Loblolly pine hydrology and productivity across the southern United States

Mcnulty, S.G.; Vose, J.M.; Swank, W.T.

Forest Ecology and Management 86(1-3): 241-251


ISSN/ISBN: 0378-1127
DOI: 10.1016/s0378-1127(96)03744-9
Accession: 002886822

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Concern over future changes in water yield and timber production in southern pine forests has increased the need for a well tested and validated forest ecosystem model which can be used to predict potential climate change effects on forest processes. However, before a model is used to project potential climate change impacts on forests, it should first be validated across a wide range of climates and site conditions. We used PnET-IIS, a physiologically-based, monthly time-step model that uses soil, vegetation, and climate parameter inputs to predict evapotranspiration, drainage, soil water stress and net primary productivity for loblolly pine (Pinus taeda) stands across the southern United States. Sensitivity analyses and model validation of predicted net primary productivity (NPP) were conducted. Predicted hydrology and productivity were most sensitive to temperature driven parameters (e.g. optimal temperature for photosynthesis, and changes in air temperature). Values of PnET-IIS predicted NPP were compared with measured annual site basal area growth from 12 stands located from eastern Texas to eastern Virginia, from the year of site canopy closure to 1990. Annual basal area growth ranged from 4.2 to 26.8 cm-2 per tree year-1. Annual basal area growth was significantly correlated with predicted NPP (r-2 = 0.30, P lt 0.005, n = 164), and the correlation improved when annual basal area growth was averaged by site (r-2 = 0.66, P lt 0.005, n = 12). Total annual precipitation was the single climate variable which best correlated with annual basal area growth (r-2 = 0.14, P lt 0.005, n = 164). These result indicate that PnET-IIS could be useful in predicting the effect of changing patterns of precipitation and air temperature on southern pine hydrology and productivity.