International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 3(2), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 76 Aboveground Biomass Partitioning and Invasibility of Sida acuta Burm. f. in Indian dry TropicsSinghal Shilpy and Narayan Rup Department of Botany, I. P. (Post-Graduate) College, Bulandshahr-203001, INDIA Available online at: www.isca.in, www.isca.me Received 18th January 2014, revised 23rd January 2014, accepted 12th February 2014 AbstractThe pantropical malvaceous invasive weed Sida acuta Burm. f. was investigated for its varying morphological traits including its biomass allocation strategy to different above-ground organs at two contrasting sites: bank of polluted Kali river (KRB) and city-vegetation neighbouring the Ganga canal around Yamunapuram (YPM) in a peri-urban region in Indian dry tropics. Sixty plant individuals from each site at differing stage of their growth were clipped off from the base for the biomass measurements of their stem (stem-axis + branch), leaves and reproductive parts (flowers + capsules). The morphological traits studied were: shoot length, basal diameter and number of branches, leaves and flowers/capsules. Surface soil samples of both the study sites were analyzed for soil moisture, pH, organic C, available P and exchangeable K. S. acuta population at YPM site had significantly higher shoot length and stem-axis mass fraction. Biomass partitioning to different components was variable: stem (41-45%), leaf (47-52%) and reproductive parts (14-16%). Mean plasticity indices for plant-level traits were relatively higher at KRB site. Biomass of leaf, stem and reproductive parts was strongly correlated with total aboveground biomass. While leaf allocation declined significantly with plant size, stem allocation increased. Biomass allocation pattern of S. acuta populations did not show significant change with change of study sites in the present study, possibly due to comparable disturbance, soil and site conditions. In conclusion, invasiveness of this alien weed in peri-urban anthropo-ecosystems could be attributed mainly to its superior competitive ability manifested through higher allocation to photosynthetic and support organs. Keywords: Peri-urban ecosystem, exotic, invasive, biomass allocation, phenotypic plasticity. Introduction Biological invasion is presently considered to be an important driver of global change.Invasion of native communities by exotic species, particularly the invasive ones, is recognized the world over as the second largest threat to biodiversity1,2,3,4. The tropics experience greater pressure of invasive species, as the process of plant species invasion gets accelerated with increased anthropogenic interventions. The increasing human population and improved trans-continental transport have increased the scales of movement of non-native species. The current exacerbated rate of invasion constitutes one of the most important effects that humans have begun to witness on the earth ecosystemThe ecological consequences of invasion by aliens have become an important global concern in light of their impact on alteration in the structure and function of the invaded ecosystems. The ecosystem level consequences of invasion are, however, still little understood and there is an urgent need of studies on biological invasions in India particularly in dry tropics that are rapidly facing urbanization-driven ecological modifications. The urban and peri-urban ecosystems in Indian dry tropics have often been reported to harbour a large number of alien species which possibly followed the anthropogenic activities in this region. The weedy vegetation in these anthropo-ecosystems has also been reported to be infested with many invasive/naturalized invaders. The mosaic of vegetation, here, has Parthenium hysterophorus, Ageratum conyzoides and Chenopodiummuraleas the dominant alien invasives10,11. Despite the recognized dominating influence of the exotic alien species across diverse peri-urban anthropo-ecosystems12,13, the information on invasive growth characteristics of the alien species is inadequate. Among them, the malvaceous weed Sida acuta Burm. f. is frequently seen in abundance across diverse land uses: degraded pastures, waste- and disturbed-places and roadsides14,15. This pantropical species is recognized as invasive alien weed in India16,17,18. Thus, this invasive species having annual-perennial