Vegetative Growth Response Research Articles

A study on the growth of Gorontalo local upland rice Ponda merah accession against drouhgt and shade stresses

The aim of this study was to determine the vegetative growth response of Gorontalo local upland rice Ponda Merah accession against drought and shade stresses. The study was conducted in Sipatana Village, West Bulotadaa Subdistrict, Gorontalo City, from May to October 2017, examined using randomized block design with 4 replications. The first factor observed was the drought treatment which consisted of two levels; irrigation until the inundation height of 1.5 cm and irrigation carried out if the potential of groundwater reaches - 30 to -35.9 kPa. The second factor was shades which consisted of 3 levels; 0% shade, 25% shade, and 50% shade. The results showed that Gorontalo local upland rice Ponda merah accession was able to adapt well to drought stress, shade stress, and combination of both which were characterized by high values of plant dry weight 49,88 g under drought stress condition, 84,08 g under 50% shade condition and 44,61 g in drought + 50% shade condition and chlorophyll content 0.148 mg.g−1 under drought stress condition, 0,168 mg.g−1 under 50% shade condition and 0,202 mg.g−1 in drought +50% shade condition.

FERONIA cytoplasmic domain: node of varied signal outputs.

The receptor-like kinase (RLK) FERONIA (FER), located on the plasma membrane, belongs to the Catharanthus roseus RLK1-like kinase family (CrRLK1L) and participates in widespread biological processes in plants in a context-dependent fashion. Genetic studies in Arabidopsis illustrated the versatile roles that FER plays in fertilization, vegetative growth, defense and stress responses, cell-wall homeostasis, as well as protein synthesis. These studies also helped to identify genes and signal pathways involved in FER signal transduction. Despite increasingly larger numbers of studies discussing how FER senses its ligand, Rapid alkalinization factor (RALF) peptides, and further regulates downstream factors, few have shown the mechanisms of how FER mediates the specific regulation of downstream signals in context of the phosphorylation of its cytoplasmic domain. As understanding this would help in better understanding the diversity and complexity of FER function, this paper aims to review the roles of FER in regulating different signal outputs from the view of the role of its cytoplasmic domain.

Effect of decreasing soil frozen depth on vegetation growth in the source region of the Yellow River for 1982–2015

Climate warming impacts on frozen ground degradation may cause large-scale consequences to terrestrial ecosystems within the source region of the Yellow River (SRYR). Spatial and temporal variations in the soil frozen depth (SFD) in SRYR were estimated using the Stefan equation for 1982–2015 and SFD effects on alpine vegetation were analyzed. Mean SFD during 1982–2015 decreased at a rate of 6.01 cm/10a, and the areal extent of the SFD greater than 160 cm decreased by 26.3%. Normalized difference vegetation index (NDVI) in the growing season (NDVIgr) discontinuously increased at a rate of 0.003/10a, increasing in 1982–2000 and declining in 2001–2015. The NDVIgr was significantly correlated to the decreasing SFD, showing a stronger relationship than that with temperature and precipitation. Comparisons before and after 2000 showed that negative relationships between SFD and NDVIgr became positive. Responses of vegetation growth to frozen ground degradation depended on different rates of decreasing SFD. Rapid decreases in SFD after 2000 led to increased evapotranspiration and reduced soil water, which negatively affected vegetation growth. Negative impacts of human activities on vegetation changed to positive contributions from the periods of 1982–2000 to 2001–2015; however, the effect was less than that of climate change and frozen ground degradation. This study provides a foundation for research on frozen ground changes and the impacts on ecological environments.

Vegetation growth variation in relation to topography in Horqin Sandy Land

Abstract Water availability is a major limiting factor for vegetation growth in semi-arid areas. Soil moisture availability is related to topography, which therefore, influences vegetation growth. To examine the response of vegetation growth to topography, we calculated an index of vegetation growth (GRNDVI) and analyzed its distribution along a topography index in Horqin Sandy Land, Inner Mongolia, China. Cropland growth improved and then deteriorated as topography increased, while wetness initially increased and then declined. In contrast, grassland growth initially declined and then improved with increasing topography, while wetness continuously declined. Grassland growth was affected by soil moisture and by different plant species. Cover and height of herbaceous species decreased from flat to hilltop while the cover and height of shrub species increased, especially those species with stronger drought tolerance. Different optimal land use scenarios were proposed based on water availability and topographic position. In the lowest areas, wetlands are proposed to promote natural habitat for aquatic plants and animals. In low areas, water facilities could be constructed and crops planted to supply food. In the middle area, grassland should be utilized to provide some pastures. In the upper and highest areas, drought tolerant shrubs should be planted to stabilize slopes and enhance native biodiversity and ecological integrity. The study could be used as a functional model to reduce desertification in semi-arid areas through optimizing land utilization, maintaining and enhancing ecological integrity and promoting sustainable development.

Responses of Australian Dryland Vegetation to the 2019 Heat Wave at a Subdaily Scale

AbstractSatellite solar‐induced chlorophyll fluorescence (SIF) products from the Global Ozone Monitoring Experiment 2 (GOME‐2) and Orbiting Carbon Observatory 2 (OCO‐2) are used to investigate the responses of vegetation growth to the 2019 heat wave in Australia. Both satellite SIF data sets are more sensitive to water and heat stress than is the greenness‐based vegetation index (enhanced vegetation index). Moreover, the OCO‐2 SIF observations show a more significant reduction and earlier response to the heat stress than does GOME‐2 SIF, indicating that the two satellite SIF data sets differ in how they monitor the drought and heat wave event due to the different timing of observations. Eddy covariance measurements confirm the different responses of dryland vegetation to the 2019 heat wave at a subdaily time scale. The differences in the timing of the satellite SIF products can be used to assess different elements of the impact of heat and water stress on Australian dryland ecosystems.

In-silico analysis of cucumber (Cucumis sativus L.) Genome for WRKY transcription factors and cis-acting elements

WRKY genes, comprises one among a large clan of transcription factor (TFs) genes in the plant kingdom, playing a fundamental role in the vegetative and reproductive growth, development and stress responses of a plant. In spite of several studies on cucumber (Cucumis sativus L.), WRKY genes and their interaction with stress response is limited. The present study, on the whole genome of cucumber was analyzed for WRKY genes which recognized 62 CsWRKY genes associated with the proteins obtained from lineages of supplementary plants. The physicochemical properties reveal the CsWRKY gene is ser-rich TF (6.70–18.40 %). The chromosomal distribution showed that all putative CsWRKY genes were distributed in seven chromosomes, enriched on chromosome 3 and 6 and least on chromosome 5. Based on phylogenetic analysis, along with motif determination and gene structure analysis, CsWRKYs are categorized as a Group I, II and III. The Group II further subdivided as Groups IIa-e. In the present study, it was observed that Group II WRKY-TFs was the largest group containing 43 WRKY genes containing a single WD (WRKY domain - WRKYGQK/WRKYGKK) and C2H2 type zinc finger structure (C-X4-5-C-X23-H-X1-H). The data also revealed that chromosome 3 and 5 contained all the three major groups and chromosome 6 contained I and II WRKY genes with uneven distribution. STRING analysis of selected CsWRKY proteins expressed in response to abiotic stress interacts with the CsMAPK proteins. Analysis of cis-acting elements and results suggest that CSWRKY genes play important role in response to biotic and abiotic stress. Response also predicted the candidate gene expression in cucumber during its development under different cellular condition.

Vegetative growth and yield response of Amaranthus hybridus to mycorrhizal fungi (Glomus mosseae) inoculation, organic and micronutrient fertilizer application

This study was carried out at the Faculty of Agriculture Teaching and Research farm, University of Benin during the early planting season in April 2016 to evaluate the growth response of Amaranthus hybridus and some soil physical and chemical properties as influenced by organic and micronutrient fertilizers, mycorrhizal inoculum. In this experiment four treatments (poultry manure + cow dung + pig manure (PCP), poultry manure + mycorrhiza (Pm), poultry manure + mycorrhiza + foliar blend (PmMF) and control (C) were replicated four times and arranged in a randomized complete block design (RCBD) in a plot size of 70m2 . Soil samples were taken prior and after the trial at a 0-15cm depth for analysis. Results revealed that the soil (sand, silt and clay) and the textural class remained the same (loamy sand) and the micronutrient had no significant effect on the treated plots; however, all the treatments showed a significant increase in the soil pH, organic carbon, organic matter, NPK and Mg and a slight decrease in Ca and Na when compared to the pre-trial soil indicating an increase in residual soil nutrient status. Nutrient content N, P, K, plant height (51.13cm), number of leaves (67.80), stem girth (5.61cm), leaf area (194.87cm2 ) and yield (7.51 t/ ha) were significantly higher in plots treated with PM when compared to other treatments PMF, PCP and control in that order, with control having the lowest values of plant height (19.13 cm), number of leaves (26.00) stem girth (2.80 cm) leaf area (57.76 cm2 ) and yield (0.80 t/ha). Also, significantly higher spores, root arbuscules, root vesicle and root hyphae were recorded in PM (66.20,13.60,9.80,13.40) and PMF (74.40,10.50,11.10,10.50) treatment when compared to other treatments PCP and control.

Characterization of non-canonical G beta-like protein FvGbb2 and its relationship with heterotrimeric G proteins in Fusarium verticillioides.

Fusarium verticillioides is a fungal pathogen that is responsible for maize ear rot and stalk rot diseases worldwide. The fungus also produces carcinogenic mycotoxins, fumonisins on infested maize. Unfortunately, we still lack clear understanding of how the pathogen responds to host and environmental stimuli to trigger fumonisin biosynthesis. The heterotrimeric G protein complex, consisting of canonical Gα, Gβ and Gγ subunits, is involved in transducing signals from external stimuli to regulate downstream signal transduction pathways. Previously, we demonstrated that Gβ protein FvGbb1 directly impacts fumonisin regulation but not other physiological aspects in F. verticillioides. In this study, we identified and characterized a RACK1 (Receptor for Activated C Kinase 1) homolog FvGbb2 as a putative Gβ-like protein in F. verticillioides. The mutant exhibited severe defects not only in fumonisin biosynthesis but also vegetative growth and conidiation. FvGbb2 was positively associated with carbon source utilization and stress agents but negatively regulated general amino acid control. While FvGbb2 does not interact with canonical G protein subunits, it may associate with diverse proteins in the cytoplasm to regulate vegetative growth, virulence, fumonisin biosynthesis and stress response in F. verticillioides.

Effect of Blended NPS Fertilizer Rates on Growth Performance of Tomato (Solanum lycopersicum L) at Wolaita Sodo University, Ethiopia

Filed experiment was conducted as Wolaita sodo University, college of agriculture and department of horticulture filed site to evaluate the response of vegetative growth of tomato to different rate of NPS application. The size of total plot is 7.5m X 5.5m (41.25m 2 ) and the size of each plot was 1.50m X 1.50m (2.25m 2 ). Three rate of blended NPS fertilizer at 80kg /ha, 160kg/ha and 240kg/ha with control (check). The experiment was lay out with 12 plots having 3 blokes and each block have four plots. The data on plant height per plant, the primary branches per plant, and the number of leaves per plants were collected from three plants of the middle rows of each plot and subjected to statistical analysis using ANOVA with computing the treatment by least significance difference at 5 %. As the result the number of leaf number shows significant (P 0.05) different. This shows the tomato crop requires high amount NPS supply enough to maintain the branch, plant height, and the leaf number of tomato vegetative growth. Application of 240kg/ha of blended NPS fertilizer did showed significant factors for all growth parameters. Hence, as this research revealed that application of 240kg/ha was the optimum level for effective vegetative performance of tomato. However, to come up concrete recommendation the study should be repeated across the season and up to yield . Keywords : Tomato, blended NPS fertilizer, Plant height, Leaf number, branch number DOI : 10.7176/JNSR/9-24-01 Publication date: December 31 st 2019

Vegetative Growth Response of Eggplant (Solanum aethiopicum L.) to Combined Effects of Fertilizer Types and Irrigation Regimes Applied on Littoral Tertiary Soil in Côte d’Ivoire

