**3.4. Relationships between foliage biomass and remote sensing indices**

As shown in Table 4, the Landsat-based *SR* can explain 81% variations in measured foliage biomass within the Porcupine caribou habitat. The explanation power of other Landsatbased indices in the descending order is 76% for the ratio of B4/B5, 71% for SWVI, and 67% for NDVI. Single band reflectance of Landsat has lower power of explanation.


Table 4. Correlation coefficients (*r*), coefficient of determination (*r*2), and standard estimation error (*SEE*, in g m-2) between foliage biomass (*Bf*) and remote sensing signals for foliage biomass measured at the 21 sites along the Dempster Highway in 2006 and in the Ivvavik National Park in 2008. Remote sensing indices include Landsat red band reflectance (B3), near-infrared band reflectance (B4), shortwave infrared band reflectance (B5), ratio of B4/B5, simple ratio (SR = B4/B3), normalized differential vegetation index (NDVI = (B4 - B3)/(B4 + B3)), and shortwave vegetation index (SWVI = (B4 - B5)/(B4 + B5)).

In comparison with results for aboveground biomass shown in Table 3, Landsat-based vegetation indices have a much improved power of explanation for foliage biomass (Table 4). This is in good agreement with the fact that optical sensors mainly capture canopy information, thus the optical sensor data are more suitable for estimation of canopy parameters such as foliage biomass than aboveground biomass, as demon stared by

Validation

0.1 1 10 100 **Estimated aboveground biomass (t ha-1)**

Fig. 7. A 1:1 comparison between estimated and measured aboveground biomass values for the validation sites along the Dempster Highway transect measured during the summer of 2006 and in the Ivvavik National Park during the summer of 2008. For clarity over the low

As shown in Table 4, the Landsat-based *SR* can explain 81% variations in measured foliage biomass within the Porcupine caribou habitat. The explanation power of other Landsatbased indices in the descending order is 76% for the ratio of B4/B5, 71% for SWVI, and 67%

 B3 B4 B5 SR NDVI B4/B5 SWVI *r* **-0.73 0.52 -0.54 0.90 0.82 0.87 -0.84**  *r*<sup>2</sup> 0.53 0.27 0.29 0.81 0.67 0.76 0.71 *SEE* **31.4 39.1 38.6 20.6 26.4 21.9 25.2**  Table 4. Correlation coefficients (*r*), coefficient of determination (*r*2), and standard estimation error (*SEE*, in g m-2) between foliage biomass (*Bf*) and remote sensing signals for foliage biomass measured at the 21 sites along the Dempster Highway in 2006 and in the Ivvavik National Park in 2008. Remote sensing indices include Landsat red band reflectance (B3), near-infrared band reflectance (B4), shortwave infrared band reflectance (B5), ratio of B4/B5, simple ratio (SR = B4/B3), normalized differential vegetation index (NDVI = (B4 - B3)/(B4 +

In comparison with results for aboveground biomass shown in Table 3, Landsat-based vegetation indices have a much improved power of explanation for foliage biomass (Table 4). This is in good agreement with the fact that optical sensors mainly capture canopy information, thus the optical sensor data are more suitable for estimation of canopy parameters such as foliage biomass than aboveground biomass, as demon stared by

**3.4. Relationships between foliage biomass and remote sensing indices** 

for NDVI. Single band reflectance of Landsat has lower power of explanation.

B3)), and shortwave vegetation index (SWVI = (B4 - B5)/(B4 + B5)).

0.1

biomass range, the results are shown on the log-log scale.

1

10

**Measured aboveground biomass (t ha-1)**

100

previous studies (Franklin & Hiernaux, 1991; Hall et al., 1995; Chen & Cihlar 1996; Turner et al., 1999; Brown et al., 2000; Chen et al., 2002; Wylie et al., 2002; Phua & Saito, 2003; Laidler & Treitz, 2003; Lu, 2004). The best fit relationship between foliage biomass (*Bf*, g m-2) and Landsat-based simple ratio (*SR*) over the Porcupine caribou habitat is given as follows

$$B\_f = \begin{array}{c} 16.62 \text{SR} \text{ - } 1.1906 \text{ } \text{ } \tag{9}$$

with *r*2 = 0.81, *SEE* = 20.6 g m-2, *F*= 81, *P* = 2.7×10-8, and *n* = 21 (Fig. 8).

