Browsing by Subject "PLANT-COMMUNITIES"

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  • Rogers, Paul C.; Pinno, Bradley D.; Šebesta, Jan; Albrectsen, Benedicte R.; Li, Guoqing; Ivanova, Natalya; Kusbach, Antonín; Kuuluvainen, Timo; Landhäusser, Simon M.; Liu, Hongyan; Myking, Tor; Pulkkinen, Pertti; Wen, Zhongming; Kulakowski, Dominik (2020)
    Across the northern hemisphere, six species of aspen (Populus spp.) play a disproportionately important role in promoting biodiversity, sequestering carbon, limiting forest disturbances, and providing other ecosystem services. These species are illustrative of efforts to move beyond single-species conservation because they facilitate hundreds of plants and animals worldwide. This review is intended to place aspen in a global conservation context by focusing on the many scientific advances taking place in such biologically diverse systems. In this manner, aspen may serve as a model for other widespread keystone systems where science-based practice may have world implications for biodiversity conservation. In many regions, aspen can maintain canopy dominance for decades to centuries as the sole major broadleaf trees in forested landscapes otherwise dominated by conifers. Aspen ecosystems are valued for many reasons, but here we highlight their potential as key contributors to regional and global biodiversity. We present global trends in research priorities, strengths, and weaknesses based on, 1) a qualitative survey, 2) a systematic literature analysis, and 3) regional syntheses of leading research topics. These regional syntheses explore important aspen uses, threats, and research priorities with the ultimate intent of research sharing focused on sound conservation practice. In all regions, we found that aspen enhance biodiversity, facilitate rapid (re)colonization in natural and damaged settings (e.g., abandoned mines), and provide adaptability in changing environments. Common threats to aspen ecosystems in many, but not all, regions include effects of herbivory, land clearing, logging practices favoring conifer species, and projected climate warming. We also highlight regional research gaps that emerged from the three survey approaches above. We believe multi-scale research is needed that examines disturbance processes in the context of dynamic climates where ecological, physiological, and genetic variability will ultimately determine widespread aspen sustainability. Based on this global review of aspen research, we argue for the advancement of the “mega-conservation” strategy, centered on the idea of sustaining a set of common keystone communities (aspen) that support wide arrays of obligate species. This approach contrasts with conventional preservation which focuses limited resources on individual species residing in narrow niches.
  • Marsman, Floor; Nystuen, Kristin O.; Opedal, Oystein H.; Foest, Jessie J.; Sorensen, Mia Vedel; De Frenne, Pieter; Graae, Bente Jessen; Limpens, Juul (2021)
    Questions Changes in climate and herbivory pressure affect northern alpine ecosystems through woody plant encroachment, altering their composition, structure and functioning. The encroachment often occurs at unequal rates across heterogeneous landscapes, hinting at the importance of habitat-specific drivers that either hamper or facilitate woody plant establishment. Here, we assess: (1) the invasibility of three distinct alpine plant community types (heath, meadow andSalixshrubland) byPinus sylvestris(Scots pine); and (2) the relative importance of biotic (above-ground interactions with current vegetation, herbivory and shrub encroachment) and microclimate-related abiotic (soil temperature, moisture and light availability) drivers of pine seedling establishment success. Location Dovrefjell, Central Norway. Methods We conducted a pine seed sowing experiment, testing how factorial combinations of above-ground removal of co-occurring vegetation, herbivore exclusion and willow transplantation (simulated shrub encroachment) affect pine emergence, survival and performance (new stem growth, stem height and fraction of healthy needles) in three plant communities, characteristic of alpine tundra, over a period of five years. Results Pine seedling emergence and survival were similar across plant community types. Herbivore exclusion and vegetation removal generally increased pine seedling establishment and seedling performance. Within our study, microclimate had minimal effects on pine seedling establishment and performance. These results illustrate the importance of biotic resistance to seedling establishment. Conclusion Pine seedlings can easily establish in alpine tundra, and biotic factors (above-ground plant interactions and herbivory) are more important drivers of pine establishment in alpine tundra than abiotic, microclimate-related, factors. Studies aiming to predict future vegetation changes should thus consider local-scale biotic interactions in addition to abiotic factors.
