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1、1,1,Lili Zhou, Xiangqing Ma *, Pengfei Wu Fujian Agriculture and Forestry University (FAFU), Forestry College October, 2015,Leaf resorption efficiency and relating to foliar and soil nutrient status of Chinese fir plantations in South China,Outline,Background,2,Materials and methods,3,Discussion,4,1
2、,Conclusion,5,Results,Background,Nutrient resorption before leaf abscission is an important nutrient conservation mechanism used by perennial plants respond to changes in nutrient availability. Resorption efficiency (RE) is defined as the percentage of nutrient concentration between senesced and gre
3、en leaves. Globally, nutrient resorption is estimated to provide 31% of the annual demand for plant N and 40% for P.,Why is this study carried out?,Senesced,Nutrient RE varied among species, ecosystems, plant life-forms, functional types and biomes. In recent times, many studies reported that the re
4、sorption process could be regulated by leaf nutrient status and soil nutrient availability. However, there are not consistent results on how the nutrient in leaf and soil affect the Nutrient RE.,Why is this study carried out?,Senesced,Chinese fir and site characteristics : Less litterfall and less n
5、utrient return Fast growing and great nutrient requirement Decline in soil fertility Successive cropping and short rotation,Standing wood volume of the second and third rotations declined 30-40% and 45-50%,Why is this study carried out?,In Chinese fir plantations, the decline in soil fertility cant
6、maintain the fast growing and great nutrient requirement. So, we hypothesize1) Chinese fir species may develop conservation strategies through great nutrient resorption from senesced leaves. 2) leaf or soil nutrient concentration and stoichiometric may affect the nutrient resorption process.,Why is
7、this study carried out?,Materials and methods,Study site,Young stage,Mature stage,Over-mature stage,(2610 N, 11727E),Mid-subtropical marine monsoon Annual average temperature of 19C Annual average rainfall of 1749 mm Average annual sunshine is 1840 h A frost-free period of 300 d.,Study site,Experime
8、ntal design,Table 1 The basic characteristics of different development stages of Cunninghamia lanceolata plantations,Chose different developmental stages Three 20 m 20 m plots were established in each stand Investigated the DBH and height and chose five sample tress in each stand,Leaf and soil sampl
9、ing and analysis,The green leaves: Collected in April, July, October 2012 and January 2013 Collected from five representative trees Collected from lower, upper half and outer portions of the crown, Then pooled for each plot (500-1000 g per plot). The senesced leaves: Collected in every month since F
10、ebruary 2012 10 1m1m litter traps was set randomly on each plot The traps were made of nylon nets with a 1-mm sieve, set about 50cm above the ground. Soil sampling: Collected from five sampling points From 0-20, 20-40, and 40-60 cm depths,Calculation of RE and stoichiometric ratios,Nutrient resorpti
11、on efficiency (RE) Nutrient RE=100%1-(nutrient)senescence/(nutrientgreen (1),(Nutrient)senesced=(Nutrient)senesced MLCF (2) Nutrient RE=100%1-(Nutrient)senesced/(nutrient)green (3) Where MLCF was 0.745 for coniferous species (Verguz et al. 2012),Results,Foliar nutrient resorption efficiency,NRE and
12、PRE did not vary significantly among the stands ranging from 49-54% and 70-72% respectively KRE generally decreased with stand age from 78% to 67% NRE and PRE were significantly different among seasons The interaction between sampling season and stand age was not significant.,Foliar nutrient concent
13、ration and stoichiometry,Soil nutrient concentration and stoichiometry,Table 2 Concentrations of soil hydrolysable N, available P and available potassium at different depths with Chinese fir stand development,The mean N and K concentrations was highest in the young stage and lowest in mature stage.
14、Available P had the lowest value in over-mature stand. Soil depth had significant effect on soil nutrient concentration The concentration of N, P and K decreased with soil depth across the stands,Table 3 Soil N:P, N:K and K:P among soil depth with Chinese fir stand development,Soil nutrient concentr
15、ation and stoichiometry,N: K ratio increased with stand age, and was significantly higher in the mature and over-mature stands K:P ratio increased with soil depth except in over-mature stand while N:P and N:K ratios decreased with soil depth Stand stage had a significant effect on soil N:P and N:K r
16、atios There were no interaction between soil depth and stand age on stoichiometric ratios of N, P and K.,Relationship between resorption, nutrient concentration and stoichiometry in leaf and soil,Table 4 Pearson bivariate correlations among nutrient REs and nutrient concentration and stoichiometry i
17、n green and senesced leaves. Significances are shown as: *p0.05; * p 0.01.,Conclusions,Conclusions,The PRE (71%) and KRE(74) were higher than NRE (51%), suggesting that Chinese fir might preferably resorb P and K from senescing leaves before abscission. The NRE, PRE and KRE were significantly influe
18、nced by seasons compared to stand stage. The correlation results showed that nutrient REs were mostly affected by leaf nutrient status, but not soil nutrient concentration and stoichiometry. As a result, nutrient resorption may be an important mechanism to conserve nutrients in these Chinese fir stands.,
