Long-term Average Rainfall Research Articles

Rainfall reliability and maize production in the Bamenda Highlands of Cameroon

The long-term average rainfall for a given period (month, season or year) scarcely indicates reliability because rainfall in low latitudes varies significantly from one year to the other. The less variable rainfall is, the more reliable it is, as the index of variability measures the likelihood of repetition in the mean amount of rainfall. This study bridges some gaps in related studies in the Bamenda Highlands, such as a study assessing climate change impacts on food security, where the Rainfall Anomaly Index was used and another study on the impact of rainfall on maize production using the Standardized Precipitation Index. The objectives of this study are to assess rainfall reliability and establish the impact of rainfall reliability on maize production. Rainfall data were collected from 15 stations, while maize output was collected for four localities. Results revealed that rainfall is still reliable for 13 stations, with a coefficient of variations of 9.62 to 18.54 %, while Ndop and Ndawara recorded unreliable rainfall of 23.14 % and 30.97 % respectively. Rainfall reliability was complemented by the Standardized Precipitation Index, which showed that only 53.45 % of rainfall episodes were normal to sustain maize production, while 46.55 % were events of rainfall deficits. Maize production has been decreasing in Ndu, Oku and Nkum while increasing in Ndop. These findings reflect the realities of other tropical mountainous regions in the world. Faced with future climatic uncertainties, farmers should embrace agroecological practices, climate-smart agriculture, conservation agriculture, Nature-based Solutions, Ecosystem-based Adaptation and diversification of production systems and livelihood sources to ensure food security.

Crops in crises: Shocks shape smallholders' diversification in rural Ethiopia

Crop diversity plays a central role in smallholder farmers' ability to cope with and adapt to shocks. Shifting crop varieties and diversifying the crop portfolio are common risk reduction strategies. This paper addresses the influence of covariate climate shocks and idiosyncratic socioeconomic shocks on crop variety use and crop species diversification by smallholder farmers using nationwide balanced panel data (2011/12, 2013/14, & 2015/16) from rural households in Ethiopia combined with village-level historical monthly rainfall and temperature data. We apply correlated random effects models, which control for time-invariant household unobservables. Past exposure to drought shocks increased the use of improved seed varieties in general and for wheat, while long-term average rainfall and lagged flood shocks enhance crop species diversity. Lagged temperature shocks increase improved seed use and crop species diversity. However, recurrent drought exposure and exposure to relatively more severe drought shocks significantly reduced overall agricultural activity. Idiosyncratic shocks, to a much lesser degree, influenced seed use and crop diversification decisions compared to covariate drought shocks. Heterogeneity analysis revealed that drought shock exposure on farmers with less than average farm sizes and other assets - compared to those better-off – increased their relative reliance on local seed use, reduced crop diversification, and reduced improved seed use. The results are robust to various sensitivity checks. Our findings are relevant for policy responses aiming to strengthen smallholders' ability to cope with and adapt to shocks: farmers' seed-based risk reduction strategies rely on access to seeds from both formal and informal seed systems, but policies addressing economic inequality are needed to enhance access to improved seeds and crop diversity for resource-poor socioeconomic groups.

Environmental variation effects fertility in tropical beef cattle.

The northern Australia beef cattle industry operates in harsh environmental conditions which consistently suppress female fertility. To better understand the environmental effect on cattle raised extensively in northern Australia, new environmental descriptors were defined for 54 commercial herds located across the region. Three fertility traits, based on the presence of a corpus luteum at 600 d of age, indicating puberty, (CL Presence, n = 25,176), heifer pregnancy (n = 20,989) and first lactation pregnancy (n = 10,072) were recorded. Temperature, humidity, and rainfall were obtained from publicly available data based on herd location. Being pubertal at 600 d (i.e. CL Presence) increased the likelihood of success at heifer pregnancy and first lactation pregnancy (P < 0.05), underscoring the importance of early puberty in reproductive success. A temperature humidity index (THI) of 65–70 had a significant (P < 0.05) negative effect on first lactation pregnancy rate, heifer pregnancy and puberty at 600 d of age. Area under the curve of daily THI was significant (P < 0.05) and reduced the likelihood of pregnancy at first lactation and puberty at 600 days. Deviation from long-term average rainfall was not significant (P < 0.05) for any trait. Average daily weight gain had a significant and positive relationship (P < 0.05) for heifer and first lactation pregnancy. The results indicate that chronic or cumulative heat load is more determinantal to reproductive performance than acute heat stress. The reason for the lack of a clear relationship between acute heat stress and reproductive performance is unclear but may be partially explained by peak THI and peak nutrition coinciding at the same time. Sufficient evidence was found to justify the use of average daily weight gain and chronic heat load as descriptors to define an environmental gradient.

