HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Turner, B. L. Articles by Romero, T. E. PubMed Articles by Turner, B. L. Articles by Romero, T. E. Agricola Articles by Turner, B. L. Articles by Romero, T. E. Related Collections Tropical Soils Nutrient Cycling Forest Soils

SOIL CHEMISTRY

Short-Term Changes in Extractable Inorganic Nutrients during Storage of Tropical Rain Forest Soils

Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama

^* Corresponding author (TurnerBL{at}si.edu).

The nutrient status of tropical forests is commonly assessed by measuring inorganic nutrients extracted from soil, yet samples from remote research sites may be stored for prolonged periods of time before analysis. We assessed the influence of soil storage conditions on extractable nutrients in three lowland tropical forests soils from the Republic of Panama. The soils spanned a strong rainfall gradient and contained contrasting chemical and physical properties. Storage treatments were: (i) room temperature (22°C in the dark), (ii) refrigerated (4°C in the dark), (iii) air dried (10 d at 22°C and 55% humidity), and (iv) frozen (–35°C). Ammonium and NO₃ were extremely unstable and concentrations changed considerably within hours of sampling. Phosphate extracted by anion-exchange membranes also changed rapidly following sampling, although cations (Ca, K, and Mg) extracted in Mehlich-3 solution were less influenced by storage. Soil pH declined slowly in all samples during field-moist storage (4 and 22°C). Freezing and air drying generally caused significant changes in extractable nutrients, although the effects varied among soils and nutrients. We therefore conclude that inorganic nutrients should be extracted from tropical forest soils within 24 h of sampling, and preferably on the day of sampling for N fractions, to ensure that values represent field conditions. Where this is not possible, rapid air drying or storage of field-moist samples may be acceptable for some measurements (e.g., PO₄, cations, pH), but are unlikely to provide realistic measurements of inorganic N.

Abbreviations: AEM, anion exchange membrane • ICP–OES, inductively coupled plasma optical-emission spectrometry