Tall-grass Communities Research Articles

Dynamics of Seed Productivity of the Endemic Species Anemonastrum biarmiense (Juz.) Holub (Ranunculaceae) in the South Ural Reserve

Five-year dynamics of seed productivity of the high-mountain endemic species Anemonastrum biarmiense (Juz.) Holub in the territory of the South Ural Reserve is presented. The collection of seed material was carried out in three cenopopulations (Dunan-Sungan, Yusha and Naratash), two of which are associated with tall grass communities of the Polygonion krascheninnikovii Kashapov 1985 union, the third cenopopulation is part of the tundra-like communities of the spruce-birch crooked forest of the Calamagrostion arundinaceae (Luquet 1926) Oberdorfer 1957 union. A brief description of the weather conditions of the growing year is given with a graph of minimum temperatures from May to July 2015–2021, where the largest number of days with frost was noted for 2017 (9 days), and not noted at all for 2021. A description of the morphological heterogeneity is given. Seeds of A.biarmiense, while it was found that the seeds of plants are most often characterized by an ellipsoidal shape, less often an ellipsoidal one with a base narrowed into a stem. The spherical shape of the seeds is more common in forest cenopopulations, and the ellipsoidal shape is more common in meadow ones. Seeds with a wavy and even edge are observed equally often. The metric and quantitative parameters of A. biarmiense seed productivity in natural cenopopulations from 2015 to 2021 are given. Most of the metrics increase in 2016, 2018 and decrease in 2015, 2017 with worsening weather conditions. Among the quantitative indicators, the largest number of ovules and seeds per seedling, fl ower-bearing shoot and individual were found in the meadow cenopopulations of Yusha, Dunan-sungan of the forest belt, and in the Naratash CP of the subalpine belt, their number is reduced. Accordingly, a higher seed productivity coeffi cient was found in the open meadow communities of the forest belt, and a lower one in the crooked forest belt. Characterizing the weather conditions of the growing year, most of the maximum values were found in 2016, when the climatic conditions were the most favorable during the growing season. The minimum values of seed productivity indicators were noted in 2017 and 2021, characterized by the least favorable weather conditions throughout the growing season. The lowest variability of seed productivity traits was found for the length and width of the seed, the highest – for the weight of seeds and the number of unfulfilled seeds per seed, flowering shoot and plant. The amplitude of variability for all studied parameters of seed productivity varies in a wide range among the observed cenopopulations in the belt of spruce crooked forests on the ridge. Naratash, while in the narrowest range, variation of signs in the Yusha and Dunan-sungan CP was revealed.

Comparison of Carbon, Nitrogen, and Sulfur in Coastal Wetlands Dominated by Native and Invasive Plants in the Yancheng National Nature Reserve, China

The rapid invasion of the plant Spartina alterniflora in coastal wetland areas can threaten the capacity of their soils to store carbon (C), nitrogen (N), and sulfur (S). In this study, we investigated the spatial and temporal distribution patterns of C, N and S of both soil and (native and invasive) plants in four typical coastal wetlands in the core area of the Yancheng National Nature Reserve, China. The results show that the invasive S. alterniflora greatly influenced soil properties and increased soil C, N and S storage capacity: the stock (mean ± standard error) of soil organic carbon (SOC, (3.56 ± 0.36) kg/m3), total nitrogen (TN, (0.43 ± 0.02) kg/m3), and total sulfur (TS, (0.69 ± 0.11) kg/m3) in the S. alterniflora marsh exceeded those in the adjacent bare mudflat, Suaeda salsa marsh, and Phragmites australis marsh. Because of its greater biomass, plant C ((1193.7 ± 133.6) g/m2), N ((18.8 ± 2.4) g/m2), and S ((9.4 ± 1.5) g/m2) storage of S. alterniflora was also larger than those of co-occurring native plants. More biogenic elements circulated in the soil-plant system of the S. alterniflora marsh, and their spatial and temporal distribution patterns were also changed by the S. alterniflora invasion. Soil properties changed by S. alterniflora’s invasion thereby indirectly affected the accumulation of soil C, N and S in this wetland ecosystem. The SOC, TN, and TS contents were positively correlated with soil electrical conductivity and moisture, but negatively correlated with the pH and bulk density of soil. Together, these results indicate that S. alterniflora invasion altered ecosystem processes, resulted in changes in net primary production and litter decomposition, and increased the soil C, N and S storage capacity in the invaded ecosystems in comparison to those with native tallgrass communities in the coastal wetlands of East China.

