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The Indian Ocean tsunami of December 2004 had far reaching consequences for agriculture in Aceh province, Indonesia, and particularly in Aceh Barat district, 150 km from the seaquake epicentre. In this study, the spatial distribution and temporal dynamics of soil and groundwater salinity and their impact on tree crops were monitored in Aceh Barat from 2006 to 2008. On 48 sampling points along ten transects, covering 40 km of coastline, soil and groundwater salinity were measured and related to mortality and yield depression of the locally most important tree crops. Given a yearly rainfall of over 3000mm, initial groundwater salinity declined rapidly from over 10 to less than 2 mScm-1 within two years. On the other hand, seasonal dynamics of the groundwater table in combination with intrusion of saline water into the groundwater body led to recurring elevated salinity, sufficient to affect crops. Tree mortality and yield depression in the flooded area varied considerably between tree species. Damage to coconut (65% trees damaged) was related to tsunami run-up height, while rubber (50% trees damaged) was mainly affected by groundwater salinity. Coconut yields (-35%in average) were constrained by groundwater Ca2+ and Mg2+, while rubber yields (-65% on average) were related to groundwater chloride, pH and soil sodium. These findings have implications on planting deeprooted tree crops as growth will be constrained by ongoing oscillations of the groundwater table and salinity. [ABSTRACT FROM AUTHOR]

Competition for nutrients and water between crops and associated hedgerows reduces overall performance of contour hedgerow systems and hampers its acceptance by rural communities in tropical mountainous regions. Therefore, it is imperative to better understand competition leading to a decline in crop response close to hedges. In the highlands of North East Thailand spatial variability in grain yield of maize ( Zea mays L., cv. Suwan 1) was assessed for two contour hedgerow systems based on Brachiaria ruziziensis Germain et Evrard (Ruzi grass) barriers or Leucaena leucocephala (Lam) de Wit hedges without or with fertilizer (60 kg N ha−1 and 14 kg P ha−1). Available $$NO^{ - }_{3} - N$$ was analyzed across the slope. In addition, shoot N concentration and δ13C values in leaves were measured for maize plants in the center of the alley and in the row next to and at the upper side of barriers or hedges. Despite variable field conditions, δ13C values were significantly ( p < 0.05) less depleted close to the barriers or hedges, except for 2 out of 16 plots, suggesting that water deficiency was not the main driver for spatial variability along the alleys. The negative correlation between 13C isotopic discrimination and available $$NO^{ - }_{3} - N$$ in the soil, with R 2 ranging from 0.5 ( p < 0.10) to 0.9 ( p < 0.01), assigned a major role to N availability in the reduced crop response towards the barriers. The proposed framework of 13C isotopic discrimination, together with plant and soil N data, is a new approach and was shown to be suitable to determine N and water competition between hedgerows and crops grown in alleys under field conditions. [ABSTRACT FROM AUTHOR]

The relationships between 13C isotopic discrimination and water stress are well documented for C3 and C4 plants. However, the application in the field is hampered by complex interaction patterns with other common stress factors, such as nutrient deficiency. In addition, questions arise if temporal reductions in water availability during crop growth can be traced back using δ13C data in the field. The objective of this study therefore is to assess the potential use of δ13C observations to quantify water stress and its dynamics in maize ( Zea mays L.) grown under low to high nitrogen availability, and to develop tools based on δ13C values for its diagnosis in the field. In a pot experiment, carried out in a screen house in Ibadan, Nigeria, we grew maize for 60 days under four watering regimes, (i) optimum (at field capacity) during 60 days, (ii) optimum from 0 to 30 days and stressed (50% field capacity) from 30 to 60 days, (iii) stressed from 0 to 30 days and optimum from 30 to 60 days, and (iv) stressed throughout the 60 days. Nitrogen was applied at three rates (none, moderate (45 kg N ha−1) and high (120 kg N ha−1)). Plants were sampled after 30 and 60 days. At 60 days, leaves developed during the first 30 days were sampled separately from those developed between 30 and 60 days. Shoot production showed a clear water–nitrogen interaction. Nitrogen response increased with decreasing water stress, in particular from 30 to 60 days. δ13C values ranged from −12.42‰ to −10.80‰. Overall, a clear and significant water and nitrogen effect ( P<0.0001) on the isotopic discrimination in maize was observed, opposite in direction from C3 plants. δ13C values decreased with increasing water stress, but increased with decreasing nitrogen availability, particularly when combined with limited water supply. In addition, isotopic discrimination was observed to be variable within plant, and could be related to a water stress in that growth period, in which the plant parts were developed. This shows that δ13C values measured in different plant parts at harvest can be used as a historical account on how water availability varied during the entire cropping cycle. [ABSTRACT FROM AUTHOR]

