Economic potential of the huizache, Acacia Pennatula (Mimosoideae) in central veracruz, Mexico

Economic Potential of the Huizache, Acacia pennatula (Mimosoideae) in Central Veracruz,MexicoAuthor(s): Silvia E. Purata, Russell Greenberg, Verónica Barrientos and Jorge López-PortilloReviewed work(s):Source: Economic Botany, Vol. 53, No. 1 (Jan. - Mar., 1999), pp. 15-29Published by: Springer on behalf of New York Botanical Garden PressStable URL: http://www.jstor.org/stable/4256148 .

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ECONOMIC POTENTIAL OF THE HUIZACHE, ACACIA PENNATULA

(MIMOSOIDEAE) IN CENTRAL VERACRUZ, MEXICO1

SILVIA E. PURATA, RUSSELL GREENBERG, VERONICA BARRIENTOS AND

JORGE LOPEZ-PORTILLO

Purata, Silvia E., (Instituto de Ecologia, A.C. Apdo. Postal 63, Xalapa 91000, Ver., Mexico) Russel Greenberg (Smithsonian Migratory Bird Center, National Zoological Park, Washington DC 20008, USA) Ver6nica Barrientos and Jorge L6pez-Portillo (Instituto de Ecologfa, A. C. Apdo. Postal 63, Xalapa 91000, Ver., Mexico). ECONOMIC POTENTIAL OF THE HUIZACHE, ACACIA PENNATULA (MIMOSOIDEAE) IN CENTRAL VERACRUZ, MEXICO. Economic Botany 53(]):15-29, 1999. Acacia pennatula is a native tree found commonly on cattle pastures and other disturbed sites in the mid-elevation zone of Veracruz, Mexico. The pods are a favorite food source for free ranging cattle. Pod collection and production has been commercialized at a small scale. The results of this study strongly suggest that the management of acacia trees for pod production has the potential for providing an environmentally sound, locally derived food source for cattle while maintaining tree cover on pasture lands. Soil type has a strong influence on stand structure and pod production; the largest pod crops with the largest and most nutritious pods are found on Andosols and Acrisols, as opposed to the unproductive Regosols. We suggest that the current system could be expanded by promotion and marketing of the pods and improved management of the acacia stands.

EL POTENCIAL ECON6MICO DEL HUIZACHE, AcAcIA PENNATULA (MIMOSACEAE) EN LA REGION CEN-

TRAL DE VERACRUZ, MExICO. Acacia pennatula es un dirbol nativo que se encuentra coml'nmente en los pastizales y sitios perturbados de la zona de mediana altitud de la regi6n central del estado de Veracruz, Mexico. Sus vainas son una fuente de alimento para el ganado de libre pastoreo. La colecta y comercializaci6n de las vainas se ha realizado a pequenia escala. Los resultados de este estudio sugieren que el manejo de los drboles de acacia para la produccion de vaina tiene un gran potencial como fuente alimenticia para el ganado, con la ventaja de ser un sistema ambientalmente adecuado y localmente producido, en el que ademds se mantiene la cubierta arborea en los pastizales. Tambikn encontramos que el tipo de suelo tiene una fuerte influencia en la estructura de los huizachales y en la producci6n de vainas; en los Andosoles y Acrisoles se producen las mayores cosechas y las vainas son de mayor tamanio y calidad nutricional que las producidas en los Regosoles. Sugerimos que el sistema actual puede ser expandido a trave's de la promoci6n y mercadeo de las vainas v un sistema mejorado de manejo de los huizachales.

Key Words: Acacia pods, livestock fodder, silvopastoral system.

The state of Veracruz is one of the richest and most diverse regions of Mexico, a country known to have one of the most diverse biotas in the world. Paradoxically Veracruz also stands as the first national producer of cattle with 70% of its territory occupied for this purpose (Barrera 1992; Barrera, Lopez and Palma 1993). The mid-elevation zone of Central Veracruz, has tra- ditionally been a coffee and sugar cane producing area. This region is largely deforested and also supports large expanses of cattle pasture

I Received 18 June 1997; accepted 9 June 1998.

which have existed for over four hundred years, but have expanded rapidly over the last fifty (Bernard 1985; Skerritt 1992). With the advent of cattle pasture has come a concomitant spread of Acacia pennatula (Schlech. & Cham.) Benth., a thorny legume that grows to 12 m in height. Acacia pennatula is one of several species of acacia, out of the approximately 175 New World species that are primarily associated with livestock pasture (Chazaro 1977; Gutierrez and Ar- mesto 1981; Travest 1992). Like the other livestock-associated acacias and mesquites (Proso- pis spp.), Acacia pennatula has often been re-

Economic Botany 53(1) pp. 15-29. 1999 ? 1999 by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A.



16 ECONOMIC BOTANY [VOL. 53

s7ew

E rw ! S N f 1r

mnsd Ancdsol Rego1 * Towns

Fig. 1. The study area with localities, sampling sites, and their soil types.

garded as a highly invasive "weedy" species with the noxious property of considerable thorniness, rendering the plant a potential threat to productive pasture land (Chazaro 1977; Gomez, Signoret, and Abufn 1970). The fact that the thorns are a widely recognized attribute of acacias is underscored by the common name huizache used throughout Mexico. This name is derived from the Nahuatl word for "thorn" or "spine," huitztli, and ixachi, that means "in great amount" (Cabrera 1978:83).

In contrast to the view of the livestock-associated acacia as pest species, these species are often used for wood products and for livestock fodder based on the copious crops of pods that they produce. The use of pods for cattle fodder is well known for certain ecologically similar African species of Acacia (Coe and Beentje 1991; Fagg and Stewart 1994; Nair 1990; Na- tional Research Council 1979) as well as species of Prosopis (Felker and Bandurski 1979). For example, acacia pods are known to be used by tribal groups that tend cattle in east Africa (Coe and Beentje 1991) and the production of mes-

quite pods has been commercialized at moderate to large scales in Mexico, Brazil and Ecuador (Silbert 1988). However, the use and potential value of Neotropical acacias is poorly docu- mented (but see Chazaro 1977). The purpose of this study was to explore and document the uses of a common acacia in Central Veracruz, Mex- ico, and to analyze its economic potential and ecological value.

DISTRIBUTION AND NATURAL HISTORY

Acacia pennatula is sparsely distributed in a number of xeric habitats such as deciduous forests, thorn scrub and savanna from Mexico (most states) to Colombia (Matuda 1981:20; Mc Vaugh 1987:133; Rzedowski 1978; Siegler and Ebinger 1988; Standley and Steyermark 1946). Patches of pure A. pennatula are restricted, at least in Mexico, to mid-elevation sites where the climax vegetation is oak woodland. Rzedowski (1978:281) considers that the A. farnesiana-A. pennatula association represents a seral stage of the oak woodland at altitudes below 1500 m a.s.l.



1999] PURATA ET AL.: HUIZACHE IN VERACRUZ 17

Livestock (especially cattle and horses) is the dominant agent for the formation of these acacia groves; the animals ingest the seed pod and pass the seeds unharmed, spreading them via their dung around the edges of existing patches of acacia. The close association between acacia and livestock may have an evolutionary basis. The grazing and browsing of large mammals may favor the growth of this spiny plant over the rapid growth of other pioneer species (Brown 1960). In addition, grazing reduces fire frequency which may favor the spread of acacia in a fire- adapted grassland system. The firm, indehiscent pods of Acacia pennatula are similar to those of species in Africa which are dispersed by large mammals (ungulates, giraffes, and elephants) in natural savanna systems (Coe and Coe 1987; Gwynne 1969). Such adaptations or traits are explained by Janzen and Martin (1982) as anachronisms, that were useful before the Pleistocene extinction of the great megaherbivores that roamed the savannas and open formations of North and South America (Owen-Smith 1987; Webb 1977,1978). The existing acacia savannas were probably not long ago dominated by oaks until recent increases in wood cutting and the arrival of cattle, factors that ultimately favor the shift towards an acacia-dominated savanna. Aca- cia may also have been dominant during earlier periods with higher grazing and browsing pres- sures by the megaherbivores.

THE USES OF ACACIA Currently, the livestock-associated New

World acacias produce a variety of useful products. The most widespread use is for fuelwood and on-site construction materials. In addition, the bark of some species can provide commer- cially useful tanning agents and the floral nectar of A. farnesiana (L.) Willd., is used as an active ingredient in perfume production (Fagg and Stewart 1994; Gomez, Signoret, and Abuin 1970). Acacia pennatula is used commonly as a source of fuelwood and building materials, particularly fence posts (Chazaro 1977; Durr 1994: 25; N. M. Keilbach, pers. comm.). Greenberg, Bichier and Sterling (1997) for example, found that ranchers in the Ocosingo Valley of Chiapas, Mexico, maintain acacia woodlots of 1-50 ha primarily for fence-post production.

Acacia pennatula produces an abundant crop of indehiscent pods which are commonly eaten by livestock, at least in Mexico and Northern

Nicaragua (Chaizaro 1977; Duff 1994; Green- berg, Bichier and Sterling 1997; N. M. Keilbach pers. comm.). The pods have both high protein and high fiber content, which makes them ap- propriate fodder (Chaizaro 1977). There are at least two reports of regular human consumption of flour from the seeds or pods of this species (Gentry 1942; Kunkel 1984:5). Whereas, in many areas, ranchers simply release livestock into huizachales during the season of ripe pod production, in the region of Xalapa, Veracruz, the pods are also sold at small off-farm trading posts. Because of the commercial possibilities, we focus most of the discussion in this paper on the production, collection and marketing of acacia pods.

METHODS

STUDY SITES

We selected an area of 138 km2 around Xal- apa, Veracruz, Mexico, located on the slopes of the Cofre de Perote (96?35'-96?45'W and 19023'-19032'N) for our study. Altitude varies from 700 to 1600 m a.s.l. (Fig. 1). The climate is humid and temperate with a mean annual tem- perature around 1 80C and an average annual rainfall of 151 cm (Soto and Gomez 1990). Three main soil types are recognized: Acrisol humico (Humults), Andosol humico (Hydran- depts) and Regosol eutrico (Orthents, Psam- ments) (SARH 1982; SPP 1984). Acrisols are well developed acid soils with a low base satu- ration, more than 100 cm deep and rich in organic mater. Andosols are derived from volcanic materials, moderately developed, more than 100 cm deep and relatively rich in organic mater. The Regosols are poorly developed and shallow soils (44 cm deep) and in the study area they have a lithic phase with a hard crust on the sur- face (locally known as "tepetate") however their fertility is good.

The natural vegetation of the region is tran- sitional between temperate and tropical. In our study area, three main natural vegetation types can be recognized: cloud forests with a combi- nation of boreal and tropical elements, between 1200 and 1600 m a.s.l.; a mixture of cloud forest and oak woodlands, occurring at altitudes between 1000 and 1200 m; and oak savanna (10- 15 m trees), between 600 and 1100 m. However, only patches of natural vegetation remain. Much of the vegetation between 1000-1200 m has




been replaced by coffee plantations, and higher and lower elevation areas are dominated by in- duced pastures, old-fields, maize and sugar cane. Acacia can be found in grazed areas of all three vegetation zones.

We examined maps and interpreted aerial photographs to determine the current distribution of the acacia groves in our study area. To- pographic maps (scale 1:50 000) and aerial pho- tos scale (1:90 000) were used. From September 1994 to August 1995, we surveyed the area for acacia groves or acacia trees in pastures, coffee plantations and old-fields and selected twenty sites for more detailed investigation of stand structure and pod productivity.

ACACIA STAND STRUCTURE AND PRODUCTIVITY

Twenty sites ranging from 0.5 to 3 ha were sampled with the nearest neighbor technique (Clark and Evans 1954). The following parameters were measured or estimated for a total of 50 individuals on each site: distance to nearest neighbor, total height, basal perimeter and two perpendicular crown diameters. These data allow us to examine the stand structure and to infer the pattern of colonization of the land by acacia, and to infer also some of the important external characteristics that may affect commu- nity structure and pod production. We used two- way Analysis of Variance (ANOVA) to determine the amount of variation in tree size (basal tree diameter) explained by soil type.

Additionally, in February 1996, at the time of pods ripening, we estimated the number of pods in 10 trees in 10 out of the 20 sampling sites (n = 100 trees). Our purpose was to establish a regression between tree size and pod crop, so we sampled the first trees encountered in the different size classes found on a particular plot. We were interested in how soil type affected the tree size-pod crop relationship. The 10 sampling sites were distributed across the three soil types with two on Acrisol, three on Regosol and five on Andosol. A log-linear model using General- ized Linear Models (McCullagh and Nelder 1983) was used to analyze the relation between number of pods per tree and basal tree diameter, total tree height and soil type.

In addition to estimating pods, we collected 100 from each tree, took the weight, and measured the length and maximum width with dial calipers. A subsample of the pods without seeds

was ground into flour for nutritional analyses, we analyzed pods with seeds taken out because cattle do not metabolize the seeds and we were interested in pod's contribution to animal nutrition. A sample of 30 g of dry pods with three replicates per each of six localities was used, comparing nitrogen percentage by the improved Kjeldahl method for nitrate-containing samples (Horwitz 1980:126) crude protein by the Kjel- dahl method (Horwitz 1980:126) and mineral and moisture content by the ashes and drying in vacuo at 95-100?C respectively (Horwitz 1980: 136).

PODS USE AND COMMERCIALIZATION

During the 1995 production season (March- April) we followed the commercial process associated with acacia pods through repeated visits to a collecting/selling post in Alborada, Vera- cruz. (Fig. 1). During these visits we gathered the following information from pod collectors: name, age, occupation, place of collection, collecting time, number of trees visited, number of previous years collecting and total weight of pods collected on a daily basis. We also gathered information regarding previous years production and sales. During the 1996 season we obtained similar data from an additional three collecting/ selling posts in the neighboring village of Las Lomas. We were able to locate and interview four ranchers who had purchased pods from the posts. We asked their opinions on how pods compared to other feed supplements, the quan- tity used, and the ingredients of mixtures in- volving pods. In addition, we determined other uses of acacia, whether it is actively controlled, and its general acceptability as a range and shade tree plant.

USE OF PODS BY FREE-RANGING CATTLE

In most analyses of the value of pods as for- age for livestock, there has been no estimate of the consumption of the resource by free-ranging cattle with access to trees on the pasture. In order to make a crude estimate of the use of acacia pods, we surveyed pastures on two dairy ranches in the suburb of Briones, Coatepec, and counted the number of acacia seeds found in each cow patty encountered. Separate transects were established through portions of pastures with low densities of acacias and those with no acacias to see if distance from trees affected the estimates. We found no significant difference be-




TABLE 1. THE MEASURED STRUCTURAL PARAMETERS FOR THE TWENTY SAMPLING SITES. (SN) SITE NUM-

BER, (L) LOCALITY, (ST) SOIL TYPE, (D) BASAL TREE DIAMETER IN CM, (TH) TOTAL HEIGHT IN M, (C)

CANOPY COVER IN M2, AND (DNN) DISTANCE TO NEAREST NEIGHBOR IN METERS.

SN L ST D TH C DNN

1 Chavarrillo 3 Regosol 2.48 1.34 2.94 1.12 2 Chavarrillo 1 Regosol 2.50 1.23 2.05 0.97 3 Est. Chavarrillo 1 Regosol 3.46 0.86 3.23 2.28 4 Chavarillo 2 Regosol 4.35 1.46 8.95 1.43 5 Lencero Regosol 5.81 5.92 7.31 1.28 6 Chavarrillo-hornos Regosol 5.98 2.16 8.83 1.47 7 Est. Chavarrillo 2 Regosol 8.33 2.34 17.24 3.51 8 Est Chavarrillo 3 Regosol 20.82 6.14 56.42 6.00 9 San Antonio 1 Andosol 8.30 3.80 28.12 2.87

10 San Antonio 2 Andosol 9.55 2.56 30.74 3.30 11 Carr. a Otilpan 3 Andosol 13.88 3.43 39.28 4.69 12 Carr. a Otilpan 2 Andosol 14.50 4.46 45.23 6.72 13 Trancas Andosol 15.75 6.78 27.80 3.36 14 Carr. a Otilpan 1 Andosol 23.58 8.42 73.92 5.83 15 Tesoreria Andosol 24.01 9.58 54.49 4.14 16 Jardin Botanico Andosol 31.52 10.57 102.94 9.15 17 Consolopa Andosol 33.98 11.47 120.74 7.38 18 Plan Cafetal Acrisol 43.70 9.92 162.15 7.03 19 Plan II Acrisol 50.45 11.01 164.82 17.64 20 Loma Acrisol 51.88 10.10 224.40 15.62

tween transects and we present the pooled data in this paper. We use the average number of seeds/pod, the average weight of a pod (measured at the site) combined with the average def- ecation frequency of healthy dairy cattle (Fraser 1985) to estimate the daily consumption of acacia pods by cattle on these ranches.

NUTRITIONAL ANALYSIS OF PODS

Because we recommend that pods and seeds be ground to produce feed, we have compared the nutritional content of the pod flour (collected in Ocosingo, Chiapas) to alternative cattle feeds. The analyses were completed at the laboratories of the Northeastern Dairy Herd Improvement Association (Ithaca, New York). Because selenium is a potential problem with material from arid-land plants (National Research Council 1976) we had a sample analyzed for selenium content by Corning-Hazleton Laboratories (Minn.).

RESULTS

POD CHARACTERISTICS AND PRODUCTION

There is high variation in pod productivity among sites. Individuals of Acacia pennatula produce from less than 50 to as many as 15 000

pods per tree with a mean of 604, 1959 and 2058 pods per tree on the Regosols, Andosols and Ac- risols respectively. The pods are variable in length from 4.8 to 12.8 cm, but the pod weight (x = 3.98 SE =.06 n = 550) is unrelated to variation in pod shape. The pods are made of a dry, fibrous material with a hard coat. Trees flower in May and pods develop on the trees within one to two months. Unripe (green) pods remain on the tree up to 9-10 months gradually turning dark brown in March-April and subse- quently falling to the ground. All pods that are consumed by animals are taken off the ground. Uneaten pods accumulate on the ground beneath the parent plant and the seeds germinate (if they survive attacks by bruchid beetles and fungi) only after the mesocarp surrounding the seeds has decomposed (6 to 8 months in this area). Otherwise, pods are consumed by livestock and germinate within a few days after they are de- posited in dung.

ACACIA STAND STRUCTURE AND SOIL TYPE

Acacias show considerable between-stand variation in size of tree (mean basal diameter) and density of acacia stems (nearest neighbor distance, Table 1). We found that these two var-




18

16

14

t 12

10 0

c 8

o 6

40

2

0 0 10 20 30 40 50 60

Diameter (cm) Fig. 2. Regression line of the relationship between distance to nearest neighbor and diameter. A point

corresponds to site avefage.

iables were significantly correlated across stands (r =0.92, Fig. 2) so that woodlots with larger trees had a lower density as well. Acacias growing on Acrisols (Fig. 3) were significantly larger

Fig. 3. Acacia tree in a shade coffee plantation on Acrisol.

in terms of mean height, trunk diameter, and canopy diameter than those growing on Ando- sols (Fig. 4). In turn, those growing on Andosols were larger than those found on Regosol soils (Fig. 5) (Table 2).

Fig. 4. Acacia trees in a pastureland on Andosol.




-= Fig. 5. Acacia trees in pastureland on Regosol.

MANAGEMENT AND STAND STRUCTURE

With the exception of the three sites which are coffee plantations on Acrisol soils (18-20), all other sites are or have been used for livestock. On the Regosol soils, (sites 1-8) plant growth is relatively poor, especially during the dry season (Feb-Apr). Therefore no intensive cattle raising can be practiced. Only in site 8, where the owner provides extra feed in the form of grass and corn stalks to the animals, were cattle actually observed. On this site, acacia trees have the largest sizes and number of pods per tree for that soil type, and the owner is fa- vorably disposed towards acacia trees. In sites 1 to 7, cattle are introduced only for short periods and in very low numbers. In most of these sites acacias have invaded recently, most of the trees are very small (diameter <11.5 cm) and older individuals are few or non-existent.

On the Andosols (sites 9-17), site 15 has been abandoned for some time and has a fence that excludes cattle. The site has no acacia seedlings. Sites 9, 10 and 13 are semi-abandoned and show signs of cattle presence. Sites 11, 12, 14, 16 and 17 are intensively managed for livestock. Aca- cias are abundant and trees are managed for

TABLE 3. RELEVANT FACTORS TO EXPLAIN THE

NUMBER OF PODS PER A. PENNATULA TREE, CAL-

CULATED ON THE BASIS OF A LOG-LINEAR MODEL

(GLM USING A POISSON DISTRIBUTION).

Factor c2 d.f. P

Diameter 66199 1 <0.0001 Soil type 15916 2 <0.0001 Diameter* soil type 4547 2 <0.0001

fence-post production. Density is controlled either by tree cutting or seedling removal from unwanted sites and pods are eaten off the ground by cattle. All sites on the Acrisol soils are coffee plantations with acacia trees interspersed among other shade trees. All seedlings are removed and no regeneration is taking place.

SOIL TYPE AND POD PRODUCTION

Pod production is strongly related to tree diameter, which in turn is correlated with tree height and cover. The model that best explained pod production includes tree diameter, soil type and their interaction (Table 3). In sites with rich soils (Andosols and Acrisols), such as sites 16, 17, 19 and 20, trees attain maximum productivity, while on open sites with poor soils, such as sites 4 and 6, few pods are produced and many trees do not produce pods at all (Fig. 6).

No one reported collecting pods from huizachales in open sites or grasslands; commercial collection is done on the coffee plantations. However, not all productive sites were harvested (i.e., 16 and 17) and these had great amounts of pods that rotted on the ground. In addition to intrinsic differences in soil type, the productive sites on coffee plantations may have benefited from chemical fertilization-a view held by several local informants. In addition to between-site variation in production, there is also tremendous

TABLE 2. MEAN AND STANDARD ERROR OF THE STRUCTURAL PARAMETERS FROM A. PENNATULA SAMPLED

SITES. DIFFERENT LETTERS IN A ROW INDICATE SIGNIFICANT DIFFERENCES BETWEEN SOIL TYPES (P <

.0001).

