Depth distribution of soil water sourced by plants at the global scale : a new direct inference approach

Funding Information Fondazione Cassa di Risparmio di Padova e Rovigo. Grant Number: Bando Starting Grants 2015Peer reviewedPostprin

Response of soil organic matter dynamics to conversion from tropical forest to grassland as determined by long-term incubation

Understanding soil organic carbon (SOC) responses to land-use changes requires knowledge of the sizes and mean residence times (MRT) of specific identifiable SOC pools over a range of decomposability. We examined pool sizes and kinetics of active and slow pool carbon (C) for tropical forest and grassland ecosystems on Barro Colorado Island, Panama, using long-term incubations (180 days) of soil and stable C isotopes. Chemical fractionation (acid hydrolysis) was applied to assess the magnitude of non-hydrolysable pool C (NHC). Incubation revealed that both grassland and forest soil contained a small proportion of active pool C (<1%), with MRT of ∼6 days. Forest and grassland soil apparently did not differ considerably with respect to their labile pool substrate quality. The MRT of slow pool C in the upper soil layer (0-10 cm) did not differ between forest and grassland, and was approximately 15 years. In contrast, changes in vegetation cover resulted in significantly shorter MRT of slow pool C under grassland (29 years) as compared to forest (53 years) in the subsoil (30-40 cm). The faster slow pool turnover rate is probably associated with a loss of 30% total C in grassland subsoil compared to the forest. The NHC expressed as a percentage of total C varied between 54% and 64% in the surface soil and decreased with depth to ∼30%. Grassland NHC had considerably longer MRTs (120 to 320 years) as compared to slow pool C. However, the functional significance of the NHC pool is not clear, indicating that this approach must be applied cautiously

Soil CO2 efflux in an old-growth southern conifer forest

This is the research data set underlying the article "Soil CO₂ efflux in an old-growth southern conifer forest (<i>Agathis australis</i>) – magnitude, components, and controls" which is published in the journal SOIL (doi:10.5194/soil-2016-21).<br><br>Total soil CO₂ efflux, autotrophic and heterotrophic respiration, and soil data was measured in the University of Auckland Huapai reserve as part of a research project on carbon cycling in an old-growth kauri forest. Measurements were conducted between August 2012 and January 2014. <br><br><br

Decoupling of the urban vegetation productivity from climate

Urbanization is causing profound alterations of ecosystem functions at local and regional scales. The need to maximize ecosystem services to improve the livability of cities is resulting in intensive management of urban vegetation, which is likely generating new conditions for the ecosystem functioning. In this paper, we address the association between vegetation functioning (i.e., primary productivity) and climate in urban and adjacent non-urban areas in Auckland, New Zealand. We used time series analysis of integrated vegetation indices derived from satellite images (MODIS) to estimate a proxy of primary productivity of urban and non-urban vegetation. We analyzed the interannual variability of vegetation productivity in relation to climate fluctuations. In Auckland?s urban area the variability of primary productivity was not associated with any of the climatic variables considered, while in the non-urban area (i.e. reference area) vegetation productivity was strongly associated with cumulative rainfall during the growing season. Our results suggest that the productivity of urban vegetation may be undergoing a decoupling from the regional climate. If a decoupling of ecosystem functions from climate becomes a general pattern in urban areas it could have significant effects on urban vegetation planning and management. In a context of increased variability, urban ecosystems could constitute stable habitats and they will probably contribute to the viability of vulnerable populations.Fil: Paolini, Leonardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. University of Auckland; Nueva ZelandaFil: Schwendenmann, Luitgard. The University Of Auckland. Faculty Of Science; Nueva ZelandaFil: Aráoz, Ezequiel. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Powell, Priscila Ana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentin

Isotopic composition of CO2 in gasoline, diesel and natural gas combustion exhaust in Vancouver, BC, Canada

The isotopic composition (δ¹³ and δ¹⁸) in atmospheric carbon dioxide (CO₂) originating from gasoline and diesel vehicle exhaust and from natural gas combustion was determined. Gasoline and diesel samples were taken in the exhaust of representative vehicles of the fleet in Vancouver, BC, Canada between November 2013 and May 2014. The fleet average gasoline exhaust (which contained a fraction bioethanol) was determined with a δ¹³C of -27.27 (±0.93)‰ and a δ¹⁸O of -12.46 (±3.45)‰ (w.r.t. VPD-CO₂). The fleet average for diesel vehicles exhibited a slightly lower δ¹³C of -28.81 (±0.40)‰ and a δ¹⁸O of -18.63 (±0.72)‰ close to unfractionated combustion. For natural gas, samples were taken from a open torch using the city’s natural gas supply network at different dates over the year. The mean δ¹³C for natural gas samples was -41.64 (±0.82)‰, while the mean δ¹⁸O was lower than for internal combustion engines at -22.74 (±0.56)‰. In conclusion, δ¹³C depends on the fuel type and origin and there is evidence that δ¹⁸O is fractionated in the combustion process and presence and state of catalytic converters causes different δ¹⁸O.Arts, Faculty ofGeography, Department ofLand and Food Systems, Faculty ofNon UBCUnreviewedFacult

