Contrasting changes in palatability following senescence of the lichenized fungi Lobaria pulmonaria and L. scrobiculata

Epiphytic lichens can contribute significantly to ecosystem nutrient input because they efficiently accumulate atmospheric mineral nutrients and, in the case of cyanolichens, also fix nitrogen. The rate at which carbon and other nutrients gained by lichens enters the ecosystem is determined by lichen litter decomposability and by invertebrate consumption of lichen litter. In turn, these processes are driven by the secondary compounds present in senesced lichens. Therefore, we explored how lichen palatability and concentrations of secondary compounds change with tissue senescence for Lobaria pulmonaria, a green-algal lichen with cyanobacterial cephalodia, and Lobaria scrobiculata, a cyanobacterial lichen. During senescence both lichens lost 38–48 % of their stictic acid chemosyndrome, while m-scrobiculin and usnic acid in L. scrobiculata remained unchanged. Snails preferred senesced rather than fresh L. pulmonaria, while senesced L. scrobiculata were avoided. This provides evidence that species with labile secondary compounds will have higher turnover rates, through consumption and decomposition, than those producing more stable secondary compounds.     

Nitrate sequestration by corticolous macrolichens during winter precipitation events

Nitrogen is an essential nutrient in the biogeochemistry of forested ecosystems. The influence of canopy lichens on the winter biogeochemistry of nitrate in broadleaved deciduous forests is examined and it is hypothesized that nitrate sequestration will not differ between winter precipitation events. Rejection of this hypothesis would mean that meteorological conditions of winter precipitation events have a detectable influence on nitrate sequestration by canopy lichens and nitrate input to the forest floor. Canopy lichens of the genus Parmelia were found to influence winter nitrate stemflow inputs to forest soils differentially. Epiphytic lichens on an individual Carya glabra Mill. (pignut hickory) canopy tree, centrally located within the stand of an open deciduous forest, actively sequestered nitrate leached from the tree's woody frame, lowering aqueous stemflow inputs at the tree base. The quantities of nitrate sequestered by corticolous lichens during the 2 February 1999 mixed-precipitation event were significantly greater than those during all other precipitation events examined. Greater rates of nitrate uptake during the 2 February 1999 event may be attributed to (1) its intermediate rain intensity, which would have soaked the lichen thalli in a nutrient-rich bath, and (2) an air temperature range between -2 degrees C and 8 degrees C that would have increased viscosity and surface tension of stemflow drainage, thereby decreasing stemflow velocity and increasing the contact time of stemflow water on the lichen thalli. Other precipitation events were either too cold to promote metabolic activity by canopy lichens or too warm and intense for an optimal contact time of stemflow with lichen thalli, resulting in lower quantities of nitrate sequestered. Meteorological conditions of winter precipitation events have been documented to influence sequestration of nitrate by corticolous lichens and decrease aqueous stemflow inputs to the forest floor of broadleaved deciduous forests.     

云南哀牢山原生林及次生林群落附生地衣物种多样性与分布

附生地衣是森林附生植物的重要类群之一, 在维护森林生态系统的物种多样性以及水分和养分循环等方面发挥着重要作用。作者于2005年12月至2006年5月利用树干取样法调查了云南哀牢山徐家坝地区原生山地常绿阔叶林及其次生群落栎类萌生林、滇山杨(Populus bonatii)林和花椒(Zanthoxylum bungeanum)人工林中525株不同种类和径级树木距地面 0–2.0 m处附生地衣的组成和分布, 并收集了各个群落地面上凋落的地衣, 分析了林冠层附生地衣的物种组成。研究结果表明, 该区森林中附生地衣物种比较丰富。共收集到附生地衣61种, 分属17科29属, 其中原生林、栎类萌生林、滇山杨林和花椒人工林分别有51、53、46和23种。在树干距地面 0–2.0 m位置, 各群落中的附生地衣组成明显不同;但在林冠层中, 各群落内的附生地衣基本相似。原生林中附生地衣种类较多, 但分布不均匀。树干附生地衣的Shannon-Wiener和Simpson多样性指数以栎类萌生林最高, 分别为2.71和0.89;花椒林和滇山杨林次之, 分别为2.43–2.45和0.88–0.89;原生林最低, 为1.25和0.67。树干方位、宿主种类和宿主径级等都对附生地衣的物种组成和多样性有着重要影响, 附生地衣更多地出现于树干南向方位, 云南越桔(Vaccinium duclouxii)的附生地衣最为丰富, 胸径5.0–25.0 cm的树木上附生地衣较多。哀牢山山地森林群落中丰富的附生地衣种类及物种多样性在维系本区山地森林生态系统生物多样性格局方面具有重要的作用。     

