Intermediate Successional Stages Research Articles

Avian Reproductive Output in European Forest Successions

Data on North American land bird communities have supported the prediction of traditional succession theory that annual reproductive output of organisms would decrease in the course of succession. To test the universality of this idea the average clutch size, brood number and egg production per season (both unweighted and weighted with species abundance) were calculated for 11 European forest successions (58 successional stages altogether). The average clutch size and egg production weighted with species abundance were observed to increase significantly in the course of succession; the other two were not significantly correlated with the successional age. Migratory habit (sedentary species, short-distance migrants and long-distance migrants were distinguished) explained 50% of the variation in egg production unweighted with species abundance and 60% in egg production weighted with species abundance. The pattern observed deviates from theoretical expectations and data from North America. The most probable reason for the between-continent difference is the habitat choice of tropical migrants, whose annual egg production is fairly low in both continents. In North America tropical migrants prefer mature forest (resulting in a low mean egg production there), but in Europe they inhabit early and intermediate successional stages (resulting in a low mean egg production there).

Factors Structuring Fish Assemblages Along a Bog Lake Successional Gradient

Three alternate and distinct fish assemblages were identified in 43 northern Wisconsin lakes encompassing a gradient from bog ponds to small, oligotrophic lakes having little bog character. Multivariate analysis of physical/chemical variables identified three general environmental factors that influence community type and species richness. These factors are: (1) habitat size and heterogeneity; (2) lake productivity— pH; and (3) winter oxygen concentrations. Ordination of lake fish assemblages along these environmental gradients revealed that two factors, lake pH and winter anoxia, were especially crucial in determining assemblage type. Maintenance of these discrete assemblages is also the result of biotic interactions (exclusion of cyprinids due to predation or competition from centrarchids). A centrarchid assemblage dominated lakes across a wide range of habitat types and pH, providing winter anoxia does not occur. Lakes with low winter oxygen concentrations harbor a cyprinid assemblage if the pH is above 5.2—5.4. Lakes that are acidic and also have low winter oxygen contain only two physiologically hardy species comprising the Umbra—Perca assemblage: central mudminnow (Umbra limi) and yellow perch (Perca flavescens). Five fishless lakes had physical and chemical characteristics similar to lakes with an Umbra—Perca assemblage. Within the fish assemblages, no subgroups of closely associated species were evident. For Umbra—Perca lakes, few environmental differences were evident between lakes having (1) no fish, (2) central mudminnows only or, (3) yellow perch and central mudminnows. The sequential loss of species along a gradient from oligotrophic seepage lakes to bog ponds reflected the increased harshness of the chemical environment and the loss of near—shore habitat zones. Species that are specialized zooplanktivores, that utilize hard—bottom substrates for spawning for feeding activities, or that are intolerant of low pH were limited to lakes with little bog character. Lakes in intermediate stages of succession contain acid—tolerant species that are food and habitat generalists. Lakes near the final stages of senescence contained only yellow perch and central mudminnows. The location of bog lakes at the lower end of several environmental gradients makes them valuable sites for studying the influence of environmental factors and biotic interactions on the structure of aquatic communities.

Community structure of estuarine meiobenthos

Meiofaunal samples were collected from intertidal mudflats in the lower, middle and upper reaches of the Tamar estuary, South West England in April and October, 1982. Species abundance and biomass patterns of nematodes and copepods did not follow the expected trends in relation to salinity: the lowest species diversity (below neutral model predictions), the steepest ranked species abundance curves and the greatest departure from the theoretical lognormal distribution of numbers and biomass of individuals among species were found at the middle rather than the upper site. Huston's (1979) dynamic equilibrium hypothesis is invoked to explain these phenomena, but the hypothesis remains to be tested. Intense macrofaunal predation and disturbance, together with more pronounced environmental fluctuations, may eliminate competitive exclusion at the upper site resulting in a relatively high species diversity. The absence of such population reduction mechanisms at the middle site results in competitive exclusion and lowered diversity. The major nematode species at the upper site have certain opportunistic characteristics, and at the middle site conservative characteristics, which support the contention that these are respectively successional and climax communities. The lower site may represent an intermediate successional stage with the highest diversity. The apparent correlation between the abundances of 3 copepod and 1 nematode species with changes in salinity at the middle and upper sites between April and October is thought to result from passive suspension and transport of these species upstream during the summer: there is a distinct fine-scale vertical stratification of species in the sediment at the middle site, with the species in question having an extreme surficial distribution.

