Roger C. Anderson

Ecosystems of disturbed ground

Hardbound. As the human population inexorably grows, its cumulative impact on the Earths resources is hard to ignore. The ability of the Earth to support more humans is dependent on the ability of humans to manage natural resources wisely. Because disturbance alters resource levels, effective management requires understanding of the ecology of disturbance. This book is the first to take a global approach to the description of both natural and anthropogenic disturbance regimes that physically impact the ground. Natural disturbances such as erosion, volcanoes, wind, herbivory, flooding and drought plus anthropogenic disturbances such as foresty, grazing, mining, urbanization and military actions are considered. Both disturbance impacts and the biotic recovery are addressed as well as the interactions of different types of disturbance. Other chapters cover processes that are important to the understanding of disturbance of all types including soil proc

WHITE-TAIL DEER (ODOCOILEUS VIRGINIANUS) INFLUENCE ON STRUCTURE AND COMPOSITION OF TSUGA CANADENSIS FORESTS

(1) The effect of heavy and light deer browsing on the composition and structure of eastern hemlock forests was investigated in Wisconsin, United States. (2) Sugar maple rapidly replaced hemlock when both were heavily browsed but reproduction in hemlock soon recovered upon removal of browsing. (3) White-tailed deer have a substantial influence on the reproduction of hemlock, and on the potential of this species to replace itself in forests where hemlock is the dominant tree species.

Interaction of vascular plants and vesicular-arbuscular mycorrhizal fungi across a soil moisture-nutrient gradient

SummaryAbundance and distribution of vascular plants and vesicular-arbuscular mycorrhizal (VAM) fungi across a soil moisture-nutrient gradient were studied at a single site. Vegetation on the site varied from a dry mesic paririe dominated by little bluestem (Schizachyrium scoparium) to emergent aquatic vegetation dominated by cattail (Typha latifolia) and water smartweed (Polygonum hydropiperoides). Plant cover, VAM spore abundance, plant species richness, and number of VAM fungi represented as spores, had significant positive correlations with each other and with percent organic matter. The plant and VAM spore variables had significant negative correlations with soil pH and available Ca, Mg, P and gravimetric soil moisture. Using stepwise multiple regression, Ca was found to be the best predictor of spore abundance. Test for association between plant species and VAM fungal spores indicated that the spores of Glomus caledonium are associated with plants from dry, nutrient poor sites and spores of gigaspora gigantea are positively associated with plants occurring on the wet, relatively nutrient rich sites. Glomus fasciculatum was the most abundant and widely distributed VAM fungus and it had more positive associations with endophyte hosts than the other VAM fungi. We found no relationship between beta niche breadth of plant species and the presence or absence of mycorrhizal infection. However, our data suggest that some plant species may vary with respect to their infection status depending upon soil moisture conditions that may fluctuate seasonally or annually to favor or hinder VAM associations.

Herbaceous Response to Canopy Cover, Light Intensity, and Throughfall Precipitation in Coniferous Forests

Measurements of canopy opening, understory light, throughfall precipitation, and understory herb response in leaf surface area per square meter in pine forests on light—textured soils in northern Wisconsin show that the understory herb layer is more responsive to differences in throughfall precipitation determined by canopy opening than to difference in light. Canopy opening controls both the level of light reaching the herb layer and the proportion of total precipitation reaching the litter layer, but the light levels are apparently considerably above the minimum thresholds for these species. On the light—textured soil—moisture recharge in the surface layers, as influenced by canopy opening, exerts the major control over the total cover of herbaceous species. Moisture content of the lower litter layers and upper soil layer, where most of the northern understory herbs are rooted, is greatly influenced by variations in throughfall determined by canopy opening.

Effect of Garlic Mustard [Alliaria petiolata (Beib. Cavara & Grande)] Extracts on Plants and Arbuscular Mycorrhizal (AM) Fungi

Abstract We examined the effects of garlic mustard (Alliaria petiolata) leachates on germination of arbuscular mycorrhizal (AM) fungal spores, colonization of plant roots by AM fungi and germination and root growth of monocot and dicot plants under laboratory conditions. In the field we examined the effect of garlic mustard on AM inoculum potential (MIP). Water leachates of garlic mustard prevented germination of spores of the AM fungus Gigaspora rosea, inhibited the formation of AM associations with tomato (Lycopesicum esculentum) and significantly reduced germination of tomato seeds. Garlic mustard leachates also reduced root length of tomato and sorghum (Sorghum bicolor) seedlings. Under field conditions we found a significant negative correlation between the density of garlic mustard and the mycorrhizal inoculum potential of the soil in which the plants grew. These results suggest that garlic mustard may reduce the competitive abilities of native plants by interfering with the formation of mycorrhizal associations and root growth.

Evolution and origin of the Central Grassland of North America: climate, fire, and mammalian grazers1

Abstract Grasslands are a widespread vegetation type that once comprised 42% of the plant cover on earths surface. Features commonly shared among grasslands are climates with periodic droughts, landscapes that are level to gently rolling, high abundances of grazing animals, and frequent fires. World-wide expansion of grasslands occurred 8 to 6 MaBP and was associated with increasing abundance of grasses using the C4 photosynthetic pathway, a decline in woodlands, and coevolution of mammals adapted to grazing and open habitats. Beginning with Transeaus seminal paper on the prairie peninsula in 1935, North American ecologists debated the relative importance of fire and climate in determining the distribution of grasslands. In the 1960s, a major research interest was the response of prairies to fire, especially the productivity of burned and unburned grasslands. Understanding mechanisms for increased productivity on burned prairies began in the late 1960s and continued into the middle 1980s. During the past 20 to 25 years, grassland research has focused on the coevolution of grasses and mammalian grazers and fire-grazing interactions that affect habitat heterogeneity and diversity across trophic levels. While this paper does not follow a chronological development of our understanding of grasslands, all of these major research interests are considered.

