For. Stud. China, 2012, 14(1): 30–35DOI 10.1007/s11632-012-0109-2 RESEARCH ARTICLE

*Author for correspondence. E-mail: fjwcz@126.com

Monthly variation in litterfall and the amount of nutrients inan Aleurites montana plantation

LIN Han, HONG Tao, WU Cheng-zhen*, CHEN Hui, CHEN Can, LI Jian, LIN Yong-ming, FAN Hai-lan

Fujian Agriculture and Forestry University, Fujian Forest Ecological System Process and Management Key Laboratory, Fuzhou 350002, P. R. China

© Beijing Forestry University and Springer-Verlag Berlin Heidelberg 2012

Abstract In this study, the dynamics of monthly variation in litterfall and the amount of nutrients, i.e., organic C, N, P and K, in an Aleurites montana plantation were analyzed, based on a fi eld study and experiments over one year. The results show that the litterfall mass of A. montana collected generally presents an ascending trend with maximum defoliation occurring in the autumn and winter (October–December), accounting for 75.67% of the total amount of annual litterfall. The sequence in the amount of nutrients in A. montana litter was as follows: organic C > N > K > P; their monthly amounts show various dynamic curves. Similar to the dynamics of the mass of monthly litterfall, the monthly returns of C, N, P and K generally show an ascending trend with their peak values all occurring in December. The mass of A. montana litterfall and the dynamics of its monthly nutrient return provide, to a certain degree, a scientifi c reference for planting and fertilizing A. montana.

Key words Aleurites montana, litterfall, monthly variation, nutrient amounts

1 Introduction

Trees of Aleurites are hardwoods of the Euphorbia-ceae family. Among the six commonly planted species of Aleurites, A. montana is largely found between 22°–34°N and 102°–122°E. With its straight stem and average height of 10 m, A. montana has adapted to the warm and humid climate of sub-tropical regions and grows optimally at temperatures from 20°C to 30°C. Characteristics of drought tolerance, cold resistance and fast growth contribute to its wide distribution in Fuzhou City, Fujian Province, China, even at low win-ter temperatures of about 0°C. The optimal soil envi-ronment for A. montana is a fertile and well-drained acidic or neutral sandy loam, with pH between 5.5 and 6.5. In Fujian Province, it is a recommended local species for its fast growth, short development cycle, less pruning, strong sprouting, low planting cost and high ecological and economic benefits. One reason for planting A. montana is to obtain the fruits for oil, a clean and non-polluting substitute for an industrial paint. Hence, it is a good choice for bio-energy plan-tations as well as for timber production (Chen and Zhang, 2008).

In studies of forest ecosystem functions, great im-

portance is always attached to forest litterfall in order to examine material recycling, relationships between forest and soil and the self-fertilizing mechanism in forest ecosystems (Wu et al., 2000; Guo et al., 2006). Litter layer plays a signifi cant role in water conserva-tion and affects the non-biotic environment of forest ecosystems by hydrological processes, which in turn affect forest regeneration. The biomass of fully-devel-oped forests no longer increases and the nutrients ab-sorbed by vegetation return to the soil mainly by way of litterfall, forming a micro nutrient cycle within a region (Moorhead and Sinsabaugh, 2006). In the nutri-ent cycle among vegetation, litterfall and soil in forest ecosystems, vegetation actively absorbs nutrients from the soil to support its growth; in the process of decay and decomposition, the contained nutrients gradually return to the soil. As a vehicle of nutrients, litter is the bond connecting vegetation and soil in the nutrient cycle (Lin et al., 2004). Most of the nutrients obtained in an ecosystem, over 90% of N and P and over 60% of other nutrient elements, are generated in nutrient recycling from vegetation to soil (Chapin et al., 2002). Therefore, given the condition that overall fertiliza-tion can hardly be applied to plantations, the nutrient return from litterfall contributes greatly to material cy-

LIN Han et al.: Monthly variation in litterfall and the amount of nutrients in an Aleurites montana plantation 31

cling, nutrient balance, forest growth and soil fertility maintenance inside forest ecosystems. In general, in the study of forest litterfall, the emphasis is placed on the mass and decomposition of litterfall.

