International Research Journal of Biological Sciences ___________________________________ ISSN 2278-3202Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 73 The Potentials of Nitrogen Fixing Tree Species for Forest Restoration in the PhilippinesCombalicer M.S.1*, Lee D.K., Park Y.D.3 and Bae K.K.4 Department of Forest Biological Sciences, College of Forestry and Natural Resources, University of the Philippines Los Bańos, College, Laguna 4031, PHILIPPINES Park Chung Hee School of Policy & Saemaul, Yeungnam University 280, Daehak-ro, Gyeongsan-si, Gyeongsangbuk-do, REPUBLIC OF KOREA Department of Forest Resources, College of Life & Environmental Science, Daegu University, Gyeongbuk 712-714, REPUBLIC OF KOREA Department of Forest and Natural Resources Management, SUNY College of Environmental Science and Forestry, Syracuse, NY 13210, USA Available online at: www.isca.in, www.isca.me Received 28th January 2014, revised 3rd March 2014, accepted 2nd April 2014Abstract A/Ci curve (net CO assimilation rate, A, versus calculated internal CO concentrations, C), foliage and soils for chemical properties were measured in some 20-year-old nitrogen fixing tree species for reforestation in the Philippines including Acacia auriculiformis, Acacia mangium and Pterocarpus indicus to determine their differences based on the derived parameters, maximum Rubisco carboxylation rate (Vcmax) and maximum capacity for electron transport rate (Jmax). Results of the study showed that parameters, derived from the A/C curve (Vcmax and Jmax), were significantly high in both A. mangium and A. auriculiformis. These species have the ability to survive in various conditions and could also serve as nurse species for other native species. This would eventually lead to subsequent succession by more site-demanding species in the future. The implication of this study is very crucial as it provided better insights about the nature of A. mangium and A. auriculiformis for reforestation purposes. Therefore, more attention should be given to ecophysiological researches by including a variety of species either exotic or native to provide greater understanding of their ecophysiological differences which would better aid forest restoration works. Keywords: Assimilation rate, electron transport rate, internal CO concentrations, Rubisco carboxylation. IntroductionDeforestation in the Philippines has received considerable attention over the past several decades. Approximately 15.4 million of forest area disappeared by deforestation through illegal logging, shifting cultivation, fuel wood gathering, and forest fires in the Philippines. Recently, at national and regional levels, trees have been planted for forest restoration in the degraded areas. At the same time, people have been interested in choosing appropriate tree species, which can survive and grow well in a barren area. For example, in tropical forests of Southeast Asia regions, in a broad perspective, studies recommended native, fast growing, and nitrogen (N) fixing tree species. However, the tree characteristics among the generally recommended tree species are not well known. Nitrogen fixing trees are well recognized for their contribution in restoring degraded areas and in improving the productivity of the land. There are various kinds of N fixing trees, either exotic or endemic, in the countries which are being used for reforestation activities needing appropriate breeding program. Measurement of photosynthesis potential is one of the best ways to compare tree species to expect their growth rates during a short period. A/C curve (net CO assimilation rate, , versus calculated internal CO concentrations, ) analysis has become a useful tool to estimate leaf photosynthesis under different environmental conditions. The response function also represents the basis of using various plant physiology models. Through the analysis of A/C curves the rates of carboxylation, ribulose biphosphate (RuBP) regeneration, triose phosphate export out of the chloroplast, maximum carboxylation capacity cmax), maximum capacity for electron transport rate (max), and velocity for