Is Resistance to Mountain Pine Beetle Associated with Genetic Resistance to White Pine Blister Rust in Limber Pine?

Limber pine (Pinus flexilis James) co-evolved with the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) and is now also challenged by the non-native pathogen Cronartium ribicola (J.C. Fisch.) that causes the lethal disease white pine blister rust (WPBR). Previous research suggests that trees infected with WPBR can be preferred hosts for MPB. Using resin duct traits associated with MPB resistance, we tested for a relationship between resistance to MPB and WPBR in limber pine, in the absence of either biological agent. These analyses will help evaluate if MPB historically may have contributed to natural selection for WPBR resistance in advance of WPBR invasion, and could help explain the unusually high frequency of the dominant Cr4 allele for complete resistance to WPBR in limber pine populations of the Southern Rocky Mountains. Resin duct production, density and relative duct area did not differ between healthy trees previously inferred to carry the dominant Cr4 allele and trees that lack it at 22 sites, though some duct traits varied with elevation. MPB resistance does not appear to have played an evolutionary role in contributing to the high frequency of Cr4 in naïve populations, however, MPB may affect the future evolution of resistance to WPBR in the pines where the two pests coincide and WPBR will affect forest recovery after MPB epidemics. MPB-WPBR interactions in a changing climate will affect the future trajectory of limber pine

Fire and High-Elevation, Five-Needle Pine (Pinus aristata & P. flexilis) Ecosystems in the Southern Rocky Mountains: What Do We Know?

Rocky Mountain bristlecone pine (Pinus aristata Engelm) and limber pine (P. flexilis James) are high-elevation, five- needle pines of the southern Rocky Mountains. The pre-settlement role of fire in bristlecone and limber pine forests remains the sub- ject of considerable uncertainty; both species likely experienced a wide range of fire regimes across gradients of site productivity and connectivity of fuels and flammable landscapes. In dense stands and more continuous forests, stand history reconstructions provide evidence for infrequent, high-severity fires. Limber pine can be dispersed long distances by Clark’s nutcrackers (Nucifraga colum- biana), and in the high-elevation subalpine forests of the northern Colorado Front Range, it is an early colonist of extensive, high- severity burns. However, this relationship with fire may not be general to the southern Rockies. The degree to which high-severity fire was typical of bristlecone pine, and the spatial extent of such fires, is uncertain. Following fire, bristlecone pine regeneration tends to be constrained to burn edges or beneath surviving trees. In both five-needle pines, regeneration dynamics take decades to centuries. Where open stands border grassy openings both species frequently exhibit fire scars indicative of fairly frequent but low- intensity fire; because of the great ages attained by both species, they offer potentially very long fire history reconstructions in such settings. Whether or not fire suppression has led to declines in either species—through successional shifts to shade-tolerant com- petitors or by shifts to a stand replacing fire-regime—remains an open question that deserves further inquiry. In any case, re-estab- lishing pre-settlement fire regimes, whatever they were, may not be as important as determining appropriate disturbance regimes given current conditions and management objectives. Both species are highly susceptible to rapid declines caused by white pine blister rust (Cronartium ribicola) and mountain pine beetles (Dendroctonus ponderosae). In the face of these threats, and uncertain consequences of climate change, fire management (both prevention and applica- tion) can be a tool to promote resilient landscapes. Appropriate fire management may be used to conserve valuable stands, pro- mote regeneration and diversify age class structures, and/or alter the balance between these species and their competitors. Many of these themes and questions indicate the need for further basic and applied research

Carbon Costs of Constitutive and Expressed Resistance to a Non-Native Pathogen in Limber Pine - Fig 2

<p><b>Mean (A) total heights, (B) annual growth increments and (C) relative growth rates of Uninoculated and Inoculation Survivor bulk lots of limber pine following inoculation with <i>C</i>. <i>ribicola</i> in September, 2009.</b> Relative growth rate was calculated as the ln of plant height at the end of one year minus the ln of the plant’s height at the end of the previous year. Statistically significant differences are denoted as follows: *: P < 0.05, **: P < 0.01; ***: P < 0.001.</p

Leaf life span and the mobility of "non-mobile" mineral nutrients : the case of boron in conifers

mineral nutrients – the case of boron in conifers. Silva Fennica 36(3): 671–680. Nutrient conservation is considered important for the adaptation of plants to infertile environments. The importance of leaf life spans in controlling mean residence time of nutrients in plants has usually been analyzed in relation to nutrients that can be retranslocated within the plant. Longer leaf life spans increase the mean residence time of all mineral nutrients, but for non-mobile nutrients long leaf life spans concurrently cause concentrations in tissues to increase with leaf age, and consequently may reduce non-mobile nutrient use effi ciency. Here we analyze how the role of leaf life span is related to the mobility of nutrients within the plant. We use optimality concepts to derive testable hypotheses, and preliminar-ily test them for boron (B), a nutrient for which mobility varies among plant species. We review published and unpublished data and use a simple model to assess the quantitative importance of B retranslocation for the B budget of mature conifer forests and as a mechanism for avoiding toxicity

Response of net CO₂ assimilation rate to intercellular CO₂ concentration for R and S families of limber pine.

<p>Curves were taken at a leaf temperature of 25°C, PPFD of 1,800 μmol photons m^-2 s^-1 and leaf-to-air vapor pressure difference of 1.6 kPa; net CO₂ assimilation rate is expressed on a total leaf surface area basis. Statistically significant differences are denoted by an * for P < 0.05.</p

Parameters of leaf-level resource investment and photosynthetic resource-use for R and S families of limber pine.

<p>Parameters of leaf-level resource investment and photosynthetic resource-use for R and S families of limber pine.</p

Development, phenology and early growth of R and S seedling families of limber pine.

<p>Development, phenology and early growth of R and S seedling families of limber pine.</p