Distribución diferencial de dos especies de muérdago enano sobre Pinus hartwegii en el área natural protegida “Zoquiapan y Anexas”, Estado de México

Dwarf mistletoes (Arceuthobium spp.) are important plants in temperate forests of Mexico due to their high incidence. At the south side of the Papayo Hill in the “Zoquiapan y Anexas” Natural Protected Area, Mexico State, both, Arceuthobium vaginatum subsp. vaginatum and A. globosum subsp. grandicaule coexist within the same zone and, frequently, on the same host tree of the species Pinus hartwegii. We studied the vertical distribution of both species on the stem, and we registered that A. vaginatum is found more frequently to lower heights of the pines than A. globosum. These results suggest that the nutritional resources are taken in a differential manner, causing a probable competitive relation between the two species.Los muérdagos enanos (Arceuthobium spp.) son plantas importantes en los bosques templados de México debido a su alta incidencia. Al sur del cerro Papayo en el Área Natural Protegida “Zoquiapan y Anexas”, Estado de México, coexisten Arceuthobium vaginatum subsp. vaginatum y A. globosum subsp. grandicaule incluso en el mismo árbol hospedero de la especie Pinus hartwegii. Al estudiar su disposición vertical en el tronco se registra que A. vaginatum se distribuye a menor altura en los pinos que A. globosum. Esto sugiere que la eficiencia de obtención de recursos nutricionales del hospedero podría ser diferencial, por lo que es posible que haya una relación de competencia entre ambas especies

Effects of Dwarf Mistletoe on Stand Structure of Lodgepole Pine Forests 21-28 Years Post-Mountain Pine Beetle Epidemic in Central Oregon

Lodgepole pine (Pinus contorta) forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae) epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes. Dwarf mistletoe (Arceuthobium americanum) also influences stand structure and occurs frequently in post-mountain pine beetle epidemic lodgepole pine forests. Few studies have incorporated both disturbances simultaneously although they co-occur frequently on the landscape. The aim of this study is to investigate the stand structure of lodgepole pine forests 21–28 years after a mountain pine beetle epidemic with varying levels of dwarf mistletoe infection in the Deschutes National Forest in central Oregon. We compared stand density, stand basal area, canopy volume, proportion of the stand in dominant/codominant, intermediate, and suppressed cohorts, average height and average diameter of each cohort, across the range of dwarf mistletoe ratings to address differences in stand structure. We found strong evidence of a decrease in canopy volume, suppressed cohort height, and dominant/codominant cohort diameter with increasing stand-level dwarf mistletoe rating. There was strong evidence that as dwarf mistletoe rating increases, proportion of the stand in the dominant/codominant cohort decreases while proportion of the stand in the suppressed cohort increases. Structural differences associated with variable dwarf mistletoe severity create heterogeneity in this forest type and may have a significant influence on stand productivity and the resistance and resilience of these stands to future biotic and abiotic disturbances. Our findings show that it is imperative to incorporate dwarf mistletoe when studying stand productivity and ecosystem recovery processes in lodgepole pine forests because of its potential to influence stand structure

Datos preliminares sobre el papel del venado cola blanca Odocoileus virginianus (Artiodactyla: Cervidae) como dispersor de semillas

El papel del venado cola blanca como dispersor endozoócoro de semillas se evaluó a través de la estimación del número de semillas y especies encontradas en las muestras fecales, y el análisis del efecto del paso por el tracto digestivo sobre el porcentaje y la velocidad de germinación en semillas de una especie focal (Acacia schaffneri). En total se encontraron 369 semillas en 98 grupos de pellets. La mayoría de las semillas se apreciaban dañadas o inmaduras, sólo 67 semillas (31 morfoespecies) germinaron. El porcentaje de germinación de semillas de A. schaffneri defecadas tendió a ser mayor que la germinación de semillas control. En nuestro estudio el venado figura como depredador de semillas y ocasionalmente como dispersor de semillas. Sin embargo, nuestros resultados con animales en cautiverio muestran que el venado puede incrementar el porcentaje de germinación de algunas especies.The role of white-tailed deer in endozoochorus seed dispersal was evaluated by estimating the number of seeds and seed species found in fecal samples and assessing the effect of gut passage on germination percentage and speed for a focal seed species (Acacia schaffneri). A total of 369 seeds were found in 98 pellet groups. Most seeds appeared to be damaged or immature, and only 67 seeds (31 morphospecies) germinated. Germination percentage of defecated seeds of A. schaffneri tended to be higher than germination of control seeds. In our study site white-tailed deer appears to be acting mainly as a seed predator for ingested seeds, and occasionally as a seed disperser. Nevertheless, our results using captive animals suggest that white-tailed deer may improve seed germination of particular plant species

