模拟酸雨对红壤区茶树器官氮磷含量及其化学计量比的影响

Influence of simulated acid rain on nitrogen and phosphorus contents and their stoichiometric ratios of tea organs in a red soil region,China

以红壤区25年生茶园为对象,开展pH 4.5、pH 3.5、pH 2.5及自来水(对照)4种强度模拟酸雨处理原位试验,于处理第3年收集茶树体不同功能根系和不同年龄枝、叶,测定氮(N)、磷(P)含量,并计算化学计量比和酸雨响应敏感度.结果表明:土壤pH值、硝态N和有效P随酸雨强度增加而显著降低.吸收根N含量随酸雨强度增加而提高,pH 2.5处理下吸收根N含量与对照相比显著提高32.9%;储藏根P含量随酸雨强度增强而显著降低;同时酸雨处理显著提高吸收根N/P.新叶和老叶N、P含量对不同强度酸雨处理响应不敏感,但酸雨处理增加了老叶N/P,且在pH 3.5处理下达到显著水平.酸雨处理对枝条的影响与其年龄有关,新枝N含量和N/P在低强度酸雨(pH 4.5)处理下显著增加,而老枝N含量和N/P对酸雨处理响应不敏感.吸收根、新叶和新枝N含量对酸雨响应敏感度分别高于储藏根、老叶和老枝,而储藏根和叶片P含量对酸雨响应敏感度高于其他器官.茶树器官N含量对酸雨处理较为敏感,适度酸雨可增加幼嫩器官N含量和N/P,改变茶树体N、P的循环和平衡.

A 25-year-old tea plantation in a typical red soil region was selected for an in situ simulated acid rain experiment treated by pH 4.5, 3.5, 2.5 and water （control, CK）. Roots with different functions, leaves and twigs with different ages were collected to measure nitrogen （N） and phosphorus （P） contents in the third year after simulated acid rain treatment. The N/P and acid rain sensitivity coefficient of tea plant organs were also calculated. The results indicated that with the increase of acid rain intensity, the soil pH, NO3--N and available P decreased, while the absorption root N content increased. Compared with the control, the N content in absorption root was in- creased by 32.9% under the treatment of pH 2.5. The P content in storage root significantly de- creased with enhanced acid rain intensity, and the acid rain treatment significantly enhanced N/P of absorption root. Young and mature leaf acid rain, but the mature leaf N/P was N, P contents were not sensitive to different intensities of significantly increased under pH 3.5 treatment compared with the control. The effects of acid rain treatments differed with tea twig ages. Compared with the control, low intensity acid treatment （pH 4.5） significantly increased young twig N content and N/ P, while no signi-fieant differences in old twig N content and N/P were observed among four acid rain treatments. Acid rain sensitivity coefficients of absorption root, young leaf and twig N contents were higher than that of storage root, old leaf and twig, respectively. And the storage root and leaf P had higher acid rain sensitivity coefficient than other tea organs. In sum, tea organs N content was sensitive to acid rain treatment, and moderate acid rain could increase young organ N content and N/P, and change the cycle and balance of N and P in tea plantation.