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Effects of Plot Design on Estimating Tree Species Richness and Species Diversity
No full textSpecies richness and diversity substantially affect forest structures and function and are critical indicators of sustainable forest management. Sampling surveys are widely used in forest inventories because they efficiently assess forest characteristics. However, an appropriate sample plot design is required. The objectives of this study were to evaluate the effects of plot design on estimating species richness and species diversity using a simulation. A 20 ha census plot was established in a temperate forest to obtain the true values of species richness and species diversity. One single plot design and nine cluster plot designs were evaluated. The results indicated significant differences in forest species richness and species diversity for different plot designs. The cluster plot design with a square subplot configuration (SCONFIG) and extent of ground area covered by a cluster (EGROUND) of 500 m(2) exhibited the best performance (accuracy, precision) in estimating forest species richness. In contrast, a rectangular cluster plot with an EGROUND of 1000 m(2) was more suitable for assessing species diversity. This study demonstrates that cluster plots outperform a single plot for evaluating species richness and species diversity in temperate forests
Developing long-term conservation priority planning for medicinal plants in China by combining conservation status with diversity hotspot analyses and climate change prediction
No full textBackground Medicinal plants have always played an important role in the history of human health. However, the populations and sustainable use of medicinal plants have been severely affected by human activities and climate change. Little is known about the current conservation status and distribution pattern of medicinal plants. In this study, based on accurate geographical distribution information of 9756 medicinal plants, we identified diversity hotspots and conservation gaps, evaluated conservation effectiveness of nature reserves, and predicted suitable habitat areas for medicinal plants in China to provide scientific guidance for their long-term conservation and sustainable use. Results A total of 150 diversity hotspot grid cells, mainly concentrated in central and southern China, were identified. These only accounted for 5% of the total distribution area but contained 96% of the medicinal plants of the country. The hotspot grid cells included all traditional hotspot areas, but we also detected three new hotspots, namely Mufu-Lushan Mountains, Tianshan-Altai Mountains, and Changbai Mountains. The current national and provincial nature reserves protect 125 hotspot grid cells, which harbor 94% of all medicinal plants. However, 25 hotspot grid cells, distributed in the Tianshan-Altai Mountains and Hengduan Mountains, are located outside the national and provincial nature reserves. An analysis of the predicted effects of climate change indicated that the suitable habitat areas will shift from southern to northern China, and that southern China will face a considerable loss of suitable habitat areas, while the east and west parts of China will encompass remarkably more suitable habitat areas in the future. Conclusions The current conservation networks have achieved high conservation effectiveness with regard to medicinal plants; however, the conservation gaps we identified should not be neglected, and conservation planning needs to take into account the predicted shifts of some hotspots of medicinal plants due to climate change
Genome-Resolved Metagenomics Reveals Distinct Phosphorus Acquisition Strategies between Soil Microbiomes
No full textEnhancing soil phosphate solubilization is a promising strategy for agricultural sustainability, while little is known about the mechanisms of how microorganisms cope with differing phosphorus availability. Using a combination of genome-resolved metagenomics and amplicon sequencing, we investigated the microbial mechanisms involved in phosphorus cycling under three agricultural treatments in a wheat-maize rotation system and two natural reforestation treatments. Available soil phosphorus was the key factor shaping bacterial and fungal community composition and function across our agricultural and reforestation sites. Membrane-bound quinoprotein glucose dehydrogenase (PQQGDH) and exopolyphosphatases (PPX) governed microbial phosphate solubilization in agroecosystems. In contrast, genes encoding glycerol-3-phosphate transporters (ugpB, ugpC, and ugpQ) displayed a significantly greater abundance in the reforestation soils. The gcd gene encoding PQQGDH was found to be the best determinant for bioavailable soil phosphorus. Metagenome-assembled genomes (MAGs) affiliated with Cyclobacteriaceae and Vicinamibacterales were obtained from agricultural soils. Their MAGs harbored not only gcd but also the pit gene encoding low-affinity phos-phate transporters. MAGs obtained from reforestation soils were affiliated with Microtrichales and Burkholderiales. These contain ugp genes but no gcd, and thereby are indicative of a phosphate transporter strategy. Our study demonstrates that knowledge of distinct microbial phosphorus acquisition strategies between agricultural and reforestation soils could help in linking microbial processes with phosphorus cycling. IMPORTANCE The soil microbiome is the key player regulating phosphorus cycling proc-esses. Identifying phosphate-solubilizing bacteria and utilizing them for release of recal-citrant phosphate that is bound to rocks or minerals have implications for improving crop nutrient acquisition and crop productivity. In this study, we combined functional metagenomics and amplicon sequencing to analyze microbial phosphorus cycling proc-esses in natural reforestation and agricultural soils. We found that the phosphorus ac-quisition strategies significantly differed between these two ecosystems. A microbial phosphorus solubilization strategy dominated in the agricultural soils, while a microbial phosphate transporter strategy was observed in the reforestation soils. We further iden-tified microbial taxa that contributed to enhanced phosphate solubilization in the agro-ecosystem. These microbes are predicted to be beneficial for the increase in phosphate bioavailability through agricultural practices
Connected function of PRAF/RLD and GNOM in membrane trafficking controls intrinsic cell polarity in plants
No full textCell polarity is a fundamental feature underlying cell morphogenesis and organismal development. In the Arabidopsis stomatal lineage, the polarity protein BASL controls stomatal asymmetric cell division. However, the cellular machinery by which this intrinsic polarity site is established remains unknown. Here, we identify the PRAF/RLD proteins as BASL physical partners and mutating four PRAF members leads to defects in BASL polarization. Members of PRAF proteins are polarized in stomatal lineage cells in a BASL-dependent manner. Developmental defects of the praf mutants phenocopy those of the gnom mutants. GNOM is an activator of the conserved Arf GTPases and plays important roles in membrane trafficking. We further find PRAF physically interacts with GNOM in vitro and in vivo. Thus, we propose that the positive feedback of BASL and PRAF at the plasma membrane and the connected function of PRAF and GNOM in endosomal trafficking establish intrinsic cell polarity in the Arabidopsis stomatal lineage
Tree rings reveal a growth-decline event in AD 1875-1883 in a Tibetan plateau juniper forest
No full textForest declines under global warming have received much attention in studies of forest ecology, yet such events in periods before climate warming have been less studied because of shortage in documentation of past decline events. Here we used dendroecological techniques to identify forest decline events in the past five and a half centuries for a juniper forest near Lhasa of Tibet, China. Data of tree ring-widths were obtained from 42 relatively old trees after sample collection, measurement and crossdating. Radial growth of these trees was significantly and positively correlated with total precipitation in May and June. Persistent and severe growth reductions, lasting for at least eight years, were identified for each sample. We found that greater than 35% of the trees exhibited persistent and severe growth reductions in the interval A.D. 1875-1883, suggesting a growth decline event in the forest. This growth decline was the most severe event in the past five and half centuries. The weakened Indian monsoon in A.D. 1875-1878, which would result in extreme and prolonged droughts at spatially large scale in the monsoon zone, was most likely the driving force for the forest decline event discovered in this study. Our results suggested that future risk of juniper forest declines in central Tibetan plateau will be related to extreme droughts which could be amplified by warming. The study highlighted the importance of examining growth trajectory of individual trees in assessing forest health in a long perspective
Aerobic environments in combination with substrate additions to soil significantly reshape depth-dependent microbial distribution patterns in Zoige peatlands, China
No full textClimate warming is leading to the water table drawdown in peatlands, and a shift in the structure and productivity of vegetation communities. These events may alter the availability of oxygen and substrate utilized by soil microbes, which may impact the microbial decomposition rate in the different peat layers. We investigated the bacterial and fungal communities in surface (0-25 cm), subsurface (25-75 cm) and deep (> 76 cm) layers, and assessed the response of these communities to aerobic conditions and substrate of varying complexity additions to soils in Zoige peatlands, China. Bacterial and fungal communities varied in different peat layers, with the largest community sizes in the surface layer. The aerobic incubation significantly altered bacterial and fungal community compositions in the subsurface and deep layers. Both bacterial and fungal community size increased by 155% and 53% in the deep layer, respectively. Under aerobic conditions, substrate additions to soils significantly shifted fungal community compositions across all soil layers but not bacteria. Soil substrate increased the fungal community size by 130%-1000% in the subsurface layer without substantially altering bacterial abundance in any of the layers. Our results highlight the importance of vertical stratification in bacterial and fungal communities and the depth-dependent changes that occur under the influence of an aerobic environment and changes in the quality of the substrate. We suggest that fungi may be more sensitive to climate change than bacteria, especially in subsurface layers. Thus, this is an essential factor that needs to be considered when analyzing the role of microbes in peatland carbon dynamics
Coordination among Water Transport, Photosynthesis and Nutrition under Climate Change: Stronger Responses of a Native than an Invasive Herb
No full textClimate change will impact all plant physiological processes including water transport, photosynthesis, and nutrient assimilation. How these processes are coordinated in response to climate change is not fully understood. Here we tested how these processes will respond to elevated CO2 concentration ([CO2]) and temperatures for two herbaceous species (an invasive and a native Eupatorium species in East Asia; family Asteraceae) and whether these processes are coordinated using a controlled experiment. We also investigated the differences between these two species, and the structural basis for changes in physiology. Leaf photosynthetic capacity (A(max), measured under ambient conditions) increased significantly in the native species, while that of the invasive species did not change under elevated [CO2] and temperatures. The leaf hydraulic conductance (K-leaf) of both species tended to increase under elevated temperatures and [CO2], with that of the native species increasing to a greater extent. Changes in K-leaf and A(max) were coordinated, and K-leaf was closely associated with leaf minor vein density across treatments. The increased photosynthetic capacity of the native species was probably related to an increased N investment in photosynthesis; its leaf N decreased but chlorophyll concentration increased inviting detailed studies in N partitioning. No coordination between water use (water transport, stomatal conductance, and water use efficiency) and leaf tissue nutrient (N, P) concentrations was found, probably owing to the active control in nutrient uptake. Thus, photosynthesis is coordinated with water transport in response to climate change, while the coordination between water use and nutrient accumulation can be absent due to active control. Our results also suggest that global climate change will not necessarily fuel more positive responses in invasive plants than native plants
Label-free quantitative proteomics reveals the antibacterial mechanism of rosemary essential oil against Salmonella enterica serovar Typhimurium
No full textRosemary essential oil (REO) shows various biological functions and is widely used in the cosmetic and pharmaceutical industries. Salmonella enterica serovar Typhimurium infection treated by antibiotics leads to serious drug resistance and public health hazard. REO as an antibiotic alternative has become the focus of considerable research efforts. However, knowledge regarding the S. Typhimurium growth characteristics and proteomic responses to REO exposure remains unclear. Here, we evaluated the commonalities and differences in chemical compositions of REOs extracted from Salvia rosmarinus cultivars, 'Algarve' (AL), 'Dutch Mill' (DM), and 'Majorca Pink' (MP) using gas chromatography-mass spectrometry. The three REOs displayed distinct chemical composition profiles, and the DM-REO, predominantly composed of 1,8-cineole and alpha-pinene, had the highest antibacterial activity. Sublethal levels of DM-REO caused irreversible cell membrane damage, longer lag phases, decreased growth rates, and lower maximum optical densities of S. Typhimurium. The underlying molecular regulatory mechanisms of S. Typhimurium under sublethal DM-REO treatment were investigated using label-free quantitative proteomics. Four hundred thirty-six differentially expressed proteins mainly involved in metabolism, ABC transporters, two-component system, quorum sensing, bacterial chemotaxis, and flagellar assembly were identified. The phenotypic observation test showed that DM-REO significantly inhibited S. Typhimurium motility and quorum sensing. These results increase our understanding of the antibacterial mechanism of REO inhibition in S. Typhimurium
Chilling Accumulation Is Not an Effective Predictor of Vegetation Green-Up Date in Inner Mongolian Grasslands
No full textChilling accumulation (CA) might be reduced under a warming climate, which raises a critical question: is vegetation green-up date (VGD) altered by varing CA? If the answer is yes, existing thermal-time models should be modified to include a chilling component. By collating observations from eight long-term (1982-2019) field experiments across Inner Mongolia, we quantitatively assessed the responses of VGD of 27 grass species to CA in this region. The results indicated that effect of CA on VGD is in general negligible for most grass species. As excepted, rather than CA, VGD was predominantly determined by other climatic attributes such as heat requirement (HR) and precipitation. These results demonstrate the robustness of existing thermal-time models without a chilling component to predict variations in VGD of major plant species in Inner Mongolian temperate grasslands. Plain Language Summary Low temperature in winter (i.e., chilling) is recognized as an important regulator on plant spring phenology in the following year. Growing studies have highlighted the need to include a chilling factor in thermal-time phenology models. To date, the effect of chilling on vegetation green-up date (VGD) has seldom been explored in temperate grasslands. In this study, we collated a comprehensive data set of field observations of VGD from eight long-term experimental sites in Inner Mongolia, China, to address this issue. It was found that chilling accumulation (CA) has very limited impact on dynamics of VGD, particularly for individual grass species. Introducing CA into models cannot significantly improve the performances of models treating heat requirement (HR) and precipitation as predictor variables in predicting VGD dynamics. Consequently, there is no need to incorporate a chilling component into existing VGD phenology models in the study region
Partitioning of beta-diversity reveals distinct assembly mechanisms of plant and soil microbial communities in response to nitrogen enrichment
No full textNitrogen (N) deposition poses a serious threat to terrestrial biodiversity and alters plant and soil microbial community composition. Species turnover and nestedness reflect the underlying mechanisms of variations in community composition. However, it remains unclear how species turnover and nestedness contribute to different responses of taxonomic groups (plants and soil microbes) to N enrichment. Here, based on a 13-year consecutive multi-level N addition experiment in a semiarid steppe, we partitioned community beta-diversity into species turnover and nestedness components and explored how and why plant and microbial communities reorganize via these two processes following N enrichment. We found that plant, soil bacterial, and fungal beta-diversity increased, but their two components showed different patterns with increasing N input. Plant beta-diversity was mainly driven by species turnover under lower N input but by nestedness under higher N input, which may be due to a reduction in forb species, with low tolerance to soil Mn2+, with increasing N input. However, turnover was the main contributor to differences in soil bacterial and fungal communities with increasing N input, indicating the phenomenon of microbial taxa replacement. The turnover of bacteria increased greatly whereas that of fungi remained within a narrow range with increasing N input. We further found that the increased soil Mn2+ concentration was the best predictor for increasing nestedness of plant communities under higher N input, whereas increasing N availability and acidification together contributed to the turnover of bacterial communities. However, environmental factors could explain neither fungal turnover nor nestedness. Our findings reflect two different pathways of community changes in plants, soil bacteria, and fungi, as well as their distinct community assembly in response to N enrichment. Disentangling the turnover and nestedness of plant and microbial beta-diversity would have important implications for understanding plant-soil microbe interactions and seeking conservation strategies for maintaining regional diversity