Responses Of The Young Chinese Fir Plantation To Simulated Nitrogen And Sulfur Deposition

The injury of acid deposition on forest ecosystems is gradually becoming a global issue of great concern with the effects of the global acid deposition on forest ecosystems becoming increasingly serious. Acid deposition will lead to forest decline, soil acidification, accumulation of toxic substances and a reduction in biodiversity. Chinese fir (Cunninghamia lanceolate), a unique sub-tropical fast-growing coniferous in China, is a important timber trees. It's a typical forest ecosystems of subtropical regions and is one of the most important economic species in China. Nitrogen compounds and sulfur compounds are the main precursor substances of the acid deposition. It's a pressing demand to ecology to research the effect of nitrogen and sulfur deposition on forest ecosystem for forest management and production.The effects of nitrogen and sulfur to the growth of young Chinese fir plantation and plant nutrient balance and the effects of the soil physical and chemical properties by the quadratic rotatio-northogonal combination design were studied,built regression model and estimating critical loads of nitrogen and sulfur deposition for different indexs.The results indicated that:(1) The tree height and diameter growth of young Chinese fir plantation was promoted significantly by the nitrogen and sulfur deposition. As the effect to the tree height, nitrogen played am important parts by the nitrogen deposition than sulfur deposition and reverses to tree diameter.(2) There was no significant effect of decreasing the organic carbon concentration of the Chinese fir leaf and branch by nitrogen and sulfur deposition. The nitrogen concentration of the leaf and branch was promoted by nitrogen deposition significantly. There was no significant effect to leaf nitrogen concentration by sulfur deposition and the branch nitrogen concentration was promoted by the sulfur deposition significantly. The C/N of the Chinese fir leaf and branch was inhibited by the nitrogen and sulfur deposition significantly and nitrogen deposition played am important parts than sulfur deposition.(3) The N, K, Ca element loss of the Chinese fir leaves and branches was promoted by the nitrogen and sulfur loads and nitrogen deposition played am important parts than sulfur deposition and the leaf elements loss was easier than branch elements to be affected by acid deposition. There was no significant effect to the leaf and branch Mg concentration by nitrogen and sulfur deposition.(4) The N/P, N/K, N/Ca, N/Mg values of the leaves and branches were increased by nitrogen and sulfur deposition significantly and the effect by nitrogen deposition was bigger than the effect by sulfur deposition. After one year treatment, the leaf N/P, N/K, N/Ca, N/Mg values were respectively 6.73~9.51, 0.91~1.20, 0.69~0.96, 4.21~5.8; the branch N/P, N/K, N/Ca, N/Mg values were respectively 5.67~8.79, 0.58~0.91, 0.57~0.96, 2.85~4.37.(5) The leave/brance of N,P,K,Ca was significantly descreased by nitrogen and sulfur deposition.The leaves/brance of C and Mg had no significant effect of nitrogen and sulfur deposition.(6) The soil organic carbon concentration may be decreased by nitrogen and sulfur deposition and there was no significant effect. The nitrogen concentration of the three soil layers ware increased by the nitrogen deposition and decreased by the sulfur deposition and the effect was rather obvious of the top soil layer. The C/N value of the 0~20 cm soil layer was increased by sulfur deposition significantly and the effect was getting obvious day by day and sulfur deposition can increase the C/N value and there was no significant effect by sulfur deposition of the 20~40 cm soil layer. Sulfur deposition can decrease the C/N value of the 40~60 cm soil layer and there was no significant effect. The C/N value of the three soil layers can be decreased by nitrogen deposition and the effect got more significant with the acid treatment day by day and got weaker with the depth getting deeper.(7) The loss of soil sulfur can be promoted by nitrogen deposition and the soil effective sulfur concentration can be increased by sulfur deposition and the effect got weaker with the depth getting deeper. There was significant interaction between the two factors of nitrogen and sulfur deposition in 0~20 cm and 20~40 cm soil layers.(8) There was no significant effect to total soil P concentration by nitrogen and sulfur deposition and there was obvious effect to the soil effective P concentration. The soil effective P concentration was decreased by nitrogen and sulfur deposition in 0~40 cm soil layer and promoted in 40~60 cm soil layer. The effective P concentration of 0~20 cm, 20~40 cm, 40~60 cm were respectively 6.43%, 2.67% and 1.84%.(9) There was no obvious effect of total soil K concentration and may be inhibited by the nitrogen and sulfur deposition. The soil effective K concentration was decreased with the mount of the nitrogen and sulfur deposition increasing and with the time going by. The soil effective K concentration was increased with the sulfur deposition increasing and the effect was getting weaker as the treatment time goes by. The effect of the soil effective K concentration was changed from inhibiting to promoting with the soil getting deeper and the deposition time goes by. The effective K concentration in total K concentration was 5.4%~7.4% and there was no obvious change by the nitrogen and sulfur deposition.(10) There was no obvious differences of soil exchangeable Al concentration by nitrogen and sulfur deposition from top soil layer to deep soil layer and the exchangeable acid was decrease as the soil layer getting deeper. The soil exchangeable Al and acid concentration can be decreased by nitrogen and sulfur deposition and the effect of the nitrogen deposition was bigger than the sulfur deposition. The value of exchangeable Al to exchangeable acid of 0~20 cm, 20~40 cm, 40~60 cm soil layers were respectively 0.90, 0.91 and 0.98 before the acid treatment and were changed to 0.80~0.86, 0.88~0.94 and 0.96~1.04 after one year acid treatment.(11) The soil of the Chinese fir of 0~20 cm layer was effected by nitrogen and sulfur deposition significantly except the soil exchangeable Al concentration and there was obvious change of soil exchangeable Al concentration in 20~40 cm soil layer.(11)The total sulfur and effective exchange of acid and total phosphorus were significantly negatively correlated in 0~20 cm soil layer. The available phosphorus and potassium and exchangeable acid and exchangeable Al were significantly related. There was significantly negatively correlated between total P, exchangeable Al and available P with highly significant correlation of exchangeable Al and exchangeable acid.