Grass Canopy Research Articles

Hybrid retrieval of grass biophysical variables based-on radiative transfer, active learning and regression methods using Sentinel-2 data in Marakele National Park

Biophysical variables such as leaf area index (LAI) and leaf chlorophyll content (LCC) are cited as essential biodiversity variables. A comprehensive comparison and integration of retrieval methods is needed for the estimation of biophysical variables such as LAI and LCC over a multispecies grass canopy. This study tested an assortment of five potentially robust, nonparametric regression methods (NPRMs) for inversion of radiative transfer model (RTM) to retrieve grass LAI and LCC in the Marakele National Park (MNP) of South Africa. The NPRMs used were, namely (i) Partial least squares regression (PLSR), (ii) Principle components regression (PCR), (iii) Kernel ridge regression (KRR), (iv) Random forest regression (RFR), and (v) K-nearest neighbours regression (KNNR). Furthermore, the study attempted to constrain the inversion process by using active learning (AL) techniques which ensured the selection of informative samples from a large pool of RTM simulations. Results show the most accurate grass LAI and LCC retrievals had lower relative root mean squared errors (RRMSEs) of 39.87% and 16.58% respectively. These findings have significant implications for the development of transferable rangeland monitoring systems in protected mountainous regions.

P38 Evaluation of the forage canopy of Cenchrus clandestinus grass on milk production and enteric methane emissions with holstein cows

P38 Evaluation of the forage canopy of Cenchrus clandestinus grass on milk production and enteric methane emissions with holstein cows

Agronomic performance and soil chemical composition when using poultry litter as organic fertilizer in Mombasa Guinea grass production

ABSTRACT The use of poultry litter as organic fertiliser will enhance the agronomic performance of Panicum maximum cv. Mombasa grown in the Brazilian Cerrado region. The objective of this research work was to verify the effect of poultry litter as a source of phosphorus (P) for Mombasa guinea grass production, as well as its effect on the chemical composition of clayey soil. Throughout two years, six fertilisation strategies were tested: control, without organic or chemical fertilisation; 25% organic fertiliser and 75% inorganic fertiliser; 50% organic fertiliser and 50% inorganic fertiliser; 75% organic fertiliser and 25% inorganic fertiliser; 100% organic fertiliser; 100% inorganic fertiliser, represented by triple superphosphate (46% P2O5). Over the two years of evaluation, using 75 and 100% of poultry litter led to the highest values in forage mass accumulation rate and production (Year 1st: 106.91 kg ha−1 and 105.99 kg ha−1; Year 2nd: 98.29 kg ha−1 and 111.41 kg ha−1). These organic fertiliser proportions promoted increases in P concentration in the 0–0.05 m and 0.05–0.10 m layers. A partial (75%) or total (100%) use of poultry litter as organic fertiliser has a positive influence on forage production in the forage canopy of Mombasa guinea grass.

Light competition is the key factor determining spatio-temporal variability in legume proportion within Marandu palisadegrass–forage peanut mixed pastures

Context Understanding ecology in grass–legume pastures can help support strategies aimed at maintaining canopy stability in terms of botanical composition. Aims This 2-year study evaluated spatial variability, focusing on plant structural characteristics in a Marandu palisadegrass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster cv. Marandu]–forage peanut (Arachis pintoi Krapov. and W.C. Greg. cv. BRS Mandobi) mixed canopy under grazing in continuous stocking management. Methods The pasture was managed with canopy height of 20–25 cm. The experimental area had a permanent sample grid containing 50 pre-established and georeferenced plots. Principal component analysis was performed, and spatial dependence structure of the first principal component and structural variables were separately characterised by geostatistical analysis. Key results There was spatial dependence of the structural characteristics, with marked spatial heterogeneity in the distribution of all variables. Taller grass canopies caused competition for light between species, reducing legume contribution and inducing more erect forage peanut growth habit. Conversely, in areas with lower grass canopy height, forage peanut botanical composition increased to up to 70%, as it propagated more effectively by stoloniferous propagation. Conclusions The canopy structure spatial variability of a Marandu palisadegrass–forage peanut mixed pasture determines the overall average pasture grass/legume proportion. In regions with taller canopies, Marandu palisadegrass was favoured, while in areas with shorter canopy, forage peanut proportion was promoted. Satisfactory legume proportions can be reached in the canopy despite areas with reduced legume contribution. Implications Our findings using geostatistical techniques facilitate the development of useful and innovative tools allowing better comprehension for the management of mixed pastures.

