Growth performance of dipterocarp species planted under Poring bamboo (Gigantochloa levis)

Transcription

1 Sepilok Bulletin 17 & 18: (2013) Growth performance of dipterocarp species planted under Poring bamboo (Gigantochloa levis) F.R. Chia Forest Research Centre, Sabah Forestry Department, P.O. Box 1407, Sandakan, Sabah, Malaysia. Abstract. A study was carried out to assess the survival and growth performance of 7-yearold dipterocarp species planted under Poring bamboo (Gigantochloa levis). Six dipterocarp species namely Dryobalanops lanceolata, Parashorea tomentella, Shorea beccariana, S. pilosa, S. mecistopteryx and S. smithiana were included in this assessment. The survival rates for these dipterocarp species ranged from 25 to 65% and D. lanceolata had the highest survival rate. S. beccariana outperformed other species with the mean annual increment in height and DBH (diameter at breast height) of 0.83 m/year and 1.13 cm/year respectively. These results indicate that Poring bamboo is a suitable shelter crop for the early establishment of dipterocarp species. Keywords: dipterocarps, Poring bamboo, shelter crop INTRODUCTION Dipterocarp forest is the most valuable forest in Sabah. The dipterocarp forest is disappearing owing to over-harvesting with no significant scale of planting. The long gestation period together with unpredictable risks and market price are the main reasons that discourage foresters and planters from investing in this group of indigenous tree species. However, this problem might be resolved by intercropping dipterocarp species with cash crops that can generate income while the trees grow. Dipterocarp species need moderate shade of 20-30% in relative light intensity for early growth (Kamo & Jamalung 2009). Thus a shelter crop is needed to provide moderate level of shade for the initial survival of these species. Different dipterocarp species need different forest light regimes for maximum growth (Philipson et al. 2012). Poring bamboo can be a potential shelter crop due to its small leaf biomass (Chia & Kamo 2005) and economic value. Poring bamboo provides different light regimes as its density is hard to control (Chia 2009) thus creating heterogeneous light environment. Dipterocarp species like Dryobalanops lanceolata, Shorea beccariana, S. pilosa and S. parvifolia were reported to show much higher mortality at the clear-cut site (33-67%) than in the thinned plots (0-16%) 7 months after planting (Kamo et al. 2007). Chia 47

2 (2009) also indicated that Poring bamboo is a feasible shelter crop for dipterocarps due to its high production rate and the ability of dipterocarps to grow underneath. However, this initial finding was only based on 1 year data which could not provide any conclusive evidence as dipterocarp species are regarded as slow-growing species and time is needed to study their performance. The initial (first 2 years) growth data for dipterocap species are not considered as reliable for drawing conclusions as the initial size of the seedlings could influence the future growth and survival of these species (Kamo et al. 2007, Philipson et al. 2012). Therefore this study was carried out to assess the survival and growth performance of dipterocarp species over a period of 7 years in a Poring bamboo plantation. MATERIALS & METHODS The study plot is located in Sungai Daling (5 44'N, 'E), approximately 61 km west of Sandakan. The soil is loam and clay loam of the Tanjung Lipat family (Acres & Folland 1975). The plot covered an area of 1 ha and comprised 11 rows of Poring bamboo (105 clumps in total). It was divided into 4 small blocks with 2 rows per block. Each block consisted of 4 thinning treatments: 0, 20, 60 and 80% of all culms in each clump during establishment. The preliminary findings indicated that growth of dipterocarp seedlings was not affected by thinning intensity of the bamboo (Chia 2009). Thus, thinning was stopped after the first year. The light intensity in this plot ranged from 15 to 23% in the first year of assessment where 60% thinning treatment had the highest relative light intensity of 23% and no thinning was 15%. It was assumed that light intensity was about 15% at 7 years as no thinning was carried out, and culm production of the Poring bamboo stagnated at 4 years after thinning (Chia 2006). Six dipterocarp species were planted under Poring bamboo namely Dryobalanops lanceolata (Kapur Paji), Parashorea tomentella (Urat Mata Beludu), Shorea beccariana (Seraya Langgai), S. pilosa (Kawang Bulu), S. mecistopteryx (Kawang Burung) and S. smithiana (Seraya Timbau) with 4 m x 5 m spacing in the existing plantation. There were 4 replicates with 12 seedlings per replicate. Each species comprised 2 seedlings per replicate. Mortality, growth performance in terms of height and DBH (diameter at breast height) were assessed for 7 consecutive years. RESULTS & DISCUSSION Results on the survival and growth performance of the 6 dipterocarps at the age of 7 years are summarized in Table 1. The survival for the 6 dipterocarp species ranged from 25 to 65% at the age of 7 years. D. lanceolata had the highest survival rate of 65% while others had less than 50% survival, notably Shorea species. S. mecistopteryx had the lowest survival rate of 25%. The survival rate of 25-40% for Shorea species is considered good as it is still within the range of final crop density of 60 trees per ha as recommended for S. leprosula (Ang 2002) based on the calculation of 500 trees per ha in this plot. 48

