Papers by Cristina Martínez-garza
Botanical Sciences, 2012
Autor para la correspondencia: [email protected] Resumen: La perturbación de la selva est... more Autor para la correspondencia: [email protected] Resumen: La perturbación de la selva estacional debido a la ganadería extensiva y la extracción de madera altera la comunidad de hierbas. El objetivo del presente estudio fue evaluar la riqueza, biomasa, composición y uso tradicional de las herbáceas nativas y ruderales en 120 cuadrantes de 0.25 m 2 distribuidos aleatoriamente en diez sitios de 50 × 50 m: cuatro sitios con selva secundaria excluida de la perturbación por 32 meses, tres sitios con selva secundaria bajo perturbación crónica desde hace > 30 años y tres sitios con selva conservada en la Sierra de Huautla, estado de Morelos, México. La perturbación de la selva estacional ha provocado un cambio en la composición y un aumento en la riqueza de hierbas. La disminución en la densidad de árboles, directamente por extracción o indirectamente por el pastoreo, tuvo un efecto mayor en la riqueza de hierbas al favorecer el establecimiento de ruderales. Sin embargo, dado que se sospecha que el ganado dispersa a las ruderales, probablemente en áreas sin ganado habrá una menor densidad de ruderales aún en un escenario de perturbación por extracción selectiva. Más herbáceas nativas que ruderales tienen algún uso tradicional y el 50% sólo se encontraron en los hábitats secundarios, de donde no han sido desplazadas, aún después de décadas de actividades humanas. La creación de mosaicos de selva conservada, hábitats excluidos y otros bajo uso agropecuario permitirá el mantenimiento de la comunidad de hierbas en coexistencia con las actividades económicas de la región.
Background/Question/Methods Ecological restoration re-establishes some native species and encoura... more Background/Question/Methods Ecological restoration re-establishes some native species and encourages immigration of others from surrounding landscape. We ask what landscape context and conditions pre-exist for an experimental restoration near Los Tuxtlas, Veracruz, Mexico. Twenty-four 30x30 m plots were fenced in active pasture in 2006 and planted with 10 animal-dispersed tree species (8 plots), 10 wind-dispersed tree species (8 plots) or left as unplanted controls (8 plots) in 2006-7 as a test of dispersal limitation from nearby oldgrowth forest and isolated pasture trees. Reported here are seed rain from the landscape and seedling emergence from seed rain and pre-existing seed banks through June 2007, before appreciable growth or any reproduction of experimental plantings could directly add recruits or attract dispersal agents that might transport them. Results/Conclusions Early results indicate different patterns of seed fall and seedling emergence of trees dispersed by animals a...
Integrated Environmental Assessment and Management, 2015
Ecological risk assessment as currently practiced has hindered consideration of ecosystem service... more Ecological risk assessment as currently practiced has hindered consideration of ecosystem services endpoints and restoration goals in the environmental management process. Practitioners have created barriers between procedures to clean up contaminated areas and efforts to restore ecosystem functions. In this paper we examine linkages between contaminant risk assessment approaches and restoration efforts with the aim of identifying ways to improve environmental outcomes. We advocate that project managers and other stakeholders use an ecological planning framework, with restoration options included upfront in the risk assessment. We also considered the opportunities to incorporate ecosystem services as potential assessment endpoints in the Problem Formulation stages of a risk assessment. Indeed diverse perspectives of stakeholders are central to understand the relevance of social, cultural, economic, and regional ecology as influences on future use options for the landscape being restored. The measurement endpoints used to characterize the existing ecological conditions for selected ecosystem services can also be used to evaluate restoration success. A regional/landscape/seascape focus is needed throughout the risk assessment process so that restoration efforts play a more prominent role in enhancing ecosystem services. In short, we suggest that practitioners begin with the question of "how can the ecological risk assessment inform the decision on how best to restore the ecosystem?" This article is protected by copyright. All rights reserved KEY WORDS: ecological planning framework, landscape perspective, valued ecological resources, ecosystem services Acc e p ted P r e p r i nt This article is protected by copyright. All rights reserved
Semiextensive cattle grazing has been one of the main causes of the degradation of the Tropical D... more Semiextensive cattle grazing has been one of the main causes of the degradation of the Tropical Dry Forests (TDF) in México, affecting its ecological processes, including the seed dispersal by vertebrates and the regeneration of this vegetation. We evaluated the contribution that the frugivorous bat ensemble has on the seed rain on sites of a successional gradient (three unexcluded conserved plots, three were excluded from disturbance by cattle ranching and extraction of wood and they have restoration plantings and three perturbed unexcluded plots) at the TDF of Sierra de Huautla, Morelos México. We used mist nets to capture frugivorous bats and seed traps (1 m in diameter), that we checked twice a day (at dawn and at sunrise). During the wet season of 2012 we accumulated 13,360 m/hr/net of capture-effort for bats and 648 seed rain samples (324 diurnal and 324 nocturnal). Our capture success has been low and a NDMS analysis show us that the frugivorous bat ensemble do not differ by ...