  • Tóth, Zsolt; Szlavecz, Katalin; Epp Schmidt, Dietrich J.; Hornung, Erzsébet; Setälä, Heikki; Yesilonis, Ian D.; Kotze, D. Johan; Dombos, Miklós; Pouyat, Richard; Mishra, Saket; Cilliers, Sarel; Yarwood, Stephanie; Csuzdi, Csaba (2020)
    In urban landscapes, humans are the most significant factor determining belowground diversity, including earthworms. Within the framework of the Global Urban Soil Ecology and Education Network (GLUSEEN), a multi-city comparison was carried out to assess the effects of soil disturbance on earthworms. In each of five cities (Baltimore, USA; Budapest, Hungary; Helsinki and Lahti, Finland; Potchefstroom, South Africa), covering four climatic and biogeographical regions, four habitat types (ruderal, turf/lawn, remnant and reference) were sampled. The survey resulted in 19 species belonging to 9 genera and 4 families. The highest total species richness was recorded in Baltimore (16), while Budapest and the Finnish cities had relatively low (5–6) species numbers. Remnant forests and lawns supported the highest earthworm biomass. Soil properties (i.e. pH and organic matter content) explained neither earthworm community composition nor abundance. Evaluating all cities together, earthworm communities were significantly structured by habitat type. Communities in the two adjacent cities, Helsinki and Lahti were very similar, but Budapest clearly separated from the Finnish cities. Earthworm community structure in Baltimore overlapped with that of the other cities. Despite differences in climate, soils and biogeography among the cities, earthworm communities were highly similar within the urban habitat types. This indicates that human-mediated dispersal is an important factor shaping the urban fauna, both at local and regional scales.
  • Staehr, Peter A.; Asmala, Eero; Carstensen, Jacob; Krause-Jensen, Dorte; Reader, Heather (2018)
    Long-term deterioration of water quality is known to reduce the importance of benthic ecosystem metabolism in shallow coastal ecosystems, but drivers of spatial and short-term variability in ecosystem metabolism are poorly understood. We addressed this knowledge gap through detailed seasonal measurements of ecosystem metabolism across depth gradients from shallow (2 to 3 m) eelgrass-dominated to deeper (4 to 5 m) muddy regions of a shallow, productive estuary. Combined measurements of gross primary production (GPP), respiration (R) and, by difference, net ecosystem production (NEP) by the open-water diel oxygen technique and in situ chamber incubations showed high importance of shallow eelgrass habitats for metabolism at the system scale. Seasonal variations in GPP, R and NEP increased with light availability and temperature with highest NEP in all habitats during the warm and sunny mid-summer. The shallow eelgrass-dominated and neighboring habitats were seasonally net autotrophic (NEP = 0.54 and 0.31 mg O2 m-2 d-1, respectively), compared to net heterotrophy (NEP = -0.26 mg O2 m-2 d-1) at the deeper muddy site. Detailed studies along depth gradients further confirmed the role of eelgrass as a key driver of spatial differences in ecosystem metabolism across the estuary. Strong northerly winds (>8 m s-1) caused short-term (<24 h) periods of similar oxygen dynamics and similar apparent productivity in shallow and deeper waters, indicative of efficient lateral mixing, while calm periods (<4 m s-1) enabled formation of ‘pockets’, i.e. water masses with limited connectivity, which exacerbated the metabolic differences between shallow and deep sites.
