Soil feedback does not explain mowing effects on vegetation structure in a semi-natural grassland

Ground Cover Management in Olive Groves Reduces Populations of Philaenus spumarius (Hemiptera: Aphrophoridae), Vector of Xylella fastidiosa

Philaenus spumarius (Linnaeus, 1758) (Hemiptera: Aphrophoridae) is considered the main vector of Xylella fastidiosa (Wells Raju et al. 1986) (Xathomonadales: Xanthomonadaceae), agent of the Olive Quick Decline Syndrome in Southern Europe. To limit the spread of the disease, it is of primary importance to identify effective control measures against the vector. Besides chemical control, cultural practices could potentially help reducing vector activity and population density. Here, we tested the effectiveness of three different ground cover management practices in controlling vector populations in olive groves in the Abruzzo region (Central Italy). We compared tillage (two tillage operations in spring followed by two cuts in summer), frequent mowing (four cuts from spring to summer) and a control (two cuts in summer) by sampling vectors both in the ground vegetation and in the tree canopy. In late spring, after the peak of the population, tillage reduced P. spumarius density by 60%, while frequent mowing only reduced the density by 20% compared to control plots. The differences tended to disappear with time. The treatments had the same effect on the vector density in both the ground vegetation and tree canopy. The vectors were more concentrated in the ground cover at the beginning of the season while in summer both the canopy and ground vegetation had the same vector density. Our findings suggest that tillage is a viable option for the containment of P. spumarius, as frequent mowing did not achieve sufficient control efficacy.

Disentangling the Effects of Disturbance from Those of Dominant Tall Grass Features in Driving the Functional Variation of Restored Grassland in a Sub-Mediterranean Context

Land abandonment in sub-Mediterranean grasslands causes the spread of tall-grasses, affecting biodiversity and ecosystem functioning. Mowing allows the recovery of the coenological composition after invasion, but the mechanisms acting at the fine-scale are poorly investigated. Since 2010 in the Central Apennines, we fenced a grassland invaded by Brachypodium rupestre, divided it into two areas, half of each was mowed biyearly and half remained unmown. In 2017 we selected ten 20 × 20 cm experimental units per half-area, collecting data on species occurrences, plant traits, B. rupestre height and phytomass. We used generalized linear mixed-effect modelling to disentangle the role of mowing from the impact of B. rupestre features in driving the community functional variations. Mowing was the main driver in the recovery process, acting as an abiotic filter (enhancement of tolerance-avoidance strategies). Furthermore, the reduction of weaker competitor exclusion processes fostered the increase of functional variation between coexisting species. Both drivers acted on different plant traits (e.g., mowing on life span, vegetative propagation types and plant height, mowing and B. rupestre features on space occupation types, seed mass and leaf anatomy), generally enhancing the extent of functional strategies related to resource acquisition and storage, reproduction, space occupation and temporal niche exploitation.

The effect of abandonment on vegetation composition and soil properties in Molinion meadows (SW Poland)

Intermittently wet meadows of the Molinion alliance, as with many other grasslands of high-nature value, have become increasingly exposed to abandonment due to their low economic value. The potential consequences of land abandonment are the decrease in species diversity and environmental alterations. The issue of land-use induced changes in plant species composition and soil physico-chemical parameters have been rarely studied in species-rich intermittently wet grasslands. In this study we attempt to i) to identify determinants of plant species composition patterns and ii) to investigate the effect of cessation of mowing on vegetation composition and soil properties. The study was conducted in an area of 36 ha covered with Molinion meadows, comprising of mown sites and sites that were left unmown for 10 years. In total, 120 and 80 vegetation plots were sampled from mown and unmown sites, respectively. In these plots we measured plant community composition and soil physico-chemical parameters. The results have shown that the two groups of variables (soil properties and management) differ considerably in their ability to explain variation in plant species data. Soil variables explained four-fold more variation in plant species composition than management did. The content of soil organic matter, moisture, total nitrogen and exchangeable forms of potassium, calcium and magnesium were significantly higher in mown than in unmown grassland systems. The results revealed that soil organic matter was the component of the soil most strongly affected by management, followed by moisture, magnesium, calcium and potassium in that order. Each of these soil parameters was negatively correlated with the abundances of woody plants and invasive species. We concluded that low-intensity, late time of mowing is suitable grassland management practice to ensure high plant species diversity and sustainability of the grassland ecological system while cessation of mowing not only lead to reduced plant species richness and diversity, but also to reduced nutrient levels in grassland soils.

Effects of mowing on methane uptake in a semiarid grassland in northern China

BACKGROUND

Mowing is a widely adopted management practice for the semiarid steppe in China and affects CH(4) exchange. However, the magnitude and the underlying mechanisms for CH(4) uptake in response to mowing remain uncertain.

METHODOLOGY/PRINCIPAL FINDINGS

In two consecutive growing seasons, we measured the effect of mowing on CH(4) uptake in a steppe community. Vegetation was mowed to 2 cm (M2), 5 cm (M5), 10 cm (M10), 15 cm (M15) above soil surface, respectively, and control was set as non-mowing (NM). Compared with control, CH(4) uptake was substantially enhanced at almost all the mowing treatments except for M15 plots of 2009. CH(4) uptake was significantly correlated with soil microbial biomass carbon, microbial biomass nitrogen, and soil moisture. Mowing affects CH(4) uptake primarily through its effect on some biotic factors, such as net primary productivity, soil microbial C\N supply and soil microbial activities, while soil temperature and moisture were less important.

CONCLUSIONS/SIGNIFICANCE

This study found that mowing affects the fluxes of CH(4) in the semiarid temperate steppe of north China.