Low Potential Evapotranspiration Research Articles

Groundwater table prediction and seasonal variation influenced by short rotation willow plantation on marginal riparian lands of the Prairie potholes in Canada

Shallow groundwater consumption via phreatophytic transpiration and resulting vegetation-linked groundwater table (GWT) fluctuation is a typical soil hydrological process in wetland riparian areas. However, upland and riparian land use alterations may further influence the shallow GWT fluctuation, temporally and spatially. In this multi-year field study, we investigated whether introducing short rotation willow (SRW) positively or negatively affects the shallow GWT, soil water availability, and soil health on marginal riparian lands of the Prairie Pothole Region (PPR). We compared the impact of SRW on these parameters to two common land uses: annual crop (AC) and pasture (PA). Depth to GWT was monitored via data loggers from 28 wells in two semi-arid PPR sites. The GWT depth varied by land use practices only in site B (p < 0.001; PA > SRW = AC) but not significantly in site A (p = 0.325), and the patterns were inconsistent between sites. In GWT depth prediction, the performance of Artificial Neural Network (ANN) was better than Autoregressive Integrated Moving Average (ARIMA) models but was inconsistent alike with field observations. The GWT depth responded to seasonal precipitation and potential evapotranspiration (ET) patterns. The monthly GWT fluctuations peaked between June and August due to increased precipitation, while they were lower during May and September with reduced precipitation; however, these variations were not significant (p > 0.05). Higher precipitation and lower potential ET throughout the wet year (i.e., in 2014) significantly (p < 0.05) raised GWT (i.e., decreased depth to GWT) under all land uses, and vice versa. Our study indicated that planting SRW in marginal riparian land of the PPR would not negatively impact shallow GWT or soil water availability. Moreover, the SRW plantation could also help manage soil salinity without severely depleting the soil's nutrient pools or diminishing soil quality and health indicator parameters measured during the first rotation.

Tolerance to waterlogging determines the effectiveness of biodrainage in mitigating runoff in hillslope-scale simulations

Reversal of land degradation in agricultural systems through a wide range of natural resources management tailored to the specific climate, soil, and topography is crucial. This is especially critical for subsistence farming systems such as the Ethiopian Highlands, subject to some of the highest soil erosion rates in the world. Although biodrainage is widely and successfully used for waterlogging and erosion control in arid regions, it is not widely applied in sub-humid places like the Ethiopian Highlands. Beginning with field observations of the complex vertical soil profiles and variations in lithology and soil hydraulic properties along a hillslope ridge-channel transect in the Debre Mawi watershed of the Abay (Upper Blue Nile) Basin in the Ethiopian Highlands, we construct a synthetic model hillslope in HYRDUS-2D. For the growing season coinciding with the rainy season, known as Kiremt, we calibrated the hillslope water storage using observations of water table elevation. The synthetic hillslope is then used to test the feasibility of biodrainage to mitigate saturation, a major driver of gullying and soil loss in the area, and to identify plant traits to which such mitigation is sensitive. The simulation results using bare soil, eucalyptus and maize land covers revealed that in spite of low potential evapotranspiration during the Kiremt season, biodrainage with Eucalyptus can reduce the occurrence and duration of saturation of the top 0.6 m surface soil profile of the hillslope. Of the different plant traits explored, the maximum soil water potential at which the crop can transpire at potential rates, and the LAI, which controls potential evaporation rates via the crop coefficient, provide the most important controls on the effectiveness of biodrainage in desaturating the hillslope. We conclude that biodrainage strategies to mitigate soil erosion in sub humid locales merits further investigation through empirical trials. However, implementation of biodrainage strategies should be subject to thoughtful consideration of the implications for socio-economic outcomes and the local environment.

Direct development in Atlantic Forest anurans: What can environmental and biotic influences explain about its evolution and occurrence?

