Detailed 3D plant architectural data have numerous applications in plant science, but many existing approaches for 3D data collection are time-consuming and/or require costly equipment. Recently, there has been rapid growth in the availability of low-cost, 3D cameras and related open source software applications. 3D cameras may provide measurements of key components of plant architecture such as stem diameters and lengths, however, few tests of 3D cameras for the measurement of plant architecture have been conducted. Here, we measured Salix branch segments ranging from 2–13 mm in diameter with an Asus Xtion camera to quantify the limits and accuracy of branch diameter measurement with a 3D camera. By scanning at a variety of distances we also quantified the effect of scanning distance. In addition, we also test the sensitivity of the program KinFu for continuous 3D object scanning and modeling as well as other similar software to accurately record stem diameters and capture plant form (<3 m in height). Given its ability to accurately capture the diameter of branches >6 mm, Asus Xtion may provide a novel method for the collection of 3D data on the branching architecture of woody plants. Improvements in camera measurement accuracy and available software are likely to further improve the utility of 3D cameras for plant sciences in the future.

Aims: Mineral-associated organic matter, mainly derived from microbial by-products, persists longer in soil compared to particulate organic matter (POM). POM is highly recalcitrant and originates largely from decomposing root and shoot litter. Theory suggests that root traits and growth dynamics should affect carbon (C) accumulation into these different pools, but the specific traits driving this accumulation are not clearly identified. Methods: Twelve herbaceous species were grown for 37 weeks in monocultures. Root elongation rate (RER) was measured throughout the experiment. At the end of the experiment, we determined morphological and chemical root traits, as well as substrate induced respiration (SIR) as a proxy for microbial activity. Carbon was measured in four different soil fractions, following particlesize and density fractionation. Results: In N2-fixing Fabaceae species, root biomass, RER, root diameter, hemicellulose content and SIR, were all positively correlated with increased C in the coarse silt fraction. Root diameter and hemicellulose content were also negatively correlated with C in the POM fraction, that was greater under non N2-fixing Poaceae species, characterized by lignin-rich roots with a high carbon:nitrogen ratio that grew slowly. The accumulation of C in different soil pools was mediated by microbial activity. Conclusions: Our results show that root traits determine C input into different soil pools, mediated primarily by microbial activity, thus determining the fate of soil organic C. We also highlight that C in different soil pools, and not only total soil organic C, should be reported in future studies to better understand its origin, fate and dynamics. Abbreviations Abbreviation Meaning C Carbon POM Particulate organic matter C:N Carbon-nitrogen ratio in plant tissue and/or soil N2-fixing Dinitrogen fixing t0 Time zero, beginning of the experiment t37 Time 37 weeks, end of the experiment ΔC Delta carbon, as difference between carbon at time 0 and carbon at time 37, in different fractions (mg C g-1 soil) CPOM Carbon in the coarse POM 200-2000 µm fraction (mg C g-1 soil) CfinePOM Carbon in the fine POM 50-200 µm fraction (mg C g-1 soil) CSILT Carbon in the 20-50 µm coarse silt fraction (mg C g-1 soil) C SILT+CLAY Carbon in the fine silt+clay <20 µm fraction (mg C g-1 soil) ΔCSUM Sum of delta carbon in different fractions, ΔCSUM = ΔCPOM + ΔCfinePOM + ΔCSILT + ΔCSILT+CLAY (mg C g-1 soil) RER Root elongation rate (mm d-1) RLP Root length production (m) RERNEW, RLPNEW RER and RLP of 'new' roots initiated during the 2 weeks interval between measurements REROLD, RLPOLD RER and RLP of 'old' roots, initiated more than 2 weeks before the measurement SIR Substrate induced respiration (µg C-CO2 g-1 soil h-1

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Developmental plasticity, the acclimation of plants to their local environment, is known to be crucial for the fitness of perennial organisms such as trees. However, deciphering the many possible developmental and environmental influences involved in such plasticity in natural conditions requires dedicated statistical models integrating developmental phases, environmental factors, and interindividual heterogeneity. These models should be able to analyse retrospective data (number of leaves or length of annual shoots along the main stem in the present case). In this study Markov switching linear mixed models were applied to the analysis of the developmental plasticity of walnut saplings during the establishment phase in a mixed Mediterranean forest. In the Markov switching linear mixed models estimated from walnut data sets, the underlying Markov chain represents both the succession and lengths of growth phases, while the linear mixed models represent both the influence of climatic factors and interindividual heterogeneity within each growth phase. On the basis of these integrative statistical models, it is shown that walnut saplings have an opportunistic mode of development that is primarily driven by the changing light environment. In particular, light availability explains the ability of a tree to reach a phase of strong growth where the first branches can appear. It is also shown that growth fluctuation amplitudes in response to climatic factors increased while interindividual heterogeneity decreased during tree development.

Plant root traits are diverse and variable, and the way in which they interact has consequences for fundamental functions such as anchorage, or services such as soil fixation. Here, we characterize mechanical traits related to anchorage (tensile strength, strain, stiffness and toughness) at both intra‐ and inter‐specific levels and examine how they covary with other traits related to the root economics space. We grew twelve herbaceous species from contrasting taxonomical families in a common garden experiment. For each species, we excavated root systems and measured mechanical, morphological and chemical traits at two locations (proximal versus distal) for two root types (absorptive versus transport roots). At the intraspecific level, transport roots tended to be stronger and tougher than absorptive roots and could extend further before failure, but were as stiff as absorptiveroots. Where the root was sampled (proximalversus distal) had a limited effect on any root mechanical trait. The five monocots (Poaceae) had stronger and tougher root material than the seven dicots (Fabaceae, Plantaginaceae and Rosaceae), but there were no differences in stiffness. At the interspecific level, mechanical traits covaried positively and were strongly and positively correlated with specific root length (a trait related to the ‘do‐it‐yourself' soil exploration strategy), and negatively with root diameter (a trait related to the ‘outsourcing' soil exploration strategy) and root tissue density (a trait related to root lifespan). We demonstrate the important role of species' taxonomical subgroup (monocot versus dicot) and root type in governing mechanical trait variation at both intra‐ and inter‐specific levels. Our results can be regarded as the first evidence of a link between root mechanical robustness and the root economics space, through a strong association with the ‘do‐it‐yourself' soil exploration strategy.