Species-specific responses of plant intrinsic water-use efficiency (iWUE) to multiple environmental drivers associated with climate change, including soil moisture (θ), vapor pressure deficit (D), ...and atmospheric CO2 concentration (c
a), are poorly understood.
We assessed how the iWUE and growth of several species of deciduous trees that span a gradient of isohydric to anisohydric water-use strategies respond to key environmental drivers (θ, D and c
a). iWUE was calculated for individual tree species using leaf-level gas exchange and tree-ring δ13C in wood measurements, and for the whole forest using the eddy covariance method.
The iWUE of the isohydric species was generally more sensitive to environmental change than the anisohydric species was, and increased significantly with rising D during the periods of water stress. At longer timescales, the influence of c
a was pronounced for isohydric tulip poplar but not for others.
Trees’ physiological responses to changing environmental drivers can be interpreted differently depending on the observational scale. Care should be also taken in interpreting observed or modeled trends in iWUE that do not explicitly account for the influence of D.
When stressed by low soil water content (SWC) or high vapor pressure deficit (VPD), plants close stomata, reducing transpiration and photosynthesis. However, it has historically been difficult to ...disentangle the magnitudes of VPD compared to SWC limitations on ecosystem‐scale fluxes. We used a 13 year record of eddy covariance measurements from a forest in south central Indiana, USA, to quantify how transpiration and photosynthesis respond to fluctuations in VPD versus SWC. High VPD and low SWC both explained reductions in photosynthesis relative to its long‐term mean, as well as reductions in transpiration relative to potential transpiration estimated with the Penman‐Monteith equation. Flux responses to typical fluctuations in SWC and VPD had similar magnitudes. Integrated over the year, VPD fluctuations accounted for significant reductions of GPP in both nondrought and drought years. Our results suggest that increasing VPD under climatic warming could reduce forest CO2 uptake regardless of changes in SWC.
Key Points
Forest transpiration and photosynthesis respond to fluctuations in both vapor pressure deficit and soil moisture
Elevated VPD can reduce photosynthesis by the same magnitude as soil drying to levels typical of droughts
Rising VPD due to climatic warming could drive drought‐like flux responses in forests even if soil moisture does not decrease
Though rates of sexual assault are high among college women, some studies find even greater prevalence rates among women who are sorority members. This study examined the association between familial ...risk factors (e.g., child physical abuse), PTSD symptoms, and proximal risk factors (e.g., sexual risk behavior) with three sexual assault types (i.e., coercive, incapacitated by alcohol or drugs, and physically forced) among sorority and non-sorority women at a large Midwestern university. Participants completed a paper-and-pencil survey that included measures of different sexual assault types, childhood maltreatment, parental rejection, PTSD symptoms, and sexual and substance use behaviors. A fully recursive path model was estimated to examine the pathways to three different sexual assault types. Results revealed that sorority women experienced coercive and incapacitated sexual assault more so than non-sorority women though there was no significant difference for physically forced sexual assault. Sorority women also reported engaging in more sexual risk behaviors, which was in turn, associated with all three sexual assault types. Sorority women also reported heavier alcohol use, which in turn, was positively associated with coercive and incapacitated sexual assault. These findings have implications for prevention among college undergraduate women.
Although dating violence is prevalent among college students, little is known about how both attachment style and participation in risky behaviors contribute to this pattern of violence. To address ...this literature gap, we examine the role of poor parenting, child abuse, attachment style, and risky sexual and drug use behaviors on dating violence perpetration among 1,432 college students (51% female). Path analysis results revealed that females were more likely to report greater attachment anxiety but lower attachment avoidance compared with males. Correlates of attachment anxiety included child physical abuse, witnessing parental violence, and poorer maternal relationship quality whereas attachment avoidant behavior was linked to more physical abuse and poorer maternal relationship quality. Females were more likely to perpetrate dating violence as were those with greater attachment anxiety and lower attachment avoidance. Other correlates of dating violence perpetration included sexual and drug risk behaviors. Finally, distal factors (i.e., more child physical abuse and poorer maternal relationship quality) also were associated with dating violence perpetration. Study implications are also discussed.
