High Plant Species Diversity Research Articles

Microhabitat Segregation of Three Species of Pocket Mice (Genus Chaetodipus) in Coastal Baja California, Mexico

Abstract I compared vegetation and substrate characteristics at capture locations of three syntopic species of pocket mice (Chaetodipus: Heteromyidae) to determine differences in microhabitat affinities of these ecologically similar rodents in coastal Baja California, Mexico. Principal components analysis revealed that capture locations of C. spinatus had disproportionately higher cover of medium and large rocks, and tended to have higher plant species diversity than capture locations of the other two species. C. spinatus and C. arenarius, the two smallest species, differed most in their microhabitat affinities, suggesting spatial segregation that may minimize competition for similar food resources. C. arenarius was captured most often at sites with the finest-textured soils, whereas C. rudinoris, the largest species, was widespread and frequently associated with gravel and small rocks. No species showed any apparent preference for plant species or significant amounts of overhead cover, a conclusion suppo...

Southern marl prairies conceptual ecological model

About 190,000 ha of higher-elevation marl prairies flank either side of Shark River Slough in the southern Everglades. Water levels typically drop below the ground surface each year in this landscape. Consequently, peat soil accretion is inhibited, and substrates consist either of calcitic marl produced by algal periphyton mats or exposed limestone bedrock. The southern marl prairies support complex mosaics of wet prairie, sawgrass sawgrass (Cladium jamaicense), tree islands, and tropical hammock communities and a high diversity of plant species. However, relatively short hydroperiods and annual dry downs provide stressful conditions for aquatic fauna, affecting survival in the dry season when surface water is absent. Here, we present a conceptual ecological model developed for this landscape through scientific concensus, use of empirical data, and modeling. The two major societal drivers affecting the southern marl prairies are water management practices and agricultural and urban development. These drivers lead to five groups of ecosystem stressors: loss of spatial extent and connectivity, shortened hydroperiod and increased drought severity, extended hydroperiod and drying pattern reversals, introduction and spread of non-native trees, and introduction and spread of non-native fishes. Major ecological attributes include periphyton mats, plant species diversity and community mosaic, Cape Sable seaside sparrow (Ammodramus maritimus mirabilis), marsh fishes and associated aquatic fauna prey base, American alligator (Alligator mississippiensis), and wading bird early dry season foraging. Water management and development are hypothesized to have a negative effect on the ecological attributes of the southern marl prairies in the following ways. Periphyton mats have decreased in cover in areas where hydroperiod has been significantly reduced and changed in community composition due to inverse responses to increased nutrient availability. Plant species diversity and community mosaics have changed due to shifting gradients to more terrestrial or more aquatic communities, displacement of native communities by non-natives, expansion of woody plants, high-intensity dry season fires, tree-island burnout, and reduced microtopography resulting from alligator population decline. Cape Sable seaside sparrow populations are threatened by nest destruction resulting from extended hydroperiods, drying pattern reversals, and high intensity dry season fires, as well as by the expansion of woody plants into graminoid wetland habitats. Populations of marsh fishes and associated aquatic fauna that constitute the aquatic prey base for higher vertebrates have decreased in density and changed in species composition and size structure due to loss of wetland spatial extent, shortened hydroperiod, increased drought severity, loss of aquatic drought refugia in solution holes and alligator holes, and spread of exotic fishes. American alligator populations have declined in the Rocky Glades, and alligator holes have filled with sediment, as a result of shortened hydroperiod and increased drought severity. Habitat options for wading birds to forage during the early dry season and during unusually wet years have been reduced due to loss of spatial extent and shortened hydroperiod.

