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Yield and quality properties of silage maize and their influencing factors in China
No full textSilage maize (Zea mays L.) is one of the most important forages in the world, and its yield and quality properties are critical parameters for livestock production and assessment of forage values. However, relationships between its yield and quality properties and the controlling factors are not well documented. In this study, we collected 5,663 observations from 196 publications across the country to identify the relationships between yield and quality properties of silage maize and to assess the impact of management practices and climatic factors on its yield and quality in China. The average dry matter yield of silage maize was (19.98 +/- 6.93) Mg ha(-1), and the average value of crude protein, ether extract, crude ash, crude fiber, acid detergent fiber, neutral detergent fiber, nitrogen-free extract, and relative feed value was 7.86%+/- 1.71%, 2.53%+/- 1.01%, 5.05%+/- 1.66%, 23.97%+/- 6.34%, 27.62%+/- 7.12%, 51.60%+/- 9.85%, 59.68%+/- 7.72%, and 131.17 +/- 31.49, respectively. In general, its nutritive value decreased as its yield increased. Increasing planting density could increase the yield but inhibit the nutritive values, while increasing fertilization could benefit the nutritive values. Geographically, the yield increased and the nutritive value decreased from warm (south) to cold (north) regions. The length of growth duration was a major controlling factor for the patterns of these properties. Our findings provide insights for police-makers to make strategy for achieving high yield and good quality of silage maize and help local people to implement better management practices
Differential impacts of adult trees on offspring and non-offspring recruits in a subtropical forest
No full textAn important mechanism promoting species coexistence is conspecific negative density dependence (CNDD), which inhibits conspecific neighbors by accumulating host-specific enemies near adult trees. Natural enemies may be genotype-specific and regulate offspring dynamics more strongly than non-offspring, which is often neglected due to the difficulty in ascertaining genetic relatedness. Here, we investigated whether offspring and non-offspring of a dominant species, Castanopsis eyrei, suffered from different strength of CNDD based on parentage assignment in a subtropical forest. We found decreased recruitment efficiency (proxy of survival probability) of offspring compared with non-offspring near adult trees during the seedling-sapling transition, suggesting genotype-dependent interactions drive tree demographic dynamics. Furthermore, the genetic similarity between individuals of same cohort decreased in late life history stages, indicating genetic-relatedness-dependent tree mortality throughout ontogeny. Our results demonstrate that within-species genetic relatedness significantly affects the strength of CNDD, implying genotype-specific natural enemies may contribute to population dynamics in natural forests
Quantifying the shape of urban street trees and evaluating its influence on their aesthetic functions based on mobile lidar data
No full textStreet trees are important components of an urban green space and understanding and measuring their ecological and cultural services is crucial for assessing the quality of streets and managing urban environments. Currently, most studies mainly focus on evaluating the ecological services of street trees by measuring the amount of greenness, but how to evaluate their aesthetic functions through quantitative measurements of street trees remain unclear. To address this problem, we propose a method to assess the aesthetic functions of street trees by quantifying the shape of greenness inspired by assessments of skyline aesthetics. Using a state-of-the-art mobile mapping system, we collected downtown-wide lidar data and panoramic images in Jinzhou City, Hebei Province, China. We developed a method for extracting the canopy line from the mobile lidar data, and then identified two basic elements, peaks and gaps, from street canopy lines and extracted six indexes (i.e., richness of peaks, evenness of peaks, frequency of peaks, total length of gaps, evenness of gaps and frequency of gaps) to describe the fluctuations and continuities of street canopy lines. We analyzed the abundance and spatial distribution of these indexes together with survey responses on the streets' aesthetics and found that most of them were significantly correlated with human perception of streets. Compared to indexes of amount of greenness (e.g., green volume and green view index), these shape indexes have stronger influences on the physical aesthetic beauty of street trees. These findings suggest that a comprehensive assessment of the aesthetic function of street trees should consider both shape and amount of greenness. This study provides a new perspective for the assessment of urban green spaces and can assist future urban greening planning and urban landscape management
Dynamics of diverse coherences in primary charge separation of bacterial reaction center at 77 K revealed by wavelet analysis
