| The landscape pattern of source and sink have an important influence on the nitrogen and phosphorus transfer process of water in the basin,and the interception function of sink landscape is very important for the regulation of regional water eutrophication.Take Hani Rice Terrace wetland landscape and water of it as the research object,and obtained 114 surface water samples under different landscape types in December 2017 and June 2018,then analysis the temporal and spatial characteristics of total nitrogen?TN?,total phosphorus?TP?of water on three scales including watersheds,small watersheds and landscape types,and using the eutrophication index and intercept rate to evaluate the import-export balance of nutrients of water in wetland.Based on the Google Earth high resolution remote sensing images in 2017,the"source-sink"theory,and using the lorenz curve and the sink location-weighted landscape index?SLWLI?to analyse the major functions of the landscape within a watershed?diffusion or interception?,then calculate the contribution of different sink landscape and identify the key sink landscapes in the watersheds.According to the balance of import-export situation of nitrogen and phosphorus in wetland water and the results of identification of key sink landscapes,some measures about landscape pattern adjustment were put forward as follows:?1?Temporal and spatial differential characteristics of water conventional parameter and TN,TP?1?Temporal differential characteristics:the pH value,temperature,conductivity,TN and TP in rainy season are higher then dry season of Hani Rice Terrace wetland water.?2?Spatial differential characteristics:the wetland water are weak alkaline,the temperature difference of it is not big,but the conductivity difference is large in all study scales.In watershed scales,the TN and TP concentrations of water present Bibo river>Zhena river>Malizhai river>Geta river>Yaobiluo river>Bimeng river.In small watershed scales,the TN and TP concentrations from high to low in order:Amengkong>Jinzhuzhai>Dayutang>Longshuba>Yakou>Huangcaolin,which have the same order as the watershed scales roughly.In landscape types,the order of TN and TP concentration present village area>rice terraced area>forest area>river.?2?The analysis of import-export balance of nitrogen and phosphorus in water?1?At the scale of watersheds,the analysis of eutrophication index?PI?and interception rate showed that TN and TP of water were both higher in rainy season than those of dry season.In space,the results of PI value and interception rate showed that the nutrients in Bibo river are heavy surplus,the nutrients in Zhena and Malizhai river are mild surplus,Geta and Yaobiluo river are balance in import and export.?2?At the small watershed scales,the analysis of eutrophication index?PI?and interception rate are both irregular in season.In space,the results of PI value and interception rate showed that the nutrients of water in Amengkong are heavy surplus,and nutrients of water in Huangcaoling are balance in import and export.?3?At landscape types,PI value and interception rate are irregular in the season.In space,the results of PI value and interception rate showed that the nutrients in village area are heavy surplus.?3?Evaluation of source and sink landscapes functions and identification of key sink landscapes?1?The area characteristics of source and sink landscape:on the scales of watersheds and small watersheds,source and sink landscape area shows the proportion of sink landscapes are very high,the proportion of source landscapes are small.?2?Spatial distribution characteristics of source and sink landscapes:on the scale of watersheds,the distribution of source and sink landscape is unreasonable related to relative distance factors;The distribution related to relative elevation and slope factors are relatively balanced.On the scale of small watersheds,the distribution of source and sink landscapes are reasonable in relative distance,relative elevation and slope factors.?3?Evaluation of source and sink landscapes functions:on the scales of watersheds and small watersheds,the values of SLWLI?distance,SLWLI?elevation,SLWLI?slope and SLWLI are all higher than 0.5,which indicating that the landscape of these watersheds are dominated by sink landscapes,and the landscape function is dominated by the sink function?interception function?.Secondly,the SLWLI?distance,SLWLI?elevation,SLWLI?slope and SLWLI values of TN are higher than TP,indicating that the interception function of Hani Rice Terrace wetland for TN is better than TP.?4?Identification of key sink landscapes:on the scales of watersheds and small watersheds,the contribution rate of woodland and rice terraced field to TN,TP are higher than 28%in all sink landscapes,indicating that woodland and rice terraced field are the key sink landscapes.And grassland,water area are the secondary sink landscapes tanks to the contribution rate of interception to TN,TP are less than 8%,and play an auxiliary role.?4?Optimization and control measures of landscape patternWe should start with three links:control source,adjustment process and lifting sink.On the watershed scales,the drought of rice terraced field is prohibited,and the key sink landscape in the watersheds—forest land and rice terraced field is need to protect and maintain because the unreasonable distribution of source and sink landscapes in relative distance factor.Secondly,the other source landscapes should be replaced by key sink landscape—forest land.On the small watershed scales,the source should be reduced and the sink increased.In addition,the function of the sink landscapes should be improved.Overall,we should give priority to protect and maintain the key landscape,and supplemented with the regulation and optimization of the secondary landscapes,control the source of the high-load landscapes and improve the interception function of sink landscapes,only through above measures can we control the problems about the nutrients balance in water. |
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