Climate has a larger effect than stand basal area on wood density in Pinus ponderosa var. scopulorum in the southwestern USA

Abstract

& Key message Stand basal area of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) in the US Southwest has little effect on the density of the wood produced, but climatic fluctuations have a strong effect. Wood density increases during drought, particularly if the drought occurs in late winter/early spring. Future droughts, as are predicted to increase in the US Southwest, may lead to production of smaller radial increments of higher density wood in ponderosa pine. & Context Forest restoration treatments in the US Southwest are generating large quantities of small-diameter logs. Due to negative perceptions about ponderosa pine wood quality, this material is often seen as a "waste disposal" problem rather than a high-value resource. & Aims Our objective was to understand more about variation in southwestern US ponderosa pine wood density, an important indicator of wood quality. Specifically, we investigated the effect of stand basal area on wood density, and the effect of annual and quarterly climatic variation on wood density. & Methods We collected samples from 54 trees grown at six different basal area levels from a replicated stand density experiment. Pith-to-bark strips were used in an X-ray densitometer to obtain annual density and growth measurements from 1919 to the present. & Results Stand density had a strong effect on growth rate, but little effect on wood density. However, climatic variation did influence wood density, which increased in drought years before quickly returning to pre-drought levels.

Wood density of 38 Dalbergia and 29 Diospyros malagasy species and its relationship with climate and tree diameter

“…However, average CWD for the Diospyros genus is higher in humid bioclimates, where there is more precipitation, than in subhumid bioclimates. These results are in line with previous research by Vaughan et al (2019) who observed an increase in wood density during drought conditions. Similarly, Ibanez et al (2016) found that aridity conditions characterized by low precipitation and high temperatures promote the formation of highdensity wood.…”

Exploring new frontiers in forecasting forest growth, yield and wood property variation

“…Two papers addressed this knowledge gap. Vaughan et al (2019) showed in Pinus ponderosa that it is not growth rate, per sé, which is closely tied to variation in wood properties (in their case, focussing on wood density as an indicator) but rather annual climate peculiarities which lead to variation in the timing and extent of transitions into latewood production. Erasmus et al (2020), looking at Pinus patula, found a clear effect of tree spacing.…”