Grassland Intensification Research Articles

Direct and indirect effects of agricultural intensification on a host-parasitoid system on the ribwort plantain (Plantago lanceolata L.) in a landscape context

Intensification of land use is known as a major driver of worldwide decline in biodiversity. Trophic interactions might be especially affected by a changing landscape structure due to agricultural intensification. In this study we investigated the effects of increasing land use intensity on a tritrophic system at different spatial scales in a landscape context. We examined two weevil species, Mecinus labilis Herbst and M. pascuorum Gyllenhal, as well as their common parasitoid, Mesopolobus incultus Walker, living on a common native herb, the ribwort plantain (Plantago lanceolata L.), at 76 sites in three geographic regions in Germany. The effect of land use intensity on species abundances was analysed across a range of spatial scales (100–2000 m) around the study sites. In all three regions and across most spatial scales, an increasing proportion of intensively managed grasslands in the surrounding landscape directly negatively influenced herbivore abundance. An increasing proportion of semi-natural habitats had a direct positive influence on herbivore abundance. The abundance of M. labilis was best explained at radii of r = 1500–2000 m, that of M. pascuorum at r = 100–500 m. The parasitoid, M. incultus, was indirectly influenced by land use intensity via the density of its two hosts. Agricultural intensification of grasslands can profoundly affect the abundance of their herbivorous and entomophagous fauna at landscape scale. This may have important implications for landscape management and the conservation of higher trophic level organisms in agricultural landscapes.

Economic valuation of cultural ecosystem service changes to a landscape in the Swiss Alps

Traditionally managed agrarian landscapes provide several cultural ecosystem services (CES). Still, CES are often not adequately considered in decision-making – partly because of challenges in their quantification and economic valuation. We show that a state-of-the-art application of an economic valuation method to CES can generate meaningful data for supporting real-world, regional decision-making processes. After qualitative pre-studies (semi-structured interviews, stakeholder workshop) and a pilot study (n=117), a discrete choice experiment (n=252 respondents) was administered to a random sample of citizens in the Visp region of the Central Swiss Alps, a site with traditional agrarian landscapes. The design of the choice experiment followed an ecosystem services approach, and uses visualizations to support valuation of aesthetic landscape changes. A response rate of 43% was achieved. Citizen support was expressed for agricultural heritage (P<0.001) and biodiversity-rich dry grasslands (P<0.001). Aesthetic impacts of settlement extension (P<0.001) and of grassland intensification (P<0.001) reduced the economic value of development options impacting the Visp landscape. Estimated marginal willingness-to-pay ranged from 410 CHF (1 CHF approx. 0.8 EUR in 2013)/person/year for 60 additional ha of dry grassland to −833 CHF for the visual impact of settlement expansion (by changes of the tax bill).

Long-term nutrient fertilization and the carbon balance of permanent grassland: any evidence for sustainable intensification?

Abstract. Sustainable grassland intensification aims to increase plant yields while maintaining the ability of soil to act as a sink rather than sources of atmospheric CO2. High biomass yields from managed grasslands, however, can be only maintained through long-term nutrient fertilization, which can significantly affect soil carbon (C) storage and cycling. Key questions remain about (1) how long-term inorganic vs. organic fertilization influences soil C stocks, and (2) how soil C gains (or losses) contribute to the long-term C balance of managed grasslands. Using 43 years of data from a permanent grassland experiment, we show that soils not only act as significant C sinks but have not yet reached C saturation. Even unfertilized control soils showed C sequestration rates of 0.35 Mg C ha−1 yr−1 (i.e. 35 g C m−2 yr−1; 0–15 cm depth) between 1970 and 2013. High application rates of liquid manure (i.e. cattle slurry) further increased soil C sequestration to 0.86 Mg C ha−1 yr−1 (i.e. 86 g C m−2 yr−1) and a key cause of this C accrual was greater C inputs from cattle slurry. However, average coefficients of slurry-C retention in soils suggest that 85 % of C added yearly through liquid manure is lost possibly via CO2 fluxes and organic C leaching. Inorganically fertilized soils (i.e. NPK) had the lowest C-gain efficiency (i.e. unit of C gained per unit of N added) and lowest C sequestration (similar to control soils). Soils receiving cattle slurry showed higher C-gain and N-retention efficiencies compared to soils receiving NPK or pig slurry. We estimate that net rates of CO2-sequestration in the top 15 cm of the soil can offset 9–25 % of GHG (greenhouse gas) emissions from intensive management. However, because of multiple GHG sources associated with livestock farming, the net C balance of these grasslands remains positive (9–12 Mg CO2-equivalent ha−1 yr−1), thus contributing to climate change. Further C-gain efficiencies (e.g. reduced enteric fermentation and use of feed concentrates, better nutrient management) are required to make grassland intensification more sustainable.

Tropical grasslands: A pivotal place for a more multi-functional agriculture.

Tropical grasslands represent a pivotal arena for the sustainable intensification of agriculture in the coming decades. The abundant ecosystem services provided by the grasslands, coupled with the aversion to further forest destruction, makes sustainable intensification of tropical grasslands a high policy priority. In this article, we provide an inventory of agricultural initiatives that would contribute to the sustainable intensification of the tropical grassland agro-ecosystem, and we recommend a shift in the scientific priorities of animal scientists that would contribute to realization of a more agro-ecological and multi-functional agriculture in the world's tropical grasslands.

Some clarification of the impacts of grassland intensification on food production, nitrogen release, greenhouse gas emissions and carbon sequestration: using the example of New Zealand.

Abstract We used an established, process-based model of the dynamics of carbon (C) and nitrogen (N) cycling between plants, soils and animals in grazed temperate pastures to clarify expectations of how some major components of intensification affect the outcomes (short-term and long-term) of alternative systems for food production and environmental impact We use the example of New Zealand, due to its clear recent history of intensification, the level of concern and hence nature of research undertaken there. A transition from low-input drystock, to dairy (lactation) systems with higher N inputs in fertilizer, and/or C and N inputs in supplements, reveals how at the same intermediate N input, food yield (per ha) can be doubled, while environmental N release halved, with minimal impact on C sequestration. We stress the sources of sustained changes in N release (e.g. nitrate/nitrous oxide) are altered inputs (fertilizer/supplements) and less so animal numbers in response to these. Much of the increased efficiency is due to 'improved' N partitioning in lactating (cf. dry) animals. A reversion to dry-stock (or 'de-stocking') therefore offers greater environmental challenge, unless N inputs decline accordingly. Responses to supplements (being a source of C) re-inforce how the driving limitation to the grazed ecosystem is C capture per ha, and we highlight the need for a renewed focus on fundamental research on plant C uptake per ha per unit of N input We offer a graphical method for visualizing the outcomes of options, and their trade-offs, with implications for policy and future research direction.

Long-Term Grassland Intensification Impacts on Particle-Size Soil Carbon Fractions: Evidence from Carbon-13 Abundance

Proper management of grassland ecosystems for improved productivity can enhance their potential to sequester atmospheric CO₂ in the soil. However, the direction and extent of soil C changes in response to improved grassland management or land-use conversion varies depending on the ecoregion or management practice. The objectives of this study were to: (i) assess the long-term (>20-yr) impact of grassland management intensification on soil C fractions after conversion of native rangelands to silvopasture and sown pasture ecosystems; and (ii) determine the contribution of sown grass species to soil C sequestration in both the labile and more stable soil C fractions. Experimental sites consisted of a gradient of management intensities ranging from native rangeland (lowest), to silvopasture (intermediate), to sown pasture (highest). After 22 yr following land-use conversion from native rangeland to silvopasture or sown pasture, total soil C stocks (0–30-cm depth) were greater under silvopasture (69.2 Mg C ha⁻¹) and sown pasture (62.0 Mg C ha⁻¹) than native rangeland (40.9 Mg ha⁻¹). Conversion to sown pasture increased particulate organic C concentration (10.6 g C kg⁻¹) compared with native rangeland (6.3 g C kg⁻¹), while silvopasture increased the mineral-associated C fraction (5.7 vs. 10 g C kg⁻¹ for native rangeland and silvopasture, respectively). Isotopic analysis indicated that the C₄ grass component contributed significantly to soil C accumulation within these ecosystems. Data also showed that grassland management intensification has the potential to promote soil C sequestration, and the use of strategic management practices such as integration of trees can improve soil C stability under similar subtropical conditions.

