Effects of 9 years of continuous field phosphorus fertilization on adsorption of dissolved organic matter in tropical forest soil

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Abstract
For many years, there has been a prevailing belief that the activity of soil microorganisms in tropical forests is limited by the availability of phosphorus (P). This belief has traditionally found support in experimental research, consistently demonstrating that the addition of P leads to an increase in heterotrophic soil respiration. However, we have introduced an alternative hypothesis that challenges this conventional perspective. Our proposition suggests that the evidence traditionally utilized to substantiate this belief is, in fact, an outcome of increased carbon (C) availability resulting from abiotic processes initiated by the release of organic matter from soil mineral surfaces, which occurs as a consequence of P addition. Indeed, our previous study has empirically established two significant findings: (i) the acceleration of soil respiration through P fertilization, accompanied by the absence of concurrent stimulation in litter decomposition, and (ii) the immediate increase in extracted DOC resulting from the laboratory introduction of P prior to extraction. In the present study, we have expanded upon the existing body of evidence by providing field-based support that soils subjected to P fertilization display a reduced ability to adsorb newly introduced DOC. The prolonged period of 9 years of continuous fertilization tended to diminish the adsorption capacity of experimentally added DOC, which probably facilitated the acquisition of C by soil microorganisms and thus contributed to the stimulation of soil respiration in our study site. Building upon our previous findings, we propose that the traditionally used evidence to substantiate microbial P limitation is, in fact, a consequence of abiotically increased C availability resulting from P addition.

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