Dense Grass Research Articles

Effect of Brown Manuring and Herbicide Application on Weed Parameters on Aerobic Rice under Varying Planting Geometry

A Field Experiment was conducted at Main Rice Research Centre, Navsari Agricultural University, Navsari during kharif 2021. The experiment was carried out in randomized block design with factorial concept with three replication. The results revealed that density of grasses, sedges, broad-leaved weeds and thus total weed density were significantly higher in 40 cm line sowing at 20 DAS and 40 DAS. Weed dry weight at 60 DAS and at harvest was also significantly higher with 40 cm line sowing. Hand weeding twice at 20 and 40 DAS recorded no weed at 20 DAS and at 40 DAS and was closely followed by Pendimethalin 750 g a.i. ha-1 (PE) + Bispyribac sodium 40 g ha-1 at 30 DAS. Considerably lower weed dry weight at 60 DAS and at harvest was recorded with Hand weeding twice at 20 and 40 DAS which was at par with Pendimethalin 750 g a.i. ha-1 (PE) + Bispyribac sodium 40 g ha-1 at 30 DAS. Numerically higher weed control efficiency at 60 DAS and at harvest and lower weed index was also recorded by Hand weeding twice at 20 and 40 DAS followed by Pendimethalin 750 g a.i. ha-1 (PE) + Bispyribac sodium 40 g ha-1 at 30 DAS. Weed smothering efficiency was found to be higher with Pendimethalin 750 g a.i. ha-1 (PE) + Brown Manuring at 60 DAS and at harvest.

Effects of pasture‐burning management on anuran communities in subtropical Brazilian grasslands

AbstractAnthropogenic fire is a worldwide event that affects many ecosystems and organisms. In Southern Brazil, grassland management with fire has been highly employed since the mid‐18th century. Although the practice is regulated by federal law (prescribed fire), there is no detailed information about the impacts of this practice on the small, non‐volant fauna. We evaluated the effect of fire management on anuran species richness and community composition in Brazilian grassland areas that have adopted this practice for more than 15 years. Our results show that burning practices lead to a reduction of anuran richness. About 37% of the species occur exclusively in sites free of fire. Sites with fire management have low densities of taller grass and shrubs, which could reduce habitat availability for some anuran species. Nestedness and turnover components of beta diversity did not differ within and between treatments, but there was a tendency for a nestedness organization of the community in burned sites, suggesting that sites with fire management are a subsample of sites where fire is absent. Our results pointed out that prescribed fire practices have potentially negative effects on the anuran diversity. These results suggest that the changes in vegetation, in particular percentages of shrub cover, affect habitat suitability for some species. Therefore, anuran communities tend to become less diverse and lack arboreal species where fire occurs.Abstract in Portuguese is available with online material.

Productivity of summer greengram (Vigna radiata) under different nitrogen levels and weed management practices

A field investigation was carried out during summer season, 2022 at ARS, Faculty of Agricultural Sciences, SOADU, Bhubaneswar to study the effect of nitrogen levels and weed management practices on Weed growth and productivity of summer greengram (Vigna radiata L.). The experiment was laid out in split plot design with three replications comprising fifteen treatment combinations. Treatments consisted of three nitogen levels in main plot and five weed management practices in subplot. The predominant weeds in the experimental plots were Poa annua, Digitaria sanguinalis, Echinochloa colona, Cleome viscose, Ageratum conyzoides, Portulaca oleracea, and Melochia corchorifolia. Results revealed that among the different levels of nitrogen, the lowest density and dry weight of grasses, broadleaved and total weeds was recorded with application of 75% N. Among the weed management practices, two hand weeding at 15 and 30 DAS, registered significantly lowest density and biomass of all categories of weeds as well as total weeds and it was closely followed by pre-emergence application of ready-mix pendimethalin + imazethapyr 0.75 kg/ ha at 45 DAS. Application of 125% N registered highest seed (832.30 kg/ ha) and stover yield (2189.64 kg/ ha) and along with high yield attributing characters like number of pods/ plant (25.54) and seeds/ pod (6.39) as compared to others and it was at par with application of 100% N. Among the weed management practices, two hand weeding at 15 and 30 DAS recorded highest seed yield (930.56 kg/ ha) and stover yield (2397.11 kg/ ha) of greengram along with higher yield attributing characters like number of pods/ plant (27.73), seeds/ pod (7.29) and number of branches/ plant (8.94) and it was closely followed by pre-emergence application of ready-mix pendimethalin + imazethapyr at 0.75 kg/ ha.

