Carbon in Global Boreal and Alpine Soils Under Climate Change-Driven Land Use: sampling sites

Teagasc, Ireland

• Two Teagasc sites were used (Johnston Castle and Oak Park) due to the regionalization of agriculture in Ireland (Johnston Castle is primarily pasture research, Oak Park is primarily grain crops).
• Oak Park had sites for Pasture, Wheat, and Natural (forest) replicates.
• Oak Park was flat with no obvious water sources, and grew maize, wheat, barley, and canola/rapeseed. The forest was a mixture of bramble/briar deciduous with a surprising amount of ground ivy, and another area of mature conifer. Pasture was grazed occasionally, and lush.
• Johnston Castle had sites for Pasture, Natural (forest), Abandoned (Agroforestry Ash), and Converted (former Ash).
• Johnston Castle had rolling terrain with small valleys and local ponds (artificial and natural) criss-crossing the forest. The forest appeared mature deciduous with a lot of magnolias (?), but mostly litter forest floor. Pasture was on a long slope immediately below the converted plots, and had been recently grazed by cattle (dropping evident, grass clipped).
• Agroforestry (Ash) site had been full Ash plantation similar to Leeds until four months prior to sampling, at which point blighted Ash were cut down and shredded (similar to land conversion). However, some disease-resistant Ash were left intact, allowing sampling of ‘agroforestry plots’, albeit very sparse, but still containing ferns and other forest plants at tree bases. Hypothesis: there are differences between converted (former Ash) and Ash samples (i.e. even fragments will retain forest-like soil characteristics).
• Converted soil was very loose and contained wood shavings/chips from conversion.
• All soil from both locations appeared to be of similar geologic origin (dark grey hue).
• Sampling was performed in two days (one at each site), samples refrigerated then processed.

Leeds, England

• Soils were collected from Spen Farm, a research farm of the University of Leeds primarily researching pigs.
• Samples were taken for Wheat, Pasture, Forest, and Agroforestry (abandoned), with the latter being subsampled for different tree types (Ash, Cherry, Hazel, and Sycamore).
• Spen Farm was mostly flat with slight gradations in terrain and no obvious water sources on the farm itself. In addition to pigs, the farm had some sheep and grew mostly wheat and canola/rapeseed with some Maize on rotation, as well as agroforestry plots containing 39 yr old hazel, ash, cherry, and sycamore trees in four blocks across the farm, and a single block of poplar trees. Small native forest with mature deciduous trees/open forest floor was present as well.
• A Highway was adjacent to one edge of the farm.
• Hedgerows predominated and separated different land use types.
• Pig activity was confined to areas of the farm not sampled; nonetheless, pig manure was applied to at least the wheat fields.
• Pasture was grazed by sheep.
• Substantial data should exist on eddy covariance and soil respiration in one of the wheat fields.
• Sampling was performed in one afternoon, soils immediately processed.
• Agroforestry site had very clear distinctions in forest floor between different species, ranging from chaotic weeds (cherry/sycamore) to bare and covered in shells (hazelnut). Hypothesis: different tree types result in different soil parameters.

FiBL

• Soils were collected from two sites: the FibL DOK trials at Therwil south of Basel (40-yr old conventional vs organic trials), and Landqart (alpine valley on upper Rhine), due to a lack of native alpine vegetation and abandoned land near the DOK trials.
• Basel (DOK) had samples for Native (forest), pasture (not grazed?), and two types of wheat (pure mineral fertilizer, and mineral fertilizer with manure).
• Basel (DOK) had flat land where the DOK trials were (valley bottom), but adjacent pasture and native forest was on the side of a hill. No water sources at the DOK trial itself, but streambed ran through the forest and near pasture. The trials grew a fixed 40-yr rotation that includes maize, soybean, green manure, potatoes, winter wheat, and ‘artificial alpine prairie’; I only sampled the 2022 wheat plots. Forest was (partly mature) deciduous, but an obvious fragment with a high water table in parts. It was not clear if pasture was grazed.
• Landqart had samples for Native (forest), abandoned/native alpine meadow, pasture (grazed), and wheat.
• Landqart had slightly rolling flat land, with the exception of the abandoned/native alpine meadow, which was all on small hillocks. Water sources not evident except drainage ditches near forest. Forest was a mixture of coniferous and deciduous trees of mixed maturity (some young, some old). Pasture was lush and grazed by horses and sheep. To the best of my knowledge, only wheat grew in the fields. Abandoned/native alpine meadow was ungrazed and unmowed to allow for pollinator sanctuary, and had very obvious insect presence.
• Soil at Basel (DOK) was loess; soil at Landqart was alluvial Rhine River or eroded Alp mountain, and was rockier, and much more influenced by the close presence of the alps.
• Forest was fragmented generally, but had more conifers than UK or Ireland. I would have had to go up into the mountains to find large, ‘pure’ forest.
• Substantial published data exists on the DOK trials.
• Sampling was performed in each location within one day, but refrigeration had to occur before processing.