Effect of Grass Components on the Temporal Response of Surface Soil Water to Precipitation and Air Temperature in the Loess Plateau

The Loess Plateau of China is facing increasingly serious challenges related to water shortage issues despite the successful vegetation restoration. Surface soil water (0–40 cm) is crucial to water transfer and discharge in the soil-plant-atmosphere continuum, which is controlled by precipitation (P), air temperature (Ta), and plant components. This study selected one typical grass species and set different treatments of natural condition (NC), removing litter (CR), and only roots (OR), to analyze the responses of soil water storage (W) and its change (∆W) to P and Ta at different time scales (including daily, weekly and monthly scales). The results showed that P had significantly positive effects on W and ∆W, while Ta negatively influenced W and ∆W. Meanwhile, Ta also controlled the significance of P affecting W. P contributed more (53–63%) to ∆W variation at the daily scale, but Ta showed more effect (73–80%) at the weekly scale, and both of them contributed more than 77% at the monthly scale. P and Ta existed a threshold phenomenon for increasing soil water, where P thresholds were higher than 0.93, 4.98, and 28.17 mm and Ta threshold were lower than 28.69, 28.89, and 29.96°C at the daily, weekly and monthly scales, respectively. Moreover, grass components also affected the responses of ∆W to P and Ta, and the OR treatment displayed the lowest sensitivity and had the lowest loss rate of soil water. The total infiltration, total loss amount, and rainwater retention rate exhibited: NC > CR > OR. Overall, grass canopy and litter improved soil water condition, and the roots most strongly protected soil water after infiltration. This study can provide a better understanding of surface soil water responding to climate change under drought stress with water shortage implications, and may strength the management of grassland in semi-arid region.

Using digital photography to monitor changes in biocrusts and ground cover in a savanna rangeland

Biocrusts form a living soil cover in Australia’s northern savannas, delivering essential ecosystem services. More accessible tools are needed to quantify and monitor ground cover, including biocrusts, as current methodologies are time-consuming, expensive, or specialised. At Victoria River Research Station (Northern Territory, Australia), long-term fire research plots were used to monitor the response of low vegetative ground and soil covers for different burning intervals and seasons. Mobile phone photographs were analysed using machine-learning software and a derived decision tree-based segmentation model (DTSM). The resulting data were compared to visual in-field assessment by trained researchers. Visual assessments and photographs were taken at two time points during the post-fire recovery period, mid-wet and dry seasons, at three burning intervals (2, 4, and 6 years) and for two different burning times, early or late dry season. DTSM-derived grass and litter cover were statistically similar to field observations in the burnt and unburnt plots. Biocrust cover derived from DTSM also matched field observations in fire treatments and unburnt control plots in the dry season, except when obscured by grass or litter. In the wet season, DTSM underestimated biocrust cover in some treatments, and DTSM did not detect biocrust obscured under dense grass cover. Nevertheless, biocrust pigment analysis confirmed a significant presence of biocrusts both on seemingly bare soil and under the grass canopy. We concluded that mobile phone photographs are suitable for monitoring dry-season ground cover. When similar colours of grass and litter cover were combined, the modelled accuracy reached 95–97%. With some refinements, DTSM analysis of photographs could accurately quantify the impact of fire disturbance on biocrusts and grass cover. However, it would be advantageous to improve the model by additional field records to determine how much biocrust occurs under the grass. This study provides land managers with an efficient method of recording ground cover over time to aid land-condition assessments.