Abstract: Soil erosion is a serious problem in the forest-savanna transition zone or derived savanna of West Africa and Nigeria and needs to be reduced to maintain soil quality and to ensure food security. In 2007, the use of the fallout radionuclide 137Cs as a tracer for estimating the magnitude of medium-term (40–50 years) rates of soil redistribution was tested at a research station in Ibadan, Nigeria, to investigate, for the first time, its applicability in the derived savanna of West Africa. Because of the traditional tillage practice for cassava cultivation of creating downslope oriented ridges and furrows during the annual ploughing, there was a need to adapt the 137Cs approach to these specific condition. The mean inventory was determined for cores collected from both ridges and furrows at different positions down the slope and this value was used to estimate the downslope variation in the longer term soil redistribution rate. The mean 137Cs reference inventory obtained for an undisturbed site was 568±138Bqm−2. The average inventory for the upper slope of the cassava field (423±323Bqm−2) was generally lower than the average inventory for the middle slope (509±166Bqm−2) and for the lower slope (606±245Bqm−2) and these results provided clear evidence of the downslope movement of soil. The mean 137Cs inventory for the study area within the cassava field (496±273Bqm−2) was 13% lower than the reference inventory, indicating that some of the soil mobilised and redistributed by erosion had been exported beyond the field. Using 137Cs data set and the conversion model mass balance model 2 (MBM2), the gross erosion rate from the cultivated site was estimated to be 18.3tha−1 year−1 and the net erosion rate 14.4tha−1 year−1, providing a sediment delivery ratio of 78%. These estimates are comparable to the rates generated by conventional soil loss measurements made close to the study site. The study demonstrates that the 137Cs technique can be successfully used to obtain data on medium-term soil redistribution in the derived savanna of Nigeria, and that it could be a useful tool for supporting the improvement of soil conservation on farmland in West Africa. [Copyright &y& Elsevier]

The Northern Antarctic Peninsula (NAP) and the West Antarctic Ice Sheet (WAIS) are likely to respond rapidly to climate changes by increasing the collapse of peripheral ice shelves and the number of days above 0 °C. These facts make this region a representative hotspot of the global sea level rise and the location of one of the global climate tipping points (thresholds in the Earth system whose changes may become irreversible, if exceeded). Understanding the climate evolution of the NAP, based on past evidences, may help infer its future scenario. Herein, from a comprehensive survey of lacustrine sedimentation in proglacial and periglacial lakes/ponds, we investigated the impact of climate changes on the terrestrial environment in two complementary time scales (Late Holocene and contemporary age). For the longer time scale, regional climate database and biogeochemical properties of Lake Long/NAP sediment core, suggest warming between 4.0 and 2.0 kyr BP following a cooling phase towards the present, that endorse previously suggested Late Holocene Neoglacial (LHN). We attribute the LHN phase to a combined action of long-term decline in total solar irradiance, the Andean volcanism and the El Niño Southern Oscillation. For the contemporary age, we found a rapid coupled response of atmosphere/cryosphere/lithosphere to present warming levels., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Cassava ( Manihot esculenta Crantz) is an important root crop, which despite its drought tolerance suffers considerable yield losses under water deficit. One strategy to increase crop yields under water deficit is improving the crop's transpiration efficiency, which could be achieved by variety selection and potassium application. We assessed carbon isotope composition in bulk leaf material and extracted carbohydrates (soluble sugar, starch, and cellulose) of selected leaves one month after inducing water deficit to estimate transpiration efficiency and storage root biomass under varying conditions in a greenhouse experiment. A local and improved variety were grown in sand, supplied with nutrient solution with two potassium levels (1.44 vs. 0.04 mM K + ) and were subjected to water deficit five months after planting. Potassium application and selection of the improved variety both increased transpiration efficiency of the roots with 58% and 85% respectively. Only in the improved variety were 13 C ratios affected by potassium application (up to - 1.8‰ in δ 13 C of soluble sugar) and water deficit (up to + 0.6‰ in δ 13 C of starch and soluble sugar). These data revealed a shift in substrate away from transitory starch for cellulose synthesis in young leaves of the improved variety under potassium deficit. Bulk δ 13 C of leaves that had fully developed prior to water deficit were the best proxies for storage root biomass (r = - 0.62, r = - 0.70) and transpiration efficiency (r = - 0.68, r = - 0.58) for the local and improved variety respectively, making laborious extractions redundant. Results obtained from the youngest fully developed leaf, commonly used as a diagnostic leaf, were complicated by remobilized assimilates in the improved variety, making them less suitable for carbon isotope analysis. This study highlights the potential of carbon isotope composition to assess transpiration efficiency and yield, depending on the chosen sampling strategy as well as to unravel carbon allocation processes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Van Laere, Merckx, Hood-Nowotny and Dercon.)

