Interaction and functional dynamics of anthropogenic and soil factors on the vegetation of river island Krčedinska ada (Danube, Serbia)

Nedovoljno  je  informacija  o  strukturnim  promenama  vegetacije  šumo pašnjaka, uključujući i njihovu vezu sa  abiotičkim faktorima. U ovom radu stavljen je akcenat na vezu između različitih stadijuma ciklusa  šumo  pašnjaka  i  važnih  sredinskih  varijabli  sa  ciljem razumevanja  dinamičnosti  ovog  odnosa  i  procesa  koji  dovode  do degradacije  šumo  pašnjaka.  Istorijske  promene  vegetacijske strukture na Krčedinskoj adi u protekle 44 godine identifikovane su pomoću analize avio i satelitskih snimaka. Stvarni podaci sa terena (24  vegetacijska  plota)  i  CCA  analiza  korišteni  su  kako  bi  se analizirala  veza  između  biljnih  zajednica  i  prisutnih  sredinskih faktora. Odabrana su tri dominantna strukturna tipa vegetacije:  GR (grazing)  -  plotovi  pod  ispašom;  WC  (woody  cover)  -  plotovi šikarastog tipa sa dominacijom visokog žbunja i drvenastih vrsta čija visina premašuje 2 m;  TR (transitional)  -  prelazna forma između livadske i drvenaste vegetacije sa trnovitim žbunjem visine manje od 2  m.  Odabran  je  sledeći  set  sredinskih  parametara:  GI  (intenzitet ispaše), Ind  učestalost plavljenja), E (nadmorska visina), i zemljišni parametri: TN (ukupni azot), AP (dostupni fosfor), K (kalijum), Mg (magnezijum),  Ca  (kalcijum),  pH,  C/N  (odnos  ugljenika  i  azota)  i NB (nitrificirajuće bakterije).Klasifikacija  biljnih  vrsta  iz  različtih  sukcesivnih  stadijuma  prema CSR  Grime-ovom  modelu  dodatno  je  doprinela  razumevanju dinamičnosti  vegetacijskih  sukcesija  a  analiza  uticaja  invazivnih biljnih  vrsta  na  zemljišne  parametre  doprinela  je  razumevanju fluktuacija  zemljišnih  parametara  i  usmeravanju  restauracijskih mera. Analiza promena zemljišnog pokrivača pomoću satelitskih snimakapokazala je da su u prošlosti biljne zajednice na Krčedinskoj adi bile sa  većom  populacijom  zeljastih  vrsta  i  očuvanih  šuma  vrbe  bez prisustva  degradiranih  sastojina.  Ove  zajednice  velikim  delom  su zamenjene  dominantno  žbunastim  pokrovom  što  ukazuje  na progresivan tip sukcesije na ostrvu a može se dovesti u vezu sa (1) sečom vrbovih šuma i (2) znantno većim brojem stoke u prošlosti.Rezultati  analize  satelitskih  snimaka  u  skladu  su  sa  rezultatima terenskog  istraživanja  koji  takođe  ukazuju  na  progresivan  tip sukcesije  s  obzirom  da  je,  prema  CSR  kategorizaciji  biljnih  vrsta, glavna sukcesijska trajektorija na ostrvu CSR/CS – C selekcija. CCA  analiza  rađena  u  svrhu  identifikacije  uticaja  sredinskih parametara  na  distribuciju  i  sastav  biljnih  vrsta,  pokazala  je  da intenzitet  ispaše  (GI)  ima  najveći  uticaj  na  oblikovanje  biljnih zajednica. Analiza  uticaja  invazivnih  biljnih  vrsta  na  zemljišne  parametre, pokazala  je  da  se  izdvojene  grupe  plotova  (FraxP,  AcerN,  AmorF, Mix i Control) međusobno  značajno razlikuju u odnosu na zemljišne parametre:  Hm, N, C i NB  te ukazuju na aditivan efekat invazivnih vrsta  na  pomenute  parametre.  Aditivan  efekat  koji  ispitivane invazivne  vrste  pokazuju  na  sadržaj  zemljišnih  nutrijenata  ukazuje na modifikaciju zemljišnih uslova u pravcu stabilizacije i/ili ubrzanja invazije  kao  i  otežavanja  ponovnog  uspostavljanja  nativne vegetacije.  Dodatno,  aditivan  efekat  ispitivanih  invazivnih  vrsta ukazuje  na  mogućnost  ekološkog  nasleđa  koje  invazivne  vrste ostavljaju za sobom i nakon potencijalnog uklanjanja.There  is  insufficient  information  on  structural changes  within  wood-pasture, including  their relationship with abiotic influences. This thesis addresses  the  links  between  important environmental  variables  and  different  stages  of the  wood- pasture  cycle,  with  the  aim  of understanding  fluctuations  in  this  relationship and  processes  that  follow  wood-pasture degradation.  Satellite  and  aerial  image interpretation  was  used  to  identify  structural vegetation  shifts  over  44  years  under significantly  declining  livestock  numbers  and ground  truthing  data  of  24  plots  to  assess  the current  field  scenario.  Canonical correspondence  analysis  (CCA)  was  employed to  evaluate  the  relationship  between  plant communities  and   invironmental  influences. Three  dominant  structural  vegetation  types  – grazing  plots  (GR),  transitional  habitats  with thorny  shrubs  (TR)  and  woody  encroachment (WC)  -  were surveyed and  the  following set of variables  was  chosen:  grazing  intensity  (GI), inundation  frequency  (Ind),  elevation  (E),  soil total  nitrogen  (TN),  soil  available  phosphorus (AP), soil potassium (K), soil magnesium (Mg), soil  calcium  (Ca),  soil  pH  (pH),  soil  carbon  to nitrogen ratio (C/N) and soil nitrifying bacteria (NB).  Classification  of  plants  from  different succession  stages  according  to  Grimes  CSR model,  gave  its  contribution  to  understand vegetation  dynamics  while  the  analysis  of invasive plant species influence on soil variables helped  to  understand  the  fluctuations  of  soil variables and to advice on restoration measures.Interpretation  of  satellite  images  revealed dominance of wood-pasture  habitats in the  past,which  alternated  structurally  between  more open  and  more   closed  physiognomies  i.e. indicates progressive succession pathway which is  in  accordance  with  CSR  plant  species categorization  which  revealed  that  the  main succession trajectory on the island is CSR/CS  – C  selection.  CCA  with  ground  truth  data  and forward  selection  revealed  grazing  intensity  as the  predominant  ecological  driver  modifying vegetation structure and the soil nutrient pool, as well  as  transitioning  vegetation  between  open herbaceous and closed woody cover. One of the  interesting  findings  is  also  the  additive  effect invasive  species  Fraxinus  pennsylvanica,  Acer negundo  and  Amorpha  fruticosa  have  on  soil variables  Hm,  N,  C  and  NB.  Additive  effect these  species  demonstrate  on  soil  factors indicates  that  soil  modification  is  directed towards  stabilization  and/or  acceleration  of invasion  and  inhibition  of  native  species  reestablishment.  Additionaly,  additive  effect  of invasive  species  implies  the  possibility  of ecological  legacy  even  after   potential  removal. This finding, due to its practical implications in nature reserves  across Europe, demands further research

