氮沉降对神农架川金丝猴主食地衣生长和营养特性的影响与作用机理研究

Rhinopithecus roxellana is a critically endangered monkey endemic to the south-western part of China, they discontinuously distribute in some high mountains of Sichuan Province, Hubei Province, Yunnan Province and Gansu Province. Nitrogen deposition is a worldwide pollution that would lead to a decraese of biodiversity, China is one of the most polluted country in the world. Obviously, habitats of R. roxellana also are menaced by nitrogen deposition under such a global background. Some epiphyte lichens, including Usnea longissima, U. montis-fuji, U. aciculifera, U. luridorufa, et al, are important food of R. roxellana. It is reported that these lichens totally account for 16.5~90.0% of their winter food. So lichen population establishment and survial, biomass accumulation, and thalli nutritional composition are highly relevant to population developement of R. roxellana. Based on the fact that these lichens inhabit in a cool and clean environment similar to acidophytic lichens, and U. longissima is an indicator of clean and poor nitrogen environment, we propsoe that lichens foraged by R. roxellana lichens would be sensitive to nitrogen deposition, and that nitrogen deposition would influence lichen population establishment, biomass growth, population suvial and nutritional composition. Consequently, these nitrogen sensitivity would have direct consequence on survival of this endangered monkey. In this application, we want to investigate the potential effect of nitrogen deposition on lichen supply of R. roxellana in Shennongjia Reservewe, and find potential resolution to mitigate the negative impact. Two independent filed trials were designed in our application, one was uesed to monitor effects of nitrogen deposition on linchen diaspore establishment, another one was designed to investigate effects of nitrogen deposition on growth and surviaval of transplanted lichen. In this application, 2~3 years nitrogen deposition (0.6 Kg.ha-1.a-1, 6 Kg.ha-1.a-1, 12.5 Kg.ha-1.a-1, 25 Kg.ha-1.a-1 and 50 Kg.ha-1.a-1) will be simulated with an auto-controlled spraying system, then lichen establishment, biomass, survial, chemical and physiological traits will be invetigated timely. Our aims are projected on the following questions: ①How will future nitrogen deposition affect lichen diaspore establishment? ②How wiil future nitrogen deposition affect lichen growth and survival?③How will thalli nutrition composition and secondary compound concentration respond to nitrogen deposition? ④What's the mechanism of each lichen species responding to nitrogen deposition? Answering these questions will not only be helpful to the management of winter food resource of R. roxellana, but also be benificial to the lichens diversity, lichens conservation and restoration of Central China.

我国是世界三大氮沉降中心之一，包括川金丝猴栖息地在内的部分森林生态系统的健康已受到氮沉降威胁。松萝等地衣植物是川金丝猴的越冬主食，主要栖息于冷凉、潮湿、洁净的高山区，是对氮沉降较为敏感的植物类群之一。因此，氮沉降可能对其生长动态和营养成分等产生重大影响，进而影响川金丝猴的种群维持。然而，氮沉降对川金丝猴主食地衣生长、营养特性的影响及其作用机理的研究尚未起步。本申请以神农架川金丝猴主食的7种地衣为对象，采用全自动喷雾系统精细而长期地模拟未来可能的氮沉降强度，定期调查各地衣种群的定居、生长与存活动态，研究氮沉降对川金丝猴主食地衣生物量的影响；同时，测定地衣主要营养成分和次生代谢物的含量变化，研究氮沉降对地衣营养成分的影响；进而研究氮沉降背景下地衣膜稳定性、光合特性、藻菌平衡和矿质营养利用特性变化，揭示地衣健康受损的机理。本研究将为氮沉降背景下川金丝猴冬季食源植物资源管理和危害解除提供理论支撑。

氮沉降可能对川金丝猴主食地衣生长、存活及营养产生重要影响。在研究神农架地区的树生地衣多样性、氮沉降强度及林冠雨的氮磷营养特征的基础上，研究了川金丝食源地衣的氮敏感性及氮沉降对其生长、存活与营养的影响及其作用机理。结果表明，①神农架地区具有较高的树生地衣多样性，川金丝猴栖息地及周边次生林拥有树生地衣52种和51种，树种多样性是其重要维持机制。②该地区的湿氮沉降强度达到了11.89 kg N•ha-1•y-1，氮胁迫能对该地区树生地衣建群种的PSⅡ、叶绿素组成和细胞膜完整性产生显著影响，因而普遍具有氮敏感性。③氮沉降增加使川金丝猴食源地衣体生长速率和繁殖体存活率下降。较低的氮沉降对长松萝（＜12.5 Kg•ha-1•y-1）、小刺褐松萝（＜6.25 Kg•ha-1•y-1）和桦树松萝（＜6.25 Kg•ha-1•y-1）具有施肥效应，生物量分别增加17.18% ~31.21%、20.31% ~31.21%和4.12%和13.77%，超过上述阈值时生长受抑制；0.625-50.0Kg•ha-1•y-1使粗毛松萝生物量下降42.98 - 96.00%，但使杯树花日本变种的生物量增加52.82%~20.97%；长松萝、小刺褐松萝、桦树松萝、杯树花日本变种和粗毛松萝的繁殖体存活的敏感阈值为50.0 Kg•ha-1•y-1、12.5 Kg•ha-1•y-1、25.0 Kg•ha-1•y-1、6.25 Kg•ha-1•y-1和25.0Kg•ha-1•y-1。④氮沉降增加对各地衣粗蛋白、可溶性蛋白、可溶性糖、粗纤维和灰分均存在显著影响，过量氮沉降导致地衣种特异性的营养成分含量降低。⑤本研究证实川金丝猴食源地衣普遍具有过量吸收利用氨氮的能力，氮沉降胁迫经破坏地衣共生体藻与菌平衡关系、诱发磷营养缺乏、降低氮同化关键酶GS和NR的活性等途径，使地衣共生体健康受损。神农架地区丰富的树生地衣多样性及其普遍的氮敏感性，警示了该地区地衣多样性和川金丝猴保育面临着现实的氮沉降威胁，提出了采取补磷缓措施缓解氮沉降威胁的潜在途径，或在冬季对川金丝猴进行人工食物投放，或者采取措施促进地衣替代性食源植物的生长，以应对氮沉降导致的川金丝猴冬季营养亏缺的可能途径。本研究不仅对我国川金丝猴保育研究具有重要的学术和应用价值，还对我国地衣科学、环境科学和生态学的发展具支撑作用。