LAND MAPPING.pdf

RESEARCH Multiple-purposes Land Mapping and Resources Inventory SILVIA DIANA MATTEUCCI Universidad Nacional Experimental Francisco de Miranda Coro, Venezuela

AiDA COLMA Universidad Nacional Experimental Francisco de Miranda Coro, Venezuela

LAURA PLA* Escuela de Postgrado Facultad de Agronomia, UCV Maracay, Venezuela

ABSTRACT / A land classification and resources inventory of Falc6n State was underiaken with the aim of gathering base- line information to help in development planning. The study

area, located in northwestern Venezuela, comprises an eco- logically diverse region, due both to its varied geomorphology and to its history of human occupation. A landscape approach was used. Qn the basis of photointerpretation, examination of existing literature, and field work, uniform land units (physiognomic units) were delineated and described in terms of landform, soil, vegetation, drainage pattern, and climate. These were grouped in homogeneous units (HU) on the basis of their potential natural vegetation through the delimitation of climax complexes. The last hierarchy, the land systems, comprise the geomorphogenetically related HU. The results are presented at different levels of generalization and integration, in verbal and cartographic descriptions, and they are stored in standardized formats to ensure ease of comprehension and han- dling and to meet different needs. This report describes the methods employed for the survey and data presentation, and discusses its applicability and limitations.

FalcOn State, in northwestern Venezuela, comprises 24,750 km 2 of a mosaic of landscapes whose intricacy is due to the extreme variations in relief and topography and to the history of human occupation. An inventory of land types and natural resources was required to serve as a basis for land-use planning at the state level. Because there was scarce and scattered previous information, a reduced research team, an intricately dissected landscape, availability of fairly recent photoeoverage and good cartographic sheets at scale 1/100,000, and the need to give an answer in a short time, a landscape approach (Mabbutt 1968) was selected.

The integrated approach, introduced by Christian and Stewart (1953), and applied since then to various situations (UNESCO 1968, Stewart 1968, FAO 1976, Jurdant and others 1974, Beckett and others 1972) has proved adequate for the study of undeveloped regions. The method is based on the concept that it is possible to identify recurring land-units of similar genesis, charac- terized by distinctive topography, vegetation, and soils. These land-units can be assembled in land systems on the basis of their geographic and genetic relationships (Christian 1958). The correlations between topography, vegetation, and soils arise from a long history of land-

KEY WORDS: Land classification; Topography; Natural resources inventory

*Present address: Universidad Nacional Experimental Francisco de Miranda, Coro, Venezuela.

scape formation (Christian 1952). In regions in which human activity has partially changed the natural vegetation, land-units can be assigned to the correct category by extrapolation of natural vegetation remnants to culti- vated neighbouring segments of similar landform, soils and relationships to other landforms (Christian 1958). In regions with a long history of human occupation, the patterns that result from land use may be correlated with landform and soils. In such cases, recognition of land- units and land systems is done through the identification of those patterns (Christian and Stewart 1968, Satyana- rayan and Dhruvanarayan 1968).

Falc6n State is in an intermediate situation, in which land use has been extensive but recent. Thus, it is not imprinted in the landscape. Shifting agriculture has caused a gamut of seral stages, and has been so intense and inadequate to natural environmental conditions, that natural vegetation remnants are almost absent. Accord- ingly, the basic methodology was modified to meet the local conditions and needs.

This article describes the methods employed to obtain a hierarchical classification of the land and a natural resources inventory, it shows examples of the formats used for presentation of results, and it discusses the applicability and limitations of the results obtained.

The Study Area

Falc6n State is located in northwestern Venezuela, between latitudes 10o18 ' and 12o13 ' N, and longitudes

Environmental Management Vol. 9, No. 3, pp. 231-242 9 1985 Springer-Verlag New York Inc.

