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Global patterns of forest autotrophic carbon fluxesBanbury Morgan, RebeccaHerrmann, ValentineKunert, NorbertBond-Lamberty, BenMuller-Landau, Helene C.Anderson-Teixeira, Kristina J.DOI: info:10.1111/gcb.15574
Banbury Morgan, Rebecca, Herrmann, Valentine, Kunert, Norbert, Bond-Lamberty, Ben, Muller-Landau, Helene C., and Anderson-Teixeira, Kristina J. 2021. "Global patterns of forest autotrophic carbon fluxes." Global Change Biology
ID: 158908
Type: article
Authors: Banbury Morgan, Rebecca; Herrmann, Valentine; Kunert, Norbert; Bond-Lamberty, Ben; Muller-Landau, Helene C.; Anderson-Teixeira, Kristina J.
Abstract: Carbon (C) fixation, allocation, and metabolism by trees set the basis for energy and material flows in forest ecosystems and define their interactions with Earth's changing climate. However, while many studies have considered variation in productivity with latitude and climate, we lack a cohesive synthesis on how forest carbon fluxes vary globally with respect to climate and one another. Here, we draw upon 1,319 records from the Global Forest Carbon Database, representing all major forest types and the nine most significant autotrophic carbon fluxes, to comprehensively review how annual C cycling in mature, undisturbed forests varies with latitude and climate on a global scale. Across all flux variables analyzed, rates of C cycling decreased continuously with absolute latitude-a finding that confirms multiple previous studies and contradicts the idea that net primary productivity of temperate forests rivals that of tropical forests. C flux variables generally displayed similar trends across latitude and multiple climate variables, with no differences in allocation detected at this global scale. Temperature variables in general, and mean annual temperature or temperature seasonality in particular, were the best single predictors of C flux, explaining 19%-71% of variation in the C fluxes analyzed. The effects of temperature were modified by moisture availability, with C flux reduced under hot and dry conditions and sometimes under very high precipitation. Annual C fluxes increased with growing season length and were also influenced by growing season climate. These findings clarify how forest C flux varies with latitude and climate on a global scale. In an era when forests will play a critical yet uncertain role in shaping Earth's rapidly changing climate, our synthesis provides a foundation for understanding global patterns in forest C cycling.
Leaf turgor loss point shapes local and regional distributions of evergreen but not deciduous tropical treesKunert, NorbertZailaa, JosephHerrmann, ValentineMuller-Landau, Helene C.Wright, S. JosephPerez, RolandoMcMahon, Sean M.Condit, Richard C.Hubbell, Steven P.Sack, LawrenDavies, Stuart J.Anderson-Teixeira, Kristina J.DOI: info:10.1111/nph.17187
Kunert, Norbert, Zailaa, Joseph, Herrmann, Valentine, Muller-Landau, Helene C., Wright, S. Joseph, Perez, Rolando, McMahon, Sean M., Condit, Richard C., Hubbell, Steven P., Sack, Lawren, Davies, Stuart J., and Anderson-Teixeira, Kristina J. 2021. "Leaf turgor loss point shapes local and regional distributions of evergreen but not deciduous tropical trees." New Phytologist
ID: 158537
Type: article
Authors: Kunert, Norbert; Zailaa, Joseph; Herrmann, Valentine; Muller-Landau, Helene C.; Wright, S. Joseph; Perez, Rolando; McMahon, Sean M.; Condit, Richard C.; Hubbell, Steven P.; Sack, Lawren; Davies, Stuart J.; Anderson-Teixeira, Kristina J.
Abstract: The effects of climate change on tropical forests will depend on how diverse tropical tree species respond to drought. Current distributions of evergreen and deciduous tree species across local and regional moisture gradients reflect their ability to tolerate drought stress, and might be explained by functional traits. We measured leaf water potential at turgor loss (i.e. 'wilting point'; pi(tlp)), wood density (WD) and leaf mass per area (LMA) on 50 of the most abundant tree species in central Panama. We then tested their ability to explain distributions of evergreen and deciduous species within a 50 ha plot on Barro Colorado Island and across a 70 km rainfall gradient spanning the Isthmus of Panama. Among evergreen trees, species with lower pi(tlp) were associated with drier habitats, with pi(tlp) explaining 28% and 32% of habitat association on local and regional scales, respectively, greatly exceeding the predictive power of WD and LMA. In contrast, pi(tlp) did not predict habitat associations among deciduous species. Across spatial scales, pi(tlp) is a useful indicator of habitat preference for tropical tree species that retain their leaves during periods of water stress, and holds the potential to predict vegetation responses to climate change.
Preliminary indications for diverging heat and drought sensitivities in Norway spruce and Scots pine in Central EuropeKunert, NorbertDOI: info:10.3832/ifor3216-012v. 13No. 289–91
Kunert, Norbert. 2020. "Preliminary indications for diverging heat and drought sensitivities in Norway spruce and Scots pine in Central Europe." iForest - Biogeosciences and Forestry 13 (2):89– 91.
ID: 154848
Type: article
Authors: Kunert, Norbert
Abstract: Massive and increasing tree mortality is currently observed in the two conifer species Norway spruce and Scots pine in Central Europe. Consecutive dry years are made responsible for this phenomenon. Leaf trait measurements, in specific leaf osmotic potential (πosm) and leaf water potential at turgor loss (πtlp), indicate that the underlying mechanisms for tree mortality are most likely different between the two species. πtlp of spruce was highly negative, revealing a potentially high drought tolerance of the species. πtlp of Scots pine was less negative, suggesting a higher susceptibility to drought stress. I conclude that the mortality of Norway spruce might be caused by rising temperatures and that the summer temperatures in the past years were beyond the species thermal tolerance threshold. Overall, I want to highlight and enhance the discussion that the search for suitable species for a climate change adapted forest should go in both directions, i.e., species should be chosen to make the forest fit for both increasing drought and heat stress.
Leaf turgor loss point at full hydration for 41 native and introduced tree and shrub species from Central EuropeKunert, NorbertTomaskova, IvanaDOI: info:10.1093/jpe/rtaa059v. 13No. 6754–756
Kunert, Norbert and Tomaskova, Ivana. 2020. "Leaf turgor loss point at full hydration for 41 native and introduced tree and shrub species from Central Europe." Journal of Plant Ecology 13 (6):754– 756.
ID: 156840
Type: article
Authors: Kunert, Norbert; Tomaskova, Ivana
Abstract: The last years, Central European forests have suffered from drought as a direct consequence of climate change. All these forests have a long manageme
Tree height and leaf drought tolerance traits shape growth responses across droughts in a temperate broadleaf forestMcGregor, Ian R.Helcoski, RyanKunert, NorbertTepley, Alan J.Gonzalez‐Akre, Erika B.Herrmann, ValentineZailaa, JosephStovall, Atticus E. L.Bourg, Norman A.McShea, William J.Pederson, NeilSack, LawrenAnderson‐Teixeira, Kristina J.DOI: info:10.1111/nph.16996
McGregor, Ian R., Helcoski, Ryan, Kunert, Norbert, Tepley, Alan J., Gonzalez‐Akre, Erika B., Herrmann, Valentine, Zailaa, Joseph, Stovall, Atticus E. L., Bourg, Norman A., McShea, William J., Pederson, Neil, Sack, Lawren, and Anderson‐Teixeira, Kristina J. 2020. "Tree height and leaf drought tolerance traits shape growth responses across droughts in a temperate broadleaf forest." New Phytologist
ID: 157275
Type: article
Authors: McGregor, Ian R.; Helcoski, Ryan; Kunert, Norbert; Tepley, Alan J.; Gonzalez‐Akre, Erika B.; Herrmann, Valentine; Zailaa, Joseph; Stovall, Atticus E. L.; Bourg, Norman A.; McShea, William J.; Pederson, Neil; Sack, Lawren; Anderson‐Teixeira, Kristina J.
