Robert L. Mathiasen, Ph.D. - Professor
Forest health, ecology and systematics of dwarf mistletoes (Arceuthobium spp.),
Forest Management Practices Influence Forest Health in Northern Arizona
Forest health is rapidly becoming an important subdiscipline of forestry and especially
in northern Arizona where past forest management practices have greatly influenced
the health of forest ecosystems. Years of wildfire suppression, livestock grazing
and some timber harvesting practices have converted the forests of northern Arizona
to what many people perceive as an unhealthy forest landscape. Densely stocked,
even-aged stands of small-diameter pines have replaced the more open pine forests
of yesterday. This has created a forest ecosystem with high potential for wildfire,
decreased nutrient cycling, high levels of dwarf mistletoe and perhaps the potential
for serious outbreaks of bark beetles.
There are many definitions of forest health ranging from what have been defined
as utilitarian perspectives to more ecosystem oriented concepts. Faculty within
the School of Forestry at Northern Arizona University (NAU), including myself, have
adopted an ecosystem perspective on forest health which also recognizes that societal
values must be considered as part of the forest health equation. We define forest
health as a relative condition of a forest based on selected ecological indicators
and the collective value judgements of stakeholders of that forest. This definition
incorporates the principle of using ecological indicators to measure forest health
and includes the concept that value judgements about the condition of forests guides
whether or not the forest ecosystems being evaluated are healthy or not.
We are currently examining many facets of ponderosa pine forest ecosystems in northern
Arizona and how past and present forest management practices influence their health.
Many NAU faculty, including myself, are interested in identifying and measuring
important ecological indicators of forest health. Thus far, my research in this
area is concentrating on examining the diversity and abundance of ectomycorrhizal
fungi in ponderosa pine forests in different disturbance regimes and comparing these
with undisturbed sites. This research is part of a larger forest health research
effort being conducted by several faculty in the School of Forestry - the Stand
Treatment Impacts on Forest Health (STIFH) project.
I am also conducting research on the interactions of wildlife with dwarf mistletoes
(Arceuthobium spp.). We are examining wildlife use of dwarf mistletoe-induced witches'
brooms in Douglas-fir and hope to start a similar study in ponderosa pine in the
near future. I am also interested in studying the diversity and abundance of passerine
birds in dwarf mistletoe-infested ponderosa pine forests compared with non-infested,
but otherwise similar forests in northern Arizona.
Another major aspect of my research on dwarf mistletoes is related to the host range,
impact and systematics of hemlock dwarf mistletoe in the Pacific Northwest and British
Columbia. I am conducting a cooperative research project with the Canadian Forestry
Service on the host range and taxonomy of shore pine dwarf mistletoe. I am also
conducting field research on the hemlock dwarf mistletoe populations which parasitize
true firs (Abies spp.) in central Oregon. I also plan to start a research project
on the distribution, host range and systematics of the dwarf mistletoes parasitizing
hard pines in the Siskiyou-Klamath Mountain Region of northern California and southern
Oregon in 1998.
I am beginning research on the ecology, host range, impact and systematics of mistletoes
in Central America, both on dwarf mistletoes and on true mistletoes in the genus
Psittacanthus. This work is being conducted in cooperation with the USDA Forest
Service and I hope to expand that cooperation to include forest management agencies
in Honduras and Belize.
Dr. Mathiasen has conducted research in Central America and Mexico over the last
several years. His collaborators include the Honduran Foundation for Agricultural
Research, the Universidad Nacional Agraria, and the Comision Nacional Forestal (CONAFOR).
Dr. Mathiasen facilitated a project between the USDA Forest Service and CONAFOR
in Durango Mexico.
B.A., California State University, Stanislaus, 1972
M.S., Colorado State University, 1974
M.A., Northern Arizona University, 1984
Ph.D., University of Arizona, 1977
Office: Building 82 - Room 002
Mathiasen, R. L. 2011. Susceptibility of conifers to three dwarf mistletoes in the
Klamath- Siskiyou Mountains. Western Journal of Applied Forestry 26: 13-18.
Mathiasen, R. L., and C. M. Daugherty. 2010. Susceptibility of Brewer spruce (Picea
breweriana) to dwarf mistletoes (Arceuthobium spp., Viscaceae). Northwest Science
84: 295- 301.
Mathiasen, R. L., and C. M. Daugherty. 2009. Additional morphological measurements
of Arceuthobium siskiyouense and A. monticola (Viscaceae). Journal of the Botanical
Research Institute of Texas 3: 741-749.
Mathiasen, R. L., C. M. Daugherty, and B. P. Reif. 2009. Arceuthobium rubrum (Viscaceae)
in Mexico. Madroño 56: 99-103.
