**4. Conclusions**

Aboveground biomass was measured at 43 sites in the summer of 2004 along the Dempster Highway, which goes through the winter and summer ranges of the Porcupine caribou habitat. The measured aboveground biomass ranged 10-100 t ha-1 for sparsely forested woodlands, 1-100 t ha-1 for the low-high shrub sites, and 0.5-10 t ha-1 for mixed graminoidsdwarf shrub-herb sites.

Bathurst caribou calving ground, in comparison with 460 g m-2 for the Porcupine caribou calving ground. Of the 63 g m-2 forage over the Bathurst caribou calving ground, 33 g m-2 was lichen and moss, 14 g m-2 was stand dead, and only 16 g m-2 was vascular biomass. On the contrast for the Porcupine caribou calving ground, 50 g m-2 was lichen and moss, 250 g m-2 was stand dead, and 160 g m-2 was vascular biomass. The live biomass over the Porcupine calving ground was 10 time that over the Bathurst calving ground. In addition, the high value of stand dead over the Porcupine calving ground also suggest the high foliage biomass value over previous years. The difference in calving ground foliage biomass collaborates well with the fact that cows of the Bathurst herd leave calving ground soon after giving birth while those of Porcupine herd stay for a much longer period (Griffith et

calving ground (g m-2) 63 - 106 17 - 94 This study, Chen et al.

calving ground (g m-2) <sup>78</sup> <sup>24</sup> This study, Chen et al.

summer range (g m-2) 14 – 198 17 - 267 This study, Chen et al.

summer range (g m-2) <sup>69</sup> <sup>43</sup> This study, Chen et al.

Milk production (l d-1) 2.02 1.09 – 1.79 Griffith et al. (2001) Calve growth rate (g d-2) 493 150 - 407 Griffith et al. (2001) Cow body weight range (kg) 83 - 96 66 - 78 Griffith et al. (2001)

The difference in calving ground forage availability, in turn, results in difference in caribou biological measures (Table 5). For example, the body weights of Porcupine cows are about 20% higher than that of Bathurst herd (Griffith et al., 2001). The Bathurst cow milk production was 1.09 – 1.79 liter per day, against 2.02 liter per day by an average Porcupine caribou cow, with the corresponding calve growth rate being 150 -407 gram per day for the Bathurst herd against 493 gram per day for that of the Porcupine herd

Aboveground biomass was measured at 43 sites in the summer of 2004 along the Dempster Highway, which goes through the winter and summer ranges of the Porcupine caribou habitat. The measured aboveground biomass ranged 10-100 t ha-1 for sparsely forested woodlands, 1-100 t ha-1 for the low-high shrub sites, and 0.5-10 t ha-1 for mixed graminoids-

Table 5. Comparison of measured and area-averaged foliage biomass values between Porcupine caribou habitat and Bathurst caribou habitat. The area-averaged values were calculated from the circa 2000 baseline foliage biomass maps. Field measurement of foliage biomass over the Bathurst caribou habitat was conducted during the summer of 2005 (Chen et al., 2011). Also included in the comparison are cow milk production, calve growth rate,

Porcupine Bathurst *Data sources* 

(2011)

(2011)

(2011)

(2011)

al., 2001).

Measured foliage biomass,

Measured foliage biomass,

and cow body weight.

(Table 5).

**4. Conclusions** 

dwarf shrub-herb sites.

Area-averaged foliage biomass,

Area-averaged foliage biomass,

Foliage biomass was measured at 10 non-forested sites along the Dempster Highway in the summer of 2006, and again in the summer of 2008 at 11 non-forested sites in the Ivvavik National Park located at northern tip of Yukon, which overlaps with the calving ground and summer range of the Porcupine caribou herd. The measured foliage biomass ranged 0.95-2 t ha-1 for low-high shrub sites, 0.38-0.92 t ha-1 for mixed graminoids-dwarf shrub-herb sites, 0.63-1.06 t ha-1 for coastal tussock sites, and < 0.2 t ha-1 for hill-top rock lichen sites.

When all data points were pooled together, the best relationship between aboveground biomass and remote sensing data was found to be with the combination of JERS-1 backscatter and Landsat B4/B5, with *r*2 = 0.72. Validation using aboveground biomass measurements at foliage biomass measurement sites gives similar result, with the slope = 0.91, *r*2 = 0.90, and *SEE* = 1.5 t h-1 over measured aboveground biomass range from 0 to 18.16 t h-1. Similar validation results were obtained using aboveground biomass measurements at 33 sites around Yellowknife, Northwest Territories, and Lupin Gold Mine, Nunavut Territories in a previous study (Chen et al., 2009a), with *r*2 = 0.81, slope =1.17, and *SEE* = 9.67 t h-1 over measured aboveground biomass range from 0.9 to 103.3 t h-1.

For the foliage biomass, the Landsat-based simple ration gives the best fit, with *r*2 = 0.81, *SEE* = 20.6 g m-2, *F*= 81, *P* = 2.7×10-8, and *n* = 21.

Appling these relationships to the mosaic of Landsat and JERS-1 images covering the entire Porcupine caribou habitat, we produced baseline maps of aboveground biomass and foliage biomass for the Porcupine caribou habitat. The foliage biomass map reveals that on average the amount of seasonal peak foliage biomass in the calving ground of the Porcupine caribou herd was similar to that in the summer range, and was even higher if only the concentrated calving ground over the Northern Alaska and Yukon coastal plain is concerned. To the contrast, the average seasonal peak foliage biomass in the calving ground of the Bathurst caribou herd was much lower than that in the summer range during the same time period. The difference in calving ground foliage biomass collaborates well with the fact that cows of the Bathurst herd leave calving ground soon after giving birth while those of Porcupine herd stay for a much longer period, which in turn partially explain why the Porcupine caribou calves can have several times higher growth rate and the body weights of Porcupine cows are about 20% higher than that of Bathurst herd.

It should be emphasized, however, that assessment of the impacts of climate change on the Porcupine caribou habitat requires integration of various information sources from remote sensing products, climate records, and other relevant tempo-spatial data. Furthermore, there are many other factors besides the habitat, such as harvest, predators, diseases/parasites, industrial development, extreme weather events, climate change, and pollution, may influence the abundance of a caribou herd. Therefore, this work is just one of the first steps towards informed and proper decision-making that balances the needs of caribou habitat protection and industrial development under a global change environment.
