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Effects of fertilization on the nutrient and organic matter dynamics of reclaimed coal-mined areas and native grasslands in Southeastern British Columbia Ziemkiewicz, Paul F.

Abstract

Reclamation of coal mining disturbances has been undertaken on a large scale in British Columbia since 1972. Mining occurs primarily in a narrow belt in southeastern B.C. from the international boundary northward parallel to the continental divide to the headwaters of the Elk River at elevations of 1,000 m to 2,300 m. Since reclamation began, most treated areas have been fertilized annually as a precaution against reclamation failure. While this practice has often maintained productive and attractive reclamation sites it was not known whether the maintenance fertilization was necessary and what effect it was having on plant community development. To answer these questions two productive reclaimed areas and two adjacent native, undisturbed grasslands were selected. One set of plots was amid montane vegetation and the other amid subalpine vegetation. On each of the four sites, paired plots were established and shoot, detritus and root biomass levels were measured over a 14-month period. One of the paired plots was fertilized in the spring. N, P and K analyses were done on soil and plant samples so that organic matter and nutrient flux in the four plant community compartments could be expressed as mass per unit ground surface. Two phases in reclaimed area development, were identified. The development phase was characterized by detritus accumulation and minor root mass turnover in the fall. Fertilization had a profound influence on this phase mainly in stimulating shoot production though root production was stimulated to a lesser degree. The withdrawal of maintenance fertilization resulted in a severe drop in production and nutrient accumulation with a large part of yearly N and P uptake immobilized in surface detritus by fall. The subalpine reclaimed area represented this phase. The data indicate that maintenance fertilization will be necessary to prevent degeneration of the plant community. The montane reclaimed area represented the mature phase of development. This phase may not indicate attainment of a steady state, but it appeared to be capable of storing and cycling sufficient nutrients that withdrawal of maintenance fertilization resulted in no apparent adverse effects. Rather, due to the midsummer drought, fertilization of this reclaimed area inhibited root production while it stimulated shoot production. The additional shoot production could not be maintained through the dry period, so that shoot standing crop through the summer was not influenced by fertilization. The native areas were characterized by massive root systems which caused the bulk of nutrient exchanges to occur within plant and from root to soil to root. Thus the surface detritus system played a minor role in nutrient cycling relative to the reclaimed areas. Fertilization of natives areas stimulated shoot production and detrital decomposition so root:shoot ratios narrowed and detritus levels dropped after fertilization. The reclaimed areas were less stable than the native areas in relation to water and nutrient stress. However, the montane reclaimed area seemed self-sufficient in. nutrients and should continue to develop without annual fertilization. The subalpine reclaimed area is not nutrient self-sufficient and will require continued treatment.

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