Karst Research Articles

A Review of the Application of the Soil and Water Assessment Tool (SWAT) in Karst Watersheds

Karst water resources represent a primary source of freshwater supply, accounting for nearly 25% of the global population water needs. Karst aquifers have complex recharge characteristics, storage patterns, and flow dynamics. They also face a looming stress of depletion and quality degradation due to natural and anthropogenic pressures. This prompted hydrogeologists to apply innovative numerical approaches to better understand the functioning of karst watersheds and support karst water resources management. The Soil and Water Assessment Tool (SWAT) is a semi-distributed hydrological model that has been used to simulate flow and water pollutant transport, among other applications, in basins including karst watersheds. Its source code has also been modified by adding distinctive karst features and subsurface hydrology models to more accurately represent the karst aquifer discharge components. This review summarizes and discusses the findings of 75 SWAT-based studies in watersheds that are at least partially characterized by karst geology, with a primary focus on the hydrological assessment in modified SWAT models. Different karst processes were successfully implemented in SWAT, including the recharge in the epikarst, flows of the conduit and matrix systems, interbasin groundwater flow, and allogenic recharge from sinkholes and sinking streams. Nonetheless, additional improvements to the existing SWAT codes are still needed to better reproduce the heterogeneity and non-linearity of karst flow and storage mechanisms in future research.

Grain for Green Project May Not Threaten Ecosystem Sustainability by Degrading Water Availability in Humid Karst Landscapes

AbstractGrain for Green project could result in high evapotranspiration (ET), exacerbate water shortage, and intensify conflicts in water demand between ecosystems and humans in many water‐limited areas. However, it is still unclear how vegetation restoration would influence ET in humid karst regions where abundant precipitation but quick leakage. Particularly, it is challenging that existing ET measurement methods are not applicable simultaneously for various ecosystems in such highly heterogeneous and fragmented landscapes. To solve this issue, this study, for the first time, develops a new ET measurement system, by integrating multi‐techniques, to quantify ET for multiple vegetation restoration types and identify their controlling factors in a humid karst region for three consecutive years. The results show that (a) for different succession stages during natural restoration, the ET of secondary forest (680 ± 7 mm yr−1) > shrub (564 ± 16 mm yr−1) > grass (546 ± 12 mm yr−1) > cropland (513 ± 8 mm yr−1) (P < 0.05); (b) ET of all ecosystems are far less than that of precipitation (1,059 ± 63 mm yr−1) but closer to potential ET (849 ± 11 mm yr−1), and soil moisture has been maintained at >0.20 cm3cm−3 in the growing season; (c) solar radiation and vapor pressure deficit are the two predominant factors on the ET (P < 0.01), while there is no significant relationship between ET and soil moisture (P > 0.05). The results suggest that vegetation restoration returned from cropland in humid karst regions increased ET but may not induce water scarcity for vegetation sustainability, at least under normal climatic conditions.

Spatial Pattern Characteristics and Factors for the Present Status of Rural Settlements in the Lijiang River Basin Based on ArcGIS.

In China, rural settlements have undergone significant changes in response to dramatic socioeconomic shifts. However, there has not been any report on rural settlements in the Lijiang River Basin. In this study, ArcGIS 10.2 (including hot spot analysis and kernel density estimation) and Fragstats 4.2 (such as the landscape pattern index) software were used to analyze the spatial pattern and causes of rural settlements in the Lijiang River Basin. The Lijiang River Basin is mainly dominated by micro- and small-sized rural settlements with small areas. Moreover, the results of a hot spot analysis showed that micro- and small-sized rural settlements were mainly located in the upper reaches, and medium- and large-sized rural settlements were mainly located in the middle and lower reaches. The kernel density estimation results showed that the distribution characteristics of the rural settlements in the upper, middle, and lower reaches were significantly different. The spatial forms of rural settlements were affected by physiographic factors such as elevation and slope, karst landforms, and river trunk channels as well as the national policy system, tourism economic development, town distribution, historical heritage, and minority culture. This study is the first to systematically elaborate on the rural settlement pattern and its internal logic from the perspective of the Lijiang River Basin, providing a basis for the optimization and construction of the rural settlement pattern.

Coastal landscape classification using convolutional neural network and remote sensing data in Vietnam

The length of global coastline is about 356 thousand kilometers with various dynamic natural and anthropogenic. Although the number of studies on coastal landscape categorization has been increasing, it is still difficult to distinguish precisely them because the used methods commonly are traditional qualitative ones. With the leverage of remote sensing data and GIS tools, it helps categorize and identify a variety of features on land and water based on multi-source data. The aim of study is using different natural – social profile data obtained from ALOS, NOAA, and multi-temporal Landsat satellite images as input data of the convolutional-neural-network (CvNet) models for coastal landscape classification. Studies used 900 cut-line samples which represent coastal landscapes in Vietnam for training and optimizing CvNet models. As a result, nine coastal landscapes were identified including: deltas, alluvial, mature and young sand dunes, cliff, lagoon, tectonic, karst, and transitional landscapes. Three CvNet models using three different optimizer types classified the landscapes of other 1150 cut-lines in Vietnam with the accuracies about 98% and low loss function value. Excepting dalmatian, karst and delta coastal landscapes, five others distribute heterogeneous along the coasts in Vietnam. Therefore, the evaluation of additional natural components is necessary and CvNet model have ability to update new landscape types in variety of tropical nation as a step toward coastal landscape classification at both national and global scales.

A New Agricultural Drought Disaster Risk Assessment Framework: Coupled a Copula Function to Select Return Periods and the Jensen Model to Calculate Yield Loss

China is one of the regions with the most frequent drought disasters and serious social and economic losses. Agricultural drought is the most serious natural disaster. Due to climate change, the regional agricultural drought risk assessment has always been the focus of the academic circle. This study takes Zunyi City as an example, which is the most typical city of karst landform development. The monthly precipitation data set of ground meteorological observation stations in Zunyi City from 1956 to 2020 was selected, and the drought characteristic variables were extracted by the coupled use of the precipitation anomaly percentage (Pa) index and the theory of runs. A copula function was applied to establish the joint distribution model of characteristic variables, obtaining the drought frequency and drought return periods. Combined with the Jensen model, the agricultural drought loss rate under different drought return periods in the target year (2020) was calculated and evaluated. The results showed that the Gumbel-Hougaard copula function was suitable for the joint distribution of drought joint variables in Zunyi City. From 1956 to 2020, fewer droughts occurred in Zhengan and Wuchuan, and the most droughts took place in Fenggang, Meitan, and Yuqing. The average drought duration in each county was about 1.5 months, and the average drought severity was about 0.35 in spatial distribution. Crop loss rate caused by drought increased and the affected area expanded with the increase of drought return periods (5, 10, 20, 50, and 100 years) in temporal distribution. Meanwhile, the drought disaster was most drastic in the eastern region, followed by the south, north, west, and central area. The results were highly consistent with the historical drought in Zunyi City, which verified the validity of the model. This study could provide scientific knowledge for drought resistance and reasonable mitigation programing for the security of the regional agricultural production and the sustainability of social and economic development.

Diversity of protist genera in periphyton of tufa-depositing karstic river

PurposeIn aquatic ecosystems, protists play a crucial role and cover numerous ecological functions. The karstic Krka River (Croatia) is a unique hotspot for high diversity of aquatic organisms, especially protists. The main objective of the present study was to obtain a detailed overview of the protist community structure in the periphyton of the Krka River and to determine the differences in protist diversity along the river.MethodsProtist diversity was detected by amplicon sequencing of the hypervariable region V9 of the 18S rRNA gene, using the universal eukaryotic primer pair.ResultsThe three main groups of protists were as follows: Ciliophora, Cercozoa, and Bacillariophyta. In terms of abundance of protist OTUs, the shade plot revealed an evident difference from the upstream to downstream river section, which increased between locations from Krka spring to Skradinski buk. Diversity was explored using measures of alpha and beta diversity. Alpha diversity showed an increasing trend in the downstream direction of the river. The location effect, or clustering/grouping of samples by location, was confirmed by the PERMANOVA permutation test of beta diversity.ConclusionThe combination of alpha and beta diversity can help provide deeper insight into the study of diversity patterns, but also point out to decline in species diversity and allow for effective ways to protect aquatic karst habitats in future management.

Active and Relict Contact Karst morphological forms of the corrosional plain (Slavinski ravnik, SW Slovenia)

So far, the longest known unroofed cave in Slovenia has been found on the Slavinski ravnik, southwest of Postojna. From its position on the surface, its shape, and its containing sediments, we can infer its spatial and temporal development, as well as the processes and evolution of the contact karst in its hinterland. The corrosional plain Slavinski ravnik is a small area of the Dinaric Karst in Slovenia, located at the contact between impermeable flysch and karstified carbonate rocks, where many contact karst features formed. Due to erosion, multi-phase regional tectonic uplift, and sedimentation, a paragenetic cave system, active and relict blind valleys have formed. During the geomorphological mapping, elements were examined and drawn using ESRI ArcMap and Golden Software Surfer, and the stages of their formation were observed. During the survey, the active cave system Markov spodmol and Vodna jama v Lozi, the relict unroofed cave Brezstropa jama v Lozi, Biščevci blind valley, Sajevško polje blind valley, Ivačevci blind valley, and Sajevško polje sediment accumulation were studied. The changing hydrological regime, the allogenic sediments, the distribution of active and relict ponors, and the placement of active and relict elements of these contact karst forms, show different stages of formation and subsequent development of the northern border of Slavinski ravnik. The geomorphological map of these contact karst features and their following studies give us an insight into the morphogenesis of the southern karst periphery of the Postojna Basin as an exceptional - relatively small but highly variable Slovenian contact karst site.

Environmental heterogeneity increases the conservation value of small natural features in karst landscapes

Local biodiversity hotspots are often located within regions where extreme and variable environmental – e.g., climatic and soil – conditions occur. These areas are conservation priorities. Although environmental heterogeneity is recognised as an important determinant of biodiversity, studies focusing on the effects of multiple environmental heterogeneity components in the same ecosystem are scarce. Here we investigate how topography and related microclimatic variables and soil properties may influence the biodiversity and conservation value of karst landscapes. Karst landscapes of the world contain millions of dolines (i.e. bowl- or funnel-shaped depressions) that may function as ‘small natural features’ with a disproportionately large role in maintaining biodiversity relative to their size. We assessed the diversity of microclimates, soils and vegetation and their relationships in six microhabitats (south-facing slopes, east-facing slopes, west-facing slopes, north-facing slopes and bottoms of dolines, and the adjacent plateau) for nine large dolines in a grassland ecosystem. Although there were remarkable differences among the conservation value of these microhabitats (e.g., representation of different species groups, presence of ‘climate relicts’), each microhabitat had an important role in maintaining species that are rare or absent in other microhabitats in the landscape. We found that the studied dolines exhibited highly variable environmental conditions and promoted a high diversity of vegetation types with unique species composition, contributing to the topographic, climatic, soil, vegetation and land cover heterogeneity of karst landscapes. Therefore, our findings highlight that dolines may function as local biodiversity hotspots and have a crucial conservation importance. As dolines are widespread topographic features in many karst landscapes throughout the world, our results could be directly applied to other regions as well. An integrated approach is urgently needed to provide guidelines for landscape management, promoting the retention of the microhabitat diversity of small natural features for species vulnerable to climate change and/or various disturbances.

Hydrological Characteristics of the Bakony Region (Hungary)

In this study, the karst systems (karst types) of the Bakony Region are classified and described. The karst features and the groundwater (karstwater) flow, their horst (block) types and the hydrological cycle of horst types were taken into consideration. In the mountains, regional flow with a hypogene branch (hypogene karst system) and epigene karsts systems of local flow were distinguished. Among local epigene systems, epigene karst system, mixed epigene karst system, complex mixed epigene karst system, incomplete epigene karst system and semi-closed epigene karst system were distinguished. Local epigene systems are only temporarily (but not all of them) separated from the regional system that developed below and around them. During their development, separated local systems are more and more becoming the descending branches of regional systems.

The Ratio Distribution of Evapotranspiration to Precipitation well Related With Soil Thickness in Karst Watershed of Southwest China

AbstractEvapotranspiration (ET) is predominant variable for water management in various types of ecosystems, and it has been intensively studied through in situ measuring and modeling methods. However, it is challenging to measure actual ET and upscale it to regional level for karst landscapes, where aquifers typically show remarkable and rapid responses to precipitation events. There is an urgent need to quantify water fluxes to provide reliable evidence for the protection and sustainable management of karst water resources. Therefore, in this study, five plots were built to observe actual ET based on Thermal Dissipation Probes, redesigned ventilated chamber and in‐site microlysimeters in a karst watershed in southwest China. Then, three models (Penman‐Monteith‐Leurning, PML; Remote Sensing‐Priestley and Taylor; and Hargreaves) were constructed to upscale ET estimation to the regional level based on Landsat‐8 images and MODIS data. The results showed that: (a) The PML model performed better than other models (p < 0.01) with higher R2 values (0.72 for MODIS images and 0.87 for Landsat‐8 images); (b) Daily ET exhibited significant seasonal variability and different spatial distribution, and yearly ET exhibited well related with soil thickness (R2 = 0.58); (c) Daily ET had a slightly positive correlation with DEM, however, had a negative correlation with ground temperature. This study is helpful to improve accuracy of measured and estimated ET by combining remote sensing data, and it has important implications for upscaling it to regional level. It suggests that ET is strongly regulated by constant supply of water, vegetation coverage, and available energy in karst catchments.

Genetic Diversity and Differentiation of Chinese Fir around Karst Landform in Guangxi

The karst geo-ecosystems are fragile environments. The largest karst region in the world is located in southwestern China, within which the Guangxi province is one of the main areas. Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), an evergreen species, is an important fast-growing timber tree in southern China. In the present study, we examined the genetic diversity and spatial genetic differentiation of Chinese fir in sampling localities around the karst landform region of Guangxi by genotyping 330 individuals from 11 sampling localities with 22 novel polymorphic microsatellite loci. High levels of gene flow have homogenized Chinese fir in Rongshui, Nandan, and Tiane sites, which are speculated to be the primary center of gene exchange and diversity for Chinese fir around the karst landform in Guangxi. Significant isolation by distance pattern was found among nine sampling localities. A moderate level of genetic differentiation (FST = 0.089, Dest = 0.139) between sampling localities was detected. Structure analysis divided Chinese fir into three subgroups (K = 3). With higher differentiation and less genetic variation than in the central population, marginal populations of Cangwu and Pubei were identified in the south of the karst landform. An effective conservation strategy focusing on the maintenance of genetic variation for marginal populations of the species was proposed.

One new species of Aneumastus D.G. Mann et Stickle (Bacillariophyceae) from Krka River, Croatia

Karst rivers in Croatia are common phenomena and known biodiversity hotspots for many different groups of organisms. Due their importance from a natural, cultural and socio-economic point of view, most of them are protected as National Parks. Diatoms in these habitats are not well known, and recently detailed study has been started. During observations of samples from Lake Visovac on Krka River, one <i>Aneumastus</i> species with specific morphological features, has been recorded. The species is characterized by linear valves with almost parallel margins in the mid-valve, rostrate apices and striae that are partly biseriate, coarsely punctate and distantly spaced. In this study, it is described as a new species <i>Aneumastus </i><i>visovacensis</i> sp. nov. Its morphology is documented with light and scanning electron microscopy, described in detail, and compared with the most similar species from <i>A. tusculus </i>species complex.

RETRACTED: A tropical soil (Ferralsol) identified in the northernmost part of the Mediterranean (Istria, Croatia)

Terra rossa soils on the Istrian peninsula are generally considered polygenetic relict soils. They overlie and mark the youngest subaerial unconformity in the northwestern part of the Adriatic Carbonate Platform and are susceptible to erosional and redepositional processes. Terra rossa soils represent a valuable archive of information that can be used to understand present and past soil formation processes in the context of climate variability and landscape dynamics, especially in low-lying parts of the karst landscape where thicker deposits are typically found. We studied a 3 m thick terra rossa profile in a karst depression on the northernmost part of the southwestern Istrian planation surface and analysed the micromorphology, physical/chemical properties, geochemistry, bulk and clay mineralogy, and composition of heavy and light mineral fractions. The profile shows several signs of colluviation and polygenesis with clay distribution along the profile, clearly indicating lithic discontinuities. Kaolinization, along with iron oxide formation, is the dominant process in the studied profile. Ferralitization and lessivage processes were diagnosed throughout the profile, with intense clay translocation occurring despite the extremely stable soil microaggregates. In accordance with the WRB system, the profile is classified as Lixic Rhodic Ferralsol (Clayic, Aric). This implies that some terra rossa soils, previously classified as e.g. Cambisols or Luvisols, might actually be Ferralsols or other tropical soils (e.g. Lixisols), in which relict properties are preserved in the present climate. The finding of a Ferralsol in the study area indicates the old age of the surface of the karst depression and provides the first data on the burial history of the southwestern Istrian planation surface. We suggest the older Quaternary interglacials, the mid-Piacenzian Warm Period (Pliocene) and the Miocene Climatic Optimum as favourable periods for the formation of the studied soil.

