BIOTROPIA Vol. 29 No. 1, 2022: 69 - 80 DOI: 10.11598/btb.2022.29.1.1627 69 LITTERFALL, LITTER DECOMPOSITION AND NUTRIENT RETURN OF REHABILITATED MINING AREAS AND NATURAL FOREST IN PHANGNGA FORESTRY RESEARCH STATION, SOUTHERN THAILAND JETSADA WONGPROM1*, ROONGREANG POOLSIRI2, SAPIT DILOKSUMPUN2, CHATCHAI NGERNSAENGSARUAY3, SAMITA TANSAKUL2 AND WASAN CHANDAENG1 1Forestry Research Center, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand 2Department of Silviculture, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand 3Department of Botany, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand Received 3 August 2021 / Accepted 20 December 2021 ABSTRACT Litterfall and litter decomposition play important roles in the maintenance of nutrient cycling and rehabilitation of degraded lands. Litterfall, litter decomposition and nutrient return were investigated in a 27-year- old Acacia mangium plantation on sandy and clay sites, and in a mixed plantation at the Phangnga Forestry Research Station, Phangnga Province, Thailand. Additionally, secondary and primary forests were investigated and compared with the values obtained from the Acacia mangium and the mixed plantations. The results indicated that litter production in A. mangium plantation on sandy and clay sites, and in mixed plantations (15.47, 11.68 and 7.89 t/ha/yr, respectively) was higher than that in the secondary and primary forests (6.34 and 6.92 t/ha/yr, respectively). The rate of litter decomposition was the greatest in the secondary forest (3.01/yr) and the lowest occurred in the primary forest (1.15/yr). The decomposition rate of the mixed leaf litter between native trees and A. mangium in plantations was higher than that of only A mangium leaf, except in the mixed plantations. A high initial nitrogen concentration in A. mangium could accelerate litter decomposition and improve litter quality in the mixed litter. In addition, the nutrient return in plantations was higher than that in the secondary and primary forests, especially for N. Increased litter production, high decomposition rate and nutrient return from A. mangium plantation had important roles in nutrient cycling, suggesting that a mixed plantation consisting of A. mangium and native trees should be considered for the reclamation of mining land. Keywords: litter decomposition, litterfall, mining rehabilitation, nutrient return, tropical forest INTRODUCTION Mining operations have been undertaken on a global scale as the raw minerals obtained play an important role in economic and infrastructure development. A high level of mineral production has been reported in Asian countries (Reichl et al. 2017). The ill-effects of mining cause severe impacts on the ecosystem, including soil degradation, water and air pollution, and loss of wildlife habitat. The vegetation richness and soil properties are destroyed by mining activities, resulting in the degradation of the ecosystem (Bell & Donnelly 2006; Tripathi et al. 2016). Improving environmental conditions in mining areas using natural methods takes a long time (Oktavia et al. 2015). Barriers to natural regeneration include environmental factors such as water, soil pH and soil properties (Thaiutsa & Rungruangsilp 1990; Tripathi et al. 2016). Forest plantations have been established on degraded lands to improve the soil properties and ecosystem function (Singh et al. 2004; Zhang et al. 2014; Oktavia et al. 2015). Rehabilitation in such areas by planting nitrogen-fixing trees has been recommended and they have been planted on many sites as *Corresponding author, email: fforjdw@ku.ac.th mailto:fforjdw@ku.ac.th BIOTROPIA Vol. 29 No. 1, 2022 70 they grow well and have a high aboveground biomass and litter production (Dutta & Agrawal 2003; Singh et al. 2004). Acacia mangium is the most preferred species for reclamation efforts in mining land (Martpalakorn 1990; Oktavia et al. 2015) and other degraded lands (Kamo et al. 2008). Soil properties and microclimate under such plantations are improved, resulting in the accelerated natural regeneration of native forest species (Parrotta 1999; Inagaki et al. 2010). Litter production and decomposition play important roles in nutrient cycling and the improvement of soil fertility in terrestrial ecosystems (Goma-Tchimbakala & Bernhard- Reversat 2006; Paudel et al. 2015). On degraded lands, litterfall and litter decomposition are keys to restoring the ecology and soil properties because the litter is a nutrient source (Lugo 1992; Parsons & Congdon 2008). Nutrient contents of plants are closely related to tree species, especially nitrogen which is abundant in nitrogen-fixing trees (Parrotta 1999; Singh et al. 2004). Tree composition and forest type are the main factors influencing the quality of the litter produced (Parrotta 1999; Zhou et al. 2006; Tang et al. 2010; Paudel et al. 2015). In addition, climatic factors can significantly affect litterfall (Zhou et al. 2006; Scherer-Lorenzen