共查询到20条相似文献，搜索用时 15 毫秒
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Efforts to eradicate invasive plants in restorations can unintentionally create conditions that favor reinvasion over the establishment of desired species, especially when remnant invasive propagules persist. Reducing resources needed by the invader for seedling establishment, however, may be an effective strategy to prevent reinvasion. Propagules of Phalaris arundinacea persist after removal from sedge meadow wetlands and reestablish quickly in posteradication conditions, hindering community restoration. A study was conducted in two experimental wetlands with controlled hydrologic regimes to determine if reducing light by sowing short‐lived, nonpersistent native cover crops or immobilizing soil N by incorporating soil–sawdust amendments can prevent Phalaris reinvasion, allowing native communities to recover. A 10‐species perennial target community and Phalaris were sown with high‐diversity, low‐diversity, or no cover crops in soils with or without sawdust, and seedling emergence, establishment, and growth were measured. High‐diversity cover crops reduced light, decreasing Phalaris and target community seedling establishment by 89 and 57%, respectively. Short‐term nitrogen reduction in sawdust‐amended soils delayed Phalaris seedling emergence and decreased Phalaris seedling establishment by 59% but did not affect total target community seedling establishment. The target community reduced Phalaris seedling establishment as effectively as cover crops did. In plots where the target community was grown, amending soils with sawdust further reduced Phalaris seedling growth but not establishment. Results show that use of cover crops can reduce seedling establishment of desired species and is counterproductive to restoration goals. Further, establishing target species is more important and practical for limiting Phalaris reinvasion than is immobilizing nitrogen. 相似文献
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The interaction between simulated cotyledon herbivory and interspecific competition was studied in a greenhouse experiment using two species of trees, Acer rubrum and Quercus palustris, which commonly invade abandoned agricultural fields. Herbivory treatments were applied as a gradient of cotyledon removal for A. rubrum with 0, 25, 50, 75, and 100% of cotyledon tissue removed. Cotyledons from Q. palustris were clipped and removed (control, early, and late removal) to create a gradient of seed reserve availability. The competition treatment consisted of plugs of old-field vegetation that filled the pots with perennial cover. Mortality of seedlings was higher with competition. There was a significant interaction between herbivory and competition with the highest mortality occurring with competition at the highest intensity of herbivory in both species. Herbivory reduced biomass for Q. palustris only, while competition reduced biomass in both species. Neither species showed an interaction between herbivory and competition for growth. There was a significant interaction between herbivory and competition on allocation patterns for both species, with greater allocation to roots with competition at the highest intensity of herbivory. This study demonstrates the potential for cotyledon herbivory and competition to interact, altering the invasion of tree seedlings into abandoned agricultural land. 相似文献
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Survival,growth, and photosynthesis of tree seedlings competing with herbaceous vegetation along a water-light-nitrogen gradient 总被引：1，自引：3，他引：1
Davis Mark A. Wrage Keith J. Reich Peter B. Tjoelker Mark G. Schaeffer Toni Muermann Carolyn 《Plant Ecology》1999,145(2):341-350
In herbaceous dominated patches and ecosystems, tree establishment is influenced partly by the ability of woody seedlings to survive and grow in direct competition with herbaceous vegetation. We studied the importance of season long wet and dry spells on the competitive interactions between herbaceous vegetation and oak seedlings along a light and nitrogen gradient in an infertile secondary successional grassland in central North America. We conducted a field experiment in which seedlings of bur oak (Quercus macrocarpa) and northern pin oak (Q. ellipsoidalis) were exposed to two levels of light (full sun and 80% shade), three levels of nitrogen input (0, 5, 15 g m–1 yr–1), and three levels of water input (low, medium and high). In addition, seedlings were grown with and without the presence of surrounding herbaceous vegetation under both light and all three water levels. Seedling survival, growth, and rate of photosynthesis were significantly affected by competition with herbaceous vegetation and these effects varied along the multiple resource gradient. Overall, seedling survival of both species was significantly greater in wetter and shaded plots and when surrounding herbaceous vegetation was removed and was lower in nitrogen enriched plots. We found that soil water was significantly affected by varying inputs of water, light, and the presence or absence of herbaceous vegetation, and that seedling survival and rate of photosynthesis were highly correlated with available soil water. Our findings show that the impact of season long wet and dry spells on tree seedling success in grasslands can be affected by light and soil nitrogen availability. 相似文献