Investigation on immiscible N2 WAG and SWAG after water flooding in the paleo-subterranean river of fractured-vuggy reservoirs

The complex spatial distribution of caves and fractures results in the low oil recovery after water flooding in paleo-subterranean river of fractured-vuggy reservoirs. This paper tries to solve the problem of how to adopt water-alternating-gas (WAG) and simultaneous-water-and-gas (SWAG) to enhance oil recovery in paleo-subterranean river reservoirs. Aiming at this objective, we constructed one physical experimental and numerical model according to the geological section in Tahe Oilfield. The research on water flooding, WAG, and SWAG were carried out through experiments and simulations. The results show that there were four kinds of remaining oil after water flooding in the paleo-subterranean river karst reservoirs, i.e., blind end remaining oil, shielded remaining oil, attic remaining oil, and corner remaining oil. WAG can extract the shielded remaining oil, attic remaining oil, and part of the corner remaining oil efficiently, while SWAG can only work on the attic remaining oil. In addition, too low injection rate lacked driving force support and restricted the expansion of the swept zone. Too small gas-water ratio and slug size can’t play a good role in gas displacement. This paper is the first systematic study of the paleo-subterranean river reservoirs, and the results can provide a basis for production practice.

The distribution, sources and health risk of polycyclic aromatic hydrocarbons (PAHs) in sediments of Liujiang River Basin: A field study in typical karstic river

The accumulation of PAHs in sediments of Liujiang River Basin were investigated to disclose the sources, input processes and toxicity risk of PAHs in a typical karstic river. The results revealed the concentrations of ∑15PAHs are ranging from 111.97 to 593.39 ng/g, most of which are centralized in upstream and midstream of Liujiang River. Positive Matrix Factorization identified PAHs are mainly from the mixed combustion of oil and coal, biomass combustion and oil products leaking. Redundancy analysis manifested mixed accumulation should be the main approach of PAHs that inputting sediment. The values of RQNCs and RQMPCs suggested the moderate contamination of PAHs. The higher HQ and ILCR indicated the ingestion of PAHs are the main way to impact public health, while children should be more susceptible to PAHs. The values of HQ and ILCR indicated the overall low non-carcinogenic risk of PAHs, but relatively high carcinogenic risk of PAHs.

Spatio-Temporal Variations of Ecosystem Water Use Efficiency and Its Drivers in Southwest China

Water use efficiency (WUE) has garnered considerable attention at global and regional levels. However, spatio-temporal variations of WUE and related influencing factors in the complex karst landforms of southwest China require further elucidation. Herein, the ratio of gross primary productivity (GPP) to evapotranspiration (ET) obtained through the PML-V2 product was used to characterize ecosystem WUE, the spatio-temporal variations to ecosystem WUE, and responses to temperature, precipitation, and the enhanced vegetation index (EVI) in southwest China. The results showed that: (1) The ecosystem WUE in southwest China decreased with increasing latitude and altitude. Spatially, the ecosystem WUE fluctuates in a “W” pattern with increasing longitude because of the karst landforms’ distribution patterns. (2) The non-significant trend in increased ecosystem WUE during 2003–2017 may be associated with significant increases in the ET offsetting part of the GPP contribution to ecosystem WUE. Spatial distribution of changes in WUE is similar to GPP owing to the dominant role of GPP in changes to ecosystem WUE. (3) The multi-year average ecosystem WUE was lower in karst than in non-karst landforms; however, vegetation restoration projects have contributed in significantly increasing variation rate of ecosystem WUE in karst than that in non-karst landforms. (4) Temperature, precipitation, and EVI were generally positively correlated with ecosystem WUE and were important factors for the increase in ecosystem WUE. EVI characterized vegetation restoration indicators showed that the ecological engineering construction in the study area was effective and was the dominant factor of ecosystem WUE change in 59.59% of the study area. The results of this study are important for further understanding carbon and water cycling processes in karst regions.

Modelling daily streamflow in a temporary karst river system: comparing three approaches using the SWAT model

ABSTRACT This work tests different options for simulating hydrology in basins with karst areas. The Soil and Water Assessment Tool (SWAT) model was applied to the Canale d’Aiedda (Puglia, Italy), a Mediterranean temporary karst river basin. Different basin delineations and model parameterizations were adopted that include: (i) cutoff of the karst areas (configuration A); (ii) basin set-up including the karst areas (configuration B) and (iii) model parameterization considering a bypass flow in karst sub-basins (configuration C). The model performance was satisfactory for daily streamflow for configurations B and C and good for A. A better simulated large floods. C presented the best fit for monthly streamflow from May to July. Regarding the water balance, C showed higher values of surface runoff and lower values of total water yield than A and B. Bypass flow proved to be a valid option to improve the simulation of the hydrological processes in karst areas.