LUKE, Finland

• Soils were collected from a single site near Maaninka, Finland (near Kuopio). It was within 100 metres of a lake, and was a mineral soil converted from forest.
• Samples were taken for wheat, pasture (non-grazed), abandoned farmland (forested birch), and forest (4 reps due to high diversity of tree types).
• The land gently sloped in the wheat field towards the lake, but was mostly flat in the pasture. The pasture had a mixture of forbs, primarily clover and a grass (timothy?) and did not appear grazed, while the wheat field was uniform wheat. The forested areas were completely flat, but had some ditches along field edges. Forest canopy was broken by different sorts of trees in different stages of growth (e.g. birch, scots pine, etc.), as well as a road. Abandoned land (mostly very young <20 yr-old birch) was highly sloped and closest to the lake, and was bisected by multiple small dry streams.
• Overall land patterns near Maaninka featured patchy farmland on different types of soil interspersed with living forest. This contrasted strongly with England/Ireland/Saskatoon’s large stretches of mostly unbroken farmland.
• A highway was adjacent to the edge of the Abandoned, Wheat, and Pasture portions, as well as some of the Forest.
• Substantial data should exist from an eddy covariance tower in the pasture field.
• Samples were taken in one day and refrigerated before processing (LUKE ran samples for N analysis) by Semberg Sanni (LUKE).
• Soil texture appeared to be mostly silty with some clay (loam?).
• Abandoned samples taken on a local farmer’s land with permission; the rest were LUKE or associated farmer research sites.

Mongolia

• Soils were collected from two very distinct geographical locations: in the province of Dornod (Дорнод) near Choibalsan (Чойбалсан) (far eastern decaying agricultural region), and in the province of Selenge (Сэлэнгэ) near Darkhan (Дархан) and south of Khutul (Хөтөл) (northern major agricultural region).
• Dornod had samples for wheat (both from steppe and from high clay riverbottom), native steppe/prairie, converted steppe/prairie pasture (alfalfa), and abandoned steppe/prairie farmland.
• Dornod had mostly flat land with sudden drops to local rivers or waterways with significant erosion, as well as small lakes and ponds spread at random in the landscape. Steppe was considered overgrazed by Dr. Anaarma Sharkhuu and contained a mixture of various native plants. All but the wheat samples were on formerly irrigated agricultural land during the Soviet era (pre-1990), but abandoned since then and reverting to native steppe (alfalfa ‘pasture’ was part of this). The only exception was the river bottom land (wheat), which has been continuously farmed/irrigated since at least 1985.
• Darkhan had samples for wheat, native steppe/prairie, overgrazed pasture, and various forms of tillage/herbicides for weed management, as well as some native forest.
• Darkhan had rolling land with some elevation (many hillocks with flat or gently rolling valleys in-between) and much less erosion. Most crops nearby were rapeseed/canola and wheat. According to Dr. Sharkhuu, this breadbasket has a ‘weather dome’ effect that causes the highest temperatures in summer (usually >40C) and the lowest in winter (< -40C) compared to the rest of Mongolia. Steppe was clearly overgrazed, while agricultural plots appeared productive and uniform in stand density. Forests were only found on north-facing hills/mountains, and had mostly deciduous (birch) trees with some coniferous and a lush undergrowth of various forbs and berries. Some plots were experimental plots for long-term tracking of C cycling in soil in conjunction with some German institutions.
• Soil texture at the Dornod location had wide range between sandy and loess (steppes), and heavy clay (wheat). Soil at the Darkhan location was loess with less variation.
• Forest was very location-dependent; as per various Mongolian scientists, the extra radiation on south-facing slopes causes irreversible melting of permafrost and permanent transition from forest to steppe, hence, all forests were north-facing, but rich in understorey biodiversity (e.g. berries, vines, etc.).
• Dornod samples (excepting native steppe/prairie and wheat) were taken at the Northeast Asian Environmental and Agricultural Research Centre, with alfalfa taken from their alfalfa trials. Darkhan sites were mixture of local farmer fields and local scientist research plots.
• Sampling was performed over multiple days, with samples experiencing a delay at higher temperatures (minimum 24 hours) prior to refrigeration. This was impossible to avoid as the samples were taken in remote locations from the ‘home base’ of Ulaanbaatar (4-12 hours distant).

