Seasonal dynamics of nitrogen cycling for a Prosopis woodland in the Sonoran Desert

Prosopis woodlands in the Sonoran Desert have levels of above-ground biomass and productivity much higher than those predicted for desert plant communities with such low levels of precipitation. A stand ofP. glandulosa near the Salton Sea, California, has 13,000 kg ha^?1 aboveground biomass and a productivity of 3700 kg ha^?1 yr^?1. Such a high level of productivity is possible because Prosopis is decoupled from the normal limiting factors of water and nitrogen availability. Soil nitrogen contents for the upper 60 cm of soil beneath Prosopis canopies have 1020 g m^?2 total nitrogen, 25 per cent of which is in the form of nitrate. Such accumulations of nitrogen may be the result of active symbiotic nitrogen fixation. Early estimates suggest that about 25–30 kg N ha^?1 yr^?1 is fixed in these stands. Since Prosopis covers only 34% of the ground surface and its water resources are not limiting, much higher levels of nitrogen fixation and productivity may be possible in managed stands at greater densities.     

Meta-analysis of standing crop reduction byRhinanthus spp. and its effect on vegetation structure

We performed a quantitative literature review on the effect of the root hemiparasiteRhinanthus on vegetation standing crop. (1) Across all available experimental studies in mixed vegetation and in pots, above-ground biomass of co-occurring species is generally reduced, with on average 40% and 60% of the value in the controls respectively. Total above-ground biomass, as the sum of parasite biomass and biomass of co-occurring species, decreases in most cases. For field experiments this reduction amounts, on average, to 26% of the control value. This implies that there is no compensation by the parasites’ biomass for the loss of biomass of co-occurring species due to parasite infection. This can be attributed to the low resource-use efficiency of hemiparasites. Meta-analysis confirmed these trends. (2) In pot experiments, the negative effect of the parasite on the above-ground biomass of the host increases with the number ofRhinanthus plants. In field experiments, we found no relationship between biomass reduction andRhinanthus density. (3) Total above-ground biomass reduction in field experiments increases with standing crop of the vegetation. However, reduction in above-ground biomass of co-occurring species seems to decrease with standing crop. Functional and species diversity buffer the community against negative effects ofRhinanthus. (4) In field experiments, functional groups are affected differently byRhinanthus spp. Grasses and legumes are mostly strongly reduced by the hemiparasites. Non-leguminous dicots mostly benefit from the presence ofRhinanthus. (5) In one out of four weeding experiments,Rhinanthus spp. has a significant (positive) effect on species number. However, the response of plant diversity to invasion of parasitic plants requires further research.     

Plant biomass and nutrient levels of a tropical macrophyte (Cyperus papyrus L.) receiving domestic wastewater

The aboveground biomass and nutrient content ofCyperus papyrus were determined in a small tropical swamp receiving domestic wastewater. It was found that the biomass (4,955 g.m^–2 dry weight) was the highest ever reported for papyrus. The levels of both nitrogen and phosphorus in the plant organs were very high. The nitrogen concentrations of the various plant organs were 4.8% roots, 8.4% rhizomes, 4.5% scales, 4.8% culms, and 6.2% umbels on dry weight basis. As to phosphorus the concentrations were 0.09% roots, 0.11% rhizomes, 0.09% scales, 0.10% culms, and 0.13% umbels. The high biomass and nutrient contents of the plants may have been caused by the high nutrient levels in the surrounding water. Comparison of the nitrogen to phosphorus ratios in the plants to those in the surrounding water showed that the plants stored very high amounts of nitrogen.     

Die jahreszeitliche Entwicklung zweierBolboschoenus-Bestände am Greifswalder Bodden

Throughout the growth season of 1976 the seasonal changes relating to phenology and height of every shoot as well as to density and above-ground biomass in the harvesting areas were investigated at two monospecific stands ofBolboschoenus maritimus.     