Mathiasen, R. L., and C. M. Daugherty. 2009. Arceuthobium abietinum subspecies wiensii,
a new subspecies of fir dwarf mistletoe (Viscaceae) from northern California and
southern Oregon. Madroño 56: 118-126.
Scott, J. M., and R. L. Mathiasen. 2009. Bristlecone pine dwarf mistletoe: Arceuthobium
microcarpum subsp. aristatae (Viscaceae), a new subspecies of western spruce dwarf
mistletoe from northern Arizona. Journal of the Botanical Research Institute of
Texas 3: 13-22.
Mathiasen, R. L. 2009. Comparative susceptibility of conifers to knobcone pine dwarf
mistletoe. Western North American Naturalist 69 (3): 42-48.
Mathiasen, R. L., and C. M Daugherty. 2009. First report of mountain hemlock dwarf
mistletoe (Arceuthobium tsugense subsp. mertensianae) on sugar pine (Pinus lambertiana)
from Oregon. Plant Disease 93: 321.
Mathiasen, R. L., and C. M. Daugherty. 2008. Distribution of red fir (Abies magnifica
A. Murray) and noble fir (Abies procera Rehder) in Oregon based on dwarf mistletoe
host specificity. Northwest Science 82: 108-119.
Kenaley, Shawn, Robert L. Mathiasen, and E. James Harner. 2008. Mortality associated
with a bark beetle outbreak in dwarf mistletoe-infested ponderosa pine stands in
northern Arizona. Western Journal of Applied Forestry 22: 113-120.
Mathiasen, R. L., C. M. Daugherty, B. E. Howell, J. C. Melgar, and S. E. Sesnie.
2007. New morphological measurements of Psittacanthus angustifolius and Psittacanthus
pinicola (Loranthaceae). Madroño 54: 156-163.
Hoffman, Chad, Robert Mathiasen, and Carolyn Sieg. 2007. Dwarf mistletoe effects
on fuel loadings in ponderosa pine forests in northern Arizona. Canadian Journal
of Forest Research 37: 662-670.
Mathiasen, R. L. 2007. A new combination for Hawksworth’s dwarf mistletoe. (Viscaceae).
Novon 17: 217-221.
Mathiasen, R. L., and C. M. Daugherty. 2007. Arceuthobium tsugense subsp. amabilae,
a new subspecies of hemlock dwarf mistletoe(Viscaceae) from Oregon. Novon 17: 222-227.
Mathiasen, R., B. Howell, and G. Garnett. 2007. First report of Arceuthobium aureum
subsp. aureum in Mexico. Plant Disease 91: 469.
Hedwall, S. J., and R. L. Mathiasen. 2006. Wildlife use of Douglas-fir dwarf mistletoe
witches’ brooms in the Southwest. Western North American Naturalist 66 (4): 450-455.
Mathiasen, R., A. Sediles, and S. Sesnie. 2006. First report of Arceuthobium hondurense
and Struthanthus deppeanus in Nicaragua. Plant Disease 90: 1458.
Kenaley, Shawn, Robert L. Mathiasen, and Carolyn M. Daugherty. 2006. Selection of
dwarf mistletoe-infected ponderosa pines by bark beetles, Ips spp. (Coleoptera:
Scolytidae), in northern Arizona. Western North American Naturalist 66: 279-284.
Parker, T. J., K. A. Clancy, and R. L. Mathiasen. 2006. Interactions among fire,
insects, and pathogens in coniferous forests of the interior western United States
and Canada. Agricultural and Forest Entomology 8: 167-189.
Mathiasen, Robert L., William K. Olsen, and Carleton B. Edminster. 2006. Site index
curves for white fir in the southwestern United States developed using a guide curve
method. Western Journal of Applied Forestry. 21 (2): 87-93.
Mathiasen, R. L., and C. M. Daugherty. 2006. Additional taxonomic studies of Arceuthobium
pendens (Viscaceae): a rare dwarf mistletoe from central Mexico. Madroño 53 (1):
Mathiasen, R. L., and C. M. Daugherty. 2005. Susceptibility of conifers to western
hemlock dwarf mistletoe in the Cascade Range of Washington and Oregon. Western Journal
of Applied Forestry 20: 94-100.
Howell, B. E., and R. L. Mathiasen. 2004. Growth impacts of Psittacanthus angustifolius
Kuijt on Pinus oocarpa Schiede in Honduras. Forest Ecology and Management 198: 75-88.
Parker, T. J., and R. L. Mathiasen. 2004. A comparison of rating systems for dwarf
mistletoe- induced witches' brooms in ponderosa pine. Western Journal of Applied
Forestry 19: 54-59.
Garnett, G., R. L. Mathiasen, and C. L. Chambers. 2004. A comparison of wildlife
use in broomed and unbroomed ponderosa pine trees in northern Arizona. Western Journal
of Applied Forestry 19: 42-46.
Shaw, D. C., D. A. Watson, and R. L. Mathiasen. 2004. Comparison of dwarf mistletoe
(Arceuthobium spp., Viscaceae) in the western United States with mistletoes (Amyema
spp., Loranthaceae) in Australia - ecological analogs and reciprocal models for
ecosystem management. Australian Journal of Botany 52: 481-498.
Nickrent, Daniel L., Miguel A. GarcÃa, Maria P. MartÃn, and Robert L. Mathiasen.
2004. A phylogeny of all species of Arceuthobium (Viscaceae) using nuclear and chloroplast
DNA sequences. American Journal of Botany 91: 125-138.
Daugherty, C. M., and R. L. Mathiasen. 2003. Incidence of mistletoes in the pinyon-juniper
woodlands of the Coconino National Forest, Arizona. Western North American Naturalist
Mathiasen, R. L., J. Melgar, J. Beatty, C. Parks, D. L. Nickrent, S. Sesnie, C.
Daugherty, B. Howell, and G. Garnett. 2003. New distributions and hosts for mistletoes
parasitizing pines in southern Mexico and Central America. Madrono 50: 115-121.
Wass, E. F., and R. L. Mathiasen. 2003. A new subspecies of hemlock dwarf mistletoe
(Arceuthobium tsugense subsp. contortae, Viscaceae) from British Columbia and Washington.
Novon 13: 268-276.
Mathiasen, R. L., and C. M. Daugherty. 2002. Adult sex ratio of Arceuthobium gillii
(Viscaceae). Madrono 49: 12-15.
Mathiasen, Robert L., and Christopher S. Albion. 2001. Sporocarp production of ectomycorrhiza
associated with ponderosa pine in four stand types in northern Arizona. Harvard
Papers in Botany 6: 147-154.
Mathiasen, Robert L., and Carolyn M. Daugherty. 2001. Susceptibility of foxtail
pine and western white pine to limber pine dwarf mistletoe in northern California.
Western Journal of Applied Forestry 16: 58-60.
Shaw, David, Elizabeth A. Freeman, and Robert L. Mathiasen. 2000. Evaluating the
accuracy of ground-based hemlock dwarf mistletoe rating: a case study using the
Wind River Canopy Crane. Western Journal of Applied Forestry 15: 8-14.
Daugherty, C. M., and R. L. Mathiasen. 2000. Adult sex ratio of Phoradendron juniperinum
in ten severely infected Juniperus monosperma in northern Arizona. Madrono 46: 169-176.
Mathiasen, R. L., and K. Marshall. 1999. Dwarf mistletoes in the Siskiyou-Klamath
Mountain Region. Natural Areas Journal 19: 379-385.
Mathiasen, R. L. 1999. Comparative susceptibility of subalpine firs to Douglas-fir
dwarf mistletoe. Canadian Journal of Plant Pathology 21: 45-51.
Mathiasen, R.L. 1998. Infection of young western larch by larch dwarf mistletoe
in northern Idaho and western Montana. Western Journal of Applied Forestry 13(2)
Mathiasen, R.L. 1996. Dwarf mistletoes in forest canopies. Northwest Science 70:61-71.
Mathiasen, R.L. 1994. Natural infection of new hosts by hemlock dwarf mistletoe.
USDA Forest Service Research Note RM-RN-530, 6 p.
Geils, B.W., and R.L. Mathiasen. 1990. Intensification of dwarf mistletoe on Southwestern
Douglas-fir. Forest Science 36:955-969.
Mathiasen, R.L., F.G. Hawksworth, and C.B. Edminster. 1990. Effects of dwarf mistletoe
growth and mortality of Douglas-fir in the Southwest. Great Basin Naturalist 50:173-179.
Mathiasen, R.L., C.B. Edminster, and F.G. Hawksworth. 1990. Infection of young Douglas-firs
by dwarf mistletoe in the Southwest. Great Basin Naturalist 50:67-71.
Mathiasen, R.L., and F.G. Hawksworth. 1988. Dwarf mistletoes on western white pine
and whitebark pine in northern California and southern Oregon. Forest Science 34:429-440.
Mathiasen, R.L., and E.A. Blake. 1984. Relationships between dwarf mistletoes and
habitat types in western coniferous forests. Pp. 111-116 in USDA Forest Service
General Technical Report RM-111.