Evaluation of isoprene light response curves for bryophyte-dominated ecosystems and implications for atmospheric composition

Isoprene is emitted from numerous plant species in response to light and temperature and parameterisations of these relationships, based on observations from a few vascular plant species, have been shown to be broadly applicable to many different vegetation types. Here, we investigate their performance when applied to an ecosystem dominated by bryophytes. Over a six-week period, emissions of isoprene were measured above a Scottish peat bog. The light response derived on the basis of both canopy-scale flux and whole-plant enclosure measurements, deviated from the classical response, showing no sign of saturation within the observed range. We attribute this response to the canopy architecture of moss hummocks, which may attenuate light differently compared to a grass canopy. Both existing big-leaf and canopy-level emission algorithms, developed for vascular plants but commonly used for moorland vegetation, failed to replicate the observed fluxes, overestimating at low light intensities (<1000 μmol m−2 s−1 photosynthetically active radiation) and underestimating during daytime clear sky conditions. The light response was optimised for bryophyte-dominated ecosystems using measured fluxes and incorporated into the EMEP4UK chemical transport model and applied exclusively to moorland. The revised parameterisation resulted in a small reduction in the average annual isoprene emissions in the northern latitudes (5%), but peak isoprene emissions and concentrations increased by up to a factor of two. Yet, no significant change in average or maximum surface ozone concentrations was observed, reflecting that the northern latitudes are in a chemical regime that is strongly NOx limited, in part due to the spatial segregation with the urban sources of NO x . We conclude that, the anticipated increase in isoprene emissions from the northern latitudes in response to climate change is unlikely to contribute towards ozone-related air quality issues, as long as NO x pollution does not increase. However, the non-saturating light response may be equally applicable to non-vascular plants elsewhere, including in the tropics.

Photosynthesis, Respiration, and Thermal Energy Dissipation in Leaves of Two Phenotypes of Plantago media L. under Environmental Conditions

The ability to maintain the balance between the absorbed light energy and energy used in photosynthesis is a key factor of plant adaptation to variable environmental conditions. In this work, diurnal variations in photosynthesis, respiration, thermal energy dissipation, and the activity of the antioxidant system were studied in hoary plantain (Plantago media L.) growing on an open slope (sun plants) and under natural shading in the herbage (shade plants). The highest leaves net photosynthetic rate (Pn) was observed early in the morning and amounted to 2.6 and 9.2 μmol CO2/m2 s in shade and sun plants, respectively. In the daytime, the Pn values of sun plants decreased significantly (threefold) along with the decrease in stomatal conductance; changes of both parameters developed concurrently with the increase in insolation and air temperature. The Pn changes in leaves of shade plants were less pronounced and weakly dependent on stomatal conductance. The leaves of shade plants contained comparatively high amounts of soluble carbohydrates, whereas the sun plant leaves accumulated larger amounts of starch. In the daytime, nonphotochemical quenching (NPQ) of chlorophyll a fluorescence in photosystem II of sun plant leaves could be as large as 2.6 rel. units, which was four- to fivefold higher than NPQ in shade plants. In leaves of sun plants in the morning and evening hours, the ratio of cytochrome pathway (CP) and the alternative (AP) respiratory pathways was approximately 1.0, whereas this ratio decreased to 0.4 during the day, synchronously with an increase in NPQ. The CP/AP ratio in shade plant leaves remained constant throughout the diurnal cycle and equaled 1.4, indicating a comparatively high energy efficiency of respiration in shaded plants growing under the grass canopy. The leaves of sun plants featured an increased content of superoxide anion radical and hydrogen peroxide as well as the elevated activity of antioxidant enzymes (superoxide dismutase, guaiacol peroxidase) that control the accumulation of reactive oxygen species. The results emphasize the importance of coordinated changes in energy-dissipating processes and the activity of the antioxidant system for maintaining the energy and redox balance in phototrophic tissues during long-term adaptation of plants to environmental conditions, excessive insolation in particular.