Establishment of vegetation in broadened field boundaries in agricultural landscapes

Three field experiments with broadened permanent field boundaries were established in agricultural landscapes near Uppsala (southern Sweden). One aim was to test methods for increasing the amount of non-cultivated areas with high plant species diversity and at the same time suppressing the occurrence of weeds. The treatments consisted of re-establishing or broadening boundary strips, sowing a mixture of ley grasses and clover, of wild meadow species, or planting bushes. All treatments were managed by yearly mowing and taking away of the plant material. The vegetation was examined on two occasions during a 10-year period. At the second occasion, a set of untreated field boundaries (reference boundaries) in the vicinity of each experiment was examined for comparison. Sowing meadow species changed the species composition substantially compared to untreated boundaries. Out of 32 sown species, 22 remained after 10 years. These species are normally found in well-managed meadows or pastures. Species that did not establish or disappeared tended to be either adapted to moist or to dry conditions. Sowing meadow species kept the abundance of weeds on a lower level than sowing clover and grasses or free regeneration at one site and kept weed abundance lower or at least not higher than in reference boundaries.

Functional stability, substrate utilisation and biological indicators of soils following environmental impacts

Stability of a soil property to perturbation comprises both resistance and resilience. Resistance is defined as the ability of the soil to withstand the immediate effects of perturbation, and resilience the ability of the soil to recover from perturbation. Functional stability is used here to describe the stability of a biological function to perturbation, rather than the stability of physical structure or chemical properties. The function chosen for this study was the short-term decomposition of added plant residues, and the perturbations were copper and heat stresses. Previous studies had shown that functional stability was reduced greatly in soils with experimentally reduced biodiversity. The objective of this study was to determine the relative sensitivity of functional stability and potential indicators of biological status to detect alteration of field soils by various environmental impacts. Functional stability, protozoan populations and substrate mineralisation kinetics, were measured on paired soils with: high or low plant species diversity; hydrocarbon pollution or not; extensive or intensive agricultural management practices. Substrate mineralisation kinetics were poorly related to the soil’s antecedent conditions and were stimulated significantly by hydrocarbon pollution. Protozoan populations were potentially useful for detecting differences within soil type, but will require greater taxonomic input to be most useful. Functional stability, particularly resistance, was able to quantify differences between and within soils. The potential development of the technique in relation to soil health is discussed.

Estimation of plant species richness from systematically placed plots in a managed forest ecosystem

A Danish managed forest of 325 hectares was sampled for plant species richness in a regular 100 × 100 m grid using four nested quadrates of 2, 4, 25, and 200 m2, respectively, at each sample point. The survey resulted in total counts of 161, 171, 224, and 289 species depending on size of quadrates. A list of more than 370 species, however, was accumulated for the forest based on the present study, the literature, and additional personal observations. It was shown that species richness estimators and especially the log-log estimator resulted in improved estimates of species richness. It was also shown that a search strategy in which plots with high habitat diversity in the immediate neighbourhood or plots close to forest roads were chosen first was more effective than a random search strategy. The random strategy, on the other hand, was more efficient than emphasising core areas of major habitat types in the beginning of the search. The study has clearly demonstrated that a managed forest ecosystem with its mixture of open areas and different stands can harbour a very high plant species diversity (in this case ca. 25% of the total Danish flora in only 325 hectare). It is also shown, however, how difficult and time consuming it is to count all species in a heterogeneous ecosystem.

Effects of Pine and Hardwood Basal Areas After Uneven-Aged Silvicultural Treatments on Wildlife Habitat

Abstract Uneven-aged management (UEAM) is becoming increasingly popular in the southeastern United States. However, effects of UEAM on wildlife habitat have not been adequately documented. We examined response of habitat within stands of varying levels of pine and hardwood basal area under an uneven-aged management regime in southern Mississippi. Summer and winter trends in understory biomass were similar across treatments. Time since disturbance influenced plant productivity. Stands with lower basal areas tended to have higher browse production, denser and higher vertical habitat structure, more woody, vine, and fern biomass, greater total biomass, and higher plant species diversity and richness. Pine basal area had little influence on browse production relative to effects of hardwood basal area. Although stands with higher basal area had less biomass, a higher proportion of biomass was composed of preferred browse. We recommend that forest managers create stands of varying levels of pine and hardwood basal areas to provide for diverse needs of many wildlife species. South. J. Appl. For. 23(3):151-157.

