Soil carbon determination for long‐term monitoring revisited using thermo‐gravimetric analysis

Soils and the vadose zone are the major terrestrial repository of carbon (C) in the form of soil organic matter (SOM), more resistant black carbon (BC), and inorganic carbonate. Differentiating between these pools is important for assessing vulnerability to degradation and changes in the C cycle affecting soil health and climate regulation. Major monitoring programs from field to continent are now being undertaken to track changes in soil carbon (SC). Inexpensive, robust measures that can differentiate small changes in the C pools in a single measurement are highly desirable for long-term monitoring. In this study, we assess the accuracy and precision of thermo-gravimetric analysis (TGA) using organic matter standards, clay minerals, and soils from a national data set. We investigate the use of TGA to routinely differentiate between C pools, something no single measurement has yet achieved. Based on the kinetic nature of thermal oxidation of SC combined with the different thermodynamic stabilities of the molecules, we designed a new method to quantify the inorganic and organic SC and further separate the organic biogeochemically active SOM (as loss on ignition, LOI) from the resistant BC in soils. We analyze the TGA spectrums of a national soil monitoring data set (n = 456) and measure total carbon (TC) using thermal oxidation and also demonstrate a TC/LOI relationship of 0.55 for soils ranging from mineral soils to peat for the United Kingdom consistent with previous monitoring campaigns

Co-located ecological data for exploring top- and subsoil carbon dynamics across grassland-woodland contrasts

Soil organic carbon (SOC) is a soil health indicator and understanding dynamics changing SOC stocks will help achieving net zero goals. Here we present four datasets featuring 11,750 data points covering co-located aboveground and below-ground metrics for exploring ecosystem SOC dynamics. Five sites across England with an established land use contrast, grassland and woodland next to each other, were rigorously sampled for aboveground (n = 109), surface (n = 33 soil water release curves), topsoil, and subsoil metrics. Commonly measured soil metrics were analysed in five soil increments for 0–1 metre (n = 4550). Less commonly measured soil metrics which were assumed to change across the soil profile were measured on a subset of samples only (n = 3762). Additionally, we developed a simple method for soil organic matter fractionation using density fractionation which is part of the less common metrics. Finally, soil metrics which may impact SOC dynamics, but with less confidence as to their importance across the soil profile were only measured on topsoil (~5–15 cm = mineral soil) and subsoil (below 50 cm) samples (n = 2567)

Can pasture‐fed livestock farming practices improve the ecological condition of grassland in Great Britain?

Abstract Livestock farming in Great Britain (GB) faces multiple pressures. Yet, grassland managed for livestock is the most extensive habitat in GB and is key to cultural landscapes and their biodiversity and soil health. This study analysed a nationally representative dataset of over 940 large (200 m2) Neutral (agriculturally semi‐improved) and (agriculturally) Improved Grassland plots from the GB Countryside Survey (CS) to assess relationships between key grassland sward and soil variables. Analysis also looked at how these variables changed over time as plots switched between these grassland types. Data from grassland plots managed by Pasture‐Fed Livestock Association (PFLA) farmers were compared to CS plot data to assess the impacts of their practices on these variables. Plant species richness in Neutral grassland types in CS plots was positively associated with total soil invertebrate abundance (total taxa) and soil N and C and negatively associated with soil P. There were negative relationships between the covers of Lolium sp. (Neutral only), legumes and forbs and soil C and moisture variables. Grassland swards on PFLA member farms were characteristic of Neutral grassland. PFLA plots were more species rich and contained more legume and forb species and lower proportions of Lolium perenne than those on Improved Grassland. Vegetation height was greater in PFLA plots than in CS plots of either Improved or Neutral Grassland. Unlike CS Neutral Grassland plots, soil properties in PFLA plots were not significantly different from those for Improved Grassland for any measured variable (soil carbon concentration [C], bulk density, pH, nitrogen [N], phosphorus [P]). Higher species richness in grasslands is associated with positive measures of soil health. PFLA plant communities contain relatively high species richness and tall vegetation, which is positive for biodiversity. Lack of positive measures of soil health associated with higher species richness recorded in PFLA grassland (as opposed to CS grassland) may reflect time lags in soil responses to management, as evidenced through an analysis of the impacts of land‐use change over time on CS plot characteristics. Our findings indicate that pasture‐fed livestock approaches may be beneficial for grassland and wider ecosystems

Soil metrics and vegetation data from pasture fed livestock farms across Great Britain, 2018.