  • Majekova, Maria; Paal, Taavi; Plowman, Nichola S.; Bryndova, Michala; Kasari, Liis; Norberg, Anna; Weiss, Matthias; Bishop, Tom R.; Luke, Sarah H.; Sam, Katerina; Le Bagousse-Pinguet, Yoann; Leps, Jan; Götzenberger, Lars; de Bello, Francesco (2016)
    Functional diversity (FD) is an important component of biodiversity that quantifies the difference in functional traits between organisms. However, FD studies are often limited by the availability of trait data and FD indices are sensitive to data gaps. The distribution of species abundance and trait data, and its transformation, may further affect the accuracy of indices when data is incomplete. Using an existing approach, we simulated the effects of missing trait data by gradually removing data from a plant, an ant and a bird community dataset (12, 59, and 8 plots containing 62, 297 and 238 species respectively). We ranked plots by FD values calculated from full datasets and then from our increasingly incomplete datasets and compared the ranking between the original and virtually reduced datasets to assess the accuracy of FD indices when used on datasets with increasingly missing data. Finally, we tested the accuracy of FD indices with and without data transformation, and the effect of missing trait data per plot or per the whole pool of species. FD indices became less accurate as the amount of missing data increased, with the loss of accuracy depending on the index. But, where transformation improved the normality of the trait data, FD values from incomplete datasets were more accurate than before transformation. The distribution of data and its transformation are therefore as important as data completeness and can even mitigate the effect of missing data. Since the effect of missing trait values pool-wise or plot-wise depends on the data distribution, the method should be decided case by case. Data distribution and data transformation should be given more careful consideration when designing, analysing and interpreting FD studies, especially where trait data are missing. To this end, we provide the R package "traitor" to facilitate assessments of missing trait data.
  • De Frenne, Pieter; Lenoir, Jonathan; Luoto, Miska; Scheffers, Brett R.; Zellweger, Florian; Aalto, Juha; Ashcroft, Michael B.; Christiansen, Ditte M.; Decocq, Guillaume; De Pauw, Karen; Govaert, Sanne; Greiser, Caroline; Gril, Eva; Hampe, Arndt; Jucker, Tommaso; Klinges, David H.; Koelemeijer, Irena A.; Lembrechts, Jonas J.; Marrec, Ronan; Meeussen, Camille; Ogee, Jerome; Tyystjarvi, Vilna; Vangansbeke, Pieter; Hylander, Kristoffer (2021)
    Forest microclimates contrast strongly with the climate outside forests. To fully understand and better predict how forests' biodiversity and functions relate to climate and climate change, microclimates need to be integrated into ecological research. Despite the potentially broad impact of microclimates on the response of forest ecosystems to global change, our understanding of how microclimates within and below tree canopies modulate biotic responses to global change at the species, community and ecosystem level is still limited. Here, we review how spatial and temporal variation in forest microclimates result from an interplay of forest features, local water balance, topography and landscape composition. We first stress and exemplify the importance of considering forest microclimates to understand variation in biodiversity and ecosystem functions across forest landscapes. Next, we explain how macroclimate warming (of the free atmosphere) can affect microclimates, and vice versa, via interactions with land-use changes across different biomes. Finally, we perform a priority ranking of future research avenues at the interface of microclimate ecology and global change biology, with a specific focus on three key themes: (1) disentangling the abiotic and biotic drivers and feedbacks of forest microclimates; (2) global and regional mapping and predictions of forest microclimates; and (3) the impacts of microclimate on forest biodiversity and ecosystem functioning in the face of climate change. The availability of microclimatic data will significantly increase in the coming decades, characterizing climate variability at unprecedented spatial and temporal scales relevant to biological processes in forests. This will revolutionize our understanding of the dynamics, drivers and implications of forest microclimates on biodiversity and ecological functions, and the impacts of global changes. In order to support the sustainable use of forests and to secure their biodiversity and ecosystem services for future generations, microclimates cannot be ignored.
