Banca de QUALIFICAÇÃO: MERY INGRID GUIMARÃES DE ALENCAR

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : MERY INGRID GUIMARÃES DE ALENCAR
DATE: 27/03/2024
TIME: 14:00
LOCAL: Google Meet
TITLE:

Litter-mixing effects on decomposition: patterns and mechanisms in aquatic and terrestrial ecosystems

KEY WORDS:

non-additive effects; litter-mixing effects; tropical forests; functional traits; litter diversity; functional diversity

PAGES: 196
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

The diversity loss has several consequences for ecosystem processes. Although decomposition is essential for the cycling of matter and flow energy in ecosystems, it is still unclear how the diversity loss can affect the decomposition. Thus, we aimed to evaluate the effect of litter diversity on decomposition (hereafter litter-mixing effects), specifically by assessing the general patterns and mechanisms at different taxonomic levels, time scales, and ecosystem types. In Chapter I, through a meta-analysis, we evaluated how the species-specific responses in mixtures can alter the occurrence, direction (i.e. positive or negative), and magnitude of decomposition compared to monocultures. Our results indicate that in order to accurately understand the litter-mixing effects, it is necessary to evaluate the species-specific responses in mixtures. And that the functional litter dissimilarity and litter identity were the main factors mediating the litter-mixing effects in aquatic and terrestrial ecosystems. In chapter II, also through a meta-analysis, we evaluated the complementarity effects between labile litter (i.e. higher nutrient concentration) and refractory litter (i.e. lower nutrient concentration), since there is a consensus that labile litter accelerate the decomposition of refractory litter, while refractory litter decrease the decomposition of labile litter, however this premise has never been directly tested. To classify leaf litter from various studies into labile and refractory litter, our results indicate that labile litter showed no changes in decomposition when interacting with refractory litter; while refractory litter had an antagonistic response when interacting with labile litter. To evaluate the litter-mixing effects considering ecosystem type, presence or absence of decomposers, and decomposition stage, we observed a preponderance of antagonistic responses in both litter types. To directly evaluate the responses of labile and refractory litter in mixtures, we highlight patterns that challenge the current direction in the effects of complementarity between litter with different nutrient concentrations. In Chapter III, we evaluated the litter-mixing effects at intraspecific level diversity in aquatic and terrestrial ecosystems, using flower and leaf litter of Tabebuia aurea (Silva Manso) Benth. & Hook. f. ex. S. Moore as a model. Our results indicate that flower litter has a higher concentration of nutrients such as N, P, and K and a higher water retention capacity, indicating that flower litter can be considered a labile litter, while leaf litter had a higher concentration of Ca, Mg, and Na. Our results indicate that the litter-mixing effects may be important at the intraspecific level between different organs and that these effects were stronger in terrestrial ecosystems. In this chapter we highlight a possible secondary role of flowers in ecosystems in the cycling of organic matter. In Chapter IV, we tested the generality of flower litter as labile organic matter and leaf litter as refractory organic matter in the terrestrial ecosystem. Specifically, we evaluated patterns and predictors of flower and leaf litter on decomposition at the intra- and inter-specific levels for 29 species. Our results indicate that flower litter had higher concentrations of N, P, and K, while leaf litter had higher density, Ca, Mg, and Na. And that the decomposition of both litter type was predicted by leaching rate, P, Ca, Mg, and Na. Overall, the observed differences in decomposition rates and litter traits between the litter types indicate differences between flowers and leaves in the potential litter-mixing effects. In Chapter V, we evaluated the litter-mixing effects in different temporal dynamics, using an experimental approach simulating different litterfall input regimes. Specifically, we evaluated how an intermittent or seasonal litterfall input regime affect the occurrence, direction, and magnitude of litter-mixing effects in aquatic and terrestrial ecosystems. We simulated the two litterfall input regimes over 240 days and assessed the influence of richness effect (1, 2 and 4 species) and species composition, totaling 704 microcosms. In addition, we evaluated the temporal dynamics of 11 functional litter traits. We did not find a clear pattern between the litterfall input regimes and litter-mixing effects. However, we observed the preponderance of litter-mixing effects in aquatic ecosystem, probably related to different nutrient dynamics and the concentration of nutrients in the water column. Thus, the results obtained in the thesis contribute to advancing knowledge of litter-mixing effects in previously unexplored contexts and to directly compare aquatic and terrestrial ecosystems. In addition, we also highlight the importance of evaluating species-specific responses to better understand the litter-mixing effects.

COMMITTEE MEMBERS:
Presidente - 1714892 - ADRIANO CALIMAN FERREIRA DA SILVA
Interna - 1677189 - GISLENE MARIA DA SILVA GANADE
Externo à Instituição - ALAN MOSELE TONIN - UnB