TRACE GAS EXCHANGES IN MIDWEST CROPPING SYSTEMS
Location: Soil, Water, and Air Resources Research Unit
Title: SOIL CARBON AND TREE LITTER DYNAMICS IN A RED CEDAR-SCOTCH PINE SHELTERBELT
Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 2007
Publication Date: October 7, 2007
Citation: Sauer, T.J., Cambardella, C.A., Brandle, J.R. 2007. Soil carbon and tree litter dynamics in a red cedar-scotch pine shelterbelt. Agroforestry Systems. 71:163-174.
Interpretive Summary: A shelterbelt is one to several rows of trees planted across a field to break the wind. Shelterbelts are often used in semiarid areas to protect crops and to prevent wind erosion. After the trees are planted in a field, the leaves and needles from the trees fall to the ground each autumn to form a layer of tree litter that decomposes on the soil surface. Some of this organic material ends up in the soil as soil organic carbon. In this study, soil and the tree litter on the soil surface were sampled across a 35 yr-old shelterbelt in Nebraska. The litter samples were analyzed for carbon and nitrogen and the soil samples were sampled for carbon, nitrogen, pH, sand, silt, clay, and several nutrients. The results of this study showed that the concentration of carbon in the surface soil beneath the shelterbelt was about 50% greater than in the fields on both sides of the shelterbelt. There was also a lot of carbon stored in the tree litter. Changes in soil properties gave some indication that greater soil carbon under the shelterbelt was due to decomposition of the tree litter and maybe carbon carried in on wind-blown dust particles. This research is important to growers, scientists, and policy-makers interested using agroforestry practices like shelterbelts to improve soil quality and increase carbon storage in soil.
Carbon sequestration in the woody biomass of shelterbelts has been investigated but there have been no measurements of the C stocks in soil and tree litter under this agroforestry practice. The objective of this study was to quantify C stored in surface soil layers and tree litter within and adjacent to a 35 yr-old shelterbelt in eastern Nebraska. The 2-row shelterbelt was composed of eastern red cedar (Juniperus virginiana) and scotch pine (Pinus sylvestris). A sampling grid was established across a section of the shelterbelt on Tomek silt loam (fine, smectitic, mesic Pachic Argiudolls). Four soil cores were collected at each grid point, divided into 0-7.5 and 7.5-15 cm depth increments, and composited by depth. Soil samples were analyzed for total, organic, and inorganic C, total N, texture, pH, and nutrient content. Under the shelterbelt, all surface litter in a 0.5 x 0.5 m square at each grid point was collected before soil sampling, dried, weighed, sorted, and analyzed for total C and N. Average soil organic carbon (SOC) in the 0-15 cm layer within the shelterbelt (3994 g m**-2) was significantly greater than in the cultivated fields (3623 g m**-2). The tree litter contained an additional ~1300 g C m**-2. Patterns of litter mass and soil pH and texture suggested increased organic inputs by tree litter and deposition of wind-blown sediment may be responsible for greater SOC beneath the shelterbelt. Further research is needed to identify the mechanism(s) responsible for the observed spatial patterns of SOC within and adjacent to the shelterbelt and to quantify the C in biomass and deeper soil layers.