Plant Species Diversity and Management of Temperate Forage and Grazing Land Ecosystems

Abstract

More than a century since Charles Darwin stated that diverse grasslands produce more herbage than monocultures, scientists still debate the relationship between species diversity and ecosystem function. Postulated benefits of diversity in experimental grasslands include greater and more stable primary production along with more efficient nutrient use. These benefits have been extrapolated to forage and grazing land systems with little supporting objective data. Most information on the potential benefits of increased plant diversity comes from studies of synthesized grasslands that have not included domestic grazing animals. We explore this debate relative to the management of temperate forage and grazing lands. Plant species diversity refers to the number of species (richness) and their relative abundance (evenness) within a defined area. Plant relations influence biodiversity responses through positive (e.g., facilitation, N2 fixation, hydraulic lift) and negative interactions (e.g., competitive exclusion, allelopathy). Early 20th century research on complex mixtures of forage species (limited to grasses and legumes) for pasture indicated equivocal results regarding benefits of species‐rich mixtures and typically recommended using the best adapted species in simple grass–legume mixtures. Recent research indicates potential herbage yield benefits from species‐rich mixtures for pastures. Limited animal productivity research on species‐rich mixtures indicates variable responses and much more research is needed. Grazing land productivity is a primary focus for biodiversity benefits because of the direct economic relevance to producers. However, taking a broader view of the multifunctionality of grazing lands to include environmental and aesthetic benefits to humans reveals a great scope for using biodiversity in grazing land management.

An ecological economic assessment of risk-reducing effects of species diversity in managed grasslands

“…For instance, higher diversity has been found to reduce the vulnerability of grassland to climatic extreme events such as droughts as well as to pests and diseases (e.g. Kahmen et al, 2005, Lin 2011, Sanderson et al, 2004, Vogel et al, 2012. The higher temporal stability of production resulting from higher species diversity might be additionally valued by farmers because a less volatile biomass production increases the utility of a risk-averse decision maker.…”

Biodiversity for multifunctional grasslands: equal productivity in high-diversity low-input and low-diversity high-input systems

“…These services include ecosystem processes with direct functional benefits in an agricultural context such as yield, decomposition, nutrient leaching, pollination, soil conservation and resistance to weed invasion along with forage stability under changing climatic conditions. Other goals comprise ecologically important services such as enhanced carbon sequestration and the mitigation of greenhouse gas emissions as well as non-market benefits such as land conservation, the maintenance of landscape structure or even aesthetic values (Sanderson et al, 2004).…”

“…If these results were also valid under nutrient-rich conditions, management for increased species diversity would be an ecological approach to enhancing the multifunctionality of grasslands (Sanderson et al, 2004;Hector and Loreau, 2005;Hooper et al, 2005) and could even provide additional benefits for biodiversity conservation (Robertson and Swinton, 2005;Tscharntke et al, 2005). Strong evidence for this approach comes from the European-wide COST experiment which recently showed that even a moderate increase of plant species richness from 1 to 4 species had strong positive effects in intensively managed grasslands (Kirwan et al, 2007).…”

“…These high-diversity low-input grasslands usually have low yields (Tallowin and Jefferson, 1999). Sanderson et al (2004) reviewed agricultural studies combining biodiversity with fertilisation and/or grazing in pastures and found equivocal results where much of the positive effects of biodiversity were attributed to the sampling effect (inclusion of a highly productive species). The only ecological experiment including fertilisation on intensively managed grasslands was again part of the COST experiment and showed a positive effect of species mixtures even under very high levels of nitrogen addition (450 kg N ha −1 y −1 , Lüscher et al, 2008).…”

Durability of Artificial Sward With the Participation of Red Fescue Situated Along the Slopes of the Central Balkan Mountain Vi. State of Mixed Sward of Red Fescue, Kentucky Bluegrass and Birdsfoot Trefoil

“…The presence of weeds was higher in low level of soil gleying, at a high part of the slope. It is considered that the poorer soils create conditions for increase in the species diversity [SANDERSON et al, 2004] . The contradiction with the results of the mentioned author could be due to difference in the geographical conditions [PEETERS and JENSSENS, 1998 ] or to the peculiarities of the species composition of the discussed plant communities.…”