  • Juottonen, Heli; Kieman, Mirkka; Fritze, Hannu; Hamberg, Leena; Laine, Anna M.; Merila, Paivi; Peltoniemi, Krista; Putkinen, Anuliina; Tuittila, Eeva-Stiina (2022)
    Peatlands are carbon dioxide (CO2) sinks that, in parallel, release methane (CH4). The peatland carbon (C) balance depends on the interplay of decomposer and CH4-cycling microbes, vegetation, and environmental conditions. These interactions are susceptible to the changes that occur along a successional gradient from vascular plant-dominated systems to Sphagnum moss-dominated systems. Changes similar to this succession are predicted to occur from climate change. Here, we investigated how microbial and plant communities are interlinked with each other and with ecosystem C cycling along a successional gradient on a boreal land uplift coast. The gradient ranged from shoreline to meadows and fens, and further to bogs. Potential microbial activity (aerobic CO2 production; CH4 production and oxidation) and biomass were greatest in the early successional meadows, although their communities of aerobic decomposers (fungi, actinobacteria), methanogens, and methanotrophs did not differ from the older fens. Instead, the functional microbial communities shifted at the fen-bog transition concurrent with a sudden decrease in C fluxes. The successional patterns of decomposer versus CH4-cycling communities diverged at the bog stage, indicating strong but distinct microbial responses to Sphagnum dominance and acidity. We highlight young meadows as dynamic sites with the greatest microbial potential for C release. These hot spots of C turnover with dense sedge cover may represent a sensitive bottleneck in succession, which is necessary for eventual long-term peat accumulation. The distinctive microbes in bogs could serve as indicators of the C sink function in restoration measures that aim to stabilize the C in the peat.
  • Asevedo, Lidiane; Ranzi, Alceu; Kalliola, Risto; Pärssinen, Martti; Ruokolainen, Kalle; Cozzuol, Mário Alberto; Rodrigues do Nascimento, Ednair; Negri, Francisco Ricardo; Souza-Filho, Jonas P.; Cherkinsky, Alexander; Trindade Dantas, Mario Andre (2021)
    We report the first radiocarbon datings and carbon (d13C) and oxygen (d18O) stable isotopes data to reconstruct the paleoecology of medium to large herbivorous mammals from late Quaternary of southwestern Amazon (Acre and Rond^onia states, Brazil). AMS 14C dates for Neochoerus sp. (29,072 - 27,713 Cal yr BP), Notiomastodon platensis (25,454 - 24,884 Cal yr BP) and Eremotherium laurillardi (11,320 - 11,131 Cal yr BP) support the Lujanian ages. All fossils have low d13C and d18O isotopic values that suggest C3-dominated environments from closed canopy forests to wooded savannas, agreeing with paleovegetation reconstitution. Most species were browsers (piC3¼100%; Niche breadth, BA¼0), where the key species with the largest body mass, N. platensis (~6,300 kg) and E. laurillardi (~3,500 kg), possibly had a more generalized browser diet in closed-canopies to woodlands. Their diet distinguished from the C3/C4 generalist Trigodonops lopesi (~1,900 kg), which foraged in wooded savannas (piC3¼70%; BA¼0.72), similarly with its relative Toxodon platensis (~1,800 kg) that had a browse-dominated mixed feeder diet (piC3 84%, BA 0.38) in Peruvian and Bolivian Amazon localities. Palaeolama major (~280 kg) was possibly a strictly folivorous within forest canopies, whereas Tapirus sp. (~250 kg) and Mazama sp. (~40 kg) were browsers in closed-canopies to woodlands. Holmesina rondoniensis (~120 kg) was a browser but not restricted, where could also feed on herbaceous from understories in woodlands, and Neochoerus sp. (~200 kg) feeding predominantly herbaceous plants in wooded savannas (piC3¼~69%; BA¼0.75). We estimate that the interspecific competition could have been avoid by different feeding strategies, although more investigations are still needed to better understand their ecological interactions in the habitats of the southwestern Amazon during the late Quaternary.
  • Fraser, Danielle; Villasenor, Amelia; Toth, Aniko B.; Balk, Meghan A.; Eronen, Jussi T.; Barr, W. Andrew; Behrensmeyer, A. K.; Davis, Matt; Du, Andrew; Faith, J. Tyler; Graves, Gary R.; Gotelli, Nicholas J.; Jukar, Advait M.; Looy, Cindy; McGill, Brian J.; Miller, Joshua H.; Pineda-Munoz, Silvia; Potts, Richard; Shupinski, Alex B.; Soul, Laura C.; Lyons, S. Kathleen (2022)
    Biotic homogenization-increasing similarity of species composition among ecological communities-has been linked to anthropogenic processes operating over the last century. Fossil evidence, however, suggests that humans have had impacts on ecosystems for millennia. We quantify biotic homogenization of North American mammalian assemblages during the late Pleistocene through Holocene (similar to 30,000 ybp to recent), a timespan encompassing increased evidence of humans on the landscape (similar to 20,000-14,000 ybp). From similar to 10,000 ybp to recent, assemblages became significantly more homogenous (>100% increase in Jaccard similarity), a pattern that cannot be explained by changes in fossil record sampling. Homogenization was most pronounced among mammals larger than 1 kg and occurred in two phases. The first followed the megafaunal extinction at similar to 10,000 ybp. The second, more rapid phase began during human population growth and early agricultural intensification (similar to 2,000-1,000 ybp). We show that North American ecosystems were homogenizing for millennia, extending human impacts back similar to 10,000 years.