Hooking-up among college students presents an increased risk of sexual victimization, perhaps due to increased contact with potential perpetrators in a risky context. However, little work has ...examined factors that might increase the risk of victimization associated with hooking-up, and few studies examine victimization among both men and women. To address this gap in the literature, we utilize data from 702 college women and 677 college men to explore childhood sexual abuse, family violence, sexual minority (SM) status, and problematic alcohol use as potential moderators of the association between hooking-up and three forms of sexual victimization: coerced, incapacitated, and forced. Results of regression analyses indicate several significant interactions and significant main effects. For example, SM men and women were each at an increased risk of forced and incapacitated victimization when hook-up frequency was high compared with non-SM students.
Though college women report high rates of sexual assault, less is known about how protective and risk factors are uniquely associated with assault among heterosexual and sexual minority women. As ...such, the current study examined protective factors (i.e., maternal relationship quality and religiosity) and risk factors (i.e., child sexual abuse, parent substance misuse, and risky behaviors) for coercive sexual assault and total sexual assault and whether they vary by sexual orientation among college women. Data were gathered in the 2013–2014 academic year at two large public universities in the United States, one in the Midwest and one in the Southeast. Data for the current study included 755 college women, 72 (9.5%) of whom identified as sexual minority. Bivariate results showed that heterosexual women reported greater maternal relationship quality and greater religiosity compared to sexual minority women, while sexual minority women reported more risky sexual behaviors and having experienced more coercive sexual assault than heterosexual women. Multivariate results revealed that child sexual abuse, parent drinking problems, maternal relationship quality, heavy drinking, hooking up, and risky sexual behaviors were significantly associated with total sexual assault. Significant correlates of coercive sexual assault included child sexual abuse, maternal relationship quality, hooking up, and risky sexual behaviors. The relationship between maternal relationship quality and total sexual assault varied by sexual orientation as did the relationship between hooking up and coercive sexual assault. These findings have implications for targeted interventions to improve prevention of sexual assault among heterosexual and sexual minority college women.
Most patients with hepatitis C virus (HCV) infection perceive some degree of disease-related stigma. Misunderstandings about diseases may contribute to disease-related stigma. The objective of this ...study was to evaluate patient-level knowledge about HCV infection transmission and natural history and its association with HCV-related stigma among HCV-infected patients. We conducted a cross-sectional survey study among 265 patients with HCV in Philadelphia using the HCV Stigma Scale and the National Health and Nutrition Examination Survey (NHANES) Hepatitis C Follow-up Survey (2001–2008). The association between HCV knowledge and HCV-related stigma was evaluated via linear regression. Overall knowledge about HCV transmission and natural history was high, with >80% of participants answering ≥9 of 11 items correctly (median number of correct responses, 9 82%), HCV-related knowledge was similar between HIV/HCV-coinfected and HCV-monoinfected participants (p = 0.30). A higher level of HCV-related knowledge was associated with greater perceived HCV-related stigma (β, 2.34 (95% CI, 0.51–4.17; p = 0.013). Results were similar after adjusting for age, race, ethnicity, HIV status, education level, stage of HCV management, time since diagnosis, and history of injection drug use. In this study, increased HCV-related knowledge was associated with greater perceptions of HCV stigma. Clinicians may consider allotting time to address common misconceptions about HCV when educating patients about HCV infection, which may counterbalance the stigmatizing impact of greater HCV-related knowledge.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Familial responses to lesbian, gay, bisexual, transgender, and queer (LGBTQ) young people’s identities range on a spectrum from rejection to acceptance and these reactions strongly impact family ...relationships and young adult well-being. Less is known, however, about how family members’ reactions may differ based on young people’s contexts of socioeconomic status. Through a qualitative, life course analysis of in-depth interview data from 46 LGBTQ college students and LGBTQ homeless young adults, our study highlights the diverse, contextual nuances of young people’s “linked lives” within their families. We find that the context of socioeconomic status influenced how a young person managed family rejection. Conversely, processes of familial acceptance were also connected to life course transitions that worked in some cases to enhance LGBTQ young adults’ family relationships. Finally, the intricacy of familial reactions to a young person’s LGBTQ identity transcended socioeconomic contexts as many respondents shared similar experiences of rejection and acceptance. These findings have implications for understanding how young people manage family relationships across different contexts of socioeconomic status and how these experiences can shape their life course trajectories. Results from this study can inform LGBTQ youth service providers by tailoring intervention programs that account for contextual social diversity.
