The influence of prescribed crown fire on lodgepole pine dwarf mistletoe (Arceuthobium americanum) populations 33 years post-fire

2018 ◽  
Vol 48 (3) ◽  
pp. e12419 ◽  
Author(s):  
S. M. Ritter ◽  
C. M. Hoffman ◽  
J. E. Stewart ◽  
T. Zimmerman
2004 ◽  
Vol 118 (4) ◽  
pp. 595 ◽  
Author(s):  
Brock Epp ◽  
Jacques C. Tardif

The Lodgepole Pine Dwarf Mistletoe (Arceuthobium americanum Nutt. ex Engelm.) is an important pathogen of Jack Pine (Pinus banksiana Lamb.). Dwarf Mistletoe alters tree form, suppresses growth, and reduces volume and overall wood quality of its host. Stem analysis and a 3-parameter logistic regression model were used to compare the growth of heavily and lightly to non infected Jack Pine trees. At the time of sampling, no significant reduction in diameter at breast height and basal area were observed in heavily infected trees. However, a significant reduction in height and volume and an increase in taper were observed in heavily infected trees. Growth models predicted a 21.1% lower basal area, 23.4% lower height and 42.1% lower volume by age 60 for the high infection group.


Botany ◽  
2017 ◽  
Vol 95 (3) ◽  
pp. 337-346
Author(s):  
Dylan J. Ziegler ◽  
Cynthia Ross Friedman

Dwarf mistletoes (DM), genus Arceuthobium, are dioecious parasitic flowering plants having prolonged life cycles lasting six years, culminating with explosive discharge of the single seed from the fruit. Arceuthobium americanum Nutt. ex Engelm., the lodgepole pine dwarf mistletoe, infects lodgepole pine (Pinus contorta subsp. latifolia (Engelm.) Critchfield) in western North America, compromising the forest economy. Highly reduced flowers appear no later than two years following shoot development, with female flowers appearing and persisting for over two years. Development of the pistillate plant, including initiation of floral growth, has not been fully explored. Here, we used environmental scanning electron microscopy to demark phenological waypoints throughout the pistillate plant’s development. As successive crops of female flowers emerged every year, up to three generations of flowers/fruit could be found on a single shoot in late summer; we used these three generations to delineate specific developmental stages. Vegetative shoots could initiate growth at any time within the growing season, could assume a terminal position, could also adopt sympodial branching, but were never whorled or adventitious. Floral branches, however, could initiate adventitiously from older nodes in a whorled pattern, and could house flowers/fruits of any generation. Vegetative and floral units were structurally homogeneous, suggesting shared developmental pathways.


Botany ◽  
2008 ◽  
Vol 86 (5) ◽  
pp. 539-543 ◽  
Author(s):  
Aditya Chhikara ◽  
Cynthia M. Ross Friedman

The lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm., is a dioecious angiosperm that parasitizes conifers in western Canadian forests, causing significant yearly timber loss. A striking consequence of dwarf mistletoe infection is a marked reduction in the size of the needles located distal to the infection. The purpose of this work was to use microscopy, cytochemistry, and biochemical analysis to determine whether this reduction was associated with changes in needle anatomy and (or) starch content. Furthermore, we wanted to investigate whether these potential changes were affected by the gender of the infecting dwarf mistletoe plant. We developed a ratio (R) that evaluated the position of the two vascular bundles relative to the size of the needle, and found that bundles from male-infected trees were positioned significantly closer together than in needles from female-infected or uninfected trees (p < 0.05). Using the periodic acid – Schiff’s (PAS) reaction for cytochemical identification of starch in situ, we determined that needles from uninfected trees had abundant starch grains compared with needles from infected trees; colourimetric analysis for total starch content corroborated our PAS data. This is the first report of this phenomenon in lodgepole pine, and further supports the use of needle characteristics to assess tree health.


2006 ◽  
Vol 36 (4) ◽  
pp. 1006-1016 ◽  
Author(s):  
J P Brandt

While lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm., is one of the most damaging pests of jack pine (Pinus banksiana Lamb.) in western Canada, no studies have examined the life cycle of this parasite in this pathosystem. Twenty-five jack pine trees in a plantation in Edmonton, Alberta, were inoculated with seeds of A. americanum in the fall of 1998 and 1999; these inoculants were monitored until the dwarf mistletoe plants that arose completed their life cycle. Ninety-two percent of inoculated seeds overwintered on their host. Seventy percent of these seeds germinated, mostly in May. Of these germinants, 69% developed holdfasts. Sixty-eight percent of germinants that developed holdfasts infected their host and produced shoots, primarily between July and August in the second season after inoculation. Of the 56 plants that developed from the 175 inoculations, 34 were pistillate plants and 19 were staminate plants, and 3 immature plants died because the host branch died. Pistillate plants flowered significantly earlier than staminate plants (4.1 vs. 4.7 years). Most pistillate plants produced seed in the fifth year, although one plant produced seed in 4 years. Thus, A. americanum probably has a 5-year life cycle on jack pine.


