植物根系养分捕获塑性与根竞争

为了更有效地从土壤中获取养分, 植物根系在长期的进化与适应中产生了一系列塑性反应, 以响应自然界中广泛存在的时空异质性。同时, 植物根系的养分吸收也要面对来自种内和种间的竞争。多种因素都会影响植物根竞争的结果, 包括养分条件、养分异质性的程度、根系塑性的表达等。竞争会改变植物根系的塑性反应, 比如影响植物根系的空间分布; 植物根系塑性程度差异也会影响竞争。已有研究发现根系具有高形态塑性和高生理塑性的植物在长期竞争过程中会占据优势。由于不同物种根系塑性的差异, 固定的对待竞争的反应模式在植物根系中可能并不存在, 其响应随竞争物种以及土壤环境因素的变化而变化。此外, 随着时间变化, 根系塑性的反应及其重要性也会随之改变。植物对竞争的反应可能与竞争个体之间的亲缘关系有关, 有研究表明亲缘关系近的植物可能倾向于减小彼此之间的竞争。根竞争对植物的生存非常重要, 但目前还没有研究综合考虑植物的各种塑性在根竞争中的作用。另外根竞争对群落结构的影响尚待深入的研究。     

不同养分环境下木荷种源生长和根系发育对邻株竞争响应的差异

研究同质和异质养分环境中邻株竞争对3个木荷种源生长和根系发育的影响,揭示了不同种源木荷生长竞争能力差异原因.结果表明: 与同质养分环境相比,3个木荷种源在异质养分环境中具有苗高生长量大、干物质积累量高和根系增生明显等特点.在异质养分环境下,福建建瓯种源木荷苗木生长量显著高于浙江龙泉和江西信丰种源,与杉木混植时尤为突出,这与其根系形态可塑性高和拓殖能力强有关,混植时,福建建瓯种源木荷的根长、根表面积和根体积等根系生长量较单植显著增长20.4 %～69.0%,其根系在富养表层大量增生的同时快速向深层贫养层拓殖,占有了更多的空间和资源,提高了觅养能力,使其生长优势更为明显,而浙江龙泉和江西信丰种源根系生长和深层土壤根系分布受邻株竞争影响不同程度的降低.纯植时,可能由于根系自我识别作用,3个木荷种源的根系生长发育均受到抑制,导致福建建瓯种源苗木生长量显著减小,而浙江龙泉种源苗高和干物质积累增长明显,这与其根系生理可塑性有关.建议生产上选用觅养效率高和竞争能力强的福建建瓯种源木荷,采用混交造林的方式提高木荷人工林生产力.     

不同养分环境下邻株竞争对木荷和杉木生长、细根形态及分布的影响

以木荷和杉木为试验材料,模拟异质和同质两种森林土壤养分环境,设计单植、两株纯植和两株混植3种栽植方式,开展盆栽试验研究木荷与杉木混交造林增产及木荷生长竞争优势形成的原因.结果表明: 与同质养分环境相比,异质养分环境中木荷与杉木混植时两树种均具有较高的苗高和干物质积累量,且木荷竞争优势明显,这与其根系可塑性强有关.混植的木荷各径级细根大量增生,其根系总长度、表面积和体积比杉木高80%～180%.木荷细根在垂直方向上采用了补偿性的生长策略,即除占据富养表层外,还在低养分斑块中大量增殖以获得更大的竞争优势.木荷与杉木的细根在土壤中的拓殖深度不同,生态位分化,缓解了两树种根系对养分的强烈竞争,提高了混植产量.纯植的木荷由于根系自我识别作用,抑制了根系的生长,使得纯植产量较低.细根在空间上错开和均匀分布可能是木荷纯林结构稳定的原因之一.建议在生产中采用块状整地和表层施肥等措施,改善土壤养分分布状况,营建混交林促进木荷和杉木生长,而对已营造的木荷人工纯林,可以及时调控林分密度促进林木生长.     

Intra- and interspecific dominance hierarchies and variation in foraging tactics of two species of stream-dwelling chars

Aggressive interactions, foraging behavior, habitat use and diet were studied in sympatric populations of white-sported char,Salvelinus leucomaenis, and Dolly Varden,Salvelinus malma, in a Japanese mountain stream. Underwater observations on individuals of both species revealed two distinct behavioral regimes: aggressive drift foragers and non-aggressive benthos foragers. Aggressive drift foragers defended partial territories around focal points from which they made forays to capture invertebrates drifting in the water column. Non-aggressive benthos foragers cruised around and beneath cobble in large foraging ranges that overlapped each other. Intra- and interspecific, size-dependent dominance hierarchies were recognized among aggressive drift foragers, whereas non-aggressive benthos foragers showed no such relationships. Terrestrial invertebrates were the most abundant prey in the diets of drift foragers, whereas a very small proportion of the diet of benthos foragers was made up of these taxa. Benthos foragers showed more complex diet composition than drift foragers. These results suggest that non-aggressive benthos foragers may avoid not only interference but also exploitative competition by using alternative foraging tactics. The proportion of drift foragers to benthos foragers among white-spotted char was more than 35 times that among Dolly Varden. The significant difference in the proportion of each species using the two types of foraging strategy results in interspecific food segregation in sympatric populations.     

大别山五针松种内和种间竞争强度

通过对安徽省岳西县大别山五针松群落内的53株对象木及2079株竞争木的调查,运用Hegyi单木竞争模型分析了大别山五针松的种内和种间竞争强度。结果表明,大别山五针松的种内和种间竞争强度分别为17.11%和82.89%,说明竞争主要来自种间。大别山五针松的伴生种较多,种内与主要伴生种间的竞争关系为短柄枹大别山五针松种内黄山松满山红茅栗金缕梅紫茎四照花灯台树鹅耳枥。竞争强度随对象木胸径的增大而减小,当对象木的胸径小于25cm时,所受到的竞争强度较大;当胸径在25cm以上时,竞争强度变化很小,二者符合幂函数关系(CI=AD-B),所得的预测模型能很好的预测大别山五针松种内和种间竞争强度。     

Fine root responses to temporal nutrient heterogeneity and competition in seedlings of two tree species with different rooting strategies

There is little direct evidence for effects of soil heterogeneity and root plasticity on the competitive interactions among plants. In this study, we experimentally examined the impacts of temporal nutrient heterogeneity on root growth and interactions between two plant species with very different rooting strategies: Liquidambar styraciflua (sweet gum), which shows high root plasticity in response to soil nutrient heterogeneity, and Pinus taeda (loblolly pine), a species with less plastic roots. Seedlings of the two species were grown in sandboxes in inter‐ and intraspecific combinations. Nutrients were applied in a patch either in a stable (slow‐release) or in a variable (pulse) manner. Plant aboveground biomass, fine root mass, root allocation between nutrient patch and outside the patch, and root vertical distribution were measured. L. styraciflua grew more aboveground (40% and 27% in stable and variable nutrient treatment, respectively) and fine roots (41% and 8% in stable and variable nutrient treatment, respectively) when competing with P. taeda than when competing with a conspecific individual, but the growth of P. taeda was not changed by competition from L. styraciflua. Temporal variation in patch nutrient level had little effect on the species’ competitive interactions. The more flexible L. styraciflua changed its vertical distribution of fine roots in response to competition from P. taeda, growing more roots in deeper soil layers compared to its roots in conspecific competition, leading to niche differentiation between the species, while the fine root distribution of P. taeda remained unchanged across all treatments. Synthesis. L. styraciflua showed greater flexibility in root growth by changing its root vertical distribution and occupying space of not occupied by P. taeda. This flexibility gave L. styraciflua an advantage in interspecific competition.     

Do past experience and competitive ability influence foraging strategies of parasitoids under interspecific competition?

Abstract 1. In solitary parasitoids, several species can exploit the same host patch and competition could potentially be a strong selective agent as only one individual can emerge from a host. In cereal crops, Aphidius rhopalosiphi and A. ervi share the grain aphid Sitobion avenae as host. 2. The present work studied foraging strategies of both species on patches already exploited by the other species. The study analysed larval competition in multi‐parasitised hosts and compared the foraging behaviour of females with and without previous experience. 3. It was found that A. ervi wins larval competition three times more often than A. rhopalosiphi. Both species spent less time on patches exploited by a heterospecific than on unexploited ones. When they foraged on heterospecifically exploited patches, experienced females induced less mortality in aphids than inexperienced ones. 4. Although A. rhopalosiphi is a specialist on cereal aphids and is the most abundant species due to its early appearance in the season, S. avenae is still a profitable host for A. ervi, because: (i) A. rhopalosiphi leaves patches partially exploited, (ii) A. ervi wins larval competition in three out of four multi‐parasitised hosts, and (iii) A. ervi is only slightly deterred by the cornicular secretions of the host and can thus easily parasitise hosts.     

立地条件差异对天然东北红豆杉(Taxus cuspidata)种间竞争的影响

立地因子空间梯度特征是影响种间竞争的重要因素。通过研究主要竞争树种及竞争强度随海拔、坡向、坡位和坡度等立地因子变化的规律,揭示不同立地条件对天然东北红豆杉种间竞争的影响,为濒危东北红豆杉种群的保护与恢复提供理论指导。研究结果表明：东北红豆杉的种间竞争压力主要来自紫椴、臭冷杉、色木槭、红松、青楷槭、枫桦、花楷槭等7个树种,主要竞争树种以小径级个体居多。立地因子差异对种间竞争强度和主要竞争树种的排序有明显影响。东北红豆杉在阴坡受到的种间竞争压力是阳坡的3.27倍,主要树种的竞争强度显著高于阳坡,竞争树种的排序发生更迭;随着坡位的提升,东北红豆杉受到的种间竞争压力明显增加,主要竞争种类和强度也发生变化;坡度增加,种间竞争强度增加,主要竞争树种排序发生变化;海拔对种间竞争的影响总体不大,但影响主要竞争树种的竞争强度和排序。     

Giving-up densities of foraging gerbils: the effect of interspecific competition on patch use

We studied the effect of a dominant species, Gerbillus pyramidum (Egyptian sand gerbil), on the patch use of its subordinate competitor, G. andersoni allenbyi (Allenby's gerbil), to better understand interspecific competition between the two species. We used manipulated resource patches (seed trays) covered with cages with two adjustable species-specific gates (either opened or closed to the bigger-dominant species, but always opened to the subordinate one). We recorded species tracks around and on the seed trays and giving-up densities (GUDs) of seeds in the trays after each night of foraging. G. a. allenbyi depleted seed patches to a lower level whenever G. pyramidum was given the opportunity to forage on the seed trays (i.e., present on the grid). This result held regardless of whether G. pyramidum was actually present at a particular station. We suggest that competition from G. pyramidum occurs both directly by interference, in which G. a. allenbyi is forced to be active in the late part of the night, and indirectly by exploitation via resource depletion by G. pyramidum in the early part of the night. The results suggest that interspecific competition from G. pyramidum reduces seed availability and the richness of the environment for G. a. allenbyi enough to affect the marginal value of energy for G. a. allenbyi individuals and cause them to experience lower costs of predation and manifest lower GUDs.     

Effects of elevated CO2 on the interspecific competition between two sympatric species of Aphis gossypii and Bemisia tabaci fed on transgenic Bt cotton

Abstract Effects of elevated CO₂ (twice ambient vs. ambient) and Bt Cry1Ac transgene (Bt cotton cv. 33^B vs. its nontransgenic parental line cv. DP5415) on the interspecific competition between two ecologically similar species of cotton aphid Aphis gossypii and whitefly biotype‐Q Bemisia tabaci were studied in open‐top chambers. The results indicated that elevated CO₂ and Bt cotton both affected the population abundances of A. gossypii and biotype‐Q B. tabaci when introduced solely (i.e., without interspecific competition) or two species coexisted (i.e., with interspecific competition). Compared with ambient CO₂, elevated CO₂ increased the population abundances of A. gossypii and biotype‐Q B. tabaci as fed on Bt and nontransgenic cotton on 45 (i.e., seedling stage) and 60 (i.e., flowering stage) days after planting (DAP), but only significantly enhanced aphid abundance without interspecific competition on the 45‐DAP nontransgenic cotton and 60‐DAP Bt cotton, and significantly increased whitefly abundance with interspecific competition on the 45‐DAP Bt cotton and 60‐DAP nontransgenic cotton. In addition, compared with nontransgenic cotton at elevated CO₂, Bt cotton significantly reduced biotype‐Q B. tabaci abundances without and with interspecific competition during seedling and flowering stage, while only significantly decreasing A. gossypii abundances without interspecific competition during the seedling stage. When the two insect species coexisted, the proportions of biotype‐Q B. tabaci were significantly higher than those of A. gossypii on Bt and nontransgenic cotton at the same CO₂ levels, and elevated CO₂ only significantly increased the percentages of biotype‐Q B. tabaci and significantly reduced the proportions of A. gossypii on seedling and flowering nontransgenic cotton. Therefore, the effects of elevated CO₂ were favorable for biotype‐Q B. tabaci to out‐compete A. gossypii under the predicted global climate change.     

4种寄生蜂在草地贪夜蛾卵上的种群增长潜能及优势蜂种间竞争

为明确入侵性重大农业害虫草地贪夜蛾卵期优势寄生蜂种类,采用生命表方法评价了夜蛾黑卵蜂、短管赤眼蜂、螟黄赤眼蜂和松毛虫赤眼蜂这4种寄生蜂在草地贪夜蛾卵上的种群增长潜力,并观察比较了短管赤眼蜂和夜蛾黑卵蜂这两种优势蜂种在草地贪夜蛾卵上的竞争行为。结果表明,供试的4种寄生蜂对草地贪夜蛾卵均表现出良好的寄生适应性,内禀增长率（rm）与周限增长率（λ）从大到小依次为短管赤眼蜂（rm, 0.3449; λ, 1.4118）、夜蛾黑卵蜂（rm, 0.2842; λ, 1.3286）、螟黄赤眼蜂（rm, 0.1960; λ, 1.2165）和松毛虫赤眼蜂（rm, 0.1751; λ, 1.1913）。当夜蛾黑卵蜂与短管赤眼蜂竞争寄生同一草地贪夜蛾卵块时,两种蜂的子代羽化率均显著低于各自单独寄生时。草地贪夜蛾卵在被夜蛾黑卵蜂寄生后1 h、24 h及48 h均可被短管赤眼蜂寄生,夜蛾黑卵蜂的子代羽化率分别为21.15%（1 h）、36.68%（24 h）和25.52%（48 h）,均高于短管赤眼蜂的子代羽化率10.94%（1 h）、23.13%（24 h）和5.23%（48 h）;而当短管赤眼蜂先寄生时,虽然寄生后1 h、24 h和48 h的卵粒也能被夜蛾黑卵蜂寄生,但所羽化的子代均为短管赤眼蜂,羽化率分别为42.62%（1 h）、46.93%（24 h）和38.66%（48 h）。本研究表明,与螟黄赤眼蜂和松毛虫赤眼蜂相比,短管赤眼蜂和夜蛾黑卵蜂在草地贪夜蛾卵上表现出更强的种群增长潜能;夜蛾黑卵蜂与短管赤眼蜂竞争寄生同一寄主卵块时,两者寄生能力均会受到不同程度的抑制,但短管赤眼蜂的竞争力明显强于夜蛾黑卵蜂。     

Experimental evidence for root competition effects on community evenness in one of two phytometer species

AimsPlant–plant interactions, being positive or negative, are recognized to be key factors in structuring plant communities. However, it is thought that root competition may be less important than shoot competition due to greater size symmetry belowground. Because direct experimental tests on the importance of root competition are scarce, we aim at elucidating whether root competition may have direct or indirect effects on community structure. Indirect effects may occur by altering the overall size asymmetry of competition through root–shoot competitive interactions.     

不同起始密度对3种赤潮微藻种间竞争的影响

通过共培养的方法,研究了不同起始密度对赤潮异弯藻和中肋骨条藻、塔玛亚历山大藻和赤潮异弯藻、塔玛亚历山大藻和中肋骨条藻之间种间竞争的影响。结果表明1赤潮异弯藻对中肋骨条藻的生长有一定的抑制作用,随着初始接种时赤潮异弯藻细胞密度的提高,这种抑制作用愈加明显。2塔玛亚历山大藻和中肋骨条藻与塔玛亚历山大藻和赤潮异弯藻之间的种间竞争结果相类似,即起始密度比例为A∶S(H)=1∶4时,中肋骨条藻和赤潮异弯藻分别在竞争中占优势;当起始密度比例为A∶S(H)=1∶1和A∶S(H)=4∶1,塔玛亚历山大藻在竞争中占优势。     

Coexistence between two fruit fly species is supported by the different strength of intra‐ and interspecific competition

1. Unravelling the strength and modes of interspecific interactions between resident and introduced species is necessary in order to understand the basis of their coexistence or the displacement of the former by the latter. In Argentina, the indigenous Tephritidae fly Anastrepha fraterculus overlaps its distribution and host fruit with the introduced species Ceratitis capitata. 2. This study focused on the relative strength of intra‐ and interspecific competition during the larval stage as a potential factor supporting coexistence. Classical competition experiments (addition and substitution) were conducted between larvae of the two species reared in artificial larval diet. The study evaluated whether a temporal separation between oviposition events affects the outcome of the competition. 3. When both species started to consume the resource at the same time, A. fraterculus experienced a negative effect in larval survival, pupal weight and duration of larval stage, while for C. capitata, pupal weight decreased. When A. fraterculus started feeding 1 day earlier than C. capitata, the negative effects became milder, and when the temporal separation increased, these effects were reversed. Substitution experiments showed an increase in pupal weight when larvae had to share the resource with heterospecific larvae, and showed negative effects suffered for both species when they shared the resource with conspecific individuals. 4. These results suggest that intraspecific competition is stronger than interspecific competition, and a differential oviposition preference could generate an asynchrony of these species in nature. Such mechanisms could favour coexistence between A. fraterculus and C. capitata in an environment previously occupied only by the former.     

Phosphorus sources and availability modify growth and distribution of root clusters and nodules of native Australian legumes

A variety of native Western Australian legumes produced root clusters in sand culture confirming field and published observations. In general, these legumes grew equally well when supplied with organic or inorganic sources of phosphorus. The nitrogen content of shoots and roots varied little among treatments for all species, however, phosphorus content was always greater in plants supplied with inositol‐P. The plasticity of root growth in response to localized placement of organic and inorganic sources of phosphorus was demonstrated using a simple ‘split root’ technique. Total root dry weight was, on average, more than doubled in P‐amended sand when compared with non‐amended sand. Root clusters tended to be produced in areas of relatively high phosphorus concentration and nodules in areas of low phosphorus concentration. Levels of phosphorus in lateral roots grown in P‐amended sand were significantly different from lateral roots grown in the corresponding non‐amended sand. Growth increases averaging 70% for white sand to over 100% for yellow sand indicated a large degree of ‘plasticity’ in roots under conditions of heterogeneous supply of phosphorus. Spatially exclusive development of organs for the acquisition of nutrients is discussed in relation to requirements for carbon in organ production and maintenance.     

匍匐茎草本植物形态可塑性、整合作用与觅食行为研究进展

综述了匍匐茎型克隆植物在形态可塑性、整合作用及觅食行为方面的研究进展。资源斑块性分布是生境异质性的特征之一,适应于异质性生境,匍匐茎植物对环境资源表现了一系列可塑性反应。本文着重从匍匐茎植物对光、水、肥的可塑性反应及其整合作用以及觅食行为等方面的研究进行总结分析,以期对匍匐茎型克隆植物进行更广泛深入的研究。     

种间竞争对香蒲与芦苇生长的影响

为了探究种间竞争对香蒲（Typha domingensis）与芦苇（Phragmites australis）生长的影响,利用根系分隔盆栽试验研究了3种不同分隔方式条件下香蒲与芦苇的种间竞争特性,包括塑料膜分隔（根系完全分隔,无相互作用,无物质交换）、尼龙网分隔（根系部分分隔,无相互作用,有物质交换）和不分隔（根系完全相互作用,有物质交换）,分析了香蒲与芦苇根系形态和地上部生长的变化,探究香蒲与芦苇种间竞争的差异。结果发现（1）在尼龙网分隔和不分隔处理中芦苇具有明显的劣势。与塑料膜分隔处理相比,芦苇的总生物量、植株密度在尼龙网分隔和不分隔处理中分别减少了39.14%、49.41%和82.08%、79.22%,总根长、总根表面积、总根体积分别减少了40.53%、44.84%、62.52%和85.7%、82.45%、89.67%,且均具有极显著差异（P<0.01）;根系分隔方式也影响芦苇的株高、茎粗和叶片数,表现为不分隔 > 塑料膜分隔 > 尼龙网分隔。（2）与塑料膜分隔处理相比,香蒲总生物量在尼龙网分隔和不分隔中虽有增加,但差异不显著,植株密度和株高在尼龙网分隔和不分隔处理中都有增加且具有显著差异（P<0.05）,其总根长、总根表面积、总根体积在尼龙网分隔中分别增加了57.93%、26.5%、8.04%,但在不分隔处理中分别减少了11.57%、14.92%、11.39%（P<0.05）,虽然根系的相互作用对香蒲根系的生长具有促进作用,但植物种间根系相互作用越强,对两者的生长越不利。（3）在不同的分隔方式中,芦苇与香蒲间也存在明显变化。在不分隔处理中,香蒲的生物量和植株密度是芦苇的1.7倍和6.74倍,与塑料膜分隔处理相比增加了6倍,表明芦苇与香蒲根系的完全相互作用,显著削减了芦苇的繁殖生长,增加了香蒲的根系分蘖。（4）通过种间相互作用强度（RII值）分析也表明,尼龙网分隔和不分隔处理下芦苇表现为抑制作用（RII值为负值）,香蒲表现为促进作用（RII值为正值）。香蒲与芦苇互作对芦苇具有抑制作用,说明种间相互作用是能改变植物的适应性和植物群落的繁殖,同时也表明植物根系不仅在吸收土壤中的水和养分中起着关键作用,在种间关系中也起着重要作用。因此利用种间竞争控制植物生长,可以为保护生物多样性和生态系统的功能提供有效的技术支撑。