New Zealand

• Soils were collected from two distinct locations on South Island: farms in the Canterbury Plains west of Christchurch (pasture and wheat), and the Hinewai Reserve on the Akaroa Peninsula south of Christchurch (converted and native forest). Additionally, samples were graciously donated by Dr. Paul Mudge (Landcare Research Hamilton) from his published project, Changes in soil C, N and d15N along three forest–pasture chronosequences in New Zealand, as North Island.volcanic soils representing a chronosequence to be analyzed for soil respiration and other abiotic parameters.
• Canterbury farms were sampled for Pasture (grazed) and Wheat at two separate farms (Phoenix Farm and Lill Farm).
• Canterbury locations were mostly flat and irrigated on similar soils. Sometimes roads run between the pasture and wheat fields. Pasture appeared to be italian ryegrass.
• Hinewai was sampled for Natural (old growth kanuka forest) and partly abandoned Pasture (converted forest). Samples were not able to be taken for true abandoned.
• Hinewai was at the top of an old volcanic caldera, with sudden drops in elevation from the top. Samples were only taken from relatively flat and even sections however. Pasture was mixed grasses and weeds, while Forest was 140 yr old (?) and centered around the Kanuka tree.
• Dr. Mudge samples were taken from a chronosequence of different soils representing a gradient from natural New Zealand forest to pine plantation to differing ages of dairy farm near Tokoroa (converted from pine plantation 2, 5, 40, and 50 yr prior to sampling).
• Dr. Mudge samples were taken from mature forest, pine monoculture plantation, and dairy pastures dominated by white clover and ryegrass. The landscape was relatively level due to terracing.
• Soil texture was “Templeton” class (Canterbury), a silty loam, and “firm brown” Akaroa yellow brown loess (Hinewai) overlying volcanic material. North Island samples were volcanic in origin (“Taupo Pumice” class).
• The Hinewai Reserve was at one time completely converted to agriculture with a few patches of old forest. Hugh Wilson, the head of the Reserve, has worked for thirty years on regenerating the forest, specializing in successfully transitioning pasture to gorse to forest.
• Farms were associated with Landcare Institute (both North and South Island), while Hinewai is an independent Reserve focusing on forest regeneration.
• Sampling was performed within a single day at each location by Landcare Research Lincoln, and was refrigerated immediately and processed. Dr. Mudge samples were dried and sieved to 2mm when originally processed; details found in original paper.

