Study On Long-term Productivity Of Poplar Plantation Based On Forecast Model

The long-term productivity of poplar plantation in the northern of Jiangsu province and themiddle-lower Yangtze area was studied in this paper by the methods of simulation and predictionusing Forest Ecosystem Management Model (FORECAST model). Based on the collection andloading of the ecological data of poplar plantation, and the calibration and operation of the model,the stemwood biomass and soil available nitrogen content of poplar plantation were simulatedand compared in good, medium and poor sites with different management measures. The effectof different management measures on long-term productivity of poplar plantation wereinvestigated in order to find the optimum management measures to improve the timber yield andmaintain long-term productivity. The main results and findings were summarized as follows:(1) The higher timber yield was reached using the stand density3000stems/hm~2and5000stems/hm~2than1000stems/hm~2. There were no significant differences in timber productionbetween two densities,3000stems/hm~2and5000stems/hm~2, however, the site quality with thedensity of3000stems/hm~2declined more slowly than5000stems/hm~2within75a simulationperiod.(2) The higher timber yield was obtained in poplar plantation with a long rotation of20years. This rotation of20years can also maintain the stability of the sites long-term productivity.Compared with the plantation rotation20a, plantation rotation15a had nearly the same timberyield in the90a simulation period but the stability of the long-term productivity was lower,therefore it should add fertilizer and extend rotation lenth at the later part of the managementperiod to maintain the long-term stability of productivity.(3) Nitrogen addition increased the soil available nitrogen and timber yield in themanagement of poplar plantation. The worse the sites quality was, the better the effect ofnitrogen addition on increasing the yield was.(4) A large number of weeds in the sites lead to the decrease of timber yield, the worse sitesquality, and the more decrease of yield.(5) Different harvest methods had the significantly influence on long-term productivity ofpoplar plantation. The stem-harvesting method brought the most nutrients reserved, retarded thespeed of soil degradation and improved the forest long-term productivity.