Effect of nitrogen addition and drought on above-ground biomass of expanding tall grasses <Emphasis Type="Italic">Calamagrostis epigejos</Emphasis> and <Emphasis Type="Italic">Arrhenatherum elatius</Emphasis>

Tall expansive grasses act as serious weeds since they spread intensively and are a important threat to biodiversity of various plant communities. A field experiment was set up based on three sets of paired plots, where Calamagrostis epigejos and Arrhenatherum elatius dominated and a mixture of both these tall grasses occurred. Parallel plots were treated by additional amounts of nitrogen (50 kg N ha⁻¹) for six years (2002–2007). Above-ground biomass was harvested in both wet (2004) and dry (2007) years, separated in individual fractions, and weighed to determine the above-ground biomass. We wanted to know if a higher nitrogen availability in dry year can support above-ground growth of expansive tall grasses C. epigejos and A. elatius and what their competitive ability of these tall grasses in mixture is in dry conditions. Drought resulted in a decrease in above-ground biomass production of studied tall expansive grasses, and, in a relative increase in mortality of A. elatius shoots in comparison with C. epigejos. Drought can substantially reduce the effect of applied nitrogen on above-ground growth of expansive tall grasses. However, A. elatius appears to be producing more above-ground biomass after application of N even in relatively dry conditions.     

Microclimate and evapotranspiration in two wet grassland communities

Vertical profiles of soil temperature and of the dry and wet bulb temperature of the air, relative humidity and wind velocity were measured within and above stands ofJunco-Molinietum Preising 1951 (facies ofDeschampsia caespitosa) andCaricetum gracilis Almquist 1929 on selected sunny days during the growing season. Evapotranspiration was computed by means of the heat-budget equation. The principal difference between the two communities has been found in the soil temperature. The stand of theCaricetum gracilis occupies a habitat with a cooler soil and with a higher ground water level than the stand of theJunco-Molinietum coeruleae, facies ofDeschampsia caespitosa. The evapotranspiration per unit ground area was higher by some 20% in theCaricetum gracilis. The evapotranspiration per unit above-ground biomass was much the same in both communities.     

Impact of hemiparasitic Rhinanthus angustifolius and R. minor on nitrogen availability in grasslands

Root hemiparasites like Rhinanthus angustifolius C.C. Gmel and R. minor L. have a potential to accelerate the restoration of semi-natural grasslands because they may decrease above-ground biomass of the vegetation. This, in turn, may be beneficial for species diversity. It is known that hemiparasites often accumulate high nutrient concentrations in their above-ground parts, resulting in high quality litter. Because of the short life cycle of many parasitic plants, litter is released early in the season and the main part is not removed from the grassland by hay-making. This has been shown to yield an increased nutrient availability locally. We performed an introduction experiment with R. angustifolius and R. minor in three semi-natural grasslands in Flanders (Belgium). In the second year after sowing, the above-ground nitrogen (N) content of the grasses and of the potential host vegetation (excluding the hemiparasite), was increased in the parasitized plots. The reduction of grass (and legume) above-ground biomass in parasitized plots resulted in a decrease in the total above-ground N uptake of grasses, host and total vegetation (ex- and including the parasite, respectively) of the parasitized plots compared to the control. Furthermore, with a tracer experiment (¹⁵N), we demonstrated that the N from the added tracer was relatively less available in parasitized plots, suggesting larger soil N pools in these treatments. This is probably the consequence of increased mineralization, resulting from the high-quality, parasitic litter. Further experiments should be conducted to investigate the impact of hemiparasitic Rhinanthus spp., e.g. on the availability of other nutrients such as phosphorus.     

Allocation plasticity and modular structure in clonal graminoids in response to waterlogging

Three clonal rhizomatous graminoids (Carex gracilis, C. vesicaria andCalamagrostis canescens) co-dominants of Central European marshlands, were examined for their response to waterlogging. A three-year growth study was carried with treatments where the water level was (a) below, (b) at, and (c) above the soil surface to assess the changes in allocation of plant biomass and modular structure. In waterlogged plants total biomass production was lower. The relatively greater shoot systems of waterlogged plants were characterized by the production of a greater number of tiller modules (of the order of 20%). Roots were the most supressed organs both in sedges andC. canescens. Higher leaf area ratios and specific leaf areas in stressed plants indicate the relative enlargement of photosynthetic structures where stems form a significant component of the shoot (LWR <0.5 as inCalamagrostis) in unstressed conditions; above-ground biomass in stressed plants decreased. But where leaves form a major part of the shoot (LWR>0.5 as in sedges) then above-ground biomass and rhizomes in stressed plants increased and leaf area index became higher. Variation of the mean module biomass in particular species was also associated with the LWR characteristics: modules ofCarex gracilis andC. vesicaria were stable in biomass in all the treatments and reached 0.97±0.04 g and 0.44±0.03 g, respectively; inCalamagrostis the biomass of tillers varied. The number of modules increased in all species under waterlogging regardless of the architectural and reallocation differences between species. The increase in clonal modules is regarded as a general adaptive response to the stress of waterlogging.     

植物地上部氮素损失及其机理研究现状与展望

植物地上部气态氮化合物挥发是氮素损失的重要途径, 同时也是大气NH₃和N₂O的重要来源, 因此, 研究植物氮素挥发损失对于大气环境保护和提高氮肥利用率具有重要意义。该文综述了各种气态氮化物(NH₃、NO、NO₂、N₂O和N₂)损失及其机理, 结果表明, 活性氮源积累和同化的不平衡, 是植物氮素挥发损失的主要因素; 环境条件(光、温、水、肥、气)和植物生理病害、衰老等因素, 均可引起植物活性氮源积累和同化的不平衡, 导致植物地上部氮素的挥发损失, 但各种气体氮化物能否从叶面挥发, 还要取决于气体氮化物的补偿点; NH₃和N₂O是主要的植物氮素损失形态, 主要氮素挥发损失发生在生育后期, 但不同氮素损失形态对植物生育期的响应并未完全相同。该文较完整地归纳总结了植物氮素挥发损失的作用机理, 指出了目前研究尚需要解决的重要问题: 1)氮素损失形态间的内在关系并不清楚, 尚不能完整地解释植物氮素挥发损失机制, 尤其是酶催化协同机制; 2)植物叶际气态氮化物交换(包括吸收和释放)作用及其机理也未完全清楚, 因而难以正确评估植物氮素的挥发损失; 3)植物衰老对增强氮素挥发损失有明显促进效果, 但有关其生理机制尚不完全清楚; 4)缺乏可行的抑制植物氮素挥发技术方法, 故还难以有效缓解肥料氮的挥发损失, 提高氮肥利用率。     

Nutrient limitation and plant species composition in temperate salt marshes

Addition of inorganic nitrogen, phosphorus and potassium in a factorial design in two ungrazed Wadden-Sea salt marshes at low and high elevations showed that nitrogen was the limiting nutrient. No effects of nutrient addition were detected in the 1st year, probably due to a considerable rainfall deficit during the growing season. In the 2nd year, which was more humid, only nitrogen addition caused significant effects in both the low salt marsh dominated by Puccinellia maritima and the high marsh dominated by Festuca rubra. No two-way or three-way interactions with phosphorus or potassium were found. In the low marsh, nitrogen addition had a negative effect on the biomass of Puccinellia, but a positive effect on the biomass of Suaeda maritima and on the total above-ground biomass. Puccinellia was replaced by Suaeda after nitrogen addition, due to shading. In the high salt marsh, no significant effects of fertilizer application on total above-ground biomass were found, due to the weak response of the dominant species Festuca rubra, which accounted for 95% of total biomass. The biomass of Spergularia maritima increased, however, as a response to nitrogen addition.The shoot length of Festuca was positively affected by nitrogen fertilization. It is suggested that stands of Festuca reached maximal biomass at the study site without fertilization and that its growth was probably limited by self-shading. Received: 22 September 1996 / Accepted: 5 April 1997     

Sexual differences in biomass and nutrient allocation of first-year Silene dioica plants

Reproductive and somatic biomass, nitrogen (N), and phosphorus (P) pools were compared between females and males in 1st-year plants of Silene dioica. We estimated irretrievable resources allocated to seeds, pollen, flowers, and unrecovered summer leaf investment by collecting plant parts at abscission throughout the season. At the end of the season, we determined resources lost through senescent stems and autumn leaf turnover and resources stored in perennial roots and overwintering buds. Sexual differences in allocation patterns depended on the resource used for comparison, and whether absolute or proportional resource pools were assessed. Total resource pools in terms of biomass and N were similar for females and males. However, male plants acquired relatively more P. The proportional reproductive investment, i.e., reproductive effort, was similar for males and females in terms of biomass and N. In terms of P, male reproductive effort was higher. There was no difference between sexes in the proportional and relative biomass allocated to perennial roots and overwintering buds. However, in terms of absolute and relative N allocation to below-ground parts, females had larger reserves than males. Females, moreover, had a larger proportion of their P in below-ground parts. However, as male total P pools were larger, absolute P reserves did not differ between sexes. The high reproductive effort and N depletion of below-ground parts in males resulted largely from higher flower production compared to females. In females, seeds were the major component of reproductive effort. These results show that if biomass and nutrient allocation are assessed in parallel for dioecious plants, we obtain a more complete view of their sexual differences. Received: 07 May 1998 / Accepted: 30 October 1998     

养分添加对天山高寒草地植物多样性和地上生物量的影响

为揭示高寒草地物种多样性和地上生物量以及二者之间关系对养分添加的响应模式,该研究以天山高寒草地为对象,通过两年的多重养分添加实验,研究氮(N)、磷(P)、钾(K)3种养分单独和组合添加对天山高寒草地群落物种多样性和地上生物量的影响。结果表明:(1)养分添加使当地植物物种多样性不同程度地减少,其中以N+P、N+K、N+P+K添加的效应最为显著,多重养分添加导致的土壤生态位维度降低是当地物种丧失的重要原因。(2)养分添加能显著提高群落地上生物量,其中N为第一限制养分,解除N限制后P和K成为限制养分, N+P+K复合添加对地上生物量的提高最为显著。(3)养分添加两年后,地上生物量与物种丰富度之间无显著回归关系且地上生物量增加主要是由于禾草类生物量增加导致,说明地上生物量主要由少数优势种决定而非群落物种数。     

Transpiration of a 64-year old maritime pine stand in Portugal

Alpine plant species have been shown to exhibit a more pronounced increase in leaf photosynthesis under elevated CO₂ than lowland plants. In order to test whether this higher carbon fixation efficiency will translate into increased biomass production under CO₂ enrichment we exposed plots of narrow alpine grassland (Swiss Central Alps, 2470 m) to ambient (355 μl l^-1) and elevated (680 μl l^-1) CO₂ concentration using open top chambers. Part of the plost received moderate mineral nutrient additions (40 kg ha^-1 year^-1 of nitrogen in a complete fertilizer mix). Under natural nutrient supply CO₂ enrichment had no effect on biomass production per unit land area during any of the three seasons studied so far. Correspondingly, the dominant species Carex curvula and Leontodon helveticus as well as Trifolium alpinum did not show a growth response either at the population level or at the shoot level. However, the subdominant generalistic species Poa alpina strongly increased shoot growth (+47%). Annual root production (in ingrowth cores) was significantly enhanced in C. curvula in the 2nd and 3rd year of investigation (+43%) but was not altered in the bulk samples for all species. Fertilizer addition generally stimulated above-ground (+48%) and below-ground (+26%) biomass production right from the beginning. Annual variations in weather conditions during summer also strongly influenced above-ground biomass production (19–27% more biomass in warm seasons compared to cool seasons). However, neither nutrient availability nor climate had a significant effect on the CO₂ response of the plants. Our results do not support the hypothesis that alpine plants, due to their higher carbon uptake efficiency, will increase biomass production under future atmospheric CO₂ enrichment, at least not in such late successional communities. However, as indicated by the response of P. alpina, species-specific responses occur which may lead to altered community structure and perhaps ecosystem functioning in the long-term. Our findings further suggest that possible climatic changes are likely to have a greater impact on plant growth in alpine environments than the direct stimulation of photosynthesis by CO₂. Counter-intuitively, our results suggest that even under moderate climate warming or enhanced atmospheric nitrogen deposition positive biomass responses to CO₂ enrichment of the currently dominating species are unlikely.     

Nutrient accumulation byPinus caribaea in its native savanna habitat

Summary Concentrations of P, N, K, Ca, and Mg in above-ground tissues ofP. caribaea were sampled in the species'native savanna habitat. Concentrations were relatively low, but some evidence of higher consumption of K and Ca was found in trees grown on more fertile soils. Regressions were developed to predict the quantities of nutrients sequestered in above-ground tree tissues, and estimates made of the quantities stored in above-ground stands of this species in its native habitat and in several plantations elsewhere. Estimates were also made of the nutrient removals to be expected by harvesting these stands in different ways. Nutrient quantities stored in stands generally exceed those extractable from savanna surface soils, and it is suggested that inputs from the atmosphere are the most probable alternate nutrient source. A comparison of these inputs for tropical areas with the quantities required for stand growth in the savanna, and harvesting removals, suggests that an adequate supply of all elements except P exists, provided that capture by pine is effective. However, atmospheric inputs generally fall below the storage and harvest removal rates for fast growing exotic plantations of this species suggesting that multiple rotations of these plantations at current growth rates may not be feasible without artifical fertilization.     

植物种群自疏过程中构件生物量与密度的关系

不论是在对植物种群自疏规律还是在对能量守衡法则的研究中,个体大小(M)大多针对植物地上部分生物量,地下部分和构件生物量及其动态十分重要又多被忽视。以1年生植物荞麦为材料研究了自疏种群地下部分生物量、包括地下部分的个体总生物量以及各构件生物量与密度的关系。结果表明:平均地上生物量和个体总生物量与密度的异速关系指数(γabove-ground和γindividual)分别为-1.293和-1.253,与-4/3无显著性差异(P>0.05),为-4/3自疏法则提供了有力证据;平均根生物量-密度异速指数γroot(-1.128)与-1无显著性差异(P>0.05),与最终产量恒定法则一致;平均茎生物量-密度异速指数γstem(-1.263)接近-4/3(P>0.05),平均叶生物量-密度异速指数γleaf(-1.524)接近-3/2(P>0.05),分别符合-4/3自疏法则与-3/2自疏法则;而繁殖生物量与密度的异速关系指数γreproductive(-2.005)显著小于-3/2、-4/3或-1(P<0.001)。因此,不存在一个对植物不同构件普适的生物量-密度之间的关系。光合产物在地上和地下构件的生物量分配格局以及构件生物量与地上生物量之间特异的异速生长关系导致不同构件具有不同的自疏指数。无论对于地上生物量还是个体总生物量,荞麦种群能量均守衡,而对于地下生物量,荞麦种群能量不守衡。     

基于树木起源、立地分级和龄组的单木生物量模型

以马尾松(Pinus massoniana)和落叶松(Larix)的大样本实测资料为建模样本,以独立抽取的样本为验证样本,把样本按起源、立地和龄组进行分级,采用与材积相容的两种相对生长方程,分普通最小二乘和两种加权最小二乘,对地上部分总生物量、地上各部分生物量和地下生物量进行模型拟合和验证,使用决定系数、均方根误差、总相对误差和估计精度等8项统计量对结果进行分析。结果表明:两个树种地上部分总生物量,立地分类方法,模型的拟合结果和适用性都最优;马尾松VAR模型较优,而落叶松CAR模型较好;两种加权最小二乘方法,在建模样本和验证样本中表现得不一致。在建模样本中,加权回归2(权重函数1/f^0.5)略优于加权回归1(权重函数1/y^0.5),但在验证样本中,加权回归1却明显优于加权回归2。而同时满足建模样本拟合结果最优和验证样本检验结果最优的组合中,只有加权回归1。两个树种地上部分各分量生物量,模型拟合结果和适用性,均为干材最优,树叶最差、树枝和树皮居中,样本分类、模型类型和加权最小二乘方法对干材生物量的影响,规律和地上部分总生物量相同;样本分类、模型类型和加权最小二乘方法的最优组合,用验证样本检验的结果,总相对误差树枝不超过±10.0%,树皮不超过±5.0%,树叶马尾松不超过±30.0%,落叶松不超过±20.0%。两个树种地下部分(根)生物量,样本按龄组分类方法,模型拟合结果最优,与材积相容的模型总体上优于与地上部分总生物量相容模型。     

Restoration of Species‐Rich,Nutrient‐Limited Mountain Grassland by Mowing and Fertilization

Mowing and management to reduce nutrient levels have often been successfully used to restore species‐rich grasslands in various parts of Europe. However, such treatments have failed to restore the species‐rich Central European mountain grasslands dominated by Polygonum bistorta. P. bistorta builds an extensive underground rhizome system that monopolizes available nutrients in these nutrient‐poor grasslands, enabling this species to persist at high densities even in the presence of mowing. Therefore, we tested a restoration approach using a factorial combination of fertilization and mowing, as well as a litter removal treatment. The experiment was run over 5 years and species composition response to these treatments was recorded at two spatial scales. Mowing suppressed flowering and cover of P. bistorta and promoted target grassland species and richness. Fertilization prevented nutrient impoverishment and increased height and dominance of the broad‐leaved grasses with which many species‐rich grassland herbs could coexist. The additive effect of the mowing/fertilization treatments was strong enough to act as a driver of P. bistorta suppression and associated community change. The litter removal treatment, however, had little effect on plant composition. The experiment demonstrates that in nutrient‐limited grasslands, increasing nutrient levels in addition to mowing to manage competition for light can be used to control dominants. This contrasts with restoration of systems where after abandonment increased nutrient levels lead to the establishment of tall dominants that suppress other species by competition for light.     

