Spatial - Ecological Assessment of Land-use / Land-cover: Caparo River Valley, Republic of Trinidad & Tobago

2008-08-07T22:25:46Z

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Spatial - Ecological Assessment of Land-use / Land-cover: Agriculturally-disturbed "Tropical Moist Forest (Cool Dry Transition)" in the Caparo River Valley, Republic of Trinidad & Tobago

Authors: Karl Ramjohn, Floyd B. Lucas, Carol L. Ramjohn & Winston Johnson, Tropical Environment Research & Management Center, Trinidad & Tobago. January 2006

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ECOSYSTEMCLASSIFICATION & FUNCTIONAL DYNAMICS

Beard(1946) classified the study area as being predominantly Seasonal Evergreen Forest (mixed Crappo-Guatecare). Beard�s study (which remains as the onlycomprehensive ground-based island-wide assessment of flora) focussed on classificationsbased on dominants within the community, mainly from an economic timber andForestry management perspective. Those classifications represent conditions ~60years ago, and several of the species assemblages described by Beard (1946) areno longer recognizable, having undergone significant alterations, fragmentationand conversion into secondary forest and other land-uses (Ramjohn et al.2001, Joseph 1999, Nelson 1999).

A more recent study by Nelson(2004), which attempted classification of indigenous forests based on alandscape-ecology and ecosystem-management perspective, delineated Trinidad into two majorterrestrial eco-regions � Dry Forest and Moist Forest. According to thatstudy, the project site (confluence of the Caparo andMamoral Rivers) is locatedapproximately on the boundary between the two eco-regions; thus it may beregarded as being within a transition zone between two significant moistureregimes. Based on maps prepared by Nelson (2004), the middle and upper reachesof the Caparo Basin would be in thewetter region supporting �Tropical Moist Forest�, with the lower catchment in the drier region classified as �Tropical Moist Forest, Cool DryTransition�.

The long history of agriculturalactivity in the Caparo Valley has resulted insignificant alterations to the native vegetation and forests. In general,higher-quality closed-canopy forest remains only as a few patches in this area(Nelson 2004). These forested remnants largely persist on the higher slopes ofthe occasional spurs and ridges, such as the area immediately north of theproject site. The higher-integrity forest remnants persist as patches embeddedin a wider (macro-habitat) matrix of cultivated areas, grassland/lastro and secondary forest. As a result of the traditionalland-use patterns, much of the vegetation resources in the immediate vicinityof the confluence are of agricultural origin. Therefore, while natural andsemi-natural vegetation exists in the surrounding area, the agronomic aspectsof the biological environment will have a more dominant role in defining thesite�s ecological character.

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From an ecosystem perspective,agricultural production systems may be regarded as restructured and simplifiednatural environments, as they rely on plant-based biomass productivity throughphotosynthesis, nutrient recycling via microbial activity, etc. However,their functioning requires subsidised ecological processes, and their habitatstructure and complexity (as well as spatial arrangement of biota) areintentionally simplified and controlled, to focus on the productivity of asmall number of targeted elements. Agricultural ecosystems are land-use unitscomprising soil, crop, tree, weed, livestock, pathogen and insect sub-systemsthat continuously interact to transform solar energy, water, nutrients, labourand other (e.g., agro-chemical) inputs into biomass yields as food, feed, fuel,fibre and pharmaceuticals.

Furthermore, even in areas of Trinidad where secondaryforests have regenerated via natural succession (subsequent to agriculturalabandonment), the historical land-use patterns areoften critical factors in determining the ecological integrity of the�replacement� ecosystem. Depending on the type of previous cropping systems,physical and biological remnants of the agricultural activities may stronglyinfluence (either beneficially or adversely) their natural sucessiontrajectories, as well as ecosystem structure and function, and related trendsin their biodiversity and other natural resources.

Archival land-use maps indicate that in thispart of Trinidad, agriculture was dominated by Cocoa (Theobromacacao) and Coffee (Coffea arabica) production to the north of the Caparo Valley BrassoRoad, with Sugar Cane (Saccharum sp.) cultivation dominating to the south of the road. Thus, the projectsite was in an effective boundary zone between the two major historicalexport-cropping systems of economic importance. At present, there is little Cocoa production remaining in theimmediate area, although Sugar Cane cultivation still takes place within partsof the study site. Much of the agricultural land formerly under Cocoa was subsequently cultivated withCitrus (Citrus sp.), especially a 1200-acre site downstream in the Palmiste/Todds� Road area. In the wider study area, landstill under Cocoa/Coffee production is located higher in the catchment of the Caparo River, such as BenjiTrace (approaching Flanagin Town).

Table-01: UTM Coordinates of Vegetation Survey

Table-02: Vegetation Species Recorded for Caparo / Mamoral Site Surveys

VEGETATION CHARACTERISTICS & LAND-COVER QUALITY

The project site for the surveys wascentred in the area surrounding the confluence of the Caparo and Mamoral Rivers. Assuch, the primary focus for site characterization was on the area around CarrCaparo Trace, Carr Mamoral Trace, Lynch Trace (Mamoral Road),and the stretch of the CaparoValley Brasso Roadadjacent to the proposed development. However, to assist in fitting theproposal into the existing land-use and development patterns of its landscapeunit (in the context of cumulative impacts), an overview of ecologicalconditions was obtained by paying brief visits to other areas along the CaparoValley Brasso Road (both north and south of the site), including Palmiste,Todds� Road, Chickland/Caparo Road, Santa Phillipa Road, Benji Trace andFlanagin Town.

The vegetation surveys at the site (andsurrounding areas) revealed four broad classes that can be used to describe theland-use/land-cover from a spatial/ecological perspective. These are summarizedin Table-03:

Table-03: Summary of Land-use / Land Cover at Project Site

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IMAGE-01: EXAMPLES OF LAND-COVER / TERRESTRIAL VEGETATION AT CAPARO / MAMORAL

Image-01-01:Semi-closed Riparian Vegetation Community, Caparo River (Downstream ofConfluence) {Photo: Karl Ramjohn, January 2006}

Image-01-02:Open/disturbed Riparian Vegetation Community, Caparo River (Upstream ofConfluence) {Photo: Karl Ramjohn, January 2006}

Image-01-03: Semi-open Riparian Vegetation Community, Caparo River (Upstream of Confluence) {Photo: Karl Ramjohn, January 2006}

Image-01-04: Flat grassland in river valley backed by forested ridge ofhigher elevation, Carr Mamoral Trace {Photo: Karl Ramjohn, January 2006}

Image-01-05: Grassland along Caparo Valley Brasso Road (Riparianvegetation along Caparo River, background) {Photo: Floyd Lucas,December 2005}

Image-01-06: Mixed forest land-cover on edge of Mamoral Cemetary, Lynch Trace {Photo: Karl Ramjohn, January 2006}

IMAGE-02: EXAMPLES OF AGRICULTURAL VEGETATION AT CAPARO / MAMORAL

Image-02-01: Small-scale food cropping on banks of Caparo River, off Carr Caparo Trace {Photo: Karl Ramjohn, January 2006}

Image-02-02: Cassava (Manihot escuelenta) cultivation along Caparo River, off Carr Mamoral Trace {Photo: Floyd Lucas, December 2005}

Image-02-03: Sugar Cane (Saccharum officinarum) cultivation along Caparo River, Carr Mamoral Trace {Photo: Karl Ramjohn, January 2006}

Image-02-04: Pigeon Peas (Cajanus cajun) and other food crop cultivation, Lynch Trace {Photo: Karl Ramjohn, January 2006}

Image-02-05: Citrus Estate at Todds' Road, off Caparo Valley Brasso Road (north of site) {Photo: Floyd Lucas, December 2005}

Image-02-06: Cocoa / Coffee Estate at Benji Trace, off Caparo ValleyBrasso Road (south of site) {Photo: Karl Ramjohn, January 2006}

RIVERBANK VEGETATION

Asnoted on Table-03, three main classes of vegetation were found growing in theriparian zone along the Caparo and Mamoral Rivers within the studyarea:

(i) Semi-closedriparian community

(ii) Semi-openriparian community

(iii) Open /disturbed riparian community

(i) Semi-closedriparian community

Typical examples ofthis class along the river bank are indicated on Image 01-01 and arepresentative example of the vegetation was surveyed at Site V-03 and alongthe boundary of Site V-02. The classifications as �semi-closed� and �semi-open�do not represent absolute distinctions (in that no physical measurements ofcanopy-closure were done). However, they were based on visual inspection andother on-site observations of the ecosystem processes/functions such asmicro-climate/micro-habitat conditions, in terms of the degree of �shade�provided to the river channel by the riparian communities, as well as otherambient indicators of moister conditions, such as communities of mosses on theriverbanks (above the high-water mark) and on the branches/trunks, the presenceof Myceteae, and the degree (and likely dynamics) ofplant-derived organic matter (e.g., leaf litter) on the forest floor.

In terms of their ecology, these patchesmay be seen as representing higher-quality habitats along the river. However,this represents the habitat conditions in terms of their form and functionaldynamics, as opposed to their botanical representativeness(i.e., presence or absense of native trees andrelated plant assemblages). They persist mainly in areas of the riverbank onCarr Mamoral Trace that are too steep or narrow to becultivated and have regenerated to more �natural� conditions.

The main trees identified in these areasincluded Jamoon (Syzygiumcumini), Hog Plum (Spondiasmombin), Angelin (Andira inermis), L�Epinet (Fagara marticensis), Water Immortelle (Erythrinafusca), Conore (Lonchocarpus domingensis),Milkwood (Sapium glandulosum) and Manjak (Cordia collococca).These can generally be regarded as widely distributed native trees often foundin riparian or other water-associated habitats. In these areas, their structuralsignificance is in the provision of conditions bearing higher resemblence to natural canopy. The presence of Roseau (Bactris major), Balisier(Heliconia bihai)and Souhari (Calathealutea), as well as stands of larger graminoid-type vegetation such as Bamboo (Bambusa vulgaris)and Wild Cane (Gynerium sagittatum)and vines like Dutchman�s Pipe (Aristolochiagrandiflora), would assist in sealing off thehabitat edge (with respect to direct sunlight) thereby enhancing themicro-climate conditions experienced here. Moisture-holding plants like Balisier also provide niche micro-habitat conditions thatsupport specialized aquatic faunal communities.

Unlike other areas (such as Carr Caparo Trace), the river channel does not appear to havebeen dredged at these locations, which is also likely to have a role in themaintenance of the observed conditions. The river banks are typically steepwith a drop of ~2.5 to 5 m to the river. Within the river channel itself, therewas a high degree of heterogeneity in the substrate (in terms of depth andtopography), with rocky areas and significant amounts of semi-submergedbranches and trunks. Beyond the (average) high-water mark in the channels,thick communities of encrusting mosses were observed to have colonized the heavy-claysubstrate on the sloping banks. Micro-habitats of mosses and similarcommunities were also observed on the trunks and branches of the standing treesin the more-shaded areas.

Overall, the vegetation patches withmicro-climate supporting semi-closed riparian communities may be viewed asminor pockets of higher productivity, biological resource value, andcarbon/energy storage (organic matter pools) in the wider landscape ofagricultural and other disturbed habitat surrounding the Caparo/MamoralRiver system.

(ii) Semi-open riparian community

Typical examples of this class along theriver bank are indicated on Image 01-03 and a representative example of thevegetation was surveyed at Site V-07. Superficially, the �semi-open� areas appearto support similar conditions to the �semi-closed� riparian habitat describedabove. However, there is considerably less of a canopy development with the�shaded� conditions in the channel mostly resulting from thick stands of Bamboo(Bambusa vulgaris)and occasional (lower density of) trees. As such, the habitat is more open todirect solar radiation for several hours each day.

The trees recorded for these areasincluded Mountain Immortelle (Erythrina poeppigiana), Water Immortelle (Erythrinafusca), Angelin (Andira inermis),Hog Plum (Spondias mombin),Black Fiddlewood (Vitex divarcata),Milkwood (Sapium glandulosum), Manjak (Cordia collococca)and Jereton (Scheffleramorotoni), together with pioneer species likeWild Tobacco (Acnistus arborescens)and Bois Canot (Cecropiapeltata). The moister conditions have led to theriverbanks being widely colonized by Wild Dasheen (Colocosiaesculenta); however, there was little evidence ofBalisier or other Heliconiaspecies.

