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Productive Grasslands (productive + grassland)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Resource regulation by a twig-girdling beetle has implications for desertification

ECOLOGICAL ENTOMOLOGY, Issue 2 2008
B. D. DUVAL
Abstract 1.,Resource regulation by insects is the phenomenon by which herbivory enhances resources for the progeny of the herbivore. This report provides an example of resource regulation with implications for desertification in the Chihuahuan Desert of North America. 2.,Female Oncideres rhodosticta beetles chew girdles around mesquite (Prosopis glandulosa) stems before ovipositing in those stems. The mesquite plants respond by producing compensatory stems below the girdle. Mesquite volume was significantly correlated with the total number of beetle girdles across a suite of low shrub density grassland and high shrub density dune sites, and plants in dune sites had more old and new girdles than mesquite in grasslands. 3.,Smaller, younger shrubs in grassland responded more vigorously to girdling than did larger, older shrubs in dune landscapes. Stems on shrubs within grassland produced significantly more and longer compensatory stems per girdle than stems on shrubs in dunes. Soil capture by individual plants positively correlated with stem density, and stem density is increasing in the younger plants as a response to beetle damage. 4.,This study suggests that the interaction between O. rhodosticta and mesquite is an example of resource regulation that increases the stem density and soil capture ability of mesquite. Because the conversion of productive grasslands to mesquite dune landscapes is one of the most important drivers of desertification in the Chihuahuan Desert, feedbacks between organisms that promote an increase in the size and soil capture ability of mesquite may exacerbate desertification. [source]

Enhancing diversity of species-poor grasslands: an experimental assessment of multiple constraints

JOURNAL OF APPLIED ECOLOGY, Issue 1 2007
RICHARD F. PYWELL
Summary 1Many grasslands in north-west Europe are productive but species-poor communities resulting from intensive agriculture. Reducing the intensity of management under agri-environment schemes has often failed to increase botanical diversity. We investigated biotic and abiotic constraints on diversification by manipulating seed and microsite availability, soil fertility, resource competition, herbivory and deficiencies in the soil microbial community. 2The effectiveness of 13 restoration treatments was investigated over 4 years in a randomized block experiment established in two productive grasslands in central-east and south-west England. 3Severe disturbance involving turf removal followed by seed addition was the most effective and reliable means of increasing grassland diversity. Disturbance by multiple harrowing was moderately effective but was enhanced by molluscicide application to reduce seedling herbivory and by sowing the hemiparasite Rhinanthus to reduce competition from grasses. 4Low-level disturbance by grazing or slot-seeding was ineffective in increasing diversity. Inoculation with soil microbial communities from species-rich grasslands had no effect on botanical diversity. Nitrogen and potassium fertilizer addition accelerated off-take of phosphorus in cut herbage but did not cause a reduction in soil phosphorus or increase botanical diversity. 5Different grazing management regimes had little impact on diversity. This may reflect the constraining effect of the July hay cut on species dispersal and colonization. 6Synthesis and applications. Three alternative approaches to grassland diversification, with different outcomes, are recommended. (i) High intervention deturfing, which would create patches with low competitive conditions for rapid and reliable establishment of the target community. For reasons of cost and practicality this can only be done over small areas but will form source populations for subsequent spread. (ii) Moderate intervention (harrowing or slot-seeding) over large areas, which would establish a limited number of desirable, generalist species that perform well in restoration. This method is low cost and rapid but the increases in biodiversity are less predictable. (iii) Phased restoration, which would complement the above approaches. Productivity and competition are reduced over 3,5 years using Rhinanthus or fertilizers to accelerate phosphorus off-take. After this time harrowing and seeding should allow a wide range of more specialist species to establish. However, further research is required to determine the long-term effectiveness of these approaches. [source]

Long-term effects of cutting frequency and liming on soil chemical properties, biomass production and plant species composition of Lolio-Cynosuretum grassland after the cessation of fertilizer application

APPLIED VEGETATION SCIENCE, Issue 3 2010
Michal Hejcman
Abstract Question: Is there any effect of cutting frequency and liming on P and K availability in the soil, biomass production and plant species composition after cessation of fertilizer application? Location: Eifel Mountains, SW Germany. Methods: The long-term Grassland Extensification and Nutrient Depletion Experiment was established on a fertilized and mown pasture (Lolio-Cynosuretum) in 1993. Treatments were: (1) two cuts per year without liming, (2) two cuts with liming, (3) four cuts without liming, (4) four cuts with liming and (5) continued intensive mowing as the control. Results: From 1993 to 2006, the plant available P concentration in the soil decreased substantially, whereas K concentration decreased only slightly. Biomass production decreased from 7 to 5 t DM ha,1. These trends were affected by cessation of NPK fertilizer application but not by cutting frequency or liming. In 2007, substantial differences in species composition between the control and the two-cut and four-cut treatments were recorded, whereas liming had no effect. Higher species richness was recorded in cut treatments compared to the control, but no effects of cutting frequency or liming were observed. Ellenberg indicator values indicated that soil nutrients influenced changes in species composition only marginally. Conclusions: The decrease in productivity and available soil P and K in favor of species richness was not achieved to any greater extent by four cuts than by two cuts, or by lime application. Although species richness slightly increased, we conclude that the restoration of low productive grasslands cannot be achieved by cutting management. [source]

Perennial grassland dynamics on fertile plains: Is coexistence mediated by disturbance?

AUSTRAL ECOLOGY, Issue 2 2008
TOM LEWIS
Abstract The response of grasslands to disturbance varies with the nature of the disturbance and the productivity of the landscape. In highly productive grasslands, competitive exclusion often results in decreased species richness and grazing may allow more species to coexist. Once widespread, grasslands dominated by Dichanthium sericeum (Queensland bluegrass) and Astrebla spp. (Mitchell grass) occur on fertile plains but have been reduced in extent by cultivation. We tested the effects of exclusion of livestock grazing on these grasslands by comparing the floristic composition of sites in a nature reserve with an adjacent stock reserve. In addition, sites that had been cultivated within the nature reserve were compared with those where grazing but no cultivation had occurred. To partition the effects of temporal variation from spatial variation we sampled sites in three different years (1998, 2002 and 2004). Some 194 taxa were recorded at the nature reserve and surrounding stock routes. Sampling time, the occurrence of past cultivation and livestock grazing all influenced species composition. Species richness varied greatly between sampling periods relating to highly variable rainfall and water availability on heavy clay soils. Native species richness was significantly lower at previously cultivated sites (13,22 years after cultivation), but was not significantly influenced by grazing exclusion. After 8 years it appears that reintroducing disturbance in the form of livestock grazing is not necessary to maintain plant species richness in the reserve. The highly variable climate (e.g. droughts) probably plays an important role in the coexistence of species by negating competitive exclusion and allowing interstitial species to persist. [source]