Despite the importance of A. montana, this species has not attracted suffi cient attention; long and relevant research on this species is seldom carried out in China. Liang (2005) briefly introduced graft techniques of A. montana seedlings. In a preliminary study, Zhang (2009) studied seedling raising techniques and nurs-ery stock growth of A. montana. Fan et al. (2008) cloned the SAD gene of A. montana and analyzed the construction of a fi lamentous fungi expression vector. Wei et al. (2005) studied the effect of foliage spraying with rare earth solution on the growth and physiologi-cal indices of A. montana seedlings. Ling et al. (1995) compared the wood anatomy of Vernicia fordii, A. montana and A. moluccana. However, only a few re-ports of studies on A. montana litterfall are available. Therefore, based on previous research, our study aims to evaluate the litterfall mass of an A. montana planta-tion, analyze the dynamics of nutrients in A. montana litterfall and provide a reference for maintaining long-term soil fertility and exploring and cultivating A. montana as a bio-energy species.

2 Materials and methods

2.1 Site description

Our experimental field was located at the Tongkou National Forestry Center of Minhou County, towards the east of Daiyun Mountain, southwest of Fuzhou City in the eastern part of Fujian Province (26°09′N, 119°14′E), at an elevation of 192 m a.s.l., with gra-dients of 31°–38° and 15 km from the city center. Located in the south of the mid-subtropics and west of the Fuzhou Basin, the soil is classifi ed as silt, clay and fi ne sand with granite bedrock.

The area has a mid-subtropical marine monsoon cli-mate, with short winter and long summer days, a mild climate and abundant rainfall. The average annual temperature is 19.6°C with the lowest average tem-perature of 10.2°C in January, an extreme minimum temperature of –2.6°C in February and March, a high average temperature of 28.7°C in July and maximum temperatures of 40°C in July and August. The aver-age amount of annual sunshine is 1888 h and annual precipitation 1413.7 mm, with 130–170 rainy days mainly in spring and summer. The average relative hu-midity is 75%. The frost-free period is 326 d while the frost season falls only in January and February.

The A. montana plantation, established in 1992, covers an area of 1.1 ha, with a density of 930 trees

per hectare and average DBH (diameter of breast height) of 18.1 cm. The soil is mainly a red soil of light clay, with a pH of 5.6.

2.2 Collection and disposal of litterfall

A sample plot of 400 m2 was selected in the plantation for our survey of stand age, density, height, DBH and soil. Ten 1 m × 1 m litter traps were laid out randomly within the sample plot to collect litterfall material, marked as sample Nos. 1–10. The traps were made of nylon nets with a 1-mm sieve, set 50 cm above the ground. The litter from these traps was collected at the end of each month from January 2008 to December 2008.

The litter collected each month was oven-dried at 60°C to a constant weight and weighed on an electron-ic balance to calculate the amount of monthly litterfall. After weighing, the litter was crushed and stored for determining the amounts of nutrient elements present.

2.3 Analysis of amounts of nutrients

The amount of N was determined by the semi-micro-Kjeldahl method, P by Mo-Sb colorimetry, K with a flame photometer and organic C by the potassium bichromate titrimetric method under oil-bath heating (Guan, 1986; Zhou, 1987).

3 Results and analysis

3.1 Dynamics of monthly litterfall mass

The mass of litterfall in a stand varies by months, contributing to the complex interactions of eco-factors (i.e., precipitation, temperature and wind) and bio-fac-tors (i.e., germination, growth and blossoming) (Law-rence, 2005; Polyakova and Billor, 2007; Scherer-Lorenzen et al., 2007).

During our research, litterfall was collected every month except in January, because persistent heavy rainfall at the end of 2007 caused majority of leaves, twigs and branches fallen in December and nothing was collected in January 2008 (Table 1). The mass of litterfall collected in the following months generally presented a progressive trend from February to De-cember in 2008. The amounts of litter were relatively small from February to April, i.e., a total amount of 1.24 t·ha−1. This probably results from the biotic char-acteristics of A. montana as a deciduous tree which germinates and sprouts mainly during this period. The litter collected from May to September showed

Forestry Studies in China, Vol.14, No.1, 201232

its progressive trend, mainly owing to ecological fac-tors, i.e., climate and temperature during this period. The intermittent drizzle in May and severe convection weather in June led to the defoliation of organs devel-oping in the early growing season. Frequent thunder-storms, tropical storms and typhoons in the summer caused extensive non-physiological defoliation. Most defoliation occurred in autumn and winter, i.e., in Oc-tober (7.36 t·ha−1), November (11.60 t·ha−1) and De-cember (24.99 t·ha−1), owing to dry and cold climatic conditions and strong winds along with physiological defoliation of this species. The results show that of the entire year-round mass of 58.08 t·ha−1, the amount of litterfall from October to December (43.95 t·ha−1) amounted to 75.67%, with a maximum of litterfall mass in December, accounting for 43.03% of the total.

3.2 Dynamics of monthly amounts of nutrients from A. montana litterfall

From our experiments, we conclude that the amount of organic C comprised the major part of litter ele-ments compared with others. As shown in Fig. 1, the graph of organic C largely presents a bimodal pattern, occurring in March–April and June, respectively. In May, the amount of organic C sharply decreased to 133.23 g·kg−1, the lowest for the whole year. After the increase in June, it gradually decreased and then in-creased after October. The large amount of organic C in the litterfall further proves that organic C released by litter decomposition is an important source of soil organic C and C, in the form of gas, returning to the atmosphere from litter decomposition plays a signifi -cant role in the global C budget.

The amount of N was the next largest to C of the nutrient elements in A. montana litterfall. As seen in Fig. 2, the amount of N gradually increased from February, reached its maximum in June (19.34 g·kg−1)

and then gradually decreased to its lowest level in De-cember (8.29 g·kg−1), generally presenting a unimodal pattern, similar to the studies of N in other species (Qi and Wang, 2010). As an important element, N affects the growth of A. montana and its concentration in the litter is closely associated with the rate of litter de-composition.

As an important element in cell walls and karyon, P is indispensable for plants especially in energy stor-age and transformation. In the acid soils of the tropics and subtropics, P is strongly fi xed and hard to absorb by plants, which limits their growth and development. In A. montana litter, the lowest level of P occurred in February (0.67 g·kg−1), while in March, May, June and July, the levels of P were comparatively high, all more than 1.00 g·kg−1, with the peak level occurring in May (1.10 g·kg−1). After July, the values of P gradually de-creased to their low level in December (0.69 g·kg−1) (Fig. 3).

In the litter of A. montana, the variation in levels of K largely presented a unimodal pattern. As shown in Fig. 4, the values of K were high in April, July, Sep-tember, October and November, all above 5.00 g·kg−1. The peak value occurred in April (7.96 g·kg−1), while the lowest were seen in March (2.88 g·kg−1) and June (2.61 g·kg−1). The role of K in plants mainly lies in its adjustment (i.e., adjustment in opening and closing of pores), water uptake by roots, enzyme activity, mate-rial transportation and infiltration. The occurrence of its peak value in April, the period critical for the growth of the species, contributes to the growth of A. montana.

3.3 Amounts of monthly nutrient returns from A. montana litterfall

The average monthly returns of C, N, P and K can be calculated by multiplying the amount of nutrient

Table 1 Monthly amounts of litterfall of A. montana (t·ha−1) Sample Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.1 0 0.02 0.01 0 0.15 0.27 0.13 0.11 0.39 0.56 0.94 3.052 0 0.03 0.04 0.02 0.07 0.24 0.30 0.20 0.39 1.32 1.85 3.373 0 0.12 0.03 0.01 0.05 0.22 0.35 0.15 0.46 0.25 0.66 2.554 0 0.05 0.05 0.01 0.10 0.17 0.21 0.15 0.29 0.41 0.77 2.365 0 0.06 0.01 0.02 0.07 0.17 0.16 0.20 0.29 0.12 0.70 2.056 0 0.10 0.08 0.01 0.18 0.24 0.34 0.49 0.40 1.49 0.95 2.377 0 0.11 0.01 0.03 0.20 0.50 0.47 0.33 0.48 0.43 1.20 2.318 0 0.13 0.07 0.07 0.17 0.48 0.35 0.13 0.47 0.65 1.26 1.629 0 0.02 0.02 0.01 0.08 0.25 0.18 0.14 0.44 1.07 1.40 2.0310 0 0.01 0.07 0.03 0.11 0.17 0.33 0.10 0.58 1.08 1.87 3.29Total 0 0.65 0.38 0.21 1.19 2.70 2.82 1.99 4.19 7.36 11.60 24.99

LIN Han et al.: Monthly variation in litterfall and the amount of nutrients in an Aleurites montana plantation 33

with the mass of monthly litterfall (Lin et al., 2005). In terms of annual nutrient returns of litterfall, the re-turn of C was dominant, followed by N and K, while the return of P was the smallest. The monthly return of C generally showed an ascending trend (Fig. 5), starting from a very low level in February to May, only accounting for 3.16% of the annual return. The average monthly return of C from June to November was 140.15 kg·ha−1, less than the monthly average of annual C return of 162.49 kg·ha−1. The C return in De-cember contributed disproportionately to the annual C return, which reached 890.10 kg·ha−1 in a single month, amounting to as much as 50% of the total an-

nual return. The annual N return was 66.42 kg·ha−1 and the dy-

namics of monthly N return were very similar to that of the C return (Fig. 6). The N returns from February to April were the smallest during the year, with a total of 1.46 kg·ha−1 in three months. The N returns in the following four months were still below the monthly average of annual N return, ranging from 1.76–5.22 kg·ha−1. The N returns in the remaining months were all above the monthly average and that of Decem-ber alone accounted for 31.19% of the total annual amount.

