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Impacts of experimental warming and moderate grazing on ecosystem carbon exchange and its compositions in an alpine meadow on the eastern Qinghai-Tibetan Plateau
No full text青藏高原高寒生态系统碳循环对气候变暖和放牧等的响应依然存在很大不确定性.采用开顶式温室模拟增温,采用刈割和牲畜粪便归还相结合的方法模拟中度放牧,研究气候变暖和中等强度放牧对青藏高原东部高寒草甸生态系统碳交换、生态系统光合、生态系统呼吸与土壤呼吸的影响.结果显示:模拟气候变暖和中度放牧显著改变青藏高原东部高寒草甸生态系统净碳交换及其组分,并且生态系统碳循环的响应随时间呈现不同的变化.增温显著提高净生态系统碳交换和生态系统光合,增加生态系统净碳固定;中度放牧降低生态系统呼吸和土壤呼吸,而对生态系统净碳交换、生态系统光合的影响存在明显季节动态变化,即在处理初期(8月上旬)明显降低,而后逐渐上升,在生长季后期、末期(9月中下旬-10月份)显著高于对照;增温和中度放牧未表现明显的交互作用,增温+放牧处理增加了季节性平均净生态系统碳交换和生态系统光合,但没有显著影响季节平均生态系统呼吸.增温和中度放牧的交互作用对碳交换的影响存在时间尺度上的变化.本研究表明,在未来气候变暖和中等强度放牧的背景下,青藏高原东部高寒草甸碳汇功能有可能增强
Evolution of nuchal glands, unusual defensive organs of Asian natricine snakes (Serpentes: Colubridae), inferred from a molecular phylogeny
No full textA large body of evidence indicates that evolutionary innovations of novel organs have facilitated the subsequent diversification of species. Investigation of the evolutionary history of such organs should provide important clues for understanding the basis for species diversification. An Asian natricine snake, Rhabdophis tigrinus, possesses a series of unusual organs, called nuchal glands, which contain cardiotonic steroid toxins known as bufadienolides. Rhabdophis tigrinus sequesters bufadienolides from its toad prey and stores them in the nuchal glands as a defensive mechanism. Among more than 3,500 species of snakes, only 17 Asian natricine species are known to possess nuchal glands or their homologues. These 17 species belong to three nominal genera, Balanophis, Macropisthodon, and Rhabdophis. In Macropisthodon and Rhabdophis, however, species without nuchal glands also exist. To infer the evolutionary history of the nuchal glands, we investigated the molecular phylogenetic relationships among Asian natricine species with and without nuchal glands, based on variations in partial sequences of Mt-CYB, Cmos, and RAG1 (total 2,767 bp). Results show that all species with nuchal glands belong to a single clade (NGC). Therefore, we infer that the common ancestor of this clade possessed nuchal glands with no independent origins of the glands within the members. Our results also imply that some species have secondarily lost the glands. Given the estimated divergence time of related species, the ancestor of the nuchal gland clade emerged 19.18 mya. Our study shows that nuchal glands are fruitful subjects for exploring the evolution of novel organs. In addition, our analysis indicates that reevaluation of the taxonomic status of the genera Balanophis and Macropisthodon is required. We propose to assign all species belonging to the NGC to the genus Rhabdophis, pending further study
Tree species mixture inhibits soil organic carbon mineralization accompanied by decreased r-selected bacteria
No full textMixed-tree species plantations demonstrate higher productivity, soil carbon sequestration capacity, and various soil nutrient contents relative to single-species plantations. Despite the critical role of soil microbes in mediating soil various biogeochemical processes, the effects of tree species mixtures on bacterial community structure and ecological function remain unclear. High-throughput 16S rRNA gene sequencing was used to examine the composition of soil bacterial communities in five single-species plantations and three corresponding mixed plantations. The plantations were established on the same initial substrate, and sampling was conducted in 68 relatively spatially-independent sites. Our results showed tree species mixture significantly altered the soil bacterial community composition and structure, compared with single-species plantations. Especially, Tree species mixture increased the relative abundance of K-strategists (Acidobacteria) and decreased the relative abundance of r-strategists (Proteobacteria and Bacteroidetes). The changes on soil bacterial community composition were largely explained by low molecular weight (LMW; < 250 Da) compounds of dissolved organic C (DOC). Tree species mixture significantly decreased soil C mineralization rates, and there was a negative relationship between soil C mineralization rates and the abundance of K-strategists and a positive relationship for r-strategists. Our results provide preliminary evidence that tree species mixture can significantly alter soil bacterial community composition and their implications on soil organic matter mineralization. This study represents an important step forward in understanding the underlying mechanisms by which plant-microbe interactions influence functions of belowground ecosystems
Lambertellin from Pycnoporus sanguineus MUCL 51321 and its anti-inflammatory effect via modulation of MAPK and NF-kappa B signaling pathways
No full textLambertellin (1) and ergosta-5,7,22-trien-3-ol (2) were isolated from the solid rice fermentation of the plant pathogenic fungus Pycnoporus sanguineus MUCL 51321. Their structures were elucidated using comprehensive spectroscopic methods. The isolated compounds were tested on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Lambertellin (1) exhibited promising inhibitory activity against nitric oxide (NO) production with IC50 value of 3.19 mu M, and it significantly inhibited the expression of inducible NO synthase (iNOS) and cyclooxygenase 2 (COX-2). Lambertellin (1) also decreased the expression of pro-inflammatory cytokines IL-6 and IL-1 beta. The study of the mechanistic pathways revealed that lambertellin (1) exerts its anti-inflammatory effect in LPS-stimulated RAW 264.7 macrophage cells by modulating the activation of the mitogen activated protein kinase (MAPK) and nuclear factor kappa B (NF-kappa B) signaling pathways. Therefore, lambertellin (1) could be a promising lead compound for the development of new anti-inflammatory drugs
