Different estimates of the growth of Prosopis caldenia (Burk.) were related in the area of the “caldén” forest, Province of San Luis: trunk diameter, treetop coverage and total tree height to infer the annual growth percentage. The number of trees per hectare and their distribution was calculated based on size. Pod production per hectare was evaluated to determine forage potential

Gabutti, G E

Privitello, M.J L

English

University of Kentucky

Session 13 - Constraints on Forage and Grassland Production 13-3ABSTRACTDifferent estimates of the growth of Prosopis caldenia (Burk.) wererelated in the area of the “caldén” forest, Province of San Luis: trunkdiameter, treetop coverage and total tree height to infer the annualgrowth percentage. The number of trees per hectare and theirdistribution was calculated based on size. Pod production per hectarewas evaluated to determine forage potential.KEY WORDSProsopis caldenia (Burk.), growth, density, productionINTRODUCTION“Caldén” is an arboreal species from the leguminous family, asubfamily of the “mimosoideas”, abundant in the “Caldén” District,in the “Espinal Province”. It forms xerophytic open forests of about8 to 10 metres high (Cabrera, 1976). The “caldén” forest area coversapproximately 10% of the surface of the province of San Luis and itis characterized by sandy to loamy sand soils (Anderson, 1970). Itsclimatic regime permits its classification as a semi-arid area. Theannual average precipitation is 545 mm , 27% in spring, 42% insummer, 28% in autumn and 3% in winter. The average Julytemperature is 9.3°C and the average January temperature is 24.4°C;the extreme temperatures are -14.2°C and 43°C, the frost period isapproximately 177,83 days (Orquín, 1983).Phytosociologic, edaphic and microclimatic studies of the area(Orquín, 1983,  1987; Losada, 1983) show the ecologic importanceof the “Caldén” forest, in addition to the importance of wood as asource for different uses and as a forage in winter, especially duringprolonged drought (Alfonso, 1951), since pods have an appropiateprotein level: 15% and a good energetic value (Privitello, 1988;Menvielle, 1985). There are no previous studies about “caldén”growth except for those of “caldén” forestry mass increase in theforests of La Pampa, Argentina (Lasalle, 1962).The autecology study of the species included three objectives:1. Relate different estimates of tree growth: trunk diameter, totalheight and treetop coverage.2. Estimate the number of trees per hectare and their distribution asrelated to the trunk diameter.3. Determine the production of “caldén” pods.MATERIALS AND METHODSThe studies were conducted at “Rancho Grande” Establishment, 15km SW of Villa Mercedes, Province of San Luis, in a “caldén” forestcommunity stand. Eighty three “caldenes” were identified andlabelled at 1.20 m height to measure the tree trunk perimeter everyyear in the same place. According to the trunk perimeter, they weregrouped in 10 width class intervals of 0.20 m being the Ist= 0 - 0.20m, the IInd= 0.21 - 0.40 m and the same successively to the intervalIXth; in the Xth interval trees with widths over 1,80 m were situated.The measurements that were carried out once a year, in July-August,in the latent season of the “caldén” during four years (1981/1984)were:- Trunk perimeter (P) with a tape measure, from where the diameterwas calculated (D=P/¶).- The height of the tree with clinometer.