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1. Gradients of geochemical change in relic charcoal hearth soils, Northwestern Connecticut, USA

   https://doi.org/https://doi.org/10.1016/j.catena.2020.104991  

   Donovan, S. (February 2021, Catena)

   null (Ed.)

   Relic charcoal hearths (RCHs) have produced distinct legacy effects in forest soils around the world. Recently, LiDAR imagery has revealed thousands of 18th–early 20th century RCHs in Litchfield County, Connecticut, USA; however, the effects of RCHs on a landscape-scale are not well-documented, particularly fine-scale heterogeneity within RCHs and surrounding soils. This study examines the long-term impacts of charcoal production by measuring RCH soil chemical and physical properties from three perspectives: (1) compared to adjacent reference sites (RSadj), (2) laterally at systematic distances away from the RCH center, and (3) vertically within the RCH soil profile. Mean charcoal abundance was greater in RCH sites than RSadj (p < 0.01). Soil organic carbon (SOC), total C, and extractable Ca2+, Mg2+, Na+ were greater in RCH sites as compared to RSadj (p < 0.01), and available phosphorus (p < 0.01), K+, and trace elements (Mo, Ag, Hg, and Se) were lower (p < 0.05). In vertical profiles, many RCHs had 2 charcoal-rich layers within the anthropic epipedon, demonstrating multiple episodes of charcoal production. Peaks in SOC, C:N, Ca2+, Mg2+ corresponded with charcoal-rich layers. Systematic transect sampling across the RCH boundary identified charcoal fragments in soils at distances up to 25 m beyond the RCH boundary, increasing the surface-level (0–15 cm) area of impact for an individual RCH by more than 30×, from a 5-m radius (RCH area = 78.5 m2) to a 30-m radius (total area of impact = 2826 m2). These findings capture fine-scale variations within and among RCH and reference sites and contribute to estimating the total area of forest soils impacted by historical charcoal production. 

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2. Relict soil evidence for post-Miocene aridification in the Atacama Desert of South America

   https://doi.org/10.1130/B37356.1  

   Amundson, Ronald; Heimsath, Arjun; Jungers, Matt; Balan, Simona; Ebeling, Angela; Nishiizumi, Kunihiko; Ewing, Stephanie; Shuster, David; Caffee, Marc W; Pfeiffer, Marco; et al (July 2024, Geological Society of America Bulletin)

   Abstract Deep exposures of soil profiles on Miocene or Mio-Pliocene alluvial deposits were studied along a 500 km N-S transect in the Atacama Desert. These ancient deposits, with excellent surface preservation, now stand many meters above a broad incised Plio-Pleistocene alluvial terrain. Total geochemical analyses and mass balance calculations allowed the establishment of elemental gains, losses, and redistribution in the soils. From north to south (presently hyperarid to arid), the ancient soils reveal an increase in losses of rock-forming elements (Si, Al, Fe, K, Mg). Additionally, rare earth elements (REE) show losses with increasing southerly latitude and systematic patterns with soil depth. Some REEs appear to be unique chemical tracers of exogenous dust and aerosol additions to the soils. The removal of major elements and REEs is impossible in the present climate (one of salt and dust accumulation), revealing that for a significant period following the deposition of the alluvium, soils were exposed to rainfall, chemical weathering, and mass loss—with a geographical pattern that mirrors the present rainfall gradient in the region. Following the cessation of weathering, the pre-weathered soils have undergone enormous dust and salt accumulations, with the rates and types of salt accumulation consistent with latitude: (1) carbonate in the south and (2) sulfate, chlorides, and nitrates to the north. The quantity, and apparent rates, of salt accumulation have a strong latitudinal trend. Isotopes of sulfate have predictable depth patterns based on isotope fractionation via vertical reaction and transport. The relict hyperarid soils are geochemically similar to buried Miocene soils (ca. 10–9 Ma) in the region, but they differ from older Miocene soils, which formed in more humid conditions. The overall soil record for the Atacama Desert appears to be the product of changes in Pacific Ocean sea surface temperatures over time, and resulting changes in rainfall. The mid-Miocene was relatively humid based on buried soil chemistry and evidence of fluvial activity. The mid to late Miocene cooling (ca. 10–5.5 Ma) appears to have aridified the region based on paleosol soil chemistry. Pliocene to earliest Pleistocene conditions caused weathering of the relict soils examined here, and regional fluvial activity. Since the earliest Pleistocene, the region has largely experienced the accumulation of salts and, except for smaller scale oscillations (glacial-interglacial), has experienced protracted hyperaridity. 

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3. Soil physical and chemical properties of gypsum & non-gypsum soils from the Chihuahuan and Mojave Deserts in 2023

   https://doi.org/10.6073/pasta/01123dd2785f8ff3cb314a837d3bb6fd  

   Gobbie, Katelyn G; Pietrasiak, Nicole; Drenovsky, Rebecca E (January 2024, Environmental Data Initiative)

   This dataset contains data for soil physical and chemical properties of gypsum and non-gypsum soils in the northern Chihuahuan and eastern Mojave Deserts. Data were obtained from 20 study sites total, 10 located on soils derived from gypsum parent material and 10 located on soils derived from non-gypsum parent materials. Sites were grouped into 10 pairs, in which every gypsum site was partnered with a non-gypsum site located in the same region. Apart from soil type, partnered-site characteristics (topography, climate, elevation, slope, aspect, and presence of biocrusts) were held relatively constant. Site info and characteristics data can be accessed at knb-lter-jrn.210616001. Soil physical properties included: percent gravel, percent < 2mm fraction, soil aggregate stability, and soil compaction. Soil chemical properties were: percent gypsum content, pH, EC, and soil soluble concentrations of calcium, magnesium, potassium, sulfur, and phosphorus. The resulting soil data was used to understand physical and chemical differences between gypsum and non-gypsum soils and to examine how biocrust community types and moss species abundance and composition were associated with the measured soil variables. This study and dataset are complete. 

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4. Long‐term nitrogen deposition inhibits soil priming effects by enhancing phosphorus limitation in a subtropical forest

   https://doi.org/10.1111/gcb.16718  

   Wang, Xiaohong; Li, Shiyining; Zhu, Biao; Homyak, Peter M.; Chen, Guangshui; Yao, Xiaodong; Wu, Dongmei; Yang, Zhijie; Lyu, Maokui; Yang, Yusheng (April 2023, Global Change Biology)

   Abstract It is widely accepted that phosphorus (P) limits microbial metabolic processes and thus soil organic carbon (SOC) decomposition in tropical forests. Global change factors like elevated atmospheric nitrogen (N) deposition can enhance P limitation, raising concerns about the fate of SOC. However, how elevated N deposition affects the soil priming effect (PE) (i.e., fresh C inputs induced changes in SOC decomposition) in tropical forests remains unclear. We incubated soils exposed to 9 years of experimental N deposition in a subtropical evergreen broadleaved forest with two types of¹³C‐labeled substrates of contrasting bioavailability (glucose and cellulose) with and without P amendments. We found that N deposition decreased soil total P and microbial biomass P, suggesting enhanced P limitation. In P unamended soils, N deposition significantly inhibited the PE. In contrast, adding P significantly increased the PE under N deposition and by a larger extent for the PE of cellulose (PE_cellu) than the PE of glucose (PE_glu). Relative to adding glucose or cellulose solely, adding P with glucose alleviated the suppression of soil microbial biomass and C‐acquiring enzymes induced by N deposition, whereas adding P with cellulose attenuated the stimulation of acid phosphatase (AP) induced by N deposition. Across treatments, the PE_gluincreased as C‐acquiring enzyme activity increased, whereas the PE_celluincreased as AP activity decreased. This suggests that P limitation, enhanced by N deposition, inhibits the soil PE through varying mechanisms depending on substrate bioavailability; that is, P limitation regulates the PE_gluby affecting soil microbial growth and investment in C acquisition, whereas regulates the PE_celluby affecting microbial investment in P acquisition. These findings provide new insights for tropical forests impacted by N loading, suggesting that expected changes in C quality and P limitation can affect the long‐term regulation of the soil PE. 

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5. Elephant megacarcasses increase local nutrient pools in African savanna soils and plants

   https://doi.org/10.5194/bg-22-1583-2025  

   Reed, Courtney G; Budny, Michelle L; du_Toit, Johan T; Helcoski, Ryan; Schimel, Joshua P; Smit, Izak_P J; Strydom, Tercia; Tallian, Aimee; Thompson, Dave I; van_Coller, Helga; et al (January 2025, Biogeosciences)

   Abstract. African elephants (Loxodonta africana) are the largest extant terrestrial mammals, with bodies containing enormous quantities of nutrients. Yet, we know little about how these nutrients move through the ecosystem after an elephant dies. Here, we investigated the initial effects (1–26 months postmortem) of elephant megacarcasses on savanna soil and plant nutrient pools in the Kruger National Park, South Africa. We hypothesized that (H1) elephant megacarcass decomposition would release nutrients into soil, resulting in higher concentrations of soil nitrogen (N), phosphorus (P), and micronutrients near the center of carcass sites; (H2) carbon (C) inputs into the soil would stimulate microbial activity, resulting in increased soil respiration potential near the center of carcass sites; and (H3) carcass-derived nutrients would be absorbed by plants, resulting in higher foliar nutrient concentrations near the center of carcass sites. To test our hypotheses, we identified 10 elephant carcass sites split evenly between nutrient-poor granitic and nutrient-rich basaltic soils. At each site, we ran transects in the four cardinal directions from the center of the carcass site, collecting soil and grass (Urochloa trichopus, formerly U. mosambicensis) samples at 0, 2.5, 5, 10, and 15 m. We then analyzed samples for C, N, P, and micronutrient concentrations and quantified soil microbial respiration potential. We found that concentrations of soil nitrate, ammonium, δ15N, phosphate, and sodium were elevated closer to the center of carcass sites (H1). Microbial respiration potentials were positively correlated with soil organic C, and both respiration and organic C decreased with distance from the carcass (H2). Finally, we found evidence that plants were readily absorbing carcass-derived nutrients from the soil, with foliar %N, δ15N, iron, potassium, magnesium, and sodium significantly elevated closer to the center of carcass sites (H3). Together, these results indicate that elephant megacarcasses release ecologically consequential pulses of nutrients into the soil which stimulate soil microbial activity and are absorbed by plants into the above-ground nutrient pools. These localized nutrient pulses may drive spatiotemporal heterogeneity in plant diversity, herbivore behavior, and ecosystem processes. 

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