Leaf litter inputs decrease phosphate sorption in a strongly weathered tropical soil over two time scales

Abstract

In strongly weathered soils, leaf litter not only returns phosphorus (P) to the soil environment, it may also modify soil properties and soil solution chemistry, with the potential to decrease phosphate sorption and increase plant available P. Using a radioactive phosphate tracer ( 32 P) and 1 h laboratory incubations we investigated the effect of litter inputs on phosphate sorption over two time scales: (1) long-term field litter manipulations (litter addition, control and litter removal) and (2) pulses of litter leachate (i.e. water extracts of leaf litter) from five species. Leachate pulse effects were compared to a simulated throughfall, which served as a control solution. Soil receiving long-term doubling of leaf litter maintained five-fold more phosphate in solution than the litter removal soil. In addition to the quantity of phosphate sorbed, the field litter addition treatment decreased the strength of phosphate sorption, as evaluated through extraction of sorbed 32 P using a weakly acidic ammonium fluoride solution (Bray 1). In litter removal soil, leachate pulses significantly reduced phosphate sorption in comparison to the throughfall control for all five species evaluated. However, the ability of leachate pulses to reduce phosphate sorption decreased when soil had received field litter inputs. Across soils the effect of leachate pulses on phosphate sorption increased with net sorption of dissolved organic C, with the exception of leachate from one species that had a higher index of aromatic C concentration. These results demonstrate that litter inputs, as both long-term inputs and short-term leachate pulses, can decrease the quantity and strength of phosphate sorption, which may increase the biological availability of this key nutrient.

Seasonal changes in soil organic matter after a decade of nutrient addition in a lowland tropical forest

“…A further treatment (four replicate plots) included calcium and magnesium (from dolomitic limestone) and micronutrients. Rates of N and K are similar to the annual amounts of these nutrients in litter fall (Sayer and Tanner 2010;Wright et al 2011), but the rate of P addition is approximately tenfold greater than P in annual litter fall to overcome the inherent high P fixation capacity of the soil at this site (Schreeg et al 2013).…”

Impact of Simulated Changes in Water Table Depth on Ex Situ Decomposition of Leaf Litter from a Neotropical Peatland

“…By contrast, water-extractable N increased with time as N was released from the more recalcitrant litter fractions. The rapid leaching of P was probably due to release of inorganic P present in vacuoles and rapid metabolism of P held in molecules such as nucleic acids and ATP (Schreeg et al 2012). There was also a loss of C from all fractions, albeit less rapid, reflecting a combination of microbial respiration and leaching of C (Wright and Reddy 2001).…”

“…The relative contributions of carbon to peatlands from fine litter, including leaves, coarse woody debris and roots are broadly similar, with fine litter input being marginally greater (Mahli et al 2011). Decomposition of leaf litter is important for the rapid return of nutrients to the ecosystem (Schreeg et al 2012) and may also make an important contribution to peat formation (Brady 1984;Yule and Gomez 2009).…”

Oxygen isotope ratios of plant available phosphate in lowland tropical forest soils

“…This Technique has provided valuable information on soil P dynamics in different ecosystems worldwide (Zohar et al, 2010;Angert et al, 2011Angert et al, , 2012Tamburini et al, 2012;Gross et al, 2013;Gross and Angert, 2015), but has not so far been applied in tropical soils. We took advantage of two long-term and well-studied field experiments in lowland tropical forest in Panama: an experiment initiated in 1998 involving factorial P, nitrogen (N) and potassium (K) additions Yavitt et al, 2011;Sayer et al, 2012;Mirabello et al, 2013;Schreeg et al, 2013;Turner and Wright, 2014), and a second experiment initiated in 2003 at the same site involving litter manipulation (removal and addition) (Sayer and Tanner, 2010;Vincent et al, 2010;Sayer et al, 2012). These experiments allowed us to isolate the role of nutrients and leaf litter status in the soil P cycle and study the processes that mediate soil P dynamics, while controlling other soil properties such as texture and organic matter content.…”

“…This process was shown to affect the quantities and strength of phosphate sorption to the soil in the same site (Schreeg et al, 2013). Even though no difference was found in the soil microbial C or N in the upper 10 cm of soils from the L þ control, K and L À plots six years after the start of the experiment (Sayer et al, 2012), we suggest that the microbial phosphate turnover rate (measured by us nine years after the start of the experiment) was significantly slower in the L þ plots, as inferred from the significantly larger difference between the incubation steady state values and the values measured in the incubations of these soils (1.1‰, Fig.…”