Pattern and process in above-ground and below-ground components of grassland ecosystems

Abstract. This paper describes patterns of below-ground components in grassland ecosystems. It provides estimates of the contribution of below-ground organs to the total phytomass of the community and of different species to the below-ground phytomass; it describes the distribution of above- and below- ground organs of different species and the spatial and temporal correlation between above-ground and below-ground phyto-mass – both total standing crop and net primary production. 10 Siberian grasslands (meadows and steppes) were investigated during 15 yr. Ca. 70 % of the living phytomass is located in the soil and no less than 70 % of the net primary production is allocated in below-ground organs. Phytomass distribution in the soil layer is more homogeneous than above-ground. For some species the spatial distribution within 1-m² plots of the green and below-ground phytomass is similar, for others it is quantitatively or qualitatively different. According to the dominance-diversity curve, the above-ground size hierarchy is much stronger than the below-ground one. The active growth of above- and below-ground organs of a species may occur at different times of the season and it varies from year to year. Allocation of organic substances to rhizomes and roots occurs simultaneously and with proportional intensity.     

Ecosystems succession and biological turnover

Ecosystem succession and development of biological turnover are analyzed in a succession series from solonchakous meadow to meadow steppe in the forest steppe zone of Western Siberia. Characteristics of flow processes, biological turnover, and functional and structural diversity of ecosystems are considered. From the initial stages of succession to the final ones the intensity of abiotic flows drops, the degree of openness of the ecosystem decreases sharply and the role of biological turnover grows. The reserves of chemical elements in biomass, net primary production and biogeocenotic activity are maximal at the intermediate stages of succession. Humus reserves in soil increase from the initial stages of succession to the final ones. The diversity of soil processes is maximal at the initial stage of succession, the diversity of life form types, cenotic groups and ecological types of plants at the intermediate stages, and species diversity-in the final stage.     

Effects of above-ground plant species composition and diversity on the diversity of soil-borne microorganisms

A coupling of above-ground plant diversity and below-ground microbial diversity has been implied in studies dedicated to assessing the role of macrophyte diversity on the stability, resilience, and functioning of ecosystems. Indeed, above-ground plant communities have long been assumed to drive below-ground microbial diversity, but to date very little is known as to how plant species composition and diversity influence the community composition of micro-organisms in the soil. We examined this relationship in fields subjected to different above-ground biodiversity treatments and in field experiments designed to examine the influence of plant species on soil-borne microbial communities. Culture-independent strategies were applied to examine the role of wild or native plant species composition on bacterial diversity and community structure in bulk soil and in the rhizosphere. In comparing the influence of Cynoglossum officinale (hound's tongue) and Cirsium vulgare (spear thistle) on soil-borne bacterial communities, detectable differences in microbial community structure were confined to the rhizosphere. The colonisation of the rhizosphere of both plants was highly reproducible, and maintained throughout the growing season. In a separate experiment, effects of plant diversity on bacterial community profiles were also only observed for the rhizosphere. Rhizosphere soil from experimental plots with lower macrophyte diversity showed lower diversity, and bacterial diversity was generally lower in the rhizosphere than in bulk soil. These results demonstrate that the level of coupling between above-ground macrophyte communities and below-ground microbial communities is related to the tightness of the interactions involved. Although plant species composition and community structure appear to have little discernible effect on microbial communities inhabiting bulk soil, clear and reproducible changes in microbial community structure and diversity are observed in the rhizosphere. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structural equation modelling reveals plant-community drivers of carbon storage in boreal forest ecosystems

Boreal forest ecosystems are important drivers of the global carbon (C) cycle by acting as both sinks and sources of atmospheric CO₂. While several factors have been proposed as determining the ability of boreal forest to function as C sinks, little is known about their relative importance. In this study, we applied structural equation modelling to a previously published dataset involving 30 boreal-forested islands that vary greatly in their historic fire regime, in order to explore the simultaneous influence of several factors believed to be important in influencing above-ground, below-ground and total ecosystem C accumulation. We found that wildfire was a major driver of ecosystem C sequestration, and exerted direct effects on below-ground C storage (presumably through humus combustion) and indirect effects on both above-ground and below-ground C storage through altering plant-community composition. By contrast, plant diversity influenced only below-ground C storage (and even then only weakly), while net primary productivity and decomposition had no detectable effect. Our results suggest that while boreal forests have great potential for storing significant amounts of C, traits of dominant plant species that promote below-ground C accumulation and the absence of wildfire are the most important drivers of C sequestration in these ecosystems.     

Concordance between plant species,oribatid mites and soil in a Mediterranean stone pine forest

Biological interactions between above-ground and below-ground organisms are not clearly defined among communities with regard to compositional patterns. The study investigates the concordance of species assemblages between vascular plants and oribatid mites and soil chemical properties with special attention to the role of vegetation structure, i.e. tree, shrub and herbaceous cover, for biological components. Data were collected in a Mediterranean coastal Nature Reserve using sampling design based on random selection of plots with cover of stone pine (Pinus pinea L.) exceeding 15%. Agreement of distribution patterns was verified by Spearman’s rank correlation coefficient applied to pairs of matrices of plot scores by principal component analysis (plants, mites and soil) and the Mantel test. The feasible role of vegetation cover on plant and mite assemblages was tested by redundancy analysis (RDA). Significant correlations were found for biological assemblages, indicating congruent plant–mite compositional patterns. On the other hand, the hypothesis of concordance between biological communities and soil was rejected. Moreover, RDA showed that vegetation cover was a driver of both plant and oribatid mite assemblages. In particular, herbaceous cover proved to be a good proxy for the two biological communities investigated, with different taxa linked to forest clearings and to areas with denser tree cover. Our results indicate that soil features were not of primary importance for below-ground and above-ground community assemblages in the study area. In the light of our findings and ongoing threats in coastal areas, we recommend that management measures be directed at maintenance of diversified vegetation structure, which may ensure above-ground and below-ground biodiversity with diverse biological community assemblages.     

Carbon balance of a tropical savanna of northern Australia

Through estimations of above- and below-ground standing biomass, annual biomass increment, fine root production and turnover, litterfall, canopy respiration and total soil CO₂ efflux, a carbon balance on seasonal and yearly time-scales is developed for a Eucalypt open-forest savanna in northern Australia. This carbon balance is compared to estimates of carbon fluxes derived from eddy covariance measurements conducted at the same site. The total carbon (C) stock of the savanna was 204±53 ton C ha^–1, with approximately 84% below-ground and 16% above-ground. Soil organic carbon content (0–1 m) was 151±33 ton C ha^–1, accounting for about 74% of the total carbon content in the ecosystem. Vegetation biomass was 53±20 ton C ha^–1, 39% of which was found in the root component and 61% in above-ground components (trees, shrubs, grasses). Annual gross primary production was 20.8 ton C ha^–1, of which 27% occurred in above-ground components and 73% below-ground components. Net primary production was 11 ton C ha^–1 year^–1, of which 8.0 ton C ha^–1 (73%) was contributed by below-ground net primary production and 3.0 ton C ha^–1 (27%) by above-ground net primary production. Annual soil carbon efflux was 14.3 ton C ha^–1 year^–1. Approximately three-quarters of the carbon flux (above-ground, below-ground and total ecosystem) occur during the 5–6 months of the wet season. This savanna site is a carbon sink during the wet season, but becomes a weak source during the dry season. Annual net ecosystem production was 3.8 ton C ha^–1 year^–1.     

Understory Plant Community Composition Is Associated with Fine-Scale Above- and Below-Ground Resource Heterogeneity in Mature Lodgepole Pine (Pinus contorta) Forests

Understory plant communities play critical ecological roles in forest ecosystems. Both above- and below-ground ecosystem properties and processes influence these communities but relatively little is known about such effects at fine (i.e., one to several meters within-stand) scales, particularly for forests in which the canopy is dominated by a single species. An improved understanding of these effects is critical for understanding how understory biodiversity is regulated in such forests and for anticipating impacts of changing disturbance regimes. Our primary objective was to examine the patterns of fine-scale variation in understory plant communities and their relationships to above- and below-ground resource and environmental heterogeneity within mature lodgepole pine forests. We assessed composition and diversity of understory vegetation in relation to heterogeneity of both the above-ground (canopy tree density, canopy and tall shrub basal area and cover, downed wood biomass, litter cover) and below-ground (soil nutrient availability, decomposition, forest floor thickness, pH, and phospholipid fatty acids (PLFAs) and multiple carbon-source substrate-induced respiration (MSIR) of the forest floor microbial community) environment. There was notable variation in fine-scale plant community composition; cluster and indicator species analyses of the 24 most commonly occurring understory species distinguished four assemblages, one for which a pioneer forb species had the highest cover levels, and three others that were characterized by different bryophyte species having the highest cover. Constrained ordination (distance-based redundancy analysis) showed that two above-ground (mean tree diameter, litter cover) and eight below-ground (forest floor pH, plant available boron, microbial community composition and function as indicated by MSIR and PLFAs) properties were associated with variation in understory plant community composition. These results provide novel insights into the important ecological associations between understory plant community composition and heterogeneity in ecosystem properties and processes within forests dominated by a single canopy species.     

Below-ground spatial pattern of rhizomes in a grassland community and its relevance to above-ground spatial pattern

Studies of spatial patterns in grassland plant communities have focused on above-ground patterns, ignoring the fact that in clonal plant communities, such as those found in grasslands, above-ground spatial structure must reflect below-ground horizontal growth. The present study examines, at both a fine and a coarse spatial scale, relationships between rhizome and ramet distribution. At the coarse scale, the dominance of species differed between above- and below-ground; some species dominated only above- or below-ground, and others dominated in both layers. At the fine scale, a single species' ramet aggregation above-ground significantly differed from its rhizome aggregation below-ground, for many species. Even for a given species, quantitative relationships between above- and below-ground dominance varied among localities. The variation in spatial pattern among species can be explained by attributes of clonal growth form, including rhizome size, rhizome origin and pattern of above-ground ramet aggregation. Using these parameters of clonal growth, four major space occupation patterns were described for mountain grassland species. For species with a high abundance of evenly distributed rhizomes, ramets either i) reflect rhizome distribution, or ii) do not fully reflect rhizome distribution, but rather are spatially aggregated, and rhizomes are typically developed below-ground. For species with a low abundance of rhizomes, ramets either iii) reflect rhizome distribution and rhizomes are typically of above-ground origin, or iv) do not reflect rhizome distribution and are aggregated only at the growing tips of rhizomes. Spatial correlation above-ground among species was the same as below-ground for some pairs of species but was significantly different for other pairs. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of different clipping intensities on above- and below-ground production in simulated herbaceous plant communities

We studied the effect of clipping on above- and below-ground production in different plant communities through a factorial experiment. We designed five pasture systems with different species composition, perennials/annuals ratio and soil water availability, recreating different altitudinal locations, and simulated a gradient of grazing intensity by clipping with different heights and frequencies. Response patterns of above- and below-ground production were similar, increasing with the higher clipping frequency and decreasing with altitude. These results suggest that high grazing intensity stimulate above-ground production, but only in certain situations of species composition, density, diversity, perennials/annuals ratio and water availability. This stimulus, however, is unsustainable over time, and the lower clipping frequencies are those that favour the maintenance of production.     

Structure,productivity and energy flow in an alpine grassland in the Garhwal Himalaya

Abstract. Structure, primary production and energy flow were studied in ungrazed and grazed alpine meadows in the Garhwal Himalaya, India. In grazed grasslands, the cover of graminoids increased, the biomass of palatable species was reduced by about 50%, but the biomass of unpalatable species increased, due to reduced competition from the better-foraged species. Generally, 32% of live shoot and root biomass was consumed during a growing season. Also, above-ground plant productivity increased as a result of plant regrowth, while below-ground productivity decreased. Flow and storage of energy in ungrazed and grazed alpine grasslands showed an accumulation of 10.1 and 8.5 kJ/yr with energy conversion efficiencies of 0.7 and 0.6% respectively. Ca. 46% of the net energy accumulated was consumed by herbivores on the grazed grassland. Only 26% of the net captured energy disappeared from the system in the growing season, mainly via root and litter decomposition.     

Below-ground herbivory limits induction of extrafloral nectar by above-ground herbivores

Background and Aims Many plants produce extrafloral nectar (EFN), and increase production following above-ground herbivory, presumably to attract natural enemies of the herbivores. Below-ground herbivores, alone or in combination with those above ground, may also alter EFN production depending on the specificity of this defence response and the interactions among herbivores mediated through plant defences. To date, however, a lack of manipulative experiments investigating EFN production induced by above- and below-ground herbivory has limited our understanding of how below-ground herbivory mediates indirect plant defences to affect above-ground herbivores and their natural enemies.Methods In a greenhouse experiment, seedlings of tallow tree (Triadica sebifera) were subjected to herbivory by a specialist flea beetle (Bikasha collaris) that naturally co-occurs as foliage-feeding adults and root-feeding larvae. Seedlings were subjected to above-ground adults and/or below-ground larvae herbivory, and EFN production was monitored.Key Results Above- and/or below-ground herbivory significantly increased the percentage of leaves with active nectaries, the volume of EFN and the mass of soluble solids within the nectar. Simultaneous above- and below-ground herbivory induced a higher volume of EFN and mass of soluble solids than below-ground herbivory alone, but highest EFN production was induced by above-ground herbivory when below-ground herbivores were absent.Conclusions The induction of EFN production by below-ground damage suggests that systemic induction underlies some of the EFN response. The strong induction by above-ground herbivory in the absence of below-ground herbivory points to specific induction based on above- and below-ground signals that may be adaptive for this above-ground indirect defence.     

Spatial patterns of plant diversity below-ground as revealed by DNA barcoding

Our understanding of the spatial organization of root diversity in plant communities and of the mechanisms of community assembly has been limited by our ability to identify plants based on root tissue, especially in diverse communities. Here, we test the effectiveness of the plastid gene rbcL, a core plant DNA barcoding marker, for investigating spatial patterns of root diversity, and relate observed patterns to above-ground community structure. We collected 3800 root fragments from four randomly positioned, 1-m-deep soil profiles (two vertical transects per plot), located in an old-field community in southern Ontario, Canada, and extracted and sequenced DNA from 1531 subsampled fragments. We identified species by comparing sequences with a DNA barcode reference library developed previously for the local flora. Nearly 85% of sampled root fragments were successfully sequenced and identified as belonging to 29 plant species or species groups. Root abundance and species richness varied in horizontal space and were negatively correlated with soil depth. The relative abundance of taxa below-ground was correlated with their frequency above-ground (r = 0.73, P = 0.0001), but several species detected in root tissue were not observed in above-ground quadrats. Multivariate analyses indicated that diversity was highly structured below-ground, and associated with depth, root morphology, soil chemistry and soil texture, whereas little structure was evident above-ground. Furthermore, analyses of species co-occurrence indicates strong species segregation overall but random co-occurrence among confamilials. Our results provide insights into the role of environmental filtering and competitive interactions in the organization of plant diversity below-ground, and also demonstrate the utility of barcoding for the identification of plant roots.     

Nitrogen losses from perennial grass species

Nitrogen losses from plants may occur through a variety of pathways, but so far, most studies have only quantified losses of nutrients by above-ground litter production. We used ¹⁵N pulse labelling to quantify total nitrogen losses from above- and below-ground plant parts. Using this method we were able to include also pathways other than above-ground litter production. To test the hypothesis that species from nutrient-poor habitats lose less nitrogen than species from more fertile soils, six perennial grasses from habitats with a wide range of nutrient availability were investigated: Lolium perenne, Arrhenatherum elatius, Anthoxanthum odoratum, Festuca rubra, F. ovina and Molinia caerulea. The results of an experiment carried out in pots in a green-house at two fertility levels show that statistically significant losses occur through pathways other than above-ground litter production. In the low fertility treatment, most (70%) losses from L. perenne occurred by litter production, but in Ar. elatius, F. rubra, F. ovina and M. caerulea, more than 50% of labelled N losses took place by root turn-over, leaching or exudation from roots. When nutrient supply increased, the ¹⁵N losses in above-ground dead material increased in all species and in Ar. elatius, A. odoratum and F. rubra the ¹⁵N losses via other pathways decreased. Ranked according to decreasing turnover coefficient the sequence of species was: L. perenne, A. odoratum, F. rubra, F. ovina, Ar. elatius, M. caerulea. These results suggest that species adapted to sites with low availability of nutrients lose less nitrogen (including above- and below-ground losses) than species adapted to more fertile soils.     

Lack of competition between barnacle geese Branta leucopsis and pink-footed geese Anser brachyrhynchus during the pre-breeding period in Svalbard

The feeding ecology of barnacle geese and pink-footed geese was studied in Sassendalen, Svalbard during the pre-nesting period (late May) to assess the potential for inter-specific competition. Barnacle geese fed almost exclusively (97%) by grazing above-ground plant material, mostly (79%) along snow edges in moss-mat habitats. Pink-footed geese fed mostly (93%) by excavating below-ground parts of plants, mostly (56%) away from snow and were more evenly distributed between habitat types. Barnacle goose faeces contained mostly (62%) moss, that of pink-footed geese mostly (48%) below-ground plant storage organs (especially Bistorta viviparum L.). Principal components analysis of dropping contents showed no overlap in species diet in allopatry or sympatry. There was little overlap in diet and feeding ecology of the two species at this pre-nesting feeding site. Hence, unless increased goose feeding densities affect future vegetation density and composition, under present circumstances, increasing numbers of either species is unlikely to affect foraging conditions for the other at this important stage in the annual cycle. However, such changes could have local density-dependent intra-specific effects.     

A comparison of the annual production and biomass in three monospecific stands of the seagrass Thalassia hemprichii (Ehrenb.) aschers.

Annual production and biomass data were collected in three seagrass communities of Thalassia hemprichii (Ehrenb.) Aschers. from Papua New Guinea. Leaf growth rates, determined by the marking technique, resulted in a growth rate of 8.3 mm day^?1 for the youngest leaves. Production of above-ground plant parts was assessed by the plastochrone interval. The annual mean values were 9.3, 10.0 and 9.9 days for Sites 1, 2 and 3, respectively. Annual mean total above-ground production amounted to 2.1 mg ADW shoot^?1 day^?1 at Site 1, and 5.5 and 4.5 mg ADW shoot^?1 day^?1 for Sites 2 and 3, respectively; 73–89% of the total net production was contributed by the leaves. Rhizome production was correlated to the plastochrone interval of the leaves. Annual mean biomass of leaves amounted to 16–27% of the total biomass. The mean biomass of the other plant parts remained constant during the year. The annual mean turnover time of the different plant parts (above- and below-ground) varied considerably between the sites.     

人工林生产力年龄效应及衰退机理研究进展

研究人工林生长规律具有重要的经济和生态意义。同龄林林分郁闭后,地上部净初级生产量随着林龄增加而降低的现象近几十年引起了林业工作者的兴趣和注意并成为研究热点。多数研究试图通过光合生理、林分营养、生物量分配和林分结构等随林龄的变化规律来解释林分生产力衰退机理。研究认为,林分郁闭后水分传输阻力的增加减少了树木的光合能力;林地养分的减少使得根系生物量分配增加,导致林分叶面积减少,树木光合能力下降;对资源的竞争使得树木优势度发生变化,资源利用率降低。光合能力、林分叶面积和资源利用率的降低以及根系生物量分配的增加是林分生产力衰退的关键,而林分呼吸和林木衰老的作用不大。今后深入研究树体水分运输及其补偿机制、逆境下根系的生长过程及适应机制,并跟踪研究林分生长规律,更有助于揭示人工林生产力衰退的实质。     

Facilitation and inhibition: changes in plant nitrogen and secondary metabolites mediate interactions between above-ground and below-ground herbivores

To date, it remains unclear how herbivore-induced changes in plant primary and secondary metabolites impact above-ground and below-ground herbivore interactions. Here, we report effects of above-ground (adult) and below-ground (larval) feeding by Bikasha collaris on nitrogen and secondary chemicals in shoots and roots of Triadica sebifera to explain reciprocal above-ground and below-ground insect interactions. Plants increased root tannins with below-ground herbivory, but above-ground herbivory prevented this increase and larval survival doubled. Above-ground herbivory elevated root nitrogen, probably contributing to increased larval survival. However, plants increased foliar tannins with above-ground herbivory and below-ground herbivory amplified this increase, and adult survival decreased. As either foliar or root tannins increased, foliar flavonoids decreased, suggesting a trade-off between these chemicals. Together, these results show that plant chemicals mediate contrasting effects of conspecific larval and adult insects, whereas insects may take advantage of plant responses to facilitate their offspring performance, which may influence population dynamics.     

Comparison of early development of three grasses: Lolium perenne, Agrostis stolonifera and Poa pratensis

BACKGROUND AND AIMS: To improve the management of grass communities, early plant development was compared in three species with contrasting growth forms, a caespitose (Lolium perenne), a rhizomatous (Poa pratensis) and a caespitose-stoloniferous species (Agrostis stolonifera). METHODS: Isolated seedlings were grown in a glasshouse without trophic constraints for 37 d (761 degrees Cd). The appearance of leaves and their location on tillers were recorded. Leaf appearance rate (LAR) on the tillers and site-filling were calculated. Tillering was modelled based on the assumption that tiller number increases with the number of leaves produced on the seedling main stem. Above- and below-ground parts were harvested to compare biomass. KEY RESULTS: Lolium perenne and A. stolonifera expressed similar bunch-type developments. However, root biomass was approx. 30 % lower in A. stolonifera than in L. perenne. Poa pratensis was rhizomatous. Nevertheless, the ratio of above-ground : below-ground biomass of P. pratensis was similar to that of L. perenne. LAR was approximately equal to 0.30 leaf d(-1) in L. perenne, and on the main stem and first primary tillers of A. stolonifera. LAR on the other tillers of A. stolonifera was 30 % higher than on L. perenne. For P. pratensis, LAR was 30 % lower than on L. perenne, but the interval between the appearance of two successive shoots from rhizomes was 30 % higher than the interval between two successive leaf stages on the main stem. Above-ground parts of P. pratensis first grew slower than in the other species to the benefit of the rhizomes, whose development enhanced tiller production. CONCLUSIONS: Lolium perenne had the fastest tiller production at the earliest stages of seedling development. Agrostis stolonifera and P. pratensis compensated almost completely for the delay due to higher LAR on tillers or ramets compared with L. perenne. This study provides a basis for modelling plant development.     

Study on Over-compensation Growth of Cleistogenes squarrosa Population in Inner Mongolia Steppe

Cleistogenes squarrosa ((Trin.) Keng) is a C4 plant and a short, perennial grass with drought tolerance that tends to occupy the medium degradation grassland in Inner Mongolia steppe. It is an ideal plant suitable for the studies on compensation or over-compensation growth because its important value of population is the maximum in the medium disturbance in Inner Mongolia steppe. The results showed that the over-compensation existed for net primary productivity (NPP) of Cleistogenes squarrosa population because the plant morphotypes remaining in the population were characterized by a higher density with small individual plant in moderate stocking rate (1.33 sheep·hm-2 during 138 days of growth seasons). As for an individual plant, grazing reduced the height and biomass per plant, but the above-ground net photosynthesis efficiency or above-ground net primary productivity (ANPP) was increased and it almost did not affect the below-ground net primary productivity (BNPP) in the moderate stocking rate. However, the lower compensation of ANPP was a greater cost with BNPP in heavy stocking rate (>4.00 sheep·hm-2 during 138 days of growth season). From this study, it appears that the plant-herbivore association might be regarded as mutualistic in moderate grazing because not only the ANPP of the population was increased, but also was the efficiency of herbage utilization. However, the compensation of ANPP was attained at the cost of BNPP, therefore, the association between plant and herbivore might trade-off in heavy grazing because the temporary higher efficiency of herbage utilization could not keep the sustainable development of the population. The results support the grazing optimization hypothesis.     

Early recovery signs of an Australian grassland following the management of Parthenium hysterophorus L.

Parthenium weed (Parthenium hysterophorus L.) is believed to reduce the above- and below-ground plant species diversity and the above-ground productivity in several ecosystems. We quantified the impact of this invasive weed upon species diversity in an Australian grassland and assessed the resulting shifts in plant community composition following management using two traditional approaches. A baseline plant community survey, prior to management, showed that the above-ground community was dominated by P. hysterophorus, stoloniferous grasses, with a further high frequency of species from Malvaceae, Chenopodiaceae and Amaranthaceae. In heavily invaded areas, P. hysterophorus abundance and biomass was found to negatively correlate with species diversity and native species abundance. Digitaria didactyla Willd. was present in high abundance when P. hysterophorus was not, with these two species, contributing most to the dissimilarity seen between areas. The application of selective broad leaf weed herbicides significantly reduced P. hysterophorus biomass under ungrazed conditions, but this management did not yet result in an increase in species diversity. In the above-ground community, P. hysterophorus was partly replaced by the introduced grass species Cynodon dactylon L. (Pers.) 1 year after management began, increasing the above-ground forage biomass production, while D. didactyla replaced P. hysterophorus in the below-ground community. This improvement in forage availability continued to strengthen over the time of the study resulting in a total increase of 80% after 2 years in the ungrazed treatment, demonstrating the stress that grazing was imposing upon this grassland-based agro-ecosystem and showing that it is necessary to remove grazing to obtain the best results from the chemical management approach.