Reconstrucción del historial de incendios y estructura forestal en bosques mixtos de pino-encino en la Sierra Madre Oriental

Abstract Forest fires have had a remarkable relevance since the extraordinary fire season in 1998, due to their direct contribution to deforestation, changes in forest structure, species composition, and recently to their impact on the increment of carbon dioxide in the atmosphere. Nevertheless, there is a lack of detailed information about fire impact on forest structure, species composition, and forest dynamics in the Sierra Madre Oriental (SMO). In order to explain possible changes in those factors, this study has examined a chronosequence (134 years), which was determined by analysing tree ring samples in post-fire cohorts of different ages. The objectives of this study were to: (1) determine forest fire historical range of occurrence, (2) quantify present forest structure and tree species composition along a fire chronosequence in order to determinate reference areas to assist restoration programs, and (3) increase the understanding of disturbance patterns in mixed pine-oak forest in this region. The study revealed significant differences between post-fire cohorts in terms of woody species rich- ness, stand composition, and structure. High tree diversity was generally found in young stands, while the intermediate and major ones showed the lowest diversity. In old stands, tree diversity was increased again.Resumen Los incendios forestales en México han tenido gran relevancia después de la temporada de incendios en 1998 debido a su contribución directa a la deforestación, el cambio en la estructura y composición del bosque. Además, recientemente se considera su participación directa en el incremento de bióxido de carbono en la atmósfera. Sin embargo, es muy escaso el conocimiento que se posee acerca de los efectos de los incendios sobre la estructura, composición y dinámica de los bosques de la Sierra Madre Oriental (SMO). En este trabajo, se presenta una cronosecuencia de incendios forestales (134 años) determinada a través del análisis de anillos de crecimiento en cohortes post-incendio con diferentes edades. Los objetivos del estudio fueron: (1) establecer y determinar el rango histórico de la ocurrencia de incendios forestales, (2) evaluar parámetros dendrométricos para conocer la estructura presente y así establecer sitios de referencia para programas de restauración ecológica y (3) incrementar nuestro conocimiento en los procesos de disturbio en los bosques mixtos de pino-encino en la SMO. El estudio revela que existieron diferencias significativas entre las cohortes post incendios en términos de riqueza de especies, composición y estructura del rodal. La estructura forestal fue menos diversa en rodales jóvenes comparados con los intermedios, maduros y sobremaduros. Una alta diversidad de especies arbóreas fue generalmente encontrada en rodales jóvenes, mientras que en los rodales intermedios y maduros mostraron la diversidad más baja

Carbon and nitrogen stocks and below ground allometry in temperate mangroves

Mangroves play an important role in the storage of carbon (C) and nitrogen (N) within estuarine systems, yet are being lost at an alarming rate throughout the tropics. In contrast, temperate mangroves have increased in area at many locations in recent decades. Field surveys, sediment sampling, allometry, and C and N analysis were used to determine total C and N stocks in five temperate Avicennia marina subsp. australasica forests in New Zealand. This is the first study developing allometric functions to estimate root biomass C and N stocks for A. marina. A. marina forests stored 117.1 ± 16.8 t C ha-1 and 15.4 ± 1.0 t N ha-1 in above and below ground biomass and sediment to 100 cm depth. Below ground biomass and sediment C and N stocks contributed 88 ± 3% and 99% ± 0.4% to total C and N stocks, respectively, emphasising the importance of below ground biomass and sediment in mangrove ecosystems. The results of this study can be used to inform management decisions for estuarine and coastal ecosystems, currently undergoing rapid changes in mangrove area

Leaf age-related and diurnal variation in gas exchange of kauri (Agathis australis)

New Zealand kauri (Agathis australis) (D.Don) Lindl. is a large and long-lived tree species endemic to the species-rich forests of the north of the North Island. Agathis australis are culturally and ecologically significant, but little is known about their ecophysiology. In particular, environmental drivers of fluxes of carbon and water for A. australis trees have not been quantified. We measured leaf gas exchange to explore the effect of leaf age, tree size, foliar nitrogen concentration, photosynthetically active radiation (PAR) and vapour pressure deficit (D) on assimilation rates (A) and stomatal conductance (gs). We also measured carbon isotope discrimination of leaves and applied an optimal stomatal behaviour model. Both gs and A were highest for year one leaves (130 mmol m−2 s−1 and 5 μmol m−2 s−1, respectively) then declined with leaf age to < 80 mmol m−2 s−1 and < 3 μmol m−2 s−1, respectively, in 4–5-year-old leaves. Instantaneous water use efficiency (A/gs) was highly variable, but there was no leaf age-related pattern. Our diurnal results indicate that A. australis gs peaks early in the day (before 0900 h at 250 mmol m−2 s−1) and A is comparatively low, remaining below 9 μmol m−2 s−1 throughout the day. Overall, water use efficiency is low based on intrinsic water use efficiency and the stomatal model. Isotopic analysis indicated moderate water use efficiency over the life of leaves compared to other temperate conifers. This information is valuable for modelling carbon and water fluxes of A. australis and for improving our understanding of the threat of summer droughts to these forest giants