life-form is likely to have high phenotypic plasticity that enabled it to successfully colonize in diverse alien environments. Compared with native species, the successful invasive species are generally reported to have greater stress tolerance and can thus acclimate to a larger range of environmental conditions19,20. Biomass allocation is often assumed as an important plant trait that allows the plants to optimize growth under varying soil scarce and growth stage conditions. An invasive plant species must be able to use fluctuating resources better21, particularly in resource-scarce site conditions in and around urbanizing landscapes in peri-urban ecosystems. Therefore, greater phenotypic plasticity is likely to confer greater vigour on invasive species22,23,24. Despite recognition of this weed’s advancing abundance in dry tropics across a variety of habitat International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 77 conditions, there exists little authentic information regarding biomass allocation pattern to its different organs that could be its important invasive characteristics, particularly in peri-urban areas in dry tropics. The present work aimed at investigating the morphological traits and allocational plasticity of Sida acuta at two contrasting habitat conditions to understand its invasibility. Material and Methods Study area: The present study was carried out at Bulandshahr (28º04’ and 28º43’ N lat. and 77º08’ and 78º28’ E long.), located in the western part of Uttar Pradesh. The district is situated 237.44 m above sea level and lies in the Ganga and Yamuna Doab. The vegetation, here mainly comprised of mosaic of annual weeds and ruderals. The soil of the district includes broad belt of excellent alluvial soils formed from depositions by the Ganga and Yamuna river. The major developed cities around Bulandshahr, whose brunt of development it has faced, include Delhi (72 km), Noida (58 km), Meerut (69 km), Aligarh (69 km) and Ghaziabad (52 km) which are well connected with roads and railways. To accomplish the objectives of present study two study sites were selected. First study site was the bank of polluted Kali (black) river (KRB). This site witnessed the dumping of urban and sewage wastes. Agricultural fields, however, lay along its banks in the adjoining areas. The second site was the patches of vegetation around Yamunapuram colony (YPM) near Gang nahar canal. This site witnessed intensive transportation and human settlement activities interspersed with areas infested by weeds and ruderals. 1 km area was selected at each site for intensive study. The climate of the study area was semi-arid having three seasons: rainy, winter and summer. The monthly mean minimum temperature ranged from 8.0ºC (Jan) to 28.0ºC (Jun) and the mean maximum from 20.1ºC (Jan) to 41.5ºC (Jun). Annual mean rainfall was 642.3 mm having the maximum rainfall in the month of August (222.2 mm). Soil analysis: Six representative surface-soil samples (0-10 cm) were randomly collected from each of the two study sites (KRB and YPM). The soil samples were air-dried and sieved (2 mm). Physico-chemical characteristics of soil samples were estimated that included soil-moisture content, pH, total organic carbon (Walkley and Black method)25, available Phosphorous and exchangeable Potassium26. The other micro-nutrients estimated were: available S, Zn, Fe, Mn and Cu25. Plant-level measures: A total of one hundred and twenty individuals were randomly selected from two study sites (sixty each) at different stages of their growth (July – October) between 2008 and 2009. The selected individuals were carefully clipped off from the base at soil surface. Shoot length (SL) of the fresh individuals was measured from the shoot-top to bottom of the plant where the stem entered the soil. Basal diameter of all plant individuals was also measured. Plants were separated into different components, stem (stem-axis and branch), leaves and reproductive parts (flower and capsule). All plant components were then separately oven-dried at 80 C for 48 h and weighed to the nearest 0.001 g to determine component biomass and above-ground biomass (AGB). The component mass fractions (stem-axis mass fraction, SAMF; branch mass fraction, BMF; stem (stem-axis + branches) mass fraction, SMF; leaf mass fraction, LMF and reproductive part (flowers + capsules) mass fraction, RPMF) were calculated as the biomass of each component in relation to the above-ground biomass. Leaf area of 100 randomly selected fresh leaves from each site was measured by digital leaf area meter (Systronics). Plasticity indices and Statistical analysis: The plant component mass fractions (SMF, LMF and RPMF) were studied in relation to total above-ground biomass (log scale). Biomass allometric relationships between each component mass fraction and total above-ground biomass were assessed through linear regression model27. Component mass fractions (SAMF, BMF, SMF, LMF and RPMF) were regressed against shoot length using second order polynomial regression model to determine the biomass allocation changes with increasing plant size. The degree of plasticity among mature individuals (in reproductive phase) was compared by estimating the plasticity index (PI) for each trait28. The index extreme range includes zero (no plasticity) and one (maximum plasticity). It is evaluated as the difference between the maximum and minimum values of the trait divided by the maximum value at a site. The mean plasticity indices for plant-traits were evaluated for each species by averaging all variables. Pearson product–moment correlation coefficients were generated to evaluate the linear association between traits and total above-ground biomass of plant individuals at both sites. The difference in the morphological traits of plants at two sites was statistically (SPSS 17.0) examined by t-tests (two tailed). Results and Discussion Plant level traits: Mean shoot length of sampled plant individuals was significantly higher (p0.05) (table 1) at YPM site compared to KRB site. In contrast, BD/SL was higher at KRB site (p0.001). On the mean basis, total number of branches, leaves, reproductive parts (flowers + capsules), biomass of stem-axis, branch, stem (stem axis + branch), leaf, reproductive parts and above-ground biomass were higher at YPM site, albeit the difference was not significant. The leaf biomass per leaf was significantly higher at YPM site (p0.05). In terms of component mass fractions, the stem-axis mass fraction (SAMF) was significantly higher (p0.001) at YPM site compared to KRB. While SMF was higher at YPM site, LMF International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 78 was higher at KRB site, although the differences were not significant. Table-1 Plant- and leaf-level traits (mean ± SE) of Sida acuta at Kali river bank (KRB) and Yamunapuram (YPM) study sites in a dry tropical peri-urban region Traits KRB YPM p value (t Test) Shoot length (SL) (cm) 27.47 ± 2.91 38.97 ± 3.26 0.05 Basal diameter (BD) (cm) 0.39 ± 0.04 0.39 ± 0.03 ns BD/SL ratio 0.02 ± 0.001 0.01 ± 0.001 0.001 Branch no. 14.23 ± 1.09 16.03 ± 1.17 ns Total Leaf no. 165.2 ± 34.4 169.5 ± 31.8 ns No. of rep parts (flowers + capsules) 245.4 ± 61.6 281.4 ± 56.5 ns Stem-axis biomass (g) 1.31 ± 0.28 1.67 ± 0.33 ns Branch biomass (g) 2.76 ± 0.81 2.98 ± 0.81 ns Stem biomass (g) 2.92 ± 0.75 3.46 ± 0.84 ns Leaf biomass (g) 1.17 ± 0.20 1.47 ± 0.26 ns Single leaf biomass (g) 0.008 ± 0.001 0.011 ± 0.001 0.05 Reproductive part biomass (g) 1.78 ± 0.53 2.11 ± 0.62 ns Shoot biomass (AGB) (g) 4.95 ± 1.19 5.98 ± 1.37 ns Stem-axis mass fraction (SAMF) 0.27 ± 0.01 0.33 ± 0.01 0.001 Branch mass fraction (BMF) 0.23 ± 0.02 0.21 ± 0.02 ns Stem mass fraction (SMF) 0.41 ± 0.02 0.45 ± 0.02 ns Leaf mass fraction (LMF) 0.52 ± 0.03 0.47 ± 0.03 ns Rep part mass fraction (RPMF) 0.14 ± 0.02 0.16 ± 0.03 ns Leaf area (cm 2 ) 6.18 ± 0.57 6.35 ± 0.59 ns Plasticity indices: The plasticity indices (PIv) of plant traits of Sida acuta ranged from 0.52 to 0.99 at KRB site and from 0.37 to 0.98 at YPM site (table 2). The mean plasticity was relatively higher at KRB site. Here, the plasticity indices for all plant traits (BD/SL ratio, SAMF, BMF, SMF and LMF) were higher compared to YPM site. RPMF, however, was much comparable at these two sites. Pearson product correlation: Various plant traits, such as shoot length, basal diameter, number of branches, leaf and reproductive parts (flower + capsule), biomass of plant components (stem-axis, branch, leaf, reproductive part) were strongly and positively correlated with total above-ground biomass (AGB) of plants at both sites (KRB and YPM) (table 3). BD/SL ratio was positively related to AGB at KRB site while negatively related at YPM site although these relations were not significant. LMF was strongly and negatively correlated at both