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Shifts in soil fungi and extracellular enzyme activity with simulated climate change in a tropical montane cloud forest
Abstract
Tropical montane cloud forests are vulnerable to climate change. The cloud layer is lifting, causing warmer and drier conditions. With climate change, tropical ecosystems have the potential to accentuate global CO 2 emissions because of their significant influence over global C cycling. Unfortunately, we do not know how this will affect belowground communities, like soil fungi, and the vital ecosystem processes they control. We performed a soil translocation experiment along an elevation gradient in Monteverde, Costa Rica to assess how fungal communities , soil decomposition, and extracellular enzyme activity (EEA) of C-degrading enzymes may shift with climate change. Soils were translocated to four lower elevation sites. These sites spanned 4 °C increases in temperature and a 20% decline in soil moisture. We used microbial cages to isolate the fungal community and monitor how soil fungi would respond to warmer, drier conditions. Fungal abundance and diversity increased with warmer and drier conditions. Fungal communities also shifted. Specifically, we found changes in the richness of fungal phyla. Richness of lichen-forming fungi, pathogens, wood saprotrophs, and yeasts increased. In addition, we found that EEA was higher under warmer and drier conditions. Our results suggest that high elevation soils may shift towards an increased capacity to decompose C under future climate conditions. Moreover, with climate change, animals or plants in tropical montane cloud forests may be exposed to a greater richness of fungal pathogens. Overall, our study reveals that the lifting cloud layer may affect the fungal community within these forests, which in turn may affect both the structure and function of these forests.
... In the past decade, the response of litter decomposition to warming has been widely studied in terrestrial ecosystems using in situ altitudinal and latitudinal temperature gradients, as well as field heating methods (Bothwell et al., 2014;Christiansen et al., 2017;Liu et al., 2017a;Looby and Treseder, 2018;van Meeteren et al., 2008;Morrison et al., 2019;Prieto et al., 2019). These studies showed positive, negative, or neutral effects of warming on leaf decomposition (Bothwell et al., 2014;Christiansen et al., 2017;Liu et al., 2017a;Looby and Treseder, 2018;Morrison et al., 2019;Ye et al., 2022). ...
... In the past decade, the response of litter decomposition to warming has been widely studied in terrestrial ecosystems using in situ altitudinal and latitudinal temperature gradients, as well as field heating methods (Bothwell et al., 2014;Christiansen et al., 2017;Liu et al., 2017a;Looby and Treseder, 2018;van Meeteren et al., 2008;Morrison et al., 2019;Prieto et al., 2019). These studies showed positive, negative, or neutral effects of warming on leaf decomposition (Bothwell et al., 2014;Christiansen et al., 2017;Liu et al., 2017a;Looby and Treseder, 2018;Morrison et al., 2019;Ye et al., 2022). One of the key sources for the inconsistence among these studies may be the different response of soil and/or litter moisture to warming, which is a key limiting abiotic factor of litter decomposition. ...
... For this reason, many studies have examined the relationships between extracellular enzyme activities and litter decomposition rates (Nowacki and Abrams, 2000;Allison and Vitousek, 2004;Waring, 2013). For instance, C-degrading enzyme activities (e.g., cellobiohydrolase and polyphenol oxidase) are positively correlated with litter mass loss, and warming generally increases litter decomposition rates via increasing extracellular enzyme activities (Waring, 2013;Suseela et al., 2014;Looby and Treseder, 2018). Furthermore, microbial biomass C (MBC) and N (MBN) is strongly related to microbial activity, e.g., extracellular enzyme activities are commonly positively correlated with MBC. ...
Litter decomposition is a fundamental ecosystem process, influencing soil carbon storage, nutrient availability, and forest productivity. Climate change may affect litter decomposition and thus nutrient dynamics via altering plant phenology, litter quality, and the composition of soil microbial communities. However, the effects of climate change on litter decomposition are not well understood, especially in tropical and subtropical forest ecosystems, which are less temperature limited. We conducted a manipulative study to assess how soil warming affects litter decomposition rates and its relation to litter chemistry, extracellular enzyme activities, and microbial biomass in an evergreen broad-leaved forest in subtropical China. The temperature at 0–10 cm soil depth was experimentally increased by 4 °C, starting from June 2016 to October 2017. Soil warming did not affect litter mass loss during the initial stage (0–270 day), but reduced litter mass loss by 12.9 % at the later stages (days 350 to 450). Structural equation modeling showed that litter moisture content was reduced by warming, but this was not the main effector leading to the reduction in late-stage litter decomposition in the warming treatment. The model suggested that warming reduced litter decomposition rates likely indirectly, through its negative effects on extractable organic carbon and microbial biomass (e.g., microbial carbon and nitrogen), and on litter enzyme activities (a composite variable of β-glucosidase, cellobiohydrolase, acid phosphatase, and phenoloxidase). These results show that warming may slow down litter carbon cycling, but this subtropical forest ecosystem did not affect litter N and P cycling and soil nutrient availability.
... The stability of dominant species tends to positively affect the stability of community productivity Ma et al., 2017), thereby positively affecting soil fungal diversity. Moreover, some results have shown that the response of soil fungal diversity to elevated temperature might be largely fungal functional group-specific (Geml et al., 2015;Treseder et al., 2016); for instance, warming increased the richness of wood saprotrophs and fungal pathogens in a tropical forest (Looby and Treseder, 2018). Many results have demonstrated that the influence of N addition on soil fungal diversity depends on the type of ecosystem (N-limited or N-rich) and the dose of N addition (Zhou et al., 2016). ...
... Some studies have found that warming has a significant impact on the soil fungal community structures in several ecosystems (Looby and Treseder, 2018;Che et al., 2019); however, several studies have found that short-term warming does not affect the structure of the soil fungal communities in alpine grasslands (Hayden et al., 2012;Zhang T, et al., 2016). In the present study, warming significantly altered the soil fungal community structure ( Figure 5) and increased the relative abundance of Ascomycota, which might explain the soil carbon (C) loss caused by global warming because Ascomycota is a saprotrophic fungus that plays an important role in soil organic carbon decomposition (Xiong et al., 2014). ...
Soil microbial communities have been influenced by global changes, which might negatively regulate aboveground communities and affect nutrient resource cycling. However, the influence of warming and nitrogen (N) addition and their combined effects on soil microbial community composition and structure are still not well understood. To explore the effect of warming and N addition on the composition and structure of soil microbial communities, a five-year field experiment was conducted in a temperate meadow. We examined the responses of soil fungal and bacterial community compositions and structures to warming and N addition using ITS gene and 16S rRNA gene MiSeq sequencing methods, respectively. Warming and N addition not only increased the diversity of soil fungal species but also affected the soil fungal community structure. Warming and N addition caused significant declines in soil bacterial richness but had few impacts on bacterial community structure. The changes in plant species richness affected the soil fungal community structure, while the changes in plant cover also affected the bacterial community structure. The response of the soil bacterial community structure to warming and N addition was lower than that of the fungal community structure. Our results highlight that the influence of global changes on soil fungal and bacterial community structures might be different, and which also might be determined, to some extent, by plant community, soil physicochemical properties, and climate characteristics at the regional scale.
... These in situ warming experiments have also been complemented by translocation experiments across tropical mountain gradients, where soil mesocosms have undergone temperature incubations in Costa Rica (Looby & Treseder, 2018) and Peru (Nottingham, Whitaker, et al., 2019;Zimmermann et al., 2012). across an elevation gradient in Peru found that warming resulted in increased heterotrophic respiration rates and declines in labile C after 2 years (Zimmermann et al., 2012), and substantive declines in soil C after 5 years (Nottingham, Whitaker, et al. (2019); responses that represented the combined warming of upland soils and cooling of lowland soils. ...
... In another study from the same site, 2 and 11 years of warming led to, respectively, 77% and complete adaptation of community growth to the new temperature, with T min increasing by 0.3°C with each 1°C warming (Nottingham et al., 2021; Figure 3a, see green dashed lines). Although several mechanisms could contribute to this thermal growth adaptation, community compositional shifts appear to be important, as observed in warmed soil from temperate zones (Donhauser et al., 2020;Rousk et al., 2012) and in two separate montane forest soil warming studies, in Peru (Nottingham, Whitaker, et al., 2019) and Costa Rica (Looby & Treseder, 2018). ...
Climate warming could destabilise the Earth's largest terrestrial store of reactive carbon (C), by accelerating the decomposition of soil organic matter. A third of that C store resides in the tropics. The potential for tropical soils to sequester C, or to act as an additional source of CO 2 , will depend on the balance of C inputs and outputs, mediated by the response of soil microbial communities and their activity to perturbation.
We review the impact of warming on microbial communities and C storage in humid tropical forest soils over multiple time‐scales.
Recent in situ experiments indicate high sensitivity of tropical forest soil C mineralisation to warming in the short term. However, whether this will translate into long‐term soil C decline remains unclear. At decadal time‐scales, high sensitivity of soil C mineralisation to warming is consistent with the correlation between the inter‐annual variation in the tropical land surface temperature and atmospheric CO 2 growth rate, and with simulations using the Carnegie‐Ames‐Stanford Approach biosphere model. This observed sensitivity may further contribute to climatic change over millennial time‐scales, suggested by radiocarbon dating of organic matter in river basins showing a twofold acceleration in tropical soil C release during the late‐glacial warming period. However, counter to this evidence, long‐term stability of tropical soil C is suggested by observed steady‐state soil C turnover across temperature gradients with elevation, and by the presence of C in tropical soils that pre‐dates the Holocene Thermal Maximum and late‐glacial warming periods.
To help reconcile these recent experimental findings and long‐term observations, we propose mechanisms to explain tropical soil C and microbial responses to warming across multiple time‐scales. Combined in situ experimental and monitoring approaches—large‐scale and cross‐site—are urgently needed to resolve the interplay of these mechanisms across spatial and temporal scales, to shape a better understanding of the relationship between soil microbes and C storage in tropical soils.
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... We approximated a high fungal functional diversity (10 fungal guilds) at the small-scale, which reinforces our findings of a high alfa-and beta-diversity estimates in the same sites. Moreover, the observation of saprobes as the larger functional guild in soil, agrees with previous work at the large scale suggesting these fungi are key players in MCF nutrients cycling (Looby & Treseder, 2018). In addition, the high abundance of fungal lineages implicated in nitrogen dynamics such as Glomeromycota and Mucoromycota, advocate N-mediated rhizopheric fungal interactions with plants (Bonfante, 2020). ...
... Consequently, this system stores more soil C than lowland forests (Grieve, Proctor & Cousins, 1990;Raich et al., 2006; thereby contributing to climate change mitigation), being particularly susceptible to climate change (Bradford et al., 2016). We speculate that the high abundance of saprotrophs supports former postulates on MCF soil functional modifications under climate change, where (1) global C cycling changes occur as a result of exponential increases in decomposition rates with higher temperatures, releasing CO 2 from the soil (Benner, Vitousek & Ostertag, 2010); and (2) selected fungal groups such as pathogens and wood saprotrophs proliferate (Looby & Treseder, 2018;Pounds, Fogden & Campbell, 1999;Pounds et al., 2006). In this setting, additional studies are required for a better understanding of the mechanisms underpinning directional species turnover in other systems with similar environmental conditions. ...
Montane cloud forests are fragile biodiversity hotspots. To attain their conservation, disentangling diversity patterns at all levels of ecosystem organization is mandatory. Biotic communities are regularly structured by environmental factors even at small spatial scales. However, studies at this scale have received less attention with respect to larger macroscale explorations, hampering the robust view of ecosystem functioning. In this sense, fungal small-scale processes remain poorly understood in montane cloud forests, despite their relevance. Herein, we analyzed soil fungal diversity and ecological patterns at the small-scale (within a 10 m triangular transect) in a pristine montane cloud forest of Mexico, using ITS rRNA gene amplicon Illumina sequencing and biogeochemical profiling. We detected a taxonomically and functionally diverse fungal community, dominated by few taxa and a large majority of rare species (81%). Undefined saprotrophs represented the most abundant trophic guild. Moreover, soil biogeochemical data showed an environmentally heterogeneous setting with patchy clustering, where enzymatic activities suggest distinctive small-scale soil patterns. Our results revealed that in this system, deterministic processes largely drive the assemblage of fungal communities at the small-scale, through multifactorial environmental filtering.
... Indeed, decomposition of SOM (Zimmermann et al. 2009) and litter (Salinas et al. 2011) increase markedly when transplanted to lower elevations in the tropics. Activities of C-degrading enzymes also increased in litter transplanted to lower sites along a dry elevation gradient in California (Baker et al. 2018) and a wet elevation gradient in Costa Rica (Looby and Treseder 2018). Along the gradient in Costa Rica, fungal diversity also increased in soils moved to lower elevations. ...
... The observational studies in this review have been instrumental in developing the leading theories of the ecological and evolutionary factors that shape microbial diversity and communities-such as, that the richness of microbial communities are shaped by resource ecology (Peay et al. 2017), and that the compositions of fungal and bacterial community are tightly linked to temperature (Nottingham et al. 2018a). In addition, future climate conditions may increase rates of decomposition through changes in extracellular enzyme activity (Baker et al. 2018) and changes in the fungal community (Looby and Treseder 2018). However, a greater emphasis on manipulative experiments is needed to improve our predictive power and provide information that can be used in dynamic models. ...
Mountains have a long history in the study of diversity. Like macroscopic taxa, soil microbes are hypothesized to be strongly structured by montane gradients, and recently there has been important progress in understanding how microbes are shaped by these conditions. Here we summarize this literature and synthesize patterns of microbial diversity on mountains. Unlike for flora and fauna which often display a mid-elevation peak in diversity, we found a decline (34% of the time) or no trend (33%) in total microbial diversity with increasing elevation. Diversity of functional groups also varied with elevation (e.g. saprotrophic fungi declined 83% of the time). Most studies (82%) found climate and soils (especially pH) were the primary mechanisms driving shifts in composition, and drivers differed across taxa-fungi were mostly determined by climate, while bacteria (48%) and archaea (71%) were structured primarily by soils. We hypothesize the central role of soils-which can vary independently of other abiotic and geographic gradients-in structuring microbial communities weakens diversity patterns expected on montane gradients. Moving forward, we need improved cross-study comparability of microbial diversity indices (i.e. standardizing sequencing) and more geographic replication using experiments to broaden our knowledge of microbial biogeography on global gradients.