232 s.O. Matteucci and others

70=00 9

........ ~ FALCON STATE, VENEZUELA

( " ~ J '~' / ,,' P~AGUA,*' /

" E'S'E22R,.,ME. I . , , .# / /A / / / / ! , / / : /

,,._..,,_.~ ---~. - KM ~ SEMIARID ZONE .~,.. LIMIT between ZONES

LIMIT between PROVINCES . d [----'7 SUBHUMIO ZONE

Figure l. Physiographic provinces and climatic zones in Falc6n State, Venezuela.

68~ and 71~ W. Topographic diversity results in heterogeneous hydrological conditions and in a mosaic of landscapes arranged in a parallel pattern in an ENE- WSW direction. Five physiographic provinces occupy the territory: the Coastal Plains, the Coastal Piedmont, Falc6n Ranges, the Central Valleys, and the Eastern Maritime Valleys (Figure 1).

Geology and Geomorphology Most of Falc6n's territory is underlain by Tertiary

sediments, which outcrop in the uplands. Several epi- sodes of continental and marine deposition in the geosyn- cline, which occupied most of the study area, produced interbedded shales and sandstones, with layers of conglomerate and limestone. Falc6n Ranges started uplifting in the Lower Miocene, and tectonic mo~,ements continued up to the end of the Pliocene. The lowlands are overlain by Quaternary deposits.

The Coastal Plains Province comprises the Paraguana Peninsula, the isthmus, and the alluvial plains to the west of these. Relief is low and even. The highest elevation corresponds to an isolated hill (815 m) in the peninsula. The shore, subjected to the trade winds from the ENE, is overlain by recent sand deposits, in segments of beaches or of dunes. The rivers, which traverse the plain s from south

to north, are intermittent and carry flash floods with suspended sediments in the rainy season.

The Piedmont Province constitutes a belt of transi- tional topography, with erosional and depositional landforms, located between the coastal plains and the mountain ranges. Its elevation goes from 100 m to 400 m toward its southern border. It consists mainly of a succession of tilted fault block ridges that stretch parallel tO the mountain ranges and are formed by interbedded sandstone and shale.

The Falc6n Ranges Province occupies 44% of the study area and encompasses three parallel ridges sepa- rated by wide valleys. The northern and medium ridges are divided into three main mountain masses by gorges and valleys through which inner rivers flow northward and discharge into the Venezuelan Gulf. The slopes are steep and the relief is great, formed by knife-edged divides and V-shaped ravines. The elevation ranges from 200 to 1500 m (800 m on the average). To the east, some mountain remnants are found within the Eastern Mari- time Valleys Province. On top of these remnants, as well as on the easterly mountain mass of the northerly ridge, karst landscapes have developed. The thick limestone masses reach a height of up to 350 m of exposed rocks.

The Central Valleys Province encompasses the syncli-

Land Mapping and Resources Inventory 233

Table 1. Field questionnaire, a

Date: Aerial photo no.: Cartographic sheet no.:

Nearest settlement: (Name) UFI no.: Questionnaire no.:

A) Physical environment Altitude: Soil texture: Landform: External drainage: Stoniness class: Soil color: Water sources: Litter coverage: %

Slope: Erosion: Microtopography: Rockiness class: Type of fragments: Land use

type: degree:

B) Vegetation structure

Growth form Height (x) xmax xmin

Leaf % Cover Periodicity Thorniness

Texture Size Shape

C) Flora Species % Cover Spatial pattern Phenological stage Growth form

aEach of the four parts (data on location; physical environmental attributes; vegetation structure, flora) goes on a separate sheet. The ranks and classes for the physical parameters are shown in Table 2. Growth-form cover is assessed according to Fosberg's scale (Fosberg 1967); for spedes cover the Braun-Blanquet scale was modified to include the intermediate classes 6%-15% and 16%-25% cover. 2, = average growth-form height; xmax and xmin refer to maximum and minimum heights of the green mass.

nal valleys between the mountain ranges. Topographic relief is low and mostly plain or undulating, except for some low foothills and elongated, narrow buttes. Rivers are intermittent and dried water courses are overlain by salt deposits from the gypsiferous shales of the neighbouring highlands.

