Application of carbon isotope analysis to ancient maize agriculture in the Petexbatún region of Guatemala

The ancient Maya subsisted in an environment limited by shallow soils and unpredictable weather patterns until their collapse ∼A.D. 800–900. Ancient subsistence can be a difficult subject, with little physical evidence of agricultural artifacts and structures. This study characterized soil profiles and utilized changes in stable carbon isotope ratios of soil organic matter (SOM) to locate and interpret areas of ancient C₄ plant growth and maize (Zea mays) cultivation among the Maya. The investigation indicated some of the challenges the Maya faced, including shallow and sloped soils in some areas. The C₄ plant signature was found in seasonal wetland soils on the opposite side of the Laguneta Aguateca from the ruins of Aguateca, but not in the perennial wetlands on the immediate side. No C₄ plant signature was detected in the shoulder and backslope soils. Based on these findings, the ancient Maya of Aguateca probably adapted to their environment by farming rich toeslope soils. It is possible that maize was also grown in the seasonal wetlands adjacent to the site. If the steep backslope soils around Aguateca were used in ancient agriculture, the evidence has probably eroded away. © 2007 Wiley Periodicals, Inc.     

Soil properties and stable carbon isotope analysis of landscape features in the Petexbatún region of Guatemala

Soil properties and stable carbon isotope ratios contained in the soil organic matter (SOM) were used to investigate the change in vegetative history of land cleared anciently for maize (Zea mays L.) agriculture in the Petexbatún region of Guatemala. Maize and other C⁴ plants associated with land clearance leave a carbon isotopic signature in the SOM different from the C³ plants of native forest vegetation. Soil profiles were collected from various landscape features around the Classic Maya site of Aguateca: control locations (areas likely not used in ancient agriculture), defensible locations (areas near defensive walls), rejolladas (natural karst depressions), upland locations (well‐drained soils atop the Aguateca escarpment), and bajos (seasonal and perennial wetlands). The chemical and physical properties of the profiles were examined and the soils were taxonomically classified to the great group level. The changes in d¹³C with soil depth were determined and compared statistically. The ¹³C enrichment of the SOM in bajo and rejollada profiles were similar and were significantly (p < 0.05) greater than the control, defensible, and upland soils. This isotopic signature of sustained C⁴ vegetation was likely associated with forest clearance and ancient Maya agriculture. Both the bajo and rejollada landscape features appear to have been valuable agricultural resources for ancient Maya. © 2009 Wiley Periodicals, Inc.     

Platforms in the akalche at E1 Mirador,Peten, Guatemala and their implications

Late Preclassic Period platforms were surveyed and test-excavated in a seasonal swamp or akalche, at the large ancient lowland Maya site of El Mirador in Peten, Guatemala. Pedological, hydrological, and archaeological evidence suggest that the climatic and hydrological regimes were drier than they are today to permit habitation and warrant the investment in labor. Nevertheless, observations of present conditions, including the clayey soils, indicate that the akalche was almost as inhospitable in antiquity as it is today, that it had the same extremely poor agricultural potentials and that intensive wetland cultivation would have necessitated sizeable investments in dams to dampen the extreme seasonal fluctuations in water levels. Dams are not observed, and evidence is elicited to indicate that they would be readily observable today had they been emplaced here in antiquity. We offer evidence suggesting that these platforms had domestic functions, but we are forced to conclude that intensive wetland cultivation did not sustain them nor this large regional center as a whole. We argue, instead, that these habitations constitute evidence for population pressures on urban upland resources, especially building sites and perhaps agricultural land. Akalche households appear to have sustained themselves, at least in part, by foraging for animal and plant foods, cordage products, building materials, and firewood. The data are inadequate to decide if these structures housed full or part time specialists, or if they were self-sufficient in subsistence. © 1994 John Wiley & Sons, Inc.     

Spatial and Physical Characteristics of Rejolladas in Northern Yucatán,Mexico: Implications for Ancient Maya Agriculture and Settlement Patterns

This study evaluates the importance of rejolladas to the Ancient Maya in and around the Classic Maya center of Xuenkal, Yucatán State, Mexico. Rejolladas are collapse sinkholes with bases above the local water table. We present a spatial and physical analysis of 186 rejolladas in a 10 × 10 km area centered on Xuenkal. Basal diameters range from ∼22 to 264 m, areas range from 0.04 to 5.48 ha, and depths range from 4 to 12 m. Spatial density ranges from 0 to 8 rejolladas/km² with higher densities coinciding with known Ancient Maya settlements. Within Xuenkal, residential groups tend to be organized around and focused on the rejolladas. Some rejolladas have modified slopes that may be remnants of terraces or entry paths. High‐resolution satellite imagery analysis demonstrates that rejolladas have denser and healthier vegetation than the surrounding landscape especially in the dry season. Microclimate data demonstrate that the bottom of rejolladas has less extreme diurnal temperature ranges, lower daytime highs, higher atmospheric moisture, and significantly higher and more stable soil moisture. Based on the archaeology at Xuenkal, it appears that the Ancient Maya recognized and actively exploited these environmental microniches for intensive cultivation both locally and regionally.     

Nitrogen cycle model of agroecosystem in the karst region of Guizhou Province

According to the transport theory of soil solutes and the conditions of soil, geology and climate in the karst region of Guizhou Province, a numerical simulation model of edaphic nitrogen element transport under field conditions is initially established. In this model, NO⁻ ₃ and NH⁺ ₄ are regarded as soil solutes. Transformation mechanisms such as biological release, bio-immobilization, ammonium adsorption-desorption, nitration-denitrification and factors of crop root uptaking are considered in this model. It is hoped that the data from this model could directly be used to guide agricultural production in this region and offer feasible ways to improve the use of nitrogen element, sustainable development of agriculture in karst mountainous areas and natural environment.     

Using in‐field phosphate testing to rapidly identify middens at Piedras Negras,Guatemala

Recent studies have promoted using soil phosphate analysis to detect ancient Maya sites by delimiting areas of occupation based on decomposed organic matter. Refuse associated with human activity increases organic matter around areas of ancient human habitation. Theoretically, the highest concentration of organic matter—detectable by phosphate analysis—should be directly associated with areas of refuse disposal. Thus, the objective of this study is to investigate the potential of phosphate analysis to detect residential middens in Piedras Negras, Guatemala. This paper presents the results of a sensitive, in‐field phosphate analysis method applied as a midden prospection tool in residential areas. Phosphate concentration is correlated with artifact data obtained from a total of 37 test pits excavated in areas of varying phosphate concentration in three residential sites. A positive correlation between phosphate concentration and ceramic density indicates the potential of this method in defining and orienting excavations of residential areas. © 2001 John Wiley & Sons, Inc.     

Biogeochemical studies of a Native American runoff agroecosystem

Research on soil fertility is presented in the context of runoff agriculture, a venerable farming system that has been used for millennia in arid to semiarid regions, where water is a major limiting resource for crop production. The agroecology of runoff farming was studied with the Zuni to evaluate nutrient and hydrologic processes, management, maize productivity, and soil quality in some of the oldest recognized fields in the United States. This ancient Southwest agriculture has functioned without conventional irrigation or fertilization by tapping into biogeochemical processes in natural watersheds connected to fields. Carefully placed fields are managed on alluvial fans and other valley margin landforms to intercept runoff and associated sediment and organic debris transported from adjoining forested uplands. We report on research to evaluate and link nitrogen and phosphorus, two key nutrients for crop production, in watershed, soil, and crop components of this agroecosystem. Nutrient data have been collected by observational and experimental methods for each component and the transport of nutrients from watershed to field to maize. The condition of Zuni agricultural soils suggests that their knowledge and management of soils contributed to effective conservation. This study and others indicate the need for further long‐term monitoring and experimental research on watersheds, runoff processes, field soils, and crops across a range of arid to semiarid ecosystems. © 2007 Wiley Periodicals, Inc.     