... T he tropical montane cloud forest (TMCF) is one of the most biodiverse ecosystems on Earth (Bubb et al. 2004, Cayuela et al. 2006, Hamilton 2012 and also one of the most threatened, owing to pressures imposed by land-use change and climate change (Karmalkar et al. 2011, González-Espinosa et al. 2012, Williams-Linera et al. 2015, Looby and Treseder 2018. It is estimated that 2.5 percent of the world's forested area comprises cloud forests (Bubb et al. 2004), of which approximately 41 percent are found in Latin America (Mulligan 2010, Scatena et al. 2010. ...
... In general, soil-related research on TMCF ecosystems is scarce, with only a few scientific articles available (Bautista-Cruz and del Castillo 2005). Moreover, the soil information provided is often rather descriptive (Trujillo-Miranda et al. 2018) and theme-specific, e.g., soil fungi (Looby and Treseder 2018), leaf traits and soils (Hernández-Vargas et al. 2019), or N-fixing trees and soil N (Rhoades et al. 1998). ...
The tropical montane cloud forest is one of the most biodiverse ecosystems on Earth and is one of the areas most threatened by anthropogenic disturbance. This study assessed the temporal impact on soil properties (organic carbon, total nitrogen, cation exchange capacity, bulk density) following establishment of native tree species in two degraded tropical montane cloud forest areas with different soil types and land-use intensities in south-east Mexico. In Pueblo Nuevo, Chiapas, Pinus chiapensis and Alnus spp. were established at two sites with humic Nitisols with low and moderate disturbance levels, respectively. In Xalapa, Veracruz, plum pine (Podocarpus matudae), American hornbeam (Carpinus caroliniana), Oaxaca walnut (Juglans pyriformis Liebm.), and sweetgum (Liquidambar styraciflua) were established on a grassland-covered humic Andosol with a high level of disturbance. After 16 years, soil properties had generally improved, although in the initial years after planting, the values declined, indicating a possible negative impact because of disturbance during tree establishment. Land-use intensity prior to tree establishment influenced the level of recovery in soil properties. The Pueblo Nuevo sites, with low to moderate disturbance levels, regained soil quality faster than the highly disturbed Xalapa site, despite better initial soil quality in the latter.
... The richness of Ascomycota increases at a warmer temperature and dry weather, while the richness of Cryptomycota deceases under the same conditions. Changes in the community are also dependent on the moisture content in soil [27]. ...
... The main hydrolytic enzymes involved in labile to intermediate C decomposition are α-glucosidase (AG) that degrades starch, ß-glucosidase (BG) and cellobiohydrolase (CBH) that degrade cellulose and ß-xylosidase (BX) that degrades hemicellulose. The change in their enzymatic activity depended on both temperature and precipitation [27]. While elevated temperatures influence soil fungi growth patterns, lower temperatures (below 30°C) can increase their secondary metabolism, a process that results in an array of natural products. ...
The global climate change can influence agricultural productivity by altering the plant-microbe interactions. Plant-associated fungi play important roles in these interactions by regulating nutrient transformation in soils, nutrient availability for plants and plant health and growth. The abiotic stressors that increase with the changing climate result in significant alterations in these processes. These alterations are either as a response to the changing biology of the plant or due to the direct effect of the stressors on the fungi. In this chapter we retrospect the current knowledge on the plant-associated fungi and discuss the effects of the changing climate on their interactions with their hosts. The goal of this review is to emphasize the need for more research on plant-fungal interactions that can increase the resilience of crops to climate change.
... Saprophytic fungi decompose plant litter, transfer litter-derived C into soil, translocate soil-derived inorganic N up into the litter layer and assimilate carbon and other nutrients into fungal biomass, play a vital role in C and N cycle (Frey et al., 2003). While, pathogenic fungi, can infect certain plants, animals or other fungi (Gilbert and Webb, 2007;Dagenais and Keller, 2009;Looby and Treseder, 2018), causing diseases, and changing their community composition and structure. Mycorrhizal fungi, can form mutualistic symbiosis with most terrestrial plants and confer lots of benefits, such as improving plant uptake of mineral nutrients and water to exchange for carbohydrates (Smith and Read, 2008) and protecting host plant from biotic (Affokpon et al., 2011) and abiotic stresses Wu et al., 2018). ...
... By contrast, the richness and abundance of mycorrhizal fungi would decrease following high dose N input owing to the decline of dependence of plant on them under increased N availability, soil acidification and changes in aboveground plant community (Rousk et al., 2010;Huang et al., 2014;Chen et al., 2017;Barnes et al., 2018). On the other hand, saprophytic fungi can be affected by soil temperature and humidity conditions (Meier et al., 2010;Looby and Treseder, 2018), and are likely to benefit from enhanced rainfall (Barnes et al., 2018), which may be mediated by microclimate, soil moisture and other processes. Similarly, increased moisture caused by elevated rainfall can promote the growth, proliferating and dispersal of existing pathogenic fungi (Woods et al., 2005;La Porta et al., 2008) and the emergence of new pathogenic fungi favoring wet conditions. ...
Nitrogen (N) deposition and intensified rainfall can strongly affect soil microbial community, but compared with available studies on bacteria, those on soil fungi are quite limited. Here we carried out a field experiment in a mixed deciduous forest of China to study the influences of increased N deposition and rainfall on soil fungi by using quantitative PCR and high-throughput sequencing method. The results demonstrated that (1) N addition significantly increased fungal abundance and alpha diversity (richness, Shannon index and Invsimpson index), changed fungal community composition at OTU level, and marginally increased the relative abundance of Ascomycota and Zygomycota, while water addition showed no remarkable effects on fungal abundance, biodiversity and community composition. (2) N addition significantly increased the richness of saprotrophic fungi and pathogenic fungi, and the relative abundance of saprotrophic fungi, but water addition only slightly increased the abundance of pathogenic fungi. (3) Fungal composition dissimilarity closely correlated with the disparity of soil parameters as a whole. Soil NH4+-N exhibited strong positive correlation with the richness of pathogenic fungi and mycorrhizal fungi, while both soil moisture and NH4+-N tightly correlated with soil fungal abundance and alpha diversity indices. We concluded that in this N-limited but non-water-limited forest ecosystem, N deposition posed stronger effects on soil fungi than increased rainfall, partially mediated by changes in soil properties.
... Recent research has also highlighted how climate changes affected soil microbial communities, with direct effects tracing back as far as 1,000 years ago, with paleoclimate imprinting on contemporary soil bacteria (Fordham et al., 2017;Liu et al., 2023;Luo et al., 2019). Climate change also strongly affects bacterial richness and community through pH, soil properties, and soil organic carbon concentration in forest ecosystems on a global scale (Looby and Treseder, 2018;Zheng et al., 2020). However, the impacts of climate change on soil microbial communities remain understudied in grassland systems. ...
Livestock grazing has a significant impact on the biodiversity of nature grassland ecosystems, which is mainly regulated by climate factors. Soil microbes are essential components of biogeochemical cycles. However, the coupling effects of grazing with MAT (mean annual temperature) and MAP (mean annual precipitation) on soil microbial communities remain inconsistent. Our study considered the various climates in four grasslands as natural temperature and precipitation gradients combined with grazing intensity (GI). We collected and analyzed vegetation and soil physiochemical properties from four grasslands. Our results showed that climate factors (CF) changed β diversity of soil bacteria and fungi while grazing intensity and their interaction merely affected fungi β diversity. Furthermore, climate factors and grazing intensity impacted changes in vegetation and soil physiochemical properties, with their interaction leading to changes in EC and MBC. Our analysis revealed that climate factors contributed 13.1% to bacteria community variation while grazing intensity contributed 3.01% to fungi community variation. Piecewise SEM analysis demonstrated that MAT and MAP were essential predictors of bacteria β diversity, which was significantly affected by vegetation and soil carbon and nitrogen. At the same time, MAP was an essential factor of fungi β diversity and was mainly affected by soil nitrogen. Our study indicated that bacteria and fungi β diversity was affected by different environmental processes and can adapt to specific grazing intensities over time.
... In addition, understory vegetation not only fosters a positive interaction with microbial communities but also plays an important role in maintaining ecosystem stability [83]. Climate-vulnerable cryptogamic plants in montane cloud forests may also alter the structure and function of fungal community [84]. For example, the sampling site at the elevation of 1100 m lies in a C. lanceolata forest, which likely leads to enhanced deterministic processes in the soil fungal community (Figure 3d). ...
Revealing the assembly mechanisms of the soil microbial community, which is crucial to comprehend microbial biodiversity, is a central focus in ecology. The distribution patterns of microbial elevational diversity have been extensively studied, but their assembly processes and drivers remain unclear. Therefore, it is essential to unravel the relationship between the deterministic and stochastic processes of the microbial community assembly and elevational gradients. Here, our study built upon previous physicochemical analyses of soil samples collected along an elevational gradient (900–1500 m) in Daiyun mountain, a subtropical forest located in southeastern China. Using the phylogenetic-bin-based null model analysis (icamp) and multiple regression on matrices approach, we explored the major drivers that influence the assembly processes of soil bacterial and fungal community across elevations. The results showed that: (1) bacterial rare taxa exhibited a broad habitat niche breadth along the elevational gradient; (2) homogeneous selection and homogenizing dispersal proved to be the most important assembly processes for the bacterial and fungal community; (3) soil phosphorus availability mediated the relative importance of deterministic and stochastic processes in the soil microbial community. Notably, the relative abundance of dominant microbial taxa controlled by homogeneous selection and homogenizing dispersal increased with increasing soil phosphorus availability. Collectively, the assembly processes of microbial elevational communities of the subtropical mountains in China can be explained to some extent by variations in the soil phosphorus availability. This conclusion provides valuable insights into the prediction of soil microbial diversity and phosphorus nutrient cycling in subtropical montane forests.
... Although there is no study about plant pathogens under elevated CO 2 in agricultural ecosystems, a recent study using a global meta-analysis and a 9-year field experiment found that warming increased the abundances of fungal plant pathogens [21]. Soil pathogenic fungi might proliferate under warming, affecting the functions and structure of the forest [40]. In this study, the relative abundances of symbiotrophic fungi were significantly decreased under elevated CO 2 and warming. ...
Climatic change conditions (elevated CO2 and warming) have been known to threaten agricultural sustainability and grain yield. Soil fungi play an important role in maintaining agroecosystem functions. However, little is known about the responses of fungal community in paddy field to elevated CO2 and warming. Herein, using internal transcribed spacer (ITS) gene amplicon sequencing and co-occurrence network methods, the responses of soil fungal community to factorial combinations of elevated CO2 (550 ppm), and canopy warming (+2 °C) were explored in an open-air field experiment for 10 years. Elevated CO2 significantly increased the operational taxonomic unit (OTU) richness and Shannon diversity of fungal communities in both rice rhizosphere and bulk soils, whereas the relative abundances of Ascomycota and Basidiomycota were significantly decreased and increased under elevated CO2, respectively. Co-occurrence network analysis showed that elevated CO2, warming, and their combination increased the network complexity and negative correlation of the fungal community in rhizosphere and bulk soils, suggesting that these factors enhanced the competition of microbial species. Warming resulted in a more complex network structure by altering topological roles and increasing the numbers of key fungal nodes. Principal coordinate analysis indicated that rice growth stages rather than elevated CO2 and warming altered soil fungal communities. Specifically, the changes in diversity and network complexity were greater at the heading and ripening stages than at the tillering stage. Furthermore, elevated CO2 and warming significantly increased the relative abundances of pathotrophic fungi and reduced those of symbiotrophic fungi in both rhizosphere and bulk soils. Overall, the results indicate that long-term CO2 exposure and warming enhance the complexity and stability of soil fungal community, potentially threatening crop health and soil functions through adverse effects on fungal community functions.
... Although there is no study about plant pathogens under elevated CO 2 in agricultural ecosystems, a recent study using a global meta-analysis and a 9-year eld experiment found that warming increased the abundances of fungal plant pathogens (Delgado-Baquerizo et al., 2020). Soil pathogenic fungi might proliferate under warming, affecting the functions and structure of the forest (Looby and Treseder, 2018). In this study, the relative abundances of symbiotrophic fungi were signi cantly decreased under elevated CO 2 and warming (Table 3). ...
Fungal communities play essential roles in ecosystems and are involved in soil formation, waste decomposition, nutrient cycling, and plant nutrient supply. Although studies have focused on soil bacterial community responses to climate change in agricultural ecosystems, only few have investigated the dynamic changes in the diversity and complexity of fungal communities in paddy fields. Herein, using internal transcribed spacer (ITS) gene amplicon sequencing and co-occurrence network methods, the responses of soil fungal community to factorial combinations of elevated CO 2 (550 ppm) and canopy warming (+2°C) were explored in an open-air field experiment in Changshu, China, for 10 years. Elevated CO 2 significantly increased the operational taxonomic unit (OTU) richness and Shannon diversity of fungal communities in both rice rhizosphere and bulk soils, whereas the relative abundances of Ascomycota and Basidiomycota were significantly decreased and increased, respectively, by elevated CO 2 . Co-occurrence network analysis showed that elevated CO 2 , warming, and their combination increased the network complexity and negative correlation of the fungal community in rhizosphere and bulk soils, suggesting that these factors enhanced the competition of microbial species. Warming resulted in a more complex network structure by altering topological roles and increasing the numbers of key fungal nodes. Principal coordinate analysis indicated that rice growth stages rather than elevated CO 2 and warming altered soil fungal communities. Specifically, the changes in diversity and network complexity were greater at the heading and ripening stages than at the tillering stage. Furthermore, elevated CO 2 and warming significantly increased the relative abundances of pathotrophic fungi and reduced those of symbiotrophic fungi in both rhizosphere and bulk soils. Overall, the results indicate that long-term CO 2 exposure and warming enhance the complexity and stability of soil fungal community, potentially threatening crop health and soil functions through adverse effects on fungal community functions.
... Multiple soil transplant and litter decomposition experiments have found that increasing temperatures, altered water status or both can change decomposition rates and have a negative influence on the capacity of TMF soils to retain organic matter, potentially turning the systems into carbon emitters (e.g. Becker & Kuzyakov, 2018;Looby & Treseder, 2018;Nottingham et al., 2019bNottingham et al., , 2016. Higher temperatures also make nutrients more readily available, with potential cascading effects on vegetation and other soil properties (Dantas de Paula et al., 2021). ...
In spite of their small global area and restricted distributions, tropical montane forests (TMFs) are biodiversity hotspots and important ecosystem services providers, but are also highly vulnerable to climate change. To protect and preserve these ecosystems better, it is crucial to inform the design and implementation of conservation policies with the best available scientific evidence, and to identify knowledge gaps and future research needs. We conducted a systematic review and an appraisal of evidence quality to assess the impacts of climate change on TMFs. We identified several skews and shortcomings. Experimental study designs with controls and long-term (≥10 years) data sets provide the most reliable evidence, but were rare and gave an incomplete understanding of climate change impacts on TMFs. Most studies were based on predictive modelling approaches, short-term (<10 years) and cross-sectional study designs. Although these methods provide moderate to circumstantial evidence, they can advance our understanding on climate change effects. Current evidence suggests that increasing temperatures and rising cloud levels have caused distributional shifts (mainly upslope) of montane biota, leading to alterations in biodiversity and ecological functions. Neotropical TMFs were the best studied, thus the knowledge derived there can serve as a proxy for climate change responses in under-studied regions elsewhere. Most studies focused on vascular plants, birds, amphibians and insects, with other taxonomic groups poorly represented. Most ecological studies were conducted at species or community levels, with a marked paucity of genetic studies, limiting understanding of the adaptive capacity of TMF biota. We thus highlight the long-term need to widen the methodological, thematic and geographical scope of studies on TMFs under climate change to address these uncertainties. In the short term, however, in-depth research in well-studied regions and advances in computer modelling approaches offer the most reliable sources of information for expeditious conservation action for these threatened forests.
... Fungal and protist saprophytes are important components involved in the remineralization of more refractory materials, including polysaccharides and lignocelluloses (Panno et al., 2013;Seymour et al., 2018). Recent studies have indicated that a large portion of enzyme production is contributed by soil (sediment) fungi (Looby and Treseder, 2018;Wentzel et al., 2019). Aquatic fungi, however, have been frequently overlooked for a long period, yet potentially play important roles in organic carbon cycling and food web dynamics (Grossart et al., 2019). ...
... The C-metabolizing enzyme BG is associated with a relatively unstable carbon pool and is a major component of cellulase, mainly involved in the hydrolysis of glycosidic bonds between atomic groups in cellulose [27]. In our study, soil warming increased the activity of BG, which is consistent with the results of Caitlin et al. [28]. Moreover, we found that BG activity was significantly negatively correlated with SOC and SWC (Table A1), indicating that the SOC decomposition rate and SWC level may be the main factors affecting its activity under warming conditions [29]. ...
In order to explore the influence of climate warming on soil microbial metabolism in the ecosystem and reveal the relationship between soil microbial metabolism limitation and environmental factors, in this study, the effects of warming on soil enzyme activities and nutrient availability were investigated by setting underground heating cables at 2 °C and 4 °C soil warming in a typical Quercus acutissima forest in the northern subtropics, and enzyme stoichiometric models were used to evaluate the limits of soil microbial metabolism. The results showed that soil warming significantly increased the activities of β-1,4-glucosidase (BG) and L-leucine aminopeptidase (LAP), and significantly increased the contents of nitrate nitrogen (NO3−-N) and available phosphorus (AP) in soil. The soil warming increased soil microbial C limitation and alleviated soil microbial P limitation. Our study showed that the change of soil microbial C and P limitation caused by warming may cause a large amount of SOM decomposition in a short period, leading to a large fluctuation of soil carbon turnover, which is not conducive to the stability of the soil C pool. This study provides important insights linking microbial metabolism to soil warming and improves our understanding of C cycling in forest systems.
... We set up eight replicate wells for each soil sample. After 3 h incubation at 25 • C under dark conditions, we added 5 µL NaOH (0.5 M) to stop the reaction, and the fluorescence was determined as described by Looby and Treseder [39]. We used nmol g −1 soil h −1 to express the EEA. ...
Soil extracellular enzymatic activity (EEA) and extracellular enzymatic stoichiometry (EES) within aggregates indicate variations in soil-nutrient effectiveness and the nutrient requirements of microorganisms. However, the responses of soil EEA and EES after introducing N2-fixing tree species into Eucalyptus plantations are poorly understood. Therefore, we examined soils from a 15-year-old pure Eucalyptus urophylla plantation (PP) and mixed E. urophylla and Acacia mangium plantation (MP) based on the theory of EEA and EES at the aggregate scale. Aggregates were separated into four fractions using a dry-sieving procedure: >2, 1–2, 0.25–1, and
... For example, a study in Puerto Rico found that throughfall exclusion altered soil C chemistry and increased the potential activities of hydrolytic C-acquiring enzymes, though a legacy of previous throughfall exclusion reduced these effects (Bouskill et al. 2013(Bouskill et al. , 2016a. Similarly, a study in a Costa Rican cloud forest found that the potential activities of extracellular fungal C-acquiring enzymes increased under warmer and drier conditions (Looby and Treseder 2018), and a laboratory study emphasized that optimal moisture and temperature conditions for enzyme activity can vary among organisms (Gomez et al. 2021). Thus, changes in moisture can alter enzyme production and activity, with the potential for ecosystem-scale alterations in nutrient cycling. ...
Changes in precipitation represent a major effect of climate change on tropical forests, which contain some of the earth’s largest terrestrial carbon (C) stocks. Such changes are expected to influence microbes, nutrients, and the fate of C in tropical forest soils. To explore this, we assessed soil microbial biomass, potential extracellular enzyme activities, and nutrient availability in a partial throughfall exclusion experiment in four seasonal lowland tropical humid forests in Panama with wide variation in precipitation and soil fertility. We hypothesized that throughfall exclusion would reduce microbial biomass and activity and accentuate dry season soil nutrient accumulation, with larger effects in wetter, less drought-resistant forests. We observed a baseline seasonal pattern of decreased microbial biomass and increased extractable dissolved organic C (DOC), total dissolved nitrogen (TDN), nitrate (NO3⁻), and resin-extractable phosphorus (P) in the dry season, with the strongest patterns for nitrogen (N). However, potential enzyme activities showed no consistent seasonality. In line with seasonal drying, throughfall exclusion decreased soil microbial biomass in the wet season and increased TDN and NO3⁻, especially in the dry season. In contrast to seasonal drying, throughfall exclusion decreased DOC and did not affect resin-extractable P, but slightly decreased potential phosphatase activities. Potential enzyme activities varied among sites and sampling times, but did not explain much variation in microbial biomass or substrate availability. We conclude that reduced rainfall in tropical forests might accentuate some dry season patterns, like reductions in microbial biomass and accumulation of extractable nutrients. However, our data also suggest new patterns, like reduced inputs of DOC to soils with drying, which could have cascading effects on soil ecological function and C storage.
... Density of fungal isolates was expressed as "colony forming units" (CFU) per g dry substrate. An analysis of the diversity of microfungal communities was based on species richness and evenness (J=H/H max , where H is the Shannon-Wiener index) (Krebs, 1999). To analyze spatial variations in the community structure, four major groups were chosen: Penicillium spp. ...
In this study, we focused on the effects of microclimatic, climatic, and anthropogenic factors on culturable microfungal communities in the soil of the north-facing slope (NFS) and the south-facing slope (SFS) at the Metzar “Evolution Canyon” in the Golan Heights, Israel. Using the soil dilution plate method, 94 species from 47 genera were isolated. The communities’ composition was subjected to pronounced interslope variations in both summer and winter. Whereas xerotolerant melanin-containing species and thermotolerant Aspergillus spp. predominated in the SFS soil, peaking in the summer, mesophilic Penicillium spp. were especially abundant in the NFS soil. The quantitative parameter—density of microfungal isolates—exhibited the strongest seasonal variations, showing that it was the most sensitive to the fluctuation in soil temperature and moisture. Comparison of microfungal communities in the currently recovered and previously disturbed SFS soil showed that intensive pasturage followed by soil degradation led to the simplification of communities, decreased their diversity level, and resulted in the prevalence of species with different ecological preferences. Comparison of the native NFS communities isolated in the summers of 2002 and 2019 revealed changes in the community structure, which could be related to global warming. These changes were associated with stress-tolerant fungal traits, which may be useful under increasing soil temperature and desiccation.
... We found that climate warming had no significant effect on the relative abundance of subsoil Ascomycota. This result aligned with reported results for tropical montane cloud forest soil (Looby and Treseder 2018). One explanation for this resistance to warming might be that Ascomycetes have regular septa with central pores which may be plugged by specialized organelles, thereby forming a structure that boosts water conservation (Treseder et al. 2014). ...
Purpose
Nitrogen (N) deposition and warming may influence microbially mediated processes and functioning of ecosystem. Our study aimed to examine how soil bacterial and fungal community composition, diversity, and interactions respond to N deposition and warming.
Materials and methods
High-throughput sequencing and bioinformatic analysis were performed to explore microbial community composition and diversity, and cohesion analysis was adopted to assess the microbial interactions after 11 consecutive years ammonium nitrate supplementation and warming in a desert steppe of Inner Mongolia, Northern China.
Results
Our results demonstrated nitrogen supplementation, warming, and N supplementation plus warming affected the bacterial and fungal community structures, and the effects were soil depth-dependent. N supplementation improved the relative abundance of copiotrophic groups (Bacteroidetes and Betaproteobacteria) and restrained oligotrophic groups (Chloroflexi, Deltaproteobacteria, and Acidobacteria) at 0–2 cm depth. N supplementation plus warming significantly increased the relative abundance of Ascomycota at 2–5 cm depth. N supplementation and N supplementation plus warming significantly reduced bacterial diversity. The redundancy analysis demonstrated that pH and N availability significantly contributed to the variation in bacterial and fungal community, respectively. N supplementation and warming simplified bacterial connectivity and improved positive cohesion: negative cohesion ratio, while warming increased fungal connectivity and reduced positive cohesion: negative cohesion ratio.
Conclusion
The effects of N supplementation and warming on bacterial and fungal community structure were soil depth-dependent. N supplementation and N supplementation plus warming reduced bacterial diversity. N supplementation and warming simplified bacterial interactions. The bacterial community was more sensitive to nitrogen supplementation and warming than fungal community.
... This is consistent with previous knowledge that soil symbiotic fungi and pathogenic fungi have different suitable environmental conditions. Soil pathogenic fungi may proliferate under warmer and drier conditions, leading to increased plant disease [65]. Similarly, the relative abundance of soil pathogenic fungi in dry valley shrubs was significantly higher than in other vegetation types, implying that potential plant pathogens could cause root rot and other diseases in dry valley shrubs (Figure 2d). ...
Soil fungi play an integral and essential role in maintaining soil ecosystem functions. The understanding of altitude variations and their drivers of soil fungal community composition and diversity remains relatively unclear. Mountains provide an open, natural platform for studying how the soil fungal community responds to climatic variability at a short altitude distance. Using the Illumina MiSeq high-throughput sequencing technique, we examined soil fungal community composition and diversity among seven vegetation types (dry valley shrub, valley-mountain ecotone broadleaved mixed forest, subalpine broadleaved mixed forest, subalpine coniferous-broadleaved mixed forest, subalpine coniferous forest, alpine shrub meadow, alpine meadow) along a 2582 m altitude gradient in the alpine–gorge region on the eastern Qinghai–Tibetan Plateau. Ascomycota (47.72%), Basidiomycota (36.58%), and Mortierellomycota (12.14%) were the top three soil fungal dominant phyla in all samples. Soil fungal community composition differed significantly among the seven vegetation types along altitude gradients. The α-diversity of soil total fungi and symbiotic fungi had a distinct hollow pattern, while saprophytic fungi and pathogenic fungi showed no obvious pattern along altitude gradients. The β-diversity of soil total fungi, symbiotic fungi, saprophytic fungi, and pathogenic fungi was derived mainly from species turnover processes and exhibited a significant altitude distance-decay pattern. Soil properties explained 31.27−34.91% of variation in soil fungal (total and trophic modes) community composition along altitude gradients, and the effects of soil nutrients on fungal community composition varied by trophic modes. Soil pH was the main factor affecting α-diversity of soil fungi along altitude gradients. The β-diversity and turnover components of soil total fungi and saprophytic fungi were affected by soil properties and geographic distance, while those of symbiotic fungi and pathogenic fungi were affected only by soil properties. This study deepens our knowledge regarding altitude variations and their drivers of soil fungal community composition and diversity, and confirms that the effects of soil properties on soil fungal community composition and diversity vary by trophic modes along altitude gradients in the alpine–gorge region.
... brown rot, soft rot, and white rot fungi (Goodell et al., 2008) efficiently decompose the recalcitrant lignocellulose matrix that other organisms are unable to decompose (Boer et al., 2005). Recent research has highlighted the role of other fungi in both decomposition forming and maintaining stable soil organic matter (SOM) pools due in part to their ability to produce a wide variety of extracellular enzymes (Sun et al., 2005;Brzostek et al., 2015;Averill, 2016;Looby and Treseder, 2018). Because fungi play an important role in organic matter degradation in soil, change in fungal biomass is a sensitive indicator of the biogeochemistry of soil function, and thus there is a need for simple and accurate tools to estimate fungal total mass and within that biomass, necromass and their turnover rates. ...
