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Decoupling between Plant Productivity and Growing Season Length under a Warming Climate in Canada’s Arctic

American Journal of Climate Change 2016年第3期5卷 334-359页

作者： Wenjun Chen Paul Zorn Lori White Ian Olthof Yu Zhang Robert Fraser sylvain leblanc Canada Centre for Remote Sensing Natural Resources Canada Ottawa Canada Parks Canada Agency Gatineau Canada Wildlife Landscape Science Directorate Environment Canada Ottawa Canada

Given the short duration of growing season in the Arctic, a strong correlation between plant productivity and growing season length (GSL) is conventionally assumed. Will this assumption hold true under a warming climate? In this study, we addressed the question by investigating the relationship between net primary productivity of leaves (NPPleaf) and GSL for various tundra ecosystems. We quantified NPPleaf and GSL using long-term satellite data and field measurements. Our results indicated that the relationship was not significant (i.e., decoupled) for 44% to 64% of tundra classes in the southern Canadian Arctic, but significant for all classes in the northern Canadian Arctic. To better understand the causes of the decoupling, we further decomposed the relationship into two components: the correspondence of interannual variations and the agreement of long- term trends. We found that the longer the mean GSL for a tundra class, the poorer the correspondence between their interannual variations. Soil moisture limitation further decoupled the relationship by deteriorating the agreement of long-term trends. Consequently, the decoupling between NPPleaf and GSL would be more likely to occur under a warming climate if the tundra class had a mean GSL > 116 (or 123) days with a dry (or moist) soil moisture regime.

关键词： Net Primary Productivity Growing Season Length Arctic Tundra Decoupling Remote Sensing Soil Moisture Regime

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Does Dust from Arctic Mines Affect Caribou Forage?

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Journal of Environmental Protection 2017年第3期8卷 258-276页

作者： Wenjun Chen sylvain G. leblanc H. Peter White Christian Prevost Brian Milakovic Christine Rock Greg Sharam Harry O’Keefe Laura Corey Bruno Croft Anne Gunn Sjoerd van der Wielen Adeline Football Boyan Tracz Jody Snortland Pellissey John Boulanger Canada Centre for Remote Sensing Natural Resources Canada Ottawa Canada ERM Environmental Ressources Management Vancouver Canada Dominion Diamond Ekati Corporation Yellowknife Canada Environment and Natural Resources GNWT Yellowknife Canada Circum Arctic Rangifer Monitoring and Assessment Network Salt Spring Island Canada Tlicho Government Behchoko NT Canada Wek’èezhìi Renewable Resources Board Yellowknife Canada Integrated Ecological Research Ltd. Nelson Canada

This study explores how dust from the Ekati Diamond Mine potentially affects the availability and quality of forage on the seasonal range of the Bathurst caribou herd. Understanding the effects of dust as a source of disturbance is important because the Bathurst caribou population has declined by 93% since the middle 1980s and there are reports that caribou in general may avoid mining projects. There are several challenges for quantifying dust impacts: 1) Natural variations (e.g., topography, natural disturbance, and soil pH) may also impact forage availability and quality for caribou. To minimize their masking effect, we stratified survey sites into seven land cover classes and selected the most populous class (i.e., the dwarf shrub) for assessing the impact. 2) Within class variation (e.g., the proportion of area covered by rocks where vascular plants and lichen do not grow) can further skew the analysis. We eliminated this problem by examining only the area not covered by rocks. 3) Coarse and fine suspended particulates have different spatial coverages, chemical compositions, and pH values. Consequently, their impacts on caribou forage can be different. To distinguish their impacts, we sampled two areas: transects from the Misery Haul Road that has been in active use vs. those from a rarely used spur road outside the Misery Camp. We sampled percent vegetation cover, soil pH, and dust on leaves along these transects during the summers of 2015 and 2016. Our results indicated that the amount of dust on leaves in a zone of ~1000 m from the Misery Haul Road was 3 - 9 times than that of background sites. The zone of reduced lichen percent cover was also about 1000 m. In contrast, these road dust-induced changes in caribou forage were not observed for the dust-free transect from the spur road.

关键词： Mining Arctic Caribou Habitat Road Dust PM2.5 Vegetation Cover Lichen Soil pH Dust Deposition

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