  • Mikola, Juha Tapio; Silfver, Tarja Hannele; Rousi, Matti (2018)
    Facilitative plant-plant interactions are common in harsh environments such as Arctic and alpine tree lines. In Fennoscandia, mountain birch dominates tree lines, but mixes with Scots pine in less severe areas. Using over 30-yr. old Scots pine common gardens, established at three locations near the present Scots pine tree line, we tested (1) if mountain birch can facilitate Scots pine numbers and (2) if improved soil fertility under mountain birch canopies has a role in facilitation. We counted the number of pines within 1-m and 3-m radii of the tallest mountain birch vs. a random spot in 70-75 planting plots and sampled soil for nutrients at 0.3-, 1- and 3-m distance to the birch in ten plots in each location. Number of Scots pines was 29% higher within a 1-m radius of a mountain birch than of a random spot. This effect did not depend on location, although the locations differed significantly in soil fertility, and no effect was detected within a 3-m radius. Concentrations of water, NH4, NO3 and PO4 decreased significantly with increasing distance to a mountain birch, but only in the least fertile location. Mountain birch can significantly facilitate Scots pine in tree line conditions. However, unlike we expected, improved soil fertility under birch canopies may not have a general role in facilitation.
  • Ryberg, Eleonor E.; Väliranta, Minna; Martinez-Cortizas, Antonio; Ehrlen, Johan; Sjostrom, Jenny K.; Kylander, Malin E. (2022)
    Boreal peatlands are facing significant changes in response to a warming climate. Sphagnum mosses are key species in these ecosystems and contribute substantially to carbon sequestration. Understanding the factors driving vegetation changes on longer time scales is therefore of high importance, yet challenging since species changes are typically affected by a range of internal and external processes acting simultaneously within the system. This study presents a high-resolution macrofossil analysis of a peat core from Store Mosse bog (south-central Sweden), dating back to nearly 10 000 cal. a BP. The aim is to identify factors driving species changes on multidecadal to millennial timescales considering internal autogenic, internal biotic and external allogenic processes. A set of independent proxy data was used as a comparison framework to estimate changes in the bog and regional effective humidity, nutrient input and cold periods. We found that Store Mosse largely follows the expected successional pathway for a boreal peatland (i.e. lake -> fen -> bog). However, the system has also been affected by other interlinked factors. Of interest, we note that external nutrient input (originating from dust deposition and climate processes) has had a negative effect on Sphagnum while favouring vascular plants, and increased fire activity (driven by allogenic and autogenic factors) typically caused post-fire, floristic wet shifts. These effects interactively caused a floristic reversal and near disappearance of a once-established Sphagnum community, during which climate acted as an indirect driver. Overall, this study highlights that the factors driving vegetation change within the peatland are multiple and complex. Consideration of the role of interlinked factors on Sphagnum is crucial for an improved understanding of the drivers of species change on short- and long-term scales.