Fungi are critical components of the soil food web. Fungi are important as organic matter decom-posers, nutrient recyclers, and fungal hyphae play a role on the formation of soil aggregates that can increase water infiltration, improve water holding capacity, and sequester soil carbon (C). Ergosterol is a sterol found ubiquitously in cell membranes of filamentous fungi and is commonly used as a marker compound for fungal biomass. In contrast, the analysis of chitin is potentially effective way to monitor changes in total fungal mass (biomass and necromass) under different environmental conditions, because chitinis a more stable compound than ergosterol. By combining this analysis with our previously developed ergosterol method, we can determine both live fungal biomass and by subtraction, fungal necromass, thus providing useful information on the turnover dynamics of total fungal mass. We developed a sample preparation method based on extraction and conversion of chitin to chitosan, after which chitosan is measured by Asymmetrical Flow Field-Flow Fractionation (AF4). Our results show that this analytical method is a simple, fast, and cost-effective technique for the quantitative analysis of chitin from field-collected soils. The detection limit of this method is 6 μg g-1 chitin (chitosan) in dry soil. The final method linear range is 20-500 μg g-1 for chitin and 0.4-10 mg g-1 for fungal biomass. The developed chitin based and existing ergosterol based fungal estimation methods were used for the soil analysis. These methods can combine to determine the living and total fungal biomass.
... Saprotrophic fungi usually degrade cellulose and lignin to sustain heterotrophic growth (Hu et al., 2021). The richness of wood saprotrophs increases under warm and dry conditions (Looby and Treseder, 2018), and wood decomposition prefers a smaller C:N ratio (Hu et al., 2021). Thus, the increasingly higher temperatures and continuous N input might favor the shift. ...
The phyllosphere plays a role in alleviating air pollution, potentially leveraging the native microorganisms for further enhancement. It remains unclear how phyllospheric microorganisms respond to nitrogen oxide (NOx) pollution and participate in abatement. Here, we exposed Schefflera octophylla to NOx to reveal microbial succession patterns and interactions in the phyllosphere. During exposure, phyllospheric ammonium (NH4⁺-N) significantly increased, with different alpha diversity changes between bacteria and fungi. Community successions enclosed core taxa with relatively excellent tolerance, represented by bacterial genera (Norcardiodes, Aeromicrobium) and fungal genera (Talaromyces, Acremonium). The exposure eliminated specific pathogens (e.g., Zymoseptoria) and benefitted plant growth-promoting populations (e.g., Talaromyces, Exiguobacterium), which might favor plant disease control, improve plant health and thus buffer NOx pollution. Cooccurrence networks revealed more negative correlations among bacteria and closer linkages among fungi during exposure. Our results also showed a functional shift from the predominance of pathotrophs to saprotrophs. Our study identified microbial successions and interactions during NOx pollution and thus enlightened prospective taxa and potential roles of phyllospheric microorganisms in NOx remediation.
... As elevation increases, the decomposition rate is expected to decrease as a result of a combined effect of lower temperature (Conant et al., 2011) and slowed down metabolic efficiency of cold-adapted decomposers (Rubenstein et al., 2017). Overall, there is evidence that plant productivity (Malhi et al., 2017), and decomposition from soil organisms (Looby & Treseder, 2018) all decrease with elevation, while soil organic matter content and carbon storage increases. ...
Ecosystem productivity is largely dependent on soil nutrient cycling which, in turn, is driven by decomposition rates governed by locally adapted below-ground microbial and soil communities. How climate change will impact soil biota and the associated ecosystem functioning, however, remains largely an open question.
To address this gap, we first characterized differences in soil microbial and nematode communities as well as functional characteristics from soils collected from the foothills or in sub-alpine elevations of the Alps. We next performed a full-factorial reciprocal transplant common garden experiment at two elevations, and asked whether elevation-related functional and taxonomic differences are maintained or can be altered depending on the local climatic conditions. For this, we separately transplanted soil microbial and nematode communities from low and high elevation in their home or opposite elevation in pots added with a common plant community.
We found evidence for taxonomic and functional differentiation of the microbial and nematode communities when collected at high or low elevation. Specifically, we observed a decrease in microbial diversity and activity at high elevation, and additionally, through nematodes' functional characterization, we found increased fungal-dominated energy channels at high elevation.
Moreover, according to the reciprocal transplant experiment, while we found little effect of soil biodiversity change based on elevation of origin on plant growth and plant community composition, soils inoculated with microbes originating from low elevation respired more than those originating from high elevation, particularly when at low elevation. This observation correlates well with the observed faster carbon degradation rates by the low elevation microbial communities.
Climate change can reshuffle soil communities depending on organism-specific variation in range expansion, ultimately affecting soil fertility and carbon-cycle dynamics.
... Furthermore, plants belong to an ecosystem interacting with multiple microorganism communities, which are also affected by climate change. Studies have shown that climate changes would affect soil microbial diversity, abundances, and activities [120][121][122]. Oliveira et al. (2020) [123] studied the impact of warming and drought on fungal communities showing that under these conditions some phytopathogenic fungi, like Curvularia, Albifimbria, and Fusarium species were more abundant. ...
The climate changes expected for the next decades will expose plants to increasing occurrences of combined abiotic stresses, including drought, higher temperatures, and elevated CO2 atmospheric concentrations. These abiotic stresses have significant consequences on photosynthesis and other plants’ physiological processes and can lead to tolerance mechanisms that impact metabolism dynamics and limit plant productivity. Furthermore, due to the high carbohydrate content on the cell wall, plants represent a an essential source of lignocellulosic biomass for biofuels production. Thus, it is necessary to estimate their potential as feedstock for renewable energy production in future climate conditions since the synthesis of cell wall components seems to be affected by abiotic stresses. This review provides a brief overview of plant responses and the tolerance mechanisms applied in climate change scenarios that could impact its use as lignocellulosic biomass for bioenergy purposes. Important steps of biofuel production, which might influence the effects of climate change, besides biomass pretreatments and enzymatic biochemical conversions, are also discussed. We believe that this study may improve our understanding of the plant biological adaptations to combined abiotic stress and assist in the decision-making for selecting key agronomic crops that can be efficiently adapted to climate changes and applied in bioenergy production.
... Soil microorganisms were hard to decipher, since they could be opportunistic (sensitive or tolerant) to freezing-thawing cycles [41,42]. Sensitive fungi have been sabotaged during rapid climate change [43], and recovery of these sensitive microorganisms is difficult since available water can be constrained [44]. Fungi with desiccation tolerance can remain active and produce biomass during water limitations and sub-zero temperatures [45]. ...
Rice is a staple food for the world’s population. However, the straw produced by rice cultivation is not used sufficiently. Returning rice straw to the field is an effective way to help reduce labor and protect the soil. This study focused on the effect of water-covered depth with the freeze–thaw cycle on rice straw decomposition and the soil fungal community structure in a field in Northeast China. The field and controlled experiments were designed, and the fungal ITS1 region was tested by high-throughput sequencing for analyzing the fungal communities in this study. The results showed that water coverage with the freeze–thaw cycle promoted the decomposition of rice straw and influenced the fungal community structure; by analyzing the network of the fungal communities, it was found that the potential keystone taxa were Penicillium, Talaromyces, Fusarium, and Aspergillus in straw decomposition; and the strains with high beta-glucosidase, carboxymethyl cellulase, laccase, lignin peroxidase, and manganese peroxidase could also be isolated in the treated experiment. Furthermore, plant pathogenic fungi were found to decrease in the water-covered treatment. We hope that our results can help in rice production and straw return in practice.
... *p < 0.05; **p < 0.01; ***p < 0.001 biotic factor affecting the levels of EA (Kaiser et al. 2010). Fungi are often claimed to be responsible for the production of the majority of extracellular enzymes in soil that degrade labile and recalcitrant C and N polymers (Schneider et al. 2012;Looby and Treseder 2018). We found that both F:B and G + :G − ratio were significantly correlated with EA in the open area (Table 4), and our previous study has shown that F:B and G + :G − ratio in the open area are significantly higher and lower, respectively, than the afforested lands . ...
Soil organic matter (SOM) decomposition is regulated by a complex set of enzymes. However, the influences of biotic and abiotic factors on spatial variations of soil enzyme activity (EA) within ecosystems remain unresolved. Here, we measured EA at different locations within two afforested lands (coniferous woodland and leguminous shrubland), and simultaneously collected data on soil physico-chemical, vegetation-related, and microbial properties to identify the determinants of EA spatial patterns. The results showed that soil organic C and total N contents were the predominant abiotic factors in regulating absolute EA (EA per unit of oven-dry soil mass) in both afforested lands, while soil pH was the predominant factor in regulating specific EA (EA per unit of microbial biomass (MB)). However, the predominant biotic factors varied with the afforested type: the root biomass and MB were the determinants of EA in the shrubland, whereas the tree distribution, litter and root biomass, and bacterial biomass were the determinants in the woodland. Vegetation-related factors (i.e., litter and root biomass) indirectly influenced soil EA by regulating the soil abiotic factors. Compared with the MB, microbial community composition had a minor impact on EA. The variance of specific EA (EA per unit of MB or SOM) explained by selected factors was much lower than that of absolute EA. In addition, the enzymatic C/N ratio within ecosystems did not follow a general pattern (1:1) observed at a global scale. Our results provide novel experimental insight into ecosystem-level spatial variability of C and N cycling via enzymes, suggesting that soil abiotic factors are more reliable than biotic factors to reflect EA spatial patterns across afforested systems.
... Due to greater exposure to solar radiation, elevated soil temperature may rapidly increase enzyme activity and consequently higher organic carbon degradation and mineralization Rev Bras Cienc Solo 2022;46:e0210109 rates (Hou et al., 2016;Liu et al., 2019). This is a highly undesirable effect given our scenario of increased global average temperatures and the intensified greenhouse effect (Hassan et al., 2015;Looby and Treseder, 2018). However, temperature increases above the optimal limits for enzymes can reduce their half-life, substrate affinity and catalytic efficiency due to conformational changes and protein denaturation (Wallenstein et al., 2010;Alvarez et al., 2018). ...
Extracellular soil enzymes are fundamental for the functioning of ecosystems. Several processes in the soil depend on the activity of these enzymes, including plant decomposition, soil organic matter formation/mineralization, and nutrient cycling. Moreover, extracellular enzyme activity occurs in the soil and is therefore influenced by environmental factors. Due to the high sensitivity to these factors, extracellular enzymes are used for monitoring soil quality. This review aimed to present the main contributions of soil enzymes to agriculture, emphasizing the dynamics of elements in the soil and the environmental factors that modulate enzyme activity. With this knowledge, the relationship of extracellular enzymes to soil quality is demonstrated and their use as a tool for soil monitoring. Finally, the evolution of research on soil enzymes in Brazil is presented, and the perspectives of basic and applied studies necessary to expand the knowledge and use of enzymes in soil management are pointed out. Soil enzymes play a key role in numerous soil processes, thereby making them useful indicators of productive capacity and soil quality. Research on enzymes in soil has developed significantly in the last two decades, which has made it possible for farmers to analyze and interpret enzyme activity in the soil in the laboratory.
... Fungi are the primary decomposers in soil and typically dominate the decomposition of the polymerised fraction of residues, such as cellulose and lignin (Poll et al., 2008;Zhan et al., 2021). The co-decomposition of RS and MV could affect the fungal community because fungi are sensitive to changes in nutrient availability and ecological niches (Looby and Treseder, 2018). A previous study confirmed that fungal abundance and diversity were higher in residue mixtures than in the presence of single residues (Santonja et al., 2017), because of an increase in the diversity of associated niches and substrates for fungal decomposers. ...
The co-incorporation of rice straw (RS) and milk vetch (MV) into paddy fields has been increasingly applied as a sustainable farming practice in southern China. Our previous study revealed the contribution of bacteria to the co-decomposition of the RS and MV mixture, although additional underlying factors driving the co-decomposition process need to be clarified. The present study further determined the succession of fungal communities and enzyme activity in the co-decomposition process of the RS and MV mixture. The results showed that non-additive synergistic effects on biomass loss were observed in 55.6% of the sampled RS and MV mixture during the co-decomposition process, stimulating mixture decomposition. Overall fungal abundance was 19.6-30.6% higher in the RS and MV mixture throughout the study than in the single residue. Fungal diversity and community structure were mainly affected by the sampling date rather than the type of residue. Specifically, mixing RS and MV significantly increased the abundance of Peziza sp. and Reticulascus tulasneorum (lignocel-lulose-and lignin-decomposing fungi) and exhibited higher activities of C-and N-related hydrolases than monospecific residues. Random forest (RF) models showed that bacteria contributed more to the residue decomposition and activities of C-related hydrolases, N-related hydrolases, and oxidases than fungi. However, both RF and partial least squares path models revealed that fungal abundance and community structure directly or indirectly affected the residue decomposition rate. These findings showed that mixing RS and MV could stimulate their decomposition by enhancing C-related hydrolase activity and Peziza sp. and Reticulascus tulas-neorum abundance.
... >1000 yrs) temperature differences can drive changes in the microbial community (Looby et al., 2016;Nottingham et al., 2018), although for many sites elevation-related variation in other factors such as rainfall, geology and plants are more important for determining community composition (Geml et al., 2014;Singh et al., 2014;Selmants et al., 2016). The experimental translocation of soil across tropical elevation gradients, to impose temperature change (Tito et al., 2020), has also been shown to change the microbial community composition after 10 months (Looby and Treseder, 2018) and five years (Nottingham et al., 2019b); whether these community shifts under short to medium term (e.g. 1-10 yrs) temperature change are associated with altered growth-adaptation of the community is not yet clear. ...
The response of soil microbial activity to climate warming has been predicted to have a large destabilising effect on the carbon cycle. However, the nature of this feedback remains poorly understood, especially in tropical ecosystems and across annual to decadal timescales. We studied the response of bacterial community growth to 2 and 11 years of altered temperature regimes, by translocating soil across an elevation gradient in the tropical Andes. Soil cores were reciprocally translocated among five sites across 3 km in elevation, where mean annual temperature (MAT) ranged from 26.4 to 6.5oC. The bacterial community growth response to temperature was estimated using a temperature Sensitivity Index (SI): the log-ratio of growth determined by leucine incorporation at 35oC:4oC. Bacterial communities from soil translocated to their original site (controls) had a growth response assumed to be ‘adapted’ to the original MAT. Translocating soil downslope (warming) resulted in an increased SI relative to their original growth response, and vice versa under cooling, indicating community-level adaptation over the incubation period to the altered MAT. The average level of adaptation (i.e., the extent to which SI converged on the control values) was 77% after 2 years, and was complete after 11 years. The adaptive response was greater when soil was warmed rather than cooled: instances of complete adaptation of SI occurred in soils after 2 years when warmed, but only after 11 years when they were cooled. Taken together, our results show that the majority of the growth adaptation to warming by the bacterial community occurs rapidly, within 2 years, whilst growth adaptation to cooling occurs within a decade. Our analysis demonstrates rapid warm-adaptation of bacterial community growth, with potential consequences for the temperature sensitivity of soil carbon cycling in response to future climate warming.
... Among microbial parameters, only fungal community composition was a significant factor influencing wood decay (Table 1). Saprotrophic fungi colonizing soil, litter and wood are considered to be the most efficient decomposers (van der Wal et al., 2013;Eichlerová et al., 2015), and among them, wood saprotrophs degrade or modifying recalcitrant carbon, like lignin (Folman et al., 2008;Looby and Treseder, 2018). In the young forest, even though total fungal abundance was lower, relative abundance of wood saprotrophs was higher than in old and uncut forests (Fig. 6) which may contribute to higher decomposition rate there. ...
Wood decomposition is regulated by microbial community and soil conditions and plays an important role in global carbon cycling. Among many factors, local conditions, associated with forest age and the leaf litter adjacent to decaying wood may directly and indirectly influence microbial colonization and rate of decay. In this study, wood sticks with and without leaf litter were buried in young (50–70 years), old (120–150 years) and uncut (over 200 years) forests at the Smithsonian Environmental Research Center (SERC), Maryland, USA to test hypotheses about woody and foliar litter interaction during decomposition and whether decay rates are associated with differences in microbial community and soil properties. At the early stages of decomposition, wood mass loss in the young forests was significantly higher than that in other two forests but was not different between old and uncut forests. Adjacent foliar litter increased functional diversity of wood colonizing fungi, and enhanced decay in old and uncut stands. Factors, significantly correlated with decomposition, included fungal community composition, soil moisture, pH and C:N ratio. This study highlights the importance of local factors, such as land use and forest age affecting wood decomposition rates.
... The extreme climatic events, such as successive simulated droughts and flood are major evidence of climate change impacting the vegetation and human in any part of the globe [8,14,17,18]. It has been reported in the literature that populations of forest pests and diseases such as the spruce beetle, pine beetle, spruce budworm, woolyadelgid, soil fungi and extracellular enzyme activity are increasing as a result of climate change [19]. The effect of this extreme climatic event was examined by Raquel, Montalto [20] and Loeb [21], and the studies investigated the impacts of successive simulated droughts and floods on some plant species (i.e. ...
Purpose of Review
The impacts of climate change on biodiversity in the last three decades have increasingly assumed from significant to threatening proportions and this causes major global concerns. This study aims at examining the recent and future impacts of global climate change on both ecological resources and human well-being. This review study is based on the general concept of ecological resilience: that coping with climate change stresses and disturbances depends on social resilience, political and environmental strategies accessible in a community. The study assessed over 300 peer-reviewed publications, both articles and books, which linked climate change impacts on ecosystems to social/health resilience of people in the specific regions. Publications on that were focused on general impacts of climate change on global ecology, ecosystem distribution shifts and phenology change; the ecological and social/health resilience, in the tropic and polar regions, were reviewed.
Recent Findings
The major finding of this study is that there is considerable variation in magnitudes and patterns of responses to climate change in different regions, even with an overall review of scientific studies on the global ecosystem and human health. Despite this, what is obvious is that change in the ecosystem in Polar Regions will continue to have significant impacts on the global environment, flora, fauna and ultimately human well-being.
Summary
There are many uncertainties, though, on the possible effects of climate change ecosystem and soils and their severe biological, social, cultural and economic consequences. Notwithstanding these uncertainties, the impacts of climate change on both ecosystem and human socio-cultural activities are very likely to become even more widespread in the near future.
... Soil fungi may play a role in determining soil EEA as they are responsible for a large portion of enzyme production. Shifts in the fungal community could affect decomposition through changes in EEA (Looby and Treseder 2018). However, little is known about how soil fungi and EEA would change with the degree of degradation and the duration of enclosure in rangeland. ...
Degradation and enclosure can change plant composition and soil properties , thereby alter soil microbial community, diversity and activity. This study used high-throughput sequencing and microplate fluorometric to determine the patterns of soil fungal community and extracellular enzyme activity (EEA) under degradation and restoration on the Tibetan Plateau. Three degradation (including: non-degraded, DN; moderately degraded, DM; and severely degraded, DS) and three enclosure (including: 5 years, EI; 10 years, EII; and 15 years, EIII) treatments were set up. DM and DS increased the species richness of fungi compared with DN. EI decreased the fungal diversity compared with DS while EII significantly increased it. DM significantly increased EEA while DS had no significant effect on any EEA compared to DN. EI decreased EEA (significant for βX), EII increased EEA (significant for βG) compared with DS while EIII had no significant effect. This variation of EEA among different degradation and enclosure treatments could be partially explained by soil properties and fungal community but had no relation with plant properties. The degradation could change soil fungi and extracellular enzyme activity and may adversely affect vegetation health in the alpine ecosystem. Enclosure could partially reverse these changes, but long-term field experiments are still needed. ARTICLE HISTORY
... After incubation in the dark at 25°C for 3 h, 5 µL 0.5 M NaOH was added to each well to terminate activity. Fluorescence was measured at 365 nm excitation and 450 nm emission with a fluorescence microplate reader (Thermo Multiskan Spectrum; Looby and Treseder, 2018). Activity of oxidase (PhOχ and perox) was determined with L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate and L-DOPA plus 0.3% H 2 O 2 to measure perox activity (Saiya-Cork et al., 2002). ...
Microbial communities and their associated enzyme activities affect carbon (C), nitrogen (N), and phosphorus (P) metabolism in soils. We used phospholipid fatty acids (PLFAs) analysis and extracellular enzyme activity assays to evaluate the effects on topsoil microbial community and nutrient transformation of converting Chinese fir (CF) plantations to native broadleaf (Castanopsis hystrix [CH] and Mytilaria laosensis [ML]) plantations in this study. We found that CH and ML plantations had significantly higher soil organic C (SOC), total N (TN), NH4⁺-N, soil C/N ratios (C/Nsoil), soil C/P ratios (C/Psoil) and soil N/P ratios (N/Psoil) but significantly lower total P (TP) compared to CF plantations. A distinct shift in soil microbial community composition, but not microbial biomass was evident 23 years after stand conversion. Redundancy analysis (RDA) showed that soil microbial community composition was substantially influenced by litterfall mass (LF), TP, N/Psoil, SOC, fine root biomass (FR), C/Nsoil, TN, litter C/N ratios (C/Nlitter), and C/Psoil; of these, LF appeared to be the primary driver of differences in soil microbial community composition (p < 0.05). In addition, the total activity of hydrolytic enzymes involved in C metabolism (β-glucosidase and cellobiohydrolase), N metabolism (N-acetyl-glucosaminidase), and P metabolism (acid phosphatase) increased significantly in the two native broadleaf plantations, whereas the total activity of oxidase (phenol oxidase) decreased significantly. Furthermore, the change trends of specific enzyme activity (i.e., enzymes per unit microbe) were similar to total enzyme activity. The dynamics of soil microbial enzymatic activity after stand conversion provide a functional link between changes in microbial community composition and soil nutrient transformation. Our findings suggest a mechanism in native, non-N2-fixing broadleaf tree species that stimulates soil nutrient transformation in subtropical planted forests with low P via increases in the quantity and quality of litter and the physiological function per unit of microbial biomass.
... Climate change is expected to increase the mean temperature by more than 2 � C and alter precipitation patterns in the upcoming decades, including substantial rainfall increases or decreases of at least 20% in some tropical regions (IPCC, 2018;Chadwick et al., 2016;Brown and Caldeira, 2017). These changes will affect not only the growth of aboveground vegetation but also the belowground soil environment and directly or indirectly affect the dynamics of soil microbial communities (Flury and Gessner, 2011;Amend et al., 2016;Looby and Treseder, 2018;Oliveira et al., 2020). The shifts in their communities are expected to affect ecosystem functions, such as decomposition, nutrient cycling, and plant-microbe interactions, through changes in extracellular enzyme activities (EEA) (Bouskill et al., 2016). ...
Climate change is expected to affect rainfall dynamics and the global average temperature. Here, we evaluated the effects of those changes, the intense water deficit and warming (+2 °C), on a tropical grassland soil. We tested the correlation between soil extracellular enzyme activities (EEA) and soil respiration (CO2 efflux) and temperature and soil water content (SWC). A climate change simulation was performed in a field experiment using a temperature free-air-controlled enhancement facility. SWC was the main driver of changes in EEA. The most affected enzymes were β-glucosidase, xylanase and phosphatase. As SWC declined, the potential activity of β-glucosidase and xylanase decreased, while the activity of phosphatase and CO2 efflux increased (P < 0.01). Thus, intense drought periods are likely to have a greater influence on the rates of decomposition and mineralization in the evaluated soil than is the 2 °C increase in mean temperature.
... Soil temperature and soil pH decrease, while soil moisture and soil C:N ratios increase (Marrs et al., 1988), which influence decomposition through changes in microbial communities and extracellular enzyme activity (de Boer et al., 2006). Extracellular enzyme activity is higher under warmer, drier conditions in tropical forests (Looby and Treseder, 2018). Although responses of plants to climate have been widely studied aboveground, parallel changes occur belowground where soils, strongly nutrient limited in mountains (Tanner et al., 1998), play a major role in plant growth (Fisher et al., 2013;Mohl et al., 2019). ...
Premise:
Clouds have profound consequences for ecosystem structure and function. Yet, the direct monitoring of clouds and their effects on biota is challenging especially in remote and topographically complex tropical cloud forests. We argue that known relationships between climate and the taxonomic and functional composition of plant communities may provide a fingerprint of cloud base height, thus providing a rapid and cost-effective assessment in remote tropical cloud forests.
Methods:
To detect cloud base height, we compared species turnover and functional trait values among herbaceous and woody plant communities in an ecosystem dominated by cloud formation. We measured soil and air temperature, soil nutrient concentrations, and extracellular enzyme activity. We hypothesized that woody and herbaceous plants would provide signatures of cloud base height, as evidenced by abrupt shifts in both taxonomic composition and plant function.
Results:
We demonstrated abrupt changes in taxonomic composition and the community- weighted mean of a key functional trait, specific leaf area, across elevation for both woody and herbaceous species, consistent with our predictions. However, abrupt taxonomic and functional changes occurred 100 m higher in elevation for herbaceous plants compared to woody ones. Soil temperature abruptly decreased where herbaceous taxonomic and functional turnover was high. Other environmental variables including soil biogeochemistry did not explain the abrupt change observed for woody plant communities.
Conclusions:
We provide evidence that a trait-based approach can be used to estimate cloud base height. We outline how rises in cloud base height and differential environmental requirements between growth forms can be distinguished using this approach.
... Studies have shown that many archaea are capable of ammonia oxidation and thus are important in the nitrogen cycle (Tripathi et al., 2015). As the primary decomposers, soil fungi produce extracellular enzymes that break down specific forms of carbon (Looby & Treseder, 2018). Therefore, changes in the assembly and activity of soil microbial communities can affect the Responsible editor: Huaiying Yao Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11368-020-02608-0) ...
PurposeThe knowledge regarding how different soil microbial groups change in subalpine forest areas after clear-cutting is limited. To bridge this gap, we studied the change patterns of the different soil microbial community assemblies and their determining factors in subalpine areas.Materials and methodsField measurements and sampling were conducted in three stands at different stages of natural restoration (BF, broadleaf forest; MF, mixed coniferous and broadleaf forest; and PCF, primeval coniferous forest) after clear-cutting in western Sichuan Province, China. Three soil microbial group (bacteria, fungi, and archaea) community assemblies, edaphic properties, soil nematodes, tree diameter at breast height, plant richness, and understory vegetation biomass were examined and statistically analyzed.Results and discussionThe α-diversity of the three microbial groups in the BF and MF stands was significantly higher than that in the PCF stand. The difference between the stands was greater than the difference within the stands for all three microbial groups. The changes in the three microbial groups were all significantly associated with shifts in soil carbon, soil total nitrogen, soil available nitrogen, and tree species composition. The bacterial and archaeal communities were also closely related to the bacterivore number. Acidobacteria, Actinobacteria, Bacteroidetes, Planctomycetes, Basidiomycota, Ascomycota, and Thaumarchaeota were the main phyla that responded to environmental variation.Conclusions
The three soil microbial groups all showed regular trends across the three different stands. The changes in the soil microbial community assembly were mainly attributed to the differences in soil nutrients, tree species composition, and feeding traits of soil nematodes.