The Impact of Multiple Species Invasion on Soil and Plant Communities Increases With Invasive Species Co-occurrence

Despite increasing evidence indicating that invasive species are harming biodiversity, ecological systems and processes, impacts of multiple species invasion and their links with changes in plant and soil communities are inadequately documented and remain poorly understood. Addressing multiple invaders would help to ward against community-wide, synergistic effects, aiding in designing more effective control strategies. In this work, correlative relationships are examined for potential impacts of three co-occurring invasive plant species, Amorpha fruticosa, Fraxinus pennsylvanica, and Acer negundo, on soil conditions and native plant diversity. The research was conducted in riparian ecosystems and included the following treatments: (1) co-occurrence of the three invasive plant species, (2) occurrence of a single invasive species, and (3) control, i.e., absence of invasive species. Co-occurrence of three invasive plant species caused higher direct impact on soil properties, soil functioning, and native plant diversity. Soil in mixed plots (those populated with all three invaders) contained higher levels of nitrifying bacteria, organic matter, nitrogen, and carbon as well as lower carbon to nitrogen ratio as compared to single species invaded plots and control plots. Furthermore, native plant diversity decreased with invasive plants co-occurrence. Differences in soil conditions and lower native plant diversity revealed the interactive potential of multiple invasive species in depleting biodiversity and eroding soil functionality, ultimately affecting ecological and biogeochemical processes both below and above ground. Our results highlight the need to prevent the impact of multispecies invasion, suggesting that riparian ecosystems affected by co-occurring invaders should be prioritized for invasion monitoring and ecological restoration

