Total Plant Material Research Articles

Quantifying the impact of management on the three-dimensional structure of boreal forests

Forest management practices modify the composition and three-dimensional structure of boreal forests. Such changes affect light regimes, microclimate and habitat availability in forests, thus contributing to the regulation of ecosystem functioning and biodiversity. Compared to traditional even-aged forestry, prevalent in Fennoscandia since the mid-20th century, uneven-aged forestry has emerged as an alternative approach that may lead to more diverse and resilient forests, as well as a more sustainable provision of ecosystem services. However, the biophysical impacts of uneven-aged strategies have not yet been robustly quantified. Here, we present a detailed assessment of the structural characteristics of even-aged and uneven-aged boreal forest stands in southern Finland, aiming to clarify how these different management approaches regulate three-dimensional forest structure. Using terrestrial laser scanning, we derived and compared several structural traits closely linked to forest functioning. We found that, although different management types result in similar patterns in total plant material, they differ significantly on how plant material is allocated within vertical strata. Moreover, we demonstrated that commonly used structural diversity metrics cannot not capture the morphological intricacies arising from the three-dimensional dispersion of plant material inside the forest stand. Our results highlight the dynamic nature of even-aged forests, where the structural characteristics change with the rotation, whereas uneven-aged forest structures are more stable over time. Precise quantification of forest structure will help to understand which attributes impact the environmental functions and conditions that modify ecosystem services, and how these are altered with forest management.

Effects of seasonal grazing and annual mowing on floristic composition and plant diversity in the Saral rangeland, Kurdistan, Iran

This study examined the impact of long-term (40 years) seasonal grazing and annual scythe mowing on changes in plant diversity, floristic composition and plant functional groups in the cold semi-arid rangelands of Mangahul-Zardawan located in Saral, Kurdistan. In this investigation, 900 plots (2 m2) were sampled in grazed (450 plots) and mowed sites (450 plots) to measure vegetation and plant characteristics. Data were collected in two consecutive growing seasons from late May to early June in 2017 and 2018. Both years recorded below average rainfall. The results showed that after 40 years, seasonal grazing compared to scythe mowing increased canopy cover and species richness of different functional groups including annuals, perennial grasses, perennial forbs and total vegetation. On the other hand, both the total above-ground plant material and the palatability index were higher for the mowed than the grazed sites, although scythe mowing had caused the Boraginaceae family to disappear. Based on these results, the mean of total plant material (above-ground live + standing dead + litter) was substantially higher in the mowed area, where two-year mean totals were 271 g/m2 compared with 216 g/m2 for the grazed area. In terms of a three-level palatability classification (high, medium and low), only the plants with moderate palatability differed in contribution between the sites, with mowed sites having a significantly greater proportion of this class than the grazed sites. Our results suggested that in the long term, grazing can maintain species richness and the typical floristic composition of rangelands; but when socio-economic issues have priority, mowing has more advantages. In rangelands with the same ecological and geographic conditions, users and managers can choose the most appropriate management approach based on their long- and short-term policies.

Crescimento inicial e biomassa de espécies utilizadas como adubação verde em sistema de aleias

Objetivou-se com este trabalho avaliar o crescimento inicial de espécies perenes como gliricídia (Gliricidia sepium) e ingá-xixica (Inga heteraphylla) e o desempenho da produção de biomassa de espécies herbáceas, como a crotalária juncea (Crotalaria juncea L.) e feijão-de-porco (Canavalia ensiformis DC.), utilizadas para adubação verde. O monitoramento do crescimento das espécies foi acompanhado por seis meses. Para avaliar a biomassa, as plantas foram podadas rente ao solo, onde foi obtido o material vegetal total para determinar o peso de massa verde, e retiraram-se quatro amostras de cada parcela para obter o peso da massa seca. O crescimento em altura final para o ingá-xixica foi de 0,77 m e de 1,81 m para a gliricídia. As taxas de crescimento absoluto (TCA) para altura total (Ht) diferem entre ambas as espécies, onde a média da gliricídia apresenta maior valor, de 5,06 cm mes-1 em Ht, e a de ingá-xixica é de 2,68 cm mês-1. Na avaliação de biomassa total observou-se diferença entre as duas espécies, tanto para massa verde como para a seca, destacando-se o feijão de porco nas duas avaliações com maior produtividade de biomassa fresca de 8,6 t ha-1 e seca 1,6 t ha-1. Para indicação no uso como adubação verde, a espécie perene gliricídia, apresentou os melhores parâmetros dendrometricos e, a espécie herbácea feijão de porco, a maior produção de biomassa.

Comparing the effects of continuous grazing and long term exclosure on floristic composition and plant diversity in rangeland ecosystems of Saral, Iran

Continuous grazing as the most common land us in Kurdistan rangeland is practiced wildly. Along with continuous grazing, long term exclosure has been implemented in research site in Saral. The main objective of this study was to investigate the changes in plant diversity, floristic composition and plant groups of the major life forms in response to 40 years of continuous grazing and long terrm exclosure in Saral rangelands, Iran. This research was conducted in cold semi-arid rangeland of Baharestan located in Saral’s agricultural and natural resources station (including grazed and excluded sites). In total, six transects were sampled in both grazed and excluded sites and ten plots were randomly placed per transect to measure vegetation and plant characteristics. Sampling was carried out in late May to early June (peak biomass) in 2017. T test was used to compare the means of total plant material, and Shannon’s diversity index was used based on the total cover percentage in both grazed and exclosure sites. Our results indicated that long-term grazing exclosure significantly increased canopy covers and species richness of annuals, perennial grasses, perennial forbs and shrubs. Conversely, continuous grazing caused some species to disappear namely Ferula haussknechtii and Prangos ferulacea. There was statistically a significant difference between litter and total plant material in experimental sites (p < 0.001). Apart from palatability, exclosure increased floristic diversity by 17.8%. Our findings elucidated that exclosure in degraded vegetation is an effective strategy and management policy to recover and restore missing vegetation cover.

Effect of added nitrogen on plant litter decomposition depends on initial soil carbon and nitrogen stoichiometry

Increasing organic carbon inputs to agricultural soils through the use of pastures or crop residues has been suggested as a means of restoring soil organic carbon lost via anthropogenic activities, such as land use change. However, the decomposition and retention of different plant residues in soil, and how these processes are affected by soil properties and nitrogen fertiliser application, is not fully understood. We evaluated the rate and extent of decomposition of 13C-pulse labelled plant material in response to nitrogen addition in four pasture soils of varying physico-chemical characteristics. Microbial respiration of buffel grass (Cenchrus ciliaris L.), wheat (Triticum aestivum L.) and lucerne (Medicago sativa L.) residues was monitored over 365-days. A double exponential model fitted to the data suggested that microbial respiration occurred as an early rapid and a late slow stage. A weighted three-compartment mixing model estimated the decomposition of both soluble and insoluble plant 13C (mg C kg−1 soil). Total plant material decomposition followed the alkyl C: O-alkyl C ratio of plant material, as determined by solid-state 13C nuclear magnetic resonance spectroscopy. Urea-N addition increased the decomposition of insoluble plant 13C in some soils (≤0.1% total nitrogen) but not others (0.3% total nitrogen). Principal components regression analysis indicated that 26% of the variability of plant material decomposition was explained by soil physico-chemical characteristics (P = 0.001), which was primarily described by the C:N ratio. We conclude that plant species with increasing alkyl C: O-alkyl C ratio are better retained as soil organic matter, and that the C:N stoichiometry of soils determines whether N addition leads to increases in soil organic carbon stocks.

Intrinsic isotopic 13C labelling of polyphenols

The intrinsic isotopic labelling of plants with 13CO2 is an effective method to generate highly labelled compounds using photosynthesis and avoiding labour-intensive complex organic syntheses. In this study, the intrinsic isotopic labelling of polyphenols in parsley, spinach and peppermint is shown for the first time. The plants were grown in an atmosphere where 12CO2 was replaced by 13CO2, in order to generate highly labelled compounds. The total content of 13C as well as the individual polyphenols were analysed by Isotopic Ratio-MS and HPLC–Iontrap-MSn.After 34days of plant growth under 13CO2, degree of labelling was found to be higher than 90atom% 13C for most polyphenols, predominantly consisting of highly and fully labelled isotopomers; the total plant material contained more than 88atom% 13C. Such highly labelled compounds can be used in future studies to dissect both metabolism and bioavailability of polyphenols in humans.

Processes affecting genetic structure and conservation: a case study of wild and cultivated Brassica rapa

When planning optimal conservation strategies for wild and cultivated types of a plant species, a number of influencing biological and environmental factors should be considered from the outset. In the present study Brassica rapa was used to illustrate this: to develop Scandinavian conservation strategies for wild and cultivated B. rapa, DNA-marker analysis was performed on 15 cultivated and 17 wild accessions of B. rapa plus 8 accessions of the cross compatible B. napus. The B. rapa cultivars were bred in Sweden and Finland in 1944-1997 and the wild B. rapa material was collected from Denmark, Sweden and United Kingdom. The B. napus accessions were bred within the last 20 years in the Scandinavian countries. Results were based on scoring of 131 polymorphic ISSR markers in the total plant material. A Bayesian Markov chain Monte Carlo (MCMC) approach implemented in NewHybrids demonstrated a clear distinction of B. rapa and B. napus individuals except for three individuals that seemed to be backcrosses. The backcrossed hybrids descended from two Swedish populations, one wild and one escaped. The overall pattern of genetic variation and structure in B. rapa showed that cultivated and wild B. rapa accessions formed two almost separated clusters. Geographical origin and breeding history of cultivars were reflected in these genetic relationships. In addition, wild populations from Denmark and Sweden seemed to be closely related, except for a Swedish population, which seemingly was an escaped cultivar. The study point to that many processes, e.g. spontaneous introgression, naturalisation, breeding and agricultural practise affected the genetic structure of wild and cultivated B. rapa populations.

Effects of simulated green turtle regrazing on seagrass abundance, growth and nutritional status in Moreton Bay, south-east Queensland, Australia

In some parts of their range, green turtles maintain grazing plots in seagrass beds by regular regrazing. The effects of simulated repeated grazing on subtropical seagrasses in Moreton Bay, Australia were investigated in a manipulative experiment over summer. Three seagrass species were subjected to two different clipping frequencies (simulating turtle cropping) and compared with unclipped controls over a 3.5-month summer period for the effects on seagrass biomass, leaf size and regrowth rates and water-soluble carbohydrate (WSC) and starch content. The order of the seagrass species’ relative tolerance to simulated grazing was Halophila ovalis &gt; Zostera capricorni &gt; Cymodocea serrulata. Frequent regrazing of the green turtle’s preferred seagrass, H. ovalis, resulted in an increase in leaf regrowth rate so that standing biomass of leaves and total plant material was maintained, suggesting an increase in productivity. Furthermore, whole-plant concentrations of WSC increased significantly in clipped H. ovalis plants relative to unclipped controls. In contrast, leaf biomass of the seagrass species less preferred by turtles, Z. capricorni and C. serrulata, decreased in response to repeated leaf removal relative to controls, despite maintenance of leaf regrowth rates. C. serrulata responded to repeated clipping with a reduction in leaf size and a decrease in rhizome WSC concentration. Z. capricorni also produced fewer and smaller new leaves. The ability of the preferred species, H. ovalis, to increase production of nutrient-rich standing crop in response to regrazing has major implications for green turtles and other seagrass grazers.

A study on nitrate reductase activity (NRA) of geophytes from Mediterranean environment

