Biomass and nutrient accumulation following large-scale disturbance of a northern hardwood ecosystem

I investigated the spatial pattern of revegetation and consequent biomass and nutrient accumulation following whole-tree harvest of watershed 5 at Hubbard Brook Experimental Forest (HBEF). Soil disturbance was the primary factor regulating biomass and nutrient accumulation. Combining permanent plot studies of vegetation and disturbance with allometric biomass equations, I examined these relationships over six years.; The recovering northern hardwoods community at W5 was dominated by pin cherry. On average, biomass accumulated from about 2 tons/ha in 1984 (year one after the harvest) to more than 32 tons/ha in 1989 (year six). 137 kg N, 12 kg P, 85 kg K, 95 kg Ca and 18 kg Mg per hectare were accumulated by plants.; Differences in biomass and nutrient accumulation, species composition and plant densities were found among different intensities of forest floor disturbance (classified as undisturbed, scarified and severely disturbed) associated with the harvest. Two important mechanisms causing these differences were: (1) Disturbance changed the soil organic matter content and decomposition conditions with concomitant effects on soil water and nutrient availabilities; (2) The different regeneration strategies represented among the dominant plants were influenced by the degree of forest floor disturbance.; An analysis of qualitative patterns of spatial variation in vegetation recovery and nutrient availability suggests a patchy pattern of nutrient loss from the watershed. Areas of high N loss were associated with areas where limited availability of revegetation propagules resulting in temporary reductions in plant uptake.; A computer model, REGROW, was developed to simulate early successional pattern by applying ecological field theory and a continuous-time Markovian approach. REGROW predicts vegetation dynamics by calculating the growth of each individual plant from its resource availabilities which are calculated through scanning its influencing domain. Competition among plants is factored in by calculating the overlap of the resource domains of competing plants. Photosynthesis is abstracted in a continuous-time Markovian model connecting resource availabilities to plant growth. Following a process for parameter estimation and model calibration, REGROW successfully simulated vegetation development of W5 at HBEF and illustrated the effects of initial density and composition on forest development.