The Role of Photodegradation in Surface Litter Decomposition Across a Grassland Ecosystem Precipitation Gradient
The Role of Photodegradation in Surface Litter Decomposition Across a Grassland Ecosystem Precipitation Gradient
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DOI：
10.1007/s10021-010-9353-2
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发表时间：
2010-08-01
期刊：
影响因子：
3.7
通讯作者：
Sinsabaugh, R. L.
中科院分区：
文献类型：
--
作者：
Brandt, L. A.;King, J. Y.;Sinsabaugh, R. L.
中温、半干旱和干旱草原生态系统中凋落物分解模式的差异不能仅仅通过温度、湿度和凋落物化学的变化来准确解释。我们假设，紫外线（UV）辐射通过光降解增强草原生态系统中的分解，更是如此，在干旱相比，梅西奇生态系统，并在凋落物中，是更多的微生物分解（与高相比，低木质素浓度）。在为期2年的实地研究中，我们操纵的紫外线辐射量达到凋落物层在三个草原网站在明尼苏达州，科罗拉多，和新墨西哥州，美国，分别代表中，半干旱和干旱草原生态系统。两种常见的草落叶类型的对比木质素：N被放置在每个网站的屏幕下，要么通过所有的太阳辐射波长或通过所有，但紫外线波长。分解速度一般较快，当垃圾暴露在紫外线辐射在所有三个网站。与我们的假设相反，在分解过程中的光降解的贡献是不一致的更大，在更干旱的网站或具有较高的木质素含量的垃圾。此外，在最干旱的网站，暴露于紫外线辐射不能解释的分解速率比预期的更快的气候限制或缺乏N固定分解凋落物。虽然光降解在分解过程中起着重要的作用，在更广泛的草原网站比以前记录的，它不能完全解释草原生态系统之间的差异，对比干旱的分解率。
Differences in litter decomposition patterns among mesic, semiarid, and arid grassland ecosystems cannot be accurately explained by variation in temperature, moisture, and litter chemistry alone. We hypothesized that ultraviolet (UV) radiation enhances decomposition in grassland ecosystems via photodegradation, more so in arid compared to mesic ecosystems, and in litter that is more recalcitrant to microbial decomposition (with high compared to low lignin concentrations). In a 2-year field study, we manipulated the amount of UV radiation reaching the litter layer at three grassland sites in Minnesota, Colorado, and New Mexico, USA, that represented mesic, semiarid, and arid grassland ecosystems, respectively. Two common grass leaf litter types of contrasting lignin:N were placed at each site under screens that either passed all solar radiation wavelengths or passed all but UV wavelengths. Decomposition was generally faster when litter was exposed to UV radiation across all three sites. In contrast to our hypothesis, the contribution of photodegradation in the decomposition process was not consistently greater at the more arid sites or for litter with higher lignin content. Additionally, at the most arid site, exposure to UV radiation could not explain decomposition rates that were faster than expected given climate constraints or lack of N immobilization by decomposing litter. Although photodegradation plays an important role in the decomposition process in a wider range of grassland sites than previously documented, it does not fully explain the differences in decomposition rates among grassland ecosystems of contrasting aridity.