International Journal of Plant Sciences, 2005
We asked whether the ability of individual plants to adjust leaf traits during ontogeny reflected... more We asked whether the ability of individual plants to adjust leaf traits during ontogeny reflected immediate morphological means of responding to current light availability or was consistent with a developmental strategy to meet predictable future light conditions. We determined leaf mass per unit area (specific leaf mass, SLM), leaf area, toughness, and water content of seedlings, juveniles, and adults of eight nonpioneer tropical tree species of different maximum mature heights ranging from 8 to 40 m. For SLM and leaf area, immediate responses to environmental conditions, reported as the ratio of leaf traits in sun and shade environments (leaf plasticity), were similar for seedlings, juveniles, and adults of all species irrespective of maximum mature height. For toughness and water content, leaf plasticity at different ontogenetic stages depended on species identity. To facilitate comparisons across species, developmental changes were reported as the correlations between the ratio in leaf traits for three ontogenetic stages (developmental leaf change) and maximum mature height. Tall species showed greater change in SLM and leaf area from seedling to adult stages than short species, as might be expected of taxa that experience more heterogeneous light environments during their lives. Leaf traits changed in response to current light levels during ontogeny, but the magnitude of the response is related to the adult habitat of a species.
Forest Ecology and Management, 2013
ABSTRACT Functional traits may predict tree growth rates and survival in plantings aimed to accel... more ABSTRACT Functional traits may predict tree growth rates and survival in plantings aimed to accelerate natural succession in pastures. We evaluate the growth and survival of 24 tree species used for forest restoration in pastures in the wet tropics in Mexico for 42 months. We relate their performance to 13 underlying functional traits that are important for leaf display, tree architecture and reproduction. Pioneers realized both faster growth rates and higher survival than non-pioneer species. No consistent ontogenetic cross-overs in species growth and survival were found during 42 months, which implies that species performance early after planting (12 months) predicted performance well after 42 months, probably because environmental conditions changed little over time in these early-successional pastures. Nine out of 12 functional traits were good predictors of growth rates and/or survival measures across all 24 species or for pioneer or non-pioneer species separately. Growth rates and survival were positively related to crown size and negatively to seed mass, but they were – surprisingly – not related to the leaf traits we measured. Multivariate plant trait axes explained species growth rates and survival better than individual traits only for the non-pioneer species group. Selection of additional traits may be needed for better predictions of overall performance of restoration plantings. Combining the basic science of functional ecology with the applied goals of forest management and restoration allow us to select the best mid-term performing tree species for planting in pastures using a short-term screening of growth and survival rates. Pioneers and non-pioneer species with small seeds and large crown length are good candidates for plantings in pastures since they have the best mid-term performance.
