Bernardo Contreras
National Forestry Corporation
La Serena, Chile
INTRODUCTION
Algarrobo (Prosopis chilensis (Mol.) Stuntz) is one of the arboreal species with interesting prospects for utilization in afforestation plans, under the extremely constraining ecological conditions found at Region IV.
The irregular and scanty rainfall and the degree of soil deterioration do not make it easy to select species suitable for use in this area. There are two alternatives to face the problem: 1) to introduce exotic species which performance and provenance suggest good adaptation probabilities, and 2) to study and develop indigenous species from the zone, assumed to be already adapted to those ecological conditions.
Aware of the degree of soil deterioration, the low availability of desirable plant species and the need to incorporate new areas into economic production, the National Forestry Corporation of Chile has endeavoured to collect data on various economically attractive species either native to this area or typical of arid regions.
Algarrobo fulfills the condition of being a native species adapted to the soil and climatic conditions occurring at the area. It still occurs at many areas, despite the intense exploitation which has depleted its numbers, and it is used intensively as a source of fuelwood and charcoal, or to harvest its fruit. This is the best background to support the utilization of this species in afforestation programmes.
Both at home and abroad, this species has major importance in land reclamation and arid and semi-arid land incorporation into productive uses. Its timber can be used in carpentry and flooring, in addition to its fuel value (2); pods have been consumed since ancient times by people native to its natural range (16); alternatively, collected and stored pods are used as animal fodder for two months a year, with a feeding value matching that of barley and maize (16).
Besides being a source of fodder for livestock and of wood for carpentry, algarrobo has considerable importance throughout the world as fuel in desert regions, as in these areas, according to IREN-CORFO and CIFCA (1978), consumption of energy derived from fuelwood is very high, 50% for cooking purposes and 35% for heating; in warm regions, the energy for cooking purposes amounts to 80–90%. This is vitally important now that fossil fuels are becoming increasingly scarce and expensive, as energy consumption grows concurrently with the population. Therefore, considering that the tendency is to obtain this energy from wood, fuelwood sources must be made available.
In its natural stands, this species shows variations in height, amount or presence of thorns, taste of the pods, pod yields and number of folioles (16); this coincides with what has been observed in the populations found at Region IV (10), where variations were observed in fruit size and shape, amount of branches and size of the crown.
This paper aims at the establishment of the degree of difference in the form, conductive to the identification of the morphologic species or morphotypes, to which end the analysis of main components will be used.
Considering the productive characteristics of the species and its adaptation to arid environments, the study of the polymorphism of the most relevant traits of individuals from different populations is very important, with the purpose of assessing the degree of significance of this diversity and identifying morphotypes suitable for future utilization in afforestation programmes with the species.
2. GENERAL DATA ON PROSOPIS CHILENSIS (ALGARROBO)
2.1 Brief Description
Algarrobo belongs to the family Leguminosae (Mimosoideae), genus Prosopis and species Prosopis chilensis.
It a fast-growing round-crowned tree; it reaches a height of 3–10 m; branches are flexuose, knotty and partly thorny; in young shoots strong thorns grow profusely; leaves are deciduous, uni-tri-yugate; petiole 1.5 to 12 cm long; leaflet 8 to 24.5 cm long; 10–29 pairs of folioles per leaflet; flowers racemose, usually greenish-white-yellowish in color; calix 1 mm long, petals 3 mm long, stamens 5–6 mm long; ovary pubescent; fruit a linear legume, compact, with parallel edges, yellowish, 12–18 cm long, 1–18 cm wide and 0.6 cm thick; mesocarp sweet, edible; brown oval-shaped seeds 6–7 mm long (2).
2.2 Range
Its natural range is very ample, and it occurs in Peru, Bolivia and the central-northern part of Chile; in the Argentinian Northeast it can be found in the provinces of Salta, Tucumán, Catamarca, La Rioja, San Juan, Mendoza, San Luis and Córdoba; in Southern Peru it occurs up to 2,900 m elevation. Looser (1962) gives a detailed historical range for this species, but confined solely to the province of Santiago and the surrounding area. According to this author, the southern border of its range would be located in the vicinity of the San Francisco station, at the former O'Higgins Province, presently Region VI; the eastern border: the Chacabuco Farm, Peldehue, Baños de Colina; the western border: Lampa, Pudahuel, Isla de Maipo. According to Reiche (1973), other sectors where the species occurs are located in the province of Copiapó, and its range extends from the Northern End to the Central Zone.
Other authors state that its natural range is from Atacama to Santiago (Central Zone) (7, 8).
2.3 Main Characteristics
2.3.1 Habit, growth and stem
The tree can reach 3–10 m in height (2) and up to 80 cm in diameter; under good conditions it growths fast; the stem is short and ramified from very near the base; the branches have generous knots where the thorns, leaves and flowers grow (7). Individuals with no thorns have been observed (16). The stem, which is yellow-greenish and smooth-surfaced when young, turns gray-reddish with age, with some ridges and cracks running the length of its bark (15). It is common to observe that a tar-like substance is exuded through folds in the bark, initially gray-brown and later, through oxidation, turning dark brown to black (15). Stumps sprout easily.
2.3.2 Flowers and Fruit
a) Flowers. They occur in cylindrical bunches (7), yellowish-greenish in color (17). Flowers are good bee fodder (15), are hermaphrodite and germinate by epigenesis (7).
b) Fruit. Fruit is an indehiscent legume with varying size and shape (15); ripe, its color is straw-yellow and is 12–18 cm long, 1–1.8 cm wide and 0.6 cm thick (2, 27); its mesocarp is granulous, sweet and with high nourishing value (2). It is for this reason that its pods are excellent food (17). According to Medina (1942), the fruit weighs an average of 10.40 g, with a maximum of 15 g and a minimum of 5 g. This same author published a paper in 1942 where he reported obtaining 6.17 liters of 51.9° ethyl alcohol from 35 kg of fruit. This means that from 100 kg he would have obtained 17.67 litres of 51.9° alcohol which, with subsequent rectification, would have yielded 9 litres of absolute anhydrous alcohol.
2.3.3 Wood
Its wood is dark brown, frequently with a purple hue; it is very hard and the vein is irregular, but easy to work (17). It has applications in carpentry, floors, and as poles and fuel (28).
2.4 Environmental Adaptations and Requirements
The elements helping a plant live under water stress are root dispersion, foliar morphology and physiological adaptations, which are complemented by stomatal opening, photosynthesis and biochemical changes (8).
Algarrobo, native to arid zones, has small leaves (microphylla), a very efficient adaptation to prevent overheating and, thereby, excessive transpiration (7).
According to Alfaro (1973), algarrobo presents distinct foliar absorption. Its roots penetrate deeply searching for the groundwater table (7), frequently reaching depths up to 10 m and, occasionally, even 20 m (16).
Usually they receive 200–400 mm yearly rainfall, but very well established individuals have been found thriving at places with rainfall below 75 mm. They normally tolerate 8–11 rainless months, and can easily withstand long droughts (16, 17).
This tree can stand very high temperatures, typical of desert zones; it is not adapted to cold weather and requires temperatures of around 27° C to grow well. Trees raised from seedlings have been reported to withstand temperatures as low as -5° C, but for very short periods of time (17). it requires substantial sunlight to develop well. In Northern Chile it reaches maturity at the age of 30–35 years, whereas in the Central Zone it takes 50 years to reach full development (19).
As regards it range in altitude, it is recommended to plant this tree between 340–1,200 m above sea level (asl), although in Peru it has been found growing at altitudes of up to 2,900 m asl.
It grows well on flat soils with little slope, where its roots can reach the groundwater table quickly. It normally grows on the flat lands, without reaching the foothills (7). According to Tinto (1974), in Argentina it shows similar soil requirements, preferably loose and deep soils, or stony-sandy soils.
3. MATERIAL AND METHOD
3.1 Studied Sites
The sites where the study was to be conducted were selected by making a field reconaissance of the areas with confirmed sizable algarrobo populations.
Four places were selected, as follows:
Sampling was carried out as a the second stage, including the delimitations of the above populations on Military Geographic Institute (IGM) charts, serving as a previous basis for subsequent populational charts.
3.2 Selection of Variables
Faced with both qualitative and quantitative traits, the latter were chosen as a matter of convenience in the method. These are known as metric traits.
Sokal and Sneath (1973) explain the convenience of taking at least two standpoints as reference when selecting traits in taxonomic practices: 1) to use all kinds of traits from all parts of the individual and from all the stages in the life cycle; 2) to use all the traits which vary within the study group and not solely traditional diagnostic traits.
It was determined that the traits or variables considered for the study would be extracted from various parts of the plant, such as the leaves, thorns, branches and fruit; likewise, the measurements made were focused in the assessment of the variations observed within the populations and among the populations, grouping them according to their position.