The New Homelessness Revisited Lee, Barrett A.; Tyler, Kimberly A.; Wright, James D.
Annual review of sociology,
01/2010, Letnik:
36, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The new homelessness has drawn sustained attention from scholars over the past three decades. Definitional inconsistencies and data limitations rendered early work during this period largely ...speculative in nature. Thanks to conceptual, theoretical, and methodological progress, however, the research literature now provides a fuller understanding of homelessness. Contributions by sociologists and other social scientists since the mid-1990s differentiate among types of homelessness, provide credible demographic estimates, and show how being homeless affects a person's life chances and coping strategies. Agreement also exists about the main macro- and micro-level causes of homelessness. Active lines of inquiry examine public, media, and governmental responses to the problem as well as homeless people's efforts to mobilize on their own behalf. Despite the obstacles faced when studying a stigmatized population marked by high turnover and weak anchors to place, recent investigations have significantly influenced homelessness policy. A greater emphasis on prevention should further strengthen the research-policy nexus.
•Multiple methods were used to partition CO2 and H2O fluxes from a temperate forest.•Between methods, daytime summer evaporation was 6–18% of evapotranspiration.•Daytime summer respiration was 7–22% ...of gross primary production.•A method based on flux variance similarity compared well with other methods.•The flux variance similarity method was sensitive to estimated water use efficiency.
The eddy covariance (EC) method is routinely used to measure net ecosystem fluxes of carbon dioxide (CO2) and evapotranspiration (ET) in terrestrial ecosystems. It is often desirable to partition CO2 flux into gross primary production (GPP) and ecosystem respiration (RE), and to partition ET into evaporation and transpiration. We applied multiple partitioning methods, including the recently-developed flux variance similarity (FVS) partitioning method, to a ten-year record of ET and CO2 fluxes measured using EC at Morgan Monroe State Forest, a temperate, deciduous forest located in south-central Indiana, USA. While the FVS method has previously been demonstrated in croplands and grasslands, this is the first evaluation of the method in a forest. CO2 fluxes were partitioned using nonlinear regressions, FVS, and sub-canopy EC measurements. ET was partitioned using FVS and sub-canopy EC measurements, and sub-canopy potential evapotranspiration was calculated as an additional constraint on forest floor evaporation. Leaf gas exchange measurements were used to parameterize a model of water use efficiency (WUE) necessary for the FVS method. Scaled leaf gas exchange measurements also provided additional independent estimates of GPP and transpiration. There was good agreement among partitioning methods for transpiration and GPP, which also agreed well with scaled leaf gas exchange measurements. There was higher variability among methods for RE and evaporation. The sub-canopy flux method yielded lower estimates of evaporation and RE than FVS and lower estimates of RE than the nonlinear regression method, likely due to the exclusion of flux sources within the canopy but above the top of the sub-canopy tower for the sub-canopy flux method. Based on a sensitivity test, FVS flux partitioning was moderately sensitive to errors in WUE values, and underestimates of WUE significantly reduced the rate at which the algorithm was able to produce a physically valid solution. FVS partitioning has unique potential for retroactive ET partitioning at EC sites, because it relies on the same continuous measurements as EC and does not require additional specialized equipment. FVS also has advantages for partitioning CO2 fluxes, since it does not rely on the mechanistic assumptions necessary for the commonly used nonlinear regression technique.
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