橡胶人工林养分循环通量及特征

对不同树龄的PR107无性系橡胶人工林N、P、K 3种元素的养分循环通量及特征进行了研究.结果表明:(1)橡胶林生态系统养分循环通量中养分总吸收量为315.28～949.13 kg/hm2,总存留量为282.78～714.51 kg/hm2,总归还量为32.50～205.74 kg/hm2,胶乳总损失量为10.18～37.73 kg/hm2,土壤中养分总输入量为111.73～652.79 kg/hm2,总输出量为315.28～949.13 kg/hm2,平均亏损量为-249.94 kg/hm2,各循环通量都随着树龄的增加而增大,其中3种养分元素的大小顺序均为N>K>P;(2)胶林生态系统养分循环特征参数中吸收系数随林分生长呈凸抛物线变化(先增大后减小),归还系数逐渐上升,存留系数不断下降,周转时间加快,而6a后,胶林的枯落物养分平衡指数与土壤养分平衡指数开始下降,胶园土壤养分收支失衡,另外,产胶对养分的利用效率在14a前后表现为先升高后降低;(3)不同元素循环特征参数有差异.吸收系数、归还系数中的大小顺序为N>P>K,存留系数为K>P>N,枯落物养分平衡指数为K>N>P,土壤养分平衡指数为P>N>K,养分利用率为P>K>N,表明N的流动性大,故循环速率最快,循环水平最高,其次是K,而P的循环速率最慢,水平最低.

Feature and flux of nutrient cycling in rubber plantation

Rubber plantations are one of the most successful types of artificial forests. The flux and characteristic parameters of 3 cycling nutrient elements (N, P, K) were studied in a rubber (Hevea brasiliensis) plantation of Clone PR107 at different ages. The results show that: (1) The flux of nutrients were found to increase with the age of the growth, which ranged as N>K>P. The total nutrient absorption, retention, return and nutrient of rubber latex in rubber plantation ecosystem were estimated to be 315.28-949.13kg · hm-2 · a-1, 282.78-714.51kg · hm-2 · a-1, 32.50-205.74kg · hm-2 · a-1 and 10.18-37.73kg · hm-2 · a-1. The nutrient input and output in soil ranged from 111.73kg.hm-2.a-1 to 652.79kg · hm-2 · a-1, and 315.28kg · hm-2 · a-1 to 949.13kg · hm-2 · a-1,and the loss of nutrient in soil was just -249.94 kg · hm-2 · a-1;(2) Characteristic parameters of nutrient cycling changed with increasing age. Both absorption and return coefficients increased, retention coefficient decreased, and soil and litter nutrient equilibrium index declined as well after 6 years. The litter decomposition limited the rate of nutrient cycling, which resulted in nutrient imbalance in the soil. Nutrient utilizing efficiency was reduced after the first growth up to 14 years;(3) There were differences of the characteristic parameter of nutrient cycling for each element. Absorption and return coefficient both ranked in the following order: N>P>K, retention coefficient and nutrient utilizing efficiency followed the sequence K>P>N and P>K>N, but the soil and litter equilibrium index stood in the order of P>N>K and K>N>P. It′s also indicated that the liquidity of elements were the largest in N, second in K, and least in P, and so were the cycling rate and level.