A Method Proposal for Throughfall Measurement in Grassland at Plot Scale in Temperate Climate: ‘Interception Tubes’

While net precipitation entering the soil is commonly measured in woody ecosystems, there is a lack of field measurements for herbaceous vegetation. Small canopy heights and fragile stem structures are the primary challenges for net precipitation sampling in grasslands under field conditions. We designed a new in situ device, “interception tubes”, for throughfall sampling in temperate grasslands. The instrument allows a natural development of grass canopy and sampling at multiple locations. Although it does not strictly separate throughfall and stemflow, the dominant part of the collected water is throughfall. We tested the interception tubes for splash loss with a drip experiment. Next, we evaluated the tubes’ measurements in a field installation at 25 locations both with and without vegetation cover. Also, we used measurements of gross precipitation, canopy height and soil water content to check the plausibility of the measurements. The experiment showed splash loss for the tubes is small ( &amp;lt; 3%) for the typical rain drop size for the growing season in the region, as well as for throughfall drops of lower falling velocity. In the uncovered period, splash loss corrected tubes’ measurements were generally smaller than classical funnel measurements. But the statistical model revealed that the slope of their relationship is close to unity (0.92) when accounting for topography and was probably related to wind effects. During the covered period, grass height systematically reduced below canopy precipitation measured by the tubes, indicating that they can capture spatial canopy drip patterns under denser grass foliage. The canopy height also altered the wind effect on the tube measurements. As in forest ecosystems, below canopy precipitation patterns were temporally stable and smaller events increased the spatial heterogeneity. The measured below canopy precipitation was between 95% and 22% that above, and grass height amplified the loss. The soil water balance showed the tubes underestimated soil water input at peak grass height, which suggests enhanced occurrence of stemflow in tall grass. Despite the underestimation of stemflow, the interception tubes are a suitable method for estimating the canopy effect on throughfall patterns in temperate grasslands, and stemflow can be quantified by additional soil moisture measurements.

Interference of weeds in ruziziensis grass pastures

The aim of this study was to assess the effect of increasing periods of coexistence of weed plants with Urochloa ruziziensis on the canopy structure and productivity of a pasture already established with this forage species. The experiment was a randomized blocks design with four replications, and treatments consisted of seven increasing periods of coexistence of forage grass with weed plants: 0 (control), 15, 30, 45, 60, 75 and 90 days after regrowth (DAR). The main morpho-structural and productive characteristics of the forage plants were determined at the end of the experimental period (90 DAR). The ratio of the first green leaf height to the tiller height increases, while the leaf to stem ratio diminishes as the period of interaction with the infesting community increases. The number of green leaves per tiller and the tiller height diminishes as the period of coexistence with weed plants increases. The presence of weed plants interferes negatively with all parameters of the grass canopy structure and productivity of a grazing land already established with Urochloa ruziziensis, suggesting that measures of control of the infesting community should be adopted up to 17 days of regrowth of the forage plant.

Improved Quadrant Analysis for Large-Scale Events Detection in Turbulent Transport

Quadrant analysis has been widely used to investigate the turbulent characteristics in the atmospheric boundary layer (ABL). Although quadrant analysis can identify turbulent structures that contribute significantly to turbulent fluxes, the approach to the hyperbolic hole and its parameter, referred to as hole size, remains uncertain and varies among different studies. This study discusses an improved quadrant analysis with an objective definition of the hole size for the isolation of large coherent structures from small-scale background fluctuations. Eddy covariance data collected 50 m above the grass canopy were used to analyze and evaluate the proposed method. This improved quadrant analysis ensures that the detected large coherent eddies play a dominant role in transporting fluxes, occupying 10% of the total time, with mean flux contributions ranging from 62% to 95% for momentum and 35–104% for scalars. The separated background small-scale eddies are isotropically characterized by a comparable time duration and flux contributions in each quadrant. It is observed that under an unstable atmosphere, large-scale ejections are more active than sweeps, while under stable conditions, they are equally important. Furthermore, mechanical-driven transport under near-neutral conditions only enhances ejection and sweep motions of momentum. In contrast, the buoyancy-driven scenarios under unstable conditions enhance the large-scale activities of sensible heat alone.