This set of data includes records of vegetation species and characteristics, soil quality metrics and aspects of farm management relating to a single field on each sampled farm. Data were collected in 2018, from farms across Great Britain belonging to the Pasture Fed Livestock Association (PFLA). The data were collected by the UK Centre of Ecology & Hydrology, during a project funded by the BBSRC, seeking to evidence the impacts of pasture fed livestock approaches on grassland parameters, in particular, sward composition and associated soil qualities

Soil metrics, vegetation species and biomass data, and field management information from pasture fed livestock farms across Great Britain, 2019

This set of data includes records of vegetation species and characteristics, soil quality metrics and aspects of management relating to a single field on each sampled farm. Data were collected in 2019, from farms across Great Britain belonging to the Pasture Fed Livestock Association (PFLA). The data were collected by the UK Centre of Ecology & Hydrology, during a project funded by the BBSRC, seeking to evidence the impacts of pasture fed livestock approaches on grassland parameters, in particular, sward composition and associated soil qualities

Soil carbon determination for long‐term monitoring revisited using thermo‐gravimetric analysis

Abstract Soils and the vadose zone are the major terrestrial repository of carbon (C) in the form of soil organic matter (SOM), more resistant black carbon (BC), and inorganic carbonate. Differentiating between these pools is important for assessing vulnerability to degradation and changes in the C cycle affecting soil health and climate regulation. Major monitoring programs from field to continent are now being undertaken to track changes in soil carbon (SC). Inexpensive, robust measures that can differentiate small changes in the C pools in a single measurement are highly desirable for long‐term monitoring. In this study, we assess the accuracy and precision of thermo‐gravimetric analysis (TGA) using organic matter standards, clay minerals, and soils from a national data set. We investigate the use of TGA to routinely differentiate between C pools, something no single measurement has yet achieved. Based on the kinetic nature of thermal oxidation of SC combined with the different thermodynamic stabilities of the molecules, we designed a new method to quantify the inorganic and organic SC and further separate the organic biogeochemically active SOM (as loss on ignition, LOI) from the resistant BC in soils. We analyze the TGA spectrums of a national soil monitoring data set (n = 456) and measure total carbon (TC) using thermal oxidation and also demonstrate a TC/LOI relationship of 0.55 for soils ranging from mineral soils to peat for the United Kingdom consistent with previous monitoring campaigns

Vegetation plot data from the UKCEH Countryside Survey, Great Britain, 2020 and 2021

This dataset consists of plant species presence and abundance in different sizes of plots recorded from 159 1km squares across Great Britain in 2020 and 2021, as part of a rolling soil and vegetation monitoring program of 500 1km squares, beginning in 2019 and repeated every 5 years. The UKCEH Countryside Survey is a unique study or 'audit' of the natural resources of the UK's countryside. The sample sites are chosen from a stratified random sample, based on a 15 by 15 km grid of GB. Surveys have previously been carried out in 1978, 1984, 1990, 1998 and 2007 by the UK Centre for Ecology & Hydrology (UKCEH) and predecessors, with repeated visits to the majority of squares. The countryside is sampled and surveyed using rigorous scientific methods, allowing us to compare new results with those from previous surveys. In this way, we can detect the gradual and subtle changes that occur in the UK's countryside over time. In addition to vegetation data, soil data are also gathered by the current phase of the Countryside Survey. This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability

Soil physical, chemical, and biological properties (0-1 m) at five long-term grassland-to-woodland land use contrasts across England, 2018-2019