Ecological role of reindeer summer browsing in the mountain birch (<Emphasis Type="Italic">Betula pubescens</Emphasis> ssp. <Emphasis Type="Italic">czerepanovii</Emphasis>) forests: effects on plant defense,litter decomposition,and soil nutrient cycling

Mammalian herbivores commonly alter the concentrations of secondary compounds in plants and, by this mechanism, have indirect effects on litter decomposition and soil carbon and nutrient cycling. In northernmost Fennoscandia, the subarctic mountain birch (Betula pubescens ssp. czerepanovii) forests are important pasture for the semidomestic reindeer (Rangifer tarandus). In the summer ranges, mountain birches are intensively browsed, whereas in the winter ranges, reindeer feed on ground lichens, and the mountain birches remain intact. We analyzed the effect of summer browsing on the concentrations of secondary substances, litter decomposition, and soil nutrient pools in areas that had been separated as summer or winter ranges for at least 20 years, and we predicted that summer browsing may reduce levels of secondary compounds in the mountain birch and, by this mechanism, have an indirect effect on the decomposition of mountain birch leaf litter and soil nutrient cycling. The effect of browsing on the concentration of secondary substances in the mountain birch leaves varied between different years and management districts, but in some cases, the concentration of condensed tannins was lower in the summer than in the winter ranges. In a reciprocal litter decomposition trial, both litter origin and emplacement significantly affected the litter decomposition rate. Decomposition rates were faster for the litter originating from and placed into the summer range. Soil inorganic nitrogen (N) concentrations were higher in the summer than in the winter ranges, which indicates that reindeer summer browsing may enhance the soil nutrient cycling. There was a tight inverse relationship between soil N and foliar tannin concentrations in the winter range but not in the summer range. This suggests that in these strongly nutrient-limited ecosystems, soil N availability regulates the patterns of resource allocation to condensed tannins in the absence but not in the presence of browsing.     

How lichens impact on terrestrial community and ecosystem properties

Lichens occur in most terrestrial ecosystems; they are often present as minor contributors, but in some forests, drylands and tundras they can make up most of the ground layer biomass. As such, lichens dominate approximately 8% of the Earth's land surface. Despite their potential importance in driving ecosystem biogeochemistry, the influence of lichens on community processes and ecosystem functioning have attracted relatively little attention. Here, we review the role of lichens in terrestrial ecosystems and draw attention to the important, but often overlooked role of lichens as determinants of ecological processes. We start by assessing characteristics that vary among lichens and that may be important in determining their ecological role; these include their growth form, the types of photobionts that they contain, their key functional traits, their water‐holding capacity, their colour, and the levels of secondary compounds in their thalli. We then assess how these differences among lichens influence their impacts on ecosystem and community processes. As such, we consider the consequences of these differences for determining the impacts of lichens on ecosystem nutrient inputs and fluxes, on the loss of mass and nutrients during lichen thallus decomposition, and on the role of lichenivorous invertebrates in moderating decomposition. We then consider how differences among lichens impact on their interactions with consumer organisms that utilize lichen thalli, and that range in size from microfauna (for which the primary role of lichens is habitat provision) to large mammals (for which lichens are primarily a food source). We then address how differences among lichens impact on plants, through for example increasing nutrient inputs and availability during primary succession, and serving as a filter for plant seedling establishment. Finally we identify areas in need of further work for better understanding the role of lichens in terrestrial ecosystems. These include understanding how the high intraspecific trait variation that characterizes many lichens impacts on community assembly processes and ecosystem functioning, how multiple species mixtures of lichens affect the key community‐ and ecosystem‐level processes that they drive, the extent to which lichens in early succession influence vascular plant succession and ecosystem development in the longer term, and how global change drivers may impact on ecosystem functioning through altering the functional composition of lichen communities.     

Litterfall of epiphytic macrolichens in Nothofagus forests of northern Patagonia,Argentina: Relation to stand age and precipitation

Abstract: The objective of this study was to analyse how stand age and precipitation influence abundance and diversity of epiphytic macrolichens in southern beech Nothofagus forests, estimated by lichen litter sampling. Five sites of Nothofagus dombeyi (Mirbel) Oersted were selected in Nahuel Huapi National Park, Argentina. At each site, lichen fragments from the forest floor were collected at 12.5 m² plots in pairs of young and mature N. dombeyi forest. Additionally, two sites with multi‐aged subalpine Nothofagus pumilio (Poepp. et Endl.) Krasser forest were investigated in a similar manner. Average litterfall biomass per stand varied from less than 1 kg ha^?1 in a young low‐precipitation stand to a maximum of 20 kg ha^?1 in a mature high‐precipitation stand. In places with higher precipitation, litterfall biomass in N. dombeyi forest was considerably higher in old stands as compared with young ones. In places with less than 2000 mm of precipitation, differences in biomass were less pronounced. Old humid stands contained about twice as many taxa in the litter as old low‐precipitation stands and young stands in general. Mature stands in low‐precipitation sites only contained 17% of the litter biomass as compared with mature stands in high‐precipitation sites. Epiphytic lichen composition changed from predominating fruticose lichens (Usnea spp. and Protousnea spp.) in low‐precipitation stands to Pseudocyphellaria spp., Nephroma spp. and other foliose lichens, in the high‐precipitation stands. There were no clear differences in the proportion of fruticose and foliose lichens between young and old stands. Fruticose lichens dominated litter biomass in both N. pumilio sites.     

The weight of the crust: Biomass of crustose lichens in tropical dry forest represents more than half of foliar biomass

In recent years, our ecological knowledge of tropical dry forests has increased dramatically. However, the functional contributions of whole ecosystem components, such as lichens, remain mostly unknown. In these forests, the abundance of epiphyte crustose lichens is responsible for the characteristic white bark on most woody plants, conspicuous during the dry season, but the amount of resources that the lichen component represents remains unexplored. We estimated lichen biomass in a Mexican tropical dry forest using the bark area of trees, the dry mass of lichens per unit area and the percentage of bark covered by lichens, together with previously known tree densities. The lowest 2.5 m of the forests main trunks contained 188 kg/ha of lichen biomass, with lichens covering 85% of the available bark for trees <12 cm DBH and 38% for trees >12 cm. Total epiphytic lichen biomass was 1.34–1.99 Mg/ha. Lichen biomass represented 61% of the foliar biomass in the forest. To our knowledge, this is the first time that a lichen biomass estimate is provided for an ecosystem in which crustose lichens are the dominant lichen growth form. Crustose lichens are typically considered to contribute little to the total lichen biomass and to be difficult to include in ecological analyses. The high lichen biomass in this ecosystem implies a significant ecological role which so far is unexplored. We suggest the crustose lichen component should not be underestimated a priori in ecological studies, especially in ecosystems with abundant lichen cover.     

Seasonal grazing effects by semi-domesticated reindeer on subarctic mountain birch forests

In northern Fennoscandia, the spatial and temporal grazing practices of semi-domesticated reindeer (Rangifer tarandus tarandus) vary, which implies different grazing effects dependent on natural conditions as well as management regime (i.e., timing and intensity of grazing). We compared density and biomass of main plant groups in semi-dry mountain birch forests exposed to either long-term summer or winter grazing in three reindeer herding districts in the northernmost Finland. Percent plant cover, height, and biomass of reindeer lichens (Cladonia spp.) and dwarf shrubs (Vaccinium uliginosum, Calluna vulgaris, and Betula nana) were lower on summer ranges compared with winter ranges. The biomass of other dwarf shrubs (Vaccinium myrtillus and V. vitis-idaea), and graminoids and herbs, and the % cover of non-vegetated bare soil and litter were, however, higher on summer ranges than on winter ranges. Young mountain birch shoots (Betula pubescens ssp. czerepanovii) were less frequent on summer ranges than on winter ranges. The total leaf biomass under the browsing height of reindeer (<1.5 m) was also lower on summer ranges compared with winter ranges. Especially in drier and nutrient poor mountain birch forests, intensive summer grazing reduces the quantity of lichens and total plant biomass which affects the ecological state and productivity of these forests and also reduces especially their winter grazing value for reindeer. Therefore, in addition to regulating the maximum sustained numbers of reindeer, pasture rotation systems that effectively protect dry and nutrient poor vegetation from summer grazing and trampling should be encouraged.     

雪被斑块对川西亚高山森林6种凋落叶冬季腐殖化的影响

亚高山森林凋落叶腐殖化是联系植物与土壤碳库和养分库的重要通道, 在冬季可能受到雪被斑块的影响。该文采用凋落物网袋法, 于2012年11月-2013年4月研究了川西亚高山森林不同厚度雪被斑块(厚雪被、中雪被、薄雪被和无雪被)下优势树种岷江冷杉(Abies faxoniana)、方枝柏(Sabina saltuaria)、四川红杉(Larix mastersiana)、红桦(Betula albo-sinensis)、康定柳(Salix paraplesia)和高山杜鹃(Rhododendron lapponicum)凋落叶在不同雪被关键期(雪被形成期、雪被覆盖期和雪被融化期)的腐殖化特征。结果表明: 亚高山森林冬季不同厚度雪被斑块下6种凋落叶均保持一定程度的腐殖化, 其中红桦凋落叶腐殖化度最大, 达4.45%-5.67%; 岷江冷杉、高山杜鹃、康定柳、四川红杉和方枝柏凋落叶腐殖化度分别为1.91%-2.15%、1.14%-2.03%、1.06%-1.97%、0.01%-1.25%和0.39%-1.21%。凋落叶腐殖质在雪被形成期、融化期和整个冬季累积, 且累积量随雪被厚度减小而增加, 但在雪被覆盖期降解, 且降解量随雪被厚度减小而增大。相关分析结果表明, 亚高山森林凋落叶前期腐殖化主要受凋落叶质量影响, 且与氮和酸不溶性组分呈极显著正相关, 而与碳、磷、水溶性和有机溶性组分呈极显著负相关。表明冬季变暖情景下雪被厚度的减小可能促进亚高山森林凋落叶腐殖化, 但凋落叶腐殖化在不同雪被关键期受雪被斑块和凋落叶质量的调控。     

Effects of snowpack on early foliar litter humification during winter in a subalpine forest of western Sichuan

亚高山森林凋落叶腐殖化是联系植物与土壤碳库和养分库的重要通道, 在冬季可能受到雪被斑块的影响。该文采用凋落物网袋法, 于2012年11月-2013年4月研究了川西亚高山森林不同厚度雪被斑块(厚雪被、中雪被、薄雪被和无雪被)下优势树种岷江冷杉(Abies faxoniana)、方枝柏(Sabina saltuaria)、四川红杉(Larix mastersiana)、红桦(Betula albo-sinensis)、康定柳(Salix paraplesia)和高山杜鹃(Rhododendron lapponicum)凋落叶在不同雪被关键期(雪被形成期、雪被覆盖期和雪被融化期)的腐殖化特征。结果表明: 亚高山森林冬季不同厚度雪被斑块下6种凋落叶均保持一定程度的腐殖化, 其中红桦凋落叶腐殖化度最大, 达4.45%-5.67%; 岷江冷杉、高山杜鹃、康定柳、四川红杉和方枝柏凋落叶腐殖化度分别为1.91%-2.15%、1.14%-2.03%、1.06%-1.97%、0.01%-1.25%和0.39%-1.21%。凋落叶腐殖质在雪被形成期、融化期和整个冬季累积, 且累积量随雪被厚度减小而增加, 但在雪被覆盖期降解, 且降解量随雪被厚度减小而增大。相关分析结果表明, 亚高山森林凋落叶前期腐殖化主要受凋落叶质量影响, 且与氮和酸不溶性组分呈极显著正相关, 而与碳、磷、水溶性和有机溶性组分呈极显著负相关。表明冬季变暖情景下雪被厚度的减小可能促进亚高山森林凋落叶腐殖化, 但凋落叶腐殖化在不同雪被关键期受雪被斑块和凋落叶质量的调控。     

Ice encapsulation protects rather than disturbs the freezing lichen

Arctic and alpine terricolous lichens are adapted to harsh environments and are tolerant to extremely low temperatures when metabolically inactive. However, there are reports indicating that freezing can be lethal to metabolically active lichens. With a projected warmer and more unstable climate, winter precipitation at high latitudes will fall more frequently as rain, causing snowmelt and encapsulating terricolous lichens in ice or exposing them to large temperature fluctuations. Lichens are a major winter food source for reindeer in most parts of the circumpolar region. A laboratory experiment tested how three hydrated reindeer forage lichen species covered by snow, encapsulated in ice, or uncovered responded to storage at freezing temperatures and subsequent warming. Photosynthetic performance (maximal fluorescence of dark-adapted samples and net photosynthetic rates) was significantly lower in lichens not insulated by snow or ice, whereas there were few differences between the snow and ice treatments. It is suggested that snow and ice provide sufficiently moist environments to improve extracellular and reduce intracellular ice nucleation activity. Ice encapsulation, which is often lethal to vascular plants, did not have any negative effects on the studied lichens. The results indicate that complete snow and ice melt followed by refreezing can be detrimental to terricolous lichen ecosystems. Reduced lichen biomass will have a negative effect both on reindeer winter survival and the indigenous peoples who herd reindeer.     

Non-dominant trees significantly enhance species richness of epiphytic lichens in subtropical forests of southwest China

Host species has an important influence on the distribution of epiphytic lichens in forests. However, the importance of non-dominant trees in shaping lichen communities has been poorly studied owing to the relative rarity of individuals. The importance of dominant and non-dominant trees for distribution of epiphytic lichens was determined in eight subtropical forests in southwestern China. Dominant trees supported more abundant total and exclusive lichen species only in secondary forests. The occurrence of non-dominant trees promoted lichen diversity within forest types and influenced lichen communities on both tree groups. The effects of total tree species on lichen distribution largely resulted from the presence of non-dominant trees. Dominant and non-dominant trees supported distinct lichen assemblages within forest types, and ordination analyses showed a clear separation. Our study, therefore, reinforces the importance of non-dominant trees for conserving epiphytic lichens, and highlights that lichen assemblages are shaped by both dominant and non-dominant trees.     

