Combined effects of snow depth and nitrogen addition on ephemeral growth at the southern edge of the Gurbantunggut Desert,China

Water and nitrogen （N） inputs are considered as the two main limiting factors affecting plant growth.Changes in these inputs are expected to alter the structure and composition of the plant community,thereby influencing biodiversity and ecosystem function.Snowfall is a form of precipitation in winter,and snow melting can recharge soil water and result in a flourish of ephemerals during springtime in the Gurbantunggut Desert,China.A bi-factor experiment was designed and deployed during the snow-covering season from 2009 to 2010.The experiment aimed to explore the effects of different snow-covering depths and N addition levels on ephemerals.Findings indicated that deeper snow cover led to the increases in water content in topsoil as well as density and coverage of ephemeral plants in the same N treatment; by contrast,N addition sharply decreased the density of ephemerals in the same snow treatment.Meanwhile,N addition exhibited a different effect on the growth of ephemeral plants：in the 50％ snow treatment,N addition limited the growth of ephemeral plants,showing that the height and the aboveground biomass of the ephemeral plants were lower than in those without N addition; while with the increases in snow depth （100％ and 150％ snow treatments）,N addition benefited the growth of the dominant individual plants.Species richness was not significantly affected by snow in the same N treatment.However,N addition significantly decreased the species richness in the same snow-covering depth.The primary productivity of ephemerals in the N addition increased with the increase of snow depth.These variations indicated that the effect of N on the growth of ephemerals was restricted by water supply.With plenty of water （100％ and 150％ snow treatments）,N addition contributed to the growth of ephemeral plants; while with less water （50％ snow treatment）,N addition restricted the growth of ephemeral plants.

The Njiki’s Fundamental Theorem-Definition on Fractions in the Mathematical Set ℚ and by Extension in ℝ and ℂ, for the Purpose of Leading to the Construction of Some Algebraic Structures as Its Theoretical Applications and for the Practical Ones

The purpose of the research in the NJIKI’s fundamental THEOREM-DEFINITION on fractions in the mathematical set ℚand by extension in ℝand ℂand in order to construct some algebraic structures is about the proved EXISTENCE and the DEFINITION by NJIKI of two INNOVATIVE, IMPORTANT and TEACHABLE operations of addition or additive operations, in ℚ, marked ⊕and +α,β, and taken as VECTORIAL, TRIANGULAR, of THREE or PROPORTIONAL operations and in order to make THEM not be different from the RATIONAL ONE, +, but to bring much more and new information on fractions, and, by extension in ℝand ℂ. And the very NJIKI’s fundamental THEOREM-DEFINITION having many APPLICATIONS in the everyday life of the HUMAN BEINGS and without talking about computer sciences, henceforth being supplied with very interesting new ALGORITHMS. And as for the work done in the research, it will be waiting for its extension to be done after publication and along with the research results concerned.

Impact of nitrogen addition on plant community in a semi-arid temperate steppe in China

Increased nitrogen （N） deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels （0, 3, 6, 12, 24, and 48 g N/（m2-a）） were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/（m2.a） above ambient N deposition （1.2 g N/（m2.a））, led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses （PB） but decrease perennial forbs （PF）, and induce a slight change in the biomass of shrubs and semi-shrubs （SS）. The biomass of annuals （AS） and perennial rhizome grasses （PR） accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups.

The Rich-Gini-Simpson quadratic index of biodiversity

The Gini-Simpson quadratic index is a classic measure of diversity, widely used by ecologists. As shown recently, however, this index is not suitable for the measurement of beta diversity when the number of species is very large. The objective of this paper is to introduce the Rich- Gini-Simpson quadratic index which preserves all the qualities of the classic Gini-Simpson index but behaves very well even when the number of species is very large. The additive partitioning of species diversity using the Rich-Gini- Simpson quadratic index and an application from island biogeography are analyzed.

关帝山3个典型森林群落优势种的氮素利用策略差异

【目的】研究关帝山林区华北落叶松林、白桦林和沙棘林3个典型森林群落优势种的新生枝叶氮含量、地上生物量和氮利用效率对5个土壤施氮梯度的差异化响应,阐明3个森林群落优势种不同的氮利用功能特性和氮利用策略,为氮沉降背景下的森林质量提升和精准经营提供理论依据。【方法】采用野外5梯度土壤氮(0、9、18、27和36 g·m^(−2) a^(−1))添加试验的方法,比较3个森林群落优势种和群落总体的新生枝叶氮含量、地上新增生物量和氮利用效率对土壤不同施氮量的响应;采用线性模型拟合地上新增生物量随新生枝叶氮含量、氮利用效率和土壤氮素供应水平的变化过程;通过构建结构方程模型,分析土壤氮添加影响地上新增生物量的作用路径。【结果】3个群落优势种的新生枝叶氮含量总体表现为华北落叶松<白桦<沙棘,新生叶氮含量显著高于新生枝,两者的差异表现为白桦>华北落叶松>沙棘,生长盛期的枝叶氮含量都高于末期,生长期之间的差异也表现为白桦>华北落叶松>沙棘;新生枝和新生叶在生长盛期和末期的氮含量都有随施氮量增加而增加的趋势,但3个优势种的变化表现出显著不同的趋势,饱和施氮量和饱和氮含量均表现为华北落叶松<白桦<沙棘;3个群落新生枝叶生物量都随施氮量的增大而升高,但递增率拟合结果表现为华北落叶松林>沙棘林>白桦林;群落氮利用效率都随施氮量增大而降低,以华北落叶松林的降幅最大,沙棘林最小,也随优势树种枝叶氮储量的升高而降低,以白桦林降幅最大,沙棘林最小;群落优势种和群落类型对群落新生枝叶氮储量和氮素利用效率直接作用显著,也受施氮量的影响,进而正向驱动群落新增生物量积累。【结论】华北落叶松林、白桦林和沙棘林3个森林群落新增生物量的差异主要取决于群落类型及其优势种的差异,直接受群落优势种的氮利用效率和新生枝叶氮含量的影响,并受土壤供氮水平的调节;三者的氮利用策略分异表现在氮需求、氮利用效率、环境氮敏感性、饱和氮供应水平4个方面;依次表现为“低需求-高效率-高敏感-低饱和”、“较低需求-低效率-较高敏感-较低饱和”和“固氮型-高需求-低效率-低敏感-高饱和”3个氮利用策略类型,可为不同氮沉降情境或林地氮含量水平下的林分优势树种选择、结构调控和林地精准管理提供依据。

延河流域本氏针茅(Stipa bungeana)分布预测——广义相加模型及其应用

物种分布预测,对于物种的保护、利用和恢复具有重要意义。利用广义相加模型(GAM,Generalized Additive Model),对延河流域典型地带性物种本氏针茅(Stipa bungeana)的空间分布预测进行研究,以期为该流域本氏针茅草地的保护、恢复等提供依据。结果表明,本氏针茅分布的环境梯度较广,在坡度、坡向、温度与降雨的各个梯度上都有分布,除高平地和侵蚀剧烈的沟道外,各种地形部位上亦可以存在。建立的广义相加模型表明,本氏针茅的分布主要取决于年均蒸发量和温度季节变化两个因子,而非单纯的降雨、温度因素。从其分布概率看,本氏针茅在延河流域大部分地区都有可能分布,但其分布集中区主要在中北部,与实际观测相符。模型检验表明,建立的模型满足统计要求。

长期降水变化和氮添加对青藏高原高寒草原物种多样性和生产力的影响

在全球气候变化背景下,降水变化和氮添加草地物种多样性和生产力,但高寒草原研究较少,尤其是长期水氮控制试验。为此,本试验于青海省三角城种羊场紫花针茅高寒草原开展降水变化和氮(N)添加野外控制试验,从植被盖度、物种多样性指数及地上生物量进行测定,研究高寒草原长期降水变化和N添加对其物种多样性及生产力的影响。降水增加处理使群落盖度显著增加,而降水减少使群落盖度显著降低;N添加使高寒草原物种多样性指数均显著降低;N添加与降水增加处理对地上生物量有显著的促进作用,但降水减少对地上生物量的影响则相反;地上生物量与物种多样性指数呈极显著的负相关关系(P<0.01)。本研究将为我国草原生态系统的保护及草原管理提供科学依据,同时也为后续的生态模型的建立和科学的预测提供理论依据。

Climatic Control on Forests and Tree Species Distribution in the Forest Region of Northeast China

North-east （NE） China covers considerable climatic gradients and all major forests types of NE Asia. in the present study, 10 major forest types across the forest region of NE China were sampled to Investigate forest distribution in relation to climate. Canonical correspondence analysis （CCA） revealed that growing season precipitation and energy availability were primary climatic factors for the overall forest pattern of NE China, accounting for 66% of the explanatory power of CCA. Conversely, annual precipitation and winter coldness had minor effects. Generalized additive models revealed that tree species responded to climatic gradients differently and showed three types of response curve： （i） monotonous decline; （ii） monotonous Increase; and （iii） a unimodai pattern. Furthermore, tree species showed remarkable differences in limiting climatic factors for their distribution. The power of climate in explaining species distribution declined significantly with decreasing species dominance, suggesting that the distribution of dominant species was primarily controlled by climate, whereas that of subordinate species was more affected by competition from other species.

