The role of the tree as an indicator of dynamics of development of the ngoko area, chad

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*Corresponding author: Frédéric REOUNODJI ISSN: 0976-3031

Research Article

THE ROLE OF THE TREE AS AN INDICATOR OF DYNAMICS OF DEVELOPMENT OF

THE NGOKO AREA, CHAD

Denis GAUTIER

1

,

Frédéric REOUNODJI*

2

, Nicolas KARR

3

and TAPSOU

4

1

Researcher at CIRAD, Montpellier, France

2

Teacher-researcher at the University of N'Djamena, Chad

3

Montpellier, France

4

Researcher at IRAD, Maroua, Cameroon

DOI: http://dx.doi.org/10.24327/ijrsr.2019.1010.4117

ARTICLE INFO ABSTRACT

Starting from the hypothesis that the tree, a perennial element of the landscape, bears in its forms of integration with the rural systems of Sahelo-Sudanese Africa, the marks of processes of development of space, we have attached ourselves to finely analyze our systematic forest inventory data and model their spatial distribution, in order to understand the processes involved. Thus, the average height of the trees in the fallow / bush plots informed us about their age. The report "strain rate / stalk density" informed us about the origin and age of the parks. The cartography of this information revealed to us a spatial process of agricultural development by the inhabitants of Ngoko in "center periphery", with an asymmetry of the expression of the halos between the southern and northern parts of the soil, because of the localization. from the center of the village. Land, wood and fertility resources are moving away from the center of Ngoko, whose territory seems to tend towards saturation uniformity.

INTRODUCTION

The Ngoko territory in southern western Chad is highlighted by a community of agro-pastoralists, Musey, who founded the village in 1974. Agricultural development developed from the habitat grouped in the center of the territory, on the basis of cotton-cereals or cotton-cereals-peanut rotations, followed by fallows whose duration has narrowed with time. These cropping systems are associated with domestic (mainly Musey) and extensive (Fulani) pastoral farming.

The integration between agriculture and animal husbandry is quite successful, leaving corridors for livestock passage between crops and pastures (Gautier et al., 2006). This equilibrium is however threatened by the continuation of the conquest of agricultural lands in a territory in the process of land saturation. Based on the idea that the tree, a perennial element of the landscape, bears on it and in its forms of integration with the rural systems of Sahelo-Sudanese Africa, the marks of the processes of enhancement of space, we hypothesized that a detailed spatial analysis of the forest inventory data could inform us about the development processes of the Ngoko space.

After presenting the inventory method and its results, we were interested in the spatial distribution of agroforestry types and the processes that can be highlighted.

The Inventory Method

The forest inventory protocol had to meet two requirements: cover the entire small rural study area, so that inventory data could be cross-checked with mapping and survey data; to distinguish at least the cultivated sectors from the non-cultivated sectors.

We thus opted for a sampling inventory, systematic and stratified. Plots were set up every 200 meters, along 200-square meters of equidistant strips, to survey the entire territory. The sizes of the plots were 80m x 80m if the inventory point fell in the fields and 20m x 20m if it fell in natural formation. The survey rates were thus 16% for the parks, which is a lot, but is a response to the great heterogeneity of these parks, and 1% for natural formations, which corresponds to the figures announced in the literature.

International Journal of

Recent Scientific

Research

International Journal of Recent Scientific Research

Vol. 10, Issue, 10(E), pp. 35509-35513, October, 2019

Copyright © Denis GAUTIER and Frédéric REOUNODJI, 2019, this is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.

DOI: 10.24327/IJRSR

CODEN: IJRSFP (USA)

Article History: Received 13th July, 2019 Received in revised form 11th August, 2019

Accepted 8th September, 2019 Published online 28th October, 2019

Key Words:

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Denis GAUTIER and Frédéric REOUNODJI., The Role of the Tree as an Indicator of Dynamics of Development of the Ngoko Area, Chad

Figure 1 Schematic of the applied forest inventory method

In addition to the plot description sheet (soil type, topography, traces of erosion, grazing, cultivation), measurements were made of:

 for plots in growing areas: the circumference and height of the trees, the treatment they have undergone (coppicing, pruning, debarking, annealing), as well as the circumference of recent stumps;

 for plots in non-cultivated areas: the relative rate of overlap of the different vegetation layers, the circumference of all trees more than 5 cm in circumference, as well as the traces of exploitation on the trees.

In practice, some raised plots were straddling two types and required us to move forward or back along the transect to have a homogeneous plot. If we add to this the fact that we were traveling on the compass, the measurements we made do not form a perfect checkerboard with a mesh size of 200 x 200 m, as shown by the projection of the record of these points on the merits. ofNgoko map. Nevertheless, thanks to this method, we have been able to inventory the entire territory of Ngoko by raising 141 plots, including 83 in cultivated areas and 58 in fallow-bush areas.

RESULTS OF THE INVENTORY

Overall characteristics of the two major types of land use

The characterization of the two major types of land cover that we have distinguished and their comparison can be done by dendrometric parameters (density, basal area), the distribution of the stems according to the circumference and the specific composition. The distribution of the stems according to the circumference in particular is an interesting parameter to be considered in order to discriminate the different types between them, to evaluate the mode of management that applies to it and the durability of the management.

In the fields, an aging park will tend to have a majority of individuals in the strong circumference classes and few in the weak ones; a park under construction will tend to have a majority of individuals in small diameters and few in large ones; finally, a mature park managed with a concern for sustainability will present a good distribution of different classes of circumference.

For fallow bush, the distribution of circumference classes gives an idea of the age of the stand and, possibly, the operating pressure for the fuelwood it receives.

In summary, the two major types of enhancement of the space integrating the tree can be characterized as follows.

 The Ngoko wooded park is moderately supplied (about 22 trees / ha, 75% over 20 cm tall), with fairly largeProsopisafricana, medium Anogeissusleiocarpus, some large Ficusingens, and stems of small sections. of Terminalia avicenioides, Combretummicranthum and Detariummicrocarpum. It can be assumed that the construction of these parks is rather recent (low percentage of stems of large circumference), that the peasants selected trees to constitute them some 10-20 years ago and that they do not are not yet in the stage of selecting young people to replace them (low percentage of stems of small circumferences).

 Ngoko's fallow and bush consist of numerous low to medium diameter stems of Combretummicranthum, Terminalia avicenioides and Detariummicrocarpum, some stems larger than the average Anogeissusleiocarpus, and a small number of stems. other species, in varying diameters. It is likely that these stands are rather young, so that most have already been exploited.

Characterization and typology of fallows / bush

In order to classify bush fallows, especially in relation to their age, and thus to the age of their cultivation, the parameter which seemed to us the most representative is the height of the stand.

The observation of the stand structure distinguishes 3 main classes:

 low fallow land, less than 1.5 m, which corresponds to fallow land about one year old;

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 Fallows of more than 3 m, which will be considered as old fallow (3 years old or more) or bush, without it seems useful to us to distinguish it.

Characterization and typology of trees in cultivated area

In order to understand the dynamics of cultivation of Ngoko, we were interested in distinguishing during our treatments inventory data, which was in the order of recent or old clearing. The clearings

In the inventories, a number of plots of cultivated areas clearly appeared to be cleared, and were noted as such in the field. However, a number of plots, which were simply noted as crop areas at the time of the inventory, have apparently become apparent in the processing of the data as cleared. This is particularly the case of plots on which many strains are located. It has therefore become necessary to develop simple criteria for discriminating newly cleared fields from cultivated areas for some time.

Characterization of clearings

One of the parameters measured during the inventory seems interesting to characterize the clearings: the strain rate. However, this criterion does not appear sufficient. On the one hand, we do not note a sudden variation in the strain rate which would have allowed, ideally, to discriminate cleared fields from the others. On the other hand, even with a high stocking rate, a plot may very well be located in an old crop area and the number of trees in the plot may be small. The total number of stems therefore also appears as a factor to be taken into account. We thus crossed the two parameters: strain rate and number of stems.

Figure 2 Strains rate of plots of growing areas

Two two types of cultivated areas are distinguished according to the location of the plots:

Plots with a large number of stems and a high rate

considered to be clearly cleared; the limit may be set at more than 54 trees in the plot;

Plots cultivated for a long time, with a low rate of strains (less than 50%).

