Modeling rhizosphere carbon and nitrogen cycling in <i>Eucalyptus</i> plantation soil

Abstract

Abstract. Vigorous Eucalyptus plantations produce 105 to 106 km ha−1 of fine roots that probably increase carbon (C) and nitrogen (N) cycling in rhizosphere soil. However, the quantitative importance of rhizosphere priming is still unknown for most ecosystems, including these plantations. Therefore, the objective of this work was to propose and evaluate a mechanistic model for the prediction of rhizosphere C and N cycling in Eucalyptus plantations. The potential importance of the priming effect was estimated for a typical Eucalyptus plantation in Brazil. The process-based model (ForPRAN – Forest Plantation Rhizosphere Available Nitrogen) predicts the change in rhizosphere C and N cycling resulting from root growth and consists of two modules: (1) fine-root growth and (2) C and N rhizosphere cycling. The model describes a series of soil biological processes: root growth, rhizodeposition, microbial uptake, enzymatic synthesis, depolymerization of soil organic matter, microbial respiration, N mineralization, N immobilization, microbial death, microbial emigration and immigration, and soil organic matter (SOM) formation. Model performance was quantitatively and qualitatively satisfactory when compared to observed data in the literature. Input variables with the most influence on rhizosphere N mineralization were (in order of decreasing importance) root diameter > rhizosphere thickness > soil temperature > clay concentration. The priming effect in a typical Eucalyptus plantation producing 42 m3 ha−1 yr−1 of shoot biomass, with assumed losses of 40 % of total N mineralized, was estimated to be 24.6 % of plantation N demand (shoot + roots + litter). The rhizosphere cycling model should be considered for adaptation to other forestry and agricultural production models where the inclusion of such processes offers the potential for improved model performance.

Modelling the Rhizosphere Priming Effect in Combination with Soil Food Webs to Quantify Interaction between Living Plant, Soil Biota and Soil Organic Matter

“…Model testing at the level of whole soil horizon reflects the situation with a complete exudate uptake and utilisation by microorganisms due to N of exudates and N mining, and complete microbial biomass consumption by soil microfauna. The simulation results quantitatively assess the contribution of PE to the total CO 2 emission as an important process that can reach up to one third of the CO 2 emission from the whole soil that also was experimentally confirmed [ 11 , 40 ]. The impact of PE on CO 2 emission from soil and on N mineralisation was consimilar.…”

“…There are also models of the priming for specific sites and for rhizosphere processes related to exudate dynamics [ 39 , 40 ]. Finzi et al [ 41 ] used a combination of two microbial decomposition models [ 42 , 43 ] to study exudate flux in the rhizosphere with the conclusion that about one third of CO 2 emission in forest ecosystem is produced by priming.…”

Nitrate Uptake from an Aquifer by Two Plantation Forests: Plausibility Strengthened by Process-Based Modelling

“…Input values for soil organic C, C:N ratio, and pH were set to measured values at the sites or nearby where available, or else left as the acquired SLGA values. Inputs of N from precipitation [27], non-symbiotic N fixation [28], and rhizosphere priming [29], which are processes not specifically simulated in APSIM and poorly quantified generally, were together set at 10 kg ha −1 year −1 applied in equal 3-monthly instalments. Seedlings were provided with 40 kg N ha −1 at planting as nitrate.…”

Modelagem de base processual aplicada ao crescimento e produtividade do eucalipto

“…O modelo APSIM Next Generation tem sido utilizado para simular espécies silviculturais, tais como plantações de eucalipto (Valadares et al, 2018;Elli, et al, 202a;Elli, et al, 2020b), pinus e até mesmo em sistemas agroflorestais (Smethurst et al, 2017). A estrutura do APSIM Next Generation inclui uma coleção de classes genéricas de software, como órgãos e funções de plantas, que podem ser montadas e parametrizadas (Brown et al, 2018;Zhu et al, 2021).…”

“…Waring, 1997) tem se destacado por sua base fisiológica, desenvolvida por relações empíricas e de base fisiológica mais complexa, a partir de medidas experimentais e cálculos de campo (Gupta e Sharma, 2019 . O APSIM Next Generation Eucalyptus também tem sido amplamente utilizado em plantações de eucalipto pela capacidade de simular o crescimento da biomassa acima do solo do eucalipto em uma ampla gama de condições edáficas e de manejo (Valadares 2018;Elli et al, 2020b) e impactos da mudança climática na produtividade da cultura .…”