Interpretations of climate change on grazing systems: the comparison of Arctic and Subarctic carex

Abstract

Stresses imposed by climate change are altering arctic and subarctic ecosystem structure and function. On the Yukon-Kuskokwim River Delta (YKD) in subarctic western Alaska, Pacific Black Brant geese (Branta bernicla nigricans) are losing their available grazing lawns of shortstatured Carex subspathacea due to its conversion into a taller, less nutritious growth form. However, C. subspathacea on Alaska's Arctic Coastal Plain (ACP) grows in extensive lawns that remain short even when ungrazed. Our goal was to compare the growth responses between arctic C. subspathacea and subarctic C. subspathacea when grown in arctic and subarctic conditions. We used reciprocal common gardens to study the variation in height, tiller density, aboveground biomass, and green leaf nitrogen percentage between these reputed taxa. We explored the growth responses that occur in C. subspathacea when grown in the arctic and subarctic using linear mixed effect models. We found that environmental differences between these regions influence the morphology of these taxa. Subarctic C. subspathacea is phenotypically plastic, and was able to grow tall in subarctic conditions, while remaining short in the Arctic. However, arctic C. subspathacea was short in both gardens, suggesting arctic C. subspathacea will not grow tall under warming conditions. Understanding the functional causes of the difference between these two grazing systems is important for predicting the effects of future climate change on both regions. This study provides insight to how changing climate will impact these different growth forms and affect future grazing dynamics along arctic and subarctic coasts.