Trade-offs between pasture production and farmland bird conservation: exploration of options using a dynamic farm model

In European grassland landscapes, grazing and mowing play a key role for the maintenance of high-quality habitats that host important bird populations. As grasslands are also key resources for cattle feeding, there is a need to develop management strategies that achieve the double objective of production and biodiversity conservation. The objective of this study was to use a modelling approach to generate recognisable patterns of bird dynamics in farms composed of different land use proportions, and to compare their production and ecological dimensions. We developed a dynamic model, which linked grassland management to bird population dynamics at the field and farm levels. The model was parameterised for two types of suckling farms corresponding to contrasting levels of grassland intensification and for two bird species of high conservation value. A viability algorithm was used to define and assess viable management strategies for production and ecological performance so as to draw the shape of the relationship between both types of performances for the two types of farms. Our results indicated that, at the farm level, there was a farming system effect with a negative and non-linear relationship linking performance. Improving bird population maintenance was less costly in extensive farms compared with intensive farms. At the field level, the model predicted the timing and intensity of land use, maximising either production or ecological performance. The results suggested that multi-objective grassland management would benefit from public policies that consider levels of organisation higher than the field level, such as the farm or the landscape.

Management Intensification Impacts on Soil and Ecosystem Carbon Stocks in Subtropical Grasslands

Proper management of grassland ecosystems for improved pasture productivity can also enhance their potential to serve as sinks for anthropogenic carbon (C). We assessed the long-term (>22 yr) effects of grassland intensification (conversion of native rangeland to slash pine-bahiagrass silvopasture or bahiagrass-sown pasture) on above- and belowground C stocks in a subtropical ecoregion. Soil cores (0- to 30-cm depth) were collected from five equidistant quadrats (20 × 20 m) established along a diagonal transect within each of the experimental units. Root and aboveground biomass responses to grassland intensification were also evaluated. Management intensification resulted in increased soil organic C (SOC) stocks from 41 Mg ha-1 in the native rangeland to 62 and 69 Mg ha-1 in sown pasture and silvopasture, respectively. Additional C storage occurred in the live biomass of slash pine trees in silvopasture (58 Mg ha-1), while the C accruing to woody biomass in native rangeland (3 Mg ha-1) was lost after conversion to sown pasture. Conversion to tree-integrated silvopastoral ecosystem favored the sequestration of a more stable mineral-associated C fraction (41.8 Mg ha-1; ∼200% increase) compared with the native rangeland. Ecosystem C was greater in silvopasture (144 Mg ha-1) and in sown pasture (83 Mg ha-1) relative to the reference native rangeland (69 Mg ha-1). This research supports growing evidence that increasing intensity of grassland management is beneficial for soil and ecosystem C sequestration in the long term; however, shifts in the allocation of C into ecosystem pools will likely have implication for biochemical cycling within this subtropical ecoregion.

What plant traits tell us: Consequences of land-use change of a traditional agro-forest system on biodiversity and ecosystem service provision

Traditional agro-forest systems (TAFS) link the two ecosystems forest and grassland and are an attractive, species-rich land-use type in the European cultural landscape. In the past decades, particularly in mountainous regions, socio economic changes have resulted in their abandonment or intensification of use. Our study employed plant traits to analyze and understand the consequences that abandonment and intensification have on plant species diversity, functional diversity and the provision of ecosystem services of larch (Larix decidua) grassland, a TAFS in the European Alps. By applying commonly used traits such as growth form and pollination agent, together with less used traits such as flower color and edible or healing plants, we found highest plant species diversity in traditionally managed larch meadows and larch pastures, while functional diversity was seen to be high also in abandoned larch grasslands. We further show that provision of the ecosystem services scenic beauty and pollination is best in traditionally managed larch meadows and larch pastures. Regarding the provision of edible or healing plants, the largest species pool was found in traditionally managed larch meadows, while the highest species coverage was found in intensively managed larch meadows. Summarizing our results, we deduce that both the abandonment and intensification of larch grasslands result in a loss of plant diversity and a decrease in provided ecosystem services. Consequently, enhancement of our knowledge through further investigation of TAFS is essential for the maintenance and conservation of these valuable cultural ecosystems.

Disentangling direct and indirect effects of experimental grassland management and plant functional-group manipulation on plant and leafhopper diversity

BackgroundPlant biodiversity can affect trophic interactions in many ways, including direct bottom-up effects on insects, but is negatively affected by agricultural intensification. Grassland intensification promotes plant productivity, resulting in changes in plant community composition, and impacts on higher trophic levels. Here, we use a novel grassland management experiment combining manipulations of cutting and fertilization with experimental changes in plant functional group composition (independent of management effects) to disentangle the direct and indirect effects of agricultural management on insect herbivore diversity and abundance. We used leafhoppers as model organisms as they are a key insect taxon in grasslands and react rapidly to management changes. Leafhoppers were sampled between May and September 2010 using standardized sweep netting and pan traps.ResultsPlant diversity, functional group composition and management regime in grasslands affected leafhopper species richness and abundance. Higher cutting frequencies directly led to decreasing leafhopper species richness, presumably due to the higher disturbance frequency and the reduction in food-resource heterogeneity. In contrast, fertilizer application had only a small indirect negative effect via enhanced aboveground plant biomass, reduced plant diversity and changes in functional group composition. The manipulated increase in grass cover had contrasting direct and indirect effects on leafhopper species richness: grass cover directly increased leafhopper species richness, but negatively affected plant diversity, which in turn was positively related to leafhopper species richness. In conclusion, insect diversity is driven in complex direct and indirect ways by grassland management, including changes in functional group composition.ConclusionsThe availability of preferred food sources and the frequency of disturbance are important direct and indirect drivers of leafhopper species richness, interacting in complex ways with plant diversity and food resource heterogeneity.

Intensification of grassland and forage use: driving forces and constraints

The increasing demand for safe and nutritional dairy and beef products in a globalising world, together with the needs to increase resource use efficiency and to protect biodiversity, provide strong incentives for intensification of grassland and forage use. This paper addresses the question: ‘Does intensification of grassland and forage use lead to efficient, profitable and sustainable ecosystems?’ We present some notions about intensification of agricultural production, and then discuss the intensification of grassland-based dairy production in The Netherlands, Chile and New Zealand. Finally, we arrive at some conclusions. External driving forces and the need to economise (the law of the optimum) provide strong incentives for intensification, that is, for increasing the output per unit surface area and labour. The three country cases illustrate that intensification of grassland use is a global phenomenon, with winners and losers. Winners are farmers who are able to achieve a high return on investments. Losers are small farmers who drop out of the business unless they broaden their income base. The relationship between intensification and environmental impact is complex. Within certain ranges, intensification leads to increased emissions of nutrients and greenhouse gases to air and use of water per unit surface area, but to decreased emissions when expressed per unit of product. The sustainability of a grassland-based ecosystem is ultimately defined by the societal appreciation of that system and by biophysical and socioeconomic constraints. In conclusion, intensification may lead to more efficient and profitable and, thereby, more sustainable grassland ecosystems. This holds especially for those systems that are currently not sustainable because they are either underutilised and of low productivity or over-exploited and unregulated, and as long as the adapted systems meet societal and ecological constraints.

Coupling carbon and nitrogen cycles for environmentally sustainable intensification of grasslands and crop-livestock systems

The C sequestration capacity of grassland soils depends on both the net primary production of the ecosystem that determines the C flows from atmosphere to vegetation and soil, and on the mean residence time of C within the different compartments. Within grassland ecosystems, C and N cycles are strongly coupled by elemental stoichiometry of plant autotrophy and of soil microbial heterotrophy. Plasticity in plant form and function, plant species diversity and regulation of biological N fixation all contribute to stabilize the C:N ratio of organic matter inputs to soil. Soil processes such as the priming effect and nitrate leaching tend to restore stoichiometry by releasing elements in excess. Nevertheless, domestic herbivores tend to uncouple the C and N cycles, by releasing digestible C as CO2 and CH4, and by returning digestible N at high concentrations in urine patches. At low stocking density, herbivores enhance soil N cycling and net primary productivity, leading to an increased soil C sequestration, which however declines at high stocking density. Assuming no overgrazing, the environmental impacts of grassland intensification are therefore controlled by a trade-off between increased C–N coupling by vegetation and increased C–N decoupling by animals. Stimulation of vegetation by adequate N and P fertilizer applications increases the C flows from the atmosphere to the soil, while increasing stocking density reduces mean C residence time within the system.Intensification of grassland productivity by manipulation of both primary production and stocking density leads to complex responses in terms of environmental impacts: as intensification increases, positive impacts, such as C sequestration are progressively impaired by negative impacts linked to excessive active N forms. Hence, in each unique environmental setting, a threshold level of grassland intensification can be determined above which any additional animal production would be associated with unacceptable environmental risks. Improved grassland management and integration with crop systems may help minimize the harmful environmental effects of C–N decoupling by domestic herbivores, thereby enhancing synergies among food production, biodiversity and various other ecosystem services.

Advances in the conservation of dry grasslands: Introduction to contributions from the seventh European Dry Grassland Meeting

Dry grasslands in Europe are mostly of zoo-anthropogenic origin, but nevertheless they are among the most diverse plant communities of the world at small spatial scales, and they support a significant proportion of the biodiversity of the continent. Both agricultural intensification and abandonment of former dry grasslands caused dramatic losses in area and quality of this habitat type during recent decades. Here we report from the 7th European Dry Grassland Meeting, organised by the European Dry Grassland Group (EDGG) in Smolenice, Slovakia, in 2010. Under the motto “Succession, restoration and management of dry grasslands” one hundred researchers from throughout Europe discussed conservation issues of this threatened habitat type. We give a brief introduction to those nine articles that are included in this Special Feature. With contributions from many different countries and various dry grassland types, they address issues of conservation value, succession, management as well as regeneration and restoration. We conclude that the diversity of dry grasslands and their conservation problems require further research to develop adequate management techniques under changing frame conditions. However, also the frame conditions, such as the incentives for certain land use practices provided by the Common Agricultural Policy of the European Union need to be addressed if long-term success in conservation of dry grasslands is intended.

The importance of pre‐thicket conifer plantations for nesting Hen Harriers Circus cyaneus in Ireland

Hen Harriers Circus cyaneus are threatened across much of their range and their conservation requires appropriate habitat management. The locations of 148 Hen Harrier nests found in the Republic of Ireland during national breeding surveys in 2000 and 2005 were used to assess nest‐site selection. The distribution of these nests was compared to distributions of randomly located points to investigate selection at the scale of the nest‐site and landscape. The main nesting habitats selected were pre‐thicket stage of first and, particularly, second rotation plantations, mostly of exotic conifers. There was no evidence that the area of post‐closure plantations negatively affected Hen Harrier nest distribution. There was a positive correlation across study areas between changes in numbers of Hen Harrier nests between 2000 and 2005 and changes in the area of pre‐thicket second rotation plantations over the same period. The overall effect of plantation forests on breeding Hen Harriers in Ireland therefore appears to be positive. However, this study did not consider the effects of plantation habitats on breeding success. Improved grassland was strongly avoided as a nesting habitat. Furthermore, after controlling for the influence of nesting habitat on nest location, landscapes with a high percentage cover of improved grassland were also avoided. Further agricultural intensification of grassland in areas where Hen Harriers breed is likely to have a negative impact on this species. These results are required for the development of management strategies for the conservation of this species.

Use of unimproved and improved lowland grassland by wintering birds in the UK

In the last 50 years, intensification of agricultural grassland management has led to over 97% of all grassland being ‘improved’ in the UK. Despite grassland being an important habitat for birds in Europe, both in terms of area and preference by several species of conservation concern, the impact of grassland intensification on both breeding and wintering birds is poorly understood. This study compared habitat characteristics and bird diversity, in winter, between improved and unimproved lowland grassland in England comprising 44 unimproved fields (350 ha) and 59 improved fields (290 ha) at 7 paired sites. Key habitat differences were found between grassland types. These included, on improved fields, a denser sward, less surface water, more dung flies and more fields with seeding grass. Species that are dependent on soil invertebrates (particularly earthworms) were found to be more numerous on unimproved grassland, whilst generalist insectivores such as corvids were much more numerous on improved grassland. Grassland improvement may have been one important factor behind the recent increases in numbers of some corvid species in the UK.

Environmental Impacts of Nitrogen and Phosphorus Cycling in Grassland Systems

Agricultural intensification of grassland has led to serious imbalances between inputs of nutrients (in purchased fertilizers, feeds and atmospheric deposition) and outputs (mainly milk and meat). Excess nutrients are lost into the wider environment with consequences for soil, water and atmospheric quality. This paper examines the environmental impacts of nitrogen and phosphorus use by the grassland-based agricultural industry of Northern Ireland. Results are presented from a recently completed experimental programme, which was undertaken to define the losses associated with nitrogen inputs to grazed grassland. Also examined is the contention that P use in grassland agriculture is now the major cause of the P enrichment of Lough Neagh, the largest lake in the British Isles. A combination of strategies involving fertilizer management, manure management and dietary manipulation can have a significant impact on the flow and excesses of N and P in grassland systems. However, the rate at which improved management strategies will be introduced in practice depends on regulatory controls, the applicability of new techniques and the financial implications.

Environmental modifications for improved grassland production

Abstract The most important environmental limitations to grassland production are set by the moisture regime, the physiography, soil conditions, temperature, vegetation present, entomological and microbiological factors of the environment. The significant features of these factors are discussed. Modifications which can be applied to overcome these limitations and the resultant degree of grassland intensification (veld, reinforced veld and planted pastures) which can be achieved are suggested and illustrated by means of diagrams. The result of the modifications is determined by the factor which places the greatest limitation on herbage production. Improved grassland productivity resulting from modification of the environment can be spectacular and is illustrated by specific examples.