Different environmental and biological factors can originate and support different alternative life histories in different taxonomic groups. Likewise, these factors are important for the processes that assemble and structure communities. Amphibians, besides being highly susceptible to environmental conditions, have various reproductive strategies, such as the direct development of individuals. Several hypotheses have been raised about possible selective pressures related to the emergence of direct development in anurans, as well as the relationship between environmental characteristics and the occurrence of these species. Such investigations, however, have mainly focused on specific clades and/or regions. Here, we use structural equation modelling to investigate the relationships between different abiotic (temperature, precipitation, humidity, and terrain slope) and biotic (phylogenetic composition and functional diversity) factors and the proportion of species with direct development in 766 anuran communities of the Atlantic Forest, a biome with a vast diversity of anuran species and high environmental complexity. Anuran communities with higher proportions of direct developing species were found to be mainly influenced by low potential evapotranspiration, low temperature seasonality, and high functional diversity. Phylogenetic composition and terrain slope were also found to be important in determining the occurrence of these species in Atlantic Forest communities. These results show the importance of these factors in the structuring of these communities and provide important contributions to the knowledge of direct development in anurans.

On Transient Semi‐Arid Ecosystem Dynamics Using Landlab: Vegetation Shifts, Topographic Refugia, and Response to Climate

AbstractProjecting how arid and semi‐arid ecosystems respond to global change requires the integration of a wide array of analytical and numerical models to address different aspects of complex ecosystems. We used the Landlab earth surface modeling toolkit (Hobley et al., 2017, https://doi.org/10.5194/esurf-5-21-2017) to couple several ecohydrologic and vegetation dynamics processes to investigate the controls of exogenous drivers (climate, topography, fires, and grazing) and endogenous grass‐fire feedback mechanisms. Aspect‐controlled ecosystems and historical woody plant encroachment (WPE) narratives in central New Mexico, USA are used to construct simulations. Modeled ecosystem response to climatic wetness (i.e., higher precipitation, lower potential evapotranspiration) on topography follows the Boyko's “geo‐ecological law of distribution.” Shrubs occupy cooler pole‐facing slopes in the dry end of their ecoclimatic range (Mean Annual Precipitation, MAP ≤ 200 mm), and shift toward warmer equator‐facing slopes as regional moisture increases (MAP &gt; 250 mm). Trees begin to occupy pole‐facing slopes when MAP &gt; 200 mm, and gradually move to valleys. Pole‐facing slopes increase species diversity at the landscape scale by hosting relict populations during dry periods. WPE observed in the region since the middle 1800s is predicted as a three‐phase phenomenon. Phase II, rapid expansion, requires the removal of the positive grass‐fire feedback by livestock grazing or fire suppression. Regime shifts from grassland to shrubland are marked by critical thresholds that involve grass cover remaining below 40%, shrub cover increasing to 10%–20% range, and the grass connectivity, Cg, remaining below 0.15. A critical transition to shrubland is predicted when grazing pressure is not removed before shrub cover attains 60%.

Assessment of Soil Moisture Storage In Nigeria Using Climatic Water Budgeting Approach

The estimation of soil moisture storage is fundamental to crop production, hydrological and biological processes. This study assessed soil moisture storage in Nigeria using the Climatic Water Budgeting Approach. Mean monthly air temperature and monthly rainfall data were collected from the archives of the Nigerian Meteorological Agency from 27 weather stations in Nigeria. The data were subjected to Climatic Water Budgeting Approach to compute the monthly soil moisture storage at different locations in Nigeria over two years with contrasting moisture conditions (1983 and 2003). The mean monthly air temperature data were used to estimate the monthly potential evapotranspiration (PE) while the PE in conjunction with the mean monthly rainfall and the soil water holding capacity of 250mm were used to calculate the monthly soil moisture storage. The results showed that most locations north of latitude 9°N recorded low soil moisture storage below 10 mm from April to July especially in 1983. The soil moisture storage was high in all the places in January and February due to low potential evapotranspiration and accumulated potential water loss (APWL). Most Places South of latitude 9°N recorded higher soil moisture storage between 20 mm and 100 mm from January to May compared to their counterparts north of latitude 9°N in both 1983 and 2003. The soil moisture storage attained 250 mm (100%) from July-October across Nigeria. This study concluded that the soil moisture varies spatially and temporally in Nigeria decreasing from South to North. A paired sample test revealed a significant difference between the soil moisture storage of 2003 and 1983 in Nigeria (p=.000).

Scaling mangrove aboveground biomass from site‐level to continental‐scale

AbstractAimWe developed a set of statistical models to improve spatial estimates of mangrove aboveground biomass (AGB) based on the environmental signature hypothesis (ESH). We hypothesized that higher tidal amplitudes, river discharge, temperature, direct rainfall and decreased potential evapotranspiration explain observed high mangrove AGB.LocationNeotropics and a small portion of the Nearctic region.MethodsA universal forest model based on site‐level forest structure statistics was validated to spatially interpolate estimates of mangrove biomass at different locations. Linear models were then used to predict mangrove AGB across the Neotropics.ResultsThe universal forest site‐level model was effective in estimating mangrove AGB using pre‐existing mangrove forest structure inventories to validate the model. We confirmed our hypothesis that at continental scales higher tidal amplitudes contributed to high forest biomass associated with high temperature and rainfall, and low potential evapotranspiration. Our model explained 20% of the spatial variability in mangrove AGB, with values ranging from 16.6 to 627.0 t ha−1 (mean, 88.7 t ha−1). Our findings show that mangrove AGB has been overestimated by 25–50% in the Neotropics, underscoring a commensurate bias in current published global estimates using site‐level information.Main conclusionsOur analysis show how the ESH significantly explains spatial variability in mangrove AGB at hemispheric scales. This finding is critical to improve and explain site‐level estimates of mangrove AGB that are currently used to determine the relative contribution of mangrove wetlands to global carbon budgets. Due to the lack of a conceptual framework explicitly linking environmental drivers and mangrove AGB values during model validation, previous works have significantly overestimated mangrove AGB; our novel approach improved these assessments. In addition, our framework can potentially be applied to other forest‐dominated ecosystems by allowing the retrieval of extensive databases at local levels to generate more robust statistical predictive models to estimate continental‐scale biomass values.

Crop production and soil water management in conservation agriculture, no-till, and conventional tillage systems in Malawi

Smallholder farming in southern and eastern Africa is constrained by low water-use efficiency, frequent dry spells, and drought. Conservation agriculture (CA), defined as minimal soil disturbance, year-round ground cover, and crop rotations, is being promoted as a way to sustainably improve water-use efficiency, reduce soil erosion, and boost crop production. In this study, three cropping systems – continuous no-till maize, CA rotation, and conventional tillage rotation – were established on smallholder farms in the Nkhotakota and Dowa districts, two distinct agroecological zones in Malawi. Three-year crop rotations of cassava, cowpea, and maize and cassava, soybean, and maize were implemented in CA and conventional tillage, respectively, in Nkhotakota. In Dowa, a 3-year rotation of sweet potato, bean, and maize was implemented in both CA and conventional tillage. Cropping systems were analyzed for their impact on infiltration, soil moisture content, sediment runoff, earthworm and termite abundance, and crop production from 2011 to 2014. In Nkhotakota, which had high potential evapotranspiration and low soil water-holding capacity, residue retention was positively correlated with infiltration and no-till and CA increased soil water content (0–60cm) compared to conventional tillage by an average of 20mm. In Dowa, which had lower potential evapotranspiration, eliminating tillage and retaining residue did not improve infiltration or soil water content. In 2013/2014, no-till and CA reduced sediment runoff by 1537kgha−1 and 1309kgha−1 in Nkhotakota and 346kgha−1 and 209kgha−1 in Dowa, respectively, compared to conventional tillage. Tillage and residue management did not have a significant impact on sweet potato, cassava, bean, soybean, or cowpea production. Crop rotations had the greatest impact on maize yields in 2013/14, with CA and conventional tillage rotations increasing maize yields compared to no-till maize by 2525kgha−1 and 2145kgha−1 in Dowa and 1364kgha−1 and 469kgha−1 in Nkhotakota, respectively. However, cumulative protein production was greater in no-till than CA and conventional tillage rotations in Dowa and greater than conventional rotations in Nkhotakota. Rotation crop productivity needs to be improved with better yielding grain legumes and other higher protein crops before widespread adoption of diverse rotations can occur on smallholder farms in eastern and southern Africa.

Climatic and Catchment-Scale Predictors of Chinese Stream Insect Richness Differ between Taxonomic Groups.

Little work has been done on large-scale patterns of stream insect richness in China. We explored the influence of climatic and catchment-scale factors on stream insect (Ephemeroptera, Plecoptera, Trichoptera; EPT) richness across mid-latitude China. We assessed the predictive ability of climatic, catchment land cover and physical structure variables on genus richness of EPT, both individually and combined, in 80 mid-latitude Chinese streams, spanning a 3899-m altitudinal gradient. We performed analyses using boosted regression trees and explored the nature of their influence on richness patterns. The relative importance of climate, land cover, and physical factors on stream insect richness varied considerably between the three orders, and while important for Ephemeroptera and Plecoptera, latitude did not improve model fit for any of the groups. EPT richness was linked with areas comprising high forest cover, elevation and slope, large catchments and low temperatures. Ephemeroptera favoured areas with high forest cover, medium-to-large catchment sizes, high temperature seasonality, and low potential evapotranspiration. Plecoptera richness was linked with low temperature seasonality and annual mean, and high slope, elevation and warm-season rainfall. Finally, Trichoptera favoured high elevation areas, with high forest cover, and low mean annual temperature, seasonality and aridity. Our findings highlight the variable role that catchment land cover, physical properties and climatic influences have on stream insect richness. This is one of the first studies of its kind in Chinese streams, thus we set the scene for more in-depth assessments of stream insect richness across broader spatial scales in China, but stress the importance of improving data availability and consistency through time.

Effects of deficit irrigation and groundwater depth on root growth of direct seeding rice in a column experiment

Rice is an essential crop in Iran that is grown mostly in areas where depth to groundwater is low. Root growth and water uptake of rice under shallow groundwater has not been thoroughly studied. This experiment was conducted to determine the lowland rice (cv. Ghasrodashti) root distribution above shallow groundwater in relation to deficit irrigation and groundwater depth in cylindrical greenhouse lysimeters. The irrigation treatments were continuous flood irrigation (CFI) and intermittent flood irrigation (4- and 8-day intervals IF-4 and IF-8). The groundwater depths (GWD) were 0.3, 0.45 and 0.6 m from the soil surface. In general, 40-60% of root dry weight was observed in the top 10 cm of soil in CFI treatments and IF-4 with 0.3 m GWD resulted in 20% increase in root dry weight in 10-20 cm layer compared with 0-10 cm. However, the root dry weight in 0-10 cm at 0.60 m GWD was 58% lower in intermittent irrigation compared to CFI. There was no significant difference in mean root length density in IF-4 with 0.3 m GWD compared with CFI. In general, lowland rice showed good ability to develop its root system in shallow groundwater level conditions in order to extract water due to lower soil water content in the intermittent flood irrigations. Simple equations were presented to predict the groundwater contribution to evapotranspiration based on the root length density and root weight density. Therefore, in areas with shallow groundwater depth (up to 0.45 m from the soil surface) and low potential evapotranspiration, application of IF-4 instead of CFI can be useful management especially where water scarcity is a serious problem.

Measuring and modelling above-ground carbon and tree allometry along a tropical elevation gradient

Emerging international policy aimed at reducing carbon emissions from deforestation and forest degradation (REDD+) in developing countries, has resulted in numerous studies on above-ground live carbon (AGC) in tropical forests. However, few studies have addressed the relative importance of disturbance, topography, climate, soil and methods for stem measurement, on the estimation of AGC, or the costs of improving AGC estimates by altering sample regimes. We established 18 one hectare plots containing 7201 stems, stratified along forested elevation gradients in Tanzania. We recorded a broad set of physical, climatic and edaphic predictors of AGC and tree stature. AGC estimates using stem diameter, height and wood density, gave a mean value of 174.6tha−1, compared with 229.6tha−1 when height was excluded. Regression models revealed that stems were tallest for a given diameter at mid-elevation (1000–1250m), on south-facing slopes, and without past logging. High AGC was strongly associated with shallow slopes, followed by intermediate elevation, elephant absence, low potential evapotranspiration and low soil pH. Further regression models to investigate the structural habitat features associated with AGC, revealed significant positive influence of basal area, stem density, and height:diameter ratio, rather than the mean wood density of species present. Large stems (⩾70cmdbh; 4.6% of stems) contained 52% of AGC in all plots, declining to 36% in lowland plots. We discuss the cost:benefit of different measurements and recommend a tiered approach to AGC monitoring, depending on available resources. AGC assessments in African forests could exclude small stems, but should aim to record disturbance, topography and species. Stem height is vital for AGC estimation and valuation; when excluding height our 55tha−1 over-estimation of AGC would have over-valued the carbon resource by 24% (US$3300ha−1).

Grey mould incidence is reduced on grapevines with lower vegetative and reproductive growth

The hypothesis that grey mould incidence would be positively correlated to grapevine canopy development was confirmed over a period of 3 years (2004–2006) on Aranel cultivar in an experimental vineyard near Montpellier, south France. Different levels of vine growth were generated by implementing three management schemes: (i) perennial cover crop, (ii) chemical weed control and (iii) irrigation and fertilisation. Grey mould incidence was assessed at harvest, together with various sets of variables linked with canopy microclimate, shoot vigour, vine capacity, cluster architecture, yield components and fruit composition. Significant positive correlations were observed between disease incidence and key variables of shoot vigour and vine capacity: total leaf number, leaf dry matter, leaf layer number, leaf area per metre of row, pruning mass and nitrogen accumulation. In 2004, Botrytis cinerea developed in all experimental plots because climatic and microclimatic conditions were conducive to grey mould. The climatic and microclimatic variables that significantly favoured grey mould development were: precipitation, duration of relative humidity >90% in the canopy and low potential evapotranspiration. However, in 2005 and 2006, under dry summer conditions, disease developed only in the most vigorous vines, which were both irrigated and fertilised. These vines showed a very high canopy growth, very compact clusters and a delayed fruit maturity. This evidenced that unfavourable climatic conditions for the disease development can be counterbalanced by conditions of high vine growth and associated canopy and cluster features.

Soil microbial communities of no-till dryland agroecosystems across an evapotranspiration gradient

