Grassland intensification effects cascade to alter multifunctionality of wetlands within metaecosystems

Unraveling spatial heterogeneity of soil legacy phosphorus in subtropical grasslands

Humans have profoundly altered phosphorus (P) cycling across scales. Agriculturally driven changes (e.g., excessive P-fertilization and manure addition), in particular, have resulted in pronounced P accumulations in soils, often known as "soil legacy P." These legacy P reserves serve as persistent and long-term nonpoint sources, inducing downstream eutrophication and ecosystem services degradation. While there is considerable scientific and policy interest in legacy P, its fine-scale spatial heterogeneity, underlying drivers, and scales of variance remain unclear. Here we present an extensive field sampling (150-m interval grid) and analysis of 1438 surface soils (0-15 cm) in 2020 for two typical subtropical grassland types managed for livestock production: Intensively managed (IM) and Semi-natural (SN) pastures. We ask the following questions: (1) What is the spatial variability, and are there hotspots of soil legacy P? (2) Does soil legacy P vary primarily within pastures, among pastures, or between pasture types? (3) How does soil legacy P relate to pasture management intensity, soil and geographic characteristics? and (4) What is the relationship between soil legacy P and aboveground plant tissue P concentration? Our results showed that three measurements of soil legacy P (total P, Mehlich-1, and Mehlich-3 extractable P representing labile P pools) varied substantially across the landscape. Spatial autoregressive models revealed that soil organic matter, pH, available Fe and Al, elevation, and pasture management intensity were crucial predictors for spatial patterns of soil P, although models were more reliable for predicting total P (68.9%) than labile P. Our analysis further demonstrated that total variance in soil legacy P was greater in IM than SN pastures, and intensified pasture management rescaled spatial patterns of soil legacy P. In particular, after controlling for sample size, soil P was extremely variable at small scales, with variance diminished as spatial scale increased. Our results suggest that broad pasture- or farm-level best management practices may be limited and less efficient, especially for more IM pastures. Rather, management to curtail soil legacy P and mitigate P loading and losses should be implemented at fine scales designed to target spatially distinct P hotspots across the landscape.

From invasive species stand to species-rich grassland: Long-term changes in plant species composition during Solidago invaded site restoration

Biological invasions degrade ecosystems, negatively affecting human well-being and biodiversity. Restoration of invaded agricultural ecosystems is among specific goals of European Union Biodiversity Strategy. Successful restoration of invaded lands is a long-term process that requires monitoring to assess the effects of interventions. Here, we present the results of a long-term experiment (8 years) on restoration of semi-natural grassland on abandoned arable field overgrown by invasive Solidago species (S. gigantea and S. canadensis). We examined effect of different invaders removal methods (rototilling, turf stripping, herbicide application) and seed application practices (commercial seed mixture, fresh hay) on changes in species composition and taxonomic diversity of restored vegetation. Our results showed a positive effect of grassland restoration on taxonomic diversity and species composition, manifested by a decrease in Solidago cover and an increase in cover and richness of target graminoids and forbs characteristic of grassland. The seed source had a longer lasting and still observable effect on the vegetation composition than the Solidago removal treatments, which ceased to differ significantly in their influence after the first few years. Applying fresh hay as a seed source increased the cover of grassland species such as Arrhenatherum elatius and Poa pratensis. For commercial seed mixture, we observed the high cover of Lolium perenne and Schedonorus pratensis (introduced with seed mixture) at the beginning and the slow decrease along the experiment course. The most striking effect was the fresh hay with herbicide application, which resulted in the lowest Solidago cover and the highest cover of target graminoids. Nonetheless, with years the non-chemical methods, including no treatment, gives comparable to herbicide effectiveness of restoration. Overall, during the experiment, alpha diversity increased, while beta and gamma diversity reached a species maximum in the third year, and then decreased. In conclusion, this study gives guidance to successful restoration of species-rich grasslands on sites invaded by Solidago. It should be emphasised that short-term effect differ considerably from long-term outputs, especially highlighting the importance of seed source, as well as effectiveness of environmentally friendly methods such as regular mowing to control the invader.