Characterizing the features of the low-amplitude peaks in delta Scuti stars with TESS

Abstract The presence of low-amplitude peaks over the noise in the power spectra of δ Scuti stars is frequently disregarded. These seemingly insignificant peaks, collectively referred to as grass, might contain valuable information about the origin of these stars and the reasons behind the occurrence or absence of a plateau. It is crucial to systematically parameterize the grass phenomenon throughout a comprehensive sample that covers the entire δ Scuti star parameter range. Thus, we conduct a quantitative study of long-duration, high-duty-cycle TESS light curves, leading to improved detection methods for plateaus and a deeper understanding of their nature. This approach minimizes the impact of unresolved peaks caused by mode variations over time. Additionally, we present appropriate analysis techniques to mitigate window effects and identify and eliminate spurious peaks. We demonstrate here that the grass can be effectively parameterized based on peak density. With such parameterization two distinct regimes are found: the sparse grass regime, characterized by low peak density and the absence of a plateau in the power spectra, and the dense grass regime, characterized by high peak densities and the presence of an observable plateau. Our study is the first rigorous quantification of the emergence of such a plateau in the power spectra of δ Scuti stars. Since the grass might be related with fractality, mode variability, and stellar rotation rate, its parameterization opens a new way to analyze these stars.

Spring precipitation amount and timing predict restoration success in a semi‐arid ecosystem

Abstract Successful restoration of semi‐arid ecosystems remains a challenging problem. Many studies have tried to elucidate the factors that limit seedling establishment so that mitigating actions can be taken during restoration. However, most studies have been plot‐based trials on individual sites that encompass only 1 or 2 years of meteorological variation. This limits the inferences that can be drawn. To move beyond short‐term research, we examined seedling establishment after the first growing season on 48 public lands sites undergoing restoration in the sagebrush steppe of the northern Great Basin over the course of 5 years (2016–2020), while simultaneously accounting for a broad suite of biotic (five), abiotic site (six), management (five) and weather variables (29). All these variables have been previously identified as influencing successful restoration. Using least absolute shrinkage and selection operator regression and a random forest algorithm, we identified nine variables associated with surviving seedlings at the end of the first growing season. Seedling establishment averaged 9.6 (±10.2 SD) individuals m−2. Precipitation variables accounted for 75% of the explained variation in seedling survival. April precipitation was the largest contributor and accounted for 27% of explained variation. Average length of dry period in February and number of rainfall events >5 mm March–May were also important predictors of survival, accounting for 13% and 10% of the explained variation, respectively. Only one biotic variable (annual grass density) and one management variable (drill seeding) accounted for more than 5% of the explained variance by the model. While temperature may be important in many models of seedling establishment, water availability during the emergence period (February–April) appeared to play the most important role determining the number of seedlings surviving at the end of the first growing season in this study. Synthesis and applications. The importance of April precipitation in predicting seedling establishment densities makes it a variable that should be included in restoration success forecasting models. Similarly, since dry periods and precipitation frequency combined explain nearly as much variation in establishment, efforts should be made to improve seasonal forecasting to include predictions of frequency and event size.

(Bromus rigidus)من خلال معرفة كثافة الحشائش(Triticum aestivum L)استخدام تحليل امسار للتنبؤ بفقدان نباتات القمح

The research explores the use of path analysis to predict the effect of brome grass (Bromus rigidus Roth) density on wheat (Triticum aestivum L.) yield loss. It also studies the relationship between weed density and wheat productivity. The research was conducted during the fall 2020 and spring 2021 seasons. Data were collected from experiments conducted under different densities of weeds and wheat. The statistical analysis program SPSS was used to determine the effect of competition on the amount of loss in wheat and brome productivity, using the Cousens equation and to calculate the competition coefficient between species using the Steward equation. Then, path analysis was used to predict the effect of internal and external variables on plant traits, biomass, and productivity. The results showed that increasing grass density led to a decrease in wheat productivity. The study emphasizes the importance of taking physiological factors into account in crop productivity. Recommendations include implementing measures to control weed density, adjusting wheat planting density to compete effectively with weeds, using weed-resistant wheat varieties, adopting comprehensive farm management practices, and conducting further research to enhance understanding of the interaction between wheat and weeds.