Bole epiphytic lichens as potential indicators of environmental change in subtropical forest ecosystems in southwest China

Lichen epiphytes are applied as excellent environmental indicators worldwide. However, very little is known about epiphytic lichen communities and their response to forest dynamics in subtropical China. This paper proposes the applications of the cover, diversity, and functional traits of epiphytic lichens to assess environmental changes associated with succession in subtropical forests of southwest China. Bole lichens were sampled from 120 plots of eight representative forest types in the Ailao Mountains. Total cover, species richness, diversity and community structure of bole lichens differed significantly among forest types, and the highest cover and diversity occurred in the Populus bonatii secondary forest (PBSF). Sixty-one indicator species were associated with particular forest types and more than 50% occurred in the PBSF. Both cover and diversity of most lichen functional groups varied regularly during forest succession. Lichen pioneer species were not displaced by competitively superior species as succession proceeds and cyanolichens were more prevalent in secondary forests. The results also highlight the importance of habitat variables such as canopy openness, host diversity, forest age, tree size, the size of the largest tree, tree density, and basal area on the lichen community. Consequently, our findings support the notion that epiphytic lichens, in terms of cover, diversity, species composition and functional traits can be used as effective indicators for large-scale and long-term forest monitoring. More importantly, the narrowly lobed foliose group was the best candidate indicator of environmental conditions in this region. The combined application of lichen indicator species and functional groups seemed to be a more reliable and more powerful method for monitoring forest dynamics in subtropical montane ecosystems.     

Winter grazing of reindeer in woodland lichen pasture: Effect of lichen availability on the condition of reindeer

Winter grazing of semi-domesticated reindeer (Rangifer t. tarandus) was investigated at the woodland lichen pasture (lichen approximately 550 kg DM ha⁻¹) in Kaamanen, northern Finland during the winter 1996–1997. Nine female reindeer mainly dug their food in the snow for 122 days (3 December–4 April) in a fenced area of 36.3 ha. Over half of the fenced area was lichen dominated dry pine forest. The amount of lichens in lichen forest inside the fence was estimated before and after grazing. Area of grazed and condition of reindeer as well as snow conditions were monitored. Reindeer grazed over the whole area of lichen forest in early winter but from mid-winter they tended to graze on the areas with the greatest lichen abundancy. The amount of lichens measured decreased in the latter areas by 40% and in the other part of the lichen pasture by 17%, respectively. In both of these areas the residual amounts of lichens left after grazing were similar. Of the dominant lichens, the amount of C. stellaris decreased the most and the amount of Cl. uncialis the least. During the study, the estimated average daily area grazed varied from 4 to 87 m² per reindeer. It was calculated that individual reindeer obtained 2.6 kg of lichen DM per day during the most intensive digging period when the body condition score and weight of reindeer increased. Otherwise, the body condition score and weight decreased. Reindeer finished foraging for ground lichens and started to search for arboreal lichens in mid-March when the snow layer was 70–80 cm thick and contained some hard snow layers which lifted reindeer. Both the amount of lichens in the pasture and the snow conditions essentially affect the nutritional status of reindeer in the woodland region during winter. Assuming that a reindeer is able to graze around 30 m² per day in the snow during mid and late winter, there should be, on the basis of energy demand and grazing behaviour of reindeer as well as the nutritive value of lichen, an estimated 1000 kg lichen DM ha⁻¹ available in a good condition woodland lichen pasture.     

桂西北喀斯特区原生林与次生林凋落叶降解和养分释放

凋落叶降解及养分释放研究对喀斯特生态脆弱区森林生态系统的恢复与重建具有重要指导意义。本文选取桂西北喀斯特区3种原生林与3种次生林进行比较,研究其凋落叶降解与降解过程中的营养元素释放规律以及降解速率的影响因子。结果表明,原生林凋落叶的降解速率略大于次生林。C、N、K元素在前180天释放速率较快,随后趋于稳定。次生林凋落叶总P含量在降解初始阶段呈净积累,随后净释放,而原生林的凋落叶在降解360天后仍呈现P素净积累。相关分析表明,凋落叶降解速率与凋落叶初始总N、木质素含量及木质素:N比值呈负相关,与C:N比呈正相关。综合比较发现,次生林圆叶乌桕(Sapium rotundifolium Hemsl)凋落叶的降解速率与养分释放速率较快,是喀斯特退化土地及植被恢复过程中潜在的优势种和建群种。     

Ectomycorrhizal-Dominated Boreal and Tropical Forests Have Distinct Fungal Communities,but Analogous Spatial Patterns across Soil Horizons

