Coupled modelling of hydrological processes and grassland production in two contrasting climates

[摘要] Projections of global climate models suggest that ongoing human-inducedclimate change will lead to an increase in the frequency of severe droughtsin many important agricultural regions of the world. Eco-hydrological modelsthat integrate current understanding of the interacting processes governingsoil water balance and plant growth may be useful tools to predict theimpacts of climate change on crop production. However, the validation statusof these models for making predictions under climate change is stillunclear, since few suitable datasets are available for model testing. Onepromising approach is to test models using data obtained in“space-for-time” substitution experiments, in which samples aretransferred among locations with contrasting current climates in order tomimic future climatic conditions. An important advantage of this approach isthat the soil type is the same, so that differences in soil properties arenot confounded with the influence of climate on water balance and cropgrowth. In this study, we evaluate the capability of a relatively simpleeco-hydrological model to reproduce 6 years (2013–2018) of measurements ofsoil water contents, water balance components and grass production made inweighing lysimeters located at two sites within the TERENO-SoilCan networkin Germany. Three lysimeters are located at an upland site at Rollesbroichwith a cool, wet climate, while three others had been moved fromRollesbroich to a warmer and drier climate on the lower Rhine valleyfloodplain at Selhausen. Four of the most sensitive parameters in the modelwere treated as uncertain within the framework of the GLUE (generalizedlikelihood uncertainty estimation) methodology, while the remainingparameters in the model were set according to site measurements or data inthe literature. The model satisfactorily reproduced the measurements at both sites, and somesignificant differences in the posterior ranges of the four uncertainparameters were found. In particular, the results indicated greater stomatalconductance as well an increase in dry-matter allocation below ground and asignificantly larger maximum root depth for the three lysimeters that hadbeen moved to Selhausen. As a consequence, the apparent water use efficiency(above-ground harvest divided by evapotranspiration) was significantlysmaller at Selhausen than Rollesbroich. Data on species abundance on thelysimeters provide one possible explanation for the differences in the planttraits at the two sites derived from model calibration. These observationsshowed that the plant community at Selhausen had changed significantly inresponse to the drier climate, with a significant decrease in the abundanceof herbs and an increase in the proportion of grass species. The differencesin root depth and leaf conductance may also be a consequence of plasticityor acclimation at the species level. Regardless of the reason, we mayconclude that such adaptations introduce significant additionaluncertainties into model predictions of water balance and plant growth inresponse to climate change.

[学科分类] 妇产科学