Growth rates are of fundamental importance for plants, as individual size affects myriad ecological processes. We determined the factors that generate variation in RGR among 14 species of trees and shrubs that are abundant in subtropical Chinese forests. We grew seedlings for two years at four light levels in a shade-house experiment. We monitored the growth of every juvenile plant every two weeks. After one and two years, we destructively harvested individuals and measured their functional traits and gas-exchange rates. After calculating individual biomass trajectories, we estimated relative growth rates using nonlinear growth functions. We decomposed the variance in log(RGR) to evaluate the relationships of RGR with its components: specific leaf area (SLA), net assimilation rate (NAR) and leaf mass ratio (LMR). We found that variation in NAR was the primary determinant of variation in RGR at all light levels, whereas SLA and LMR made smaller contributions. Furthermore, NAR was strongly and positively associated with area-based photosynthetic rate and leaf nitrogen content. Photosynthetic rate and leaf nitrogen concentration can, therefore, be good predictors of growth in woody species.
biomass data
These are observations on biomass, which form the core of the study. See Supplemental Figure S1 for a graphical representation. COLUMN HEADINGS: 'spcode' the number of the species (names available in 'species data' file). 'house': Which shadehouse did the seedling grow in? 'indiv' Which individual was the observation made on?, 'light' the light (in %) in the shadehouse. 'day' how many days since the start of the study did the observation occur? 'biomass': the estimated biomass on this day in grams (see Methods for details on how biomass was estimated).
biomass.csv
Species descriptions
THis is basically Table 1. It summarises chaarcteristics of each species used in the study, linking the species codes (spcode) to the famil, genus and species of each taxon. column 'deciduous' indicates whether the species is deciduous or evergreen. Max height is in meters. Successional stage gives the rough shade tolerance of the taxon.
species_data.csv
harvest data
This file contains data from the two destructive harvests. The first six columns are just like in the biomass data file. 'Harvest' indicates which of the two harvests the observation was made. 'date' gives the number of days since the start of the study of the harvest. 'height' is the height of teh measured individual. girth_1 and girth_2 are two perpendicular basal diameters of the stem. BiomassR, BiomassS, BiomassL, and BiomassA give, respectively, the individual's biomass of roots, stem, leaves and all (the sum of the three prior). THickness gives leaf thickness in micrometers (measured only at harvest 3). Leaf area is leaf area of the individual, in cm^2.
gas exchange data
This file provides details on rates of gas exchange made at the time of the second harvest. The first six columns are just as in the biomass data file. 'Area' represents the leaf area measured for photosynthetic rate in the cuvette, in cm^2. 'N' leaf nitrogen concetration, on a mass basis, in percent. 'thickness': leaf blade thickness, in micrometers. 'LMR' leaf mass ratio. 'Lcp' Light compensation point - the amount of light (in µmol m-2·s-1) at which photosynthesis is zero. 'Amax': the predicted maximal rate of photosynthesis per unit area in CO2·m-2·s-1. SLA_photo: specific leaf area, 'Amass': predicted maximal photosynthetic rate per unit leaf biomass in nmol CO2·g-1·s-1.
gas_exchange_data.csv
