Antiproliferative, genotoxic and oxidant activities of cyclosativene in rat neuron and neuroblastoma cell lines

Cyclosativene (CSV) is a tetracyclic sesquiterpene found in the essential oils of Centaurea cineraria (Asteraceae) and Abies magnifica A. Murray (Pinaceae) plants. To the best of our knowledge, its cytotoxic, genotoxic and oxidant effects have never been studied on any cell lines. Therefore, we aimed to investigate the in vitro antiproliferative and/or cytotoxic properties, antioxidant/oxidant activity and genotoxic damage potential of CSV in healthy neurons and N2a neuroblastoma (N2a-NB) cell cultures. After treatment with 10-400 ?g/ml of CSV for 24 h, cell proliferation was measured by the MTT (3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The antioxidant activity was assessed by the total antioxidant capacity (TAC) and total oxidative stress (TOS) assays. To evaluate the level of DNA damage, single cell gel alkaline electrophoresis (SCGE) was used. The MTT assay showed that the application of CSV significantly reduced cell viability in both cell types. CSV treatments at higher doses led to decreases of TAC levels and increases of TOS levels in neuron and N2a-NB cells. The mean values of the total scores of cells showing DNA damage were not found to be significantly different from the control values in both cells. In conclusion, this study suggests that CSV has weak anticancer potential.

Growth–climate relationships for six subalpine tree species in a Mediterranean climate

A better understanding of the growth–climate relationship for subalpine trees is key to improving predictions about their future distributions under climate change. In subalpine regions of Mediterranean mountains, drought is an annual event, yet many sites can have long-lasting snowpack. We analyzed the growth–climate relationship from 1896 to 2006 for the six most abundant subalpine tree species (red fir (Abies magnifica A. Murray bis), whitebark pine (Pinus albicaulis Engelm.), Sierra/Cascade lodgepole pine (Pinus contorta var. murrayana (Balf.) Engelm.), Jeffrey pine (Pinus jeffreyi Balf.), western white pine (Pinus monticola Douglas ex D. Don), and mountain hemlock (Tsuga mertensiana (Bong.) Carrière)) of the central Sierra Nevada, California, USA, a region with deep spring snowpack followed by strong summer drought. Chronologies for the six species exhibited a high degree of synchrony in their response to annual fluctuations in temperature and precipitation. For all six species, cool, wet conditions in the year prior to growth are conducive to good radial growth, as well as warm springs with sufficient moisture during the year of growth. For species more common on protected slopes, such as mountain hemlock, deep spring snowpack can limit growth. Although predictions of future precipitation trends in the region are uncertain, drought stress appears to already be increasing. If this trend continues, radial growth is likely to be inhibited for most or all species in our study. Trees growing where snowpack is deep may be least likely to suffer reduced growth.

Habitat preferences of an arboreal forage lichen in a Sierra Nevada old-growth mixed-conifer forest

The arboreal forage lichen Bryoria fremontii (Tuck.) Brodo & D.Hawksw. appears sensitive to conditions of prolonged hydration in wet forests of British Columbia. I estimated the abundance of this lichen in mixed-conifer forest canopy in the contrasting Mediterranean climate of the southern Sierra Nevada in relationship to the vertical gradient of vapor pressure deficit. Abundance was estimated by biomass in 5 m strata from the ground to the tops of 50 trees. Transplants of Bryoria thalli were installed in 18 fir trees for 1 year to assess their growth relative to distance from perennial streams. VPD generally increased with height, being significantly greater at 45 m than 5 m. Bryoria biomass averaged across tree heights was estimated as 15.9, 0.60, 0.15, 0.25, and 0.19 g·m–1 in red fir (Abies magnifica A.Murray), white fir (Abies concolor (Gordon & Glend.) Hildebr. var. lowiana (Gordon) Lemmon), incense cedar (Calocedrus decurrens (Torr.) Florin), Jeffrey pine (Pinus jeffreyi Balf.), and sugar pine (Pinus lambertiana Douglas), respectively. Transplant growth was significantly greater in trees <25 m from water (11.4%) than in trees >25 m from water (9.7%). Bryoria had strong positive associations with red fir, proximity to streams, and decreasing VPD. The sensitivity of Bryoria to prolonged hydration does not appear to be important in this climate characterized by extended summer dryness.

