Global climate models predict that in the next century precipitation in desert regions of the USA will increase, which is anticipated to affect biosphere/atmosphere exchanges of both CO(2) and H(2)O. In a sotol grassland ecosystem in the Chihuahuan Desert at Big Bend National Park, we measured the response of leaf-level fluxes of CO(2) and H(2)O 1 day before and up to 7 days after three supplemental precipitation pulses in the summer (June, July, and August 2004). In addition, the responses of leaf, soil, and ecosystem fluxes of CO(2) and H(2)O to these precipitation pulses were also evaluated in September, 1 month after the final seasonal supplemental watering event. We found that plant carbon fixation responded positively to supplemental precipitation throughout the summer. Both shrubs and grasses in watered plots had increased rates of photosynthesis following pulses in June and July. In September, only grasses in watered plots had higher rates of photosynthesis than plants in the control plots. Soil respiration decreased in supplementally watered plots at the end of the summer. Due to these increased rates of photosynthesis in grasses and decreased rates of daytime soil respiration, watered ecosystems were a sink for carbon in September, assimilating on average 31 mmol CO(2) m(-2) s(-1) ground area day(-1). As a result of a 25% increase in summer precipitation, watered plots fixed eightfold more CO(2) during a 24-h period than control plots. In June and July, there were greater rates of transpiration for both grasses and shrubs in the watered plots. In September, similar rates of transpiration and soil water evaporation led to no observed treatment differences in ecosystem evapotranspiration, even though grasses transpired significantly more than shrubs. In summary, greater amounts of summer precipitation may lead to short-term increased carbon uptake by this sotol grassland ecosystem.

We describe a hierarchical Bayesian (HB) approach to fitting the Farquhar et al. model of photosynthesis to leaf gas exchange data. We illustrate the utility of this approach for estimating photosynthetic parameters using data from desert shrubs. Unique to the HB method is its ability to simultaneously estimate plant-and species-level parameters, adjust for peaked or non-peaked temperature dependence of parameters, explicitly estimate the 'critical' intracellular [CO2] marking the transition between ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) and ribulose-1,5-bisphosphate (RuBP) limitations, and use both light response and CO2 response curve data to better inform parameter estimates. The model successfully predicted observed photosynthesis and yielded estimates of photosynthetic parameters and their uncertainty. The model with peaked temperature responses fit the data best, and inclusion of light response data improved estimates for day respiration (Rd). Species differed in Rd25 (Rd at 25°C), maximum rate of electron transport (Jmax25), a MichaelisMenten constant (Kc25) and a temperature dependence parameter (DS). Such differences could potentially reflect differential physiological adaptations to environmental variation. Plants differed in Rd25, Jmax25, mesophyll conductance (gm25) and maximum rate of Rubisco carboxylation (Vcmax25). These results suggest that plant-and species-level variation should be accounted for when applying the Farquhar et al. model in an inferential or predictive framework.

Alterations in global and regional precipitation patterns are expected to affect plant and ecosystem productivity, especially in water-limited ecosystems. This study examined the effects of natural and supplemental (25% increase) seasonal precipitation on a sotol grassland ecosystem in Big Bend National Park in the Chihuahuan Desert. Physiological responses -leaf photosynthesis at saturating light (A sat ), stomatal conductance (g s ), and leaf nitrogen [N] -of two species differing in their life form and physiological strategies (Dasylirion leiophyllum, a C 3 shrub; Bouteloua curtipendula, a C 4 grass) were measured over 3 years (2004)(2005)(2006) that differed greatly in their annual and seasonal precipitation patterns (2004: wet, 2005: average, 2006: dry). Precipitation inputs are likely to affect leaflevel physiology through the direct effects of altered soil water and soil nitrogen. Thus, the effects of precipitation, watering treatment, soil moisture, and nitrogen were quantified via multivariate hierarchical Bayesian models that explicitly linked the leaf and soil responses. The two species differed in their physiological responses to precipitation and were differentially controlled by soil water vs. soil nitrogen. In the relatively deeply rooted C 3 shrub, D. leiophyllum, A sat was highest in moist periods and was primarily regulated by deep (16-30 cm) soil water. In the shallow-rooted C 4 grass, B. curtipendula, A sat was only coupled to leaf [N], both of which increased in dry periods when soil [N] was highest. Supplemental watering during the wet year generally decreased A sat and leaf [N] in D. leiophyllum, perhaps due to nutrient limitation, and physiological responses in this species were influenced by the cumulative effects of 5 years of supplemental watering. Both species are common in this ecosystem and responded strongly, yet differently, to soil moisture and nitrogen, suggesting that changes in the timing and magnitude of precipitation may have consequences for plant carbon gain, with the potential to alter community composition.

This theoretical position article inquires into poetic methodologies in literacy research and argues for the inclusion of poetry in social science research writing. The unconventional use of poetry in research writing challenges the traditionally accepted role prose plays in academic writing. Research poetry is written from and about research subjects and data; more specifically, research found poetry is written from the words of study participants. I identify as a research poet. In particular, I am a writer of found poetry composed from my qualitative research data. The data presented in this article are from a larger study where I investigated what happened when prospective teachers wrote found poetry using young adult literature. I used the words of my study participants to write found data poems in order to analyze and represent data, seeking congruence across multiple forms of data analysis and representation. Crafting poetry from qualitative data holds implications for research methodologies. Research poetry provides academic poets with an alternative means for both analyzing and representing qualitative data. As well, research poetry may impact how scholarly texts are received by research audiences. Although research poetry holds promise for qualitative researchers, the inclusion of poetry in scholarly writing not without risk; the choice to include poetry is contested. Creating space for the poetic arts within the academy confronts conventionally accepted modes of research writing and provides access to the creative and imaginative discourse of poetry.

Neste artigo, nós apresentamos aos leitores a arte de ler poesia com as crianças. Começando com uma breve definição de poesia e como ela funciona, seguido por uma discussão sobre os benefícios da leitura de poesia com as crianças. Em seguida, examinamos a negligência do uso da poesia em escolas, bem como recomendações para lidar com essa negligência. Estas recomendações têm como foco principal orientar um trabalho de imersão com o texto poético para alunos em uma base diária, lendo poesia em voz alta para os alunos e incentivando-os a ler poesia autonomamente. Nós compartilhamos uma pesquisa sobre as preferências das crianças por poesia, a fim de orientar os professores na escolha de textos poéticos para a partilha em sala de aula. Finalmente, explicamos como ler poesia pode levar a escrever poesia. O nosso principal objetivo é fornecer aos professores e aos formadores de professores com conhecimento sobre como convidar os alunos para o mundo da poesia.http://dx.doi.org/10.14572/nuances.v21i22.1625

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