Growth, wood anatomy and stable isotopes show species-specific couplings in three Mexican conifers inhabiting drought-prone areas

Abstract

An improved understanding of how tree species will respond to warmer conditions and longer droughts requires comparing their responses across different environmental settings and considering a multi-proxy approach. We used several traits (tree-ring width, formation of intra-annual density fluctuations -IADFs, wood anatomy, ∆ 13 C and δ 18 O records) to retrospectively quantify these responses in three conifers inhabiting drought-prone areas in northwestern Mexico. A fir species (Abies durangensis) was studied in a higher altitude and slightly rainier site and two pine species were sampled in a nearby, lower drier site (Pinus engelmannii, Pinus cembroides). Tree-ring-width indices (TRWi) of the studied species showed a very similar year-to-year variability likely indicating a common climatic signal.Wood anatomy analyses done over 3.5 million measured cells and showed that P. cembroides lumen area was much smaller than in the other two species and it remained constant along all the studied period (over 64 years). Instead, cell wall thickness was widest in P. engelmannii and this species presented the highest amount of intra-annual density fluctuations. Climate and wood anatomy correlations pointed out that lumen area was positively affected by winter precipitation for all studied species, while cell-wall thickness was negatively affected by this season's precipitation in all species but P. cembroides. Stable isotope analysis showed significantly lower values of Δ 13 C for P. cembroides and no significant δ 18 O differences between the three species, although they shared a common decreasing trend. With very distinct wood anatomical traits (smaller cells, compact morphology), P. cembroides stood out as the better adapted species in its current environment and could be less affected by future drier climate. P. engelmannii and A. durangensis showed high plasticity at wood anatomical level, allowing them to promptly respond to seasonal water availability but likely gives few advantages on future climate scenarios with longer and frequent drought spells.

Tree Vitality and Forest Health: Can Tree-Ring Stable Isotopes Be Used as Indicators?

“…A growing body of evidence shows that plants can close their stomata during drought events to avoid unnecessary water loss. Consequently, stomatal conductance to CO 2 decreases and Rubisco fixes a higher-than-usual proportion of 13 C compared to 12 C. As a result, rings are formed in which the cellulose is enriched in the heavier isotope, which translates as less negative isotopic signatures and those large anomalies in their δ 13 C can be indicators of forest health [106][107][108][109]. Other studies of co-occurring healthy and dead trees found a lower i WUE in dead trees, suggesting either a reduction in photosynthesis rates or, more probably, a poor regulation of stomatal conductance [110][111][112].…”

Retrospective analysis of wood anatomical traits and tree‐ring isotopes suggests site‐specific mechanisms triggering Araucaria araucana drought‐induced dieback

“…However, the WUE i should not be considered as equivalent to instantaneous WUE, which is the ratio of assimilation (carbon gained) to transpiration (water lost) and takes into account the atmospheric water demand (Pacheco et al, 2020; Seibt et al, 2008). Thus, the equation used is the “simple” form of isotopic discrimination that does not include effects due to mesophyll conductance and photorespiration, which were not available for the study species.…”

Improvement in mechanical, physical and biological properties of eucalyptus and pine woods by raw pine resin in situ polymerization

“…These results can be attributed to the pine wood anatomy and its low specific gravity associated with the presence of long and wide tracheids prone to be filled with resin, which transversely communicate to each other by radial pits (Acosta et al, 2020c). For Pacheco et al (2020), the lumens of tracheids belonging to a pine wood are of variable diameter with an average of ≈30 μm. The incorporated resin remained well retained since both woods presented mean leaching index below 2% (Fig.…”