Study on Nutrient Content and Accumulation of Leucaena Leucocephala Stands with Different Densities

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1 nd International Conference on Material Engineering and Application (ICMEA 2015) ISBN: Study on Nutrient Content and Accumulation of Leucaena Leucocephala Stands with Different Densities Z.Y. Lie, L. Xue *, J. Li & W.L. Huang College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou , P.R. China ABSTRACT: Nutrient content and accumulation were studied in young Leucaena leucocephala stands with different densities (1, 2, 4 and 8 seedlings m 2 ) to provide theory basis for their reasonable management. The results showed that N and K contents were high and P content was low in various organs, and total nutrient content decreased in the order of leaves>bark>branches>roots>stem. Nutrient accumulation of single tree decreased with increasing stand density, whereas the nutrient accumulation of stands increased with increasing plantation density. The N or K accumulation was greater than P accumulation for each density stand. 1 INTRODUCTION Resources competition among plants increases with increasing density(li et al., 2011), which limits plant growth (Xue et al., 2012) and changes biomass accumulation and allocation (Guo et al., 2013). The individuals in high density stands have smaller space and access to decreasing light and soil resources, which leads a small biomass. Leucaena leucocephala is a perennial evergreen shrub or small tree, belonging to leucaena, Mimosoideae. It is widely distributed in tropical and subtropical regions of the world with developed root system and nodules, and it is common greening tree species growing up on barren hills in Southern China. Some researchers studied seed germination characteristics (Gong et al., 2006), natural regeneration (Ma et al., 2006; Zong, 2007), leaf nutrient content (Hao et al., 2012), soil organic carbon (Guo et al., 2012) of this species. However, to our knowledge, there is as yet no paper in the density effect on nutrient distribution of L. leucocephala. In the present study, the density effects on nutrient content and accumulation of L. leucocephala stands were reported in order to provide a reference for understanding its nutrient distribution pattern in response to density. * The study was partially supported by Foundation of Guangdong Forestry Department, China (No F15050) * Corresponding author, forxue@scau.edu.cn 483

2 2 MATERIALS AND METHODS 2.1 Study area The study was conducted at Yuejinbei Nursery ( E, N) in South China Agricultural University, Guangzhou City, Guangdong Province, China. The Nursery has a humid subtropical monsoon climate with an average annual temperature of 21.9 C and a relative humidity of 77%, respectively. The annual rainfall averages mm, occurring mainly from April to October. The experimental environment is sunny and suitable for seedling growth. 2.2 Experimental design and field studies One-year old L. leucocephala seedlings were provided by Shenzhen Techand Ecology & Environment Co., Ltd. In July 2011, these seedlings were planted in soil with four densities: 1, 2, 4 and 8 seedlings m -2, three plots, each of 20 m 20 m in size, were established in each density stand, and each density was treated with three replicates. The seedlings were watered and weeded regularly. In September 2013, all trees in each plot were felled, the biomasses of different density stands were measured. The contents of K, P and N in various organs (root, stem, branch, leaf and bark) were analyzed. The growth statuses of the seedlings were shown in Table 1. Table 1. Organ biomass (t hm 2 ) and the percentage (%) of L. leucocephala stands with different densities. Density (seed Stem (44.80) 21.09(43.51) 38.94(51.01) 54.13(50) Branch 7.11(19.50) 9.46(19.51) 11.33(14.84) 16.66(15.39) Leaf 2.65(7.28) 3.91(8.07) 6.83(8.95) 8.53(7.88) Bark 2.26(6.20) 3.09(6.38) 4.94(6.47) 6.39(5.9) Root 8.10 (22.21) 10.92(22.52) 14.3(18.73) 22.56(20.84) Total 36.46(100.00) 48.48(100) 76.34(100) (100) 2.3 Chemical analysis Samples of all organs for chemical analysis were ground. The contents of N, P and K were determined by Kjeldahl determination (CAS Nanjing Institute of Soil Science, 1978), molybdenum blue photometric method (Mukherjee & Asanuma, 1998) and Atomic absorption spectrophotometer (CAS Nanjing Institute of Soil Science, 1978), respectively. All samples were measured in triplicate, respectively. 484

3 2.4 Data analysis All statistical analyses were used Excel 2010 and the Statistical Analysis System (SAS 9.0). Differences were considered significant at the P < 0.05 level. 3 RESULTS 3.1 Effect of density on the nutrient content of seedlings Table 2. Nutrient content of various organs of different densities L. leucocephala stands (g kg -1 ). Density (seedlings m -2 ) Organ N P K Total 1 Stem 2.05± ± ± Branch 9.68± ± ± Leaf 30.57± ± ± Bark 13.68± ± ± Root 5.44± ± ± Total Stem 3.21± ± ± Branch 9.67± ± ± Leaf 38.58± ± ± Bark 14.37± ± ± Root 7.34± ± ± Total Stem 2.87± ± ± Branch 9.16± ± ± Leaf 38.67± ± ± Bark 15.16± ± ± Root 6.5± ± ± Total Stem 2.83± ± ± Branch 9.68± ± ± Leaf 36.59± ± ± Bark 14.62± ± ± Root 7.63± ± ± Total