... The extreme climatic events, such as successive simulated droughts and flood are major evidence of climate change impacting the vegetation and human in any part of the globe [8,14,17,18]. It has been reported in the literature that populations of forest pests and diseases such as the spruce beetle, pine beetle, spruce budworm, woolyadelgid, soil fungi and extracellular enzyme activity are increasing as a result of climate change [19]. The effect of this extreme climatic event was examined by Raquel, Montalto [20] and Loeb [21], and the studies investigated the impacts of successive simulated droughts and floods on some plant species (i.e. ...
Purpose of Review: The impacts of climate change on biodiversity in the last three decades have increasingly assumed from significant
to threatening proportions and this causes major global concerns. This study aims at examining the recent and future impacts of global
climate change on both ecological resources and human well-being. This review study is based on the general concept of ecological
resilience: that coping with climate change stresses and disturbances depends on social resilience, political and environmental strategies
accessible in a community. The study assessed over 300 peer-reviewed publications, both articles and books, which linked climate
change impacts on ecosystems to social/health resilience of people in the specific regions. Publications on that were focused on general
impacts of climate change on global ecology, ecosystem distribution shifts and phenology change; the ecological and social/health
resilience, in the tropic and polar regions, were reviewed.
Recent Findings :The major finding of this study is that there is considerable variation in magnitudes and patterns of responses to
climate change in different regions, even with an overall review of scientific studies on the global ecosystem and human health.
Despite this, what is obvious is that change in the ecosystem in Polar Regions will continue to have significant impacts on the
global environment, flora, fauna and ultimately human well-being.
Summary: There are many uncertainties, though, on the possible effects of climate change ecosystem and soils and their severe
biological, social, cultural and economic consequences. Notwithstanding these uncertainties, the impacts of climate change onboth ecosystem and human socio-cultural activities are very likely to become even more widespread in the near future.
... Most studies have shown that the dominance, diversity, growth, and activities of microbes are altered in response to climate change (Flury & Gessner, 2011;Amend et al., 2016;Solly et al., 2017;Looby & Treseder, 2018;Meisner, Jacquiod, Snoek, Ten Hooven & van der Putten, 2018;Ochoa-Hueso et al. 2018;Schmidt et al. 2018). Here, we observed contrasting effects of warming and drought on fungal communities. ...
Climate change is predicted to cause more extreme events, such as heatwaves, and different precipitation patterns. The effects of warming and short‐term drought on soil microbial communities, in particular fungal communities, remain largely unexplored under field conditions. Here, we evaluated how the fungal community of a tropical grassland soil responds to these changes. A field experiment was carried out in a temperature free‐air controlled enhancement (T‐FACE) facility in Ribeirão Preto, Brazil. The isolated and combined effects of drought and a 2 °C increase in temperature were investigated. Based on metabarcoding of the ITS2 region, a total of 771 OTUs were observed. While warming affected the community structure, drought affected the alpha diversity, and the interaction between warming and drought affected both diversity and structure. The change in community composition driven by warming affected only the less abundant species (>1% of the total sequences). The most affected aspect of the fungal communities was the diversity, which was increased by drought (P<0.05), mostly by reducing the dominance of a single species, as observed in the watered plots. In a phylogenetic context, some fungal taxa were favored by changes in temperature (Hypocreales) and drought (Sordariales) or disadvantaged by both (Pleosporales). It is worth highlighting that a water deficit increased the abundance of phytopathogenic fungi, such as Curvularia, Thielavia, and Fusarium species. Overall, our results provide evidence that fungal communities in tropical grassland soils have greater sensitivity to drought than to temperature, which might increase the incidence of certain soil‐borne diseases.
Patterns of microbial diversity on elevational gradients have been extensively studied, but little is known about those patterns during the restoration of earthquake-fractured alpine ecosystems. In this study, soil properties, soil enzyme activities, abundance and diversity of soil bacterial and fungal communities at four positions along a 2.6-km elevational gradient in the Snow Treasure Summit National Nature Reserve, located in Pingwu County, Southwest China. Although there were no significant changes in the soil chemical environment, bacterial and fungal communities were significantly different at different elevations. The overall fungal community presented an N-shaped diversity pattern with increasing elevation, while bacterial diversity decreased significantly with elevation. Changes in microbial diversity were associated with soil phosphorus, plant litter, and variations in dominant microbial taxa. Differences in enzyme activities among elevations were regulated by microbial communities, with changes in catalase and acid phosphatase activities mainly controlled by Acidobacteria and Planctomycetaceae bacteria, respectively (catalase: p < 0.001; acid phosphatase: p < 0.01), and those in β-glucosidase, sucrase, and urease activities mainly controlled by fungi. The β-glucosidase and sucrase were both positively correlated with Herpotrichiellaceae , and urease was positively correlated with Sebacinaceae ( p < 0.05). These findings contribute to the conservation and management of mountain ecosystems in the face of changing environmental conditions. Further research can delve into the specific interactions between microbial communities, soil properties, and vegetation to gain deeper insights into the intricate ecological dynamics within earthquake-prone mountain ecosystems.
Dissolved organic carbon (DOC) pool in seawater plays an important role in long-term carbon sequestration in seagrass meadows. Microbial activities (microbial communities and their extracellular enzymes) are the key determining factors of DOC decomposition and sequestration potential, and are affected by nutrient enrichment. However, there is little information on the response of microbial communities and carbon-degrading extracellular enzymes to nutrient loading within seagrass meadows, limiting our understanding of the driving mechanism of DOC decomposition under nutrient enrichment. Here, microbial communities (including bacteria and fungi) and representative extracellular enzyme activity (EEA) in three seagrass meadows with different nutrients levels were investigated across four seasons. Water temperature was the driving factor influencing the seasonal dynamics of EEAs. In addition, the hydrolysis rates of chitinase, β-glucosidase, and α-glucosidase were significantly higher at a high nutrient loading seagrass meadow than at a low nutrient loading meadow. Furthermore, higher relative abundance of bacterial groups, such as Actinobacteria, Bacteroidetes, Cellvibrionale, and Verrucomicrobia were in according with enhanced EEAs, suggesting that these K-strategists were likely involved in enzyme production and the subsequent remineralization of organic matter in seagrass meadows. In contrast with the bacterial community, fungal communities were not sensitive to nutrient concentrations, and there was no strong association between the given fungal groups and EEA. This may be attributed to the low taxonomic resolution of marine planktonic fungi or the minor role of fungi in EEA production. Overall, these results suggested that nutrient loading enhanced EEA levels, modified bacterial rather than fungal communities, and consequently accelerated DOC remineralization, thereby reducing DOC contribution potential of seagrass ecosystems to long term carbon sequestration.
Decomposer fungi play a fundamental role in terrestrial ecosystem dynamics. In the southwestern United States, climate change is causing more frequent and severe droughts, which may alter fungal community composition and activity. Investigating relationships between fungal traits may improve the prediction of fungal responses to drought. In this dual field and laboratory experiment, we examine whether trade‐offs occur between traits associated with drought. Specifically, we test the hypothesis that fungi sort into lifestyles specializing in growth yield, resource acquisition, and drought stress tolerance (“YAS” framework). For the field experiment, we constructed microbial “cages” containing sterilized litter and 1 of 10 fungal isolates. These cages were placed in long‐term drought and control plots in a southern Californian grassland for 6 and 12 months. We measured fungal hyphal length per unit litter mass loss for growth yield, the potential activities of four extracellular enzymes for resource acquisition, and the ability to grow in the drought versus control plots for drought stress tolerance. We compared these results with a laboratory microcosm experiment constructed with the same fungal isolates and that measured the same fungal traits. The field experiment corroborated our laboratory results, in that no trade‐offs were observed between growth yield and resource acquisition traits. However, in contrast to the laboratory experiment, drought tolerance was negatively related to extracellular enzyme activity and growth yield in the field, implying a trade‐off. Despite this observed trade‐off in the field, growth yield was not hindered by drought. We propose a modification to the YAS framework, by combining the growth yield and resource acquisition lifestyles, which may be more appropriate for this arid system. This joint laboratory and field approach contextualizes a theoretical framework in microbial ecology and improves understanding of fungal community response to climate change.
Soil enzymes are the most potent bioactive components in forest ecosystems. Cellulases and ligninases are vital carbon (C)-degrading enzymes that target different C pools. The ratio of ligninase-to-cellulase activity is good indicator for microbial soil C preference, play an important role in soil C cycling. However, our understanding of enzyme ratios and their drivers across forest ecosystems remains unclear. In this study, we hypothesized that (i) the ligninase-to-cellulase ratio increased from temperate forests to tropical forest ecosystems, and (ii) the dominant factors would be microbial abundances. About 2–3 kg of topsoil (0–10 cm) from each of the ten forest ecosystems were collected across a 3425 km gradient in China between July and August 2019. We analyzed the biogeographic patterns of ligninase and cellulase activities and the ratio of ligninase-to-cellulase activities to determine how this ratio responded to climatic factors, soil properties and substrates, and microbial abundances across the forest ecosystems along the latitudinal gradient. Our findings showed that the average soil ligninase activity was 3.49 nmol h⁻¹ g⁻¹, whereas the average soil cellulase activity was 525.26 nmol h⁻¹ g⁻¹ across the forest ecosystems sampled. The average activity ratio of ligninase-to-cellulase in tropical forest ecosystems was 27.9% higher than that in subtropical forests and 64.2% higher than that in temperate forest ecosystems. The partial least squares path model demonstrated that the ligninase-to-cellulase activity ratio was significantly negatively correlated with soil substrates (r = -0.94, p < 0.001) and significantly positively correlated with microbial abundances (r = 0.38, p < 0.01). The variation partitioning analysis further revealed that soil substrates explained 19.4% variation regarding ligninase-to-cellulase ratio, whereas microbial abundance (fungal abundance) contributed 2.8%. This study provides crucial information about the distribution of enzyme ratios along the latitude gradient, highlights the microbial utilization of recalcitrant C pools in tropical forests, and provides an insight into the response of the global C cycle under a changing climate.
Soil fungi are vital to forest ecosystem functions, in part through their role mediating tree responses to environmental factors, as well as directly through effects on resource cycling. While the distribution of these key taxa may vary with a suite of abiotic and biotic factors, the relative role of host species identity on soil fungal community composition and function remains unresolved. In this study, we used a combination of amplicon sequencing and enzymatic assays to assess soil fungal composition and associated function under three tree species, Quercus rubra, Betula nigra, and Acer rubrum, planted individually and in all combinations in a greenhouse, with added fungal inoculum collected below mature field trees. Across treatments, fungal communities were dominated by the phylum Ascomycota, followed by Basidiomycota and Mortierellomycota. Nonetheless, fungal communities differed between each of the solo planted treatments, suggesting at least some taxa may associate preferentially with these tree species. Additionally, fungal community composition under mixed sapling treatments broadly differed from solo saplings. The data also suggests that there were larger enzymatic activities in the solo treatments as compared with all mixed treatments. This difference may be due to the greater relative abundance of saprobic taxa found in the solo treatments. This study provides evidence of the importance of tree identity on soil microbial communities and functional changes to forest soils.
Permafrost peatlands are important pools of soil carbon. Soil organic carbon (SOC) mineralization and its temperature sensitivity in permafrost peatlands are crucial for predictions of soil carbon-climate feedback. However, little is known about the changes in SOC mineralization and its mechanism in response to environmental change in the permafrost peatlands of Northeastern China. We collected seven permafrost peatland soils from Greater and Lesser Khingan Mountains in Northeastern China to investigate how the responses of microbes and labile substrates control the mineralization of SOC in the laboratory incubation study. The results show that temperature and sampling sites affected the mineralization of SOC. Elevated temperatures significantly increased the rate of carbon mineralization across the peatland soils. The mean sensitivity of SOC mineralization to temperature (Q10 value) was 2.96. The increase in substrate availability and microbial abundance in parallel with the increase in temperature is responsible for the high rates of decomposition of the organic carbon pools. We found that the mineralization of soil carbon positively correlated with the concentrations of soil dissolved organic carbon (DOC), NH4⁺-N, NO3⁻-N, as well as the abundances of bacteria, fungi, methanotrophs and nirK denitrifiers. Moreover, the content of DOC positively correlated with the abundances of soil bacteria, methanotrophs and nirK denitrifiers, indicating that the influences of soil microbial abundances on carbon mineralization were strongly mediated by the availability of carbon substrates. Our findings provide novel insights into the effects of increasing temperatures on the relationship between microbial communities and labile substrates and their roles in carbon decomposition in permafrost peatlands.
The impact of forest microhabitats on physiochemical properties of the soil and that of microbial communities on tropical soils remain poorly understood. To elucidate the effect of tropical forest stand on leaf litter and soil microbial communities, we studied enzyme activities, microbial biomass, and diversity in three distinct microhabitats in terms of plant richness, diameter at breast height (DBH), and physiochemical properties of soil and litter, each associated with a different Vanilla sp. In the soil, positive correlations were found between electrical conductivity (EC) and total organic carbon (TOC) with phosphatase activity, and between nitrogen (N) and water-soluble carbon (WSC) content with urease activity (UA). In the litter, the water content was positively correlated with bacterial and fungal biomass, and N and WSC contents were positively correlated with fungal biomass. Positive correlations were found between plant richness and UA in the soil, plant richness and fungal biomass in the soil and litter, and DBH and fungal biomass in the litter. Amplicon sequencing revealed differences between microhabitats in the relative abundance of some fungal and bacterial taxa and in the bacterial community composition of both litter and soil. Bacterial richness and diversity were different between microhabitats, and, in litter samples, they were negatively correlated with DBH and plant richness, respectively. By contrast, none of the soil and litter physiochemical properties were significantly correlated with microbial diversity. Our results show that significant shifts in enzyme activity, microbial biomass, and diversity in the microhabitats were driven by key abiotic and biotic factors depending on the soil or litter sample type.
Logging and forest conversion are occurring at alarming rates in the tropical forests. These disturbances alter soil chemistry and microbial diversity, and disrupt carbon cycling through shifts in litter decomposition. Direct links between microbial diversity and soil properties such as pH are well established; however, the indirect impacts of logging and forest conversion on microbial diversity and litter decomposition are poorly understood. We investigated how soil properties and soil functions change across a forest recovery gradient in the tropical montane forests of Malaysian Borneo. We used surface (top 5 cm) soil to assess soil physicochemical properties, next-generation DNA sequencing to assess soil microbial diversity, and standardized litterbags to assess litter decomposition and stabilization. Our results show that soils of the older forests harbored significantly greater microbial diversity, decomposed litter faster, and stabilized greater amounts of litter than soils of the younger forests and converted sites. These results suggest that logging and forest conversion significantly affect soil microbial diversity and can have lasting effects on carbon cycling in tropical montane forests.
Despite the enormous size of the organic nitrogen (N) pool contained in mineral subsoils, rates of N cycling and soil exoenzyme activities are rarely measured in soils below 10 or 20 cm depth. Furthermore, assumed relationships between N mineralization rates and the activities of various decomposition exoenzymes are poorly characterized. We measured rates of gross and net N mineralization and nitrification as well as the potential activities of hydrolytic and oxidative enzymes at five soil depths (forest floor to 50 cm) in Spodosols at three hardwood forests of varying age (45 and 100 years post-harvest and old growth) at and near the Hubbard Brook Experimental Forest in New Hampshire, USA. As expected, all rates of N cycling and potential enzyme activities per unit soil mass correlated strongly with soil carbon (C) concentration, which decreased exponentially with increasing soil depth. Normalized per unit soil organic matter, N cycling rates and specific enzyme activities generally decreased little with depth within the mineral soil. Gross N mineralization rates correlated with specific activities of those enzymes that hydrolyze cellulose (β-glucosidase, cellobiohydrolase) and N-rich glucosamine polymers (N-acetylglucosaminidase), but not those that degrade protein or more complex C compounds, leading us to suggest that these N cycling measurements largely capture the N released during microbial N recycling, supported perhaps by plant C inputs rather than from decomposition of soil organic matter. Across the three stands, the youngest had a larger ratio of N- to-phosphorus-acquiring enzyme activities, consistent with expectations of greater N demand in younger than older forests. For all three stands, soil below 10 cm–50 cm contributed 30–53% of total gross and net N cycling per unit area. Overall, even though microbial N cycling and enzyme activities per unit soil mass decreased with depth, microbial processes in subsoils contributed substantially to ecosystem-scale gross N fluxes because of the sustained microbial activity per unit soil organic matter at depth and the large size of the organic matter pool in the mineral soil. These results support the inclusion of often-ignored mineral subsoils and microbial N recycling in both ecosystem N budgets and in model simulations of N cycling and limitation, which will otherwise greatly underestimate N fluxes and the importance of microbial N dynamics.
Over the long term, soil carbon (C) storage is partly determined by decomposition rate of carbon that is slow to decompose (i.e., recalcitrant C). According to thermodynamic theory, decomposition rates of recalcitrant C might differ from those of non-recalcitrant C in their sensitivities to global warming. We decomposed leaf litter in a warming experiment in Alaskan boreal forest, and measured mass loss of recalcitrant C (lignin) vs. non-recalcitrant C (cellulose, hemicellulose, and sugars) throughout 16 months. We found that these C fractions responded differently to warming. Specifically, after one year of decomposition, the ratio of recalcitrant C to non-recalcitrant C remaining in litter declined in the warmed plots compared to control. Consistent with this pattern, potential activities of enzymes targeting recalcitrant C increased with warming, relative to those targeting non-recalcitrant C. Even so, mass loss of individual C fractions showed that non-recalcitrant C is preferentially decomposed under control conditions whereas recalcitrant C losses remain unchanged between control and warmed plots. Moreover, overall mass loss was greater under control conditions. Our results imply that direct warming effects, as well as indirect warming effects (e.g. drying), may serve to maintain decomposition rates of recalcitrant C compared to non-recalcitrant C despite negative effects on overall decomposition.
Current climate change may be a major threat to global biodiversity, but the extent of species loss will depend on the details of how species respond to changing climates. For example, if most species can undergo rapid change in their climatic niches, then extinctions may be limited. Numerous studies have now documented shifts in the geographic ranges of species that were inferred to be related to climate change, especially shifts towards higher mean elevations and latitudes. Many of these studies contain valuable data on extinctions of local populations that have not yet been thoroughly explored. Specifically, overall range shifts can include range contractions at the “warm edges” of species’ ranges (i.e., lower latitudes and elevations), contractions which occur through local extinctions. Here, data on climate-related range shifts were used to test the frequency of local extinctions related to recent climate change. The results show that climate-related local extinctions have already occurred in hundreds of species, including 47% of the 976 species surveyed. This frequency of local extinctions was broadly similar across climatic zones, clades, and habitats but was significantly higher in tropical species than in temperate species (55% versus 39%), in animals than in plants (50% versus 39%), and in freshwater habitats relative to terrestrial and marine habitats (74% versus 46% versus 51%). Overall, these results suggest that local extinctions related to climate change are already widespread, even though levels of climate change so far are modest relative to those predicted in the next 100 years. These extinctions will presumably become much more prevalent as global warming increases further by roughly 2-fold to 5-fold over the coming decades.
Few studies have investigated how soil fungal communities respond to elevation, especially within TMCF (tropical montane cloud forests). We used an elevation gradient in a TMCF in Costa Rica to determine how soil properties, processes, and community composition of fungi change in response to elevation and across seasons. As elevation increased, soil temperature and soil pH decreased, while soil moisture and soil C:N ratios increased with elevation. Responses of these properties varied seasonally. Fungal abundance increased with elevation during wet and dry seasons. Fungal community composition shifted in response to elevation, and to a lesser extent by season. These shifts were accompanied by varying responses of important fungal functional groups during the wet season and the relative abundance of certain fungal phyla. We suggest that elevation and the responses of certain fungal functional groups may be structuring fungal communities along this elevation gradient. TMCF are ecosystems that are rapidly changing due to climate change. Our study suggests that these changes may affect how fungal communities are structured.
Soil enzymes are catalysts of organic matter depolymerisation, which is of critical importance for ecosystem carbon (C) cycling. Better understanding of the sensitivity of enzymes to temperature will enable improved predictions of climate change impacts on soil C stocks. These impacts may be especially large in tropical montane forests, which contain large amounts of soil C. We determined the temperature sensitivity (Q
10) of a range of hydrolytic and oxidative enzymes involved in organic matter cycling from soils along a 1900 m elevation gradient (a 10 °C mean annual temperature gradient) of tropical montane forest in the Peruvian Andes. We investigated whether the activity (V
max) of selected enzymes: (i) exhibited a Q
10 that varied with elevation and/or soil properties; and (ii) varied among enzymes and according to the complexity of the target substrate for C-degrading enzymes. The Q
10 of V
max for β-glucosidase and β-xylanase increased with increasing elevation and declining mean annual temperature. For all other enzymes, including cellobiohydrolase, N-acetyl β-glucosaminidase and phosphomonoesterase, the Q
10 of V
max did not vary linearly with elevation. Hydrolytic enzymes that degrade more complex C compounds had a greater Q
10 of V
max, but this pattern did not apply to oxidative enzymes because phenol oxidase had the lowest Q
10 value of all enzymes studied here. Our findings suggest that regional differences in the temperature sensitivities of different enzyme classes may influence the terrestrial C cycle under future climate warming.
Tropical montane forests (TMF) are associated with a widely observed suite of characteristics encompassing forest structure, plant traits and biogeochemistry. With respect to nutrient relations, montane forests are characterized by slow decomposition of organic matter, high investment in below-ground biomass and poor litter quality, relative to tropical lowland forests. However, within TMF there is considerable variation in substrate age, parent material, disturbance and species composition. Here we emphasize that many TMFs are likely to be co-limited by multiple nutrients, and that feedback among soil properties, species traits, microbial communities and environmental conditions drive forest productivity and soil carbon storage. To date, studies of the biogeochemistry of montane forests have been restricted to a few, mostly neotropical, sites and focused mainly on trees while ignoring mycorrhizas, epiphytes and microbial community structure. Incorporating the geographic, environmental and biotic variability in TMF will lead to a greater recognition of plant–soil feedbacks that are critical to understanding constraints on productivity, both under present conditions and under future climate, nitrogen-deposition and land-use scenarios.
Tropical montane cloud forests (TMCF) are characterized by short trees, often twisted with multiple stems, with many stems per ground area, a large stem diameter to height ratio, and small, often thick leaves. These forests exhibit high root to shoot ratio, with a moderate leaf area index, low above-ground production, low leaf nutrient concentrations and often with luxuriant epiphytic growth. These traits of TMCF are caused by climatic conditions not geological substrate, and are particularly associated with frequent or persistent fog and low cloud. There are several reasons why fog might result in these features. Firstly, the fog and clouds reduce the amount of light received per unit area of ground and as closed-canopy forests absorb most of the light that reaches them the reduction in the total amount of light reduces growth. Secondly, the rate of photosynthesis per leaf area declines in comparison with that in the lowlands, which leads to less carbon fixation. Nitrogen supply limits growth in several of the few TMCFs where it has been investigated experimentally. High root : shoot biomass and production ratios are common in TMCF, and soils are often wet which may contribute to N limitation. Further study is needed to clarify the causes of several key features of TMCF ecosystems including high tree diameter : height ratio.
Fungi typically live in highly diverse communities composed of multiple ecological guilds. Although high-throughput sequencing has greatly increased the ability to quantify the diversity of fungi in environmental samples, researchers currently lack a simple and consistent way to sort large sequence pools into ecologically meaningful categories. We address this issue by introducing FUNGuild, a tool that can be used to taxonomically parse fungal OTUs by ecological guild independent of sequencing platform or analysis pipeline. Using a database and an accompanying bioinformatics script, we demonstrate the application of FUNGuild to three high-throughput sequencing datasets from different habitats: forest soils, grassland soils, and decomposing wood. We found that guilds characteristic of each habitat (i.e., saprotrophic and ectomycorrhizal fungi in forest soils, saprotrophic and arbuscular mycorrhizal fungi in grassland soils, saprotrophic, wood decomposer, and plant pathogenic fungi in decomposing wood) were each well represented. The example datasets demonstrate that while we could quickly and efficiently assign a large portion of the data to guilds, another large portion could not be assigned, reflecting the need to expand and improve the database as well as to gain a better understanding of natural history for many described and undescribed fungal species. As a community resource, FUNGuild is dependent on third-party annotation, so we invite researchers to populate it with new categories and records as well as refine those already in existence.
The consequences of decline in biodiversity for ecosystem functioning is a major concern in soil ecology. Recent research efforts have been mostly focused on terrestrial plants, while, despite their importance in ecosystems, little is known about soil microbial communities. This work aims at investigating the effects of fungal and bacterial species richness on the dynamics of leaf litter decomposition. Synthetic microbial communities with species richness ranging from 1 to 64 were assembled in laboratory microcosms and used in three factorial experiments of decomposition. Thereafter, the functionality of the different microcosms was determined by measuring their capability to decompose materials with different chemical properties, including two species of litter (Quercus ilex L. and Hedera helix L.), cellulose strips and woody sticks. Incubation was done in microcosms at two temperatures (12°C and 24°C) for 120 days. The number of microbial species inoculated in the microcosms positively affected decomposition rates of Q. ilex and H. helix litters, while relationships found for cellulose and wood were not statistically significant. Diversity effect was greater at higher incubation temperature. We found lower variability of decay rates in microcosms with higher inoculated species richness of microbial communities. Our study pointed out that the relationships between inoculum microbial diversity and litter decomposition is dependent on temperature and litter quality. Therefore, the loss of microbial species may adversely affects ecosystem functionality under specific environmental conditions
Sequencing of 16S rRNA gene tags is a popular method for profiling and comparing microbial communities. The protocols and methods used, however, vary considerably with regard to amplification primers, sequencing primers, sequencing technologies; as well as quality filtering and clustering. How results are affected by these choices, and whether data produced with different protocols can be meaningfully compared, is often unknown. Here we compare results obtained using three different amplification primer sets (targeting V4, V6-V8, and V7-V8) and two sequencing technologies (454 pyrosequencing and Illumina MiSeq) using DNA from a mock community containing a known number of species as well as complex environmental samples whose PCR-independent profiles were estimated using shotgun sequencing. We find that paired-end MiSeq reads produce higher quality data and enabled the use of more aggressive quality control parameters over 454, resulting in a higher retention rate of high quality reads for downstream data analysis. While primer choice considerably influences quantitative abundance estimations, sequencing platform has relatively minor effects when matched primers are used. Beta diversity metrics are surprisingly robust to both primer and sequencing platform biases.
Linking community composition to ecosystem function is a challenge in complex microbial communities. We tested the hypothesis that key biological features of fungi - evolutionary history, functional guild, and abundance of functional genes - can predict the biogeochemical activity of fungal species during decay. We measured the activity of 10 different enzymes produced by 48 model fungal species on leaf litter in laboratory microcosms. Taxa included closely related species with different ecologies (i.e. species in different “functional guilds”) and species with publicly available genomes. Decomposition capabilities differed less among phylogenetic lineages of fungi than among different functional guilds. Activity of carbohydrases and acid phosphatase was significantly higher in litter colonized by saprotrophs compared to ectomycorrhizal species. By contrast, oxidoreductase activities per unit fungal biomass were statistically similar across functional guilds, with white rot fungi having highest polyphenol oxidase activity and ectomycorrhizal fungi having highest peroxidase activity. On the ecosystem level, polyphenol oxidase activity in soil correlated with the abundance of white rot fungi, while soil peroxidase activity correlated with the abundance of ectomycorrhizal fungi in soil. Copy numbers of genes coding for different enzymes explained the activity of some carbohydrases and polyphenol oxidase produced by fungi in culture, but were not significantly better predictors of activity than specific functional guild. Collectively, our data suggest that quantifying the specific functional guilds of fungi in soil, potentially through environmental sequencing approaches, allows us to predict activity of enzymes that drive soil biogeochemical cycles.
