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Effects of altered precipitation regimes on bryophyte carbon dynamics in a Peruvian tropical montane cloud forest

Ahlstrand, Jenny LU (2016) In Student thesis series INES NGEM01 20161
Dept of Physical Geography and Ecosystem Science
Abstract
Tropical montane cloud forests (TMCF) are unique ecosystems that are frequently surrounded by clouds which increase humidity and promote the growth of bryophytes. Several dimensions of humidity are important for the carbon dynamics of bryophytes. Climate change is therefore projected to have a large impact on them as well as on the TMCF itself. The present study aimed to investigate the effects that changing precipitation regimes will have on bryophyte carbon dynamics. Specifically changes in precipitation amounts, frequency and type i.e. if the precipitation falls as rain or is brought by cloud mist were studied through three experiments; (1) a blocked, full factorial experimental set-up tested for the effect of the three precipitation... (More)
Tropical montane cloud forests (TMCF) are unique ecosystems that are frequently surrounded by clouds which increase humidity and promote the growth of bryophytes. Several dimensions of humidity are important for the carbon dynamics of bryophytes. Climate change is therefore projected to have a large impact on them as well as on the TMCF itself. The present study aimed to investigate the effects that changing precipitation regimes will have on bryophyte carbon dynamics. Specifically changes in precipitation amounts, frequency and type i.e. if the precipitation falls as rain or is brought by cloud mist were studied through three experiments; (1) a blocked, full factorial experimental set-up tested for the effect of the three precipitation factors on bryophyte net photosynthesis and respiration, (2) the bryophyte photosynthetic performance was also measured on this set up and (3) on a second experimental set up the response of bryophyte carbon dynamics to re-wetting after increasing desiccation periods was measured. The results of the first experiment showed that precipitation amount had the clearest effect on bryophyte carbon dynamics where net ecosystem exchange (NEE) decreased most in high amount treatments. A slightly lower decrease in NEE was found with low amounts of mist compared to low amounts of rain, although the difference between the types was not significant. Furthermore, an effect from frequency was found on respiration where the effect differed most between amounts and types for the high frequency treatments while the difference was smaller for medium and low frequencies. However no interactions with frequency were found for NEE or gross primary production (GPP). In the second experiment, bryophytes generally reached a saturated photosynthesis at relatively low light levels (400 μmol photons m-2 s-1). At these light intensities or higher, the samples watered with low amounts of mist at high frequencies led to the highest maximum photosynthetic rate (Pmax) while the samples watered with high amounts of mist at low frequency gave the lowest Pmax. Thus, low amount, high frequency mist was generally most beneficial for carbon uptake. However at lower light intensities (200 μmol photons m-2 s-1) the carbon gain for the samples of low amount treatments was lower compared to samples of high amount treatments. In the third experiment, there was a clear decrease in GPP and NEE, i.e. carbon uptake, with increasing desiccation length. No trend for the respiratory response to increasing desiccation length was determined. In summary, bryophytes in TMCF seem to be well adapted to the environment they live in today, where desiccation periods are short and where low amounts of precipitation, probably in the form of mist are beneficial to bryophyte carbon uptake. This also suggests that projected changes in climate conditions in TMCF will influence bryophyte carbon dynamics negatively, leading to a decrease in carbon accumulation. Since bryophytes provide a number of important ecosystem services, a negative change in their carbon dynamics could result in biodiversity loss as well as changes in the hydrologic cycle and carbon dynamics of the TMCF. This in turn could have large scale effects on both downslope ecosystems and the people living there, as well as an impact on the world’s biodiversity. (Less)
Popular Abstract (Swedish)
Tropiska bergmolnskogar (eng: Tropical montane cloud forests; TMCF) är unika ekosystem som frekvent omges av moln vilka ökar fuktigheten och gynnar tillväxt av mossor. Koldynamiken hos mossor påverkas av fukt över flera dimensioner. Det är därför projicerat att klimatförändringen kommer få en stor påverkan på dem samt även på de TMCF. Målet med denna studie var att se hur effekterna av förändrade mängder och frekvenser av nederbörd och om den nederbörden föll som regn eller kom direkt från molnen (dimma), påverkar mossors koldynamik. Detta utfördes genom tre experiment; (1) ett grupperat fullfaktoriellt experiment där responsen på de tre nederbördsfaktorerna mättes genom skillnader i mossornas respiration och nettoutbyte av koldioxid vid... (More)
Tropiska bergmolnskogar (eng: Tropical montane cloud forests; TMCF) är unika ekosystem som frekvent omges av moln vilka ökar fuktigheten och gynnar tillväxt av mossor. Koldynamiken hos mossor påverkas av fukt över flera dimensioner. Det är därför projicerat att klimatförändringen kommer få en stor påverkan på dem samt även på de TMCF. Målet med denna studie var att se hur effekterna av förändrade mängder och frekvenser av nederbörd och om den nederbörden föll som regn eller kom direkt från molnen (dimma), påverkar mossors koldynamik. Detta utfördes genom tre experiment; (1) ett grupperat fullfaktoriellt experiment där responsen på de tre nederbördsfaktorerna mättes genom skillnader i mossornas respiration och nettoutbyte av koldioxid vid fotosyntes, (2) vidare studerades fotosyntes vid varierande ljusintensiteter under de olika nederbördsregimerna samt (3) hur mossors koldynamik svarade på varierande uttorkningsperioder. Resultaten från det första experimentet visade att nettoutbytet av koldioxid minskade mest med höga mängder