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Core Ideas We found that cultivated and never‐cultivated grassland soils had 12 and 59% of the total C pool sequestered in the micro‐within‐macro aggregate fraction, respectively. The micro‐within‐macro aggregate C increased at a rate of 27 g C m–2 yr–1 across the restoration chronosequence; 50% of total C was in this physically protected fraction after 35 yr of restoration. This is the first study to use structural equation modeling to explain soil C stocks in the micro‐within‐macro aggregate fraction. The model explains 98% of the variance in sequestered soil C, with microbial composition representing the strongest causal influence, followed by soil structure. Managing soil to sequester C can help mitigate increasing CO2 in the atmosphere. To maximize this ecosystem service, more knowledge of factors influencing C sequestration is needed. The objectives of this study were to (i) quantify recovery of the roots, microbial biomass and composition, and soil structure across a chronosequence of grassland restorations and (ii) use a structural equation model to develop a data‐based hypothesis on the relative influence of physical and biological soil properties on the soil C aggregate fraction diagnostic of sequestered C. Belowground plant biomass and tissue quality (C/N ratio), soil microbial biomass C, phospholipid fatty acid (PLFA) concentrations, soil structure, and soil C stocks in the bulk soil and each aggregate fraction were quantified from a cultivated field, prairies restored for 1 to 35‐yr (n = 6), and a never‐cultivated (native) prairie. Root biomass, microbial biomass C, arbuscular mycorrhizal fungi (AMF) PLFA biomass across the chronosequence increase to resemble native prairie following 35 yr of restoration. Many aspects of soil structure (i.e., bulk density, proportional mass of aggregate fractions, and aggregate mean weighted diameter) and the distribution C among soil fractions, including C in the micro‐within‐macro aggregate fraction (sequestered C), also became representative of native prairie within 35 yr of restoration. Total soil C stock and physically protected C increased at a similar rate (23 and 27 g C m‐2 yr‐1) respectively, across the chronosequence. After 35 yr of restoration, 50% of the total C pool was physically protected. The structural equation modeling developed by these data hypothesizes that microbial biomass C and AMF biomass (microbial composition) have the strongest causal influence on physically protected C. This model needs to be tested using independent sites to achieve greater inference.

The “environmental heterogeneity hypothesis” predicts that variability in resources promotes species coexistence, but few experiments support this hypothesis in plant communities. A previous 15‐yr test of this hypothesis in a prairie restoration experiment demonstrated a weak effect of manipulated soil resource heterogeneity on plant diversity. This response was attributed to a transient increase in richness following a post‐restoration supplemental propagule addition, occasionally higher diversity under nutrient enrichment, and reduced cover of a dominant species in a subset of soil treatments. Here, we report community dynamics under continuous propagule addition in the same experiment, corresponding to 16–20 yr of restoration, in response to altered availability and heterogeneity of soil resources. We also quantified traits of newly added species to determine if heterogeneity increases the amount and variety of niches available for new species to exploit. The heterogeneous treatment contained a factorial combination of altered nutrient availability and soil depth; control plots had no manipulations. Total diversity and richness were higher in the heterogeneous treatment during this 5‐yr study due to higher cover, diversity, and richness of previously established forbs, particularly in the N‐enriched subplots. All new species added to the experiment exhibited unique trait spaces, but there was no evidence that heterogeneous plots contained a greater variety of new species representing a wider range of trait spaces relative to the control treatment. The richness and cover of new species was higher in N‐enriched soil, but the magnitude of this response was small. Communities assembling under long‐term N addition were dominated by different species among subplots receiving added N, leading to greater dispersion of communities among the heterogeneous relative to control plots. Contrary to the deterministic mechanism by which heterogeneity was expected to increase diversity (greater variability in resources for new species to exploit), higher diversity in the heterogeneous plots resulted from destabilization of formerly grass‐dominated communities in N‐enriched subplots. While we do not advocate increasing available soil N at large scales, we conclude that the positive effect of environmental heterogeneity on diversity can take decades to materialize and depend on development of stochastic processes in communities with strong establishment limitation.