Nitrate reductase activity (NRA) in different compartments of 14 Mediterranean geophytes (bulbous, tuberous and rhizomatous) and actual mineral nitrogen (NO 3 − and NH 4 +) in their soils were investigated. The nitrate reduction capacities of each species were determined as NRA per total plant material. Differences among compartments for NRA were significant in all species. The highest NRA was found in leaves of tuberous species ( Anemone coronaria, Cyclamen coum) and of most bulbous species ( Allium flavum, Allium guttatum, Bellevelia sarmatica, Galanthus plicatus, Leucojum aestivum, Ornithogalum nutans, Tulipa sylvestris). Therefore, in this group of species the contribution of the leaves to total plant NRA was the highest. The other bulbous species ( Allium scorodoprasum, Crocus chrysanthus, Fritillaria bithynica, Muscari neglectum) and one rhizomatous taxon ( Iris suaveolens) have a different NRA distribution within the plants. In these species the highest values of NRA were found in different organs. For example, in Allium scorodoprasum the highest NRA was in tunics, and in flowers in M. neglectum. Although leaves are the main compartments reducing nitrate in most of the studied geophytes, other compartments also contribute to total plant nitrate reduction. Our results show that the nitrate reduction capacity is different among geophyte species. Even if it roughly reflects the nitrogen supply in a habitat, differences in nitrate reduction capacities of different species collected from same sites indicate that the nitrate reducing capacity is species-specific.

DETERMINATION OF RUTIN IN HYPERICUM PERFORATUM EXTRACT BY CAPILLARY ELECTROPHORESIS

A capillary zone electrophoretic (CZE) method for the determination of rutin in an ethanolic extract of the aerial parts of Hypericum perforatum (Hypericaceae) is described. The analysis was performed using a fused-silica capillary and a background electrolyte consisted of 10% ethanol and 20 mM borate buffer at pH 8.0 applied at a potential of 28 kV, vacuum injection of 1 s and detecting at 200 nm. Rutin had a migration time of 10.1 ± 0.2 min. Reproducibility was 1.26% for 9.37 × 10−5 M standard rutin. Detection limit was 2.7 × 10−6 M (S/N = 3). A well-correlated calibration equation was obtained for the mentioned conditions. The amount of rutin in the total plant material was found to be 0.21% ± 0.02.

Psoracinol, A New Lupane-Type Triterpene from Psoralea plicata

On freshly collected total plant material, we have isolated angelicin, psoralen, and a new pentacyclic triterpene of the lupane series named psoracinol. We report the structural elucidation of this new compound through chemical and spectroscopic studies

N-mineralization in polyphenol-rich plant residues and their effect on nitrification of applied ammonium sulphate

Soil was incubated under greenhouse conditions with plant residues having varying phenolic and nitrogen contents. The total plant material added in staggered applications every 4 months was 15 g kg −1 soil and the total incubation period was 12 months. The N-mineralization in these plant residues as influenced by their phenol and N contents was examined. The nitrification of applied (NH 4) 2SO 4 in these amended soils was also investigated under optimum conditions of pH. A high plant-N content resulted in increased N-mineralization of plant residue, but this effect was lowered by the presence of high concentrations of polyphenols in the decomposing residue, most probably due to increased participation of N with polyphenols in the formation of humus fractions. Soils amended with phenol-rich residues did not show any inhibition of nitrification of applied (NH 4) 2SO 4. Possible reasons are discussed. In organic matter decomposition, the quality of the leaf polyphenols appears to determine the degree of inhibition to soil nitrification.

Response of Planted South Florida Slash Pine to Simulated Cattle Damage

there is a high percentage of relatively low forage-producing grasses, such as curly mesquite, red grama, and others. This type of vegetation forms a relatively dense sod but makes little growth under heavy use or dry range conditions. There was no significant difference in total plant material between the deer-livestock exclosure and the heavy-grazed pastures. There are two major conclusions which might be drawn from this study, one being that an ungrazed or natural area has certain limitations which must be considered before it is used for comparative research studies. Vegetation in these areas does not respond like areas which are grazed to some extent. The specific vegetative association may actually deteriorate after an extended period of deferment. The other conclusion is that the use of a grazing management system in this area, such as the 4-pasture deferred rotation system, will allow the development of a highly productive vegetation complex and the maintenance and improvement of both the livestock and wildlife habitat.

Infiltration Rates: Three Soils with Three Grazing Levels in Northeastern Colorado

Highlight: The inf7uence of soil type, grazing level, and vegetation on infiltration rates were evaluated at the Central Plains Experimental Range near Nunn, Colorado. Total plant material was significantly correlated with infiltration rates on two of the three soil types tested. Heavy grazing significantly decreased infiltration rates on two of the soil types. Grazing influences did not reduce infiltration rates until after 20 minutes of simulated rainfall.