Fungi contribute extensively to a wide range of ecosystem processes, including decomposition of organic carbon, deposition of recalcitrant carbon, and transformations of nitrogen and phosphorus. In this review, we discuss the current knowledge about physiological and morphological traits of fungi that directly influence these processes, and we describe the functional genes that encode these traits. In addition, we synthesize information from 157 whole fungal genomes in order to determine relationships among selected functional genes within fungal taxa. Ecosystem-related traits varied most at relatively coarse taxonomic levels. For example, we found that the maximum amount of variance for traits associated with carbon mineralization, nitrogen and phosphorus cycling, and stress tolerance could be explained at the levels of order to phylum. Moreover, suites of traits tended to co-occur within taxa. Specifically, the genetic capacities for traits that improve stress tolerance-β-glucan synthesis, trehalose production, and cold-induced RNA helicases-were positively related to one another, and they were more evident in yeasts. Traits that regulate the decomposition of complex organic matter-lignin peroxidases, cellobiohydrolases, and crystalline cellulases-were also positively related, but they were more strongly associated with free-living filamentous fungi. Altogether, these relationships provide evidence for two functional groups: stress tolerators, which may contribute to soil carbon accumulation via the production of recalcitrant compounds; and decomposers, which may reduce soil carbon stocks. It is possible that ecosystem functions, such as soil carbon storage, may be mediated by shifts in the fungal community between stress tolerators and decomposers in response to environmental changes, such as drought and warming.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients. There are also many exceptions, sometimes because other factors such as precipitation can also vary with elevation. Given this complexity, our capacity to predict when and why the same variable responds differently among disparate elevational gradients is often limited. Furthermore, there is utility in using elevational gradients for understanding community and ecosystem responses to global climate change at much larger spatial and temporal scales than is possible through conventional ecological experiments. However, future studies that integrate elevational gradient approaches with experimental manipulations will provide powerful information that can improve predictions of climate change impacts within and across ecosystems.
Although fungal communities are known to vary along latitudinal gradients, mechanisms underlying this pattern are not well-understood. We used high-throughput sequencing to examine the large-scale distributions of soil fungi and their relation to evolutionary history. We tested the Tropical Conservatism Hypothesis, which predicts that ancestral fungal groups should be more restricted to tropical latitudes and conditions than would more recently derived groups. We found support for this hypothesis in that older phyla preferred significantly lower latitudes and warmer, wetter conditions than did younger phyla. Moreover, preferences for higher latitudes and lower precipitation levels were significantly phylogenetically conserved among the six younger phyla, possibly because the older phyla possess a zoospore stage that is vulnerable to drought, whereas the younger phyla retain protective cell walls throughout their life cycle. Our study provides novel evidence that the Tropical Conservatism Hypothesis applies to microbes as well as plants and animals.
Wildfires are a pervasive disturbance in boreal forests, and the frequency and intensity of boreal wildfires is expected to increase with climate warming. Boreal forests store a large fraction of global soil organic carbon (C), but relatively few studies have documented how wildfires affect soil microbial communities and soil C dynamics. We used a fire chronosequence in upland boreal forests of interior Alaska with sites that were 1, 7, 12, 24, 55, ~90, and ~100 years post-fire to examine the short- and long-term responses of fungal community composition, fungal abundance, extracellular enzyme activity, and litter decomposition to wildfires. We hypothesized that post-fire changes in fungal abundance and community composition would constrain decomposition following fires. We found that wildfires altered the composition of soil fungal communities. The relative abundance of ascomycetes significantly increased following fire whereas basidiomycetes decreased. Post-fire decreases in basidiomycete fungi were likely attributable to declines in ectomycorrhizal fungi. Fungal hyphal lengths in the organic horizon significantly declined in response to wildfire, and they required at least 24 years to return to pre-fire levels. Post-fire reductions in fungal hyphal length were associated with decreased activities of hydrolytic extracellular enzymes. In support of our hypothesis, the decomposition rate of aspen and black spruce litter significantly increased as forests recovered from fire. Our results indicate that post-fire reductions in soil fungal abundance and activity likely inhibit litter decomposition following boreal wildfires. Slower rates of litter decay may lead to decreased heterotrophic respiration from soil following fires and contribute to a negative feedback to climate warming.
Tropical forests are intimately linked to atmospheric CO2 levels through their significant capacity for uptake and storage of carbon (C) in biomass and soils. Increasing pressure of deforestation and forest degradation is begging the question as to what extent land use changes will affect C storage and release in tropical areas. Hitherto, many research efforts focused on aboveground C stocks in lowland tropical forests, but a considerable amount of C is stored in tropical soils as well. Some previous studies suggested that soil C storage increases with increasing altitude, while others found no relation with altitude. In this study, we addressed this controversy by quantifying soil organic C (SOC) stocks along an altitudinal gradient spanning a 3000 m altitude difference. In addition, we sampled soils in anthropogenic grasslands in proximity to forests at different altitudes to provide information on effects of land use change. Soil was sampled on 92 forest locations down to 100 cm depth in forest plots, and down to 30 cm in 13 grassland plots. We found that forest SOC stocks varied predictably with altitude in our study area, ranging between 4.8 and 19.4 kgC m− 2 and increasing by 5.1 kgC m− 2 per 1000 m increase in altitude. Soil properties (pH, bulk density, depth) and soil forming processes played an important role in this relationship with altitude. SOC stocks were not significantly different between forests and grasslands along the gradient in our study, due to a higher soil density in grasslands. When grassland SOC stocks were corrected for this difference in soil density, forest soils contained a significantly greater amount of C. In addition, while this difference was negligible at low altitudes, it tended to increase with increasing altitude. This study suggests that montane tropical forest soils consistently contain larger amounts of C compared to lowland tropical forests, and that conversion of forest to grasslands at higher altitudes might lead to larger soil C losses than previously expected.
Tropical montane cloud forests are unique among terrestrial ecosystems
in that they are strongly linked to regular cycles of cloud formation.
We have explored changes in atmospheric parameters from global climate
model simulations of the Last Glacial Maximum and for doubled
atmospheric carbon dioxide concentration (2 × CO2) conditions
which are associated with the height of this cloud formation, and hence
the occurrence of intact cloud forests. These parameters include
vertical profiles of absolute and relative humidity surfaces, as well as
the warmth index, an empirical proxy of forest type. For the glacial
simulations, the warmth index and absolute humidity suggest a downslope
shift of cloud forests that agrees with the available palaeodata. For
the 2× CO2 scenario, the relative humidity surface is shifted
upwards by hundreds of metres during the winter dry season when these
forests typically rely most on the moisture from cloud contact. At the
same time, an increase in the warmth index implies increased
evapo-transpiration. This combination of reduced cloud contact and
increased evapo-transpiration could have serious conservation
implications, given that these ecosystems typically harbour a high
proportion of endemic species and are often situated on mountain tops or
ridge lines.
Rates of ecosystem processes such as decomposition are likely to change as a result of human impacts on the environment. In southern California, climate change and nitrogen (N) deposition in particular may alter biological communities and ecosystem processes. These drivers may affect decomposition directly, through changes in abiotic conditions, and indirectly through changes in plant and decomposer communities. To assess indirect effects on litter decomposition, we reciprocally transplanted microbial communities and plant litter among control and treatment plots (either drought or N addition) in a grassland ecosystem. We hypothesized that drought would reduce decomposition rates through moisture limitation of decomposers and reductions in plant litter quality before and during decomposition. In contrast, we predicted that N deposition would stimulate decomposition by relieving N limitation of decomposers and improving plant litter quality. We also hypothesized that adaptive mechanisms would allow microbes to decompose litter more effectively in their native plot and litter environments. Consistent with our first hypothesis, we found that drought treatment reduced litter mass loss from 20.9% to 15.3% after six months. There was a similar decline in mass loss of litter inoculated with microbes transplanted from the drought treatment, suggesting a legacy effect of drought driven by declines in microbial abundance and possible changes in microbial community composition. Bacterial cell densities were up to 86% lower in drought plots and at least 50% lower on litter derived from the drought treatment, whereas fungal hyphal lengths increased by 13-14% in the drought treatment. Nitrogen effects on decomposition rates and microbial abundances were weaker than drought effects, although N addition significantly altered initial plant litter chemistry and litter chemistry during decomposition. However, we did find support for microbial adaptation to N addition with N-derived microbes facilitating greater mass loss in N plots than in control plots. Our results show that environmental changes can affect rates of ecosystem processes directly through abiotic changes and indirectly through microbial abundances and communities. Therefore models of ecosystem response to global change may need to represent microbial biomass and community composition to make accurate predictions.
Although microorganisms largely drive many ecosystem processes, the relationship between microbial composition and their functioning remains unclear. To tease apart the effects of composition and the environment directly, microbial composition must be manipulated and maintained, ideally in a natural ecosystem. In this study, we aimed to test whether variability in microbial composition affects functional processes in a field setting, by reciprocally transplanting riverbed sediments between low- and high-salinity locations along the Nonesuch River (Maine, USA). We placed the sediments into microbial 'cages' to prevent the migration of microorganisms, while allowing the sediments to experience the abiotic conditions of the surroundings. We performed two experiments, short- (1 week) and long-term (7 weeks) reciprocal transplants, after which we assayed a variety of functional processes in the cages. In both experiments, we examined the composition of bacteria generally (targeting the 16S rDNA gene) and sulfate-reducing bacteria (SRB) specifically (targeting the dsrAB gene) using terminal restriction fragment length polymorphism (T-RFLP). In the short-term experiment, sediment processes (CO(2) production, CH(4) flux, nitrification and enzyme activities) depended on both the sediment's origin (reflecting differences in microbial composition between salt and freshwater sediments) and the surrounding environment. In the long-term experiment, general bacterial composition (but not SRB composition) shifted in response to their new environment, and this composition was significantly correlated with sediment functioning. Further, sediment origin had a diminished effect, relative to the short-term experiment, on sediment processes. Overall, this study provides direct evidence that microbial composition directly affects functional processes in these sediments.
Hydrological observations were made in the forest at 680 m a.s.l. (just below the cloud cap; trees up to 32 m) and at 870 m (within the clouds; trees up to 15 m). At 870 m, rainfall was c. 25% above that of sea level; radiation was 21% and 33% below values observed at 680 m and at sea level, whereas Penman open-water evaporation E o was reduced by 19% and 31%, respectively. Short-term water balance calculations suggested average actual evapotranspiration rates (mm day -1) of 1.9 (870 m) and 2.5 (680 m; 2.0 during a dry spell of 2 weeks) and average transpiration (E t) rates of 0.85 (870 m) and 2.1 (680 m; 1.7 during dry spell). The ratio E t/E o was decidedly low for the smaller forest, and well below the potential rate made possible by incoming radiation. Possible causes of forest stunting are discussed and it is hypothesized that the stunting of the forest at 870 m is caused by a high carboxylation resistance which results in low photosynthetic rates and transpiration. -from Authors
1] Tropical montane cloud forests are characterized by persistent immersion in clouds, an important source of moisture during the dry season. Future changes in temperature and precipitation could alter cloud cover at the vegetation level and seriously affect mountain ecosystems. A regional climate modeling study that focuses on changes in the distributions of temperature and precipitation in Costa Rica shows, in general, an increase in temperature and a decrease in precipitation under the A2 scenario. At high elevations, warming is amplified and future temperature distribution lies outside the range of present-day distribution. Compared to the Caribbean side, temperature changes are greater at high elevations on the Pacific side. Model results also show significant changes in precipitation amounts and variability and an increase in the altitude of cloud formation on the Pacific side that may have serious implications for mountain ecosystems in and around Costa Rica.
With recent methodological advances, molecular markers are increasingly used for semi-quantitative analyses of fungal communities. The aim to preserve quantitative relationships between genotypes through PCR places new demands on primers to accurately match target sites and provide short amplicons. The internal transcribed spacer (ITS) region of the ribosome encoding genes is a commonly used marker for many fungal groups. Here, we describe three new primers - fITS7, gITS7 and fITS9, which may be used to amplify the fungal ITS2 region by targeting sites in the 5.8S encoding gene. We evaluated the primers and compared their performance with the commonly used ITS1f primer by 454-sequencing of both artificially assembled templates and field samples. When the entire ITS region was amplified using the ITS1f/ITS4 primer combination, we found strong bias against species with longer amplicons. This problem could be overcome by using the new primers, which produce shorter amplicons and better preserve the quantitative composition of the template. In addition, the new primers yielded more diverse amplicon communities than the ITS1f primer.
The net primary productivity, carbon (C) stocks and turnover rates (i.e. C dynamics) of tropical forests are an important aspect of the global C cycle. These variables have been investigated in lowland tropical forests, but they have rarely been studied in tropical montane forests (TMFs). This study examines spatial patterns of above- and belowground C dynamics along a transect ranging from lowland Amazonia to the high Andes in SE Peru. Fine root biomass values increased from 1.50 Mg C ha−1 at 194 m to 4.95 ± 0.62 Mg C ha−1 at 3020 m, reaching a maximum of 6.83 ± 1.13 Mg C ha−1 at the 2020 m elevation site. Aboveground biomass values decreased from 123.50 Mg C ha−1 at 194 m to 47.03 Mg C ha−1 at 3020 m. Mean annual belowground productivity was highest in the most fertile lowland plots (7.40 ± 1.00 Mg C ha−1 yr−1) and ranged between 3.43 ± 0.73 and 1.48 ± 0.40 Mg C ha−1 yr−1 in the premontane and montane plots. Mean annual aboveground productivity was estimated to vary between 9.50 ± 1.08 Mg C ha−1 yr−1 (210 m) and 2.59 ± 0.40 Mg C ha−1 yr−1 (2020 m), with consis