Contrasting patterns of community-weighted mean traits and functional diversity in driving grassland productivity changes under N and P addition

Fertilization could influence ecosystem structure and functioning through species turnover (ST) and intraspecific trait variation (ITV), especially in nutrient limited ecosystems. To quantify the relative importance of ITV and ST in driving community functional structure and productivity changes under nitrogen (N) and phosphorous (P) addition in semiarid grasslands. In this regard, we conducted a four-year fertilizer addition experiment in a semiarid grassland on the Loess Plateau, China. We examined how fertilization affects species-level leaf and root trait plasticity to evaluate the ability of plants to manifest different levels of traits in response to different N and P addition. Also, we assessed how ITV or ST dominated community-weighted mean (CWM) traits and functional diversity variations and evaluated their effects on grassland productivity. The results showed that the patterns of plasticity varied greatly among different plant species, and leaf and root traits showed coordinated variations following fertilization. Increasing the level of N and P increased CWM_specific leaf area (CWM_SLA), CWM_leaf N concentration (CWM_LN) and CWM_maximum plant height (CWM_Hmax) and ITV predominate these CWM traits variations. As a results, increased CWM_Hmax, CWM_LN and CWM_SLA positively influenced grassland productivity. In contrast, functional divergence decreased with increasing N and P and showed negative relationships with grassland productivity. Our results emphasized that CWM traits and functional diversity contrastingly drive changes in grassland productivity under N and P addition

Soil Moisture Availability at Early Growth Stages Strongly Affected Root Growth of Bothriochloa ischaemum When Mixed With Lespedeza davurica

Rainfall is the main resource of soil moisture in the semiarid areas, and the altered rainfall pattern would greatly affect plant growth and development. Root morphological traits are critical for plant adaptation to changeable soil moisture. This study aimed to clarify how root morphological traits of Bothriochloa ischaemum (a C4 herbaceous species) and Lespedeza davurica (a C3 leguminous species) in response to variable soil moisture in their mixtures. The two species were co-cultivated in pots at seven mixture ratios under three soil water regimes [80% (HW), 60% (MW), and 40% (LW) of soil moisture field capacity (FC)]. At the jointing, flowering, and filling stages of B. ischaemum, the LW and MW treatments were rewatered to MW or HW, respectively. At the end of growth season, root morphological traits of two species were evaluated. Results showed that the root morphological response of B. ischaemum was more sensitive than that of L. davurica under rewatering. The total root length (TRL) and root surface area (RSA) of both species increased as their mixture ratio decreased, which suggested that mixed plantation of the two species would be beneficial for their own root growth. Among all treatments, the increase of root biomass (RB), TRL, and RSA reached the highest levels when soil water content increased from 40 to 80% FC at the jointing stage. Our results implied that species-specific response in root morphological traits to alternated rainfall pattern would greatly affect community structure, and large rainfall occurring at early growth stages would greatly increase their root growth in the semiarid environments

Evaluating the suitability of marginal land for a perennial energy crop on the Loess Plateau of China

Abstract With a large marginal land area, the Loess Plateau in China holds great potential for biomass production and environmental improvement. Identifying suitable locations for biomass production on marginal land is important for decision‐makers from the viewpoint of land‐use planning. However, there is limited information on the suitability of marginal land within the Loess Plateau for biomass production. Therefore, this study aims to evaluate the suitability of the promising perennial energy crop switchgrass (Panicum virgatum L.) on marginal land across the Loess Plateau. A fuzzy logical model was developed and validated based on field trials on the Loess Plateau and applied to the marginal land of this region, owing to its ability of dealing with the continuous nature of soil, landscape variations, and uncertainties of the input data. This study identified that approximately 12.8–20.8 Mha of the Loess Plateau as available marginal land, of which 2.8–4.7 Mha is theoretically suitable for switchgrass cultivation. These parts of the total marginal land are mainly distributed in northeast and southwest of the Loess Plateau. The potential yield of switchgrass ranges between 44 and 77 Tg. This study showed that switchgrass can grow on a large proportion of the marginal land of the Loess Plateau and therefore offers great potential for biomass provision. The spatial suitability maps produced in this study provide information to farmers and policymakers to enable a more sustainable development of biomass production on the Loess Plateau. In addition, the fuzzy‐theory‐based model developed in this study provided a good framework for evaluating the suitability of marginal land

Chlorophenyl thiophene silicon phthalocyanine: Synthesis, two-photon bioimaging-guided lysosome target, and in vitro photodynamic efficacy

The development of efficient photosensitizers with high singlet oxygen quantum yield, strong fluorescent emission, excellent photostability, and specific organelle targeting is in great demand for the enhancement of PDT treatment efficiency. This study designed and synthesized a new two-photon photosensitizer chlorophenyl thiophene axially substituted silicon (IV) phthalocyanine (CBT-SiPc). CBT-SiPc showed specific targeting of lysosomes in living cells and good biocompatibility. Furthermore, high 1O2 generation efficiency and high PDT efficiency in MCF-7 breast cancers under irradiation were also demonstrated. The novel CBT-SiPc showed great potential in the application of lysosome-targeted and two-photon bioimaging-guided photodynamic cancer therapy

Periodical Progress in Ecophysiology and Ecology of Grassland

As one of the most important ecosystems on the planet, grasslands serve a variety of purposes in ecology, economy, culture and entertainment [...

Biomass production and relative competitiveness of a C(3) legume and a C(4) grass co-dominant in the semiarid Loess Plateau of China

Bothriochloa ischaemum L. and Lespedeza davurica (Laxm.) Schindl. are two co-dominant species of great importance in reducing soil and water loss and maintaining the distinctive natural scenery of the semiarid Loess Plateau of China. Our aim was to determine the growth and interspecific competition between these species under water stress to facilitate the prediction of community succession and guide the selection of appropriate methods of conservation and use in the area. A pot experiment was designed to investigate the effects of water stress and competition on biomass production and allocation, relative competitive ability and water use efficiency of the two species. Bothriochloa ischaemum (a C-4 perennial herbaceous grass) was planted in the same pot with L. davurica (a C-3 perennial leguminous subshrub) at density ratios of 12: 0, 10: 2, 8: 4, 6: 6, 4: 8, 2: 10, and 0:12. The response of the species to their mutual presence at the different ratios was evaluated at three levels of soil moisture (80%+/- 5% field capacity, FC (HW), 60%+/- 5% FC (MW) and 40%+/- 5% FC (LW)). Indices of aggressivity (A), competitive ratio (CR) and relative yield totals (RYTs) were calculated from the dry shoot, root and total weight data. Water stress decreased the biomass production by both species whether in monoculture or mixture, but B. ischaemum was more sensitive to water deficit. Across moisture levels, the growth of L. davurica was more adversely affected by mixed planting. Bothriochloa ischaemum had significantly (P<0.05) smaller root: shoot ratios than L. davurica and the root mass of both species tended to increase relative to shoot mass as soil water deficit increased. The aggressivity (A), competitive ratio (CR) and relative yield totals (RYTs) of B. ischaemum were positive across treatments. Bothriochloa ischaemum had much higher CR under each water treatment, but water stress considerably reduced its relative CR while increasing that of L. davurica. The RYT values of the two species indicated some degree of resource complimentarity under both water sufficient and deficit conditions. Our results suggest that it is advantageous to grow the two species together to maximize biomass production. We recommend a mixture ratio of 8: 4 of B. ischaemum to L. davurica because it gave significantly higher RYT and transpiration water use efficiency under deficit water conditions

Seedling Biomass Partition and Water Use Efficiency of Switchgrass and Milkvetch in Monocultures and Mixtures in Response to Various Water Availabilities

Seedling biomass and allocation, transpiration water use efficiency (TWUE), and species competition between switchgrass (Panicum virgatum L.) and milkvetch (Astragalus adsurgens Pall.) were investigated in a pot-cultivated experiment under different levels of water availability. The experiment was conducted using a simple replacement design in which switchgrass and milkvetch were grown in growth chamber with ten seedlings per pot, in three combinations of the two species (0:10, 5:5 and 10:0). Five water treatments included sufficient water supply (HW), gradual soil drying from HW (DHW), moderate water stress (LW), gradual soil drying from LW (DLW), and re-establishment of LW conditions after 12 days of drying from LW (RLW). Water treatments were applied over a 15-day period. Biomass production and its partitioning, and TWUE were determined at the end of the experiment. Species competitive indices (competitive ratio (CR), aggressivity (A) and relative yield total (RYT)) were calculated from the biomass dry weight data for shoots, roots and total biomass. Water stress significantly reduced seedling biomass production but increased root:shoot ratios in both monocultures and mixtures. In the RLW treatment, only switchgrass monocultures displayed compensatory biomass production and TWUE, while both species demonstrated compensatory growth in the mixture. Switchgrass was the dominant species and much more aggressive than milkvetch in the LW treatment, while in the other four treatments milkvetch was the dominant species as measured by the positive value of aggressivity and higher values of CR. The total biomass RYT values of the two species were higher than 1.0, indicating some degree of resource complimentarity. In the two-species mixture, although the biomass production was lower than that of milkvetch in the monoculture, there was better TWUE, especially under low and fluctuating water availability