<i>Pinus ponderosa</i>: a taxonomic review with five subspecies in the United States

Abstract

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Legacies of more frequent drought in ponderosa pine across the western United States

“…This resulted in 221 site-level chronologies and 19,272 ringwidth indices ('RWI'). Chronologies were classified into three regions ( Figure 1) corresponding to the geographic distribution of groups of P. ponderosa subspecies (Callaham, 2013;Little, 1971;Willyard et al, 2017), approximately corresponding to the Southwest ( (Norris, Jackson, & Betancourt, 2006).…”

Pinus ponderosa: A checkered past obscured four species

“…ponderosa . Reviews and treatments have reached very diff erent conclusions regarding whether they should be accepted and, if so, whether they are varieties of P. ponderosa , where each is distributed geographically, and which morphological characters reliably distinguish them ( Lauria, 1991( Lauria, , 1996a( Lauria, , 1997Millar and Libby, 1991 ;Kral, 1993 ;Haller and Vivrette, 2011 ;Baldwin et al, 2012 ;Callaham, 2013a ;Meyers et al, 2015 ). Th e question of taxonomic delineation also occurs more widely across Pinus subsection Ponderosae Loudon (section Trifoliae ; subgenus Pinus ).…”

Comparative technoeconomic analysis of a softwood ethanol process featuring posthydrolysis sugars concentration operations and continuous fermentation with cell recycle

“…A common species of pine in these forests is the Ponderosa pine. 4 Compared with other lignocellulosic biomasses, Ponderosa pine is a challenging feedstock because of a relatively low cellulose content ($41 wt%) combined with the generally recalcitrant nature of softwoods (due to elevated lignin content). 5 With conventional dilute acid pretreatment at 10 wt% solids loading followed by enzymatic hydrolysis, hydrolysate glucose concentrations of only 25-30 g/l are common.…”

“…Increased mixing energy requirements due to rheological changes and the so-called "solids effect" (lower sugar yield even when maintaining proportional enzyme loading) were the biggest problems identified. The causes of the "solids effect" have not been fully determined but plausible explanations include: (1) reduction in mixing efficacy, (2) reduced diffusion of inhibitory sugars and other compounds away from the enzyme, (3) reduced enzyme availability (because of increased lignin, glucose, and cellobiose concentrations), or (4) water/substrate interactions that reduce the amount of water available to the enzymes during the hydrolysis reaction. Any one of these issues (or any combination thereof) could be responsible for reduced sugar yields at high solids levels.…”

“…A common species of pine in these forests is the Ponderosa pine . Compared with other lignocellulosic biomasses, Ponderosa pine is a challenging feedstock because of a relatively low cellulose content (∼41 wt%) combined with the generally recalcitrant nature of softwoods (due to elevated lignin content) .…”