sites. On the other hand, SAMF showed negative and significant relation with AGB at YPM site only. Table-2 Plasticity indices of different plant traits of Sida acuta at Kali river bank (KRB) and Yamunapuram (YPM) study sites in a dry tropical peri-urban region. Codes: BD basal diameter, SL shoot length Plant-level traits KRB YPM BD/SL ratio 0.73 0.50 Stem-axis mass fraction (SAMF) 0.75 0.61 Branch mass fraction (BMF) 0.91 0.89 Stem mass fraction (SMF) 0.52 0.37 Leaf mass fraction (LMF) 0.80 0.73 Rep part mass fraction (RPMF) 0.99 0.98 Mean 0.78 0.68 Table-3 Pearson product-moment correlation coefficient (r) for relationships between various plant-level traits and total above-ground biomass for Sida acuta at Kali river bank (KRB) and Yamunapuram (YPM) study sites in a peri-urban dry tropical region Plant-level traits KRB YPM Shoot length (SL) (cm) .620** .790** Basal diameter (BD) (cm) .773** .801** BD/SL ratio 0.026 -0.219 Branch no. .448** .598** Total leaf no. .969** .899** No. of rep part (flower + capsule) .932** 0.901** Stem-axis biomass (g) .938** .975** Branch biomass (g) .977** .995** Stem biomass (g) .997** .996** Leaf biomass (g) .879** .919** Single leaf biomass (g) -0.153 -0.052 Reproductive part biomass (g) .945** .984** Stem-axis mass fraction (SAMF) -0.050 -.350** Branch mass fraction (BMF) .640** .736** Stem mass fraction (SMF) .566** .558** Leaf mass fraction (LMF) -.637** -.644** Rep part mass fraction (RPMF) .392* .558** **Correlation is significant at the 0.01 level (2-tailed). *Correlation is significant at the 0.05 level (2-tailed). Allocation pattern: The SMF increased significantly with increasing plant size (AGB) (figure 1). However, at lower plant size, SMF was higher at YPM site compared to KRB site and the trend reversed at higher plant sizes. In contrast to increasing pattern of SMF, LMF declined significantly with increasing plant size (R = 0.918 at KRB and 0.841 at YPM site). RPMF International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 79 increased with plant size (R = 0.211 at KRB and 0.470 at YPM site). Figure-1 Allometric relationships between plant component mass fractions (stem mass fraction, SMF; leaf mass fraction, LMF and reproductive part mass fraction, RPMF) and total above-ground biomass (log scale) of Sida acuta at KRB site (filled squares and solid line) and YPM site (open circles and dotted line) in a dry tropical peri-urban region Comparing the trends of organal mass fractions with increasing shoot length of Sida acuta at two different sites (figure 2), the LMF showed a significant and sharp decline at both sites (R = 0.999 at KRB and 0.0.995 at YPM site) (table 4). A comparable trend for SAMF, BMF and SMF was recorded at both the sites. RPMF also showed an increasing trend with the maturity of the plant. The difference in the trends of allocation of biomass to different components was not found to vary significantly with change of study sites under the present investigation. Figure-2 Variation of stem-axis mass fraction (SAMF), branch mass fraction (BMF), stem mass fraction (SMF), leaf mass fraction (LMF) and reproductive part mass fraction (RPMF) in relation to shoot length of Sida acuta at (a) Kali river bank (KRB) site and (b) Yamunapuram (YPM) site in a dry tropical peri-urban region. Curves represent best-fit second-order polynomial regression. Regression equations and R2 values are presented in table 4. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 80 Table-4 Regression equations and R values of stem-axis mass fraction (SAMF), branch mass fraction (BMF), stem mass fraction (SMF), leaf mass fraction (LMF) and reproductive part mass fraction (RPMF) with shoot length of Sida acuta at Kali river bank (KRB) and Yamunapuram (YPM) study sites in a dry tropical peri-urban region, as presented in figure 2 Site Regression equation R 2 value KRB SAMF = -0.003x 2 + 0.039x + 0.209 0.744 BMF = -0.027x 2 + 0.222x - 0.160 0.957 SMF = -0.033x 2 + 0.289x - 0.014 0.991 LMF = 0.037x 2 - 0.359x + 1.08 0.999 RPMF = 0.001x 2 + 0.008x + 0.087 0.713 YPM SAMF = -0.020x 2 + 0.121x + 0.185 0.906 BMF = 0.002x 2 + 0.061x - 0.067 0.995 SMF = -0.016x 2 + 0.176x + 0.111 0.979 LMF = 0.004x 2 - 0.157x + 0.882 0.995 RPMF = 0.004x 2 + 0.024x - 0.007 0.857 Soil Characteristics: Soil moisture content (summer), organic carbon and other investigated soil nutrients were relatively higher in KRB soils compared to those in YPM soils (table 5) albeit statistically insignificant. Soil pH was however, significantly higher at YPM site (p0.01). Table-5 Physico-chemical characteristics of Kali river bank (KRB) and Yamunapuram (YPM) soils (mean ± SE) in a dry tropical peri-urban region Soil Characteristics KRB YPM p value (t Test) Moisture content % (Summer) 0.89 ± 0.15 3.00 ± 0.92 ns pH 6.86 ± 0.09 7.24 ± 0.05 0.01 Org C 0.70 ± 0.08 0.54 ± 0.08 ns Available P (Kg/ha) 18.43 ± 2.09 13.86 ± 1.99 ns Exchangeable K (Kg/ha) 306.0 ± 11.5 241.0 ± 24.9 0.05 Available S (ppm) 14.21 ± 0.53 13.45 ± 0.49 ns Available Zn (ppm) 1.02 ± 0.10 0.93 ± 0.10 ns Available Fe (ppm) 7.18 ± 0.46 6.93 ± 0.45 ns Available Mn (ppm) 4.71 ± 0.13 4.63 ± 0.11 ns Available Cu (ppm) 0.59 ± 0.04 0.58 ± 0.03 ns Discussion: A significant alteration in biomass investment to different plant components with the change in developmental stage was revealed by the rainy annual Sida acuta in the present study. This recorded change could be attributed mainly to invasiveness and its tendency to perennial life form in the studied dry tropical peri-urban region. The biomass partitioned by this pantropical malvaceous weed to stem, although higher than the SMF reported for herbaceous species29, was within the range (0.40-0.45) for five invasive herbaceous weeds in Indian dry tropics (table 6). Amongst the support structural components, significantly greater stem-axis mass fraction (SAMF) of plants at YPM site compared to KRB site is possibly indicative of the fact that this weed invested more to its stem component for firm establishment to resist more frequent biotic interference at YPM site. However, the overall biomass partitioning to the stem was comparable at both the sites. The enhanced allocation to support structure indicated the growth strategy of this weed for strong establishment in this anthropic region. Considering allocation to three major above-ground components (leaf, stem and reproductive parts), the LMF in the present study at two sites (0.47-0.52) was much higher compared to LMF range reported for other weeds/herbs. A significantly high allocation of biomass to leaves, indicative of investment to photosynthetic tissues, reflected the invasive character of this weed to outcompete the growth performance of native/alien weeds in this region23,30,31,32. Further, the invasion success for any exotic weed in the recourse-scarce peri-urban anthropo-ecosystems must depend upon the innate quality of weed roots to acquire the available soil nutrients. About 17% root allocation by Sida acuta in Indian peri-urban ecosystems has been reported. A considerably high root allocation in resource-scarce sites in peri-urban anthropo-ecosystems, along with perennial growth tendency could be the major characteristics that contributed to the aggressiveness of this weed species here. The reproductive allocation by Sida acuta in this study, when compared with that by Ageratum conyzoides and Chenopodium murale (table 6), further corroborated the expansionist and invasive character of this weed in this region. Despite higher reproductive allocation the density of this weed appears constrained, as the number of seeds per plant varied from only 101 per plant33 to 746 seeds/ plant recorded in this study. Table-6 Comparison of biomass allocation values of different plant species, Allocation is characterized as a fraction of total biomass allocated to leaves (LMF), stems (SMF), roots (RMF) and reproductive parts (RPMF) SMF LMF RMF RPMF Herbaceous species29 0.24 0.46 0.3 - Herbaceous weeds8 0.40-0.45 0.26-0.41 0.10-0.17 0.06-0.27 Chenopodium murale L.9 0.44-0.49 0.28-0.35 0.10-0.11 0.10-0.12 Ageratum conyzoides L.10 0.18-0.51 0.27-0.38 0.08-0.09 0.13-0.36 Sida acuta Burm. f. 0.41-0.45 0.47-0.52 - 0.14-0.16 International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 81 Biomass allocation pattern reflected this weed’s growth strategy to be establishment-centric. The invasive characteristic of Sida acuta appears to be greatly expressed through its differing stem characteristic at two study sites. Despite similar mean basal diameter, the mean shoot length was significantly higher at YPM site having relatively poor soil nutrients. Accordingly, BD/SL ratio was lower here. The higher shoot length allowed better light utilization potential and avoidance of shading by neighbouring plant species34,35. A considerable growth optimization ability of this invasive weed is