Recovery of browse-sensitive tree species following release from white-tailed deer Odocoileus virginianus zimmerman browsing pressure

Abstract Deer browsing encourages the development of a vegetation dominated by non-browse or browse-tolerant species at the expense of those sensitive to browsing. For restoration or management of forests, it is crucial to understand how browse-sensitive species recover following release from browsing. As these species re-establish, or achieve former levels of dominance, they must compete with a newly established vegetation. We examined recovery of eastern hemlock Tsuga canadensis (L.) Carr, a shade-tolerant, browse-sensitive tree species, following release from intensive browsing. To examine patterns of recovery over time we used data collected from three forest sites in northern Wisconsin, USA. In an intensely browsed forest, eastern hemlock was the leading dominant in the tree stratum. However, it was absent from the seedling and sapling strata where sugar maple Acer saccharum Marsh. was the dominant species. Twelve years of protection from white-tailed deer Odocoileus virginianus browsing resulted in establishment of hemlock seedlings not present in adjacent browsed areas. In a 27-year-old exclosure, under a canopy of shade-tolerant species, there was apparent recovery of hemlock to a diameter distribution typical of an all-aged forest. In forests subjected to continuous and intensive browsing pressure from the early part of this century, periods as long as 70 years may be required for shade-tolerant trees to achieve size class distribution characteristic of all-aged forests.

ASPECTS OF THE BIOLOGY OF TRIENTALIS BOREALIS RAF.

Three species and one subspecies of Trientalis are recognized in North America, but only Trientalis borealis Raf., the northern starflower, occurs in eastern North America. The life cycle consists of three distinct phases each year: shoot development, rhizome growth, and tuber formation. Asexual reproduction by tubers is more important than reproduction by seed. Of the annual dry matter produced, 64.8% is apportioned to asexual reproduction and less than 2% to sexual tissue. Rhizome growth and tuber formation are regulated by photo—period; short days favor tuberization and long days favor rhizome growth. Tuber formation under field conditions began in July, when the photoperiod was about 15 hr. Cool nights and warm days were more favorable for the accumulation of dry matter than warm nights and days. The number of degree—hours accumulated during shoot development of northern and southern populations was similar at sites 200 miles apart on a north—south gradient, but shoot development occurred during a shorter period of time at the northern site. Seedlings of T. borealis have not been found in the field, but relatively high germination rates were achieved under laboratory conditions, Cold treatment increased the percentage germination of trientalis borealis seeds. Ninety days of stratification delayed the period of peak germination and increased the length of time before germination began after the seeds were exposed to room temperatures. The duration of germination and peak period of germination after stratification were about the same for controls and seeds exposed to 30— or 60—day periods of stratification.

The Ecology and Biology of Panax quinquefolium L. (Araliaceae) in Illinois

-A statewide study of Panax quinquefolium L. (American ginseng), a herb commonly collected for commercial sale, was conducted on 33 protected and unprotected forested sites in the northern, central and southern sections of Illinois. Within these sites, data on the tree, sapling, seedling, shrub and herbaceous strata, and on soil texture and nutrients were collected from a 0.05-ha circular plot in each site. Additional recorded site data included aspect, slope position, steepness and exposure, and disturbance from grazing or timber harvesting. Populations of Panax quinquefolium were found in stands dominated by Acer saccharum, Quercus alba or Q. rubra and with a variety of other herbaceous species common to cool, moist site conditions; 84% of the sites were located on NW-, Nand NE-facing slopes and 80% were in midto low-slope positions. Phenological events began in early May and progressed from S-N; plants were dormant by mid-October. Seeds from individuals growing on several sites within each region were planted at the time of leaf senescence. Seedlings did not appear until the 2nd spring; 66% of the seeds produced seedlings. An anatomical and morphological study of 30 whole field-collected plants indicated that plant age could be accurately determined by counting bud scale scars on the rhizome. These data were used to develop a multiple regression model to predict rhizome age from stem height and number of leaflets. For 30 field-collected and 65 forest-cultivated roots, average weight increased linearly up to age 20, the age of the oldest roots. Population age structure and fruit production on protected sites were compared with that of sites where roots had been removed by collectors. We found fewer plants of all ages on unprotected sites. Fruit production was lower on unprotected sites because fewer 5to 11yr-old plants limit fruit production and rate of population recovery after harvesting.

Numbers and Biomass of Selected Insect Groups on Burned and Unburned Sand Prairie

-Abundance and biomass of selected insect groups were sampled on adjacent burned and unburned sand prairie for 3 years following a single spring burn. The abundance of all insects combined was significantly lower on the burned site than on the unburned site in the 1 st yr postburn but not in subsequent years of the study. Of the selected insect groups, ants were significantly (P < 0.05) more abundant on the burned site than the unburned site for the 1st yr after the fire but not during the 2nd or 3rd. However, for Homoptera the pattern of abundance on burned and unburned sites was reversed. No significant differences in numbers of grasshoppers occurred between burned and unburned sites for any year. However, grasshopper biomass was significantly greater on the unburned site than on the burned site 1 yr postburn but not 2 or 3. Of the two most abundant grasshoppers, Conocephalus strictus was more abundant on the burned site than the unburned site for the 1st and 2nd yr after the burn but not the 3rd, whereas, for Melanoplusflavidus, the pattern of abundance was reversed on burned and unburned sites. The results indicate that while there were varied responses of these insects to fire, none experienced a severe decline in abundance following fire, suggesting they are adapted to habitats experiencing periodic burning.