基于物种分布模型分析环境因子对海州湾偶见种资源分布的影响

偶见种易受环境变化和人类活动等外界威胁,在生物多样性保护中具有重要参考价值,但由于其数据量较少、分析困难,目前对分布特征的研究较少,其分布与环境因子的关系尚待探究。本研究基于2013–2019年海州湾渔业资源调查数据,分析了凤鲚(Coilia mystus)、红狼牙虾虎鱼(Odontamblyopus rubicundus)和虻鲉(Erisphex pottii)3种海州湾偶见种资源分布与环境因子的关系,并比较了广义可加模型(GAM)和随机森林(RF)模型对其资源分布的拟合效果,采用交叉验证的方法对模型的预测性能进行了评价。结果显示,水深是影响春、秋季凤鲚和红狼牙虾虎鱼资源分布的最显著因子,而底层水温仅在秋季是影响虻鲉资源分布的最重要环境因子。凤鲚分布模型的方差解释率最高,其次为红狼牙虾虎鱼,虻鲉模型方差解释率最低。凤鲚、红狼牙虾虎鱼和虻鲉分布模型在春季方差解释率均低于秋季。交叉验证表明,3个物种预测结果的曲线下面积(AUC)值在0.70~0.85之间,仅秋季凤鲚的AUC值达到0.9;同时GAM预测结果的AUC值均大于RF模型,表明对于偶见种而言,GAM的预测性能优于RF模型。本研究为今后开展偶见种研究的模型选择提供了参考,对偶见种资源保护具有指导意义。

养分添加对植被生产力与群落结构稳定性影响

以内蒙古锡林郭勒退化草地为研究对象,在试验样地添加氮、磷、钾养分,采用“3414”试验设计,对草地生产力和群落结构稳定性进行评价.结果表明:复合养分在不同配比下对草地群落结构和稳定性的影响不同,在合适的氮、磷、钾配比下,草地生物量显著增加,同时可促进草地优势植被的恢复,提高群落稳定性.综合评价结果表明:在N 4.19g/m^(2)、P 1.85g/m^(2)、K 1.21g/m^(2)配比下,可显著提高优势种羊草的密度、高度和地上生物量(P<0.05),并显著降低退化指示种糙隐子草的密度和生物量(P<0.05),提高草地优势种的重要值,降低退化指示种的重要值.合理的养分调节模式是草地生态修复的重要途径.

短期围封和放牧条件下施氮对橐吾型退化草地植被的影响

氮素是植物体内各种物质的重要组成部分,添加氮素能促进植物生长,提高牧草生产力。为研究短期氮素添加对黄帚橐吾(Ligularia virgaurea)型退化草地群落多样性及草地生产力的影响,本研究在黄帚橐吾严重危害草地的自由放牧区和围封区进行氮素添加处理,分析了2年内物种重要值、植物多样性、黄帚橐吾密度以及植物地上、地下生物量的变化规律。结果表明:添加氮素后禾本科植物重要值明显升高,短期围封和氮素添加对黄帚橐吾型退化草地的多样性无显著影响;围封条件下添加氮素对禾本科地上生物量、总地下生物量以及0~10 cm地下生物量影响显著(P<0.05);处理和年份之间无明显交互作用。通过主成分综合得分得到在放牧草地添加氮素可以有效提高草地得分,该结果可为黄帚橐吾型退化草地的治理恢复提供一定理论依据。

养分添加与干扰对荒漠草原群落组成及构建的影响

运用混合线性模型、主成分分析和零模型方法,以乌拉特荒漠草原草本群落为研究对象,研究了短期养分添加(NPKμ,各10 g·m^(-2))和干扰对植物群落物种多样性、功能性状、土壤理化性质和群落构建过程的影响。结果表明:(1)干扰和交互处理显著降低物种丰富度和β多样性,短期养分添加显著降低土壤pH,增加土壤电导率。(2)干扰和养分添加处理下,优势物种沙生针茅(Stipa glareosa)、骆驼蓬(Peganum harmala)、猪毛菜(Salsola collina)和蒙古虫实(Corispermum mongolicum)的6个性状以及群落功能性状加权均值(Community-weighted mean, CWM)发生显著变化,揭示了干扰和养分添加促使群落优势种从保守型策略向获取型策略转变。(3)两种零模型结果表明,对照下的草本群落构建趋向于随机性过程,干扰和交互处理下的群落构建趋向于确定性过程,养分添加处理下的群落构建趋向于较弱的确定性过程。荒漠草原草本植物群落通过优势物种和关键功能性状的改变来响应和适应养分添加与干扰。

短期养分添加对西藏沼泽化高寒草甸地上生物量、植物多样性和功能性状的影响

N、P是植物生长发育的主要营养元素,养分添加对退化草地改良复壮起着关键作用。本研究以当雄县格达乡甲多村长期围封刈割的藏嵩草沼泽化草甸为研究对象,开展短期养分添加对地上生物量、植物多样性和功能性状的影响,明确植物多样性和群落水平功能性状对地上生物量变化的解释度。结果显示:N添加和N+P添加处理下,地上生物量至少增加39.3%和98.9%。N+P添加与单独N添加相比,显著增加了喜马拉雅嵩草、华扁穗草、禾草类群和杂类草类群的地上生物量(P<0.05);降低了藏嵩草的重要值,增加了喜马拉雅嵩草、早熟禾、鹅绒委陵菜、西藏报春的重要值。N+P添加显著提高了物种丰富度、Shannon-Wiener指数和Simpson指数;物种丰富度、Shannon-Wiener指数与地上生物量呈极显著正相关关系(P<0.01)。养分添加增加了群落水平植株高度和氮含量(P<0.05),N+P添加显著增加群落水平叶片磷含量,增加了叶比重,降低了叶干物质含量;群落水平植株高度、叶片磷含量、叶片氮含量与地上生物量呈正相关关系(P<0.01)。最小二乘结构方程和方差分解结果显示,N添加对群落水平加权性状和地上生物量有显著的正向促进作用(P<0.05),P添加对群落水平加权性状、地上生物量和植物多样性有显著的正向促进作用(P<0.05),氮、磷共同决定了地上生物量的增加。群落水平植物功能性状和植物多样性对地上生物量的总解释度为81.3%,群落水平植物功能性状对地上生物量的解释度为78.5%,植物多样性的解释度为45.5%。综上,群落水平植物功能性状和植物多样性共同决定了高寒沼泽化草甸地上生物量对氮、磷养分添加的响应变化。施氮同时配施磷肥对草地增产和生物多样性维持均有积极作用。

Effects of resource additions on species richness and ANPP in an alpine meadow community

Aims Theories based on resource additions indicate that plant species richness is mainly determined by the number of limiting resources.However,the individual effects of various limiting resources on species richness and aboveground net primary productivity(ANPP)are less well understood.Here,we analyzed potential linkages between additions of limiting resources,species loss and ANPP increase and further explored the underlying mechanisms.Methods Resources(N,P,K and water)were added in a completely randomized block design to alpine meadow plots in the Qinghai-Tibetan Plateau.Plant aboveground biomass,species composition,mean plant height and light availability were measured in each plot.Regression and analysis of variance were used to analyze the responses of these measures to the different resource-addition treatments.Important Findings Species richness decreased with increasing number of added limiting resources,suggesting that plant diversity was apparently determined by the number of limiting resources.Nitrogen was the most important limiting resource affecting species richness,whereas Pand K alone had negligible effects.The largest reduction in species richness occurred when all three elements were added in combination.Water played a different role compared with the other limiting resources.Species richness increased when water was added to the treatments with N and P or with N,P and K.The decreases in species richness after resource additions were paralleled by increases in ANPP and decreases in light penetration into the plant canopy,suggesting that increased light competitionwas responsible for the negative effects of resource additions on plant species richness.

Forest soil CO_2 fluxes as a function of understory removal and N-fixing species addition

We report on the effects of forest management practices of understory removal and N-fixing species（Cassia alata） addition on soil CO2 fluxes in an Eucalyptus urophylla plantation（EUp）,Acacia crassicarpa plantation（ACp）,10-species-mixed plantation（Tp）,and 30-species-mixed plantation（THp） using the static chamber method in southern China.Four forest management treatments,including（1） understory removal（UR）;（2） C.alata addition（CA）;（3） understory removal and replacement with C.alata（UR＋CA）;and（4） control without any disturbances（CK）,were applied in the above four forest plantations with three replications for each treatment.The results showed that soil CO2 fluxes rates remained at a high level during the rainy season（from April to September）,followed by a rapid decrease after October reaching a minimum in February.Soil CO2 fluxes were significantly higher（P 〈 0.01） in EUp（132.6 mg/（m2.hr）） and ACp（139.8 mg/（m2.hr）） than in Tp（94.0 mg/（m2.hr）） and THp（102.9 mg/（m2.hr））.Soil CO2 fluxes in UR and CA were significantly higher（P 〈 0.01） among the four treatments,with values of 105.7,120.4,133.6 and 112.2 mg/（m2.hr） for UR＋CA,UR,CA and CK,respectively.Soil CO2 fluxes were positively correlated with soil temperature（P 〈 0.01）,soil moisture（P 〈 0.01）,NO3？-N（P 〈 0.05）,and litterfall（P 〈 0.01）,indicating that all these factors might be important controlling variables for soil CO2 fluxes.This study sheds some light on our understanding of soil CO2 flux dynamics in forest plantations under various management practices.

增温和氮添加对天山高寒草地生态系统多功能性的影响

为了探究增温和氮添加对高寒草地生态系统多功能性的影响机制,在位于天山山脉南麓的巴音布鲁克高寒草地开展增温和氮添加实验.通过调查群落物种组成并测量常见的物种功能性状,分析单一生态系统功能以及生态系统多功能性对增温和氮添加的响应模式,并探究其与植物群落物种多样性、功能多样性之间的关系.结果表明:增温降低生态系统多功能性而氮添加会增加生态系统多功能性;增温通过影响初级生产力和植物养分供给影响生态系统多功能性,氮添加则通过增加初级生产力、土壤有机质和土壤肥力来提高生态系统多功能性;物种多样性和功能多样性都能很好地解释生态系统多功能性的变化,其中香农-维纳多样性指数解释效果最好.研究表明增温与氮添加这两种气候变化过程对高寒草地生态系统多功能性有着不同的作用机制,可为气候变化背景下高寒草地的生态系统功能维持提供参考依据.

Phosphorus does not alleviate the negative effect of nitrogen enrichment on legume performance in an alpine grassland

Aims Nitrogen(N)-fixing legumes,despite being highly phosphorus(P)-demanding,constitute an important plant functional group and play key roles in N-poor ecosystems such as alpine grasslands.However,legume performance,including biomass,abundance and species richness,is expected to change,because anthropogenic activities have drastically increased soil N and P availability world-wide.We conducted a field experiment to assess the effects of N and P addition,alone and in combination,on legume performance in an alpine grassland,and identified and clarified the mechanisms underlying these changes.Methods A three year field experiment of N addition(10 g N m−2 year−1),P addition(5 g P m−2 year−1),and N+P combined addition(both N and P,same amounts as solo treatments)was conducted in an alpine grassland on the tibetan Plateau in china from 2011 to 2013.Effects of nutrient addition were assessed at the community level(above-ground net primary production(ANPP),height and light intensity),functional group level(biomass,species richness,relative height,relative coverage and relative density of legumes)and species level(foliar N,P concentration of two legumes).Important findings Overall,adding N alone significantly increased ANPP by 20.82%,but adding P alone did not;whereas,addition of N and P together resulted in a large increase in ANPP(+37.03%)than addition of either alone,indicating potential co-limitation of alpine grasslands.In contrast,adding P alone significantly promoted legume perfor-mance as measured by 65.22%increase in biomass and 58.45%increase in relative abundance,while adding N alone reduced leg-ume performance as measured by 39.54%decrease in biomass and 50.36%in relative abundance.combining P and N addition did not mitigate the negative effect of N addition on legume performance and,surprisingly,suppressed legume biomass by 53.14%and relative abundance by 63.51%.N and P addition altered the balance of light competition between grasses and legumes as indicated by the changes in light levels,plant heights and litter accumulation.However,there were no obvious changes in legume species richness in response to N and P within our experimental timeframe.this study provides further evidence of the importance of P as a co-limiting nutrient in alpine grasslands,contrary to the traditional view that N limitation predominates in such regions.the contrasting effects of N and P addition on legume performance provide important insights into potential changes in legume performance in nutrient-limited grasslands following N and P enrichment under climate change,with implications for nutrient management in alpine grasslands.

四种草本植物生长性状和根性状对磷添加的响应策略

采用盆栽种植方式,对低浓度有机磷(20 mg/kg)、低浓度无机磷(20 mg/kg)和高浓度无机磷(200 mg/kg)水平下石竹、冰草、苜蓿和沙葱的生长、根形态和生理性状指标进行测定,探究内蒙古草原四种草本共存植物的磷适应策略。结果表明:与低磷环境相比,高磷环境下四种植物均具有更高的地上部生物量、氮和磷累积量、根生物量,根冠比(除沙葱外)均较低;细根植物(石竹和冰草)的总根长在低浓度有机磷环境最长,粗根植物(苜蓿和沙葱)则在高浓度无机磷环境最长,四种植物的总根长均在低浓度无机磷环境最短;四种草本植物的比根长均在低浓度有机磷环境最高,在低浓度无机磷环境最低,且细根植物的比根长显著高于粗根植物;四种植物中,沙葱具有最高的根系有机酸含量(比其他三种植物高约39倍)和酸性磷酸酶活性(高约52倍)以及最低的根呼吸速率(低约7倍),苜蓿则具有最高的平均根性状变异度。总体来看,细根植物主要是通过增加比根长和总根长,粗根植物主要通过提高根系有机酸和酸性磷酸酶活性(如沙葱)或增大根性状变异度(如苜蓿)来适应低磷环境。

Contrasting effects of N addition on the N and P status of understory vegetation in plantations of sapling and mature Larix principis-rupprechtii

Aims The productivity of forest plantations in temperate areas is often lim-ited by nitrogen(N),but may shift towards phosphorus(P)limitation with increasing atmospheric N deposition.Nutrient resorption is a nutrient conservation strategy in plants.Although data on nutrient resorption are available for overstory trees,there are few data for understory vegetation.Methods We examined leaf N and P concentrations and N and P resorption efficiencies(NRE and PRE,respectively)in eight understory species in 11-and 45-year-old Larix principis-rupprechtii stands subjected to N supplementation over a 3-year period.Important findings Leaf N concentrations and N:P ratios increased and P concentrations decreased,with N input in species within the 45-year-old stand,but not in the 11-year-old stand.NRE and PRE were not altered by N input in any of the species in either stand,but N resorption pro-ficiency decreased and P resorption proficiency increased,in the species in the 45-year-old stand.Thus,the growth of understory species may be more P-limited in the 45-versus 11-year-old stand,and nutrient resorption proficiency was more sensitive to N add-ition than nutrient resorption efficiency.These results will improve the understanding of nutrient use strategies and their responses to N addition in understory vegetation.The contrasting effects of N addition on nutrient status between stand ages cannot be ignored when modeling ecosystem nutrient cycling under global N depos-ition conditions.

The impacts of warming and nitrogen addition on competitive ability of native and invasive populations of Plantago virginica

全球变化因子(如增温和氮沉降)可能会影响生物入侵,但是这些因子如何影响入侵物种的表现并进一步调节入侵物种与本地竞争者之间的相互作用仍不清楚。本文通过为期五个月的温室实验,研究了增温(开顶式增温箱,+0.62°C)和氮添加(4.2 g N m−2)对入侵物种北美车前(Plantago virginica)原产地和入侵地种群与本地车前草(Plantago asiatica)竞争的影响。实验结果表明,在增温及其与氮添加处理(W×N)的相互作用下,P.virginica的入侵种群(PV-In)和原产地种群(PV-Na)在与本地竞争者P.asiatica竞争时具有不同的生物量分配策略。其中,PV-Na在与P.asiatica竞争时增加了地下生物量,而PV-In增加了地上生物量。我们还发现,P.virginica对增温和氮添加比P.asiatica的反应更强烈。增温显著降低了P.virginica的竞争能力,这表明P.virginica比P.asiatica对增温的响应更为敏感。同样,在竞争条件下,氮添加及其和增温交互作用减少了PV-In地下生物量,但增加了PV-Na地上和总生物量。这些发现表明,P.virginica在入侵过程中改变了生物量分配策略,PV-In展示出更具弹性的竞争能力以适应环境变化(特别是增温)。这些发现可能有助于我们预测气候变化下的植物入侵并制定相应的管理策略。