A STELLA-based model to simultaneously predict hydrological processes, N uptake and biomass production in a eucalypt plantation

Authors: OUYANG, YING - Us Forest Service (FS); Feng, Gary; RENNINGER, HEIDI - Us Forest Service (FS); LEININGER, THEODOR - Us Forest Service (FS); PARAJULI, PREM - Mississippi State University; GRACE, JOHNNY - Us Forest Service (FS)

Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2021
Publication Date: 4/21/2021
Citation: Ouyang, Y., Feng, G.G., Renninger, H., Leininger, T., Parajuli, P., Grace, J. 2021. A STELLA-based model to simultaneously predict hydrological processes, N uptake and biomass production in a eucalypt plantation. Forests. 12:515. https://doi.org/10.3390/f12050515.
DOI: https://doi.org/10.3390/f12050515

Interpretive Summary: developed. The model was calibrated with good agreements between the model predictions and the field measurements. A simulation scenario was then chosen to assess eucalyptus ANPP and WBP as well as their relationships to WUE and NUE during the entire cultivating period of 20 years. A typical annual variation pattern was observed for water use, N uptake and ANPP, with increasing from spring to fall followed by decreasing from fall to winter. The following two distinct patterns were found: (1) during the growing stage, the water use, N uptake and ANPP increased linearly with eucalyptus age, and (2) during the matured stage, the water use approached an equilibrium condition with eucalyptus age, whereas the N uptake and ANNP decreased with eucalyptus age. The highest rates of water use, N uptake, and NPP during the matured stage were, respectively, 1.52E+07cm3/ha/d, 162 g/ha/d, and 230 kg/ha/d. ANPP increased linearly with water use during the growing stage but decreased steeply with water use during the matured stage. A similar trend was found for WUE. Results indicated that water was used more efficiently in turn of eucalyptus ANPP during the growing stage. Under a maximum condition, every 1 m3 of water used by eucalyptus could produce 7 kg of net primary product for the simulation conditions used in this study. In general, the average WUE during the growing stage was 2.97 kg/m3. Unlike the case between the ANPP and water use, a linear correlation was found between the ANPP and the N uptake during the entire eucalyptus cultivating period. It is therefore much easier to estimate ANPP through N uptake than through water use because the former had a linear correlation during the entire eucalyptus cultivating period. Under a maximal condition, every 1 kg of N used by eucalypts could produce 1.08 Mg of NPP. Overall, the average NUE during the growing stage was 0.69 Mg/kg. In general, to harvest 1 Mg of woody biomass of eucalypts, it would need about 212 m3 of water and 0.005 kg of N. The ratio of water use to N use for producing 1 Mg of woody biomass was 4.24E+07. Therefore, the growth of eucalypts had a detrimental impact on water resources rather than N resources. All of our simulations results compared very well with the literature reported values, which confirmed that the STELLA developed here is capable to predict the eucalyptus WUE, NUE, ANPP, and WBP.

Technical Abstract: Eucalypt is one of the fastest growing hardwoods for bioenergy production. However, there is currently a lack of a modeling tool to estimate the biomass production in response to water use and N uptake in a growing-eucalyptus plantation. In this study, a STELLA (Structural Thinking and Experiential Learning Laboratory with Animation) model was developed to meet this need. A simulation scenario was chosen to assess eucalyptus annual net primary production (ANPP) and woody biomass production (WBP) as well as their relationships to water use efficiency (WUE) and nitrogen use efficiency (NUE) for a simulation period of 20 years. Our simulations showed that a typical annual variation pattern exited for water use, N uptake and ANPP, with increasing from spring to fall followed by decreasing from fall to winter. In general, the average WUE during the growing stage (first 13 years) was 2.97 kg/m3 and water was used more efficiently in turn of eucalyptus ANPP during this stage. A positively linear correlation was found between ANPP and water use during the eucalyptus growing stage but not the matured stage. In contrast, a positively linear correlation was found between ANPP and N uptake during the entire eucalyptus cultivating period. It is therefore easier to estimate ANPP through N uptake than through water use. Overall, the average NUE during the growing stage was 0.69 Mg/kg. In general, to harvest 1 Mg of woody biomass of eucalypts, it would need about 212 m3 of water and 0.005 kg of N. The ratio of water use to N use for producing 1 Mg of woody biomass was 4.24E+07. Therefore, the growth of eucalypts had a detrimental impact on water resources rather than N resources. This study suggests that the STELLA model developed is a useful tool to estimate eucalyptus ANPP and WBP as well as their relationships to WUE and NUE in a growing-eucalyptus plantation.