DOI: 10.5061/dryad.tmpg4f55m
title: The synergy of intrinsic ecological mechanisms of leaf nutrient resorption in temperate deciduous trees

description: Nutrient resorption is a critical process in plant nutrient conservation
 during leaf senescence. However, the underlying ecological mechanisms on
 the large variabilities in nitrogen (NRE) and phosphorous (PRE) resorption
 efficiencies remain poorly understood. We conducted a comprehensive study
 on NRE and PRE variability using 61 tree individuals of 10 temperate
 broadleaved tree species. Three potentially interrelated intrinsic
 ecological mechanisms (i.e., leaf pigments, energy residual and leaf
 senescence phenology) were verified. We found that delayed leaf senescence
 date, increased degradation of chlorophyll and carotenoids, biosynthesis
 of anthocyanins, and reduced nonstructural carbohydrates (particular
 sugars) coordinately and positively related with NRE and PRE. The
 intrinsic factors affecting the resorption efficiency were ranked in a
 decreasing order: leaf pigments &gt; energy residual &gt;
 senescence phenology. Our findings underscore the synergistic effect of
 the three ecological mechanisms on leaf nutrient resorption, and hold
 significant implications for comprehending how nutrient resorption
 responds to climate change.
description: The datset was conducted at the Maoershan Forest Ecosystem
 Research Station (45°24′N,127°40′E), Heilongjiang Province, northeastern
 China. The site has a continental monsoon climate, with a mean annual
 temperature of 2.1°C and mean precipitation of 726 mm from 2008 to
 2019. From early autumn until leaf-fall in 2022, we
 randomly marked 61 individuals from 10 tree species, at least 3 healthy
 and mature individuals were selected from each species (Table S1). The
 early autumn was carefully determined for sampling time for green mature
 leaves, by considering: (1) the N, P and chlorophyll concentrations have
 been not entering the rapid decline phase based on the seasonality of leaf
 nutrients and chlorophyll. (2) The NSC level has been past its depletion
 period during rapid summer growth, according to the carbon sink saturation
 hypothesis on leaf senescence phenology. Furthermore, none of the species
 has N-fixing symbionts, excluding the contamination of N-fixing status on
 effects of intrinsic factors on NuRE and anthocyanins. Although we found
 the NRE was lower in arbuscular mycorrhizal than ectomycorrhiza fungi
 associated trees (40.2% versus 51.2%, <em>P</em> &lt;
 0.01), we did not consider this difference between the two mycorrhizal
 association types (consistent with the results by Guo<em> et
 al.</em> 2023) because we sampled five species equally for each
 mycorrhizal type. The percentage of leaves on the
 canopy that are colored and remaining is usually recorded by a visual
 estimation every two days, 50% of the leaves on the crown changed color
 (or 10% of the leaves fallen for green autumn leafed species) as the start
 of leaf coloration, 50% of the leaves remaining as the peak of leaf-fall,
 and 90% of the leaves fallen as the end of leaf-fall. We recorded the day
 of year (DOY) for start of leaf coloration, peak of leaf-fall, and end of
 leaf-fall changes for each individual. The air temperature measured with
 HMP45C (Vaisala, Finland) at the 16 m height on the flux tower was used to
 calculate thermal time for interpreting leaf senescence
 phenology. In early September (September 4-7, 2022),
 just before leaf senescence, we manually climbed each tree to cut a small
 branch from the mid-to-upper canopy to obtain green leaves to represent
 the whole crown. Then newly fallen leaves were collected at the ground as
 the senesced leaf sample, which fairly well represented the whole crown
 because the fallen leaves were well mixed among vertical canopy layers.
 All samples were brought back to the laboratory and transferred to a
 refrigerator as soon as possible. The samples of green leaves and senesced
 leaves were then measured for (1) leaf mass per area (LMA), (2) leaf
 pigments concentrations, and (3) NSC and nutrient
 concentrations. <em>Leaf mass per
 area</em> Leaf mass per area was obtained for
 green and senescent leaves by measuring the fresh leaf area with 300-DPI
 scanned pictures and weighing the dry mass at 70°C for 48 hours.