3.2.1 General variables
3.2.2 Variables in a determined length of branch
3.2.3 Fruit and seed variables
3.3 Sampling System and Trait Measurement
3.3.1 Sampling method
Data were obtained with a sampling method aimed at covering the whole population, for which purpose sampling strips were arranged, along with selecting those individuals within the strips which bore fruit.
3.3.2 Trait measurement
The methods used for measuring the traits are detailed below, indicating the instruments or materials used for the purpose:
General variables
Breast-height diameter (BHD), taken at 1.30 m above the ground in all those individuals branching out above that point. As no diametric meter was available, an indirect method with linear measuring tape was used, transforming subsequently with the formula:
p = π × d
d = diameter (cm)
p = perimeter
π = constant (3.1416)
Variables in a section of a given branch
The following variables were measured in a given branch within a one hundred centimeter length at 50 cm from its apex (sampling unit), also labelled as subdistal meter.
Fruit and seed variables
About 100 g of fruit were collected from each selected tree, an amount determined from previous observations of Prosopis chilensis populations, where a decrease in fruit yields had been observed; i.e., this small amount insured the inclusion of trees with very low yields.
Pod dry weight. The pods were weighed when green (green weight - GW) and then heater-dried at 105° C and weighed again, to obtain the dry weight (DW), which was subsequently expressed as a percentage of the total weight or green weight, using the following algorithm:
where: GW = green weight
DW = Dry weight
3.4 Analysis Methodology
The analysis of the morphological similarity among individuals was made by means of the Analysis of Main Components, which is an ordering method for reduced spaces, applicable to sets of metric traits, and consists of analyzing and representing the individuals in a multi-varying chart having as many axis as traits or descriptive characters available.
A number of quantitative data may be obtained with this method regarding the value of the projections derived, to outline the relations among traits as well as relationships among individuals.
A computer loaded with the ACOMP program was used to process the method of analysis.
4. RESULTS
The analysis was applied by parts in each of the populations of the survey, which were also taken as a whole for the overall analysis.
4.1 Variable Codes
The need of defining codes for the variables derives from the application of this methodology in a computer. The equivalence is shown below:
Total height | (m) | V1 |
Height of ramification | (m) | V2 |
BHD | (cm) | V3 |
Number of shoots | (No) | V4 |
Crown diameter | (m) | V5 |
Number of brachyblasts | (No) | V6 |
Number of leaves per brachyblast | (No) | V7 |
Thorn length | (cm) | V8 |
Number of thorns | (No) | V9 |
Number of folioles | (No) | V10 |
Leaf width | (cm) | V11 |
Leaf length | (cm) | V12 |
Branch diameter | (cm) | V13 |
Leaf dry weight | (gr) | V14 |
Number of pods/kg | (No) | V15 |
Pod length | (cm) | V16 |
Width at center of pod | (mm) | V17 |
Pod thickness | (mm) | V18 |
Number of seeds/pod | (No) | V19 |
Number of seeds/kg | (No) | V20 |
Pod dry weight | (%) | V21 |
Number of damaged seeds | (No) | V22 |
4.2 Río Pama Population Analysis
— Distribution of the 50 individuals into 10 classes and density chart illustrating the distribution made.
4.3 Monte Patria Population Analysis
— Distribution of the 50 individuals into 10 classes and density chart illustrating the distribution made.
4.4 Corral Quemado Population Analysis
— Distribution of the 50 individuals into 10 classes and density chart illustrating the distribution made.
4.5 Quebrada Marquesa Population Analysis
— Distribution of the 50 individuals into 10 classes and density chart illustrating the distribution made.
4.6 Overall Analysis
— Distribution of the 200 individuals into 10 classes and density chart illustrating the distribution made.
5. DISCUSSION
5.1 Mean Traits of the Classifications Linked to the First Four Main Components at Río Pama
According to the findings of the analysis, and particularly from the density chart showing the distribution of the individuals, the plotted points on the 1–2 and 3–4 axis or correlation circle, three groups (types) were selected in this sector, for which some of the mean traits are included, considering for this purpose the degree of importance of the variables in the components 1, 2, 3, and 4 (1).
Group 3
Group 5
Group 9
5.2 Mean Traits of the Classifications Linked to the First Four Main Components at Monte Patria
Basing on the findings of the correlations and projection charts for individuals and variables, four groups were selected in this sector, for which the mean traits of those variables falling closer together are indicated.
Group 3
Group 4
Group 5
Group 6
5.3 Mean Traits of the Classifications Linked to the First Four Main Components at Corral Quemado.
The mean traits are indicated for the groups listed below according to the most relevant variables that could be observed at the projection and classification charts, showing a high correlation with the four main components (1).