A comparison of the annual production and biomass in three monospecific stands of the seagrass Thalassia hemprichii (Ehrenb.) aschers.

Annual production and biomass data were collected in three seagrass communities of Thalassia hemprichii (Ehrenb.) Aschers. from Papua New Guinea. Leaf growth rates, determined by the marking technique, resulted in a growth rate of 8.3 mm day^?1 for the youngest leaves. Production of above-ground plant parts was assessed by the plastochrone interval. The annual mean values were 9.3, 10.0 and 9.9 days for Sites 1, 2 and 3, respectively. Annual mean total above-ground production amounted to 2.1 mg ADW shoot^?1 day^?1 at Site 1, and 5.5 and 4.5 mg ADW shoot^?1 day^?1 for Sites 2 and 3, respectively; 73–89% of the total net production was contributed by the leaves. Rhizome production was correlated to the plastochrone interval of the leaves. Annual mean biomass of leaves amounted to 16–27% of the total biomass. The mean biomass of the other plant parts remained constant during the year. The annual mean turnover time of the different plant parts (above- and below-ground) varied considerably between the sites.     

Early recovery signs of an Australian grassland following the management of Parthenium hysterophorus L.

Parthenium weed (Parthenium hysterophorus L.) is believed to reduce the above- and below-ground plant species diversity and the above-ground productivity in several ecosystems. We quantified the impact of this invasive weed upon species diversity in an Australian grassland and assessed the resulting shifts in plant community composition following management using two traditional approaches. A baseline plant community survey, prior to management, showed that the above-ground community was dominated by P. hysterophorus, stoloniferous grasses, with a further high frequency of species from Malvaceae, Chenopodiaceae and Amaranthaceae. In heavily invaded areas, P. hysterophorus abundance and biomass was found to negatively correlate with species diversity and native species abundance. Digitaria didactyla Willd. was present in high abundance when P. hysterophorus was not, with these two species, contributing most to the dissimilarity seen between areas. The application of selective broad leaf weed herbicides significantly reduced P. hysterophorus biomass under ungrazed conditions, but this management did not yet result in an increase in species diversity. In the above-ground community, P. hysterophorus was partly replaced by the introduced grass species Cynodon dactylon L. (Pers.) 1 year after management began, increasing the above-ground forage biomass production, while D. didactyla replaced P. hysterophorus in the below-ground community. This improvement in forage availability continued to strengthen over the time of the study resulting in a total increase of 80% after 2 years in the ungrazed treatment, demonstrating the stress that grazing was imposing upon this grassland-based agro-ecosystem and showing that it is necessary to remove grazing to obtain the best results from the chemical management approach.     

Partitioning of Stored Resources Between Shoots in a Clone, and its Effects on Shoot Size Hierarchy

A theoretical study is described of the effects of the patternof partitioning of stored resources between the shoots of aclone on the development of shoot size hierarchy. When thereis an increasing convex relationship between the amount of resourcesavailable to a shoot at the start of growth and its biomassat maturity, the mode of competition between the shoots is asymmetricand the sharing of stored resources between shoots will notmaximize above-ground biomass of the clone at maturity. Underthis condition, the plant is predicted to allocate a smalleramount of its resources to storage, producing a lower below/above-groundbiomass ratio. Clonal species in which shoots compete asymmetricallyare known to have smaller below/above-ground biomass ratios.When there is an increasing concave relationship between theamount of resources available to a shoot at the start of growthand shoot biomass at maturity, the mode of competition willbe symmetric, and equal sharing of stored resources betweenall shoots at the start of growth will maximize the above-groundbiomass of the clone at maturity. If sharing of resources isthe optimal pattern of partitioning, all shoots of the cloneare predicted to be equal in size at maturity and, therefore,a size hierarchy will not develop within a clone. Copyright2001 Annals of Botany Company Clonal plants, pattern of partitioning, stored resources, shoot competition, size hierarchy, sharing of resources, symmetric competition