The results of this study show that SLR is an important factor in historical shoreline change in Hawaii and that historical rates of shoreline change are about two orders of magnitude greater than SLR. Differing rates of relative SLR around Oahu and Maui remain as the best explanation for the difference in overall shoreline trends after examining other influences on shoreline change including waves, sediment supply and littoral processes, and anthropogenic changes though, these other influences certainly remain important to shoreline change in Hawaii. Maui also had a significantly higher island-wide average shoreline change rate at − 0.13 ± 0.05 m/yr compared to Oahu at − 0.03 ± 0.03 m/yr (at the 95% Confidence Interval). Maui experienced the greatest extent of beach erosion over the past century with 78% percent of beaches eroding compared to 52% on Oahu. Shoreline change trends are checked for consistency using two weighted regression methods and by systematic exclusion of coastal regions based on coastal aspect (wave exposure) and coastal geomorphology. Historical shoreline data are optimized to reduce anthropogenic influences on shoreline change measurements. Island-wide and regional historical shoreline trends are calculated for the islands using shoreline positions measured from aerial photographs and survey charts. The islands of Oahu and Maui, Hawaii, with significantly different rates of localized sea-level rise (SLR, approximately 65% higher rate on Maui) over the past century due to lithospheric flexure and/or variations in upper ocean water masses, provide a unique setting to investigate possible relations between historical shoreline changes and SLR. The stomatal response to high plant water stress is only detectable by calculating the active controlled conductance and excluding the not controlled water losses. This increasing not controlled transpiration during the vegetation period superimposes the decrease of water loss caused by low leaf water potential and high vapor pressure deficit. The heterogeneity of the plants (the investigations were carried out with 34 different plants during the vegetation period) increases the variance of leaf conductance and by this the variance of the magnitude of the transpiration rate. It is indicated that the effect of low leaf water potential on stomata closure is intensified by an increased vapor pressure deficit. ![]() ![]() High air temperatures decrease the cuticular transpiration and by this the overall conductance.Ī low leaf water potential decreases the active controlled conductance. Thereby the overall leaf conductance also increases. The not controlled water losses increase during the vegetation period. ![]() This influence of stomatal conductance on transpiration rate is already included in the parameter PAR. The PAR regulates by the CO 2 controlling mechanism the width of the stomata. The significance of leaf conductance for the mean daily transpiration rate is based on the following reasons, which in part counteract each other: The daily water loss of Mercurialis during the vegetation period can be attributed with a coefficient of determination up to 96% to the course of PAR, air vapor pressure deficit and leaf conductance. Additionally the time was taken into account for this analysis as an independent variable. Taking the daily mean values the course of transpiration and leaf conductance as well as the course of PAR, vapor pressure deficit, air temperature and leaf water potential was plotted as a function of time during the vegetation period.īy use of simple and multiple regression analysis an attempt was made to explain the variability of transpiration and conductance during the vegetation period by those endogenous and exogenous variables, which were continuously recorded. The height of active controlled transpiration and leaf conductance was calculated. ![]() In addition the course of leaf water potential was followed during the vegetation period in leaves of plants growing near the gas exchange chamber. The measurements were carried out with a climatized gas exchange chamber. During the vegetation period of 1982 transpiration and leaf conductance of Mercurialis perennis as well as light intensity (PAR), air vapor pressure deficit and temperature of the air were measured continuously in the herb layer of a beech forest on limestone in the environs of Göttingen.
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