Group 1
Group 4
Group 5
Group 9
5.4 Mean Traits of the Classifications Linked to the First Four Main Components at Quebrada Marquesa.
Four groups were selected basing on the projections of the individuals and the variables, added to the distribution into ten classes, the main traits of which are described according to the variables which showed the best correlation with the main components.
Group 1
Group 4
Group 5
Group 8
5.5 Mean Traits of the Classifications Linked to the Four Main Components in all of the Populations Surveyed.
Three “plus groups” were selected basing on the projection of the variables on the correlation circle, the distribution of the individuals into ten classes and the order of importance of the variables in each component (1). Some of their mean traits are defined below.
Group 1
Group 3
Group 9
6. CONCLUSIONS
The variables considered in this survey generally showed good correlation among themselves and grouped sampling units around sets determined by the variations of these traits, with the exception of the variable “branch diameter” (V13) which achieved no degree of importance in the different analyses.
From the morphologic traits group, the traits which achieved more relevance where those related to the pods for the five analyses made.
The analysis shows considerable diversity in the traits, being possible to define different individuals morphologically at each population. This also happens in the overall analysis. The following morphotypes are distinguished:
Río Pama | : 3 morphotypes |
Monte Patria | : 4 morphotypes |
Corral Quemado | : 4 morphotypes |
Quebrada Marquesa | : 4 morphotypes |
Población general | : 3 morphotypes |
It would be convenient to work on the reproduction of the morphotypes identified, with the purpose of establishing —under similar soil and climatic conditions— if the morphological differences are of an environmental or genotypical nature.
As regards the analysis used, it may be concluded that it is efficient in multivariable comparations. It must be stressed that a careful selection of the variables to be used is essential.
REFERENCES
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APPENDIX
MAP SHOWING LOCATION OF SECTORS SURVEYED
(II PART)
EVALUATION OF PROSOPIS CHILENSIS PLANTATIONS AT REGION IV
1. GENERAL BACKGROUND
The National Forestry Corporation-Region IV has established a number of plantations with Prosopis chilensis, among which stand out those carried out in 1981 at various locations. These plantations are aimed at determining variations permitting an optimum management of the species. At this stage, some sectors were planted with schemes which considered different spacings.
The project has been labelled Management and Adaptation of Prosopis chilensis, with the participation of the Forestry School of the University of Chile.
In 1976 a small plantation —approximately 300 plants on 2 hectares— was established as part of the treatments on the slopes draining into the La Paloma Reservoir.
2. MATERIAL AND METHOD
2.1 Sectors surveyed
The main sectors with plantations of Prosopis chilensis in Region IV are shown below, including the planting years:
Location | Planting year | Area (ha) | Purpose of the plantation |
---|---|---|---|
LA MUÑOSANA | 1976 | 2.0 | Slope stabilization with plant cover (to check erosion) |
MONTE PATRIA (Q. Grande and Pta. de Huana) | 1981 | 13.3 | Part of the Prosopis chilensis Management and Adaptation Project |
HIGUERITAS | 1981 | 5.6 | Part of the Prosopis chilensis Management and Adaptation Project |
VARIOUS LOCATIONS (Tongoy, E. Paloma, Tipay and Tunga Norte | 1983 | — | Part of a species trial program |
2.2 Surveyed Locations
Only the more representative places were considered in the growth evaluation of this species:
The variables evaluated were: total height and collar diameter.
3. RESULTS
Location | No. trees surveyed | Height (m) | Collar diameter (cm) | ||||
---|---|---|---|---|---|---|---|
x | Sx | CV% | x | Sx | CV% | ||
LA MUÑOSANA | 70 | 2.75 | 0.69 | 25 | 5.13 | 2.09 | 40.7 |
MONTE PATRIA | 125 | 0.48 | 0.36 | 75 | 0.81 | 0.39 | 48.1 |
HIGUERITAS | 150 | 0.36 | 0.22 | 60.1 | 1.11 | 0.62 | 55.8 |
Logomorph presence and damage was detected at all sites, greatly affecting the plants. The effects are mainly reduced height gains, as this animal usually cuts off the main shoot.
4. CONCLUSIONS
Direct evaluation, without the application of a correcting factor to account for logomorph damage, may lead to wrong assessment of the growth rates.
Considerable annual growth was observed at the Muñosana sector.
Prosopis chilensis adapts well, but in the early growth stages it is greatly affected by animal attack.