<4D6963726F736F667420576F7264202D20CF2EDAC8CF20C7E1CEC7E1DE20D5C7E1CD20E3E5CFED> Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 29 ,2012 17 COMPETITION BETWEEN TWO WILD PLANT SPECIES (Imperata cylindrica and Cynodon dactylon) IN SEMI-NATURAL PASTURE. Abdulkhaliq S. Mahdi Hort. Dept.- College of Agriculture - University of Diyala-Republic of Iraq. Email: abdulsmahdi@yahoo.com ABSTRACT Very strong evidence was obtained from this observation of competition between two wild plant species (Imperata cylindrica and Cynodon dactylon), those two species living at semi-natural pasture, in competition and coexisting conditions with reduced densities. The two species have different life-forms, therefore effect of mowing activities was in benefit of C. dactylon. as creeping plant which suffer less of mowing process. The plowing disturbance plot was invaded by only species that had already exist at the plot (C. dactylon and Alhagi maurorum). There was no I. cylindrica, recover, in spite of this species was existing at the same pasture. Concluding that there is (might be) chemical (allelopathic) substances produced by C. dactylon, inhabited germination seeds of I. cylindrical. Key words: Competition, Cynodon dactylon, Impereta cylindrica, Coexisting, Allelopathy. INTRODUCTION The effect of competition not one completely eliminated the individuals species by another, but lowering the performance competing numbers (Begon et al., 1994; Kikvidze and Brooker, 2010). This is usually manifested in reduction the numbers of individuals plant by another species, this lead to negative association between two species, (Yodzis, 1986; Tilman, 1988; Violle et al., 2009). Much of details work on competition had been carried out under control conditions (Damgaard and Fayolle, 2010), since in the field is often difficult to distinguish factors involved by competition from others, which was possible caused by negative association, (Abramsky and Sallah, 1982; Andel and Aronson, 2005; Meier et al., 2009). The implication of disturbance is upset normality and change the form of community. The activity of herbivores is often disturbance in the ‘normal’ course, (Begon et al., 1994, Micintry et al., 1996; Agrawal et al., 2007 Chesson and Kuang, 2008; Bernhardt-Romermann et al., 2011). Moreover, the effects of herbivores are opening up gaps for colonization another or same species to invite those gaps. Grazing had apparently kept the aggressive dominant ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ Received for publication Aug. 21 , 2011 . Accepted for publication Oct. 18 , 2011 . Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 18 species allowed with great diversity flora to persist, (Silvertown and Lovett-Doust, 1993, Shea and Chesson, 2002; Melbourne et al., 2007). This study was carried out in semi-natural pasture, and all of the vegetation data were taken from this natural vegetation. Created gaps as disturbance events by plowing process, as well as heavy grazing on another plot by mowing activities. All these events to observe the effect of disturbance on competition between two dominant species: Imperata cylindrica and Cynodon dactylon, how they balance and coexistince in the natural conditions. MATERIALS AND METHODS The Site: The site is semi-natural pasture, near Horticulture Department, Agriculture College, University of Diyala, 50 m from the Department, across the main road, between Education Sport College, and Agriculture College. The area of pasture about (200 x 25 m). The observation period from February to July 2010. Soil analysis: The soil samples were taken randomly from the site by core (11 cm2 ) at depth 