Pollination biology in a lowland dipterocarp forest in Sarawak, Malaysia. I. Characteristics of the plant‐pollinator community in a lowland dipterocarp forest

Flowerings and flower visitors were observed continuously in alowland dipterocarp forest in Sarawak, Malaysia, for 53 mo in1992-1996. Flower visitors of 270 plant species were observed orcollected, and pollinators were assessed by observing body contact tostigmas and anthers. We recognized 12 categories of pollination systems.Among them, plants pollinated by social bees included the largest numberof species (32%) and were followed by beetle-pollinated species(20%). Pollination systems were significantly related with somefloral characters (flowering time of day, reward, and floral shape), butnot with floral color. Based on the relationships between pollinatorsand floral characters, we described pollination syndromes found in alowland dipterocarp forest. The dominance of social bees and beetlesamong pollinators is discussed in relation to the general floweringobserved in dipterocarp forests of West Malesia. In spite of high plantspecies diversity and consequent low population densities of lowlanddipterocarp forests, long-distance-specific pollinators were uncommoncompared with theNeotropics.

Biodiversity of rhizobia isolated from a wide range of forest legumes in Brazil.

Tropical forests have a high diversity of plant species; are they associated with a correspondingly rich microbial flora? We addressed this question by examining the symbiotic rhizobium bacteria that nodulate a diverse pool of forest legume species in Brazil. The 44 strains studied had been isolated from 29 legume tree species representing 13 tribes including all three subfamilies of the Leguminosae, and were chosen to represent major groups from a larger sample that had previously been characterized by SDS-PAGE of total proteins. Partial 16S rRNA gene sequence was determined, corresponding to positions 44-303 in the Escherichia coli sequence. Fifteen sequences were found, including six novel ones. However, all but one of them could be assigned to a genus because they grouped closely with sequences from previously described rhizobial species. Fast-growing strains had sequences similar to Rhizobium spp., Sinorhizobium spp. or Mesorhizobium spp., while the slow-growing strains had sequences similar to Bradyrhizobium spp. One strain with an intermediate growth rate had a unique sequence which indicated that the strain might belong to the genus Azorhizobium. Although the strains showed a variety of sequences, it was surprising that these strains isolated from taxonomically very diverse host plants in previously unexplored environments were mostly very similar to strains described previously, largely from agricultural systems.

An analysis of the flora of Legalameetse Nature Reserve, Northern Province

Over 1530 plant taxa occurring in the 18 000 ha Legalameetse Nature Reserve (LNR) on the Drakensberg escarpment of the Northern Province are listed, Taxa are listed and arranged by genus, with species arranged alphabetically within genera Annotations include authorities, collector and specimen number or alternatively a literature reference and indication of distribution or endemism and red data category. The largest family is the Asteraceae, followed in descending order by Poaceae, Fabaceae, Liliaceae and Rubiaceae. An analysis of the level of endemism and threatened taxa on the checklist for the reserve supports the listing of this area as an important centre of endemism (with 10 taxa potentially endemic to the reserve itself), which contains a high diversity of plant species requiring conservation attention. The most important habitats for conservation include dry rocky grassland, upland grassland woodland/bushveld and forest edge. The flora shows affinities with the grassland biome The number of taxa in different categories and families is compared with information available for two areas 40 km to the north and 120 km south of the study area respectively. The flora of the study is more similar to the closely situated, more tropical Westfalia area to the north, than to the southerly, more temperate area around Sabie. Seventeen taxa that occur at LNR may still need to be described.