Spatial distribution of shrubs and perennial plants under grazing disturbance in the desert steppe of Inner Mongolia

The desert steppe is unique as a transition zone from the steppe to the desert of the Eurasian Steppe. The spatial distribution of shrubs and perennial plants has changed due to long-term disturbance caused by overgrazing in the ecosystem. This study aimed to determine the degree of patchiness of shrubs and perennial plants under grazing disturbance, which is of great significance to better understand the succession mechanism of plant community in the desert steppe. This study investigated the spatial distribution of shrubs and perennial plants under four stocking rates (no grazing, CK, 0 sheep·hm−2·half year−1; light grazing, LG, 0.93 sheep·hm−2·half year−1; moderate grazing, MG, 1.82 sheep·hm−2·half year−1; heavy grazing, HG, 2.71 sheep·hm−2·half year−1) in the desert steppe of Inner Mongolia, primarily using geostatistical methods. The density of perennial grasses increased with increasing stocking rate, while its height decreased (except for HG). The density and height of the shrubs and the perennial forbs showed an exponential or gradual decline. The spatial distribution of shrubs and perennial plants is mainly affected by structural factors such as topography, soil parent material, and climate, and the density of shrubs and perennial plants is most sensitive to changes in stocking rate. An appropriate stocking rate increases the spatial heterogeneity of shrubs and perennial plants, but heavy grazing reduces the spatial heterogeneity of shrubs and perennial plants.

Successful pollinator seed mixes include low grass density and high forb richness across a range of total seeding densities

Pollinator habitat restorations and enhancements are an important approach to mitigate pollinator declines due to habitat loss and other stressors. Foraging resources can be provided by wildflower plantings grown from seed mixes composed of pollinator‐friendly plant species. Despite clear evidence on the benefits of such plantings for bees and other pollinators, there is limited knowledge on how variation in multiple seed mix design parameters affects floral resources over time. Such information is crucial to improve the effectiveness of different habitat applications and to potentially lower seed costs, which remain an impediment to adoption. We conducted an incomplete factorial field experiment to test the impacts of density, diversity, and forb:grass ratio of seed mixes on floral resource availability and phenological coverage of the resulting plantings. We quantified floral area and phenological coverage over the whole blooming season for three consecutive years in replicated plots of wildflower mixes in two regions of the U.S.A, Northern California's Central Valley and Midwestern Tallgrass Prairie. When different seed densities were fully replicated (e.g. within high forb:grass seed ratios in Minnesota, or forb‐only seedings in California), seeding density had no further impact on floral area and floral phenological coverage.

Shrub encroachment of coastal ecosystems depends on dune elevation

Woody plant encroachment is influenced by interactions between the physical environment and vegetation, which create heterogenous microenvironments some of which favor shrub recruitment through mitigation of the abiotic environment. Encroachment of native shrub, Morella cerifera into grasslands on Hog Island, Virginia has been attributed to warmer winter temperature; however, recruitment of seedlings in grasslands may be impacted by multiple factors at the level of the microhabitat. Our study focuses on a critical gap in understanding factors specifically influencing M. cerifera seedling recruitment and survival. By experimentally planting M. cerifera seedlings at varying dune elevations and grass densities, we tested hypotheses that dune elevation influences the microclimate, soil characteristics and vegetation cover and that grass cover/density is related to shrub establishment. We tested these hypotheses through gathering data from temperature data loggers, conducting soil water content and chloride analyses, and determining percent cover of grasses relative to dune elevation. Results indicate that dune elevation was positively related to moderated temperatures with reduced temperature extremes and vegetation cover/composition that led to favorable locations for M. cerifera establishment and growth. Where dune elevation is > 2 m, we document an upper limit of grass cover on natural seedling establishment, suggesting a switch from facilitative to competitive effects with grass density. Overall, our work demonstrates interactions between dune elevation and medium grass density has a facilitative influence on M. cerifera establishment and can be used for future predictions of shrub growth with rising sea-levels.

Evaluation of Visual and Functional Quality of Grass and Trees at RSJMM Heritage Golf Field in Bogor City

Abstract RSJMM Heritage Golf Club is the oldest golf course in Bogor City. The quality of a golf course depends on the quality of the grass, both visually and functionally. It is also influenced by the tree that performs as a natural challenge for the game. The objectives of this study are: (1) to evaluate the visual quality of grass and trees, (2) to evaluate the functional quality of grass, and (3) to propose maintenance plan recommendations. The methods used in this research were observation, interview, and literature review. Furthermore, the data obtained were analyzed using Pearson correlation, Binomial test, and Kruskal-Wallis test. The result shows that the average visual quality of the tree is categorized as very good. Meanwhile, the visual quality of the grass shows that grass density is classified as moderate for the green area and high for the tee box and fairway areas. The color, color uniformity, the presence of particles, and the texture of 3 areas met the standard. The functional quality of the grass indicated that pruning height in 3 areas, shoot dry weight, root dry weight, and root length other than 1 area met the standard. The elasticity of the grass is included in the category of fast and medium fast for regular play. The result of this study provides recommendations for a maintenance plan to develop the quality of RSJMM Heritage Golf Club.

Effect of rainfall interception and resting period on the soil seed bank

The ecosystems across the world are affected by diverse impacts of climate change. Climate change will also affect soil seed bank as the seed bank is determined by the plants that are above the ground. This study was conducted to determine whether rainfall interception and resting period will affect the soil seed bank or not. Rainfall interception was employed as main plot treatment at four different levels—namely, 15%, 30%, 60%, and 0%—and the main plot treatments were each replicated five times using the rainout shelters arranged as main plot treatments in a split-plot experimental design. The main plots are 49 m2 (7 m × 7 m) in size and were covered by metal frame structures with V-shaped clear acrylic bands on top without ultraviolet filter, and these plots were sub-divided into two sub-plots to determine the effect of resting periods (70 and 90 days). The soil samples were 8 cm in diameter and 20 cm in depth (1,005 cm3). We used seed emergence method rather than seed separation method to determine the soil seed bank due to the very small size of some seeds for some species. The 60% rainfall interception resulted in significantly high forb densities at both resting periods. The forb densities decreased by 32 and 35% at 15% and 30%, while they increased by 195% at 60% rainfall interception compared to 0% rainfall interception at 70-day resting period. Resting period significantly affected grass densities at 60% rainfall as the densities were higher at 70- than 90-day resting period. At 90-day resting period, grass densities were significantly higher at 0% rainfall interception than the rest of the treatments, while the grass densities were significantly lower at 60% rainfall interception. The 60% rainfall interception resulted in significantly (p< 0.05) higher total densities (forbs and grass) in both resting periods. Total density increased by 2.9% and 143.48% at 15% and 60% rainfall interception, respectively. Our results show that drought has a negative effect on grass soil seed bank, while it improves the forbs soil seed bank. Furthermore, the resting period has no significant effects on soil seed bank in grasslands.

Geographical Environment and Plant Functional Group Shape the Spatial Variation Pattern of Plant Carbon Density in Subalpine-Alpine Grasslands of the Eastern Loess Plateau, China

