| Global warming has an important and far-reaching impact on the structure and function of forest ecosystems.The changes in the structure of forest underground food networks can reflect the response of forest ecosystems to climate warming.Soil nematodes are important components of underground food webs and play an important role in material circulation and energy flow.In order to ascertain the response of forest soil nematode community to global warming,in November 2013,the soil column was used in the forest of Gongga Mountain slope to transplant the soil column at an altitude of 3200m(E0)to an altitude of 2800 m(E1),2400 m(E2),2000 m(E3),1600 m(E4)by natural warming.At the same time,for each gradient of the soil column,the uncontrol of litter and precipitation(T1 group)and the control of litter and precipitation(T2 group)were used to simulate the combined effects of temperature and precipitation and single factor of temperature.The soil nematodes and environmental factors in the T1,T2 and surrounding native forest land(CK)were monitored in November-2014 from 2014 to 2017.The main results were as follows:The temperature and soil temperature gradually increased with the decrease of elevation gradient.The average annual temperature from E0 to E4 increased by 2.11 ?,4.0 ?,6.4 ? and 8.6 ?.The air humidity and soil moisture decreased.The organic matter,total nitrogen,total phosphorus,available phosphorus,total potassium and available potassium in the T1 group increased significantly with temperature,and the soil chemical properties of the T2 group did not significantly respond to the warming.The prolongation of the warming time can significantly increase the available nitrogen and total potassium in the T1 and T2 groups.It can be seen that the single temperature change has a weak influence on soil chemical properties,and the combined effects of temperature,precipitation and falling items have a strong influence on soil chemical properties.There were significant differences in soil nematode community composition and structure between the T1 and T2 groups.In general,with the increase of temperature,the soil nematode community abundance in T1 and T2 groups increased,the richness of T1 group increased first and then decreased,and the richness of T2 groups decreased gradually.The Shannon index of T1 and T2 groups gradually decreased;Simpson index both showed an increasing trend.In addition,there are some differences in the trends of different treatments and different years.The community density and Shannon index of T1 and T2 groups were significantly lower than that of CK group,and the number of T1 group was significantly higher than that of T2 group.The Simpson index of T2 group was significantly higher than that of T1 group.The effects of environmental factors on soil nematode community density and diversity under different treatments were also different.There was a significant positive correlation between soil nematode diversity and PH,available phosphorus and soil temperature in T1 group,and soil nematode diversity in T2 group was significantly positively correlated with soil moisture and temperature.The two kinds of warming treatments of T1 and T2 have significant effects on the nutrient structure and ecological index of soil nematode community.The abundance and basic index of the two treatments' bacterial-feeding nematode increased significantly with temperature,and the maturity index and plant parasitic nematode maturity index decreased significantly with increasing temperature.The abundance trends of fungal nematodes,plant parasitic nematodes and predatory-omnivorous nematodes have differences in the trends of different treatments and different years,but the abundance and channel index of the fungal nematodes,plant parasitic nematodes,and predator-omnivorous nematodes in the T1 and T2 groups were significantly lower than those in the CK group.The nutrient structure and ecological index of soil nematode community in T1 and T2 groups were affected by various environmental factors.This study shows that the soil food network in the forest land of Gongga Mountain is a decomposition pathway dominated by bacterial decomposition.The warming treatment reduces the stability of the soil ecosystem and increases the resistance of the soil food network to disturbance.The research results show that the response of forest soil nematode community to climate warming is complex.The increase of temperature can change the structure and function of nematode food network,thus affecting the material circulation pathway and energy utilization efficiency of forest ecosystem.Long-term field control experiments also need to be established reveal the true response of soil nematodes to climate change. |
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