土壤微生物群落结构对中亚热带三种典型阔叶树种凋落物分解过程的响应

通过小盆模拟试验研究了南方红壤丘陵区典型阔叶树种香樟、白栎和青冈的凋落物分解过程中土壤微生物群落结构的异同。结果表明:(1)凋落物含氮量:白栎>香樟>青冈;碳、木质素的含量以及碳/氮比、木质素/氮比:青冈>香樟>白栎;分解速率:白栎>香樟>青冈;(2)随着凋落物分解的进程,土壤微生物群落16 ∶ 0、15 ∶ 0、i16 ∶ 0、a17 ∶ 0、17 ∶ 0、18 ∶ 2ω6,9c和10Me18 ∶ 0的含量上升,18 ∶ 0、14 ∶ 0、16 ∶ 1ω7c、18 ∶ 1ω7c、cy19 ∶ 0、i19 ∶ 0和10Me19 ∶ 0的含量下降,饱和直链脂肪酸/单不饱和脂肪酸、革兰氏阳性菌/革兰氏阴性菌以及cy19 ∶ 0/18 ∶ 1ω7c的比值都显著上升。(3)两个时期白栎凋落物处理土壤16 ∶ 0、15 ∶ 0、a15 ∶ 0、i16 ∶ 0、a17 ∶ 0、 17 ∶ 0、cy19 ∶ 0、18 ∶ 2ω6,9c、18 ∶ 1ω9c和10Me18 ∶ 0的含量显著高于香樟和青冈凋落物处理的土壤,细菌、真菌的磷脂脂肪酸含量以及磷脂脂肪酸总量显著高于香樟和青冈凋落物处理的土壤。随着阔叶凋落物的分解,变化的土壤环境对土壤微生物群落的胁迫增强,土壤微生物群落结构发生显著变化。与香樟和青冈的凋落物相比,白栎凋落物碳/氮比和木质素/氮比低、分解快,能显著改善土壤微生物群落结构,更有利于土壤肥力提高和生态系统养分循环的改善。     

采煤塌陷地不同施肥处理对土壤微生物群落结构的影响

采用磷脂脂肪酸(PLFA)分析方法,对山西长治襄垣五阳煤矿采煤沉陷区复垦土壤的微生物群落结构进行了研究。结果表明:施肥处理能够不同程度的增加土壤微生物的PLFA总量、细菌PLFA量和真菌PLFA量,其中化肥+有机肥处理下的土壤微生物PLFA总量,细菌PLFA量和真菌PLFA量增加作用比较明显,差异显著于对照处理;对不同施肥处理的复垦土壤微生物群落PLFA进行主成分分析也可得出化肥+有机肥处理下的土壤微生物的群落结构变化比较大,从因子载荷图上进一步分析可知,化肥+有机肥处理下的土壤中代表真菌的不饱和脂肪酸C18∶2ω6t、C18∶3ω6、18∶1ω9t、18∶3ω3的含量较高,这些脂肪酸将化肥+有机肥处理与单施化肥和对照处理区分开来,产生了明显的优势种群。土壤PLFA总量与土壤有机质、碱解氮、速效磷和速效钾含量都有很好的相关性,相关系数分别为0.76,0.85,0.67和0.67。     

不同坡向凋落物分解对土壤微生物群落的影响

采用空间与时间序列并用的方法,对贵州茂兰喀斯特森林阳坡和阴坡凋落物的分解特征及土壤微生物进行1年的野外调查和测定,探讨凋落物分解规律及其对土壤微生物群落的影响。凋落物在分解1年后的质量损失率约为72%,在分解过程中的碳、磷元素表现为释放,氮元素表现出富集;土壤微生物各群落磷脂脂肪酸(PLFA)在分解过程中的平均含量表现为:细菌(149.8 nmol/g)放线菌(63.9 nmol/g)真菌(31.3 nmol/g),阳坡和阴坡的微生物总PLFA在180d(559.2 nmol/g)和360d(513.6 nmol/g)的含量显著高于分解前;随分解时间的增加,阳坡细菌特征磷脂脂肪酸18:1ω7c的含量增加最大,其次是cy19:0和真菌特征磷脂脂肪酸18:1ω9c,阴坡土壤微生物PLFA含量表现出减少的趋势,细菌特征脂肪酸18:1ω7c减少量最大,约9.42 nmol/g,其次是i15:0和真菌特征脂肪酸18:1ω9c,约减少4.29—4.86 nmol/g;凋落物养分释放特征与微生物群落间的Spearman相关分析表明,真菌群落与碳元素释放率呈显著正相关关系,细菌群落与凋落物碳、磷元素的释放呈极显著正相关关系,且阳坡凋落物分解对微生物群落的影响高于阴坡。坡向和凋落物养分释放量对喀斯特森林凋落物的分解及土壤微生物群落的影响较显著,特征磷脂脂肪酸18:1ω7c、cy19:0、i15:0和18:1ω9c对环境变化的响应较为敏感。     

不同放牧与围封高寒灌丛草地土壤微生物群落结构PLFA分析

土壤微生物群落可以指示土壤质量变化,是土壤生态系统变化的预警及敏感指标。采用磷脂脂肪酸(PLFA)分析方法研究了高寒杜鹃灌丛草地不同强度放牧及围封后,土壤微生物群落结构特征的变化规律和响应。结果显示,高寒杜鹃灌丛草地土壤总PLFA量、细菌生物量、真菌生物量和放线菌生物量均随着放牧强度的增大而显著降低(P0.05)。重牧灌丛草地,围封后的土壤总PLFA量、细菌生物量、放线菌生物量、G~+/G~-和压力指数显著高于放牧处理,而细菌/真菌比显著低于放牧处理;中牧灌丛草地,围封后的土壤总PLFA量、细菌生物量、细菌/真菌比显著高于放牧处理,而真菌生物量和压力指数显著低于放牧处理;轻牧灌丛草地,围封处理的土壤各生物量和生物量比值与放牧处理无显著差异。PLFA主成分分析表明:主成分一(PC1)主要包括14:0、15:0、10Me16:0和18:1ω9c等直链饱和脂肪酸和单不饱和脂肪酸,占PC1的53.68%;主成分二(PC2)主要包括由i16:0、16:1ω7c、i17:0、cy17:0、17:0、18:1ω9t、18:0和cy19:0等支链饱和脂肪酸和环丙烷脂肪酸组成,占PC2的51.34%;各处理样地土壤微生物群落结构相似;围封处理的响应程度大于放牧处理。相关性分析表明,土壤总PLFA量、细菌生物量、真菌生物量和放线菌生物量与土壤有机碳、全氮均呈极显著正相关,细菌/真菌比值与土壤有机碳、全氮呈极显著负相关。以上表明过度放牧降低了高寒灌丛草地土壤微生物活性,显著降低了土壤微生物生物量,适度放牧和围封可维持土壤微生物群落结构的稳定,围封有利于过度放牧草地土壤微生物的恢复。     

积雪覆盖变化对大兴安岭多年冻土区土壤微生物群落结构的影响

高纬度多年冻土区是全球变化的敏感区域,揭示不同雪被覆盖条件下土壤微生物群落结构的演变规律,对于预测寒区森林生态系统对全球变化的响应具有重要意义。以大兴安岭多年冻土区白桦次生林为研究对象,采用磷脂脂肪酸法(PLFA)对比分析自然积雪和遮雪处理土壤微生物群落结构的动态变化特征。结果表明:土壤总磷脂脂肪酸含量在植被生长季初期最高,积雪稳定期最低,其中含量较高的PLFA为18:2ω6,9c、a15:0、i16:0、17:1ω8c、18:1ω9c和16:1ω5c,不同时期各优势PLFA含量存在一定差异。遮雪显著降低积雪稳定期细菌PLFA含量、增加真菌PLFA含量(P0.05),但对其他时期土壤微生物群落结构和多样性均未产生显著影响。冗余分析(RDA)表明,土壤总磷脂脂肪酸、真菌、真菌/细菌和革兰氏阴性菌与土壤含水量、pH和铵态氮均呈显著正相关,细菌和革兰氏阳性菌受土壤总磷、总氮和硝态氮影响较大。     