Impact of environmental change on a rare high-mountain tall-herb species: a case study on Achillea lingulata in the Ukrainian Carpathians

ABSTRACT Spatio-temporal trends in distribution and population size of Achillea lingulata (Asteraceae), a high-mountain tall-herb species, are analyzed in the Ukrainian Carpathians. These shifts have been revealed due to comparison of the historical literature and herbarium records with the current species distribution, as well as by the long-term monitoring of its populations under different conditions. The species demonstrates opposite dynamic patterns in different types of habitats: negative in abandoned meadows and positive in rock-associated tall-grass communities. That results in the shrinkage of the species distribution at the expense of its secondary grassland habitats, but the increase in size of the saxicolous populations. These trends are associated with the vegetation succession caused by the main drivers of environmental change in the mountains: the abandonment of traditional land use (mainly grazing) and global warming. Biological and habitat characteristics of A. lingulata are described. It has rather narrow habitat requirements and needs gap microsites for the seed recruitment, therefore their availability determines the species distribution and abundance. The post-grazing restoration succession results in denser vegetation cover and replacement of A. lingulata in the meadows. However, vegetation-free microhabitats persist around the rocky outcrops in the high-mountain zone which are most favorable habitats for the species. The evident decline of its lowermost populations implies the effect of climate change which also enhances successional changes. The Ukrainian localities of that rare Carpathian-Balkan species are confined to the northern limit of its geographical range.

Rodent burrow network dynamics under human-induced landscape transformation from desert to steppe in Kalmykian rangelands.

Rodents play an important role in rangelands through the engineering of extensive burrow systems, which provides key habitats for many animal and plant species. We have analyzed the long-term variation in the abundance and distribution of rodent burrows in grazing ecosystems of southern Russia (Kalmykia) under the landscape change from desert to steppe caused by the drastic reduction of livestock after the collapse of the USSR in the early 1990s. We conducted burrow surveys in the "desert" (1980) and "steppe" (2017) periods on 19 3-km transects. We found considerable changes in burrow abundance and distribution, as well as evidence of desert habitat fragmentation and isolation caused by the expansion of tall-grass communities. Burrows of the open-dwelling diurnal ground squirrel (Spermophilus pygmaeus), the dominant and the keystone species during the "desert" period, almost completely disappeared from the rodent burrow network by 2017, indicating significant habitat loss. In contrast, the burrows of the folivorous social vole (Microtus socialis) which was rare in the 1980s, became abundant and ubiquitously distributed. The burrow density of the desert-dwelling psammophilous midday gerbil (Meriones meridianus) decreased, while the distances between occupied patches increased, indicating desert habitat fragmentation and loss of population connectivity. Burrows of the folivorous tamarisk gerbils (M. tamariscinus) were recorded only sporadically in both 1980 and 2017. The observed changes in the rodent burrow network, the key component of grazing ecosystems, correlate with rodent species ecology and can have long-term and important consequences for ecosystem functioning.

Competitive Strategy of Subalpine Tall-Grass Species of the Northwestern Caucasus