et al. 2007; Triadiati et al. 2011). Litter fractions that fall onto the forest floor are decomposed by organisms living in the soil, and nutrients are subsequently released to the forest floor, resulting in the improved soil properties and a better forest community, which maintain forest function (Parrotta 1999). Litter quality and microclimate are related to the litter decomposed by soil microbes (Parsons & Congdon 2008; Cizungu et al. 2014; Zhong et al. 2017). Furthermore, litter decomposition varies depending on the tree species, successional stage, and forest type (Lugo 1992; Parsons & Congdon 2008; Tang et al. 2010). The efficiency of plantations in degraded land rehabilitation not only builds productivity and improves forest structure but also increases forest function such as nutrient cycling (Lugo 1992; Parrotta 1999). A high litter decomposition rate and nutrient return encouraged natural succession and increased soil nutrients (Lugo 1992; Celentano et al. 2011), which reduced the time required for the restoration process. Therefore, the objective of the current study was to evaluate the potential of A. mangium plantation for mining rehabilitation, focusing on litter production, decomposition and nutrient return in comparison to secondary and primary forests. An effort has been made to compare the rehabilitated plantation area to secondary and primary forests. MATERIALS AND METHODS Study Sites This study was carried out in an abandoned tin mining area, in the Phangnga Forestry Research Station, Phangnga Province, Southern Thailand (8˚46′5″ N, 98˚16′7″ E) (Fig. 1). Exotic trees, such as Acacia mangium and Eucalyptus camaldulensis were commonly planted for tin mining reclamation in Thailand. The mining was operated by the gravel pumping method. Landform after mining was divided into clay, sand, and gravel areas. Soil nutrients were observed to be very low (Thaiutsa & Rungruansilp 1990). The experimental plots were established in a 27-year-old A. mangium plantation, planted in a sandy soil area (AMS), in a clay soil area (AMC), and mixed plantation (MP). The planted trees in MP consisted of A. mangium, Eucalyptus camaldulensis and Dipterocarpus alatus. Litterfall, litter decomposition and nutrient return of rehabilitated mining areas – Jetsada Wongprom et al. 71 Figure 1 Location of study sites in Phangnga Province, Southern Thailand In addition, the experimental plots were established in a secondary forest (SF, located at 8˚39' 28″ N, 98˚24′ 35″ E) and a primary forest (PF, located at 8˚51' 11″ N, 98˚20′ 5″ E) as reference sites. The SF plot was in an approximately 30-year-old site abandoned after shifting cultivation. The PF plot was classified as a low tropical rainforest. Dominant native trees in the 27-year-old plantations and the secondary forest were pioneer tree species including Carallia brachiata, Aporosa planchoniana, Bridelia tomentosa, Vitex pinnata, Microcos paniculata and Eurya acuminata. Meanwhile, dominant trees in PF were Swintonia schwenckii, Dipterocarpus kerrii, Mesua ferrea, Hopea griffithii and Gluta elegans. Tree composition and dominant trees in AMS, AMC, MP, SF and PF were reported by Wongprom et al. (2020). Climatic conditions during the study were recorded at the climate station in the Takuapa District. The rainfall was 3,260.10 mm with the rainy season occurring from April to November and the dry season happening from December to March. The mean relative humidity was 83% and the mean temperature was 27.58 °C. Data on rainfall, mean temperature and relative moisture recorded during the study are shown in Figure 2. Figure 2 Climatic conditions at Takuapa District, Phangnga Province during the study Phangnga Province Bangkok Takuapa District PF PFRS SF Primary forest (PF) Secondary forest (SF) Phangnga Forestry Research Station (PFRS) N BIOTROPIA Vol. 29 No. 1, 2022 72 Litter Production Three experimental plots (each 40 x 40 m) were established in each AMS, AMC, MP, SF, and PF for estimating the amount of litterfall production. Five litter traps (each 1 x 1 m) with a 2 mm mesh size were placed 1 m above the ground in each plot. Litterfall in the traps was collected monthly for 1 year. Litterfall samples were sorted into leaf, branches, reproductive parts and miscellaneous. A. mangium litter was separated from that of the other tree species. All samples were oven-dried at 80 °C for 48 h until reaching constant weight. The samples (leaf, branches, reproductive parts and miscellaneous) were analyzed during both the rainy and dry seasons. The organic debris obtained from each site was analyzed as a single sample, as it was difficult to identify the components as they were very small and had a similar texture. Litter Decomposition and Nutrient Return Nylon bags (50 x 50 cm) with a 2 mm mesh size were used for investigating litter decomposition. Leaf having the top five Importance Value Index (IVI) trees in AMS, AMC, MP and SF, and the top seven IVI trees of PF were selected to investigate litter decomposition. Litter decomposition was divided into two classes: 1) mixed leaf litter in AMS, AMC, MP, SF and PF; and 2) pure A. mangium leaf litter in AMS, AMC, and MP. In each case, 30 g samples of air-dried leaf litter were filled into the nylon bags according to the IVI ratio of the dominant trees for each site. The IVI of trees in AMS, AMC, MP, SF and PF was reported by Wongprom et al. (2020). The litter water content was determined by first, oven- drying subsamples of air-dried litter at 80 °C for 48 h to obtain the initial dry mass. Twelve litter bags from each treatment with three replications were randomly placed in each plot. Three samples of both mixed leaf litter and pure A. mangium leaf litter were retrieved monthly. The leaf litter remaining in each bag was brushed to remove any soil particles and roots. The remaining litter was oven-dried at 80 °C for 48 h until a constant weight was recorded. The annual litter decomposition rate (k) was calculated according to the negative exponential decay model (Olson 1963) given as k = ln (X/X0)/t, where X0 is the initial dry weight, X is the dry weight remaining at the end of the study, and t is the time period in years. Nutrient return (N, P, K, Ca, and Mg) to the forest floor (kg/ha) was estimated by multiplying the amount of litter production by the nutrient concentration of litter for each site. Chemical Analysis of Litter Nutrient concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) of leaf, branches, reproductive parts and miscellaneous obtained from the study sites were determined during the rainy (April to November) and dry (December to March) seasons. Samples of each litter type in the rainy and dry seasons were mixed and analyzed. The concentration of N was measured based on dry combustion using a CNHS analyzer, while the concentrations of P, K, Ca, and Mg were determined by wet washing with NHO3-HClO4 acid (HNO3: HClO4; 5: 2). The concentration of P was analyzed using the vanadomolybdate yellow color method with a spectrometer at a wavelength of 440 nm, while the concentrations K, Ca, and Mg were analyzed using atomic absorption spectrometry. Data Analysis Nutrient concentrations of each litter sample during the rainy and dry seasons were averaged to calculate the amount of nutrients return. The annual litter production, nutrient return and litter decomposition rate among sites were analyzed using a one-way ANOVA and the means were compared with the Tukey HSD test at a 5% probability level. RESULTS AND DISCUSSION Litter Production The annual litter production was significantly different among sites (P < 0. 05). AMS had the highest litterfall followed by AMC, MP, PF, and SF (Table 1). Litterfall, litter decomposition and nutrient return of rehabilitated mining areas – Jetsada Wongprom et al. 73 Table 1 Litter production (leaf, branches, reproductive parts and miscellaneous) (t/ha/yr) of A. mangium (AM) and native trees and planted trees (NPT) in the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC), mixed plantation (MP), secondary forest (SF), and primary forest (PF) Site Leaf Branches Reproductive parts Miscellaneous Total AM NPT AM NPT AM NPT AMS 5.90a 2.85b 0.74 1.67 2.86a 0.57 0.88a 15.47a AMC 3.56ab 3.83ab 0.56 1.20 1.60b 0.50 0.43b 11.68b MP 1.52b 2.86b 0.59 1.06 0.84b 0.51 0.51ab 7.89c SF - 4.12ab - 0.76 - 0.74 0.72ab 6.34c PF - 4.72a - 0.89 - 0.72 0.59ab 6.92c F value 11.59** 8.03** 1.83ns 0.87ns 16.55** 2.02ns 4.58* 27.21** Notes: * = significant difference; ** = very significant difference; ns = non-significant difference; a - c = different superscripts in the same column indicate significant differences at P < 0.05. Litter production peaked in the dry season (December to March) (Fig. 3), as a response to the water stress, which was similar to that of other tropical forests (Triadiati et al. 2011; Cizungu et al. 2014). Leaf component was the main litter falling onto the forest floor in AMS, AMC, MP, SF and PF, and made up around 54 to 62% of the total litter. However, the amount of reproductive parts in AMS and AMC was relatively high compared to branches, especially the reproductive parts of A. mangium as it fell almost all year. A large amount of litter from A. mangium in AMS was resulted from the high tree density and crown cover, while A. mangium in AMC and MP had a low crown cover due to the high mortality rate. Litters from other trees in AMS, AMC, and MP came from native tree species. Planted trees in MP such as D. alatus and E. camaldulensis were also a main source of litter. Leaf litter is a significant contributor of annual primary production and nutrient capital in a terrestrial ecosystem (Cizungu et al. 2014; Paudel et al. 2015). Figure 3 Total monthly litter production (t/ha/yr) of the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC), mixed plantation (MP), secondary forest (SF), and primary forest (PF) BIOTROPIA Vol. 29 No. 1, 