Wfj. Parsons et al., ROOT-GAP DYNAMICS IN A LODGEPOLE PINE FOREST - ECTOMYCORRHIZAL AND NONMYCORRHIZAL FINE-ROOT ACTIVITY AFTER EXPERIMENTAL GAP FORMATION, Canadian journal of forest research, 24(8), 1994, pp. 1531-1538
Belowground responses to aboveground disturbance were studied in exper
imental gaps created in a M-year-old Pinus contorta ssp. latifolia (En
gelm. ex Wats.) Critchfield stand, southeastern Wyoming. We hypothesiz
ed that active fine root densities within the canopy gaps would remain
comparable with densities in undisturbed forest and would not decline
abruptly until a threshold number of trees had been killed, after whi
ch the root gap would be recolonized gradually and centripetally. One-
, 5-, 15-, and 30-tree clusters were felled to create a series of gaps
in the root mat of lodgepole pine forest soil. For 2 years, densities
of ectomycorrhizal (ECM) root tips were determined by intensive soil
coring in the experimental gaps and in a nearby 8-year-old clearcut. D
ata on fine-root activity were obtained using mesh screens inserted in
to the soil and incubated for up to 5 years. The results were consiste
nt with the original hypothesis, but no clear threshold gap size was o
bserved for ECM root tips. Densities of active ECM root tips measured
along transects through one of the 30-tree gaps decreased quickly with
in 5-6 m of the forest edge, and did not significantly differ from zer
o at the center of the gap; in contrast to the 2-year-old gap, active
ECM densities were fairly constant across the 8-year-old clearcut. Mor
eover, root-rip densities declined gradually with increasing gap size,
while fine root penetrations of the mesh screens were significantly l
ower in the 30-tree gaps than in the smaller gaps. During the first 3
years, fine roots intercepting the screens were nonmycorrhizal; at the
final removal, root screens that had been incubated for 1837 days in
the gaps, including the 30-tree gaps, contained ectomycorrhizal root t
ips. The root screen removal data suggested that belowground gaps pers
isted 5 years after initial clear-felling of the 30-tree clusters, but
the screens also provided evidence for closure from the edges of thes
e gaps.