Assessment and up-scaling of CO2 exchange by patches of the herbaceous vegetation mosaic in a Portuguese cork oak woodland

Li, Yuelin; Tenhunen, John; Mirzaei, Hamid; Hussain, Mubasher; Siebicke, Lukas; Foken, Thomas; Otieno, Dennis; Schmidt, Mark; Ribeiro, N. A.; Aires, Luís; Pio, Casimiro; Banza, J.; Pereira, J. S.

doi:10.1016/j.agrformet.2008.03.013

Cited by 20 publications

(19 citation statements)

References 29 publications

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“…Peak ANPP, occurring in May 2012, gave values of 241 and 235 g m −2 in the 3-and 6-weekly watering treatment, respectively. Previous single-year studies on peak ANPP of the herbaceous understorey vegetation in evergreen woodlands in Iberia report values of 195-250 g m −2 (Castro and Freitas, 2009;Hussain et al, 2009;Li et al, 2008). However, Vázquez- de-Aldana et al (2008) reported large interannual variations of ANPP over a 20-year period, values ranging from 50 to 419 g m −2 , with ANPP correlated with annual precipitation.…”

Section: Precipitation Variabilitymentioning

confidence: 88%

Resilience of montado understorey to experimental precipitation variability fails under severe natural drought

Jongen¹,

Unger

Fangueiro³

et al. 2013

Agriculture, Ecosystems & Environment

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Future climate scenarios for the Iberian Peninsula predict increasingly variable precipitation regimes, challenging key ecosystem processes in the Mediterranean biome. This study presents a large-scale water manipulation experiment, exposing the understorey vegetation in a Mediterranean oak woodland to simulations of precipitation variability. We hypothesized that, with no net changes in rainfall quantity, large infrequent precipitation events extend the period of soil moisture deficit, thereby decreasing productivity and soil nitrogen availability, accompanied by changes in plant community structure. However, the herbaceous understorey was highly resilient to increased precipitation variability. Extending the dry period between precipitation events from three to six weeks had no effect on productivity and community structure, this lack of responsiveness being attributed to phenotypic and physiological adaptations of the vegetation. However, vegetation senesced earlier, the shorter life cycle potentially influencing reproductive success. Additionally, experimental water manipulation did not affect soil nitrogen dynamics, with nitrogen being limiting in both treatments. In comparison, non-manipulated control plots experienced a severe natural wintertime drought, significantly reducing productivity and affecting species composition, but showed less indication of nitrogen limitation. Thus, although the understorey vegetation was resilient to changes in precipitation variability, long drought periods exerted highly negative effects, with the vegetation not being able to buffer the drought effects through adaptive strategies when the length of the dry period exceeded ∼10 weeks. Our results highlight the necessity for further studies investigating how climate change will influence the co-limitation of water and nitrogen availability, which in turn might affect plant productivity in Mediterranean ecosystems.

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Section: Precipitation Variabilitymentioning

confidence: 88%

Resilience of montado understorey to experimental precipitation variability fails under severe natural drought

Jongen¹,

Unger

Fangueiro³

et al. 2013

Agriculture, Ecosystems & Environment

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“…Air temperature inside and outside the chambers was logged continuously during measurements, and temperature inside the chambers was maintained within 1 • C relative to ambient temperature using ice packs. For a more detailed description of the chamber design and functioning, see Li et al (2008). As the measurements of F NET and F R were closely associated in time, estimations of gross CO 2 uptake (F A ) were made by subtraction of F R from F NET (F A = F R − F NET ).…”

Section: Co 2 and Water Vapour Fluxesmentioning

confidence: 99%

The impact of changes in the timing of precipitation on the herbaceous understorey of Mediterranean evergreen oak woodlands

Jongen¹,

Lecomte²,

Unger³

et al. 2013

Agricultural and Forest Meteorology

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Climate change scenarios for the Iberian Peninsula predict increasing temperatures and increasingly variable precipitation regimes, which will challenge the sustainability and biodiversity of Mediterranean ecosystems such as the semi-natural evergreen oak woodlands. To assess the effects of precipitation variability on productivity, species composition and vegetation gas exchange of the understorey vegetation in a typical managed cork oak woodland, a large-scale rainfall manipulation experiment was established. We studied the impacts of a change in the timing of precipitation events on this ecosystem, without altering total annual precipitation inputs. The two water manipulation treatments were: 'weekly watering treatment', where natural conditions were simulated with a normal dry period of 7 days, and '3-weekly watering treatment', with the normal dry period increased threefold to 21 days. Our experimental precipitation patterns resulted in significant differences in temporal soil moisture dynamics between the two treatments. Average soil water content (SWC) at 3 cm depth during the growing season was 16.1 ± 0.17% and 15.8 ± 0.18% in the weekly and 3-weekly watering treatments, respectively, with a mere 5% increase in the variability of SWC when extending the dry period from one to three weeks. Water infiltration into deeper soil layers (>50 cm) was significantly higher in the 3-weekly watering treatment as compared to the weekly watering treatment. This might be beneficial to Quercus suber, the tree component in this ecosystem, as its extensive tree root system enables water acquisition from deeper soil layers. However, manipulation of the within-season precipitation variability, with a shift to fewer, but larger rain events, without change in total precipitation amount, had no significant effect on aboveground net primary productivity (ANPP), belowground net primary productivity (BNPP) and species composition, with average values of peak biomass of 385 g m −2 and 222 g m −2 for ANPP and BNPP, respectively. The experimental precipitation patterns did not result in significant differences in the vegetation gas exchange between the two watering treatments. The CO 2 and H 2 O exchange parameters correlated well with air temperature. In addition, evapotranspiration showed a good correlation with SWC. Incorporating the data of SWC in the conceptual 'bucket model' showed that, independently of the watering regime, soil water availability during the life-cycle of these annual plants did not reach severe water stress conditions, which can explain the lack of a significant treatment effect in our study. In addition, our results showed that the annual plant community in these Mediterranean ecosystems is well adapted to short-term drought, through their phenological patterns and physiological adaptations.

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“…This led to an increase in total soil N input as observed between March and May. Major input of soil organic matter in the open locations of the montado ecosystem comes from the herbaceous vegetation, which actively photosynthesises during spring (Pereira et al, 2007;Aires et al, 2008;Li et al, 2008). Development of the herbaceous biomass in spring, therefore, is likely to increase N mineralization through increased inputs of labile organic compounds and total organic and respirable carbon (Hook et al, 1991).…”

Section: à2mentioning

confidence: 99%

“…The herbaceous layer has a rich biological diversity and is considered as habitats to be preserved (Moreno et al, 2005a). Due to its extent, the herbaceous layer provides a larger photosynthetic surface compared to the trees and could play a significant role in carbon fixation and ecosystem productivity (Pereira et al, 2007;Aires et al, 2008;Li et al, 2008) as well as influence soil nutrient and water balance (Joffre, 1990;Moreno et al, 2007). Due to the semiarid nature of the montado, the life cycle of the herbaceous plant community is confined to spring when soil moisture and temperatures favor their growth and development (Otieno et al, 2006;Pereira et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Herbaceous layer development during spring does not deplete soil nitrogen in the Portuguese montado

Otieno

Mirzaei

Hussain³

et al. 2011

Journal of Arid Environments

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Assessment and up-scaling of CO2 exchange by patches of the herbaceous vegetation mosaic in a Portuguese cork oak woodland

Cited by 20 publications

References 29 publications

Resilience of montado understorey to experimental precipitation variability fails under severe natural drought

Resilience of montado understorey to experimental precipitation variability fails under severe natural drought

The impact of changes in the timing of precipitation on the herbaceous understorey of Mediterranean evergreen oak woodlands

Herbaceous layer development during spring does not deplete soil nitrogen in the Portuguese montado

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