Community-level species' correlated distribution can be scale-independent and related to the evenness of abundance
No full textThe spatial distribution of species is not random; instead, individuals tend to gather, resulting in a non-random pattern. Previous studies used the independent negative binomial distribution (NBD) to model the distributional aggregation of a single species, in which the independence of the distribution of individuals of a species in different quadrats had been assumed. This way of analyzing aggregation will result in the scale-dependent estimation of the aggregation or shape parameter. However, because non-random (and therefore non-independent) distribution of individuals of a species in a finite area can be caused by either correlated or clumped distribution of individuals of a species between neighboring sites, an alternative model would assume that the distribution of individuals of a species over different sampling areas is multinomial. Here, we showed that, by assuming that regional species abundance followed a NBD while using a multinomial distribution to assign individuals of species in different non-overlapped sampling quadrats that are from a partition of the entire region (quantifying positive correlation or synchrony), the estimation of the shape parameter in this probabilistic model, which is the negative multinomial distribution (NMD), was scale-invariant (i.e., the estimated shape parameter is identical across different partitions of the study region). Accordingly, the estimation of the shape parameter was related to regional species distribution alone. This implied that, the shape parameter at the community level, using the NMD model, reflected the evenness of interspecific abundance. As a comparison, if the distribution of individuals of a single species followed independent NBDs as studied previously, the shape parameter would measure the evenness of intraspecific abundance (quantifying single-species' distributional aggregation). Moreover, our study highlighted the necessity for adjusting the model for the effects of unsampled species when studying community-level distributional patterns. Collectively, as long as a target area is partitioned into non-overlapping quadrats (no matter how their sizes vary), the proposed NMD model in this study, along with the independent NBDs model, can be jointly formulated as a framework to reconcile the scale-dependent debate on the shape parameter, unifying the relationship between inter- or intraspecific abundance and distributional patterns
Identification of QTL regions for seedling root traits and their effect on nitrogen use efficiency in wheat (Triticum aestivum L.)
No full textKey messageQTL for a wheat ideotype root system and its plasticity to nitrogen deficiency were characterized.AbstractRoot system architecture-related traits (RRTs) and their plasticity tonitrogen availability are important for nitrogen acquisition and yield formation in wheat (Triticum aestivum L.). In this study, quantitative trait loci (QTL) analysis was conducted under different nitrogen conditions, using the seedlings of 188 recombinant inbred lines derived from a cross between Kenong 9204 and Jing 411. Fifty-three QTL for seven RRTs and fourteen QTL for the plasticity of these RRTs to nitrogen deficiency were detected. Thirty of these QTL were mapped in nine clusters on chromosomes 2B, 2D, 3A, 3D, 6B, 6D, 7A and 7B. Six of these nine clusters were also colocated with loci for nitrogen use efficiency (NUE)-related traits (NRTs). Among them, three QTL clusters (C2B, C6D and C7B) were highlighted, considering that they individually harbored three stable robust QTL (i.e., QMrl-2B.1, QdRs-6D and QMrl-7B). C2B and C7B stably contributed to the optimal root system, and C6D greatly affected the plasticity of RRTs in response to nitrogen deficiency. However, strong artificial selection was only observed for C7B in 574 derivatives of Kenong 9204. Covariance analysis identified QMrl-7B as the major contributor in C7B that affected the investigated NRTs in mature plants. Phenotypic analysis indicated that thousand kernel weight might represent a concomitant above-ground trait of the hidden RRTs controlled by C7B, which are used for breeding selection. Dissecting these QTL regions with potential breeding value will ultimately facilitate the selection of donor lines with both high yield and NUE in wheat breeding programs
Mycelium- and root-derived C inputs differ in their impacts on soil organic C pools and decomposition in forests
