Growth of hartweg’s pine ( Pinus hartwegii ) parasitized by two dwarf mistletoe species ( Arceuthobium spp.)

Abstract

Abstract:Coniferous forests occupy a large extent (17 %) of the Mexican territory. Within these forests, pines are a common and sometimes dominant component; however, several abiotic and biotic factors affect pines growth. Among the main biotic factors is the parasitic effect of dwarf mistletoes. In Zoquiapan (Iztaccíhuatl Popocatépetl National Park, Central Mexico) two dwarf mistletoe species coexist parasitizing Pinus hartwegii. The aim of this study was to know the effect of Arceuthobium globosum and A. vaginatum, either individually or as a pair, on P. hartwegii growth, allometric relations, and size susceptibility. We recorded diameter at breast height (dbh) and crown spread of P. hartwegii for 3 years on individuals infested by either one of the species, both, or none, as well as the infection severity. The relative growth rate (RGR) in diameter was strongly influenced by the pines initial dbh; whereas the infecting species or severity did not show a differential effect. The allometric relation of dbh and height was affected by parasitism, where the trees infected by both species were shorter than the uninfected and infected by A. vaginatum at the same dbh. The parasitic effect does not differ among these mistletoe species.,However, the host-size structure affects the presence and severity of infection; maintaining even-age stands provides a better scenario for a milder effect of parasitism, which should be considered for managing plans. Key words: allometry, Arceuthobium globosum, Arceuthobium vaginatum, parasitic plants, pines, relative growth rate.Resumen: Los bosques de coníferas ocupan una gran extensión en el territorio mexicano (17 %). Dentro de estos bosques, los pinos son componente comunes, y en ocasiones dominantes; sin embargo, diversos factores abióticos y bióticos afectan su crecimiento. Entre los principales factores bióticos se encuentra el efecto parasítico del muérdago enano. En Zoquiapan (Parque Nacional Iztaccíhuatl Popocatépetl, Centro de México) dos especies de muérdago enano coexisten y parasitan a Pinus hartwegii. El objetivo de este estudio es el de conocer el efecto de Arceuthobium globosum y A. vaginatum, solos o en conjunto, en el crecimiento de P. hartwegii, las relaciones alométricas y la susceptibilidad por tamaños. Registramos el diámetro a la altura del pecho (dap) y la dispersión de la copa de P. hartwegii por tres años en individuos infestados por alguna de las dos especies, ambas o ninguna, así como la severidad de la infestación. La tasa relativa de crecimiento (TRC) en diámetro estuvo fuertemente influida por el dap inicial de los pinos, mientras que la especie que infecta y la severidad no mostraron un efecto diferencial. La relación alométrica del dap y la altura fue afectada por el parasitismo, ya que, dentro de una misma categoría de dap, los árboles infectados por las dos especies fueron más bajos que los no infectados y los infectados por A. vaginatum. El efecto del parásito no difirió entre especies. Sin embargo, la estructura de tamaños del hospedero afecta la ...

Dwarf mistletoes as a relevant component in temperate forest: an integral view

“…In our studies on the effect on pines growth, there is no significant difference between the relative diameter growth rate between the non-infected and infected trees. 20 However, there was a significant effect on trees' allometric (diameterheight) relationship: infected trees tend to be shorter at the same diameter than uninfected trees. 20 This effect may not be harmful for pines' fitness, although this still needs corroboration.…”

“…19 Mostly, the prevalence is strongly affected by stand structure and hosts' size, as there is a clear preference for hosts with greater diameter and crown cover as well as there is a positive correlation with pines density, being more frequent in denser stands that are in regeneration process. 19,20 However, different disturbance factors can influence their incidence, such as waste deposits, logging and fire incidence. 18 Fire incidence seems to be a natural way to control dwarf mistletoes, and population sizes of these two species fluctuate in response to fires.…”

Competition and facilitation determine dwarf mistletoe infection dynamics

“…These pines were either not infected ( N = 95), infected with A. globosum ( N = 98), with A. vaginatum ( N = 27) or with both species ( N = 56). We assessed the dwarf mistletoe infection on each tree every 6 months for 3 years using a Modified Dwarf Mistletoe Rating system (MDMR; Queijeiro‐Bolaños & Cano‐Santana ) based on Hawksworth (). The conventional DMR is not recommended for small trees or for trees with irregular branching and long poles (Hawksworth ).…”

Dwarf Mistletoe and Drought Contribute to Growth Decline, Dieback and Mortality of Junipers

“…Dwarf mistletoes are perennial hemiparasitic plants that parasitize multiple species of shrubs and trees [20]. These species have been shown to reduce longitudinal and radial growth of host trees, particularly studied in North American timber tree species (pine, fir, Douglas-fir, spruce, hemlock) of the Pinaceae family [23][24][25][26][27]. Ecophysiological studies found a lower water-use efficiency of mistletoe-infected hosts, which showed a profuse water use at the leaf and tree scales, as well as higher crown transparency and a reduction in radial growth [28][29][30].…”