(iii) Open/ disturbed riparian community

The riparian vegetation in these areasis represented by plant communities (mainly grasses and cultivated speciesother than tree crops) indicative of disturbance. This class is very common in Trinidad in areastraditionally associated with agriculture. Typical examples of this class areindicated on Image-01-02 & Image-02-01, and a representative example of thevegetation was surveyed at Site V-11, in addition to which basic observationson vegetation were made at aquatic survey Site MD-3 (which was associated withan open/disturbed habitat of this nature). In these areas, the river banks havebeen entirely cleared of trees and other native riparian vegetation, usually tofacilitate agriculture. In some parts of the study area, the open/disturbedriver banks were not cultivated at the time of the survey; however, in othersthere were crops on the banks (or in the immediate vicinity) especially by thebridges on Carr Caparo Trace (Site V-11) and Mamoral Road (Site MD-3).

The healthier riparian ecosystemsdescribed (i.e., semi-closed riparian class) were characterized bysparsely-vegetated channel slopes (primarily mosses), as a result of the moistconditions with limited sunlight penetration on the ground-level. In contrast,the banks of the open/disturbed areas were bounded by thicker vegetation suchas grasses and vines, with the immediate area of the banks dominated by WildDasheen (Colocosia esculenta),and Water Grass (Commelina erecta and Commelinadiffusia). These are supported by the perpetuallymoist organic soils with unimpeded exposure to sunlight; Dasheen in particularthrive in high-nutrient, water-saturated soils (Gouveiaet al. 1994).

Some of the river banks withopen/disturbed vegetation were associated with Sugar Cane production. However,in some areas small plots of vegetable cultivation were also seen in theriparian zone. These were mainly herbaceous crops like Cucumber (Cucumis sativus),Pak Choi (Brassicachinensis) and Lettuce (Lactucasativa), as well as Ochro(Abelmoschus esculentus)and Pigeon Peas (Cajanus cajan).

The trees present in the areasclassifiable as open/disturbed habitat had a greater tendency to be isolatedand thus not associated with the development of a canopy. These were mainlytrees commonly recorded for the study area, such as Jamoon(Syzygium cumini),Water Immortelle (Erythrina fusca), Milkwood (Sapium glandulosum),and Pink Poui (Tabebuiarosea). Close to Site V-11 a few Teak (Tectona grandis)and Caribbean Pine (Pinus Caribea) trees were observed in close association witha small cluster of Roseau Palms (Bactrismajor). Teak and Pine are two of the major (introduced) species planted bythe Forestry Division for the commercial timber industry. However, at thissite, they were not part of a forest plantation and had probably been plantedby an individual smallholder (incidental to the croppingsystem).

RIVERVALLEY VEGETATION

As noted on Table-03, three main classesof vegetation were found growing in the alluvial flat land in the low-lyingvalley areas along the Caparo and Mamoral Rivers within the studyarea:

(i) Activeagricultural land (occupied by crops)

(ii) Inactiveagricultural land (grassland / scattered trees)

(iii) Village /residential (fruit trees, ornamentals, etc.)

(i) Active agricultural land

While almost all of the flat land in thearea surrounding the Caparo/Mamoral River system maybe classified as agricultural, not all such areas were under active cultivationat the time of the vegetation surveys. Typical examples of land classifiable asbeing under �active� agriculture are indicated on Image-02-02 &Image-02-03, and representative examples of this vegetation would have beensurveyed in most of the areas within Sites V-02 to V-05 (along Carr Mamoral Trace).

The health and ecosystem function ofagricultural areas (both within and between sites) will depend on allcomponents of its ecological character: physical (climate/soils), biological �vegetation (crops, weeds, other plants) and fauna (pests, beneficial insects,livestock, and wildlife species associated with semi-open areas), human inputs(labour, energy, water, chemicals) and overall interactions. In a spatial,ecological (and commercial) sense, the most significant cultivated crops withinthe project site (Caparo/Mamoral confluence) areCassava (Manihot esculenta) and Sugar Cane (Saccharum officinarum). These two cropscover most of the larger agricultural plots under active cultivation. Smalleramounts of other short-term food crops are planted commercially in this area,such as Pigeon Peas (Cajanus cajan), Ochro(Abelmoschus esculentus),Sorrel (Hibiscus sabdariffa), Pawpaw (Carica papaya) and Banana (Musa sp.), as well as an area on Carr Mamoral Trace in which �Portugal� Oranges (Citrus sp.)are cultivated. The wider area does not have a pipe-borne water supply (relyingon water-trucks) and thus it is likely that the river is used both as a sourceand a sink for agricultural water.

