The utility model belongs to the technical field of ecological and the forest soil comprehensive experiment research of forest, concretely relates to modified forest thing normal position decomposition device that withers and falls. This device decomposes the cover including soil ring sum normal position, and the soil ring of tube -shape inserts the below ground and is used for chooseing the soil that awaits measuring, decomposing the cover, to be located the soil ring subaerial, decompose the cover including cover wall and shroud, shroud be detachable the connection with the cover wall, cover wall and shroud and be network structure, still be equipped with the fixed bolster between soil ring and the decomposition cover, still be equipped with the soil temperature and humidity sound -pipe on the fixed bolster, inside the bottom entry soil of soil temperature and humidity sound -pipe, the protruding quotation top that extends the fixed bolster in upper end, the soil temperature and humidity sound -pipe is inside to be equipped with temperature and humidity sensor, and temperature and humidity sensor is embedded on the inner wall of soil temperature and humidity sound -pipe. The utility model discloses the pedosphere that will await measuring fixes on the soil intra -annular, chooses falling object in decomposing the cover simultaneously, prevents that the analyte runs off, has effectively improved the accuracy of analyte survey.