The pedogenic Walker and Syers model under high atmospheric P deposition rates

Antonio Gallardo,Alfredo Bermúdez,Jorge Durán,Lea De Nascimento,Alexandra Rodríguez,Laura García-Velázquez,Javier Méndez,José María Fernández-Palacios

doi:10.1007/s10533-020-00657-8

Abstract

The Walker and Syers model predict that phosphorus (P) availability decreases with time leading to a final stage known as retrogression. We tested the validity of the Walker and Syers model in the Canary Islands, a soil chronosequence ranging from 300 years to 11 million years under recurrent episodes of atmospheric dust-containing P inputs. In particular, we compared our results with those from the volcanic soil chronosequences described in the Hawaii Islands and in Arizona, as they share key biological and/or geological characteristics. In three islands of the Canarian Archipelago, we selected 18 independent sites dominated by mature Pinus canariensis forests and grouped them into six age classes. For each site, soil samples were analyzed for known proxies of soil nitrogen (N), P and cations availability. We also analyzed the P. canariensis needles for N, P and cation contents. We found tendencies similar to those observed in other soil chronosequences: maximum N and P concentrations at intermediate ages and lower P concentrations in the older soils. The nutrient dynamics suggested that the older sites may indeed be approaching the retrogression stage but at lower rates than in other similar chronosequences. Differences from other chronosequences are likely due to the drier Canarian climate, the higher P deposition rates originating from the nearby Sahara Desert and the top soil horizon studied. Our results confirm the validity of the Walker and Syers model for the Canary Islands despite the influence that the high P deposition rates and the seasonally dry climate may have on soil development and P pools in P. canariensis ecosystems.

Highlights

The Walker and Syers pedogenesis model (Walker and Syers 1976) suggests that primary production in young soils should be limited by N but that this limitation should shift first to N and P co-limitation and to P limitation in the oldest soils
We studied plant and soil N and P contents in a chronosequence in the Canary Islands (Spain) including volcanic substrates ranging from a few 100 years old for the youngest sites to more than 11 My old for the oldest site
The Canary Islands receive large amounts of atmospheric dust that mostly originate in the Sahara Desert, which is less than 100 km from the Eastern Islands

Summary

Introduction

The Walker and Syers pedogenesis model (Walker and Syers 1976) suggests that primary production in young soils should be limited by N but that this limitation should shift first to N and P co-limitation and to P limitation in the oldest soils This theory is based in several biogeochemical processes. The low N content found in parent rocks (as compared to P and other nutrients) should determine low N availability in the first stages of ecosystem development. Atmospheric N fixation and rock weathering are the main processes driving the relative availability of N versus P during ecosystem development, losses can play an important role in determining nutrient limitation

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