Nitrogen resorption from needles of Pinus thunbergii Parl. growing along a topographic gradient of soil nutrient availability |
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Authors: | Tsutomu Enoki Hideyuki Kawaguchi |
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Institution: | (1) Laboratory of Forest Ecology, Faculty of Agriculture, Kyoto University, Kyoto 606–8224, Japan;(2) University Experimental Forest, Faculty of Agriculture, University of the Ryukyus, 684 Yona, Kunigami, Okinawa 905-1427, Japan |
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Abstract: | To examine the relative importance of nutrient resorption in increasing the nutrient-use efficiency of Pinus thunbergii Parl., we investigated the nitrogen contents of green and senescent needles of P. thunbergii trees growing at five positions along a slope (LS, lower slope; TR, transitional site; MS, middle slope; US, upper slope; RG, ridge) and found that soil nitrogen availability tended to decrease upslope. Nitrogen concentration in green and senescent needles decreased upslope. Nitrogen resorption efficiencies (percentage change in nitrogen content between green and senescent needles) increased upslope from 43 to 77% with decreasing soil nitrogen availability. Nitrogen resorption efficiency was related to green needle dry mass per unit length, but there was no clear correlation between nitrogen resorption efficiency and nitrogen content in green needles. We concluded that the increase in nitrogen resorption efficiency of P. thunbergii enhanced the nitrogen-use efficiency as a response to the low nitrogen availability. |
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Keywords: | nitrogen availability nitrogen resorption phenotypic response Pinus thunbergii Parl topography |
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