Climatic versus biotic constraints on carbon and water fluxes in seasonally drought-affected ponderosa pine ecosystems

We investigated the relative importance of climatic versus biotic controls on gross primary production (GPP) and water vapor fluxes in seasonally drought-affected ponderosa pine forests. The study was conducted in young (YS), mature (MS), and old stands (OS) over 4 years at the AmeriFlux Metolius sites. Model simulations showed that interannual variation of GPP did not follow the same trends as precipitation, and effects of climatic variation were smallest at the OS (50%), and intermediate at the YS (<20%). In the young, developing stand, interannual variation in leaf area has larger effects on fluxes than climate, although leaf area is a function of climate in that climate can interact with age-related shifts in carbon allocation and affect whole-tree hydraulic conductance. Older forests, with well-established root systems, appear to be better buffered from effects of seasonal drought and interannual climatic variation. Interannual variation of net ecosystem exchange (NEE) was also lowest at the OS, where NEE is controlled more by interannual variation of ecosystem respiration, 70% of which is from soil, than by the variation of GPP, whereas variation in GPP is the primary reason for interannual changes in NEE at the YS and MS. Across spatially heterogeneous landscapes with high frequency of younger stands resulting from natural and anthropogenic disturbances, interannual climatic variation and change in leaf area are likely to result in large interannual variation in GPP and NEE

Involvement of P2X and P2Y receptors in microglial activation in vivo

Microglial cells are the primary immune effector cells in the brain. Extracellular ATP, e.g., released after brain injury, may initiate microglial activation via stimulation of purinergic receptors. In the rat nucleus accumbens (NAc), the involvement of P2X and P2Y receptors in the generation of microglial reaction in vivo was investigated. A stab wound in the NAc increased immunoreactivity (IR) for P2X1,2,4,7 and P2Y1,2,4,6,12 receptors on microglial cells when visualized with confocal laser scanning microscopy. A prominent immunolabeling of P2X7 receptors with antibodies directed against the ecto- or endodomain was found on Griffonia simplicifolia isolectin-B4-positive cells. Additionally, the P2X7 receptor was colocalized with active caspase 3 but not with the anti-apoptotic marker pAkt. Four days after local application of the agonists α,βmeATP, ADPβS, 2MeSATP, and BzATP, an increase in OX 42- and G. simplicifolia isolectin-IR was observed around the stab wound, quantified both densitometrically and by counting the number of ramified and activated microglial cells, whereas UTPγS appeared to be ineffective. The P2 receptor antagonists PPADS and BBG decreased the injury-induced increase of these IRs when given alone and in addition inhibited the agonist effects. Further, the intra-accumbally applied P2X7 receptor agonist BzATP induced an increase in the number of caspase-3-positive cells. These results indicate that ATP, acting via different P2X and P2Y receptors, is a signaling molecule in microglial cell activation after injury in vivo. The up-regulation of P2X7-IR after injury suggests that this receptor is involved in apoptotic rather than proliferative effects

Narrative approach to understand people's comprehension of acquaintance rape: The role of Sex Role Stereotyping

One of the most unreported crimes is acquaintance rape. This may be the result of people's understanding of what rape is because of their rape script and their stereotypes of victim characteristics. These judgements may be moderated by sex role stereotyping (SRS). We utilised a narrative approach to understand low and high SRS participants' rape scripts. Young-adult participants described what they believed a typical rape was, followed by describing an acquaintance rape and then what they believed the stereotypical victim of each crime would be. A narrative analysis was conducted on the data. We found that the blitz script is still held by 44% of low SRS and 47% of high SRS people despite 90% of rapes being committed by an acquaintance. While acquaintance rape scripts existed, the emotional imagery and content of these depended on participants level of SRS. Stereotypical victim characteristics also depended on SRS: those with high SRS were more likely to endorse rape myth ideals in describing victims than those with low SRS. These results have implications for educating people about what rape is so that victims might feel more confident in reporting rape

Age-related changes in ecosystem structure and function and effects on water and carbon exchange in ponderosa pine

As forests age, their structure and productivity change, yet in some cases, annual rates of water loss remain unchanged. To identify mechanisms that might explain such observations, and to determine if widely different age classes of forests differ functionally, we examined young (Y, similar tO25 years), mature (M, similar to90 years) and old (O, similar tO250 years) ponderosa pine (Pinus ponderosa Dougl. ex P. Laws.) stands growing in a drought-prone region of central Oregon. Although the stands differed in tree leaf area index (LAI(T)) (Y = 0.9, M = 2.8, O = 2.1), cumulative tree transpiration measured by sap flow did not differ substantially during the growing season (100112 mm). Yet when water was readily available, transpiration per unit leaf area of the youngest trees was about three times that of M trees and five times that of 0 trees. These patterns resulted from a nearly sixfold difference in leaf specific conductance (K-L) between the youngest and oldest trees. At the time of maximum transpiration in the Y stand in May-June, gross carbon uptake (gross ecosystem production, GEP) was similar for Y and O stands despite an almost twofold difference in stand leaf area index (LAI(S)). However, the higher rate of water use by Y trees was not sustainable in the drought-prone environment, and between spring and late summer, K-L of Y trees declined fivefold compared with a nearly twofold decline for M trees and a < 30% reduction in O trees. Because the Y stand contained a significant shrub understory and more exposed soil, there was no appreciable difference in mean daily latent energy fluxes between the Y stand and the older stands as measured by the eddy-covariance technique. These patterns resulted in 60 to 85% higher seasonal GEP and 55 to 65% higher water-use efficiency at the M and 0 stands compared with the Y stand. [References: 29