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The timescales over which soil carbon responds to global change are a major uncertainty in the terrestrial carbon cycle. Radiocarbon measurements on archived soil samples are an important tool for addressing this uncertainty. We present time series (1969–2023) of radiocarbon measurements for litter (Oi/Oe and Oa/A) and mineral (0–10 cm) soils from the Hubbard Brook Experimental Forest, a predominantly hardwood forest in the northeastern USA. To estimate soil carbon cycling rates, we built different autonomous linear compartmental models. We found that soil litter carbon cycles on decadal timescales (Oi/Oe: ~7 years), whereas carbon at the organic‐mineral interface (Oa/A), and mineral soil (0–10 cm) carbon cycles on centennial timescales (~104 and 302 years, respectively). At the watershed‐level, the soil system appears to be at steady‐state, with no observed changes in carbon stocks or cycling rates over the study period, despite increases in precipitation, temperature, and soil pH. However, at the site‐level, the Oi/Oe is losing carbon (−15 g C m⁻² year⁻¹since 1998). The observed decline in carbon stocks can be detected when the Oi and Oe layers are modeled separately. This pattern suggests that the rapidly cycling litter layer at the smaller scale is responding to recent environmental changes. Our results highlight the importance of litter carbon as an “early‐warning system” for soil responses to environmental change, as well as the challenges of detecting gradual environmental change across spatial scales in natural forest ecosystems. 

Biomolecular adsorption has great significance in medical, environmental, and technological processes. Understanding adsorption equilibrium and binding kinetics is essential for advanced process implementation. This requires identifying intrinsic determinants that predict optimal adsorption properties at bio–hybrid interfaces. Solid-binding peptides (SBPs) have targetable intrinsic properties involving peptide–peptide and peptide–solid interactions, which result in high-affinity material-selective binding. Atomic force microscopy investigations confirmed this complex interplay of multi-step peptide assemblies in a cooperative modus. Yet, most studies report adsorption properties of SBPs using non-cooperative or single-step adsorption models. Using non-cooperative kinetic models for predicting cooperative self-assembly behavior creates an oversimplified view of peptide adsorption, restricting implementing SBPs beyond their current use. To address these limitations and provide insight into surface-level events during self-assembly, a novel method, the Frequency Response Cooperativity model, was developed. This model iteratively fits adsorption data through spectral analysis of several time-dependent kinetic parameters. The model, applied to a widely used gold-binding peptide data obtained using a quartz crystal microbalance with dissipation, verified multi-step assembly. Peak deconvolution of spectral plots revealed distinct differences in the size and distribution of the kinetic rates present during adsorption across the concentrations. This approach provides new fundamental insights into the intricate dynamics of self-assembly of biomolecules on surfaces. 

Soil carbon dioxide (CO2) flux, or soil respiration, is a critical control on net ecosystem carbon (C) balance. Using long-term (2002-2020) measurements at the Hubbard Brook Experimental Forest (New Hampshire, U.S.), we show that soil respiration rates have notably increased since ~2015. In 2020, cumulative summer respiration flux was approximately 90% higher than the average summer flux over the 2002–2015 period. The increase in soil respiration cannot be explained directly by temperature or pH change alone. We also found that heterotrophic microbial C mineralization and microbial biomass C have also increased rapidly since ~2015, pointing towards an increase in the bioavailability of organic C substrates. We suggest that these observations are consistent with a hypothetical increase in plant allocation of C belowground in response to changing climatic and soil conditions. Quantification of interactions among co-occurring global change factors (e.g., warming temperatures, increasing atmospheric CO2, and nutrient limitation) is needed to predict how the soil C reservoir will continue to respond to global environmental changes. 

The forest floor of Watershed 6 was first sampled in 1969-70. These data include forest floor thickness, soil mass, organic matter content, and major-element composition for samples collected since 1976. Watershed 6 has been resampled at intervals varying from one to ten years. Sampling at five to ten year intervals is expected to continue. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

{"Abstract":["This data set includes chemistry of O-horizons ("forest floor") and the 0-10 cm \nmineral soil layer in Watershed 1 at Hubbard Book. Calcium in the form of wollastonite \n(CaSiO3) was added to Watershed 1 in October 1999. The application rate was 1028 kg \nCa per ha, and the application was relatively uniform across the watershed. Pre-treatment \nforest floor surveys were completed in 1996 and 1998. The first post-treatment forest \nfloor survey was completed in 2000. This data set includes mass and thickness data for \nthe sampled layers. Chemical data include concentrations and pools of organic matter, \nC, N, Ca, Mg, K, P, Mn, Fe, Al, Cu, Pb, and Zn. Soil pH and exchangeable Al, Ca, Mg, K, \nand H are also included. Sampling is intended to continue at 4 or 5 year intervals.\n These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). \nThe HBES is a collaborative effort at the Hubbard Brook Experimental Forest, \nwhich is operated and maintained by the USDA Forest Service, Northern Research Station."]} 

We sampled soils on watershed 5 at the Hubbard Brook Experimental Forest in 1983, prior to a whole-tree harvest conducted in the winter of 1983-84. We resampled in 1986, 1991, and 1998. All sampling was performed using a quantitative soil pit method. Samples of the combined Oi and Oe horizons; the Oa horizon; 0-10 cm, 10-20 cm, and >20 cm layers of mineral soil; and the C horizon were collected. Grab samples of pedogenic mineral horizons were also taken from the sides of a subset of pits in each year. Here we report soil chemistry, mass of soil, percent rock, bulk density, and organic matter. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.