Semi-arid North Research Articles

Pollen reconstructed Holocene vegetation response to climate change and human activity in a semi-arid mountain area of north China

Understanding Holocene vegetation response regimes will improve predictions of future vegetation dynamics in mountain areas of semi-arid north China. In this paper, we statistically analyzed the relationship between a pollen record in a mountain area of semi-arid north China and influencing variables independent of pollen data, in the hope that potential vegetation forcing and response regimes can be explored. Our result suggests that the cool deciduous forest (CDF) at high elevation and the temperate deciduous forest (TDF) at middle and lower elevation were sensitive in responding to temperature before 6000 cal. yr BP, but were not sensitive to the summer monsoon (SM). Since 6000 cal. yr BP, the CDF and TDF were sensitive in responding to the SM instead of temperature. Hence, a shift of response regimes can be placed at ∼6000 cal. yr BP, which happened to be consistent with the time that forest expansion changed to deforestation. The insensitive response to the SM during the early Holocene might be attributed to the vegetation elevational movement, the topographic barrier for forest migration from refugia, and/or the topographically related high resistance and resilience of mountain forests. The sensitive response of CDF and TDF to the weakening SM since 6000 cal. yr BP was mainly caused by the cumulative moisture deficit caused by the continual weakening of the SM. Human activity had little impact on mountain forests until several centuries ago. Mountain forest expansion in response to climate warming during the early to middle Holocene can provide analogues for the prediction of forest dynamics of future warming.

Enhancement of N2O emissions by grazing is related to soil physicochemical characteristics rather than nitrifier and denitrifier abundances in alpine grassland

Grazing can degrade grassland soil and increase nitrous oxide (N2O) emissions, but the underlying mechanism is poorly understood. We investigated the relationship of soil N2O emission with nitrifying enzyme activity (NEA), denitrifying enzyme activity (DEA), and the abundances of N2O-producing and N2O-reducing functional genes, in response to three grazing intensities (none, light, intensive) over two growing seasons on an alpine grassland on Kunlun Mountain in semi-arid North China. Compared to the non-grazed control, light and intensive grazing treatments increased the 2-yr total N2O emissions by 27.5% and 68.1%, respectively. Daily N2O flux rate correlated positively with soil water-filled pore space (WFPS), temperature, and dissolved organic carbon (DOC) but not with the abundances of nitrifiers (AOB, AOA, Nitrobacter-like nxrA), nitrate reducers (narG) and denitrifiers (nirS, nirK, and nosZ). These results suggest that soil environmental factors rather than nitrifier, N2O-producer and N2O-reducer abundances were more important in determining the grazing enhancement of N2O emissions from the alpine grassland in semi-arid areas. The abundance of AOB and Nitrobacter-like nxrA but not AOA correlated positively with NEA, indicating they are good indicators for the potential nitrification in this arid alpine grassland. Reducing grazing intensity from intensive to light resulted in more above-ground biomass and N uptake in both years and less N2O emissions in 2018. These results highlight the importance of establishing a proper grazing intensity to reduce N2O emissions from the degraded grassland while maintaining productivity for livestock.

Intervención, investigación e interacción dialógica entre conocimiento popular y académico

Research and extension in communities or territories make up a meeting between two cultures, two subjects, with very different subjectivities, in their way of conceiving this relation. These academic activities can be seen from the point of view of intervention, with elements of popular education, for the participation of the subjects. Thus, the purpose of this essay is to discuss the interaction and knowledge made possible by popular education as a mediator in obtaining data and returning it to the subjects studied, from the perspective of social transformation. This question originated in the interaction between the researcher and several subjects surveyed in the semi-arid North of Minas Gerais and the Jequitinhonha Valley. The action of educational intervention by the public university with society invariably generates impacts on the population. This contributes to the transformation of the realities of the subjects, either in their personal transformation or in the transformation and development of the place studied, reaffirming their identity and ethnicity in coexistence with their territorial ecosystems.Keywords: extension; education for participation; qualitative research; popular knowledge; social development.Article received on December 17, 2019. Accepted on March 13, 2020.How to citeLOPES, Frederico Antonio Mineiro. Intervenção, pesquisa e interação dialógica entre os conhecimentos popular e acadêmico. Estudos Sociedade e Agricultura, Rio de Janeiro, v. 28, n. 2, p. 476-496, jun. 2020.