Hydrogeologic and geomorphic processes in a karst landscape and seasonably-cold climate: Linking spatial distribution and morphometric dynamics of closed depressions to bedrock fractures in a wastewater spray irrigated agricultural and forest system located at the site of the Living Filter in Central Pennsylvania, United States

The Living Filter at Pennsylvania State University in Central Pennsylvania receives on average 1.5 million gallons per day (MGD) of secondary treated wastewater effluent year-round since 1962. The objective of this study was to identify and relate any bedrock fracture traces and surface depressions to any surficial or geomorphologic processes currently underway as a result of irrigation. The Living Filter is underlain by a massive dolomite with fractures trending near N-S that were previously documented using photogrammetry. A manual process was developed in order to determine the trend and location of several fracture traces within the Astronomy site section of the Living Filter. A semi-automated isolation scheme was next used to identify and correlate closed depressions to the location of fracture traces in the Living Filter. A predominant but slight NE-SW trend was observed among fractures at N5E in the area north of the Pennsylvania Furnace Anticline. A high occurrence of depressions was noted in the area of fractures compared to non-fractured bedrock. The depressions in this area were found to have a net gain of 8000 ft2, the result of which was from the net loss of 5000 ft2 within the agricultural portion of the site and a net gain of 13,000 ft2 within the forested portion of the site. Cross sections of several depressions within cropped areas indicated a lower angle slope corresponding to a V-shape while depressions within forested areas were characterized by a traditional U-shape and previously established steeper slope. These findings will enhance the current understanding of the different morphologic characteristics of both forested and agricultural depressions in karst topography. The workflows implemented here can be implemented in similar sites that display topographical variances from the bedrock fractures.

Effects of distribution patterns of karst landscapes on runoff and sediment yield in karst watersheds

Aquatic karst landscapes are highly heterogeneous and vulnerable to environmental conditions due to carbonate rock dissolution by flowing water, freshwater movement and sediment transport. However, the landscape metrics commonly used in landscape ecology do not consider the spatial distribution of carbonate rocks in karst watersheds because these metrics are derived from land use/land cover maps. Therefore, this study investigated the effects of distribution patterns of karst landscapes on annual runoff and sediment yield in 40 heterogeneous karst watersheds in southwest China. The results show that the distribution patterns of karst landscapes significantly influenced annual runoff and sediment yield. A general linear model explained 74% of the runoff variations, indicating that the distribution pattern was the principal factor affecting runoff. Although these patterns significantly affected sediment yield, the general linear model accounted for only 52% of the sediment yield variations. Thus, the distribution patterns showed larger effects on runoff than sediment yield. This may be because landscape metrics of karst distribution patterns could not fully reflect the three-dimensional (3D) hydrogeological structure of karst watersheds. It is necessary to investigate the effects of 3D hydrogeological structures and hydrological and sediment connectivity on sediment yield. This will facilitate a more in-depth understanding of soil erosion mechanisms in karst watersheds.

Geopedological transects in karst landscapes in Campeche, Mexico

Objective: Apples cultivated in Mexico generally are smaller and softer than those produced in other geographical latitudes considered as optimal for apple production. The aim of this evaluation was determine the effect of applications with calcium, nitrogen, potassium, magnesium, sulfur and naphthaleneacetic acid (NAA), as well as the harvest date on the quality of apple fruits. Methodology ‘Golden Smoothie’ apple trees were treated foliarly with CaCl2 with and without NAA, and with a mixture of N, K, Mg and S or gypsum applied to soil for two years. Apples were harvested at 141 (regular harvest date), 161 (mid-late harvest) and 171 days (late harvest) after full bloom (DAFB) and evaluated for quality at harvest time and during their storage at 0°C for up to 179 days. Results: Foliar applications of CaCl2 significantly increased the calcium content in fruit and leaves, but fruit quality, including firmness, was not influenced. Fertilization of soil with the mixture of nutrients, including CaSO4, did not influence the fruit quality. Lately harvested fruit was 14.9% heavier but 17.1% softer than fruit picked at the commercial harvest date. Delaying of fruit harvest reduced about 43 d the storability of fruit. Based in these results, the relative softness of apples grown in Mexico is not related with its calcium content, hence unlikely to be overcome with the application of this mineral. Conclusions: Even in the control fruits, both seasons, the stored fruits do not show some physiological disorder as bitter pit