The range of ecological CSR strategies for subalpine tall-herb communities of the northwestern Caucasus (Teberda state natural biosphere reserve) has been studied by the measurement of leaves’ functional traits. These communities are developed in swales, river valleys, and runoff depressions of the subalpine belt and represent a typical element of the Caucasian flora. The dominating species are represented by tall forbs, such as Rumex alpinus, Senecio platyphylloides, Cephalaria gigantea, Ligusticum alatum, etc. To evaluate ecological strategies of plants, three functional traits, including leaf area and the weights of wet and dry leaves, have been measured. Based on these measurements, the strategy parameters have been calculated for 42 vascular plant species. The majority of plants of the subalpine tall-grass community manifest traits typical for the competitive (C) and competitive-ruderal (CR) strategies. According to the calculation algorithm, 11 species (Angelica purpurascens, A. tatianae, Cirsium chlorocomos, Heracleum asperum, H. leskovii, H. sosnowskyi, etc.) are referred to the C-strategy. The CR strategy is observed for Aconitum nasutum, Cirsium simplex, Geranium sylvaticum, Hesperis voronovii, Rumex alpestris, and some other species. Two species (Achillea millefolium and Dactylis glomerata) are characterized by the competitive and stress-tolerant (CS) strategy. The stress-tolerant (S) strategy is observed for three species (Veronica filiformis, Lilium monadelphum, and Millium effusum). Finally, the mixed CSR strategy is typical for two species (Trifolium pratense and Astrantia maxima). The majority (93%) of the species studied is characterized by clear competitive traits; the contribution of this strategy type positively correlates with the average vegetative height of a species. In addition, many of the studied species (26% on average) are also characterized by some R-strategy traits. In our opinion, this fact results from a long-term grazing history of alpine plant communities in this region. The obtained results contradict the common opinion about the domination of stress-tolerant species in highlands. This contradiction may be explained by the fact that the studied subalpine meadows are located in the most favorable habitats providing competitive advantages for rapidly-growing tall-herb species. The study confirms the hypothesis that the dominated species of the subalpine tall-grass community of the northwest Caucasus are characterized by significantly (up to 95%) manifested traits of C strategy.

Indicators of biomass and methane yields in vegetated buffer strips

Searching for available biomasses is a key factor to promote renewable energy, especially biogas. This paper examines the biogas potential of biomass from Danish buffer strips with different types of natural vegetation and the possibility of using the functional trait composition of the vegetation and the nutrient composition of the biomass as indicators for the quantity of the biomass and its biogas potential. Biomass was harvested from 73 plots in 2014 and 2015 and biomass yield, nutrient content (CNP) and methane yields were determined. Prior to harvesting, the plant communities were characterised in terms of species composition, and a cluster analysis was performed to identify species assemblages in terms of vegetation clusters. Four ecologically meaningful clusters were obtained: a tall herb fringe community, a tall grass community, a low herb and grass community and a rich fen/wet meadow community. The biomass yield was numerically higher in the tall herb fringe and the tall grass communities, while the specific methane yield was higher in the tall grass and low herb and grass communities. When all samples were analysed together, the biomass yield was positively correlated with some of the vegetation traits (Ellenberg value soil reaction and leaf dry matter content) and negatively with nitrogen and phosphorus contents in the biomass. In addition, a negative correlation was observed between the biomass yield and the specific methane yield. In contrast, the biomass yield was positively correlated with the methane yield per ha, indicating that even small differences in biomass yield can be more relevant for the methane yield per ha than differences in specific methane yields in natural vegetation. Biomass from tall herb fringe, tall grass and low herb and grass communities is suitable to be incorporated into the anaerobic digestion supply chain; and in these communities it could be possible to predict methane yield per ha, especially in tall grass community, using vegetation traits (Ellenberg values and Grimes life strategy) and phosphorus content in the biomass.

Does Regular Harvesting Increase Plant Diversity in Buffer Strips Separating Agricultural Land and Surface Waters?

Vegetated buffer strips are often established in agricultural landscapes as an ‘edge of the field’ mitigation measure against diffuse nutrient pollution of the aquatic environment. Harvesting of the vegetation has been suggested as a possible management strategy to prevent build-up of excessive amounts of nutrients in buffer soils and, at the same time, harvesting can have a positive effect on the diversity of the vegetation. However, the response of the vegetation to harvesting likely depends on taxonomic and functional characteristics. In the present study, we explored effects of harvesting frequency (by comparing harvesting once, twice and four times per year to an unharvested control) on the taxonomic and functional trait composition of four different types of plant communities in buffer strips in Denmark. We found that one to two harvests per year mediated an increase in the diversity of the vegetation in low diversity buffer strips dominated by tall and productive herbs (tall herb fringe), whereas the diversity remained unchanged in more diverse buffer strips dominated by grasses as well as in buffer strips with rich fen and wet meadow species. We also found that harvesting changed the compositional patterns in the tall herb fringe community, with an increasing abundance of grasses and a declining abundance of tall herb species, in particular at a high harvesting frequency. Concomitant with these taxonomic changes, we observed changes in the trait composition of the community. The abundance of tall species declined in the tall herb fringe and in the tall grass community. Similarly, the abundance of productive species (as indicated by high Ellenberg N and Ellenberg R values) declined in the tall herb fringe (in areas harvested four times per year). We conclude that low frequency harvesting is a promising management strategy to increase plant diversity in buffer strips with an initially low diversity and high productivity and that harvesting over time can mediate a shift in compositional patterns towards less productive species.

Effects of exposure and vegetation type on organic matter stock in the soils of subalpine meadows in the Eastern Carpathians

Slope exposure is a rarely considered factor in studies on organic matter sequestration in soil. This process depends on climate conditions and other factors. Our hypothesis assumes that soils with a northern exposure in the northern hemisphere should have a larger organic matter stock than soils with the opposite exposure as a side effect of weaker insolation. Moreover, the stock of organic matter should vary with vegetation type. The main objectives of the presented study were to examine the variation of soil organic carbon (SOC) stock and nitrogen (N) stock in soils on slopes with opposite exposure (NNE and SSW) under different vegetation types (tall-grass communities vs. Vaccinium thickets). The study area was found in the Połonina Caryńska subalpine meadow area situated in the Western Bieszczady Mountains in southeastern Poland. The mean values of SOC and N stock were significantly (p≤0.003) higher for soils with an SSW exposure (74.8 and 6.5Mgha−1, respectively) in comparison with an NNE exposure (61.3 and 5.2Mgha−1, respectively). Thus, the lower decomposition rate of organic matter in soils due to lower insolation on north-facing slopes did not result in higher organic matter stock in the soil. This is likely due to two factors: (1) high humidity together with severe and long winters throughout the studied area and (2) higher insolation on south-facing slopes. The higher mean values of both SOC and N stock were deemed significant (p≤0.007) when determined under tall-grass vegetation (69.9 and 6.1Mgha−1, respectively) versus Vaccinium thickets (66.2 and 5.2Mgha−1, respectively), regardless of exposure. Higher SOC stock and N stock in soils under tall-grasses can be explained by the higher organic matter input that these communities supply to soils every year in comparison with Vaccinium. C/N ratios calculated for the analyzed soils did not reflect any differences with respect to slope exposure or vegetation type (p<0.5).

Characterisation of the fuel and fire environment in southern Ontario’s tallgrass prairie

Prescribed burning can be an integral part of tallgrass prairie restoration and management. Understanding fire behaviour in this fuel is critical to conducting safe and effective prescribed burns. Our goal was to quantify important physical characteristics of southern Ontario’s tallgrass fuel complex prior to and during prescribed burns and synthesise our findings into useful applications for the prescribed fire community. We found that the average fuel load in tallgrass communities was 0.70 kg m–2. Fuel loads varied from 0.38 to 0.96 kg m–2. Average heat of combustion did not vary by species and was 17 334 kJ kg–1. A moisture content model was developed for fully cured, matted field grass, which was found to successfully predict moisture content of the surface layers of cured tallgrass in spring. We observed 25 head fires in spring-season prescribed burns with spread rates ranging from 4 to 55 m min–1. Flame front residence time averaged 27 s, varying significantly with fuel load but not fire spread rate. A grassland spread rate model from Australia showed the closest agreement with observed spread rates. These results provide prescribed-burn practitioners in Ontario better information to plan and deliver successful burns.

Food Composition of the Harvest Mouse (Micromys minutus) in a Western Suburb of Tokyo, Japan, with Reference to Frugivory and Insectivory

The harvest mouse (Micromys minutus) is a unique rodent that lives in grass communities and constructs spherical breeding nests from grass or sedge leaves. In Japan, the harvest mouse frequently inhabits communities of tall grasses. These grasses are very tall (>2 m), and the harvest mouse constructs spherical breeding nests as high as approximately 1 m from the ground (Kuroe et al. 2007; Hata 2011), which is much higher than the nests of European harvest mouse which constructs nests at 15–65 cm above the ground (Dickman 1986). Since the harvest mouse is very small (less than 10 g), it should require nutritious food sources (Kleiber 1961; Fancy and White 1985). Animal materials are generally rich in protein while plant leaves contain large quantities of cellulose and little protein and are less digestible for mammals (Robbins 1983). Fruits contain less fiber than leaves, and are therefore more nutritious, but contain less protein than animal materials (Robbins 1983). These facts at least partially explain why small mammals that require more energy per unit body weight than larger mammals are more likely to be insectivorous or granivorous (Pearson 1948). The tall grass communities provide few nutritious plant foods except for some herbaceous plant seeds or insects. Confirmation that the harvest mouse feeds on fruits/seeds and insects would contribute to a more general subject how small mammals that require more energy per unit weight than larger mammals select nutritious foods in food-poor habitats. Surprisingly, however, few studies have been done on the food habits of the harvest mouse. To our knowledge, only Dickman (1986) reported on the omnivorous food habits of the harvest mouse in England, but no information is available in Japan, though Ishiwaka and Masuda (2008) reported evidence that the harvest mouse controls the armyworm (Mythimna separata, Lepidoptera), which suggests that the harvest mouse feeds on insects. Therefore, we analyzed the food habits of Japanese harvest mice living in the tall grass community using fecal analyses. The objective is to quantitatively show the food habits of the harvest mouse with reference to frugivory and insectivory. The term frugivory (fruit feeding) is distinguished from granivory (seed feeding), but in the present study “frugivory” includes both frugivory and granivory because distinguishing fruit and seeds were difficult in many cases.

Diversity patterns in savanna grassland communities: implications for conservation strategies in a biodiversity hotspot

For any conservation strategy to be effective, it must be preceded by knowledge of how diversity is configured within the area of interest. Here, data from 40 savanna-grassland sites were used to examine how plant biodiversity and species composition varied across spatial scales at the Kalakad-Mundanthurai Tiger Reserve (KMTR), south India. Grasslands surveyed contained 278 plant species, and were characterized by high spatial variability in species association patterns. Fourteen distinct community assemblages were identified, organized primarily along an elevation gradient in the reserve. Overall, grasslands at KMTR were characterized by the dominance of a few, widespread species. The bulk of species richness, however, resulted from subordinate species with fairly restricted distributions. At low elevations, grasslands had high species richness and species composition differed greatly between sites. Mid-elevation grasslands contained about half the number of species present at low elevations, but sites were more similar in species composition. Richness of high-elevation grasslands was a third of that found at low elevations, but different sites harbored unique sets of species. Herbivore use of grasslands varied between communities and showed patterns that coincided with elevation. Herbivore use of low-elevation communities was high albeit variable, of mid-elevation sites was consistently low, and increased at higher elevations. Tall grass communities were the least utilized by herbivores at all elevations. Most species surveyed were rare and restricted in their distribution suggesting that conservation efforts must, perforce, encompass the entire reserve. However, differences in the structuring of diversity across elevations, and in herbivore use of grasslands, suggest that conservation efforts can be partitioned differentially across locations, specifically targeting low and high elevation grasslands in the reserve.

Relación entre la vegetación y el banco de semillas de un espartillar de Spartina argentinensis

S.R. Feldman, C. Alzugaray, and J.P. Lewis. 2007. Relationship between the soil seed bank and vegetation of tall grassland of Spartina argentinensis. Cien. Inv. Agr. 34(1):41-48. Tall grass communities of Spartina argentinensis Parodi are the most widespread plant communities in a large saline depression in Santa Fe, Argentina. The vegetation and soil seed bank for these communities have been studied. However, there is no information about the relationship between them. We worked with previous data obtained from the Federico Wildermuth Reserve, Colonia Bel Grano, Departamento San Martin, Santa Fe, Argentina (31°57’ S; 61°23’ W) and used the cover-abundance of the plant species and density of the soil seed bank for 1998 and 1999. The relationship between plant types C3 and C4 (C3/C4) and annual/perennial functional groups were determined. At the same time, the similarity index and the relationship between cover-abundance and density of the shared species was determined. According to results obtained, plant species relationship between of type C3 were more frequent in the soil seed bank, while plant species of type C4 were more abundant in the vegetation. There was no signifi cant correlation between cover-abundance in the vegetation and soil seed bank density of the common species. The similarity index was very low due to the fact that the number of species common to vegetation and soil seed bank was very low. In conclusion, there was a low relationship between species of the soil seed bank and vegetation with plant species type C3 and C4 as predominant species, respectively.

