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51 results for “Precipitation gradient”

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Data from: Genomic signatures of adaptation to a precipitation gradient in Nigerian sorghum

Evolution of plants under climatic gradients may lead to clinal adaptation. Understanding the genomic basis of clinal adaptation in crops species could facilitate breeding for climate resilience. We investigated signatures of clinal adaptation in the cereal crop sorghum (Sorghum bicolor L. [Moench]) to the precipitation gradient in West Africa using a panel (n = 607) of sorghum accessions from diverse agroclimatic zones of Nigeria. Significant correlations were observed between common-garden phenotypes of three putative climate-adaptive traits (flowering time, plant height, and panicle length) and climatic variables. The panel was characterized at >400,000 single nucleotide polymorphisms (SNPs) using genotyping-by-sequencing (GBS). Redundancy analysis indicated that a small proportion of SNP variation can be explained by climate (1%), space (1%), and climate collinear with space (3%). Discriminant analysis of principal components identified three genetic groups that are distributed differently along the precipitation gradient. Genome-wide association studies were conducted with phenotypes and three climatic variables (annual mean precipitation, precipitation in the driest quarter, and annual mean temperature). There was no overall enrichment of associations near a priori candidate genes implicated in flowering time, height, and inflorescence architecture in cereals, but several significant associations were found near a priori candidates including photoperiodic flowering regulators SbCN12 and Ma6. Together, the findings suggest that a small (3%) but significant proportion of nucleotide variation in Nigerian sorghum landraces reflects clinal adaptation along the West African precipitation gradient.

opencc-zeroDec 2017View details →

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Functional organization of woody plant assemblages along precipitation and human disturbance gradients in a seasonally dry tropical forest

Chronic anthropogenic disturbances (CAD) and rainfall are important drivers of plant community assembly, but little is known about the role played by inter and intraspecific trait variation as communities respond to these pervasive forces. Here we examined the hypothesis that lower precipitation and higher CAD reduce both intra and interspecific trait variation in Caatinga dry forests. We sampled woody plants across 15 plots along precipitation and CAD gradients and measured resource-use traits. Effects of precipitation and CAD on RaoQ functional diversity were decomposed into species turnover and intraspecific variability. We used "T-statistics" to assess the trait sorting from the regional pool to local communities (i.e. external filtering), and within-community forces leading to low trait overlap (i.e. internal filtering) at individual- and species-level. Intraspecific variability explained at least one third of the total trait variation and 46% of variation in multitrait diversity across communities. Increasing disturbance reduced multitrait diversity, while precipitation affected some particular traits, such as wood density. Overall, precipitation determined species sorting across communities, while disturbance relaxed internal filters, leading to higher trait overlap within communities due to higher intraspecific variability. Our results suggest that the woody Caatinga flora contains a substantial amount of both inter and intraspecific trait variation. This variation is not randomly distributed within and across communities, but varies according to rainfall conditions and disturbance intensity. These findings reinforce the emerging idea that human-disturbances can reorganize plant communities at multiple scales and highlight trait variability as a key biological asset for the resilience of dry forests.

opencc-zeroOct 2019View details →

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Precipitation gradients, plant biogeography, and the incidence of drip-tips in Cerrado plant species

Examining how both climate and species distribution patterns correlate with leaf morphology can give insights into the ecological and evolutionary patterns that drive adaptive selection of leaf form and function. Drip-tips are a common feature of leaves in rain forest tree species; they are thought to be an adaptation that aids leaf drying and maximizes photosynthesis in areas with high-rainfall climates. We tested whether this macroecological pattern holds true across the precipitation gradients in a non-rain forest region – the woodland savannas of Brazil known as the Cerrado – and compared our results with previous studies from Amazonia. Drip-tips were, as expected, less common overall in the drier Cerrado than in Amazonia. In addition, within the Cerrado, drip-tips were more prevalent in areas with higher rainfall as well as in Cerrado sites that were closer to Amazonia. Moreover, species that occurred across both the Cerrado and Amazonia had drip-tips more often than species that were found only in the Cerrado. These findings support the hypothesis that drip-tips are adaptive and that either the cost of retaining drip-tips is low or that in drier regions they have other benefits.

opencc-zeroMar 2020View details →

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Liana abundance and diversity increase with rainfall seasonality along a precipitation gradient in Panama

In tropical regions, rainfall gradients often explain the abundance and distribution of plant species. For example, many tree and liana species adapted to seasonal drought are more abundant and diverse in seasonally-dry forests, characterized by long periods of seasonal water deficit. Mean annual precipitation (MAP) is commonly used to explain plant distributions across climate gradients. However, the relationship between MAP and plant distribution is often weak, raising the question of whether other seasonal precipitation patterns better explain plant distributions in seasonally-dry forests. In this study, we examine the relationship between liana abundance and multiple metrics of seasonal and annual rainfall distribution to test the hypothesis that liana density and diversity increase with increasing seasonal drought along a rainfall gradient across the isthmus of Panama. We found that a normalized seasonality index, which combines MAP and the variability of monthly rainfall throughout the year, was a significant predictor of both liana density and species richness, whereas MAP, rainfall seasonality, and the mean dry season precipitation (MDP) were far weaker predictors. The strong response of lianas to the normalized seasonality index indicates that, in addition to the total annual amount of rainfall, how rainfall is distributed throughout the year is an important determinant of the hydrological conditions that favor liana proliferation. Our findings imply that changes in annual rainfall and rainfall seasonality will determine the future distribution and abundance of lianas. Models that aim to predict future plant diversity, distribution, and abundance may need to move beyond MAP to a more detailed understanding of rainfall variability at sub-annual timescales.

opencc-zeroOct 2019View details →

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Data from: A shady business: pine afforestation alters the primary controls on litter decomposition along a precipitation gradient in Patagonia, Argentina

Our understanding of the principal controls on litter decomposition is critical for our capacity to predict how global changes will impact terrestrial ecosystems. Although climate, litter quality and soil organisms clearly modulate carbon (C) and nutrient turnover, land-use change affecting plant species composition and structure can alter the relative importance of such controls. We took advantage of prior land-use changes of intentional planting of exotic forest species along a broad precipitation gradient [250–2200 mm mean annual precipitation (MAP)] in Patagonia, South America, where we established five paired sites in natural vegetation and adjacent 35-year-old pine plantations. We explored direct and interactive effects of precipitation and plant community structure on litter decomposition with in situ decomposition, common litters and reciprocal transplants, in addition to an evaluation of microenvironmental changes. Surface litter decomposition in natural vegetation (NV) was similar in all sites along the gradient, independent of litter quality, MAP or soil characteristics, while mass loss demonstrated a significant positive linear relationship with MAP in pine plantations (PP). Decomposition of common litters in PP was markedly reduced with respect to NV, which was > 50% faster at the arid extreme of the gradient. C:N ratios predicted decomposition only in PP, and differences in decomposition were highly correlated with impacts of vegetative cover on incident solar radiation. Synthesis. Concurrent changes in plant cover in NV with increasing MAP resulted in reduced incident solar radiation at the soil surface and decreased the relative importance of photodegradation as a control on surface mass loss. These changes eclipsed direct effects of water availability, litter quality and soil nutrients. In contrast, increased shade and recalcitrant litter with afforestation in PP sites combined such that photodegradation was entirely eliminated as a control and biotic decomposition was much reduced. While afforestation projects are promoted as a strategy to mitigate increased atmospheric carbon dioxide due to human activity, our results highlight that primary controls of litter decomposition were substantially altered with unexpected consequences for the C balance of these ecosystems.

opencc-zeroDec 2014View details →

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Phytolith-occluded carbon sequestration potential in three major steppe types along a precipitation gradient in Northern China

Phytolith-occluded carbon (PhytOC) is an important long-term stable carbon fraction in grassland ecosystems, and plays a promising role in global carbon sequestration. Determination of the PhytOC traits of different plants in major grassland types is crucial for precisely assessing their phytolith carbon sequestration potential. Precipitation is the predominant factor in controlling net primary productivity (NPP) and species composition of the semiarid steppe grasslands. We selected three representative steppe communities of the desert steppe, the dry typical steppe and the wet typical steppe in Northern Grasslands of China along a precipitation gradient, to investigate their species composition, biomass production and PhytOC content for quantifying its long-term carbon sequestration potential. Our results showed that (i) the phytolith and PhytOC contents in plants differed significantly among species, with dominant grass and sedge species having relatively high contents, and the contents are significantly higher in the below- than the aboveground parts. (ii) The phytolith contents of plant communities were 16.68, 17.94 and 15.85 g kg-1 in the above- and 86.44, 58.73 and 76.94 g kg-1 in the belowground biomass of the desert steppe, the dry typical steppe and the wet typical steppe, respectively; and the PhytOC contents were 0.68, 0.48 and 0.59 g kg-1 in the above- and 1.11, 0.72 and 1.02 g kg-1 in the belowground biomass of the three steppe types. (iii) Climatic factors affected phytolith and PhytOC production fluxes of steppe communities mainly through altering plant production, whereas their effects on phytolith and PhytOC contents were relatively small. Our study provides more evidence on the importance of incorporating belowground PhytOC production for estimating phytolith carbon sequestration potential, and suggests it crucial to quantify belowground PhytOC production taking into account of plant perenniality and PhytOC deposition over multiple years.

opencc-zeroDec 2021View details →

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Traits explain sorting of C4 grasses along a global precipitation gradient

Species distributions are closely associated with moisture availability, but the underlying mechanisms remain unresolved. Drought relations are especially important for plants such as C4 grasses that dominate seasonally dry ecosystems. Here, we test the hypothesis that C4 grass species sampled across global precipitation gradients show variation in survival under drought that can be explained by their traits. Our experiment subjected 18 C4 grass species to a lethal drought under controlled environmental conditions. The number of days until death was measured, along with root traits, senescence and aspects of hydraulic function. We identified two strategies; Drought avoiding species that stayed green as the water potential declined, and drought tolerating species that senesced more quickly but could extend survival via drought tolerant meristems. Plants that stay-green for longer occupied drier habitats and had the longest survival under drought, facilitated by narrow root diameter and isohydric stomatal behaviour. Plants that senesced quickly had thicker roots, an anisohydric strategy, and occupied wetter habitats. Global distributions of C4 grasses can be predicted by variation in rates of senescence, meristem survival, root traits and stomatal strategy, showing the value of these traits for understanding plant distributions in relation to climate.

opencc-zeroJan 2022View details →

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Functional diversity response to geographic and experimental precipitation gradients varies with plant community type

Precipitation is a primary determinant of plant community structure in drylands. However, the empirical evidence and predictions are lacking for how plant functional diversity in desert and steppe communities respond to altered precipitation regimes. We examined how precipitation changes along the natural and experimental gradients affect different components of functional diversity in desert-shrub and steppe-grass communities. We compared the associations of precipitation changes with community-weighted means (CWM) of six traits, functional divergence (FDvar) of each single-trait, and multi-trait functional richness (FRic) and dispersion (FDis) for shrub and grass communities along the natural and experimental gradients. We also disentangle the roles of species turnover and intraspecific variations in affecting the responses of different functional diversity to precipitation changes. We found that in general, the similar responses of functional traits or diversity to both the natural and experimental precipitation gradient were dependent on plant community type. Across both two gradients, precipitation was positively associated with CWM of plant height and negatively associated with the CWM of specific leaf area and leaf thickness in grass community, while positively associated with FDvar of four traits and FDis in shrub communities. Both species turnover and intraspecific variations contributed to the responses of grass community traits to precipitation changes across both two gradients, and to functional divergence of traits and FDis in shrub community along the natural gradient. In contrast, species turnover variations contributed to functional divergence of traits and FDis in shrub community in experiment. These results suggest that there is better concordance between the effects of naturally and experimentally increased precipitation on functional diversity of plant communities, but different mechanisms behind the relationship of functional diversity-precipitation between shrub and grass communities. Grass communities can adapt to precipitation changes by average trait differences, while shrub communities persist through the functional divergence of single-trait and multi-trait dispersion, thus highlighting the important differences in adaptive strategies between shrub and grass communities. Our findings demonstrate that the short-term responses of plant communities to manipulative precipitation changes can reflect long-term shifts at spatial scales depending on the specific functional trait and diversity.

opencc-zeroJul 2021View details →

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Data for: Precipitation gradients drive high tree species turnover in the woodlands of eastern and southern Africa

Savannas cover one-fifth of the Earth's surface, harbour substantial biodiversity, and provide a broad range of ecosystem services to hundreds of millions of people. The community composition of trees in tropical moist forests varies with climate, but whether the same processes structure communities in disturbance-driven savannas remains relatively unknown. We investigate how biodiversity is structured over large environmental and disturbance gradients in woodlands of eastern and southern Africa. We use tree inventory data from the Socio-Ecological Observatory for Studying African Woodlands (SEOSAW) network, covering 755 ha in a total of 6780 plots across nine countries of eastern and southern Africa, to investigate how alpha, beta, and phylogenetic diversity vary across environmental and disturbance gradients. We find strong climate-richness patterns, with precipitation playing a primary role in determining patterns of tree richness and high turnover across these savannas. Savannas with greater rainfall contain more tree species, suggesting that low water availability places distributional limits on species, creating the observed climate-richness patterns. Both fire and herbivory have minimal effects on tree diversity, despite their role in determining savanna distribution and structure. High turnover of tree species, genera, and families is similar to turnover in seasonally dry tropical forests of the Americas, suggesting this is a feature of semiarid tree floras. The greater richness and phylogenetic diversity of wetter plots show that broad-scale ecological patterns apply to disturbance-driven savanna systems. High taxonomic turnover suggests that savannas from across the regional rainfall gradient should be protected if we are to maximise the conservation of unique tree communities.

opencc-zeroJun 2023View details →

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