The annual return of K was 26.40 kg·ha−1 and that of P 4.49 kg·ha−1. The dynamics of monthly K and P returns during the fi rst four months were the smallest, far below their monthly averages. From August, the K and P returns sharply increased and reached their peak in December. Their returns in the last three months accounted for over 70% of the total annual amount (Figs. 7–8).

4 Discussion and conclusions

The amount of A. montana litter collected from Feb-ruary to December generally presented a progressive trend, especially from April to December, with that of August as the one exception. No litter was collected in January 2008 because A. montana is a typical decidu-ous tree and the continuous heavy rainfall at the end of the previous year led to most of leaves, twigs and branches fallen in December 2007. As a coastal city, Fuzhou is usually affected every summer by typhoons, most often in August. The integrated effect of deep convection weather along with strong winds blew away some leaves, twigs and branches, even from the plantation. This may explain the reason why the lit-ter collected in August was less than that in June and July. Maximum defoliation occurred in the autumn and winter. Of the total litterfall mass of 58.08 t·ha−1, the litter from October to December (43.95 t·ha−1) ac-counted for 75.67%.

In studies of plantations of Mytilaria laosensis, Castanopsis hystrix, Michelia macclurei and Pinus massoniana (Lu et al., 2008), the dynamics of month-ly mass of litterfall and foliage litter showed similar trends with two peaks, occurring more or less in the same months. The peaks of foliage litter mass of M. laosensis occurred in April and September, those of C. hystrix in March and September, those of M. macclu-rei in April and November and those of P. massoniana in February and September. Similarly, the peaks of total stand litterfall mass of M. laosensis occurred in April and July, those of C. hystrix in March and Octo-ber, of M. macclurei in April and December and of P.

Fig. 1 Monthly C contents in A. montana litterfall

Fig. 2 Monthly N contents in A. montana litterfall

Fig. 3 Monthly P contents in A. montana litterfall

Fig. 4 Monthly K contents in A. montana litterfall

Forestry Studies in China, Vol.14, No.1, 201234

massoniana in March and November, presenting simi-lar trends with the peaks only one month earlier or lat-er (Lu et al., 2008). Given the progressive trend rather than a bimodal distribution of A. montana litterfall in our study, its biological characteristics, especially the obvious deciduous nature in winter, may partly explain the difference in the dynamics of monthly lit-terfall.

The results show that the average monthly amounts of N, P and K in A. montana litter were 13.63, 0.88 and 4.49 g·kg−1, respectively, while those of F. hodgin-sii litterfall were 8.79, 0.54 and 3.26 g·kg−1 (Lin et al., 2005). Hence, the average monthly amounts of N, P and K in A. montana litter were 35.51%, 38.64% and 27.39% more than those of F. hodginsii. The amounts of nutrients in litterfall may partly reflect the uptake effi ciency of nutrients by plants, in that these nutrients

could be used again through nutrient return and trans-formation. Compared with F. hodginsii, A. montana has an advantage in nutrient uptake and recapture. In this sense, the high maintenance of nutrient budgets by A. montana makes it a suitable species for ecologi-cal public-benefit forests, which can improve forests with its application as well as maintain the natural productivity of eco-forests.

The total annual returns of C, N, P and K were 1884.75 kg·ha−1, of which the annual contribution was in the following order: C > N > K > P, consistent with the research in Pinus massoniana by Yao et al. (2006) and in Cinnamomum camphora by Li et al. (2011). Similar to the dynamics of the mass of monthly lit-terfall, the monthly returns of C, N, P and K generally showed an ascending trend with the peak values for each of the four elements in December. The nutrient returns are affected by the integration of soil fertil-ity, the physiological traits of the tree and its ability to transfer nutrients. The mass of A. montana litter-fall and the dynamics of its monthly nutrient returns provide, to a certain degree, a scientifi c reference for planting and fertilizing this species.

Acknowledgements

This study was sponsored in part by the Fujian Sci-tech Bureau for research in the universities of Fujian Province (No. 2008F5014). The Fujian Forest Ecolog-ical System Process and Management Key Laboratory and the Forest Ecology Research Center of the Fujian Agriculture and Forestry University (FAFU) provided major funding and logistical support and dedicated the site to long-term research. Special thanks to Professor Hong Wei for his work in establishing the research area, for statistical and fi eld assistance and to Profes-sor He Dong-jin for reviewing this paper.

