linking nutrient-cycle with a multiple-quotas approach

Hydrophytes have been widely used to reduce nutrient levels in aquatic ecosystems, but only limited species with high nutrient removal efficiencies have been implemented. Thus, it is necessary to continually explore new candidate species with high nutrient removal efficiencies. To effectively explore the nutrient removal ability of hydrophytes, a new process-based model combining the multiple-quotas approach and nutrient-cycle model was developed. The multiple-quotas approach provides a theoretical framework to conceptually explain the uptake and response of autotrophs to multiple nutrients. The developed process-based model was validated using observational data from microcosm experiments with two emergent hydrophytes, Menyanthes trifoliata and Cicuta virosa. The results showed that both M. trifoliata and C. virosa effectively reduced nitrogen (N) and phosphorus (P) in both water and sediment layers, but M. trifoliata showed a higher removal efficiency for both nutrients than C. virosa, particularly for total ammonia + ammonium-nitrogen (NH_x-N) and nitrate-nitrogen (NO₃-N) in the sediment layer (M. trifoliata: 0.579-0.976 for NH_x-N, 0.567-0.702 for NO₃-N; C. virosa: 0.212-0.501 for NH_x-N, 0.466-0.560 for NO₃-N). In addition, M. trifoliata achieved the maximum removal efficiency for N and P at higher nutrient exposure levels than C. virosa (M. trifoliata: exposure level of 0.725-0.775; C. virosa: exposure level of 0.550-0.575). The developed model well simulated the species-specific growth patterns of hydrophytes depending on the nutrient exposure level as well as the N and P dynamics in the water and sediment layers. The approach adopted in this study provides a useful tool for discovering candidate species to improve hydrophyte diversity and effectively remove nutrients from aquatic ecosystems.

Photosynthesis in a Changing Global Climate: Scaling Up and Scaling Down in Crops

Photosynthesis is the major process leading to primary production in the Biosphere. There is a total of 7000bn tons of CO2 in the atmosphere and photosynthesis fixes more than 100bn tons annually. The CO2 assimilated by the photosynthetic apparatus is the basis of crop production and, therefore, of animal and human food. This has led to a renewed interest in photosynthesis as a target to increase plant production and there is now increasing evidence showing that the strategy of improving photosynthetic traits can increase plant yield. However, photosynthesis and the photosynthetic apparatus are both conditioned by environmental variables such as water availability, temperature, [CO2], salinity, and ozone. The "omics" revolution has allowed a better understanding of the genetic mechanisms regulating stress responses including the identification of genes and proteins involved in the regulation, acclimation, and adaptation of processes that impact photosynthesis. The development of novel non-destructive high-throughput phenotyping techniques has been important to monitor crop photosynthetic responses to changing environmental conditions. This wealth of data is being incorporated into new modeling algorithms to predict plant growth and development under specific environmental constraints. This review gives a multi-perspective description of the impact of changing environmental conditions on photosynthetic performance and consequently plant growth by briefly highlighting how major technological advances including omics, high-throughput photosynthetic measurements, metabolic engineering, and whole plant photosynthetic modeling have helped to improve our understanding of how the photosynthetic machinery can be modified by different abiotic stresses and thus impact crop production.