In degraded agricultural soils, organic C levels can be increased and conserved by adopting alternative management strategies such as no-tillage and increased cropping intensity. However, soil microbial community responses to increased soil organic C (SOC) may be constrained due to water limitations in semi-arid dryland agroecosystems. The purpose of this study was to assess SOC, microbial biomass C (MBC) and community ester-linked fatty acid methyl ester (EL-FAME) composition under winter wheat (Triticum aestivum L.) in no-till systems of wheat–corn (Zea mays L.)–fallow (WCF), wheat–wheat–corn–millet (Panicum miliaceum L.) (WWCM), wheat–corn–millet (WCM), opportunity cropping (OPP), and perennial grass across a potential evapotranspiration gradient in eastern Colorado. Rotations of WWCM and OPP, in which crops are chosen based on available soil water at the time of planting rather than according to a predetermined rotation schedule, increased levels of SOC to those measured under perennial grass. However, MBC under OPP cropping accounted for the smallest fraction (2.0–3.6%) of SOC compared to other systems, in which MBC ranged from 2.4 to 6.3% of SOC. Microbial community structure was most divergent between OPP-cropped and perennial grass soils, whereas few differences were observed among microbial communities of the WCF, WCM, and WWCM rotations. Compared to perennial grass and other cropping systems, microbial biomass in OPP-cropped soil was low and contained less of the arbuscular mycorrhizal fungal biomarker 16:1ω5c. Microbial stress, as indicated by the ratio of 17:0 cy to 16:1ω7c, was greatest under OPP and WCF cropping. In contrast, soils under perennial grass contained lower ratios of bacterial:fungal EL-FAMEs and higher levels of MBC, ratios of MBC:SOC, and relative abundances of 16:1ω5c. Across locations, SOC and moisture content increased as soil texture became finer, whereas trends in MBC and community structure followed the potential evapotranspiration gradient. Soil from the high potential evapotranspiration site contained the lowest level of MBC but greater relative amounts of 16:1ω5c and lower ratios of stress indicator and bacterial:fungal EL-FAMEs compared to soil located at the moderate and low potential evapotranspiration sites. Indistinct microbial communities under WCF, WCM, and WWCM could be explained by EL-FAME limitations to detecting slight differences in microbial community structure or to the overwhelming response of microbial communities to environmental rather than management conditions. Further research is needed to assess potential legacy effects of long-term agricultural management that may mask microbial responses to recent management change, as well as to identify conditions that lead to high microbial community resiliency in response to management so that communities are similar under a given crop despite different preceding crops.

Conceptual model of sediment processes in the upper Yuba River watershed, Sierra Nevada, CA

This study examines the development of a conceptual model of sediment processes in the upper Yuba River watershed; and we hypothesize how components of the conceptual model may be spatially distributed using a geographical information system (GIS). The conceptual model illustrates key processes controlling sediment dynamics in the upper Yuba River watershed and was tested and revised using field measurements, aerial photography, and low elevation videography. Field reconnaissance included mass wasting and channel storage inventories, assessment of annual channel change in upland tributaries, and evaluation of the relative importance of sediment sources and transport processes. Hillslope erosion rates throughout the study area are relatively low when compared to more rapidly eroding landscapes such as the Pacific Northwest and notable hillslope sediment sources include highly erodible andesitic mudflows, serpentinized ultramafics, and unvegetated hydraulic mine pits. Mass wasting dominates surface erosion on the hillslopes; however, erosion of stored channel sediment is the primary contributor to annual sediment yield. We used GIS to spatially distribute the components of the conceptual model and created hillslope erosion potential and channel storage models. The GIS models exemplify the conceptual model in that landscapes with low potential evapotranspiration, sparse vegetation, steep slopes, erodible geology and soils, and high road densities display the greatest hillslope erosion potential and channel storage increases with increasing stream order. In-channel storage in upland tributaries impacted by hydraulic mining is an exception. Reworking of stored hydraulic mining sediment in low-order tributaries continues to elevate upper Yuba River sediment yields. Finally, we propose that spatially distributing the components of a conceptual model in a GIS framework provides a guide for developing more detailed sediment budgets or numerical models making it an inexpensive way to develop a roadmap for understanding sediment dynamics at a watershed scale.

