To investigate the effect of phosphorus fertilization on the regulation of photosynthetic and fruiting characteristics of winter wheat under different water treatments,and to clarify the mechanism of phosphorus application to regulate the photosynthetic productivity and promote the development of spike floret development into grains,three water treatments(severe drought treatment,W0;moderate drought treatment,Wl;and normal water treatment,W2)and two phosphorus fertilizer treatments(no phosphorus fertilizer treatment,P0;and phosphorus fertilizer treatment,P1)were set up in 2020-2022 for pot experiment.Using the massive-spike variety Zhoumai 16(V1)and the multi-spike variety Yumai 49-198(V2)as experimental materials,we analyzed the effects of phosphorus on the photosynthetic and fruiting characteristics of winter wheat of the two types of varieties under different water treatments by determining the number of fertile florets and the number of grains in the different spikes(the basal,the central,and the apical parts of the spikes),as well as the net photosynthetic rate,chlorophyll content,chlorophyll fluorescence parameter,and sucrose content of leaves.The results showed that the phosphorus fertilization could effectively increase the number of fertile florets at anthesis(W10 stage)in winter wheat,especially the most significant effect on the number of fertile florets at the basal spike position(13.74％—27.01％),followed by the top(9.57％—20.19％),and then the middle(6.97％—14.01％).For the number of grains at maturity,the phosphorus fertilizer application increased the number of spikelets per spike as well as the number of grains in each spikelet under drought stress,and then significantly increased the number of grains.In addition,the phosphorus fertilization was effective in increasing the net photosynthetic rate,chlorophyll content,photosystem Ⅱ maximum photosynthetic efficiency(Fv/Fm)and actual photochemical efficiency(ΦPSⅡ)of leaves of both types of varieties,and the effects on sucrose content varied according to water treatments,with phosphorus fertilization decreasing the sucrose content under drought treatments,and increasing the sucrose content under normal water treatments.Pathway analyses of the photosynthetic indexes of the two types of varieties with the number of fertile florets and the number of grains per spike respectively revealed that five photosynthetic indexes were positively correlated with the number of fertile florets and the number of grains per spike,among which the direct pathway coefficients of Pn and sucrose with the number of fertile florets were 1.001 and 0.435,and those with the number of grains were 0.996 and 0.626,which were much higher than those of other indexes.Finally,phosphorus application significantly increased yield by increasing spike number,grain number per spike and 1000-grain weight,among which grain number per spike reached significant level under different water treatments,spike number was significant under W1 and W2 treatments,and 1000-grain weight improvement effect was not significant.In summary,the application of phosphorus fertilizer under different water treatments could improve the photosynthetic productivity of winter wheat by regulating its photosynthetic performance to maintain normal physiological and metabolic functions,thus reducing the degradation and abortion of fertile florets and promoting the spike floret develop into grains,ultimately alleviating the damage caused by drought stress for the purpose of achieving high and stable yields.The results provide a theoretical basis and technical support for alleviating the adverse effects of drought stress on wheat growth through the application of phosphorus fertilizer.
Yongle Atoll was the largest atoll in the Xisha Islands of the South China Sea, and it was a coral reef ecosystem with important ecological and economic values. In order to better protect and manage the coral reef fish resources in Yongle Atoll, we analyzed field survey data from artisanal fishery, catches, and underwater video from 2020 to 2022 and combined historical research to explore the changes in fish species composition and community structure in Yongle Atoll over the past 50 years. The results showed that a total of 336 species of fish were found on Yongle Atoll, belonging to 17 orders and 60 families. Among them, Perciformes had the most fish species with 259 species accounting for 77.08% of the total number of species. The number of fish species in the coral reef of Yongle Atoll was exponentially correlated with its corresponding maximum length and significantly decreases with its increase. The fish community structure of Yongle Atoll changed, and the proportion of large carnivorous fish decreased significantly, while the proportion of small-sized and medium-sized fish increased. At the same time, Yongle Atoll has 18 species of fish listed on the IUCN Red List, 15 of which are large fish. The average taxonomic distinctness (Delta+, Δ+) and the variation taxonomic distinctness (Lambda+, Λ+) in 2020–2022 were lower than the historical data, and the number of fish orders, families, and genera in Yongle Atoll has decreased significantly, which indicates that the current coral reef fish species in Yongle Atoll have closer relatives and higher fish species uniformity. In addition, the similarity of fish species in Yongle Atoll was relatively low at various time periods, further proving that the fish community structure has undergone significant variation. In general, due to multiple impacts, such as overfishing, fishing methods, environmental changes, and habitat degradation, the fish species composition of Yongle Atoll may have basically evolved from carnivorous to herbivorous, from large fish to small fish, and from complexity to simplicity, leaving Yongle Atoll in an unstable state. Therefore, we need to strengthen the continuous monitoring of the coral reef ecosystem in Yongle Atoll to achieve the protection and restoration of its ecological environment and fishery resources, as well as sustainable utilization and management.
In recent years, transgenic technology has developed rapidly, but the risk of the environmental release of transgenic organisms is still a key issue. Research on the impact on biodiversity is an effective way to objectively evaluate the risk. By taking transgenic maize HGK60 with insect-resistant gene Cry1Ah and common maize Zheng 58 as control, a 2-year experiment of arthropod community biodiversity in fields of them were studied using three methods.in 2019 and 2020. The results showed that a total of 124 species and 38537 individuals were observed from the experiment, belonging to 11 orders and 40 families. There was no significant difference in the individual number and species number of herbivorous, predatory and parasitic groups in the two kinds of maize in two years. Only the individual number of HGK60 was significantly higher than that of common maize Zheng 58 at heading stage in 2019. And the percentages of individual number and species number in different groups were basically the same in the two kinds of maize at each stage in two years. Analyses of Richness index, Shannon-Wiener diversity index, Dominance index and Evenness index showed no significant difference between the two kinds of maize in two years. The similarity coefficient of the arthropod community suggested that the arthropod community composition of HGK60 was similar to that of common maize Zheng 58. Furthermore, HGK60 had no significant effect on the relative stability of the arthropod community. These results indicated that despite the presence of a relatively minor difference in arthropod community between the two kinds of maize, the planting of HGK60 had little effect on arthropod community biodiversity. The results provided some data and support for the further studies of environmental risk of transgenic crops.
Developing modern circular agriculture is helpful to promote the high ̄quality transformation of agricultural production mode in Chinaꎬ which is one of the important ways to realize agricultural sustainable development. Howeverꎬ when the agricultural production operators applied the circular agriculture model to the particular system constructionꎬ there often occurred problems such as unknown input and outputꎬ low circulation efficiency and lack of overall evaluationꎬ which led to obstacles for the efficient operation and material ̄energy utilization of modern circular agriculture systems. In this studyꎬ the modern “straw ̄sheep ̄cropland” agro ̄pastoral circular system of Donglin Village in Jiangsu Province was selected
温带荒漠积雪覆盖是土壤含水量增加的重要方式，在冻融期带来丰富的水分变化。全球气候变化导致温带荒漠积雪深度时空格局发生改变，从而影响荒漠生态系统温室气体的通量。生物结皮在维持荒漠生态系统结构和功能的稳定具有非常重要的作用，但对环境的变化较为敏感，尤其是降水变化。然而，目前有关冻融期不同积雪条件下生物结皮温室气体通量的研究十分匮乏。CH 4 是重要的温室气体，选择古尔班通古特沙漠藓和地衣2种类型生物结皮为研究对象，以裸沙为对照，设置增雪、自然降雪（对照）和除雪三种处理，通过静态箱-气相色谱法，探究CH 4 通量在冻融期的变化特征。结果表明：冻融期多数情况下积雪处理和结皮类型对CH 4 通量影响不显著。荒漠生物结皮对CH 4 整体表现为吸收作用，是荒漠生态系统CH 4 重要的“汇”。两种结皮类型及裸沙CH 4 的吸收速率呈现为地衣结皮(-10.12μg m -2 h -1 )＞藓结皮(-1.73μg m -2 h -1 )＞裸沙(-1.69μg m -2 h -1 )。CH 4 通量通常与土壤5 cm深处的温度和水分的相关性不显著，对其他土壤理化因子响应较弱。研究结果表明，积雪处理不会对冻融期生物结皮CH 4 通量产生显著影响，全球变化条件下温带荒漠积雪的改变可能对土壤CH 4 的产生和吸收影响较小。