The Eastern Marit ime Valleys Province comprises the basins of the four main rivers that flow to the east and north from the Falc6n Ranges and discharge into the Caribbean Sea. The basins are limited by low divides formed by undulating high plains or mountain remnants. The elevation goes from 300 m at the foothills to 0 m on the shoreline. Slopes are mild to null, and the plains near the coast become temporarily or permanently flooded at places.

Climate

The study area, subjected to surface trade winds from the Caribbean Sea, presents a local climatic anomaly (Lahey 1973). At this latitude, in such a marine location, abundant precipitation would be expected. However, the coastal fringe has a dry climate with limited and erratic rainfall, except for the short sections of N-S-oriented continental shorelines.

On the mountain ranges, orographic precipitation is produced, with rain shadows on the lee sides of the ridges. Rainfall is heavier, as well, in those valleys opened to the ENE. The summits are subjected to daily

cloudiness. Rainfall occurs as heavy showers within short periods of time.

On the coastal plain, mean annual temperature is of 28~ with only 1 ~176 variation over the year, although daily temperature varies an average of 10~

Two climatic zones can be delimited on the basis of precipitation to potential evapotranspiration ratio. The semiarid zone, with a ratio from 2 to 4, comprises the Coastal Plains, the Coastal Piedmont, and the Central Valleys. Mean annual rainfall ranges from 170 mm to 654 mm. Climate is demarcated into two seasons; the rainy season, by the end of the year, lasts from one to two months. The subhumid zone encompasses the Falcon Ranges and the Eastern Marit ime Valleys. Precipitation to evapotranspiration ratio ranges from 1 to 2. Mean annual precipitation is from 600 mm to 1700 ram. Rainfall is distributed in one or two rainy seasons.

An arid zone on the coastal fringe and a humid one on the mountain summits probably exist, but there are not enough meteorological records to confirm these observations. Climatic pattern, as in many mountainous regions, is very variable within short distances and largely depen- dent on topography.

Land Use

The aboriginal population that inhabited the study area practiced agriculture under irrigation; however, it probably was not until the arrival of Europeans that the

234 s.D. Matteucci and others

Table 2. Ranks and classes for the physical environmental parameters.

M

3 3 2 ,s

1 z 3 4"x~- ."5 4 3 2 1

ES EE EC

Stoniness = P No stones or very few 0 Stones covering less than 0.1% of the surface 1 Stones cover 0.1%-3% of the surface 2 Stones cover 3%-15% of the surface 3 Stones cover 15%-90% of the surface 4 Paved with stones 5

Rockiness = A No rock outcrops 0 Outcrops cover 2%-10% of the surface 1 Outcrops cover 10%-25% of the surface 2 Outcrops cover 25%-50% of the surface 3 Outcrops cover 50%-90% of the surface 4 A rock outcrop 5

Erosion Wind = EE; sheet = EL;

furrow = ES; gully = EC None 0 Slight 1 Moderate 2 Severe 3

A~i tude(m) =H 0-50 1

51-100 2 101-200 3 201-400 4 401-800 5 801-1600 6

Landform = R Plain 1 Valley 2 Hill 3 Monocline 4

Type of fragments = F None 0 Up to 7.5 cm diameter 1 7.5 to 25 cm diameter 2 Larger than 25 cm diameter 3 1+2 4 3+2 5 1+2+3 6

Microtopography = M Even 1 Dunes 2 Undulating 3 Gullied 4 Mounds 5

Runof f = D Slope (%) = S Medium 0 0-2 1 Slow 1 2-6 2 Rapid 2 6-13 3 Very slow 3 13-25 4 Ponded 4 25-55 5 Very rapid 5 >55 6

stress on the environment became significant. European occupancy in South America occurred along the coasts of what is now Falc6n State, during the early 1500s. Though initially the purpose was to settle in the region, and livestock was introduced, it soon became a transient site for exploitive groups. Several attempts at settlement failed for various reasons, including pirate assaults, and these failures partly account for the lack of an established agriculture. Nevertheless, the original vegetation has been cleared perhaps several times.