The impact of climate on the biogeochemical functioning of volcanic soils

Rainfall and the amount of water available to leach ions from soil are among the most important features determining mineral weathering, secondary mineral synthesis and soil chemical properties. Along an arid to humid climosequence on Kohala Mountain, Hawaii, we sampled 16 soil profiles and found that weathering and soil properties change in a nonlinear fashion with increased rainfall. The lavas are influenced by a strong rain shadow with mean annual precipitation (MAP) averaging 160 mm near the coast and rising to >3000 mm near the summit. A temperature decline from 24 to 15 °C with increasing elevation is matched by lower potential evapotranspiration (ET). A water balance model (monthly precipitation minus monthly ET) defines three broad climate zones along the sampling transect: an arid zone with moisture deficit in every month, an intermediate zone with moisture deficit during low-rainfall summer months and moisture surplus during high-rainfall winter months, and a humid zone with moisture surplus during every month. The annualized water balance can be ratioed with the integrated porosity of the top meter of soil to provide a leaching index. The index reaches 1 (total filling of the pore space on an annual basis) at about 1400 mm MAP. Index values >1 imply intense leaching conditions because of pore water replacement. In these 170 ka soils, leaching losses of soluble base cations and Si are nearly complete at index values >1, whereas only 60% of Al has been lost. At index values <1 leaching losses are progressively lower with the lowest rainfall sites having lost 10–20% of the original base cations and Si and none of the Al. At all sites, the secondary clay mineral assemblage is dominated by metastable noncrystalline weathering products; humid soil profiles contain very few crystalline minerals whereas the arid profiles contain halloysite, hematite, gibbsite and small amounts of carbonates. Soil surface exchange properties are influenced strongly by climatic conditions and show a dramatic threshold in base cation saturation, pH and effective cation exchange capacity (ECEC) at leaching index of 1 (1400 mm MAP). Soils with leaching index of <1 have high base cation saturation, near-neutral pH and high ECEC. At MAP >1400 mm, soil buffering capacity has been totally exhausted leading to low pH and low ECEC. The nonlinear decline in ECEC is irreversible under natural conditions; base cation depleted soils will remain so even if the climate shifts to drier conditions. In contrast, a climate shift to wetter conditions can drastically modify surface chemical properties existing in the drier soils as weathering depletes primary minerals, elements are lost to leaching, and surface chemistry is modified. There is a time-dimension implied in climate gradient studies; soils forming in recently rejuvenated landscapes contain more primary minerals and should experience loss of buffering capacity at higher rainfall. Loss of buffering capacity means that biological acidity will move more deeply into the vadose zone or into the aquatic system. The details of this transfer depend on present and past climate, and the age and erosional stability of landscapes.

The Potential of AMMI Analysis for Field Assessment of Musa Genotypes to Virus Infection

Virus-like symptoms (due to banana streak virus, cucumber mosaic virus, or both) have been observed in plants of Musa hybrids (TMPx) and local landraces included in multilocational trials in sub-Saharan Africa. Virus-like symptom incidence in these multilocational trials was analyzed using the additive main effect multiplicative interaction (AMMI) model. There were significant differences in virus-like symptom incidence among environments, which was highest in the cool, rainy season (14% to 42%) and lowest in the warm, dry season (&lt;10%). Genotypes showed significantly different responses to virus(es), which depended on the environment. There were no plants of AA and AAA bananas showing virus-like symptoms (0% incidence), whereas ABB cooking bananas and a cooking banana hybrid (ABB × AA) seldom showed virus-like symptoms (&lt;2% incidence). The AAB French plantains appeared to have a similar genotypic response to virus(es) (about 10% virus-like symptom incidence) and were regarded as less susceptible than the False Horn plantain `Agbagba', which showed virus-like symptoms in most of the environments (average 21% incidence). Hence, `Agbagba' should be considered a susceptible indicator host because it has a stable susceptible host response to Musa virus(es). Plantain hybrids (AAB × AA) showed virus-like symptoms; however, there were significant differences in genotypic response to the virus(es) among various hybrids (11% to 60%). Epistasis due to transgressive segregation may control the susceptibility of TMPx germplasm to Musa virus(es). The AMMI1 model revealed that an increase in clonal susceptibility resulted in a more unstable response to the virus. Similarly, phenotypic instability was associated with an increase in clonal resistance. Environments with very low (dry season) or very high (rainy season) incidence of virus-like symptoms had unstable virus expression. Scoring virus symptoms in cool environments with low rainfall and low potential evapotranspiration provided an unbiased assessment of genotypic response to Musa virus(es). The AMMI2 model showed that seasonal rather than locational diversity accounted for most of the interaction patterns. This finding may indicate a low level of strain differentiation in the region.