The use of manures and irrigation systems are essential ways to improve the fertility of coastline poor soils in Côte d’Ivoire and to optimize crop yields at any time of the year. The present study aims to identify the best manures and irrigation systems suitable for the vegetative growth of eggplant on the tertiary poor soils of the coast in Côte d'Ivoire. For this purpose, combinations of fertilizer (urea and organic manure from chicken droppings) and irrigation techniques (manual watering and drip irrigation system) were tested in Fisher block design. So, vegetative growth variables of Eggplant, Aub 21N / 06, grown on tertiary soil at the Marc Delorme research station of the Centre National de Recherche Agronomique (CNRA) in Southern Côte d'Ivoire were evaluated. The results showed that the growth dynamics of collar circumference, height and leaf production of eggplant irrigated by drip system and fertilized with organic manure from chicken droppings was significantly higher. The eggplants that received a treatment composed by organic or chemical manure without irrigation and those without manure and irrigation expressed lower vegetative growth. The organic manure from chicken droppings associated with the drip irrigation regime had a significant beneficial effect on the average growth rates of the collar circumference (0.0035 cm.day-1), height (0.5669 cm.day-1) and leaf production (3.12 leaves.day-1) of eggplant. It appears that organic manure from chicken droppings associated with drip irrigation regime is an agricultural innovation to disseminate to market gardeners to cultivate the eggplant on littoral tertiary soil.

Guar responses to temperature: Estimation of cardinal temperatures and photosynthetic parameters

Temperature is the primary environmental determinant of geographic distribution and productivity of plant species. There has been increased interest in the cultivation of guar [Cyamopsis tetragonoloba (L.) Taub.] in many countries including the United States due to the high demand of guar gum in the oil fracking industry. However, information on gaur response to temperature is still lacking in the current literature. An experiment was conducted using six different day/night temperature regimes (20/12, 24/16, 28/20, 32/24, 36/28 and 40/32 °C) maintained inside walk-in growth chambers of the Controlled Environment Research Facility at Oklahoma State University. The objectives of this study were to evaluate the temperature responses of vegetative growth, development, and reproduction of guar to estimate cardinal temperatures, and to evaluate photosynthetic responses to temperature gradient. The vegetative growth of guar was sensitive to low temperature (<20 °C), and has high mean cardinal temperatures (Tmin, Topt, and Tmax) for biomass accumulation (14.2, 34.1 and 48.2 °C). Plants exhibited reproductive development within a narrow range (19–31 °C) with maximum pod yields observed at a Topt of 25 °C. Higher temperature regimes (36/28 and 40/32 °C) completely suppressed flower initiation in guar. Responses of photosynthesis to both light and internal CO2 concentration (A-Ci) suggested guar photosynthetic rates increased under high temperature through an increased rate of electron transport. The identified cardinal temperatures and photosynthesis parameters can be used to develop mechanistic crop models to simulate adaptation strategies for guar. Further research is required to investigate the basis for suppression of flower bud initiation under heat stress.

Response of vegetative growth and chemical properties in tomato plant (Tariz) for organic fertilization.

The experiment was carried out in agricultural land in Sorman between 4 - 2017 to 7 - 2017, in the design of Randomized Complete Block Design (RCBD) to study the response of vegetative traits and chemical properties in the tomato plant of Tariz for organic fertilization, by 6 treatments and 3 replicates, For SPSS statistical analysis at a significant level of LSD 0.05). The experiment included four types of semi-decomposed organic fertilizer (sheep manure, cattle manure, camel manure, horse manure) in 6 treatments, in addition to the control treatment, which included four treatments for each type of organic fertilizer as: fertilizer: soil by ratio (1: 3) that is 5Kg of fertilizer : 15 kg of soil, mixed treatment of fertilizer : soil (1: 1) (10 kg of fertilizer: 10 kg of soil), and double treatment (3: 1) (15 kg of fertilizer: 5 kg soil). The seedlings were planted in experimental units of 7.20 m2. The seedlings were treated in biological control using the garlic extract for insect protection after 15 days of planting, as well as the addition of simple proportions of hay as a cover to reduce the growth of herbs. The experiment showed that the treatment of cattle manure significantly increased most of the studied morphological traits (length of root, plant length, number of flowers, number of leafy branches), as well as significant increase in fresh and dry weight of leaves and average weight of five fruits.. There were significant differences in the content of the N, P in leaves and NPK elements in the fruits, while there was a significant increase in vitamin C content in fruits for all treatments.

Differential agro-physiological responses induced by partial root-zone drying irrigation in olive cultivars grown in semi-arid conditions

Olive cultivation is mostly practiced under Mediterranean agro-ecosystems with limited availability of water. With current climate change conditions, water scarcity will continue to challenge agricultural sustainability. Therefore, great emphasis is placed on irrigation management in arid regions with the aim of increasing water use efficiency.The present study was conducted during two growing seasons (2015 and 2016) consisting of a low yields year (‘Off’ year) and a high yields year (‘On’ year), respectively. The photosynthetic performance in terms of gas exchange and chlorophyll fluorescence, as well water status, vegetative growth and yield responses of three olive cultivars (Arbequina, Arbosana and Chetoui) grown under partial root zone drying (PRD) irrigation in semi-arid conditions of Tunisia were investigated. Olive trees were subjected to four irrigation treatments which corresponded to control irrigated at 100% of the crop evapotranspiration (100%ETC) on both sides of the root system and three PRD treatments. These later were irrigated on a 14-day alternating cycle on one side of the root system and received respectively 100%, 75% and 50% of the control (100%PRD, 75%PRD and 50%PRD). In ‘Off’ year shoot length was lower in PRD irrigated trees than in control trees, mainly for Arbequina and Chetoui cultivars and the lowest values were associated with 50%PRD treatment. However, in ‘On’ year shoot length increased slightly for all treatments, whereas remained lower under PRD irrigation treatments. Relating to water status, all cultivars under PRD treatments show a clear decrease in stem water potential (Ψstem) and relative water content (RWC). A clear difference in the regulation of leaf gas exchange parameters under different irrigated regimes was observed between the studied cultivars. Results indicated that the PRD induced a decrease in maximum efficiency of photosystem II (Fv/Fm), effective efficiency of PSII (Φ PSI), stomatal conductance (gs) and transpiration rate (E). Nevertheless, this decrease did not limit the overall photosynthesis process mainly in the two cultivars Arebquina and Chetoui; since assimilation rates and intrinsic water use (WUEi) still maintained under 50%PRD treatment independently of the decreased value of fluorescence parameters.Furthermore, reducing irrigation volumes by 25% (75% PRD) and 50% (50% PRD) compared to the control (100%ETC) increased oil yield and water productivity mainly for Arbequina cultivar without significant reductions on yield components. Based on agronomic and physiological adaptations to reduce water loss, it can be concluded that Arbequina is very promising for cultivation under PRD irrigation strategy compared to Arbosana and Chetoui.

Use of some biostimulants to improve the growth and chemical constituents of sweet pepper

The experiment was conducted during two successive seasons 2016 and 2017 on sweet pepper plants to study the effect of foliar application of some natural extracts (fulvic acid at 2, 4 and 6% or algae at 1, 2 and 4 g.L-1) were applied three times along each season (after 2, 4 and 6 weeks of planting). The influence was evaluated through the response of vegetative growth, and some physical and chemical characteristics of sweet pepper fruits. The results obtained showed that the algae extract at 1 g.L-1 in most cases was better than the other spray treatments investigated to improve most fruit characteristics (length, diameter and yield of fruits), vegetative growth, and chemical properties followed by 6% fulvic acid. With regard to organic acids, malic and citric acids are the main organic acids found in sweet pepper. Malic, succinic and glutaric acids were higher in 1 g.L-1 algae extract treatment, but the concentration of citric acid was higher in 6% fulvic acid treatment. Therefore, algae extract and fulvic acid could be safely recommended as a natural biostimulants application for improving most desirable characteristics of sweet pepper grown under the same experimental condition.

Discrepancies in vegetation phenology trends and shift patterns in different climatic zones in middle and eastern Eurasia between 1982 and 2015.