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资源竞争理论及其研究进展 总被引：7，自引：0，他引：7
介绍了国外近20年来发展起来的一种新的竞争理论——资源竞争理论。该理论包含两个主要假说,即R^*-法则和资源比假说。资源竞争理论已在微生物、微藻、高等植物及浮游动物中得到广泛的实验验证。阐述了资源竞争理论形成的基础——Monod竞争模型和Droop竞争模型。对两种模型在稳态及非稳态条件下的预测性能作了比较：对于稳态下的竞争,两种模型皆能做出较好的预测,但使用Monod模型更为简便;对于非稳态下的竞争,使用Droop模型更为合理。对资源竞争理论的发展趋势作了展望。 相似文献
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Nadson R. Simões Maria Alice Mendes Colares Fábio A. Lansac‐Tôha Claudia C. Bonecker 《Austral ecology》2013,38(8):952-958
This study examined two models that are most frequently used to describe the relationship between species richness and productivity (SPR): monotonic positive and hump‐shaped models. We assessed zooplankton community diversity in response to algal productivity. The relationship between net primary productivity (NPP) and rarefied species richness was examined by fitting the data to two models and comparing them using the Akaike information criterion (AICc). Macrophyte banks with the highest net primary productivity had the highest zooplankton abundance. Our results pointed to a hump‐shaped model as the best fit to describe the relationship between zooplankton species richness and primary productivity (ΔAICc > 4). Thus, the diversity was lower at the extremes of productivity and higher at intermediate levels of productivity. We suggest that this relationship might occur because when the resource supply rates are low, environmental conditions are stressful, whereas a high availability of resources enhances competitive exclusion. Two observations supported this statement: (i) the total abundance of the community positively correlated with NPP (P < 0.05), indicating that less productive sites had few consumers and the raised productivity tended to favour the total abundance; (ii) NPP was negatively correlated with evenness (P < 0.05), indicating that productivity increased the dominance of certain species in the communities. Therefore, we challenged two of the models most frequently used to explain SPR, and discuss some mechanisms underlying a hump‐shaped SPR. 相似文献
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Muller-Landau HC Condit RS Chave J Thomas SC Bohlman SA Bunyavejchewin S Davies S Foster R Gunatilleke S Gunatilleke N Harms KE Hart T Hubbell SP Itoh A Kassim AR LaFrankie JV Lee HS Losos E Makana JR Ohkubo T Sukumar R Sun IF Nur Supardi MN Tan S Thompson J Valencia R Muñoz GV Wills C Yamakura T Chuyong G Dattaraja HS Esufali S Hall P Hernandez C Kenfack D Kiratiprayoon S Suresh HS Thomas D Vallejo MI Ashton P 《Ecology letters》2006,9(5):575-588
The theory of metabolic ecology predicts specific relationships among tree stem diameter, biomass, height, growth and mortality. As demographic rates are important to estimates of carbon fluxes in forests, this theory might offer important insights into the global carbon budget, and deserves careful assessment. We assembled data from 10 old-growth tropical forests encompassing censuses of 367 ha and > 1.7 million trees to test the theory's predictions. We also developed a set of alternative predictions that retained some assumptions of metabolic ecology while also considering how availability of a key limiting resource, light, changes with tree size. Our results show that there are no universal scaling relationships of growth or mortality with size among trees in tropical forests. Observed patterns were consistent with our alternative model in the one site where we had the data necessary to evaluate it, and were inconsistent with the predictions of metabolic ecology in all forests. 相似文献
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Questions: How do different resource and disturbance levels interact to affect competition? How do different indices of competition change the interpretation of how competition changes under different resource and disturbance conditions? Location: Greenhouse, Thompson Rivers University, Kamloops, British Columbia, Canada. Methods: Three pairs of indices that have been used to differentiate the predictions of Grime (CSR) and Tilman's (R*) theories were used to assess competition on two species of temperate bunchgrass, (Pseudorogeneria spicata and Festuca campestris) grown in a greenhouse on stress and disturbance gradients. Stress was created by manipulating the amount of water (high, low) and concentration of nutrient solution (high, low) added to pots, while disturbance was created by clipping (clipped, unclipped) in a fully factorial design. Plants were grown individually or with a single neighbour. The three pairs of indices were: (1) absolute and relative competition; (2) competitive effect and response; and, (3) competitive importance and intensity. Results: Absolute competition and competitive importance were the only indices responsive to the resource gradient, which supports CSR theory, and also the only ones to record an effect of disturbance on the strength of competition – under high resource conditions. The other indices showed few responses along the gradients, which supports R* theory. Measures of competitive effect and response did not differentiate the two theories. Conclusion: We show that some indices of competition show a decline with increased stress and disturbance, while other indices do not. Therefore, it is necessary to choose a competition index appropriate to the question being asked. Competitive importance and absolute competition were responsive to changes in stress and disturbance, while the other indices were not. 相似文献
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András Kelemen Béla Tóthmérész Orsolya Valkó Tamás Miglécz Balázs Deák Péter Török 《Ecology and evolution》2017,7(7):2432-2440
Classical old‐field succession studies focused on vegetation changes after the abandonment of annual croplands or on succession after the elimination of cultivated crops. Perennial‐crop‐mediated succession, where fields are initially covered by perennial crops, reveals alternative aspects of old‐field succession theories. We tested the validity of classical theories of old‐field succession for perennial‐crop‐mediated succession. We formulated the following hypotheses: (1) functional diversity increases with increasing field age; (2) resource acquisition versus conservation trade‐off shifts toward conservation at community level during the succession; (3) the importance of spatial and temporal seed dispersal decreases during the succession; and (4) competitiveness and stress‐tolerance increases and ruderality decreases at community level during the succession. We studied functional diversity, trait distributions and plant strategies in differently aged old‐fields using chronosequence method. We found increasing functional richness and functional divergence, but also unchanged or decreasing functional evenness. We detected a shift from resource acquisition to resource conservation strategy of communities during the succession. The role of spatial and temporal seed dispersal was found to be important not only at the initial but also at latter successional stages. We found an increasing stress‐tolerance and a decreasing ruderality during succession, while the competitiveness remained unchanged at the community level. Despite the markedly different starting conditions, we found that classical and perennial‐crop‐mediated old‐field successions have some similarities regarding the changes of functional diversity, resource acquisition versus conservation trade‐off, and seed dispersal strategies. However, we revealed also the subsequent differences. The competitive character of communities remained stable during the succession; hence, the initial stages of perennial‐crop‐mediated succession can be similar to the middle stages of classical old‐field succession. Moreover, the occupied functional niche space and differentiation were larger in the older stages, but resources were not effectively utilized within this space, suggesting that the stabilization of the vegetation requires more time. 相似文献
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Mark Rees 《Ecology letters》2013,16(3):291-298
Many experimental studies have quantified how the effects of competition vary with habitat productivity, with the results often interpreted in terms of the ideas of Grime and Tilman. Unfortunately, these ideas are not relevant to many experiments, and so we develop an appropriate resource competition model and use this to explore the effects of habitat productivity on the intensity of competition. Several mechanisms influencing the productivity–competition intensity relationship are identified, and these mechanisms explored using two classic data sets. In both cases, there is good agreement between the model predictions and empirical patterns. Quantification of the mechanisms identified by the models will allow the development of a simple predictive theory linking measures of the intensity of competition with ecosystem‐level properties. 相似文献
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Stephen C. Rossiter Marissa A. Ahlering Brett J. Goodwin Kathryn A. Yurkonis 《Restoration Ecology》2014,22(5):567-570
Litter‐removing disturbances such as fire in grasslands temporarily increase available resources for plants, opening a window of opportunity for new establishment as communities recover. At this time, new individuals or species could be added to the community as a result of germination from the local seed bank. In reconstructed grasslands this may be problematic, as the seed bank may contain a suite of undesired species reflective of prior and surrounding land uses. In two, 25‐year‐old, low‐diversity reconstructed grasslands, we tested the effect of local seed bank establishment following litter‐removing disturbance using seedling removal plots (1 m2) and plots where natural seedling establishment was allowed. Following disturbance, the vegetation was either left intact or hayed to enhance seedling establishment (a common practice following inter‐seeding efforts). Although the seed bank and seedling community were dominated by resident grasses (Andropogon gerardii and Poa pratensis), recruitment from the seed bank increased species richness and reduced evenness through the addition of forb species (including Cirsium arvense) in one of the study sites. Haying temporarily altered the abundances of the dominant grasses, but did not consistently affect seedling recruitment. Disturbances that facilitate seed bank recruitment may promote establishment of undesired species within reconstructed grassland communities, and we need to take steps to better manage the contributions into and recruitment from the seed bank to reconstruct sustainable grasslands. 相似文献
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Root:shoot (R:S) biomass partitioning is one of the keys to the plants' ability to compensate for limiting resources in the environment and thus to survive and succeed in competition. In adult plants, it can vary in response to many factors, such as nutrient availability in the soil or reserves in the roots from the previous season. The question remains whether, at the interspecific level, reserves in seeds can affect seedlings' R:S ratio in a similar way. Proper allocation to resource‐acquiring organs is enormously important for seedlings and is likely to determine their survival and further success. Therefore, we investigated the effect of seed mass on seedling R:S biomass partitioning and its interaction with nutrient supply in the substrate. We measured seedling biomass partitioning under two different nutrient treatments after 2, 4, 6, and 12 weeks for seventeen species differing in seed mass and covering. We used phylogenetically informed analysis to determine the independent influence of seed mass on seedling biomass partitioning. We found consistently lower R:S ratios in seedlings with higher seed mass. Expectedly, R:S was also lower with higher substrate nutrient supply, but substrate nutrient supply had a bigger effect on R:S ratio for species with higher seed mass. These findings point to the importance of seed reserves for the usage of soil resources. Generally, R:S ratio decreased over time and, similarly to the effect of substrate nutrients, R:S ratio decreased faster for large‐seeded species. We show that the seed mass determines the allocation patterns into new resource‐acquiring organs during seedling development. Large‐seeded species are more flexible in soil nutrient use. It is likely that faster development of shoots provides large‐seeded species with the key advantage in asymmetric above‐ground competition, and that this could constitute one of the selective factors for optimum seed mass. 相似文献
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MILENA HOLMGREN BERNAT C. LÓPEZ† JULIO R. GUTIÉRREZ‡ FRANCISCO A. SQUEO‡ 《Global Change Biology》2006,12(12):2263-2271
While climatic extremes are predicted to increase with global warming, we know little about the effect of climatic variability on biome distribution. Here, we show that rainy El Niño Southern Oscillation (ENSO) events can enhance tree recruitment in the arid and semiarid ecosystems of north‐central Chile and northwest Peru. Tree‐ring studies in natural populations revealed that rainy El Niño episodes have triggered forest regeneration in Peru. Field experiments indicate that tree seedling recruitment in Chile is much less successful than in Peru due mostly to larger mortality caused by herbivores. The dramatic impact of herbivores in Chile was derived from the combined result of slower plant growth and the presence of exotic herbivores (European rabbits and hares). The interplay of herbivory and climatic effects we demonstrated implies that rainy ENSO events may represent ‘windows of opportunity’ for forest recovery if herbivore pressure is minimized at the right moment. 相似文献
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Hypothesis: For any one time and place a ‘functional signature’ can be derived for a sample of herbaceous vegetation in a way that concisely represents the balance between the different clusters of functional attributes that are present among component species. Methods: We developed a spreadsheet‐based tool for calculating functional signatures within the context of the C‐S‐R system of plant functional types. We used the tool to calculate and compare signatures for specimen British vegetation samples which differed in management regime and location in time. Conclusion: The integrative power of the ‘C‐S‐R signature’ is useful in comparative studies involving widely differing samples. Movements in the signature can be used to indicate degree of resistance, resilience, eutrophication and dereliction. Systems of plant functional types other than C‐S‐R might also be approached in this way. Availability: The tool can be downloaded free of charge from the first author's web pages or from the journal's electronic archive. 相似文献