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.

Predation by Patiria miniata (Asteroidea) on bryozoans: Prey diversity may depend on the mechanism of succession.

In environments where frequent disturbances interrupt the successional process there will usually be many patches of habitat at intermediate stages of succession. It is then relevant to consider the factors which control local diversity during succession. In offshore kelp forests across the whole Southern Californian Bight settlement panels were rapidly colonised by two species of cyclostome bryozoans (Tubulipora tuba and T. pacifica); but cheilostome bryozoans eventually became dominant during succession because they were able to grow over Tubulipora spp. When abundant, Tubulipora spp. were apparently able to reduce the number of colonies, and hence the number of species, of cheilostome bryozoans settling on the panels. Thus the rapid colonisers may delay the process of succession and reduce the diversity of bryozoans during succession. In field and laboratory experiments we found that the asteroid Patiria miniata preys on Tubulipora spp. but not on cheilostome bryozoans. The predator speeds up the successional process and increases bryozoan diversity by reducing the cover of Tubulipora spp. Other ways in which predators may influence diversity during succession are discussed. The effect of predation may depend on the abundance of the prey and the mechanism of succession.

An ecological survey of the Royal Karnali-Bardia Wildlife Reserve, Nepal: Part III: Ungulate populations

Population density and biomass estimates for wild and domestic ungulates in the Royal Karnali-Bardia Wildlife Reserve, Nepal, are presented and compared with values obtained from other reserves in South Asia. Wild ungulate population densities varied in relation to habitat diversity; large herbivores were most numerous where early and intermediate successional stages intergraded with one another and only sparsely distributed in continuous climax sal Shorea robusta forest. Chital Axis axis was the most abundant wild ruminant in the reserve. It and the nilgai Boselaphus trago-camelus constituted 88% of the total wild herbivore biomass in the southwestern corner of Karnali-Bardia, where an intensive study was carried out. The biomass of domestic stock utilising the same study area in 1975 was computed to be 15–17 times higher than the levels attained by wild ungulates in April of 1977, nearly two years after the reserve borders had been closed to domestic grazing. Observations during the hot-dry season indicated that both wild and domestic ruminants competed for the same forage species. Among the wild ungulates, chital were decidedly the most gregarious, commonly associating in feeding aggregations of over 20 individuals on the open savannahs. Nilgai and wild boar Sus scrofa formed smaller groups while barking deer Muntiacus muntjak and hog deer Axis porcinus were primarily solitary. Chital exhibited a peak in rutting activity during the late hot-dry season and a subsequent birth peak in February. Nilgai exhibited a different pattern, breeding in January and calving during the monsoon, when optimum foraging conditions prevailed.

Inhibition of Nitrification by Climax Ecosystems. III. Inhibitors Other than Tannins

We obtained considerable evidence in earlier work that inhibition of nitrification begins during old-field succession and increases to a maximum in the climax (Rice and Pancholy, 1972, 1973). Moreover, we found that tannins and tannin derivatives appear to be important inhibitors of nitrification. In the present project, other potential phenolic inhibitors of nitrification were identified in acetone extracts of entire plants of most herbaceous species and leaves of tree species important in an intermediate stage of succession and the climax in three vegetation types in Oklahoma. Attempts were made also to identify potential inhibitors in acetone extracts of soil from the top 15 cm of the oak-pine climax. Seventeen potential inhibitors were identified from the eleven important species of plants surveyed. These were mostly phenolic acids and flavonoids, but one coumarin compound, scopolin, was found in high amounts in several species. The potential inhibitors were most common in green tops or green leaves, but roots, dead tops (of previous year), and dead leaves had high amounts of some compounds. Caffeic and ferulic acids were prominent in dead leaves or dead tops, and one flavonoid, myricetin, occurred in sizeable amounts in dead tops of Sorghastrum nutans. The aglycones of most of the compounds were tested against nitrification in soil suspensions, and all completely inhibited oxidation of NH+4 to NO−2 by Nitrosomonas at concentrations as low as 10−6 to 10−8 M. Oxidation of NO−2 to NO−3 by Nitrobacter, however, was affected much less severely by these inhibitors. The greater resistance of Nitrobacter is not significant biologically because inhibition of the first step carried out by Nitrosomonas effectively inhibits the entire process of nitrification. The 3-glucoside of quercetin, isoquercitrin, inhibited the activity of Nitrosomonas completely at the same concentration as quercetin. We found a compound in large quantities in the oak-pine climax soil which appeared in all tests to be a flavonoid aglycone, but we were never able to identify it to our satisfaction. This substance was extremely inhibitory to germination and seedling growth of ‘Crimson Giant’ radish seeds. These have hard seed coats and germinate very rapidly so most inhibitors do not affect their germination at all. It is likely that some, if not all, of the nitrification inhibitors identified may be important in inhibition of nitrification in the later stages of succession and in the climax along with the tannins.

INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS. III. INHIBITORS OTHER THAN TANNINS

We obtained considerable evidence in earlier work that inhibition of nitrification begins during old‐field succession and increases to a maximum in the climax (Rice and Pancholy, 1972, 1973). Moreover, we found that tannins and tannin derivatives appear to be important inhibitors of nitrification. In the present project, other potential phenolic inhibitors of nitrification were identified in acetone extracts of entire plants of most herbaceous species and leaves of tree species important in an intermediate stage of succession and the climax in three vegetation types in Oklahoma. Attempts were made also to identify potential inhibitors in acetone extracts of soil from the top 15 cm of the oak‐pine climax. Seventeen potential inhibitors were identified from the eleven important species of plants surveyed. These were mostly phenolic acids and flavonoids, but one coumarin compound, scopolin, was found in high amounts in several species. The potential inhibitors were most common in green tops or green leaves, but roots, dead tops (of previous year), and dead leaves had high amounts of some compounds. Caffeic and ferulic acids were prominent in dead leaves or dead tops, and one flavonoid, myricetin, occurred in sizeable amounts in dead tops of Sorghastrum nutans. The aglycones of most of the compounds were tested against nitrification in soil suspensions, and all completely inhibited oxidation of NH+4 to NO−2 by Nitrosomonas at concentrations as low as 10−6 to 10−8 M. Oxidation of NO−2 to NO−3 by Nitrobacter, however, was affected much less severely by these inhibitors. The greater resistance of Nitrobacter is not significant biologically because inhibition of the first step carried out by Nitrosomonas effectively inhibits the entire process of nitrification. The 3‐glucoside of quercetin, isoquercitrin, inhibited the activity of Nitrosomonas completely at the same concentration as quercetin. We found a compound in large quantities in the oak‐pine climax soil which appeared in all tests to be a flavonoid aglycone, but we were never able to identify it to our satisfaction. This substance was extremely inhibitory to germination and seedling growth of ‘Crimson Giant’ radish seeds. These have hard seed coats and germinate very rapidly so most inhibitors do not affect their germination at all. It is likely that some, if not all, of the nitrification inhibitors identified may be important in inhibition of nitrification in the later stages of succession and in the climax along with the tannins.

Vegetation Changes following Fire in the Pinyon-Juniper Type of West-Central Utah

Highlight: The stages of succession following fire began with weedy annuals that reached a peak within 3 to 4 years. Juniper woodlands were well developed 8.5 to 90 years following fire. Intermediate stages of succession varied, but followed a general pattern of perennial grasses, perennial grasses-shrubs, and perennial grasses-shrubs-trees. The percentage of dead sagebrush was positively correlated with density of junipers. Thirtythree years was the average minimum age at which Utah juniper produced seed. Juniper and pinyon trees in the Intermountain region have expanded their range greatly since settlement, primarily in the last 100 years. Existing speculation suggests that a major cause of this expansion, either directly or indirectly, was the reduction in fires following settlement. Some authors consider the juniper-pinyon expansion to be several times that of the original cover (Cottam and Stewart, 1940; Woodbury, 1947). In 195 1 it was estimated that this type covered about 30% of the State of Utah (Reuss and Blanch, 1951). The expansion has been primarily into the sagebrush-grass community on the lower edges of original pinyon-juniper. If unchecked, trees become dominant and eventually crowd out most herbaceous and shrub species that provide forage for livestock and big game. The purpose of this study was to examine the vegetation on burns of various ages and determine the successional patterns following fire. The study was conducted primarily on the lower slopes and foothills of the Sheeprock Mountains in Utah and surrounding areas in the vicinity of the Benmore Experimental Range; however, one area was located in the Valley Mountains west of Fayette, Utah. Fire scars of various ages are generally evident in these areas. Tree species in the areas studied were Utah juniper (Juniperus osteosperma) and singleleaf pinyon (Pinus monophylla).

INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS. II. ADDITIONAL EVIDENCE AND POSSIBLE ROLE OF TANNINS

The same nine plots were used in this study as in our previous study on inhibition of nitrification (Rice and Pancholy, 1972). These consisted of three stands representing two stages of old field succession and the climax in each of three vegetation types in Oklahoma: tall grass prairie, post oak‐blackjack oak forest, and oak‐pine forest. Soil samples were analyzed three times during the growing season of 1972 for exchangeable ammonium nitrogen, nitrate, and numbers of Nitrosomonas and Nitrobacter. Results were similar to those obtained during the entire year of 1971. The amount of ammonium nitrogen was lowest in the first successional stage, intermediate in the intermediate successional stage, and highest in the climax. The amount of nitrate was highest in the first successional stage, intermediate in the intermediate successional stage, and lowest in the climax. The numbers of nitrifiers were highest in the first successional stage usually and decreased to a very low number in the climax. These data furnish additional evidence that the nitrifiers are inhibited in the climax so that ammonium nitrogen is not oxidized to nitrate as readily in the climax as in the successional stages. This would aid in the conservation of nitrogen and energy in the climax ecosystem. Some inhibition of nitrification occurred in the intermediate stage of succession also. Previous studies of tannins indicated that these are inhibitory to nitrification, so all important plant species in the intermediate successional stage and the climax were analyzed for total tannin content. A method for extracting and quantifying condensed tannins from soils was developed and the amounts of tannins were determined in each 15‐cm level down to 60 cm in the same two plots in each vegetation type. Gallic and ellagic acids, which result from the digestion of hydrolyzable tannins in oak species, were also extracted and quantified in the climax oak‐pine forest. All the important herbaceous species, including the grasses, were found to have considerable amounts of condensed tannins. The highest amounts of tannins occurred in the oaks and pine, however. Condensed tannins, hydrolyzable tannins, ellagic acid, gallic acid, digallic acid, and commercial tannic acid (hydrolyzable tannin), in very small concentrations, were all found to completely inhibit nitrification by Nitrosomonas in soil suspensions for 3 weeks, the duration of the tests. Slightly larger concentrations were required to inhibit nitrification by Nitrobacter under similar conditions. The concentrations of tannins, gallic acid, and ellagic acid found in the soil of the research plots were several times higher than the minimum concentrations necessary to completely inhibit nitrification. The inhibition of nitrification was always greater in the climax stand than in the intermediate successional stage in each vegetation type, and the concentration of tannins in the top 15 cm of soil was always higher in the climax stand than in the intermediate successional stage. Moreover, the amounts of tannins calculated to be added to each plot each year are much less than the amounts found in the soil, indicating that the tannins accumulate over a period of time. Thus, it appears that the tannins and tannin derivatives may play a continuous and rather prominent role in the inhibition of nitrification by vegetation.

Carbohydrases in Soil as Affected by Successional Stages of Revegetation

AbstractAddition of plant materials from the first successional stage of old‐field succession caused a continuous increase in the microbial population and in activities of amylase, invertase, and cellulase for 45 days, the duration of the experiment. On the other hand, addition of plant materials from an intermediate successional stage or the climax stage resulted in an initial increase in the microbial population and in the activities of the three carbohydrases with a leveling off or decrease after 30 days. Type of organic matter added appeared to be responsible for the higher activities of the carbohydrases during the early stages of old‐field succession.