The Middle to Upper Paleolithic transition in the southern Levant: New insights from the late Middle Paleolithic site of Far’ah II, Israel

Far’ah II is an open-air site in the north western Negev desert (Israel). Previous excavations in the 1970’s revealed a rich, in situ Middle Paleolithic (MP) assemblage composed of flint and limestone artifacts, animal bones and charcoal. Renewed excavation at the site were undertaken in 2017, to re-date it and provide a more accurate constrain to the sites’ age, as well as collect samples for paleoclimatic proxies. Our new Optically Stimulated Luminescence and 14C ages together with the stable oxygen isotope signature of the loess sediments, constrain the age of the upper archaeological horizon to <49 ka. This age agrees with the younger limit of 60–50 ka, obtained by Electron Spin Resonance ages, measured in the 1990’s. The heavy δ18O values in carbonates point to cooler climatic conditions than those that prevailed during the preceding short, warm episode between 58 and 49 ka. The fauna, pollen and charcoal collected during the excavation portray a savanna-like environment with a mix of Irano-Turanian and Saharo-Arabian elements and a minor Mediterranean component. The lithic assemblage exhibits large technological variability typical of the Late MP (LMP), amongst which are technological traits that are clearly present in the Initial Upper Paleolithic (IUP) assemblages at the nearby, and roughly contemporaneous, site of Boker Tachtit. If population replacement was the trigger to the MP-UP transition, we would have expected to see a clear break in the cultural material at the onset of the Upper Paleolithic. The semi-arid north western Negev, as an interim region between the Mediterranean and Saharo-Arabian ecozones could have facilitated interaction between populations moving north or south due to fluctuating climatic conditions and changes in population pressures, possibly leading to the emergence of new technological traditions that are observed in the later UP.

A comprehensive assessment framework for quantifying climatic and anthropogenic contributions to streamflow changes: A case study in a typical semi-arid North China basin

This study proposes to jointly use six Budyko framework-based methods, hydrological simulation, sensitivity indicator method, and empirical statistics to build a comprehensive assessment framework for quantifying climatic and anthropogenic contributions to streamflow changes. To evaluate its effectiveness, we conducted a case study in a typical northern semi-arid basin named Guanting in China. On average, human activities and climate change account for 80.22–81.51% and 18.49–19.78% of the streamflow decline in the two subbasins, i.e., Shixiali and Xiangshuipu, of the study basin during the 1984–1999 and 2000–2015 periods, respectively. Precipitation change outweighs potential evapotranspiration change as a primary climatic contributor of streamflow reduction in the two subbasins. In Xiangshuipu, the average precipitation elasticity of streamflow (εP) is 2.48 ± 0.23 and 2.56 ± 0.28 for the 1984–1999 and 2000–2015 periods, respectively, while εP in Shixiali has an average εP value of 2.49 ± 0.31 and 2.66 ± 0.32 during the two periods. Difference between the ten attribution methods varies between 5% and 12%, highlighting importance of applying this developed multi-method framework to avoid overestimation/underestimation and quantify uncertainty. This proposed comprehensive change attribution method is valuable for quantitatively distinguishing the relative contributions of external factors on hydrological regime changes.

Analysis of Rainfall and Temperature Trends and Variability in Semi-arid North-eastern Ethiopia

Northeast Ethiopia is a semi-arid region that exhibits high rainfall and temperature variability. The impact of climate change has received a great deal of attention worldwide. This study focused on detecting trends in in rainfall (1983-2013) and temperature (1981-2010) at annual, seasonal and monthly time scales for six weather stations in semi-arid north eastern Ethiopia. The study also aimed to determine dry spell length, number of rainy days, onset and cessation dates, and length of growing period. The non-parametric tests such as Mann-Kendall and Sen’s Slope were used to determine climatic trends. The results indicated that both the annual maximum and minimum temperature in the study region showed an increasing trend, but only the trend for maximum temperature was significant. In the same manner, both the Belg and Kiremt seasons maximum and minimum temperature also showed an increasing trend but only trend of maximum temperature during Belg season and trend of minimum and maximum temperature during Kiremt seasons was significant. The annual and Belg season rainfall in the region showed a decreasing trend and its trend was significant. The coefficient of rainfall variability for annual and Belg season was very high which could affect agricultural production in the region. In the contrary, the trend for Kiremt season rainfall was increasing without significant trend. On the other hand, the average length of dry spell during the Kiremt season in the region was generally long that ranged from 27 days to 39 days and showed both decreasing and increasing but with no significant trend in most stations. The number of annual rainy days also showed both increasing and decreasing trends but its trend was not significant. The length of growing period in the region was relatively stable at all stations during the last 30 years period without non-significant trend. In general, from the analysis of annual, seasonal and monthly rainfall and temperature data series it can be concluded that rainfall and temperature characteristics of the study area is changing, even though some of the trends on both parameters were not statistically significant.

Nitrogen fertilizer management for enhancing productivity and nitrogen-use efficiency in Bt cotton

A field experiment was conducted at ICAR–Indian Agricultural Research Institute (IARI), New Delhi during kharif 2013–14 to study the effect of four nitrogen (N) levels on crop productivity and nitrogen-use efficiency in Bt cotton in a factorial randomised complete block design (RCBD). There were nine treatments, viz. (i) 4-N rates (100, 125, 150, and 175 kg/ha as urea), (ii) two rates of N application at sowing (0 and 30 kg N/ha) and (iii) one absolute control. Significantly higher seed cotton and lint yields were obtained with application of 175 kg N/ha along with basal application of 30 kg N/ha compared to remaining treatment combinations. Total N-uptake, N-harvest index and normalized difference vegetative index (NDVI) of Bt-cotton were significantly higher at 175 kg N/ha compared with rest of N levels. However, highest N-use efficiency indices were recorded with 150 kg N/ha. A strong and positive correlation (r2=0.804-0.835) was observed between yield and NDVI indicating that NDVI could be used for predicting the potential yield of Bt cotton in semi-arid north Indian plains.

Simulated and predicted responses of tree stem radial growth to climate change—A case study in semi-arid north central China

Precise knowledge how tree growth will respond to future climate change is essential for the adapted management of forest ecosystems. By conducting sensitivity tests, tree-ring process-based cambial growth models can provide an innovative way to better understand wood formation under different climate change scenarios. As a case study in semi-arid north central China, we used artificially increased or decreased daily climatic data as input to the Vaganov-Shashkin dynamic growth model to investigate the response of wood formation to climatic change. By calibrating the tree-ring model using daily climate data over the period 1951–2010, we found that 81% of radial growth was driven by soil moisture, while 13% of growth was controlled by temperature. During the main growing season June–August, significant differences in the integral growth rate occurred after changing precipitation by ± 30% or by decreasing temperature by 3.0 °C (p < 0.05). However, increasing temperature showed only modest effects on tree radial growth rate. During the past 60 years, a significant advancement of the starting dates of growth was detected, whereby non-significant variability was found for the ending dates of growth. Contemporaneously, the effect of previous winter temperature (previous December to current January) on cambial growth initiation declined after 1980. Significant differences in the growth onset dates only occurred when temperature was reduced by 4.5 °C or increased by 5.5 °C. Moreover, both the onset and ending dates of growth in the study region were more sensitive to cooling rather than to warming. If temperature will increase by 2°C and precipitation will increase by 30% at the end of this century as predicted by some Earth system models, tree radial growth might increase by 19% in the study region, compared to the average during the period 1952–2010. Consequently, tree stem radial growth is expected to increase under a warming and wetting climatic scenario, but will decrease under drying conditions.

Hydrogeochemical controls and human health risk assessment of groundwater fluoride and boron in the semi-arid North East region of Ghana

In this study, eighty-eight (88) samples were collected from active boreholes in the North East region of Ghana and analyzed for concentrations of the hydrogeochemical parameters. This helped in understanding the hydrogeochemistry, spatial distribution, origin of groundwater F− and B and the level to which the underlying geology influences the F− and B. Human health risks of F− and B were also assessed based on the model of the US Environmental Protection Agency. Groundwater is alkaline in this area and the dominant hydrochemical facies is Na-HCO3 facies, which is a reflection of the predominant carbonate lithology of the Oti/Pendjari Group in the region. The study reveals that the F− concentrations range from 0.05 to 13.29 mg/L with an average value of 3.26 mg/L, suggesting that majority of the boreholes have F− concentrations higher than the acceptable limit (1.5 mg/L) of WHO. The B concentrations also vary from 0.03 to 5.13 mg/L with an average of 1.52 mg/L in excess of the guideline value of 0.5 mg/L. The groundwater F− and B threats, respectively affect about 70% and 82% of boreholes in the region particularly around the northeastern, southeastern, central, and western parts. F− and B are mainly coming from geogenic sources and are controlled by hydrogeochemical factors such as semi-arid climatic conditions of the region, alkaline nature of the water, water-rock interaction, intense weathering, ion exchange, mineral dissolution and precipitation. The human health risk assessment reveals that non-carcinogenic risk for F− and B is higher in children than the adult population. About 89% of children in the study area are exposed to initial symptoms of dental and skeletal fluorosis and have higher chances of cardio-protection since no health threat is currently reported for high B in drinking water. We recommend immediate action towards mitigating the high groundwater F− to safeguard the health and livelihood of the people.

Estudo de caso: cisterna urbana, em Várzea do Poço, Bahia

O estudo de caso mostra como famílias da zona urbana do município de Várzea do Poço, no Semiárido do Norte da Bahia, conseguem suprir o fornecimento de água para o consumo humano através de cisternas urbanas. O abastecimento no centro e na periferia da cidade se dá através da rede de tubos, cuja água é oriunda da represa de São José do Jacuípe, com captação na comunidade de Barra Nova, tratada e fornecida pela EMBASA. Pela salinização da represa nos últimos anos a água tornou-se inapropriada para o consumo humano. Os moradores resgataram e aprimoraram técnicas de estocagem de água de chuva em cisternas como forma de resolver o problema da falta de água apta ao consumo humano e preparo de alimentos. As demais demandas domésticas continuam supridas pela rede pública de abastecimento. Um aspecto muito positivo é a diversificação de tamanho das cisternas, adequando-as à estrutura fundiária urbana local e ao tamanho das famílias. Um grupo de religiosas assessora a comunidade, mobilizando recursos, organizando as famílias, articulando parceiros, e auxiliando-as na formação de militância e na gestão de um fundo rotativo que permite estender o projeto a novas famílias continuamente.

A coastal settlement of the chilean semi-arid north. the memory of its ecosystem

For the construction of a historical view of the Los Vilos coastline, located in the semiarid north of Chile, an attempt is made to reach consensus on academic and local knowledge, linking the archaeological, historical and visual archives with the memory of its inhabitants. None of this knowledge is considered subaltern, forming all of it a palimpsest of meanings that contribute to the study of the memory of that territory and reflect the ecosystemic identity of those who inhabit and work on its coastline. In the stories of the present-day vileno fishermen, elements of their marine nomadic past are reiterated, which they ascribe to a “changa” tradition of which they feel a part of.

