Interception of sulfate deposition from a closed canopy to a forest gap edge canopy in a subalpine dragon spruce plantation

Reducing the threats of sulfate ion(SO42-)deposition to terrestrial ecosystems is a great challenge.The canopy interception effect on SO42-deposition has been well documented,but the interception efficiency of the gap edge remains unknown.Therefore,a subalpine dragon spruce(Picea asperata)plantation was evaluated in the upper reaches of the Yangtze River.The dynamics of the SO42-concentration in the throughfall were investigated from the gap edge to the closed canopy during the rainfall and snowfall periods from August 2015 to July 2016.The annual input of SO42-totaled 2.56 kg/ha through rainfall and 0.69 kg/ha through snowfall.The total annual net interception fluxes(NIFs)of SO42-at the gap edge and in the closed canopy were 1.48 kg/ha and 0.66 kg/ha,respectively,and the net interception ratios(NIRs)accounted for 45.40%and 20.25%,respectively.The NIF and the NIR of SO42-at the gap edge were higher than those in the closed canopy.Therefore,the results suggested that a significant amount of SO42-deposition was intercepted by the tree canopy in the subalpine plantation,with more SO42-deposition at the gap edge than in the closed canopy,which is beneficial for improving the water quality in the upper reaches of the Yangtze River via forest management.

Naphthalene exerts non-target effects on the abundance of active fungi by stimulating basidiomycete abundance

As an arthropod biocide,naphthalene has been used in studies of the ecological functions of soil fauna for decades.However,its potential non-target effects on soil microorganisms may affect soil mineralization and litter decomposition processes.Therefore,we conducted an experiment with naphthalene adding to soil surface at a rate of 100 g·m-2 per month to examine the potential non-target effects of this treatment on soil fungal phospholipid fatty acids(PLFAs),18 S rDNA gene copy numbers and community diversity in a subalpine forest of western Sichuan,China.The results showed that naphthalene addition significantly increased fungal PLFAs but did not significantly alter fungal gene copy numbers.A total of 16 phyla,62 genera and 147 Operational taxonomic units(OTUs)were identified through Illumina Mi Seq sequencing analysis.Basidiomycota and Ascomycota were the most abundant phyla in both the control and naphthalene addition plots.Naphthalene addition did not affect the diversity or structure of the soil fungal community,but the increase in some genera of Basidiomycota might contribute to the increase in fungal PLFAs in the naphthalene addition plots.These results suggest that naphthalene exerts non-target effects on the active fungal abundance by stimulating the abundance of specific taxa in subalpine forest soils.The non-target effects of naphthalene on the fungal community should be taken into consideration when it is used to exclude soil fauna.

林窗对川西亚高山凋落叶总酚和缩合单宁损失动态的影响

总酚和缩合单宁作为重要组分参与并调控森林凋落物的分解过程,其可能受到林窗直接或间接的影响。该研究以川西亚高山6种常见植物(包括方枝柏(Juniperus saltuaria)、岷江冷杉(Abies fargesii var.faxoniana)、四川红杉(Larix mastersiana)、红桦(Betula albosinensis)、康定柳(Salix paraplesia)和高山杜鹃(Rhododendron lapponicum))凋落叶为研究对象,在林窗内外不同位置(林窗中心、林冠林窗、扩展林窗、郁闭林下)进行为期3年的原位分解实验,探究凋落叶总酚和缩合单宁在3年分解过程中冬季和生长季节的动态特征。研究发现凋落叶总酚和缩合单宁均在分解第一年具有较高的损失速率,分别为10.76和8.5mg·d^(-1);林窗对酚类物质降解的影响随分解进程逐渐减弱并具有明显的季节性差异;6种凋落叶总酚含量均在生长季降低较快,且初始缩合单宁含量较高的凋落叶在第一年冬季有较高的缩合单宁损失速率。研究表明森林林窗内的凋落叶在长期分解过程中,其酚类物质的降解受凋落叶质量和季节差异的影响更为显著。研究结果有利于深入认识森林生态系统中凋落物的分解特征和物质循环过程,可为亚高山森林的有效经营管理提供一定的科学数据。

华西雨屏区麻栎人工混交林凋落物水溶性碳、氮、磷含量及化学计量比随物候节律的变化特征

为理解华西雨屏区人工林生态系统物质循环过程,以华西雨屏区典型麻栎人工混交林为对象,于2016年11月至2017年10月每月收集麻栎(Quercus acutissima)、喜树(Camptotheca acuminata)凋落物(枝、叶、果),研究凋落物水溶性碳、氮、磷含量及其化学计量比随物候节律(萌芽期、展叶期、盛叶期、落叶期)的变化特征。结果表明:喜树和麻栎凋落物的水溶性碳、氮、磷含量表现出不同的变化趋势,并且最大值和最小值各不相同。凋落物水溶性碳、氮、磷含量随树种和凋落物类型而变化。整体而言,水溶性氮和磷含量均表现为果>叶>枝,水溶性碳含量表现为叶>果>枝。物候节律显著影响了凋落物的水溶性碳、氮、磷的化学计量比,并且凋落物水溶性碳、氮、磷化学计量比随树种和凋落物类型而变化,同时树种和物候期的交互作用显著影响凋落物水溶性碳、氮、磷的化学计量比。这些结果表明,物候节律是影响麻栎人工混交林凋落物水溶性碳、氮、磷含量及其化学计量比的关键因子,并受到树种和凋落物类型的影响。

树种对土壤微生物生物量碳氮的影响:同质园实验

树木通过地上/地下凋落物输入及根系活动等过程影响土壤微生物生物量,对调节土壤环境和增加土壤肥力具有重要作用。为阐明四川盆地乡土树种对土壤微生物生物量碳(MBC)、氮(MBN)含量的影响机制,该研究采用同质园研究方法,以亚热带7种常见树种天竺桂(Cinnamomum japonicum)、油樟(C.longepaniculatum)、大叶樟(C.austrosinense)、桤木(Alnus cremastogyne)、香樟(C.camphora)、红椿(Toona ciliata)和香椿(T.sinensis)为研究对象,并以撂荒地作对照,分析了树种对不同土层MBC、MBN含量的影响。结果表明:树种显著影响土壤MBC、MBN含量及其比值。树种总体表现为正或无效应;与撂荒地相比,天竺桂树种效应最强,其0-10 cm土层MBC和MBN含量分别高于撂荒地108.2%和139.6%。7个树种和撂荒地土壤MBC、MBN含量总体随土层深度的增加而减少,而MBC:MBN剖面特征因树种而异。总体来看,树种效应大于剖面效应;相比于其他树种,天竺桂更有利于土壤微生物的生长与繁殖。

川西亚高山森林凋落物去除对土壤腐殖质动态的影响

森林凋落物作为森林土壤腐殖质的主要来源,在土壤腐殖质的形成中发挥着重要作用,但不同森林类型凋落物因其含量、组成等的不同,对土壤腐殖质的影响也不同。该研究以川西亚高山针叶林、阔叶林和针阔混交林3种不同森林类型为对象,采用凋落物原位控制实验,对比研究不同关键期凋落物去除对土壤可提取腐殖质、胡敏酸和富里酸含量及胡敏酸/富里酸、胡敏酸/可提取腐殖质的影响。主要结果:(1)土壤可提取腐殖质、胡敏酸和富里酸含量在不同森林类型中差异显著。土壤可提取腐殖质含量总体表现为针叶林>针阔混交林>阔叶林,胡敏酸含量总体表现为针阔混交林>针叶林>阔叶林,而富里酸含量则表现为针叶林>阔叶林>针阔混交林,其中3种林型中土壤腐殖质的主要成分为富里酸,总体均表现为富里酸型。不同采样时期也显著影响了土壤可提取腐殖质、胡敏酸和富里酸含量,总体均表现为先升高后下降的趋势。除个别采样时期外,凋落物去除总体降低了土壤可提取腐殖质、胡敏酸和富里酸的含量。(2)胡敏酸/富里酸和胡敏酸/可提取腐殖质的结果显示3种林型土壤总体腐殖化程度均较低,整体表现为针阔混交林>阔叶林>针叶林,凋落物去除在一定程度上有利于提高阔叶林与针阔混交林的腐殖质品质。(3)相关分析表明不同凋落物处理间土壤可提取腐殖质与土壤有机碳含量、全氮含量和土壤含水量呈显著正相关关系,与温度呈显著负相关关系。综上所述,短期的凋落物去除会降低土壤腐殖物质的含量,但不同林型间由于凋落物类型差异会导致土壤腐殖质的不同变化,说明土壤腐殖质的动态变化受凋落物类型以及环境因素的综合调控。因此,关于凋落物变化对土壤腐殖质的影响还需进一步的长期研究。