| The mate-ecosystem is a complex ecosystem of different but interrelated ecosystems through the spatial flow of material migration,energy conversion and biological migration.It studies the migration process of biological elements in the collection ecosystem,It is of great scientific value to understand the biogeochemical connection of biological elements between different ecosystems.The subalpine coniferous forest,which is located in the upper reaches of the Yangtze River and the eastern margin of the Qinghai-Tibet Plateau,is the third largest forest area in China.It is very important and can not be used in water conservation,water conservation,atmospheric CO2 storage,conservation of biodiversity Alternative ecological strategic status,is the upper reaches of the Yangtze River ecological security barrier.Therefore,it is important to study the migration of nitrogen,phosphorus and sulfur in subalpine coniferous forest-stream-river ecosystem based on agglomeration ecosystem theory,which is important for understanding the biogeochemical connection between subalpine coniferous forest and docking water body Value,for the upper reaches of the Yangtze River ecological security barrier construction provides a very important scientific basis.But so far,few studies have been reported at home and abroad.In this study,the sub-alpine coniferous forest,stream,riverbank and river were studied in this paper.The forest stream was used as a link to construct the subalpine forest-stream-river assemblage ecosystem,and dynamic monitoring and indoor This paper studied the migration characteristics of nitrogen,phosphorus and sulfur elements in the subalpine coniferous forest-stream-river ecosystem from September 2015 to August 2016,with particular emphasis on the different key And to provide a scientific basis for deep understanding of the biogeochemical cycle of subalpine coniferous forest and docking water.In the study area,the total volume of stream water is 73.74 m3.The results show that the average length of the stream is 10-255 m,0.34-1.28 m,3.70-11.72 cm,0.05-0.27 m/s and 0.01-0.15 m3/s,respectively.Further correlation analysis showed that the flow rate was significantly positively correlated with the length and water depth,and the flow rate was significantly positively correlated with the water depth and velocity.During the observation period,the total amount of samples collected was 13 times,and the total litter input in the stream area was 318.16 kg.Since the trees on both sides of the river were small in density and the flow was relatively turbulent,no litter was collected.After the litter enters the collection ecosystem,the part of the ecosystem that enters the subalpine coniferous forest includes two directions,one is directly involved in the biogeochemical cycle by decomposition,and the other is the erosion of the rain with the surface runoff and underground infiltration into the stream And river water;into the stream litter,also includes two kinds of whereabouts,one with the stream of water directly into the river,and then through the river output collection ecosystem,the second is through the cross-strait interception,deposition to the bottom of the stream,and then through the deposition The concentration of the interface between the body and the water body releases the nutrient elements,and finally enters the river to produce the subalpine coniferous forest-the stream-the river collection ecosystem.During the observation period,the total output of litter was 4.53 kg,while that of stream water was 83808.00 m3/d,which indicated that the water body was the most important output method of the integrated ecosystem.Which is the key way of element migration and output of forest ecosystem.During the observation period,the input ranges of nitrogen,phosphorus and sulfur in the input stream were 0-12.24 kg/hm2,0.05-50.70 kg/hm2 and 0.09-2.35 kg/hm2,respectively,through litter.Among them,the nitrogen and phosphorus elements of different lengths of the stream showed a relatively consistent trend,the nitrogen element input has two peaks,the first peak-is also the maximum value of the litter peak in 2015,the second peak-Litter consumption is the second peak after the peak,and in 2015 winter,nitrogen input is the smallest;and nitrogen input characteristics of the difference is that the amount of phosphorus input in the litter peak to reach the maximum peak,litter(10-20 m)(Fig.9a),the maximum input of sulfur at the peak of litter was the highest in the peak of the litter flow(Fig.9a)(0.38 kg/hm2),which is the lowest litterfall(0.17 kg/hm2)after the peak of litterfall.For the stream with a length of 20-70 m in the study area,the maximum value appears in the litter The peak value is 1.67 kg/hm2 and the litter peak is 0.47 kg/hm2.For the stream with the length between 90 and 260 m in the study area,the maximum value appears at 0.96 kg/hm2,followed by winter,0.30 kg/hm2.The total nitrogen reserves in the study area were 0.69-12.23 kg/hm2,and the characteristics of the stream significantly affected the total nitrogen reserves of the water.The total nitrogen reserves and the length of the stream,the water level,the water surface width,the flow rate and the flow rate The positive correlation was between 0.740 and 0.997.In the same stream,the relative change pattern was observed.The total nitrogen storage rate of the stream was the highest at the peak of litterfall(September 15,2015),and the lowest in winter(April 13,2016).The total phosphorus storage The range of 0.03-7.72 kg/hm2.There was a significant positive correlation between the total phosphorus reserves and the length of the stream itself in September 2015 and May-February 2016,and there was a significant positive correlation with the other time Total phosphorus reserves were positively correlated with other characteristics of the stream,but not significant.The total sulfur reserves in the stream were 4.02-9.29 g/hm2,respectively.In August 2015 and from October 2015 to May 2016,the total sulfur reserves and the length of the streams showed a significant positive correlation.In late July 2016,There was a significant positive correlation between the total sulfur reserves and the flow velocity,and the correlation coefficient was 0.750.There was a significant positive correlation between the total sulfur storage and the length of the stream during the remaining period.These results show that the effect of precipitation and stream length on the total nitrogen,total phosphorus and total sulfur reserves is the most prominent.In summary,nitrogen,phosphorus and sulfur elements are input into the subalpine coniferous forest-stream-river assemblage ecosystem through litter,and the nitrogen,phosphorus and sulfur elements are redistributed into the agro-ecosystem through the migration of litter Different ecosystems.Nitrogen,phosphorus and sulfur elements are transported into the forest stream ecosystem from the subalpine coniferous forest ecosystem by using litter and water as components in the composition of the integrated ecosystem.Since then,part of the ecosystem is transported directly to the river In the ecosystem,the other part is washed and stored with the biological remains along the erosion of the streams,and the content of nitrogen,phosphorus and sulfur increases with the change of time,which is significantly higher than that of the stream.After the concentration difference,the element is released into the water body,and the stream ecosystem is outputted with the flow of the stream,and then enters the river ecosystem.Finally,the sub-alpine coniferous forest-stream-river assembling ecosystem is output from the river ecosystem.These results provide a basic data for understanding the spatial association of nitrogen,phosphorus and sulfur elements between aquatic-terrestrial ecosystems and provide a scientific basis for the management of sub-alpine coniferous forest ecosystems in western Sichuan. |
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