田林老山中山杉木人工林生产力及营养元素循环的研究

广西田林县老山林场中山区气候冷凉潮湿,土壤肥力较高,能满足杉木速生要求。17年生杉木人工林乔木层的生物量达138.46t/ha,平均净生产量为8.15t/ha·a,与杉木中心产区相当。乔木层对N,P,K,Ca,Mg5种营养元素的吸收量为224.04kg/ha·a,其中42.3％存留在林木层,42.5％通过凋落物,15.2％通过降雨淋洗归还土壤。通过凋落物归还是N,P,Ca,Mg归还的主要途径,K的归还主要通过降雨淋洗;K,Ca,Mg的循环系数较大,分别达到0.58,0.68和0.60;N,P相对较小,分别为0.48和0.33。林木正处于生长旺盛阶段,杉木对5种营养元素的吸收量、存留量和归还量以及循环系数都有较高水平,生物量积累也较大。

STUDIES ON PRODUCTIVITY AND BIOLOGICAL CYCLING OF NUTRIENT ELEMENTS OF CUNNINGHAMIA LANCEOLATA PLANTATION IN MID-MOUNTAIN REGION OF LAOSHAN, TIANLIN COUNTY

In the mid-mountain region of Laoshan forest farm, the cold and moist climate and high soil fertility can meet the need of rapid-growth of Cunninghamia lanceolata. The biomass and mean net production of tree layer for a 17-year-old forest were 138. 46t/ha and 8. 15 t/ha.a. respectively. The mean net production was as high as in Huitong, the central growing area of Cunninghamia lanceolata, and higher than those in other border areas in China. The annual uptake of five elements(N, P, K, Ca, Mg) by tree layer was 224. 04kg/ha.a, 42. 3% of which was retained; and the rests, 42. 5% and 15. 2% were returned to the soil by litterfall and rainleaching respectively. The main way for N, P, Ca, Mg returning was through litterfall, and for K through rainleaching. The cycling coefficients were in the following order: Ca(0.68) >Mg(0. 60) >k(0.58)>N(0.48) >P(0.33). The mean cycling coefficient of the five elements was 0.58. The stand was in a luxuricant growth period. Its uptake, retention or return of nutrient elements were at high levels, the biological cycling was intense, and the biomass accumulation was in a large scale.