The rest of the plots require further analysis and are examined on a case-by-case basis to determine whether they are long cultivated or recently cleared areas. In general, they can be clearly distinguished: plots with a low number of stems (less than 7) and high rates of strains can be considered as old cultures. The remaining plots (possessing more than 7 stems) Fallows of more than 3 m, which will be considered as old fallow (3 years old or more) or bush, without it

Characterization and typology of trees in cultivated area

of cultivation of Ngoko, we were interested in distinguishing during our treatments inventory data, which was in the order of recent or old clearing.

In the inventories, a number of plots of cultivated areas clearly and were noted as such in the field. However, a number of plots, which were simply noted as crop areas at the time of the inventory, have apparently become apparent in the processing of the data as cleared. This is any strains are located. It has therefore become necessary to develop simple criteria for discriminating newly cleared fields from cultivated areas for

One of the parameters measured during the inventory seems eresting to characterize the clearings: the strain rate. However, this criterion does not appear sufficient. On the one hand, we do not note a sudden variation in the strain rate which would have allowed, ideally, to discriminate cleared fields from hers. On the other hand, even with a high stocking rate, a plot may very well be located in an old crop area and the number of trees in the plot may be small. The total number of stems therefore also appears as a factor to be taken into ossed the two parameters: strain rate and

Strains rate of plots of growing areas

Two two types of cultivated areas are distinguished according

Plots with a large number of stems and a high rate of strains, considered to be clearly cleared; the limit may be set at more

Plots cultivated for a long time, with a low rate of strains (less

The rest of the plots require further analysis and are examined case basis to determine whether they are long-cultivated or recently cleared areas. In general, they can be clearly distinguished: plots with a low number of stems (less than 7) and high rates of strains can be considered as old plots (possessing more than 7 stems)

are sorted by looking at the circumference of their trees and the rate of strains: this makes it possible to identify the "second passage" clearings, that is to say those whose young stems had already been eliminated before, and on which the farmer recently passed cut the remaining large stems. All the remaining plots were in this category.

Finally, of the 81 crop plots, 15 are classified as cleared. In addition, two plots, which had been considered as fallow bush because they were uncultivated, were added to the clearing category (very large number of stumps, large diameter stems). These are land that has just been cleared and will soon be under cultivation.

Characterization of the origin of the clearings: newly cultivated savanna or reactivated fallow

To find out if these clearings are simple crops or not, we can focus on two factors: the presence of stems (cut or not, characteristic trees rather park or bush), and the woody composition of old fallow (or bush) surroun

clearing.

With regard to the latter, it appears that three species are recurrent in these old fallows: Terminalia avicenioides, Combretummicranthum and Detariummicrocarpum. The circumferences of these species are mainly in close

for each of the plots, namely essentially:

 Terminalia avicenioides: between 8 and 20 cm;

 Combretummicranthum: between 8 and 24 cm;

 Detariummicrocarpum: between 10 and 30 cm. Thus, the presence of strains of these species in abundance on a plot, in circumferences included in these ranges, or even being inferior, indicates rather a re

had been left at rest.

The presence of strains of these same species, but in circumferences much stronger than those observed o

fallows, rather indicates a clearing carried out on an area never cultivated previously or then a very long time ago.

In addition to these two classification criteria for clearings, valuable indications are provided by large diameter trees and stumps. In the case of park trees (Prosopis, which represent only 0.5% of the basal area of

therefore very rare on these types of plots, compared with 16% for the fields; never encountered on bush

they indicate that clearing is done on an area that has been cultivated before.

If on the other hand they are typical bush trees, they allow to suppose that the plot would come from the clearing of a bush. By combining these 4 criteria, we can classify the cl according to their origin.

Fields formerly cultivated

Of the plots that have been placed in the cultivated area category, a number have a very low number of trees, or even an absence of trees. One can thus consider the distinction of 2 categories of plots in formerly cultivated zone, according to the density of the trees, the threshold being fixed at 10 stems per hectare:

 poorly planted trees (54 plots);

are sorted by looking at the circumference of their trees and the rate of strains: this makes it possible to identify the "second passage" clearings, that is to say those whose young stems had fore, and on which the farmer recently passed cut the remaining large stems. All the remaining plots were in this category.