An evaluation of the contribution of soil micromorphology to the study of ancient arable agriculture

This article provides an overview of the development of soil micromorphological studies of ancient agriculture and the current position of research in this field. The stance adopted by the authors is deliberately combative, and it is hoped that the article will stimulate discussion of the current limitations and potentialities of the technique. The findings of this review may be summarized in three proposals: (1) Soil micromorphology cannot be used at present to identify cultivation in ancient soils. Ambiguous or multiple interpretations of soil micromorphological features are unlikely to be resolved, so that the detection of large scale agricultural features in the field (cultivation marks, lynchets) will remain the most secure and direct guides to the presence of a former cultivated soil. Indirect evidence on inferred land use can be provided from pollen and land snail evidence. (2) Micromorphology should retain a key role in the determination of the impact of agriculture on soils, encompassing issues such as erosion, soil structure, fertility, and biological activity. These can be related to agricultural practice: methods of tillage, manuring, soil conservation, and fallowing. (3) Three areas of micromorphological research can be proposed that address the impact of agriculture on soil: (a) the study of well-sealed, buried agricultural soils which have a clearly understood archaeological context; (b) the study of recent soils with known agricultural histories; (c) the establishment of controlled experiments with ancient agricultural techniques. © 1998 John Wiley & Sons, Inc.     

Landuse and soil degradation in the southern Maya lowlands,from Pre-Classic to Post-Classic times: The case of La Joyanca (Petén,Guatemala)

This work focuses on the impact of Maya agriculture on soil degradation. In site and out site studies in the area of the city of La Joyanca (NW Petén) show that “Maya clays” do not constitute a homogeneous unit, but represent a complex sedimentary record. A high resolution analysis leads us to document changes in rates and practices evolving in time in relation with major socio-political and economic changes. It is possible to highlight extensive agricultural practices between Early Pre-classical to Late Pre-classical times. Intensification occurs in relation with reduction of the fallow duration during Pre-classic to Classic periods. The consequences of these changes on soil erosion are discussed. However, it does not seem that the agronomic potential of the soils was significantly degraded before the end of the Classic period.     

A review of human and natural changes in Maya Lowland wetlands over the Holocene

In the Maya Lowlands of Mexico, Belize, and Guatemala two main types of wetlands have played important roles in human history: bajos or intermittently wet environments of the upland, interior Yucatán and perennial wetlands of the coastal plains. Many of the most important Maya sites encircle the bajos, though our growing evidence for human–wetland interactions is still sparse. The deposits of these wetlands record two main eras of slope instability and wetland aggradation: the Pleistocene–Holocene transition as rainfall increased and forests eclipsed savannas and the Maya Preclassic to Classic as deforestation, land-use intensity, and drying increased. The ancient Maya adapted with terraces around these bajo margins but retracted in the Late Preclassic in some areas. The perennial wetlands of the coastal plains have different histories, and the first conceptual model of human–wetland interaction described intensive wetland agriculture in the Preclassic through Classic based on raised fields and canals. But a second model arose that interpreted the wetland stratigraphy and canals as more indicative of natural aggradation by accelerated erosion and gypsum precipitation that buried Archaic and Preclassic fields and there was little Classic era use. We present new data on a third and fourth model in this study. The third is a hybrid of the models one and two, including the Archaic to Preclassic aggradation of the second model, and the first model's Classic period fields and canals as piecemeal attempts by the Maya to adapt to these and other environmental changes. The fourth conceptual model describes a very Late/Terminal Classic, preplanned project on a floodplain. These wetland fields were short-lived, aggraded rapidly but with some reoccupation in the Postclassic. All of these new models display the burgeoning evidence for intricate Maya interactions with wetlands, and the diversity of evidence from the relatively few studies underscores the infancy of our understanding of Maya interaction with tropical wetlands.     

Use of satellite data and GIS for assessing the agricultural potentiality of the soils South Farafra Oasis, Western Desert, Egypt

Overpopulation and food security are the main global problems alert decision makers. In developing countries, such problem put extra pressure for horizontal expansion for agricultural development. The rapid sprawl of urbanized areas on the alluvial land of the River Nile and delta to accommodate the population growth has encouraged governmental and private sector for agricultural expansion in the desert. Unless there are reliable information and accurate studies for land and soil suitability, there will be a collapse of such investment. To evaluate the potential suitability of soil for agriculture development in areas of the western desert, satellite images, geographic information, and field survey including soil profiles and artesian water samples with laboratory analysis were integrated to classify the soils according their suitability for specific crop. The main land qualities of the different mapping units and the crop requirement were rated and matched to obtain the current and potential land suitability using Automated Land Evaluation System “ALES”. The study found that the main physiographic units are plateaus, hilland, mountain, and depression floor. But there are three limiting parameters for land suitability which are the lack of nutrient elements, wind erosion vulnerability, and soil texture. The study concluded that the best crops adapted with the soil conditions and could be feasible for economic use are: (1) native vegetation such as agol, sand trees, sammar, halfaa, bawaal, qordaob, bardi, and qortom; (2) filed crops such as onion, garlic, watermelon and wheat; and (3) fruits such as olive and date palms.     

Effect of per-capita land use changes on Holocene forest clearance and CO2 emissions

The centerpiece of the early anthropogenic hypothesis is the claim that humans took control of greenhouse-gas trends thousands of years ago because of emissions from early agriculture (Ruddiman, 2003, Ruddiman, 2007). A common reaction to this claim is that too few people lived thousands of years ago to have had a major effect on either land use or greenhouse-gas concentrations. Implicit in this view is the notion that per-capita land clearance has changed little for millennia, but numerous field studies have shown that early per-capita land use was large and then declined as increasing population density led to more intensive farming. Here we explore the potential impact of changing per-capita land use in recent millennia and conclude that greater clearance by early agriculturalists could have had a disproportionately large impact on CO₂ emissions.     

Eco-environmental problems and effective utilization of water resources in the Kashi Plain, western Terim Basin, China

Since ancient times, water resources, mainly from melting snow in the high mountains, have nourished a large area of an oasis in the Kashi Plain in the western Terim Basin, China. In the last half-century, however, the rapid growth of population and the overexploitation of water, soil, and biological resources have led to drought, salinization, and desertification in the area, and consequently have hindered the development of sustainable agriculture. In this study, groundwater reservoirs with sustainable water supplies equivalent to 44.65×10⁸ m³/year were identified, which has made it possible to implement several projects in the area to improve the ecological and agricultural environment. Three strategies are proposed for the integrated development and management of both surface-water and groundwater resources in the area. Electronic Publication     

Late Holocene environmental reconstruction using cave sediments from Belize

Cave sediments collected from Reflection Cave on the Vaca Plateau, Belize show variations in the δ¹³C values of their fulvic acids (FAs), which indicate periods of vegetation change caused by climatic and Maya influences during the late Holocene. The δ¹³C values range from − 27.11‰ to − 21.52‰, a shift of ∼ 5.59‰, which suggests fluctuating contributions of C₃ and C₄ plants throughout the last 2.5 ka, with C₄ plant input reflecting periods of Maya agriculture. Maya activity in the study area occurred at different intensities from ∼ 2600 cal yr BP until ∼ 1500 cal yr BP, after which agricultural practices waned as the Maya depopulated the area. These changes in plant assemblages were in response to changes in available water resources, with increased aridity leading to the eventual abandonment of agricultural areas. The Ix Chel archaeological site, located in the study area, is a highland site that would have been among the first agricultural settlements to be affected during periods of aridity. During these periods, minimal water resources would have been available in this highly karstified, well-drained area, and supplemental groundwater extraction would have been difficult due to the extreme depth of the water table.     

Effect on physico-chemical and structural properties of soil amended with distillery effluent and ameliorated by cropping two cereal plant spp.

Molasses-based distilleries are one of the most polluting industries generating large volume of wastewater. Distillery effluent (DE) on its discharge alters the physical and chemical properties of the soil. This study has been conducted to assess the distribution of heavy metals and its effect on physiochemical and structural changes of soil which has been treated with diluted and undiluted effluents. The soil has been assayed both before and after crop plantation. Out of the crop plants studied, Cicer arietinum was least effected and more effective than Pisum sativum in diminishing the heavy metals from soil. However, only at higher concentration DE has some adverse impact on the nutrient contents of the soil. Fourier transform infrared spectrum (FTIR) study of the soil indicated the presence of –OH, –NH, –COOH groups. It was also noted that the soil amended with different concentration of DE and on which Cicer and Pisum were grown has varied IR spectrum. These variations show the presence of different functional groups of soil before and after plants were grown. The presence of inorganic carbonate was found in soil planted with Cicer from 10 to 50% of DE, whereas aliphatic primary amides were observed up to 25 and 100% concentrations of DE in soil planted with Pisum. The appearance of inorganic nitrates, carbonates, aliphatic hydrocarbons and aliphatic primary amides at various concentrations of DE showed a change in functional groups probably because of the differential breakdown of parent component present in the effluent. Besides our main finding that Cicer is a very useful crop species in remediating the soil which has inflicted with even undiluted DE, it is also validated through FTIR spectra that IR technique is an efficient tool in studying the structural changes of soil and with some degree of caution may be summed up that FTIR may be used to correlate the relative efficacy of plants to transform organic contaminants.     

Soil erosion assessment and its verification using the Universal Soil Loss Equation and Geographic Information System: a case study at Boun,Korea

This study is aimed at the evaluation of the hazard of soil erosion and its verification at Boun, Korea, using a Geographic Information System (GIS) and remote sensing. Precipitation, topographic, soil, and land use data were collected, processed, and constructed into a spatial database using GIS and remote sensing data. Areas that had suffered soil erosion were analysed and mapped using the Universal Soil Loss Equation (USLE). The factors that influence soil erosion are rainfall erosivitiy (R) from the precipitation database, soil erodibility (K) from the soil database, slope length and steepness (LS) from the topographic database, and crop and management (C) and conservation supporting practices (P) from the land use database. Land use was classified from Landsat Thematic Mapper satellite images. The soil erosion map verified use of the landslide location data. Landslide locations were identified in the Boun area from interpretation of aerial photographs and field surveys.     

Evaluation of soil top-cover systems to minimize infiltration into a sanitary landfill: A case study

The design of a top-cover system is a very important aspect of the closure of sanitary landfills. Soil material properties, sequencing, and vegetation are critical to top-cover design. To date, very few field investigations have been undertaken to determine the effectiveness of these designs. Results from a field investigation of top-covers proposed for an active landfill site in south Florida are reported here. Measurements were made of each component of the water balance equation: S = [P +I] – [ET +R +Q] whereS, P, I, ET, R, andQ represent water storage, rainfall, irrigation, evapotranspiration, surface runoff, and deep seepage, respectively. Deep seepage, determined using soil water tensiometers, is the amount of water infiltrating the landfill top-cover and is therefore the upper limit of potential leachate generation.Results indicate that the locally available rock tailings (carbonate silt) is an effective topliner component of the top-cover system. The results of the field investigation also showed that the EPA water balance model used to estimate infiltration during landfill design was greater than the actual field measurements.     