In theimmediate project area, Sugar Cane cultivation is focussed mainly between the Carr MamoralRoad and the river bank (Sites V-02 to V-05); however, unlike largerestates, it is not continuous within this area and is interspersed withCassava, grassland and other vegetation. Sugar Cane is a verylarge graminoid (grass-type) vegetation (growing upto 3 m tall) and on flat land areas they are typically planted on banks toprevent inundation during the wet season. Harvesting of the crop is generallypreceded by the systematic burning of the fields. At times of harvesting thesoil in these areas is left relatively exposed, which would have ecologicalimplications associated with increased erosion potential and run-off into theriver; however, the crop season is generally within the first few months of thedry season. The larger monocultural areas of SugarCane in CentralTrinidadhave been described as representing effective �deserts� for many species ofwildlife (personal comments Graham White). However, based on observationsfor the present survey, this effect may be less drastic at the project site, asa result of the relatively small areas under Sugar Cane cultivation (and thelack of spatial continuity between such areas).

As a result of favourable soilcharacteristics and other factors, Cassava is the most commonly cultivated rootcrop in the Caparo Basin (Grant et al.1996). This is a broadleaf shrub that grows to heights of 2 m; however, thetargeted component is the root tubers (i.e., its below-ground biomass). Cassavacropping requires considerable soil disturbance and modification to organicmatter and nutrient regimes (Kellman & Tackaberry 1997). It is usually planted on banks (which arekept clear of weeds), generally at the start of the annual wet season and harvestedabout 8-9 months later (Seesahai 1996); however, thevarying size of the plants seen in the study area during January 2006 indicatesthat there is not strict adherence to this technique. A study by Grant et al.(1996) on small Cassava farms at Longdenville (lowerdown in the Caparo Basin) described theproduction system as �chemically-intensive� (fertilizers, pesticides, etc.).Relatively large monocultures of Cassava were observed along the Carr Mamoral Trace, especially in the areas surrounding sitesV-02 and V-03 (closer to the river, on the edge of the larger Sugar Canefield).

(ii) Inactive agricultural land

Typical examples of land classifiable asbeing �inactive agricultural� are indicated on Image-01-04, and representativeexamples of this vegetation would be found throughout Sites V-02 to V-05,especially in the area surrounding Site V-04. While inactive agricultural areasdominated by grassland are often described as �abandoned� or �lastro�, in this area it is considered likely that the landis used for agriculture at other times (and left in its current grassland stateas part of a fallow system).

Overall, grasslands at inactiveagricultural areas are often regarded as �fire-climax� ecosystems (especiallywhere they bound Sugar Cane cultivation), and tend to exhibit landscapesimilarity to savannas, as they are characterized by a few dominant grasstypes, with scattered individual (or occasional clumps of) trees. However, theyare structurally and functionally simpler and considerably less diverse orunique than the natural savanna ecosystems that havedeveloped in other parts of Trinidad (Armstrong et al.2004, Comeau & Clubbe1998). The graminoid-dominated inactive agriculturallands in Trinidad may also be regarded as representingareas of �arrested succession� in the natural environment (personal commentsStanley A. Temple), since the exotic (non-native) grass species typicallycolonizing these ecosystems tend to inhibit the rate at which natural forest regeration takes place.

Inactive agriculture land along Carr Mamoral Trace is dominated by coarse perennial grasses,mainly Bull Grass (Paspalum fasciculatum) with some Elephant Grass (Pennisetum purpureum)in wetter areas. The grasses are interspersed with vines such as Kudzu (Pueraria phaseoloides)and other small herbaceous flowering plants on the roadside, such as Railway Daisey (Bidens alba). Several variably-sized patches of Bamboo (Bambusa vulgaris)were also observed in the grassland areas on inactive agricultural land alongCarr Mamoral Trace. While this is a non-nativespecies in Trinidad (originating in the Asian tropics), Bamboo has becomewidespread throughout the island, especially as an early-stage sucession component of the vegetation in agricultural orother frequently disturbed areas (Teixeira & Oatham 2001), often with dispersal and colonization by�natural� means.

