Twenty-Five Year Record of Changes in Plant Cover on Tundra of Northeastern Alaska

Abstract

Northern Alaska has warmed over recent decades and satellite data indicate that vegetation productivity has increased. To document vegetation changes in the Arctic National Wildlife Refuge, we monitored plant cover at 27 plots between 1984 and 2009. These are among the oldest permanently marked and continuously monitored vegetation plots in the Arctic. We quantified percent cover of all plant species by line-point intercept sampling and assessed change over time for seven plant growth forms. Cover of bryophytes and deciduous shrubs showed slight decreasing trends. Evergreen shrubs, horsetails, and depth of thawed soil above permafrost had no trends. For lichens, graminoids, and forbs, trends varied by plant community type. Overall, vegetation in the plots changed little over the study period, in contrast to results from other studies in northern Alaska. A few plots had dramatic changes, however, which we attributed to subsidence from melting ground ice or to floodplain dynamics. Our results demonstrate that vegetation change on the Arctic Refuge coastal plain over the past quarter century has been spatially heterogeneous and facilitated by disturbance. The findings highlight the need for greater work linking plotlevel and regional remote sensing measurements of change.

NDVI exhibits mixed success in predicting spatiotemporal variation in caribou summer forage quality and quantity

“…S1), we suspect that long-term trends would be difficult to detect without regular sampling. Our projected patterns of forage biomass also did not mirror results from other studies that have quantified long-term increases in plant productivity in the Arctic, particularly for shrubs (Hill and Henry 2011, Elmendorf et al 2012, Fraser et al 2014, but see Jorgenson et al 2015). This difference likely stems in part from the relatively short duration of our study (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) compared to investigations evaluating vegetation trends since the 1980s.…”

“…Because our predicted values of N exhibited so much interannual variation ( Fig. Our projected patterns of forage biomass also did not mirror results from other studies that have quantified long-term increases in plant productivity in the Arctic, particularly for shrubs (Hill and Henry 2011, Elmendorf et al 2012, Fraser et al 2014, but see Jorgenson et al 2015). S1), we suspect that long-term trends would be difficult to detect without regular sampling.…”

A gradient of nutrient enrichment reveals nonlinear impacts of fertilization on Arctic plant diversity and ecosystem function

“…Given the short growing season and the large abundance of perennial and evergreen species with conservative growth strategies in this system (Bliss & Petersen, ) plant communities likely shift slowly, rather than abruptly, in response to environmental change and resource availability (Camill & Clark, ; Dormann & Woodin, ). In addition, previous work in this region has shown that plant percent cover in this system is unlikely to change over short (e.g., <5 years) temporal scales (Jorgenson, Raynolds, Reynolds, & Benson, ).…”

Eighteen years of ecological monitoring reveals multiple lines of evidence for tundra vegetation change

“…) concurrent with evidence of increasing thermokarst disturbances in the western Arctic (Lantz and Kokelj , Jorgenson et al. , Segal et al. , Kokelj et al.…”