Alaska

• Soils were collected from different farms near Delta Junction, Alaska. They were from mineral soils dominated by black spruce, converted to agriculture.
• Samples were taken for wheat, barley no-till, barley rotated with cover crop no-till, cover crop only no-till, barley conventional tillage, pasture (grazed), forest, and abandoned farmland.
• The land was mostly flat with some slopes in one forest location and gentle sloping in abandoned paddock. All converted land was converted using traditional Alaskan conversion (burning plant stumps and litter in field), which meant the soil has a substantial portion of biochar as well as extra-fertile ‘veins’ of high C from the burning. Forest was dominated by black spruce and mosses/lichens, with some birch. Abandoned land had fireweed and small succession trees and shrubs.
• All farmland had forest hedges between fields, which meant that the land pattern was somewhat broken up.
• Many local farmers were experimenting with no-till, but the wheat field selected was conventionally tilled to match other site locations. Most grain grown was, however, barley.
• Roads bordered almost all fields, but fields were very large.
• Pasture was grazed, but the first pasture replicate appeared to be overgrazed compared to the second and third.
• Samples were taken in one day and refrigerated, but had days before drying/processing.
• Soil texture appeared to be pure loess in all cases with some organic components from forest trees.
• Farms were sampled with the help of Phil Kaspari (Alaska Extension) and with the input of local farmer and SWCD agent Bryce Wrigley. Farms sampled were those of Phil Kaspari, Bryce Wrigley, Bob Green, and Scott Schultz.

Saskatchewan

• Soils were mostly collected from the family farm of Dr. Jeff Schoenau (University of Saskatchewan), near Central Butte, Saskatchewan (southwest of Saskatoon). They are from drier (‘brown prairie’) soils converted to agriculture. Additionally, some forest soils were gathered from spots north of Saskatoon at the prairie/forest transition.
• Samples taken at Central Butte included 100 yr annually cropped, 30 year abandoned cropland,. native prairie/steppe, native prairie-adjacent field (grazed), shelterbelt, and cattle feeding area. Additionally, wheat samples were gathered by a graduate student earlier in the year who kindly provided subsamples to me .
• The land was mostly flat with some depressions (knob/kettle glacial till topography, i.e. small dips and rises in the landscape). Prairie had typical native vegetation, cropland had winter cover, cattle feeding area had high concentrations of forage (grain) and manure. Shelterbelt had small trees/shrubs.
• Samples were taken within one day and refrigerated, but not processed for a few days.
• Soil was glacial till (brown Chernozem) for the Central Butte farm, unknown for the wheat (but likely similar), and Orthic grey and black for the forest soils (Luvisols). Texture is unknown, but seems like loess or silt.
• Farms were sampled with the help of Dr. Ryan Hangs and Dr. Jeff Schoenau (Central Butte), an unknown graduate student (wheat), and Dr. Joel Ens, Dr. Ken Van Rees, and Lyle Cowell (forest), all associated with the University of Saskatchewan.

Quebec

• Soils were collected at the Morgan Arboretum of McGill University (MacDonald Campus), near Montreal Quebec. This was due to the end of the season as well as distance to farms (logistics).
• Samples were focused on species-related effects and chronosequences, and included 200 yr old Maple, 200 yr Maple cut and replanted as maple (20 yrs old), 60 yr black walnut, 60 yr larch, 60 yr cedar, 60 yr wild ‘pasture’ (not mowed), and 60 yr arable (variable crop agriculture or grasses).
• The land had minor variable elevation with streams criss-crossing it, but mostly flat in the sampled areas (both maples excepting). Forest appeared to be mature as expected for 60+ yr old plots, with very limited understorey growth (even the 20yr maple was limited, though not as much as the rest). Pasture had diverse mixture of species of grass, forbs, etc., and was noted for being a refuge for endangered ground-nesting birds and insects. Walnut and larch plots had almost no plants in understoreys, maples and cedars had many, especially cedars. Arable appeared to be growing grasses of some kind this year.
• Drainage ditches bordered the larch and cedar plots, and streams were present in the 200yr maple plot. Small walking trails bordered all plots and were very close to the walnut plots (which were smaller and had a high edge effect).
• Samples were taken in one day, refrigerated, and dried almost immediately.
• Sample texture appeared to be high in clay, possibly a clay loam; this might indicate riverbottom clay similar to Mongolian Dornod wheat samples, especially given close proximity to the Lac des Deux Montagnes. Arboretum director noted that the Arboretum had been converted to agriculture over a century ago, but was abandoned due to difficulty in working the land (possible clay-related?).

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