Atthe inactive agricultural site surveyed along Carr MamoralTrace, one species of significance among the scattered trees was the Royal Palm(Roystonea oleracea).This very tall straight-growing palm that attains a height of 30 � 50 m, is tolerant of a wide range of environmental conditionsand is thus fairly widely distributed. Black Fiddlewood (Vitexdivaricata) is another fairly large native treeobserved in this area.

(iii) Village/ residential

This class is used to describe thevegetation typically found in the village areas adjacent to the project sitethe along the Caparo Valley BrassoValley Road (e.g., Site V-10); it is also used to account for the differencesin vegetation found at the small clusters of houses and isolated residences inthe agricultural land along Carr Caparo Trace andCarr Mamoral Trace (e.g., Sites V-02, V-03, V-04 andV-11).

The gardens of the houses usually haveornamental plants such as small palms, flowering shrubs and shade trees, manyof which are non-native species. Also, some small-scale food cropping usuallytakes place in the immediate vicinity the houses, primarily for householdconsumption (as opposed to the larger commercial production of Cassava andSugar Cane in this area). However, the main difference observed around housesis the greater presence of trees. The trees surrounding the housing areas atthe project site are predominantly fruit trees� Coconut (Cocosnucifera), Mango (Mangiferaindica), and Breadfruit (Artocarpuscommunis) with lesser amounts of Pommerac (Syzygium malaccense), Pewa (Bactris gasipaes)and Plum (Spondias purpurea)trees, as well as occasional Cashew (Anacardiumoccidentale) and Betel Nut (Areca catechu).

Roadside vegetation in these areastypically consists of widely dispersed grasses, other herbaceous plants andshrubs such as Fowl-foot Grass (Eleusine indica), Savanna Grass (Axonopus compressus),Railway Daisy (Bidens alba),Sensitive Plant (Mimosa pudica), Broom Weed (Sida acuta),Stinging Nettle (Laportia aestuans), Wild Hops (Flemingiastrobilifera), St. John�s Bush (Justicia secunda)and Candle Bush (Piper tuberculatum).

2.3.3.3 Intermediate Upland Vegetation

The immediate north of the study site ischaracterized by a comparatively steeply-sloping ridge, which rises to anelevation of ~100 m. As noted on Table 2-10, three main classes of vegetationwere observed in this area:

(i) Forest patches in higherelevations (remnant indigenous, secondary)

(ii) Hillside / valley croppingsystems

(iii) Village /residential (fruit trees, ornamentals, etc.)

(i) Forest

On higher ridges of hill to immediatenorth of site (not directly accessed for the current survey) the vegetation isdominated by tree species typical of seasonal evergreen tropical forest. Thecomposition of the plant community will be a combination of the speciesrecorded in the lowlands (which tend to be forest species that are easilydispersed) and other tree species more indicative of the natural plantcommunity.

Angelin (Andirainermis), Hog Plum (Spondiasmombin), Black Fiddlewood (Vitexdivarcata), Milkwood (Sapium glandulosum),Manjak (Cordia collococca), Olivier (Terminaliaamazonia) and Jereton (Schefflera morotoni)are some of the main species likely to be encountered in these areas, based ontheir occurrence in survey points on the edges of the forested ridge (e.g.,Sites V-12 and V-13). The main difference is that on the higher slopes, ahigher-quality canopy structure (and therefore ecological integity)is to be expected. Species such as Acurel (Trichilia oblanceolata)and Wild Chataigne (Pachirainsignis), though not encountered in the survey,may be found on steeper (less accessible) slopes. Notwithstanding this, it isless likely that the dominants of the seasonal evergreen formation (Crappo-Guatecare association) as described by Beard (1946)will remain on these slopes, particularly Crappo (Carapa guianensis)and Guatecare (Eschweilerasubglandulosa) as they are much sought after andextracted for their timber.