Forest and grassland habitats support pollinator diversity more than wildflowers and sunflower monoculture

Intensively managed agricultural landscapes often lack suitable habitats to support diverse wildlife, particularly harming pollinator communities. Besides mass flowering crops, remnant patches of natural and semi-natural vegetation may play a key role in maintaining and conserving biodiversity. Yet, the effects of different natural habitats, including forests and grasslands, on different pollinator communities are poorly understood at the landscape scale. We examined the abundance, richness, and diversity of wild bees and hoverflies, two key pollinator groups, across a land-use gradient spanning forest edges, grassland, wildflower strips, and sunflower monoculture. We also examined the distribution of hoverfly larvae trophic guilds and wild bee nesting traits across the above-mentioned land-use gradient. Finally, we evaluated the impact of landscape structure (forest, grassland, and water cover in the surrounding landscape) on pollinator community composition. Our results indicate that forest and grassland habitats supported a higher abundance and greater richness of pollinators than wildflower strips and sunflower monocultures. Furthermore, hoverflies were more sensitive to habitat and floristic homogenization than wild bees. Sunflower and wildflower habitats also hosted a lower diversity of larvae trophic guilds and wild bee nesting guilds as compared to forests and grasslands. Our study suggests that conserving and restoring forest and grassland habitats within agricultural mosaics may serve as the main ‘refuge’ for wild pollinators

Effects of Climate and Atmospheric Nitrogen Deposition on Early to Mid-Term Stage Litter Decomposition Across Biomes

Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green and Rooibos teas at 524 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect litter mass loss measured after 3 and 12 months. Our study shows that the early to mid-term mass loss at the global scale was affected predominantly by litter quality (explaining 73% and 62% of the total variance after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate were not litter-specific and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months of incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Rooibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month mass loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.5% and 1.1% of the variance, respectively. The expected changes in macroclimate and N deposition at the global scale by the end of this century are estimated to increase the 12-month mass loss of easily decomposable litter by 1.1-3.5% and of the more stable substrates by 3.8-10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term mass loss of high-quality litter by 1.4-2.2% and that of low-quality litter by 0.9-1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate.This work was performed within the TeaComposition initiative, carried out by 190 institutions worldwide. We thank for funding support for the workshop and data analysis from the ILTER. We acknowledge support by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, funded by the German Research Foundation (FZT 118), Scientific Grant Agency VEGA (Grant No. 2/0101/18), as well as by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program (Grant Agreement No. 677232). Thanks are due to FCT/MCTES for the financial support to CESAM (UIDB/50017/2020 + UIDP/50017/2020) and to the project PORBIOTA (POCI-01-0145-FEDER-022127). AI Sousa was funded by national funds through the FCT-Foundation for Science and Technology, I.P., under the project CEECIND/00962/2017. HS and CB acknowledge FCT support to cE3c through UID/BIA/00329/2013, UID/BIA/00329/2019, and UIDB/00329/2020, and the project PORBIOTA - POCI-01-0145-FEDER-022127. We are also thankful to UNILEVER for sponsoring the Lipton tea

Effects of climate and atmospheric nitrogen deposition on early to mid-term stage litter decomposition across biomes

International audienceLitter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green and Rooibos teas at 524 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect litter mass loss measured after 3 and 12 months. Our study shows that the early to mid-term mass loss at the global scale was affected predominantly by litter quality (explaining 73% and 62% of the total variance after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate were not litter-specific and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months of incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Rooibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month mass loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.5% and 1.1% of the variance, respectively. The expected changes in macroclimate and N deposition at the global scale by the end of this century are estimated to increase the 12-month mass loss of easily decomposable litter by 1.1– 3.5% and of the more stable substrates by 3.8–10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term mass loss of high-quality litter by 1.4–2.2% and that of low-quality litter by 0.9–1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate