Precipitation Changes Regulate Plant and Soil Microbial Biomass Via Plasticity in Plant Biomass Allocation in Grasslands: A Meta-Analysis

In theory, changes in the amount of rainfall can change plant biomass allocation and subsequently influence coupled plant-soil microbial processes. However, testing patterns of combined responses of plants and soils remains a knowledge gap for terrestrial ecosystems. We carried out a comprehensive review of the available literature and conducted a meta-analysis to explore combined plant and soil microbial responses in grasslands exposed to experimental precipitation changes. We measured the effects of experimental precipitation changes on plant biomass, biomass allocation, and soil microbial biomass and tested for trade-offs between plant and soil responses to altered precipitation. We found that aboveground and belowground plant biomass responded asynchronically to precipitation changes, thereby leading to shifts in plant biomass allocation. Belowground plant biomass did not change under precipitation changes, but aboveground plant biomass decreased in precipitation reduction and increased in precipitation addition. There was a trade-off between responses of aboveground plant biomass and belowground plant biomass to precipitation reduction, but correlation wasn't found for precipitation addition. Microbial biomass carbon (C) did not change under the treatments of precipitation reduction. Increased root allocation may buffer drought stress for soil microbes through root exudations and neutralize microbial responses to precipitation reduction. However, precipitation addition increased microbial biomass C, potentially reflecting the removal of water limitation for soil microbial growth. We found that there were positive correlations between responses of aboveground plant biomass and microbial biomass C to precipitation addition, indicating that increased shoot growth probably promoted microbial responses via litter inputs. In sum, our study suggested that aboveground, belowground plant biomass and soil microbial biomass can respond asynchronically to precipitation changes, and emphasizes that testing the plant-soil system as a whole is necessary for forecasting the effects of precipitation changes on grassland systems.

Species richness promotes ecosystem carbon storage: evidence from biodiversity-ecosystem functioning experiments

Plant diversity has a strong impact on a plethora of ecosystem functions and services, especially ecosystem carbon (C) storage. However, the potential context-dependency of biodiversity effects across ecosystem types, environmental conditions and carbon pools remains largely unknown. In this study, we performed a meta-analysis by collecting data from 95 biodiversity-ecosystem functioning (BEF) studies across 60 sites to explore the effects of plant diversity on different C pools, including aboveground and belowground plant biomass, soil microbial biomass C and soil C content across different ecosystem types. The results showed that ecosystem C storage was significantly enhanced by plant diversity, with stronger effects on aboveground biomass than on soil C content. Moreover, the response magnitudes of ecosystem C storage increased with the level of species richness and experimental duration across all ecosystems. The effects of plant diversity were more pronounced in grasslands than in forests. Furthermore, the effects of plant diversity on belowground plant biomass increased with aridity index in grasslands and forests, suggesting that climate change might modulate biodiversity effects, which are stronger under wetter conditions but weaker under more arid conditions. Taken together, these results provide novel insights into the important role of plant diversity in ecosystem C storage across critical C pools, ecosystem types and environmental contexts.

The effect of mineral fertilization on belowground plant biomass of grassland ecosystems

Aim of the work was to determine the effect of different doses of mineral fertilization on belowground and aboveground plant biomass production of three different types of grasslands, to state R:S ratio (root:shoot) and turnover period of belowground plant biomass of grasslands. In the contribution, we assess production of underground biomass, tillering zone and aboveground biomass on three types of grasslands – permanent grassland (PG), over-sown grassland (OSG) and temporary grassland (TG) in sub-mountain area of central Slovakia. There were applied four levels of mineral nutrition in each grassland (non-fertilized variant, var. 30 kg.ha−1P and 60 kg.ha−1 K. var. 90 kg.ha−1 N + P30K60, var. 180 kg.ha−1 N + P30K60). The root biomass has the most significant share in the total biomass of grasslands (49.9–54.2 %), followed by tillering zone (33.3–36.0 %) and with the lowest share of aboveground biomass (11.9–16.8 %). A dominant share of root biomass and tillering zone ensure significant extra-productive functions of grasslands that contribute to the stability of agriculture landscape. We recorded the lowest amounts of root mass on TG (7.31 t.ha−1) and OSG (7.76 t.ha−1), the highest amounts on PG (8.52 t.ha−1). The specific nitrogen stimulating influence on root biomass production has been proven. Production of tillering zone was lower on OSG and TG (5.11 or 5.42 t.ha−1), significantly higher on PG (5.72 t.ha−1). We observed a significantly higher production of tillering zone with variants which were fertilized with nitrogen than on non-fertilized and PK fertilized. The lowest harvests of aboveground biomass were noticed on TG (5.80 t.ha−1), significantly higher on PG and OSG (6.35 or 6.54 t.ha−1). Mineral nutrition had a significant impact on production of aboveground biomass.R:S ratio of the assessed grasslands achieved the values from 4.02 to 5.16. Higher values on PG (5.16) are indicating its higher resistance to drought. Turnover time of root biomass was the longest on PG 3.5–5.0 years, on OSG and TG 2.5–3.5 years. Based on achieved results, we recommend using the fodder plants cultivation system on PG or OSG. Permanent grasslands are proved as ecologically more stable and more resistant to drought than temporary grasslands; they can together with optimal mineral nutrition provide adequate production of root biomass (8.5 t.ha−1) and a harvest of aboveground biomass (6.3 t.ha−1).