3 Table 1. Mean annual increment (MAI) in height and DBH for dipterocarp species at the age of 7 years. Species Height (m) DBH (cm) Survival (%) Dryobalanops lanceolata Shorea pilosa Shorea mecistopteryx Shorea beccariana Shorea smithiana Parashorea tomentella D. lanceolata was found to be a shade tolerant species with a significant higher survival of 65% after 7 years. P tomentella also showed the ability to survive under this condition as no mortality was observed after 3 years unlike Shorea species with declining survival rates (Figure 1). P tomentella was identified as one of the indigenous species which can tolerate direct sunlight at the seedling stage (Kamo et al. 2007). There were several causes of mortality in this trial, notably being hit by fallen dead bamboo poles, or physically damaged by animals such as monkeys. Figures 2 and 3 show the growth patterns of the 6 dipterocarp species under Poring bamboo. Overall, these species were less than 6 m in height and P tomentella was the shortest with 4 m in height at the age of 7 years. For mean DBH, all of these species were less than 7 cm in DBH except S. beccariana with a mean DBH of 7.86 cm. S. beccariana was significantly bigger in DBH (Figure 4). There was no significant difference in height increment among these 6 species (Figure 5). The height increment was affected by the upper canopy Competition between the dipterocarps and the mature bamboo culms (Plate 2). It was observed that most of these dipterocarps had broken stems caused by fallen bamboo poles and animals (Plate 3). Hence the best time to remove the upper canopy is 3 years (Kamo et al. 2007) or at the mature age of the bamboo. Mature bamboo culms need to be thinned out to create a better environment for these timber trees to grow. S. beccariana outperformed the other species at 7 years with a height and DBH increment of 0.83 m/year and 1.13 cm/year respectively. This Shorea species outperformed D. lanceolata which has been reported earlier as one of the fastest-growing dipterocarp species (Lapongan & Pang 2009, Soerianegara & Lemmens 1994). This finding is related to the light regimes of the plot, as growth performance of the dipterocarp species was significantly different between replicates (P < 0.01). 49

4 GP eo ) Shorea pilosa 0*--Dryobalanops lanceolate Shorea smithiana Age (year) Shores mecistopteryx Shores beccariana Parashorea tomentella Figure 1. Survival of the dipterocarps over 7 years. Plate 1. Dipterocarp species growing underneath Poring bamboo (Photo: Chia Fui Ree). 50

5 Plate 2. Upper canopy competition between mature bamboo culms and dipterocarp species (Photo: Ajis Ampawih). Plate 3. Broken stem (Photo: Chia Fui Ree). 51

6 7 6 5 Ca to o 2 1 Shorea pilosa Dryobalanops lanceolata Shorea smithiana Shorea mecistopteryx Shorea beccariana Parashorea tomentella 0 Initial 6mth Age (year) Figure 2. Mean height of the dipterocarps over 7 years C 4 O , Shorea pilosa --*--Dryobalanops lanceolata Shorea smithiana IF Shorea mecistopteryx Shorea beccatiana i Parashorea tomentella Age (year) Figure 3. Mean DBH of the dipterocarps over 7 years. 52

7 Figure 4. Mean DBH of the dipterocarps (with standard error) at 7 years. Means with the same letter are not significantly different at 5% (Tukey's HSD test). Shona pilosa Shona Dryobalanops Shona mecistoptetyx lanceolate beccariana Figure 5. Mean height of the dipterocarps (with standard error) at 7 years. Means with the same letter are not significantly different at 5% (Tukey's HSD test). 53

8 CONCLUSION The survival rates for dipterocarps planted under Poring bamboo ranged from 25 to 65% at the age of 7 years. D. lanceolata recorded the highest survival rate while Shorea species recorded significantly lower rates. S. beccariana showed the highest growth rate of 0.83 m/year and 1.13 cm/year in height and DBH respectively. The ability of dipterocarp seedlings to grow after 7 years indicates that Poring bamboo is a suitable shelter crop for the early establishment of these indigenous tree species. ACKNOWLEDGEMENTS Thanks are due to all Agroforestry Section staff of the Forest Research Centre for their efforts in collecting data from the field. This research plot was established by the Japan International Research Centre for Agricultural Sciences and the Sabah Forestry Department (JIRCAS-SFD) Agroforestry Project. REFERENCES Acres, B.D. & Folland, C.J. (1975). The soils of Sabah. Vol. 2. Sandakan and Kinabatangan districts. Land Resource Study 20. Ministry of Overseas Development, Surrey, England. 164 pp. Ang, L.H. (2002). Meranti. (In) Krishnapillay, B. (ed.), A manual of forest plantation establishment in Malaysia. Malayan Forest Records No. 45. Pp Chia, F.R. (2006). Culm production management for Poring bamboo (Gigantochloa levis) plantation. Sepilok Bulletin 4: Chia, F.R. (2009). Potential of Poring bamboo (Gigantochloa levis) as a shelter crop for dipterocarp seedlings. (In) Gotoh, T. & Yokota, Y. (eds.), Development of agroforestry technology for the rehabilitation of tropical forests. JIRCAS Working Report No. 60. Pp Chia, F.R. & Kamo, K. (2005). Growth dynamics and above-ground biomass of Poring bamboo (Gigantochloa levis) stand at Sungai Daling, Sandakan, Sabah. Sepilok Bulletin 3: Kamo, K. & Jamalung, L. (2009). Facilitating establishment of indigenous tree species on degraded land in Sabah, Malaysian Borneo. (Quoted in) Chia, F.R. (2009), Potential of Poring bamboo (Gigantochloa levis) as a shelter crop for dipterocarp seedlings. (In) Gotoh, T. & Yokota, Y. (eds.), Development of agrofbrestry technology for the rehabilitation of tropical forests. JIRCAS Working Report No. 60. Pp

9 Kamo, K., Yamada, T., Inagaki, M., Abe, H., Araki, Y., Jamalung, L., Lapongan, J., Chong, F.Y., Kulip, J. & Chia, F.R. (2007). Choice of suitable nurse trees, planting species, and site conditions for underplanting. (In) JIRCAS-SFD Joint Research Project (ed.), Agroforestry approach to the rehabilitation of tropical lands by using nurse trees. Japan International Research Centre for Agricultural Sciences (JIRCAS) and Sabah Forestry Department (SFD). Pp Lapongan, J. & Pang, K.K.N. (2009). Growth performance of Kapur Paji (Dryobalanops lanceolata). (In) Gotoh, T. & Yokota, Y. (eds.), Development of agroforestry technology for the rehabilitation of tropical forests. JIRCAS Working Report No. 60. Pp Philipson, C.D., Saner, P., Marthews, T.R., Nilus, R., Reynolds, G., Turnbull, L.A. & Hector, A. (2012). Light-based regeneration niches: evidence from 21 dipterocarp species using size-specific RGRs. Biotropica 44(5): Soerianegara, I. & Lemmens, R.H.M.J. (1994). Plant resources of South-east Asia 5. (1) Timber trees: major commercial timbers. PROSEA Foundation, Bogor, Indonesia. 610 pp. 55