Boletín de la Sociedad Botánica de México
I nvestigar cómo crecen las especies sucesionales tardías en sitios sucesionales tempranos result... more I nvestigar cómo crecen las especies sucesionales tardías en sitios sucesionales tempranos resulta relevante por la alta deforestación en los trópicos que muchas veces es seguida por el abandono de las tierras y por procesos de regeneración natural (Moran et al., 994). Es importante generar conocimiento aplicado al sembrar especies sucesionales tardías fuera del bosque, ya que el determinar su crecimiento ayudaría Resumen: Para acelerar la sucesión vegetal y restaurar la vegetación en áreas degradadas (e.g., pastizales abandonados) se ha sugerido utilizar especies sucesionales tardías. Para determinar cómo la dinámica foliar está relacionada con altas tasas de crecimiento y supervivencia en sitios sucesionales tempranos, evaluamos la hipótesis de que la plasticidad en la demografía foliar está positivamente correlacionada con el establecimiento de árboles de siete especies sucesionales tardías creciendo en ambientes soleados (pastizal y borde) y obscuros (bosque secundario) en Los Tuxtlas, Veracruz, México. Se monitorearon cohortes de hojas de 57 individuos de siete especies arbóreas creciendo en los tres hábitats durante un año. Los individuos que crecieron en bosque secundario y borde tuvieron mayor supervivencia foliar y menor producción de hojas que aquellos que crecieron en pastizal. Los individuos con mayor crecimiento y supervivencia en pastizal tuvieron una plasticidad alta en su supervivencia foliar y plasticidad baja en su producción de hojas (estabilidad), mientras que los individuos en el borde y el bosque con tasas altas de supervivencia fueron aquello que tuvieron estabilidad alta en su producción foliar. Nuestros resultados indican que Nectandra ambigens, Licaria velutina y Pouteria rhynchocarpa pueden ser sembradas en pastizales ya que muestran tasas altas de crecimiento y supervivencia en esos hábitats, además alcanzan diferentes estaturas a la edad adulta por lo que proveerían de diversidad estructural al bosque resultante. Especies con supervivencia baja en pastizales como Calophyllum brasiliense, Pimenta dioica, Amphitecna tuxtlensis y Eugenia inirebensis podrían sembrarse en grandes cantidades o hasta que un dosel de pioneras se haya formado.
Plant Ecology, 1999
C. Martínez-Garza1 & R. González-Montagut2,∗∗ 1Instituto de Ecología, UNAM. AP 70-275 Mexico City... more C. Martínez-Garza1 & R. González-Montagut2,∗∗ 1Instituto de Ecología, UNAM. AP 70-275 Mexico City 04510 Mexico; (present addresses: University of Illinois, Department of Biological Sciences (M/C 066), Chicago, Illinois 60607-7060, USA; (present address: Mexican ...
Botanical Sciences
Despite accelerating environmental change, large-scale ecological restoration generally employs u... more Despite accelerating environmental change, large-scale ecological restoration generally employs un-replicated trial and error to create habitats destroyed or degraded by human activity. Trial and error is usual, following a management plan that employs the “best available practice” for each habitat type; adaptive management reflecting experience then corrects errors. Rare are simultaneous replicated trials during the initial restoration or corrective process. “Systemic experimental restoration” would design replicated planting or management contrasts at the outset of large-scale public and commercial restorations. Alternative treatments create mosaics of different manifestations of a community within a mosaic of habitat types. Replicated contrasts within habitats allow inference of cause and effect of success and failure on scales of communities, landscapes and ecosystems. For the long-term development of restoration ecology as a science, semi-natural communities of known contrastin...
Domestic livestock grazing and firewood extraction are chronic and pervasive disturbances in dry ... more Domestic livestock grazing and firewood extraction are chronic and pervasive disturbances in dry secondary forest that reduce diversity and modify composition. Exclosure of such disturbances may allow the reestablishment of original diversity. To investigate potential vegetation recovery following 30 years of perturbation, seed rain was evaluated monthly during 3 years in 96 0.78 m 2 seed traps located in eight exclosures established in 2006 in a species-poor secondary dry forest in central Mexico. Twelve additional seed traps were located outside the exclosures in 2010 for comparison purposes. Baseline diversity of seed sources (trees, P5 cm DBH) was recorded to compare standing tree composition with seed rain. Also, baseline diversity of potential primary (birds) and secondary (ants) dispersal vectors were registered to infer current plant-animal interactions. Total seed rain over 3 years within the exclosures comprised 180,375 seeds from 61 woody species, an average of 1.12 seeds/m 2 /month. Half of these species (31) and 95% of the seeds falling within the exclosures belonged to trees typical of perturbed sites. Sixty percent of all recorded seeds belonged to an early-successional, bird-dispersed shrub (Hamelia patens Jacq., Rubiaceae). Seed rain at one non-excluded plot was dominated by the wind-dispersed early-successional tree Heliocarpus sp. (Tiliaceae). Richness and seed density increased significantly in the second year of exclusion; however, by the third year, richness remained constant while seed density decreased. Seed rain was richer and more abundant during the dry season and was dominated by wind-dispersed species. Phenology, successional status and the dispersal modes of woody species explained most variance in richness and seed density of seed rain in early-successional dry forest. Seeds of early-successional species were dispersed in equal measure by abiotic and biotic vectors, whereas biotic vectors dispersed a higher density of late-successional seeds. The amount and timing of fall of abiotically dispersed seeds of the three most abundant species in the standing tree community may prolong their current domination of the landscape. However, even when richness in the seed rain within exclosures remained constant through time, composition was gradually shifting towards animal-dispersed species which may start a positive feedback producing an increase in animal visitation and a further increase of richness.
We explore processes of seed immigration and seedling recruitment before an experimental rainfore... more We explore processes of seed immigration and seedling recruitment before an experimental rainforest restoration matures enough to affect either. Twenty-four 30 9 30-m plots were fenced in 12 ha of pasture in 2006. Seeds were collected in ninety-six 1-m -2 seed traps; recruits were censused in *12,000 m 2 in which establishment was allowed. We tested effects of distance from forest, living trees, and stumps of trees cut during site preparation on seed rain in 2007 and effects of these and soil depth on recruits through June 2008. Seed fall and recruitment were not correlated with distance to forest 90-400 m away, nor to living shade trees outside the 160 9 485-m experimental grid. Recruitment differed for animal-and wind-dispersed species in a topographically complex landscape. Recruitment of wind-dispersed species was random with respect to soil depth or distance to recent stumps. Recruitment of animal-dispersed species was multimodal; partial correlations with number of stumps within 30 m of plots were significant with soil depth held constant (P \ 0.025), as were correlations of recruitment with soil depth with number of stumps held constant (P \ 0.01). Animal-dispersed recruits were often not conspecifics of adults that had been cut, indicating a legacy of attraction by fruiting trees of animals bearing seeds from distant sources. Ecological implications are that recruitment in pastures released from grazing reflects a mix of widely scattered wind-dispersed pioneers and, where animal-dispersed trees exist, multi-modal and decidedly non-random recruitment of pioneer and later successional animal-dispersed trees from seed banks.
Variability in the size distributions of populations is usually studied in monocultures or in mix... more Variability in the size distributions of populations is usually studied in monocultures or in mixed plantings of two species. Variability of size distributions of populations in more complex communities has been neglected. The effects of seeding density (35 or 350 seeds/species/m 2 ) and presence of small vertebrates on the variability of size distributions were studied for a total of 1,920 individuals of 4 species in replicated synthetic communities of 18 species in northern Illinois. End-of season height and above-ground biomass were measured for prairie perennials Dalea purpurea (purple prairie clover), Echinacea purpurea (purple coneflower), Desmanthus illinoensis (Illinois bundleflower) and Heliopsis helianthoides (early sunflower). Variability in biomass distribution of the four target species was twice as great at low than at high densities when small vertebrates were excluded. Our results suggest that interand intraspecific competition may affect all individuals more under high-density conditions, thereby reducing the variability in their biomass distributions within this community. This result, a consequence of plant-plant interaction, is obscured when small birds or mammals are present, presumably because either or both add variance that overwhelms the pattern.
Fragmentation of tropical forest is accelerating at the same time that already cleared land rever... more Fragmentation of tropical forest is accelerating at the same time that already cleared land reverts to secondary growth. Fragments inexorably lose deep-forest species to local extinction while embedded in low-diversity stands of early successional pioneer trees. 2. Pasture matrices undergoing passive secondary succession become a 'pioneer desert' from the vantage of remnant immigration, imposing a 'time tax' of loss of deep-forest plants from forest fragments. However, if seeds of deep-forest trees find pastures, or seedlings are planted there, many will prosper. 3. Bypassing early domination of pioneer trees in regenerating matrices, or enriching matrices with animal-dispersed forest trees, may stem the loss of species from forest fragments and accelerate succession far from the edges of old forest.
PloS one, 2014
Restoration of tropical forest depended in large part on seed dispersal by fruit-eating animals t... more Restoration of tropical forest depended in large part on seed dispersal by fruit-eating animals that transported seeds into planted forest patches. We tested effectiveness of dispersal agents as revealed by established recruits of tree and shrub species that bore seeds dispersed by birds, bats, or both. We documented restoration of dispersal processes over the first 76 months of experimental restoration in southern Mexico. Mixed-model repeated-measures randomized-block ANOVAs of seedlings recruited into experimental controls and mixed-species plantings from late-secondary and mature forest indicated that bats and birds played different roles in the first years of a restoration process. Bats dispersed pioneer tree and shrub species to slowly regenerating grassy areas, while birds mediated recruitment of later-successional species into planted stands of trees and to a lesser extent into controls. Of species of pioneer trees and shrubs established in plots, seven were primarily dispers...
When agricultural lands in formerly dry forest are abandoned, chronic disturbance by livestock gr... more When agricultural lands in formerly dry forest are abandoned, chronic disturbance by livestock grazing and wood extraction may set back successional processes precluding older dry forest structure from be reached. We compare cacti density, richness, diversity and evenness in twelve 50 × 50 m plots: six plots in secondary dry forest and six plots in older conserved dry forest at Sierra de Huautla, Central Mexico. Cacti were identifi ed, the life-form of each species was recorded and size was measured to assign individuals into four life-stage classes. Nine cacti species were registered across both forest types. In this dry forest, richness, diversity and evenness of cacti community increased in sites under chronic disturbance, whereas density was not signifi cantly affected. Size structure at community level in the conserved forest showed an increase of individuals with size, whereas in the secondary forest, size structure showed an uneven distribution of individuals, as in populations that regenerate by pulses. In the secondary forest, there was a lower proportion of adults and they were in average, smaller than those in the conserved forest. Chronic disturbance may eventually change cacti community structure, affecting animals that depend on large arboreal cacti for food, perches and/or refuge; therefore, maintenance of biodiversity will be at stake.
Oecologia, 2010
We explore processes of seed immigration and seedling recruitment before an experimental rainfore... more We explore processes of seed immigration and seedling recruitment before an experimental rainforest restoration matures enough to affect either. Twenty-four 30 9 30-m plots were fenced in 12 ha of pasture in 2006. Seeds were collected in ninety-six 1-m -2 seed traps; recruits were censused in *12,000 m 2 in which establishment was allowed. We tested effects of distance from forest, living trees, and stumps of trees cut during site preparation on seed rain in 2007 and effects of these and soil depth on recruits through June 2008. Seed fall and recruitment were not correlated with distance to forest 90-400 m away, nor to living shade trees outside the 160 9 485-m experimental grid. Recruitment differed for animal-and wind-dispersed species in a topographically complex landscape. Recruitment of wind-dispersed species was random with respect to soil depth or distance to recent stumps. Recruitment of animal-dispersed species was multimodal; partial correlations with number of stumps within 30 m of plots were significant with soil depth held constant (P \ 0.025), as were correlations of recruitment with soil depth with number of stumps held constant (P \ 0.01). Animal-dispersed recruits were often not conspecifics of adults that had been cut, indicating a legacy of attraction by fruiting trees of animals bearing seeds from distant sources. Ecological implications are that recruitment in pastures released from grazing reflects a mix of widely scattered wind-dispersed pioneers and, where animal-dispersed trees exist, multi-modal and decidedly non-random recruitment of pioneer and later successional animal-dispersed trees from seed banks.
Oecologia, 2004
Variability in the size distributions of populations is usually studied in monocultures or in mix... more Variability in the size distributions of populations is usually studied in monocultures or in mixed plantings of two species. Variability of size distributions of populations in more complex communities has been neglected. The effects of seeding density (35 or 350 seeds/species/m 2 ) and presence of small vertebrates on the variability of size distributions were studied for a total of 1,920 individuals of 4 species in replicated synthetic communities of 18 species in northern Illinois. End-of season height and above-ground biomass were measured for prairie perennials Dalea purpurea (purple prairie clover), Echinacea purpurea (purple coneflower), Desmanthus illinoensis (Illinois bundleflower) and Heliopsis helianthoides (early sunflower). Variability in biomass distribution of the four target species was twice as great at low than at high densities when small vertebrates were excluded. Our results suggest that interand intraspecific competition may affect all individuals more under high-density conditions, thereby reducing the variability in their biomass distributions within this community. This result, a consequence of plant-plant interaction, is obscured when small birds or mammals are present, presumably because either or both add variance that overwhelms the pattern.
Land Degradation & Development, 2013
Experimental restoration may both accelerate and elucidate natural processes of succession on deg... more Experimental restoration may both accelerate and elucidate natural processes of succession on degraded agricultural land by offering insight into factors that influence rates of succession and the composition of resulting communities. A novel study in restoration of degraded tropical agricultural land in coexistence with cattle ranching activities was established in southern Veracruz, Mexico. The experimental planting of 16 mixed-species stands of 18 pioneer and late-successional tree species was established from September to November 2006 on an eroded hillside pasture with an elevational gradient from 182 to 260 m and heterogeneous soil depths. An unusually severe dry season in 2007 killed 72 per cent of the seedlings: least squares regression suggested that survival of six pioneer and 12 late-successional species was mainly explained by initial basal diameter at planting followed by soil depth for pioneers and by elevational position on the hillside for latesuccessional species. Individuals with larger initial size at planting (>4 mm basal diameter), regardless of germination size in a growing house, survived better probably because larger seedlings developed deeper roots that found fissures in substrate underlying thin soils. Interestingly, seedlings small at planting (<4 mm basal diameter) survived as well as large seedlings in deeper (>19 cm) soils, but virtually, all small seedlings died on thin soils (<18·5 cm). Mortality in restoration plantings can be reduced by planting large seedlings of a mix of pioneer and late-successional species, recognizing that soil depth is a key criterion for survival of the smallest seedlings in a cohort.
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Papers by Cristina Martínez-garza
dicho contexto político, social y ecológico, y en
23 capítulos, presenta las experiencias de restauración llevadas a cabo en
nueve de los ecosistemas mexicanos localizados en 13 estados, con una
gran variedad de escalas, plazos y niveles de intervención, y un enfoque
social, experimental y práctico.
La obra está dirigida a investigadores, estudiantes y profesionales
mexicanos cuyo campo de acción incluya la restauración de ecosistemas.
Adicionalmente, es una herramienta para los tomadores de decisiones y
elaboradores de políticas públicas. Nuestro objetivo nal es asentar los
fundamentos para el establecimiento de una gobernanza ambiental en
términos de restauración de ecosistemas en México, en los que todos los
sectores de la sociedad puedan participar. Esperamos que la restauración
en México se transforme en una práctica de la esperanza y, sobre todo,
que fortalezca la base ecológica de la supervivencia humana