Regosols Andosols Acrisols

Diameter (cm) 6.72 (0.66)a 19.45 (0.62)b 49.67 (1.18)c Height (m) 2.68 (0.18)a 6.79 (0.17)b 10.43 (0.32)c Cover (m2) 8.63 (2.91)a 49.63 (2.74)b 188.11 (5.2 l)c Distance to nn (mi)' 2.26 (0.26)a 5.25 (0.24)b 14.71 (0.46)c

' Distance to nearest neighbor.




6000 , andosol

5000 ++ + +

+~~~~~~~

cn 4000 + a + 0 + ++

? 3000 + + acrisol ~~~~~~~~~~0 ~ ~ ~ ~ ~ ~ ~ 1

E + + 5 ++

Z 2000 + ++ + # oo

+#t / x XX +

1000 *. + regosol

03 +

0 W- l I

0 20 40 60 80 100

Tree basal diameter (cm) Fig. 6. Number of pods (P) as related to tree basal diameter (D) in three soil types (S). Lines indicate the

trends predicted by a log-linear model of the type P=D+S+D*S. Points indicate individual trees on: Regosols (O), Andosols (+), and Acrisols (*).

interannual variation in production. Apparently good years and poor years usually alternate. For example, production was much greater in 1994 and 1996 than in 1995 and 1997 (A. Vaizquez pers. comm.; pers. obs.).

CONTENT OF PODS WITH AND WITHOUT SEEDS

The results of the analysis of pod content show again a relation between general soil type and nitrogen, protein and moisture percentage (Table 4). Pods from the sites on Regosols had the lowest moisture but one of the highest mineral percentages. Previous analyses conducted with the whole pod including seeds (Chazaro 1977) and only seeds (Sotelo 1981) showed a much higher protein content, which was expect- ed since many legumes have protein-rich seeds. However, even if the pods are consumed without

metabolizing the seeds, as is the case with free ranging cattle, they are still a high quality feed.

COMMERCIAL USE OF PODS

The commercialization of pods appears to be a relatively recent phenomenon in the Xalapa region. Ch'azaro (1977) reported that buying and selling of pods probably began in approximately 1974. The scale of operation does not seem to have increased significantly during the 20 year period. The pods are collected from February to April or harvest may be displaced by one month if the end coffee harvest is extended, since most of the intermediaries and collectors also partic- ipate in coffee production. All collecting sites are coffee plantations, not pastures. Pods are collected primarily by children between 6 and 14 years old (Table 5); the few adults involved in the harvest are poor women with no other




TABLE 4. NUTRITIONAL AND WATER CONTENT IN SAMPLES OF GROUND A. PENNATULA PODS WITH SEEDS

TAKEN OUT. SOIL TYPE (ST), PROPORTION OF MINERALS (%M), PROPORTION OF WATER (%W), PROPORTION

OF NITROGEN (%N) AND PROPORTION OF PROTEIN (%P).

Localities ST %M %W %N %P

8 Est. Chav. Regosol 5.43 10.67 1.09 6.83 6 Chav. Hornos Regosol 5.69 7.67 1.27 7.92

17 Consolapa Andosol 5.15 11.00 1.34 8.25 12.C. Otilpan 2 Andosol 5.78 11.00 1.46 9.1 9. S. Antonio 1 Andosol 5.33 11.67 1.48 9.22

18. Plan Cafetal Acrisol 5.62 11.00 1.42 8.9

source of income; since pods are collected on nearby coffee plantations, there are no transport costs for collectors to place of sale. On the other hand, when orders outstrip local supply, then pods from other collecting posts are purchased in order to satisfy the demand. Collectors have open access to sites with acacia and do not pay use-rights to the coffee plantation owner.

Capital investments by the intermediate buyer are minimal. Our informant, one of the main dis- tributors, rents a small house for the eight to ten weeks of peak production, where the pods are weighed and stored in sacks. Rent of the house, a large balance, and the use of a flatbed truck for delivery are the main investments. All activities related to pod commercialization occur during the afternoon, spending from three to four hours daily. There is relatively little formal marketing of the pods beyond personal contact made with a small number of buyers. Small signs are displayed at the buying posts announcing pod request and price. In 1995, our informant gathered 8.5 metric tons, he reported gross profits of 0.10 pesos per kilogram, which amounts to approximately 30 pesos per day.

In 1996 the same buyer gathered 42.78 metric tons and in the three posts in Las Lomas a total of 60.9 metric tons were commercialized.

Since the selling post in Alborada is the best organized one with annotated statistics of collectors and kilograms delivered per day, we present the statistics for the five most frequent collectors from 1995 based on the data of that place (Table 5). According to this information, an average collector spends approximately 7.7 min- utes to collect one kilogram of pod, earning for each kilogram 0.20 and 0.35 pesos in 1995 and 1996 respectively. Based on these data, a person would need to collect 58 kg in order to get the minimum wage for a rural worker on the area, which in 1996 was around 20.00 pesos, (2.7 $US). Collection of this amount would require approximately 7.5 hours of continuous work. The mean weight of pods collected per day per worker was actually 36.11(? 13.95). In com- parison, farmers paid 0.80 pesos and 1.00 peso for a kilogram of coffee berries collected in 1995 and 1996 respectively. Coffee pickers are able to harvest from 25-100 kg of coffee per day which would have resulted in 25-100 pesos per day in 1996-a value far exceeding what acacia pickers received.

ATTITUDES OF RANCHERS TOWARD ACACIA PODS

We interviewed four ranchers who have bought pods from intermediaries. All four rated

TABLE 5. THE FIVE MOST ACTIVE COLLECTORS IN 1995 IN THE ALBORADA POST. AGE (A), NUMBER OF VISITS TO THE COLLECTING AREAS (V), HOURS SPENT COLLECTING PER DAY (H/D), KILOGRAMS COLLECTED PER DAY (KG/D), DAILY INCOME (DI.), TOTAL OF PODS COLLECTED (TKG.) IN THE NUMBER OF VISITS AND TOTAL INCOME (TI.) PER COLLECTION SEASON.

