Mule deer impede Pando's recovery: Implications for aspen resilience from a single-genotype forest

To overcome the limitations of fixed life patterns, plants can generate meristems throughout life

The fixed life pattern of plants is the most threatening factor that hinders the survival and reproduction rate of plants. Maximization of reproduction is determined by the survival rate of the organism. If part of a shoot apical meristem or root apical meristem is cut and planted in soil with appropriate nutrients and survival conditions, a cloned plant known as an ramet, may be developed. Therefore, the ability of plants to constantly produce meristems is essential for survival. In addition, meristem stem cells have enabled plants to evolve a wide variety of asexual reproductive systems. When a tree is pruned, at least one or more new meristems are formed in the surrounding area, and those meristems develop into new branches. In other cases, stem cells normally derived from meristems alone exhibit the potential for asexual reproduction through their seed-like roles. Alternatively, some plants can form somatic cells, which are important in various types of asexual reproduction. There are 125 species of plants in the genus of Kalanchoe, which are succulent plants, and most of these species are well known to reproduce asexually through somatic cells. When we cut the stem of a plant, a callus is formed at the end of the cut side. Plant callus is mainly used to develop new plant varieties in tissue culture research. Alternatively, the plant callus is also used as a material for asexual reproduction. Callus can also form if the plant is infected with bacteria such as Agrobacterium tumefaciens. Differentiated cells of a plant can reproduce asexually by acquiring the ability to function as stems through transdifferentiation. These characteristics play important roles in adapting to environmental changes and extending the lifespan of woody plants.

Phenotypic Variation in Phytochemical Defense of Trembling Aspen in Western North America: Genetics, Development, and Geography

Trembling aspen (Populus tremuloides) is arguably the most important deciduous tree species in the Intermountain West of North America. There, as elsewhere in its range, aspen exhibits remarkable genetic variation in observable traits such as morphology and phenology. In contrast to Great Lakes populations, however, relatively little is known about phytochemical variation in western aspen. This survey of phytochemistry in western aspen was undertaken to assess how chemical expression varies among genotypes, cytotypes (diploid vs. triploid), and populations, and in response to development and mammalian browsing. We measured levels of foliar nitrogen, salicinoid phenolic glycosides (SPGs) and condensed tannins (CTs), as those constituents influence organismal interactions and ecosystem processes. Results revealed striking genotypic variation and considerable population variation, but minimal cytotype variation, in phytochemistry of western aspen. Levels of SPGs and nitrogen declined, whereas levels of CTs increased, with tree age. Browsed ramets had much higher levels of SPGs, and lower levels of CTs, than unbrowsed ramets of the same genotype. We then evaluated how composite chemical profiles of western aspen differ from those of Great Lakes aspen (assessed in earlier research). Interestingly, mature western aspen trees maintain much higher levels of SPGs, and lower levels of CTs, than Great Lakes aspen. Phenotypic variation in chemical composition of aspen - a foundation species - in the Intermountain West likely has important consequences for organismal interactions and forest ecosystem dynamics. Moreover, those consequences likely play out over spatial and temporal scales somewhat differently than have been documented for Great Lakes aspen.

Myths, Wishful Thinking, and Accountability in Predator Conservation and Management in the United States