Assessment of tectonic-controlled rock fall processes threatening the ancient Appia route at the Aurunci Mountain pass (central Italy)

The Ningxia Hui Autonomous Region of China (Ningxia), one of main agriculture areas in northwest China, has been severely affected by drought. Based on observed meteorological data, outputs of 20 global climate models and drought disaster data, future climate change and relevant drought hazard in the twenty-first century were projected in Ningxia, with the scenarios of RCP2.6 and RCP4.5; the risks of people, crop, and agriculture economy to drought disasters are quantitatively assessed, with the application of physical vulnerability curve models, probability distribution functions and Monte Carlo simulation method. It is found that the climate in Ningxia is likely to have a warming and wetting tendency in the twenty-first century. The extent of drought hazard is likely to increase. The increase rate is greater under RCP4.5 than that under RCP2.6. In general, the risks of population, crop, and agriculture to drought disasters are likely to increase in Ningxia in the twenty-first century. The magnitude of increase is likely to reach the greatest in the immediate term (2016–2035), followed by the increase in the medium term (2046–2065), and the long term (2081–2100). In comparison with RCP2.6, the drought disaster risks under the scenario of RCP4.5 are likely to increase further in three periods of the twenty-first century. The findings of this work have potential to provide data support for drought disaster risk management and support risk-based decision-making.

     

Anthropogenic contamination of groundwater with nitrate in arid region: case study of southern Hodna (Algeria)

In southern Hodna, an arid region of Algeria, the extension of irrigated agriculture and overexploitation of groundwaters have led to a rupture with traditional land use by pastoralism. Due to the arid conditions, groundwaters are the only water resources for man and irrigation. This study focuses on nitrate contamination of groundwaters and its increase since the last 40 years, on the basis of two archives and recent analyses. The chemical facies of waters is sulphate-chloride, the risk of salinity is moderate to large. The sodicity risk, as estimated by the SAR, is low due to the large salinity and the sandy soil texture. Nitrate contamination of deep groundwater is a clear evidence when recent data are compared to the historical data. From 1996 to 2008, the proportion of samples with NO ₃ ^? concentrations larger than 50 mg/L increases from 24 to 61 %, the proportion of samples with NO ₃ ^? concentrations larger than 100 mg/L increases from 12 to 27 %. The study points at a general contamination of aquifers from anthropic origin: phreatic water was already contaminated when pastoralism was dominant (1967); as population increased and irrigation agriculture developed with large use of N-fertilizers and organic amendments, contamination extended spatially and vertically to deep aquifer. To remediate this contamination, fertilizers should be fractionated and limited to plant requirements on the basis of soil and plant analyses. Excess of irrigation should be avoided. Soil surface should be continuously covered to prevent nitrate leaching. Secondly, more efficient irrigation techniques, such as localized irrigation, should be implemented, with adaptation of crop systems and fertilizer inputs to arid conditions. Farmers should then be trained; simultaneously, local agronomic references that are presently lacking should be acquired.     

Environmental and cultural changes in highland Guatemala inferred from Lake Amatitlán sediments

We inferred the late Holocene environmental history of the Guatemala highlands from multiple lines of evidence in a sediment core from Lake Amatitlán. Inferred environmental changes are generally synchronous with archaeologically documented highland Maya cultural shifts. Population increases in the Middle Preclassic, Early Classic, and Late Postclassic are associated with deforestation and soil erosion. Land abandonment in the Late Preclassic, Late Classic, and Early Postclassic is associated with evidence for reforestation and soil stabilization. Diatoms indicate relatively lower lake level and greater trophic status at times of reduced human impact, from ca. 250 B.C. to A.D. 125 and from ca. A.D. 875 to 1375. Decreased water levels were probably due to drier climate, to reforestation, or both. Lake eutrophication was caused by reduced water volume combined with a legacy of long‐term agricultural activity. Our data contribute to the understanding of relations among ancient Maya culture, climate, and environment. © 2011 Wiley Periodicals, Inc.