Fungi regulate key nutrient cycling processes in many forest ecosystems, but their diversity and distribution within and across ecosystems are poorly understood. Here, we examine the spatial distribution of fungi across a boreal and tropical ecosystem, focusing on ectomycorrhizal fungi. We analyzed fungal community composition across litter (organic horizons) and underlying soil horizons (0–20 cm) using 454 pyrosequencing and clone library sequencing. In both forests, we found significant clustering of fungal communities by site and soil horizons with analogous patterns detected by both sequencing technologies. Free-living saprotrophic fungi dominated the recently-shed leaf litter and ectomycorrhizal fungi dominated the underlying soil horizons. This vertical pattern of fungal segregation has also been found in temperate and European boreal forests, suggesting that these results apply broadly to ectomycorrhizal-dominated systems, including tropical rain forests. Since ectomycorrhizal and free-living saprotrophic fungi have different influences on soil carbon and nitrogen dynamics, information on the spatial distribution of these functional groups will improve our understanding of forest nutrient cycling.     

Spontaneous restoration of epiphytic lichen biota in managed forests planted on habitats typical for temperate deciduous forest

The study examines the changes of epiphytic lichen diversity in differently aged stands developing after clear cutting and pine planting on fertile habitats typical for deciduous forests. The study was conducted within one large complex consisting of pine, mixed pine-hornbeam and typical old oak-linden-hornbeam forests in northern Poland. Epiphytic lichens were recorded in 50 study plots randomly selected within 5 forest stand classes of a different structure and age, ranging from 80 to over 220 years. Altogether 143 lichen species were recorded, of which only 41 were entirely nonspecific, and were occurring in all the studied forest stand classes. Significant differences in lichen species richness between stand classes were found and the number of species increases with the forest age. Lichen species composition also differs and its changes progress towards restoration of lichen biota typical for deciduous forest consistent with the habitat. The age of the forest has the most significant effect on the biodiversity of lichen biota. Microhabitat space provided by oaks is highly desirable since it greatly enriches lichen biota in forests. Phorophyte specificity of particular lichens were assessed. Hornbeam and oak have the greatest number of species mostly confined to them and constitute a main refuge for lichens with a high conservation value. The changes of lichen biota are basically parallel with the changes of the forest stand structure. The selection of some parts within managed pine forests that should not be assigned for cutting in the future can be a simple procedure which helps to restore and preserve forest biodiversity.     

The impact of nitrogen deposition on photobiont‐mycobiont balance of epiphytic lichens in subtropical forests of central China

Excessive nitrogen (N) deposition can impact lichen diversity in forest ecosystems, and this is a particular situation in China. Here, we examined the N uptake, assimilation, and the impact of excessive N deposition on the symbiotic balance of dominant epiphytic lichens in the subtropical forests in the Mts. Shennongjia of central China. The results show that lichen species took up, assimilated and utilized more ammonium than nitrate in a species‐specific way, following the increase of N availability. The photobiont of the lichens decreased with the increase of N concentration following an initial increase, while the mycobiont response to the N addition was not apparent. Considerable variation in response to excessive N deposition exists among the lichen species. Usnea longissima could regulate its N uptake, resulting in a stable photobiont‐mycobiont ratio among N treatments. In contrast, the photobiont‐mycobiont ratio of other four lichens increased initially but decreased when N concentration exceeded a certain level, and N stress may have broken the balance between photobiont and mycobiont of these lichens. Our results suggest that most epiphytic lichens in subtropical forest of central China could uptake and assimilate more ammonium than nitrate and that the balance between photobiont and mycobiont of many epiphytic lichens might change with the increasing N deposition load, which could impact the lichen diversity of this forest ecosystem.     

Influence of Different Forest System Management Practices on Leaf Litter Decomposition Rates,Nutrient Dynamics and the Activity of Ligninolytic Enzymes: A Case Study from Central European Forests

Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling.