How specialized is a soil specialist? Early life history responses of a rare Eriogonum to site-level variation in volcanic soils.

PREMISE: Understanding edaphic specialization is crucial for conserving rare plants that may need relocation due to habitat loss. Focusing on Eriogonum crosbyae, a rare soil specialist in the Great Basin of the United States, we asked how site-level variation among volcanic soil outcrops affected plant growth and population distribution. METHODS: We measured emergence, survival, size, and biomass allocation of E. crosbyae seedlings planted in soils collected from 42 outcrops of actual and potential habitat. We also measured phenotypic variation in the wild, documented abiotic and biotic components of E. crosbyae habitat, re-surveyed Nevada populations, and evaluated occupancy changes over time. RESULTS: Plants responded plastically to edaphic variation, growing larger and allocating relatively more to aboveground tissues in soils with greater nutrient availability and growing smaller in soils higher in copper in the field and the greenhouse. However, the chemical and physical soil properties we measured did not predict site occupancy, nor was plant phenotype in the greenhouse different when plants were grown in soils from sites with different occupation status. We observed occupation status reversals at five locations. CONCLUSIONS: Eriogonum crosbyae performed well in soils formed on hydrothermally altered rocks that are inhospitable to many other plants. Extirpation/colonization events observed were consistent with metapopulation dynamics, which may partially explain the patchy distribution of E. crosbyae among outcrops of potential habitat. While soil properties did not predict site occupancy, early life stages showed sensitivity to soil variation, indicating that seedling dynamics may be important to consider for the conservation of this soil specialist.

Monascus ruber-Fermented Buckwheat (Red Yeast Buckwheat) Suppresses Adipogenesis in 3T3-L1 Cells.

Although various treatments have been used for weight loss to date, obese people rarely have safe and effective treatment options. Therefore, the antiobesity effects of several natural compounds are being actively investigated. This study was conducted to investigate the antiadipogenic effects of Monascus ruber-fermented Fagopyrum esculentum (red yeast buckwheat, RYB) in 3T3-L1 cells. We assessed the intracellular lipid content and adipocyte differentiation by oil red O staining and the expression of genes and proteins associated with adipocyte differentiation by reverse transcription-polymerase chain reaction and western blotting in 3T3-L1 cells. RYB dose dependently inhibited 3T3-L1 cell differentiation at concentrations of 50-800 µg/mL, without cytotoxic effects. It also suppressed the expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein α, and adipocyte-specific genes, such as adipocyte fatty acid-binding protein (aP2), fatty acid synthase, and leptin, during preadipocyte differentiation into adipocytes. Furthermore, RYB reduced cyclin-dependent kinase 2 and cyclin expression and increased p21 and p27 expression, thus causing cell cycle arrest at the G1/S phase. Collectively, these results suggest that RYB may be an effective nutraceutical for weight loss as indicated by its ability to suppress adipogenesis-specific gene expression and cause cell cycle arrest at the G1/S interphase.

Beneficial insects attracted to native flowering buckwheats (Eriogonum Michx) in central Washington.

Native plant and beneficial insect associations are relatively unstudied yet are important in native habitat restoration programs aimed at improving conservation biological control in perennial crops such as wine grapes. Beneficial insects (predators, parasitoids, pollinators) attracted to 10 species of flowering native wild buckwheat (Eriogonum spp.) in central Washington were identified and counted on transparent sticky traps. Combining all categories of beneficial insects, the mean number per trap ranged from 48.5 (Eriogonum umbellatum) to 167.7 (Eriogonum elatum). Three Eriogonum spp. (E. elatum, Eriogonum compositum, and Eriogonum niveum) attracted significantly more beneficial insects than the lowest-ranked species. E. niveum attracted greatest numbers of bees and parasitic wasps, and E. elatum was highly attractive to predatory true bugs and beneficial flies. Blooming periods of Eriogonum spp. extended from mid April to the end of September. This study demonstrates the attraction of beneficial insects to native flowering buckwheats and suggests their potential as a component of habitat restoration strategies to improve and sustain conservation biological control in Washington viticulture.

Diurnal patterns of productivity of arbuscular mycorrhizal fungi revealed with the Soil Ecosystem Observatory.

