The two most important life functions that organisms carry out to persist in the environment are reproduction and growth. In this chapter we examine the role of climate and climate variability as controlling factors in the growth of one of the most important and productive of the North American boreal forest tree species, white spruce (Picea glauca [Moench] Voss). Because the relationship between climate and tree growth is so close, tree-ring properties have been used successfully for many years as a proxy to reconstruct past climates. Our recent reconstruction of nineteenth- century summer temperatures at Fairbanks based on white spruce tree-ring characteristics (Barber et al. in press) reveals a fundamental pattern of quasi-decadal climate variability. The values in this reconstruction of nineteenth-century Fairbanks summer temperatures are surprisingly warm compared to values in much of the published paleoclimatic literature for boreal North America. In this chapter we compare our temperature reconstructions with ring-width records in northern and south-central Alaska to see whether tree-growth signals in the nineteenth century in those regions are consistent with tree-ring characteristics in and near Bonanza Creek (BNZ) LTER (25 km southwest of Fairbanks) that suggest warm temperatures during the mid-nineteenth century. We also present a conceptual model of key limiting events in white spruce reproduction and compare it to a 39-year record of seed fall at BNZ. Finally, we derive a radial growth pattern index from white spruce at nine stands across Interior Alaska that matches recent major seed crop events in the BNZ monitoring period, and we identify dates after 1800 when major seed crops of white spruce, which are infrequent, may have been produced. The boreal region is characterized by a broad zone of forest with a continuous distribution across Eurasia and North America, amounting to about 17% of the earth’s land surface area (Bonan et al. 1992). The boreal region is often conceived of as a zone of relatively homogenous climate, but in fact a surprising diversity of climates are present. During the long days of summer, continental interior locations under persistent high-pressure systems experience hot weather that can promote extensive forest fires frequently exceeding 100 kilohectares (K ha). Summer daily maximum temperatures are cooled to a considerable degree in maritime portions of the boreal region affected by air masses that originate over the North Atlantic, North Pacific, or Arctic Oceans.
Remote sensing of net ecosystem productivity based on component spectrum and soil respiration observation in a boreal forest, interior Alaska