Plant production-community composition relationship associated with fungal guilds depends on grassland disturbance in surface and subsurface soils

Purpose Soil fungal guilds have been proven to influence the plant community composition-production relationship, but not much is known about their effects on surface and subsurface soils under different disturbances. Methods Here, we assessed the functional characteristics of three fungal groups using the Ribosomal Database Project (RDP) classifier and data available in FUNGuild, and we characterized the community of saprotrophic, mycorrhizal, and potential plant pathogenic fungi in surface (0–10 cm) and subsurface soils (10–20 cm) of temperate grasslands under different management practices. Results We found that grassland disturbances decreased plant aboveground production and changed plant community composition. In surface soil, antagonistic interaction between potential plant pathogens and saprotrophic fungi drove the plant community composition-production relationship. In subsurface soil, this relationship was driven by antagonistic interaction between mycorrhizal fungi and potential plant pathogens. Conclusion These findings revealed that under grassland disturbances, the surface soil fungal communities were more strongly associated with plant community composition-production relationship than those from the subsurface soil were. Potential plant pathogens played an important role in plant community composition-production relationship. This knowledge is important for predicting the shifts in ecosystem functions as a consequence of changes in soil fungal groups during grassland management.

Hydrologic Restoration of the Lac des Allemands Swamp, Barataria, Louisiana

Most of the forested wetlands of coastal Louisiana are in decline, primarily due to impoundment and increased flood duration. The Lac des Allemands swamp of Barataria Basin was a prime example of prolonged inundation prior to hydrologic restoration completed in February of 2018; the swamp had been impounded for over 60 years. To characterize restoration benefits, eight paired 625 m2 permanent sites were established close to and halfway between eight 30 m × 122 m gaps cut into the spoil bank of Bayou Chevreuil. During 2018, canopy closure increased by 20%. In addition, aboveground production of wood and leaves increased over 2017 from 2018–2020. Furthermore, natural regeneration has occurred annually and many of the seedlings are now approximately 1 m tall. In conclusion, hydrologic restoration of impounded wetlands in coastal Louisiana is an extremely cost-effective landscape restoration method.

Effects of simulated nitrogen deposition increase on plant nutritional status and physiological responses at two contrasting Beech forest sites in Italy

<p>Anthropogenic activities resulted in a significant increase in nitrogen (N) compounds in the atmosphere and their deposition back to the biosphere, with important implications on both carbon (C) and N cycles. Indeed, an increase in N deposition can increase forest productivity in N limited forest ecosystems. In addition, it can also increase N loss pathways, leading to soil acidification and nutrient imbalance. Several N manipulation experiments have been carried out for decades till now, though most of them focused on conifer forests. We consider two manipulation experiments established in 2015 on two beech (Fagus sylvatica L.) forests in Italy, Cansiglio and Collelongo sites, located on the Eastern Alps and Central Apennines, respectively. The two forests were chosen along a climate and N deposition gradient. Thus, our goal was to assess the effects of simulated N deposition increase on nutritional, physiological status and growth of beech forests from two contrasting climatic conditions. At both sites, N was added directly to the soil as NH<sub>4</sub>NO<sub>3</sub> in two doses: 30 kg N ha<sup>-1</sup> yr<sup>-1</sup> and 60 kg N ha<sup>-1</sup> yr<sup>-1</sup>. Moreover, in Cansiglio we also included a canopy N fertilization adding 30 kg N ha<sup>-1</sup> yr<sup>-1</sup>. Leaves were collected in 2016 and 2018 for the analyses of nutrients, stable C and N isotopes, and photosynthetic pigments. The aboveground production was periodically monitored with girth band and litterfall collectors. The nutrient stoichiometry analysis showed elevated N concentrations and high N:P in both forests, even in the control plots. N addition significantly increased N:P and N:S ratios in the treated plots. Changes in chlorophyll concentration were mainly related to differences between the two sites, while carotenoids were also influenced by N fertilization. After four years, we did not find an effect of the treatment (regardless of the doses) on both tree growth and leaf biomass. Altogether, our results suggest that both forests were not N limited. Finally, difference between the two manipulation approaches will be discussed in terms of leaf nutrients and C and N stable isotopes in the case of Cansiglio site.</p>

The effect of grazing and weather conditions on the productivity of Tyva dry steppes, Russia

The aim of the study. To investigate specifics of plant production process in steppe pastures in Tyva. Location and place of the study. The study was performed in 1998-2000 and 2008-2010 in five pasture ecosystems in the Ubsu-Nur depression in Tyva, Russia. Methodology. Field and laboratory work was carried out to assess the biological productivity of pasture ecosystems employing conventional geobotanical, botanical and ecological methods. Main results. The study showed that all characteristics of production process change with grazing pressure and weather conditions of the year. The highest grazing pressure was observed at the Erzin pasture, whereas the lowest pressure was found at the Yamaalyg one. The green phytomass stock (G) at the Erzin pasture during all years varied within 0.3–0.6 Mg ha-1, whereas the living belowground stock (R) during six years ranged 4.5–11.5 Mg ha-1. The Yamaalyg pasture had the lowest and the highest G of 0.5 and 1.1 Mg ha-1, respectively, with the minimal and maximal R estimates of 7.8 and 20.1 Mg ha-1, respectively. Therefore it was concluded that both under the highest (Erzin) and lowest (Yamaalyg) grazing pressure the between-years dynamics (over six years) may change as much as 2–3 times. Phytomass production was shown to vary much more. The aboveground production (ANP) at Erzin pasture was found to change from 0.4 to 1.2 Mg ha-1yr-1, i.e.3-fold. At the Yamaalyg pasture ANP changed 1.2 to 2.0 Mg ha-1yr-1. The belowground phytomass production (BNP) was shown to vary much more as compared with the aboveground production: from 2.7 to 24.5 Mg ha-1yr-1. Some production characteristics were shown to be weather-associated. At one and the same pasture (Onchalaan), depending on the weather conditions, ANP and BNP were found to vary 4 times, i.e. from 0.9 to 3.7 Mg ha-1yr-1 and from 4 to 18 Mg ha-1yr-1, respectively. The highest grazing pressure resulted in less yearly variation, as ANP ranged 0.4–0.8 Mg ha-1yr-1, and BNP ranged 5–8 Mg ha-1yr-1. Such lesser variation was apparently due to the higher resilience of the dominating herbs and grasses to grazing. Analysis of the influence of weather conditions showed that abundant summer precipitation resulted in the highest ANP estimates. No correlation was revealed between BNP and weather conditions. Overall seasonal hydrothermal conditions, such as warm and wet autumn of the preceeding year and rainy summer of the current year) were beneficial for the aboveground plant production. Conclusion. The phytomass stock the in grazed dry steppes of Tyva was found to vary more as compared with phytomass production. Belowground production showed especially drastic changes from year to year. Increased ANP almost always results in decreased belowground living phytomass stock and often in decreased BNP due to modified nitrogen turnover under grazing. The BNP estimate is extremely volatile and does not follow the aboveground phytomass dynamics.The highest BNP in 2008 could not be attributed only to weather conditions, being most likely due to the increased solar radiation. Spatial and temporal dynamics of the phytomass production showed that the maximal green phytomass and dead belowground phytomass stocks, as well as ANP, displayed greater spatial variation as compared with the temporal one. Overall we conclude that despite different methods to study phytomass production, its spatial and temporal variation is about the same.

Clipping defoliation eliminates the stimulating effects of nitrogen enrichment on the aboveground productivity of an alpine meadow

To investigate how clipping (CL) regulates the effects of nutrient addition, an experiment, including CL and nitrogen (N) addition, was conducted in an alpine meadow. Nitrogen treatment increased community coverage (48–113% higher than the control) and aboveground biomass (29–117% higher than the control), which was mainly attributed to grass growth. Both N and N + CL treatments showed a tendency to reducing species richness, while significant reduction only occurred in 2016 and 2017 in CL treatment. Clipping showed a tendency to decrease community cover (3–37% lower than the control) and aboveground biomass (2–34% lower than the control), while N + CL treatment had no effect, indicating that clipping can eliminate the simulated effects of N addition. Nitrogen addition significantly increased soil inorganic N (SIN, 528–1230% higher than the control), while SIN in N + CL was 25–48% lower than N treatment. The decrease in stimulated effects in N + CL was attributed to SIN decrease, which resulted from the aboveground biomass removal by clipping. Our results show that clipping can take away aboveground biomass and cause soil nutrients to decrease, which slows down the degraded grassland recovery. This suggests that grazing exclusion may eliminate the effect of nitrogen deposition on aboveground production in alpine grasslands.

Characterizing Livestock Production in Portuguese Sown Rainfed Grasslands: Applying the Inverse Approach to a Process-Based Model

Grasslands are a crucial resource that supports animal grazing and provides other ecosystem services. We estimated the main properties of Portuguese sown biodiverse permanent pastures rich in legumes (SBP) starting from measured data for soil organic carbon (SOC) and using the Rothamsted Carbon Model. Starting from a dataset of SOC, aboveground production (AGP) and stocking rates (SR) in SBP, we used an inverse approach to estimate root to shoot (RS) ratios, livestock dung (LD), livestock intake (LI) and the ratio between easily decomposable and resistant plant material. Results for the best fit show that AGP and belowground productivity is approximately the same (RS is equal to 0.96). Animals consume 61% of the AGP, which is within the acceptable range of protein and energy intake. Carbon inputs from dung are also within the range found in the literature (1.53 t C/livestock unit). Inputs from litter are equally distributed between decomposable and resistant material. We applied these parameters in RothC for a dataset from different sites that only comprises SOC to calculate AGP and SR. AGP and SR were consistently lower in this case, because these pastures did not receive adequate technical support. These results highlight the mechanisms for carbon sequestration in SBP.