2022 74 This study showed that the amount of litter production in AMS and AMC was higher than that in both SF and PF. A forest plantation with fast-growing trees is highly effective at building litter production compared to a natural forest (Goma-Tchimbakala & Bernhard-Reversat 2006) and secondary forest (Lugo 1992; Kamo et al. 2008). Post mining reclamation should focus on increasing the aboveground biomass and litter production to improve the ecosystem. A. mangium is one species recommended for degraded land restoration. Acacia grows well and has high aboveground biomass compared to native trees (Martpalakorn 1990; Kamo et al. 2008). However, the total litter production in MP was similar to that in PF and SF, although A. mangium had less litter production. The canopy cover of A. mangium can promote a high litterfall. Fast nitrogen-fixing tree plays important role in the early stage by rapid growth to create a canopy in order to suppress the weeds and shrubs that could obstruct the establishment of native tree understory vegetation and to increase nitrogen availability (Ingaki et al. 2010; Lanuza et al. 2018). However, the litterfall in AMS, AMC and MP was not only sourced from planted trees but also native trees through natural succession. Old plantations have high tree diversity and richness (Lugo 1992; Koonkhunthod et al. 2007), as litterfall is contributed to by native trees. Native tree species are usually pioneer trees having high growth rates (Chazdon 2014; Chen et al. 2017) and their litter production increases with succession age (Zhou et al. 2006; Feng et al. 2019). Litterfall production plays an important role in forest functions such as carbon and nutrient cycling (Moura et al. 2016; Paudel et al. 2015; Lanuza et al. 2018) because litter is a source of nutrient pools, which releases nutrient to the forest floor via litter decomposer activities (Lugo 1992; Fisher & Binkley 2000), suggesting that A. mangium should be recommended for reclamation in a mining area due to the capability of A. mangium in bringing out high litter production. Litter production in the SF and PF study sites was not different, resulting from pioneer trees producing litter in natural succession. Forest structure and tree composition of succession forests affected litter biomass (Lanuza et al. 2018). Long-lived pioneer trees and high tree diversity were observed in SF. The litter production in the SF and PF study sites was similar to that in many evergreen forests in Thailand (6.42 to 7.85 t/ha/yr) (Bunyavejchewin 2001; Glumphabutr et al. 2007). However, litter production in our study was lower than that in other tropical forests (8.30 - 13.67 t/ha/yr) (Anderson et al. 1983; Tang et al. 2010; Triadiati et al. 2011; Paudel et al. 2015). Litter Decomposition Litter decomposition of pure litter and mixed litter was significantly different among treatments (P < 0.05). The litter decomposition rate (k) ranged between 1.15 and 3.01/yr, which was classified as medium to high levels. The decomposition rate in SF was the highest, indicating litters were rapid litter decay, but not different in AMC (2.91/yr) (Table 2). The dominant trees in SF and AMC were pioneer tree species and were of similar tree composition (Wongprom et al. 2020), having thin and flexible leaves without a prominent skeleton, and so could decay easily. On the other hand, a low rate of decomposition was found in climax forest trees due to their thick, tough leaf and prominent midribs and veins. The leaf morphology of trees (leaf thickness, roughness, toughness) significantly affects the rate of litter decomposition (Liao et al. 2006; Cizungu et al. 2014). In addition, the chemical properties of leaf litter, including high N, N/ P, low C/ N and low lignin, are generally positive contributors to decomposition (Xuluc-Tolosa et al. 2003; Liao et al. 2006; Cizungu et al. 2014; Rai et al. 2016). Similarly, leaf litter in SF, AMS, AMC, and MP had a high nitrogen content, which could explain their faster rate of decomposition. Leaf litter in AMS, AMC, and MP was rich in nitrogen due to the litter produced by A. mangium. In addition, leaves of dominant pioneer trees in SF, AMS AMC and MP have thin and less rigid leaves leading to a high decomposition rate compared to PF. However, the litter decomposition of PF was of moderate level (1.15/yr), which was similar to other climax tropical forests (Hättenschwiler et al. 2011). Litterfall, litter decomposition and nutrient return of rehabilitated mining areas – Jetsada Wongprom et al. 75 Table 2 Decomposition rate of pure A. mangium and the mixed leaf in the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC), mixed plantation (MP), secondary forest (SF), and primary forest (PF) Site Type of leaf k (constant) AMS Pure A. mangium leaf 1.56bc Mixed leaf 1.64bc AMC Pure A. mangium leaf 1.88bc Mixed leaf 2.91a MP Pure A. mangium leaf 2.05b Mixed leaf 1.87bc SF Mixed leaf 3.01a PF Mixed leaf 1.15cd F value 