Fig. 8. Relationship between Landsat simple ratio and foliage biomass measured at sites along the Dempster Highway during the summer of 2006 and in the Ivvavik National Park during the summer of 2008.

Because we had only a relative small sample size of foliage biomass over the Porcupine caribou habitat, we didn't leave a fraction of the foliage biomass measurement points as validation. Nevertheless, we did find a similar relationship between Landsat-based simple ration and foliage biomass for the Bathurst caribou habitat located in Northwest Territory, Nunavut Territory, and northern Saskatchewan (Chen et al., 2011), with *r*2 = 0.86, *SEE* = 26.3 g m-2, *F*= 158, *P* = 2.6×10-12, and *n* = 27.

#### **3.5 Baseline maps of aboveground and foliage biomass**

Applying equations (7) and (8) to the co-registered and geo-referenced Landsat and JERS-1/SAR mosaics data over the Porcupine caribou habitat, we produced aboveground biomass for the Porcupine caribou habitat. Fig. 9 shows aboveground biomass distribution in circa 2000 over the Porcupine caribou habitat.

Mapping Aboveground and Foliage Biomass Over the Porcupine Caribou

Habitat in Northern Yukon and Alaska Using Landsat and JERS-1/SAR Data 245

**Yukon**

**Alaska**

Fig. 10. Foliage biomass distribution over the Porcupine caribou habitat cirac 2000. The 3-d effect was generated using the DEM data. Areas covered by water, forest, and cloud were

Fig. 10 shows the circa 2000 foliage biomass distribution of non-forest land areas in the Porcupine caribou habitat. Because of lacking foliage biomass measurements over forested land, foliage biomass was not estimated over forest areas in the Porcupine caribou habitat and areas covered forests were blocked out in Fig. 10. We also blocked out water and cloudcover areas in Fig. 10. As shown in Fig. 10, most of the northern coastal areas in Alaska and Yukon, over which the calving ground of the Porcupine caribou habitat is located, had a quite high foliage biomass from 50 to > 100 g m-2. This is a contrast to the distribution of the aboveground biomass. Over these same coastal areas the aboveground biomass was quite low. Both aboveground biomass and foliage biomass were found to be lower at high

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 (Table 5). 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 (Chen et al., 2011). This result agree well with the ground survey by Griffith et al. (2001), which suggested that on June 14, during 1998-1999, the total available forage was 63 g m-2 for the

blocked out.

mountain ridges, and coastal beaches.

Fig. 9. Aboveground biomass distribution over the Porcupine caribou habitat circa 2000. The 3-d effect was generated using the DEM data.

The amount of aboveground biomass was less than 5 t ha-1 for most area of the Porcupine caribou calving ground located in northern coastal area in both Alaska and Yukon. Along the coastal line and at high mountain ridges, the aboveground biomass further decreased to less than 2 t ha-1. For the summer and winter ranges of the Porcupine caribou habitat to the south, the values of aboveground biomass generally increased, with a large percentage of the areas having aboveground biomass in the range of 5-20 t ha-1, as well as a significant fraction of the area of 2-5 t ha-1 aboveground biomass. The areas of aboveground biomass 2- 5 t ha-1 appeared to be dominated by graminoids and herbs, while those of 5-20 t ha-1 aboveground biomass were mainly shrub land. The Porcupine summer and winter ranges also had a small fraction of area that had more than 20 t ha-1 aboveground biomass, likely associated with treed woodland. Areas of 0-2 t ha-1 aboveground biomass also occur in the summer and winter ranges of the Porcupine caribou habitat, mostly happened at high mountain ridges.

The information on foliage biomass can be more useful to local caribou management boards and researchers because it is directly related forage availability (Russell et al., 1993; Russell & McNeil, 2002; Russell et al., 2002). Using equation (9), we developed circa 2000 foliage biomass distribution over the Porcupine caribou habitat (Fig. 10).

