Most of Earth's terrestrial surface is made up of sloping landscapes. The lateral distribution of topsoil by erosion controls the availability, stock, and persistence of essential elements in the ...terrestrial ecosystem. Over the last two decades, the role of soil erosion in biogeochemical cycling of essential elements has gained considerable interest from the climate, global change, and biogeochemistry communities after soil erosion and terrestrial sedimentation were found to induce a previously unaccounted terrestrial sink for atmospheric carbon dioxide. More recent studies have highlighted the role of erosion in the persistence of organic matter in soil and in the biogeochemical cycling of elements beyond carbon
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Here we synthesize available knowledge and data on how erosion serves as a major driver of biogeochemical cycling of essential elements. We address implications of erosion-driven changes in biogeochemical cycles on the availability of essential elements for primary production, on the magnitude of elemental exports downstream, and on the exchange of greenhouse gases from the terrestrial ecosystem to the atmosphere. Furthermore, we explore fates of eroded material and how terrestrial mass movement events play major roles in modifying Earth's climate.
Air-drying and wetting of air-dried soil samples with water (i.e., rewetting) are widely used sample treatments in soil analyses. It is recognized that both air-drying and rewetting of soil samples ...affect the characteristics of organic matter (OM), but systematic evaluations are scarce. In this review, we synthesize what is known in the scientific literature concerning the types and magnitudes of effects resulting from air-drying and rewetting with respect to i) characteristics of aggregate-associated and water-extractable OM, ii) soil microbiota, and iii) decomposition of OM. Air-drying of soil samples results in the formation of new and/or stronger OM-mineral interactions as well as increased hydrophobicity and mineral surface acidity. The formation of new and enhancement of existing OM-mineral interactions may lead to an increase in perceived aggregate stability, potentially affecting estimates of amount and persistence of OM associated with soil aggregates. Compared to field moist samples, air-dried samples had 8–41% higher relative dry mass proportions in the 2–0.25mm aggregate size fraction. Pronounced changes in the amount and composition of the water-extractable OM and soil microbiota are also detected during the course of air-drying and rewetting with the potential to affect the conclusions derived from OM decomposition experiments. Air-dried soil samples were found to have 2–10 times higher amounts of water extractable organic carbon and a decrease between 3% and 69% in the microbial biomass carbon (using the substrate-induced respiration technique) compared to field moist samples. The magnitude of air-drying and rewetting derived effects on sample characteristics appears to be site and soil type specific.
•Air drying results in new or stronger organic matter–mineral interactions.•Air-drying can lead to an increase in hydrophobicity and mineral-surface acidity.•Air-drying and rewetting affect aggregate-associated and water-extractable OM.•Air-drying and rewetting impact microbiota and results of decomposition experiments.•The magnitude of effects from air-drying and rewetting are soil type specific.
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•Our method is a major improvement to the widely used Phenol–Sulfuric Acid method.•We avoided the health and environmental hazards associated with phenol use.•We developed a direct ...correlation of UV-absorbance to total carbon concentration.•We significantly reduce the waiting time prior to light absorption reading.•We differentiate between neutral and anionic carbohydrates absorbance.
A new UV spectrophotometry based method for determining the concentration and carbon content of carbohydrate solution was developed. This method depends on the inherent UV absorption potential of hydrolysis byproducts of carbohydrates formed by reaction with concentrated sulfuric acid (furfural derivatives). The proposed method is a major improvement over the widely used Phenol–Sulfuric Acid method developed by DuBois, Gilles, Hamilton, Rebers, and Smith (1956). In the old method, furfural is allowed to develop color by reaction with phenol and its concentration is detected by visible light absorption. Here we present a method that eliminates the coloration step and avoids the health and environmental hazards associated with phenol use. In addition, avoidance of this step was shown to improve measurement accuracy while significantly reducing waiting time prior to light absorption reading. The carbohydrates for which concentrations and carbon content can be reliably estimated with this new rapid Sulfuric Acid–UV technique include: monosaccharides, disaccharides and polysaccharides with very high molecular weight.
Demographics of the science, technology, engineering, and mathematics (STEM) workforce and student body in the US and Europe continue to show severe underrepresentation of Black, Indigenous, and ...people of color (BIPOC). Among the documented causes of the persistent lack of diversity in STEM are bias, discrimination, and harassment of members of underrepresented minority groups (URMs). These issues persist due to continued marginalization, power imbalances, and lack of adequate policies against misconduct in academic and other scientific institutions. All scientists can play important roles in reversing this trend by shifting the culture of academic workplaces to intentionally implement equitable and inclusive policies, set norms for acceptable workplace conduct, and provide opportunities for mentorship and networking. As scientists are increasingly acknowledging the lack of racial and ethnic diversity in science, there is a need for clear direction on how to take antiracist action. Here we present 10 rules to help labs develop antiracists policies and action in an effort to promote racial and ethnic diversity, equity, and inclusion in science.