CMBEAR: Python-Based Recharge Estimator Using the Chloride Mass Balance Method in Australia.

The chloride mass balance (CMB) method is widely used to estimate long-term rates of groundwater recharge. In regions where surface water runoff is negligible, recharge can be estimated using measurements of chloride concentrations of groundwater and precipitation, and an estimate of long-term average rainfall. This paper presents the Chloride Mass Balance Estimator of Australian Recharge (CMBEAR), a Jupyter (Python) Notebook that is set up to rapidly apply the CMB method using gridded maps of chloride deposition rates across the Australian continent. For an Australian context, the chloride deposition rate and rainfall maps have been provided. Thus, CMBEAR requires only a spreadsheet with the groundwater chloride concentration, the latitude and longitude of the sample location, and some simple user inputs. CMBEAR may be easily applied in other regions, providing that a gridded chloride deposition map is available. Recharge estimates from CMBEAR are compared against published applications of the CMB method. CMBEAR is also applied to a large dataset from the Northern Territory and is used to produce a gridded map of recharge for western Victoria. CMBEAR provides a reproducible and straightforward approach to apply the CMB method to estimate groundwater recharge.

Spatial-Temporal Trend Analysis of Rainfall Erosivity and Erosivity Density of Tropical Area in Air Bengkulu Watershed, Indonesia

Abstract There have been many studies on rainfall erosivity and erosivity density (ED). However, it was not widely developed in Indonesia as a tropical country and has unique precipitation patterns. They are indicators for assessing the potential risk of soil erosion. The Air Bengkulu Watershed is undergoing severe land degradation due to soil erosion. This study aimed to analyze spatial-temporal in rainfall erosivity and ED based on monthly rainfall data (mm). The data used consisted of 19 weather stations during the period 2006–2020 and which are sparsely distributed over the watershed. The analysis was done by using Arnold's equation. Then, the trend was tested using parametric and non-parametric statistics, and analysed with linear regression equation, and Spearman's Rho and Mann Kendall's tests. The spatial distribution of both algorithms was analysed using the inverse distance weighted (IDW) method based on the geographic information system (GIS). Unlike previous research findings, The long-term average monthly rainfall erosivity and ED revealed a general increase and decreasing trend, whereas it was found to be non-significant when both indices were observed. However, these results indicate a range from 840.94 MJ · mm−1 · ha−1 · h−1 · a−1, 552.42 MJ · mm−1 · ha−1 · h−1 · a−1 to 472.09 MJ · mm−1 · ha−1 · h−1 · a−1 in that November month followed by December and April are the most susceptible months for soil erosion. Therefore, The upstream area of the region shows that various anthropogenic activities must be managed properly by taking into account the rainfall erosivity on the environment and that more stringent measures should be followed in soil and water conservation activities.

Mapping groundwater recharge in Africa from ground observations and implications for water security

Groundwater forms the basis of water supplies across much of Africa and its development is rising as demand for secure water increases. Recharge rates are a key component for assessing groundwater development potential, but have not been mapped across Africa, other than from global models. Here we quantify long-term average (LTA) distributed groundwater recharge rates across Africa for the period 1970–2019 from 134 ground-based estimates and upscaled statistically. Natural diffuse and local focussed recharge, where this mechanism is widespread, are included but discrete leakage from large rivers, lakes or from irrigation are excluded. We find that measurable LTA recharge is found in most environments with average decadal recharge depths in arid and semi-arid areas of 60 mm (30–140 mm) and 200 mm (90–430 mm) respectively. A linear mixed model shows that at the scale of the African continent only LTA rainfall is related to LTA recharge—the inclusion of other climate and terrestrial factors do not improve the model. Kriging methods indicate spatial dependency to 900 km suggesting that factors other than LTA rainfall are important at local scales. We estimate that average decadal recharge in Africa is 15 000 km3 (4900–45 000 km3), approximately 2% of estimated groundwater storage across the continent, but is characterised by stark variability between high-storage/low-recharge sedimentary aquifers in North Africa, and low-storage/high-recharge weathered crystalline-rock aquifers across much of tropical Africa. African water security is greatly enhanced by this distribution, as many countries with low recharge possess substantial groundwater storage, whereas countries with low storage experience high, regular recharge. The dataset provides a first, ground-based approximation of the renewability of groundwater storage in Africa and can be used to refine and validate global and continental hydrological models while also providing a baseline against future change.

Climate impacts associated with reduced diet diversity in children across nineteen countries

It is widely anticipated that climate change will negatively affect both food security and diet diversity. Diet diversity is especially critical for children as it correlates with macro and micronutrient intake important for child development. Despite these anticipated links, little empirical evidence has demonstrated a relationship between diet diversity and climate change, especially across large datasets spanning multiple global regions and with more recent climate data. Here we use survey data from 19 countries and more than 107 000 children, coupled with 30 years of precipitation and temperature data, to explore the relationship of climate to child diet diversity while controlling for other agroecological, geographic, and socioeconomic factors. We find that higher long-term temperatures are associated with decreases in overall child diet diversity, while higher rainfall in the previous year, compared to the long-term average rainfall, is associated with greater diet diversity. Examining six regions (Asia, Central America, North Africa, South America, Southeast Africa, and West Africa) individually, we find that five have significant reductions in diet diversity associated with higher temperatures while three have significant increases in diet diversity associated with higher precipitation. In West Africa, increasing rainfall appears to counterbalance the effect of rising temperature impacts on diet diversity. In some regions, the statistical effect of climate on diet diversity is comparable to, or greater than, other common development efforts including those focused on education, improved water and toilets, and poverty reduction. These results suggest that warming temperatures and increasing rainfall variability could have profound short- and long-term impacts on child diet diversity, potentially undermining widespread development interventions aimed at improving food security.

The Climatic Analysis of Summer Monsoon Extreme Precipitation Events over West Africa in CMIP6 Simulations

We evaluate the capability of 21 models from the new state-of-the-art Coupled Model Intercomparison Project, Phase 6 (CMIP6) in the representation of present-day precipitation characteristics and extremes along with their statistics in simulating daily precipitation during the West African Monsoon (WAM) period (June–September). The study uses a set of standard extreme precipitation indices as defined by the Expert Team on Climate Change Detection and Indices constructed using CMIP6 models and observational datasets for comparison. Three observations; Global Precipitation Climatology Project (GPCP), Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), and Tropical Applications of Meteorology using SATellite and ground-based observation (TAMSAT) datasets are used for the validation of the model simulations. The results show that observed datasets present nearly the same spatial pattern but discrepancies in the magnitude of rainfall characteristics. The models show substantial discrepancies in comparison with the observations and among themselves. A number of the models depict the pattern of rainfall intensity as observed but some models overestimate the pattern over the coastal parts (FGOALS-f3-L and GFDL-ESM4) and western part (FGOALS-f3-L) of West Africa. All model simulations explicitly show the pattern of wet days but with large discrepancies in their frequencies. On extreme rainfall, half of the models express more intense extremes in the 95th percentiles while the other half simulate less intense extremes. All the models overestimate the mean maximum wet spell length except FGOALS-f3-L. The spatial patterns of the mean maximum dry spell length show a good general agreement across the different models, and the observations except for four models that show an overestimation in the Sahara subregion. INM-CM4-8 and INM-CM5-0 display smaller discrepancies from their long-term average rainfall characteristics, in terms of extreme rainfall estimates than the other CMIP6 datasets. For the frequency of heavy rainfall, TaiESM1 and IPSL-CMGA-LR perform better when compared with observational datasets. MIROC6 and GFDL-ESM4 displayed the largest error in representing the frequency of heavy rainfall and 95th percentile extremes, and therefore, cannot be reliable. The study has assessed how rainfall extremes are captured in both observation and the models. Though there are some discrepancies, it gives room for improvement of the models in the next version of CMIP.

Trend analysis of long-term rainfall and temperature data for Ethiopia

ABSTRACT Trend analysis for the long-term average temperature and rainfall of Ethiopia during 1901 to 2015 has been performed to understand the pattern of these important meteorological features under climate change. The rainfall characterizations viz., precipitation concentration index (PCI), seasonality index (SI), rainfall anomaly index (RAI) and departure analysis of rainfall (DAR) have been calculated and interpreted. The annual rainfall recorded for the whole period was 816.3 ± 90.82 mm/year. During kiremt (long rainy) season, maximum seasonal rainfall of 453.2 mm were recorded while, its minimum value (39.6 mm) were received in bega (dry) season, respectively. The analysis of probability distribution for the time series data showed slightly positive skewness and kurtosis in monthly, seasonal and annual rainfall from the normal distribution. The results of Modified Mann–Kendall trend analysis for average temperature revealed a significant increasing trend from 1961 to 2015. Conversely, dry season (bega) rainfall, showed an increasing trend while kiremt season rainfall with decreasing trend for the period of 1901–2015. However, annual and other seasonal rainfall did not show any statistically significant trend. Study concludes that there is an increase in the average temperature in Ethiopia but, it constitutes a high degree of stability in rainfall rate and distribution.

Intestinal Helminths and the Influence of Environmental Factors on Cattle Infection in the Altai Mountains

The purpose of the research: comparative assessment of cattle infection with intestinal helminths in various provinces and characteristics of the relationship between abiotic and anthropogenic environmental factors with the level of infection and the number of helminths in the Altai Mountains. Materials and methods. According to the results of long-term (2010–2019) ovolarvoscopic examinations, more than 2.4 thousand heads of cattle from 7 regions of the Altai Republic characterized by extensity of infection (EI) and the number of helminth eggs in 1 g of feces (NHE/g) in animals. By correlation analysis, the association of animal EI with helminths, NHE/g and abiotic and anthropogenic environmental factors in the context of farms and regions of the Altai Mountains is shown. The following parameters are estimated: long-term average annual temperature, long-term average annual rainfall, longterm average summer temperature, long-term average summer rainfall, altitude above the sea level, population density of the host, the effect of parasiticidal treatments of animals on parasite infection. Results and discussion. It was found that animals are mostly infected with intestinal helminths in the Choy region, where the EI was 61.7% when detecting NHE/g 81.8 pcs. Minimal infection of cattle by helminths was recorded in the Kosh-Agach region – 38.8% with NHE/g of 22.9 pcs. In the whole country, EI of animals is 51.8% with an egg number of 44.1 individuals in 1 g of feces. Within the physical-geographical provinces, cattle are mostly infected in Central Altai (EI – 56.5%, NHE/g – 43.6 pcs.), to a lesser extent in Southeast Altai (EI – 38.8%, NHE/g – 22.9 pcs.). According to the results of ovoscopic examinations, it was found that the most significant factors affecting the infection of animals with intestinal helminths in farms are the long-term average annual precipitation (r = 0.60 and 0.34) and the degree of anthropogenic pressure (r = -0.52 and -0.59), in the context of districts, long-term average annual temperatures (r = 0.65 and 0.55), average annual summer rainfall (r = 0.74 and 0.65). According to larvoscopy, the most significant environmental factors affecting cattle infection are long-term average annual temperature (r = 0.62 and 0.72), long-term average annual rainfall (r = 0.76) and elevation (r = -0.71 and -0.73), in farms – the degree of anthropogenic press (r = -0.65 and -0.78).

