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| Author(s): |
João Paulo Darela Filho
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Rio Claro. 2022-03-02. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro |
| Defense date: | 2021-12-14 |
| Advisor: | David Montenegro Lapola |
| Abstract | |
The Amazon Forest dieback hypothesis was postulated in early 2000, and many studies suggested that a future climate induced dieback of the Amazon Forest was a real possibility. However, the CO2 fertilization effect may possibly enhance forest productivity and biomass for decades to come, phasing out the projected forest loss. The response of the Amazon Forest to elevated CO2 effects is however uncertain. Two important features that have not been considered in vegetation model projections: (1) the potentially limiting role of nutrients, namely, nitrogen (N) and phosphorus (P), on the CO2 fertilization effect and (2) the possibility of interspecific response variation (i.e., changes in community composition). For example, different plant growth/surviving strategies are likely to differ in their responses to climate change and elevated CO2 more than they differ in terms of effects on ecosystem processes and state. Changes at the community level can have cascading effects on ecosystems and synergistic effects with other ecosystem processes, attributes, or even environmental changes. The biogeochemical cycles, mainly nitrogen and phosphorus, are increasingly recognized as important controls of the future global carbon cycle. In addition, models based on high plant functional variability rise as a promising alternative to better characterize the dynamics of changing ecosystems. This study presents an innovative modelling approach considering the fully coupling of carbon (C), N and P biogeochemical cycles, in a modeling framework that simulates the coexistence of hundreds of Plant Life-history Strategies. A never tested combination of characteristics in terrestrial ecosystem models. The new model was applied to simulate the ecosystems of the Pan-amazon in a recent climatological and historical period (1979-2016) and in a sensitivity test involving variations in temperature, precipitation, CO2, and nutrient concentration (N and P). The historical simulation was compared with reference data in a biogeochemical evaluation process, based on a protocol of wide use in the modeling of terrestrial ecosystems. The historical simulation and the data generated in the sensitivity test were the basis for the development of a multidimensional functional analysis method that was used here to accurately identify important interactions between the functional composition of the simulated vegetation and the ecosystem processes under different simulated environmental conditions. The results of the sensitivity tests were qualitatively compared to the results of experiments involving the manipulation of nutrients and climatic variables. Finally, in the light of the previous analyses, a detailed analysis of the historical simulation was performed, aiming the elucidation of the various effects on vegetation, which are caused by increased water stress, temperature, and atmospheric CO2 concentration between 1979 and 2016. The combination of greater functional diversity and the N and P cycles coupled to the C cycle in a dynamic vegetation model revealed important interactions between functional composition of the simulated area and the complex balance between C assimilation and autotrophic respiration, which ultimately make up the main control over biomass in terrestrial ecosystems. Additionally, a relevant result not foreseen in the initial plan is presented: a set of maps and an analysis of the different chemical forms of P in the soils of the study area. (AU) | |
| FAPESP's process: | 17/00005-3 - Modeling the role of nutrients for the stability of the Amazon Forest in light of climate change |
| Grantee: | João Paulo Darela Filho |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |