Nutrient Poverty Research Articles

Water-use characteristics of Palmiet (Prionium serratum), an endemic South African wetland plant

Palmiet, Prionium serratum, is an endemic wetland plant which dominates oligotrophic wetlands throughout the Cape Floristic Region, South Africa. Palmiet is often perceived as undesirable by landowners, in part because it is thought to have high water-use, although little is known about the water-use of this important wetland species. We estimated the water-use dynamics of Palmiet at the leaf scale, using stomatal conductance measurements, and at the wetland scale, by modelling evapotranspiration using remote sensing and an energy-balance model. Factors that influenced Palmiet water-use were also considered, and seasonal variations were analysed. The aim was to estimate Palmiet wetland water-use, and to develop a set of crop factors (Kc) for use in hydrological modelling of catchments containing Palmiet wetlands. Results show that Palmiet has a comparatively low stomatal conductance (11–152 mmol∙m-2∙s-1), which was lower in summer than winter, and moderate evapotranspiration for a riparian species (1 220 mm∙a-1 compared to a local reference evapotranspiration of 1 302 mm∙a-1 and A-Pan evaporation of 2 809 mm∙a-1), which was higher in summer (more energy to drive evapotranspiration and higher vapour pressure deficits). Morphological and physiological adaptations to nutrient poverty or periodic drought are suggested theories which may explain the controls on transpiration for Palmiet.

New insights on the classification of major Amazonian river water types

Traditional water classifications for Amazonian rivers are based mainly on optical characteristics that do not fully capture their complexity. Today, an increasing amount of hydrochemical data indicates that the chemical composition of Amazonian rivers varies much more than this simple classification indicates. Revising river classification based on hydrochemical properties is proposed here. In this first comprehensive review of Amazonian river chemistry, we synthesized critical information from 168 scientific publications and distinguish unusual white, black, and clearwater rivers. It is shown the distribution of such rivers across the basin and the limitations of using generalized designations for river typologies. For example, some optically clearwater rivers draining carboniferous stripes have chemical properties similar to whitewater rivers, regardless of their high transparency. Furthermore, a clear or blackwater stream that becomes turbid because of soil erosion does not become a whitewater stream. Its hydrochemical parameters of acidity and nutrient poverty depend on the geology of the catchment area and remain relatively unaffected. These insights into Amazonian river classification provide a new understanding of their baseline limnological conditions. They have implications for sustainable management of freshwater systems and for monitoring potential impacts of large development projects and climate change on the Amazonian aquatic systems.

Altitude, vegetation, paleoclimate, and radiocarbon age of the basal layer of peatlands of the Serra do Espinhaço Meridional, Brazil

Peatlands are important chronological archives of paleoenvironmental changes, since they preserve materials which enable reconstruction of paleoenvironments from the Late Pleistocene. The Serra do Espinhaço Meridional (SdEM), located in the state of Minas Gerais, Brazil, can be considered one of the main areas of tropical mountain peatlands on Earth. When climate conditions are favorable, peatland formation occurs through the combination of lithology with relief and vegetation, whereby depressions favor the accumulation of water and nutrient poverty of quartzite lithologies induces the growth of vegetation rich in C metabolites and lignin. Anaerobiosis, together with organic matter resilience, low pH, and high Al3+ content, favor the successive accumulation of organic matter in time and space. The aim of this study is to correlate the age of basal organic matter of the SdEM peatlands with their altitudes and to identify the environmental factors that acted upon peatland formation. Eleven peatlands, situated between 1244 and 2014 m a.s.l., were identified using satellite imagery and cores were sampled in the field. Eighteen cores were collected from under grasslands and forest clusters in aluminum tubes of 8 cm in diameter. The basal layers, between 15 and 397 cm deep, had carbon content, average decomposition stage of organic matter, and radiocarbon age determined. Average carbon content increases and average decomposition stage of organic matter decreases with altitude. The peatlands situated below 1370 m a.s.l. would have begun to form in the Late Pleistocene, while those situated between 1580 and 1610 m a.s.l. would have begun to form in the Early and Middle Holocene, and those situated between 1760 and 2014 m a.s.l. would have begun their formation in the Late Holocene. In the southern hemisphere, the average temperatures would have been 9 °C lower than current average temperatures between 22 and 18 kyr BP. and, from 2 to 5 °C lower between 18 and 12 kyr BP. Between 12 and 8.8 kyr BP, the average temperatures varied from +2 to - 1 °C in relation to the current average temperatures. The favorable area for the establishment of vegetation cover in SdEM was smaller in the Last Glacial Maximum (LGM) than in the warmer periods of the Holocene. The radiocarbon age of the basement layer of SdEM peatlands decreases with increased altitude. The colder climate of the Late Pleistocene limited the formation of peatlands above 1570 m a.s.l. in SdEM.

