Abstract
Vegetation properties of arctic tundra vary dramatically across its full latitudinal extent, yet few studies have quantified tundra ecosystem properties across latitudinal gradients with field-based observations that can be related to remotely sensed proxies. Here we present data from field sampling of six locations along the Eurasia Arctic Transect in northwestern Siberia. We collected data on the aboveground vegetation biomass, the normalized difference vegetation index (NDVI), and the leaf area index (LAI) for both sandy and loamy soil types, and analyzed their spatial patterns. Aboveground biomass, NDVI, and LAI all increased with increasing summer warmth index (SWI—sum of monthly mean temperatures > 0 °C), although functions differed, as did sandy vs. loamy sites. Shrub biomass increased non-linearly with SWI, although shrub type biomass diverged with soil texture in the southernmost locations, with greater evergreen shrub biomass on sandy sites, and greater deciduous shrub biomass on loamy sites. Moss biomass peaked in the center of the gradient, whereas lichen biomass generally increased with SWI. Total aboveground biomass varied by two orders of magnitude, and shrubs increased from 0 g m−2 at the northernmost sites to >500 g m−2 at the forest-tundra ecotone. Current observations and estimates of increases in total aboveground and shrub biomass with climate warming in the Arctic fall short of what would represent a ‘subzonal shift’ based on our spatial data. Non-vascular (moss and lichen) biomass is a dominant component (>90% of the photosynthetic biomass) of the vegetation across the full extent of arctic tundra, and should continue to be recognized as crucial for Earth system modeling. This study is one of only a few that present data on tundra vegetation across the temperature extent of the biome, providing (a) key links to satellite-based vegetation indices, (b) baseline field-data for ecosystem change studies, and (c) context for the ongoing changes in arctic tundra vegetation.
Highlights
The variation in arctic tundra vegetation along geographical gradients has historically been observed and documented by numerous international scientists for the regions that compose the circumpolar Arctic (e.g. Alexandrova 1970, 1980, Young 1971, Yurtsev et al 1978, Tikhomirov et al 1981, Matveyeva 1994, 1998, Yurtsev 1994, Razzhivin 1999)
Total aboveground biomass varied by two orders of magnitude, and shrubs increased from 0 g m−2 at the northernmost sites to >500 g m−2 at the forest-tundra ecotone
Strong relationships have been developed between the satellite-derived normalized difference vegetation index (NDVI) and total aboveground arctic tundra biomass for both North American and Eurasian ecosystems (Walker et al 2011b, Raynolds et al 2012), few studies have linked satellite data to particular components of tundra vegetation biomass or cover (Fraser et al 2014, Frost et al 2014, Berner et al 2018)
Summary
The variation in arctic tundra vegetation along geographical gradients has historically been observed and documented by numerous international scientists for the regions that compose the circumpolar Arctic (e.g. Alexandrova 1970, 1980, Young 1971, Yurtsev et al 1978, Tikhomirov et al 1981, Matveyeva 1994, 1998, Yurtsev 1994, Razzhivin 1999). Building on these assessments of broad spatial patterns in arctic vegetation, a methodology for examining the effects of climate variables on ecosystem properties is to utilize geographic transects (e.g. latitude) that exhibit spatial variability in one specific climatic variable, yet hold other environmental conditions relatively constant. Strong relationships have been developed between the satellite-derived normalized difference vegetation index (NDVI) and total aboveground arctic tundra biomass for both North American and Eurasian ecosystems (Walker et al 2011b, Raynolds et al 2012), few studies have linked satellite data to particular components of tundra vegetation biomass or cover (Fraser et al 2014, Frost et al 2014, Berner et al 2018)
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