极端干旱区沙土掩埋对凋落物分解速率及盐分含量动态的影响

极端干旱区由于降水稀少, 植被盖度低, 太阳辐射强烈, 以及土壤稳定性差, 导致其凋落物周转不同于非干旱区。为探究极端干旱区凋落物分解规律, 该研究利用凋落物分解袋法, 以塔克拉玛干沙漠南缘沙漠-绿洲过渡带优势物种花花柴(Karelinia caspia)、骆驼刺(Alhagi sparsifolia)和胡杨(Populus euphratica)凋落叶为研究对象, 设置不同的沙土掩埋处理: 地表、2 cm和15 cm埋深, 以模拟自然条件下凋落物分解环境, 测定分解过程中凋落物质量和水溶性盐的变化特征。结果表明: 极端干旱区凋落物分解速率与凋落物初始碳(C)含量、氮(N)含量、C:N和木质素含量的关系与非干旱区存在较大差异, 在地表处理下, 木质素含量越高, 质量损失越快。不同分解环境下凋落物质量和水溶性盐损失具有显著差异, 与15 cm埋深相比, 地表和2 cm埋深处理显著增加了凋落物的质量损失和水溶性盐总量损失。地表处理增加了凋落物分解前期的水溶性盐溶解量。该研究表明, 极端干旱区凋落物分解的驱动机制具有独特性, 由于降水稀少, 土壤微生物的活性较低, 掩埋深度不是驱动凋落物分解的主要因素, 极端干旱区凋落物的分解主要受其他非生物过程如太阳光辐射的影响。

Effects of sand burial on litter decomposition rate and salt content dynamics in an extremely arid region

Aims Due to the extremely low precipitation, low vegetation coverage, strong solar radiation, and poor soil stability, litter turnover in extremely arid areas differs from that in non-arid areas. This study aimed to determine the patterns of leaf litter decomposition of contrasting initial qualities in an extremely arid region.Methods We used the litter bag method to investigate changes of the mass and water-soluble salt content in the leaf litter of three dominant species, Karelinia caspia, Alhagi sparsifoliaand Populus euphratica,in the desert- oasis transitional zone of the southern edge of the Taklimakan Desert, in responses to three levels of sand burial treatments, including placement of letter samples at the surface, and 2 cm and 15 cm soil depths, respectively, that represented different incubation environments under natural conditions.Important findings The relationships of litter decomposition rate with the initial litter quality indicators, including carbon (C) content, nitrogen (N) content, C:N and lignin content, differed between the extremely arid sites and the non-arid sites. The litter placed on the surface had higher lignin content and faster mass loss than those subjected to other treatments. The losses of litter mass and changes in water-soluble salt content significantly varied with the level of burial treatments. Litter samples placed on the surface and at 2 cm depth had a significantly greater rate of losses in mass and water-soluble salt content than those at 15 cm depth. The surface litter had a greater amount of dissolved water-soluble salt in the early stage of decomposition. This study shows that the driving mechanism of litter decomposition in the extremely arid areas is unique. Under conditions of extremely low precipitation and the low activity of soil microorganisms, the buried depth is not the main factor driving the litter decomposition, whilst other abiotic processes such as solar radiation controlled the rate of decomposition.