- Two diameters of the treetop projection (direction E-W= anddirection N-S = d2) to calculate their coverage where C= ¶ (d1 +d2)2/16- The percentage of annual trunk diameter growth (PATDG), forthe considered period is:actual diameter - previous year diameterPATDG = _______________________________________ x 100previous year diameterThe estimated values for each year were averaged for each classinterval and the annual averages of the four years of informationwere analyzed by means of regression models. To calculate thenumber of trees per hectare and the relative density per width classinterval, the Cottam and Curtis method (1956) was applied on 280trees. “Caldén” pods were collected from four one m2 ground samplesof under treetop coverage, situating them: North, South, East andWest, in the center of the treetop projection of each labelled tree forfour years (1982, 88/89/90). The collection was carried out when100% of the pods had fallen (mid June). They were dried in oven at65°C for 48 hours and the average weight of dry matter wasdetermined from these samples. The average production per tree foreach class interval was calculated, based on the average sample valueand its treetop coverage. The total pod production per hectare wasobtained from the sum of the products between the annual averageproduction value per tree and the number of trees per hectare foreach class interval.RESULTS AND DISCUSSIONSThe trunk diameter annual averages (m), treetop coverage (m2), treeheight (m) and PATDG (%) for each width class interval are shownin table 1. The treetop coverage and the trunk diameter relation islineal and correspond to the following equation:y = -10.095 + 219.745xR = 0.993The relation of the tree height (y) and the trunk diameter (x) isadjusted to the following exponential function (Mitscherlich):y = 10.5198 - 8.5969 e-3.2768xR = 0.984The inflexion point of the curve corresponds to trees of 0.20 m indiameter (0.62 m perimeter), corresponding to width class IV inter-val and the height of six meters, being the percentage of annual heightgrowth of 40% with respect to the previous. In trees of 0.30 m indiameter (0.94 m perimeter) corresponding to class V interval thegrowth percentage falls to 21% with respect to the previous.The percentage of tree trunk diameter annual growth based on thetrunk diameter (x) corresponds to the following equation:y = 1.3965 + 22.6191 e-14.2647xR = 0.902The PATDG is independent to tree diameter from 0.40 m onwardsbeing constant in approximately 1.4% annually. A 0.40 m treediameter annual growth is 6 mm approximately for diameters lessthan 0.40 m, the PATDG is incremented at the time that plants oflesser diameter are considered, being the average annual growth of6 mm.The number of trees resulting from the application of the CottamID NO. 259AUTECOLOGY OF PROSOPIS CALDENIA (BURK.) IN THE REGION OF“CALDENAL” OF THE PROVINCE OF SAN LUIS, ARGENTINAG.E. Gabutti1 and M.J.L. Privitello11F.I.C.E.S. - U.N.S.L. Av. 25 de Mayo 384, 5730. Villa Mercedes, San Luis, ArgentinaSession 13 - Constraints on Forage and Grassland Production 13-4and Curtis method is 306 trees per hectare. The number of trees dis-tribution for each class interval (relative density) indicates that thestudied population is stationary (Odum, 1986). The relative densityand the production of pods for each width class interval is repre-sented in Figure 1. The tree average pod production of each widthclass interval, along four years, is shown in Table 1. The sum of thetotal pods production each width class interval determines the pro-duction per hectare of the forest, which is equal to 622 kg of pod drymatter (similar to the natural grassland production of the area), inyears when the tree reproductive phase is not affected. Analysingthese results it is deduced that trees in width class intervals 1 and 2present a greater number of individuals (48%) and the very low podproduction (0.66% of the total production per hectare).The production tends to increase from width class III interval onwardand two groups are differentiated: the trees from class III to VIIintervals with 42% of the individuals that contribute the 60.48% ofthe total production, and the trees above the class VII intervalrepresented only by 10% of the individuals that