不同土壤厚度、水分和种植方式对喀斯特两种草本凋落物分解质量损失和化学计量特征的影响

为了探究生长期间不同土壤厚度、水分及种植方式处理对草本植物凋落物分解质量损失和化学计量特征的的影响,采用分解袋法,在露天分解床上分解经过生长期间2种土壤厚度(对照土壤厚度和浅土处理)、2种水分(正常灌水处理和干旱处理)和2种种植方式(单种和混种)处理的苇状羊茅(Festuca arundinacea Schreb.)和黑麦草(Lolium perenne L.)凋落物,研究生长期间土壤厚度和水分减少及不同的种植方式是否通过改变两物种初始凋落物质量、产量和组分来影响自身凋落物分解。结果发现:(1)与对照组(CK)相比,在干旱组(D)和浅土+干旱组(SD),两物种地上、根系和总的凋落物质量损失率、初始N和P含量均显著增加,凋落物产量、C/N和C/P显著降低,凋落物地上组分比大体上无显著变化;而不同的种植方式处理对各组分质量损失率、元素含量、计量比、凋落物产量和组分比大体上无显著影响;(2)两物种地上、根系和总凋落物的质量损失率分别与地上、根系和总N含量呈显著正相关,与C/N呈显著负相关,与凋落量呈显著负相关,而总凋落物质量损失率与地上凋落物组分比呈显著正相关。结果表明,生长期间干旱和浅土+干旱处理能够通过影响苇状羊茅和黑麦草的初始凋落物质量、产量和组分比来加快地上、根系和总凋落物分解,其中凋落物N含量和C/N是影响两物种凋落物分解快慢的主要原因。

Effects of different soil thickness, water and planting patterns on the litter mass loss and stoichiometry characteristics of two herbs in the karst regions

Litter and its decomposition are crucial to terrestrial ecosystem functioning, and are responsible for carbon and nutrient cycles. Litter quality and quantity vary greatly with the changes of climate, soil parent materials, species distributions etc. Plants can regulate their physical and chemical properties to adapt and respond to karst habitats, i.e., shallow soil and drought, thereby produce litter with different quality, quantity and components, thus influence the litter decomposition. Previous studies have shown that the effects of water (or precipitation) and nutrient addition on litter decomposition during the decomposition period. However, the effects of soil thickness, water, and planting patterns during the growing period of plant on litter decomposition are less known. Our aim was to determine whether the decline of soil thickness and water, and different planting patterns during the growing period of two herbs would have effects on litter decomposition that affected by the initial litter quality, quantity, and components. Two perennial graminaceous grass species, Festuca arundinacea Schreb. (deep-rooted) and Lolium perenne L. (shallow-rooted) were chosen as the experimental materials. These two species are often chosen as pioneer plants in karst revegetation schemes. We manipulated three factors, soil thickness (control soil thickness:15 cm, and shallow soil:5 cm), water (normal irrigation:120 mL/3 d and drought treatment:36 mL/3 d), and planting pattern (monoculture and mixture) in a full three-way randomized block design. We collected aboveground and root litter of the plants, and placed these litters in litterbags to decompose in outdoor incubation beds for seven months. The results showed that:(1) compared with the control group (CK), the aboveground, root, and total mass loss rates, initial N and P contents of F. arundinacea and L. perenne increased in drought group (D) and shallow soil plus drought group (SD), and litter production, C/N, and C/P decreased significantly, whereas the aboveground component ratio of both species was not changed. All the above traits were not affected by the planting patterns; (2) the aboveground, root, and total mass loss rates of both species were positively correlated with the aboveground, root and total N contents, negatively correlated with C/N and litter production. The total mass loss rate was positively correlated with the aboveground component ratio for both species. The results indicated that drought and shallow soil plus drought could accelerate the litter mass loss rates of F. arundinacea and L. perenne by changing the initial litter quality, quantity, and components. Moreover, litter N content and C/N were the main factors that influenced the litter decomposition of the two species.