Grazing and Ecosystem Carbon Storage in the North American Great Plains

Isotopic signatures of 13 C were used to quantify the relative contributions of C3 and C4 plants to wholeecosystem C storage (soil+plant) in grazed and ungrazed sites at three distinct locations (short-, mid- and tallgrass communities) along an east–west environmental gradient in the North American Great Plains. Functional group composition of plant communities, the source and magnitude of carbon inputs, and total ecosystem carbon storage displayed inconsistent responses to long-term livestock grazing along this gradient. C4 plants [primarily Bouteloua gracilis (H.B.K.) Lag ex Steud.] dominated the long-term grazed site in the shortgrass community, whereas the ungrazed site was co-dominated by C3 and C4 species; functional group composition did not differ between grazed and ungrazed sites in the mid- and tallgrass communities. Above-ground biomass was lower, but the relative proportion of fine root biomass was greater, in grazed compared to ungrazed sites at all three locations. The grazed site of the shortgrass community had 24% more whole-ecosystem carbon storage compared to the ungrazed site (4022 vs. 3236 g C m )2 ). In contrast, grazed sites at the mid- and tallgrass communities had slightly lower (8%) whole-ecosystem carbon storage compared to ungrazed sites (midgrass: 7970 vs. 8683 g C m )2 ; tallgrass: 8273 vs. 8997 g C m )2 ). Differential responses between the shortgrass and the mid- and tallgrass communities with respect to grazing and whole-ecosystem carbon storage are likely a result of: (1) maintenance of larger soil organic carbon (SOC) pools in the mid- and tallgrass communities (7476–8280 g C m )2 ) than the shortgrass community (2517– 3307 g C m )2 ) that could potentially buffer ecosystem carbon fluxes, (2) lower root carbon/soil carbon ratios in the mid- and tallgrass communities (0.06–0.10) compared to the shortgrass community (0.20–0.27) suggesting that variation in root organic matter inputs would have relatively smaller effects on the size of the SOC pool, and (3) the absence of grazing-induced variation in the relative proportion of C3 and C4 functional groups in the mid- and tallgrass communities. We hypothesize that the magnitude and proportion of fine root mass within the upper soil profile is a principal driver mediating the effect of community composition on the biogeochemistry of these grassland ecosystems.

Dynamics of the soil seed bank of Spartina argentinensis tallgrass community.

Spartina argentinensis Parodi has a vicarious amphitropic distribution. In Argentina there are large areas of land covered with grasslands of this species. Fires are very frequent in these grasslands and they are a very common management technique for cattle raising. Soil seed banks comprise all sexual propagules as well as apomictic seeds. There is no information about the seed banks of Spartina argentinensis tall grasslands. The object of this paper is to analyze the seed bank of this plant community on a time sequence of four years. In spite of seeming very monotonous, this community is far from homogeneous, and the heterogeneity is indicated by the soil seed bank. Many propagules are not buried and they are exposed to environmental hazards. The most important grasses of the community including Spartina argentinensis , do not form an important seed bank. Fire has no harmful effect over any species in the bank and in many of them induces a transient seed bank enrichment. However, the seed banks of some species like Heliotropium curassavicum and Sesuvium portulacastrum are affected by fire but do not disappear completely. Spartina argentinensis Parodi tiene una distribucion vicaria anfitropica. En Argentina existen grandes areas cubiertas por pastizales de esta especie. Los incendios son frecuentes en estos pastizales y se usan como una herramienta de manejo, permitiendo el pastoreo del rebrote tier-no para la cria de ganado vacuno. El banco de semillas del suelo comprende a todos los propagulos de origen sexual, al igual que a las semillas apomicticas. No existe informacion acerca del banco de semillas de pastizales de S. argentinensis . El objetivo de este trabajo fue analizar el banco de semillas de esta comunidad a lo largo de cuatro anos. A pesar de su aparente homogeneidad, esta comunidad es muy heterogenea, lo cual se refleja en el banco de semillas. Muchos propagulos permanecen en superficie, quedando expuestos a diversos factores de riesgo impuestos por el ambiente. Las especies mas importantes, incluyendo a S. argentinensis , no forman un banco de semillas importante. El fuego no tiene un efecto deletereo sobre ninguna especie del banco y, en algunos casos, provoca un enriquecimiento transitorio. No obstante, el banco de algunas especies, tales como Heliotropium curassavicum y Sesuvium portulacastrum , se ve afectado por el fuego, aunque no desaparece del todo.

Species richness, alien species and plant traits in Central Argentine mountain grasslands

Abstract Pattern of native vegetation, distribution of alien species and variation of environmental parameters were studied in mountain grasslands in a lithologically homogeneous Cordoba mountain range in Central Argentina. CCA showed that altitude was the most important factor determining the compositional variation of the vegetation, with soil nutrient status and stoniness as additional factors. Short-grass communities, associated with the driest habitats on plateaus, showed higher small-scale native species richness than wet-turf communities in valleys and tall-grass communities on slopes. Species richness was negatively correlated with soil parameters that indicate nutrient status and water availability. Also, there was a negative correlation between soil Ca- and Mg-content and richness. High native species richness coincided with high alien species richness. When smaller units – community types – were considered, it became evident that within short-grass vegetation, the three most species-rich commun...

Influence of herbicide application on forb and arthropod communities of North American tallgrass prairies

The primary approach used for reducing “weeds” in the native grasslands of the North American Great Plains is the application of a broadleaf-selective herbicide, which could have important implications to native plant and arthropod diversity. The objectives of this study were to identify the influence of herbicides on the forb and arthropod community composition, richness, and density, and determine relationships among the forb and arthropod communities in a tallgrass prairie of the North American Great Plains. In 1994, arthropod and forb communities were evaluated in eight treatment units and then a broadleaf-selective herbicide was applied to four of these units. Sampling of arthropod and forb communities were sampled under similar conditions in 1995 for post-treatment effects. These communities were highly variable across years regardless of treatment (herbicide and no herbicide). The herbicide treatment caused a reduction in overall forb dominance the year after treatment. Species richness increased from 1994–1995 in both treatments but the increase was less in the herbicide treatment. The herbicide application had no overall effect on forb species composition. The lack of effect of herbicide on the forb community composition coupled with a significant effect on species richness suggests that an important effect of herbicide application was a reduction of rare forbs. Analysis of these tallgrass communities did not yield significant differences in arthropod abundance or richness between grasslands treated with a herbicide and grasslands not treated with a herbicide. The arthropod community was defined by extreme variability across years reflecting extreme fluctuations regardless of herbicide application.

A rodent plague on prairie diversity

Selective vole (Microtus pennsylvanicus) suppression of prairie grasses and forbs in experimental restorations suggests why many of the plants are likely to be uncommon in nature. Vole herbivory reduced densities of legumes and grasses and increased unpalatable forbs in replicated plantings in Illinois: six otherwise common species (Dalea purpurea, Desmanthus illinoensis, Elymus canadensis, Panicum virgatum, Phalaris arundinacea, Sorghastrum nutans) declined 27–89% in abundance, whereas two species (Echinacea purpurea and Rudbeckia hirta) increased by 61% and 1023%. Species number dropped by 19% and plant diversity (Simpson’s D) by 37% in one treatment to which voles had access. Plots were planted with 18 prairie species of the region, but in even distributions of 35 or 350 seeds species−1 m−2, rather than skewed in favour of large C4 grasses common in native remnants. Manipulation of plant composition and vole access revealed what are likely to be formative effects of rodent herbivory on vegetative composition. These experimental tallgrass communities appear to be assembling from plant species that voles prefer not to eat.