Microwave Scattering (1–10 GHz) From a Vertically Heterogeneous Grass Canopy

This study concerns the effects of considering vertically heterogeneous canopy structure when modeling microwave scattering from grassland with the Tor Vergata (TVG) model, which uses the matrix doubling method (MDM). The TVG model was extended with the M-volume approach to accommodate height-dependent variation in structure for every scatterer type. Used approach was to reproduce 1 – 10 GHz backscatter for all linear polarization combinations from an alpine meadow measured by a ground-based scatterometer with both the default (1-volume) and the M-volume approach with 3 volumes. Measured in-situ vegetation parameters were used to constrain the model. We found that both models were able to reproduce the angle-dependent backscattering for C- and X-band, measured on two afternoons, and the 31-day average measured radar return power for L-, S-, C-, and X-band within, or close to, the measurement uncertainty. Our analysis proved inconclusive on whether the 1- or 3-volume approach worked better for the considered grassland, but did show that the 3-volume approach allows for more flexibility in reproducing the actual angle-dependent backscattering for multiple frequencies, a flexibility that may prove necessary when more scattering angles are considered. Furthermore, predictions of the bistatic scattering coefficient at higher frequencies (C- and X-band) were significantly different between both models. For X-band with hh polarization differences up to 3 dB were found for the specular direction. We conclude that considering vertical heterogeneity of vegetation canopy structure with MDM leads to significantly different results than with the vertically homogeneous canopy approximations typically used.

Tussock and tiller population dynamics on rotationally stocked Piatã palisadegrass (

Context Integrated crop–livestock–forestry systems can be an alternative to monoculture pastures; however, the effect of the arboreal component on tillering and tussock dynamics of understorey grass canopy is not well understood. Aims Our objective was to evaluate the patterns of tillering dynamics, population stability and tussock distribution of Piatã palisadegrass (Urochloa brizantha) as affected by contrasting shading regimes in the Brazilian Amazon biome. Methods The following three shading regimes were assessed: pasture with no trees (no shading, NS), moderate shading (MS, 338 trees ha−1), and intense shading (IS, 714 trees ha−1). Pastures were rotationally grazed by dairy heifers. Paddocks from MS and IS were stratified into three sampling strips, including two closer to the tree rows (i.e. lateral) and one between the two lateral strips (i.e. central). Two methods for monitoring sward canopy light interception (LI) were used for IS regime, namely, LI taken under the tree canopy (i.e. inside) and LI was taken above the tree canopy (i.e. outside). Key results Relative to NS, there was a reduction in photosynthetically active radiation transmittance of 18.1% and 37.1% on MS and 49.9% and 52.0% on IS for central and lateral shading strips respectively. Overall, the increase in shading level was associated with a decrease in average tussock perimeter, tiller population density, and an increase in the frequency of bare ground. Conclusions Our findings clearly indicate the key role of the light environment as a determinant of Piatã palisadegrass horizontal structure. Implications It highlights the importance of planning the levels of tree density and layout in areas of crop–livestock–forestry integration.

Morphogenesis of stockpiled Marandu, Piatã, Xaraés and Paiaguás brachiariagrass cultivars

ABSTRACT The objective this study was to identify differences in the morphogenic patterns of four Urochloa brizantha cultivars (marandu, piatã, xaraés and paiaguás grasses) during the stockpiling period. A completely randomized design was used, with three replications, in experimental plots of 9m². The evaluations took place over 2 years. The grasses were stockpiled for 92 (Year 1) and 95 (Year 2) days. The leaf appearance rate of paiaguás grass was higher, compared to other grasses. In Year 1, the stem elongation rate of xaraés grass was higher than other grasses. At the end of stockpiling period of Year 1, the tiller population density (TPD) was higher in the paiaguás grass, intermediate in the xaraés and marandu grasses and lower in the piatã grass. At the end of the stockpiling period in Year 2, TPD was higher in the paiaguás grass canopy, intermediate in the marandu and piatã grasses canopies, and lower in the xaraés grass canopy. Paiaguás grass has greater leaf growth during the stockpiling period and is therefore suitable for use under stockpiled grazing. Xaraés grass has high stem elongation during the stockpiling period, which is why its use under stockpiled grazing must be accompanied by adjustments in pasture management.