Agriculture has dwindled again since about 1940 with the development of the petroleum industry, which caused people to abandon the farms in the search of higher economic gain. As a consequence, large tracts of land became desertified.

At the present time, the main activity in the semiarid zone is dryland farming, mostly goat herding at the expenses of thorn woodland and thorn scrub, without any pastural management. This causes heavy browsing pressures around the villages. Subsistence shifting agriculture is also practiced. Wood gathering for fuel is concentrated near the villages, which are small and scattered. All resources are used to support the family, which in general is otherwise unemployed. Standard of living is low, and middlemen profit from the lack of managerial techniques. The situation is somewhat different around the capital city of Coro, where commercial horticultural crops are produced under irrigation. In most of the zone, however, goats are the sole source of food and income.


Figure 2. Photocoverage employed in the delimitation of the photointerpretation units.

,~ ' FALCON STATE, VENEZUELA

"Photocoverage employed in the survey

I

=m==== ~ No photocoverage available 10 0 ~0 20 30

In the subhumid lowlands, pasturelands occupy the largest areal extent. Burning to replace forest with grass is extensively practiced. Some management techniques are applied, but most of the time these are not adapted to the natural conditions. On th.e sandy shores along the east coast there are coconut plantations, and some horticultural crops are grown in scattered places near the main roads. In the humid uplands, coffee plantations have long been abandoned, and only subsistence agriculture is practiced.

Materials and Methods

resources of the region as a whole. It became necessary to undertake a simultaneous study of vegetation and environment.

The main physiographic provinces and climatic zones were delineated (Figure 1), and a preliminary description was made. The minimum area to be classified and plotted was set at 0.25 km 2. A field questionnaire (Table 1) was prepared, tested along a N-S transect, and adjusted as necessary. Classes and ranks for the parameters used are shown in Table 2. Data collection took into account the possibility of applying a parametric approach later.

Survey Planning Stage

To determine the best way to organize the survey and to choose the most relevant environmental factors and parameters, the available literature was assessed. Con- currently, a field trip through the main roads was done to recognize the general nature of the landscape and to check some of the previously collected information.

The study area has been greatly modified by man's activity, and it showed various degrees of erosion and recovery. Many of the vegetation types now present are far removed from natural vegetation and they do not represent site potential. It was postulated that this situation would obscure the correlations between vegetation, landform, and soils, and that vegetation units would be smaller than landform units.

There was some information available, but it had been obtained at different scales and with various methods, and usually it covered restricted portions of the study area. Moreover, most of the data did not relate to the present land condition. Thus, the existing information was inadequate to appreciate properly the various

Photointerpretation

Vertical, panchromatic, 1/60,000 to 1/25,000 scale aerial photographs dated from 1960 to 1977 (Figure 2) were interpreted stereoscopically. Land segments were delineated on the basis of homogeneous image signatures including a combination of tone, pattern, and texture. Thus, the boundaries do not necessarily coincide with geomorphic divisions or specific landforms; they may reflect major changes in vegetation structure.

Deductive interpretation was employed, and a description of each unit on the basis of landform, topography, vegetation structure, drainage pattern, land use, and roads was prepared. This description was later discussed and modified as necessary during ground survey. The results were compiled on transparent xerox copies of 1/100,000 scale topographic sheets by means of an optical pantograph.

The 556 photointerpretation units obtained were numbered, and sample sites were selected. Since the aim of the survey was to gather information regarding the natural resources without an a priori decision about the


P.U.N~ 144 Name: Alto de Mujica

Climatic zone: subhumid Climate: Meteorological station: Puerto Cumarebo

Physiographic province: Coastal Piedmont Soil: orthid Soil survey: semidetailed; COPLANARH, 1975 Water sources: no Hydrological studies: no Drainage pattern: parallel

Vegetation structure: open semideciduous scrub Dominance type: Bourreria cumanensis, Phyllostylon rhamnoides,

Bulnesia arborea Land use: pastoralism (goats raising without management practises),

firewood gathering Degree of land use: slightly transformed

District: Zamora Location: 11~ , N-69~ ' W Area: 90.63 km 2 No. of UFIs: 1 Altitude: 200 m Accessibility: easy