Banana is a perennial crop and typically consists of a mother plant and one or more suckers that will serve as the next generation. Suckers are photosynthetically active, but also receive photo-assimilates from the mother plant. While drought stress is the most important abiotic constraint to banana cultivation, its effect on suckers or banana mats as a whole remains unknown. To investigate whether parental support to suckers is altered under drought stress and to determine the photosynthetic cost to the parental plant, we conducted a 13 C labeling experiment. We labeled banana mother plants with 13 CO 2 and traced the label up to two weeks after labeling. This was done under optimal and drought-stressed conditions in plants with and without suckers. We retrieved label in the phloem sap of the corm and sucker as soon as 24 hours after labeling. Overall, 3.1 ± 0.7% of label assimilated by the mother plant ended up in the sucker. Allocation to the sucker seemed to be reduced under drought stress. The absence of a sucker did not enhance the growth of the mother plant; instead, plants without suckers had higher respiratory losses. Furthermore, 5.8 ± 0.4% of the label was allocated to the corm. Sucker presence and drought stress each led to an increase in starch accumulation in the corm, but when both stress and a sucker were present, the amount was severely reduced. Furthermore, the second to fifth fully open leaves were the most important source of photo-assimilates in the plant, but the two younger developing leaves assimilated the same amount of carbon as the four active leaves combined. They exported and imported photo-assimilates simultaneously, hence acting as both source and sink. 13 C labeling has allowed us to quantify source and sink strengths of different plant parts, as well as the carbon fluxes between them. We conclude that drought stress and sucker presence, respectively causing a reduction in supply and an increase in carbon demand, both increased the relative amount of carbon allocated to storage tissues. Their combination, however, led to insufficient availability of assimilates and hence a reduced investment in long-term storage and sucker growth., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Vantyghem, Beelen, Hood-Nowotny, Merckx and Dercon.)

Rationale: Cassava production faces challenges in a changing climate. Pulse labelling cassava with 13 C-CO 2 has the potential to elucidate carbon allocation mechanisms of cassava under drought stress and with potassium application. Understanding these mechanisms could guide efforts to mitigate effects of drought in cassava cropping systems., Methods: Forty-eight cassava plants received a nutrient solution high or low in potassium. Water deficit was imposed on half of the plants at bulk root initiation stage, after which they were labelled for 8 h with 13 C-CO 2 in a 15 m 3 growth chamber. Plants were harvested 8 h, 9 days and 24 days after labelling, and separated into leaves, stems and roots. δ 13 C values of the different parts were measured using an isotope ratio mass spectrometer, from which 13 C excess was calculated., Results: Water deficit decreased transpiration (P < 0.001) and increased carbon respiration (P < 0.05). Potassium application increased assimilate distribution to the roots (P < 0.05) at 9 days after labelling, more strongly for plants under water deficit. The opposite was found at 24 days (P < 0.05) with the legacy of water deficit additionally increasing assimilate distribution to roots (P < 0.05). Youngest, fully expanded leaves contained up to 47% of initial 13 C excess at 24 days after labelling., Conclusions: Pulse labelling proved to be successful in shedding light on carbon allocation in relation to water and potassium availability. This technique, once adapted to field conditions, could further be used to improve fertilizer recommendations or change agronomic practices to cope with plant stress., (© 2022 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.)

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, immediate soil and vegetation sampling were conducted according to the action plan of nuclear emergency monitoring; however, analysing the monitoring dataset was difficult because the sampling protocols were not standardised. In this study, the sampling protocols applied just after the FDNPP accident were reviewed, and the monitoring data were analysed. The detailed protocols and results can provide a sound basis for guidelines of soil and vegetation sampling for nuclear emergency monitoring. The activity concentrations of 137 Cs and 131 I in weed samples measured immediately after the FDNPP accident were related to the air dose rate at 1 m. Consequently, vegetation sampling is recommended when the additional dose rate (above background) is higher than 0.1 μSv/h. To enhance the efficiency of a protective response in the case of a nuclear accident, predetermined sampling points for soil and vegetation sampling should be considered in the preparedness plan for nuclear emergencies. Furthermore, sampling and analytical measurement capacities (time, people, cost) during the early phase after nuclear emergencies need to be considered in the preparedness and action plan, and sampling and measurement exercises are highly recommended., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Data on reduction of radioactivity in plants are highly important for making decision on emergency response and remediation of contaminated areas. Dynamics of the 131 I and 137 Cs concentrations in the weed leaves sampled in the areas affected by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan was assessed for the period March-December 2011. The effective half-lives for 131 I and 137 Cs of 3.8-4.2 days and 7.1-13.3 days in the weed leaves were calculated for the first two months after the deposition. The approach for assessment of the aggregated transfer factors based on the ambient dose equivalent rate was suggested and validated. The geometric means of the soil to the weed leaves aggregated transfer factors were estimated for June-December 2011. Soil to crop 137 Cs- concentration ratios (buckwheat, brown rice and soybean) were estimated for 2011-2016. Soil to crop concentration ratios were found to decrease in the order of soybean > buckwheat > brown rice. The effective half-lives for 137 Cs in these crops were estimated to be between 1 and 2.5 years for the period 2011 2016, and longer than 5-7 years after 2016. It was found that these data comply with the Chernobyl related data obtained for similar conditions and complement of international documents on radionuclide transfer in agricultural environment such as the IAEA TRS 472., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Rationale: Carbon-13 ( 13 C)-labelled plant material forms the basis for experiments elucidating soil organic carbon dynamics and greenhouse gas emissions. Quantitative field-scale tracing is only possible if plants are labelled homogeneously in large quantities. By using a laser spectrometer to automatically steer the isotopic ratio in the chamber, it is possible to obtain large amounts of homogeneously labelled plant material., Methods: Ninety-six maize plants were labelled for 25 days until tassel formation in a 15 m 3 walk-in growth chamber with a continuous air δ 13 C-CO 2 value of 400‰. A Los Gatos Research laser absorption spectrometer controlled the ambient δ 13 C-CO 2 value in the chamber through steering of the mass flow controllers with 13 C-enriched and natural abundance CO 2 gas., Results: Laser absorption spectroscopy steering kept the δ 13 C value of chamber air between 368 and 426‰. The resulting 1 kg dry matter of 13 C-labelled shoots showed an average δ 13 C value of 384‰ and accuracy of 8‰ (half width of the 95% confidence interval). Only the oldest leaves showed larger heterogeneity. The growth chamber eliminated variability between plants. The δ 13 C value of the stabile material did not differ significantly from that of bulk material., Conclusions: Laser spectroscopy controlled 13 C labelling of plants in a walk-in growth chamber successfully kept the isotopic ratio of the CO 2 in the chamber air constant. Therefore, large quantities of material were labelled homogeneously at the inter- and intra-plant level, thus establishing a method to provide high-quality input for quantitative isotopic tracer studies., (© 2019 John Wiley & Sons, Ltd.)