Is Species Richness Dependent on the Neighbouring Stands? An Analysis of the Community Patterns in Mountain Grasslands of Central Argentina

We studied the spatial pattern of species richness in the mountain grasslands of central Argentina, where three distinct vegetation types occur: shortgrass in shallow soils, tallgrass in deeper soils and wet turf in moist depressions. The shortgrass community had the highest vascular plant species richness on different scales, the maximal number of vascular plant species per m 2 was 89. The richness within the shortgrass vegetation was not related to spatial location or soil depth. Small-scale species richness was significally positively related to the size of the community species pool. Within short grass and tallgrass communities, the floristic similarity between stands was higher when they were located closer to each other. This pattern was interpreted as showing the internal diaspore limitation. The number of species in shortgrass vegetation was significantly positively dependent on the proximity of tallgrass stands. Also, floristic similarity between shortgrass and other communities (tallgrass and wet turt was significantly higher when stands were located closer in space. This pattern was interpreted as showing the external diaspore limitation, called also spatial mass effect - other communities act as seed donors and increase the number of species coexisting in the shortgrass community. The mean height of the predominating species was lower in the shortgrass than in the tallgrass or wet turf communities. In communities with a tall canopy, species composition and richness were not dependent on surrounding communities, which may be explained by the relatively more significant competition for light there. In the shortgrass community, where the canopy is lower, the pattern of species richness was related to the vicinity of potential diaspore sources, which indicates the relative significance of internal and external diaspore limitation. The proportion of exotic species in the community was not related to the richness of native species. The highest proportion of exotics was observed in the wet turf community, which was also the one most heavily grazed.

Effects of Birds and Rodents on Synthetic Tallgrass Communities

We used a bird and mammal exclosure design on plowed ground to test for the effects of granivory and herbivory by small vertebrates on early stages of tallgrass prairie succession. Seed predation by birds and browsing by rodents had major and additive impacts. In high- and low-density plantings, respectively, seed-eating birds reduced plant densities by 20% and 23% and grass biomass by 24% and 34%. Meadow voles did not affect plant numbers but reduced forb biomass by 35% in high- and 57% in low-density plantings. In high- and low-density plots, respectively, birds reduced species richness by 3% and 17% without influencing diversity; selective browsing by voles on two legumes and one coneflower left species number unaffected but reduced diversity by 4% and 25% by accentuating dominance of already-prominent species. Bird effects were more pronounced in high-density plantings, while vole effects were most pronounced in low-density plantings. Results suggest that opportunistic finches and doves that seek out high seed concentrations depress tallgrass plant densities on open ground, while voles, which selectively forage on emerging vegetation, alter community structure, especially when their home ranges include low-density plant assemblages. Both results are likely to be relevant to native prairies after burns or other disturbance, and to ecological restoration.

Does grazing mediate soil carbon and nitrogen accumulation beneath C4, perennial grasses along an environmental gradient?

An experiment was conducted to evaluate the influence of long-term (>25 yrs) grazing on soil organic carbon (SOC) and total soil nitrogen (N) accumulation beneath individual plants of three perennial grasses along an environmental gradient in the North American Great Plains. The zone of maximum SOC and N accumulation was restricted vertically to the upper soil depth (0-5 cm) and horizontally within the basal area occupied by individual caespitose grasses, which contributed to fine-scale patterning of soil heterogeneity. Long-term grazing mediated SOC and N accumulation in the tall-, mid- and shortgrass communities, but the responses were community specific. SOC and N were lower beneath Schizachyrium scoparium plants in long-term grazed sites of the tall- and midgrass communities, but higher beneath Bouteloua gracilis plants in the long-term grazed site of the shortgrass community. SOC, but not N, was greater in soils beneath compared to between S. scoparium plants in an abandoned field seeded in 1941, indicating that this caespitose grass accumulated SOC more rapidly than N. SOC and N were greater in the 0-5 cm soil depth beneath a caespitose grass (S. scoparium) compared to a rhizomatous grass (Panicum virgatum) in the tallgrass community, with no significant accumulation of either SOC or N beneath P. virgatum plants. Grazing appears to indirectly mediate nutrient accumulation beneath caespitose grasses along the environmental gradient by modifying the size class distribution of plants. Populations with a greater proportion of large plants have a greater potential for biomass incorporation into soils and may more effectively capture redistributed organic matter from between plant locations. Contrasting plant responses to grazing at various locations along the environmental gradient conform to the predictions of the generalized grazing model, as the selection pressures of grazing and aridity may have also influenced the ability of caespitose grasses to accumulate nutrients in soils beneath them by mediating grazing resistance, competitive ability and population structure.