Interactions among phosphorus, pH and Eh in reforested mangroves, Vietnam: a three-dimensional spatial analysis
Julian F. Oxmann
Luitgard Schwendenmann
Rubén J. Lara
Abstract
Sediment reduction is frequently proposed to increase available phosphorus (P) but several studies found also decreases. Another important factor for P liberation is the pH. We investigated the relative importance of Eh and pH on P cycling in reforested mangroves. Sediment P compounds, pH and Eh were analysed over depth along five transects of two areas in the Saigon River Delta and compared with leaf P levels. A three-dimensional spatial approach was used to investigate pH and Eh effects on P compound distribution at different sediment depth and locate layers of predominant P uptake. Along an inundation gradient, submergence durations of 254 to 2 days per year caused a large Eh gradient within the top 20 cm, whereas Eh response was small within 20–45 cm depth. At individual layers, a correlation between Eh and Al/Fe–P was only found in the upper depth interval (0–20 cm). No significant effect of Eh or Al/Fe–P on Morgan-P (available P) was detected. Minor effects on P composition changes by the Eh were caused through generally strongly reduced sediment at deeper layers (>20 cm). In contrast, pH variations produced extreme differences in both, Ca–P and available P content at layers of apparently predominant P uptake (>20 cm). As available P was correlated with Ca–P (p < 0.001), leaf P (p < 0.001) and pH (non linear correlation) it is likely that the pH sensitive Ca–P fraction is a more effective source for mangrove tree growth than Al/Fe–P. The predominant pH effect on P uptake within these reforested mangroves differs from a proposed reduction-governed P cycling in wetlands.
Oxmann J.F., Schwendenmann L. and Lara R.J. (2009) Interactions among phosphorus, pH and Eh in reforested mangroves, Vietnam: a three-dimensional spatial analysis. Biogeochemistry 96(1-3): 73-85. 10.1007/s10533-009-9345-5
@article{Oxmann2009,
Title = {Interactions among phosphorus, pH and Eh in reforested mangroves, Vietnam: a three-dimensional spatial analysis},
Author = {Oxmann, Julian F. and Schwendenmann, Luitgard and Lara, Rubén J.},
Editor = {},
Journal = {Biogeochemistry},
Year = {2009},
Pages = {73-85},
Volume = {96},
Doi = {10.1007/s10533-009-9345-5},
Abstract = {Sediment reduction is frequently proposed to increase available phosphorus (P) but several studies found also decreases. Another important factor for P liberation is the pH. We investigated the relative importance of Eh and pH on P cycling in reforested mangroves. Sediment P compounds, pH and Eh were analysed over depth along five transects of two areas in the Saigon River Delta and compared with leaf P levels. A three-dimensional spatial approach was used to investigate pH and Eh effects on P compound distribution at different sediment depth and locate layers of predominant P uptake. Along an inundation gradient, submergence durations of 254 to 2 days per year caused a large Eh gradient within the top 20 cm, whereas Eh response was small within 20–45 cm depth. At individual layers, a correlation between Eh and Al/Fe–P was only found in the upper depth interval (0–20 cm). No significant effect of Eh or Al/Fe–P on Morgan-P (available P) was detected. Minor effects on P composition changes by the Eh were caused through generally strongly reduced sediment at deeper layers (>20 cm). In contrast, pH variations produced extreme differences in both, Ca–P and available P content at layers of apparently predominant P uptake (>20 cm). As available P was correlated with Ca–P (p < 0.001), leaf P (p < 0.001) and pH (non linear correlation) it is likely that the pH sensitive Ca–P fraction is a more effective source for mangrove tree growth than Al/Fe–P. The predominant pH effect on P uptake within these reforested mangroves differs from a proposed reduction-governed P cycling in wetlands.},
}
TY - JOUR
AU - Oxmann, Julian F.
AU - Schwendenmann, Luitgard
AU - Lara, Rubén J.
TI - Interactions among phosphorus, pH and Eh in reforested mangroves, Vietnam: a three-dimensional spatial analysis
T2 - Biogeochemistry
PY - 2009
SP - 73-85
VL - 96
DO - 10.1007/s10533-009-9345-5
AB - Sediment reduction is frequently proposed to increase available phosphorus (P) but several studies found also decreases. Another important factor for P liberation is the pH. We investigated the relative importance of Eh and pH on P cycling in reforested mangroves. Sediment P compounds, pH and Eh were analysed over depth along five transects of two areas in the Saigon River Delta and compared with leaf P levels. A three-dimensional spatial approach was used to investigate pH and Eh effects on P compound distribution at different sediment depth and locate layers of predominant P uptake. Along an inundation gradient, submergence durations of 254 to 2 days per year caused a large Eh gradient within the top 20 cm, whereas Eh response was small within 20–45 cm depth. At individual layers, a correlation between Eh and Al/Fe–P was only found in the upper depth interval (0–20 cm). No significant effect of Eh or Al/Fe–P on Morgan-P (available P) was detected. Minor effects on P composition changes by the Eh were caused through generally strongly reduced sediment at deeper layers (>20 cm). In contrast, pH variations produced extreme differences in both, Ca–P and available P content at layers of apparently predominant P uptake (>20 cm). As available P was correlated with Ca–P (p < 0.001), leaf P (p < 0.001) and pH (non linear correlation) it is likely that the pH sensitive Ca–P fraction is a more effective source for mangrove tree growth than Al/Fe–P. The predominant pH effect on P uptake within these reforested mangroves differs from a proposed reduction-governed P cycling in wetlands.
ER -