No full textTo uncover the mechanism behind the high photo-electronic conversion efficiency in natural photosynthetic complexes it is essential to trace the dynamics of electronic and vibrational quantum coherences. Here we apply wavelet analysis to two-dimensional electronic spectroscopy data for three purple bacterial reaction centers with mutations that produce drastically different rates of primary charge separation. From the frequency distribution and dynamic evolution features of the quantum beating, electronic coherence with a dephasing lifetime of similar to 50 fs, vibronic coherence with a lifetime of similar to 150 fs and vibrational/vibronic coherences with a lifetime of 450 fs are distinguished. We find that they are responsible for, or couple to, different specific steps during the primary charge separation process, i.e., intradimer charge transfer inside the special bacteriochlorophyll pair followed by its relaxation and stabilization of the charge-transfer state. The results enlighten our understanding of how quantum coherences participate in, and contribute to, a biological electron transfer reaction
A group of CLE peptides regulates de novo shoot regeneration in Arabidopsis thaliana
No full textKnown for their regulatory roles in stem cell homeostasis, CLAVATA3/ESR-RELATED (CLE) peptides also function as mediators of external stimuli such as hormones. De novo shoot regeneration, representing the remarkable plant cellular plasticity, involves reconstitution of stem cells under control of stem-cell regulators. Yet whether and how stem cell-regulating CLE peptides are implicated in plant regeneration remains unknown. By CRISPR/Cas9-induced loss-of-function studies, peptide application, precursor overexpression, and expression analyses, the role of CLE1-CLE7 peptides and their receptors in de novo shoot regeneration was studied in Arabidopsis thaliana. CLE1-CLE7 are induced by callus-induction medium and dynamically expressed in pluripotent callus. Exogenously-applied CLE1-CLE7 peptides or precursor overexpression effectively leads to shoot regeneration suppression, whereas their simultaneous mutation results in enhanced regenerative capacity, demonstrating that CLE1-CLE7 peptides redundantly function as negative regulators of de novo shoot regeneration. CLE1-CLE7-mediated shoot regeneration suppression is impaired in loss-of-function mutants of callus-expressed CLAVATA1 (CLV1) and BARELY ANY MERISTEM1 (BAM1) genes, indicating that CLV1/BAM1 are required for CLE1-CLE7-mediated shoot regeneration signaling. CLE1-CLE7 signaling resulted in transcriptional repression of WUSCHEL (WUS), a stem cell-promoting transcription factor known as a principal regulator of plant regeneration. Our results indicate that functionally-redundant CLE1-CLE7 peptides genetically act through CLV1/BAM1 receptors and repress WUS expression to modulate shoot-regeneration capacity, establishing the mechanistic basis for CLE1-CLE7-mediated shoot regeneration and a novel role for CLE peptides in hormone-dependent developmental plasticity
Climate and mycorrhizae mediate the relationship of tree species diversity and carbon stocks in subtropical forests
No full textIt is increasingly being recognized that tree species diversity has positive effects on forest ecosystem carbon (C) stock. However, at broad spatial scales, this relationship may depend on climate conditions and species mycorrhizal associations. Here, observations from 667 forest plots in subtropical China were used to investigate the effects of species diversity, mean annual precipitation (MAP), mean annual temperature (MAT) and mycorrhizal type (arbuscular or ectomycorrhizal) on the forest C stock and its components (tree C stock, shrub layer C stock, herb layer C stock, litter layer C stock, root C stock and soil C stock). We found positive effect of tree species diversity on total forest C stock. MAP had positive effects on total forest C stock and its components, while MAT had consistently negative effects on total forest C stock and most of its components. Different levels of MAP and MAT did modulate the strength of effect of species diversity on forest C stock and its components. In addition, species diversity, MAT and MAP showed a significant positive relationship with arbuscular mycorrhiza-associated tree C stock but had no or negative relationship with ectomycorrhiza-associated tree C stock. Synthesis. Our results indicate that maintaining high level of species diversity may support the buffering of negative effects resulting from climate warming. Furthermore, under climate warming the specific C stock of AM trees can increase, which can potentially promote forest C stock. Taken together, our study suggests that afforestation policies should consider not only tree species diversity to increase forest C stock but also the effects of different tree mycorrhizal types
Anatomy of Stigmaria asiatica Jongmans et Gothan from the Asselian (lowermost Permian) of Wuda Coalfield, Inner Mongolia, North China
No full textStigmaria asiatica Jongmans et Gothan is a common species from the Permo-Carboniferous of East Asia. It is characterized by a relatively slender rhizomorph and represents the underground rooting system of lowland arborescent lycopsids. This species from the Wuda Coalfield (Asselian, lower Permian) represents the recovery taxon dominating the subsequent peat-forming vegetation after a volcanic eruption destroyed the previous flora, termed the Wuda Tuff Flora (Chinese vegetational Pompeii ). It is characterized by novel downward axes, probably for access to deeper groundwater. Here, the anatomy of S. asiatica , including that of the axes and rootlets, is reported in detail for the first time. The axis contains stelar tissues, including pith, primary and secondary xylem, and phloem, and both primary and secondary cortical tissues. The primary cortex is tripartite and is divided into inner, middle, and outer zones. Secondary cortex is produced in the interior of the outer cortex splitting the outer cortex into inner and outer portions. The homogeneous pith and mesarch primary xylem maturation of S. asiatica are different from previously recorded species of Stigmaria Brongniart. Rootlets are composed of a central monarch vascular bundle surrounded by inner cortex and a ring of outer cortex. A vacant region is present between the inner and outer cortices. In some cases, connectives between the inner and outer cortices are present. According to the presented statistical analysis, it is proposed that rootlets of S. asiatica were highly branched, with at least for 7 bifurcations. Rootlets, together with the downward penetrating rhizomorph, helped to both anchor the plant and search for and absorb deep groundwater. (C) 2021 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved
Linkage of vegetation and abiotic attributes to grazing effects on biogeographical patterns of arbuscular mycorrhizal fungal communities in temperate grasslands
No full textPurpose Grazing is a traditional way of grassland management in Inner Mongolia of China. Despite important roles of arbuscular mycorrhizal fungal (AMF) communities in grassland ecosystems, few studies have specifically focused on the effects of grazing on AMF communities in grassland, particularly at regional level. Methods High-throughput sequencing technology was used to evaluate the effects of grazing on AMF communities along a 700-km transect that was characterized by a precipitation gradient and comprised of 10 pairs of ungrazed and grazed sites in temperate grasslands along the China-Mongolia border. Results Grazing significantly altered alpha and beta diversity of AMF community along the precipitation gradient from southwest to northeast. alpha diversity of AMF community was positively correlated with plant species richness and percentage cover. Furthermore, alpha diversity of AMF community displayed a positive correlation with soil moisture and organic carbon but a negative correlation with pH. The response ratio of alpha diversity of AMF community displayed positive correlation with the response ratio of percentage cover. Analyses by db-RDA (distance-based redundancy analysis) and VPA (variance partitioning analysis) revealed that both vegetation and abiotic properties were involved in the grazing-induced changes in AMF communities. Conclusions AMF communities exhibited distinct biogeographical patterns across a precipitation gradient from southwest to northeast in northern China. Grazing led to significant changes in the diversity of AMF communities at regional level. Both vegetation and abiotic attributes were linked to grazing-induced changes in AMF community of the temperate steppes
Carbon sequestration in soil and biomass under native and non-native mangrove ecosystems
No full textAims Mangrove ecosystems can help mitigate climate change by sequestering significant amounts of carbon (C) from the atmosphere and ocean, contributing to regional blue carbon stocks. However, it is unclear whether non-native species introduced in coastal wetlands can function as a more efficient carbon sink. Methods By examining two dominant mangrove species, native Kandelia obovata (KO) and exotic Sonneratia apetala Buch.-Ham. (SA), at the Qi'ao Island, China, we quantified and compared ecosystem C storage, C sequestration rate, source and stability of soil organic carbon (SOC) under different vegetation covers. Results & conclusion Our results showed that both species acted as strong carbon sinks relative to mudflat reference, with overall ecosystem C storage being comparable under KO (410 Mg C ha(-1)) and SA with different stand ages (224-452 Mg C ha(-1)), but a few times higher than corresponding unvegetated mudflat. However, by excluding SOC accumulation from prior land use (i.e., unvegetated mudflat), non-native species (i.e., SA) showed a significantly higher ecosystem carbon sequestration rate (8.2-16.4 Mg C ha(-1) yr(-1)) than native KO (4.5 Mg C ha(-1) yr(-1)), owing largely to fast biomass carbon sequestration in SA ecosystem. Relative to mudflat reference, the input of autochthonous source (mangrove tissues) contributed substantially to additional carbon sequestration under mangroves. It should be noted that the relative size of carbon sequestration in non-native mangroves is also affected by factors related to ecosystem, climate, soil properties and land use, the differences still exist among locations, and ecosystem modeling with field validation is desirable for regional estimation of carbon stocks and sequestration rates
Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment
No full textTo cope with a highly heterogeneous light environment, photosynthesis in plants can be regulated systemically. Currently, the majority of studies are carried out with various plants during the vegetative growth period. As the reproductive sink improves photosynthesis, we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field. Therefore, changes of light intensity within canopy, chlorophyll content, gas exchange, and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities. In this study, a high planting density of maize drastically reduced the light intensities in the lower canopy, and increased the difference in vertical light distribution within the canopy. With the increase of vertical heterogeneity, chlorophyll content, light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf (EL) and the fourth leaf below the ear (FLBE) were decreased gradually, and the ranges of declines in these parameters were larger at FLBE than those at EL. Leaves in the lower canopy were shaded artificially to further test these results. Partial shading (PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE. Removing the tassel and top leaves (RTL) not only improved the vertical light distribution within the canopy, but also reduced the differences in photosynthetic characteristics between the two leaves. Taken together, these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment; slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage