Przybył K, Karolewski P, Oleksyn J, Labedzki A, Reich P B
Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035, Kórnik, Poland.
Microb Ecol. 2008 Aug;56(2):332-40. doi: 10.1007/s00248-007-9350-y. Epub 2007 Dec 19.
Fungi play an important role in leaf litter decomposition due to their ability to break down the lignocellulose matrix, which other organisms are unable to digest. However, little is known regarding the factors affecting components of fungal diversity. Here, we quantified richness of internal fungi in relation to litter nutrient and phenolic concentrations, sampling season (spring or fall), and premature leaf shedding due to low precipitation and infestation of bark beetles (mainly Ips typographus and Ips duplicatus). The study was conducted in 37-year-old Norway spruce [Picea abies (L.) Karst.] stands, with three plots each in mixed forest (MF) and coniferous forest (CF) site conditions in south-central Poland. Fifty-four species of sporulating fungi were identified in 2,330 freshly fallen needles sampled during 2003-2005, including 45 species in MF and 31 in CF. The significantly higher number of species in MF was likely related to moister conditions at that site. Among isolated fungi, 22% (12 species) were identified as endophytes of Norway spruce in prior studies. During spring of 2005, we found less than half the number of isolates and fungal species at each forest site as compared to fall for the two prior years. This pattern was observed in typical soil fungi (e.g., Penicillium daleae, Penicillium purpurogenum) and endophytes/epiphytes (e.g., Aureobasidium pullulans, Alternaria alternata, Cladosporium spp., and Lophodermium piceae). Premature shedding of needles was the most likely cause of this decline because it shortened the time period for fungi to infect green needles while on the tree. For all sites and sampling periods, richness of internal fungi was strongly and positively related to the age of freshly fallen litter (assessed using needle Ca concentration as a needle age tracer) and was also negatively related to litter phenolic concentration. Richness of internal fungi in freshly fallen litter may be adversely affected by low soil moisture status, natural inhibitors slowing fungal colonization (e.g., phenolics) and biotic (e.g., insect infestation) and abiotic (e.g., drought) factors that shorten leaf life span.
真菌在落叶分解过程中发挥着重要作用，因为它们有能力分解木质纤维素基质，而其他生物无法消化这种基质。然而，关于影响真菌多样性组成的因素，我们所知甚少。在这里，我们量化了内生真菌的丰富度与凋落物养分和酚类物质浓度、采样季节（春季或秋季）以及由于降水少和树皮甲虫（主要是云杉八齿小蠹和双齿小蠹）侵害导致的叶片过早脱落之间的关系。该研究在树龄37年的挪威云杉[欧洲云杉（L.）喀斯特]林分中进行，在波兰中南部的混交林（MF）和针叶林（CF）立地条件下各设置了三个样地。在2003 - 2005年期间采集的2330枚新鲜落下的针叶中，鉴定出了54种产孢真菌，其中混交林中45种，针叶林中31种。混交林中真菌种类显著更多，这可能与该立地更湿润的条件有关。在分离出的真菌中，有22%（12种）在先前的研究中被鉴定为挪威云杉的内生菌。与前两年的秋季相比，2005年春季我们在每个林地发现的分离菌和真菌种类数量不到秋季的一半。在典型的土壤真菌（如戴尔青霉、产紫青霉）和内生菌/附生菌（如出芽短梗霉、链格孢、枝孢属和云杉散斑壳）中都观察到了这种模式。针叶过早脱落很可能是这种下降的原因，因为它缩短了真菌在树上感染绿色针叶的时间。对于所有样地和采样时期，内生真菌的丰富度与新鲜落下凋落物的年龄（以针叶钙浓度作为针叶年龄的指标进行评估）呈强烈正相关，并且与凋落物酚类物质浓度呈负相关。新鲜落下凋落物中内生真菌的丰富度可能会受到土壤湿度低、减缓真菌定殖的天然抑制剂（如酚类物质）以及缩短叶片寿命的生物（如昆虫侵害）和非生物（如干旱）因素的不利影响。