This dataset contains soil chemical, physical and biological properties for up to six soil layers between 0 and 100 cm, measured once at each of the five long-term grassland-to-woodland land use contrasts across England between November 2018 and March 2019. Each of the plots was further divided into three grids (grassland grids 1 to 3 / woodland grids 4 to 6) with grids 1 and 6 being the furthest apart. The contrast boundary is between grids 3 and 4. In each plot, nine sampling locations were randomly sampled (three in each grid). The five grassland-to-woodland contrasts were located across England: Gisburn (Gisburn-1, Gisburn-2), Alice Holt, Wytham Woods, and Kielder Forest. Common soil physical and chemical properties were measured; field water content, soil water content, electrical conductivity, bulk density, pH in DIW, pH in CaCl2, Loss-on-ignition, total soil carbon, total soil nitrogen, and total soil phosphorus. Less common properties were also measured; extractable soil nitrogen, dissolved organic carbon, soil aggregate sizes, and soil texture. And for specific soil cores these additional following properties were measured; soil density fractions and their carbon and nitrogen contents, cation exchange capacity, Sodium concentration, potassium concentration, calcium concentration, magnesium concentration, and extracellular enzyme activities. Derived metrics resulting from the bioinformatic processing of the raw sequence files are provided as part this dataset. The properties in this dataset are co-located with ANPP estimates, litter layer depth measurements, soil hydraulic measurements (soil water release curves and hydraulic conductivity), earthworm counts and identification. A file is provided to connect all co-located measurements

Topsoil physico-chemical properties from the UKCEH Countryside Survey, Great Britain, 2021

This dataset consists of measures of topsoil (0-15 cm) physico-chemical properties from soils sampled from 110 x 1 km squares across Great Britain in 2021 as part of a rolling soil and vegetation monitoring program of 500 1km squares repeated every 5 years. The properties included are: pH, soil organic matter (loss on ignition, LOI), derived carbon concentration and carbon stock (SOC), soil group, soil bulk density of fine earth, soil moisture of wet soil, fine earth volumetric water content (dry), nitrogen concentration and stock, and Olsen-phosphorus concentration. The UKCEH Countryside Survey is a unique study or 'audit' of the natural resources of the UK's countryside. The sample sites are chosen from a stratified random sample, based on a 15 by 15 km grid of GB. Surveys have been carried out in 1978, 1984, 1990, 1998 and 2007 by the UK Centre for Ecology & Hydrology (UKCEH) and predecessors, with repeated visits to most of the squares. The countryside is sampled and surveyed using rigorous scientific methods, allowing us to compare new results with those from previous surveys. In this way, we can detect the gradual and subtle changes that occur in the UK's countryside over time. In addition to soil data, vegetation species data are also gathered by the current phase of the UKCEH Countryside Survey. This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability

Topsoil physico-chemical properties from the UKCEH Countryside Survey, Great Britain, 2022

This dataset consists of measures of topsoil (0-15 cm) physico-chemical properties from soils sampled from 110 x 1-km squares across Great Britain in 2022 as part of a rolling soil and vegetation monitoring program of 500 1-km squares repeated every 5 years. The properties included are: pH, soil organic matter (loss on ignition, LOI), derived carbon concentration and carbon stock (SOC), soil group, soil bulk density of fine earth, soil moisture of wet soil, fine earth volumetric water content (dry), nitrogen concentration and stock, and Olsen-phosphorus concentration. The UKCEH Countryside Survey is a unique study or 'audit' of the natural resources of the UK's countryside. The sample sites are chosen from a stratified random sample, based on a 15 by 15 km grid of GB. Surveys have been carried out in 1978, 1984, 1990, 1998 and 2007 by the UK Centre for Ecology & Hydrology (UKCEH) and predecessors, with repeated visits to most of the squares. The countryside is sampled and surveyed using rigorous scientific methods, allowing us to compare new results with those from previous surveys. In this way, we can detect the gradual and subtle changes that occur in the UK's countryside over time. In addition to soil data, vegetation species data are also gathered by the current phase of the UKCEH Countryside Survey. This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability