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Background and aims: Measurement of grapevine size is necessary to assess carbon reserves at the level of individual vines and to estimate the carbon sequestration potential of vineyards. Methods of measurement rely mostly on traditional dendrological techniques that may be prone to error. In this study, we examined the use of structure-from-motion with multiview stereophotogrammetry (SfM-MVS) to obtain accurate measurements of vine trunk thickness and volume. SfM-MVS enables the creation of scaled, georeferenced three-dimensional models based on a set of overlapping photographs. Methods and results: The study was conducted using field-grown Vitis vinifera L. cv. Riesling vines aged 5, 22 and 46 years and pruned in a bilateral Guyot. Trunk diameter, cross-sectional area and circumference 10 cm above the grafting point were measured by traditional dendrometry, and the values obtained compared with corresponding estimates from reconstructed three-dimensional SfM-MVS models. SfM-MVS was also used to estimate total trunk volume. Correlation between measured values and modelled estimates was close to unity (0.976 ≤ R2 ≤ 0.988). The estimates for 5-year-old vines had the largest errors. Conclusions: Under adequate lighting conditions and with sufficient image resolution, SfM-MVS is able to produce accurate models of vine trunks. Significance of the study: This work serves as proof of concept for the use of SfM-MVS to measure the trunk size of field-grown grapevines of different ages. This technique, which is relatively new, is cost-effective and easy to implement. Further research is necessary to determine specific applications of SfM-MVS, in which it could supplement or replace traditional dendrological techniques.

Wine grape is usually grown under water deficit conditions that could negatively impact plant reserves, including the organic carbon storage in perennial organs such as woody stems. Assessing the carbohydrate status in woody organs is therefore of interest as it can influence vegetative growth in the successive season. In this study, we aimed to apply an on-solid colour reaction (using Lugol's iodine solution) coupled with reflectance spectroscopy detection to assess the grapevine canes' starch accumulation in response to short drought periods. We used two Vitis vinifera cultivars ('Cabernet Sauvignon' and 'Syrah') that were subjected to three different water conditions (well-watered; early water stress; late water stress) during the growing season as case study. We sampled woody stem tissue during winter rest. The results showed that water stress reduced the starch storage in 'Syrah', especially when imposed late and recovery time was not enough for carbon restoration, while 'Cabernet Sauvignon' was not affected. The results showed that the sensitivity of the method used here is adequate to assess starch accumulation differences due to drought treatments in grapevine canes. Moreover, the analytical approach appears fast, low cost, and promising for future physiological and agronomical research applications. [ABSTRACT FROM AUTHOR]

The pool size of mobile, i.e. non-structural carbohydrates (NSC) in trees reflects the balance between net photosynthetic carbon uptake (source) and irreversible investments in structures or loss of carbon (sink). The seasonal variation of NSC concentration should reflect the sink/source relationship, provided all tissues from root to crown tops are considered. Using the Smithsonian canopy crane in Panama we studied NSC concentrations in a semi-deciduous tropical forest over 22 months. In the 9 most intensively studied species (out of the 17 investigated), we found higher NSC concentrations (starch, glucose, fructose, sucrose) across all species and organs in the dry season than in the wet season (NSC 7.2% vs 5.8% of dry matter in leaves, 8.8/6.0 in branches, 9.7/8.5 in stems, 8.3/6.4 in coarse and 3.9/2.2 in fine roots). Since this increase was due to starch only, we attribute this to drought-constrained growth (photosynthesis less affected by drought than sink activity). Species-specific phenological rhythms (leafing or fruiting) did not overturn these seasonal trends. Most of the stem volume (diameter at breast height around 40 cm) stores NSC. We present the first whole forest estimate of NSC pool size, assuming a 200 t ha-1 forest biomass: 8% of this i.e. ca. 16 t ha-1 is NSC, with ca. 13 t ha-1 in stems and branches, ca. 0.5 and 2.8 t ha-1 in leaves and roots. Starch alone (ca. 10.5 t ha-1) accounts for far more C than would be needed to replace the total leaf canopy without additional photosynthesis. NSC never passed through a period of significant depletion. Leaf flushing did not draw heavily upon NSC pools. Overall, the data imply a high carbon supply status of this forest and that growth during the dry season is not carbon limited. Rather, water shortage seems to limit carbon investment (new tissue formation) directly, leaving little leeway for a direct CO2 fertilization effects. [ABSTRACT FROM AUTHOR]