Ecosystem services are strongly responsive to changes in land use intensity, especially water purification, which is highly sensitive to water pollutant emission. Increased nitrogen (N) application to cropland has potential impacts on the supply and demand for water purification through changes in land use intensity. However, there has been a lack of research focusing on the impacts of cropland N application on population exposure to water purification deficits and their cross-regional delivery network. Taking the Dongting Lake (DTL) Basin as an example, this study explored the spatial pattern of N exposure in the DTL Basin from 1990 to 2015 by integrating water purification deficit and population density. Changes in potential N exposure in 2050 were simulated based on population projection data from the Shared Socioeconomic Pathways (SSP1-5). N export pathways in the DTL Basin were clarified by constructing the N delivery network. The results showed that (1) N exposure increased significantly with increasing N application in DTL Basin. (2) The DTL surrounding area and lower reaches of the Xiangjiang River Basin had high increases of N exposure (50.2 % and 71.6 %) and high increases in N exposure due to increases in N application per unit (N influence coefficients exceeding 0.5). (3) The lower reaches of the Xiangjiang River Basin with the highest population density had the smallest decrease in N exposure (1.4 %-11.1 %) in the SSP1-5 scenarios. (4) During 1990-2015, the increase of N export to the DTL surrounding area was higher in the lower reaches sub-basins of DTL Basin. N application had a stronger impact on N delivery processes in the lower reaches of DTL Basin. Managers should distribute N applications to basins with high N retention and whose N export to the DTL surrounding area is weak. This study confirmed the strong response of water purification deficits and their population exposures to N application, and provided decision-making guidelines for water quality enhancement programs in DTL Basin from a spatial planning perspective.

The dispersal strategies of a species can affect its invasion success. Investigations into the dispersal strategies of invasive species in relation to different factors help improve our understanding of invasion mechanisms and provide knowledge for population management and invasion evaluation. Tetranychus ludeni Zacher (Acari: Tetranychidae) is an invasive species which is native to Europe but is now cosmopolitan. Here, we examined the effects of age and density on dispersal in mated females. Our results show that older females that are capable of producing more eggs within 24 h were more likely to disperse and moved longer distances than younger ones with fewer eggs. Older females spread most of their eggs out of their natal habitats and over longer distances, which reduced competition and increased offspring fitness. Females exhibited significantly increased dispersal probability and distances with an increase in population density to avoid crowding. The synchronization of dispersal and reproduction, along with the positive density-dependent dispersal strategy, may facilitate the habitat colonization and invasion speed of T. ludeni.

Rapid urbanization has resulted in the substantial population growth in metropolitan areas. However, existing research on population change of the cities predominantly draws on grid statistical data at the administrative level, overlooking the intra-urban variegation of population change. Particularly, there is a lack of attention given to the spatio-temporal change of population across different urban forms and functions. This paper therefore fills in the lacuna by clarifying the spatio-temporal characteristics of population growth in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) from 2000 to 2020 through the methods of local climate zone (LCZ) scheme and urban-rural gradients. The results showed that: (1) High population density was observed in the compact high-rise (LCZ 1) areas, with a noticeable decline along urban-rural gradients. (2) The city centers of GBA experienced the most significant population growth, while certain urban fringes and rural areas witnessed significant population shrinkage. (3) The rate of growth tended to slow down after 2010, but the uneven development of population-based urbanization was also noticeable, as urbanization and industrialization varied across different LCZ types and cities in GBA. This paper therefore contributes to a deeper understanding of population change and urbanization by clarifying their spatio-temporal contingences at landscape level.

In recent years, a surge in drought occurrences has dramatically impacted tree growth worldwide. We examined the ecological resilience of Larix principis-rupprechtii plantations with varying densities (1950, 2355, and 2595 trees·hm-2) at the Saihanba Mechanical Forest Farm, by extracting the increment cores using the standard dendrochronological method to measure individual-tree basal area increments (BAI) as part of our assessment of ecological resilience, including resistance (Rt), recovery (Rc), and resilience (Rs). The results showed that drought events occurred in 2006-2010, 2015, and 2018. The Rt for L. principis-rupprechtii plantations varied from 0.76 to 2.01 across three drought events, indicating generally high resistance, except for the plantation with 2355 trees·hm-2 during the second dry year (Rt=0.69). The Rt for the plantation with 2595 trees·hm-2 significantly decreased across all drought events, while no significant change was observed in the plantations with 1950 and 2355 trees·hm-2. The Rc showed no differences in response to a single drought event across plantation densities, with a significant upward trend for all the densities with each occurrence of drought event. There was no significant difference in the resilience of different densities of L. principis-rupprechtii to the first drought event, whereas the plantation with 2595 trees·hm-2 exhibited significantly lower Rs during the second and third drought events compared with 1950 and 2355 trees·hm-2, respectively. During the 2015 drought event, plantation with 2595 trees·hm-2 experienced a significant growth decline (radial growth change rate was -26.5%), while no such decline was observed in the plantations with 1950 and 2355 trees·hm-2. Overall, the plantation with 2595 trees·hm-2 demonstrated the lowest resilience to drought events.
近年来全球干旱事件频发,树木的生长受到严重影响。本研究选取塞罕坝机械林场不同密度(1950、2355和2595株·hm-2)的华北落叶松人工林,采集树芯,计算单木胸高断面积增量(BAI),研究华北落叶松的径向生长对干旱事件的生态弹性(抵抗力、恢复力和恢复弹力)。结果表明:干旱事件发生在2006—2010年、2015年和2018年。3次干旱期间,除第2次干旱时密度为2355株·hm-2的林分(抵抗力为0.69)外,其余林分的抵抗力为0.76~2.01,均表现出较高的抵抗力。密度为2595株·hm-2的华北落叶松的抵抗力随3次干旱事件显著降低,密度为1950和2355株·hm-2的华北落叶松的抵抗力随着3次干旱事件无显著变化。不同密度华北落叶松对同一次干旱事件的恢复力无显著差异,且均随干旱事件的发生呈显著上升趋势。不同密度华北落叶松对第1次干旱事件的恢复弹力无显著差异,密度为2595株·hm-2的华北落叶松对第二、三次干旱事件的恢复弹力分别显著低于密度为1950和2355株·hm-2的华北落叶松。密度为2595株·hm-2的华北落叶松在第2次干旱事件(2015年)时出现明显的生长衰退(生长变化率为-26.5%),而密度为1950和2355株·hm-2的华北落叶松无显著生长衰退。总的来说,密度为2595株·hm-2的华北落叶松对干旱事件的恢复弹力最差。.

The goji berry psyllid, Bactericera gobica Logniova (Homoptera: Psyllidae), is one of the most important pests on goji berry plants (Lycium barbarum L.), whose fruits are widely used in traditional Chinese medicine and food. However, chemical control is still the predominant control strategy of this pest. Recently, two species of predatory mites, Neoseiulus setarius Ma, Meng & Fan and Neoseiulus barkeri Hughes were found to be associated with B. gobica in China. To assess their predation potential against B. gobica, the functional responses of these two phytoseiid species feeding on different densities (2, 4, 8, 12, 16, 24 and 32 individuals) of B. gobica eggs and 1st instar nymphs were compared at a temperature of 25ºC ± 1º C. Logistic regression analysis revealed that both predatory mite species exhibited type Holling-II functional responses on eggs and 1st instar nymphs of B. gobica, with the predation number increased for both predators as the density of prey increased. Overall, N. setarius consumed more prey compared to N. barkeri across all levels of prey densities. Meanwhile, the highest attack rate (α = 0.0283), the lowest handling time (Th = 1.1324 h prey- 1), and the highest estimated maximum predation rate (T/Th = 21.19 prey day- 1) were all observed for N. setarius fed with 1st instar nymphs of B. gobica. These findings suggest that it is worthy considering utilizing N. setarius and N. barkeri as candidate biocontrol agents of B. gobica, with N. setarius appearing to be a more effective predator than N. barkeri.

The roles of plateau pika (Ochotona coronae) in the Tibetan Plateau are often controversial, because it is often regarded as a destructive pest or an ecosystem engineer. Here a meta-analysis using 72 paired observations was conducted to examine whether the impacts of plateau pika on environmental quality (i.e., plant and soil properties) depend on population density in the Tibetan Plateau. Pika population density was used as a proxy for disturbance intensity. The pika disturbance intensity was divided into five groups based on the number of burrows, including low disturbance intensity (LD) (9-30 burrows per ha), medium disturbance intensity (MD) (31-100 burrows per ha), high disturbance intensity (HD) (101-170 burrows per ha), extreme disturbance intensity (ED) (171-240 burrows per ha) and uncontrolled (or excessive) disturbance intensity (UD) (>241 burrows per ha). Given that sample sizes in some of the groups are small (especially for the HD), we further pooled the disturbance groups including the LD-MD and HD-UD. Overall, relative to control (i.e., no disturbing), there was a great increase (80.3%) in aboveground biomass under the LD-MD, whereas a decrease of 41.1% occurred under the HD-UD. At the same time, plant coverage, species richness, height, and belowground biomass greatly decreased only in the HD-UD. Furthermore, the effect size of plant coverage, species richness, and aboveground biomass also declined with pika burrow density significantly. With regard to soil properties, there was a significant increase in soil organic carbon, ammonium nitrogen, and soil organic carbon stock under the LD-MD, whereas a decrease under the HD-UD. In addition, soil total nitrogen, total potassium, and nitrate nitrogen increased at the LD-MD and HD-UD. Nevertheless, the effect size of these soil properties (with >20 observations) was not related to pika burrow density. In summary, there is an implication that the low and moderate disturbance of pikas is beneficial to maintain and promote ecosystem functioning in the Tibetan grasslands. In the future pikas\' eradication policy should be reconsidered in alpine grassland management.

