Spatial Simulation And Analysis Using GIS For Cold-humid Microclimatic Variables In The Surface Layer On Wetland-Landscape Scale

The changes of wetland landscape and their climatic effects under the disturbance ofhuman activities have been a hot issue in the global environmental change study. Thus,using a study site located in the northeastern Sanjiang National Nature Reserve, China, weinvestigated the spatiotemporal variations in the microclimatic variables of the surfacelayer across the wetland-farmland edge by collecting air temperature and relative humiditydata continuously along a horizontal transect at four different heights over different periods.Then, the horizontal gradients in cold-humid microclimatic variables across the edge undera light wind condition were fitted and spatiotemporal variations patterns in wetlandlandscape were analyzed by quantified indexes. On this basis, taking the Honghe NatureReserve, Nanwenghe Nature Reserve, Shuangtaihekou Nature Reserve, Xingkaihu NatureReserve, Zhalong Nature Reserve and their neighboring districts as wetlands study areas,combined with the horizontal gradient models of edge effect of cold-humid microclimaticvariables, we respectively used meteorological data and remote sensing images to simulatethe spatial distribution of microclimatic variables on wetland-landscape scale in the fiveregion based on GIS. Finally, the results of spatial simulation and spatiotemporal variationsof cold-humid gradients were compared between two data resources. The main contentsand conclusions are as follows:(1) The microclimatic features across the edge generally presented sigmoid ecologicalgradients under a light wind condition; horizontally, wetland patches cooled and moistened the adjacent farmlands during the daytime and had a warming-drying effect during thenighttime in a normal year; vertically, the absolute MEE (Magnitude of Edge Effect) of themicroclimatic variables decreased but REE (Range of Edge Effect) increased withincreasing height; in an entire day, the MEE and REE for air temperature and relativehumidity varied with the time of day; in the growing season, edge effects were stronger inthe prior period than in the later period; at the interannual scale, when compared to thefarmland, the wetland was cooler at night in a dry year, but warmer in a normal year.(2) Using meteorological data and wetland landscape-pattern data, we presented a newspatial simulation method of cold-humid microclimatic variables in the surface layer onwetland landscape scale through combining with the the horizontal gradient models of edgeeffect.(3) Spatial simulation from meteorological data showed that cold-humid variables andtheir MEE had latitude and meridional zonality; from diurnal patterns, the cooled effects ofwetland patches were obvious in the daytime, while unstable at night; from monthlyvariation, MEE values for Ta and RH had a certain variation pattern; specially, edge effectof Ta in the daytime was stronger during the pre-growth season than during the post season,the distribution of MEE for RH show “U” shape during the growth season with greatmoistening effect.(4) Considering a difference in patch interiors, we presented a improved spatialsimulation method of cold-humid microclimatic variables on wetland landscape scalecombining with the the horizontal gradient models of edge effect, using remote sensingdata and wetland landscape-pattern data.(5) Compared with the results based on meteorological data, the simulation based onremote sensing data gave more detailed surface feature in the patch interiors; thespatiotemporal patterns generally consistent with that of meteorological data, but thegradient degrees were different between two data sources. It was show that the differencein MEE for Ta was about0.44℃and MEE for RH from remote sensing data was generally3.7%lower than from meteorological data. Surface heterogeneity was a key determinant of the microclimatic edge effect in thewetland-farmland system, and local weather conditions were also important in detecting thepatterns and characteristics of wetland edge effects. The study on the horizontal gradientpatterns in cold-humid microclimatic variables across the wetland-farmland edge onwetland-landscape scale presents a new idea on the spatial simulation of climatic variableson landscape scale, of which the simulation result was superior to traditional spatialsimulation method in essence. Therefore, it provides an efficient tool for spatial scaling oflandscape ecological functions and mechanism research, and develops the methodology oflandscape ecology based on pattern-process-function theory; in addition, it is essentialpractical application to detect the wetland microclimatic variation based on wetland spatialheterogeneity and its influence on regional envrinoment.