Inhibition and facilitation of spruce during the major successional stages at Glacier Bay, Alaska (d

The complex mechanisms underlying succession were well demonstrated by the detailed studies of Chapin's research team (1994). They combined field observations, field experiments, and greenhouse experiments to explore the mechanisms underlying primary succession at Glacier Bay, Alaska. Like Morris and Wood, they found that no single factor or mechanism determines the pattern of primary succession at Glacier Bay, Alaska.  figure 18.27 summarizes the complex influences of four successional stages on establishment and growth of spruce seedlings. During the pioneer stage, there is some inhibition of spruce germination. Any spruce seedlings that become established, however, have high survivorship but low growth rates. Spruce seedling growth rates and nitrogen supplies are increased somewhat during the Dryas stage. However, this facilitation during the Dryas stage is offset by poor germination and survivorship, along with increased seed predation and mortality.