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| Home > Publications database > CLM-Apple: A Perennial Plant Functional Type for the Community Land Model CLM5 |
| Poster (Other) | FZJ-2022-00837 |
; ; ; ;
2021
Please use a persistent id in citations: http://hdl.handle.net/2128/33527
Abstract: Orchards and other perennial crops represent one percent of the total global agricultural area. A significant portion is found in Mediterranean Europe covering 16 % of the total agricultural land. Apples are one of the most popular and valuable fruits and make up one third of all European orchards, covering more than 463’000 ha. In contrast to annual crops, perennial tree crops can be productive for several decades before rotation is needed. Moreover, the standing biomass of such cultivation serves as carbon storage and thus influences the carbon cycle in a different way than annual crops. However, perennial tree crops are rarely considered in the land components of earth system models. This creates an important gap in the representation of biogeophysical and biogeochemical processes that are a consequence of such agro-ecosystems. In this work we implemented an apple tree crop sub-model named CLM-APPLE that allows the simulation of a new apple plant functional type (PFT) within the existing framework of the Community Land Model version 5 (CLM5). Similarly to the existing deciduous tree PFTs that are available in CLM5, the apple PFT is described by a perennial deciduous phenology with standing woody biomass and annual leaf shedding. During the active growth period, the phenology and the carbon and nitrogen allocation of vegetative and harvestable organs are described by distinct growth phases and are driven by a growing degree day summation. In this new PFT, both the storage pool and the photosynthetic pool contribute to tree growth since, in fruit trees, leaf and shoot development at the beginning of a growing season utilizes carbohydrate reserves and nitrogenous compounds that were accumulated during the previous season. Furthermore, agricultural practices such as transplanting, fertilization, and stem pruning are represented in the new sub-model. New parameters were introduced, calibrated, and then validated with extensive field measurements from an apple-growing region in the Adige River valley (Italy). Monthly biomass components and leaf area index (LAI), measured directly and independently over six representative plots, were used for model calibration. Additionally, multiple years of continuous soil respiration measurements, eddy covariance measurements, and yield data were used for model calibration and validation. Simulated patterns in seasonal biomass allocation and LAI showed good agreement with the observations. Similarly, the simulated average yield between 2010 and 2015 was within 5 % of the observed yield. However, the observed inter annual variability was not well represented in the simulations. Overall, the model validation using eddy covariance data demonstrated the ability of the model to represent the seasonal dynamics and magnitudes of ecosystem fluxes at the orchard level. Despite these encouraging results, an accurate representation of inter-annual yield dynamics and seasonal fluctuations of fluxes at the orchard-scale remains challenging, suggesting the existence of processes that are not yet implemented in the model. Nonetheless, the newly developed sub-model CLM-APPLE allows the exploration of the carbon allocation dynamics and ecosystem fluxes in orchards as well as their effects on the terrestrial biogeochemical cycle.
Keyword(s): Geosciences (2nd)
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