Productivity and nutrient cycling in taiga forest ecosystems

Abstract

This paper considers the productivity and nutrient cycling in examples of the major forest types in interior Alaska. These ecosystem properties are examined from the standpoint of the control exerted over them by soil temperature and forest-floor chemistry. We conclude that black spruce Piceamariana (Mill.) B.S.P. occupies the coldest, wettest sites which support tree growth in interior Alaska. Average seasonal heat sums (1132 ± 32 degree days (DD)) for all other forest types were significantly higher than those encountered for black spruce (640 ± 40 DD). In addition, black spruce ecosystems display the highest average seasonal forest-floor and mineral-soil moisture contents. Forest-floor chemistry interacts with soil temperature in black spruce to produce the most decay-resistant organic matter. In black spruce the material is characterized by the highest lignin content and widest C/N (44) and C/P (404) ratios. Across the range of forest types examined in this study, soil temperature is strongly related to net annual aboveground tree production and the annual tree requirement for N, P, K, Ca, and Mg. Forest floor C/N and C/P ratios are strongly related to annual tree N and P requirement and the C/N ratio to annual tree production. In all cases these controls act to produce, in black spruce, the smallest accumulation of tree biomass, standing crop of elements, annual production, and element requirement in aboveground tree components.

Describing condition-specific determinants of competition in boreal and sub-boreal mixedwood stands

“…Cold soil and air temperatures, which tend to be more prevalent with increasing elevation/latitude and on northerly slope aspects in northern ecosystems, are known to be key limiting factors in tree growth and reproduction (Tryon and Chapin 1983, Van Cleve et al 1983, Bonan 1992, Navratil 1996, Loehle 1998, Landhäusser et al 2001. The growth responses of trees to thermal conditions may differ markedly between broadleaf and conifer species, altering their relative dominance in mixedwood stands across environmental gradients (Van Cleve et al 1983, Landhäusser et al 2001, Landhäuss-er et al 2003.…”

“…The growth responses of trees to thermal conditions may differ markedly between broadleaf and conifer species, altering their relative dominance in mixedwood stands across environmental gradients (Van Cleve et al 1983, Landhäusser et al 2001, Landhäuss-er et al 2003. Landhäusser et al (2001) found strong positive relations between soil temperature (5-25 o C) and numerous growth characteristics (including whole-plant growth, leaf production, root production, net photosynthesis and stomatal conductance) for trembling aspen seedlings.…”

Influence of Fuel Load Dynamics on Carbon Emission by Wildfires in the Clay Belt Boreal Landscape

“…on mesic sites [48,[51][52][53]. In contrast, thick residual organic layers favor black spruce self-replacement [53,54] and accelerate the process of paludification [34,51].…”

“…Consequently, it was not surprising to predict in our study an increase in tree biomass at early successional stages for all forest types. This increase was faster for TA and JP forests, because growth rates are faster for these trees [65,72] and the low residual organic layers required for TA and JP postfire recruitment lead to the establishment of productive and dense forests [49,[52][53][54]. In contrast, BS-NS forests showed the slowest increase due to the thick residual organic layers left after fire which favor unproductive open BS self-replacement [34,48,[52][53][54].…”

“…This increase was faster for TA and JP forests, because growth rates are faster for these trees [65,72] and the low residual organic layers required for TA and JP postfire recruitment lead to the establishment of productive and dense forests [49,[52][53][54]. In contrast, BS-NS forests showed the slowest increase due to the thick residual organic layers left after fire which favor unproductive open BS self-replacement [34,48,[52][53][54]. Following the growth influx, a decrease in tree loads [34,73] was predicted at 80, 110, and 200 years for TA, JP, and BS forests, respectively.…”