Phosphorus fractionation chemistry across the Great Plains

The SGS-LTER research site was established in 1980 by researchers at Colorado State University as part of a network of long-term research sites within the US LTER Network, supported by the National Science Foundation. Scientists within the Natural Resource Ecology Lab, Department of Forest and Rangeland Stewardship, Department of Soil and Crop Sciences, and Biology Department at CSU, California State Fullerton, USDA Agricultural Research Service, University of Northern Colorado, and the University of Wyoming, among others, have contributed to our understanding of the structure and functions of the shortgrass steppe and other diverse ecosystems across the network while maintaining a common mission and sharing expertise, data and infrastructure.Includes bibliographical references.Phosphorus is one of the three important plant nutrients found in soils and has been used with great success as an index for soil and ecosystem development (Aguilar et al., 1988; Honeycutt et al., 1990; Vitousek et al., 2004). In general, phosphorus is has minimal solubility in soil because it participates in a number of secondary reactions after release from primary minerals as a result of weathering. Studies of the biogeochemical cycling of P in humid ecosystems has led to important insights about soil and ecosystem development. Arid and semi-arid ecosystems have largely been ignored under the assumption that chemical transformations are minimal. We conducted research on the biogeochemistry of P along a bioclimatic gradient in grassland ecosystems of the Great Plains. The overall goal of our research is to use a systematic approach to characterize and further quantify the P transformations in biogeographically diverse grassland ecosystems. Identifying P quantities originally contained in central Great Plains soil will allow us to assess 1) the relative importance of P in the biogeochemical behavior of grassland soils, 2) help us quantify the degree of chemical weathering in semi-arid-humid grassland ecosystems, and 3) elucidate cultural use and potential productivity of these ecosystems prior to use of commercial fertilizers. We sampled soils along a bioclimatic gradient that represent three grassland ecosystems, namely, the shortgrass steppe, the mixed-grass prairie, and the tallgrass prairie in eastern Kansas. The soils were collected from sites studied within the Long-Term Ecological Research Program in areas that had not been used for agricultural practices other than grazing. We conducted a sequential extraction procedure to identify the following P fractions: soluble, Al-bound, Fe-bound, occluded, and Ca-bound. Our results suggest that soluble P is generally below detection limits at these sites, illustrating the high turnover rate of available P in these undisturbed systems. The Al-bound fraction was variable across all sites. The Fe-bound P contributed to the total P fraction only from the mixed grass and tall grass prairies. The occluded P fraction was greatest in the shortgrass steppe, decreased dramatically as mean annual and primary production increase from west to east.NSF Grant No. 0217631

Biologic Cycling of Silica across a Grassland Bioclimosequence

The dynamics of biologic Si cycling in grassland ecosystems are largely unknown and likely to impact mineral weathering rates regionally and diatom productivity globally; key regulatory processes in the global Si cycle are closely tied to the global carbon cycle. Across a bioclimatic sequence spanning major grassland ecosystems in the Great Plains, soil biogenic silica depth distributions are similar to that of soil organic carbon; however, unlike soil organic carbon, quantities of soil biogenic silica decrease with increasing precipitation, despite an increase in annual biogenic inputs through litterfall across the same gradient. Though comprising only 1–3% of the total Si pool, faster turnover of biogenic Si and annual cycling by grasses should positively impact mineral dissolution. Our results suggest that the largest reservoir of biogenic Si in terrestrial ecosystems resides in soils, and emphasize the potential significance of grasslands in the global biogeochemical cycle of Si

Urinary exosome miR-146a is a potential marker of albuminuria in essential hypertension

BACKGROUND: There is increasing interest in using extracellular vesicle-derived microRNAs (miRNAs) as biomarkers in renal dysfunction and injury. Preliminary evidence indicates that miRNAs regulate the progression of glomerular disease. Indeed, exosomes from the renal system have provided novel evidence in the clinical setting of albuminuria. Thus, the aim of this study was to quantify the urinary miRNAs present in exosome and microvesicles (MVs), and to assess their association with the presence of increased urinary albumin excretion in essential hypertension. METHODS: Exosomes were collected from urine specimens from a cohort of hypertensive patients with (n = 24) or without albuminuria (n = 28), and from 20 healthy volunteers as a control group. Urinary exosomes were phenotyped by Western blot, tunable resistive pulse sensing, and electronic microscopy. Expression of miR-146a and miR-335* was analysed by qRT-PCR and any associations between albuminuria and exosomal miRNAs were analysed. RESULTS: Urinary miRNAs are highly enriched in exosome subpopulations compared to MVs, both in patients with or without increased albuminuria (p < 0.001), but not in the control group. High albuminuria was associated with 2.5-fold less miR-146a in exosomes (p = 0.017), whereas miR-146a levels in MV did not change. In addition, exosome miR-146a levels were inversely associated with albuminuria (r = 0.65, p < 0.0001), and discriminated the presence of urinary albumin excretion presence [area under the curve = 0.80, 95% confidence interval: 0.66-0.95; p = 0.0013]. CONCLUSIONS: Our results indicate that miRNAs were enriched in the urinary exosome subpopulation in hypertensive patients and that low miR-146a expression in exosomes was associated with the presence of albuminuria. Thus, urinary exosome miR-146a may be a potentially useful tool for studying early renal injury in hypertension

Explaining persistent cycles in a short-run context: firms’ propensity to invest and omnipotent shareholders

In this article, we develop a standard short-run Kaleckian macromodel. First, we study the stability of equilibrium and make some comparative static exercises. Then, we take into account different specifications for an endogenous propensity to invest and systematically analyze the short-run dynamics of the model. We show that when firms’ managers adopt abnormal behaviours due to pressures from shareholders regarding the propensity to invest the system exhibits persistent cycles and chaotic trajectories. The analysis emphasizes that, even in the short-run, shareholders may generate instability which represents a serious threat that should not be underestimated for a capitalist economy

Association of Southeast Asian Nations, People's Republic of China, and India Growth and the Rest of the World: The Role of Trade

This paper explores the impact of past and future growth in the Association of Southeast Asian Nations (ASEAN)1 Since the mid-1990s, ACI growth has improved the non-oil terms of trade of the developed countries. There have also been strong complementarities between ACI suppliers of intermediate inputs and PRC exports. More developed Asian countries have benefited from PRC capital goods demand. ACI growth has, however, put competitive pressures on other less-developed manufacturing exporters, worsening their terms of trade and constraining their pricing ability. ACI growth has been especially beneficial for oil and minerals commodity producers. On the other hand, net food importers and oil importing countries have been adversely affected by high import costs. , the People's Republic of China (PRC), and India - here referred to as the ACI countries - on aggregate welfare, relative wages, and global emissions in the rest of the world. It outlines several analytical frameworks, considers effects over the past decade and, based on consensus forecasts, the implications of that growth for the rest of the world in the decades to come. Future ACI growth provides opportunities and challenges for the rest of the world. For developed countries the opportunities are for selling high-end services and capital and consumer goods in the ACI markets and enjoying the benefits from intra-industry trade; the challenges will come from increased head-to-head competition in manufactured goods and services that should become more intense in future decades. For medium-income producers currently at between 30% and 60% of US levels, there will be a tougher tradeoff between more intensive competition with the PRC and serving the growing middle classes in ACI countries. For poorer countries, there will greater opportunities for becoming part of global supply chains in manufactured exports. Standard frameworks that assume internal factor mobility suggest continuing pressures for wage inequality in developed countries. But these hinge on the assumption that the ACI and developed countries will continue to produce similar products and that the ACI will specialize in unskilled labor-intensive products. In fact, as their exports become more technology - intensive and developed countries more specialized these pressures could be alleviated. On the one hand, as the "flying geese" process continues, exports from countries with lower incomes than the PRC are likely to displace PRC labor-intensive exports rather than domestic production in developed countries. On the other hand, while it may cause job loss and erode the returns to specific factors, PRC export growth is less likely to be a source of wage inequality in advanced economies

Publisher Connection: Export-Led Growth in the UAE: Multivariate Causality Between Primary Exports, Manufactured Exports and Economic Growth

The principal question that this research addresses is the validity of the Export-Led Growth hypothesis (ELG) in the United Arab Emirates (UAE) over the period 1981–2012, focusing on the causality between primary exports, manufactured exports and economic growth. Unit root tests are applied to examine the time-series properties of the variables, while the Johansen cointegration test is performed to confirm or not the existence of a long-run relationship between the variables. Moreover, the multivariate Granger causality test and a modified version of Wald test are applied to examine the direction of the short-run and long-run causality respectively. The cointegration analysis reveals that manufactured exports contribute more to economic growth than primary exports in the long-run. In addition, this research provides evidence to support a bi-directional causality between manufactured exports and economic growth in the short-run, while the Growth-Led Exports (GLE) hypothesis is valid in the long-run for UAE

Feminist-Kaleckian Macroeconomic Policy for Developing Countries

This paper reviews evidence of the gender effects of globalization in developing economies. It then outlines a set of macroeconomic and trade policies to promote gender equity. The evidence suggests that while liberalization has expanded women's access to employment, the long-term goal of transforming gender inequalities remains unmet and appears unattainable without state intervention in markets. This paper sets forth some general principles that can produce greater gender equality, premised on shifting from economies that are profit led and export oriented to those that are wage led and full-employment oriented. The framework is Kaleckian in its focus on the relationship between the gender distribution of income and macroeconomic outcomes