15 cm, in six replication, to estimate SP% (Saturation Percentage), FC% (Field Capacity), EC ds.m-1 (Electrical Conductivity), pH, Soil Texture and amount of nutrient elements (N+, P3+, K+, Na+ , Mg++ , Ca++, and Cl- ppm). The method described by Allen et al., 1974, Moor and Chapman, 1986. Vegetation: Quantitative study of vegetation was started in February 2010, three plots (15 x 5 m) were chosen randomly at the site. The first plot was used for heavy grazing, using mowing machine, cutting vegetation canopy at 3cm level. The second one was used for plowing process at 15 cm depth and removed all the rhizomes of plant thoroughly. The third one was left as natural state, represented control. The characteristics quantitative vegetation were estimated for Frequency%, vegetation cover% and density m-2. It was taken first, before any process observation. The total of relative frequency, relative density and relative dominance (Dominance = cover% + density) on subsequent month observation time represent (IVI) Importance Value Index, (Grieg-Smith, 1983; Kershaw and Looney, 1995). At the same time, the height of the individuals species were estimated as well. The quadrates used was (100 x 100 cm), taken randomly in each plot, and in outside the plot, within the site. Samples size was six replicates for each plot bimonthly. Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 19 RESULTS AND DISCUSSION Soil Characteristics: The soil tended to be alkaline, pH about 8. Soil texture was clay loam, EC was about 4 ds.m-1 . Nutrient elements were very high for Na+1 (5500 ppm), Cl-1 14600 ppm. Whereas relatively low for N+, P3+, K+ (85, 112, and 170 ppm respectively), and medium for Mg++ , Ca++ (1400 and 1600 ppm respectively, Table 1. Vegetation: The community considered of 15 species (Table 2). The dominant species were Imperata cylindrica (IVI = 140), and Cynodon dactylon (IVI = 117). Subdominant species were Alhagi maurorum and Prosopis fractum (IVI = 98, 68 respectively. Five species were regard as rare species (IVI = 5). The taller plant was Nitraria retusa (rare species) 70 cm. Whereas the taller one of the common species was Imperata cylindrica (40 cm), and the short one was Cynodon dactylon (creeping species). Table 1: Soil characteristics of the site, soil taken from depth (0 - 15 cm). SE refer to Stander Error of means. Soil Characteristics Mean SE Saturation Percentage (SP%) 44.3 1.86 Field Capacity (FC%) 24 1.00 Electrical Conductivity (EC) ds.m-1 4.2 0.95 pH 7.9 0.23 Soil Texture Sand% 30.7 2.57 Silt% 38.9 2.05 Clay% 30.5 2.27 Texture Class Clay loam N+ 85 8.7 P3+ 112 14.5 K+ 171 16.7 Mg++ 1461 246.2 Ca++ 1606 22.7 Na+ 5536 392 Cl- 14569 1397 Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 20 Table 2: Community consist of species. Important Value Index (IVI) and the tall for each species. Seq. species IVI Tall (Cm) 1 Imperata cylindrica 140 40 2 Cynodon dactylon 117 5 3 Alhagi maurorum 98 25 4 Prosopis farctum 68 31 5 Convolvulus arvensis 41 15 6 Lactuca secriola 38 21 7 Salsola kali 24 30 8 Cardaria draba 20 10 9 Malva parviflora 11 8 10 Nitrarea rutusa 5 70 11 Phragmitis communis 5 30 12 Beta vulgaris 4 10 13 Schanginia aegyptiaca 4 10 14 Plantago ovata 3 10 15 Asteriscus pygmaeus 2 10 Competition between Cynodon dactylon and Imperata cylindrica: It is obvious from Fig. 1 that there is a very strong Correlation Coefficient for the number of pairs observed (r-value = -0.544**), the negative correlation between C. dactylon and I. cylindrica is very highly significant. Disturbance events (Gap invaded), there was 5 species at this plot before the plowing process. Two species (C. dactylon and Alhagi maurorum) were growing again (Table 3). Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 21 Table 3: Plowing plot (5 x 5 m). The plant species before and after plowing with quantitative description at period from February to July 2010. Species Description February* March April May June July Cynodon dactylon Frequency% Cover% Density m-2 66.7 21.7 4.4 - - 16.7 5 0.01 22.4 10 0.33 33.3 15 0.4 Convolvolus arvensis Frequency% Cover% Density m-2 100 14.2 9.5 - - - - - Cardaria draba Frequency% Cover% Density m-2 50 9.2 4.8 - - - - - Malva parviflora Frequency% Cover% Density m-2 50 9.2 4.8 - - - - - Alhagi maurorum Frequency% Cover% Density m-2 66.7 14.2 3.3 - - - - 16.7 5 0.01 *Before plowing process Fig. 1: A scatter diagram of the relationship between vegetation cover% of Imperata cylindica and Cynodon dactylon. Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 22 Mowing: both of I. cylindrica and C. dactylon by reduction cover and density (Table 4). Species C. dactylon recovered soon, and even increased of those two characteristics. Whereas in I. cylindrica decreased of those two characteristics. Table 4: Mowing plot (5 x 5 m). Plant species before and after mowing with quantity characteristics. Species Descriptions February* March April May June July Imperata cylindrica Frequency% Cover% Density m-2 100 55.8 37.8 100 40.7 32 100 38.3 25.8 100 35 19.7 100 33.3 18.3 100 25 12.8 Cynodon dactylon Frequency% Cover% Density m-2 83.3 19.2 4 83.3 15 3 100 26.7 5.4 100 31.7 6.4 100 33.7 6.5 100 31.7 6.4 Prosopis farctum Frequency% Cover% Density m-2 - - - 33.3 1.2 0.3 33.3 1.2 0.3 33.3 1.2 0.3 Alhagi maurorum Frequency% Cover% Density m-2 - - - - 16.7 1.7 0.7 33.3 2.8 1 Salsola kali Frequency% Cover% Density m-2 - - - - 16.7 1.7 0.3 16.7 2.5 0.5 Convolvulus arvensis Frequency% Cover% Density m-2 16.7 1.7 0.7 16.7 3.3 2.3 33.3 3.3 2.2 33.3 4.2 2.5 - - Lactuca secriola Frequency% Cover% Density m-2 - 33.3 0.8 0.3 33.3 1 0.5 33.3 1.2 0.7 - - Asteriscus pygamaeus Frequency% Cover% Density m-2 - - - 16.7 0.2 0.1 16.7 0.3 0.2 - *Before mowing processes. Control: Species I. cylindrica was increased by vegetation cover 43.3% in February to 47% in July. Whereas the density increased from 20.8 m-2 to 23 m-2 for the same period. In term of C. dactylon, the increasing by vegetation cover was 10% in February to 13% in July. Whereas in density the increasing was from 2 m-2 in February to 2.7 m-2 in July. Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 23 Table 5: The control plot (5 x 5 m), as intact or natural quantitative description (no mowing or plowing processes) of species consist of this plot. Species Description February March April May June July Imperata cylindrica Frequency% Cover% Density m-2 100 43.3 20.8 100 43.3 21.7 100 45.5 21.8 100 46 22.1 100 46.4 22.4 100 47 23 Cynodon dactylon Frequency% Cover% Density m-2 33.3 10 2 33.3 11.3 2.3 50 12 2.4 50 12.7 2.5 66.7 12.9 2.6 66.7 13 2.7 Cardaria draba Frequency% Cover% Density m-2 16.7 2.1 1.2 33.3 4.2 2.3 - - - - Nitraria retusa Frequency% Cover% Density m-2 - 16.7 8.3 2.8 16.7 8.3 2.8 16.7 8.3 2.8 16.7 8.3 2.8 16.7 8.3 2.8 Prosopis farctum Frequency% Cover% Density m-2 - - 16.7 0.8 0.2 33.3 1.7 0.3 50 3.3 1 83.3 4.3 1 Alhagi maurorum Frequency% Cover% Density m-2 - - - - 66.7 9.2 2.2 66.7 9.2 2.2 Salsola kali Frequency% Cover% Density m-2 - - - - 16.7 1.7 0.2 66.7 7.1 1.4 Growth of most species were increased in March as well as the diversity of the community, according to suitable weather elements. Whereas Cardaria draba was decreased (Table 5), because this species regarded as a winter species. The soil characteristics gives an indication of