How do light and water influence Pinus pinaster Ait. germination and early seedling development?

Germination and survival in the initial months represent a critical period for forest species. Many factors have significant influences and can produce a negative effect on regeneration. To prevent this, these factors must be known and their influence must be evaluated. The influence of light and of water availability has been studied in the most important pine species in the Iberian Peninsula, the Pinus pinaster. An experimental seed-sowing was conducted in the Cuéllar experimental site (central Spain), where four different harvest intensities were applied in 2004. Four different watering regimes were performed during two consecutives summers (2006 and 2007) and seedling development was monitored during 18 months. Main findings reveal that, regarding germination and survival in the initial months, light was more important than water availability. Higher germination and survival rates were obtained when the lowest level harvest was applied. However, in terms of biomass and growth, water availability was more influential than harvest intensity. Results improved when there was greater water availability after a few months. The main conclusion of this study is that light shows a higher impact that summer rainfall with respect to germination and survival in the early stages of Mediterranean Maritime Pine.     

Changes during early development in photosynthetic light acclimation capacity explain the shade to sun transition in Nothofagus nitida

Nothofagus nitida (Phil.) Krasser, an emergent tree of the Chilean evergreen forest, regenerates under the canopy. Nonetheless, it is common to find older saplings in clear areas. We hypothesized that this transition from shade to sun during the early developmental stages is made possible by an ontogenetic increase in the light acclimation capacity of photosynthesis. To test our hypothesis, we studied photosynthetic performance and photoprotection in N. nitida saplings at different developmental stages corresponding with three different height classes (short: 16.2 cm; medium-height: 48.0 cm; and tall: 73.7 cm) grown under contrasting light conditions (photosynthetic photon flux (PPF) of 20, 300 or 600 micromol m(-2) s(-1)) until newly expanded leaves had developed. Light-saturated CO(2) assimilation rate and light compensation and saturation points increased with increasing PPF. Medium-height and tall saplings acclimated to high light had higher electron transport rates and higher proportions of open Photosystem II reaction centers than shorter plants acclimated to high light. Short saplings showed higher thermal dissipation and contents of xanthophylls than taller saplings. Only medium-height and tall saplings acclimated to high light recovered after photoinhibition. State transitions were higher in short plants growing in low light, and decreased with plant height and growth irradiance. Thus, during development, N. nitida changes the balance of light energy utilization and photoprotective mechanisms, supporting a phenotypic transition from shade to sun during its early ontogeny.     

Local and regional factors influence the structure of treehole metacommunities

Background

Abiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are also influenced by regional factors such as immigration and colonization. We used three years of monthly treehole census data to evaluate the relative influence of local and regional factors on our study system.

Results

Every species responded to at least one of three local environmental factors measured: water volume, leaf litter mass, and presence of a top predator. Several species were affected by water volume, and a non-exclusive group of species were influenced by leaf litter mass. Relative abundance of Aedes triseriatus was higher in treeholes with higher volumes of water, and relative abundances of three out of six other species were lower in treeholes with higher volumes of water. Leaf litter mass positively affected densities of Aedes triseriatus and relative abundance of several dipteran species. The density of the top predator, Toxorhynchites rutilus, affected the relative abundance of the two most common species, A. triseriatus and Culicoides guttipennis. Treeholes with T. rutilus had an average of two more species than treeholes without T. rutilus. We found little evidence of synchrony between pairs of treeholes, either spatially or temporally. There were high levels of spatial and temporal turnover, and spatial turnover increased with distance between patches.

Conclusion

The strong effects of water volume, leaf litter mass, and presence of a top predator, along with the high temporal turnover strongly suggest that species presence and density are determined by local factors and changes in those factors over time. Both low water volume and high predator densities can eliminate populations in local patches, and those populations can recolonize patches when rain refills or predators exit treeholes. Population densities of the same species were not matched between pairs of treeholes, suggesting variation in local factors and limited dispersal. Distance effects on spatial turnover also support limitations to dispersal in the metacommunity, and we conclude that the weight of evidence favors a strong influence of local factors relative to regional factors.     

Differential response of ectomycorrhizal and saprotrophic fungal mycelium from coniferous forest soils to selected monoterpenes

The mycelia of saprotrophic (SP) and ectomycorrhizal (ECM) fungi occur throughout the upper soil horizons in coniferous forests and could therefore be exposed to high concentrations of monoterpenes occurring in the needle litter of some tree species.Monoterpenes are mycotoxic and could potentially affect fungi that are exposed to them in the litter layers. In order to investigate whether monoterpenes typical of coniferous litters could influence fungal communities, we analysed the monoterpene content of freshly fallen needles of Pinus sylvestris, Picea abies and Picea sitchensis. The most abundant monoterpenes were found to be α-pinene, β-pinene and 3-carene. We evaluated the effects of these three monoterpene vapours on the biomass production of 23 SP isolates and 16 ECM isolates. Overall, 75% of ECM isolates and 26% of SP isolates were significantly inhibited by at least one of the monoterpene treatments and both intra- and inter-specific variations in response were observed.Monoterpene concentrations are highest in surface litters. The differential effects on fungal taxa may influence the spatial and temporal distribution of fungal community composition, indirectly affecting decomposition and nutrient cycling, the fundamental ecosystem processes in which fungi have a key role in coniferous forest soils.     

