Abstract
There have been a number of studies on biogeographic patterns of plant leaf functional traits; however, the variations in traits of other plant organs such as twigs are rarely investigated. In this study, we sampled current-year twigs of 335 tree species from 12 forest sites across a latitudinal span of 32 degrees in China, and measured twig specific density (TSD), twig dry matter content (TDMC), and carbon (C), nitrogen (N) and phosphorous (P) contents, to explore the latitudinal and environmental patterns of these twig traits. The overall mean of TSD and TDMC was 0.37 g cm−3 and 41%, respectively; mean twig C, N and P was 472 mg g−1, 9.8 mg g−1 and 1.15 mg g−1, respectively, and mean N:P mass ratio was 10.6. TSD was positively correlated with TDMC which was positively associated with twig C but negatively with twig N and P. There were no significant differences in TSD between conifer, deciduous-broadleaf and evergreen-broadleaf plants, but evergreen-broadleaf plants had the lowest and conifers the highest TDMC. Conifer twigs were lowest in C, N, P and N:P, whereas deciduous-plant twigs were highest in N and P and evergreen-plant twigs were highest in C and N:P. As latitude increased or temperature/precipitation dropped, TDMC and P increased, but N:P ratio decreased. Our results also showed that the patterns of twig P and N:P stoichiometry were consistent with those reported for leaves, but no significant trends in twig N were observed along the gradient of latitude, climate and soils. This study provides the first large-scale patterns of the twig traits and will improve our understanding of the biogeochemistry of carbon and other key nutrients in forest ecosystems.
Highlights
As an independent building block and one of the most active compartments of the whole plant [1,2], twigs of trees provide mechanical support and transport water and nutrients
Changes in twig dry matter content (TDMC) and N and P stoichiometry along latitudinal and environmental gradients Because twig specific density (TSD) showed a close exponential relationship with TDMC, as present before, we only reported the biogeographic patterns of the TDMC and C:N:P stoichiometry
We documented the variation in structural traits and C, N, and P stoichiometry of twigs for 335 woody species and provided the first large-scale patterns of twig traits along a gradient of climate and soils across eastern China
Summary
As an independent building block and one of the most active compartments of the whole plant [1,2], twigs of trees provide mechanical support and transport water and nutrients. Resource allocation to twigs is an important aspect of plant life-history strategy [3,4]. Latitude Patterns of Twig Traits and C:N:P Stoichiometry resources include carbon (C), nitrogen (N) and phosphorous (P) as vital elements of all living organisms [5]. Previous studies showed that twigs (twigs defined here as their shoot axes without leaves or reproductive structures) nutrient status may allow better prediction of plant resource state and potential deficiencies in N or P than leaves [6,7]. In addition to nutrient contents, twig dry matter content (TDMC) and twig specific density (TSD) are the other two important functional traits, with the former closely related to plant flammability and the latter reflecting the trade-off between plant growth rate and defensive ability [8]
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