The carbon density of subalpine-alpine grasslands (SGs) is significantly vital to sustaining the carbon cycle in global terrestrial ecosystems. However, on the Loess Plateau of China, it remains unclear how the geographical environment and plant functional groups affect the spatial variation pattern of plant carbon density in these grasslands. Here, nine typical SGs distributed in the eastern Loess Plateau with elevations ranging from 1720 to 3045 m were investigated. The biomass indices from grassland plants of different functional groups were investigated using plot surveys. The Kriging interpolation method was used to explore the spatial variation pattern of plant carbon density along geographical gradients. We found that (1) the total plant carbon density of SGs was 2676.825 g C/m2 on the eastern plateau, with 37.07%, 37.50%, and 25.43% contributed by the northern, central, and southern areas, respectively. Above- (666.338 g C/m2) and belowground (2010.488 g C/m2) carbon density accounted for 24.9% and 75.11% of the total, respectively. (2) At the horizontal scale, the plant carbon density in the northern SGs was high in the northwest and low in the southeast; in the central SGs, it was low in the northwest and high in the southeast; and in the southern SGs, it was high in the southwest and low in the northeast. At the vertical scale, plant carbon density in all SGs decreased with increasing altitude. (3) The carbon density of grasses, forbs, and sedges was 247.419 g C/m2, 26.073 g C/m2, and 23.471 g C/m2, respectively. With increased latitude, the carbon density of all functional groups (grasses, forbs, and sedges) decreased; the carbon density of forbs and grasses increased with increased longitude, while that of sedges decreased; and with increased altitude, the carbon density of all functional groups increased. In conclusion, the spatial variation pattern of plant carbon density in the SGs was not only influenced by the geographical environment but also by the plant functional groups at the horizontal and vertical scales on the eastern Loess Plateau of China.

Soil geochemistry and constraint of tree seedlings immediately after germination on Macrotermes termite mounds in the Kruger National Park, South Africa.

Macrotermes termite mounds in the Kruger National Park occupy a significant part of the savanna landscapes, occurring at densities of up to 70 km-2 and often exceeding 10 m in width and 4 m in height. The mounds are usually devoid of trees, but have dense grass cover in wet years. As a result, these mounds form large patches of grassland amongst the wooded savanna. To our knowledge, it is not known why trees are largely excluded from the mounds. We analysed soil surface nutrient concentrations on and off mounds (0-2 cm deep, n = 80) to ascertain whether the availability of nutrients could be influencing competition between grasses and tree seedlings. The results showed that potential deficiencies in P, Ca, Cu, Zn and B in soils off the mounds are likely to be constraining plant growth. Notably, only B, with an average concentration of 0.19 mg kg-1, was likely to be limiting plant growth on the mounds. Notwithstanding likely interactions with herbivory and fire, we hypothesise that because grasses are far less susceptible to deficiencies of B than dicotyledonous trees, it is likely that grass competition with tree seedlings is considerably greater on mounds than off mounds.

ANALYSIS OF ROTARY MOWER DESIGNS – CONDITIONERS

An integral operation of any technology of harvesting hay is mowing the grass, the quality of which depends on the collection of hay from a unit of area, as well as the growth of grass and the yield of grass in the following years. Modern rotary mowers are able to cut grass with high quality, regardless of the state of the stem. The main types of rotary mowers are disc and drum. Their productivity is 20-30% higher than the productivity of segment-finger mowers. The quality of hay largely depends on the drying speed of the vegetative organs of the mown plants. In order to equalize the drying speed of grass stems and leaves, rotary mowers are equipped with roller or impact (conditioners) flattening devices. The quality of grass flattening is affected by the material from which the rollers are made and the shape of their surface. With the same profile of the surface of the rollers, the efficiency of flattening with steel rollers is higher than with those covered with polymer materials. However, their work is accompanied by increased mechanical losses due to leaf breakage. In order to make the flattening rollers work smoother, rubber or polyurethane is applied to their surface. Fluted rollers flatten the grass more intensively than smooth rollers. Roller flatteners provide high-quality work when a layer of grass of uniform thickness is fed into the gap between the rollers. On the contrary, the number of unflattened stems increases. Roller-type tedders are less harsh on the grass than dynamic tedders, therefore, in order to reduce losses from breaking off leaves and inflorescences, they are recommended for working with leguminous grasses. Since the flattening devices of dynamic action are less sensitive to the unevenness of the mass supply, it is advisable to use them when mowing grasses with an uneven density of grass and cereal grasses.