Variation characteristics of rainfall erosivity in Guizhou Province and the correlation with the El Niño Southern Oscillation.

Rainfall erosivity is an important indicator that can be used to measure the ability of rain to cause erosion and is connected with the El Niño Southern Oscillation (ENSO) through the transmission of rainfall. This work aimed to explore the characteristics of rainfall erosivity in Guizhou Province and determine its correlation with ENSO. Rainfall erosivity was calculated from daily rainfall data from January 1960 to December 2017. The analyses were conducted using a daily rainfall erosivity model, inverse distance weighted (IDW) interpolation, linear regression analysis, Mann-Kendall test and correlation analysis. The long-term (1960-2017) average rainfall erosivity was 5825.60 MJ·mm·ha-1·h-1 in the study area and showed a high temporal variability with the estimates from the linear trend line ranging from -449.5 MJ·mm·ha-1·h-1/10a to 496.8 MJ·mm·ha-1·h-1/10a. According to rainfall and erosive rainfall, an uneven spatial distribution of rainfall erosivity was observed with an increasing trend from south to north. Temporal distribution of monthly rainfall erosivity was consistent with that of seasonal rainfall erosivity, and concentrated in the summer months (June to August). As the representation indices of ENSO phenomena, the Oceanic Niño Index (ONI), Southern Oscillation Index (SOI) and multivariate ENSO Index (MEI) were selected for correlation analysis with rainfall erosivity. During El Niño events, the ONI, SOI and MEI showed significant correlations (>95% confidence level) with rainfall erosivity, while during La Niña events, only the ONI and MEI were significantly correlated with rainfall erosivity, but no significant correlation was detected during the neutral period or for the entire study period. The degree of rainfall erosion is proportional to the ENSO duration; the longer the ENSO duration, the greater the rainfall erosivity. These findings could help predict soil erosion and be used to develop further adaptation measures to prevent water and soil loss.

Drought and its legacy modulate the post-fire recovery of soil functionality and microbial community structure in a Mediterranean shrubland.

The effects of drought on soil dynamics after fire are poorly known, particularly its long-term (i.e., years) legacy effects once rainfall returns to normal. Understanding this is particularly important for nutrient-poor soils in semi-arid regions affected by fire, in which rainfall is projected to decrease with climate change. Here, we studied the effects of post-fire drought and its legacy on soil microbial community structure and functionality in a Cistus-Erica shrubland (Spain). Rainfall total and patterns were experimentally modified to produce an unburned control (natural rainfall) and four burned treatments: control (natural rainfall), historical control (long-term average rainfall), moderate drought (percentile 8 historical rainfall, 5months of drought per year), and severe drought (percentile 2, 7months of drought). Soil nutrients and microbial community composition (ester-linked fatty acid approach) and functionality (enzyme activities and C mineralization rate) were monitored during the first 4years after fire under rainfall treatments, plus two additional ones without them (six post-fire years). We found that the recovery of burned soils was lower under drought. Post-fire drought increased nitrate in the short term and reduced available phosphorus, exchangeable potassium, soil organic matter, enzyme activities, and carbon mineralization rate. Moreover, drought decreased soil total microbial biomass and fungi, with bacteria becoming relatively more abundant. Two years after discontinuing the drought treatments, the drought legacy was significant for available phosphorus and enzyme activities. Although microbial biomass did not show any drought legacy effect, the proportion of fungi and bacteria (mainly gram-positive) did, being lower and higher, respectively, in former drought-treated plots. We show that drought has an important impact on soil processes, and that some of its effects persist for at least 2years after the drought ended. Therefore, drought and its legacy effects can be important for modeling biogeochemical processes in burned soils under future climate change.

Characteristics of meteorological droughts in northwestern India

This study analyses regional drought characteristics (frequency, severity, and persistence) of meteorological droughts occurred in the northwestern parts falling under arid and semiarid regions of India with mean annual rainfall ranging between 100 and 900 mm. A drought is defined as a season or a year with rainfall less than 75% of corresponding mean at a place. Long-term monthly rainfall records (1901–2013) of 90 districts of north-west India located in the states of Punjab, Haryana, Rajasthan and Gujarat are used in the analysis. The percentage departure of seasonal rainfall from long-term average rainfall has been used for identification of onset, termination, and quantification of drought severity. The average frequency varied from once every 3–4 years. The westerly districts have an average drought return period of 3 years, while districts lying toward the east had droughts once every 4 years. Only four of the 90 districts in the study area experienced droughts once every 5 years. Persistent droughts of 2, 3, and 4 year duration occurred widely. Severe droughts occurred in the years 1904, 1905, 1911, 1918, 1931, 1939, 1985, 1986, 1987, 1993, and 2002, with an average frequency of severe drought events of one in 10 years. The analysis presented in this paper improves understanding of the regional drought characteristics and will inform drought mitigations and strategies in these arid and semiarid areas.

Productivity of strawberry plants growing under dry and wet conditions in subtropical Queensland

The effect of growing environment on the performance of two strawberry (Fragaria ×ananassa) cultivar/breeding lines ('Festival' and 'Breeding Line 1') was studied in south-eastern Queensland, Australia. Plants were grown under tunnels or outdoors. Supplementary over-head irrigation was given to the plants outdoors to provide a water supply (irrigation + rainfall) about twice that of the long-term average rainfall for the area. Half the plants under the tunnels or outdoors received the standard sprays to control grey mould, while the other half of the plants received none of these sprays. The yields of the plants in the dry environment under the tunnels (without over-head irrigation) were more than double the yields of the plants in the wet environment outdoors (with over-head irrigation). This result indicates that losses that may occur during a wetter than average season. The plants under the tunnels had lower incidences of rain damage and grey mould than the plants outdoors. There were higher incidences of powdery mildew, and of small and misshaped fruit under the tunnels. Only cultivars with some resistance to powdery mildew should be grown under protected cropping. Spraying reduced the incidence of grey mould outdoors but not under the tunnels. Crops growing under protected cropping in Queensland probably do not need to be sprayed for grey mould.

Spatial distribution and temporal trends of rainfall erosivity in mainland China for 1951–2010

Rainfall erosivity is an important factor for estimating soil erosion rates. Understanding the spatial distribution and temporal trends of rainfall erosivity is especially critical for soil erosion risk assessment and soil conservation planning in mainland China. However, reports on the spatial distribution and temporal trends of rainfall erosivity for China, especially of its eight soil erosion regions, are still lacking, which reduces the accuracy of predicting soil losses, assessing soil erosion risks and evaluating the effects of soil conservation measures. Additionally, the lack of the most suitable spatial interpolation method in mainland China, to some degree, has reduced the applicability and reliability of the interpolation results. In this study, long-term (1951–2010) daily rainfall data from 756 national weather stations were assembled to characterize the spatial and temporal patterns of annual rainfall erosivity across mainland China. Sixteen spatial interpolation methods were compared to select the most suitable one for accurately mapping the spatial distribution of rainfall erosivity, and the Mann-Kendall test was employed to detect the temporal trends. The results indicated that 1) the universal co-kriging method with the aid of elevation was superior to the other spatial interpolation methods; 2) long-term average rainfall erosivity increased from the northwest to the southeast, ranging from 31 to 30,051MJmmha−1h−1a−1; 3) overall, rainfall erosivity across China and water erosion regions experienced an insignificant increasing trend over the study period. Significant decreasing trends were observed in the northwest Loess Plateau region (0.01 level), the northeast black soil region and the north earth and gravel mountain region (0.05 level). Significant increasing trends (0.05 level) were found in the southern red soil hilly region and the southwest Karst region; and 4) two lines were identified according to the temporal trends of rainfall erosivity from the east to the west. In total, this study offers useful information both for soil erosion prediction and land management practices of mainland China.

Fluctuations in bird numbers on sewage treatment ponds in an arid environment, South Africa

Regular twice-monthly counts of birds associated with water at the Prince Albert sewage disposal facility recorded 69 species, of which 16 species (23.5%) were waterbirds (ducks, Red-knobbed Coot Fulica cristata and Little Grebe Tachybaptus ruficollis) and 21 species were shorebirds (30.9%). The remainder of the species were birds of reed beds (11; 16.2%), weedy or shrubby habitats around the edges of the ponds (12; 17.6%) or that hawked prey over the ponds (9; 13.2%). The numbers of shorebirds and waterbirds were positively and significantly correlated and were highly variable over time. There were no movements to the sewage facility by waterfowl specifically to moult. The presence of both waterbirds and shorebirds showed an historic movement pattern, with peak numbers correlated with long-term average peak rainfall months.

The UK’s wet and stormy winter of 2013/2014

The <scp>UK</scp>’s wet and stormy winter of 2013/2014

Modifying rainfall patterns in a Mediterranean shrubland: system design, plant responses, and experimental burning

Global warming is projected to increase the frequency and intensity of droughts in the Mediterranean region, as well as the occurrence of large fires. Understanding the interactions between drought, fire and plant responses is therefore important. In this study, we present an experiment in which rainfall patterns were modified to simulate various levels of drought in a Mediterranean shrubland of central Spain dominated by Cistus ladanifer, Erica arborea and Phillyrea angustifolia. A system composed of automatic rainout shelters with an irrigation facility was used. It was designed to be applied in vegetation 2 m tall, treat relatively large areas (36 m2), and be quickly dismantled to perform experimental burning and reassembled back again. Twenty plots were subjected to four rainfall treatments from early spring: natural rainfall, long-term average rainfall (2 months drought), moderate drought (25% reduction from long-term rainfall, 5 months drought) and severe drought (45% reduction, 7 months drought). The plots were burned in late summer, without interfering with rainfall manipulations. Results indicated that rainfall manipulations caused differences in soil moisture among treatments, leading to reduced water availability and growth of C. ladanifer and E. arborea in the drought treatments. However, P. angustifolia was not affected by the manipulations. Rainout shelters had a negligible impact on plot microenvironment. Experimental burns were of high fire intensity, without differences among treatments. Our system provides a tool to study the combined effects of drought and fire on vegetation, which is important to assess the threats posed by climate change in Mediterranean environments.

Periodic variation in kernel oil content and fatty acid profiles of Calophyllum innophyllm L.: A potential biodiesel feedstock in Australia

Variation in oil content and fatty acid profiles of a native Australian biodiesel feedstock species Calophyllum inophyllum were studied in two different fruiting periods (winter 2008 and autumn 2009) and in three different northern Queensland provenances (Cardwell, Townsville, Yeppoon). Oils were extracted by standard n-hexane double extraction and fatty acid profiles were determined by ISO 5508 and 5509 methods using gas chromatography. C. inophyllum provenances have demonstrated a significant periodic variation in oil content and fatty acid profile, and as a result alter the quality of fatty acid methyl esters (biodiesel). FAP of majority of kernel oil sources were found to vary significantly (P < 0.05) with seasonal variation in temperature and longterm average rainfall.

The importance of preferential flow in controlling groundwater recharge in tropical Africa and implications for modelling the impact of climate change on groundwater resources

An improved water table fluctuation technique for estimating recharge is applied to a sustained (10-year) groundwater level monitoring record in Uganda, a rare dataset for tropical Africa, and compared against results from soil moisture balance models (SMBMs) and unsaturated flow models. The results show that recharge is directly proportional to rainfall (long-term average rainfall is around 1200 mm/a), even during times when high soil moisture deficits are anticipated. This indicates that preferential and/or localized flow mechanisms dominate the recharge behaviour. SMBMs and unsaturated flow models, based on uniform flow governed by the Richards equation, are shown to be inappropriate for estimating recharge in this location underlain by lateritic soils. Given the large spatial coverage of lateritic soils both globally and in tropical Africa, and despite the convenience of physically based uniform flow models and, in particular, SMBMs, concern is raised over the use of such models for recharge estimation, and thus for exploring future trends due to climate or land use change, unless backed up by sufficient hydraulic data to enable the recharge processes to be confirmed. More research is needed to assess how widespread preferential flow may be within other major soil groups and climate zones.