Leaf litter nitrogen concentration as related to climatic factors in Eurasian forests

Abstract

Aim The aim of this study is to determine the patterns of nitrogen (N) concentrations in leaf litter of forest trees as functions of climatic factors, annual average temperature (Temp, ° C) and annual precipitation (Precip, dm) and of forest type (coniferous vs. broadleaf, deciduous vs. evergreen, Pinus , etc.). LocationThe review was conducted using data from studies across the Eurasian continent.Methods Leaf litter N concentration was compiled from 204 sets of published data (81 sets from coniferous and 123 from broadleaf forests in Eurasia). We explored the relationships between leaf litter N concentration and Temp and Precip by means of regression analysis. Leaf litter data from N 2 -fixing species were excluded from the analysis. ResultsOver the Eurasian continent, leaf litter N concentration increased with increasing Temp and Precip within functional groups such as conifers, broadleaf, deciduous, evergreen and the genus Pinus . There were highly significant linear relationships between ln(N) and Temp and Precip ( P < 0.001) for all available data combined, as well as for coniferous trees, broadleaf trees, deciduous trees, evergreen trees and Pinus separately. With both Temp and Precip as independent variables in multiple regression equations, the adjusted coefficient of determination ( ) was evidently higher than in simple regressions with either Temp or Precip as independent variable. Standardized regression coefficients showed that Temp had a larger impact than Precip on litter N concentration for all groups except evergreens. The impact of temperature was particularly strong for Pinus . ConclusionsThe relationship between leaf litter N concentration and temperature and precipitation can be well described with simple or multiple linear regression equations for forests over Eurasia. In the context of global warming, these regression equations are useful for a better understanding and modelling of the effects of geographical and climatic factors on leaf litter N at a regional and continental scale.

Global pattern of leaf litter nitrogen and phosphorus in woody plants

“…A number of studies have attempted to establish relationships between climate factors and N and P concentration for Mean annual temperature ( o C) Latitude the leaf-litter of woody plants at a regional (Aerts, 1997;Liu et al, 2006) and global scale (Aerts, 1997;McGroddy et al, 2004;Yuan and Chen, 2009b). Our study use a new dataset to establish the general patterns in N and P concentrations and N:P ratios in leaf-litter of woody plants at a global level, showing some inconsistent results with previous studies.…”

“…Aerts (1997) reported that both leaf-litter N and P concentrations follow a positive but non-linear relationship with actual evapotranspiration based on a dataset concerning cool and warm temperate sites, the Mediterranean and the humid lowland tropics. Liu et al (2006) reported that leaf-litter N concentration increased linearly with mean annual temperature (MAT,…”

“…During recent years, we have compiled a global dataset of leaf-litter N and P of woody plants based on a survey of the literature and the Eurasian dataset of Liu et al (2006). Although this dataset shares 44 papers with Yuan and Chen's (2009b) meta-analysis of global trends of leaf-litter N and P reported, this amounts to only 13% of their dataset.…”

“…Both can affect the functional type of vegetation and the rate of chemical processes (Liu et al, 2006;Yuan and Chen, 2009b). Other climatic factors that have been implicated include actual evapotranspiration (AET, mm) which when integrated with precipitation it can describe the water balance (Aerts, 1997).…”

“…To achieve these objectives we compiled a global data set of N and P concentrations and N:P ratios for the leaf-litter of woody plants, by expanding a data set of 204 samples for Eurasia (Liu et al, 2006) to a total of 677 samples worldwide.…”