documented by relatively higher total above-ground biomass at YPM compared to KRB site. However, the higher mean plasticity index at KRB site indicated greater plastic response to environmental variability here at highly polluted Kali river bank, as enhanced phenotypic plasticity is commonly suggested to play an important role in successful invasion of new habitats by alien species36,37. Amongst the three major above-ground components investigated here, the leaf allocation declined with plant size. On the other hand, stem and reproductive allocation increased. The initially higher leaf allocation in plants at younger stage of development is often suggested to meet the accelerated growth requirements, and it decreased with the maturity of the plants38. Despites the frequent occurrence of Sida acuta across various anthropo-ecosystems in the peri-urban region in Indian dry tropics39, it has not been reported as the top leading dominant in any plant community amongst the vegetation mosaic here12,39. This could be attributed partially to its relatively poor ability to show pronounced differential biomass allocation pattern with the alteration in environmental conditions. This is evident from the present study, where insignificant alteration in the biomass allocation was observed across two study sites, albeit shift in the biomass partitioning to different components with ontogeny was clearly revealed in this study. However, variation in shoot biomass of S. acuta under the light/shade condition as well as in intra-specific competitive situations, has also been reported40. Conclusion In conclusion, the invasiveness of Sida acuta, as evinced in the present study could be attributed to higher biomass allocation strategy to photosynthetic and support organs. References 1.Pauchard A. and Shea K., Integrating the study of non-native plant invasions across spatial scales, Bio. Invas.,, 399- 413 (2006)2.Hong Ji., Kim J., Choi O., Cho K-Suk. and Ryu H., World J. Microbiol. Biotechnol., 21, 381–384 (2005) 3.Pimentel D., McNair S., Janecka J., Wightman J., Simmonds C., O ’ Connell C., Wong E., Russel L., Zern J., Aquino T. and Tsomondo T., Economic and environmental threats of alien plant, animal, and microbe invasions, Agr.Ecosyst. and Environ., 84, 1–20 (2001) 4.Drake J. A., di Castri F., Grooves R. H., Kruger F. J., Mooney H. A., Rejmanek M. and Williamson M., Biological Invasion: A global perspective, JohnWiley, Chichester, UK (1989) 5.Raizada P., Ingress of Lantana in dry tropical forest fragments: Edge and shade effects, Curr. Sci., 94(2), 180-182 (2008) 6.Sharma G. P., Plant invasions: Emerging trends and future implications, Curr. Sci., 88(5), 726-734 (2005) 7.Simberloff, D., How much information on population biology is needed to manage introduced species?, Conserv. Biol., 17(1), 83-92 (2003) 8.Gupta S., An ecological investigation on biomass production and allocation pattern of some weed flora at Bulandshahr, Ph.D. Thesis, CCS University, Meerut, India (2008) 9.Gupta S. and Narayan R., Phenotypic plasticity of Chenopodium murale across contrasting habitat conditions in peri-urban areas in Indian dry tropics: Is it indicative of its invasiveness? Plant Ecol., 213(3)493-503 (2012) 10.Chaudhary N. and Narayan R., Exotic invasive Ageratum conyzoides L. in Indian dry tropics: A preliminary investigation of its biomass allocation pattern and plant traits, J. Plant Dev. Sci., 5(3), 249-254 (2013) 11.Chaudhary N. and Narayan R., The Advancing Dominance of Ageratum conyzoides L. and Lantana camara L. in a dry Tropical Peri-urban Vegetation in India, Int. Res. J. Environ. Sci., 2(11), 88-95 (2013) 12.Gupta S. and Narayan R., Brick kiln industry in long-term impacts biomass and diversity structure of plant communities, Curr. Sci.,99(1)72–79 (2010)13.Gupta S. and Narayan R., Plant diversity and dry-matter dynamics of peri-urban plant communities in an Indian dry tropical region, Ecol. Res.,26(1)67–78 (2011) 14.Mann A., Gbate M. And Umar A. N., Sida acuta subspecie acuta: Medicinal and economic palnt of Nupeland, Jube Evans Books and Publication, 241 (2003)15.Flanagan G. J., Hills L. A. and Wilson C. G., The successful biological control of spinyhead Sida, Sida acuta(Malvaceae), by Calligrapha pantherina (Col: Chrysomelidae) in Australia's Northern Territory. In: Proceedings of the X International Symposium on Biological Control of Weeds, Bozeman, Montana, USA, 4-14 July, 1999 [ed. by Spencer, N. R.]