 <em>Leaf pigment concentration</em>
 One hundred mg of fresh leaves was weighed and moved into
 centrifuge tubes with steel beads for chlorophyll and carotenoids, and 200
 mg of fresh leaves frozen in liquid nitrogen was crushed in centrifuge
 tubes with glass beads for anthocyanins, before measurement. Chlorophyll
 and carotenoids were extracted using acetone- absolute alcohol- deionized
 water in a 4.5:4.5:1 ratio ultrasonic extraction in darkness, while
 Anthocyanins were extracted by hydrochloric acid methanol-solution in a
 2:98 ratio ultrasonic extraction in the dark, and the extracted solutions
 were balanced with corresponding pH buffers for measurement. Chlorophyll,
 carotenoids, and anthocyanins in the extracted solutions were measured
 using a spectrophotometer at different wavelengths (Eqs. 1-8). Leaf water
 content relative to fresh mass was also measured for converting
 fresh-mass-based pigments concentrations to dry-mass-based concentrations
 (%DM). Chlorophyll and carotenoids concentrations were calculated as
 follows: Chla
 (mg/g)=12.55A<sub>663.2</sub>-2.79A<sub>646.8</sub>                                                                             (1) Chlb (mg/g)=21.50A<sub>646.8</sub>-5.10A<sub>663.2</sub>                                                                             (2) Total chl (mg/g)=7.15A<sub>663.2</sub>+18.71A<sub>646.8</sub>                                                                       (3) Carotenoids (mg/g)=1000A<sub>470</sub>-1.82Chla+85.02Chlb/198                                              (4) where Chla is the concentration of chlorophyll a; Chlb is the concentration of chlorophyll b; total Chl is the total chlorophyll concentration; A<sub>663.2</sub> is the absorbance value of the sample at 663 nm; A<sub>646.8</sub> is the absorbance value of the sample at 647 nm; A<sub>470</sub> is the absorbance value of the sample at 470 nm. The anthocyanins concentration (only for senescent leaves) was measured with a pH differential method: C<sub>ac</sub> (mg/mL)=δA×Mw/(s×L)                                                                                             (5) where C is the total anthocyanins concentration; ΔA is the difference of absorptance at two pH values (Eq. 6); DF is dilution factor established in D; s indicates that the molar absorptivity of the final mixture is ; Mw is the standard molecular weight of the final mixture of ; and L indicates the optical range of the cuvette (1 cm).  δA=[A<sub>510nm</sub>(pH1.0)-A<sub>700nm</sub>(pH1.0)] - [A<sub>510nm</sub>(pH4.5)-A<sub>700nm</sub>(pH4.5)]                       (6) Then, we corrected the volumetric concentration (C<sub>ac</sub>) with a standard curve using cyanidin-3-glucoside as the equivalent:  C<sub>0</sub>=1.1974×C<sub>ac</sub>-0.0004                                                                                                 (7) Volume concentrations were converted to anthocyanins concentration based on fresh mass:  TAC=C<sub>0</sub>×V<sub>1</sub>×V<sub>2</sub>×DF/m                                                                                                 (8) DF is the equilibrium dilution factor, V<sub>1</sub> and V<sub>2</sub> are the volume of the extractant and equilibrium constant volume. The water content of senesced leaves was used to convert the anthocyanins concentration based on fresh mass to that based on dry mass. <em>Leaf nonstructural carbohydrate concentration</em> The NSC was determined by an improved phenol-sulfuric acid method, which used enzymatic degradation of starch and thus avoided the overestimation of starch concentration caused by hydrolyzed hemicellulose and cellulose components by sulfuric acid. The NSC was defined as soluble sugars and starch, and the sum of the two referred to as total NSC (TNC), expressed as a percentage of dry mass (%DM). The concentrations of soluble sugar and starch were determined based on the sucrose standard curve. <em>Leaf nutrient concentration</em> N and P for green and senescent leaves were digested with concentrated sulfuric acid and hydrogen peroxide, and then measured using a continuous flow analyzer (AA3, Bran+luebbe, Germany).
description: # The synergy of intrinsic ecological mechanisms of leaf nutrient
 resorption in temperate deciduous trees
 This dataset is supporting
 for “The synergy of intrinsic ecological mechanisms of leaf nutrient
 resorption in temperate deciduous trees”. It included 61 tree individuals
 of 10 species. Three potentially interrelated intrinsic ecological
 mechanisms (i.e., leaf pigments, energy residual and leaf senescence
 phenology) were verified. These data are also invaluable in explore the
 senesced leaf traits. ## Description of the data and file structure The
 dataset is available as a csv file, including 33 variables. The data for
 each tree individual is listed. The variable name and unit (in the
 parentheses) are listed below. 1.       Chinese_name, the name of tree
 species in Chinese from . 2.      
 Latin_name, the scientific name of tree species from
 . 3.       NRE, nitrogen resorption
 efficiency (%) 4.       PRE, phosphorus resorption efficiency (%) 5.      
 StartDOY, start of leaf coloration (or leaf fall) (DOY) 6.       PeakDOY,
 peak of leaf fall (DOY) 7.       EndDOY, end of leaf fall (DOY) 8.      
 TNC_green, total nonstructural carbohydrates in green leaves (mg/g)
 9.       SSugars_green, soluble sugars in green leaves (mg/g) 10.   
 Starch_green, starch in green leaves (mg/g) 11.    Chl_green, chlorophyll
 in green leaves (mg/g) 12.    Chla_green, chlorophyll a in green leaves
 (mg/g) 13.    Chlb_green, chlorophyll b in green leaves (mg/g) 14.   
 Car_green, carotenoids in green leaves (mg/g) 15.    N_green, nitrogen in
 green leaves (mg/g) 16.    P_green, phosphorus concentration in green
 leaves (mg/g) 17.    TNC_sen, total nonstructural carbohydrates in
 senesced leaves (mg/g) 18.    SSugars_sen, total nonstructural
 carbohydrates in senesced leaves (mg/g) 19.    Starch_sen, total
 nonstructural carbohydrates in senesced leaves (mg/g) 20.    Chl_sen,
 chlorophyll in senesced leaves (mg/g) 21.    Car_sen, carotenoids in
 senesced leaves (mg/g) 22.    TAC_sen, total anthocyanins in senesced
 leaves (mg/g) 23.    N_sen, nitrogen in senesced leaves (mg/g) 24.   
 P_sen, phosphorus in senesced leaves (mg/g) 25.    DeltaChl, degradation
 of chlorophyll (mg/g) 26.    DeltaCar, degradation of carotenoids (mg/g)
 27.    DeltaChl_per, degradation percentage of chlorophyll (%) 28.   
 DeltaChla_per, degradation percentage of chlorophyll a (%) 29.   
 DeltaChlb_per, degradation percentage of chlorophyll b (%) 30.   
 DeltaCar_per, degradation percentage of carotenoids (%) 31.    DeltaTNC,
 change of total nonstructural carbohydrates (%) 32.    DeltaTNC_per,
 change percentage of total nonstructural carbohydrates (%) 33.    CDD_15,
 cooling degree days (°C·d)