Finally, of the 81 crop plots, 15 are classified as cleared. In addition, two plots, which had been considered as fallow bush se they were uncultivated, were added to the clearing category (very large number of stumps, large diameter stems). These are land that has just been cleared and will soon be under

Characterization of the origin of the clearings: newly ated savanna or reactivated fallow

To find out if these clearings are simple crops or not, we can focus on two factors: the presence of stems (cut or not, characteristic trees rather park or bush), and the woody composition of old fallow (or bush) surrounding this island of

With regard to the latter, it appears that three species are recurrent in these old fallows: Terminalia avicenioides, Combretummicranthum and Detariummicrocarpum. The circumferences of these species are mainly in close intervals, for each of the plots, namely essentially:

Terminalia avicenioides: between 8 and 20 cm; Combretummicranthum: between 8 and 24 cm; Detariummicrocarpum: between 10 and 30 cm. Thus, the presence of strains of these species in abundance on a plot, in circumferences included in these ranges, or even being inferior, indicates rather a re-cultivation of a clearing which

The presence of strains of these same species, but in circumferences much stronger than those observed on the old fallows, rather indicates a clearing carried out on an area never cultivated previously or then a very long time ago.

In addition to these two classification criteria for clearings, valuable indications are provided by large diameter trees and tumps. In the case of park trees (Prosopis, which represent only 0.5% of the basal area of the Ngoko bush and fallow land, therefore very rare on these types of plots, compared with 16% for the fields; never encountered on bush-fallow plots), rather indicate that clearing is done on an area that has been

If on the other hand they are typical bush trees, they allow to suppose that the plot would come from the clearing of a bush. By combining these 4 criteria, we can classify the clearings

Of the plots that have been placed in the cultivated area category, a number have a very low number of trees, or even an absence of trees. One can thus consider the distinction of 2 of plots in formerly cultivated zone, according to the density of the trees, the threshold being fixed at 10 stems per

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Denis GAUTIER and Frédéric REOUNODJI., The Role of the Tree as an Indicator of Dynamics of Development of the Ngoko Area, Chad

 those that resemble a park with trees (12 plots). Summary of types distinguished by data processing

For the cultivated areas (83 plots), 66 have been cultivated long enough for the strains to have been removed (80%) (crops for at least 10 years), while 17 are apparently cleared where many strains persist ( 20%). There is therefore a significant part of the territory of Ngoko, mainly located in the north, which has been cultivated since a recent date. Was not the land of this village still saturated to allow this extension, or have the limits of the village recently been extended to allow this extension and to desaturate the soil? In detail, of the 66 plots in long-cultivated fields, 54 have little or no trees (82%) while the remaining 12 plots (18%) have a significant tree density (22 trees / ha). ). In the majority of cultivated areas, it can be said that the tree is little integrated or eliminated as and when culturing.

For fallow-bush areas (58 plots), 17 were classified as 1-year fallow (29%), 26 as 2-year fallow (45%) and 15 as fallow 3 years or older (26%). From these relative frequencies, we can say that in Ngoko, fallows are mostly short-lived, 2 or even a single year. One wonders if this leaves the ground time to recover and how long these rotations are short? It is, in any case, a sign of saturation of the land in the areas near the village. The long-term fallows, for their part, are located along the Mayo where they constitute the cattle corridors, and most of them in the most northern part of the land, in the recent conquest zone.

Figure 3 Mapping of inventoried agroforestry types

Analysis of the Spatial Distribution of the Types

If we look more closely at the spatial distribution of the plots that we have inventoried and classified according to agroforestry system types, we can notice that they are not randomly distributed, but that they can instead be grouped into halos. This halo organization is supported by the correspondences that can be established between the location of the identified agroforestry types and that of the cultures obtained by lifting with the planchette (Réounodji, 2001). Outside the village and its concessions planted with trees (tutelary trees, shade trees, fruit trees) and the zone of mayo which constitutes a corridor of passage for the animals, we can identify the following geographical zones, arranged according

to a gradient Intensity decreasing from the heart of the village to its borders:

 around the village, a first halo of fields, cultivated for a long time and according to intensive modes, with a very weak integration of the tree and short fallows;

 around this first halo, an area of medium cultivation intensity with fallow periods that can pass to two years and especially a relatively large presence of the tree in the field which is probably the witness of a rather old clearing, but not yet enough to have eliminated all the trees by repeated cultivation and firing;

 around this second halo, an area of intensivity of cultivation which decreases again with fallow periods which spend a majority of one to two years, and especially of fallow cultivation identified thanks to the large number of strains;

 finally, in the last halo, but only on the northern outer edge of the Ngoko terroir, a clearing front with fallow bushes of more than 3 years and recent clearings where the tree still has an important place.