No full textWhile multiple lines of evidence suggests that root carbon (C) can significantly impact the soil organic C (SOC) pool and subsequent C cycles via rhizosphere priming effects, the relative magnitude of the effects that root- and fungal-derived C inputs have in driving the priming of SOC decomposition are currently unknown. In this study, we used ingrowth cores and stable C isotope analyses to quantify root- and mycelium-derived C sequestered in soil labile and recalcitrant C pools and their relative contributions to the decomposition of native SOC in a spruce-fir-dominated coniferous forest on the eastern Tibetan Plateau, China. The results showed that new C sequestered in the soil labile C pool was primarily (77%) from mycelium-derived C, while 60% of the root derived C sequestered in the soil was incorporated into the recalcitrant pool. Furthermore, although the total native SOC pool was not significantly influenced by new C derived from both roots and mycelia, mycelium derived C induced a remarkably greater negative priming effect (-12.0%) on the native labile C pool than did root-derived C (-5.8%); in contrast, mycelium-derived C induced a greater positive priming effect (13.8%) than root-derived C (7.1%) on the native recalcitrant C pool. Collectively, our findings suggest that mycelium-derived C make a greater contribution to the newly sequestered C in the soil labile C pool than root-derived C, thereby inducing a remarkably greater positive priming effect on the decomposition of native soil recalcitrant C. Therefore, mycelium-derived C inputs may play a dominant role in soil C dynamics and long-term C storage, at least in alpine forest ecosystems where ectomycorrhizal mutualisms dominate
Water Holding Capacity of Soils and Ground Covers in a Forest-shrub Ecotone of the Source Area of Minjiang River
No full text通过野外调查和室内试验,定量评价了岷江源头区交错带云杉针叶林、云杉针叶林山生柳灌丛交错区(乔灌)和窄叶鲜卑花灌丛3个林型的地被物(枯落物和苔藓)和土壤持水特征.结果表明:3个林型地被物储量差异显著,其大小顺序为乔灌(72.67t/hm~2)>针叶林(43.87t/hm~2)>灌丛(11.00t/hm~2);针叶林和乔灌的苔藓层的储量分别为27.00,44.71t/hm~2,占地被物总储量的61.5%以上.地被物层最大持水总量表现为乔灌(21.23mm)>针叶林(11.33mm)>灌丛(2.45mm);针叶林和乔灌枯落物层的最大持水量分别为7.45,12.12mm,均大于苔藓层的最大持水量;针叶林和乔灌枯落物层和苔藓层最大持水量分别是其储量的4.3~4.4,1.4~2.0倍.土壤容重随土层深度增加而增大,持水能力则随土层深度增加而降低;020cm最大持水量大小顺序为乔灌(153.70mm)>灌丛(132.28mm)>针叶林(128.25mm).综合地被物持水和土壤持水,交错带生态系统的持水能力在不同林型间差异显著,其最大持水量表现为乔灌(174.93 mm)>针叶林(139.58 mm)>灌丛(134.73 mm),其中,土壤层是生态系统持水能力的主导层,占综合持水量的87.9%以上.研究结果有利于全面认识岷江源头区生态水文效应
Call Characteristics of Two Sympatric and Morphologically Similar Tree Frogs Species, Polypedates megacephalus and Polypedates mutus (Anura: Rhacophoridae), from Hainan, China
Get PDFAnuran calls are usually species-specific and therefore valued as a tool for species identification. Call characteristics are a potential honest signal in sexual selection because they often reflect male body size. Polypedates megacephalus and P. mutus are two sympatric and morphologically similar tree frogs, but it remains unknown whether their calls are associated with body size. In this study, we compared call characteristics of these two species and investigated any potential relationships with body size. We found that P. megacephalus, males produced six call types which consisting of three distinct notes, while P. mutus males produced five types consisting of two types of notes. Dominant frequency, note duration, pulse duration, and call duration exhibited significant interspecific differences. In P. megacephalus, one note exhibited a dominant frequency that was negatively correlated with body mass, snout-vent length, head length, and head width. In P. mutus, the duration of one note type was positively correlated with body mass and head width. These differences in call characteristics may play an important role in interspecific recognition. Additionally, because interspecific acoustic variation reflects body size, calls may be relevant for sexual selection. Taken together, our results confirmed that calls are a valid tool for distinguishing between the two tree-frog species in the field
Sex Ratio and Sexual Size Dimorphism in a Toad-headed Lizard, Phrynocephalus guinanensis
Get PDFPhrynocephalus guinanensis has sexual dimorphism in abdominal coloration, but its ontogenetic development of sexual size dimorphism (SSD) is unknown. Using mark-recapture data during four days each year from August from 2014 to 2016, we investigated the development of sex ratios, SSD, sex-specific survivorship and growth rates in a population of P. guinanensis. Our results indicated that the sex ratio of males to females was 1:2.8. Males had a lower survival rate (6%) than females (14%) across the age range from hatchling to adult, which supported the discovered female-biased sex ratio potentially associated with the low survival rate of males between hatchlings and juveniles. Male-biased SSD in tail length and head width existed in adults rather than in hatchling or juvenile lizards. The growth rates in body dimensions were undistinguishable between the sexes during the age from hatchling to juvenile, but the growth rate in head length from juvenile to adult was significantly larger in males than females. Average growth rate of all morphological measurements from hatchling to juvenile were larger compared with corresponding measurements from juvenile to adult, but only being significant in tail length, head width, abdomen length in females and snout-vent length in males. We provided a case study to strengthen our understanding of the important life history traits on how a viviparous lizard population can survive and develop their morphology in cold climates