4 From the Table 2, the N and K contents in various organs of 1 seedling m -2 stand decreased in the order of leaf> bark> branch> root> stem and P content decreased in the order of leaf> branch>bark>root>stem, while N, P and K contents of 2 seedlings m -2 stand decreased in the order of leaf> bark> branch> root> stem; Distribution of N, P and K contents for 4 and 8 seedlings m -2 stands had different patterns (Table 2). The N content was high and P content was low in each density stand. In all density stands, N content was the highest in leaves, whereas P was the highest in leaves and branches and K was the highest in leaves and bark. However, N, P and K content were the smallest in stem. Total nutrient content (N, P and K) of various organs of each density stand decreased in the order of leaf>bark>branch>root>stem. 3.2 Accumulation and distribution of nutrients in the single average seedling Nutrient accumulation of per plant was obtained using single average yield multiplied by each organ nutrient (Table 3). Average nutrient accumulation of L. leucocephala individuals decreased with increasing density with values of g, g, g and g for 1, 2, 4 and 8 seedlings m -2, respectively, indicating that low density was favorable to nutrient accumulation in individuals. The nutrient accumulation of 1, 2, 4 and 8 seedlings m -2 stands decreased in the order of branch>leaf>root>bark>stem, leaf>branch>stem>root>bark, leaf>branch>stem>bark>root and branch>leaf>stem>root>bark, respectively. Average N or K accumulation in individuals was greater than P. 486

5 Table 3. Accumulation and distribution of nutrients in the single average seedling(g seedling -1 ). Density (seedlings m-2) Organ N P K Total Stem Branch Leaf Bark Root Total Stem Branch Leaf Bark Root Total Stem Branch Leaf Bark Root Total Stem Branch Leaf Bark Root Total Effect of density on stand nutrient accumulation Biomass multiplied by nutrient content obtained stand nutrient accumulation. Nutrient accumulation reached 99.71, 65.12, and g m -2 for 1, 2, 4 and 8 seedlings m -2 stands, respectively (Table 4). In general, the nutrient accumulation of L. leucocephala stands increased with increasing stand density. N or K accumulation was greater than P in each density stand, and N accumulation was the highest in leaves and lowest in the bark, and P or K accumulation was the highest in branches. Overall, N, P and K accumulation of L. leucocephala was great in high-density stands mostly due to their massive biomass. 487

6 The percentage of nutrient accumulation in leaves, branches, and bark was much more than the percentage of their biomass (Table 1). The N, P and K accumulation of branches and leaves accounted for 52.5% ~ 60.5% of nutrient accumulation of stands. Total nutrient accumulation of branch and leaves was the largest due to their high nutrient content and medium biomass. Although stem accounted for almost half of stand biomass, its N, P and K accumulation accounted for only 12.34% to 19.87% of stand nutrient accumulation due to its low nutrient content. Stand biomass and organ biomass increased with increasing stand density, and organ biomass decreased in the order of stem>root>branch>leaf>bark. Among organs, stem had the largest percentage of stand biomass with a range from 43.5% to 51%, while the bark had the smallest biomass, accounting for only 5.9% to 6.5%. Table 4. The nutrient accumulation (g m -2 ) and distribution of L. leucocephala stands. Density (seedlings m -2 ) Organ N P K Total Stem 3.35(12.96) 0.13 (4.74) 4.56 (12.47) 8.03 (12.34) Branch 6.88 (26.65) 1.37 (49.53) 15.39(42.11) 23.63(36.29) Leaf 8.10 (31.36) 0.54 (19.52) 7.10 (19.43) (24.17) Bark 3.09 (11.97) 0.33 (11.81) 4.90 (13.42) 8.32 (12.78) Root 4.41(7.06) 0.40 (14.40) 4.59(12.57) 9.40(14.43) Total (100) 2.76 (4.23) (56.11) (100) Stem 6.77 (15.57) 0.78 (19.82) 12.26(23.44) 19.81(19.87) Branch 9.15 (21.03) 1.20(30.27) 15.53(29.7) 25.87(25.94) Leaf (34.73) 0.84(21.28) 10.53(20.13) 26.47(26.54) Bark 4.45(10.22) 0.40(10.06) 7.21(13.79) 12.05(12.09) Root 8.06(18.43) 0.73 (18.58) 6.77 (12.95) 15.52(15.56) Total 43.48(43.61) 3.94(3.95) 52.29(52.45) 99.71(100) Stem 11.18(17.25) (15.78) 13.04(20.90) 25.19(18.89) Branch 10.38(16.02) (41.50) 17.90(28.69) 30.84(23.13) Leaf 26.43(40.81) (22.26) 13.38(21.44) 41.19(30.89) Bark 7.49(11.57) (10.25) 11.74(18.81) 19.86(14.90) Root 9.29(14.35) (10.20) 6.33(10.15) 16.26(12.19) Total 64.77(48.57) (4.63) 62.40(46.80) (100) Stem 15.32(17.17) (9.36) 16.35(18.60) 32.48(17.48) Branch 16.12(18.07) (43.20) 29.39(33.44) 49.25(26.51) Leaf 31.21(34.99) (19.48) 15.42(17.55) 48.32(26.01) Bark 9.35(10.48) (12.09) 14.58(16.59) 24.97(13.44) Root 17.22(19.30) (15.87) 12.14(13.81) 30.73(16.54) Total 89.21(48.02) (4.67) 87.88(47.31) (100) 488