Figure 4 The halo-distribution of agroforestry types

The analysis of the spatial distribution of the different agroforestry types that we have been able to highlight shows a development of the space in halos of decreasing intensity from the heart of the village. This center-periphery model of space enhancement results in a gradient of density and diversity of trees, but also of fertility and consequently of rotation.

There is, however, an asymmetry in the expression of this spatial model. On the one hand, halos are more developed in the south than in the north. This is due to the establishment of the village in the center of the soil, but on the southern edge of the stream that crosses it. On the other hand, there is a slight lengthening of the southern halos along the road. This dissymmetry is very interesting to note since the current processes in the northern part of the village territory are probably the same as those that took place in the southern part of the village some ten years ago.

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Table I Area of different areas of development of space

Type of enhancement Area (km2) % of the total S

Town 0,5 6

Low background 0,7 9

Halo 1 1,9 23

Halo 2 2,0 24

Halo 3 1,6 19

Clearing front 1,6 19

Total 8,3 100

The different types of development are fairly evenly distributed in space. It can be noted in particular that the areas of high to medium intensity, including the village, represent only about half of the territory, which therefore does not seem so saturated that it can be heard in the speeches of the agents of the development operating in Ngoko and farmers themselves. The land saturation is actually effective in the south, Ngoko cultivation plots touching those of neighboring villages and even overlapping with them. To the north, the process of saturation is underway and still leaves room for long-term fallows, cattle corridors and land conflicts due to conquest, proof that there is still land to conquer. There may, however, be some concern for livestock corridors when this process is completed in the north, fallows will gradually disappear and land conquests will be made.

CONCLUSION

The detailed analysis of our forest inventory data and their projection by GIS in the appropriate space by the village has allowed us to build a dynamic vision of the development of this territory, based on two analysis tools. statistics: inventory and mapping. We were helped for that by the object we worked on, the tree, which offers us the privilege of not moving and being long enough to pass on a certain amount of information about the history of the agricultural development of the place where it is planted: by its development in width and height; by the marks of maintenance, exploitation or elimination which it carries; by the plant associations in which he participates. By crossing these indices with their location and observing all these crossings at the scale of the village territory, we obtain a dynamic vision of the development of this territory. This vision allows us to formulate hypotheses about future processes and to anticipate these processes through research supporting development.

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Gautier G., Ankogui-Mpoko G-F., Reounodji F., Njoya A., Seignobos C., 2002. Farmers and breeders: two communities, two dominant activities, for which territorial integration? In Jamin J.Y., SeinyBoukar L. 'African savannahs: changing spaces, actors facing new challenges. Conference proceedings, May 2002, Garoua, Cameroon, N'Djamena, Chad, 15 p.

Reounodji, F. (2003). Spaces, rural societies and natural resource management practices in the savannahs of south-west Chad: towards agriculture-livestock integration (unpublished doctoral thesis). University Paris 1 Panthéon-Sorbonne, Paris, France.

Reounodji F., 2001. Dynamics of space occupation and local management of natural resources in southwestern Chad. Case of the agro-pastoral soil of Ngoko. Mid-term report of a thesis in geography. Prasac / Lrvz / Ird, 37 p.

Seignobos C., 2000. Terroirs Prasac: Towards a confirmation of choices ?.Prasac, N'Djamena, Chad, 69 p.

How to cite this article:

Denis GAUTIER and Frédéric REOUNODJI., 2019, The Role of the Tree as an Indicator of Dynamics of Development of the Ngoko Area, Chad . Int J Recent Sci Res. 10(10), pp. 35509-35513. DOI: http://dx.doi.org/10.24327/ijrsr.2019.1010.4117

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