川西高山林线交错带凋落叶分解初期转化酶特征

胞外酶对于有机质的降解具有重要的作用。在凋落物分解过程中,酶活性不仅受到凋落物种类或基质质量的影响,还受到环境因素的影响。转化酶催化蔗糖水解为葡萄糖和果糖,因此在凋落物分解早期,转化酶比降解难分解物质的酶具有更重要的作用。以川西高山林线交错带12种代表性凋落叶为研究对象,对林线交错带不同植被类型下的凋落叶转化酶活性以及物种和环境因子对转化酶活性的影响进行了研究。结果表明:同一植被类型下,12个物种转化酶活性具有极显著差异(P0.01)。物种、环境因子及其交互作用对转化酶活性有极显著的影响(P0.01)。初始纤维素含量与转化酶活性极显著正相关(P0.01)。初始木质素和总酚含量与转化酶活性极显著负相关(P0.01),能够共同解释转化酶活性变异的50.8%。不同植物生活型中,禾草类转化酶活性均为最高,这可能与禾草类较高的初始纤维素含量、较低的木质素和总酚含量有关。多元线性回归分析表明,凋落叶含水量能单独解释转化酶活性变量的62.1%,是环境因子中最重要的变量。从植被类型来看,大多数物种的转化酶活性在针叶林中均极显著高于高山草甸和灌丛(P0.01),这可能与针叶林中凋落叶的含水量最高且雪被最厚有关。历经一个雪被期分解后,凋落叶初始质量与环境因子的综合作用能够解释转化酶活性变异的79.1%,表明川西高山林线交错带凋落叶分解前期转化酶活性主要受初始木质素含量、总酚含量和含水量的调控。在全球气候变化情景下,凋落物水分含量的变化将会强烈的影响凋落叶分解前期的转化酶活性。

Leaf litter invertase activity in the early stage of litter decomposition in alpine timberline ecotone of western Sichuan, China

Extracellular enzyme plays a crucial role in litter decomposition for the degradation of organic matter. In the course of litter degradation, enzyme activity is not only influenced by the litter species or substrate quality, but also affected by environmental factors. Invertase catalyses the hydrolysis of sucrose to glucose and fructose; thus, invertase is more essential than enzymes related to recalcitrant material degradation in the early litter decomposition period. We investigated the invertase activity of 12 representative leaf litter in alpine timberline ecotone of western Sichuan, China. The effects of species and environmental factors on invertase activity were also studied. The results showed that invertase activities of 12 species were significantly different under the same vegetation type (P < 0.01). The effects of species, environmental factors, and their interactions on invertase activity were highly significant (P < 0.01). In addition, the relationship between the initial cellulose content and invertase activity was positively and extremely significant (P < 0.01). Moreover, there was a significant and negative correlation between invertase activity and initial lignin and total phenol content, respectively (P < 0.01). The lignin and total phenol content can explain the 50.8% variation in invertase activity. Invertase activity of graminoids was the highest among all plant life forms, which likely occurs due to the higher initial cellulose content and lower lignin and total phenol content of graminoids. Multiple linear regression analysis showed that leaf litter moisture can explain the 62.1% variation in invertase activity and was the most important environmental factor variable. From the perspective of vegetation type, the invertase activity of most species in the coniferous forest was significantly higher than that of species in the alpine meadow and shrubs (P < 0.01), which may be caused by the highest litter moisture content and snow depth in the coniferous forest. After a snow cover period decomposition, the comprehensive effect of leaf litter quality and environmental factors on invertase activity can explain the 79.1% variation in invertase activity, indicating that invertase activity was mainly controlled by lignin, total phenol content, and leaf litter moisture in the alpine timberline ecotone of western Sichuan. In the global climate change scenario, the change in moisture content of the litter will strongly influence invertase activity in the early stage of litter decomposition.