Dietary overlap of three ungulate species in the Palava Biosphere Reserve

The Palava Biosphere Reserve (South Moravia, Czech Republic) contains a vaiety of habitat types and maintains a high diversity of plant and animal species. Within this unique region is situated a game reserve for ungulate species. This paper presents the results of dietary similarity and dietary overlap of three ungulate species: the wild goat ( Capra aegagrus) the mouflon ( Ovis musimon) and roe deer ( Capreolus capreolus) within the reserve, including competition and coexistence of these species. The qualitative and quantitative similarity of diet of all three animal species varies between 20 and 96%. The greatest similarity was found for the goat and mouflon diet and lowest for the roe deer and mouflon. There was marked competition for food during the winter months, as all three species consume large amounts of broad-leaved sprouts. This intensive browsing has had a considerable negative impact on the vegetation.

Responses of a C4 Grass and Three C3 Forbs to Variation in Nitrogen and Light in Tallgrass Prairie

In tallgrass prairie, high plant species diversity results not from a large number of grass species, but from a large number of forb (nongrass, herbaceous) species. Forbs exhibit morphological, life history, and ecophysiological characteristics that contrast sharply with those of the dominant C4 grasses. Success of the subdominant forbs varies strongly with topographic position and burning regime, and landscape scale patterns of abundance are well documented. But comparatively little is known about the mechanisms determining these patterns in persistent tallgrass prairie forbs. To elucidate these mechanisms, (1) leaf—level physiological characteristics of the dominant C4 grass, Andropogon gerardii, and four co—occurring C3 forbs were measured in response to natural and experimentally manipulated gradients of N availability, and (2) seasonal light environments of forbs in contrasting topographic positions and burning regimes and their morphological and physiological responses in these environments were compared to determine whether resource availability and utilization patterns contributed to patterns of forb distribution and abundance. The effects of burning regime and topographic position on maximum rate of photosynthesis (A) and stomatal conductance to water vapor (g) measured at the leaf level were not consistent with patterns of forb abundance. Nitrogen did not appear to limit forb physiological processes, even though increased N availability resulted in higher tissue N concentrations and greater biomass. There was no consistent increase in (A) or decrease in (g) in response to fertilization. However, (A) at low light levels was as much as 67% higher in fertilized Vernonia baldwinii and A. gerardii compared to unfertilized plants. Greater light availability to forbs in the canopy was associated with lower grass biomass production in uplands compared to lowlands and in unburned compared to burned sites. Forbs did not appear to adjust morphologically (leaf area and plant height) to different light environments at different sites. As a result, as much as 90% of forb leaf area in the burned lowland was displayed in low light, whereas as little as 30% of forb leaf area was in low light in the uplands at midseason. Estimates of potential whole—plant carbon uptake, based on leaf area distribution relative to available light and (A) as a function of light availability, agreed well with patterns of forb abundance and production. Differences in light availability may account for much of the variability in forb abundance related to burning regime and topographic position by limiting carbon gain in forbs more in burned lowlands than in other sites.

Comparative Gas Exchange and Nitrogen Responses of the Dominant C4Grass Andropogon gerardii and Five C3Forbs to Fire and Topographic Position in Tallgrass Prairie During a Wet Year

High plant species diversity in tallgrass prairie results not from a large number of grass species but, rather, from a large number of forb (nongrass, herbaceous) species. Although morphological characteristics of tallgrass prairie forbs differ strongly from those of the grasses and their patterns of abundance vary substantially with burning regime and topographic position, comparatively little is known about the ecology of persistent tallgrass prairie forbs. We measured leaf-level physiological characteristics of the dominant C4 grass, Andropogon gerardii, and five co-occurring C3 forb species in response to burning regime and topographic position to determine if there were either absolute or seasonal differences in resource utilization patterns that could contribute to the patterns of forb distribution and abundance in tallgrass prairie. In a wet year, neither fire nor topographic position affected leaf-level physiological characteristics in the grass and forbs studied, and thus responses were not consi...