7.905* Notes: * = significant difference; a - d = different superscripts in the same column indicate significant differences at P < 0.05. Climate conditions and soil microbials significantly affect litter decomposition (Berg & McClaugherty 2008). This study indicated that rainfall and relative humidity in the study sites were of similar conditions. However, soil microbials could be different because soil properties in AMS, AMC, and MP were of poor soil compared to that in SF and PF, especially in terms of total N and OM (Wongprom et al. 2020), leading to low diversity and abundance of soil microbials (Zhang et al. 2016). Soil nutrients, N and P and Organic Matter (OM) are significantly correlated with soil microbials (Zhang et al. 2016; Ngugi et al. 2020). Low decomposition rate of litter was found in the PF study site. Microclimate conditions may slightly affect litter decomposition. Litter quality of the restored forest may significantly determine litter decomposition. Meanwhile, litter decomposition rate changes depending on successional stage and tree composition (Moura et al. 2016; Lanaza et al. 2018). A study conducted by Xuluc-Tolosa et al. (2003) indicated that pioneer trees in the early succession phase has a higher decay rate than tree species in the late succession phase because pioneer trees have a high initial N concentration and low C/N. Pioneer tree species have high nutrient resorption efficiency and high leaf nutritional quality, especially N concentration (Gomes & Luizão 2012). Our study showed that a litter mixture of A. mangium and native trees generally resulted in a faster decay than the decay of PF litter. This result could be affected by synergistic effects of mixed litter with high litter quality and a high initial N concentration. Mass loss is positively correlated with initial N concentration (Liu et al. 2016). Thus, poor litter quality is improved. Mixing litters from various trees accelerate the mass loss, enhance the nutrient release and nutrient cycling (Liu et al. 2016; Trogisch et al. 2016; Cizungu et al. 2016) and different litter components may change the litter chemical components and the decomposer community (Gartner & Cardon 2004). Nutrient Concentration in Litter and Nutrient Return Nutrient concentration in litter produced by A. mangium in this study varied among components (leaf, branches and reproductive parts). However, the N concentration was greater than that of P, K, Ca, and Mg (Fig. 4). Nutrient concentration in the leaf and branches litters of A. mangium in all sites followed the order of N>Ca>K>Mg>P, except for the reproductive parts, where the K concentration was higher than that of Ca. BIOTROPIA Vol. 29 No. 1, 2022 76 Figure 4 Nutrient concentration of pure A. mangium leaf, branches and reproductive parts of the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC) and mixed plantation (MP) N concentration in the litter of other trees (native tree species in AMS, AMC, MP, SF and PF, and planted trees in MP) was the highest for all litter components, and was especially high in the litter miscellaneous component. The P concentration was relatively high in the miscellaneous and reproductive parts components, while the concentrations were similar for K, Ca and Mg in the leaf, branches, reproductive parts and miscellaneous components. The nutrient concentration of leaf, branches, reproductive parts and miscellaneous for the other tree species in AMS, AMC, MP, SF, and PF are shown in Figure 5. Figure 5 Nutrient concentration of mixed leaf, branches, reproductive parts and miscellaneous litter of native tree species in the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC), secondary forest (SF), and primary forest (PF) and planted trees and native tree species in mixed plantation (MP) Litterfall, litter decomposition and nutrient return of rehabilitated mining areas – Jetsada Wongprom et al. 77 The nutrient return of N, P, K, Ca and Mg from litters to forest floor was significantly different among sites. N contributed the highest nutrient return to the forest floor in all sites. The large amounts of N, P, K, Ca and Mg returned in AMS, AMC, and MP were mostly from the litter of the planted trees, especially A. mangium (Table 3). A. mangium is the dominant tree with a large size and crown cover, although the tree density is low, particularly in the AMC and MP sites (Wongprom et al. 2020). Litters from planted trees in a plantation are still the main nutrient source to the forest floor, although the vegetation composition are shifted after restoration. Leaf litter was the main source of nutrient return in all sites. However, nutrient return from miscellaneous and reproductive parts of A. mangium was relatively high. The annual nutrient return of AMS, AMC and PF followed a pattern of N>Ca>K>Mg>P, while that of MP and SF followed a pattern of N>K>Ca>Mg>P (Table 4). The annual nutrient return of N, P, Ca and Mg to forest floor in AMS