Arbuscular mycorrhizal (AM) fungi are the most abundant plant symbiont and a major pathway of carbon sequestration in soils. However, their basic biology, including their activity throughout a 24-h day : night cycle, remains unknown. We employed the in situ Soil Ecosystem Observatory to quantify the rates of diurnal growth, dieback and net productivity of extra-radical AM fungi. AM fungal hyphae showed significantly different rates of growth and dieback over a period of 24 h and paralleled the circadian-driven photosynthetic oscillations observed in plants. The greatest rates (and incidences) of growth and dieback occurred between noon and 18:00 h. Growth and dieback events often occurred simultaneously and were tightly coupled with soil temperature and moisture, suggesting a rapid acclimation of the external phase of AM fungi to the immediate environment. Changes in the environmental conditions and variability of the mycorrhizosphere may alter the diurnal patterns of productivity of AM fungi, thereby modifying soil carbon sequestration, nutrient cycling and host plant success.

Facilitation and interference of seedling establishment by a native legume before and after wildfire.

In semi-arid ecosystems, heterogeneous resources can lead to variable seedling recruitment. Existing vegetation can influence seedling establishment by modifying the resource and physical environment. We asked how a native legume, Lupinus argenteus, modifies microenvironments in unburned and burned sagebrush steppe, and if L. argenteus presence facilitates seedling establishment of native species and the non-native annual grass, Bromus tectorum. Field treatments examined mechanisms by which L. argenteus likely influences establishment: (1) live L. argenteus; (2) dead L. argenteus; (3) no L. argenteus; (4) no L. argenteus with L. argenteus litter; (5) no L. argenteus with inert litter; and (6) mock L. argenteus. Response variables included soil nitrogen, moisture, temperature, solar radiation, and seedling establishment of the natives Elymus multisetus and Eriogonum umbellatum, and non-native B. tectorum. In both unburned and burned communities, there was higher spring soil moisture, increased shade and reduced maximum temperatures under L. argenteus canopies. Adult L. argenteus resulted in greater amounts of soil nitrogen (N) only in burned sagebrush steppe, but L. argenteus litter increased soil N under both unburned and burned conditions. Although L. argenteus negatively affected emergence and survival of B. tectorum overall, its presence increased B. tectorum biomass and reproduction in unburned plots. However, L. argenteus had positive facilitative effects on size and survival of E. multisetus in both unburned and burned plots. Our study indicates that L. argenteus can facilitate seedling establishment in semi-arid systems, but net effects depend on the species examined, traits measured, and level of abiotic stress.

Microsatellite primers for the narrowly endemic shrub Eriogonum giganteum (Polygonaceae).

PREMISE OF THE STUDY: Microsatellite primers were designed for Eriogonum giganteum var. formosum, an endemic shrub of San Clemente Island, to investigate population structure, genetic diversity, and demographic history. METHODS AND RESULTS: Twelve polymorphic microsatellite loci were isolated from the California Channel Island endemic Eriogonum and were screened for variability. The primers amplified one to eight alleles in the target taxon. Many primers also amplified in conspecific and congeneric (E. arborescens, E. fasciculatum, E. grande, E. latifolium, and E. parvifolium) taxa and in the closely related Chorizanthe valida. The total number of alleles per locus for all taxa screened ranged from three to 24. CONCLUSIONS: These primers will be useful for conservation genetic and evolutionary studies within the California Channel Island endemic Eriogonum.

The role of plant-soil feedbacks in driving native-species recovery.

The impacts of exotic plants on soil nutrient cycling are often hypothesized to reinforce their dominance, but this mechanism is rarely tested, especially in relation to other ecological factors. In this manuscript we evaluate the influence of biogeochemically mediated plant-soil feedbacks on native shrub recovery in an invaded island ecosystem. The introduction of exotic grasses and grazing to Santa Cruz Island, California, USA, converted native shrublands (dominated by Artemisia californica and Eriogonum arborescens) into exotic-dominated grasslands (dominated by Avena barbata) over a century ago, altering nutrient-cycling regimes. To test the hypothesis that exotic grass impacts on soils alter reestablishment of native plants, we implemented a field-based soil transplant experiment in three years that varied widely in rainfall. Our results showed that growth of Avena and Artemisia seedlings was greater on soils influenced by their heterospecific competitor. Theory suggests that the resulting plant-soil feedback should facilitate the recovery of Artemisia in grasslands, although four years of monitoring showed no such recovery, despite ample seed rain. By contrast, we found that species effects on soils lead to weak to negligible feedbacks for Eriogonum arborescens, yet this shrub readily colonized the grasslands. Thus, plant-soil feedbacks quantified under natural climate and competitive conditions did not match native-plant recovery patterns. We also found that feedbacks changed with climate and competition regimes, and that these latter factors generally had stronger effects on seedling growth than species effects on soils. We conclude that even when plant-soil feedbacks influence the balance between native and exotic species, their influence may be small relative to other ecological processes.

