ALBERT

Description: Recent Pan-Arctic shrub expansion has been interpreted as a response to a warmer climate. However, herbivores can also influence the abundance of shrubs in arctic ecosystems. We addressed these alternative explanations by following the changes in plant community composition during the last 10 years in permanent plots inside and outside exclosures with different mesh sizes that exclude either only reindeer or all mammalian herbivores including voles and lemmings. The exclosures were replicated at three forest and tundra sites at four different locations along a climatic gradient (oceanic to continental) in northern Fennoscandia. Since the last 10 years have been exceptionally warm, we could study how warming has influenced the vegetation in different grazing treatments. Our results show that the abundance of the dominant shrub, Betula nana, has increased during the last decade, but that the increase was more pronounced when herbivores were excluded. Reindeer have the largest effect on shrubs in tundra, while voles and lemmings have a larger effect in the forest. The positive relationship between annual mean temperature and shrub growth in the absence of herbivores and the lack of relationships in grazed controls is another indication that shrub abundance is controlled by an interaction between herbivores and climate. In addition to their effects on taller shrubs (〉 0.3 m), reindeer reduced the abundance of lichens, whereas microtine rodents reduced the abundance of dwarf shrubs (〈 0.3 m) and mosses. In contrast to short-term responses, competitive interactions between dwarf shrubs and lichens were evident in the long term. These results show that herbivores have to be considered in order to understand how a changing climate will influence tundra ecosystems.

Description: These data originate from 11 soil profiles sampled in northern Finland in September 2020 as part of the PeCHEc project. 8 sites were sampled on the Kutuharjue Field Research Station, a reindeer research station run by the Reindeer Herders' Association of Finland. Additional 3 sites were collected in the area around the station in the Muotkatunturi reindeer herding district as reference sites for the different landscape types found. In total, 5 sites with mineral soil (profiles with fixed volume cylinders) and 6 sites with peat (peat corer) were sampled in tundra, grassland and birch forest landscapes, covering a range of 5 different reindeer grazing intensities: a) exclosure site with no grazing (intensity 1), b) occassional migration route (intensity 2), c) regular migration route (intensity 3), d) frequent migration route (intensity 4), e) pasture (intensity 5). Analysis took place at the facilities of AWI between October 2020 and August 2021. All samples taken from the cores were analyzed for water content, bulk density, TOC, TN and δ13C. Additional radiocarbon measurements were done for selected samples of all sites. For mineral soil samples, both from mineral soil sites as well as from the bottom of the peat cores, grain size composition was determined. TC and TN were measured at AWI Potsdam CARLA Laboratory using a vario EL III Element Analyzer. TOC was measured at the same laboratory using a varioMAX C Element Analyzer. δ13C was measured at AWI Potsdam Stable Isotope Laboratory using a Delta V Advantage Isotope Ratio MS supplement equipped with a Flash 2000 Organic Elemental Analyzer. Grain size composition was determined using a Malvern Mastersizer 3000 equipped with a Malvern Hydro LV wet-sample dispersion unit. Statistics were calculated for this using Gradistat 8.0. Radiocarbon dating was carried out using the Mini Carbon Dating System (MICADAS) at AWI Bremerhaven.