Dinámica temporal de la infestación por muérdago enano (Arceuthobium globosum y A. vaginatum) en Zoquiapan (Parque Nacional Popocatépetl), México

Dwarf mistletoes are forest parasites of great impact on temperate forests, both at the biological and the economical level; however, little is known about the temporal dynamics of their infestation. The aim of this study was to know how the incidences of Arceuthobium vaginatum and A. globosum change through time in the Zoquiapan region, inthe Iztaccíhuatl Popocatépetl National Park, Mexico. For two and a half years (november 2008 to may 2011), it was registered the incidence of dwarf mistletoe (proportion of infected trees), hosts abundance, and the abundance of pines smaller than 2 m in height on 24 plots of 3 300 m2. It was found that infestation dynamics varies greatly, between species and plots, and that A. vaginatum showed a greater incidence than A. globo-sum (Z = 44.09, P < 0.000 1). Also, the occurrence of fires and logging apparently affected the mistletoe incidence, and even, in some cases, mistletoe regrowth was observed. The incidence of A. vaginatum had a negative correlation with small pines abundance (rs = - 0.414, P < 0.05), which could be indicating that there is a negative effect on sapling recruitment. It is necessary to incorporate the occurrence of stochastic phenomena (like fires) to dwarf mistletoe management programs, to improve the conservation of forest resources.Los muérdagos enanos se encuentran entre los parásitos forestales que tienen mayor impacto biológico y económico en los bosques templados; sin embargo, se sabe poco acerca de la dinámica temporal de la infestación. El objetivo de este trabajo fue conocer cómo cambia en el tiempo la incidencia de Arceuthobium vaginatum y A. globosum sobre Pinus hartwegii en la región de Zoquiapan, dentro del Parque Nacional Iztaccíhuatl Popocatépetl, México. Durante dos años y medio (noviembre 2008 a mayo 2011) se registró la incidencia de muérdago (proporción de árboles infestados), la abundancia de hospederos y la abundancia de pinos menores a 2 m en 24 parcelas de 3 300 m2. Se encontró que la infestación es altamente variable entre fechas, especies y sitios, sin embargo, A. vaginatum mostró una mayor incidencia que A. globosum (Z = 44.09, P < 0.0001). Asimismo, la ocurrencia de incendios y la tala parecen haber afectado la incidencia de los muérdagos, e incluso, en algunos casos, se observaron rebrotes severos. La incidencia de A. vaginatum tuvo una correlación negativa con la abundancia de pinos menores a 2 m (rs = - 0.414, P < 0.05), por lo que esta especie pudo estar afectando el reclutamiento de individuos juveniles, mientras A. globosum no mostró una correlación significativa. Es necesario tomar en cuenta los sucesos estocásticos (como incendios) en los planes de manejo del muérdago enano, para mejorar la conservación de los recursos forestales

Distribución diferencial de dos especies de muérdago enano sobre Pinus hartwegii en el área natural protegida "Zoquiapan y anexas", Estado de México

Dwarf mistletoes (Arceuthobium spp.) are important plants in temperate forests of Mexico due to their high incidence. At the south side of the Papayo Hill in the �Zoquiapan y Anexas� Natural Protected Area, Mexico State, both, Arceuthobium vaginatum subsp. vaginatum and A. globosum subsp. grandicaule coexist within the same zone and, frequently, on the same host tree of the species Pinus hartwegii. We studied the vertical distribution of both species on the stem, and we registered that A. vaginatum is found more frequently to lower heights of the pines than A. globosum. These results suggest that the nutritional resources are taken in a differential manner, causing a probable competitive relation between the two species.Los muérdagos enanos (Arceuthobium spp.) son plantas importantes en los bosques templados de México debido a su alta incidencia. Al sur del cerro Papayo en el Área Natural Protegida �Zoquiapan y Anexas�, Estado de México, coexisten Arceuthobium vaginatum subsp. vaginatum y A. globosum subsp. grandicaule incluso en el mismo árbol hospedero de la especie Pinus hartwegii. Al estudiar su disposición vertical en el tronco se registra que A. vaginatum se distribuye a menor altura en los pinos que A. globosum. Esto sugiere que la eficiencia de obtención de recursos nutricionales del hospedero podría ser diferencial, por lo que es posible que haya una relación de competencia entre ambas especies

Data from: Competition and facilitation determine dwarf mistletoe infection dynamics