  • Li, Xiaofei; Zhong, Zhiwei; Sanders, Dirk; Smit, Christian; Wang, Deli; Nummi, Petri; Zhu, Yu; Wang, Ling; Zhu, Hui; Hassan, Nazim (2018)
    While positive interactions have been well documented in plant and sessile benthic marine communities, their role in structuring mobile animal communities and underlying mechanisms has been less explored. Using field removal experiments, we demonstrated that a large vertebrate herbivore (cattle; Bos tarurs) and a much smaller invertebrate (ants; Lasius spp.), the two dominant animal taxa in a semi-arid grassland in Northeast China, facilitate each other. Cattle grazing led to higher ant mound abundance compared with ungrazed sites, while the presence of ant mounds increased the foraging of cattle during the peak of the growing season. Mechanistically, these reciprocal positive effects were driven by habitat amelioration and resource (food) enhancement by cattle and ants (respectively). Cattle facilitated ants, probably by decreasing plant litter accumulation by herbivory and trampling, allowing more light to reach the soil surface leading to microclimatic conditions that favour ants. Ants facilitated cattle probably by increasing soil nutrients via bioturbation, increasing food (plant) biomass and quality (nitrogen content) for cattle. Our study demonstrates reciprocal facilitative interactions between two animal species from phylogenetically very distant taxa. Such reciprocal positive interactions may be more common in animal communities than so far assumed, and they should receive more attention to improve our understanding of species coexistence and animal community assembly.
  • Parducci, Laura; Alsos, Inger Greve; Unneberg, Per; Pedersen, Mikkel W.; Han, Lu; Lammers, Youri; Salonen, J. Sakari; Väliranta, Minna M.; Slotte, Tanja; Wohlfarth, Barbara (2019)
    The lake sediments of Hasseldala Port in south-east Sweden provide an archive of local and regional environmental conditions similar to 14.5-9.5 ka BP (thousand years before present) and allow testing DNA sequencing techniques to reconstruct past vegetation changes. We combined shotgun sequencing with plant micro- and macrofossil analyses to investigate sediments dating to the Allerod (14.1-12.7 ka BP), Younger Dryas (12.7-11.7 ka BP), and Preboreal (
  • Maliniemi, Tuija; Happonen, Konsta; Virtanen, Risto (2019)
    Experimental evidence shows that site fertility is a key modulator underlying plant community changes under climate change. Communities on fertile sites, with species having fast dynamics, have been found to react more strongly to climate change than communities on infertile sites with slow dynamics. However, it is still unclear whether this generally applies to high-latitude plant communities in natural environments at broad spatial scales. We tested a hypothesis that vegetation of fertile sites experiences greater changes over several decades and thus would be more responsive under contemporary climate change compared to infertile sites that are expected to show more resistance. We resurveyed understorey communities (vascular plants, bryophytes, and lichens) of four infertile and four fertile forest sites along a latitudinal bioclimatic gradient. Sites had remained outside direct human disturbance. We analyzed the magnitude of temporal community turnover, changes in the abundances of plant morphological groups and strategy classes, and changes in species diversity. In agreement with our hypothesis, temporal turnover of communities was consistently greater on fertile sites compared to infertile sites. However, our results suggest that the larger turnover of fertile communities is not primarily related to the direct effects of climatic warming. Furthermore, community changes in both fertile and infertile sites showed remarkable variation in terms of shares of plant functional groups and strategy classes and measures of species diversity. This further emphasizes the essential role of baseline environmental conditions and nonclimatic drivers underlying vegetation changes. Our results show that site fertility is a key determinant of the overall rate of high-latitude vegetation changes but the composition of plant communities in different ecological contexts is variously impacted by nonclimatic drivers over time.
  • Korrensalo, Aino; Alekseychik, Pavel; Hajek, Tomas; Rinne, Janne; Vesala, Timo; Mehtätalo, Lauri; Mammarella, Ivan; Tuittila, Eeva-Stiina (2017)
    In boreal bogs plant species are low in number, but they differ greatly in their growth forms and photosynthetic properties. We assessed how ecosystem carbon (C) sink dynamics were affected by seasonal variations in the photosynthetic rate and leaf area of different species. Photosynthetic properties (light response parameters), leaf area development and areal cover (abundance) of the species were used to quantify species-specific net and gross photosynthesis rates (P-N and P-G, respectively), which were summed to express ecosystem-level P-N and P-G. The ecosystem-level P-G was compared with a gross primary production (GPP) estimate derived from eddy covariance (EC) measurements. Species areal cover, rather than differences in photosynthetic properties, determined the species with the highest P-G of both vascular plants and Sphagna. Species-specific contributions to the ecosystem P-G varied over the growing season, which, in turn, determined the seasonal variation in ecosystem P-G. The upscaled growing season P-G estimate, 230 gCm (-2), agreed well with the GPP estimated by the EC (243 gCm (-2)). Sphagna were superior to vascular plants in ecosystemlevel P-G throughout the growing season but had a lower P-N. P-N results indicated that areal cover of the species, together with their differences in photosynthetic parameters, shape the ecosystem-level C balance. Species with low areal cover but high photosynthetic efficiency appear to be potentially important for the ecosystem C sink. Results imply that func-tional diversity, i. e., the presence of plant groups with different seasonal timing and efficiency of photosynthesis, may increase the stability of C sinks of boreal bogs.