contribute the 38.86%of the total production.In conclusion, “caldén” is a slow growth species and there is a relationwith the PAGDT up to 0.40 m. For the trees to reach this value 60 to70 years must elapse. For this reason it is not convenient to cut themdown if their  maximum growth potential is expected. The 50% ofthe “caldenes” of this forest with 20 to 25 years old, a diameter greaterthan 12.7 cm (width class  interval III) and an annual growth averageof 6 mm contribute the total production of pods. Forests with treesolder than 25 years can be considered a valuable forage resourceduring winter in the “Caldenal” region, in years when treereproductive phase is not affected.REFERENCESAlfonso, J.L. 1951. El caldén. Conferencia en el Seminario FranciscoP. Moreno de la Soc.Cient. Arg. pp 1-20.Anderson, D.L.; J.A. del Aguila y A.E. Bernardón. 1970. Lasformaciones vegetales en la Provincia de San Luis. Rev. Invest.Agrop. Serie 2,7(3), pp 157-158.Cabrera, A.L. 1976. Regiones Fitogeográficas Argentinas. Enc.Arg.de Agric. y Jard., Segunda Edición, 2(1). Buenos Aires. pp 28-36.Cottam, G. and Curtis, J.T. 1956. The Use of Distance Measuresin Phytosociological Sampling. Ecology, 37. pp 451-460.Lasalle, J.C. 1962. El incremento de la masa forestal de caldén (P.caldenia Burk.) en los bosques de La Pampa. Argentina. Rev. ForestalArg. VI(2) pp 44-50.Losada, D.; L. Orquín; M. Delgado; E. Gabutti y J. Bertón. 1983.Intercepción de las precipitaciones y su distribución en unacomunidad de bosque de caldén (P. caldenia). IDIA Sup. 36. pp 115-119.Menvielle, E.E. y Hernández, O.A. 1985. El valor nutritivo de lasvainas de caldén (P.caldenia Burk.). Rev.Arg.Prod.Animal 5(7-8)pp 435-439.Odum, E.P. 1986. Fundamentos de Ecología. Interamericana, p. 224.Orquín, L.; D. Losada; M. Delgado; E. Gabutti y J. Bertón. 1983.El estado de degradación de la vegetación en un área del bosque decaldén (P.caldenia Burk.). IDIA Sup.36 pp 224-230.Orquín, L.; C. Peña y D. Losada. 1987. Efectos de la tala y usoagropecuario en un suelo de bosque xerófilo. Ecología N°8 pp 81-89.Privitello, M. y E. Gabutti. 1988. Producción de vainas de caldén(P.caldenia Burk.) y análisis de la calidad forrajera. VI CongresoForestal Argentino. Tomo I pp 169-171.Table 1Behaviour of the annual average of the treetop coverage values, trunk diameter, tree height and production per tree, of each width classinterval, along four years. “Rancho Grande”, San Luis, ARGENTINAFigure 1Relative density distribution and pod production per hectare for eachwidth class interval, Rancho Grande, San Luis, ARGENTINA.WIDTH CLASS INTERVALSYEAR I II III IV V VI VII VIII IX XTreetop coverage 1981 5.0 9.1 23.2 36.2 47.5 71.3 90.1 96.3 97.3 176.4  (m*) 1982 5.5 8.3 21.2 37.8 43.6 72.7 90.1 96.3 96.5 171.71883 6.7 11.2 24.5 42.7 57.0 76.0 90.6 93.8 106.1 190.81984 7.7 12.3 27.7 42.2 55.1 80.4 86.3 93.3 113.9 186.1Trunk diameter 1981 0.044 0.092 0.160 0.225 0.282 0.347 - - 0.552 0.863   (m) 1982 0.050 0.096 0.161 0.228 0.288 0.354 0.424 0.474 0.552 0.8531983 0.054 0.103 0.170 0.234 0.298 0.361 0.430 0.479 0.559 0.8651984 0.062 0.110 0.176 0.240 0.303 0.374 0.435 0.483 0.564 0.841Tree height 1982 3.2 4.5 5.2 6.1 7.2 8.2 8.5 9.5 8.4 10.2   (m) 1983 3.3 4.7 5.4 6.5 7.23 8.5 9.5 8.4 10.21984 3.4 4.6 5.5 6.5 7.1 7.7 8.8 8.4 8.3 10.1Production per tree 1982 0.00 0.00 0.83 2.65 3.83 7.25 - - 6.07 29.14   (kg) 1988 0.00 0.05 0.81 1.59 2.77 1.84 4.17 2.85 2.95 0.001989 0.04 0.11 1.99 4.23 3.74 4.08 6.33 6.36 4.86 8.301990 0.02 0.03 0.82 3.20 2.51 3.36 4.72 4.14 4.12 5.10

Autecology of Prosopis Caldenia (Burk.) in the Region of  Caldenal  of the Province of San Luis, Argentina

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Autecology of Prosopis Caldenia (Burk.) in the Region of Caldenal of the Province of San Luis, Argentina

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