1. Interspecific interactions have a fundamental role in plant population dynamics, as they may set the conditions for species coexistence. Parasitic plants, like dwarf mistletoes, offer the opportunity to study competition for resources that are different from those consumed by most plants, allowing for a better understanding of the interaction. 2. We explored how interspecific interactions between two dwarf mistletoe species (Arceuthobium), co-infecting the same host species (even sharing the same individual tree of Pinus hartwegii) affect their infection dynamics at two different stages of population development (colonization of new hosts and subsequent growth), and if heterogeneity in resource availability (host density and size structure) affects these interactions. For that purpose, we integrated these processes into a spatially-explicit model of density-dependent population growth. 3. We found that self-regulation (density-dependence) was strong for both species; however the intensity and sign of interspecific interactions changed depending on host size and demographic process. Population growth in A. globosum was reduced by competition, except for smaller hosts where A. globosum growth was facilitated by A. vaginatum. A. vaginatum was facilitated by A. globosum regardless of host size. Colonization of new hosts by A. globosum was enhanced by previous infection by the other species, showing intraguild facilitation. 4. Demographic importance of interactions depended on stand structure: in homogeneous, low-density forests, facilitation predominates, increasing the population sizes of both species, whereas the opposite occurs in heterogeneous and dense forests. Both species achieved stable coexistence, fulfilling the invasibility criterion because each mistletoe species can invade a forest that is already infected by the other species. 5. Synthesis. Despite the fundamentally different mechanisms underlying the interactions between mistletoes compared with non-parasitic plants, our results reveal that their behaviour at the population level is similar. Stabilizing mechanisms, like strong self-limiting population growth, allow dwarf mistletoe coexistence. Interactions shift as populations develop, and they depend largely on environmental factors such as forest structure. Intraguild mutualism is shown as a relevant process for colonization of new spaces, highlighting the complexity of competitive/facilitative interactions between parasitic plants, a formerly unexplored subject. Interactions can only be fully understood when integrating all their components at the population level. Analysing these interactions may contribute to the understanding of plant-plant interactions in general, and convey interesting implications for forest management

AgneMichelleForestryEffectsDwarfMistletoe_SupportingInformation.zip

Lodgepole pine (Pinus contorta) forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae) epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes. Dwarf mistletoe (Arceuthobium americanum) also influences stand structure and occurs frequently in post-mountain pine beetle epidemic lodgepole pine forests. Few studies have incorporated both disturbances simultaneously although they co-occur frequently on the landscape. The aim of this study is to investigate the stand structure of lodgepole pine forests 21–28 years after a mountain pine beetle epidemic with varying levels of dwarf mistletoe infection in the Deschutes National Forest in central Oregon. We compared stand density, stand basal area, canopy volume, proportion of the stand in dominant/codominant, intermediate, and suppressed cohorts, average height and average diameter of each cohort, across the range of dwarf mistletoe ratings to address differences in stand structure. We found strong evidence of a decrease in canopy volume, suppressed cohort height, and dominant/codominant cohort diameter with increasing stand-level dwarf mistletoe rating. There was strong evidence that as dwarf mistletoe rating increases, proportion of the stand in the dominant/codominant cohort decreases while proportion of the stand in the suppressed cohort increases. Structural differences associated with variable dwarf mistletoe severity create heterogeneity in this forest type and may have a significant influence on stand productivity and the resistance and resilience of these stands to future biotic and abiotic disturbances. Our findings show that it is imperative to incorporate dwarf mistletoe when studying stand productivity and ecosystem recovery processes in lodgepole pine forests because of its potential to influence stand structure

AgneMichelleForestryEffectsDwarfMistletoe.pdf

Lodgepole pine (Pinus contorta) forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae) epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes. Dwarf mistletoe (Arceuthobium americanum) also influences stand structure and occurs frequently in post-mountain pine beetle epidemic lodgepole pine forests. Few studies have incorporated both disturbances simultaneously although they co-occur frequently on the landscape. The aim of this study is to investigate the stand structure of lodgepole pine forests 21–28 years after a mountain pine beetle epidemic with varying levels of dwarf mistletoe infection in the Deschutes National Forest in central Oregon. We compared stand density, stand basal area, canopy volume, proportion of the stand in dominant/codominant, intermediate, and suppressed cohorts, average height and average diameter of each cohort, across the range of dwarf mistletoe ratings to address differences in stand structure. We found strong evidence of a decrease in canopy volume, suppressed cohort height, and dominant/codominant cohort diameter with increasing stand-level dwarf mistletoe rating. There was strong evidence that as dwarf mistletoe rating increases, proportion of the stand in the dominant/codominant cohort decreases while proportion of the stand in the suppressed cohort increases. Structural differences associated with variable dwarf mistletoe severity create heterogeneity in this forest type and may have a significant influence on stand productivity and the resistance and resilience of these stands to future biotic and abiotic disturbances. Our findings show that it is imperative to incorporate dwarf mistletoe when studying stand productivity and ecosystem recovery processes in lodgepole pine forests because of its potential to influence stand structure