First report of cyromazine resistance in a population of UK house fly (Musca domestica) associated with intensive livestock production

BACKGROUND: House fly control in livestock‐rearing facilities is heavily reliant on the use of the larvicide cyromazine. While extensive use of this compound has led to the development of resistance in several countries, no elevated tolerance has so far been reported from the United Kingdom. RESULTS: Tolerance to cyromazine in larvae derived from a field strain collected at an intensive pig unit was significantly elevated over that of insects taken from a susceptible laboratory strain. Resistance factors (RFs) of 2.9 and 2.4 were returned for assays initiated with eggs and neonate larvae respectively. The RF for field strain larvae exposed from neonate increased significantly to 3.9 and 5.6 following rounds of selection at 1.0 and then 1.5 mg kg^?1 cyromazine. CONCLUSION: Low‐level resistance to cyromazine in UK house flies is reported here for the first time. The geographic extent of this resistance is unknown but, if widespread, may lead to control failures in the future, and indicates that careful stewardship of this compound in the United Kingdom is now required. © Crown copyright 2010. Reproduced with permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Mechanism of acylation stimulating protein resistance induced by fatty acid in 3T3-L1 adipocytes and preadipocytes

AIM: To evaluate the potential acylation stimulating protein (ASP) resistance in both adipocytes and preadipocytes under the conditions by which insulin resistance is produced by the stimulation of free fatty acids (FFA), and to explore the mechanism of ASP resistance on post-receptor level. METHODS: 3T3-L1 preadipocytes were induced to differentiate. Then the cells were treated with oleate or palmitate at concentration of 0 mmol/L (FFA-free DMEM/F12), 0.125 mmol/L, 0.5 mmol/L or 1.0 mmol/L overnight. Glucose transport was assessed by ［3H］ 2-deoxyglucose uptake to evaluate insulin resistance and ASP resistance. Both non-FFA treated and FFA treated 3T3-L1 cells were cultured with ASP at concentration of 5.0 μmol/L for 4 h, then the cell proteins were extracted, and the expressions of guanine nucleotide binding protein beta (Gβ), guanine nucleotide-binding protein alpha-q/11(Gαq/11), phosphorylated-protein kinase Cα (p-PKCα) and phosphorylated-protein kinase Cζ (p-PKCζ) were measured by Western blotting. RESULTS: Both adipocytes and preadipocytes were responsive to ASP. ASP stimulation increased glucose transport by 198% in adipocytes and by 287% in preadipocytes (P<0.01 vs PBS). FFA at concentration of 0.125 mmol/L did not change ASP-stimulated glucose transport significantly, but high dose of oleate or palmitate effectively reduced the ASP response with a significant reduction by 47% (P<0.05 for oleate) and 34% (P<0.05 for palmitate) at 1 mmol/L FFA in adipocytes. Similarly in preadipocytes, glucose uptake rates were decreased by 43% (P<0.05 for oleate) and 62% (P<0.01 for palmitate) at 1 mmol/L FFA. Effects were comparable to those obtained with insulin. After overnight incubation with oleate or palmitate in adipocytes and preadipocytes, Gβ, Gαq/11, p-PKCα and p-PKCζ were downregulated both in the absence of ASP treatment and in the presence of ASP treatment in adipocytes. At concentration of 1.0 mmol/L, oleate inhibited the expressions of ASP-induced Gβ, Gαq/11, p-PKCα and p-PKCζ in adipocytes by 47％, 44%, 39% (P<0.05, P<0.01) and 20% (P>0.05), respectively. Palmitate also effectively blocked the expressions of ASP (at concentration of 1.0 mmol/L)-induced Gβ, Gαq/11, p-PKCα and p-PKCζ by 50%, 43%, 44% and 43% (P<0.05, P<0.01) in adipocytes. In preadipocytes, oleate only inhibited ASP-induced p-PKCα and p-PKCζ significantly by 39% and 19%, respectively (P<0.05). However, overnight exposure of 3T3-L1 preadipocytes to 1 mmol/L palmitate leaded to 45%, 50%, 52% and 21% (P<0.05, P<0.01) inhibition of ASP-induced expressions of Gβ, Gαq/11, p-PKCα and p-PKCζ, respectively. CONCLUSION: Oleate and palmitate inhibit ASP-mediated stimulation of glucose transport both in adipocytes and preadipocytes. The study provides direct evidence of ASP resistance under the condition of insulin resistance induced by FFA in a cellular model. The mechanism of action involves both changes in expression of C5L2 as well as signaling parameters. Fatty acid-induced ASP resistance may contribute to the physiological abnormalities associated with insulin resistance and obesity phenotype.     

Predicting abundance and productivity of blueberry plants under insect defoliation in Alaska

Unprecedented outbreaks of defoliating insects severely damaged blueberry crops near Port Graham on the Kenai Peninsula in Alaska from 2008-2012. The Native people in this region rely heavily on gathered blueberries and other foods for sustenance and nourishment. Influences of topography and stand structure on blueberry abundance and fruiting were examined and used to develop spatial models to predict abundance and productivity of blueberry plants. Fruiting was associated with decreased canopy density, a low basal area and southwesterly aspects. Stands with relatively high site indices have greater abundance of blueberry plants, while the opposite trend was observed with productivity. Results demonstrate the feasibility of modeling the abundance and productivity of blueberry plants using easily obtained satellite imagery in conjunction with a well-organized field data collection system.