Soil and Leaf Micronutrient Composition in Contrasting Habitats in Podzolized Sands of the Amazon Region

María Antonieta Sobrado

doi:10.4236/ajps.2013.410235

Abstract

Plant macronutrient distribution in podzolized sands of the Amazon caatinga has received attention in several studies; however, the distribution of micronutrients has not been assessed. Soil micronutrient availability has been hypothesized to reflect contrasting habitat characteristics as well as fundamental differences in substrate, and leaf micronutrient composition may reflect the macronutrient content needed to maintain balance for leaf cell functions. In this study, soil and leaf samples were obtained in a toposequence (valley, slope, and mound). Available soil micro- and macronutrients as well as total leaf content were measured by inductively coupled plasma-atomic emission spectrometer and mass spectroscopy. Soil Zn (-1) and B (-1) as well as Cu (-1) levels were very low. Soil Mn was low in the valleys and slopes (0.62-0.87 mg·kg-1), but higher in the mound (6.59 mg·kg-1). Soil Fe (11.48-21.13 mg·kg-1) was well above the critical level in all of the habitats. Leaf micronutrients Cu, B, Zn, and Fe were below the critical levels for tropical crops of 3-7, 20-70, 15-20, and 72 mg·kg-1, respectively. Leaf Mn (88 mg·kg-1) and Al (-1) were below the accumulators level. A strong relationship between leaf micro- and macronutrients suggests the maintenance of a homeostatic elemental composition, which may favour photosynthetic function. Therefore, the local distribution of species may be shaped by their abilities to maintain a balance of micronutrient collected through roots under critically low levels of available Zn, B, and Cu whilst excluding potentially deleterious ions of Mn, Fe, and Al.

Highlights

Micronutrient availability and cycles in tropical areas are poorly understood, even though such information is imperative for a thorough understanding of the complexities of major element cycles in these habitats [1]
That the leaf micronutrient composition of species thriving in different habitats may reflect the macronutrient content at particular sites in order to maintain the ion balance for leaf cell functions
Soil pH was significantly different across sites, with the lowest (3.33 ± 0.06) and highest (4.22 ± 0.03) values found in the waterlogged valley bottoms and sandy mounds, respectively (p < 0.05)

Summary

Introduction

Micronutrient availability and cycles in tropical areas are poorly understood, even though such information is imperative for a thorough understanding of the complexities of major element cycles in these habitats [1]. The interactions among elements within plant cells tend to reflect the regulatory network involved in the homeostasis of the ionome [5,6] These interactions and the balance of ions in plant tissue may have an ecophysiological significance as well, which requires further investigation in order to gain insight into these processes. It was hypothesized that soil micronutrient availability may reflect contrasting habitat characteristics, AJPS and that the leaf micronutrient composition of species thriving in different habitats may reflect the macronutrient content at particular sites in order to maintain the ion balance for leaf cell functions. The micronutrient composition of soils and leaves of dominant tree species within the toposequence of the caatinga vegetation was assessed. Differences in the dominant species thriving in each of these contrasting sites were determined

Methods

Results

Discussion

Conclusion