J Plant Ecol ›› 2014, Vol. 7 ›› Issue (6): 526-534.DOI: 10.1093/jpe/rtu001

• Research Articles • Previous Articles     Next Articles

Phosphorus limitation on photosynthesis of two dominant understory species in a lowland tropical forest

Feifei Zhu1,2, Xiankai Lu1 and Jiangming Mo1,*   

  1. 1 Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Xingke Road, Tianhe, Guangzhou 510650, China; 2 Graduate University of the Chinese Academy of Sciences, Yuquan Road, Shijingshan, Beijing 100049, China
  • Received:2013-10-23 Accepted:2014-01-14 Published:2014-11-20
  • Contact: Mo, Jiangming

Abstract: Aims Elevated nitrogen (N) deposition in tropical regions may accelerate ecosystem phosphorus (P) limitation. However, it is not explicitly addressed that how changes in soil N and P availability affect foliar nutrients and photosynthesis of plants in tropical forests. In this study, we examined the effects of N and P additions on foliar nutrients and net photosynthesis of two dominant understory species, Randia canthioides (R. canthioides) and Cryptocarya concinna (C. concinna) in an N-saturated old-growth tropical forest (>400-year-old) in southern China.
Methods A full factorial NP addition experiment (2×2) was established in 2007 and continued through August 2010. Four treatments, including control, N addition (150kg N ha-1 year-1), P addition (150kg P ha-1 year-1) and NP addition (150kg N ha-1 year-1 plus 150kg P ha-1 year-1) were set up in this experiment. Photosynthetic traits (maximum photosynthetic CO2 assimilation (A max), stomatal conductance (g s), leaf transpiration (E), light saturating point, concentrations of chlorophyll a/b and foliar nutrients (N and P) of the two species were measured with standard methods.
Important findings Three years of N addition had no significant effects on any measured photosynthetic parameter of either species. However, N addition significantly elevated foliar N and P concentrations of one species (R. canthioides), resulting in lower photosynthetic nitrogen use efficiency (PNUE). N treatments decreased foliar P concentration of the other (C. concinna), resulting in increased photosynthetic phosphorus use efficiency, which was potentially related to N-induced P shortage. In contrast, positive effects of P treatments on g s of R. canthioides, A max and chlorophyll a+b of C. concinna were observed. P treatments also elevated foliar P and PNUE of both species, implying P induced more efficient use of N. Our results suggested a more important role of P than N on influencing photosynthetic traits of these two understory species. Alleviation of P shortage through P addition may enhance photosynthetic performances of some understory species in N-rich tropical forests.

Key words: N saturation, P limitation, photosynthesis, lowland tropical forests, southern China

摘要:
Aims Elevated nitrogen (N) deposition in tropical regions may accelerate ecosystem phosphorus (P) limitation. However, it is not explicitly addressed that how changes in soil N and P availability affect foliar nutrients and photosynthesis of plants in tropical forests. In this study, we examined the effects of N and P additions on foliar nutrients and net photosynthesis of two dominant understory species, Randia canthioides (R. canthioides) and Cryptocarya concinna (C. concinna) in an N-saturated old-growth tropical forest (>400-year-old) in southern China.
Methods A full factorial NP addition experiment (2×2) was established in 2007 and continued through August 2010. Four treatments, including control, N addition (150kg N ha-1 year-1), P addition (150kg P ha-1 year-1) and NP addition (150kg N ha-1 year-1 plus 150kg P ha-1 year-1) were set up in this experiment. Photosynthetic traits (maximum photosynthetic CO2 assimilation (A max), stomatal conductance (g s), leaf transpiration (E), light saturating point, concentrations of chlorophyll a/b and foliar nutrients (N and P) of the two species were measured with standard methods.
Important findings Three years of N addition had no significant effects on any measured photosynthetic parameter of either species. However, N addition significantly elevated foliar N and P concentrations of one species (R. canthioides), resulting in lower photosynthetic nitrogen use efficiency (PNUE). N treatments decreased foliar P concentration of the other (C. concinna), resulting in increased photosynthetic phosphorus use efficiency, which was potentially related to N-induced P shortage. In contrast, positive effects of P treatments on g s of R. canthioides, A max and chlorophyll a+b of C. concinna were observed. P treatments also elevated foliar P and PNUE of both species, implying P induced more efficient use of N. Our results suggested a more important role of P than N on influencing photosynthetic traits of these two understory species. Alleviation of P shortage through P addition may enhance photosynthetic performances of some understory species in N-rich tropical forests.