| The concept of meta-ecosystem is an important extension of spatial ecology,which has a potential of integrating the communities,ecosystems and landscapes,and is of great significance for understanding the biogeochemical linkage between neighbored ecosystems.Carbon is the crucial structural component of organisms in geosphere,the major ingredient of soil organic matter in the terrestrial ecosystem,and the basic components in both the lithosphere and atmosphere,as a consequence of which an understanding of carbon flux among different ecosystems can provide with key scientific evidences for cross-border ecosystem management.However,little information has been available on the carbon migration in the mountain forest–stream-river meta-ecosystem.The subalpine forest in western Sichuanlocates in the eastern margin of the Qinghai-Tibet Plateau and in the upper reaches of the Yangtze River,which plays crucial and irreplaceable roles in conserving water,sequestering atmospheric carbon,indicating global climate change,and nursing biodiversity.In particular,the carbon output from these ecosystems is of ecological significance for maintaining the productivity and carbon balance in the butted stream and river ecosystems.As yet,the carbon migration process in the subalpine forest-stream-river meta-ecosystem remains unclear.In order to understand the carbon biogeochemical linkages between subalpine coniferous forest ecosystem and the butted streams and rivers in the upper reaches of the Yangtze River,the carbon migration process in a subalpine coniferous forest-stream–river meta-ecosystem was therefore investigated in the Alpine Forest Ecosystem Research Station of Sichuan Agricultural University,which locates in the Miyaluo Forest Region in Lixian County,Sichuan Province.The litter quantity in 15streams from neighboured forest ecosystem,the carbon concentrations in the litter,sediment,and stream and river waters were measured at different critical periods from September 2015 to August 2016 based on the intercept dam,sampling and chemical analysis.Meanwhile,the flow of the studied 15 streams have been also monitored.The results are as follows.?1?The results showed that the input of the litter carbon in the study area was 111.89g/m2and the annual output was 2.05 mg/m2.Indicating that most of the carbon in the stream input from the litter was retained in the stream.The dissolved carbon output ranges from 0.2×10-3-1.26 kg/d,with an average of 0.10 kg/d,with dissolved organic carbon in the range of 0.1×10-3-0.68 kg/d,with an average of 0.04 kg/d dissolved inorganic carbon output range of 0.1×10-3-0.68 kg/d,the average value of 0.06 kg/d.The annual output of the stream per unit area was 73.37×10-3g/m2,29.98×10-3g/m2for dissolved organic carbon,43.39×10-3g/m2dissolved inorganic carbon.It was found that the dissolved carbon output of the stream was mainly inorganic carbon.?2?The average carbon storage of the subalpine coniferous forest-stream-river meta-ecosystem was 57.07 kg/m2,the average carbon storage of the river was 12.50 kg/m2,and the average carbon storage of the stream was 44.57 kg/m2.The average carbon storage of the stream was about 3.5 times that of the river.In the water,the dissolved carbon storage range of the river was 2.06-7.44 mg/m2,the dissolved inorganic carbon storage was1.08-3.94 mg/m2,the dissolved organic carbon storage was 0.94-3.51 mg/m2.The range of the range was 0.22-4.79 mg/m2,0.10-2.80 mg/m2for dissolved inorganic carbon,0.02-1.27mg/m2for dissolved organic carbon.In the sediments,the carbon storage range of the river was 1069.17-50329.52 g/m2,and the carbon storage range of the stream was521.99-678048.35 g/m2.It can be seen that the subalpine coniferous forest-stream-river meta-ecosystem is mainly stored in sediments and the sediment of the stream has more carbon Storage.?3?Confluent characteristics of carbon and inorganic carbon in the study area were basically the same,while the convergence characteristics of organic carbon are different.The total carbon and inorganic carbon in the length of 100 m above the main performance of the upstream concentration was greater than the downstream concentration,and less than 100 meters of the stream of carbon and inorganic carbon mainly for the upstream concentration was lower than the downstream concentration,and in the organic carbon,the There was no obvious change in the confluence of the streams,since the TOC concentration of the organic carbon concentration changes with the flow,litter and runoff.?4?The carbon storage capacity of the streams is the highest among the sediments,and the water is at least.The total storage capacity of the forest streams in the different periods was 9.73-13.01kg/m2,1.13-14.18 g/m2for litter,0.65-1.45 mg/m2for water,sediment and litter accounted for an average of 99.97%and 0.03%of the total carbon storage.The trend of sediment storage in forest streams was basically the same,which shows that the storage capacity was the highest in the early and late growth season,and the storage was the lowest in winter,the peak of storage was reached from September to October?peak of litter?November?winter?the lowest reserves,at the same time,in 2016April-May?early growth season?the second peak.The dynamics of litter and water carbon storage were basically the same,showing bimodal type,which showed the lowest storage in winter and peaked in October?litter peak?and from April to May?early growth season?.In addition,the carbon content of the subalpine coniferous forest-stream-river meta-ecosystem was mainly in the form of sediments in the process of migration from forest to river.Through the study of carbon storage of different components,we can further understand the distribution pattern of carbon storage in meta-ecosystem.At the same time,it was found that water is an important form of carbon migration,and the carbon output through water body is very large every year,and inorganic carbon is the main form of carbon output in subalpine coniferous forest.These results provide a data base for deep understanding of biogeochemical cycling in subalpine coniferous forests and provide new ideas for subalpine forest water resources protection and management. |
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