Publications

Marks, S; Surfleet, C; Malama, B (2024). Estimating and Modeling Pinus contorta Transpiration in a Montane Meadow Using Sap-Flow Measurements. FORESTS, 15(10), 1786.

Abstract
This study quantifies the transpiration of encroached lodgepole pine (Pinus contorta var. murryana (Grev. & Balf.) Engelm.) in a montane meadow using pre-restoration sap-flow measurements. Lodgepole pine transpiration and its response to environmental variables were examined in Rock Creek Meadow (RCM), Southern Cascade Range, CA, USA. Sap-flow data from lodgepole pines were scaled to the meadow using tree survey data and then validated with MODIS evapotranspiration estimates for the 2019 and 2020 growing seasons. A modified Jarvis-Stewart model calibrated to 2020 sap-flow data analyzed lodgepole pine transpiration's correlation with solar radiation, air temperature, vapor pressure deficit, and soil volumetric water content. Model validation utilized 2021 growing season sap-flow data. Calibration and validation employed a Markov Chain Monte Carlo (MCMC) approach through the DREAM(ZS) algorithm with a generalized likelihood (GL) function, enabling parameter and total uncertainty assessment. The model's scaling was compared with simple scaling estimates. Average lodgepole pine transpiration at RCM ranged between 220.6 +/- 25.3 and 393.4 +/- 45.7 mm for the campaign (mid-July 2019 to mid-August 2020) and 100.2 +/- 11.5 to 178.8 +/- 20.7 mm for the 2020 partial growing season (April to mid-August), akin to MODIS ET. The model aligned well with observed normalized sap-velocity during the 2020 growing season (RMSE = 0.087). However, sap-velocity, on average, was underpredicted by the model (PBIAS = -6.579%). Model validation mirrored calibration in performance metrics (RMSE = 0.1233; PBIAS = -2.873%). The 95% total predictive uncertainty confidence intervals generated by GL-DREAM(ZS) enveloped close to the theoretically expected 95% of total observations for the calibration (94.5%) and validation (81.8%) periods. The performance of the GL-DREAM(ZS) approach and uncertainty assessment in this study shows promise for future MJS model applications, and the model-derived 2020 transpiration estimates highlight the MJS model utility for scaling sap-flow measurements from individual trees to stands of trees.

DOI:
10.3390/f15101786

ISSN:
1999-4907