Enrique Figueroa

Contrasting strategies to cope with drought by invasive and endemic species of Lantana in Galapagos

This study compares how Lantana camara, an invasive species, and L. peduncularis, an autochthonous one, cope with drought in Galapagos. Soil surface temperature was the abiotic environmental parameter that best explained variations in photosynthetic stress. Higher soil surface temperatures were recorded in the lowlands and in rain-shadow areas, which were also the driest areas. L. peduncularis, with a shallow root system, behaved as a drought-tolerant species, showing lower relative growth rates, which decreased with leaf water content and higher photosynthetic stress levels in the lowlands and in a northwest rain-shadow area in comparison with higher and wetter locations. Its basal and maximal fluorescences decreased at lower altitudes, reflecting the recorded drops in chlorophyll concentration. In contrast, L. camara with a deep root system behaved as a drought-avoiding species, showing leaf and relative water contents higher than 55% and avoiding permanent damage to its photosynthetic apparatus even in the driest area where it showed very low chlorophyll content. Its relative growth rate decreased more in dry areas in comparison to wetter zones than did that of L. peduncularis, even though it had greater water content. Furthermore, L. camara showed higher water contents, growth rate, and lower photosynthetic stress levels than L. peduncularis in the arid lowlands. Thus, L. peduncularis maintained lower maximum quantum efficiency of photosystem II photochemistry (Fv/Fm) than L. camara even at sunrise, due to higher basal fluorescence values with similar maximal fluorescence, which indicated permanent damage to PSII reaction centres. Our results help to explain the success and limitations of L. camara in the invasion of arid and sub-arid environments.

Potential of Spartina maritima in Restored Salt Marshes for Phytoremediation of Metals in a Highly Polluted Estuary

Sedimentary abiotic environment, and concentration and stock of nine metals were analyzed in vegetation and sediments to evaluate the phytoremediation capacity of restored Spartina maritima prairies in the highly polluted Odiel Marshes (SW Iberian Peninsula). Samples were collected in two 10 –m long rows parallel to the tidal line at two sediments depths (0–2 cm and 2–20 cm). Metal concentrations were measured by inductively coupled plasma spectroscopy. Iron, aluminum, copper, and zinc were the most concentrated metals. Every metal, except nickel, showed higher concentration in the root zone than at the sediment surface, with values as high as ca. 70 g Fe kg–1. The highest metal concentrations in S. maritima tissues were recorded in its roots (maximum for iron in Spartina roots: 4160.2 ± 945.3 mg kg–1). Concentrations of aluminum and iron in leaves and roots were higher than in superficial sediments. Rhizosediments showed higher concentrations of every metal than plant tissues, except for nickel. Sediment metal stock in the first 20 cm deep was ca. 170.89 t ha–1. Restored S. maritima prairies, with relative cover of 62 ± 6%, accumulated ca. 22 kg metals ha–1. Our results show S. maritima to be an useful biotool for phytoremediation projects in European salt marshes.

Plant Zonation in Restored, Nonrestored, and Preserved Spartina maritima Salt Marshes

ABSTRACT Curado, G.; Rubio-Casal, A.E.; Figueroa, E., and Castillo, J.M., 2014. Plant zonation in restored, nonrestored, and preserved Spartina maritima salt marshes. This study analyzes the vegetation zonation and the abiotic environment (sediment elevation, pH, redox potential, and electrical conductivity) 2.5 years after salt marsh restoration using Spartina maritima and Sarcocornia perennis plantations in the Odiel Marshes (SW Iberian Peninsula) in comparison with preserved and degraded marshes. Restored marshes presented higher species richness (10 spp.) than nonrestored (6 spp.) and preserved (3 spp.) marshes, as a result of milder abiotic conditions (more oxygenated sediments than preserved marshes) and higher habitat diversity (sandy patches at higher elevations). Marshes restored using S. maritima (planted at a density of 1 clump m−2) achieved a similar relative cover to preserved marshes (ca. 50%) 2.5 years after transplanting. Spartina maritima showed higher tiller height in preserved (40 ± 2 cm) than in restored marshes (34 ± 1 cm). Sarcocornia perennis cover was similar in the three areas, being concentrated at higher elevations in the tidal gradient. Our results show the success from the point of view of vegetation of restoring European low salt marshes using S. maritima and S. perennis plantations, since they are able to reproduce, 2.5 years after restoration, the typical zonation pattern.

Combined effect of diuron and simazine on photosystem II photochemistry in a sandy soil and soil amended with solid olive-mill waste

Diuron (3-(3,4-dichlorophenyl)- = 1,1-dimethylurea) and simazine (6-chloro-N 2, N 4-diethyl-1,3,5-triazine-2,4-diamine) are soil-applied herbicides used in olive crops. The objective of this study is to investigate the effect of these herbicides on Photosystem II photochemistry of Olea europaea L., and whether the amendment of soil with an organic waste (OW) from olive oil production industry modifies this effect. For this purpose, herbicide soil adsorption studies, with unamended and OW-amended soil, and chlorophyll fluorescence measurements in adult olive leaves, after one, two and three weeks of soil herbicide treatment and/or OW amendment, were performed. Soil application of these herbicides reduced the efficiency of Photosystem II photochemistry of olive trees due to chronic photoinhibition, and this effect is counterbalanced by the addition of OW to the soil. OW reduces herbicide uptake by the plant due to an increase in herbicide adsorption.

Avian communities in Spartina maritima restored and non-restored salt marshes

Capsule Salt marsh restoration with the native halophytes Spartina maritima and Zostera noltii can lead to significant improvement in habitat, increasing bird diversity over a 2-year period. Aims To assess the evolution of the avian communities in S. maritima restored salt marshes 2 years after planting, in comparison with adjacent non-restored marshes in the Odiel Marshes (southwest Iberian Peninsula). Methods Bird censuses were conducted from October 2008 to September 2009 in rectangular plots in three locations in both restored and non-restored marshes during high tides and low tides. Results A total of 44 bird species, including 20 shorebird species, were recorded. Most species belonged to Charadriidae, Scolopacidae, Laridae and Sterninae. Eight threatened bird species were recorded in restored marshes. Ecological diversity of the avian communities varied between 1.13 and 1.77. Restored marshes showed higher ecological diversity and evenness and lower Simpson dominance index than non-restored marshes. Conclusion Salt marsh restoration with the native halophytes S. maritima and Z. noltii can lead to significant short-term (over 2 years) improvements in bird diversity.

Variation in tussock architecture of the invasive cordgrass Spartina densiflora along the Pacific Coast of North America

Some introduced species spread rapidly beyond their native range and into novel habitats mediated by a high degree of phenotypic plasticity and/or rapid evolutionary responses. In this context, clonality has been described as a significant factor contributing to invasiveness. We studied the abiotic environment and the responses of different tussock architecture traits of the invasive cordgrass Spartina densiflora Brongn. (Poaceae). A common garden experiment and field studies of S. densiflora in salt marshes across a wide latitudinal gradient from California (USA) to British Columbia (Canada) provided a model system for an integrated study of the potential mechanisms underlying the response of invasive S. densiflora populations to changes in environmental conditions. Our results showed that S. densiflora is able to adjust to widely variable climate (specifically, air temperature and the duration of the growing season) and sediment conditions (specifically, texture and hypoxia) through phenotypical plastic key functional tussock traits (e.g. shoot density, height, above- and below-ground biomass allocation patterns). Root biomass increased in coarser sediments in contrast to rhizomes, which were more abundant in finer sediments. Above-ground biomass and leaf area index increased mainly with air temperature during summer, and more robust (taller and wider) shoots were associated with more oxygenated sediments. In view of our results, S. densiflora appears to be a halophyte with a high degree of phenotypic plasticity that would enable it to respond successfully to changes in the abiotic conditions of salt marshes driven by global climate change, such as increasing salinity and temperatures.

Competition from native hydrophytes reduces establishment and growth of invasive dense-flowered cordgrass (Spartina densiflora)

Experimental studies to determine the nature of ecological interactions between invasive and native species are necessary for conserving and restoring native species in impacted habitats. Theory predicts that species boundaries along environmental gradients are determined by physical factors in stressful environments and by competitive ability in benign environments, but little is known about the mechanisms by which hydrophytes exclude halophytes and the life history stage at which these mechanisms are able to operate. The ongoing invasion of the South American Spartina densiflora in European marshes is causing concern about potential impacts to native plants along the marsh salinity gradient, offering an opportunity to evaluate the mechanisms by which native hydrophytes may limit, or even prevent, the expansion of invasive halophytes. Our study compared S. densiflora seedling establishment with and without competition with Phragmites australis and Typha domingensis, two hydrophytes differing in clonal architecture. We hypothesized that seedlings of the stress tolerant S. densiflora would be out-competed by stands of P. australis and T. domingensis. Growth, survivorship, biomass patterns and foliar nutrient content were recorded in a common garden experiment to determine the effect of mature P. australis and T. domingensis on the growth and colonization of S. densiflora under fresh water conditions where invasion events are likely to occur. Mature P. australis stands prevented establishment of S. densiflora seedlings and T. domingensis reduced S. densiflora establishment by 38%. Seedlings grown with P. australis produced fewer than five short shoots and all plants died after ca. 2 yrs. Our results showed that direct competition, most likely for subterranean resources, was responsible for decreased growth rate and survivorship of S. densiflora. The presence of healthy stands of P. australis, and to some extent T. domingensis, along river channels and in brackish marshes may prevent the invasion of S. densiflora by stopping the establishment of its seedlings.

Predation on Seeds of Invasive Lantana camara by Darwin's Finches in the Galapagos Islands

Abstract Observations on birds feeding on fruits of the invasive shrub Lantana camara (Supirrosa) were conducted on Santa Cruz Island, Galapagos (Ecuador) in the Dry Zone during the 2009 dry season. The endemic ground finches Geospiza magnirostris (Large Ground Finch) and G. fortis (Medium Ground Finch) were recorded eating Lantana seeds with G. fortis the main consumer (>90% of records). Both finch species crushed the seeds and ate the embryos, discarding the exocarp and empty seed coats. They also dropped entire fruits to the ground, which could contribute to short-distance dispersal, but both finches also consumed fruits of L. camara on the ground. Density of L. camara seedlings under adult plants was higher in rockier areas than in bare soil since seeds were less accessible to predators and/or found more suitable microsites for germination and establishment. Both species of finches serve as short-distance dispersers, but mainly as seed predators of L. camara fruits.

Public Perceptions and Uses of Natural and Restored Salt Marshes

Abstract Only a few restoration projects incorporate public perception in their monitoring. However, participation of local people is a key process if social benefits are to be achieved. This study analyses, through a survey, citizens’ perceptions and usage of natural and restored coastal marshes in the city of Huelva (southwest Iberian Peninsula, Spain), as well as landscape preferences. Most of Huelva’s citizens recognised the benefits of coastal marshes (75%), a perception which increased with level of education. The majority of the respondents showed a low level of knowledge about the eco-lo-gical services and functions of salt marshes. In addition, visitor numbers to the studied restoration project increased by 27% after restoration. Regarding landscape preferences, most of the respondents preferred the native Chenopodiaceae salt marsh, and the native Spartina maritima landscape was chosen less often. In light of our results, environmental education campaigns should be carried out in the city of Huelva to increase its citizens’ knowledge of salt marshes.

Effect of herbicide and soil amendment on growth and photosynthetic responses in olive crops

Diuron [3-(3,4-dichlorophenyl)- = 1,1-dimethylurea] and simazine (6-chloro-N 2, N 4-diethyl-1,3,5-triazine-2,4-diamine) are soil-applied herbicides used in olive crops. The objective of this study is to investigate the combined effect of these herbicides and the amendment of soil with an organic waste (OW) from the olive oil production industry on the growth and photosynthetic apparatus of adult olive trees and to compare the results with those obtained by Redondo-Gómez et al.[ 1 ] for two-year-old trees. For this purpose, growth rate, gas exchange and chlorophyll fluorescence parameters were measured in 38-year-old olive trees, after one and two months of soil herbicide treatment and/or OW amendment. Soil co-application of OW and herbicide increases the quantum efficiency of Photosystem II (PSII) and the assimilation of CO2 in olive trees, which led to a higher relative growth rate of the branches and leaves in length. Herbicide treatment reduced the photosynthetic efficiency in olive trees after two months of soil application, while this reduction is evident from week one in younger trees.