Identifying the global drivers of soil priming is essential to understanding C cycling in terrestrial ecosystems. We conducted a survey of soils across 86 globally-distributed locations, spanning a ...wide range of climates, biotic communities, and soil conditions, and evaluated the apparent soil priming effect using
C-glucose labeling. Here we show that the magnitude of the positive apparent priming effect (increase in CO
release through accelerated microbial biomass turnover) was negatively associated with SOC content and microbial respiration rates. Our statistical modeling suggests that apparent priming effects tend to be negative in more mesic sites associated with higher SOC contents. In contrast, a single-input of labile C causes positive apparent priming effects in more arid locations with low SOC contents. Our results provide solid evidence that SOC content plays a critical role in regulating apparent priming effects, with important implications for the improvement of C cycling models under global change scenarios.
Soil and human security in the 21st century Amundson, Ronald; Berhe, Asmeret Asefaw; Hopmans, Jan W. ...
Science (American Association for the Advancement of Science),
05/2015, Letnik:
348, Številka:
6235
Journal Article
Recenzirano
Odprti dostop
Global soil resources under stressThe future of humanity is intertwined with the future of Earth's soil resources. Soil provides for agriculture, improves water quality, and buffers greenhouse gases ...in the atmosphere. Yet human activities, including agricultural soil erosion, are rapidly degrading soil faster than it is naturally replenished. At this rate, human security over the next century will be severely threatened by unsustainable soil management practices. Amundson et al. review recent advances in understanding global soil resources, including how carbon stored in soil responds to anthropogenic warming. Translating this knowledge into practice is the biggest challenge remaining.Science, this issue 10.1126/science.1261071 Human security has and will continue to rely on Earth's diverse soil resources. Yet we have now exploited the planet's most productive soils. Soil erosion greatly exceeds rates of production in many agricultural regions. Nitrogen produced by fossil fuel and geological reservoirs of other fertilizers are headed toward possible scarcity, increased cost, and/or geopolitical conflict. Climate change is accelerating the microbial release of greenhouse gases from soil organic matter and will likely play a large role in our near-term climate future. In this Review, we highlight challenges facing Earth's soil resources in the coming century. The direct and indirect response of soils to past and future human activities will play a major role in human prosperity and survival.
Application of ultrasound to disperse soil aggregates has been critical in enabling researchers to separate and analyze aggregate building blocks that include organic and mineral particles as well as ...mineral associated organic matter. But the forces generated in the process may also alter the dispersion products and, thus, potentially interfere with the interpretation of experimental results. This review summarizes present knowledge on experimental conditions that may lead to physical damage and chemical modifications of aggregate building blocks. The energy level at which physical disintegration of organic particles could be detected was as low as 60 J mL-¹. Physical damage of sand- and silt-sized mineral particles was observed to commence at energy levels exceeding 700 J cm-³. No evidence was found for the disintegration of particles within the clay-size fraction of soils even though studies analyzing pure minerals such as kaolinite revealed particle breakage after application of energy amounts > 12,000 J cm-³. Here we outline a strategy to minimize artifacts such as physical damage of mineral or organic particles resulting from ultrasonication by adopting a stepwise dispersion protocol involving successively higher energy levels, accompanied by a sequential separation of organic and mineral compounds.
Soil organic matter (SOM) processes in dynamic landscapes are strongly influenced by soil erosion and sedimentation. We determined the contribution of physical isolation of organic matter (OM) inside ...aggregates, chemical interaction of OM with soil minerals, and molecular structure of SOM in controlling storage and persistence of SOM in different types of eroding and depositional landform positions. By combining density fractionation with elemental and spectroscopic analyses, we showed that SOM in depositional settings is less transformed and better preserved than SOM in eroding landform positions. However, which environmental factors exert primary control on storage and persistence of SOM depended on the nature of the landform position considered. In an annual grassland watershed, protection of SOM by physical isolation inside aggregates and chemical association of organic matter (complexation) with soil minerals, as assessed by correlation with radiocarbon concentration, were more effective in the poorly drained, lowest‐lying depositional landform positions, compared to well‐drained landform positions in the upper parts of the watershed. Results of this study demonstrated that processes of soil erosion and deposition are important mechanisms of long‐term OM stabilization.
Key Points
Eroding and depositional landform positions vary in terms of soil carbon storage
Mechanisms of SOM stabilization depend on nature of landform position considered
Significant fraction of SOM in depositional positions can be easily mineralized
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