Effect Of Warming In Growing Season And Non-growing Season On Soil Nematode Community In Typical Grassland Of Inner Mongolia

Climate warming caused by human activities has seriously affected the processes of terrestrial ecosystems.Warming not only changes the distribution of bioorganisms and interactions among different species,but also affects biodiversity,ecosystem services and functions.The magnitude of climate warming is significant different between growing season and non-growing season.The warming amplitude in nongrowing season is higher than that in growing season.However,most of the previous experimental warming studies have only concerned about the warming in growing season,but few experiments have considered the difference and interactions between the warming in growing season and non-growing season.Soil nematode is the most abundance metazoan fauna community in terrestrial ecosystem,plays an important role on the regulation of the nutrient cycle,and is very sensitive to environmental changes.Therefore,soil nematode is commonly used as environmental indicators.However,the previous studies concerning on the effects of climate warming on soil nematode community lack the data verification for the effects of seasonal fluctuations of climate warming on structures and functions of soil nematode community.A simulative warming experiment including control,growing season warming,non-growing season warming and annual warming treatments was conducted with open top chambers(OTC)in 2016 in typical grassland of Inner Mongolia Autonomous Region,China.Soil nematodes were collected by improved Berman funnel method in April,June,August and October of 2020 at the depth of 0-10 cm and 10-20 cm,respectively.The collected nematode were identified with classical method.Effects of non-growing season warming,growing season warming and their interactions on the variables of nematode community structure were analyzed with the result of identification.Effect mechanisms of different seasonal warming on soil nematode community structure were further detected with the changes of soil temperature,soil water content,soil nutrient contents,plant community abundance,coverage,aboveground biomass and root biomass under different treatments.The results showed that:1.Growing season warming significantly increased ammonia nitrogen content,p H,and total nitrogen content by 30.19%,0.28,and 5.65% in 0-10 cm soil layer,respectively.In addition,growing season warming significantly reduced the abundance of bacterial-feeding nematodes by 12.24% and 8.78%,and decreased the nematode channel ratio index by 0.09 and 0.08 in the 0-10 cm and 10-20 cm layers,respectively.Growing season warming significantly increased trophic diversity index by 1.94 in 0-10 cm layer,but decreased the basal index by 7.50 and increased the structure index 7.59 in the 10-20 cm layer,respectively.Growing season warming significantly reduced the anti-interference ability of soil nematode community,and elevated the community connectivity and the length of food web.Moreover,effects of growing season warming on the abundance of bacteria-feeding nematodes,basal index and structural index significantly fluctuated among different months.In 0-10 cm layer,growing season warming significantly reduced the abundance of bacterialfeeding nematodes in April and August,but did not affect it in other two months.Growing season warming reduced structural index in June,but increased structural index in August,October,respectively.2.Non-growing season warming elevated the belowground biomass by 22.02%,but decreased the abundance of total soil nematode community by 20.07% in 0-10 cm soil layer.Non-growing season warming significantly decreased ammonia nitrogen content by 17.38% in 10-20 cm soil layer.In addition,non-growing season warming significantly decreased the abundance of omnivorous-predatory nematodes by 5.42%,increased basal index by 6.41,and decreased structure index by 11.11.Non-growing season warming significantly improved the anti-interference ability of soil nematode community,and reduced the connectivity and length of food web.Furthermore,the abundance of omnivorous-predatory nematodes fluctuated among different months due to the warming in non-growing season.3.Growing season warming and non-growing season warming interactively affected the structures and functions of soil nematode community,as well as the related environmental variables.Non-growing season warming inhibited the effect of non-growing season warming on some variables.For example,growing season warming significantly reduced the underground biomass and the C:N ratio by 25.57% and 0.22 without non-growing season warming in 0-10 cm soil layer.However,Under the non-growing season warming treatment,growing season warming significantly increased the underground biomass and C:N ratio by 33.34% and 0.36 in 0-10 cm soil layer.Growing season warming significantly decreased the abundance of fungal-feeding nematodes,the basal index,and the enrichment index by 7.84%,14.70,and 1.77;but increased the abundance of omnivorous-predatory nematodes,the nematode channel ratio index by 6.13%,0.06 and 18.43 in the 10-20 cm layer without non-growing season warming.However,growing season warming significantly elevated the abundance of fungal-feeding nematodes and enrichment index by 8.83%,and 8.20,and decreased the basal index,omnivorous-predatory nematodes,nematode channel ratio index,and structure index by 0.30,2.24%,0.22,and 3.26 in the 10-20 cm soil layer under the non-growing season warming.The results of this study showed that the effects amplitude and mechanism of non-growing season and growing season warming on soil nematode community structure varied with different months.The results are helpful to more accurately evaluate the impact of climate warming on terrestrial ecosystem processes without considering the difference of warming amplitude in different seasons in the future climate warming research.In addition,the interactions between non growing season warming and growing season warming on the structures of soil nematode community shows that the impacts of non-growing season warming on ecosystem structure can not be ignored.Therefore,in the future global change research,we should pay more attention to the seasonal difference of climate warming,especially the impacts of non-growing season warming on ecosystem structures to further understand the regulating mechanism of global climate change on ecosystem process.