English

Abstract

Lands mined for coal and reclaimed under the Surface Mining Control and Reclamation Act (SMCRA) can be used to produce woody biomass. This study evaluates woody biomass production on SMCRA-reclaimed lands after ripping to reduce soil compaction. Four species treatments were established at two planting densities on three Wise County, Virginia, mine sites. Here, we review experimental treatment effects on biomass production after three years, and we compare results to those of two other current studies that are also evaluating biomass production on post-SMCRA mined lands. After three growing seasons, black locust produced more volume and biomass than other planted species. High-density plantings produced greater per-hectare biomass than low-density plantings. For black locust, sycamore, and a hybrid poplar clone (Populus trichocarpa x P. deltoides, clone 52-225), per-tree volume growth increments were nominally greater in year three than in year two, and fertilizers applied after year two nominally increased growth. A low-density red oak planting and a mix of red oak and eastern cottonwood planted at high density produced low amounts of biomass compared to other species. The Wise County study's hybrid poplars are growing less rapidly than hybrid poplars of the same clonal variety growing on VA, WV, and OH mine sites in a multi-state study, and its black locust biomass production is comparable to the best performing of the multi-state study's hybrid poplars. In a third study, ninety-eight hybrid poplar genotypes of three taxons (P. deltoides x P. trichocarpa (DT and reciprocal), P. deltoides x P. nigra (DN), and P. deltoides x P. maximowiczii (DM)) completed two years of growth on a VA mine site. Average biomass production by the DM clones exceeded production on the multi-state trial's best performing site and is comparable to the Wise County study's black locust production over comparable time periods. Within each taxon including DM, growth by the fastest growing genotypes is exceeding taxon means by factors of >2x. In both the Wise County and the multi-state study, significant effects by site and other non-species factors on biomass production are apparent, but which factors are driving performance differences is not clear. In order for biomass production on post-SMCRA mine sites to achieve commercial potential, factors causing the major growth differences observed in these studies must be understood and managed.