Responses of plant nutrient resorption to phosphorus addition in freshwater marsh of Northeast China.

Rong Mao,Chang-Chun Song,De-Hui Zeng,Xin-Hou Zhang

doi:10.1038/srep08097

Abstract

Anthropogenic activities have increased phosphorus (P) inputs to most aquatic and terrestrial ecosystems. However, the relationship between plant nutrient resorption and P availability is still unclear, and much less is known about the underlying mechanisms. Here, we used a multi-level P addition experiment (0, 1.2, 4.8, and 9.6 g P m−2 year−1) to assess the effect of P enrichment on nutrient resorption at plant organ, species, and community levels in a freshwater marsh of Northeast China. The response of nutrient resorption to P addition generally did not vary with addition rates. Moreover, nutrient resorption exhibited similar responses to P addition across the three hierarchical levels. Specifically, P addition decreased nitrogen (N) resorption proficiency, P resorption efficiency and proficiency, but did not impact N resorption efficiency. In addition, P resorption efficiency and proficiency were linearly related to the ratio of inorganic P to organic P and organic P fraction in mature plant organs, respectively. Our findings suggest that the allocation pattern of plant P between inorganic and organic P fractions is an underlying mechanism controlling P resorption processes, and that P enrichment could strongly influence plant-mediated biogeochemical cycles through altered nutrient resorption in the freshwater wetlands of Northeast China.

Highlights

Anthropogenic activities have increased phosphorus (P) inputs to most aquatic and terrestrial ecosystems
D. angustifolia leaf and stem biomass generally declined, while G. spiculosa leaf and stem biomass increased with increasing P addition levels (Table 1)
In this study, adding P with different levels generally had the similar effects on plant nutrient resorption parameters across the three hierarchical levels. These findings provided evidence that there existed a threshold for P enrichment-induced effects on plant nutrient resorption

Summary

Introduction

Anthropogenic activities have increased phosphorus (P) inputs to most aquatic and terrestrial ecosystems. The relationship between plant nutrient resorption and P availability is still unclear, and much less is known about the underlying mechanisms. Our findings suggest that the allocation pattern of plant P between inorganic and organic P fractions is an underlying mechanism controlling P resorption processes, and that P enrichment could strongly influence plant-mediated biogeochemical cycles through altered nutrient resorption in the freshwater wetlands of Northeast China. Phosphorus enrichment generally increases P concentration in mature leaves and reduces plant P resorption proficiency (i.e. the level to which nutrient concentration is reduced in senesced organs7) in fertilization studies[12,13,14]. Knowledge about the allocation patterns of P fractions in plants is needed to unravel the underlying mechanism controlling the response of plant P resorption to increased P inputs. Different lowercase letters in the same rows indicated significant differences among the four treatments

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Conclusion