Characterization of Prairie Mole Cricket Chorusing Sites in Oklahoma

-Prairie mole crickets Gryllotalpa major were known historically from the southern tallgrass prairie region of North America, but have declined substantially and are now restricted to prairie fragments in Missouri, Kansas, Arkansas and Oklahoma. Surveys of calling males in Oklahoma from 1987 through 1991 located sixty distinct chorusing sites, 70% of which were located within the historical tallgrass prairie biome. Chorusing sites were characterized by higher silt content and higher plant diversity than sites where crickets did not call. Adequate silt content of the soil may be critical to proper burrow construction. Higher plant species diversity on chorusing sites is probably the result of past land management practices such as mowing for hay. Although presently secure in Oklahoma, prairie mole cricket populations may be threatened in the future by land use changes and continued habitat fragmentation.

The late quaternary palaeoecology of a floristic kingdom: the southwestern Cape South Africa

The southwestern Cape Province of South Africa is the core region of the Cape Floristic Kingdom, one of six such large-scale phytogeographical units and by far the smallest. The region possesses one of the richest plant communities in the world when measured in terms of plant species numbers per unit area and many different hypotheses have been advanced in order to explain this prolific diversity. Historical processes and evolutionary development through time are frequently invoked as explanations, but remarkably little is known of the historical biogeography of the region and fossil-bearing sediments have yielded only a fragmented picture of the temporal development of the flora. Late Quaternary terrestrial sediments offer an opportunity to investigate the more recent history of the flora, although here too there exist several constraints which limit the precision of palaeoecological and palaeoenvironmental reconstructions. For the moment, knowledge of late Quaternary vegetation history is restricted to upland sites of organic sediment accumulation, although an increasingly detailed picture of vegetation development against a backdrop of environmental changes is emerging. This paper reviews the evidence from several fossil pollen-bearing sediments in the mountains of the southwestern Cape and presents a vegetation history for the last 14,500 years. We draw the somewhat surprising conclusion of relative vegetation stability during the time of marked climatic and environmental dynamism elsewhere. The hypothesis that assumed limited vegetation change could be a consequence of high species richness coupled with low pollen identification resolution is tested using multiple-discriminant analysis. It is argued that apparently subtle shifts in vegetation community patterns did indeed prevail during the late Quaternary. This possibly has some important implications for the evolution and maintenance of high plant species diversity in the Cape Floristic Region.

River management and conservation issues on formerly braided river systems; the case of the River Tay, Scotland

Abstract Although the present-day River Tay, Scotland is generally confined to a single course and exhibits limited lateral mobility, historical maps (1747–53) reveal that during the eighteenth and nineteenth centuries a braided river channel pattern was more characteristic of a number of reaches on the piedmont valley floor. Possible explanations of the change in channel pattern include flood embankment construction, flow regulation by impoundment and possibly a change in flood magnitude and frequency, and alterations in sediment supply. Areas of former braiding isolated from the main channel by embankments or incorporated into the floodplain sediments, exhibit a greater susceptibility to erosion and are prone to flood embankment breaches. In contrast, river channel reaches still exhibiting unconfined braiding tendencies have been designated areas of high conservational value due to large expanses of gravel at different stages of vegetation colonization and high plant species diversity. It is suggested that the identification of areas of former braiding and reaches prone to braiding is useful for land use management both for improved flood protection and floodplain habitat conservation.

Australian vegetation during the Tertiary: Macrofossil evidence

The Australian Tertiary plant macrofossil record, although very incomplete, offers a unique insight into past vegetation composition and dynamics, and the effect of changing climate both on vegetation composition and plant evolution. During the Early Tertiary, southeastern Australia supported complex rainforests with a very high diversity of woody plant species. The prevailing climate included a moderate mean annual temperature and, more importantly, very little temperature variability away from the mean. As well as this, rain fall was high throughout the year, and humidity was also very high. There is no extant analogue either for this climate or for the vegetation it supported. As the climate cooled and temperature extremes developed, and rainfall declined and became more seasonal, rainforests in southeastern Australia declined in species numbers. Many taxa became extinct or migrated (or were restricted in range) northwards into the mid-high elevation equatorial rainforests where they, or their descendants, still occur. Some rainforest taxa evolved in response to the changing climate in southeastern Australia, although many of these were ultimately unsuccessful and became extinct in the region. As the climate further deteriorated, non-rainforest vegetation expanded in the drier and colder areas, although many of the taxa present in these expanding ecosystems may have had their origin in nutrient-poor rainforests.

The influence of peers, lineage and environment on food selection of the criollo goat ( Capra hircus)

The food selection of 56 criollo goats ( Capra hircus) grazing the same pastures was compared with the previous history of each individual and with lineage relationship inside the flock. The observations were carried out on natural tropical savannas of Martinique (French West Indies), characterized by high plant species diversity and fast evolution rate under grazing pressure. Diets of translocated animals varied with the origin of goats on the island, even though they grazed the same pastures for 4 years. On these fast changing savannas, diets of cohorts born on successive years partially reflected the pasture composition of their year of birth. The selection of one to several plant species characterized each lineage. But groups of peer kids also showed different dietary characteristics from their parents. Diet selection in goats is thus influenced both by the composition of pastures grazed during the first year of life and by the social environment including family and peers.

Pteridophyte Species Diversity in the Central Peruvian Amazon: Importance of Edaphic Specialization

habitats in the Amazon basin had been overlooked as a partial explanation of the extremely high plant species diversity there. This approach requires evidence of edaphic specialization as a species characteristic, in combination with the presence of soil or topographic variability at a particular site. Gentry (1986, 1988) provided further indications that this is a potent explanation of species diversity patterns among numerous tree and liana species in the Amazon. Edaphic and topographical specialization has recently been shown for various vascular plant species by researchers in lowland forest in Costa Rica (Lieberman et al., 1 985), Panama (Hubbell & Foster, 1983), French Guiana (Lescure & Boulet, 1985), the Brazilian Amazon (Campbell et al., 1986), and the Ecuadorian Amazon (Balslev et al., 1987). Here we report observations made on pteridophytes in a study area with obvious edaphic differences in the western Amazon basin. We tested the hypothesis that the presence of these differences would result in increased species richness of the pteridophytes.

Studies on mycorrhizal associations in Harvard Forest, Massachusetts

An estimate was made of the abundance of different types of mycorrhizal associations in two plant communities of conifers and hardwoods in the Harvard Forest. Lists of plant species, the coverage of their foliage in the canopy and understorey layers, and the types of mycorrhizal associations for 45 species common in these communities are presented. Of the species examined, 91 % were mycorrhizal, representing most of the known major types, viz. ectomycorrhiza, vesicular–arbuscular mycorrhiza (VAM), ericoid, and monotropoid mycorrhiza. Of the 45 species studied, 22% of the species showed ectomycorrhizal, and 71 % VAM associations. A direct spore count was a more reliable method than the most probable number method for determining VAM occurrence in the soil. Spore numbers ranged from 4.4 to 11.8 spores/g oven-dried soil. In conifer stands, ectomycorrhizae were most common, although VAM were also observed in the conifer species. In hardwood stands, VAM were more frequent than in conifer stands, but mycorrhizae were heterogeneous and included a good proportion of the ericoid type. Ectomycorrhizae were more common in communities of low diversity; VAM occurred more frequently in communities of high plant species diversity.

The Effects of Short-term Disturbance on a Freshwater Macrophyte Community

ABSTRACT Areas of a freshwater macrophyte community were disturbed (vegetation removal) to test the hypothesis that the high plant species diversity found in the macrophyte community could be explained in part by disturbance. Three removal treatments were undertaken and the disturbed areas were observed for up to three years. The size, shape and extent of disturbance had an effect on the pattern of plant re-establishment. In narrow clearings, shading by bordering plants appeared to inhibit plant recruitment in the year of the disturbance. In the following year(s) the vegetation on the disturbed areas was indistinguishable from the surrounding vegetation. In broader areas where only the above-ground biomass was removed, some plants regrew from the remaining rhizomes. On large clearings from which both above-ground and some rhizomes were removed, annual macrophyte species became established. Thereafter, there was a successional sequence on the removal area.