21 research outputs found
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Contribution of Calcium Oxalate to Soil-Exchangeable Calcium
Acid deposition and repeated biomass harvest have decreased
soil calcium (Ca) availability in many temperate forests worldwide, yet
existing methods for assessing available soil Ca do not fully characterize
soil Ca forms. To account for discrepancies in ecosystem Ca budgets, it
has been hypothesized that the highly insoluble biomineral Ca oxalate
might represent an additional soil Ca pool that is not detected in standard
measures of soil-exchangeable Ca. We asked whether several standard
method extractants for soil-exchangeable Ca could also access Ca held in
Ca oxalate crystals using spike recovery tests in both pure solutions and
soil extractions. In solutions of the extractants ammonium chloride, ammonium
acetate, and barium chloride, we observed 2% to 104% dissolution
of Ca oxalate crystals, with dissolution increasing with both solution molarity
and ionic potential of cation extractant. In spike recovery tests using
a low-Ca soil, we estimate that 1 M ammonium acetate extraction dissolved
sufficient Ca oxalate to contribute an additional 52% to standard measurements
of soil-exchangeable Ca. However, in a high-Ca soil, the amount
of Ca oxalate spike that would dissolve in 1 M ammonium acetate extraction
was difficult to detect against the large pool of exchangeable
Ca. We conclude that Ca oxalate can contribute substantially to standard
estimates of soil-exchangeable Ca in acid forest soils with low soil-exchangeable
Ca. Consequently, measures of exchangeable Ca are unlikely
to fully resolve discrepancies in ecosystem Ca mass balance unless the
contribution of Ca oxalate to exchangeable Ca is also assessed.Keywords: Exchangeable Ca, Soil calcium extraction, Soil analysis, Calcium oxalat
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Calcium oxalate contribution to calcium cycling in forests of contrasting nutrient status
Calcium oxalate (Ca oxalate) is an insoluble biomineral that forms in plants and fungi, and occurs in soils
across many types of ecosystems. Assessing how Ca oxalate may shape ecosystem Ca cycling requires
information on the distribution of Ca oxalate among plant biomass, detritus, and mineral soil, and how
it varies with ecosystem Ca status. We compared two Douglas-fir forests of contrasting ecosystem Ca
availability, and found that Ca oxalate was partitioned similarly among plant biomass, detritus and mineral
soil major ecosystem compartments at both sites, and total pools of Ca oxalate were greater in the
high-Ca forest. However, the proportional importance of Ca oxalate was greater in the low-Ca than
high-Ca forest (18% versus 4% of actively cycling ecosystem Ca, respectively). And calcium oxalate in mineral
soil, which is of particular interest as a potential long-term Ca reservoir, was a larger portion of total
available Ca (exchangeable Ca plus Ca oxalate Ca) in the low-Ca site than the high-Ca site (9% versus 1% of
available soil Ca, respectively). Calcium oxalate was the dominant form of Ca returned from plants to soil
as leaf litterfall at the high-Ca site, yet calcium oxalate disappeared rapidly from decomposing litter
(0.28 yrā»Ā¹ or faster) at both sites. We conclude that accumulation of Ca oxalate in forest ecosystems
appears most closely related to overall Ca supply for live biomass pools, and that the accumulation of
Ca oxalate in forest floor and mineral soil is limited by rapid microbial degradation of putatively unavailable
Ca oxalate.Keywords: Leaf litter decomposition, Calcium cycling, Exchangeable calcium, Soil nutrients, Microbial degradation, Calcium oxalateKeywords: Leaf litter decomposition, Calcium cycling, Exchangeable calcium, Soil nutrients, Microbial degradation, Calcium oxalat
Using art and story to explore how primary school students in rural Tanzania understand planetary health: a qualitative analysis
Background The global planetary health community increasingly recognises the need to prepare students to investigate and address connections between environmental change and human health. As we strive to support education on planetary health themes for students of all ages, understanding studentsā concepts of linkages between the health of people and animals, and their shared environments might advance educational approaches. Children living in villages bordering Ruaha National Park in Iringa Region, Tanzania, have direct experience of these connections as they share a water-stressed but biodiverse environment with domestic animals and wildlife. Livelihoods in these villages depend predominantly on crop and livestock production, including extensive pastoralist livestock keeping. Through qualitative research, we aim to explore and describe Tanzanian primary school studentsā understanding of connections between human health and the environment
Transference of Citizen Science Program Impacts: A Theory Grounded in Public Participation in Scientific Research
Citizen science is known for increasing the geographic, spatial, and temporal scale from which scientists can gather data. It is championed for its potential to provide experiential learning opportunities to the public. Documentation of educational outcomes and benefits for citizen scientists continues to grow. This study proposes an added benefit of these collaborations: the transference of program impacts to individuals outside of the program. The experiences of fifteen citizen scientists in entomology citizen science programs were analyzed using a constructivist grounded theory methodology. We propose the substantive-level theory of transference to describe the social process by which the educational and attitudinal impacts intended by program leaders for the program participants are filtered by citizen scientists and transferred to others. This process involves individual and external phases, each with associated actions. Transference occurred in participants who had maintained a long-term interest in nature, joined a citizen science program, shared science knowledge and experiences, acquired an expert role to others, and influenced change in others. Transference has implications for how citizen scientists are perceived by professional communities, understanding of the broader impacts and contributions of citizen science to wicked problems, program evaluation, and the design of these programs as informal science education opportunities
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Calcium-oxalate in sites of contrasting nutrient status in the Coast Range of Oregon