  • Meyer, Nele; Silfver, Tarja; Karhu, Kristiina; Myller, Kristiina; Sietiö, Outi-Maaria; Myrsky, Eero; Oksanen, Elina; Rousi, Matti; Mikola, Juha (2021)
    Warming will likely stimulate Arctic primary production, but also soil C and N mineralization, and it remains uncertain whether the Arctic will become a sink or a source for CO2. Increasing insect herbivory may also dampen the positive response of plant production and soil C input to warming. We conducted an open-air warming experiment with Subarctic field layer vegetation in North Finland to explore the effects of warming (+3 degrees C) and reduced insect herbivory (67% reduction in leaf damage using an insecticide) on soil C and N dynamics. We found that plant root growth, soil C and N concentrations, microbial biomass C, microbial activity, and soil NH4+ availability were increased by both warming and reduced herbivory when applied alone, but not when combined. Soil NO3- availability increased by warming only and in-situ soil respiration by reduced herbivory only. Our results suggest that increasing C input from vegetation under climate warming increases soil C concentration, but also stimulates soil C turnover. On the other hand, it appears that insect herbivores can significantly reduce plant growth. If their abundance increases with warming as predicted, they may curtail the positive effect of warming on soil C concentration. Moreover, our results suggest that temperature and herbivory effects on root growth and soil variables interact strongly, which probably arises from a combination of N demand increasing under lower herbivory and soil mineral N supply increasing under higher temperature. This may further complicate the effects of rising temperatures on Subarctic soil C dynamics.
  • Happonen, Konsta; Muurinen, Lauralotta; Virtanen, Risto; Kaakinen, Eero; Grytnes, John-Arvid; Kaarlejarvi, Elina; Parisot, Philippe; Wolff, Matias; Maliniemi, Tuija (2021)
    Aim Land use is the foremost cause of global biodiversity decline, but species do not respond equally to land-use practices. Instead, it is suggested that responses vary with species traits, but long-term data on the trait-mediated effects of land use on communities are scarce. Here we study how forest understorey communities have been affected by two land-use practices during 4-5 decades, and whether changes in plant diversity are related to changes in functional composition. Location Finland. Time period 1968-2019. Major taxa studied Vascular plants. Methods We resurveyed 245 vegetation plots in boreal herb-rich forest understories, and used hierarchical Bayesian linear models to relate changes in diversity, species composition, average plant size, and leaf economic traits to reindeer abundance, forest management intensity, and changes in climate, canopy cover and composition. We also studied the relationship between species evenness and plant size across both space and time. Results Intensively managed forests decreased in species richness and had increased turnover, but management did not affect functional composition. Increased reindeer densities corresponded with increased leaf dry matter content, evenness and diversity, and decreased height and specific leaf area. Successional development in the canopy was associated with increased specific leaf area and decreased leaf dry matter content and height in the understorey over the study period. Effects of reindeer abundance and canopy density on diversity were partially mediated by vegetation height, which had a negative relationship with evenness across both space and time. Observed changes in climate had no discernible effect on any variable. Main conclusions Functional traits are useful in connecting vegetation changes to the mechanisms that drive them, and provide unique information compared to turnover and diversity metrics. These trait-dependent selection effects could inform which species benefit and which suffer from land-use changes and explain observed biodiversity changes under global change.