Multiple Hybrid Phase Transition: Bootstrap Percolation on Complex Networks with Communities

Bootstrap percolation is a well-known model to study the spreading of rumors, new products or innovations on social networks. The empirical studies show that community structure is ubiquitous among various social networks. Thus, studying the bootstrap percolation on the complex networks with communities can bring us new and important insights of the spreading dynamics on social networks. It attracts a lot of scientists' attentions recently. In this letter, we study the bootstrap percolation on Erd\H{o}s-R\'{e}nyi networks with communities and observed second order, hybrid (both second and first order) and multiple hybrid phase transitions, which is rare in natural system. Moreover, we have analytically solved this system and obtained the phase diagram, which is further justified well by the corresponding simulations

Growth peak of vegetation and its response to drought on the Mongolian Plateau

Global change in recent decades has caused severe degradation of grassland ecosystems in arid and semi-arid regions in the world. In the context of global change, the maximum gross primary production (GPPmax) and its response to drought on the Mongolian Plateau (MP) remain unclear. Here, we used long time-series datasets (temperature, precipitation, GPP) and calculated GPPmax, timing of GPPmax (TGM), and Standardized Precipitation Evapotranspiration Index (SPEI) to explore the changes in peak growth of vegetation and its response to drought on the MP from 1982 to 2018. Our results show that GPPmax and TGM presented high spatial heterogeneity. The mean GPPmax was 336 g C·m−2 over the past three decades, with a decreasing trend at a rate of 0.32 g C·m−2·year−1; the mean TGM was on DOY (day of year) 197, with little year-to-year change, TGM received the time-lag effect (mostly 1, 2, 10 months in time scale) of drought was found in 35.3% of the MP, while the cumulative effect of drought on TGM occurred only 16.3% of the MP. These results reveal changes in vegetation growth peaks on the MP and their response to drought over three decades and can contribute to our understanding of the response and feedbacks of MP vegetation to global change

Variation and adaptation of leaf water content among species, communities, and biomes

Leaf water content (LWC) is essential for the physiological activities in plants, but its spatial variation and the underlying mechanisms in natural plant communities are unclear. In this study, we measured the LWC of 5641 plant species from 72 natural communities in China, covering most terrestrial ecosystems, to answer these questions. Our results showed that LWC, on average, was 0.690 g g ^–1 , and was significantly higher in forests and deserts than in grasslands. LWC was significantly different among different plant life forms, and ranked on averages in the following order: herbs > shrubs > trees. Interestingly, LWC decreased with increasing humidity and increased in dry environments. Furthermore, the variations of LWC in plant communities were higher in arid areas and those species with lower LWC in a plant community were more sensitive to changing environments. These results demonstrated the adaptations of plants to water regime in their habitats. Although, phylogeny has no significant effect on LWC, plant species both in forests and grasslands evolve toward higher LWC. Variations of LWC from species to community to biome represent the cost-effective strategy of plants, where plant species in drier environment require higher input to keep higher LWC to balance water availability and heat regulation. This systematic investigation fills the gaps on how LWC varies spatially and clarifies the different adaptation mechanisms regulating LWC across scales