辽东山区不同林龄日本落叶松人工林土壤微生物、养分及酶活性

对辽宁省抚顺市大孤家林场11、20、34和47年生日本落叶松人工纯林表层土壤(0~5 cm)微生物群落结构、养分及酶活性进行了研究.结果表明: 土壤微生物、养分及酶活性各项指标基本呈现11或47年林龄较高,而20或34年林龄较低.随林龄增加,土壤地力呈现衰退趋势,土壤微生物群落结构及酶活性变化对地力衰退呈现响应趋势,不同林龄真菌群落结构的差异较细菌显著.典范对应分析(CCA)表明,土壤养分含量及pH值对微生物群落结构的季节变化没有影响,但对在不同林龄间微生物的变化有影响.土壤全氮、有机碳、C/N、速效氮和pH值对不同林龄细菌分布影响较大,土壤速效磷、全钾、交换性镁离子和pH值对真菌分布影响较大.细菌与真菌群落主要的T RFs片段与氮、磷的相关性都较高,而真菌群落与有机碳、钾的相关性高于细菌群落.11和47年林龄微生物群落与土壤养分、酶活性的相关性高于20与34年.因此,土壤微生物(尤其是土壤真菌)可以敏感地指示土壤肥力的变化.     

海拔梯度变化对中亚热带黄山松土壤微生物生物量和群落结构的影响

全球变暖对陆地生态系统造成一系列生态问题,使这些问题将随着全球平均气温的升高而进一步加剧。海拔梯度变化是研究气候变暖对陆地生态系统影响的一种重要手段。目前为止利用海拔梯度对微生物影响的研究尚未定论,其主要原因是忽略了植被类型的影响。因此,以中亚热带戴云山的3个海拔(1300、1450、1600 m)的黄山松(Pinus taiwanensis)林为研究对象,探究沿海拔梯度的变化,森林土壤微生物生物量和微生物群落结构的响应变化。结果表明:土壤碳氮磷养分(SOC、TN、TP)、微生物生物量氮(MBN)、微生物生物量磷(MBP)和丛枝菌根真菌(AMF)、革兰氏阴性菌(GN)、真菌(Fungi)、总磷脂脂肪酸(T_(PLFA)),细菌∶真菌(F∶B)均随海拔升高显著下降,而革兰氏阳性菌∶革兰氏阴性菌(GP∶GN)随海拔升高呈相反的趋势。冗余分析(RDA)表明,温度(T)和可溶性有机氮(DON)是影响微生物群落结构的最重要的环境因子。研究表明:与1600 m海拔相比,1300 m海拔温度较高,土壤有机质矿化作用较强,土壤速效养分及微生物生物量随之增加,从而提高(Fungi)、细菌(Bacteria)等。因此,未来气候变暖将通过改变土壤碳氮磷养分来影响本区域微生物群落组成结构。这对进一步深入了解气候变化对山地生态系统土壤养分循环过程具有重要意义。     

