A comparison of planting and natural succession after a forest fire in the northern Sierra Nevada

Published source details Bock J.H., Raphael M. & Bock C.E. (1978) A comparison of planting and natural succession after a forest fire in the northern Sierra Nevada. Journal of Applied Ecology, 15, 597-602.
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Summary

Approximately 15,000 ha of mixed pine Pinus and fir Abies coniferous forest in the northern Sierra Nevada mountains of California (southwest USA) was burned during the Donner Ridge Fire of 1960. This study compared two areas of the burnt forest that that had received different post-fire management. One was planted with Jeffrey pine Pinus jeffreyi and sprayed with 2,4,5-T herbicide to control shrubs, the other was allowed to follow the course of natural succession.

Management: Two sites (plots) of similar topography and vegetation prior to the fire were selected. The ‘control plot' (14.8 ha) received little management, except for felling of some standing dead trees a few years after the fire. Natural succession had led to stands of shrubs interspersed with open areas and many young pines, mostly P.jeffreyi with some Sierra lodgepole pine P.murrayana.

In the second area (4.1 ha) 4 km to the south, brush and dead trees were cut and burned in 1962. In 1965, 1-year old Jeffrey pine seedlings (approximately 25 cm tall) were planted at a density of about 400/ha. In 1971 and 1972 the area was sprayed from a helicopter with herbicide (2,4,5-T with thickener) to kill invading shrubs. Trees of undesired species (P.murrayana and white fir Abies concolor) were cut down and Jeffrey pine trees thinned to about 200/ha.

Vegetation monitoring: The sites were compared in summer 1975. Both were subdivided into 33 x 66 m plots in which all living trees were identified and counted. Species occurrence (trees, shrubs and herbs) was recorded at 1 m intervals along transects. More detailed measurements were made of two colonising species (and potential competitors with Jeffrey pine seedlings), the woody shrub, wax currant Ribes cereum, and the herbaceous perennial, woolly mule-ears Wyethia mollis. Their abundances were determined by counting plants present within 3 x 30.5 m strips in the study plots.

In 1975, more Jeffrey pine trees were present on the control (average 52.5 trees/2.2 ha) than the plantation (44.5/2.2 ha). The number of Jeffrey pine seedlings (control 2.2/2.2 ha; plantation 2.4/2.2/ha), neither of these differences was significant.

Lodgepole pine was much more abundant on the control site (average 5.1 trees/2.2 ha) compared with the plantation (0.4 /2.2 ha). The density of lodgepole seedlings was more similar (control 0.2 seedling/2.2 ha; plantation 0.4/2.2 ha). Fir (Abies sp.) absent in the plantation, was present at low density (0.8/2.2 ha) on the control site.

Shrubs and herbs were greatly reduced by herbicide application but grasses increased. Wax currant (normally a minor component of the natural shrub community), however flourished in the planted area. Herbicide application led to a general reduction in plant species richness and diversity.

Conclusions: Establishment of Jeffrey pine was not enhanced by planting seedlings with subsequent herbicide scrub control, as opposed to natural successional processes.

Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://links.jstor.org/sici?sici=0021-8901%28197808%2915%3A2%3C597%3AACOPAN%3E2.0.CO%3B2-4