References

Chapin F S III, Matson P A, Mooney H A. 2002. Principles of Terrestrial Ecosystem Ecology. New York: Springer-Verlag

Chen J Z, Zhang S S. 2008. Aleurites montana, the renewal and repairing wood species in ecological public welfare forests. Subtrop Agric Res, 4(2): 101–104 (in Chinese with English abstract)

Fan M H, Li J Y, Fan Z Q, Tian M, Ni S. 2008. Cloning and characterization of SAD from Vernicia montana and con-struction of filamentous fungi expression vector. Acta Bot Boreal-Occident Sin, 28(1): 18–22 (in Chinese with English abstract)

Guan S Y. 1986. Soil Enzyme and Study Method. Beijing: China Agriculture Press (in Chinese)

Guo J F, Yang Y S, Chen G S, Lin P, Xie J S. 2006. A review on litter decomposition in forest ecosystem. Sci Silv Sin, 42(4):

Fig. 5 Monthly returns of C of A. montana litterfall

Fig. 6 Monthly returns of N of A. montana litterfall

Fig. 7 Monthly returns of K of A. montana litterfall

Fig. 8 Monthly returns of P of A. montana litterfall

LIN Han et al.: Monthly variation in litterfall and the amount of nutrients in an Aleurites montana plantation 35

93–100 (in Chinese with English abstract)Lawrence D. 2005. Regional-scale variation in litter production

and seasonality in tropical dry forests of southern Mexico. Biotropica, 37: 561–570

Li J B, Yan W D, Ma X H. 2011. Litter fall production and nutrient dynamics of Cinnamomum camphora in subtropical region. J Cent South Univ Forest Technol, 31(5): 220–228 (in Chinese with English abstract)

Liang J R. 2005. Grafting and seedling culture techniques of Aleurites montana. Spec Econ Anim Plant, (5): 28 (in Chi-nese)

Lin B, Liu Q, Wu Y, He H. 2004. Advances in the studies of forest litter. Chin J Ecol, 23(1): 60–64 (in Chinese with Eng-lish abstract)

Lin C F, Li Z, Niu Z P, Zhang Y L, Han Y G, Chen G S. 2005. Litterfall nutrient dynamics in Fokienia hodginsii plantation. J Fujian Agric Forest Univ (Nat Sci Edn), 34(1): 63–66 (in Chinese with English abstract)

Ling J Q, Zhang X Y, Chen Y T. 1995. The comparative wood anatomy of Vernicia fordii, Vericia montana and Aleurites moluccana (Euphorbiaceae). Acta Sci Nat Univ Pek, 31(6): 745–751 (in Chinese with English abstract)

Lu L H, Jia H Y, He R M, Li J L, Tan S Y. 2008. A preliminary study on litter falls of six kinds of plantations in the tropi-cal South Asia. Forest Res, 21(3): 346–352 (in Chinese with English abstract)

Moorhead D L, Sinsabaugh R L. 2006. A theoretical model of litter dacay and microbial interaction. Ecol Monogr, 76(2): 151–174

Polyakova O, Billor N. 2007. Impact of deciduous tree species on litterfall quality, decomposition rates and nutrient circula-tion in pine stands. Forest Ecol Manage, 253: 11–18

Qi Z M, Wang K Y. 2010. Litter production and nutrient return of vegetations in subalpine timberline ecotone of west Sich-uan, China. Chin J Ecol, 29(3): 434–438 (in Chinese with English abstract)

Scherer-Lorenzen M, Bonilla J L, Potvin C. 2007. Tree species richness affects litter production and decomposition rates in a tropical biodiversity experiment. Oikos, 116: 2108–2124

Wei R P, Xue L, Chen H Y, Peng Y Q, Xu S K. 2005. Effects of foliage spraying with rare earth on growth and physiologi-cal index of Vernicia montana seedlings. Sci Silv Sin, 41(2): 164–168 (in Chinese with English abstract)

Wu C Z, Hong W, Jiang Z L, Zheng F H. 2000. Advances in re-search of forest litter-fall in China. Acta Agric Univ Jiangxi, 22(3): 405–410 (in Chinese with English abstract)

Yao R L, Ding G J, Wang Y. 2006. The annual variation feature of litter and nutrient restitution in different density Pinus massoniana plantation. J Nanjing Forest Univ, 30(5): 83–86 (in Chinese with English abstract)

Zhang X. 2009. Preliminary study on the seedling-raising techniques and nursery stock’s growth rhythm of Aleurites montana. Subtrop Agric Res, 5(3): 159–161 (in Chinese with English abstract)

Zhou L K. 1987. Soil Enzymology. Beijing: Science Press (in Chinese)

(Received February 28, 2011 Accepted April 12, 2011)