Collector A V H/D KG/D DI ($) T.KG. TI. ($)

1 1 1 1 1 6 35.8 7.2 394 78.8 2 9 9 4 16.1 3.2 145 29.0 3 12 7 4 46.6 9.3 326 65.2 4 10 6 5 26.0 5.2 156 31.2 5 9 6 4 37.0 7.4 222 44.4




TABLE 6. THE NUTRITIONAL CONTENT OF ACACIA PODS (P) WITH SEEDS, COMPARED TO RECOMMENDED

RATIONS (R). ALL VALUES (EXCEPT MOISTURE CONTENT) ARE DONE ON A DRY WEIGHT BASIS.

P RI Max.

% Moisture 11.3 % Crude protein 12.1 13 % Acid Detergent Fiber 23.0 21 % Neut. Detergent Fiber 27.8 17 % Calcium 0.95 0.43 % Phosphorous 0.15 0.31 % Magnesium 0.26 0.26 % Potassium 1.47 0.80 % Sodium 0.012 0.18 Iron (ppm) 303 50 1000 Zinc (ppm) 17 40 500 Copper (ppm) 4 10 80 Manganese (ppm) 11 40 1000 Molybdenum 4.2 6 % Sulfur 0.21 0.20 5 Selenium 0.21 0.10 5

' Recommended rations for 500 kg cow producing 11 kg of milk (National Research Council recommendations in Church 1984).

acacia pods as a highly desirable feed. Two no longer purchase pods either because they are more difficult to purchase or because pods are available for free-ranging cattle from trees on their property. Three of the four also use the acacia wood frequently for fence posts and fuelwood.

The ranchers we interviewed feed approximately 2 kg of pod per adult animal on a daily basis throughout the year. One kilogram of feed supplement (17% protein) cost on the retail market ca. 1.75 pesos, while 1 kg of pod costs 0.45 pesos to the ranchers. The pods are chopped and mixed with other ingredients with the pods com- prising approximately 40% of the mixture by weight. Because the pods are chopped and not milled, the seeds remain indigestible. The recipes for the mixtures are developed individually by each rancher. The following are examples of two such recipes: 1) mix 69.4 kg of chopped acacia pods, 23.8 kg molasses, and 6.9 kg lard to make each 100 kg of mixture; to each 3 kg of this mixture, add 2 kg of raw bananas. 2) mix 46 kg of chopped acacia pod, 36 kg orange pulp, 12 kg molasses, and 6 kg corn kernels to make 100 kg of mixture.

Although relatively few ranchers purchased the pods at the time of this study, cattle commonly feed on pods on ranches with acacia trees. Based on the two ranches surveyed, we found seeds in 99% of the cattle patties surveyed

and the number of seeds averaged 102 (14 SE, N = 98) and 147 (13 SE, N = 63) seeds per patty at the two dairy pasture sites. Pods at the site contained an average of 8 intact seeds (0.2 SE, N = 40) and weighed an average of 3.8 g (0.14 SE, N = 75). Based on this we estimate the average paddy contained material from 12.8 and 18.4 pods, respectively, which represented 48.7 and 69.9 g of seed pod consumed. The average healthy dairy cow produces approximately 15 paddies per day (Fraser 1985), so we estimate that cattle on these pastures consumed an average of 730 g and 1049 g of pods per day. This is only about half of what ranchers who use pods provide for their cattle.

NUTRITIONAL CONTENT OF ACACIA PODS

The nutritional content of acacia pods with seeds is compared to the requirements for a lac- tating dairy cow (Table 6). The content of the pod is similar to the dietary requirements for protein and fiber and provides adequate amounts of calcium, potassium, magnesium, iron and sulfur. The calcium to phosphorous ratio is consid- erably higher than recommended and the abso- lute levels of phosphorous are low. In addition, levels of sodium, zinc, copper and manganese are low. None of the minerals including selenium, reach levels that are known to be toxic. It would be interesting to examine the nutrient content of the acacia pod recipes to see if the




lacking minerals are compensated in the other ingredients. It should be emphasized that the flour contains ground seeds which are known to have approximately 30% crude protein content (Sotelo 1981). This explains the discrepancy between the protein values reported in our com- parative analysis (see section on Content of pods with and without seeds in the Results) as these samples were tested without seeds. In addition, free-ranging cattle would be acquiring the 9% protein measured from the pods without seeds since they do not digest the seeds. We present the nutritional analysis with ground seeds since this is the common way of presenting other leguminous seed pods (such as mesquite) and grinding the seed increases protein content and eliminates the possibility of unwanted seed dis- semination.

OTHER LOCAL USES

Acacia trees are coppiced and branches are used for fuelwood and fence posts; the wood makes sturdy fence posts, and the tree is faster growing than oak. However, acacia posts have to be replaced every 3-5 years, which requires the continued maintenance of some acacias on the ranch.

The local clay tile industry of Chavarrillo (see Fig. 1) has historically used large quantities of acacia wood to burn in their kilns. However, the parchment from coffee beans is now the pre- ferred energy source. According to kiln owners, burning with coffee parchment or with acacia wood costs approximately the same (25 pesos per burn). However, obtaining acacia wood is becoming more difficult since it is prohibited by law to harvest entire trees and therefore few people are still involved in selling wood to the kiln owners. In contrast, coffee processing mills where parchment can be purchased are com- monplace throughout this area of the Xalapa region.