BEDROCK MORTARS IN THE SEMIARID NORTH OF CHILE (30° S.): TIME, SPACE, AND SOCIAL PROCESSES AMONG LATE HOLOCENE HUNTER-GATHERERS

Bedrock mortars recur in the record of many prehispanic communities. However, few studies discuss their relationship with social processes. In the present work, we discuss a regional study of bedrock mortars in the semiarid north of Chile, specifically the Limarí River basin (30° S). Using a combination of formal, spatial, contextual, archaeobotanical, and absolute dating analyses, we assess the chronology of bedrock mortars and how they related to social processes of hunter-gatherer populations of the region (2000 BC to AD 1000). In particular, we suggest that an increase in production of bedrock mortars among pottery-using hunter-gatherer groups (AD 1–1000) can be observed, associated with a greater intensity of plant collection and use, and a diminution in the importance of hunting. This situation led to a set of new social relationships structured on the practice of collective grinding and shared use of bedrock mortars. These results show the importance of this material record as a means of approaching aspects of prehispanic social life, and demonstrates a methodological framework within which to interrogate this materiality by combining different analytical levels of bedrock mortars’ variability.

Dental Health and Diet of Two Prehistoric Populations from Chile's Semiarid North

This investigation examines dental health and diet of two prehistoric populations from Chile's semiarid north. Trace element and dental paleopathological analyses have been conducted on skeletal remains of hunter-gatherers of the Archaic period (n=99, ca. 1,800 BC) and agriculturalists of the Diaguita period (n=82, 1,000-1,500 AD). Archaeological and historical evidence indicates that the Diaguita diet primarily incorporated cultivated and wild plants, but also included pastoralism and marine resources. By contrast, the subsistence of Archaic peoples was primarily based on marine resources. Concentration values of the elements strontium and barium (mean log ratio values for Archaic = -0.7985, n=38; for Diaguita = -0.5475, n=53) support the archaeological evidence for subsistence mode, and thus for diet, of both populations. These concentrations fall within the ranges determined for various archaeological New World populations with similar subsistence and dietary patterns. Based on the differences in subsistence and diet, the variations in dental health between the two populations were investigated. The analysis to date has revealed that both populations suffered from infectious (antemortem tooth loss, abscesses, caries, alveolar recession), degenerative (calculus deposition), and developmental (enamel hypoplasia) dental pathologies. The differences in frequencies of some of the infection processes are statistically significant between the two populations (p,0.05), but overall do not seem to demonstrate, as many other studies have (Larsen, 1984; Schmucker, 1985; Murphy, 1993), as sharp decline in dental health from the hunter-gatherer population.

Long-term surface water changes and driving cause in Xiong’an, China: from dense Landsat time series images and synthetic analysis

China’s government statement recently reported the plan of constructing Xiong’an New Area, which aims to phase out some extra capital functions from Beijing and to explore an innovative urban development mode with the priority in eco-environmental protection. The New Area is located in the semi-arid North China Plain (NCP) and is home to NCP’s largest natural freshwater wetland, Baiyangdian Lake. A comprehensive realization of surface water dynamics would be crucial for policy-makers to outline a sustainable environment development strategy for New Area. In this study, we used a total of 245 time slices of cloud-free Landsat images to document the continuous changes of water bodies within Xiong’an City during 1984–2016 and to provide detailed evidence of water presence and persistency states and changes under the influences of climate change and human actions. Our results reveal that the New Area water body areas varied dramatically during the past 33 years, ranging from 0.44 km2 in April 1988 to 317.85 km2 in February 1989. The change of surface water area was not characterized by a monotonically decreasing tendency. The evolution processes can be divided into four sub-stages: the first extreme desiccation in mid-1980s, the wet stage with the most extensive inundation areas and strong inter-annual fluctuations from late-1988 to late 1999, another desiccation stage in early 2000s, and the overall recovering stage between 2007 and 2016. We also mapped the maximum water inundation extents and frequencies of all-season, pre-wet season (February-May) and post-wet season (September-December) for the 33 years and different sub-periods. Although there is good agreement between time series of surface water area evolution in the New Area and station-based precipitation and evaporation variations, multiple lines of evidences reviewed in previous research indicate that the degraded Baiyangdian Lake was also tightly associated with human activities from various aspects, including dam construction, groundwater extraction, agricultural irrigation, etc. We highlighted the current status of exploring the driving mechanism of surface water changes and existing problems, and then offer recommendations.