Changes in vegetation phenology directly reflect the response of vegetation growth to climate change. In this study, using the Normalized Difference Vegetation Index dataset from 1982 to 2015, we extracted start date of vegetation growing season (SOS), end date of vegetation growing season (EOS), and length of vegetation growing season (LOS) in the middle and eastern Eurasia region and evaluated linear trends in SOS, EOS, and LOS for the entire study area, as well as for four climatic zones. The results show that the LOS has significantly increased by 0.27 days/year, mostly due to a significantly advanced SOS (−0.20 days/year) and a slightly delayed EOS (0.07 days/year) over the entire study area from 1982 to 2015. The vegetation phenology trends in the four climatic zones are not continuous throughout the 34‐year period. Furthermore, discrepancies in the shifting patterns of vegetation phenology trend existed among different climatic zones. Turning points (TP) of SOS trends in the Cold zone, Temperate zone, and Tibetan Plateau zone occurred in the mid‐ or late 1990s. The advanced trends of SOS in the Cold zone, Temperate zone, and Tibetan Plateau zone exhibited accelerated, stalled, and reversed patterns after the corresponding TP, respectively. The TP did not occurred in Cold‐Temperate zone, where the SOS showed a consistent and continuous advance. TPs of EOS trends in the Cold zone, Cold‐Temperate zone, Temperate zone, and Tibetan Plateau zone occurred in the late 1980s or mid‐1990s. The EOS in the Cold zone, Cold‐Temperate zone, Temperate zone, and Tibetan Plateau zone showed weak advanced or delayed trends after the corresponding TP, which were comparable with the delayed trends before the corresponding TP. The shift patterns of LOS trends were primarily influenced by the shift patterns of SOS trends and were also heterogeneous within climatic zones.

Responses of vegetation growth to temperature during 1982-2015 in Xinjiang, China.

Combined with the normalized difference vegetation index (NDVI) dataset, vegetation type data, and meteorological data, we revealed the variation of vegetation growth responses to air temperature in the growing-season during 1982-2015 in Xinjiang, using the moving-windows based partial correlation analysis, the unitary linear regression analysis and GIS spatial analysis. Results showed that, in the whole growing-seasons of study period, there was a significant downturn trend in the responses of vegetation growth to temperature. At the seasonal scale, the downturn trend was obvious especially in summer and autumn, while it was in adverse in spring. During the whole gro-wing season, the responses of different vegetation types to air temperature change showed a decreasing trend. Seasonally, the responses of grassland and forest to temperature change showed a significant increase, while that of shrubland and desert were exactly the opposite in spring. The responses of all natural vegetation (grassland, shrubland, desert and forest) to temperature change showed a significant decreasing trend in summer, whereas their responses in autumn had no significant statistical characteristics. Spatially, the decreasing influence of temperature on the vegetation growth during the growing season in Xinjiang was universal, which might be due to the change in precipitation and solar radiation.

Mulching combined with regulated deficit irrigation can be successfully applied to young pear trees

We investigated the effects of water stress (regulated deficit irrigation - RDI) and mulching on the vegetative growth response of young 'Williams' pear trees. Using a water budget methodology, four levels of irrigation, specifically 100% of evapotranspiration (ET) as control and deficits of 80, 60 and 40%, were applied to 10 trees during the season, 5 of which were mulched with wood chips at a 20-cm layer. The experiment was conducted in Kosovo during 2013, 2014 and 2015 in a three- to five-year-old pear orchard using a nested experimental design. We found significant changes in a series of vegetative growth parameters. Irrigation levels significantly influenced all parameters. Mulching had a positive effect on all parameter values measured. Our results confirmed that a moderate water stress reduces excessive vegetation growth, especially canopy volume, leaf surface and area, LAI and shoot length. It can be concluded that regulated deficit irrigation can be successfully applied to young pears too with significant water saving.

Respons Tanaman Jahe Merah (Zingiber Officinale) Terhadap Ekstrak Bawang Merah dan Pupuk Hayati Trichoderma

This study aims to determine the vegetative growth response of saplings of red ginger (Zingiber officinale) to the administration of red onion extract and Trichoderma biological fertilizer. Experiments were arranged factorially using a completely randomized design (CRD). The first factor is the concentration of red onion extract which consists of three levels, namely: 0 gr, 125 gr, and 250 gr per liter of shallot extract; the second factor is Trichoderma biological fertilizer, consisting of: without biological fertilizer and with Trichoderma biological fertilizer. Each combination of treatments was repeated 4 times, to obtain 24 experimental units. The variables observed were plant height (cm), number of leaves, increase in stem diameter (cm), stover wet weight (gr), and dry stover weight (gr) at 24-60 days after planting (DAP). Data were analyzed by variance at the level of 5% to determine the effect of treatment, to find out the differences between treatments were carried out by 5% HSD. The results showed that there was a significant interaction effect between red onion extract and Trichoderma biofertilizer on the increase of high growth of red ginger tillers at 36 and 48 DAP. Both factors and their interactions were not significant for the number of leaves, stem diameter, wet weight, and dry stover weight. The treatment of 125 gr/l shallot extract and Trichoderma biofertilizer produced the highest response of the number of leaves and stem diameter at 60 DAP.

Connectivity-Mediated Ecohydrological Feedbacks and Regime Shifts in Drylands

Identified as essential mechanisms promoting alternative stable states, positive feedbacks have been the focus of most former studies on the potential for catastrophic shifts in drylands. Conversely, little is known about how negative feedbacks could counterbalance the effects of positive feedbacks. A decrease in vegetation cover increases the connectivity of bare-soil areas and entails a global loss of runoff-driven resources from the ecosystem but also a local increase in runoff transferred from bare-soil areas to vegetation patches. In turn, these global resource losses and local resource gains decrease and increase vegetation cover, respectively, resulting in a global positive and a local negative feedback loop. We propose that the interplay of these two interconnected ecohydrological feedbacks of opposite sign determines the vulnerability of dryland ecosystems to catastrophic shifts. To test this hypothesis, we developed a spatially explicit model and assessed the effects of varying combinations of feedback strengths on the dynamics, resilience, recovery potential, and spatial structure of the system. Increasing strengths of the local negative feedback relative to the global positive feedback decreased the risk of catastrophic shifts, facilitated recovery from a degraded state, and promoted the formation of banded vegetation patterns. Both feedbacks were most relevant at low vegetation cover due to the nonlinear increase in hydrological connectivity with decreasing vegetation. Our modelling results suggest that catastrophic shifts to degraded states are less likely in drylands with strong source–sink dynamics and/or strong response of vegetation growth to resource redistribution and that feedback manipulation can be useful to enhance dryland restoration.

Predictability of tropical vegetation greenness using sea surface temperatures**This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form

Much research has examined the sensitivity of tropical terrestrial ecosystems to various environmental drivers. The predictability of tropical vegetation greenness based on sea surface temperatures (SSTs), however, has not been well explored. This study employed fine spatial resolution remotely-sensed Enhanced Vegetation Index (EVI) and SST indices from tropical ocean basins to investigate the predictability of tropical vegetation greenness in response to SSTs and established empirical models with optimal parameters for hindcast predictions. Three evaluation metrics were used to assess the model performance, i.e., correlations between historical observed and predicted values, percentage of correctly predicted signs of EVI anomalies, and percentage of correct signs for extreme EVI anomalies. Our findings reveal that the pan-tropical EVI was tightly connected to the SSTs over tropical ocean basins. The strongest impacts of SSTs on EVI were identified mainly over the arid or semi-arid tropical regions. The spatially-averaged correlation between historical observed and predicted EVI time series was 0.30 with its maximum value reaching up to 0.84. Vegetated areas across South America (25.76%), Africa (33.13%), and Southeast Asia (39.94%) were diagnosed to be associated with significant SST-EVI correlations (p < 0.01). In general, statistical models correctly predicted the sign of EVI anomalies, with their predictability increasing from ∼60% to nearly 100% when EVI was abnormal (anomalies exceeding one standard deviation). These results provide a basis for the prediction of changes in greenness of tropical terrestrial ecosystems at seasonal to intra-seasonal scales. Moreover, the statistics-based observational relationships have the potential to facilitate the benchmarking of Earth System Models regarding their ability to capture the responses of tropical vegetation growth to long-term signals of oceanic forcings.