GIS-Based Extrapolation of land Use-Related Nitrous Oxide Flux in the Atlantic Zone of Costa Rica

I estimated the areal nitrous oxide (N2O) flux from 281,347 ha of Costa Rican lowland covered with primary and secondary forest, pastures and banana plantations by linking the DeNitrification-DeComposition (DNDC) model with a Geographic Information System (GIS). Generalized soil, texture and land use maps were overlaid to yield unique combinations of N2O flux control factors. Overlay patches were associated with the nearest of seven available meteorological stations. Monte Carlo-based sensitivity analysis was used to identify DNDC's key driving variables and required map attributes. Clay content, initial soil organic carbon (SOC), bulk density, and pH were selected as key driving variables. For 217 patch classes, DNDC simulations were carried out with climate data for seven different years. The estimated average areal flux was 6.8 kg N2O-N ha-1 yr-1. Possible applications of the GIS-DNDC interface presented include estimation of long-term areal flux dynamics from a changing land use mosaic, and prediction of areal fluxes resulting from alternative land use scenarios.     

Optimizing land use distribution to minimize nutrient depletion: a case study for the Atlantic Zone of Costa Rica

Nutrient depletion may be reduced by effective land use planning using a nutrient balance model and linear programming techniques to optimize the distribution of land use over different land units. This technique plans the geographical distribution of land utilization types and creates a more sustainable basis for agriculture in an area. In contrast with traditional land use planning where land utilization types are matched with land units on the basis of maximizing present agricultural production, this approach focuses on long-term effects.

A case study was carried out in an area of 3340 ha in the southern part of a settlement scheme in the Atlantic Zone of Costa Rica. Land units vary between young fertile volcanic soils and relatively old, leached unfertile soils. Land utilization types vary between extensively grazed pasture and intensively cultivated annual and perennial crops. Information on land units with its land qualities and on land utilization types was stored in a geographical information system which was integrated with a nutrient balance model (NUTBAL). This model, initially developed for Kenya and calibrated for local conditions in Costa Rica, was based on separate assessments of 5 nutrient input factors: mineral fertilizers, organic manure, wet and dry deposition, nitrogen fixation and sedimentation, and 5 nutrient output factors: harvested product, crop residue removal, leaching, denitrification and erosion. For every combination of land unit and land utilization type the nutrient balance was modelled. With a linear programming model, the land utilization types were distributed over the different land units, such that nutrient depletion was minimized in the area within a set of boundary conditions. Two different scenarios were elaborated. One in which all land utilization types were redistributed and one in which the location of forest areas was fixed at their present location.

The optimized land use distribution based on current land use types was compared with the actual distribution which had an average nutrient depletion of 22, 5 and 13 kg ha⁻¹ yr⁻¹ for respectively N, P and K. There was little difference in nutrient depletion between the two scenarios. The first scenario resulted in a nutrient depletion of 18, 3 and 9 kg ha⁻¹ yr⁻¹ and the second one in 19, 3 and 10 kg ha⁻¹ yr⁻¹ for N, P and K respectively. However, there was a large difference with the actual situation on one hand and the two scenarios on the other. In both cases there was a slight increase in the estimated agricultural production. The introduction of a nutrient depletion model in land use planning seems to constitute a useful complement to the existing procedures.     

Soil organic carbon in some land uses of Costa Rica

The native vegetation in the Tropics is increasingly replaced by crops, pastures, tree plantations, or settlements with contradictory effects on soil organic carbon (SOC). Therefore, the general objective was to estimate the SOC stock depth distribution to 100-cm depth in soils of Costa Rica and to assess their theoretical carbon (C) sink capacity by different management practices. A study was established in three ecoregions of Costa Rica: the Isthmian-Atlantic Moist Forest (AM), the Pacific Dry Forest (PD), and the Montane Forest (MO) ecoregions. Within each ecoregion, three agricultural land uses and a mature forest were sampled to 100-cm depth. The SOC stock in 0–100 cm depth was 114–150 Mg C ha^?1 for AM, 76–165 Mg C ha^?1 for PD, and 166–246 Mg C ha^?1 for MO. Land use had only weak effects on SOC concentrations and stocks except at PD where both were lower for soils under mango (Mangifera indica) and pasture. This may indicate soil degradation which was also supported by data on SOC stratification. However, it was generally unclear whether differences among land uses within each ecoregion already existed particularly at deeper depths before land-use change, and whether the sampling approach was sufficient to investigate them. Nevertheless, about 26–71% of Costa Rica's total C emissions may be offset by SOC sequestration in agricultural and forest soils. However, ecoregion-specific practices must be implemented to realize this potential.     

Deforestation trends in the Atlantic Zone of Costa Rica: A case study

In this study we have tried to link a quantitative inventory of deforestation to possible factors driving forest clearing, like accessibility and soil quality. The Study Area covered 395 km² in the Atlantic Zone of Costa Rica. Basic information came from aerial photographs taken in 1952, 1960, 1971 to 73, 1981 and 1984. Photo interpretations were digitized and processed with the help of a monoplotting programme. Three phases in deforestation were distinguished:

• 1 The period before 1960, characterized by a gradual increase in the rate of deforestation, with preferential clearing along rivers and on fertile soils.
• 2 The period 1960-1972. This period shows an increased clearing rate caused by a new centre of colonization, Cariari. Furthermore, banana plantations entered the area and main roads were constructed. Deforestation took place preferentially along roads and on fertile soils.
• 3 In the period 1972-1984 the remaining forest ‘islands’ were cleared at an accelerated rate. This was because only small areas of forest were left by this period. Also between 1972 and 1984 the fertile soils were cleared most rapidly.

     

脆弱草原带农牧交错区村域尺度土地利用结构定量分析

村级规划是现行土地利用规划的延伸和完善,全面揭示村域土地利用结构特征是村级土地利用规划编制必不可少的前提条件。该文以四子王旗中部乌兰察布丘陵区西南8个乡镇54个村(社区)组成的典型的脆弱草原带农牧交错区为研究区域,以其所辖村(社区)为分析单元,利用2013年遥感影像解译数据,运用计量地理方法和GIS技术,定量分析村域土地利用结构特征,为脆弱草原带农牧交错区村级土地利用规划的编制提供参考依据。结果表明:研究区土地利用多样化指数平均值为0.71,所辖各村(社区)多样化指数介于0~0.77之间,土地利用类型多样化程度总体处于中等偏上水平;各村(社区)集中化指数介于-0.33~1之间,集中化程度总体呈现为中等偏下的状态;土地组合类型相对较丰富,半数以上的村(社区)地类组合类型以耕地-林地-牧草地为主,37%的村(社区)以耕地-林地为主,空间分布上基本形成了一个集最单一和最齐全组合类型的中心区域和以此为中心的3条南北带状分布区域及最外侧对称分布的2个地段,在这些不同区域和地段内耕地、林地和牧草地呈现出相间分布的特点;土地利用程度综合指数平均值为243.05,各村(社区)综合指数值介于213.83~400之间,土地利用程度总体水平较高;受地形、海拔及人类生产投入水平的影响,各类用地在各村(社区)的区位意义不尽相同,其中耕地和林地区位意义相对较突出,而对半干旱草原地区来说,牧草地区位意义并不突出。据此,脆弱草原带农牧交错区的土地利用,在完善灌丛林生态体系的同时加强牧草地保护和农田基本建设是确保草原生态安全和经济稳定发展的必然选择。     

利用云模型评价开发区的土地集约利用状况

针对当前开发区土地集约评价中权重确定方法受主观性影响较大的问题,该文提出基于云模型的权重确定方法。将云模型引入开发区土地集约利用评价,并以桂林国家级高新技术产业开发区为例,进行实证研究。研究结果表明桂林高新区土地利用集约度综合分值为0.889,用地供需基本平衡;从土地利用状况而言,其土地利用强度较高、工业用地水平较强;就用地效益而言,工业用地产出强度较好,高新技术产业用地产出强度较高;从管理绩效来看,截止评价时点,区内无闲置土地,监管成效显著。基于云模型确定权重值的方法具备结果更加客观,算法容易实现的优点,有助于促进土地集约利用的科学评价,为桂林高新区土地集约利用政策依据。     

Association of soil organic carbon with physically separated soil fractions in different land uses of Costa Rica

Abstract

Yams (Dioscorea spp.) are known to be very demanding in terms of soil fertility. The influence of deleterious soil fertility on the growth of yams, however, has not yet been studied. A field study was carried out in Côte d'Ivoire, in a fertile forest site and in a low fertility savanna site, submitted to identical climatic conditions, to determine how soil fertility affects Leaf Area Index, Leaf Area Ratio, Crop Growth Rate, Tuber Bulking Rate, Radiation Interception, Radiation Use Efficiency and final tuber yields in D. alata and D. rotundata, grown in the presence of adequate fertilizers. While germination and establishment of both species were not affected by the site, growth parameters of D. alata were superior to those of D. rotundata. This resulted in higher yields of D. alata, when compared to D. rotundata. Only the radiation use efficiency was higher in D. rotundata than in D. alata. Both species reached higher Crop growth rate and Tuber bulking rate and produced higher fresh tuber yields at the forest site than at the savanna site, reflecting the known demand of yams for high fertility soil. Correlation analyses showed significant relationships between the mean Leaf Area Index measured over the entire growth period, Tuber Growth Rate calculated between tuber initiation and harvest, and fresh tuber yields, suggesting that the development of leaf area is determining the growth rate of the tuber which itself determines the fresh tuber yield. The decrease in D. alata tuber yields at the savanna site was explained by a decrease in Leaf Area Index, while the decrease in D. rotundata tuber yields at this site was explained by a decrease in Radiation Use Efficiency. Both effects might have been the consequence of a suboptimal nitrogen and potassium nutrition at the savanna site.     

Weather and maize yield relationships in the tropical region of Guanacaste,Costa Rica

Maize production in the Guanacaste region of tropical Costa Rica shows considerable fluctuations. The coefficient of variation from the mean yield ranges from 17 to 27% depending on the crop district.The available sparse data sets were used to develop a simple agrometeorological model to provide an objective tool for management decisions, including a rational insurance policy for crop yields, and an objective early warning system of crop production. The model must be updated as more data sets become available. The transfer to a developing country of techniques developed in the U.S. for weather/yield relationships is discussed.Rainfall amounts and distribution during the reproductive stage is the main meteorological factor affecting maize yield. Simple rainfall/yield relationships explain only some 12% of maize yield variability in tropical Guanacaste, while a weighted stress index developed by Shaw in the U.S. explained some 38% of the variability. Making use of the simple model developed for the region, it can be shown that moisture stress during the reproductive period will reduce yields in 7 out of 10 years, with severe drought conditions occurring in 1 or 2 years. The simple weighted stress index can be used to provide an early warning system.     

Reproductive biology of the Hawksbill Eretmochelys imbricata at Tortuguero,Costa Rica,with notes on the ecology of the species in the caribbean

From 1955 through 1983, 246 hawksbills Eretmochelys imbricata have been tagged as they came ashore to nest at Tortuguero, Costa Rica, a beach they share with a large colony of green turtles Chelonia mydas. Nesting hawksbills average 82 cm in straight carapace length and grow at a mean rate of 0·3 cm year⁻¹. Mean clutch size is 158 eggs; clutch size is poorly correlated with female body size. Average time from egg deposition to hatching emergence is 58·5 days. Mean emergence success ff hatchling is 58·3% in all clutches and 91·6% in clutches that produced hatchlings. The internesting interval averaged between 16 and 17 days. Site-fixity of females both within and between seasons was examined; a greater degree of site-fixity was exhibited between seasons than within. The distribution of hawksbill nesting activity at Tortuguero is spatially similar to, but temporally different from, that of the green turtle. There is increasing evidence from tag returns that the Tortuguero hawksbill may also share the feeding grounds of the Tortuguero green turtle in the Miskito Cays, Nicaragua. Notes on the movements and feeding habits of juveniles on their feeding grounds are included.Following a decline from 1956, there has been no consistent trend in the number of hawksbills nesting at Tortuguero since 1972. However, the mean carapace length of hawksbills has shown a steady decline, suggesting that the population is not demographically stable. The stability of an entire population cannot be determined from monitoring the number of nesting turtles each year.     

Reducing runoff by managing crop location at the catchment level,considering agronomic constraints at farm level

Runoff and erosion cause frequent damage through muddy floods in the loess belt of Northern Europe. One possibility for reducing damage is to lower runoff on agricultural land by spatially alternating different crops at the catchment level. But crop location results from decisions taken at the farm level. This study aimed to assess the existing leeway to modify crop location in the farms of a catchment, in order to reduce runoff at the catchment's outlet. The case study was the Bourville catchment (1086 ha), cultivated by 28 farmers and located in Pays de Caux, France. First, crop location rules in the 14 main farms of the catchment were analysed on the basis of surveys carried out with farmers, distinguishing spatial constraints from temporal ones. These rules made it possible to simulate crop location on each farm territory for the 2001–2002 crop year. Each field of the catchment was classified depending on whether one or several crops could be sown, taking into account both field history and farmer decision rules. Then two extreme scenarios of crop location in the Bourville catchment were built. Runoff simulation at the outlet with the STREAM model showed that runoff could be reduced while sticking to current farmer decision rules in terms of crop location. Depending on rainfall event characteristics, runoff reduction varied between 13·5 per cent and 4·5 per cent. Copyright © 2006 John Wiley & Sons, Ltd.     

Movements and activities of white-lipped peccaries in Corcovado National Park, Costa Rica

The conservation of remnant populations of white-lipped peccaries in Central America depends on adequate documentation of their habitat needs and behavior. Thus, we monitored the activity patterns, local distributions, and home ranges of 36 (25F:11M) radio-marked white-lipped peccaries, all members of a single “super” herd, in part of Corcovado National Park, their largest stronghold in Costa Rica, during 1996-1998. Peccaries were diurnal all year with a period of reduced activity during the middle of the day. They were found more often than expected (vs. random use) in primary forest during February to May, in secondary and coastal forest during June to September, and in herbaceous swamp during October to January, corresponding to relative fruit abundance. Overall, the peccary herd ranged over an area of <40 km², but use of the area shifted seasonally and movements were reduced when fruit was most abundant. Our data agree with the suggestion that peccary density may be higher where the interspersion or close proximity and mix of seasonally important habitats is high, and thus where peccaries do not have to travel as far for food. Habitat interspersion is therefore a significant conservation concern and should be addressed to make certain that peccary populations are not limited.     

乡镇土地集约利用评价及驱动因素分析

土地集约节约利用越来越成为人们关注的问题,对其进行科学评价也成为焦点.通过对武安市乡镇土地集约利用状况的调查,构建了适合乡镇土地集约度评价的指标体系,采用多因素综合评定法对乡镇土地集约度进行了评价,将武安市乡镇土地利用划分为4个集约等级.为了增强某些重要评价因素的显著性,提出了方差分析无量纲化算法,同时通过土地集约的相关性分析,找出土地集约利用的驱动力因素,分析了主要驱动因素的作用规律,并提出调整和提高土地集约利用的途径和措施.     

Exploring biophysical potential and sustainability of wheat cultivation in Uruguay at the national level

Abstract. A methodology is presented that explores soil survey information at the national level (1:1 M), generating sustainability indicators for wheat cultivation in Uruguay. Potential yields were calculated for simplified crop production situations under several constraints, such as limitation of water availability calculated from soil physical properties and climatic conditions, and limitation of nutrient availability calculated from soil fertility and climatic conditions. Land quality sufficiency was examined by comparing these yields with the constraint-free yield conditioned only by solar radiation, temperature and the crop's photosynthetic properties. Crop growth was simulated only for areas suitable for the defined agricultural use. Model runs were repeated with inclusion of a topsoil loss scenario over 20 years as defined from an erosion risk analysis. Comparison between crop growth simulations for the two situations, gives an indication of the changes in land quality status, which supplies an indicator for agroecological sustainability.
On the basis of crop growth simulation it is concluded that wheat production constraints in Uruguay appear to be mainly related to water availability limitations, while nutrient availability is near optimal for the suitable soils. The simulated loss of topsoil impacts most on soil physical properties, expressed in reduced water-limited yields. Soil fertility status, evaluated by change in nutrient-limited yields, was little affected by the scenario.     

Evaluating the land use potential of gypsiferous soils from field pedogenic characteristics

Abstract. Although gypsiferous soils cover approximately 100 million ha in the world, it is only in the past two decades that their pedogenic and agronomic properties have been better understood and their classification improved. There is still no method to assess adequately their production potential.
This paper focuses on gypsum accumulation forms as diagnostic criteria for a rapid soil suitability appraisal in the field. Pseudomycelia, gypsum spots, powdery coatings and other localized in situ precipitations usually indicate soils with less than 15% gypsum. Depending on their intensity and depth of occurrence in the root zone, they define a soil environment which is suitable for semi-sensitive and semi-tolerant crops. Continuous gypsum accumulations characterize soils or horizons with high (e.g. more than 25%) gypsum contents, and these can be used only for tolerant crops.
The land use potential of gypsiferous soils is primarily determined by: (a) the depth of the impermeable layer, (b)the gypsum content within the root zone, and (c) the crop tolerance level. A method is proposed to assess the land suitability of gypsiferous soils on the basis of these criteria.     

