Soils and their effects on Brazilian Caatinga vegetation

• Autor(a) principal: Brunello, Alexandre Tadeu
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/59/59139/tde-29062023-140152/
• topic: δ15N do solo; Above-ground biomass; Atributos funcionais; Biomassa acima do solo; Caatinga; Caatinga; Climatic gradients; Edaphic gradients; Functional traits; Gradientes climáticos; Gradientes edáficos; Materiais de origem do solo; Pedogênese; Pedogenesis; Semiarid soils; Soil δ15N; Soil parent materials; Soils; Solos; Solos semiáridos

Soil properties have long been overlooked in studies that attempt to disentangle the potential influence of multiple drivers on vegetation properties. This lack of a systematic approach to how soils influence vegetation is markedly evident in studies focusing on seasonally dry tropical forests (SDTFs). An intensive soil and vegetation sampling in 29 study plots across the seasonal dry Caatinga domain (that is, a geographic comparison approach) allowed evaluating variations in several soil properties among three geological affiliations [that is, sedimentary (SSED), metamorphic (SMET) and karst (SKAR)], and investigating to which extent these properties relate to variations in above-ground woody biomass (AGBW), communityweighted mean traits and functional diversity indexes. The soil properties varied systemically among geological affiliations, with some properties, however, showing substantially higher variation than others. For example, weathering-associated metrics such as effective cation exchange capacity (IE) and total reserve bases (ΣRB) were found to decrease following SKAR > SMET > SSED, while total soil phosphorus concentrations ([P]T) were relatively higher at the SKAR sites. Moreover, the distribution of main soil exchange cations (that is, Ca, Mg, K, Na, and Al) in the soil sortive complex reflected the original soil parent materials, with soil base cations being generally higher at the SKAR and SMET sites. In contrast, exchangeable aluminium levels were generally higher at the SSED sites. Nitrogen dynamics, addressed by soil δ15N values, was found to be primarily modulated by climatic forces [that is, aridity index (AI) and the seasonality of the precipitation (Ψ)]. However, a role for IE on soil δ15N values was also suggested, especially at the wetter sites. The AGBW was found to be influenced by both soil and climate. For instance, mean annual precipitation (PA) and soil fertility (represented by calcium) positively influenced AGBW levels. Furthermore, interactions between long-term climatic water deficit (CWD) and both [Ca]ex and the maximum plant-available soil water content (θP) suggest that AGBW in Caatinga is driven by complex interactions. Soil properties were also related to community functional properties, with all community-weighted mean maximum stem diameter (CWMdmax), community-weighted mean wood density (CWMwd), functional richness (FRic), functional evenness (FEve), and functional divergence (FDiv) being influenced by soil properties. In that regard, an inverse relationship was found between soil base cations and CWMwd. In contrast, soil base cations had a positive influence on CWMdmax. Finally, several soil nutritional metrics positively influenced FRic, while only a few elements inversely influenced both FEve and FDiv metrics. These relationships are thought to reflect vegetation trade-offs between investment in secondary growth and water-economy strategies. Collectively, these results provide information on the multiple ways through which soils can affect vegetation structure and functioning.