3C

G

20

10-

Puerto Cumarebo (13 m)

17

27.7~ 474 rnm

'"~' M k M .; '] ~ ~ 6 N 6

f lOO

8o

g L"-:

.20

Figure 3. Example of ecogram of a physiognomie unit. The references of symbols employed in the eeogram, as well as the ranks and classes of the parameters, are shown in Table 2.

economic activity to be developed, collection of field data was planned for all those units that differed in one or more of the attributes employed to describe it. Extrapola- tions to supposedly similar units were not accomplished without confirmatory ground observations.

Field Work

A weekly itinerary was planned every fortnight, so that field data collected during one week could be systematized, the photointerpretation revised, and boundaries corrected as necessary during the next week. in the field, each unit was traversed as far as' roads permitted, in order to verify its uniformity and the general consistency between its description and field conditions. Details not visible on the aerial photo were added to the descriptions, which were modified as necessary. On the chosen sites, the questionnaire was answered after examination of the site and discussions between the team members. Ground photographs were taken to supplement descriptions. Plant samples were taken for later identification when they were not recog-

nized on the field. During traveling, boundaries between units were checked and changed as necessary on the photographs and sheets. There was more boundary checking in the east, where photocoverage was outdated.

Interpretation of Field Data and Compilation of Maps

The field investigations confirmed what had been hypothesized during the first stage, that is, that the photointerpretation units were associated with the landforms and present vegetation structure, as determined by differences in past and present land-use practices. These units represented a series of seral stages, from seminatu- ral ecosystems to fully transformed systems. In the former, basic ecosystem components and their interrela- tions are not yet damaged, though there has been some use of resources, mainly vegetation; they comprise land tracts in which selective wood gathering or browsing on natural vegetation has occurred. The transformed systems comprise land segments where the natural ecosystem has been ehangedby total deforestation for cultiva- tion or for cattle raising, or for urban or industrial


Table 3. Example of the format employed for the description of a land system.

Land system: Alineaci6n Septentrional Oriental (X) Area: 1190 km 2 Elevation: 20-500 m Slope: 2%-25% Geology and geomorphology: undulating plains, underlain by Tertiary interbedded shales and sandstone, overlain by Qua-

ternary alluvial deposits; with scattered rounded low hills underlain by marl with thick marine limestone strata outcrop- ping in the summit

Climate: 1000-1192 mm of annual average precipitation; one or two rainy seasons.lasting 8 months, with peaks in July and December; short dry spell at the beginning of the year

Drainage pattern: radial on the hills, trellis to pinnated

The system comprises two homogeneous units (HU):

HU Landform Soils Vegetation Land use

Xa Undulating plains Fine-textured saline so i ls Deciduous seasonal forest; Cattle raising on de- dominance type: Z. forested lands pterota, Machaerium spp., Eugenia spp.

Xb Low hills Red latheritic on the Cloud forest on the sum- Subsistence farming slopes; deep organic on mits; dominance type: the summits Eugenia spp.

Human population is concentrated along the main road, which traverses the system in the E-W direction; human density is less than 0.1 person/ha; physiographic units: 141,149, 148, 162, 163, I64; I65, 167-P, 200, 20I-P

development. Intermediate stages comprise both units where woodcutting or goat browsing has been more intensive, and long-abandoned fields in different stages of secondary succession, including areas where excessive grazing or untimely deforestation have resulted in severe erosion and have caused a significant productive loss. Relict natural vegetation is almost nonexistent. Thus, differences between photointerpretation units are due to landform and present condition of vegetation as well as tO the direction of succession changes, which can be either toward recovery or to desertification. The starting stage of secondary succession and the rate and direction of change are important factors to be considered in a tropical zone with the climatic and topographic conditions prevailing in Falc6n, since changes in habitat can be faster than vegetation recovery, thus precluding restora- tion toward the natural vegetation type. In such a case, a different stable community may replace the natural vegetation type in a progressive secondary succession, or desertification may occur if succession is regressive.'