2003 ◽  
Vol 33 (6) ◽  
pp. 997-1009 ◽  
Author(s):  
R C Godfree ◽  
R O Tinnin ◽  
R B Forbes

The relationships between abundance of dwarf mistletoe (Arceuthobium americanum Nutt.) and the canopy structure of stands of lodgepole pine (Pinus contorta var. murrayana (Grev. & Balf.) Engelm.) were investigated in the central Oregon pumice zone. Foliage height profiles were generated for stands containing light, moderate, and heavy infestations of A. americanum, and the vertical distribution of P. contorta foliage was modeled using the Weibull distribution. Stand-level changes in the Weibull parameters σ (scale parameter) and c (shape parameter) as well as other canopy indices were related to the abundance of A. americanum, the density of competing tree species, and stand-level abiotic factors. Foliage intercept diagrams showed that heavily infested stands had more foliage in the lower canopy and less in the upper canopy than lightly infested stands, but that total canopy height and canopy volume were similar regardless of infestation level. We also found that dwarf mistletoe abundance was strongly related to σ (r = –0.74, p < 0.001) and c (r = –0.54, p < 0.0001). Since heavily infested stands contained fewer large but many more small P. contorta than lightly infested stands, we conclude that A. americanum causes the canopy of infested stands to change, in part, by inducing demographic changes in populations of the host tree. These results illustrate the significant effects that dwarf mistletoes can have on the structural diversity of conifer forest communities and have important consequences for the conservation and management of these systems.


Botany ◽  
2009 ◽  
Vol 87 (12) ◽  
pp. 1177-1185 ◽  
Author(s):  
Shannon K. Kelly ◽  
Cynthia M. Ross Friedman ◽  
Ron G. Smith

The lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm., is a parasitic angiosperm that infects conifers in western Canadian forests. A striking feature of the Arceuthobium life cycle is explosive seed dispersal, triggered by hydrostatic build-up within the fruit, localized in a tissue called “viscin.” Viscin is composed of two cell types: “viscin cells” that accrue pressure in their hydrated mucilage, and “vesicular cells” with a previously undetermined function. The objective of this work was to investigate the development and composition of vesicular cells using microscopy, cytochemistry, and gas chromatography – mass spectroscopy. We found that vesicular cells are initiated from mesocarp cells lining the viscin cells. As development of the seed progresses, vesicular cells form a single layer, enlarge, and become isodiametric. Later, the cells make up all of the remaining 3–4 outer mesocarp layers. Concomitant with enlargement, intracellular triacylglycerides (TAGs) largely composed of 16-carbon and 18-carbon fatty acids, accumulate. Immediately prior to discharge, vesicular cell boundaries become indistinct, and the cell contents become confluent, creating a lipid mass between the viscin cells and the exocarp. Vesicular cells and their resulting lipid mass likely function in discharge by acting as a hydrophobic barrier to water loss and (or) as a repellant, resistant layer.


1989 ◽  
Vol 4 (1) ◽  
pp. 27-28 ◽  
Author(s):  
Kathryn Robbins ◽  
David W. Johnson ◽  
Frank G. Hawksworth ◽  
Thomas H. Nicholls

Abstract Ethephon is an ethylene-releasing plant growth regulator that induces abscission of dwarf mistletoe (Arceuthobium americanum) aerial shoots on lodgepole pine (Pinus contorta) when applied from the ground. However, ethephon was not effective when applied by helicopter in two Colorado tests, because it did not come into enough direct contact with dwarf mistletoe shoots to induce abscission. West. J. Appl. For. 4(1):27-28, January 1989.


Botany ◽  
2017 ◽  
Vol 95 (3) ◽  
pp. 347-356 ◽  
Author(s):  
Dylan J. Ziegler ◽  
Cynthia Ross Friedman

Arceuthobium americanum Nutt. ex Engelm., the lodgepole pine dwarf mistletoe, is a dioecious parasitic flowering plant infecting lodgepole pine (Pinus contorta subsp. latifolia (Engelm.) Critchfield) in the Pacific Northwest, compromising timber value by stunting the host’s growth. The plant disperses its seeds by explosive discharge, and thus understanding its reproduction is an integral step toward managing its spread. The life cycle of Arceuthobium americanum occurs over five to six years, and the fruit matures over two consecutive growing seasons, dispersing in the second. Using low-vacuum environmental scanning electron microscopy (eSEM), we examined branching architecture as well as the morphology and anatomy of fruits during their second year of development up to explosive discharge. We found that branching patterns shifted from opposite-decussate to verticillate after several years’ growth. In addition, the perianth parts (sepals), style, and stigma persisted through the season, and the fruit’s abscission zone developed slightly distal to the end of the pedicel. Stomata, found only on the sepals, were located in crypts surrounded by two subsidiary cells, and stomatal density significantly decreased during development. The decline in stomatal density along with the thick pericarp cuticle may function in retaining water inside the fruit to facilitate discharge and (or) provide a heating mechanism through reduced transpiration.


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