Predators can strongly influence prey populations not only through consumptive effects (CE) but also through non-consumptive effects (NCE) imposed by predation risk. Yet, the impact of NCE on bioenergetic and stoichiometric body contents of prey, traits that are shaping life histories, population and food web dynamics, is largely unknown. Moreover, the degree to which NCE can evolve and can drive evolution in prey populations is rarely studied. A 6-week outdoor mesocosm experiment with Caged-Fish (NCE) and Free-Ranging-Fish (CE and NCE) treatments was conducted to quantify and compare the effects of CE and NCE on population densities, bioenergetic and stoichiometric body contents of Daphnia magna, a keystone species in freshwater ecosystems. We tested for evolution of CE and NCE by using experimental populations consisting of D. magna clones from two periods of a resurrected natural pond population: a pre-fish period without fish and a high-fish period with high predation pressure. Both Caged-Fish and Free-Ranging-Fish treatments decreased the body size and population densities, especially in Daphnia from the high-fish period. Only the Free-Ranging-Fish treatment affected bioenergetic variables, while both the Caged-Fish and Free-Ranging-Fish treatments shaped body stoichiometry. The effects of CE and NCE were different between both periods indicating their rapid evolution in the natural resurrected population. Both the Caged-Fish and Free-Ranging-Fish treatments changed the clonal frequencies of the experimental Daphnia populations of the pre-fish as well as the high-fish period, indicating that not only CE but also NCE induced clonal sorting, hence rapid evolution during the mesocosm experiment in both periods. Our results demonstrate that CE as well as NCE have the potential to change not only the body size and population density but also the bioenergetic and stoichiometric characteristics of prey populations. Moreover, we show that these responses not only evolved in the studied resurrected population, but that CE and NCE also caused differential rapid evolution in a time frame of 6 weeks (ca. four to six generations). As NCE can evolve as well as can drive evolution, they may play an important role in shaping eco-evolutionary dynamics in predator-prey interactions.

暂无摘要。

COVID-19 has been massively transmitted for almost 3 years, and its multiple variants have caused serious health problems and an economic crisis. Our goal was to identify the influencing factors that reduce the threshold of disease transmission and to analyze the epidemiological patterns of COVID-19. This study served as an early assessment of the epidemiological characteristics of COVID-19 using the MaxEnt species distribution algorithm using the maximum entropy model. The transmission of COVID-19 was evaluated based on human factors and environmental variables, including climate, terrain and vegetation, along with COVID-19 daily confirmed case location data. The results of the SDM model indicate that population density was the major factor influencing the spread of COVID-19. Altitude, land cover and climatic factor showed low impact. We identified a set of practical, high-resolution, multi-factor-based maximum entropy ecological niche risk prediction systems to assess the transmission risk of the COVID-19 epidemic globally. This study provided a comprehensive analysis of various factors influencing the transmission of COVID-19, incorporating both human and environmental variables. These findings emphasize the role of different types of influencing variables in disease transmission, which could have implications for global health regulations and preparedness strategies for future outbreaks.

Bean beetle (Callosobruchus maculatus) exhibits clear phenotypic plasticity depending on population density; However, the underlying molecular mechanism remains unknown. Compared to low-density individuals, high-density individuals showed a faster terminal oocyte maturity rate. Four insulin-like peptide (ILP) genes were identified in the bean beetle, which had higher expression levels in the head than in the thorax and abdomen. The population density could regulate the expression levels of CmILP1-3, CmILP2-3, and CmILP1 as well as CmILP3 in the head, thorax, and abdomen, respectively. RNA interference results showed that each CmILP could regulate terminal oocyte maturity rate, indicating that there was functional redundancy among CmILPs. Silencing each CmILP could lead to down-regulation of some other CmILPs, however, CmILP3 was up-regulated in the abdomen after silencing CmILP1 or CmILP2. Compared to single gene silencing, silencing CmILP3 with CmILP1 or CmILP2 at the same time led to more serious retardation in oocyte development, suggesting CmILP3 could be up-regulated to functionally compensate for the down-regulation of CmILP1 and CmILP2. In conclusion, population density-dependent plasticity in terminal oocyte maturity rate of bean beetle was regulated by CmILPs, which exhibited gene redundancy and gene compensation.