All those photointerpretation units that were found to be similar after field inspection and that were stationed in the same physiographic province were combined in a physiognomic unit (PU), and described in terms of landform, geology, climate, physical habitat conditions, and present vegetation structure and dominance type. The 269 physiognomie units thus obtained were mapped at 1/250,000 scale.

The potential natural vegetation (Mueller-Dombois

and Ellenberg 1974, Westhoff and Van der Maarel 1978) was used as a criterion to obtain the homogeneous units (HU). A land segment potential natural vegetation was judged on the basis of stratification and complexity, diversity of growth forms, composition of woody species, and presumed direction of succession. Climax complexes (Whittaker 1978) were identified, and contiguous communities in similar habitat types that belonged to the same complex were combined.

The homogeneous units were gathered in systems, on the basis of the prevailing landform and of the geologic history. The physiognomic units, homogeneous units, and land systems areas were measured on the map.

Results

The hierarchical classification produced 269 physiognomie units, grouped in 38 homogeneous units and 15 systems. The physiognomic units are mapped at 1/ 250,000 scale, and identified by numbers and the name of a settlement within it. The homogeneous units and the systems are mapped at a 1/1,000,000 scale. The latter are named after their geographical position and identified by a roman number, and the former are identified by the system's roman number followed by a letter.

In order that the information can meet different needs, it is presented at various levels of integration and generalization. Thematic maps and reports are presented for


Table 4. Summary of the main characteristics of Falc6n State land systems, a

System and area Geology Major soils

Landform Major Altitude drainage vegetation and pattern type slope

Present land use

I Quaternary al- 2260 km 2 luvial deposits

II 550 km 2

II I 1130 km 2

IV 1360 km z

V 1440 km 2

VI 1300 km 2

VII 4230 km 2

VII I 1070 km 2

IX 590 km 2

Interbedded sandstone and shale, Mio- cene to Plio- cene

Same as I

Interbedded sandstone and shale Mio- cene to Plio- cene

Eocene to Mio- cenesand- stones and

conglomerate

Eocene to Plio- cene interbedded sandstone and shale

Heterogeneous: same as V, sandstone and conglomerate, marine limestone

Same as VII

Tertiary gyp- sipherous shales

Floodplain, par- Medium tex- From thorn 0-160 m allel stream- tured, locally woodland to 0%-4% lines clayey and deciduous

saline. Cam- seasonal for- borthids, Tor- est in a N-S riorthents, gradient Pateargids, Haplargids

Dissected coas- Shallow, stony, Thorn scrub 0-160 m tal plain; ra- saline. Or- and thorn 0%-6% dial and trel- thents, Or- woodland lis drainage thids, Argids

Same as I, sand Medium dunes to tlae textured coast Orthents,

Orthids, Camborthids, Salorthids, Haplargids, Psamments

Tilted fault- Shallow lithic block ridges, soils, rock some plains & outcrops. Or- hills; trellis thents, Or- drainage thids, Argids,

Camborthids Mountains bor- Shallow, lithie

dered by low on eroded hills, trellis slopes; or- and pinnate ganic on the drainage summits; red-

dish brown elsewhere. Orthents, Or- thids, Argids, Tropepts, Us- talfs

Same as V Same as V

Same as V, small undulating upland plains

Mountains and hills; complex slopes

Mountains, bor- dered by low foothills; radial and trellis drainage

Thorn woodland

Thorn woodland

Deciduous seasonal forest; cloud forest

Deciduous seasonal forest

Same as V; Same as V; de- limestone out- forested for crops, same as pasture seed- V and Ren- ing dolls, Ustolls

Same as VII Same as V

Shallow lithic soils with rock outcrops; red clayey. Orthents, Tropepts, Us- talfs, Ustults, Orthids, Us- terts

Pasture, remnants of deciduous seasonal forest

0-100 m 0%-4%

160-500 m 0%-25%

200-800 m 6%-13%

200-800 m 15%-55%

400-1200 m 2%-40%

300-1500 m 15%-55%

160-800 m 6%-25%

Goat herding on natural vegetation to the N; cattle on seeded pasture to the S

Unused mar- ginal lands; goat herding

Horticultural crops under irrigation

Goat herding on natural vegetation, subsis- tencefarming

Cattle raising, subsistence farming

Cattle raising to the W; goat herding on rangelands

Cattle raising, subsistence farming; sugarcane

Subsistence ~rming

Cattle raising


Table 4. Continued.

