Determinants of variation in heath vegetation structure on coastal dune fields in northeastern South America

Abstract

Despite its implications for carbon storage, animal conservation, and plant regeneration, the variation in the structure of heath vegetation in South America is still poorly studied. In this study, we aimed at examining the edaphic and topographic determinants of this variation along 85 plots (5 9 5 m) randomly distributed in a restinga heath vegetation occurring on coastal dune fields in northeastern Brazil. We carried out a PCA analysis to reduce eleven vegetation descriptors into a small number of structural gradients, which were then assessed by a stepwise standard least-squares multiple regression to reveal the effects of the abiotic environment on structure. The three following hypotheses were tested: (1) both soils and topography are important to explain variation in vegetation structure at local scale; (2) herbaceous plants, cactus, and woody plants show differential responses to soil and topographic variations; and (3) soil acidity and salinity are more important determinants of herbaceous cover than woody plant variation. PCA analysis revealed three major structural gradients related to biomass, herbaceous cover, and leaning plants, respectively. These gradients were only related to calcium and nitrogen contents, which partially supports our first hypothesis. Our results also suggest that different groups of plants have different responses to abiotic gradients that are exposed. The effect of the soil acidity and salinity did not appear to present an immediate strong influence on the herbaceous community. It seems that a reduced number of edaphic factors promote the variation in vegetation structure in the restinga heath vegetation.

Common species distribution and environmental determinants in South American coastal plains

“…A number of researchers have found that soil nutrients, aluminum content, acidity, percentage of sand, and amount of organic matter are related to changes in heath vegetation physiognomy from marsh to scrub to forest (Silva et al. ) as well as to local community structure both locally (Scarano , Santos‐filho et al. ) and regionally (Marques et al.…”

“…Its structure varies from open herbaceous vegetation on beaches and the windward slopes of sand dunes to mosaics of scrub and short forest patches on the leeward slopes of sand dunes and coastal plains (Silva et al. ). We studied heath communities along the Brazilian coast, which corresponds to ~60% of the Atlantic coast of South America and extends ~9000 km from the Oiapoque River (04.19° N, 51.60° W) to the Brazil/Uruguay border (33.70° S, 53.42° W; Fig.…”

“…Restinga heath vegetation occurs as a complex of vegetation types that covers beaches, sand dunes, and coastal plains as well as river and lagoon margins on sandy soils along the eastern South American coast (Marques et al 2011). Its structure varies from open herbaceous vegetation on beaches and the windward slopes of sand dunes to mosaics of scrub and short forest patches on the leeward slopes of sand dunes and coastal plains (Silva et al 2016). We studied heath communities along the Brazilian coast, which corresponds to~60% of the Atlantic coast of South America and extends~9000 km from the Oiapoque River (04.19°N, 51.60°W) to the Brazil/Uruguay border (33.70°S, 53.42°W; Fig.…”

“…These conditions impose severe limitations to plant growth (Marques et al 2015). A number of researchers have found that soil nutrients, aluminum content, acidity, percentage of sand, and amount of organic matter are related to changes in heath vegetation physiognomy from marsh to scrub to forest (Silva et al 2016) as well as to local community structure both locally (Scarano 2002, Santos-filho et al 2013) and regionally (Marques et al 2011). Adaptations to poor soil conditions have been found in restinga species like shallow root systems, aluminum toxicity avoidance through accumulation in the roots or silicate compounds in leaves, timing of phenological events to optimize nutrient cycling, and small leaves with increased thickness (Marques et al 2015).…”

Weak whole‐plant trait coordination in a seasonally dry South American stressful environment

“…A stem vulnerability index was calculated using vessel diameter and vessel density (Scholz et al., ). The main stem length and stem diameter at soil level were obtained from Silva, Silva, and Souza ().…”