Importance of resin ducts in reducing ponderosa pine mortality from bark beetle attack

Abstract

The relative importance of growth and defense to tree mortality during drought and bark beetle attacks is poorly understood. We addressed this issue by comparing growth and defense characteristics between 25 pairs of ponderosa pine (Pinus ponderosa) trees that survived and trees that died from drought-associated bark beetle attacks in forests of northern Arizona, USA. The three major findings of our research were: (1) xylem resin ducts in live trees were >10% larger (diameter), >25% denser (no. of resin ducts mm(-2)), and composed >50% more area per unit ring growth than dead trees; (2) measures of defense, such as resin duct production (no. of resin ducts year(-1)) and the proportion of xylem ring area to resin ducts, not growth, were the best model parameters of ponderosa pine mortality; and (3) most correlations between annual variation in growth and resin duct characteristics were positive suggesting that conditions conducive to growth also increase resin duct production. Our results suggest that trees that survive drought and subsequent bark beetle attacks invest more carbon in resin defense than trees that die, and that carbon allocation to resin ducts is a more important determinant of tree mortality than allocation to radial growth.

Temperature-driven range expansion of an irruptive insect heightened by weakly coevolved plant defenses

“…3). High resin flow can delay beetle progress while induced defenses are being activated, thus reducing the likelihood of beetles being able to initiate aggregation, and has been associated with reduced levels of attack incidence (19). This overall low investment in three components of defense-induced biosynthesis, relative composition of bioactive compounds, and resin flow-is even more striking considering that long-lived plants usually have the greatest allocation to defense (32).…”

“…In 2012, we established transects that extended from stands with a high component of lodgepole pine, through more evenly distributed stands, to nearly pure whitebark stands near Big Sandy Lake, also in Bridger-Teton National Forest (42.74°N, 109.19°W). We examined for signs of attack from 20 to 21 June to [17][18][19] October in 2011, and 1-2 July to 11-12 September in 2012. Each tree was visited weekly through July 29 (2011) and August 15 (2012) and then again at the end of the season.…”

“…These defenses consist of resin exudation that pitches out or delays attacking adults, and allelochemicals, particularly monoterpenes, that repel or kill the adults, prevent egg hatch, and inhibit or kill their symbionts (18)(19)(20). Monoterpenes occur at relatively low concentrations in constitutive (preattack) phloem, but are rapidly biosynthesized at the point of attack and accumulate to toxic levels within a few days (21)(22)(23).…”

Factores anatómicos, dendrométricos y climáticos implicados en la producción de resina de Pinus pinaster AIT. : aplicación a la mejora de los métodos de resinación

“…Esto se correspondería con una estrategia para generar una red más densa de canales pero con un coste de síntesis de resina similar, haciéndolos más estrechos. Sin embargo esta estrategia no puede generalizarse en este género ya que otros estudios encontraron que los individuos con mayor resistencia presentaban canales resiníferos de mayor tamaño que los susceptibles (Kane & Kolb, 2010). Patologías relevantes como el nematodo del pino (Bursaphelenchus xylophilus) presenta, según recientes estudios, una estrecha relación con la anatomía de P.…”

“…Las reservas de carbono han sido estudiadas en relación con distintos aspectos del sistema de defensa del pino; varios estudios muestran que la actividad del metabolismo secundario es función de las reservas de carbohidratos disponibles Kane & Kolb; aunque esta relación se vuelve más compleja como respuesta a los balances entre crecimiento y defensa que se dan en situaciones de estrés . Los resultados también sugieren una relación entre el tamaño de la planta y la inducción de resistencia; árboles con mayores diámetros, alturas y crecimientos anuales mostraron reacciones más fuertes a la herida que los pies menos vigorosos incrementando en mayor medida las características anatómicas relacionadas con el sistema de canales (Tabla 4).…”