4 research outputs found
Co2 exchange and biomass development of the herbaceous vegetation in the portuguese montado ecosystem during spring
Montado are spatially heterogeneous ecosystems that are economically important for the production of
cork and herbaceous biomass that provide fodder for animals. Understanding of how trees and the
herbaceous layer interact to determine pasture yield and the overall CO2 exchange of the herbaceous
layer is crucial. Portable chamberswere used to study CO2 exchange by the herbaceous layer component
of the montado ecosystem in southern Portugal. Biomass, Net herbaceous layer CO2 exchange (NEE) and
respiration (Reco) were measured in the open and understory locations between March and May, during
the active growing period. Parameter fits on the NEE data were performed using empirical hyperbolic
light response model, while ecosystem respiration (Reco) data were fitted with a two-parameter
exponential model. Annual green biomass productions were 405.8 9.0 and 250.6 6.3 g m 2 in the
open and the understory, respectively. The respective maximum NEE during the day were 24.0 2.9 and
9.6 2.2 mmol m 2 s 1 while maximum Reco were 20.6 2.2 and 10.0 1.6 mmol m 2 s 1, occurring in
April. Photosynthetic photon flux density (PPFD) explained more that 70% of variations in daytime NEE while
soil temperature at 10 cm depth (Tsoil) explained >50% of the variations in Reco under non-limiting soil
moisture conditions. Both the herbaceous layer communities shared similar plant functional types and no
significant difference in nutrient nitrogen (N) occurred between them. The two herbaceous layer components
shared similar physiological characteristics and differences that arose in their CO2 uptake capacities and
green biomass production were the result of microclimatic differences created by tree shadin
Herbaceous layer development during spring does not deplete soil nitrogen in the portuguese montado
Available at ScienceDirectNitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of
2004e2006 to determine how the herbaceous layer development influences soil N availability in the
montado ecosystem of southern Portugal. Highest (246.6 52.7 g m 2) and lowest (123.2 89.5 g m 2)
peak biomass occurred in 2006 and 2005 respectively. Total soilNwithin the top 20 cmsoil profile ranged
between 0.2 0.1% in February and 0.41 0.2% inMay,while available soil N was lowest (5 2 mg g 1soil)
in February but increased three-to-five fold in March and was >17.5 mg g 1soil at senescence in May.
Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May.
There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input
and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of
organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical
component of the montado that contributes to N recharge and cycling within the ecosyste