DisCUSSION POTENTIAL BENEFITS OF ACACIA

PRODUCTION

The conversion of forests and arable land to pastures for livestock grazing is one of the main environmental problems in Mexico (Gomez- Pompa et al. 1993; Toledo et al. 1989). A major ecological impact of livestock production is the cultivation of land to produce grains and other ingredients for supplemental feed. Substitution

of basic grains for human consumption -mainly corn- to produce grains for animal feed supplements -mainly sorghum- has had a strong effect on the economy and the nutrition of poor rural people in Mexico. With the production of grain for livestock feed comes the use of fossil fuel for cultivating land and harvesting crops as well as processing and transporting the feed product, the exposure of tilled soil to erosion, and the use of agrochemicals for fertilization, weed and pest control.

It has been suggested repeatedly that increased reliance on perennial legumes for fodder would reduce the environmental impact of cattle feed production (Felker and Bandurski 1979; National Academy of Sciences 1979). In the case of acacia pods, we have found little or no chemical inputs, the ability to produce the pods locally, and the elimination of the need to till, plant and mechanically harvest. In addition, acacia is a native tree and there is no need to nat- uralize a plant from another region. Finally, acacia is a multiple use tree. Its wood is commonly used for fuel or building material and can be obtained by thinning the stand or coppicing individual trees. Acacia also grows readily in grazed or degraded lands where it would be difficult to establish other trees. The presence of trees on pasture land provides habitat for a number of species of migratory birds (Greenberg, Bichier, and Sterling 1997) and other organisms that would otherwise find pastures inhospitable. Finally, acacia appears to be a nitrogen-fixing tree. The amount of soil nitrogen under acacia trees is approximately double that found under adjacent pastures (unpubl. data from Chiapas). Acacia can provide a supplemental source of income for agricultural workers. In the region, coffee harvest represents an important economic activity for rural workers, pod season starts just after coffee harvest ends, therefore there is little overlapping of both activities. Since a high proportion of acacia pods are gathered from trees that form the canopy of shade coffee plantations, it might provide an additional incentive to maintain the shade cover in these plantations which has benefits for the conservation of biodiversity (Perfecto et al. 1996). However, because at this point, since the coffee farm owner receives no payment for pods collected, it is unclear that such an incentive exists. In fact, managers of coffee plantations perceive problems with acacia. Because of its shallow and expansive root




system, it dries out the soil and competes with coffee plants. How serious a problem this is requires further research.

POTENTIAL PROBLEMS WITH ACACIA

The major problems associated with acacia in- volve the ease with which it spreads into area where it is not wanted (Fagg and Stewart 1994). Although Acacia pennatula foliage has high crude protein and low tannin content (unpubl. data) and therefore may, like other acacias (Fagg and Stewart 1994), be highly palatable, the thorniness of young acacia is often considered an undesirable feature for pasture management. However, in Central Veracruz and Chiapas, we have found that while ranchers place considerable effort in controlling acacia, by cutting or occasionally using herbicides on seedlings, they seldom attempt to eliminate it. Acacias are pur- posefully maintained in low density savannas or in small woodlots, as a source of wood and for- age for free-ranging cattle. Spreading is not a problem in coffee plantations because there is no livestock; in addition, the canopy is dense and the seedlings will not develop in shade and there is intensive weeding of ground vegetation. A related problem is that, unmanaged, acacias form dense thickets of small trees that are unproductive. Systematic thinning of stands as they become established should increase pod production and provide a source of wood, as well.

CURRENT USE AND NEAR-TERM PROSPECTS

At the time of the study, the collection of acacia pods in Central Veracruz was small scale- much smaller even than the production systems for Prosopis pods in Central Mexico (Silbert 1988). We estimate that the total production of acacia pods in the Xalapa region during a good year is on the order of a few hundred tons. The acacia pod enterprise has been active for at least 20 years, but still involves few individuals, without support from any outside institutions or or- ganizations. We found little evidence of active marketing of the product. Despite the fact that the scientific evidence suggests that acacia pods are an excellent fodder, and the general enthu- siasm of ranchers who purchase and use the pods, we found relatively little general aware- ness of the benefits of pod production. There- fore, we see it as an activity that is currently little developed, but with a definite growth po-

tential, especially if demand increases through marketing and promotion and the management of acacia and handling of the pods becomes more efficient. For example, a cooperative producing mesquite pods in Matehuala, San Luis Potosi, was able to increase demand and thus affect considerable increases in the price of mesquite pods over a period of a few years (Silbert 1988).

RECOMMENDATIONS FOR MANAGEMENT

The data on stand structure suggests that acacia will be more productive if the stands are thinned so that fewer larger trees dominate; similar recommendations have been made for mesquite pod production. Thinning can provide wood as the acacia stand matures. It should be noted that the benefits to the conservation of migratory songbird populations appear to be great- est where the acacia stand forms a closed canopy of larger trees (Greenberg, Bichier and Sterling 1997). There is also indication that acacias are more productive on sites with more fertile soils. Increasing the collection and marketing of pods on good sites (many of which are now not harvested) would provide pods for ranchers located on sites with poor potential for pod production. Harvesting and processing of pods, even on lands that have free-ranging cattle which con- sume them, would increase the efficiency of the system and eliminate the need for extensive control. Pods are relatively dry and can be stored, thus increasing their seasonal availability. This is especially important, since trees on many ranches appear to produce a superabundance of seed pods that rot on the ground before they are consumed. Harvesting and feeding processed pods would allow more control of the diet of livestock. In addition, milling the pods as is done with mesquite pods in San Luis Potosi (Sil- bert 1988) and acacia pods in Ocosingo, Chiapas (pers. obs.) and northern Nicaragua (N. M. Keil- back, pers. comm.) would make the nutrition of the seeds available to the livestock and reduce the unwanted spread of seedlings in pastureland. The nutritional analysis suggests that available protein would increase substantially if the seeds were milled and rendered digestible and there appears that the seeds are not toxic (see section on Nutritional Content of Acacia Pods in the Re- sults; Sotelo 1981).




POTENTIAL FOR EXPANDING THE MARKET

Presently, the information that has been developed on the potential for pod use has been poorly disseminated. There is only one published paper on the subject (Chaizaro 1977) and two bachelor theses (Cervantes 1984; Murrieta 1984). However, the news is spreading by word of mouth and the past two years have seen an increase in the number of ranchers using acacia pods in the Xalapa region. For example, the Al- borada collection post experienced nearly a four- fold increase in sales (8.5 to 40 metric tons) between 1995 and 1996, though this may also be related to the periodicity of pod production (see section on Soil type and pod production).

So far the marketing of acacia pods has been strictly local. However, the possibility exists of entering the acacia pods in the small, but fast- growing, organic cattle feed market (Gips et al. 1994). Since acacia can be grown without chemical inputs, organic certification could increase the price for the producers and collectors. There are potential problems with attempting to expand the market of acacia beyond the region. First, the nutritional quality of the pods requires further detailed investigation to determine if it is an attrac- tive enough product. Second, the variable year to year production may complicate the formation of stable markets. And finally, ways to store the pods or flour without substantial loss to insects and rodents need to be developed. The mesquite pod industries of Mexico, Brazil, and Ecuador have thrived despite these problems. Silbert (1988) suggests that fluctuations in pod production may be dampened using simple irrigation systems. The problem of fungal and insect infes- tation of stored pods can be addressed through the development of more efficient (solar?) drying systems. The potential environmental benefits of this mode of fodder production should make further work in these areas worthwhile.

CONCLUSIONS

Acacia pennatula is a native, multi-use tree with tremendous potential for providing livestock feed, as well as a source of wood for fuel and building materials (particularly fence posts). The current use of acacia pods is restricted to the largely unquantified and unappreciated use by free ranging cattle and a small scale "cot- tage" industry of pod collection and sales to ranchers with few acacia on their property.

However, there are good possibilities to expand and promote the silvopastoral system, with an ample campaign that would reach producers and collectors, providing accurate information on pods quality for livestock feed. This would have an impact on pod price and hence would be an incentive towards the establishment and management of acacia woodlots on the ranches. This is confirmed by a growing interest from local farmers to use the pod when they are told about its high nutrition quality and relatively low price. Our studies of stand structure and pod productivity suggest possible avenues for future management. We found a clear relationship between stand density and tree size, which in turn is related to soil type and pod production. Pro- duction can be increased by concentrating on sites with better soils and systematically thinning the stands as they develop.

ACKNOWLEDGMENTS

This project was supported financially by the Smithsonian Migratory Bird Center. Thanks are due to Laurie Hunter who conducted background literature research. Armando Vaizquez was most helpful during our visits to his collecting post in Alborada, Veracruz.

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BOOK REVIEW

Maize Seed Industries in Developing Countries. Mi- chael L. Morris (ed.). 1998. Lynne Rienner Publi- cations Inc., 3 Henrietta Street, Covent Garden, London WC2E 8LU England, xiii + 401 pp. (hardcover). $50.95 hardcopy, $29.95 paperback. ISBN 1-55587-789-3 (hardcover), ISBN 1-55587-790-7 (paperback).

This book explores the paradox that although a green revolution has occurred with two of the world's pre-eminent cereal crops, wheat and rice, a comparable change has not yet occurred with maize, the third part- ner of the grain triumvirate that forms the cornerstone of the global food supply. Although plant breeding research has produced improved varieties and hybrids, and improved technologies have been employed to boost maize production in industrialized countries, these advancements have not been adopted by most farmers in the developing world who still plant pre- dominantly traditional varieties of maize. In this edited volume, various authors address different aspects of this issue, and describe how maize is produced and distributed under contrasting models in different countries. The particular viewpoint of the editor is that this situation is economically undesirable for developing countries. A key objective in researching and writing the book was greater understanding and clarification of the obstacles to adoption of modern hybrids and prac- tices in order that solutions can be identified for jump- starting a green revolution in maize.

The book is arranged into four parts. The first three chapters provide an economic conceptual background with a discussion of maize production in the developing world, and descriptions of the world maize economy and maize seed industries. The second part, en- titled "From Breeders' Plots to Farmers' Fields: Func- tions and Processes," describes how corn varieties are

developed by conventional breeding and biotechnolo- gy, how seed is increased and stored, marketed and distributed, who adopts and plants hybrid maize seed, how quality control is insured and intellectual property rights of hybrid germplasm are protected. The third section presents case studies for growing maize in nine countries: the United States, Brazil, Mexico, India, Thailand, Malawi, Zimbabwe, Turkey, and China. The fourth section is a summary chapter that predicts future directions for maize seed industries.

This book has many merits. It is unusual to find an edited volume with multiple authors that is such a pleasure to read. Every chapter is well written, interesting, and highly informative. I know of no other book that describes the multiple dimensions of maize seed production as thoroughly and concisely as this one does. The maize plant is an unusual system especially suited to crossing and producing recombinant hybrids from which a tremendous amount of genetic diversity can be selected. The hybrid maize seed industry is an American phenomenon that resulted from a unique blend of science, business, politics, and agriculture. It is fascinating to read how the American model has been adapted and modified to fit different economic, political, and cultural systems around the world. It would be helpful to have a companion volume that addresses why farmers in non-industrialized countries are reluctant to adopt hybrid maize varieties from the anthropological and ecological perspectives to counter balance the assumption that policy in developing countries should be driven by the economic and industrial paradigm.

MARY EUBANKS BOTANY DEPARTMENT

DUKE UNIVERSITY DURHAM, NC 27708-0338



Economic potential of the huizache, Acacia Pennatula (Mimosoideae) in central veracruz, Mexico

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