System Landform and drainage area Geology pattern Major soils

Major Altitude vegetation and

type slope Present land use

X Eocene to Plio- Undulating Fine textured, 1190 km 2 cene interbed- plains with saline,

ded shale and scattered low patches of sandstone; hills; radial reddish soils. marl and pinnate Orthents,

drainage Tropepts, Us- talfs, Ustults, Camborthids, Chromus- tens, Torrior- thents

XI Quaternary al- Gently undulat- Same as X and 1310 km 2 luvial deposits ing plains, lo- Ustifluvents,

in tectonic ba- calized sea- Argids, Or- sin sonal and thids, Usterts,

permanent Ustolls flooding; dendritic to parallel drainage

XII Same as XI Flat lowlands, Same as X 3240 km z seasonal and

permanent flooding, bor- dered by low hills; parallel or dendritic

x I i I Eocene to Mio- Undulating Shallow, lithic 1470 km z cene interbed- plains, low or fine tex-

ded sandstone foothills and tured overlain and shale elongated by salt de-

buttes; Den- posits in dried dritic and water courses. pinnate Orthents, Or- drainage thids, Argids

XIV Quaternary de- Intermountain Medium to fine 680 km 2 posits valleys; textured. Or-

featherlike thents, Or - drainage thids, Argids

XV Upper Creta- Low, flat plains Very heteroge- 2530 km z ceous to Pa- with isolated nous, medium

leocene ig- hills; den- to fine tex- neous rocks, dritic very tured. Tor- Tertiary de- sparse to dif- riorthents, posits fuse drainage Torripsam-

ments, Cam- borthids, Aq- uents, Zor- rerts, Orthids, Orthents

Pasture, patches 20-500 m Cattle raising, of deciduous 2%-25% subsistance seasonal for- farming est

Same as X, patches of deciduous seasonal forest with upper layer of scle- rophyllus trees

Same as XI

0-160 Cattle raising 0%-1%

80-300 m Cattle raising, 0.1%- 16% permanent

crops (coconut)

Thorn scrub 80-200 m Goat herding on and thorn 2%-6% natural vege- woodland ration

Pasture, decid- 375-600 m Cattle raising, uous seasonal 6%- 13% goat herding forest, gallery on natural re- forest getation

Thorn scrub, 0-100 m Goat herding on thorn wood- (830 m) natural vege- land, dry ev- 0%-1% tation, subsis- ergreen bush- tence farm- land ing, annual

crops

aThe names of the systems are given in the legend of Figure 4.

major environmental factors: climate, geology and geomorphology, vegetation, soils, and hydrology.

Each physiognomic unit is described on a standardized format or ecogram, as shown in Figure 3. The polygonal figure shows the physical nature of the habitat,

and was constructed in the fashion of the Lutz phyto- graphs (Shimwell 1971). Each axis represents a physical parameter. The parameters were ranked in such a way that the higher the value, the more limiting was the condition. The lowest value for each parameter lies on

240 s.o. Matteucci and others

",, t - "

71000 , 70~30 '

70000 9

Villa

LAND SYSTEMS IN FALCON STATE

69~ ' I 69000 , 68~ I

t 11o30,

11000 9

KM

1'0 0 10 20 30

,-~ Boundary between systems ,"" Boundary between homogeneous units

Figure 4. Land systems and homogeneous units (HU) in Falc6n State. Land systems are indicated with roman numbers and HUs with letters:/, Planicie Aluvial Occidental; II, Sureo de Urumaco; III, Planicie Aluvial Mitare-Seeo; IV, Piedemonte Costero; V, Serran[a Bariro-Pedregal; 111, Alineaci6n Central Occidental; VII, Alineaci6n Meridional; VIII, Serranla de San Luis; IX, Alineaci6n Central Oriental; X, Alineaei6n Septentrional Oriental; XI, Cuenea del Hueque; XII, Valles Mar~timos; XIII, Sistema de Depresiones; )(IV, Valles Intermontanos; XV, Peninsula de Paraguan~.

