Terrestrial Plant Biomass Research Articles

Stable isotope differentiation of freshwater and terrestrial vascular plants in two subarctic regions

Several keystone herbivores in boreal forests feed on both freshwater and terrestrial plants. Quantifying the amount of freshwater and terrestrial plant biomass in the diets of these species is paramount to understanding their dietary ecology and role in mediating trophic linkages across these ecosystems. We examined the potential to distinguish freshwater and terrestrial plant sources with δ13C and δ15 N stable isotope analysis. We collected freshwater and terrestrial vascular plants that are consumed by vertebrate herbivores from 2 distinct and geographically distant subarctic regions in Canada. We consistently observed more positive isotopic values in freshwater than terrestrial vascular plants (+1.8 to 10.4%0 for δ13C and up to +3.2%0 for δ15N) whether the aquatic plants grew in lakes or rivers. We could correctly classify 71 to 100% of plant isotope values into freshwater and terrestrial groups at a locality with cluster analyses of both δ13C and δ15N values. Submergent freshwater and terrestrial plants were the most isotopically differentiated, whereas emergent freshwater plants growing near shorelines contributed to some isotopic overlap between freshwater and terrestrial categories. Collectively, these results establish that site-specific δ13C and δ15N separation between freshwater and terrestrial vascular plants can be used to quantify their respective contribution to herbivore diets and document trophic linkages across freshwater-terrestrial interfaces.

Molecular characterization of urban organic aerosol in tropical India: contributions of primary emissions and secondary photooxidation

Abstract. Organic molecular composition of PM10 samples, collected at Chennai in tropical India, was studied using capillary gas chromatography/mass spectrometry. Fourteen organic compound classes were detected in the aerosols, including aliphatic lipids, sugar compounds, lignin products, terpenoid biomarkers, sterols, aromatic acids, hydroxy-/polyacids, phthalate esters, hopanes, Polycyclic Aromatic Hydrocarbons (PAHs), and photooxidation products from biogenic Volatile Organic Compounds (VOCs). At daytime, phthalate esters were found to be the most abundant compound class; however, at nighttime, fatty acids were the dominant one. Di-(2-ethylhexyl) phthalate, C16 fatty acid, and levoglucosan were identified as the most abundant single compounds. The nighttime maxima of most organics in the aerosols indicate a land/sea breeze effect in tropical India, although some other factors such as local emissions and long-range transport may also influence the composition of organic aerosols. However, biogenic VOC oxidation products (e.g., 2-methyltetrols, pinic acid, 3-hydroxyglutaric acid and β-caryophyllinic acid) showed diurnal patterns with daytime maxima. Interestingly, terephthalic acid was maximized at nighttime, which is different from those of phthalic and isophthalic acids. A positive relation was found between 1,3,5-triphenylbenzene (a tracer for plastic burning) and terephthalic acid, suggesting that the field burning of municipal solid wastes including plastics is a significant source of terephthalic acid. Organic compounds were further categorized into several groups to clarify their sources. Fossil fuel combustion (24–43%) was recognized as the most significant source for the total identified compounds, followed by plastic emission (16–33%), secondary oxidation (8.6–23%), and microbial/marine sources (7.2–17%). In contrast, the contributions of terrestrial plant waxes (5.9–11%) and biomass burning (4.2–6.4%) were relatively small. This study demonstrates that, in addition to fossil fuel combustion and biomass burning, the open-burning of plastics in urban area also contributes to the organic aerosols in South Asia.

Why the world is green, the waters are blue and foodwebs in small streams in the atlantic rainforest are predominantly driven by microalgae?

Normal 0 21 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} The question “Why is the world green?” has been debated and researched ever since the seminal paper of Hairston et al. (1960). Three main hypotheses were generated to explain why a large part of terrestrial plant biomass is not eaten by herbivores: (1) predators control herbivores (especially folivores), (2) plant defenses inhibit herbivores, and render the plant biomass relatively unavailable, and (3) different controls operate in regions of different productivity. Aquatic systems, especially those of plankton, tend to have much less plant biomass than terrestrial systems, and generally a much higher proportion of the living plant biomass is consumed by herbivores. Thus open-water aquatic systems appear transparent blue or green. They also often display cascading relationships in which changes at one trophic level have effects at two or more levels below. The orthodoxy for small streams shaded by forest is that they receive much organic matter from the surrounding forest and this provides the main source of energy and material for the food web. Some recent search in tropical streams shows that microalgae provide a greater proportion of the primary source than does allochthonous material. This may be a specifically tropical phenomenon, or perhaps a tendency that is more accentuated in the tropics. Exclusion experiments show trophic cascades and strong interactions between fauna (particularly shrimps) and allochthonous substrates. But the functional interactions (shredding of litter, removal of benthic material) are not trophic -- the animals are herbivores or predators of herbivores based on microalgae. We can speculate that the apparent wastage of allochthonous material is at least partly due to the inherent costs that a detritivore would have in processing the more intractable and less nutritive food source (litter) in conditions of higher predation and competition, which are possibly more stringent in the tropics.

δD values of individual n-alkanes from terrestrial plants along a climatic gradient – Implications for the sedimentary biomarker record

The compound-specific hydrogen isotope composition ( δD) of sedimentary n-alkanes is increasingly used as a palaeoclimate proxy. To explore the origin of the hydrogen isotope signal of n-alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n-alkane composition and δD values of 31 plant biomass samples (Birch ( Betula), Beech ( Fagus), Oak ( Quercus), Alder ( Alnus), Hornbeam ( Carpinus) and Myrtle ( Myrtus) as well as non-stomata containing Sphagnum, Cladonia and moss) from 14 sites along a climatic gradient from Northern Finland to Southern Italy. Eleven of the sites were previously investigated for the n-alkane δD values in adjacent lake sediments and are compared to the leaf wax n-alkane δD values. The distribution of terrestrial n-alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake. Evidently, n-alkane distributions within the same species at different sites were found to be variable. These findings complicate the use of certain n-alkane distributions in sediments as a palaeoenvironmental indicator. δD values of plant biomass n-alkanes show a significant positive correlation with the precipitation δD values. Biomass n-alkane δD values are in general less negative than the associated sedimentary n-alkanes of terrestrial origin, possibly due to the stronger evapotranspiration during the summer, when sampling took place. This suggests, that n-alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn, when most leaves are incorporated into the sediment. The variability of the δD values from non-stomata containing plants is much higher than for broadleaf trees, since stomata can regulate water loss through evapotranspiration. The average chain length (ACL) of n-alkanes from deciduous tree leaves increases from North to South. With increasing ACL the hydrogen isotopic fractionation ( ε) between source water and n-alkanes also increases. Our results prove that terrestrial n-alkane δD values record the δD value of precipitation, modified by the amount of isotope enrichment in the leaf water due to plant anatomy (stomata vs. no stomata) and site specific meteorological conditions, such as evapotranspiration, relative humidity and soil moisture. Therefore, terrestrial n-alkanes in lake sediments can deliver information on changes in these parameters over geological timescales. In lake sediments where aquatic n-alkanes, such as n-C 17 record the lake water δD value, the isotopic difference between terrestrial and aquatic n-alkanes could therefore be used to reconstruct changes in evapotranspiration.

Environmental constraints on life histories in Antarctic ecosystems: tempos, timings and predictability

Knowledge of Antarctic biotas and environments has increased dramatically in recent years. There has also been a rapid increase in the use of novel technologies. Despite this, some fundamental aspects of environmental control that structure physiological, ecological and life-history traits in Antarctic organisms have received little attention. Possibly the most important of these is the timing and availability of resources, and the way in which this dictates the tempo or pace of life. The clearest view of this effect comes from comparisons of species living in different habitats. Here, we (i) show that the timing and extent of resource availability, from nutrients to colonisable space, differ across Antarctic marine, intertidal and terrestrial habitats, and (ii) illustrate that these differences affect the rate at which organisms function. Consequently, there are many dramatic biological differences between organisms that live as little as 10 m apart, but have gaping voids between them ecologically. Identifying the effects of environmental timing and predictability requires detailed analysis in a wide context, where Antarctic terrestrial and marine ecosystems are at one extreme of the continuum of available environments for many characteristics including temperature, ice cover and seasonality. Anthropocentrically, Antarctica is harsh and as might be expected terrestrial animal and plant diversity and biomass are restricted. By contrast, Antarctic marine biotas are rich and diverse, and several phyla are represented at levels greater than global averages. There has been much debate on the relative importance of various physical factors that structure the characteristics of Antarctic biotas. This is especially so for temperature and seasonality, and their effects on physiology, life history and biodiversity. More recently, habitat age and persistence through previous ice maxima have been identified as key factors dictating biodiversity and endemism. Modern molecular methods have also recently been incorporated into many traditional areas of polar biology. Environmental predictability dictates many of the biological characters seen in all of these areas of Antarctic research.

The use of terrestrial plant biomass as a parameter in the fugacity model

A new compartment, the terrestrial plant biomass, is proposed for inclusion in the fugacity model. Two possibilities of calculation have been developed and exemplified: the first considers the plant as a whole, the second takes into account foliage, trunk and roots separately.