Conductivity gradients as inferred by electromagnetic-induction meter (EM38) readings within a salt-affected wetland in Saskatchewan, Canada

The change from deep-rooted grass and shrub vegetation to annual-cropping dryland farming has contributed to serious soil salinization challenges on the semi-arid North American Great Plains. In some cases, cultivation of the Great Plains has increased the availability of water, causing dominant sulfate salts to travel from the uphill areas to depressions where it will surface when water evaporates at the soil surface. A potential solution could include the replanting of the native deep-rooted vegetation, which requires knowledge of the spatial distribution of soil salinity. This study tested the soil factors influencing electromagnetic-induction meter (EM38) readings of soil salinity distribution around wetlands. The objectives were to: (1) predict growth and survival of Salix dasyclados Wimm. (cv. ‘India’) along a salinity gradient in a small wetland, and (2) investigate whether newly established willows affected water-table fluctuations, which would indicate their phreatophytic nature or their ability to obtain their water supply from the zone of saturation. Results indicated significantly lower salinity values for sampling points with EM38 readings above 175 and 250 mS m−1 for height and survival, respectively. In addition, diurnal fluxes of the water table in areas of good willow growth and lower salinity indicated that cultivar ‘India’ was phreatophytic in these areas and therefore has great potential for being used to combat saline seeps.

Movilidad y dieta en el valle de el mauro (31° 57’ S. - 71° 01’ W.), norte semiárido de Chile, entre 8350-929 cal. ap.

El valle de El Mauro se localiza a 40 km del Océano Pacífico (1000 msnm) en el extremo meridional del Norte Semiárido de Chile. Para contribuir al conocimiento de la movilidad y dieta prehispánica en el valle se analizó el radiocarbono y los isótopos de estroncio ( ?? Sr/ ?? Sr), oxígeno (?¹ ? O), nitrógeno (?¹ ? N) y carbono (?13C) de 21 individuos y un entierro múltiple (NMI=3). Los datos indican el arribo esporádico de individuos de origen y/o hábitat costeros entre 8350-3000 cal. AP. Posterior a 3000 cal. AP las inhumaciones se hicieron frecuentes, ya no de foráneos sino de individuos locales. Poco después de 2000 cal. AP y hasta 900 cal. AP las inhumaciones siguieron siendo frecuentes, también de individuos locales. En toda la secuencia temporal (8350-929 cal. AP) se consumieron eminentemente recursos terrestres/locales del valle. La carne terrestre fue parte de la dieta hasta ca. 2000 cal. AP. Luego se detectaron dos grupos: uno que mantuvo dietas que incorporaban carne y otro prácticamente vegetariano. En toda la secuencia se observó un consumo puro o preferente de plantas C3, pero después de ca. 2000 cal. AP se detectó la incorporación de plantas C4 o CAM en el grupo con dieta vegetariana.

Comparison of SWAT and GWLF Model Simulation Performance in Humid South and Semi-Arid North of China

Watershed models have gradually been adapted to support both decision and policy making for global environmental pollution control. In this study, two watershed models with different complexity, the Soil and Water Assessment Tool (SWAT) and the Generalized Watershed Loading Function (GWLF), were applied in two catchments in data scarce China, namely the Tunxi and the Hanjiaying basins with contrasting climatic conditions (humid and semi-arid, respectively). The performances of both models were assessed via comparison between simulated and measured monthly streamflow, sediment yield, and total nitrogen. Time series plots as well as four statistical measures (the coefficient of determination (R2), the Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS), and RMSE (root mean square error)—observations standard deviation ratio (RSR)) were used to estimate the performance of both models. The results show that both models were generally able to simulate monthly streamflow, sediment, and total nitrogen loadings during the simulation period. However, SWAT performed better for detailed representations, while GWLF could produce much better average values of the observed data. Thus, GWLF offers a user-friendly prospective alternative watershed model that requires little input data and that is applicable for areas where the input data required for SWAT are not always available. SWAT is more suitable for projects that require high accuracy and offers an advantage when measured data are scarce.