Evaluating urbanization,fragmentation and land use/land cover change pattern in Istanbul city,Turkey from 1971 TO 2002

Spatiotemporal analysis of landscape dynamics is crucial in formulating an appropriate set of actions in landscape management. This paper presents a large scale analysis of the spatiotemporal structure of Istanbul, a highly urbanized city in Turkey, from 1971 to 2002 using forest cover type maps analysed with geographical information systems (GIS) and a spatial statistics programme. The quantitative evidence indicated that increasing population and expanding urbanization caused drastic changes to the temporal and spatial dynamics of land use/land cover pattern in Istanbul. There was a net increase of 5387·3 ha in total forested areas (1·0 per cent) due to mainly reforestation activities even though the population increased three times over a 31‐year period. Increase in number of patches and decrease in mean patch size together demonstrated that the landscape developed into a more fragmented structure that would negatively affect biodiversity and the resilience of the ecosystems. In conclusion, plain increase in forest areas may not always be a favourable situation. The quality, composition and the configuration of forest landscape should also be analysed to present the dynamics of ecosystem in terms of ecological and economical sustainability over a longer time and larger area. Copyright © 2008 John Wiley & Sons, Ltd.     

我国可持续发展农业土地利用评价指标体系研究--农业土地永续利用评价指标体系

可持续发展农业土地利用是社会经济系统可持续发展的关键,对可持续发展农业土地利用的评价有利于指导这一战略的实现。可持续发展农业土地利用包括农业土地总量动态平衡和农业土地永续利用两个方面。研究可持续发展农业土地利用评价指标体系中的农业土地永续利用评价指标体系;这些指标具有动态性、地域性、服务又服从于社会生态经济可持续发展的特性。     

Modelling of event-based soil erosion in Costa Rica,Nicaragua and Mexico: evaluation of the EUROSEM model

This study was undertaken as part of a larger project to evaluate the impact of soil erosion on soil productivity in Costa Rica, Nicaragua and Mexico. An important part of the overall project consists of the use of the event-based EUROSEM model (European Soil Erosion Model) to predict soil erosion rates. This paper evaluates the use of the model both for single event and yearly soil loss estimations using erosion plot data from Nicaragua and data obtained through rainfall simulator experiments in Costa Rica and Mexico. EUROSEM was calibrated based on the hydrographs followed by the sedigraphs in Costa Rica and Mexico and this was followed by a model validation. In Nicaragua, model calibration was done using total soil loss values for 1993 and the model was consecutively validated using plot data for 1994 and 1995. The study stresses the importance of calibrating the model for individual catchments, and that the total area of plant stems and soil cohesion are crucial calibration parameters when modelling grassland with cover percentages above 60%. EUROSEM generally did not perform well on single event simulations in terms of simulating hydrographs and sedigraphs. Whereas the difference between observed and simulated total soil loss was between 0.0% and 100.0%, differences in total discharge, peak run-off rate and peak soil loss ranged between 2.0% and 326.5%. The difference was attributed to the model's inability to model crusting. The application of the model for yearly soil loss predictions looks promising with simulated and observed total soil loss values in Nicaragua differing by between 2.5% and 5.0%.     

Observations on the geographic distribution, ecology and conservation status of several Phaseolus bean species in Costa Rica

Interest in bean genetic resources of Central America has resumed because of disease pressures (e.g., web blight, BGMV) and limitations of current bean varieties. As most of the diversity in landraces has been explored, focus is now on the exploration of wild forms of the primary gene pool and wild species of the secondary gene pool. A germplasm collection was carried out in the field and resulted in the collection of 29 wild populations for six Phaseolus species; it complemented field work done in 1987. Nine more populations were found for P. costaricensis, 10 for wild P. lunatus, one for P. oligospermus, one for P. tuerckheimii, four for wild P. vulgaris and four for P. xanthotrichus. Ninety-three herbarium voucher specimens were collected for 19 populations of the six species (deposited at CR). These results confirm the presence of wild P. vulgaris on both slopes of the central valley of Costa Rica, namely in the life zones bh-MB and bmh-P, and of P. costaricensis in the life zone bmh-MB. These life zones of limited range in Costa Rica have been heavily modified, thus fully justifying the germplasm collection for ex situ conservation. For both species the range of distribution in Costa Rica has been almost completely sampled. The life characteristics of each species that are relevant for their conservation in situ are briefly reviewed. Distribution ranges of each wild bean species are compared with the present extension of national parks, protected areas and fauna/flora sanctuaries, and suggestions for expanding such protected areas are made.