(ii) Hillside / valley croppingsystems

Typical examples of higher land underagricultural use (hillside / valley cropping) are indicated on Image-02-04, andrepresentative examples of this vegetation were surveyed at Sites V-06 andV-12. While the higher land and ridges of the hill formation to the north of theproject site remains primarily under forest or forest-derived vegetation cover,some agriculture was observed to be taking place. For example, while mostcultivation along Carr Mamoral Trace was within theflat alluvial valley (already described), some cultivation was observed on thelower slopes of the ridge to the extreme north of this area. Such activityfocussed on Cassava (Manihot esculenta) cultivation andappeared to be having only a minor �footprint� impact, in relation toencroachment on the bulk of the surrounding upland forest vegetation andstructure.

In relation to this higher elevationfeature, the main area of hillside/valley cropping was on a lower part of theridge (~30 m), in the eastern part of the project site. In that area, thesouth-facing slope is bounded by Carr Mamoral Traceand was not under active cultivation at the time of the survey, dominated bygrassland with tall isolated trees (mainly on the top of the ridge). Thenorth-facing slope is bounded by Lynch Trace (Site V-06 just north of Mamoral Cemetery) and this slope wasextensively cultivated by a monoculture of Pigeon Peas (Cajanus cajan). Lynch Trace alsoaccesses the forest on the adjacent higher parts of the hill, and in thevalleys of this area cultivation of almost exclusively Pigeon Peas with lesseramounts of Ochro (Abelmoschusesculentus) was observed. However, this area canbe distinguished from the flatland agriculture surrounding the Caparo/Mamoral confluence by the higher degree offorest-derived vegetation surrounding the plots.

Generally, the entire hillsides are notunder crops, the cultivated areas are patches of plots, which exist in closeassociation with the upland forest and forest-derived ecosystems. The roadsidealong Lynch Trace was dominated by forest-edge vegetation such as Bois Canot (Cecropia peltata), Bois Flot (Ochroma pyramidale),Wild Tobacco (Acnistus arborescens),Black Sage (Cordia cussaravica)and extensive stands of Bamboo (Bambusa vulgaris). However, larger trees were observed in thesurroundings including Mountain Immortelle (Erythrinapoeppigiana), Water Immortelle (Erythrina fusca), Roble (Platymiscium trinitatis), and Hog Plum (Spondiasmombin) as well as palms such as Carat (Sabal mauritiiformis)and Royal Palm (Roystonea oleracea).

Other areas with hillside/valleycropping were surveyed on the northern side of the ridge (Site V-13), accessedvia Carr Caparo Trace. The main crops observed wereCassava and Sugar Cane. However, an even higher diversity of native trees wasobserved in this area (several of which were not recorded for the lowland partsof the study area) including Cuchape (Coccoloba latifolia),Olivier (Terminalia amazonia),Cocorite (Attaleamaripa), Kiskidee (Vismia cayennensis),Bois d�Orme (Guazumaulmifolia), L�Epinet (Fagara marticensis)and Juniper (Genipa americana),as well as Teak (Tectona grandis) and Mahogany (Swieteniamacrophylla).

(iii) Village/ residential

This area is an effectivelylinear/clustered settlement along parts of the ridge road (accessed from Carr Caparo Trace), with the houses surrounded by (andinterspersed with) secondary forest and agriculture. Representative examples ofthis vegetation were surveyed at Site V-12. In addition to the typicalornamental plants, fruit trees and small-scale cropping at the houses (asdescribed for the flat land areas on Carr MamoralTrace), the plant community in this area contains tree species that areremnants of the wider forest areas, such as on the higher elevations on theadjacent ridge (immediately south of the houses).

Species such as Hog Plum (Spondias mombin), Manjak (Cordia collococca), Bois d�Orme (Guazuma ulmifolia),Jereton (Scheffleramorototoni) and Black Poui(Tabebuia chrysantha)were recorded on the southern side of the road. On the opposite side of theroad there were a few Teak (Tectona grandis), Castilloa Rubber (Castilla elastica),Mahogany (Swietenia macrophylla)and Mango (Mangifera indica)which are all introduced species and most likely planted in the area in thepast. Roadside vegetation consisted of Bull Grass (Paspalumfasciculatum), Wild Hops (Flemingiastrobilifera) and the vine Kudzu (Pueraria phaseoloides).

SPATIAL� ECOLOGICAL DATA REPRESENTATION

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The first blog : Hydro Terrestrial

Spatial - Ecological Assessment of Land-use / Land-cover: Caparo River Valley, Republic of Trinidad & Tobago