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1. Effect of nitrogen fertilization on central tendency and spatial heterogeneity of soil moisture, pH and dissolved organic carbon and nitrogen in two bioenergy croplands#

   https://doi.org/10.1002/jpln.202100311  

   Wang, Xuehan ; Jian, Siyang ; Gamage, Lahiru ; Li, Jianwei ( March 2022 , Journal of Plant Nutrition and Soil Science)

   Soil moisture, pH, dissolved organic carbon and nitrogen (DOC, DON) are important soil biogeochemical properties in switchgrass (SG) and gamagrass (GG) croplands. Yet their spatiotemporal patterns under nitrogen (N) fertilization have not been studied.

   The objective of this study is to investigate the main and interactive effects of N fertilization and bioenergy crop type on central tendencies and spatial heterogeneity of soil moisture, pH, DOC and DON.

   Based on a 3‐year long fertilization experiment in Middle Tennessee, USA, 288 samples of top horizon soils (0–15 cm) under three fertilization treatments in SG and GG croplands were collected. The fertilization treatments were no N input (NN), low N input (LN: 84 kg N ha⁻¹in urea) and high N input (HN: 168 kg N ha⁻¹in urea). Soil moisture, pH, DOC and DON were quantified. And their within‐plot variations and spatial distributions were achieved via descriptive and geostatistical methods.

   Relative to NN, LN significantly increased DOC content in SG cropland. LN also elevated within‐plot spatial heterogeneity of soil moisture, pH, DOC and DON in both croplands though GG showed more evident spatial heterogeneity than SG. Despite the pronounced patterns described above, great plot to plot variations were also revealed in each treatment.

   This study informs the generally low sensitivity of spatiotemporal responses in soil biogeochemical features to fertilizer amendments in bioenergy croplands. However, the significantly positive responses of DOC under low fertilizer input informed the best practice of optimizing agricultural nutrient amendment.

    

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2. Soil extracellular oxidases mediated nitrogen fertilization effects on soil organic carbon sequestration in bioenergy croplands

   https://doi.org/10.1111/gcbb.12860  

   Duan, Jianjun ; Yuan, Min ; Jian, Siyang ; Gamage, Lahiru ; Parajuli, Madhav ; Dzantor, Kudjo E. ; Hui, Dafeng ; Fay, Philip A. ; Li, Jianwei ( June 2021 , GCB Bioenergy)

   Nitrogen (N) fertilization significantly affects soil extracellular oxidases, agents responsible for decomposition of slow turnover and recalcitrant soil organic carbon (SOC; e.g., lignin), and consequently influences soil carbon sequestration capacity. However, it remains unclear how soil oxidases mediate SOC sequestration under N fertilization, and whether these effects co‐vary with plant type (e.g., bioenergy crop species). Using a spatially explicit design and intensive soil sampling strategy under three fertilization treatments in switchgrass (SG:Panicum virgatumL.) and gamagrass (GG:Tripsacum dactyloidesL.) croplands, we quantified the activities of polyphenolic oxidase (PHO), peroxidase (PER), and their sum associated with recalcitrant C acquisition (OX). The fertilization treatments included no N fertilizer input (NN), low N input (LN: 84 kg N ha⁻¹ year⁻¹in urea), and high N input (HN: 168 kg N ha⁻¹ year⁻¹in urea). Besides correlations between soil oxidases and SOC (formerly published), both descriptive and geostatistical approaches were applied to evaluate the effects of N fertilization and crop type on soil oxidases activities and their spatial distributions. Results showed significantly negative correlations between soil oxidase activities and SOC across all treatments. The negative relationship of soil oxidases and SOC was also evident under N fertilization. First, LN significantly depressed oxidases in both mean activities and spatial heterogeneity, which corresponded to increased SOC in SG (though by 5.4%). LN slightly influenced oxidases activities and their spatial heterogeneity, consistent with insignificant changes of SOC in GG. Second, HN showed trends of decrease in soil oxidase activities, which aligned with the significantly enhanced SOC in both croplands. Overall, this study demonstrated that soil oxidase activities acted as sensitive and negative mediators of SOC sequestration in bioenergy croplands and optimizing fertilizer use particularly in switchgrass cropland can improve for both carbon sequestration and environmental benefit.