and AMC was significantly higher than that in SF and PF, especially for the nitrogen. Meanwhile, the annual nutrient return of N, P, Ca, and Mg in SF was similar to that in PF. Forest community on a restored site and in a secondary forest can accelerate litter decomposition and nutrient cycling because the litter quality is improved. Nutrients returned to the forest floor can promote natural regeneration and tree growth, resulting in a complex forest structure in the long term, especially as N is a significant nutrient in developing a forest community and establishing seedlings and saplings during mining restoration and natural succession in a degraded land (Zhao et al. 2013; Lei et al. 2015). Fast litter decomposition of restored sites resulted in high nutrient depositions, especially N. In the current study, N was the major nutrient return in AMS, AMC and MP, and was significantly higher than that in SF and PF. The high N return may be resulted from A. mangium due to the Acacia being a nitrogen-fixing tree. Moreover, the return of P, K, Ca and Mg to the soil of the rehabilitated sites was greater than that in PF. Soil nutrients of A. mangium plantation in an abandoned mining area are higher compared to that in an abandoned mining area without the A. mangium plantation, especially in terms of N and soil organic matter (Wongprom et al. 2020). Therefore, the study result indicated that A. mangium improves soil chemical properties through nutrient cycling processes. N flux of nitrogen-fixing tree plays an important role in the early succession (Moura et al. 2016). Table 3 Nutrient return (kg/ha/yr) of A. mangium (AM) litter and native trees and planted trees (NPT) litter in the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC), and mixed plantation (MP) Site N P K Ca Mg AM NPT AM NPT AM NPT AM NPT AM NPT AMS 18.96a 7.12 0.94a 0.49 2.07a 1.48b 2.92a 2.14ab 1.91a 1.20b AMC 10.97a 6.52 0.68a 0.52 1.37a 2.93a 2.08ab 2.64a 1.41a 1.94a MP 5.47b 6.42 0.30b 0.49 0.85b 2.73a 1.11b 1.91b 0.62b 1.56ab F value 26.37** 1.09ns 18.39** 0.37ns 14.95** 29.01** 14.48** 6.19* 15.66** 12.36** Notes: * = significant difference; ** = very significant difference; ns = non-significant difference; a - b = different superscripts in the same column indicate significant differences at P < 0.05. Table 4 Nutrient return (kg/ha/yr) of litter to the forest floor in the 27-year-old A. mangium plantation in sandy soil area (AMS), clay soil area (AMC), mixed plantation (MP), secondary forest (SF), and primary forest (PF) Site N P K Ca Mg AMS 26.09a 1.43a 3.56b 5.06a 3.12a AMC 17.49b 1.19a 4.30a 4.72a 3.36a MP 11.89c 0.79b 3.58b 3.03b 2.18bc SF 8.26c 0.63b 4.21ab 2.72b 1.74bc PF 7.47c 0.61b 2.77c 3.20b 1.28c F value 53.60** 33.78** 15.87** 22.75** 34.63** Notes: ** = significant difference; a - c = different superscripts in the same column indicate significant differences at P < 0.05. BIOTROPIA Vol. 29 No. 1, 2022 78 Fast-growing tree plantations are commonly planted for wood production. However, they are also planted for forest restoration in degraded lands. High litter production and litterfall are significant parts in restoration processes (Parrotta 1999). The N nutrient returned to the forest floor from nitrogen-fixing tree plantations was significantly higher than that from a non- nitrogen-fixing tree plantations and for other nutrients (Bernhard-Reversat 1996). The litter decomposition of nitrogen-fixing trees positively affect the acceleration of nutrient release and nutrient deposition to promote vegetation development and improve soil properties (Lugo 1992; Ruiz-Jaén & Aide 2005; Lanuza et al. 2018), suggesting that A. mangium plantation should be used for improving nutrient cycling in mining reclamation. Nutrient cycling is a key process for mining rehabilitation, relating to vegetation succession and soil development in the mining area. CONCLUSION A. mangium plantation is an effective way for mining rehabilitation compared to the reference sites. A. mangium plantation showed relatively high litter production and litter decomposition rate which could modify the litter quality in the litter mixture. Mixed litter sourced from nitrogen-fixing trees and native trees in plantations can enhance litter decomposition, which can result in higher levels of soil improvement and revegetation. AMS, AMC and MP had high levels of nutrient return compared to that in SF and PF, leading to contributing high levels of soil nutrients to forest floor, particularly N. The litter mixture in MP decomposed more rapidly compared to that in PF with improved the litter quality. A mixed plantation consisting of A. mangium and native tree species could be considered for reclamation efforts in mining area and other similar degraded lands. ACKNOWLEDGMENTS Financial support for this study was provided by the Kasetsart University Research and Development Institute (KURDI) in Bangkok, Thailand. We are grateful to the staff at the Phangnga Forestry Research Station for their assistance during the field work. REFERENCES Anderson J, Proctor MJ, Vallack HW. 1983. Ecological studies in four contrasting lowland rain forests in Gunung Mulu National Park, Sarawak: III. Decomposition processes and nutrient losses from leaves litter. J Ecol 71:503-27. Bell FG, Donnelly L J. 2006. Mining and its impact on the environment. London (UK): Taylor and Francis. 