Blue intensity parameters derived from Ponderosa pine tree rings characterize intra-annual density fluctuations and reveal seasonally divergent water limitations

Abstract

Key message A set of novel parameters extracted from fine-spatial resolution blue intensity profiles characterizes intra-annual density fluctuations in Ponderosa pine and complements information on climate sensitivity obtained from radial growth. Abstract Rapidly rising evaporative demand threatens forests in semi-arid areas around the world, but the timing of stem growth response to drought is often coarsely known. This is partly due to a shortage of sub-annual growth records, particularly outside the Mediterranean region where most intra-annual density fluctuation (IADF) chronologies are based. We anticipate that an automated, cost-effective, and easily implementable method to characterize IADFs could foster more widespread development of sub-annual chronologies. We applied a peak detection algorithm to fine-spatial resolution blue intensity (BI) profiles of Ponderosa pine tree rings from two sites in southern Arizona (*300 m elevation difference). Out of seven BI parameters that characterize IADFs, peak height, width, and area showed satisfactory chronology statistics. We assessed the response of these BI and radial growth parameters to six monthly resolved climate variables and to the onset date of the North American summer monsoon. Radial growth at the lower-elevation site depended mainly on winter precipitation, whereas the higher site relied on spring and monsoon precipitation. A regular May-June drought period promoted IADFs in early ring portions at both sites. Yet, IADFs at the higher site were only formed, if spring was sufficiently humid to assume enough radial growth. Late-position IADFs were caused by a weak monsoon and additionally promoted by favorable conditions towards the end of the growing season. The contrast between sites is likely attributable to a three-week difference in the growing season onset, emphasizing the importance of growth phenology for drought impacts on forests in the US Southwest.

Increasing radial and latewood growth rates of Larix cajanderi Mayr. and Pinus sylvestris L. in the continuous permafrost zone in Central Yakutia (Russia)

“…In addition, dendrochronological statistical measures (e.g., mean sensitivity and expressed population signal) were obtained from ARSTAN. Due to the high correlation between EW and LW chronologies (mean correlations r = 0.7 for larch and r = 0.5 for pine), a linear regression was used to remove the dependence of LW on EW (Babst et al 2016), obtaining an adjusted latewood index (LW adj ) (Meko and Baisan 2001) non-correlated with EW chronology (Stahle et al 2009).…”

Latitudinal gradients in tree ring stable carbon and oxygen isotopes reveal differential climate influences of the North American Monsoon System

“…The sites and sampled trees were selected from montane forest ecosystems, which were dominated by Pinus ponderosa, and based on the following criteria: (1) excluding sites with large surrounding watersheds that could contribute runoff water to the observed site; (2) selecting medium-aged trees (e.g., 100-150 years); (3) selecting sites with evidence of low tree-to-tree canopy competition, and no evidence of past-century land use changes; (4) selecting trees that showed signs of vigorous recent growth with a well-formed and symmetrical crown; and (5) selecting trees with no or minimal occurrence of IADFs, which are indicative of a significant influence of the hyperarid period before the onset of summer rainfall [Schulman, 1938;Wright et al, 2001;Leavitt et al, 2002;Babst et al, 2016]. The last criterion served our goal to study growth responses to winter and summer precipitation, rather than presummer drought.…”

“…IADFs are common in Ponderosa pine trees from strongly drought-limited sites in the southwestern U.S. Here IADFs can be distinguished from the actual LW in that they lack sharp terminal boundaries [Babst et al, 2016]. These anatomical differences are the expression of cambium phenological processes related to temperature and water availability during incipient cellular division and subsequent formation and thickening of secondary cell walls [Vaganov et al, 2006].…”

Moisture‐driven xylogenesis in Pinus ponderosa from a Mojave Desert mountain reveals high phenological plasticity

“…scopulorum Engelm. ), which is a common dominant species in the mountain ranges of the American Southwest, respond to moisture stress by stopping radial growth, which leads to "locally absent rings" (St George, Ault, & Torbenson, 2013) but can also resume their growth during monsoonal storms, forming earlywood-type bands within the latewood called false rings or Intra Annual Density Fluctuations (IADFs; Babst et al, 2016). Isotopic composition of ponderosa pine tree rings has revealed a range of site-dependent water-use strategies with respect to the dominant climatic regime (warm-vs. cold-season precipitation; L. P. Kerhoulas, Kolb, & Koch, 2013;Leavitt, Wright, & Long, 2002;Szejner et al, 2016).…”