triose phosphate utilization can be determined. This has also proven to be advantageous in developing prediction models of CO2 assimilation for plants, to predict the effects of climate change on photosynthesis as a basis for scaling up from leaf to whole plant and/or ecosystem, and to assess the influence of occurring stresses, such as drought, salinity, extreme temperatures, and others on the photosynthetic capacity of the plant. Aside from the photosynthesis capacity, it is also critical to understand the foliage and soil nutrientsto determine which tree species can continuously grow. Foliar nutrient content has been considered as an effective measure of the nutritional status of plants and has been frequently reported to be good indicator of photosynthetic rate and height and biomass increments in different types of species. By absorbing nutrients from the soil, most plants grow in good condition. International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 74 While it is quick and easy to acquire the A/C response curves, and non-destructive, this has not been well documented in the Philippines due to unavailability of sophisticated equipment. Hence, in this study A/Ci curve, foliage and soil chemical properties were measured in three of the most frequently planted species for forest reforestation in the Philippines, including Acacia auriculiformis, Acacia mangium and Pterocarpus indicus, having similar age (20-year-old) to determine their differences based on the derived parameters, such as cmax and max, and leaf N and C concentration. Material and MethodsStudy sites: The study sites are in Mt. Makiling Forest Reserve (MMFR) and La Mesa Watershed in the Philippines (figure-1). MMFR is located in Los Bańos, about 65 km away from Metro Manila (1408’14”N latitude, 12111’33”E longitude). It has two pronounced seasons: wet season (May to December) and dry season (January to April). The average annual precipitation, monthly temperature and monthly relative humidity measure ~2,700 mm, 20.9 to 25.9C, and 33% to 92%, respectively. The plots were establishedon the southwest slope of Mt. Makiling which is the Sitio Kay Inglesia having ~500 m asl. The area experienced cultivation and perennial forest fires until the 1990s. La Mesa Dam Watershed (1445’N latitude and 12105’E longitude) (figure -1) is located in Metro Manila, 10 km away from Quezon City. It has two pronounced seasons: dry season (January to April) and wet season (May to December). January is the coolest month while March is the hottest. The average annual rainfall, monthly temperature and monthly relative humidity measures 2,700 mm, 24.2 to 26.6C and 22% to 94%, respectively. This study site has an elevation of ~110 m asl. Field measurements were carried out in the 20-year-old plantations of A. auriculiformis,A. mangium and P. indicusin the MMFR, Philippines. These trees are all shade-tolerant, N fixing and fast growing species. Acacia auriculiformis is a well-known tropical species valuable for forestry especially in Southeast Asia and the Indian sub-continent. This species is rapidly growing with nicequality of wood and can tolerate a different climatic and soil condition. Similarly, Acacia mangium has the same characteristics and it is well-known for its ability to compete with and suppress weedy species like Imperata cylindrica and Eupatorium. Pterocarpus indicus is known in Southeast Asia for its good quality of timber and is indigenous in the Philippines (called Narra). Figure-1 Location of the study site: Mt. Makiling Forest Reserve and La Mesa Watershed in the Philippines International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 75 Field layout: Three sampling plots (20 m x 20 m) were established in each of the 20-yr-old A. auriculiformis,A. mangiumand P. indicus stand in MMFR, Lagunaand La Mesa Watershed in 2008 and data were gathered up to 2010.The sites have similar amount of rainfall, temperature and relative humidity. Diameter at breast height (DBH) was measured at 1.3 m aboveground of all the trees within each plot using a diameter tape while the basal area (BA) was calculated by getting the sum of individual trees’ basal areas. Leaf nitrogen and carbon concentrations: Five (5) discs wereobtained from each leaf sample (five leaf samples per plot per species) and were finely ground after oven-drying at 60C for48 hr. To measure the leaf nitrogen, leaf samples were analyzed at the Analytical Services Laboratory of the Soils and Agro-ecosystems Division, College of Agriculture, UPLB, Laguna, Philippines. The leaf carbon concentration was analyzed at the National Instrumentation Center for Environmental Management, College of Agriculture and Life Sciences (CALS), Seoul National University (SNU), Republic of Korea. Litterfall: Litterfall was collected monthly for one year (January 2009 to January 2010) for all three species in each plot. Four 0.25 m litter traps made of fine nylon screen were mounted on wooden poles approximately 0.5 m from the ground and randomly distributed in each plot. In the laboratory, the litter was dried at 65C for approximately 48 hr (or until constant weight was obtained) and ground to pass a 1-mm sieve. Samples were sorted into fractions, which included leaves, non-leaves (branches/twigs), and reproductive part (flowers and fruits). Total litter was obtained by adding their weights. Foliage and soil analysis: Foliage and fresh litter samples (300 g) were combined to make a single sample as representative of each plot. Nutrients analyzed in the Analytical Services Laboratory of the Soils and Agro-ecosystems Division, College of Agriculture, University of the Philippines Los Bańos, Laguna, Philippines included Ca, K, N, Mg, P, Cu, Fe, Mn and Zn. Nitrogen productivity was calculated as the ratio of the annual net primary productivity (ANPP) and the amount of foliage N. At a depth of 0 - 30 cm using soil auger, soil samples were collected from four random positions in each plot. Samples were put into plastic bags and labeled. The fresh weight of the soils was obtained and were air-dried for 2 to 3 weeks, pulverized and sieved in 2-mm mesh wire. Thereafter, the samples were brought in the Laboratory of the Silviculture and Restoration Ecology, Department of Forest Sciences, CALS, SNU, Republic of Korea to estimate the organic matter using “loss-on-ignition” method. Soil samples (~250 g per plot) were oven-dried at 105\rC before being ignited in an electric muffle furnace at 600\rC for 4 hr. The weight of samples before and after ignition was measured. Calculation for the organic matter content (OM) is as follows:  \n \r\r \r \n \r\r\r\r Other soil samples were then brought to the analytical services laboratory of the soils and agro-ecosystems division, College of Agriculture, UPLB, Laguna, Philippines. Soil properties, such as total N, K, P, Ca and Mg as well as pH and CEC were determined. A/Ci curve and estimation of derived parameters (Vcmax and max): A/C response curves were obtained in the different portions of the sampled tree (upper, middle, and lower) between September and October 2010. One portion (e.g. upper) of a tree was measured in a day. Field measurements were conducted at day time (8:00 a.m. to 4:00 p.m.) under natural conditions using Li-Cor 6400 Portable Photosynthesis System (Li-Cor Inc., NE, USA) equipped with a leaf chamber (standard) and injection system (CO). Leaves were retained in their natural orientation. The condition of the cuvette was maintained at a photosynthetic photon flux density (PPFD), relative humidity and leaf temperature of 2000 µmol m-2-1, 60-70%, 25C, respectively. Cuvette’s ambient CO concentration () was controlled with a CO mixer having a series of 30, 20, 10, 40, 50, 60, 80, 100, 160, and 200 Pa. After attaining a steady state, measurements were recorded with 2% coefficient of variation. At each value, CO leakage was determined into and out of the empty cuvette. The equations provided in the Li-Cor operator’s manual was used. The rate of maximum Rubisco carboxylation (cmax, µmol CO-2-1) was derived by estimates of related to the initial slope of the A/Ccurve. The A/Ci curve was obtained by extrapolating the linear fitted model within 50-200 µmol-1i using the linear equation, A=k C + i; where is the initial slope of the A/Ccurve and may be described as carboxylation efficiency (CE), and –i/k was equal to * in the absence of mitochondrial respiration10. The rate of maximum Rubisco carboxylation cmax) and the rate of dark respiration in µmol m-2-1) were calculated using the following equations11: !"#"$%&#($#"$%&#( "13+&*1$#"$%&#(4!"1$5.Where c was 404.9 µmol mol-1and was 278.4 mmol mol-1 at 25C, and was 210 mmol mol-1. PPFD saturated rate of maximum electron transport (max µmol m-2-1) was calculated using the following equation11,12:  *7"$/"$9"+(&13+.Weather data: Microclimate condition of the area, such as air temperature, relative humidity, and soil temperature, was measured using HOBO data logger from July 2007 up to February 2010.The data were downloaded in the field every six months. It was observed that the highest mean air temperature in International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 76 March and April in all the study sites ranged from 24.1C to 26.6C and 24.5C to 26.6C in 2007 and 2008, respectively. Statistical analysis: Using a statistical software package (SPSS 16.0 program, SPSS Inc., Chicago, Illinois, USA), all statistical tests were performed. To estimate the derived parameters (cmax, d and max), regression analysis based on measured data was used. The means of variables among the stands were compared using paired t-test. Each variable was replicated into three. For multiple comparisons, Duncan’s multiple range test (DMRT) was used. Results and DiscussionBasal area: Basal area (BA) was determined by getting the total tree cross-sectional area in a stand at breast height which is 1.3 m from the ground. Among the stands, BA was significantly highest in the A. mangium (78.8 m h-1) followed by A. auriculiformis (75.4 m h-1) and P. indicus (15.4 m h-1) stand (figure-2). Stand BA is one of the quantitative measures of stand density along with other quantitative measures including the number of stems per acre and stand volume. Density also influences largely the yield and yield components of plants13. In terms of aboveground biomass estimation, simple linear relationship using BA was shown to be appropriate14. Basal area, a frequently calculated parameter in forest inventories, is certainly related to AGB, as may be realized from the fact that aboveground biomass is calculated out of the same data source - the DBH of all individual trees in the stand. In terms of species composition and other ecosystem activities, these are largely influenced by anthropogenic disturbances, climatic change among others15. Total leaf nitrogen and carbon concentrations: Nitrogen content of the leaves is one of the most important components that determine the important physiological processes in higher plants including respiration and photosynthesis16. Light is one of the major factors that regulates photosynthesis, and thereby influencing leaf characteristics such as carbon concentration and carbon/nitrogen ratio. It was found out that the total leaf nitrogen (N) and carbon (C) concentrations among the sampled tree species at different portions of the canopy and the stands were not significantly different (p�0.05) (figure- 3 and 4).The total N increases with shade treatment due to the changes in the specific leaf area17. In this study, it was found out in A. auriculiformis and P. indicus stands that total N increases with leaf area while total C was unaffected. Species exposed under insufficient amount of light have the tendency to increase the splitting of N into chlorophyll in the thylakoids18. Plants also induce the adaptive mechanisms to available light condition at different levels, such as the fraction of biomass, the investment of N. Litterfall: Annual litterfall (January 2009 to January 2010) of the study sites ranged from 2.30 to 5.72 tons ha-1 yr-1 (table - 1). It is shown in table - 1 and figure – 6 the monthly litterfall of the different sampled species. The values in this study is almost similar with the range of values obtainedin the tropical forests of Karnataka in India (3.4 to 4.2 tons ha-1 yr-119. The amount of litterfall was highest in the 20-yr-old A. auriculiformis and A. mangium (5.47 and 5.72 tons ha-1 yr-1, respectively). When compared with other categories, the contribution of leaf litter to the total litter was higher while the contribution of barks/twigs and reproductive part was low. Figure-2 Species basal area observed in the study. Each bar represents the mean (with standard error). Means with the same letter are not significantly different at 5% level by DMRT (Note: AA – Acacia auriculiformis, AM – Acacia mangium, and PI – Pterocarpus indicus) -20.00.020.040.060.080.0100.0120.0AAAMPIBasal Area (mha-1Species International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 77 Figure-3 Leaf nitrogen concentration of the 20-yr-old stand of Acacia auriculiformis (AA), A. mangium (AM) and P. indicus (PI)in the different portions of the canopy (lower, middle and upper). Each bar represents the mean (with standard error). Means with the same letter are not significantly different at 5% level by DMRT (Note: AA – Acacia auriculiformis, AM – Acacia mangium, and PI – Pterocarpus indicus) Figure-4 Leaf carbon concentration of the 20-yr-old stand of Acacia auriculiformis (AA), A. mangium (AM) and P. indicus (PI)in the different portions of the canopy (lower, middle and upper). Each bar represents the mean (with standard error). Means with the same letter are not significantly different at 5% level by DMRT (Note: AA – Acacia auriculiformis, AM – Acacia mangium, and PI – Pterocarpus indicus) abbc 0.51.52.53.54.5AAAMPIPercentage (%)Species Lower Middle Upper abababab 102030405060AAAMPIPercentage (%)Species Lower Middle Upper International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 78 Figure-5 Monthly litterfall of the different stands from January 2009 to January 2010 Table – 1 Litter production (tons ha-1 yr-1) in the 20-yr-old Acacia auriculiformis, Acacia mangium and Pterocarpus indicus stands Stands Foliar litter Branches/ Twigs Reproductive parts Total litterfall A. auriculiformis 2.68±0.5 1.93±0.2 0.86±0.1 5.47±0.6 A. mangium 4.10±0.4 1.19±0.1 0.44±0.1 5.72±0.6 P. indicus 2.45±0.2 0.83±0.1 0.81±0.2 4.08±0.1 As the amount of litterfall becomes higher the productivity in the stand also increases20. Different factors are affecting the patterns of litterfall in a forest ecosystem, including species composition, successional stage in its development and other microclimatic factors21. Hence, disparity in the patterns of litterfall is observed in this study as shown by the three species. The average amount of annual litterfall was greater in the 20-yr-old A. auriculiformis and A. mangium stands. The observed deviation in litterfall pattern may possibly be influenced bythe species composition. Gliricidia sepium, Leucaena leucocephala, Ficus septica, Gmelina arborea, Pterocarpus indicus, Syzigium nitidum, Swietenia macrophylla, Calliandra calothyrsus, and Arthocarpus heterophyllusare the other species that contribute greatly in addition to the common species (A. auriculiformis) to the total litter production. Likewise, in the A. mangium stand, L. leucocephala, F. septica, P. indicus, S. nitidum, S. macrophyllaand C. calothyrsusgreatly contributed in the total litter production. Consequently, it can be infer in this study that the composition of the species and their contribution to litter production are crucial in determining the total litter of the community as demonstrated byA. auriculiformis and A. mangium stands. Yearly cycle of environmental parameters largely affects the periodicity of litterfall. The highest amount of litterfall (0.45 to 0.77 tons ha-1 yr-1) happened from January to April, which is dry season in the Philippines (figure-5). This is also the same with the results of other studies having higher yield during summer, e.g. deciduous plantations. Climate change could also be a contributory factor in the changes that is occurring in the forest22. Foliage and soil analyses: The analysis of foliage is important in determining the nutrient status of the plant and for appropriate application of fertilizers. The level of nutrients in the plant often varies. However, in this study the foliage nutrients did not much vary among the species (p�0.05) (table -2). The important factor controlling the growth of plantation is the nutrients which can be made available to the plant through fertilizer application. This amount of nutrients could vary depending on the species, age and the productivity of the stand23. Overall, the 20-yr-old A. auriculiformis (267.23 kg kg-1 yr-1) and A. mangium (221.72 kg kg-1 yr-1) had the highest increase in plant dry mass per unit plant N per unit time(NP).The N deposition effect, CO level increase in the atmosphere, and forest management practices can contributeto the increase in NP24. The role of nitrogen fixing species is important in enriching the nitrogen content in the soil. It was suggested in earlier studies the use of N fixing species could improve quality and quantity of litters as well as increase the above and belowground productivity25. Soil analysis: In terms of soil pH and N, insignificant difference p�0.5) was observed in all the stands while other nutrients 0.10.20.30.40.50.60.70.80.9 Litterfall (tons ha-1yr-1) Months A.Auriculiformis A. mangium P. indicus International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 79 exhibited significant difference (p0.03) (table - 3). The soil organic matter (SOM), K, Ca, Mg and CEC were high in the 20-yr-old A. auriculiformis stand (6.25% and 2.53 cmol(+)/kg, 10.7 cmol(+)/kg, 5.2 cmol(+)/kg, and 38.3 cmol (+)/kg, respectively) and A. mangium stand (5.79%, 2.03 cmol(+)/kg, 8.9 cmol(+)/kg, 4.7 cmol(+)/kg, and 32.3 cmol(+)/kg, respectively). The higher soil nutrients in MMFR could be attributed to its quite low soil temperature and elevation. A/Ci curve and estimation of derived parameters (Vcmax and max): In all the studied species, strong relationship (=0.81 to0.92) was observed between A and . Based on the analysis, it was found out that, upper portion of the canopy ofA. mangiumstand had the highest A/Crate with peak value of 12.78 µmol CO2 -2-1 under 600 µmol mol-1 , while the lowest peak rate was obtained by P. indicus stand in the lower portion of the canopy with value of 8.87 µmol CO2 -2-1 under 600 µmol moli (figure - 6). There are many underlying assumptions in the analysis of A/Ccurves or net photosynthesis. By estimating cmax on the A/Ccurve the influence of the i value on the Rubisco and electron transportwas examined. There’s a considerable variability among the species in terms of , in which environment explains part of this variation and therefore produces different patterns of response26. Also, at the species level, varied in concert with assimilation capacity and stomatal conductance. At community level, there is no seasonal influence over . cmax and max are key parameters of the A/C model and they vary by species. These parameters also vary with temperature27. Analysis of the cmax and max gives us insight into the potential to photosynthesize at a given CO concentration that is independent of stomatal limitations28. For instance, highly productive herbaceous species were reported to have consistently higher rates of both cmax and max than slower growing woody species. In this study, it was observed that cmaxand maxare significantly different (p0.01) among the studied species (figure - 7). The highest cmax and max observation was obtained by 20-yr-old A. mangium with an average value of 72.24 µmol CO m-2-1 and 210.15 µmol E m-2-1, respectively. Table - 2 Foliar nutrients and nitrogen productivity (NP) of 20-yr-old Acacia auriculiformis, Acacia mangium and Pterocarpus indicusstands Species/Age class Ca(%) K (%) Mg (%) N (%) P (%) Cu (ppm) FeCu (ppm) Mn (ppm) Zn (ppm) NP (kg kgyr-1) Acacia auriculiformis 2.44 a (0.20) 0.25 ab (0.10) 0.32 ab (0.02) 2.84 ab (0.02) 0.06 ab (0.10) 1.1 a (0.17) 332 c (0.48) 208 b (0.04) 44 b (0.42) 267.23 a (0.31) Acacia mangium 1.85 ab (0.02) 0.05 ab (0.10) 0.41 ab (0.03) 3.18 a (0.50) 0.05 ab (0.10) 1.3 a (0.12) 1220 a (0.39) 272 a (0.11) 39 b (0.54) 221.72 ab (0.29) Pterocarpus indicus 2.39 a (0.50) 0.35 a (0.10) 0.65 a (0.06) 3.19 a (0.50) 0.16 a (0.10) 0.9 ab (0.23) 2985 b (0.25) 233 ab (0.13) 86 a (0.21) 143.80 bc (0.41) Standard errors of the means are given in parentheses. Means within a column with the same letter are not significantly different at 5% level by DMRT Table - 3 Soil characteristics of 20-yr-old Acacia auriculiformis, Acacia mangium and Pterocarpus indicus stands in Mt. Makiling Forest Reserve, Philippines Age class pH OM (%) N (%) P (ppm) K (cmol(+)/kg) Ca (cmol (+)/kg) Mg (cmol (+)/kg) CEC (cmol (+)/kg) Acacia auriculiformis 4.9 a (0.30) 6.25 a (0.10) 0.35 a (0.08) 0.6 b (0.19) 2.53 a (0.61) 10.7 a (2.18) 5.2 a (2.67) 38.3 a (2.68) Acacia mangium 4.6 a (0.10) 5.7 a (0.2) 0.33 a (0.04) 1.3 ab (0.23) 2.03 ab (0.52) 8.9 ab (2.44) 4.7 a (2.44) 32.3 ab (2.71) Pterocarpus indicus 4.7 a (0.10) 3.55 b (0.2) 0.25 ab (0.03) 3.1 a (0.77) 0.35 b (0.08) 7.9 ab (1.92) 2.8 ab (0.23) 13.6 b (0.53) Standard errors of the means are given in parentheses. Means within a column with the same letter are not significantly different at 5% level by DMRT International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 80 Figure – 6 A/Ccurves of 20-yr-old (A) Acacia auriculiformis, (B) Acacia mangium, and (C) Pterocarpus indicus stands in the lower, middle and upperportions of the canopy, Values are the mean ± S.D. (n = 3) (a) (b) (c) Figure-7 Estimated Vcmaxand max of the 20-yr-old (A) Acacia auriculiformis, (B) Acacia mangium and (C) Pterocarpus indicus stands in the lower, middle and upper portions of the canopy =0.81=0.86=0.92 -21012140200400600Net CO2 Assimilation rate , µmol CO-2-1Intercellular CO concentration µmol mol-1) Lower Middle Upper =0.83=0.87=0.83 -21012140200400600Net CO Assimilation rate A,µmol CO-2-1Intercellular CO concentration , µmol mol-1 Lower Middle Upper =0.82=0.85=0.88 -210120200400600Net CO Assimilation rate (A, µmol CO-2-1Intercellular CO concentration µmol mol-1 Lower Middle Upper 5010015020025062636465666768697071LowerMiddleUpper max (µmol E m-2-1cmax(µmol CO-2-1Parts of the canopy Vcmax Jmax 50100150200250606264666870727476LowerMiddleUpper max (µmol E m-2-1cmax(µmol CO-2-1Parts of the canopy Vcmax Jmax 17417617818018218418618819019219453545556575859LowerMiddleUpper max (µmol E m-2-1cmax(µmol CO2 -2-1Parts of the canopy Vcmax Jmax International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 3(6), 73-82, June (2014) Int. Res. J. Biological Sci. International Science Congress Association 81 cmax parameter is important to describe precisely the Rubisco activity which describes the efficiency of the Calvin cycle. Based on theA/Ci curve analysis, it is assumed that is nearly equal to chloroplast CO concentrations. The lower cmaxis influenced by the reduced amount of resource allocation to photosynthetic processes (i.e.Rubisco and chlorophyll per unit N), high amount of inactivated Rubisco, or lower stomatal conductancevalues29. As a whole, A/C , cmaxand max were found highest in the A. auriculiformis and A. mangium stands than P. indicus. A/Cdeclined due to high temperature that reduces the capacity for electron transport and increases the rate of CO2 evolution from other sources and photorespiration30. Conclusion The study revealed that parameters derived from the A/C curve cmax and max), were high in both A. mangium and A. auriculiformis that gives us insight of the potential of these species to photosynthesize at a given CO concentration. Also, based on the results obtained, A. auriculiformis and A. mangiumexhibited better performance as they had the highest value in terms of NP as influenced by their higher leaf area, biomass accumulation and N inputs. Since A. auriculiformis and A. mangium species are fast growing and could easily develop their growth and coverage, they had an advantage of gaining more height and DBH over the native species. The implication of this ecophysiological study is very crucial as it provided a great degree of generalization about the nature of A. mangium and A. auriculiformis in choosing them for reforestation purpose. It is also about high time to include ecophysiological studies in doing species trial for forest plantations in the country. 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