Photodegradation driven by solar radiation has been confirmed as an important driving factor for litter decomposition. However, previous single-site studies could not quantify the relative contribution of variation in solar radiation to litter decomposition. To address it, we conducted a field experiment in Heshan National Field Research Station of Forest Ecosystem, Guangdong (Heshan Station, south subtropical climate), Jigongshan Ecological Research Station, Xinyang, Henan (Jigongshan Station, north subtropical climate) and Daqinggou Ecological Research Station, Institute of Applied Ecology, Chinese Academy of Sciences (Daqinggou Station, temperate climate) at intervals of 10 degrees. We examined litter decomposition of Populus davidiana and Larix olgensis, two species with significant differences in initial litter quality through an in-situ spectral-attenuation experiment. Treatments included full-spectrum, No-UV-B (attenuating UV-B radiation <315 nm) and No-UV & Blue (attenuating all UV and blue wavelengths <500 nm). After nearly 1-year decomposition, litter dry mass remaining of P. davidiana and L. olgensis under full-spectrum treatment was lowest at Heshan (30.2% and 36.3%), and highest at Jigongshan (37.3% and 45.8%). Among all sites, litter dry mass remaining was lowest under the full-spectrum, and lower than that of No-UV-B and No-UV & blue. UV and blue light significantly increased litter mass loss of P. davidiana and L. olgensis, with contributions of 59.7% and 57.0% (Heshan), 46.4% and 42.1% (Jigongshan), and 39.0% and 45.9% (Daqinggou), respectively. The contribution of UV-A and blue light (315-500 nm) was greater than UV-B (280-315 nm); the cumulative irradiance, soil temperature and moisture were the main driving factors for litter photodegradation.
太阳辐射的光降解作用被证实是凋落物分解的一个重要控制因子,但过去单一气候样点的研究结果无法量化太阳辐射变化对凋落物分解的相对贡献。鉴于此,本研究从南至北,以10个纬度为间隔,依次选择广东鹤山森林生态系统国家野外科学观测研究站(鹤山站,南亚热带气候)、河南信阳鸡公山生态研究站(鸡公山站,北亚热带气候)和中国科学院沈阳应用生态研究所大青沟沙地生态实验站(大青沟站,温带气候)为样点,选用初始性状差异显著的山杨和长白落叶松凋落物作为标准化样品,开展原位光谱滤除的凋落物分解试验,设置全光照、滤除紫外线(UV)-B和滤除紫外线及蓝光3种光谱处理,研究沿纬度梯度凋落物光降解的变化特征及其驱动因子。结果表明: 经过近1年的分解,全光照处理下山杨和长白落叶松凋落物的干重剩余率在鹤山站最低(分别为30.2%和36.3%),在鸡公山站最高(分别为37.3%和45.8%)。全光照处理下凋落物干重剩余率最低,显著低于滤除UV-B处理和滤除紫外线及蓝光处理。太阳辐射的紫外线及蓝光波段对山杨和长白落叶松凋落物质量损失均具有显著的促进作用,贡献分别为59.7%和57.0%(鹤山站)、46.4%和42.1%(鸡公山站)以及39.0%和45.9%(大青沟站),且UV-A及蓝光(315～500 nm)的贡献大于UV-B(280～315 nm)的贡献;累积辐照量、土壤温度、湿度是影响凋落物光降解的主要因子。.
Keywords: carbon cycle; litter decomposition; regional change; solar radiation.