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The Chinese government is considering ways to reconstruct Eucalyptus plantation monocultures in order to improve their ecosystem services. However, the effects of competition or facilitation of Eucalyptus on native species during the reconstruction have not been identified, especially during the formation of novel ecosystems. To better understand these relationships, in this study we tested the effects of competition and facilitation of Eucalyptus on three target species (Schima superba, Michelia macclurei, and Castanopsis fissa), in Eucalyptus plantations with different ages and understory vegetation. The results showed that the survival and growth of S. superba and M. macclurei were not sensitive to plantation age and understory removal treatment. The survival of C. fissa in understory removal was significantly higher and the growth of C. fissa increased gradually with increasing plantation age. The relative neighbor effect (RNE) index for growth indicated that the relationship between Eucalyptus and target species switched from competition to facilitation with an increase in plantation age. A redundancy analysis (RDA) showed that survival was positively correlated with soil water content and soil phosphorus. Growth was positively correlated with soil organic matter and soil nitrogen and negatively correlated with soil bulk density. Our results indicate that plantation age, understory vegetation, and species‐specific traits of target seedlings could change the competition and facilitation roles of Eucalyptus. Higher survival and growth rates indicated that C. fissa was an appropriate species for the reconstruction of mature Eucalyptus plantations and understory removal will benefit the process. 相似文献
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磷限制下大型海藻与微藻间资源竞争理论的实验验证 总被引：1，自引：0，他引：1
用一次性培养法结合Monod方程测得海洋微藻-亚心型扁藻(Tetraselmis subcordiformis (Wile) Hazen)与大型海藻-孔石莼(Ulva pertusa Kjellm.)磷限制下的生长动力参数.孔石莼具有较低的半饱和生长常数及最大生长率,其分别为0.016 μmol/L和0.16 d-1,而亚心型扁藻的半饱和生长常数和最大生长率分别是0.021 μmol/L 和0.83 d-1. 两种藻类间的营养竞争实验采用半连续培养法在磷限制条件下进行,实验过程中,分别对两者施予相同或不同的去除率,使两者享有相同或不同的资源需求值R*.由Monod方程所作的竞争预测与实验观察结果的比较显示:仅在两种藻类间的资源需求值R*差异显著(t检验,P＜0.01)时,Monod方程才能对竞争结果作出较为准确的预测;在两种藻类享有相同的资源需求值R*时,亚心型扁藻在竞争中取代孔石莼.Monod模型仅能部分预测大型海藻与海洋微藻间的竞争结果. 相似文献
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DAVID L. GORCHOV JAY O'NEILL DENNIS WHIGHAM DOUGLAS A. NOE 《Plant Species Biology》2011,26(3):221-234
Although plant invasions are often associated with disturbance, localized disturbances can promote invasion either by: (i) creating sites where individuals establish; or (ii) enabling an invader to colonize the entire stand. The former is expected when both establishment and survival to reproductive age require disturbed conditions, whereas the latter should occur in systems when either establishment or survival are limited to disturbed sites. We investigated the role of localized disturbance, specifically treefalls, in the invasion of the Asian Rubus phoenicolasius in a deciduous forest in Maryland, USA. We investigated the density and demography of R. phoenicolasius in treefall gaps of various sizes, but identical age to non‐gap areas, using Classification and Regression Tree (CART) analyses to identify the most important predictors. To explore how the demography of established individuals responds to disturbed versus undisturbed conditions, we carried out a garden experiment with three different levels of shade (5, 12 and 22% full sun). We found vegetative and sexual reproduction, and seedling establishment, to be limited to large gaps in an old stand, but not in a stand in an earlier age of succession. However, in the garden experiment, established plants were able to survive and grow under all shade treatments. These findings indicate that R. phoenicolasius requires disturbances such as treefalls to establish in forests, but established plants will survive canopy closure, leading to stand‐wide invasion. Managers should be able to prevent invasion, however, by inspecting large gaps for new recruits every 3 years. 相似文献
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磷限制下大型海藻与微藻间资源竞争理论的实验验证(英文) 总被引：6，自引：0，他引：6
用一次性培养法结合Monod方程测得海洋微藻_亚心型扁藻 (Tetraselmissubcordiformis (Wile)Hazen)与大型海藻_孔石莼 (UlvapertusaKjellm .)磷限制下的生长动力参数。孔石莼具有较低的半饱和生长常数及最大生长率 ,其分别为 0 .0 16 μmol/L和 0 .16d-1,而亚心型扁藻的半饱和生长常数和最大生长率分别是 0 .0 2 1μmol/L和 0 .83d-1。两种藻类间的营养竞争实验采用半连续培养法在磷限制条件下进行 ,实验过程中 ,分别对两者施予相同或不同的去除率 ,使两者享有相同或不同的资源需求值R 。由Monod方程所作的竞争预测与实验观察结果的比较显示 :仅在两种藻类间的资源需求值R 差异显著 (t检验 ,P <0 .0 1)时 ,Monod方程才能对竞争结果作出较为准确的预测 ;在两种藻类享有相同的资源需求值R 时 ,亚心型扁藻在竞争中取代孔石莼。Monod模型仅能部分预测大型海藻与海洋微藻间的竞争结果。 相似文献