Calcium (Ca) is an essential macronutrient that is increasingly recognized as a biogeochemical factor that influences ecosystem structure and function. Progress in understanding the sustainability of ecosystem Ca supply has been hampered by a lack of information on the various forms and pools of Ca in forest ecosystems. In particular, few studies have investigated the role of Ca-oxalate (Ca-ox), a ubiquitous and sparingly soluble biomineral formed by plants and fungi, on Ca cycling. I investigated Ca-ox pools in two young Douglas-fir forests in the Oregon Coast Range, and found that Ca-ox comprised 4 to 18% of total ecosystem Ca in high- and low-Ca sites, respectively, with roughly even distribution in vegetation, detritus and mineral soil to 1 m depth. The proportion of ecosystem Ca existing as Ca-ox varied by ecosystem compartment but was highest in needle litterfall, foliage and branches. Calcium-ox could be a large amount of Ca in mineral soil; across nine sites comprising a local soil Ca gradient, we found as much as 20% of available Ca in 0 - 10 cm depth mineral soil occurs as Ca-ox. Ca-ox was the dominant form of Ca returned from plants to soil, but disappeared as rapidly as bulk Ca from decomposing litter, suggesting an important pathway for Ca recycling. In mineral soil, Ca-ox was a larger portion of total available Ca in the low-Ca site, which had lower Ca-ox concentrations overall, suggesting that Ca-ox has limited potential to buffer against Ca depletion in forests where Ca is in shortest supply. I investigated foliar chemistry as a method for diagnosis of nutrient deficiencies in high and low-Ca sites where Ca varied inversely with soil nitrogen (N), and which had received fertilization with urea (for nitrogen, N), lime, and calcium chloride three years prior. Foliar vector diagrams suggested N limitation at the low-N site and N sufficiency at the high-N site, but did not suggest Ca deficiency at either site after urea, lime and Ca-chloride fertilization. The high-Ca site displayed 20-60 times higher concentrations of foliar Ca-oxalate than the low-Ca site, although this was unaffected by fertilization. Soil nitrification responded to both N and lime fertilization at both sites, suggesting that fertilization with N may stimulate nitrification that could accelerate soil Ca loss. I also investigated how Ca-ox may influence cation tracers such as Ca and strontium (Sr) ratios (i.e., Ca/Sr) and Ca-isotopes (ā“ā“Ca/ā“ā°Ca), which are used to identify sources and pathways of Ca cycling in ecosystem studies. Laboratory synthesis of Ca-ox crystals exhibited preference for Ca over Sr, and for ā“ā°Ca over ā“ā“Ca. In the field, discrimination between Ca and Sr was detected in bulk plant tissues due to Ca-ox accumulation, suggesting that Ca-ox accumulation related to tree Ca supply status could influence interpretations of Ca/Sr as a tracer of Ca cycling. I also found that standard methods of soil exchangeable Ca extraction could dissolve Ca-ox crystals and potentially contribute an additional 52% to standard measurements of exchangeable-Ca pools in low-Ca sites, thus complicating long-standing interpretations of available soil Ca pools and dynamics in many studies. Results of this work show overall that Ca-ox is found in large quantities in plants, detritus, and mineral soil in forest ecosystems, and is a more dynamic component of ecosystem Ca cycling than previously recognized
Using art and story to explore how primary school students in rural Tanzania understand planetary health: a qualitative analysis
Background The global planetary health community increasingly recognises the need to prepare students to investigate and address connections between environmental change and human health. As we strive to support education on planetary health themes for students of all ages, understanding studentsā concepts of linkages between the health of people and animals, and their shared environments might advance educational approaches. Children living in villages bordering Ruaha National Park in Iringa Region, Tanzania, have direct experience of these connections as they share a water-stressed but biodiverse environment with domestic animals and wildlife. Livelihoods in these villages depend predominantly on crop and livestock production, including extensive pastoralist livestock keeping. Through qualitative research, we aim to explore and describe Tanzanian primary school studentsā understanding of connections between human health and the environment
Using art and story to explore how primary school students in rural Tanzania understand planetary health: a qualitative analysis
Background The global planetary health community increasingly recognises the need to prepare students to investigate and address connections between environmental change and human health. As we strive to support education on planetary health themes for students of all ages, understanding studentsā concepts of linkages between the health of people and animals, and their shared environments might advance educational approaches. Children living in villages bordering Ruaha National Park in Iringa Region, Tanzania, have direct experience of these connections as they share a water-stressed but biodiverse environment with domestic animals and wildlife. Livelihoods in these villages depend predominantly on crop and livestock production, including extensive pastoralist livestock keeping. Through qualitative research, we aim to explore and describe Tanzanian primary school studentsā understanding of connections between human health and the environment
Measurement of Socio-Scientific Reasoning (SSR) and Exploration of SSR as a Progression of Competencies
Socio-scientific reasoning (SSR) is key to helping students take informed positions around socio-scientific issues (SSI). SSR comprises four competencies: recognising complexity of SSIās, multiple perspectives around SSIās, the need for ongoing inquiry around SSIās, and skepticism around different partiesā claims made about SSIās. The Quantitative Assessment of SSR (QuASSR) provides a promising measurement framework, but there are still important questions around the ability of this instrument to measure transfer across different scenarios and change in SSR over an intervention. Further, prior work suggests that the four competencies may constitute a progression. We explored the ability of the QuASSR to measure transfer of SSR across three different SSIās using 2-faceted and multi-faceted Rasch models. We used path analysis to test the hypothesis that competencies associated with SSR formed a progression. We found transfer or neartransfer of SSR across the three scenarios, and that the competencies comprise a unidimensional hierarchy. Perspective-taking is a necessary bridge between studentsā understanding of complexity and the higher-level competencies of inquiry and skepticism. Inquiry and skepticism were found to be conditionally independent upon accounting for perspective-taking, supporting the idea that seeing multiple perspectives around SSIās is central to development of the other SSR competencies. (PsycInfo Database Record (c) 2021 APA, all rights reserved