Functional capabilities of bacterial biofilms on gold particles.

Gold particles contain gold and other toxic, heavy metals, making them 'extreme' geochemical microenvironments. To date, the functional capabilities of bacterial biofilms to deal with these conditions have been inferred from taxonomic analyses. The aims of this study are to evaluate the functional capabilities of bacterial communities on gold particles from six key locations using GeoChip 5.0 and to link functional and taxonomic data. Biofilm communities displayed a wide range of functional capabilities, with up to 53 505 gene probes detected. The capability of bacterial communities to (re)cycle carbon, nitrogen, and sulphur were detected. The cycling of major nutrients is important for maintaining the biofilm community as well as enabling the biogeochemical cycling and mobilisation of heavy and noble metals. Additionally, a multitude of stress- and heavy metal resistance capabilities were also detected, most notably from the α/β/γ-Proteobacteria and Actinobacteria. The multi-copper-oxidase gene copA, which is directly involved in gold resistance and biomineralisation, was the 15th most intense response and was detected in 246 genera. The Parker Road and Belle Brooke sites were consistently the most different from other sites, which may be a result of local physicochemical conditions (extreme nutrient poverty and sulphur-richness, respectively). In conclusion, biofilms on gold particles display wide-ranging metabolic and stress-related capabilities, which may enable them to survive in these niche environments and drive biotransformation of gold particles.

Deep history of wildfire in Australia

Australian plant species vary markedly in their fire responses, and the evolutionary histories of the diverse range of traits that lead to fire tolerance and fire dependence almost certainly involves both exaptation and traits that evolved directly in response to fire. The hypothesis that very long-term nutrient poverty in Australian soils led to intense fires explains many of the unusual responses to fire by Australian species, as does near global distribution of evidence for fire during the Cretaceous, possibly driven by high atmospheric oxygen concentration. Recent descriptions of leaf fragments from a Late Cretaceous locality in central Australia have provided the first fossil evidence for ancient and possibly ancestral fire ecology in modern fire-dependent Australian clades, as suggested by some phylogenetic studies. The drying of the Australian climate in the Neogene allowed the rise to dominance of taxa that had their origin in the Late Cretaceous, but had not been prominent in the rainforest-dominated Paleogene. The Neogene climatic evolution meant that fire became an important feature of that environment and fire frequency and intensity began to grow to high levels, and many fire adaptations evolved. However, many plant species were already in place to take advantage of this new fire regime, and even though the original drivers for fire may have changed (possibly from high atmospheric oxygen concentrations, to long, hot, dry periods at different times in different parts of the continent), the adaptations that these species had for fire tolerance meant they could become prominent over much of the Australian continent by the time human colonisation began.

Integrating food poverty and minimum cost diet methods into a single framework: a case study using a Nepalese household expenditure survey.

Current tools assessing affordability of nutritious diets are incomplete. "Food poverty" uses expenditure data to identify households unable to acquire a diet adequate in energy but does not consider other nutrients. The "minimum cost of a nutritious diet" method provides a threshold for purchasing a nutritious diet but must rely on other data to identify "nutrient-poor" households. Integrating both methods into a single framework using a common data source, we sought to jointly estimate the proportions of a population that are food and nutrient poor. Household expenditure data from the 2010/11 Nepal Living Standards Survey were used, focusing on representative samples of households from the mountain region (n = 401) and Kathmandu (n = 857). Food poverty thresholds were set at the cost for a low-income household to purchase a basket of foods providing adequate energy following the Cost of Basic Need method. Linear optimization was used to calculate a "nutrient poverty" threshold. Household expenditures were used to determine food and nutrient poverty rates. The food and nutrient poverty thresholds were 13,294 and 18,628 rupees/person/year, respectively, in the mountain region and 14,610 and 22,945 rupees/ person/year, respectively, in Kathmandu. In the mountain region, 34% of households were both food and nutrient poor and 24% were just nutrient poor. In Kathmandu the percentages were 7% and 14%, respectively. This approach, integrating two commonly used tools, provides a more nuanced interpretation of economic access to a nutritious diet and an opportunity to improve the design and targeting of nutrition and food security interventions.

Aerosol capture by small trees in savannas marginal to treeless grassland in South Africa

Aerosols play important roles in soil genesis and plant nutrition, at both local and intercontinental scales, by redistributing nutrients through the atmosphere. Aerosol capture by tree crowns is a possible mechanism by which trees significantly augment their nutrition, particularly in trace elements. Forests capture considerable amounts of aerosols relative to adjacent grasslands, but the extent to which aerosol capture occurs in small, scattered trees in savanna and the effect that such capture has on soil nutrients are unknown. We analyzed spatial variations in elemental concentration in topsoils near indigenous trees (<8m tall) in short savannas marginal to treeless grassland in South Africa, by comparing samples taken immediately adjacent to tree trunks, under tree crowns and in the open. Soils adjacent to tree trunks were significantly enriched in Ca, Zn and Sr, and enriched in most study sites in As, Se and Mo compared with soils in the open. Soils adjacent to tree trunks were also significantly impoverished in Be, V, Fe and Co, and impoverished in most study sites in Ti, Cr, Mn and Ni compared with soils in the open. The elemental content of aerosols differs according to the aerosol origin. In natural, non-industrial aerosols, all elements (except Al and Si) are differential from the average particle of similar size in the sense that their concentrations in the aerosols particles exceed the Earth's crustal averages. Most of the elements identified in this study as showing enrichment adjacent to tree trunks were strongly differential elements indicating atmospheric accretion. By contrast, most elements that showed impoverishment adjacent to tree trunks were weakly differential elements of ambivalent origin. This suggests that aerosol capture by tree crowns may be a significant source of enrichment of certain elements in soils under small trees at the edges of savanna. The relative impoverishment of certain elements (e.g. Fe) shown in our study could reflect the soil conditions prior to tree establishment, suggesting that the establishment of the seedlings of savanna trees may occur predominantly within micro-sites of relative soil nutrient poverty where intensity of grass competition is least. Our study confirms that several, possibly antagonistic, mechanisms influence nutrient content under trees, resulting in a complex pattern of enrichment and impoverishment in topsoils. Augmentation of nutrients such as Zn through aerosol capture may have adaptive value for the trees studied given that many soils in South Africa tend to be Zn-poor.

Constraint on woody cover in relation to nutrient content of soils in western southern Africa

The influence of soil nutrients on woody plants is poorly understood. Are trees – fire and other disturbance factors being equal – generally promoted by nutrient‐rich or by nutrient‐poor soils? To determine the edaphic parameters controlling woody cover, we sampled soils and summed the extent of the crowns of trees and tall shrubs on 364 plots at 20 sites in Namibia and adjacent South Africa, ranging from desert lichen‐fields to caesalpiniaceous woodland with associated mean annual rainfall of 11 mm to 535 mm. Our analysis included the macro‐nutrients N, P, Mg, K and Ca and the trace elements Mn, Fe, Cu and Zn. A boundary line analysis showed that woody cover was densest, with the greatest large‐scale heterogeneity, at intermediate nutrient contents, but consistently constrained at extreme nutrient richness as well as poverty. If aridity exerted the ultimate constraint at extreme nutrient richness, no such correlation with climate apparently applies at extreme nutrient poverty, where our graphs show an ‘oligotrophic decline’. Notwithstanding the importance of water, we suggest that extreme nutrient richness and poverty both favour grasses over tree seedlings. This is because catabolic dystrophy – a regime in which the supply of catabolic nutrients shortfalls their demand – is unlikely in environments where nutrient richness allows catabolic rates to match anabolic rates or where nutrient poverty constrains anabolic rates. We also reason that surpluses of photosynthate resulting from dystrophy can be allocated to lignin and that the potential for woody growth thus corresponds to soils of intermediate nutrient content. This explains why woody cover is consistently but not homogeneously densest in nutritionally intermediate plots in our dataset. Hence, the abundance of woody plants in various biomes may be determined partly by soil nutrient content, particularly of Cu, Zn, and other elements indispensible for catabolism.

Conifer–Angiosperm Interactions: Physiological Ecology and Life History

Worldwide, conifers are most successful on sites subject to chronic stresses that limit productivity (low temperatures, nutrient poverty, poor drainage). They are poorly represented in the lowland tropics but are often important in montane tropical forests. Here I explore some functional differences between leaf and xylem traits of conifer and angiosperm trees and their implications for the distributions of these two groups on environmental gradients. Analysis of a global data set shows that compared with angiosperm trees, conifers tend to have longer-lived leaves with greater mass per area (LMA) and lower mass-based photosynthetic capacity. As leaf life span is thought to be the main determinant of nutrient retention time, the prominence of conifers on infertile soils worldwide is at least partly attributable to thrifty use of nutrients through long leaf life spans. Furthermore, because leaf life span correlates with litter decomposition rates, these leaf trait differences could potentially influence the competitive balance between conifers and angiosperms via positive feedbacks on nutrient cycling. Although scaling of leaf life span with LMA is similar in the two groups, angiosperms achieve slightly longer leaf life spans than conifers of similar photosynthetic capacity. This might be caused by less-efficient leaf display in conifers, resulting in the useful life span of leaves being curtailed by self-shading. Representatives of both lineages have narrower conduits in the temperate zone than in the lowland tropics/subtropics, reflecting selection for resistance to freeze-thaw embolism in cold climates. However, conduit diameters of conifers and angiosperm trees differ more in tropical and subtropical forests than at higher latitudes. This probably reflects mechanical constraints on maximum tracheid diameters in the homoxylous wood of conifers, preventing this group from producing the highly conductive wood typical of fast-growing angiosperm pioneers in tropical forests. This pattern might explain why coexistence of conifers and angiosperms is more common in temperate forests and on tropical mountains than in the lowland tropics. Impairment of angiosperm carbon gain by freeze-thaw embolism during cold weather may further narrow performance differences between the two lineages on temperate sites. Differences in canopy residence time probably deserve more attention as a determinant of conifer-angiosperm coexistence in many temperate forests, the longer life span of conifers compensating for infrequent recruitment.

Ecology of Australia: the effects of nutrient‐poor soils and intense fires

Australia, the flattest, driest, and geologically oldest vegetated continent, has a uniquely high proportion of nutrient-poor soils. We develop a "Nutrient-Poverty/Intense-Fire Theory," which postulates that most anomalous features of organisms and ecosystems of Australia are the evolutionary consequences of adaptations to nutrient poverty, compounded by intense fire that tends to occur as a result of nutrient poverty. The fundamental tenet of the theory is that plants growing in environments with plentiful light and periodic adequate moisture, but on soils poor in phosphorus, zinc, and other indispensible nutrients, can synthesize carbohydrates in excess of the amount that can be combined with, or catalyzed by, these nutrients for metabolism and production of nutrient-rich foliage and reproductive tissues. They use this "expendable energy" to produce well-defended foliage, large quantities of lignified tissues, and readily digestible exudates. Rapid accumulation of nutrient-poor biomass, a result of low rates of herbivory, provides fuel for intense fire. Intense fire exacerbates nutrient poverty by volatilizing certain micronutrients critical for animals. Anomalous features of organisms of Australia that can be explained by this theory, rather than by climate or phylogenetic history alone, include the following: most woody plants have long-lived, durable foliage; plants defend their tissues primarily with carbon-rich but nutrient-poor compounds; an unusually high proportion of plants protects seeds from fire and granivores in sturdy, woody capsules or follicles; plants allocate unusually large amounts of expendable energy to production of carbon-based exudates, such as nectar and gums; an unusually high proportion of plant species is pollinated by vertebrates that average larger size than pollinators on other continents; herbivores are small and have slow metabolism; there are no ruminants, mammals that eat mainly subterranean plant matter, or fungus-culturing termites and ants; vegetation dominated by leaf-spinescent plants is more extensive than vegetation dominated by stem-spinescent plants; nitrogen-fixing plants are major components of most vegetation types; there is a higher proportion of myrmecochorous plant species than on any other continent; there are hardly any stem-succulent and few leaf-succulent, perennial, non-halophytic plant species; and an unusually high proportion of bird species breeds cooperatively. Although the Nutrient-Poverty/Intense-Fire Theory can provide plausible explanations for these anomalous features, some puzzles remain, among them the great success of introduced herbivores, the lack of grazers on extensive grasslands on cracking clays, the apparently low productivity of ants, and the prominence of the parasitic plants of Australia. By examining the ratios of available energy to nutrients, particularly scarce nutrients, ecologists may identify processes not previously recognized as important for life forms or biotic adaptation on other continents.

Nutrition and Early Growth of Pinus sylvestris L. on Extensively Meliorated Sandy Mine Spoil Soils

Based on common reclamation practice for lignite-rich and strongly acidic mine spoil soils today lignite-poor sandy mine spoils, which are more favorable for plant growth, are also reclaimed using the same intensive soil improvement measures to establish forest stands. The present study shows that intensive amelioration measures, e.g. loosening of the spoil, liming of the substratum and application of mineral fertilizers, are not a prerequisite for successful development of pine stands (Pinus sylvestris L.) on these substrata. The success of afforestation on these substrata depends more on the weather conditions after planting than on the soil conditions. In 1996 high temperatures and a long drought period after planting led to high mortality rates among the pine seedlings. Without any fertilization (K) and amelioration with silicate rock powder (W) the mortality rate amounted to 40% and 37%, respectively. Thus, amelioration with N-enriched silicate rock powder (RF) increased the mortality rate to 78% and re-planting was necessary. However, if planting takes place with sufficiently high soil water contents in the rooting zone (1997 and 1998) the mortality rate decreased to 11% on the control (K). Under these climatic conditions soil amelioration (W, RF) led to a mortality rate of up to 63%. Fertilization is not necessary at afforestation. Despite the nutrient poverty of the sandy substratum, nutrient storage in these raw soils is high enough to cover the nutrient demand of the pine seedlings during the first years after planting. Six years after application of silicate rock powder the effect of fertilization is seen in a larger growth as compared to the untreated control and to fertilization with N-enriched silicate rock powder (RFII and RFIII). Both, fertilization with silicate rock powder and N-enriched silicate rock powder led to improved N-, P-, K- and Mg-nutrition status of the pine needles compared to the untreated control. Three years after fertilization, N-, and K-concentrations in pine needles are higher compared to NPK-mineral fertilization. With regard to sustainability and from the ecological point of view silicate rock powder can be recommended as an alternative to the traditional reclamation practice of using mineral fertilizers.

Historical biogeography and the origin of stomatal distributions inBanksiaandDryandra(Proteaceae) based on their cpDNA phylogeny

Banksia and Dryandra have undergone extensive speciation and adaptive radiation, especially in Australia's isolated Southwest Botanical Province. We derive a phylogeny for these groups based on cpDNA sequences and use it to reconstruct their historical biogeography and evolution of leaf traits thought to be adapted to drought and/or nutrient poverty. Slowly evolving regions (trnL intron, trnL/trnF spacer) are used to resolve large-scale relationships; faster evolving regions (rp116 intron, psbA/trnH and trnT/trnL spacers) are used to resolve relationships among closely related species. Banksia is paraphyletic with respect to Dryandra. The lineage underwent a basal split into two clades (here named /Cryptostomata and /Phanerostomata), and four infrageneric taxa supported by morphological cladistic analyses (series Spicigerae, Abietinae, Tetragonae, and Banksia) are not monophyletic. Dispersal-vicariance analysis resolves a southwestern Australian origin for the lineage, with two later expansions to the east followed by vicariance events. Stomatal crypts arose with the /Cryptostomata, which is characterized by tough, long-lived leaves and common in southwestern Australia. Sequestering of stomata also arose multiple times in /Phanerostomata, which is characterized by softer, short-lived leaves and common in moister coastal areas, via inrolling of the margins of narrow leaves and restricting stomata to shallow pits. The hypothesis that sclerophylly preadapted the plants to xeromorphy is supported in the case of shallow stomatal pits and deep stomatal crypts, but not narrow, needle-like leaves.

The Cape Peninsula, South Africa: physiographical, biological and historical background to an extraordinary hot-spot of biodiversity

The Cape Peninsula, a 470 km2 area of rugged scenery and varied climate, is located at the southwestern tip of the Cape Floristic Region, South Africa. The Peninsula is home to 2285 plant species and is a globally important hot-spot of biodiversity for higher plants and invertebrates. This paper provides a broad overview of the physiography, biological attributes and history of human occupation of the Peninsula. The Peninsula is characterized physiographically by extremely high topographical heterogeneity, very long and steep gradients in annual rainfall, and a great diversity of nutrient-poor soils. Thus, the Peninsula supports a high number of habitats and ecological communities. The predominant vegetation is fynbos, a fire-prone shrubland, and 12 broadly characterized fynbos types have been described on the Peninsula. Animal community structure, especially with regard to invertebrates, is poorly known. Vertebrate community structure is probably strongly influenced by nutrient poverty and recurrent fire. Generally, most vertebrates are small and typically occur in low numbers. Some invertebrates play keystone roles in facilitating ecological processes. Human occupation of the Peninsula was limited, until relatively recently, by nutrient poverty. After Dutch colonization in 1652, direct and indirect impacts on the natural ecosystems of the Peninsula escalated dramatically, and by 1994, some 65% of original natural habitat was either transformed by urbanization and agriculture, or invaded by alien plants. Nonetheless, there is still excellent potential to conserve the Cape Peninsula's remaining biodiversity.

Dispersal Adaptations of Some Acacia Species in the Australian Arid Zone

Most Australian representatives of the genus Acacia have diaspores with arillate appendages indicative of adaptation for active dispersal by animals. Based on physical and chemical characteristics of these arils and mechanisms of diaspore presentation, a number of arid zone acacias can be distinguished as probable ornithochores, myrmecochores, or species lacking active dispersal by animals. Two factors suggest that dispersal adaptations are evolutionarily labile in the face of changing selection pressures. Both myrmecochores and ornithochores are prevalent in each of the three largest taxonomic sections of the Australian subgenus Phyllodineae. Second, diaspores of at least one species, Acacia ligulata, exhibit geographic variation, resembling those of myrmecochores in one population and ornithochores in a second population. The colorful lipid—rich arils of avian—dispersed species are nutritionally more valuable than the relatively small, white appendages of ant—dispersed species with similar—sized propagules. While ants often collect the diaspores of ornithochorous acacias, we have no evidence that birds use the arils of myrmecochores. Patterns of seedling establishment on ant mounds, and under the canopies of trees where birds perch and defecate, are consistent with these observations. Exploitation of diaspores by birds may help to reduce the destruction of seeds by parasitoids and, in part, compensate for the higher aril expenditures (per milligram of propagule) in avian—dispersed species. Dispersal of seeds by both ants and birds directs seeds to microhabitats where nutrients are concentrated and water resources are more plentiful and/or are used more efficiently. Similarities between mound and subcanopy microhabitats may have facilitate evolutionary transitions between myrmecochory and ornithochory. The nutrient poverty that generally characterizes Australian soils has possibly played a role in selecting for seed dispersal by ants and birds in this genus as well as in many other Australian plants.