Paleofire reconstruction for high-elevation forests in the Sierra Nevada, California, with implications for wildfire synchrony and climate variability in the late Holocene

Here, we present two high-resolution records of macroscopic charcoal from high-elevation lake sites in the Sierra Nevada, California, and evaluate the synchroneity of fire response for east- and west-side subalpine forests during the past 9200 yr. Charcoal influx was low between 11,200 and 8000 cal yr BP when vegetation consisted of sparse Pinus-dominated forest and montane chaparral shrubs. High charcoal influx after 8000 cal yr BP marks the arrival of Tsuga mertensiana and Abies magnifica, and a higher-than-present treeline that persisted into the mid-Holocene. Coeval decreases in fire episode frequency coincide with neoglacial advances and lower treeline in the Sierra Nevada after 3800 cal yr BP. Independent fire response occurs between 9200 and 5000 cal yr BP, and significant synchrony at 100- to 1000-yr timescales emerges between 5000 cal yr BP and the present, especially during the last 2500 yr. Indistinguishable fire-return interval distributions and synchronous fires show that climatic control of fire became increasingly important during the late Holocene. Fires after 1200 cal yr BP are often synchronous and corroborate with inferred droughts. Holocene fire activity in the high Sierra Nevada is driven by changes in climate linked to insolation and appears to be sensitive to the dynamics of the El Niño–Southern Oscillation.

Post-fire survival and flushing in three Sierra Nevada conifers with high initial crown scorch

With growing debate over the impacts of post-fire salvage logging in conifer forests of the western USA, managers need accurate assessments of tree survival when significant proportions of the crown have been scorched. The accuracy of fire severity measurements will be affected if trees that initially appear to be fire-killed prove to be viable after longer observation. Our goal was to quantify the extent to which three common Sierra Nevada conifer species may ‘flush’ (produce new foliage in the year following a fire from scorched portions of the crown) and survive after fire, and to identify tree or burn characteristics associated with survival. We found that, among ponderosa pines (Pinus ponderosa Dougl. ex. Laws) and Jeffrey pines (Pinus jeffreyi Grev. & Balf) with 100% initial crown scorch (no green foliage following the fire), the majority of mature trees flushed, and survived. Red fir (Abies magnifica A. Murr.) with high crown scorch (mean = 90%) also flushed, and most large trees survived. Our results indicate that, if flushing is not taken into account, fire severity assessments will tend to overestimate mortality and post-fire salvage could remove many large trees that appear dead but are not.

Geographic variation in chloroplast haplotypes in the California red fir-noble fir species complex and the status of Shasta red fir

I present the results of a molecular investigation into taxonomically unresolved issues of the California red fir – noble fir species complex. Samples were collected throughout the range of California red fir ( Abies magnifica A. Murray), from the southern Sierra Nevada to the region in northern California and southern Oregon where morphological variation has suggested it hybridizes with noble fir ( Abies procera Rehder). Two rbcL sequences were found within A. magnifica and showed perfect linkage with variation at the chloroplast trnD locus. Only populations in the region of hypothesized hybridization were polymorphic for rbcL. One haplotype is unique to A. magnifica in the southern part of its range, and the other is identical to that found in A. procera to the north, supporting a broad zone of hybridization. There was no evidence for a cryptic geographic barrier between the two species. A single A. procera tree from southwestern Washington also had the A. magnifica haplotype, suggesting that introgression from A. magnifica may be widespread. The type locality of Abies magnifica var. shastensis Lemmon was polymorphic, whereas the disjuct southern A. magnifica var. shastensis was monomorphic for rbcL. I also present corrections, based on replication, to two rbcL sequences for A. magnifica previously deposited in GenBank.