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| Submitter's Name |
Maryada Shrestha |
| Session Name |
Poster Session - Agricultural/Silvicultural Water |
| Poster Number |
9 |
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| Author(s) |
Maryada Shrestha, Graduate Student (Presenting Author) |
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Rosvel Bracho-Garrillo,
Postdoctoral Associate |
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Timothy Martin, Professor |
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Jason Vogel, Assistant Professor |
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Contrasting water use efficiency and export for two different pine management systems |
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Forests in the southeastern US cover about one third of the forested land areas in the conterminous USA. Forests provide clean water and carbon sequestration and forest management can greatly affect the dynamics of these ecosystem services. We examined tradeoffs in water use, water yield and biomass accumulation (water use efficiency, WUE) for two types of managed pine: A naturally regenerated mixed stand of longleaf pine (Pinus palustris Mill) and slash pine (Pinus elliottii) managed to resemble natural forests (age ~60 years), and plantations of slash pine managed for fiber (age 5-25 years). The older forest was burned in the spring at approximately 2-year intervals. We measured evapotranspiration (ET) and carbon fluxes (net ecosystem production, NEP) using the eddy covariance approach along with biometric estimations of woody biomass increment (IW). Measurements covered 21-years of the plantation forest, and 17-years in the natural forest, capturing a broad range in climatic variability from extreme droughts to tropical storms. Mean annual ET was 724 ± 118 mm for the natural forest and 958 ± 108 mm for the plantations. The ET to precipitation (P) ratios was 0.67 ± 0.13 for the natural forest and 0.85 ± 0.15 for the plantations. Water use efficiency was estimated as the amount of biomass (C) accumulated (NEP) per Kg of water used (ET) and woody biomass (IW) produced per Kg of water used. We found that WUE for plantations as NEP/ET (1.28 ± 0.36 gC KgH2O-1) or IW/ET (0.67 ± 0.11 gC KgH2O-1) was higher than WUE for natural forest as NEP/ET (0.77 ± 0.40 gC KgH2O-1) or IW/ET (0.26 ± 0.10 gC KgH2O-1). These results suggest that relative to pine plantations, management for natural forests results in greater water yield to the local hydrologic system but lower rates of ecosystem carbon sequestration. |
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