    

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3. Evaluation of eastern gamagrass as dual‐purpose complementary bioenergy and forage feedstock to switchgrass

   https://doi.org/10.1111/gcbb.13054  

   Kieffer, Christina ; Hui, Dafeng ; Matamala, Roser ; Li, Jianwei ; Tyler, Donald ; Dzantor, E. Kudjo ( April 2023 , GCB Bioenergy)

   Switchgrass (SG) is considered a model bioenergy crop and a warm- season peren-nial grass (WSPG) that traditionally served as forage feedstock in the United States. To avoid the sole dependence on SG for bioenergy production, evaluation of other crops to diversify the pool of feedstock is needed. We conducted a 3- year field ex-periment evaluating eastern gamagrass (GG), another WSPG, as complementary feedstock to SG in one- and two- cut systems, with or without intercropping with crimson clover or hairy vetch, and under different nitrogen (N) application rates. Our results showed that GG generally produced lower biomass (by 29.5%), theoreti-cal ethanol potential (TEP, by 2.8%), and theoretical ethanol yield (TEY, by 32.9%) than corresponding SG under the same conditions. However, forage quality meas-ures, namely acid detergent fiber (ADF), crude protein (CP), and elements P, K, Ca, and Mg were significantly higher in GG than those in SG. Nitrogen fertilizer signifi-cantly enhanced biomass (by 1.54 Mg ha−1), lignin content (by 2.10 g kg−1), and TEY (787.12 L ha−1) in the WSPGs compared to unfertilized treatments. Intercropping with crimson clover or hairy vetch did not significantly increase biomass of the WSPGs, or TEP and TEY in unfertilized plots. This study demonstrated that GG can serve as a complementary crop to SG and could be used as a dual- purpose crop for bioenergy and forage feedstock in farmers' rotations. 

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4. Fertilization (NPK) alter dryland biogeochemical processes

   https://doi.org/10.6073/pasta/3b66861166da7a9f5311ffef86a6b147  

   Yogi, Purbendra N ( January 2022 , Environmental Data Initiative)

   Nutrient augmentation is one major global change disturbance that could have cascading effects on local plant and microbial communities thus altering biogeochemical properties (Peñuelas et al. 2012). While many studies have investigated fertilization effects on community change and ecosystem processes, less work has been done in dryland ecosystems (Schimel 2010), where nutrient availability often comes as pulses correlated with rain events (Collins et al. 2008). We leveraged an ongoing fertilization experiment (NutNet) at the Sevilleta to answer the question: How does fertilization alter dryland biogeochemical processes, and how does this effect change seasonally? To explore this topic, we specifically measure three important soil hydrolase enzymes, N-acetyl- glycosaminidase (NAG), phosphatase (AP), and β- glucosidase (BG), microbial biomass, and soil nitrogen levels at 5 points along a seasonal gradient within the NutNet plots. 

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5. Exploring Trait Trade-Offs for Fungal Decomposers in a Southern California Grassland

   https://doi.org/10.3389/fmicb.2021.655987  

   Alster, Charlotte J. ; Allison, Steven D. ; Glassman, Sydney I. ; Martiny, Adam C. ; Treseder, Kathleen K. ( April 2021 , Frontiers in Microbiology)

   null (Ed.)

   Fungi are important decomposers in terrestrial ecosystems, so their responses to climate change might influence carbon (C) and nitrogen (N) dynamics. We investigated whether growth and activity of fungi under drought conditions were structured by trade-offs among traits in 15 fungal isolates from a Mediterranean Southern California grassland. We inoculated fungi onto sterilized litter that was incubated at three moisture levels (4, 27, and 50% water holding capacity, WHC). For each isolate, we characterized traits that described three potential lifestyles within the newly proposed “YAS” framework: growth yield, resource acquisition, and stress tolerance. Specifically, we measured fungal hyphal length per unit litter decomposition for growth yield; the potential activities of the extracellular enzymes cellobiohydrolase (CBH), β -glucosidase (BG), β -xylosidase (BX), and N-acetyl- β - D -glucosaminidase (NAG) for resource acquisition; and ability to grow in drought vs. higher moisture levels for drought stress tolerance. Although, we had hypothesized that evolutionary and physiological trade-offs would elicit negative relationships among traits, we found no supporting evidence for this hypothesis. Across isolates, growth yield, drought stress tolerance, and extracellular enzyme activities were not significantly related to each other. Thus, it is possible that drought-induced shifts in fungal community composition may not necessarily lead to changes in fungal biomass or decomposer ability in this arid grassland. 

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