Description: These data originate from 10 soil profiles sampled in northern Finland in June 2022 as part of the PeCHEc project. All sites were sampled on the Kutuharju Field Research Station, a reindeer research station run by the Reindeer Herders' Association of Finland. 8 sites are located on the reindeer winter ranges, while 1 site (S-2P) located on the reindeer summer ranges. 1 site (E-1M-B) is a reindeer exclosure site. In total, 5 sites with mineral soil (profiles with fixed volume cylinders) and 5 sites with peat (peat corer) were sampled in tundra, grassland and birch forest landscapes, covering a range of 5 different reindeer grazing intensities: - exclosure site with no grazing (intensity 1) - occassional migration route (intensity 2) - regular migration route (intensity 3) - frequent migration route (intensity 4) - pasture / supplementary feeding site (intensity 5). Analysis took place at the facilities of AWI between July and October 2022. All samples taken from the cores were analyzed for TOC, TN, δ13C and THg (total mercury). TN was measured at AWI Potsdam CARLA Laboratory using a rapidMAX N Element Analyzer. TOC was measured at the same laboratory using a soliTOC cube Element Analyzer. δ13C was measured at AWI Potsdam Stable Isotope Laboratory and GFZ Potsdam Stable Isotope Laboratory using Delta V Advantage Isotope Ratio MS supplements equipped with Flash 2000 Organic Elemental Analyzers. THg was determined using a DMA-80 evo Direct Mercury Analyzer.

Description: These data originate from 10 soil profiles sampled in northern Finland in June 2022 as part of the PeCHEc project. All sites were sampled on the Kutuharju Field Research Station, a reindeer research station run by the Reindeer Herders' Association of Finland. 8 sites are located on the reindeer winter ranges, while 1 site (S-2P) located on the reindeer summer ranges. 1 site (E-1M-B) is a reindeer exclosure site. In total, 5 sites with mineral soil (profiles with fixed volume cylinders) and 5 sites with peat (peat corer) were sampled in tundra, grassland and birch forest landscapes, covering a range of 5 different reindeer grazing intensities: - exclosure site with no grazing (intensity 1) - occassional migration route (intensity 2) - regular migration route (intensity 3) - frequent migration route (intensity 4) - pasture / supplementary feeding site (intensity 5). Analysis took place at the facilities of AWI between July and October 2022. All samples taken from the cores were analyzed for water content, bulk density, TOC, TN, δ13C and THg (total mercury). Additional radiocarbon measurements were done for selected samples. For mineral soil samples, both from mineral soil sites as well as from the bottom of the peat cores, grain size composition was determined. TN was measured at AWI Potsdam CARLA Laboratory using a rapidMAX N Element Analyzer. TOC was measured at the same laboratory using a soliTOC cube Element Analyzer. δ13C was measured at AWI Potsdam Stable Isotope Laboratory and GFZ Potsdam Stable Isotope Laboratory using Delta V Advantage Isotope Ratio MS supplements equipped with Flash 2000 Organic Elemental Analyzers. THg was determined using a DMA-80 evo Direct Mercury Analyzer. Grain size composition was determined using a Malvern Mastersizer 3000 equipped with a Malvern Hydro LV wet-sample dispersion unit. Statistics were calculated for this using Gradistat 8.0. Radiocarbon dating was carried out using the Mini Carbon Dating System (MICADAS) at AWI Bremerhaven.

Description: These data originate from 10 soil profiles sampled in northern Finland in June 2022 as part of the PeCHEc project. All sites were sampled on the Kutuharju Field Research Station, a reindeer research station run by the Reindeer Herders' Association of Finland. 8 sites are located on the reindeer winter ranges, while 1 site (S-2P) located on the reindeer summer ranges. 1 site (E-1M-B) is a reindeer exclosure site. In total, 5 sites with mineral soil (profiles with fixed volume cylinders) and 5 sites with peat (peat corer) were sampled in tundra, grassland and birch forest landscapes, covering a range of 5 different reindeer grazing intensities: - exclosure site with no grazing (intensity 1) - occassional migration route (intensity 2) - regular migration route (intensity 3) - frequent migration route (intensity 4) - pasture / supplementary feeding site (intensity 5). Analysis took place at the facilities of AWI between July and October 2022. All samples taken from the cores were analyzed for water content and bulk density. For mineral soil samples, both from mineral soil sites as well as from the bottom of the peat cores, grain size composition was determined. Grain size composition was determined using a Malvern Mastersizer 3000 equipped with a Malvern Hydro LV wet-sample dispersion unit. Statistics were calculated for this using Gradistat 8.0.