Fig. 9. Aboveground biomass distribution over the Porcupine caribou habitat circa 2000. The

The amount of aboveground biomass was less than 5 t ha-1 for most area of the Porcupine caribou calving ground located in northern coastal area in both Alaska and Yukon. Along the coastal line and at high mountain ridges, the aboveground biomass further decreased to less than 2 t ha-1. For the summer and winter ranges of the Porcupine caribou habitat to the south, the values of aboveground biomass generally increased, with a large percentage of the areas having aboveground biomass in the range of 5-20 t ha-1, as well as a significant fraction of the area of 2-5 t ha-1 aboveground biomass. The areas of aboveground biomass 2- 5 t ha-1 appeared to be dominated by graminoids and herbs, while those of 5-20 t ha-1 aboveground biomass were mainly shrub land. The Porcupine summer and winter ranges also had a small fraction of area that had more than 20 t ha-1 aboveground biomass, likely associated with treed woodland. Areas of 0-2 t ha-1 aboveground biomass also occur in the summer and winter ranges of the Porcupine caribou habitat, mostly happened at high

The information on foliage biomass can be more useful to local caribou management boards and researchers because it is directly related forage availability (Russell et al., 1993; Russell & McNeil, 2002; Russell et al., 2002). Using equation (9), we developed circa 2000 foliage

biomass distribution over the Porcupine caribou habitat (Fig. 10).

3-d effect was generated using the DEM data.

mountain ridges.

Fig. 10. Foliage biomass distribution over the Porcupine caribou habitat cirac 2000. The 3-d effect was generated using the DEM data. Areas covered by water, forest, and cloud were blocked out.

Fig. 10 shows the circa 2000 foliage biomass distribution of non-forest land areas in the Porcupine caribou habitat. Because of lacking foliage biomass measurements over forested land, foliage biomass was not estimated over forest areas in the Porcupine caribou habitat and areas covered forests were blocked out in Fig. 10. We also blocked out water and cloudcover areas in Fig. 10. As shown in Fig. 10, most of the northern coastal areas in Alaska and Yukon, over which the calving ground of the Porcupine caribou habitat is located, had a quite high foliage biomass from 50 to > 100 g m-2. This is a contrast to the distribution of the aboveground biomass. Over these same coastal areas the aboveground biomass was quite low. Both aboveground biomass and foliage biomass were found to be lower at high mountain ridges, and coastal beaches.

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 (Table 5). 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 (Chen et al., 2011). This result agree well with the ground survey by Griffith et al. (2001), which suggested that on June 14, during 1998-1999, the total available forage was 63 g m-2 for the

Mapping Aboveground and Foliage Biomass Over the Porcupine Caribou

Habitat in Northern Yukon and Alaska Using Landsat and JERS-1/SAR Data 247

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,

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

For the foliage biomass, the Landsat-based simple ration gives the best fit, with *r*2 = 0.81,

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

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

This study is financially supported by grants from the Canadian IPY program through a project entitled "Climate Change Impacts on Canadian Arctic Tundra Ecosystems (CiCAT): Interdisciplinary and Multi-scale Assessments", Canadian Space Agency's Government Related Initiatives Program (GRIP) through a project entitled "ParkSPACE: Towards an Operational Satellite-based System for Monitoring Ecological Integrity of Arctic National Parks", and from the Earth Sciences Sector, NRCan's "Climate Change Geosciences

protection and industrial development under a global change environment.

0.63-1.06 t ha-1 for coastal tussock sites, and < 0.2 t ha-1 for hill-top rock lichen sites.

t h-1 over measured aboveground biomass range from 0.9 to 103.3 t h-1.

*SEE* = 20.6 g m-2, *F*= 81, *P* = 2.7×10-8, and *n* = 21.

cows are about 20% higher than that of Bathurst herd.

**5. Acknowledgment** 

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 al., 2001).


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, and cow body weight.

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 (Table 5).
