Edward A. Hansen

Soil carbon sequestration beneath hybrid poplar plantations in the North Central United States

Hybrid poplar plantations grown on tilled agricultural lands previously in prairie, sequester significant quantities of soil carbon. Comparisons are made between hybrid poplar plantations and adjacent row crops or mowed grass. Establishing and tending plantations often results in early soil carbon loss, but soil carbon is significantly related (positive) to tree age. Increasing tree age eventually results in a net addition of soil carbon from plantations older than about 6 to 12 years of age. Soil carbon loss under trees occurred most frequently from the surface 30 cm early in the plantation history—evidence that the loss was due to mineralization. Soil carbon gain was most significant in the 30–50 cm layer and was attributed to tree root growth. Soil carbon accretion rate beneath 12- to 18-year-old poplar plantations exceeded that of adjacent agricultural crops by l.63 ± 0.16 Mg ha−1 yr−1. There was a significant crop × soil depth interaction for bulk density with bulk density lower beneath trees in the 0–30 cm layer and higher in the 30–50 cm layer. There was little evidence of carbon trapping of wind-blown organic detritus by tree plantations in the prairie environment.

Sand Bed Load in a Brook Trout Stream

Abstract An experimental introduction of sand sediment into Hunt Creek in the northern Lower Peninsula of Michigan that increased the bed load 4-5 times resulted in a significant reduction of brook trout (Salvelinus fontinalis) numbers and habitat. The brook trout population declined to less than half its normal abundance. The growth rate of individual fish was not affected. Population adjustment to the poorer habitat was via a decrease in brook trout survival rates, particularly in the egg to fry and/or the fry to fall fingerling stages of their life cycle. Habitat for brook trout and their food organisms became much poorer, as judged by the drastic reductions of both. Stream morphometry changed considerably, the channel becoming wider and shallower. Furthermore, sand deposition aggraded the streambed and eliminated most pools. The channel became a continuous run rather than a series of pools and riffles. Water velocities increased, as did summer water temperatures. Relatively small sand bed-load concent...

Hybrid poplar spacing/productivity relations in short rotation intensive culture plantations☆

Abstract It is often argued that in short rotation intensive culture plantations, biomass productivity increases with narrower tree spacings. Biomass productivity and tree spacing relations were studied for up to 16 years in northern Wisconsin hybrid poplar plantations. Maximum mean annual biomass increment was 12.8 Mg ha −1 yr −1 for Populus clone NE-41 planted at a l m 2 spacing. Productivity differences related to spacing were found to be minor. Productivity was influenced mainly by clone, irrigation and disease. A hypothesis is proposed that time to canopy closure is linearly related to time to maximum mean annual biomass productivity. Wide spacing and wide-crown trees that permit wider tree spacing allow longer rotations, which can lower costs and increase flexibility in management.

Biomass and nitrogen dynamics in an irrigated hybrid poplar plantation

Abstract A 3-year study measured the effects of ground cover treatments and N fertilization on biomass and nitrogen dynamics in an irridiated hybrid poplar (Populus deltoides Bartr. X P. trichocarpa Torr. and Gray, clone NC-9922) plantation in northern Wisconsin, U.S.A. Annually fertilized (112 kg N ha−1 year−1) and unfertilized plots were maintained weed free (bare soil), allowed to revegetate with native weeds, or seeded to birdsfoot trefoil (Lotus corniculatus L.). Biomass and N in trees and ground-cover vegetation were sampled before and after each growing season. Trees in bare-soil plots responded to fertilization primarily in the third growing season, but total biomass of 3-year-old trees was not increased by annual fertilization. In plots with a ground cover,fertilization increased tree growth but cover crop treatment had no effect. Ground cover biomass peaked during the second growing season, but declined thereafter, primarily due to reductions in below-ground biomass. Estimated recovery of fertilizer N was low in bare soil plots after 3 years, with 2% in the ‘perennial’ portion of the trees and 13% in the leaf litter. In contrast, recovery in the cover crop plots was 44%–51% in years 2–4. During that period, both biomass and N pool dominance shifted from primarily cover crop to primarily trees. The ground cover appeared to reduce tree growth in years 1–3, but total tree biomass after 4 years was greater in fertilized plots with ground cover (22.7 Mg/ha) than in fertilized bare soil plots (16.7 Mg/ha). Biomass production in fertilized trefoil plots in the fourth year (15.1 Mg ha−1 year−1, excluding leaves) exceeds that of local forests by 50%, and may be comparable to corn productivity in the area.

Sand Sediment in a Michigan Trout Stream Part II. Effects of Reducing Sand Bedload on a Trout Population

Abstract This is the second of a two-part sedimentation study. A sediment basin excavated in a Michigan trout stream reduced the sandy bedload sediment by 86% (from 56 ppm down to 8 ppm). Following the reduction in bedload, trout numbers increased significantly during the next 6 years. Small or young trout increased about 40% throughout the treated area. Larger and older trout increased in that part of the treated area that had an erodible sand bed. Although trout production increased 28%, growth rate of the trout changed but little. Both brown trout (Salmo trutta) and rainbow trout (Salmo gairdneri) populations responded similarly to the bedload reduction. However, statistical tests were more conclusive for brown trout than for rainbow trout because of the lower year-to-year variation of the brown trout population. The results suggested that in-stream sediment basins are an effective means for removing sand bedload and that even small amounts of moving-sand bedload sediments can have a major impact on a ...

Response of Three Populus Species to Drought

Describes how irrigation significantly increased growth in three Populus species and most clones during a drought year. Clonal response to drought varied within each of the species.

Sand Sediment in a Michigan Trout Stream Part I. A Technique for Removing Sand Bedload from Streams

Abstract Techniques for erosion control such as stream-bank stabilization and revegetation of eroding upland areas reduce only part of a streams sediment load. This study on Poplar Creek in Michigan (one of two papers) demonstrated that an in-stream sediment basin can trap and remove almost all sand bedload sediments. Other advantages of sediment basins are that they can (1) produce downcutting to create deeper pools and improve streambed composition, and {2) keep critical fisheries spawning areas relatively free of sediment. Sediment basins should be used with caution in streams with erodible beds that have no areas of erosion-resistant streambed to prevent possible excessive downcutting. Sediment basins can be used with other techniques to improve fish habitat, or they can be used alone to renovate sand-choked streams not amenable to the usual erosion-control treatments.