5 research outputs found
Decomposition and nutrient release in halophytes of a Mediterranean salt marsh
This study dealt with the decomposition and nutrient release from the halophytes Atriplex portulacoides,
Arthrocnemum macrostachyum, Limoniastrum monopetalum, and Spartina densiflora, the dominant species
in the Castro Marim salt marsh, Portugal. Environmental effects on decomposition were also assessed.
The study was carried out for one year using the in situ litterbag technique. S. densiflora showed a lower
decomposition rate (k = 0.003 day−1) than the other study species (k = 0.005–0.009). Study species showed
similar decomposition patterns, that is, the weight loss mostly occurred during the autumn–winter period
(study beginning in November). This indicates that temperature in this period did not hamper the decomposition
process. The decomposition rate was positively affected by the initial N concentration (r2 = 0.87,
P < 0.05) and negatively by the C:N ratio (r2 = 0.86, P < 0.05) in decomposing materials. At the end of the
study, S. densiflora and L. monopetalum, the species with lower initial N concentrations, retained much
higher proportion of initial N (89–109%) than the others (5–14%). Also, S. densiflora with the lowest P
concentration retained higher proportion of initial P (48%) than the others (5–20%). Release of K and
Mg were also slower from S. densiflora and was associated with their initial low concentration in this
species. The lowest Mn release was observed from A. macrostachyum and also in relation to the lowest
initial concentration. Our study supports the hypothesis that decomposition patterns of marsh species
are mostly associated with differences regarding their morphology and chemical composition. Given the
higher resistance of S. densiflora to decomposition, its progressive spreading may result in accumulation
of organic detritus overtime in invaded salt marshes
BIOACTIVE COMPOUNDS AND MORPHOLOGY IN OPUNTIA SPP. FRUITS FROM PORTUGUESE ECOTYPES
The Opuntia spp. has minimal soil and water requirements, and the O. fi cus-indica, in particular is sought to be an
alternative for the Mediterranean region agricultural economy. The morphology, bioactive compounds and antioxidant
properties of fruits were studied in twenty Portuguese ecotypes belonging to four Opuntia species (O. fi cus-indica, O.
robusta, O. dillenii and O. elata). The ecotypes were compared with the O. fi cus-indica cultivars ‘Bianca’, ‘Gialla’ and
‘Rossa’. The fruits from Opuntia spp. ecotypes displayed variability in morphological and bioactive characteristics.
Among O. fi cus-indica ecotypes, the orange pulp fruits were larger, heavier and had a higher percentage of pulp as well
as a lower percentage of seeds compared to the white pulp fruits. However, the weight of 100 seeds was lower in the
white pulp ecotypes. The OFI-04 ecotype contrasted the other OFI ecotypes due to its pale yellow pulp, ovoid shape,
and low seed weight per fruit as well as the amount of seeds as a percentage of pulp weight. The O. dillenii ecotypes had
the highest betalain content, total phenolic compounds, and antioxidant activity, while O. elata had the highest ascorbic
acid content. Both O. dillenii and O. elata had the highest acidity values. The red pulp cv. Rossa had the highest betalain
content among the O. fi cus-indica populations, followed by the orange and white pulp ecotypes. The highest amount
of total phenolic compounds was found in the white pulp O. fi cus-indica ecotypes. The hierarchical clustering analysis
revealed that the ecotypes could be grouped into four major groups, and geographical origin was unrelated to the clustering
pattern. This study provides original data on the morphology and bioactive compounds of Opuntia spp. fruits from
Portuguese ecotypes.CERNAS-IPCB and Forest Research Center are
funded by Foundation for Science and Technology (Portugal)
with the grants UID/AMB/00681/2013 and UID/
AGR/00239/2013, respectively.
The Foundation for Science and Technology (Portugal)
SFRN/BSAB/113895 scholarship funded MMR
Leaf-level responses to light in two co-occurring Quercus (Quercus ilex and Quercus suber): leaf structure, chemical composition and photosynthesis
We studied morphological, biochemical
and physiological leaf acclimation to incident Photon-
Photosynthetic-Flux-Density (PPFD) in Quercus ilex
(holm oak) and Quercus suber (cork oak) at Mediterranean
evergreen oak woodlands of southern Portugal.
Specific leaf area (SLA) decreased exponentially with
increasing PPFD in both species. Q. ilex had lower
SLA values than Q. suber. Leaf nitrogen, cellulose and
lignin concentration (leaf area-based) scaled positively
with PPFD. Maximum rate of carboxylation
(Vcmax), capacity for maximum photosynthetic electron
transport (Jmax), rate of triose-P utilization (VTPU)
and the rate of nonphotorespiratory light respiration
(Rd) were also positively correlated with PPFD in both Quercus species, when expressed in leaf area but
not on leaf mass basis. Q suber showed to have higher
photosynthetic potential (Vcmax, Jmax
m and VTPU
m ) and a
higher nitrogen efficient nitrogen use than Q.ilex. Leaf
chlorophyll concentration increased with decreasing
PPFD, improving apparent quantum use efficiency
(U) in both Quercus species. We concluded that, in
Q.ilex and Q.suber, leaf structural plasticity is a
stronger determinant for leaf acclimation to PPFD
than biochemical and physiological plasticity