Quantitative model of trophic interactions in Beibu Gulf ecosystem in the northern South China Sea

A mass-balanced model was constructed to determine the flow-energy in a community of fishes and invertebrates in the Beibu Gulf, northern South China Sea using Ecopath and Ecosim software. Input parameters were taken from the literature, except for the biomass of fish groups which was obtained from trawl surveys during October 1997 to May 1999 in the study area. The model consisted of 16 functional groups （boxes）, including one marine mammal and seabirds, each representing organisms with a similar role in the food web, and only covered the main trophic flow in the Beibu Gulf ecosystem. The results showed that the food web of Beibu Gulf was dominated by the detrital path and benthic invertebrates played a significant role in transferring energy from the detritus to higher trophic levels; phytoplankton was a primary producer and most utilized as a food source. Fractional trophic levels ranged from 1.0 to 4.08 with marine mammals occupying the highest trophic level. Using network analysis, the system network was mapped into a linear food chain and six discrete trophic levels were found with a mean transfer efficiency of 16.7% from the detritus, 16.2% from the primary producer within the ecosystem. The biomass density of the commercially utilized species estimated by the model is 8.46 t/km^2, only O. 48% of the net primary production.

Application of N: P Stoichiometry to Ecology Studies

Stoichiometry has long been addressed in the studies of ecosystem ecology, but it was almost ignored for a long time. Until recently, ecologists have become aware that stoichiometry could provide a new tool to study ecology from genes to the biosphere. Among this trend, N:P stoichiometry is used actively in ecological interactions since nitrogen (N) and phosphorus (P) are the two most important elements in most ecosystems. This article reviews the application of N:P stoichiometry to the studies of ecological problems at different levels, including ecosystem, community and species. Meanwhile, we also provide the cellular basis of N:P stoichiometry, identify the shortages in the use of N:P stoichiometry theory, and put forward some perspectives for future research to be conducted.

Impact of climate change on the small mammal community of the Yukon boreal forest

Long-term monitoring is critical to determine the stability and sustainability of wildlife populations,and if change has occurred,why.We have followed population density changes in the small mammal community in the boreal forest of the southern Yukon for 46 years with density estimates by live trapping on 3-5 unmanipulat­ed grids in spring and autumn.This community consists of 10 species and was responsible for 9%of the ener­gy flow in the herbivore component of this ecosystem from 1986 to 1996,but this increased to 38%from 2003 to 2014.Small mammals,although small in size,are large in the transfer of energy from plants to predators and decomposers.Four species form the bulk of the biomass.There was a shift in the dominant species from the 1970s to the 2000s,with Myodes rutilus increasing in relative abundance by 22%and Peromyscus maniculatus decreasing by 22%.From 2007 to 2018,Myodes comprised 63%of the catch,Peromyscus 20%,and Microtus species 17%.Possible causes of these changes involve climate change,which is increasing primary production in this boreal forest,and an associated increase in the abundance of 3 rodent predators,marten(Martes ameri­cana),ermine(Mustela ermine)and coyotes(Canis latrans).Following and understanding these and potential future changes will require long-term monitoring studies on a large scale to measure metapopulation dynamics.The small mammal community in northern Canada is being affected by climate change and cannot remain sta­ble.Changes will be critically dependent on food-web interactions that are species-specific.

Impact of rewilding,species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem

Community and ecosystem changes are happening in the pristine boreal forest ecosystem of the Yukon for 2 reasons.First,climate change is affecting the abiotic environment(temperature,rainfall and growing season)and driving changes in plant productivity and predator-prey interactions.Second,simultaneously change is occurring because of mammal species reintroductions and rewilding.The key ecological question is the impact these faunal changes will have on trophic dynamics.Primary productivity in the boreal forest is increasing because of climatic warming,but plant species composition is unlikely to change significantly during the next 50-100 years.The 9-10-year population cycle of snowshoe hares will persist but could be reduced in amplitude if winter weather increases predator hunting efficiency.Small rodents have increased in abundance because of increased vegetation growth.Arctic ground squirrels have disappeared from the forest because of increased predator hunting efficiency associated with shrub growth.Reintroductions have occurred for 2 reasons:human reintroductions of large ungulates and natural recolonization of mammals and birds extending their geographic ranges.The deliberate rewilding of wood bison(Bison bison)and elk(Cervus canadensis)has changed the trophic structure of this boreal ecosystem very little.The natural range expansion of mountain lions(Puma concolor),mule deer(Odocoileus hemionus)and American marten(Martes americana)should have few ecosystem effects.Understanding potential changes will require long-term monitoring studies and experiments on a scale we rarely deem possible.Ecosystems affected by climate change,species reintroductions and human alteration of habitats cannot remain stable and changes will be critically dependent on food web interactions.