三叶鬼针草与不同本地植物竞争对土壤微生物和土壤养分的影响

入侵植物三叶鬼针草(Bidens pilosa)对我国农牧业生产造成了重大的损失。本文主要研究三叶鬼针草入侵与不同本地植物竞争对土壤微生物群落结构和土壤养分的影响。利用磷脂脂肪酸方法(phospholipid fatty acids,PLFAs)测定土壤微生物群落组成,同时测定土壤养分和酶活性,并利用Canoco4.5软件分析了土壤微生物、土壤养分和土壤酶活性的相关性。结果表明:(1)三叶鬼针草对革兰氏阳性菌、革兰氏阴性菌、丛枝菌根真菌等土壤微生物具有较强的聚集能力,且其根际土壤聚集的微生物类群与本地植物种类密切相关。(2)三叶鬼针草入侵显著增加了入侵地土壤的有机碳含量,降低了铵态氮的含量;土壤中的速效钾、速效磷和硝态氮的含量则与本地植物种类密切相关。(3)相关性分析表明,16:00和16:1ω5c对铵态氮的含量影响较大,而三叶鬼针草入侵地16:00和16:1ω5c的含量显著高于裸土对照,进而推测这一状况导致了铵态氮含量的降低。(4)15:1 anteiso A和18:1ω5c与速效钾的含量呈显著正相关,而其含量在狗尾草(Setaria viridis)中显著高于其他处理,三叶鬼针草与狗尾草混种处理中土壤中速效钾的含量高于其他处理。以上结果说明,三叶鬼针草通过改变土壤微生物群落结构影响了土壤酶活性和土壤养分,且这种改变与入侵地本地植物种类有关。     

培养条件下二氯喹啉酸对土壤微生物群落结构的影响

为探讨除草剂二氯喹啉酸对土壤微生物群落结构的影响,在25℃黑暗培养条件下,采用磷脂脂肪酸法(Phospholipid Fatty Acid,PLFA)分析了二氯喹啉酸(0对照、83.3和166.6μg/kg干土)处理对淹水和不淹水水田土壤微生物群落结构的影响。结果表明,在实验处理的60 d内,不淹水水田土壤在83.3μg/kg二氯喹啉酸处理后对土壤微生物生物总量、细菌生物量及真菌生物量有抑制作用,而166.6μg/kg二氯喹啉酸处理后各生物量指标均显著增加,但是两种浓度处理均使土壤真菌/细菌比值下降,说明二氯喹啉酸处理会使不淹水水田土壤微生物稳定性下降;淹水水田土壤在83.3μg/kg二氯喹啉酸处理下,对土壤微生物生物总量和真菌生物量有促进作用,对细菌生物量有一定的抑制作用,166.6μg/kg二氯喹啉酸处理对土壤微生物生物总量、细菌及真菌生物量均有促进作用,从真菌/细菌比值上看,不同浓度处理与对照无显著差异,说明二氯喹啉酸对淹水生物稳定性无明显干扰。PLFA主成分分析表明,不同浓度处理的两种土壤微生物群落均以含14∶0、15∶0、16∶0和18∶2n6c的微生物为优势种群。     

贺兰山东坡不同海拔典型植被带土壤微生物磷酸脂肪酸分析

土壤微生物在维持干旱区森林生态系统功能稳定方面具有重要作用,但有关干旱区微生物群落结构及多样性沿海拔分布规律研究较少,采用磷酸脂肪酸(PLFA)法定量分析贺兰山自然保护区东坡不同海拔典型植被带(荒漠草原HM、蒙古扁桃MG、油松林YS、混交林HJ、青海云杉林QH)土壤微生物群落结构特征及多样性。结果表明,不同海拔植被带土壤中共检测出59种PLFA生物标记,YS土壤中生物标记的含量明显高于其他植被类型,5个植被带共有且含量较高的PLFA生物标记为16:0、18:1ω9c、18:1ω7c、10Me 16:0和18:2ω6c,特征微生物的含量在不同植被带土壤中分布不同,细菌分布数量最大,其次是真菌、放线菌,原生动物分布数量最小。聚类分析发现,不同植被带土壤PLFA生物标记可分成不同的类群,16:0、18:1ω9c和18:1ω7c基本在每个植被带都会单独聚为一类。对不同植被带所共有的PLFA生物标记绘制热图,发现不同的PLFA生物标记在不同植被带分布不同,YS植被带PLFA生物标记分布最高。不同植被带土壤微生物群落多样性显示,HJ土壤中微生物多样性指数大于其他植被类型,HM土壤中微生物多样性指数...     

Dinitrogen-fixing Acacia species from phosphorus-impoverished soils resorb leaf phosphorus efficiently

Nitrogen (N) and phosphorus (P) resorption from senescing leaves were studied, and the contribution of N and P cycling through litterfall to soil nutrient patchiness was investigated for four Acacia species in the Great Sandy Desert in north-western Australia. N and P concentrations of mature and recently shed leaves were analysed and compared; soils under the canopies of the shrubs and soils in gaps (open areas) between the shrubs were also analysed and compared for N and P concentrations. Mature leaf P concentrations of the plants were considerably lower than the global average values, and N : P ratios of mature leaves were high. Plants derived 0-75% of their leaf N from symbiotic N(2)-fixation. N-resorption efficiency was between 0 and 43%, and P-resorption efficiency was between 32 and 79%; all plants were more efficient at P resorption than at N resorption, and litter N : P ratios were significantly higher than mature leaf N : P ratios. Soils of the study sites were P-impoverished. Total soil N and P concentrations were higher under the canopy than in gaps, but bicarbonate-extractable P concentration was higher in gaps. Nutrient cycling through litterfall results in soil nutrient patchiness and forms 'islands of fertility' under the canopies of the shrubs.     

Limiting nutrient patchiness and its rôle in phytoplankton ecology

Limiting nutrient patchiness is examined as a factor affecting the community structure and species succession of natural phytoplankton communities held in ammonia limited continuous culture at a dilution rate of 0.3 day^?1. It was found that under a homogeneous distribution of the limiting nutrient members of genus Chaetoceros dominated and when ammonia was added daily (patchy distribution), Skeletonema dominated. Intermediate patchiness gave rise to an assemblage dominated by both Chaetoceros and Skeletonema. The nutrient uptake ability of each assemblage was determined three weeks after experiment initiation. Each assemblage was best able to optimize uptake of ammonia under its particular patchy nutrient regime. Optimization of a patchy environment took place by an increased maximal uptake rate (V_max) while optimization of a homogeneous environment appeared to take place by increased substrate affinity (i.e., low K_s).This study demonstrates that limiting nutrient patchiness can alter the relative abundance of populations within a community based on each population's ability to exploit the limiting resource under a particular degree of patchiness. We also show that coexistence of two populations might be expected due to the patchiness of a single limiting nutrient. The importance of patchiness in relation to other factors which determine community structure is discussed.     

Physiological integration impacts nutrient use and stoichiometry in three clonal plants under heterogeneous habitats

Physiological integration facilitates clonal plants to deal with heterogeneous resources. However, little is known about how nutrient patchiness affects its use and stoichiometry in clonal plants. We conducted an experiment with Cynodon dactylon, Glechoma longituba, and Potentilla reptans to address the effects of physiological integration on nutrient use efficiency and N:P ratios. For C. dactylon, the effects of nutrient patchiness on N use efficiency (NUE), P use efficiency (PUE), and N:P ratio were stronger in daughter ramets than in parent ramets; for G. longituba, nutrient patchiness affected PUE and N:P ratio of parent and daughter ramets, but not NUE; for P. reptans, nutrient patchiness decreased NUE, PUE, and N:P ratio, regardless of parent or daughter ramets. PUE was associated with N:P ratios in three clonal plants and this association of NUE with N:P ratios varied with species. Our findings suggest that physiological integration alters nutrient use efficiency and N:P ratios of clonal plants under patchy nutrients and that these effects are linked to clonal species identity.     

Feeding preference as a main determinant of microscale patchiness among terrestrial nematodes

Soil biota are responsible for essential ecosystem services such as carbon storage, nutrient cycling and water retention. However, assessment of the condition of soil biota is hampered by an overwhelming level of diversity. With representatives in all trophic levels of the food web, nematode communities can be used as bioindicators. Accurate assessment of nematode assemblages requires insight into the distribution of specimens with distinct food preferences. With the availability of taxon‐specific quantitative PCR assays, distribution patterns of multiple nematode groups can be investigated simultaneously. Here, microscale patchiness of 45 nematode taxa was studied on 12 sampling sites (each with four adjacent microplots) located on arable fields or semi‐natural grasslands (‘system’), and on marine, river clay or sandy soils (‘soil type’). From each microplot, five composite samples were collected. Contrary to our expectations, an increase in the number of cores per composite sample did not result in more accurate measurements, and apparently the levels of microscale patchiness of the taxa are low compared to what has been reported for oligophagous plant‐parasites. System and soil type did not affect microscale distribution. To investigate the level of patchiness in more detail, detection probability (DP) and variability of abundances were calculated. Common and widespread bacterivorous and fungivorous taxa had DP ≥ 90%, confirming low level of microscale patchiness. With DPs of 40%–70%, predators and most omnivores showed degrees of local clustering. An overview of mean variabilities of abundances is presented that offers insight into how feeding preferences impact the microscale distribution both between and within trophic groups.     

On limiting nutrient patchiness and phytoplankton growth: a conceptual approach

A theoretical framework is developed to explore the effectsof limiting nutrient patchiness on phytoplankton growth. Growthrate is represented as a function of the average ambient substrateconcentration in the medium, the degree of patchiness and thepatch duration. Phytoplankton growth, in relation to the externalsubstrate concentration, is mediated by the cell quota for thelimiting nutrient. Two general conclusions can be drawn from this study. Firstthe degree of patchiness in the environment can affect individualgrowth rates and thus alter community structure even thoughthere is no change in the average ambient nutrient concentration.Second, for patch-adapted populations, the apparent K_s for growthcan be lowered significantly by making the distribution of thelimiting nutrient patchy with respect to time. The insightswhich this model provides into future experimental methodologiesare also discussed. ¹ Address for reprints ² also Dept. Botany ³ also Institute of Applied Mathematics     

Soil nutrient patchiness and plant genotypes interact on the production potential and decomposition of root and shoot litter: evidence from short-term laboratory experiments with Triticum aestivum

Aims

The purpose of this study was to test the hypotheses that soil nutrient patchiness can differentially benefit the decomposition of root and shoot litters and that this facilitation depends on plant genotypes.

Methods

We grew 15 cultivars (i.e. genotypes) of winter wheat (Triticum aestivum L.) under uniform and patchy soil nutrients, and contrasted their biomass and the subsequent mass, carbon (C) and nitrogen (N) dynamics of their root and shoot litters.

Results

Under equal amounts of nutrients, patchy distribution increased root biomass and had no effects on shoot biomass and C:N ratios of roots and shoots. Roots and shoots decomposed more rapidly in patchy nutrients than in uniform nutrients, and reductions in root and shoot C:N ratios with decomposition were greater in patchy nutrients than uniform nutrients. Soil nutrient patchiness facilitated shoot decomposition more than root decomposition. The changes in C:N ratios with decomposition were correlated with initial C:N ratios of litter, regardless of roots or shoots. Litter potential yield, quality and decomposition were also affected by T. aestivum cultivars and their interactions with nutrient patchiness.

Conclusions

Soil nutrient patchiness can enhance C and N cycling and this effect depends strongly on genotypes of T. aestivum. Soil nutrient heterogeneity in plant communities also can enhance diversity in litter decomposition and associated biochemical and biological dynamics in the soil.     

Population Genetic Structure of a Sandstone Specialist and a Generalist Heath Species at Two Levels of Sandstone Patchiness across the Strait of Gibraltar

Many habitat specialist species are originally composed of small, discontinuous populations because their habitats are naturally fragmented or patchy. They may have suffered the long-term effects of natural patchiness. Mediterranean heathlands, a representative habitat in the Strait of Gibraltar region, are associated with nutrient-poor, acidic sandstone soils. Sandstone soil patches in the African side of the Strait (Tangier) are, in general, smaller and more scattered than in the European side (Algeciras). In this study, we analyze the effect of this sandstone patchiness on the population genetic diversity and structure of two Erica species from these Mediterranean heathlands that differ in their edaphic specificity, E. australis, sandstone specialist, and E. arborea, generalist. Average levels of within-population genetic diversity and gene flow between populations were significantly lower in Tangier (high sandstone patchiness) than in Algeciras (low patchiness) for the sandstone specialist, whereas no differences between both sides of the Strait were detected in the edaphic generalist. Since most endemic species in Mediterranean heathlands of the Strait of Gibraltar are sandstone specialists, these results highlight an increased vulnerability to loss of genetic diversity and local extinction of the heathland endemic flora in the Tangier side of the Strait of Gibraltar.     

Dynamics induced by delay in a nutrient–phytoplankton model with diffusion

In this paper, a nutrient–phytoplankton model described by a couple of reaction-diffusion equations with delay is studied analytically and numerically. The aim of this research is to provide an understanding of the impact of delay on the nutrient–phytoplankton dynamics. Significantly, the delay can not only induce instability of a positive equilibrium, but also promote the formation of patchiness (an irregular pattern) via Hopf bifurcation. However, if the delay does not exist, the positive equilibrium is always globally asymptotically stable when it exists. In addition, the numerical analysis indicates that the input rate and the loss rate of nutrient also play an important role in the growth of phytoplankton, which supports that eutrophic conditions may be a significant reason inducing phytoplankton blooms. Numerical results are consistent with the analytical results.     

资源异质性环境中三种匍匐茎草本植物克隆内资源共享和分株功能特化(英文)

研究了 3种来自中国北方林下、草地和碱化草甸匍匐茎型克隆草本植物绢毛匍匐委陵菜 (PotentillareptansL .var.sericophyllaFranch .)、鹅绒委陵菜 (P .anserinaL .)和金戴戴 (Halerpestesruthenica (Jacq .)Qvcz .)对由高光照低养分斑块和低光照高养分斑块组成的资源交互斑块性生境的适应性对策。当生长于高光照低养分条件下分株(HL分株 )与生长于低光照高养分条件下分株 (LH分株 )之间的匍匐茎连接时 ,3种克隆植物HL分株、LH分株以及整个分株对系统 (HL分株 LH分株 )的生物量均得到显著提高。同时 ,LH分株根冠比显著增加 ,而HL分株根冠比显著下降。这表明 ,当互连分株置于由低光照高养分斑块和高光照低养分斑块组成的异质性环境中时 ,3种植物克隆分株均发生了环境诱导的功能特化。克隆内资源共享以及克隆内不同分株的功能特化有利于整个分株系统对局部丰富资源的获取 ,从而能够缓解资源交互斑块性生境对克隆植物的不利影响     

Evolutionary Divergences in Root Exudate Composition among Ecologically-Contrasting Helianthus Species

Plant roots exude numerous metabolites into the soil that influence nutrient availability. Although root exudate composition is hypothesized to be under selection in low fertility soils, few studies have tested this hypothesis in a phylogenetic framework. In this study, we examined root exudates of three pairs of Helianthus species chosen as phylogenetically-independent contrasts with respect to native soil nutrient availability. Under controlled environmental conditions, seedlings were grown to the three-leaf-pair stage, then transferred to either high or low nutrient treatments. After five days of nutrient treatments, we used gas chromatography-mass spectrometry for analysis of root exudates, and detected 37 metabolites across species. When compared in the high nutrient treatment, species native to low nutrient soils exhibited overall higher exudation than their sister species native to high nutrient soils in all three species pairs, providing support for repeated evolutionary shifts in response to native soil fertility. Species native to low nutrient soils and those native to high nutrient soils responded similarly to low nutrient treatments with increased exudation of organic acids (fumaric, citric, malic acids) and glucose, potentially as a mechanism to enhance nutrition acquisition. However, species native to low nutrient soils also responded to low nutrient treatments with a larger decrease in exudation of amino acids than species native to high nutrient soils in all three species pairs. This indicates that species native to low nutrient soils have evolved a unique sensitivity to changes in nutrient availability for some, but not all, root exudates. Overall, these repeated evolutionary divergences between species native to low nutrient soils and those native to high nutrient soils provide evidence for the adaptive value of root exudation, and its plasticity, in contrasting soil environments.