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Open Access
Biomass production and root distribution pattern of selected acacias
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2014) Mereena, M J; KAU; Jamaludheen
A field study was conducted with acacia species on an 18-year-old stand with 3m×3m spacing at the arboretum of College of Forestry, Thrissur, Kerala to evaluate the growth, biomass production, carbon sequestration and nutrient accumulation in four acacia species viz. Acacia auriculiformis, Acacia mangium, Acacia crassicarpa and Acacia aulacocarpa. The objective of the study included quantifying the biomass production potential, harvest related nutrient export from the site, characterising the root distribution pattern of these trees and to develop allometric equations for aboveground biomass, aboveground C sequestration, volume and bole volume. The above ground biomass was estimated from 20 destructively sampled trees from each species and the belowground biomass was estimated following root excavation of average sized trees of each species. Significant differences were observed for the tree growth parameters except DBH. Acacia aulacocarpa recorded the highest growth rates in terms of height closely followed by Acacia auriculiformis. Among the species, Acacia auriculiformis recorded the highest stand total biomass (432.08 Mg ha-1) and the lowest by Acacia mangium (367.76 Mg ha-1). The most important component of total biomass undoubtedly, was the bole while foliage contributed least to biomass yield. Maximum aboveground and belowground biomass was recorded for Acacia auriculiformis (336.29 Mg ha-1and 95.79 Mg ha- 1respectively). Carbon sequestration potential was estimated for both aboveground and belowground biomass. Maximum mean tree C sequestration was recorded for Acacia auriculiformis (176.38 kg C tree-1) followed by Acacia aulacocarpa (165.54 kg C tree-1). The bole portion sequester major portion of C (63.61% to 71.28%) followed by root portion (19.1% to 23.78%). MAI in total stand C sequestration was maximum for Acacia auriculiformis (10.89 Mg C ha-1yr-1) closely followed by Acacia aulacocarpa (10.22 Mg C ha-1yr-1). Stand level biomass C sequestration in the leaf and twig portion varied significantly among the acacias. Soil C sequestration under each species was estimated upto one meter depth. Maximum soil organic carbon (SOC) was accumulated in the surface soil (0-20 cm) for all the species. Acacia auriculiformis (77.96 Mg C ha-1) recorded the highest total SOC followed by Acacia mangium (74.75 Mg C ha-1). The treeless plots consistently recorded the lowest value of SOC in all the depth zones. Nutrient concentrations (N, P and K) in the biomass components were recorded highest for the leaf portion and the highest stand nutrient accumulation was recorded for the bole portion. The order of nutrients in the plant were N> K> P. The nutrient accumulation in the stand level was also recorded highest for Acacia auriculiformis. The order of nutrient accumulation in the soil was N> P> K. No significant variation was observed in root distribution pattern of different acacia species. However, the maximum root spread was recorded for Acacia mangium (5.23 m) and root length for Acacia crassicarpa (1.49 m
Open Access
Biomass production, carbon sequestration and nutrient flux in Ailanthus triphysa (DENNST.) Alston
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2014) Sukanya, S; KAU; Kunhamu, T K
A field study was carried out to evaluate the biomass production, carbon sequestration and nutrient dynamics in a 22-year-old Ailanthus triphysa stand managed at variable densities viz., 2360 trees ha-1, 1560 trees ha-1, 900 trees ha-1 and 560 trees ha-1. Total number of 80 trees (20 from each density regime) was destructively sampled for the biomass and carbon stock assessment. Also nutrient stocks (N, P and K) in various tissue types were assessed following standard procedures. The soil carbon and nutrient contents were assessed for one meter soil depth at regular depth intervals. The average stand height and bole height were 12.84 m and 8.19 m respectively which varied significantly with stand density with maximum value recorded for 1560 trees ha-1. The average dbh, mean tree volume and bole volume put in by the 22- yearold A. triphysa stand was 18.78 cm, 0.15 m3 and 0.16 m3 respectively which however could not yield a predictable trend with stand density. Despite this, the stand volume exhibited a proportional increase with stand density. The mean tree biomass production by the stand was 129.81 kg tree-1 that varied with stand density. Biomass production at stand level showed a consistent increase with increasing stand density with highest produced corresponding to 2360 trees ha-1 stand (384.67 Mg ha-1) and lowest for 560 trees ha-1 stand (93.86 Mg ha-1). Component wise biomass allocation was highest for stemwood (63 %) followed by roots (20 %) for all the density regimes while twig portion registered the least (0.97 %). The mean tree C stocks and corresponding MAI for A. triphysa at 22 years of stand age were 74.54 kg tree-1 and 3.38 kg tree-1 yr-1 respectively which was comparable with many fast growing MPT’s similar growth habit in humid tropics. Elemental carbon storage at stand level showed proportionate increase with density (177.00 Mg ha-1, 2360 tree ha-1; 140.47 Mg ha-1, 1560 tree ha-1; 49.06 Mg ha-1, 900 trees ha-1 and 43.33 Mg ha-1, 560 trees ha-1). Allometric models were developed for total aboveground biomass, bole biomass, aboveground carbon sequestration, total volume and bole volume using dbh and height as predictor variables. Among various models tried single variable (dbh) quadratic equations were best fitting with high R2 value. The nutrient concentration varied substantially among various biomass components with foliage registering highest N, P and K concentration (%). Tissue nutrient concentration followed the general order: leaves> twig> branch> root> stemwood. Biomass nutrient stocks at stand level varied considerably with stand density which was closely following biomass production trends. Nutrient storage followed the order N > P > K with highest stocks corresponding to stemwood followed by roots, branchwood, leaves and twigs. High nutrient accumulation in the stemwood suggests possible higher levels of nutrient export from the site through harvest. Transfer of nutrient rich leaf biomass into the soil at harvest would be a viable strategy in this context that replenish the nutrient loss through harvest. Carbon and nutrient contents in the soil were substantially higher in all sampled depths implying the dominant role of trees in improving the soil productivity in wooded systems. Study converges to the generalization that A. triphysa trees have a good potential for volume and biomass production under proper silvicultural management regimes.
Open Access
Soil productivity changes under selected indigenous forest tree species with special reference to beneficial microflora
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2014) Lakshmy, A; KAU; Jamaludheen, V (Guide)
A field investigation was conducted with four important indigenous tree species viz. Hopea parviflora Bedd., Artocarpus hirsutus Lamk., Pterocarpus marsupium Roxb, and Pterocarpus santalinus L.f. of about 30 years of age and planted at 2 m×2 m spacing at Kerala Forest Research Institute sub-centre Nilambur, India for a period of one year (May 2013 to May 2014). The specific objective of the study was to monitor the soil productivity changes due to long term occupancy of four indigenous trees with special reference to the beneficial soil microflora. The rhizosphere soil samples were collected for the isolation and enumeration of microbial population at quarterly interval for a period of one year. The population of bacteria, fungi, actinomycetes, nitrogen fixing bacteria, phosphate solubilising bacteria and potash solubilising bacteria were estimated by serial dilution method. The soil physico-chemical properties and the growth of trees were also observed. The highest microbial population, during the entire study period, was recorded in Artocarpus hirsutus and the lowest in treeless control plot. Artocarpus hirsutus recorded the maximum bacteria, fungi, actinomycetes, nitrogen fixing bacteria and phosphate solubilising microorganism. Potash solubilizing bacteria were recorded maximum in Hopea parviflora plots. The highest bacterial population observed in late summer and rainy season and the lowest recorded during early summer season. The highest fungal population recorded in late summer season and the lowest during winter season. Early summer season recorded the highest actinomycetes population and lowest in late summer season. The highest population of nitrogen fixing bacteria and phosphate solubilising microorganism observed in the winter season and the lowest population during early summer season. Potash solubilizing bacteria recorded highest during the summer seasons (late summer-Ι and late summer-II seasons) and lowest in the rainy season. In the final sampling (late summer) also, A. hirsutus was found to harbour maximum bacteria, nitrogen fixing bacteria, phosphate solubilising bacteria and potash solubilising bacteria. However, the highest fungi and actinomycetes associated with Pterocarpus santalinus. The long term occupancy of the indigenous tree species was found to have influenced the soil physico-chemical properties. The soil moisture and bulk density was distinctively superior in the wooded lands as compared to the treeless open area. The soil organic carbon (2.25%), available nitrogen (17.80 kg ha-1), total nitrogen (0.16%) and exchangeable potassium (70.70 kg ha-1), were also significantly higher in H. parviflora. The most acidic soil was also found in H. parviflora while the least acidic was A. hirsutus plots. The maximum height (12.41m) and the dbh (16.25 cm) were recorded in Pterocarpus santalinus The present study throws light into the intimate relation between the types and nature of soil microflora populations and their positive influence on the microsite enrichment aspects of promising indigenous tree species. The information will aid in preferential selection of these tree species along with crops into different tree farming systems where the ecosystem sustainability is of greater relevance. In general, all the four indigenous tree species recorded significantly higher microflora population and greatly improved physico-chemical properties than treeless plot due to long term occupancy of trees.
Open Access
Soil productivity changes under selected exotic forest tree species with special reference to beneficial microflora
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2014) Tejkaran, Patidar; KAU; Jamaludheen, V
A field investigation was carried out with four exotic tree species (Acacia auriculiformis, A. mangium, Casuarina equisetifolia and Swietenia macrophylla) planted at 2 m × 2 m spacing and of about 30 years age at Kerala Forest Research Institute sub-centre Nilambur during 2013-2014. The specific objective of the study was to examine the variations in soil productivity, with special reference to the beneficial microflora, due to long term occupancy of these trees. The rhizosphere soils were collected for isolation and enumeration of soil microflora like actinomycetes, bacteria, fungi, N-fixing bacteria, P-solubilises and Ksolubilising bacteria population at quarterly interval for a period of one year. The soil physico-chemical properties under the trees were also assessed. It was found that, over the years, the tree species influenced the soil physico-chemical properties. The lowest bulk density and pH were associated with tree plots compared to the treeless plots. However, the soil moisture content was not significantly different. The soil organic carbon, total nitrogen and exchangeable potassium were significantly higher (2.15%, 0.13% and 80.15 kg ha -1 respectively) in S. macrophylla and the lowest (1.38%, 0.07% and 52.34 kg ha -1 respectively) in treeless control plot. Available nitrogen and available phosphorus were significantly higher (71.6 kg ha -1 and 4.42 kg ha respectively) in A. mangium and the lowest (39.05 kg ha -1 and 4.08 kg ha -1 -1) in treeless plot. Tree species greatly influenced the soil microflora population. In general, microflora population was higher in tree plots than the treeless control. During the entire period of study, A. auriculiformis had highest mean bacteria, fungi and nitrogen fixing bacteria population while the highest population of phosphorus solubilizing microorganism and potash solubilizing bacteria was recorded in A. mangium. The highest mean population of actinomycetes was associated with C. equisetifolia. Seasonal variation in microflora population was obvious. Actinomycetes population was, generally, the lowest during rainy season and the peak population during early summer season and late summer-II. The bacterial population was the maximum during rainy season and the lowest during early summer season. The fungal population was more in both the late summer (2013 and 2014) seasons and the lowest in the winter season. Nitrogen fixing bacteria population was highest in the late summer-I and found to decrease through the rainy season and winter season. The populations of phosphate solubilizers and potash solubilizing bacteria were highest in late summer-I season and lowest in the rainy season (phosphate solubilizer) and winter season (potash solubilising bacteria). A. mangium had the maximum height (19.90 m) followed by C. equisetifolia, A. auriculiformis and the lowest was for S. macrophylla. Diameter at breast height was also highest in A. mangium (24.31 cm) followed by S. macrophylla, A. auriculiformis and C. equisetifolia The present study highlighted the influence of tree species on microflora population. Microflora population was found to be significantly higher in tree species compared to nearby treeless control plot and was found to be varying according to seasons. All the tree species have shown higher soil nutrient content than treeless plot. These four exotic tree species in the present study is seen to take part actively in the improvement of soil quality and soil health which are the major determinants of sustainable soil productivity.
Open Access
Bamboo (Dendrocalamus strictus (Roxb.) Nees) based agroforestry system: planting density effects on biomass accumulation, carbon sequestration, root distribution pattern and understorey crop productivity
(Department of silviculture and agroforestry, College of forestry, Vellanikkara, 2014) Bhimappa Kittur; KAU; Sudhakara, K
A field experiment was undertaken at Vellanikkara, Thrissur in a seven year old bamboo (Dendrocalamus strictus (Roxb.) Nees) stand planted at 4x4, 6x6, 8x8, 10x10, and 12x12 m spacings to assess rhizosphere competition and understorey (turmeric, ginger and chittaratha) productivity, to explore the root activity and distribution pattern in bamboo, to determine the understorey photosynthetically active radiation (PAR), leaf area index of bamboo (LAI) and aboveground biomass production, nutrient uptake and carbon sequestration as a function of planting density. Detailed investigation on the physico-chemical attributes of the soil was also done. Results reveal that understorey turmeric and ginger height, shoot length, number of tiller and leaves were significantly lesser due to close spacings (4x4 and 6x6 m) of bamboo, but NPK uptake, dry matter production, rhizome yield and oleoresin content were significantly higher in wider spacings (10x10 and 12x12 m) of bamboo. The chittaratha responded better in control plot followed by widest spacing (12x12 m) of bamboo. Due to competition of bamboo about 89% decline in 32P absorption by turmeric at closest spacing (4x4 m) of bamboo as compared to sole turmeric plot. The recovery of 32P by bamboo from the treated turmeric was significantly decreased with increasing distance from the turmeric beds. The recovery of 32P by bamboo in > 8x8 m spacings was nil. The other factors attributed to reduction in growth and yield of understorey crops may be high LAI of bamboo and low understorey PAR. The LAI of bamboo in 4x4 m spacing was 678 % higher compared to 12x12 m spacing. At 12 noon the understorey PAR increased from 107 µmol/sec per m2 in 4x4 m to 1019 µmol/sec per m2 in 12x12 m spacings of bamboo against the overstorey PAR (1033 µmol/sec per m2). The maximum rooting intensity of bamboo was within 0-30 cm soil depth and up to 4.45 m lateral distance under all the spacings. However, in wider spacings (10x10 and 12x12 m) the roots were distributed beyond 30 cm depth and spread laterally up to 8.75 m. The deeper spread of roots in wider spacings may enable clumps to capture nutrients that would otherwise be leached from the upper horizons of the soil profile. The root activity of bamboo was studied by 32P at varying depths (50 cm and 1 m) and lateral distances (50 cm, 1 m and 2 m). At closest spacing (4x4 m), the 32P absorption by bamboo (15th DAA) at 50x50 cm depth and lateral distance was significantly higher (809 cpm) which gradually decreased by placing 32P beyond 1 m (448 cpm) and 2 m lateral distances (196 cpm). However, in wide spacings (12x12 m) the lateral spread of active roots were more at greater depth (1 m); this helps pumping of soil nutrients from the deeper layers. The bulk density of soil increased with increasing depth of soil and spacings of bamboo. The N, P and K content of soil significantly decreased with increasing spacing of bamboo. Closest spacing (4x4 m) of bamboo recorded maximum amount (2109 kg/ha) of total N and 10x10 m spacing had lowest (1430 kg/ha). The available P at surface soil (0-20 cm) ranged from 12.86 kg/ha under bambooless control plot to 21 kg/ha at closest spacing. The available P up to 1 m soil depth was highest (42 kg/ha) in closest spacing and decreased with increasing spacing of bamboo. The total available K up to 1 m depth of soil in closest spacing was 35% higher compared to widest spacing. The amount of soil organic carbon (SOC) in the whole soil at 0-20 cm was highest (11.50 Mg/ha) due to 4x4 m spacing and lowest (6.61 Mg/ha) due to widest spacing (12x12 m). The total SOC up to 1 m depth in closest spacing declined by 143% compared to widest spacing. The SOC in silt and clay fraction (<53 µm) was highest (16 Mg/ha) in closest spacing (4x4 m) and lowest (5.20 Mg/ha) in bambooless control plot at 20-50 cm soil depth. The SOC in macro sized fraction (>250-2000 µm) in closest spacing was 9 Mg/ha at 0-20 cm depth; this decreased to 2.27 Mg/ha at 80-100 cm depth. Due to decrease of bamboo spacing from 12x12 to 4x4 m, the clump DBH decreased from 1.61 to 1.06 m. The crown spread, number of live culms and MAI of bamboo also increased due to increasing spacing. Due to closest spacing (4x4 m), culm wood biomass decreased by 54% compared to widest spacing (12x12 m) of bamboo. The twig biomass recorded maximum (28%) at 6x6 m and 8x8 m spacing of bamboo and minimum (19%) in closest spacing. The total aboveground biomass in closest spacing was 112 kg/clump which increased to 271 kg/clump due to 12x12 m spacing. At stand level, the culm wood biomass was maximum (49 Mg/ha) in densest stand (625 clumps/ha); this decreased to 11.49 Mg/ha due to least dense stand (69 clumps/ha). The twig and leaf biomass reduction in least dense stand was 206% and 114% compared to densest stand. The total aboveground biomass at densest stand was 274% more compared to least dense stand. Nutrient removal at harvest from the site depends on both nutrient concentration of different plant parts and biomass yield. Nutrient concentration (NPK) in aboveground biomass under all the spacings of bamboo decreased in the order of: leaf>twig>culm wood>dried wood. The total N accumulation in the aboveground biomass was highest (323 kg/ha) in densest stand and lowest (108 kg/ha) in least dense stand. Aboveground biomass P accumulation in densest stand increased by 161% than the least dense stand. The total amount of K accumulated in aboveground biomass ranged from 354 kg/ha in densest stand to 157 kg/ha in the least density of 69 clumps/ha. Higher amount of NPK was retained mainly in the culm wood followed by twig, leaf and dried wood mass. However, dense stands can store significantly higher amount of nutrients in its biomass. The carbon partitioning among the aboveground parts in bamboo show that almost 57-68% was in stem, whereas twigs, leaf and dried wood stored 20-30%, 4-8% and 3-6% in all the spacings of bamboo. The C storage in culm wood varied from 35 kg/clump at closest spacing to 79.12 kg/clump in widest spacing of bamboo. The consistent increase in aboveground C stock with increasing spacings of bamboo might be due to more number of culms per clump and in turn higher dry matter production. At stand level, the total C accumulation in the aboveground biomass was highest (32 Mg/ha) in densest bamboo stand compared to 8.85 Mg/ha in the least dense stand. The study clearly revealed that wider spacings (10x10 and 12x12 m) of bamboo are ideal for better growth and productivity of understorey crops. Even though chittaratha perform best in open condition, among the varying spacings of bamboo, the widest spacing (12x12 m) of bamboo is best. The dense stands of bamboo had the potential of higher aboveground biomass production, nutrient storage and carbon accumulation. However, the study recommends wider spacings (12x12 m) for clump-wise biomass production/C storage and nutrient uptake.

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