good texture, and tend to alkaline (pH =7.9) as in Table 1. Salinity was slightly high (EC = 4 sd.m-1). The evidence of salinity was monitored in high state of Na+ (5500 ppm) and Cl-1 (14600 ppm). In general, the nutrition elements were not very good balance. Therefore the diversity of the community was limited, only 15 species (Whatkinson, 1984; Violle et. al., 2009). It is well known that I. cylindrica blooms when the ground water near the surface of soil. Both species (I. cylindrica and C. dactylon) have ability to resist effect of light salinity as in this case (4 sd.m-1), particularly by C. dactylon. Very obvious from Fig. 1, that there was a strong competition between I. cylindrica and C. dactylon. The life-form of those two species were different (40 cm for I. Mahdi Diyala Agricultural Sciences Journal, 4( 1 ) 17 – 27 ,2012 24 cylindrica, and 5 cm for C. dactylon). Therefore the mowing process (represent heavy grazing) was in benefit for C. dactylon. Unselective grazer (mowing machine) was still have differential effects on the growth of different species. Tall plant species (I. cylindrica) usually suffer more than those which are short one (creeping form as C. dactylon). The species with large underground storages, here C. dactylon, might recover early and benefit from reduction of competition and invade new space, (MacCdonald and Lieffers, 1993; Agrawal, et al., 2007; Bernhardt-Romermann, et al., 2011). It is obvious from Table 5, as a control, that both species are in balance coexistence, they increased by vegetation cover and density at approximately the same proportion. Therefore the effect of heavy grazing on the community, depends on which group of species suffers most, here. I. cylindrica, (Harper, 1977; Damgaard and Fayolle, 2010). Having in mind that any gap which appears is rapidly very often invaded by seeding product. In this case seeds are either in the act of dispersal or component of persistent seed bank in soil. Which seed plant developed first to established gaps, and then which species existing at seed bank, the successful seedling rapidly established (Mahdi, 1988; Fridley et al., 2007; Thomson et al., 2010). Whereas no evidence of invading gaps by I. cylindrica in plowing plot, (Table 3) outside this plot. There were no any seedling appeared by this species, in spite of this species is in dominant state in the site. Might be at least that seeds bank in this plot had not received seeds from even a short distance. Another possibility are the seeds of I. cylindrica is unable to germinate, might be because chemical substances (allelopathy) by C. dactylon, inhibited the seeds germination of I. cylindrica. (Rice, 1984, Saadawi et al., 1993; Thorpe et al., 2009). 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Harper and Row, New York, USA.   . في حقل شبه طبيعي )ألثيل و ألحلفا(ية لتنافس بين نوعين من ألنباتات ألبرا صالح مهدي الخالق عبد .لعراقا- جامعة ديالى - كلية ألزراعة - قسم البستنة و هندسة الحدائق المستخلص أستطاع هذا ألبحث أن يبرز ألتنافس ألقوي بين نوعين من ألنباتات ألبرية هما ألثيل و ألحلفا في حقل شبه باختزال كثافتيهما بسبب ألتنافس وبحكم أالختالف في طبيعي، حيث إن ألنوعين في حالة توازن في ألطبيعة ألشديد تأثير ألرعي كان لقد .ألتربة والبذور في داخل ألرايزومات و مقدار خزين ألحياة شكل فقط نمت عليها فقد والمزالة منها جميع ألرايزومات، ألمساحة ألمحروثة أما. ألثيل لصالح )ألحش( بالرغم من هر ألحلفا،تظ ولم وهي ألثيل وألعاقول، أألنواع ألتي كانت موجودة أصالً في هذه ألمساحة او تعارض بايوكيميائي(نستنتج أنه ربما هناك مواد كيمياوية مثبطة .في ألحقل تحت ألدراسة وجودها   . من قبل ألثيل أفشلت إنبات بذور ألحلفا) ليلوباثيأ . ألتعارض ألبايوكيميائي ألثيل، ألعقول، ألتعايش، لتنافس، أ :يةلمفتاحا لكلماتا