547 p. Berg B, McClaugherty C. 2008. Plant litter decomposition, humus formation, carbon sequestration. Heidelberg (DE): Springer-Verag Berlin. Bernhard-Reversat F. 1996. Nitrogen cycling in tree plantations grown on a poor sandy savanna soil in Congo. Appl Soil Ecol 4:161-72. Bunyavejchewin S. 2001. Ecological studies of tropical semi-evergreen rain forest at Sakaerat, Nakhon Ratchasima, Northeast Thailand, II. Litterfall. In: Silvicultural Research Report. Bangkok (TH): Royal Forest Department. Celentano D, Zahawi R A, Finegan B, Ostertag R, Cole RJ, Holl KD. 2011. Litterfall dynamics under different tropical forest restoration strategies in Costa Rica. Biotropica 43:278-87. Chazdon RL. 2014. Second growth: The promise of tropical forest regeneration in an age of deforestation. Chicago (US): University of Chicago Press. 472 p. Chen L, Xiang W, Wu H, . Lei P, Zhang S, Ouyang S, Deng X, Fang X. 2017. Tree growth traits and social status affect the wood density of pioneer species in secondary subtropical forest. Ecol Evol 7:5366-77. Cizungu L, Staelens J, Huygens D, Walangululu J, Muhindo D, Cleemput OV, Boeckx P. 2014. Litterfall and leaf litter decomposition in a central African tropical mountain forest and Eucalyptus plantation. For Ecol Manage 326:109-16. Dutta RK, Agrawal P. 2003. Restoration of opencast coal mine spoil by planting exotic tree species: a case study in dry tropical region. Ecol Eng 21:143-51. Feng C, Wang Z, Ma Y, Fu S, Chen HYH. 2019. Increased litterfall contributes to carbon and nitrogen accumulation following cessation of anthropogenic disturbances in degraded forests. For Ecol Manage 432:832-9. Fisher RF, Binkley D. 2000. Ecology and management of forest soils. New York (US): John Wiley and Sons. 456 p. https://www.sciencedirect.com/science/article/pii/0929139396000960#! Litterfall, litter decomposition and nutrient return of rehabilitated mining areas – Jetsada Wongprom et al. 79 Gartner TB, Cardon ZG. 2004. Decomposition dynamics in mixed-species leaf litter. Oikos 104:230-46. Glumphabutr P, Kaitpraneet S, Wachrinrat C. 2007. Aboveground biomass and litterfall of natural evergreen forest in eastern region of Thailand. Kasetsart J (Nat Sci) 41:811-22. Goma-Tchimbakala J, Bernhard-Reversat F. 2006. Comparison of litter dynamics in three plantations of an indigenous timber-tree species (Terminalia superba) and a natural tropical forest in Mayombe, Congo. For Ecol Manage 229:304-13. Gomes ACS, Luizão FJ. 2012. Leaf and soil nutrients in a chronosequence of secondary-growth forest in Central Amazonia: Implications for restoration of abandoned lands. Res Ecol 20:339-45. Hättenschwiler S, Coq S, Barantal S, Handa IT. 2011. Leaf traits and decomposition in tropical rainforests: revisiting some commonly held views and towards a new hypothesis. New Phytol 189:950-65. Inagaki M, Kamo K, Titin J, Jamalung L, Lapongan, Miura S. 2010. Nutrient dynamics through fine litterfall in three plantations in Sabah, Malaysia, in relation to nutrient supply to surface soil. Nutr Cycling Agroecosyst 88:381-95. Kamo K, Vacharangkura T, Tiyanon S, Viriyabuncha C, Nimpila S, Duangsrisen B, Thaingam R, Sakai M. 2008. Biomass and dry matter production in planted forests and an adjacent secondary forest in the grassland area of Sakaerat, Northeastern Thailand. Tropics 17:209-24. Koonkhunthod N, Sakurai K, Tanaka S. 2007. Composition and diversity of woody regeneration in a 37-year-old teak (Tectona grandis L.) plantation in Northern Thailand. For Ecol Manage 247: 246-54. Lanuza O, Casanoves F, Zahawi RA, Celentano D, Delgado D, Holl KD. 2018. Litterfall and nutrient dynamics shift in tropical forest restoration sites after a decade of recovery. Biotropica 50(3):491-8. Lei H, Peng Z, Yigang H, Yang Z. 2015. Vegetation succession and soil infiltration characteristics under different aged refuse dumps at the Heidaigou open coal mine. Glob Ecol Conserv 4:255-63. Liao JH, Wang HH, Tsai CC, Hseu ZY. 2006. Litter production, decomposition and nutrient return of uplifted coral reef tropical forest. For Ecol Manage 235:174-85. Liu C, Liu Y, Guo K, Zhao H, Qiao X, Wang S, Zhang L, Cai X. 2016. Mixing litter from deciduous and evergreen trees enhances decomposition in a subtropical karst forest in southwestern China. Soil Biol Biochem 101:44-54. Lugo AE. 1992. Comparison of tropical tree plantations with secondary forest of similar age. Ecol Monogr 62:1-41. Martpalakorn M. 1990. Tree species trials on mined spoils at Amphoe Takuapa, Changwat Phangnga [Dissertation]. Bangkok (TH): Kasetsart