nederbörd. En något mindre minskning i nettoutbyte förekom med låga mängder dimma jämfört med låga mängder regn, skillnaden mellan de två nederbördstyperna var dock inte signifikant. Vidare hittades också en effekt från nederbördsfrekvens på mossornas respiration där hög frekvens visade störst skillnader mellan mäng och typ av nederbörd medan medium och låg frekvens visade mindre sådana skillnader. Ingen interaktion med frekvens hittades för bruttoproduktionen eller netto utbyte av koldioxid. Det andra experimentet visade att mossor generellt uppnådde sin maximala fotosyntetiska kapacitet vid en relativt låg ljusintensitet (400 μmol fotoner m-2 s-1). Vid denna eller högre ljusintensitet gav låga mängder dimma med hög frekvens den högsta maximala fotosyntesen (Pmax) medan höga mängder dimma med låg frekvens gav den lägsta Pmax. Det verkar därmed som att låga mängder dimma med hög frekvens var mest fördelaktigt för mossors kolupptag. Vid lägre ljusintensitet (200 μmol fotoner m-2 s-1) var kolupptaget dock lägre i prover vattnade med låga mängder nederbörd jämfört med höga. I det tredje experimentet visade både bruttoproduktionen och nettoutbytet av koldioxid en linjär nedåtgående trend med längre uttorkningsperiod. Respiration visade dock ingen klar trend. Sammanfattningsvis verkar mossor i TMCF vara väl anpassade till den miljö de lever i idag med korta uttorkningsperioder och där låga mängder nederbörd, troligtvis i form av dimma är mest fördelaktigt för mossors kolupptag. Detta tyder också på att projicerade förändringar i nederbördsregimer tyder på att deras kommer påverka mossors koldynamik negativt och att deras kolupptag kommer vara mindre än idag. Då mossor utför viktiga ekosystemtjänster kan en negativ förändring av deras koldynamik leda till förlust av biodiversitet och förändringar av hydrologin och kolcykeln i TMCF. På en större skala skulle detta i sin tur påverka ekosystem på lägre altituder och de människor som bor där samt få en stor påverkan på världens biodiversitet. (Less)
Please use this url to cite or link to this publication:
author
Ahlstrand, Jenny LU
supervisor
organization
course
NGEM01 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
precipitation, tropical mountain cloud forest, Bryophytes, Peru, carbon dynamics, physical geography and ecosystem science
publication/series
Student thesis series INES
report number
402
language
English
id
8894979
date added to LUP
2016-11-15 13:28:37
date last changed
2018-05-14 03:44:57
@misc{8894979,
  abstract     = {Tropical montane cloud forests (TMCF) are unique ecosystems that are frequently surrounded by clouds which increase humidity and promote the growth of bryophytes. Several dimensions of humidity are important for the carbon dynamics of bryophytes. Climate change is therefore projected to have a large impact on them as well as on the TMCF itself. The present study aimed to investigate the effects that changing precipitation regimes will have on bryophyte carbon dynamics. Specifically changes in precipitation amounts, frequency and type i.e. if the precipitation falls as rain or is brought by cloud mist were studied through three experiments; (1) a blocked, full factorial experimental set-up tested for the effect of the three precipitation factors on bryophyte net photosynthesis and respiration, (2) the bryophyte photosynthetic performance was also measured on this set up and (3) on a second experimental set up the response of bryophyte carbon dynamics to re-wetting after increasing desiccation periods was measured. The results of the first experiment showed that precipitation amount had the clearest effect on bryophyte carbon dynamics where net ecosystem exchange (NEE) decreased most in high amount treatments. A slightly lower decrease in NEE was found with low amounts of mist compared to low amounts of rain, although the difference between the types was not significant. Furthermore, an effect from frequency was found on respiration where the effect differed most between amounts and types for the high frequency treatments while the difference was smaller for medium and low frequencies. However no interactions with frequency were found for NEE or gross primary production (GPP). In the second experiment, bryophytes generally reached a saturated photosynthesis at relatively low light levels (400 μmol photons m-2 s-1). At these light intensities or higher, the samples watered with low amounts of mist at high frequencies led to the highest maximum photosynthetic rate (Pmax) while the samples watered with high amounts of mist at low frequency gave the lowest Pmax. Thus, low amount, high frequency mist was generally most beneficial for carbon uptake. However at lower light intensities (200 μmol photons m-2 s-1) the carbon gain for the samples of low amount treatments was lower compared to samples of high amount treatments. In the third experiment, there was a clear decrease in GPP and NEE, i.e. carbon uptake, with increasing desiccation length. No trend for the respiratory response to increasing desiccation length was determined. In summary, bryophytes in TMCF seem to be well adapted to the environment they live in today, where desiccation periods are short and where low amounts of precipitation, probably in the form of mist are beneficial to bryophyte carbon uptake. This also suggests that projected changes in climate conditions in TMCF will influence bryophyte carbon dynamics negatively, leading to a decrease in carbon accumulation. Since bryophytes provide a number of important ecosystem services, a negative change in their carbon dynamics could result in biodiversity loss as well as changes in the hydrologic cycle and carbon dynamics of the TMCF. This in turn could have large scale effects on both downslope ecosystems and the people living there, as well as an impact on the world’s biodiversity.},
  author       = {Ahlstrand, Jenny},
  keyword      = {precipitation,tropical mountain cloud forest,Bryophytes,Peru,carbon dynamics,physical geography and ecosystem science},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Effects of altered precipitation regimes on bryophyte carbon dynamics in a Peruvian tropical montane cloud forest},
  year         = {2016},
}