Large predators are thought of as ecological keystone species, posterchildren of conservation campaigns, and sought-after targets of tourists and photographers. At the same time, predators kill livestock and huntable animals, and occasionally people, triggering fears and antipathy among those living alongside them. Until the 1960’s government-sponsored eradication and persecution campaigns in the United States prioritized interests of livestock producers and recreational hunters, leading to eradication of wolves and bears over much of their range. Without large predators, subsidized by changes in agricultural practices and milder winters, ungulate populations erupted, triggering negative ecological impacts, economic damage, and human health crises (such as tick-borne diseases). Shifting societal preferences have ushered in more predator-friendly, but controversial wildlife policies, from passively allowing range expansion to purposeful reintroductions (such as release of wolves in Yellowstone National Park). Attempts to restore wolves or mountain lions in the U.S. and protecting coyotes appear to enjoy strong public support, but many state wildlife agencies charged with managing wildlife, and recreational hunters continue to oppose such efforts, because they perceive predators as competitors for huntable animals. There may be compelling reasons for restoring predators or allowing them to recolonize their former ranges. But if range expansion or intentional releases of large predators do not result in ecosystem recovery, reduced deer populations, or Lyme disease reductions, conservationists who have put their reputation on the line and assured decision makers and the public of the important functional role of large predators may lose public standing and trust. Exaggerated predictions by ranchers and recreational hunters of greatly reduced ungulate populations and rampant livestock killing by large carnivores may lead to poaching and illegal killing threatening recovery of predator populations. How the return of large carnivores may affect vegetation and successional change, ungulate population size, other biota, livestock and human attitudes in different landscapes has not been appropriately assessed. Societal support and acceptance of living alongside predators as they expand their range and increase in abundance requires development and monitoring of social, ecological and economic indicators to assess how return of large predators affects human and animal and plant livelihoods.

The Woody Planet: From Past Triumph to Manmade Decline

Woodiness evolved in land plants approximately 400 Mya, and very soon after this evolutionary invention, enormous terrestrial surfaces on Earth were covered by dense and luxurious forests. Forests store close to 80% of the biosphere’s biomass, and more than 60% of the global biomass is made of wood (trunks, branches and roots). Among the total number of ca. 374,000 plant species worldwide, approximately 45% (138,500) are woody species—e.g., trees, shrubs or lianas. Furthermore, among all 453 described vascular plant families, 191 are entirely woody (42%). However, recent estimations demonstrate that the woody domination of our planet was even greater before the development of human civilization: 1.4 trillion trees, comprising more than 45% of forest biomass, and 35% of forest cover disappeared during the last few thousands of years of human dominance on our planet. The decline in the woody cover of Planet Earth did not decelerate during the last few centuries or decades. Ongoing overexploitation, land use and climate change have pushed ten thousand woody species to the brink of extinction. Our review highlights the importance, origin and past triumph of woody species and summarizes the unprecedented recent decline in woody species on our planet.

Past Management Spurs Differential Plant Communities within a Giant Single-Clone Aspen Forest

Sustainable aspen ecosystems hold great promise for global biodiversity conservation. These forests harbor relatively high species diversity, yet are threatened by fire suppression, land development, timber-focused management, extended droughts, and chronic herbivory. “Pando” is a high-profile quaking aspen (Populus tremuloides) forest in Utah, USA which is putatively the ‘largest living organism on earth.’ Pando comprises an estimated 47,000 genetically identical stems, but is threatened by human impacts. Our interest in the present study is whether changes to the giant organism were affecting understorey vegetation and whether discrete zones are displaying divergent community compositions. For instance, recent research has demonstrated strong herbivory impacts that are affecting portions of Pando differentially. This study consists of 20 randomly distributed vegetation survey plots within three de facto management regimes (hereafter, management group or type) along an herbivory protection gradient: No Fence, 2013 Fence (total protection), and 2014 Fence (imperfect protection). The plant survey was supplemented by previously-established forest and herbivore measurements to test for community assemblage explanatory agents. Sixty-eight species were found across the entire study. Analyses indicated strong links between management group orientation, species assemblages, and tree density/canopy openings. We found distinct evidence that within management group species composition was more similar than across groups for two of the three pairings. However, the other pairing, the most successfully protected area and the completely unprotected area, was not statistically distinct; likely a result a deteriorating overstorey in these two areas, whereas the third management type (2014 Fence) exhibited higher canopy cover. Indicator species analysis found that a small group of plant species had statistical allegiances to specific management groups, suggesting resource preference selection within Pando. Ordination analysis searching for causal factors reached two broad conclusions: (1) aspen regeneration, and therefore long-term resilience, is being negatively affected by chronic animal browsing and (2) current understorey species diversity is highest where forest canopy gaps are abundant. Future research at the massive Pando clone will continue informing linkages between understorey communities and overstorey-driven ecological pathways.