University Retrieved from Kasetsart University. Moura PM, Althoff TD, Oliveira RA, Souto JS, Souto PC, Menezes RSC, Sampaio EVSB. 2016. Carbon and nutrient fluxes through litterfall at four succession stages of Caatinga dry forest in Northeastern Brazil. Nutr Cycling in Agroecosyst 105:25-38. Ngugi MR, Fechner N, Neldner VJ, Dwnnis PG. 2020. Successional dynamics of soil fungal diversity along a restoration chronosequence post-coal mining. Res Ecol 28:543-52. Oktavia D, Setiadi Y, Hilwan I. 2015. The comparison of soil properties in heath forest and post-tin mined land: basic for ecosystem restoration. Procedia Environ Sci 28:124-31. Olson JS. 1963. Energy storage and the balance of producers and decomposers in ecological systems. Ecol 44:322-31. Parrotta JA. 1999. Productivity, nutrient cycling, and succession in single- and mixed-species plantations of Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala in Puerto Rico. For Ecol Manage 124:45-77. Parsons SA, Congdon RA. 2008. Plant litter decomposition and nutrient cycling in North Queensland tropical rain-forest communities of differing successional status. J Trop Ecol 24: 317-27. Paudel E, Dossa GGO, Xu J, Harrison RD. 2015. Litterfall and nutrient return along a disturbance gradient in a tropical montane forest. For Ecol Manage 353:97-106. Rai A, Singh AK, Ghosal N, Singh N. 2016. Understanding the effectiveness of litter from tropical dry forests for the restoration of degraded lands. Ecol Eng 93:76-81. Reichl C, Schatz M, Zsak G. 2017. World mining data. Federal Ministry of Science, Research and Economy, Vienna (Austria). 255 p. Ruiz-Jaén MC, Aide TM. 2005. Vegetation structure, species diversity, and ecosystem processes as measures of restoration success. For Ecol Manage 218:159-73. Scherer-Lorenzen M, Bonilla JL, Potvin C. 2007. Tree species richness affects litter production and decomposition rates in a tropical biodiversity experiment. Oikos 116:2108-24. https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Koichi+KAMO https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Tosporn+VACHARANGKURA https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Sirin+TIYANON https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Chingchai+VIRIYABUNCHA https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Suchat+NIMPILA https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Bunnasart+DUANGSRISEN https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Rattana+THAINGAM https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=Masaharu+SAKAI BIOTROPIA Vol. 29 No. 1, 2022 80 Singh AN, Raghubanshi AS, Singh JS. 2004. Impact of native tree plantations on mine spoil in a dry tropical environment. For Ecol and Manage 187:49-60. Tang JW, Cao M, Zhang JH, Li MH. 2010. Litterfall production, decomposition and nutrient use efficiency varies with tropical forest types in Xishuangbanna, SW China: a 10 year study. Plant Soil 335:271-88. Thaiutsa B, Rungruansilp C. 1990. Impacts of tin mining on soil properties. Thai J For 9:73-82. Triadiati S, Tjitrosemito E, Guhardja E, Sudarsono I, Qayim I, Leuschner C. 2011. Litterfall production and leaf litter decomposition at natural forest and cacao agroforestry in central Sulawesi, Indonesia. Asian J Biol Sci 4:221-34. Tripathi N, Singh RS, Hills CD. 2016. Reclamation of mine-impacted land for ecosystem recovery. London (UK): John Wiley and Sons. Trogisch S, He JS, Hector A, Scherer-Lorenzen M. 2016. Impact of species diversity, stand age and environmental factors on leaf litter decomposition in subtropical forests in China. Plant Soil 400: 337-50. Wongprom J, Poolsiri R, Diloksumpun S, Ngernsaengsaruay C. 2020. Soil properties and tree composition in a 27-year old Acacia mangium Willd. plantation on abandoned mining area at Phangnga Forestry Research Station. Biotropia 27:125-33. Xuluc-Tolosa FJ, Vester HFM, Ramı´rez-Marcial N, Castellanos-Albores J, Lawrence D. 2003. Leaf litter decomposition of tree species in three successional phases of tropical dry secondary forest in Campeche, Mexico. For Ecol Manage 174:401-12. Zhang Y, Yang JY, Wu HL, Shi CQ, Zhang CL, D. Li X, Feng MM. 2014. Dynamic changes in soil and vegetation during varying ecological recovery conditions of abandoned mines in Beijing. Ecol Eng 73:676-83. Zhao Z, Shahrour I, Bai Z, Fan W, Feng L, Li H. 2013. Soil development in opencast coal mine spoils reclaimed for 1-13 years in the West-Northern Loess Plateau of China. Eur J Soil Biol 55:40-6. Zhong Y, Yan W, Wang R, Shangguan Z. 2017. Differential responses of litter decomposition to nutrient addition and soil water availability with long-term vegetation recovery. Biol Fertil Soils 53:939-49. Zhou G, Guan L, Wei X, Zhang D, Zhang Q, Yan J, Wen D, Liu J, Liu S, Huang Z, Kong G, Mo J, Yu Q. 2006. Litterfall production along successional and altitudinal gradients of subtropical monsoon evergreen forest broadleaved forests in Guangdong, China. Plant Ecol 188:77-89.