Relevance of wood anatomy and size of Amazonian trees in the determination and allometry of sapwood areaAparecido, Luiza Maria Teophilodos Santos, JoaquimHiguchi, NiroKunert, NorbertDOI: info:10.1590/1809-4392201800961v. 49No. 11
Aparecido, Luiza Maria Teophilo, dos Santos, Joaquim, Higuchi, Niro, and Kunert, Norbert. 2019. "Relevance of wood anatomy and size of Amazonian trees in the determination and allometry of sapwood area." Acta Amazonica 49 (1):1.
ID: 149682
Type: article
Authors: Aparecido, Luiza Maria Teophilo; dos Santos, Joaquim; Higuchi, Niro; Kunert, Norbert
Abstract: Hydrological processes in forest stands are mainly influenced by tree species composition and morpho-physiological characteristics. Few studies on anatomical patterns that govern plant hydraulics were conducted in tropical forest ecosystems. Thus, we used dye immersion to analyze sapwood area patterns of 34 trees belonging to 26 species from a terra firme forest in the central Brazilian Amazon. The sapwood area was related with wood anatomy and tree size parameters (diameter-at-breast-height - DBH, total height and estimated whole-tree volume). Exponential allometric equations were used to model sapwood area using the biometrical variables measured. Sapwood area traits (cross-section non-uniformity and heartwood visibility) varied significantly among and within species even though all were classified as diffuse porous. DBH was strongly and non-linearly correlated with sapwood area (R-2 = 0.46, P < 0.001), while no correlation was observed with vessel-lumen diameter (P = 0.94) and frequency (P = 0.58). Sapwood area and shape were also affected by the occurrence of vessel obstruction (i.e., tyloses), hollow stems and diseases. Our results suggest that sapwood area patterns and correlated variables are driven by intrinsic species characteristics, microclimate and ecological succcssion within the stand. We believe that individual tree sapwood characteristics have strong implications over water use, hydrological stand upsaling and biomass quantification. These characteristics should be taken into account (e.g., through a multi-point sampling approach) when estimating forest stand transpiration in a highly biodiverse ecosystem.
A new automated stem CO2 efflux chamber based on industrial ultra-low-cost sensorsBrändle, JohannesKunert, NorbertDOI: info:10.1093/treephys/tpz104v. 39No. 121975–1983
Brändle, Johannes and Kunert, Norbert. 2019. "A new automated stem CO2 efflux chamber based on industrial ultra-low-cost sensors." Tree physiology 39 (12):1975– 1983.
ID: 152942
Type: article
Authors: Brändle, Johannes; Kunert, Norbert
Abstract: Tree autotrophic respiratory processes, especially stem respiration or stem CO2 efflux (Estem), are important components of the forest carbon budget. Despite the efforts to investigate the controlling processes of Estem in the last years a considerable lack in our knowledge remains on the abiotic and biotic drivers affecting Estem dynamics. It has been strongly advocated that long-term measurements would shed light into those processes. The expensive scientific instruments needed to measure gas exchange has prevented from applying Estem measurements on a larger temporal and spatial scale. Here, we present an automated closed dynamic chamber system based on inexpensive and industrially broadly applied CO2 sensors reducing the costs for the sensing system to a minimum. The CO2 sensor was cross-calibrated with a commonly used gas exchange system in the laboratory and in the field, and we found very good accordance of these sensors. We tested the system under harsh tropical climatic conditions, characterized by heavy tropical rainfall events, extreme humidity, and temperatures, in a moist lowland forest in Malaysia. We recorded Estem of three Dyera costulata trees with our prototype over various days. The variation of Estem was large among the three tree individuals and varied by 7.5-fold. However, clear diurnal changes in Estem were present in all three tree individuals. One tree showed high diurnal variation in Estem and the relationship between Estem and temperature was characterized by a strong hysteresis. The large variations found within one single tree species highlights the importance of continuous measurement to quantify ecosystem carbon fluxes.
Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree speciesHilman, BoazMuhr, JanTrumbore, Susan E.Kunert, NorbertCarbone, Mariah S.Yuval, PäWright, S. JosephMoreno, GerardoPérez‑Priego, OscarMigliavacca, MircoCarrara, ArnaudGrünzweig, José M.Osem, YagilWeiner, TalAngert, AlonDOI: info:10.5194/bg-16-177-2019v. 16No. 1177–191
Hilman, Boaz, Muhr, Jan, Trumbore, Susan E., Kunert, Norbert, Carbone, Mariah S., Yuval, Pä, Wright, S. Joseph, Moreno, Gerardo, Pérez‑Priego, Oscar, Migliavacca, Mirco, Carrara, Arnaud, Grünzweig, José M., Osem, Yagil, Weiner, Tal, and Angert, Alon. 2019. "Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree species." Biogeosciences 16 (1):177– 191.
ID: 152373
Type: article
Authors: Hilman, Boaz; Muhr, Jan; Trumbore, Susan E.; Kunert, Norbert; Carbone, Mariah S.; Yuval, Pä; Wright, S. Joseph; Moreno, Gerardo; Pérez‑Priego, Oscar; Migliavacca, Mirco; Carrara, Arnaud; Grünzweig, José M.; Osem, Yagil; Weiner, Tal; Angert, Alon
Abstract: Author: Hilman, Boaz et al.; Genre: Journal Article; Published in Print: 2017-01; Open Access; Title: Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree species
Understanding the controls over forest carbon use efficiency on small spatial scales: Effects of forest disturbance and tree diversityKunert, NorbertEl-Madany, Tarek S.Aparecido, Luiza Maria T.Wolf, SebastianPotvin, CatherineDOI: info:10.1016/j.agrformet.2019.02.007v. 269-270136–144
Kunert, Norbert, El-Madany, Tarek S., Aparecido, Luiza Maria T., Wolf, Sebastian, and Potvin, Catherine. 2019. "Understanding the controls over forest carbon use efficiency on small spatial scales: Effects of forest disturbance and tree diversity." Agricultural and Forest Meteorology 269-270:136– 144.
ID: 150937
Type: article
Authors: Kunert, Norbert; El-Madany, Tarek S.; Aparecido, Luiza Maria T.; Wolf, Sebastian; Potvin, Catherine
Abstract: Tropical forests are characterized by their high photosynthetic activity. Results from pantropical studies show that on average only 30% of the products from photosynthesis are allocated to new biomass compared to on average 50% in temperate forest systems. Why those forests have a low carbon use efficiency (CUE) remains unknown. We present a synthesis of studies from two tropical sites with a similar methodological setup allowing the evaluation of the ecophysiological responses of tree communities to diversity effects and forest disturbance. Here we use xylem sap flux derived gross primary productivity (GPP) that was modeled with eddy covariance data for a seven-year-old planted forest with plots of varying tree species diversity in Panama and an old-growth forest with a distinct disturbance gradient in an Amazonian moist lowland forest. Additionally, net primary productivity (NPP) was calculated from inventory data. We found evidence that GPP is relatively stable with forest disturbance but GPP increases with tree species richness. Lowest CUE with only 35% of GPP allocated to growth was present in undisturbed forest patches. Light forest disturbance had a positive effect on CUE and 62% of GPP was allocated to grow new biomass. Monospecific stands had a higher CUE than diverse tree stands. We conclude that two factors are controlling CUE in tropical forests leading to low CUE. First, forest disturbance leads to a higher allocation of carbon towards growth. Second, a great fraction of GPP is used for processes dedicated to species complementarity. This improves the overall performance of diverse forest stands compared to monocultures.
Specific leaf area for five tropical tree species growing in different tree species mixtures in Central PanamaKunert, NorbertZailaa, JosephDOI: info:10.1007/s11056-019-09706-zv. 50No. 6873–890
Kunert, Norbert and Zailaa, Joseph. 2019. "Specific leaf area for five tropical tree species growing in different tree species mixtures in Central Panama." New Forests 50 (6):873– 890.
ID: 150590
Type: article
Authors: Kunert, Norbert; Zailaa, Joseph
Abstract: Leaf traits have been shown to explain a great fraction of differences in growth rates in trees. With this study, we evaluate if differences in growth performance of different species mixtures in a tropical tree plantation can be attributed to the plasticity of the specific leaf area index. We compare the specific leaf area of five native Panamanian tree species growing in monospecific stands, stands containing two or three tree species and stands containing all five tree species. We could confirm the commonly observed interspecific linear relationship between leaf dry mass per leaf area. Despite the general relationship, a plasticity of the specific leaf area was detected for certain species in different mixture types. In general, the plasticity was lower for sun leaves than for shade leaves and the expression of leaf trait plasticity depended largely on the species. We performed an additive partitioning of mixture effects and the analysis resulted in strong complementarity effects on plot level. We speculate that leaf plasticity might increase the ability of certain tree species to use light more efficiently in mixed species stands. The resulting complementarity between species allows mixed stands an optimized light resource use and higher productivity. Accordingly, relative growth rate on plot level scaled linearly with specific leaf area of a given stand. Establishing mixed reforestation stands covering a wider range of tree leaf functional traits, such as assembling tree species characterized by different specific leaf area, might favor the expression of the trait plasticity and thus the overall plantation performance.
Living on borrowed time - Amazonian trees use decade-old storage carbon to survive for months after complete stem girdlingMuhr, JanTrumbore, SusanHiguchi, NiroKunert, NorbertDOI: info:10.1111/nph.15302v. 220No. 1111–120
Muhr, Jan, Trumbore, Susan, Higuchi, Niro, and Kunert, Norbert. 2018. "Living on borrowed time - Amazonian trees use decade-old storage carbon to survive for months after complete stem girdling." New Phytologist 220 (1):111– 120.
ID: 148481
Type: article
Authors: Muhr, Jan; Trumbore, Susan; Higuchi, Niro; Kunert, Norbert
Abstract: Nonstructural carbon (NSC) reserves act as buffers to sustain tree activity during periods when carbon (C) assimilation does not meet C demand, but little is known about their age and accessibility; we designed a controlled girdling experiment in the Amazon to study tree survival on NSC reserves. We used bomb-radiocarbon (C-14) to monitor the time elapsed between C fixation and release ('age' of substrates). We simultaneously monitored how the mobilization of reserve C affected delta(CO2)-C-13. Six ungirdled control trees relied almost exclusively on recent assimilates throughout the 17 months of measurement. The Delta C-14 of CO2 emitted from the six girdled stems increased significantly over time after girdling, indicating substantial remobilization of storage NSC fixed up to 13-14 yr previously. This remobilization was not accompanied by a consistent change in observed delta(CO2)-C-13. These trees have access to storage pools integrating C accumulated over more than a decade. Remobilization follows a very clear reverse chronological mobilization with younger reserve pools being mobilized first. The lack of a shift in the delta(CO2)-C-13 might indicate a constant contribution of starch hydrolysis to the soluble sugar pool even outside pronounced stress periods (regular mixing).
Tropical tree diversity enhances light capture through crown plasticity and spatial and temporal niche differencesSapijanskas, JurgisPaquette, AlainPotvin, Catherine JeanneKunert, NorbertLoreau, MichelDOI: info:10.1890/13-1366.1v. 95No. 92479–2492
Sapijanskas, Jurgis, Paquette, Alain, Potvin, Catherine Jeanne, Kunert, Norbert, and Loreau, Michel. 2014. "Tropical tree diversity enhances light capture through crown plasticity and spatial and temporal niche differences." Ecology 95 (9):2479– 2492.
ID: 118957
Type: article
Authors: Sapijanskas, Jurgis; Paquette, Alain; Potvin, Catherine Jeanne; Kunert, Norbert; Loreau, Michel
Tree diversity enhances tree transpiration in a Panamanian forest plantationKunert, NorbertSchwendenmann, LuitgardPotvin, Catherine JeanneHölscher, DirkDOI: info:10.1111/j.1365-2664.2011.02065.xv. 49No. 1135–144
Kunert, Norbert, Schwendenmann, Luitgard, Potvin, Catherine Jeanne, and Hölscher, Dirk. 2012. "Tree diversity enhances tree transpiration in a Panamanian forest plantation." Journal of Applied Ecology 49 (1):135– 144.
ID: 112561
Type: article
Authors: Kunert, Norbert; Schwendenmann, Luitgard; Potvin, Catherine Jeanne; Hölscher, Dirk
Relating the X-band opacity of a tropical tree canopy to sapflow, rain interception and dew formationSchneebeli, MarcWolf, SebastianKunert, NorbertEugster, WernerMatzler, ChristianDOI: info:10.1016/j.rse.2011.04.016v. 115No. 82116–2125
Schneebeli, Marc, Wolf, Sebastian, Kunert, Norbert, Eugster, Werner, and Matzler, Christian. 2011. "Relating the X-band opacity of a tropical tree canopy to sapflow, rain interception and dew formation." Remote Sensing of Environment 115 (8):2116– 2125.
ID: 111290
Type: article
Authors: Schneebeli, Marc; Wolf, Sebastian; Kunert, Norbert; Eugster, Werner; Matzler, Christian
Abstract: First paragraph: Tropical rain forests play a dominant role in the earth's water balance. An important fraction of the hydrological cycle amounts to rain water interception and its subsequent re-evaporation. According to Lawrence et al. (2007), transpiration is the dominant process of evapotranspiration with a contribution of 58%, followed by interception evaporation (33%) and soil evaporation (9%). Rain interception is rather difficult to measure accurately. The most frequently used technique is the measurement of throughfall by setting up several rain-gages below the canopy and one or more above the canopy. The difference of the collected water is assumed to be withheld by the canopy. There are some major drawbacks to this method: Due to the complex structure of a forest canopy, the spatial variability of the throughfall is very large, hence numerous rain gages are needed in order to achieve representative and accurate sampling (Kimmins, 1973). Direct evaporation of intercepted rain water is another effect that cannot be tackled with the throughfall method, wherefore reliable measurements can only be conducted during night time. A promising technique is the attenuation measurement of a 10 GHz signal over a horizontal path through a Douglas fir stand as reported in Bouten et al. (1991). They observed a distinct linear relation of the attenuated signal to intercepted rain. The authors then employed this attenuation method in several upcoming studies as a monitoring tool for water interception in forest canopies ([Bouten et al., 1996] and [Vrugt et al., 2003]). Czikowsky and Fitzjarrald (2009) reported on a new interception estimation technique that estimates the excess evaporation following rain events with eddy covariance flux measurements. Recently, a global assessment of canopy interception from satellite data was published in Miralles et al. (2010). The authors used an analytical interception model (Valente et al., 1997) and fed it with satellite data of precipitation, lightning frequency and canopy fraction. It was found that the interception loss is sensitive to the rainfall volume, rain intensity and the forest cover. Some of these findings will be confirmed in the article at hand. Compared to intercepted rain, very little is known about the importance of dew formation and dew evaporation, most likely because no established measurement technique is available so far to measure the dew amount in a forest canopy. It is although known that dew not only promotes diseases of plant crops and is therefore an important parameter in agriculture (for tropical conditions see e.g. Holliday, 1980), according to Kabela et al. (2009), dew "also may contaminate remotely sensed measurements of important ecosystem variables such as soil moisture, land surface temperature, and vegetation biomass". Dew duration is relatively easy to measure by using electrical devices that change their resistance or capacity when becoming wet ([Kidron et al., 1965] and [Noffsinger, 1965]). However, methods for measuring dew amounts (e.g. weighing dew gages, weighing lysimeters) are limited and solely used for measurements close to the ground (Agam & Berliner, 2006).