Fall‐planted cover crops are a strategy for scavenging residual reactive N. In the northern U.S. Corn Belt, the short growing season continues to limit adoption of cover crops. Planting cover crops following wheat (Triticum aestivum L.) in a three‐crop rotation (wheat [cover crop]–corn [Zea mays L]–soybean [Glycine max L. (Merr.)]) increases establishment time. Two cover crops noted for N scavenging, annual ryegrass (Lolium perenne L. ssp. multiflorum (Lam.) Husnot) and radish (Raphanus sativus L. ‘Tillage’), were selected. We hypothesized that corn yield could be maintained with less N fertilizer when following a cover crop compared with no cover crop as determined by direct comparison and regression analyses. The study was repeated 3 yr and had three cover crop treatments: annual ryegrass, radish, and the no‐cover‐crop control. A second treatment, factorially applied in corn years, was N application rates relative the recommended rate of 0× (0 kg N ha–1), 0.25× (39–48 kg N ha–1), 0.5× (78–95 kg N ha–1), and 1× (157–190 kg N ha–1). When cover crops were planted after wheat, about 60 kg N ha–1 yr–1 was measured in the roots and shoots of radish and annual ryegrass, representing 35 or >60% of the inorganic N in the soil. Corn yield averaged 5% higher following radish and 13% lower following annual ryegrass compared with the no‐cover control. Both cover crops scavenged residual N, but neither cover crop treatment supported the hypothesis that corn yield could be maintained with less N fertilizer compared with no cover crop.

Plant community assembly outcomes can be contingent upon establishment year (year effects) due to variations in the environment. Stochastic events such as interannual variability in climate, particularly in the first year of community assembly, contribute to unpredictable community outcomes over the short term, but less is known about whether year effects produce transient or persistent states on a decadal timescale. To test for short-term (5-year) and persistent (decadal) effects of establishment year climate on community assembly outcomes, we restored prairie in an agricultural field using the same methods in four different years (2010, 2012, 2014, and 2016) that captured a wide range of initial (planting) year climate conditions. Species composition was measured for 5 years in all four restored prairies and for 9 and 11 years in the two oldest restored prairies established under average precipitation and extreme drought conditions. The composition of the four assembled communities showed large and significant differences in the first year of restoration, followed by dynamic change over time along a similar trajectory due to a temporary flush of annual volunteer species.Sown perennial species eventually came to dominate all communities, but communities remained distinct from each other in year five. Precipitation in June and July of the establishment year explained short-term coarse community metrics (i.e., species richness and grass/forb cover), with wet establishment years resulting in a higher cover of grasses and dry establishment years resulting in a higher cover of forbs in restored communities. Short-term differences in community composition, species richness, and grass/forb cover in restorations established under average precipitation and drought conditions persisted for 9-11 years, with low interannual variability in the composition of each prairie over the long term, indicating persistently different states on a decadal timescale. Thus, year effects resulting from stochastic variation in climate can have decadal effects on community assembly outcomes.

Procedures are outlined whereby enthalpy, entropy, and Gibbs' free energy could be determined for biological material from heat of combustion, chemical analysis, and entropy determinations. Some criteria for determining possible energy pathways between species are derived from their free energy concentrations. Rarely will a pathway be thermodynamically impossible.

Today, the majority of the web's content and user data is controlled by a few large tech companies. There is a growing movement to devolve this control evenly across the entire internet, representing the transition to Web3. In order for this movement to be successful, technologies and protocols must be developed to enable web users to use the web securely without trusting any other user. That is, today's web is structured so that users must trust these companies, so trustless alternatives haven't already been developed. Broadly, this movement emphasizes developing peer-to-peer networks, blockchains, and distributed storage systems. These systems make use of cryptographic primitives to guarantee security.<br>

The ‘environmental heterogeneity hypothesis’ (EHH) has been proposed as a mechanism that enables species coexistence through resource partitioning. In accordance with this hypothesis, plant diversity is predicted to increase with variability in resources, but there has been weak support for this hypothesis from experimental studies. The objectives of this research were to 1) characterize how resource availability and heterogeneity (coefficient of variation) change as plant communities develop using sequentially restored grasslands, 2) determine if resource heterogeneity relates to plant diversity (effective number of species, richness and evenness) and 3) reveal if the strength of resource heterogeneity–diversity relationships is different among levels of resource availability. We quantified means and coefficients of variation in soil nitrate and light availability in grasslands established on former agricultural lands for different times and their relationship to plant diversity using a geostatistically‐informed design. Nitrate availability decreased exponentially with restoration age, but no directional change in nitrate heterogeneity across the chronosequence occurred due to high resource variability in some restorations. Light availability also decreased exponentially across the chronosequence, but there was no directional change in light heterogeneity. Nitrate heterogeneity was positively correlated with both plant richness and plant effective number of species at high levels of nitrate availability. However, no nitrate heterogeneity correlation was detected at low levels of nitrate availability. Light heterogeneity was positively correlated with plant effective number of species at low levels of light availability. However, no light heterogeneity correlation was detected at high levels of light availability. Plant evenness was not correlated with resource heterogeneity at any resource availability level. These results support the positive heterogeneity–diversity relationship predicted by EHH, and uniquely that this relationship develops within a decade of plant community development, but can be obscured by resource availability.