Nitrogen and phosphorus additions alter nutrient dynamics but not resorption efficiencies of Chinese fir leaves and twigs differing in age

Abstract

It is unclear how or even if phosphorus (P) input alters the influence of nitrogen (N) deposition in a forest. In theory, nutrients in leaves and twigs differing in age may show different responses to elevated nutrient input. To test this possibility, we selected Chinese fir (Cunninghamia lanceolata) for a series of N and P addition experiments using treatments of +N1 - P (50 kg N ha(-1) year(-1)), +N2 - P (100 kg N ha(-1) year(-1)), -N + P (50 kg P ha(-1) year(-1)), +N1 + P, +N2 + P and -N - P (without N and P addition). Soil samples were analyzed for mineral N and available P concentrations. Leaves and twigs in summer and their litters in winter were classified as and sorted into young and old components to measure N and P concentrations. Soil mineral N and available P increased with N and P additions, respectively. Nitrogen addition increased leaf and twig N concentrations in the second year, but not in the first year; P addition increased leaf and twig P concentrations in both years and enhanced young but not old leaf and twig N accumulations. Nitrogen and P resorption proficiencies in litters increased in response to N and P additions, but N and P resorption efficiencies were not significantly altered. Nitrogen resorption efficiency was generally higher in leaves than in twigs and in young vs old leaves and twigs. Phosphorus resorption efficiency showed a minimal variation from 26.6 to 47.0%. Therefore, P input intensified leaf and twig N enrichment with N addition, leaf and twig nutrients were both gradually resorbed with aging, and organ and age effects depended on the extent of nutrient limitation.

Transcriptome Characterization of the Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook.) and Expression Analysis of Candidate Phosphate Transporter Genes

“…Unigenes c219691, c213460, and c193149, whose gene functional annotations were identified as the pathogenesis-related protein Bet v I family, thaumatin-like protein, and translationally-controlled tumor protein, respectively, had a relatively high expression level across the root, stem, and leaf transcriptions. Research over the past 20 years has provided clear evidence that the limited availability of phosphorus in forest soil is widespread and plays an important factor in the declining productivity of Chinese fir plantations over successive rotations [1,12,[14][15][16]. Therefore, we have selected the unigenes with the functional annotations of inorganic phosphate transporter activity for further analysis.…”

“…Furthermore, the successive rotation patterns characteristic of Chinese fir plantations amplify the lack of available P in forest soil [6]. Thus, the mass application of phosphate fertilizer has been commonly used in Chinese fir plantations across the country, which is now causing serious issues of soil and water pollution [12].…”

“…As a result, extensive research has been conducted on more efficient methods of P fertilization, cultivation, and breeding of Chinese fir over the past 20 years [1,12,[14][15][16]. One effective strategy for reducing the use of P fertilizers is the selecting and breeding of Chinese fir genotypes with high P acquisition and utilization efficiencies in areas where P availability is limited [17].…”

“…Unfortunately, for Chinese fir, there is a significant lack of genomic information and genetic tools, which severely encumbers molecular breeding and functional genomic research in this important timber species [2,23]. To date, there is no report available on studies of the PHT genes identification or functional analysis on Chinese fir, even though considerable research has been published on the physiology and ecology of trees grown under conditions of serious P deficiency [1,12].…”

Phosphorus addition affects soil nitrogen dynamics in a nitrogen‐saturated and two nitrogen‐limited forests

“…In contrast to this view, Bahr et al . () showed a negligible effect when the forest received addition of both N and P. Studies in N‐limited forests have also produced inconsistent results, showing both positive (Chen et al ., ) and negligible effects (Corbin et al ., ; Homeier et al ., ; Martinson et al ., ). More importantly, the previous studies lacked consistency in experimental method and soil type; thus, the comparability of their results was weak.…”