Levantamento florístico e composição químico-bromatológica do estrato herbáceo em áreas de Quixelô e Tauá, Ceará

Abstract

Floristic survey was conducted of the component herbaceus in five ecological sites in the municipalities of Taua and Quixelo, Ceara, to ascertain the species of higher occurrence and a potential forage through the dete rmination of chemical bromatol ogic and fractions that make up the nitrogen compounds and carbohydrates a nd of estimate total digestible nutrients (TDN). In area of about 1ha for each site, were sampled 20 points in site s I, II, IV and V and 10 points in the III using a rectangular frame w ith dimension of 1.45 x 0.70 m. In these points was determined to coverege the soil, counted li ve plants which were within the frame, then separated by species an d identified botany. The floristic para meters the stratum herbaceous evaluated were: number of families, genera, sp ecies and individuals, frequency of families and species, percentage of the aggregate inde x IGA, diversity estimated by index of Shannon- Wiener (H '), dominance by Simpson ( C), samp le sufficiency, absolute density (AD) and relative density (RD). Were determined the le vels dry matter (DM), crude protein (CP), ash (MM), organic matter (OM), stratum ether (EE) , neutral detergent fiber (NDF) and acid detergent fiber (ADF). The data on chemical-bromatologic composition were submitted to descriptive and multivariate analysis, with gr ouping of areas two step clustering using the SAS statistical package. It was determined the fraction A of the nitrogen compounds, B1 fraction, fraction B3, fraction C and B2 frac tion determined by the difference between the total nitrogen and the fractions A, B1, B3 and C. The carbohydrates tota l, C fraction, fraction B2 and the fractions of carbohydrates with high rates of degradation rumen (A+B1). We used the equations of the NRC (2001) for prediction of the energy value and calculate the ED, EM P and EL L . The flora herbaceous ecological in the fi ve sites was represented by 22 families, 47 genera and 54 species, totali ng 16.679 individuals. The numb er of parcels was enough to estimate the reality of floristic composition, as evidenced by the no entry of new species in ecological sites. The diversity for sites I, II, III, IV and V was 0.98, 0.92, 0.94, 0.94 and 0.97 nats/individuals for the index of Shannon-Wi ener (H ') and of 0.87, 0.97, 0.95, 0.85 and 0.86 nats/individuals for the index of dominance by Simpson (C), thus showing, low floristic diversity. The pattern of dist ribution was uniform for the si tes II, III, IV and V with xvi percentages of 88, 100, 96.55 and 1 00%, respectively. The ecological site I with 90.63% of the plant community has tended to group together . For the chemical composition of the result of clustering analysis allowed the formation of three distinct groups: sites I and IV (in the municipalities of Quixelo and Ta ua); sites II and III (Quixelo) and ecological site V (Taua). The ordination of five ecological sites based on the correlation of levels DM, MM, EE, CP, NDF and ADF. There was significant effect (P <0.01) for all variables within each ecological site. There was wide variation in chemical composition, with levels ranging from DM 5 to 85% , CP 6 to 22% , EE 2.4 to 12% , NDF from 36 to 90%, FDA from 22.5 to 49 , 5% for MM and more than 40% of the species showed an average of 10% in MS. For fraction A (non-protein nitrogen - NNP) of nitrogen compounds were obt ained values of 56.66% to 77.46% - Waltheria indica L. for the Macroptilium lathyroides (L) Urb. Aeschynomene rudis Benth and Stylosanthes humilis Kunth. presented, respectively, over fraction of B1 (14.13 and 19.41%) compared with other avaluated species. For the B2 fraction values of ranged from 34.06 and 32.21% for Paspalum conspersum Schrad and Waltheria indica L. respectively. The B3 fraction ranged from 0.62 to 25.70%, Waltheria indica L and Ipomoeaea hederifolia L, respectively. The C fraction of nitrogen was lower for the cenchrus equinatus (0.75%), followed by Ipomoea grandifolia (Dammer) O' Donell (1.13 %). In fractionation of carbohydrates, it was observed that th e fraction C ranged 13.49 to 52.90% for Ipomoea grandifolia (Dammer) O' Donell and Wissadula subpeltata (Kuntze) R. E. Fr, respectively. For Eragrostis pilosa (L.) P. Beauv and Senna obtusifolia (l.) H. S. Irwin & Barneby, values for the fraction A+B1, were 0.74 to 52.79%. The Macroptilium lathyroides (L) Urb., Senna obtusifolia (l.) H. S. Irwin & Barneby, Ipomoeaea hederifolia L., and Ipomoea grandifolia (Dammer) O' Donell were 82.41, 84.95, 84.07 and 86.50% of their carbohydrates in the form of fraction A+B1+B2. The energy values es timated to TDN, DE, ELL and EMP, it was observed for the Ipomoea grandifolia (Dammer) O' Donell 78.96%, 3.45, 3.08 and 1.94 Mcal/kg, respectively Macroptilium lathyroides (L) Urb 69.00%; 2.78, 2.37, 1.47 Mcal/kg, Senna obtusifolia (L.) H. S. Irwin & Barne by 67.86%, 2.94, 2.53 and 1.59 Mcal/kg, respectively, Aeschynomene rudis Benth. 65.71%, 2.94, 2.53 resp ectively and 1.59 Mcal/kg and Stylosanthes humilis Kunth. 64.82%, 2.90, 2.49 and 1.56 Mcal /kg showed higher values for other pecies. The soil covering by biomass the herbaceous stratum of the sites ecological shows wide variation. The families most fre quently in ecological sites evaluated are Commelinaceae, Convolvulaceae, Euforbiaceae, Leguminoseae, Malvaceae, Portulacácea, Poaceae and Rubiaceae . The environments studied have lo w floristic diversity. There was a uniform predominance of distribution of species in four of the sites surveyed, where only one of five sites ecological species were tendi ng to group. Most of the analyzed species, with relationship to the bromatologyc-composition, has potential for the use as forage. The conservation of the spare materi al during the rainy period can supply the protein deficiency and available fiber and to promote the mainte nance of the pattern of fermentation of the rumen, improving performance of ruminant ones in the period of forage shortage. The fractionation of carbohydrates and protein are analysis simple, not expensive and must be carried out in all feed for ruminants. The use of equations of the NRC (2001) to predict the energy values of foods was appropr iate for the conditions of this research, there is a need for validation for these species of caatinga.