7 4 DISCUSSION The present study indicated that there were significant differences in nutrient accumulation of L. leucocephala among organs. Leaves had the highest nutrient content, whereas stem had the lowest nutrient content. Nutrient content in the organs decreased in order of leaves>bark>branch>root>stem. Leaves was the important organ for photosynthesis with high metabolic and a variety of enzymes, so its nutrient content was high. Stem was composed of dead cells, so its nutrient content was low. Total nutrient content (N, P and K) decreased with decreasing density from 2 to 8 seedlings m -2, high density stands may accumulate more dry matter, which diluted nutrient content. Moreover, weed root grew densely in nutrient-rich topsoil in 1 seedling m -2, the strong competition for soil nutrients occurred between weed and seedlings, which resulted in less nutrient absorption for trees, so its nutrient content was less than 2 and 4 seedlings m -2 stands. The nutrient accumulation increased with increasing stand density, which was consistent with results of previous studies, such as the study about Pinus elliottii (Xiao, 2013), Eucalyptus grandis urophglla (Li et al., 2001), Phoebe zhennan (Lui, 2006) and Fargesia denudata (Wu, 2005). The seedling nutrient accumulation was correlated with the biomass and nutrient content. N, P and K contents of L. leucocephala increased with increasing density, which was roughly consistent with biomass distribution pattern of the seedling organs. Because the total biomass of the seedlings was significantly increased with increasing density, whereas change of nutrient content was small, therefore biomass was the dominant factor that determined nutrient accumulation. REFERENCES Gong, D.Y., Zuo, D.C. & Zuo, Z.L. (2006) Effects of different treatments on the germination characteristics of Leucaena seeds. Seed, 25 (6), Guo, T., He, B.H., Jiang, X.J., Ma, Y., Wu, Y., Xiang, M.H., Chen, Y. & Tang C.X. (2012) Effect of Leucaena leucocephala on soil organic carbon conservation on slope in the purple soil area. Chinese Journal of ecology, 32(1), Guo, Z.W., Yang, Q.P., Li, Y.C. & Chen S.L. (2013) Restrictive regulation of stand density on aboveground biomass allocation and allometric pattern of Oligostachyum lubricum. Chinese Journal of Ecology, 32(3), Hao, X.H., Hong, W., Wu, C.Z., Li, J., Wang, Y.R. & Yang, X.W. (2012) Characteristics of leaf element concentrations of twelve nutrients in Acacia confusa and Leucaena glauca in secondary forests of acid rain region in Fuzhou. Chinese Journal of Ecology. 32(22),

8 Li, Y.L., Li, Z.H., Xie, Y.J. (2001) Nutrient cycle in Eucalyptus grandis urophglla plantation. Journal of Ecology, 10, Li, L., Zhou, D.W. & Sheng, L.X. (2011) Allometric relationship between mean component biomass and density during thecourse of self-thinning for Fagopyrum esculentum populations. Chinese Journal of Ecology, 30(8), Lu, M. (2006). Dissertation for Master s Degree of Fujian Agriculture and Forestry University. Fuzhou: Fujian Agriculture and Forestry University Publishing. Ma, J.M., Li, K. & Zhang, C.S. (2006) Regeneration of Acaciaglauca and Leucaena leucacephala plantations in Yuanmou dry and hot valley. Chinese Journal of Ecology, 17(8), Maherali, H. & DeLucia, E.H. (2001) Influence of climate-driven shifts in biomass allocation on water transport and transport and storage in ponderosa pine. Oecologia, 129, Wu, F.Z. & Wang, K.Y. (2005) Effects of Fargesia denudata density on its biomass distribution pattern. Chinese Journal of Applied Ecology, 16(6), Xiao, X.C., Li, Z.H., Tang, Z.J., Shen, J.M., Gong, X.J. & Zhu, N. (2011) Effects of stand density on biomass and productivity of Pinus elliottii. Journal of Central South University of Forestry & Technology, 31(3), 13: Xue, L. & Fu, J.D. (2012) A review on factors affecting plant competition. Journal of Central South University of Forestry & Technology, 32(2), Xue, L. (1996) Nutrient cycling in a Chinese-fir (Cunninghamia Zunceolatu) stand on a poor site in Yishan, Guangxi. Forest Ecology and Management, 89, Zong, Y.C., Zheng, Y.Q., Zhang, C.H., Duan, F.W. & Wang, Z.H. (2007) Natural regeneration of Leucaena leucacephala in Yuanmou dry-hot valley. Chinese Journal of Ecology, 26(1),