Native shrub reestablishment in exotic annual grasslands: do ecosystem processes recover?

The impacts of exotic plant species on ecosystem processes are well established, motivating numerous efforts to facilitate native-species recovery. Nonetheless, how the return of native species influences ecosystem processes and how these changes feed back to influence the recovery process are poorly understood. We examined these questions in exotic annual grasslands on Santa Cruz Island, California, USA, where the removal of nonnative herbivores has led to the recovery of the native shrubs Artemisia californica and Eriogonum arborescens. To examine the influence of shrub colonization on nutrient cycling, and the mechanisms by which these changes arise, we measured available nitrogen and phosphorus, and quantified nitrogen mineralization and litterfall rates under shrubs and grasses in the field and in experimental monoculture plots. Both native shrubs altered nitrogen cycling as they colonized the grassland, but they did so in opposite directions. Eriogonum depressed nitrogen pools and mineralization rates via large inputs of nitrogen-poor litter. In contrast Artemisia increased nitrogen and phosphorus pools and nitrogen mineralization rates. Last, to determine if shrub effects on soils favor shrubs or grasses, we conducted a nitrogen and phosphorus fertilization experiment in the field. Only the exotic grass was significantly limited by nitrogen. Thus the depressed nitrogen availability associated with Eriogonum colonization is more harmful to exotic grasses than to the native shrub. By contrast, the elevated nitrogen associated with recovering Artemisia favors grasses over the shrub, possibly hindering recovery of the native. Mechanistic studies of the ecosystem ,impacts of native-plant recovery are useful for managers wishing to predict which native species return ecosystem function, and whether such changes feed back to influence native recovery.

Experimental clipping of sagebrush inhibits seed germination of neighbours.

Current views of plant communities emphasize the importance of competition for resources and colonization ability in determining seedling establishment and plant distributions. Many desert shrubs are surrounded by bare zones that lack other plants or have different suites of species beneath them compared with the open desert surrounding them. Releases of biochemicals as volatiles from leaves, leachates from litter, or exudates from roots have been proposed as mechanisms for this pattern, but such phytotoxicity has been controversial. I tested the hypothesis that experimental clipping of sagebrush foliage enhances its effect as a germination inhibitor. Germination of native forbs and grasses was reduced in association with clipped, compared with unclipped, sagebrush foliage in lath house and field experiments. Sagebrush seeds were not significantly affected. Air contact was required for this inhibition of germination. Soil contact and leaf litter were not required and added little inhibition of germination. These results suggest a potentially large, indirect, and previously overlooked role for interactions between herbivory and germination that could affect plant community structure.

A test for hydrotropic behavior by roots of two coastal dune shrubs.

Root hydrotropism could be a means by which plants forage for limited and patchy distributions of soil water. While root hydrotropism has been induced in distinctly artificial conditions, it is unclear if it operates in natural settings. Here, we tested for this possibility in seedlings of two species of dune shrubs. Growth of individual roots in sand-filled observation chambers was monitored in response to moisture-rich patches and resultant soil water gradients. Chambers were designed so that roots could intercept the moisture gradients but not the moisture-rich patches simply through gravitropism. While up to 12% of the Eriogonum parvifolium roots grew into the moisture-rich patches, comparable root growth was observed in the control. None of the Artemisia californica roots grew into the patches. Thus, in a reasonable simulation of field conditions, we found no compelling evidence for hydrotropic root behavior in seedlings of these two dune shrubs. Our results leave the ecological significance of root hydrotropism in question.