Microclimate of grass canopies and biomass accumulation are influenced by the use of caged exclosures in grazing research.

Exclosure cages are often used for estimating biomass accumulation on continuously stocked pastures in grazing experiments. The microclimate inside the cages may affect the estimates of biomass accumulation, but this has not been previously identified or quantified. We evaluated how the exclusion from grazing for 21days in Mulato II brachiariagrass (Brachiaria brizantha × Brachiaria decumbens × Brachiaria ruziziensis) pastures affected canopy air temperature (T) and relative humidity (RH) and how this related to biomass accumulation. We also evaluated the effect of the exclosure cage on wind speed (WS) and incoming solar radiation (SR), and how these impacted evapotranspiration (ET) and estimates of biomass accumulation on grazed canopies maintained at 20- and 30-cm height under continuous stocking. Regardless of canopy height, changes in canopy structure during the exclusion period up to 21days did not affect T and RH (averages of 24.3°C and 88.7%, respectively), indicating that the air circulation was not affected by the exclusion. The cage structure reduced SR by 5%, although there were times during clear days when SR was slightly greater inside the cage than outside. The cage also reduced WS by 4.4%. Smaller SR and WS resulted in less ET inside the cages than outside, although with close values (2.9 vs. 3.0mmday-1; P = 0.0494). The biomass accumulation rate was greater inside than outside the cages for both canopy heights. This overestimation would be 5.8 and 9.7% greater if the structure of the cage did not reduce the SR, WS, and ET.

Integrated modeling of canopy photosynthesis, fluorescence, and the transfer of energy, mass, and momentum in the soil–plant–atmosphere continuum (STEMMUS–SCOPE v1.0.0)

Abstract. Root water uptake by plants is a vital process that influences terrestrial energy, water, and carbon exchanges. At the soil, vegetation, and atmosphere interfaces, root water uptake and solar radiation predominantly regulate the dynamics and health of vegetation growth, which can be remotely monitored by satellites, using the soil–plant relationship proxy – solar-induced chlorophyll fluorescence. However, most current canopy photosynthesis and fluorescence models do not account for root water uptake, which compromises their applications under water-stressed conditions. To address this limitation, this study integrated photosynthesis, fluorescence emission, and transfer of energy, mass, and momentum in the soil–plant–atmosphere continuum system, via a simplified 1D root growth model and a resistance scheme linking soil, roots, leaves, and the atmosphere. The coupled model was evaluated with field measurements of maize and grass canopies. The results indicated that the simulation of land surface fluxes was significantly improved by the coupled model, especially when the canopy experienced moderate water stress. This finding highlights the importance of enhanced soil heat and moisture transfer, as well as dynamic root growth, on simulating ecosystem functioning.

A study of seasonal dynamics of herbaceous plant communities in Khakassia using ground-based and satellite data

The present study addresses the seasonal dynamics of productivity and species composition of the meadow and steppe vegetation communities in Khakassia, determined using the ground-based and satellite data of 2017. The MODIS/Terra satellite data were used to analyze the Normalized Difference Vegetation Index (NDVI) and the Land Surface Water Index (LSWI). The NDVI and LSWI were found to be related to the productivity of the meadow and steppe vegetation. The NDVI increased as the portion of the mesophyte grasses in the grass canopy became larger. The LSWI was higher in the steppe communities, which had lower projective coverage, with spots of bare soil, than in the meadow communities, with their abundant vegetation.

