Community structure - Ecosystem function relationships in the Congo Basin methane cycle depend on the physiological scale of function.

Belowground ecosystem processes can be highly variable and difficult to predict using microbial community data. Here, we argue that this stems from at least three issues: (a) complex covariance structure of samples (with environmental conditions or spatial proximity) can make distinguishing biotic drivers a challenge; (b) communities can control ecosystem processes through multiple mechanisms, making the identification of these controls a challenge; and (c) ecosystem function assessments can be broad in physiological scale, encapsulating multiple processes with unique microbially mediated controls. We test these assertions using methane (CH4 )-cycling processes in soil samples collected along a wetland-to-upland habitat gradient in the Congo Basin. We perform our measurements of function under controlled laboratory conditions and statistically control for environmental covariates to aid in identifying biotic drivers. We divide measurements of microbial communities into four attributes (abundance, activity, composition, and diversity) that represent different forms of community control. Lastly, our process measurements differ in physiological scale, including broader processes (gross methanogenesis and methanotrophy) that involve more mediating groups, to finer processes (hydrogenotrophic methanogenesis and high-affinity CH4 oxidation) with fewer mediating groups. We observed that finer scale processes can be more readily predicted from microbial community structure than broader scale processes. In addition, the nature of those relationships differed, with broad processes limited by abundance while fine-scale processes were associated with diversity and composition. These findings demonstrate the importance of carefully defining the physiological scale of ecosystem function and performing community measurements that represent the range of possible controls on ecosystem processes.

Mitigating nitrogen pollution with under-sown legume-grass cover crop mixtures in winter cereals.

Nitrogen (N) pollution from N inputs to agricultural soils contributes to widespread eutrophication and global climate change. One period susceptible to N losses is between winter grain harvest in summer and corn planting in spring in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-winter grain rotation. Cover crops used to immobilize N during this period often depend on tillage, which can exacerbate N losses. Therefore, we evaluated whether reduced-till cover crops could decrease nitrate (NO3 - ) leaching and nitrous oxide (N2 O) emissions during this period. We tested this strategy in a cropping systems experiment on a 4-ha plot in central Pennsylvania over 2 yr. This experiment compared a clover (Trifolium pratense L.)-timothy (Phleum pratense L.) cover crop no-till underseeded into a standing spelt crop with a vetch (Vicia villosa Roth)-triticale (× Triticosecale Wittm. ex A. Camus) cover crop established with tillage after spelt harvest. These systems were compared based on fortnightly N2 O emissions using static chambers (n = 4 per six sample dates) and potential NO3 - leaching using anion resin bags (n = 4 per system per year). Reduced-till cover crops minimized peak N2 O emissions during the fall compared with tilled cover crops. However, reduced-till cover crops did not decrease potentially leachable NO3 - relative to tilled cover crops despite decreases in soil inorganic N. Cover crop N isotopes revealed that clover N may have mineralized and leached over the winter. Our results suggest that reduced-till cover crops can decrease N2 O emissions to mitigate the climate impact of agriculture but that winter-hardy cover crops should be chosen to mitigate leaching.

Belowground changes to community structure alter methane-cycling dynamics in Amazonia.

Amazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with increases in soil methane (CH4) emission. To better understand the drivers of this change, we measured soil CH4 flux, environmental conditions, and belowground microbial community structure across primary forests, cattle pastures, and secondary forests in two Amazonian regions. We show that pasture soils emit high levels of CH4 (mean: 3454.6 ± 9482.3 µg CH4 m-2 d-1), consistent with previous reports, while forest soils on average emit CH4 at modest rates (mean: 9.8 ± 120.5 µg CH4 m-2 d-1), but often act as CH4 sinks. We report that secondary forest soils tend to consume CH4 (mean: -10.2 ± 35.7 µg CH4 m-2 d-1), demonstrating that pasture CH4 emissions can be reversed. We apply a novel computational approach to identify microbial community attributes associated with flux independent of soil chemistry. While this revealed taxa known to produce or consume CH4 directly (i.e. methanogens and methanotrophs, respectively), the vast majority of identified taxa are not known to cycle CH4. Each land use type had a unique subset of taxa associated with CH4 flux, suggesting that land use change alters CH4 cycling through shifts in microbial community composition. Taken together, we show that microbial composition is crucial for understanding the observed CH4 dynamics and that microorganisms provide explanatory power that cannot be captured by environmental variables.

Risk factors for posterior vitreous detachment: a case-control study.

PURPOSE: To identify possible risk factors for the development of posterior vitreous detachment (PVD). DESIGN: Retrospective case-control study. METHODS: A total of 138 cases with PVD and 114 age-matched controls were accrued from two different sites. Demographic, medical, ocular, and lifestyle data were obtained through chart review, questionnaires, and clinical examination. A 108-item semiquantitative food frequency questionnaire was also used to estimate macro- and micronutrient intake. Univariate and multivariate regression analyses were employed to identify variables significantly associated with the main outcome measure of PVD. Subgroup analysis of gender-specific variables was performed. RESULTS: Among all patients, multivariate regression analysis demonstrated female gender (odds ratio [OR] = 2.01, P = .016), myopic refraction (OR = 4.32, P < .0005), and higher intake of vitamin B6 (OR = 2.61, P = .001) to be associated with PVD after controlling for age. In the subgroup analysis of women, menopause (OR = 18.2, P < .0005), myopic refraction (OR = 3.42, P = .01), and higher intake of vitamin B6 (OR = 3.92, P = .005) were associated with PVD. Specifically, there was a significant association between vitamin B6 and PVD amongst premenopausal women but not amongst postmenopausal women. CONCLUSIONS: An association between PVD and menopause has not been documented previously. We suspect that high estrogen levels seen in premenopausal women may be protective against PVD and that hormonal changes associated with menopause may lead to changes in the vitreous, predisposing to PVD. Higher levels of intake of vitamin B6 were also associated with the development of PVD in premenopausal women possibly through an anti-estrogen effect. These findings should be investigated further with prospective studies.

Soil Incorporation of Silica-Rich Rice Husk Decreases Inorganic Arsenic in Rice Grain.

Arsenic decreases rice yield, and inorganic grain As threatens human health; thus, strategies to decrease rice As are critically needed. Increased plant-available silica (Si) can decrease rice As, yet the source of Si matters. Rice husk, an underutilized and Si-rich byproduct of rice production that contains less labile C and an order of magnitude less As than rice straw, may be an economically viable Si resource to decrease rice As, yet the impact of rice husk incorporation on As in the rice-soil nexus has not been reported. This proof-of-concept study shows that rice husk incorporation to soil (1% w/w) decreases inorganic grain As by 25-50% without negatively affecting grain Cd, yield, or dissolved CH4 levels. Rice husk is a critical yet perhaps overlooked resource to improve soil quality through enhanced nutrient availability and attenuate human health risks through consumption of As-laden grain.

Photodynamic therapy of a subretinal neovascular membrane in type 2A idiopathic juxtafoveolar retinal telangiectasis.

PURPOSE: To report the outcome of a patient with a subretinal neovascular membrane secondary to idiopathic juxtafoveolar retinal telangiectasis treated with photodynamic female therapy. METHODS: Interventional case report. A 43-year-old female with type 2A idiopathic juxtafoveolar retinal telangiectasis presented with a 2-week history of decreased vision and a subretinal neovascular membrane in the left eye. RESULTS: Visual improvement from 20/70-2 to 20/50-2 in the left eye was observed after two photodynamic therapy treatments of a juxtafoveal subretinal neovascular membrane with verteporfin, and was maintained through 7 months of follow-up. Fluorescein angiography showed no leakage specific to the subretinal neovascular membrane, but leakage from the juxtafoveal telangiectasis continued. CONCLUSION: A substantial improvement was seen in this patient after treatment of the juxtafoveal subretinal neovascular membrane by photodynamic therapy. Given the poor prognosis of these lesions, photodynamic therapy may therefore be a useful treatment for patients with subretinal neovascular membranes associated with idiopathic juxtafoveolar retinal telangiectasis.