Small‐scale fires interact with herbivore feedbacks to create persistent grazing lawn environments

Abstract Fire‐herbivory feedbacks strongly influence the formation of grazing lawns in savanna ecosystems. Preliminary findings suggest that small‐scale (<25 ha) fires can engineer grazing lawns by concentrating herbivores on the post‐burn green flush; however, the persistence of such grazing lawns over the longer term and without repeated fire is unknown. We used high‐resolution Light Detection and Ranging (LiDAR) to investigate the long‐term effects of fire manipulation on short grass structure (height, cover, volume and spatial continuity) and grazing lawn establishment in Kruger National Park, South Africa. We analysed the effects of fire exclusion and experimental burns applied over a 7‐year period (2013–2019) followed by a 1‐year cessation of burning at varying spatial scales during the early and late dry seasons. Fires contributed a fourfold increase in short grass cover, regardless of fire season or size. The distribution of grass height differed significantly between fire‐induced grazing lawns and recently unburnt parts of the landscape where controlled fires were excluded over the experimental period. The volume (corresponding to bulk density) of short grass on the landscape responded strongly to fires, with grass volume <20 cm in height increasing with both early and late dry season fires. Early dry season fires caused larger and more homogeneous short grass patches. Furthermore, early dry season fires were more influential in increasing the cover of the shortest grass height class (1–5 cm). Synthesis and applications. Our results demonstrate that fire‐induced grazing lawns can persist over the longer term, even when fires are no longer applied, leading to the creation of vertical and horizontal heterogeneity in the grass layer. Small‐scale fires, therefore, represent a feasible management approach to expanding grazing lawn extent, potentially benefiting grazer coexistence and diversity.

Johnson Grass (Sorghum halepense) Interference, its Effect on Crops Yield and Soil attributes under Different Cropping Systems and Management Practices

Johnson grass (Sorghum halepense) is one of the most detrimental and toxic weeds among the weed species. Its environment is expanding unceasingly due to deeply expanding of its rhizomes in the soil, self-pollinating reproduction strategy, accelerated growth and poor management which results in production losses of major agronomic crops. Mungbean and sorghum are important crops grown on significant acreage around the world, and a major constraint for their production losses is weeds interference. Thus, field studies were conducted to examine Johnson grass interference, control, and recovery under different management practices and cropping system and its effects on crops production and soil health. Our results indicated that the Johnson grass density was minimized by the application of plastic sheet mulch treatment under wheat-mungbean cropping system. Johnson grass competition had a significant impact on growth and grain yield of both mungbean and sorghum. The crop yield parameters; 100 grain weight and grain yield were lowest in the non-treated treatment (control), while the greatest values of these parameters were recorded in the plastic sheet mulch and post emergence herbicide treatments with wheat-mungbean cropping system. Similarly, soil building attributes; available nitrogen, available phosphorus, available potassium and organic matter content were positively affected by the interaction of plastic sheet mulch + wheat-mungbean cropping system. Besides this, benefit-cost ratio of the research shows that wheat-mungbean cropping system with application of plastic sheet mulch and post emergence herbicide also proved to be economically feasible. Overall, we have concluded that wheat-mungbean and wheat-sorghum are most resilient cropping system with the implementation of plastic sheet mulch and Post Emergence Herbicide to suppress the spread of Johnson grass under changing climatic scenarios.

Formation of grass stands of variegated alfalfa (Medicago varia, M. media) on acidic sod-podzolic soils

The article reports the results of field studies performed at the Field Experimental Station of Russian State Agrarian University – Moscow Timiryazev Agricultural Academy in 2023-2024. The authors studied the effect of the growth regulator Albit, the microbiological fertilizer Sporion and the micronutrient Aquamix on the formation of grass stands of variegated alfalfa (the Agnia and Taisia varieties) and Hungarian sainfoin (the Pavlovsky variety). The study has found that on the acidic sod-podzolic soil with a pHКCl of 4.52, variegated alfalfa (the Agnia and Taisia varieties) inoculated with strains of nodule bacteria Sinorhizobium meliloti, AK 55 and SHM 404B, respectively, formed dense grass stands. On average, over two years, variegated alfalfa of the Agnia variety provided the highest yield when using Sporion in combination with Aquamix – 5.2 t/ha; that of the Taisia variety – in variants of Albit + Aquamix and Sporion + Aquamix– 5.07 and 5.19 t/ha, respectively, which is 20.1%; 18.4, and 21.3% more compared to the control. Hungarian sainfoin has not formed a productive agrophytocenosis on the acidic soil. On average, it was inferior in yield to variegated alfalfa of the Agnia and Taisia varieties by 1.7 and 1.8 times, respectively, in all variants of the experiment.