Влияние одиночных деревьев на флористическое разнообразие и популяционную структуру редких видов растений остепненных лугов

Steppe meadows preserved in the zone of deciduous forests of European Russia. These meadows have rich floristic composition and contribute significantly in biological diversity of territories. Bryansk region is one of the forest regions, where steppe meadows are sustained. There are meadows with high floristic diversity and big numbers of rare plant species. Trees from the surrounding forest areas insinuate constantly into these meadows. Most of the young trees die from regular fires and human agricultural activity. However, some individuals survive and pass into a generative state, in which they are relatively resistant to ground fires. The influence of single trees on the floristic diversity of steppe meadows was studied at two levels of organization of living systems – coenotic and population. Polydominant steppe meadows and polydominant steppe meadows with single generative trees were studied at the coenotic level. Coenopopulations of Iris aphylla, Anemone sylvestris and Anthericum ramosum were investigated at the population level. Different methods were used in the work: geobotanical, demographic, measuring environmental factors (luminance, steepness of slopes and frequency of fires). The study showed, that polydominant steppe meadows are supported on steep slopes unsuitable for haymaking and grazing and subjected to infrequent fire. These communities have high floristic diversity. Coenopopulations of model plants (Anemone sylvestris, Anthericum ramosum and Iris aphylla) are sustained there. Their ontogenetic spectra belong to left-hand type with maximum number of individuals. Single trees have controversial influence on polidominant steppe meadow vegetation. On the one hand, the species diversity of steppe meadows increases with the appearance of single generative trees because birds use adult trees like habitats and birds carry plant diasporas. On the other hand, mature trees shade grass canopy. It leads to decline of cover and occurrence of steppe and dry-meadow species. Also it affects plants coenopopulation structure. Ontogenetic spectrum of Anemone sylvestris stays full-stages but numbers of individuals is low. Ontogenetic spectrum of Iris aphylla loses ontogenetic stages (g1, g3) with numbers of individuals twice lower than on polidominant steppe meadows. Ontogenetic spectrum of Anthericum ramosum becomes incomplete with extremely low numbers of individuals.

Effects of ryegrass canopy and roots on the distribution characteristics of eroded sediment particles during heavy rainfall events on steep loess‐cinnamon slopes in Zhangjiakou, China

AbstractTo evaluate the effects of ryegrass (Lolium perenne) canopy and roots on eroded sediment particle distribution characteristics, simulated rainfall tests were implemented on grass caopy, roots, and bare slopes. The grass coverage density were 0, 20, 40, and 60%. The results showed that ryegrass canopies mainly contributed to runoff reduction and ryegrass roots primarily contributed to erosion reduction. With increasing rainfall duration, smaller particles (clay and fine silt particles) increased and larger particles (coarse silt and sand particles) decreased in the eroded sediment on the grass slope while the opposite trend was observed for the roots and bare slopes. Moreover, the clay and sand particles were eroded as aggregates and most silt particles were transported in the form of primary particles. Compared to the original soil, larger particles in the eroded sediment mainly occurred on the grass slopes because smaller particles were intercepted by the grass canopies, while smaller particles primarily occurred in the eroded sediment of the root slopes because grass roots inhibited soil erosion. These results illustrate that grass cover can prevent the loss of small particles in the topsoil and avoid soil coarsening, which provides guidance for the comprehensive control of soil erosion.

Мозаичность естественных галофитных экосистем на границе лесостепной и степной зон Южного Урала

The patterns (mosaicity) in natural halophytic grasslands at the border of Forest-steppe and Steppe zones of South Ural were characterized by the hierarchical continuum concept theory for the Troitskiy state natural complex preserve example. It was established, that the grass canopy is fragmented by salinization impact, the individual’s random distribution is typical of halophytes and salttolerant steppe species form patterns. Only the micro-patterns (0,8 m) level is statistically significant, parcels (8 m) and coenotics (12 m) are fuzzy and fragmentation of mosaicity is observed. There are two coenotics series defined for parcels – halophytic and steppe, relating to the distribution of halophytes and steppe grasses respectively. There is clear coenosis. Separation is observed by phytodiversity and biotopes descriptions. The intracoenotic interactions between species, soil moistening variability, soil aeration and acidity (alkalinity) and soil mineralization increase (decrease) are significant for parcels and coenosis forming.