. Bozeman, USA: Montana State University, 35-41(2000)16.Khuroo A. A., Alien flora of India: taxonomic composition, invasion status and biogeographic affiliations, Bio. Invas., 1499–113 (2012) International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 76-82, February (2014) Int. Res. J. Environment Sci. International Science Congress Association 82 17.Singh K. P., State-level inventory of invasive alien plants, their source regions and use patential, Curr. Sci., 99(1), 107-114 (2010) 18.Reddy C. S., Catalogue of invasive alien flora of India, Life Sci. J., 5(2), 84-89 ( 2008) 19.van Kleunen M. and Richardson D. M., Invasion biology and conservation biology- time to join forces to explore the links between species traits and extinction risk and invasiveness, Prog. Phys. Geog., 31, 447-450 (2007) 20.Albert P., Bone E. and Holzapfel C., Invasiveness, invasibility and the role of environmental stress in the spread of non-native plants, Perspect. Plant Ecol. Evol. Syst., , 52–66 (2000)21.Davis M. A., Grime J. P. and Thompson K., Fluctuating resources in plant communities, a general theory of invasibility, J. Ecol., 88, 528–534 (2000)22.Dukes J. R., Tomorrow’s plant communities: different, but how? New Phytol., 176, 235-237 (2007)23.Durand L. A. and Goldstein G., Photosynthesis, photoinhibition, and nitrogen use efficiency in native and invasive tree ferns in Hawaii, Oecol., 126, 345–354 (2001)24.Yamashita N., Ishida A., Kushima H. and Tanaka N., Acclimation to sudden increase in light favoring an invasive over native trees in subtropical islands, Japan, Oecologia, 125, 412–419 (2000)25.Piper C. S., Soil and plant analysis: a laboratory manual of methods for the examination of soils and the determination of the inorganic constituents of plants, Interscience publishers, Inc, New York (1944)26.Allen S. E., Grismshaw H. M. and Rowland A. P., Chemical analysis. In: Moore PD, Chapman SB (eds) Methods in plant ecology, Blackwell Scientific, Oxford, pp 285–344 (1986)27.Mead R. and Curnow R. N., Statistical methods in agriculture and experimental biology, Chapman and Hall, London (1983)28.Valladares F., Sanchez-Gomez D. and Zavala M. A., Quantitative estimation of phenotypic plasticity: bridging the gap between the evolutionary concept and its ecological applications, J. Ecol., 94, 1103–1116 (2006) 29.Poorter H. and Nagel O., The role of biomass allocation in the growth response of plants to different levels of light, CO2, nutrients and water: a quantitative review, Aust. J. Plant Physiol.,27, 595–607(2000) 30.Nagel J. M. and Griffin K. L., Can gas-exchange characteristics help explain the invasive success of Lythrumsalicaria? Bio. Invas., 101-111 (2004)31.McDowell S. C. L., Photosynthetic characteristics of invasive and noninvasive species of Rubus (Rosaceae), Am. J. Bot., 89, 1431-1438, (2002)32.Baruch Z. and Goldstein G., Leaf construction cost, nutrient concentration, and net CO assimilation of native and invasive species in Hawaii, Oecol., 121, 183-192 (1999)33.Lonsdale W. M., Farrell G. and Wilson C. G., Biological control of a tropical weed: a population model and experiment for Sida acuta, J. Appl. Ecol., 32(2), 391-399 (1995)34.Standish R. J., Robertson A.W. and Williams P. A., The impact of an invasive weed Tradescantia fluminensis on native forest regeneration, J. Appl. Ecol., 38, 1253-1263 (2001)35.D’Antonio C. M., Hughes R. F. and Vitousek P. M., Factors influencing dynamics of invasive C4 grasses in Hawaiian woodland, role of resource competition and priority effects, Ecology, 82, 89-104 (2001)36.Davidson A. M., Jennions M. and Nicotra A. B., Do invasive species show higher phenotypic plasticity than native species and, if so, is it adaptive? A meta-analysis, Ecol. Lett., 14, 419-431 (2011)37.Feng Y., Wangc J. and Sangc W., Biomass allocation, morphology and photosynthesis of invasive and noninvasive exotic species grown at four irradiance levels, Acta Oecol., 31, 40-47 (2007) 38.Bloom A. J., Chapin F. S. and Mooney H. A., Resource limitation in plants- an economic analogy, Ann. Rev. Ecol. Syst., 16(1)363-392, (1985) 39.Gupta S. and Narayan R., Species diversity in four contrasting sites in a peri-urban area in Indian dry tropics, Trop. Ecol. 47(2), 229-241 (2006)40.Chaudhary R. L., Seasonal variation, dry matter production and competitive efficiency of Sida acuta Burm., under exposed and shaded conditions, Trop. Ecol., 17(1), 23-30 (1976)