Changes in soil carbon and nutrients following 6 years of litter removal and addition in a tropical semi-evergreen rain forest

Abstract

Abstract. Increasing atmospheric CO 2 and temperature may increase forest productivity, including litterfall, but the consequences for soil organic matter remain poorly understood. To address this, we measured soil carbon and nutrient concentrations at nine depths to 2 m after 6 years of continuous litter removal and litter addition in a semi-evergreen rain forest in Panama. Soils in litter addition plots, compared to litter removal plots, had higher pH and contained greater concentrations of KCl-extractable nitrate (both to 30 cm); Mehlich-III extractable phosphorus and total carbon (both to 20 cm); total nitrogen (to 15 cm); Mehlich-III calcium (to 10 cm); and Mehlich-III magnesium and lower bulk density (both to 5 cm). In contrast, litter manipulation did not affect ammonium, manganese, potassium or zinc, and soils deeper than 30 cm did not differ for any nutrient. Comparison with previous analyses in the experiment indicates that the effect of litter manipulation on nutrient concentrations and the depth to which the effects are significant are increasing with time. To allow for changes in bulk density in calculation of changes in carbon stocks, we standardized total carbon and nitrogen on the basis of a constant mineral mass. For 200 kg m −2 of mineral soil (approximately the upper 20 cm of the profile) about 0.5 kg C m −2 was "missing" from the litter removal plots, with a similar amount accumulated in the litter addition plots. There was an additional 0.4 kg C m −2 extra in the litter standing crop of the litter addition plots compared to the control. This increase in carbon in surface soil and the litter standing crop can be interpreted as a potential partial mitigation of the effects of increasing CO 2 concentrations in the atmosphere.

Litter removal in a tropical rain forest reduces fine root biomass and production but litter addition has few effects

“…This strengthens the nonsignificant trend, after 1.5 yr, for lower fine root mass in litter removal plots (Sayer et al 2006). Differences between the two sets of results are likely to be due to the fact that the earlier study was for 1 month only, whereas the current study was for 12 months; in addition effects may have strengthened over time, as litter is continuously removed, due to decreasing soil nutrient availability and increasing soil bulk density (Tanner et al 2016). In Costa Rica, in the second year of a litter manipulation experiment, litter removal did not affect fine root mass (Leff et al 2012).…”

“…Soil nutrient concentrations have been changed by both litter removal and litter addition and the effects are increasing over timemore nutrients became significantly different and the depth to which differences were seen increased (Sayer and Tanner 2010, Tanner et al 2016, Sheldrake et al 2017. Corresponding Editor: Joseph B. Yavitt.…”

“…The plots are large (45 m 9 45 m), they were trenched to 50 cm, and trenches lined with plastic, to isolate the surface soil within the plots from that in the surrounding forest. Soil nutrient concentrations have been changed by both litter removal and litter addition and the effects are increasing over timemore nutrients became significantly different and the depth to which differences were seen increased (Sayer and Tanner 2010, Tanner et al 2016, Sheldrake et al 2017. By 9 yr after the start of the experiment litter removal plots had lower: NO 3 À +NH 4 + ; "available" P; exchangeable Ca and Mg; and litter addition soils had higher: "available" P and exchangeable Ca (Sheldrake et al 2017).…”

Arbuscular mycorrhizal fungal community composition is altered by long‐term litter removal but not litter addition in a lowland tropical forest

“…Given much greater root colonisation by AM fungi in the organic horizons of the litter addition and control plots relative to the mineral soil, it is surprising that we observed no significant increase in root colonisation in the mineral soil of litter addition treatments relative to controls (Fig. a–d), where organic matter content is elevated relative to controls (Tanner et al ., ). It is possible that plant investment in AM fungi in litter addition plots is lower, due to the increases in soil fertility and tree nutrient status (indicated by marginal increases in litterfall and foliar N and P; Fig.…”

Spatial distribution of the litter carbon stock in the Cerrado biome in Minas Gerais state, Brazil

“…Studies have demonstrated that its removal, which mostly occurs by land-use changes and burning, causes negative impacts on the soil quality properties, like soil bulk density, soil organic matter and microbiological diversity (Tanner;Sheldrake;Turner, 2016). However, an excessive accumulation of organic matter in soil surface can also promote effects in soil's function which are not yet entirely understood by the science as reported by Leff et al (2012); Lajtha et al (2014a); Lajtha et al (2014b) and Bowden et al (2014).…”