the perimeter, and the values increase centripetally. Thus, the polygon shape and size give a visual indication of the physical condition of the land. The climatic diagram follows Gaussen's design (Walter and others 1975); it corresponds to the station in the unit or to the nearest station in a similar topographic position. Vegeta- tion structure is shown in a layer diagram.

In a final report, a general description of each system is given, as shown in the example of Table 3. Ground photographs and stereograms are added to illustrate major features. The distribution of the systems and homogeneous units is presented in the map (Figure 4). A summary of the main characteristics of the 15 land systems is given in Table 4.

Discussion

Land surveys endeavour to divide a region into com- prehensive units. If the task is carried out on the basis of sound ecological principles, the classification approaches a natural system with standardized attributes. Hence, the

results can be used for various purposes. Uniform land tracts can be assessed and classified in terms of their suitability for one or more forms of land use or for nature conservation, taking into account those attributes relevant for the purpose at hand. The classification can also serve as a framework for the extrapolation of the results of site research, or for the choice of sites or resources on the basis of a global appreciation.

Even though parametric methods for land classification that permit extensive statistical treatment and com- puterized analysis of data are now available, the landscape approach allows quick identification of uniform segments at various levels of generalization, an d provides a framework for objective data gathering. The use of a "poor man's approach," in which conventional data collection and analysis, as required for a parametric method, are replaced as far as possible by a maximum of less formal observations, is of great practical value as a first approximation to a regional land survey of large regions. In some situations, it is the only applicable approach. Limitations imposed on the results can be


overcome by further study of selected land tracts, once those with less potential for the desired purpose are eliminated. Gaps of knowledge with reference to biologi- cal and physical attributes, identified in the course of the first approximation, can be filled, as detailed studies are undertaken in the chosen land units. At this stage, the assumed degree of uniformity in landform, geology, soil, and vegetation within a certain land category should be subjected to rigorous correlation tests, in order to verify the basic assumptions. Thus, the system not only allows the collection of additional data, but it also permits the improvement of the model through an iterative process.

There is a discussion over terminology, as regards the definition of different categories of land-units. This is due to the fact that the names proposed by the Australian researchers are used with various connotations by different authors. In order to avoid adding to the confusion, we preferred to give other names to our land-units. However, the physiognomic unit is equivalent to the land facet as defined by Perrin and Mitchell (cited in Cooke 1977) as "one or more land elements grouped for practical purposes; part of a landscape which is reasonably homogeneous and fairly distinct from surrounding terrain." From the practical point of view, these units would respond uniformly to a certain management practice; they may constitute the basis for the delimitation and identification of agroecosystems. The homogeneous units represent an intermediate category between CSIRO's land-unit and land system. They were introduced to account for situations in which, within a land system, there exist units evolving towards recovery and units suffering a desertification process; thus, though their landform and soils do not differ greatly at the present moment, they differ in their potential natural vegetation. Similar responses to management practices cannot be expected. Land systems, described in terms of major landform and geologic history, are equivalent to CSI- RO's complex land systems (Christian and Stewart 1968).

In this survey, scant regard was given to the human factor. Following FAO's recommendation (FAO 1976) and in view of the extension and complexity of the area, the social analysis was left for a future stage in the survey of selected zones. The results of the survey allow for the choice of promising sites and resources on the basis of the physical and biotic characteristics only. The final decision requires consideration of the cultural and economic components of the system.

Acknowledgments

The research reported herein was supported by the Research and Development Convention (National

Research Council, Venezuelan Science Research Insti- tute, University Institute of Technology of Coro, Central University of Venezuela, National University Francisco de Miranda). The preparation of the manuscript was financed by the National Research Council of Venezue- la.

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