Weed communities after decades of mineral fertilization and tillage treatments in a corn–soybean rotation

Abstract Soil fertility and disturbance can potentially modify weed dynamics in a corn–soybean rotation. Knowing how added mineral fertilizers and tillage influence weed populations in the long term can provide insight into weed community shifts, which may affect future weed management requirements. The first objective of this study was to evaluate the effect of 24 to 25 years of nitrogen and phosphorus fertilization treatments and tillage (moldboard vs. no-till) on weeds (density, biomass, and composition) before and after herbicide applications in 2016/corn and 2017/soybean. The second objective was to evaluate the effect of the same treatments 6 yr after no postemergence weed management in 2022/corn. Since the last evaluation performed in 2004, weed density, richness, and diversity increased, and more annual grasses were observed under both tillage regimes. No fertilization effect was observed on any weed variables, including composition, except for increased biomass when left to grow all season after crop planting. In managed plots, the density and biomass of annuals and perennials were generally higher in no-till, and discrepancies were highest for annual grass densities before herbicide application. Weed species richness and diversity based on counts were equivalent between tillage regimes, but total biomass was distributed between more species in no-till. Higher weed densities and concurrent weed biomass, observed in no-till, reduced crop yields in 2016/soybean only. The combination of low crop diversity and low use of residual herbicides during the trial potentially led to the observed species shifts and increased weed density.

Imprint of selective logging on seed regeneration of Brachystegia spiciformis Benth. in dry miombo woodland in Zimbabwe

Woodlands that have been affected by selective logging are ubiquitous in southern Africa but how this harvesting practice impacts seed regeneration of dominant tree species remains unclear. To address this deficiency, the study assessed the effects of different selective logging intensities on post-dispersal seed predation and seedling recruitment of Brachystegia spiciformis Benth. in Ruzawi Forest, Zimbabwe. Data were collected in blocks that were subjected to selective logging intensities of 0 % (00 L, unlogged), 5 % (05 L), 10 % (10 L), and 15 % (15 L). Ten years after logging, three transects (200×30 m) were laid in each block and five main plots (20×20 m) were laid in each transect, making a total of 60 plots. Low-intensity selective logging of 5 % did not cause any significant changes to seed predation levels, densities of true seedlings, seedling sprouts and root suckers, and soil nutrient concentrations. Seed predation was significantly greater in 10 L and 15 L sites than in unlogged and 05 L sites. As logging intensity increased, the relative importance of sexual reproduction decreased and that of vegetative reproduction increased. Canopy cover and seedling density decreased as logging intensity increased but a reverse trend was observed with grass biomass and root sucker density. Grass biomass was negatively correlated with the density of true seedlings and seedling sprouts. Soil organic C, N, P, and K were all significantly reduced in 10 L and 15 L sites than in unlogged and 5 L sites. Our results suggest that unless selective logging is practiced at very low harvest intensities, it can create opportunities for the growth of dense grass swards, potentially promoting rodent seed predation and limiting seedling recruitment. This study recommends effective use of low-impact selective logging practices as well the adoption of woodland management policies that prioritize sustainable utilization practices.

Invasive grass density negatively impacts chaparral seedling establishment

Type conversion from native shrubland to invasive annual grassland is on the rise due to global change factors such as prolonged drought and increasing fire frequency. Efforts to restore chaparral ecosystems are limited by current understanding of competitive interactions between shrub seedlings and invasive grasses as well as soil moisture requirements of chaparral seedlings. We set up a restoration experiment where we out‐planted Adenostoma fasciculatum seedlings, manipulated invasive grass density, monitored soil moisture at two depths, and tracked seedling survival and biomass. We found that higher invasive grass cover was associated with higher rates of seedling mortality but found no difference in biomass per surviving plant. Soil moisture was higher at 15 cm under the 100% weeded treatment than the 50% weeded and control treatments during January. Lower invasive cover resulted in higher richness of annual native plant species, as plots with 100% invasive removal had higher richness than 50% removal and unplanted control plots. Future restoration efforts in the chaparral will likely be more successful in increasing initial seedling establishment if invasive grass removal is included.