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Seedling Competition (seedling + competition)
Selected AbstractsDevelopment and growth characteristics of Caucasian and white clover seedlings, compared with perennial ryegrassGRASS & FORAGE SCIENCE, Issue 4 2006A. D. Black Abstract Seedling competition for resources during establishment affects the potential success of individual species within a pasture. Germination, emergence and leaf expansion are key characteristics that contribute to the competitive ability of species. In this study, development and growth characteristics of Caucasian clover, white clover and perennial ryegrass (PRG) seedlings were quantified. A base temperature of <4°C and an optimum temperature of ,27°C were found for development in each species. Thermal time (Tt) requirements for 75% of final germination were lower for Caucasian clover (46°C d) and white clover (40°C d) than for PRG (76°C d), but Tt requirements for 50% of final emergence were similar (,110°C d). The phyllochron (°C d leaf,1) for primary stem leaves was slower for Caucasian clover (109°C d) than for white clover (94°C d) and PRG (101°C d). Appearance of the first PRG tiller, which indicates the initiation of secondary leaf development, occurred after 373°C d, compared with 532°C d for the first white clover stolon. Caucasian clover crown shoots did not develop until >1180°C d. Consequently, white clover and PRG had more leaves (,15 plant,1) and faster shoot relative growth rates (,0·062 mg mg,1 d,1) than Caucasian clover (5 leaves plant,1, 0·049 mg mg,1 d,1). [source] Influence of herbivory, competition and soil fertility on the abundance of Cirsium arvense in acid grasslandJOURNAL OF APPLIED ECOLOGY, Issue 2 2000G.R. Edwards Summary 1. ,The extent to which the weed Cirsium arvense (creeping thistle) may be controlled by manipulating interspecific competition and herbivory was examined in two factorial experiments in order to identify non-chemical herbicide-based control methods for the weed. 2. ,In the first experiment, a single spring cultivation of grassland intensively grazed by rabbits led to a 25-fold increase in C. arvense cover within 3 months, the effects of which were still present the following summer. As well as destroying the competing perennial vegetation, cultivation created and dispersed small root fragments (3,5 cm in length) from which almost all shoot recruitment occurred. 3. ,Fencing the cultivated plots against rabbits decreased the cover of C. arvense because ungrazed regrowth from palatable/grazing intolerant species reduced recruitment of C. arvense seedlings and shoots. Seedling competition, in the form of a wildflower seed mix sown soon after cultivation, reduced C. arvense cover on fenced plots to pre-cultivation levels. 4. ,In the second experiment, conducted in a permanent grassland, C. arvense shoot densities on plots fenced against rabbits and treated as a hay meadow were about one-eighth of those found on rabbit-grazed plots where competing vegetation was kept short. Adventitious shoot recruitment was greater on soil disturbances such as molehills and rabbit scrapes than in intact vegetation. Seedling recruitment occurred only on soil disturbances such as molehills. 5. ,Lime and nitrogen fertilizer application to the fenced grassland increased the standing biomass of competing species, which reduced C. arvense shoot density. Outside the fences, rabbit grazing was so concentrated on the competing species of the nitrogen-fertilized and limed areas that C. arvense benefited from competitive release, exhibiting increased shoot density. Cirsium arvense showed pronounced competitive release from grasses, with greater shoot densities where grasses were removed with selective herbicides than where no plant species were removed. 6. ,Exclusion of insects and molluscs with chemical pesticides had no effect on shoot or seedling recruitment or overall shoot density on cultivated soil or in permanent grassland. 7. ,It is concluded that combinations of management procedures that encourage interspecific competition, such as sowing crops soon after cultivation and delaying grazing of them, and nitrogen fertilizer application and non- or reduced grazing of intact grasslands, will help reduce C. arvense abundance. [source] Tropical Montane Forest Restoration in Costa Rica: Overcoming Barriers to Dispersal and EstablishmentRESTORATION ECOLOGY, Issue 4 2000Karen D. Holl Abstract Tropical forests are being cleared at an alarming rate although our understanding of their ecology is limited. It is therefore essential to design restoration experiments that both further our basic knowledge of tropical ecology and inform management strategies to facilitate recovery of these ecosystems. Here we synthesize the results of research on tropical montane forest recovery in abandoned pasture in Costa Rica to address the following questions: (1) What factors limit tropical forest recovery in abandoned pasture? and (2) How can we use this information to design strategies to facilitate ecosystem recovery? Our results indicate that a number of factors impede tropical forest recovery in abandoned pasture land. The most important barriers are lack of dispersal of forest seeds and seedling competition with pasture grasses. High seed predation, low seed germination, lack of nutrients, high light intensity, and rabbit herbivory also affect recovery. Successful strategies to facilitate recovery in abandoned pastures must simultaneously overcome numerous obstacles. Our research shows that establishment of woody species, either native tree seedlings or early-successional shrubs, can be successful in facilitating recovery, by enhancing seed dispersal and shading out pasture grasses. On the contrary, bird perching structures alone are not an effective strategy, because they only serve to enhance seed dispersal but do not reduce grass cover. Remnant pasture trees can serve as foci of natural recovery and may enhance growth of planted seedlings. Our results highlight the importance of: (1) understanding the basic biology of an ecosystem to design effective restoration strategies; (2) comparing results across a range of sites to determine which restoration strategies are most generally useful; and (3) considering where best to allocate efforts in large-scale restoration projects. [source] Seed mass and seedling establishment after fire in Ku-ring-gai Chase National Park, Sydney, AustraliaAUSTRAL ECOLOGY, Issue 4 2004ANGELA T. MOLES Abstract Relationships between seed mass and several aspects of plant regeneration ecology were investigated in a post-fire environment in Ku-ring-gai Chase National Park near Sydney, Australia. We found a significant positive relationship between seed mass and time to seedling emergence (P < 0.001) and a strong negative relationship between seed mass and time between emergence and production of the first true leaf (P < 0.001). Surprisingly, we found no relationship between seed mass and seedling establishment (P = 0.21). It seems most likely that this lack of relationship is a result of the many stochastic factors affecting seedling establishment during any given recruitment episode at any given site. A cause of mortality was assigned to 56% of the 781 seedlings that died during the present study. There was no relationship between cause of death and seed mass (P = 0.28). Of the seedlings for which the cause of death was known, 57% were killed by herbivory and 21% were killed by drought. Seedling,seedling competition affected only one species. [source] | ||||||||||