MATERIALS AND METHODS
This method prevents compaction of the soil and thus distortion of the original volume used for analysis. In this study, the bulk density of the soil was the parameter in question since it contributes to soil quality and stability of terrace systems. Afterwards the dried samples were cooled down and their dry weight measured. For this process, the samples first had to be dried, then hand ground and finally ground in a planetary mill before being introduced into the EA analyzer.
Their preferred location was as low in the profile as possible and ideally underneath parts of the dry-stone wall. This would indicate that most probably the wood was burnt before the respective terrace was constructed or at approximately the same time. It is very unlikely that any material containing charcoals was introduced under or into an already existing terrace wall since it would require the removal of the wall.
Not at all sampling sites charcoals that would fit the necessary dimensions for 14 C analysis were found. In each of the profiles the locations, where charcoal pieces have been found, have been documented on the drawing with size of the piece and its depth. After analyzing which of the charcoal pieces were suitable for 14 C analysis, 18 the selected samples were brought to the AMS- 14 C laboratory at Kiel University, currently named Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, where the analysis took place.
To visualize the temporal dynamics of the terrace area extension into the mountains the data have been included in GIS Arcmap This device consists of two different sized plastic rings. In this case one ring had a diameter of 30 cm and the second one a diameter of 60 cm. The big ring is placed on the soil and pressed into it until approximately 15 cm of the ring are in the soil.
The remaining 15 cm stay above the soil surface. The smaller ring is now placed in the center of the big one and also pressed approximately 15 cm into the soil. Before measuring, water was poured into the rings to wet the surface. The measurements were then started by filling the outer ring with water, which was kept at a stable level by refilling it during the measurements.
Afterwards one liter of water was poured into the inner ring and the time until it was fully infiltrated into the soil measured. This procedure was repeated five times or until the water infiltration took longer than 20 minutes. Information gained in the interviews is evaluated jointly with the results from the laboratory analysis.
First, one exemplary soil profile is presented, then the results from the soil quality parameters investigated in this study are shown, followed by the parameters regarding stability of the terrace system under investigation, namely bulk density and water infiltration capacity. Finally, the data from the Radio Carbon Analysis are presented and the temporal extension of agricultural terraces shown. A typical dry-stone wall consists of one or more layers of stones that support the soil behind the wall FAO n. This is the most common type of supporting walls in Madeiran bench terrace systems.
We have identified three different types of dry-stone walls and an earth wall, constructed without the aid of any stone material. The comparatively thin dry-stone wall with only one layer of stones as supporting wall is similar to the other profiles investigated in terms of rock type used.
These materials were available at or close to the majority of sites that were terraced and required only short transport distances. It measures cm in height and has a thickness of approximately 70 cm. Some of the wall stones were worked to match better and to provide stability. In between the large stones, smaller ones and stone wedges have been placed to further increase stability. When removing the original soil from the proposed area of the terrace, farmers removed most of the stones in the soil and put them behind or next to the foundation of the future wall.
The lower layers within the terrace, just next to the basis, show quite a few stone deposits, while the upper two layers of soil do not have any stones or even gravel mixed in. Altogether, five different layers of soil can be distinguished in this terrace body 20 : At the bottom, a first dark brown layer of fine soil Y1 was identified. Above it, a mixed layer of stones and soil Y2 and a thin layer Y3 without stones were deposited. The two top layers Y4 and Y5, which are most important for agricultural activities and crop growth, consist of fine soil.
They are each approximately 80 cm thick and have very good structure. The dark brown color already indicates a high content of organic matter. Thus, pore space is well developed and interlinked. The soil has an extremely low specific weight and is easy to work with the typical tool used in Madeiran traditional agriculture: the hoe. Y4 has an organic matter content of These values are extraordinarily high and indicate a very sustainable and a highly effective long-term soil conservation.
In all soil samples analyzed, the organic matter contents are high, in some profiles even in the lower layers. Table 1 shows the C-org contents of the investigated soil layers. Mineral fertilizers like ashes from burned plant residues or in recent years from chemical fertilizers are also incorporated into this layer.
The low variation, ranging from 8. The low value of 4. The terrace system of Lombo das Coches is singular in most of its characteristics; it is the only one in the entire Lombadas da Ponta Delgada area that has no stone walls securing the terrace soils. The bench terraces were constructed with a thick soil cover on top of the ridge by digging the terraces into the soil and removing soil from above to slightly lower altitudes. In a former water storage basin, approximately m distant from the investigated terrace, the soil atop the solid rock has a thickness of cm.
For traditional agriculture, this implied more labor input and less favorable conditions for crop growth. Probably farmers did not have the same care for soil conservation on these less productive terraces. In the interviews most farmers explained three remarkable traditional practices in regard to maintaining a high soil organic matter content: 1 Since every farmer kept livestock goats, sheep or cattle in small stables, the so called palheiros, 22 there was need for bedding.
The material used was rarely straw, since it was a valuable product for thatching roofs. Farmers replaced straw with common bracken Pteridium aquilinium , which was collected on deforested high mountain slopes and brought down into the valleys. This material became part of the manure and was brought onto the terrace fields. Some small branches were used afterwards as fuel wood and the eaten parts of the fodder became manure.
The annual pruning of vines resulted in huge amounts of tiny branches. They were collected and placed in small ditches with depths of approximately cm into the terraces and covered with soil afterwards. Furthermore, weeds were collected on fields and public spaces along footpaths and taken onto the terrace fields for fertilization. In Terceira Lombada it was a common practice to collect leaves from the forest floor and bring them onto the terraces as additional fertilizer.
In the terrace systems collapsed dry-stone walls or signs of wall reparations that have taken place earlier on are rare. Even frequent intensive precipitation events typical for Madeira, namely the very expressed one from 23 , did not cause damage or collapse of terrace walls within the research area.
The high stability of the terraces is partly a result of the perfect adaptation to the locally given conditions, namely high infiltration capacities and high aggregate stabilities of the redeposited andosols. The terrain of the Lombadas is generally designated as steep terrain. It is very likely that the original soils in the Lombadas area belonged to this soil group. There is further indication for the former, natural soil type: the climo-toposequencial layering of soils has been described for Madeira Island and the predominate soil type in elevations above m a.
Since most terrains are situated above m a. Another important characteristic of andosols is a predominately low bulk density, resulting from a well-developed pore system. This characteristic is also present in the anthrosols of the terraces under investigation, as can be seen in table 2. According to the dating results of the sample KIA the charcoal is, with a certainty of This early period of construction indicates that farmers did not only take the travel distance from the houses to the fields into consideration, but were more concerned with the terrain conditions.
Flattish areas with thick layers of soil were preferred to areas with a likely better solar exposure, but less favorable terrain conditions. A factor that might have supported the decision of cultivating this area so early is the availability of water all year round. A tributary of the main stream Ribeira da Camisa provides sufficient quantities of water to irrigate the area. Two samples were analyzed, KIA from a depth of cm below the top of the dry-stone wall and KIA from a depth of 80cm.
With a probability of The analysis of KIA provided more precise information, with a probability of The next highest probability, with While KIA did not provide reliable results, 25 the second sample KIA revealed that the charcoal was, with a probability of Combining the two samples, it is very likely that the terraces at the steep Ladeira site were constructed in the nineteenth century.
Although this area is closest to the village and facing east, it was terraced last - probably due to a difficult access to irrigation water and the steepness of the terrain. The southernmost terrace located at approximately m a. The introduction of these into a GIS added the spatial component, which was refined by visits in the area and interviews with local farmers. Recent changes, namely the pronounced abandonment of terraces and of some of the most labor intensive agricultural practices, were observed in the landscape and described by the interview partners, too.
In regard to accessing traditional knowledge on how the land was managed and which practices have been applied over centuries the qualitative interviews gave deep insights that could not have been accessed otherwise. Until the end of the twentieth century the survival of farming families directly depended on a good harvest.
Farmers have developed the described techniques of bringing plant residues and manure onto the terraces to improve crop growth and nutrient availability over centuries. The high content of organic matter in the soil proves this careful treatment. The organic matter in the soil fulfills a number of beneficial functions: It stabilizes the soil and its pore system, thus making it resistant against erosive forces and allowing plant roots to penetrate the soil more easily Johnston Furthermore, the water storing capacity is positively influenced.
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Nevertheless, in recent years some of the most labor-intensive practices, like the collection of leaf-fodder and bedding in the mountains, have already been abandoned. This is credited to the fact that animal husbandry has nearly disappeared. Consequently, the practice of adding organic material from outside the terraced area has disappeared, too. The ongoing abandonment of agricultural activities on the terraces, created and maintained by generations of farmers over centuries, does not only leave a fragile landscape with unmaintained terrace walls, but puts a huge amount of traditional knowledge on sustainable land use at risk.
So far, the higher mountain slopes are affected most by abandonment, while the easier accessible terraces are still maintained and most traditional practices still kept alive. The investigated terrace soils have such a high water-infiltration capacity that even heavy rainfall amounts infiltrate without causing surface runoff — thus preventing soil erosion. This function is very valuable for the inhabitants of the parish, especially since the region of Madeira is known for its frequent flash-flood events Quintal ; Baioni Written sources on landscape history of Ponta Delgada and the Lombadas solely offer a generalized vision of landscape dynamics.
The lack of cadastral information prevents a detailed study of spatial dynamics concerning the extension of the cultural landscape. There are no sources available that clearly state, which area was turned into cultural land in which period. If the early terraces are further away from the settlement, than younger ones, distance was not a main preoccupation.
Since small plateaus higher up on tiny ridges were cultivated first, the terrain conditions for terracing were a more important preoccupation for farmers, maybe combined with other factors such as solar exposure of slopes, and proximity to water lines for the establishment of irrigation canals, the famous Madeiran levadas. The century long, mutual adaptation between humans and landscape is evident. Not only in the constructed heritage of terraces and irrigation channels, but in the traditional practices of soil conservation, too. The traditional knowledge is a very valuable heritage and in terms of food security and prevention of natural disasters could regain importance in the future, particularly in times marked by climatic changes.
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Advances in Agronomy , 12, pp. Pereira, Eduardo C. Ilhas de Zargo. Volume I, 4th ed. Applied Geography , 31 3 , pp. Quintal, Raimundo Ribeiro, M. Ribeiro, Orlando Lisboa: Instituto de lingua e cultura portuguesa. Ricardo, P. I taught for 16 years, the last five at the University of Porto, and it was always very frustrating for me to try to motivate them. Most of them seemed to have lost their enthusiasm and curiosity.
When I stopped teaching, in , I decided to do my best to turn this situation around, but I also realized that students already in their twenties were probably too set in their ways — too used to their own passivity — to change. So I decided to start with young children, hoping with my books to stimulate their imaginations, enhance their curiosity and communicate to them — in between the lines and with the illustrations — that the world needs their passion and enthusiasm.
I also wrote a novel for adolescents entitled Strawberry Fields Forever Ilha Teresa in Portuguese in which I tried to broach topics not usually explored in novels for young adults, including immigration and homosexuality. I would like my young readers to understand that they may have only one chance to live an authentic and fulfilled life.
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