La fecha de la cerámica más temprana en los Andes sur. Una perspectiva macrorregional mediante modelos bayesianos

The earliest pottery marks a milestone in the human history of the southern Andes. This paper proposes an approximation of the date of the earliest pottery using Bayesian chronological models. Models of 84 radiocarbon and thermoluminescence dates from 49 sites are compared among five areas in Argentina (the provinces of San Juan and Mendoza) and Chile (the semi-arid north, central, and south central). Although there are still few data, they show an intriguing pattern of very similar dates with medians between 2100–2180 cal BP (2250–1920, 68% probability, starting boundaries) in four of the areas, though some error ranges are large. The similarity of the dates is striking considering that the macro-region extends over one thousand kilometers (north–south) from 30° to 39°S and includes a diverse range of environments. The contemporaneity is even more notable because these areas include the continent’s southern limit of agriculture. It is hoped this will encourage researchers to more carefully assess this period when excavating and dating relevant contexts as well as encourage discussions on the nature of the initial adoption of ceramics in the southern Andes.

Impact of foliar application of potassium and its spray schedule on yield and quality of sweet orange (Citrus sinensis) cv. Jaffa

A field study was undertaken to extrapolate the impact of foliar application of potash and its spray schedule on yield and physical and chemical parameters of sweet orange cv. Jaffa at experimental orchard, Department of Horticulture, CCS Haryana Agricultural University, Hisar. The results revealed that foliar application of KNO? at both the doses (2 and 4%) was found significantly or marginally better than K?SO? (1.5 and 3.0%) and control (water spray) in increasing the juice content. Peel content, peel thickness and rag content was found to be influenced significantly due to different treatments on K and its spray schedule. Minimum rag content (38.11%) was recorded with foliar application of KNO? at the rate of 4% and maximum with control. Ascorbic acid and acidity were found maximum with two foliar applications of KNO? at the rate of 4% in the last week of April and August. Foliar application of KNO? at the rate of 4% was found most effective in increasing yield of sweet orange over control and other K treatments. Spray of K in the last week of April, May and August was found superior in increasing yield closely followed by two sprays in the last week of April and August. The findings signify the importance of K spray in enhancing yield and quality of sweet orange under semi-arid north western conditions of India.

Community-based groundwater and ecosystem restoration in semi-arid north Rajasthan (3): Evidence from remote sensing

Community-based measures recharging groundwater in semi-arid India has historically underpinned rural socio-ecological resilience, though are declining through technological, policy and other changes. Nevertheless, exemplars of community action are achieving catchment regeneration, including in Alwar District (Rajasthan) since the mid-1980s. This study analysed satellite remote sensing (RS) data to detect trends in groundwater and linked ecosystem services. Data from Landsat satellite missions offered a long time series and free access, though data gaps in the LandSat archive prior to 1997 limited time series analysis. ISODATA (Iterative Self Organising Data Analysis Technique) was used to analyse land cover trends, detecting increasing vegetation cover but not river rejuvenation due to limited spatial and spectral resolution. Analyses of NDVI (Normalised Difference Vegetation Index) and MSI (Moisture Stress Index) were used to assess change in vegetation cover, vigour and moisture stress over time. Analytical outputs were equivocal, although inter-annual fluctuations were observed to follow antecedent rainfall as vegetation responded to rising soil moisture and groundwater. Despite these equivocal conclusions, the research strongly suggests that analysis of RS data with improved resolution can provide surrogate indicators of change in groundwater and associated ecosystem services, supporting formulation of flexible policies incorporating local action to regenerate socio-ecological systems.