Bancos de semillas en dos estadios sucesionales de bosque andino en el noreste de Colombia

"Background: Soil seed banks play an important role in post-disturbance regeneration and succession of species from different successional stages. Questions: 1) What is the most effective method for determining the composition and structure of the soil seed bank of Andean forests? 2) What is the composition and structure of soil seed banks in old-growth forest and shrubland sites in the Andean montane tropical forest of the North Santander region of Colombia? Study site: Andean forest, Pamplona, Colombia Methods: We surveyed the soil seed bank in two successional stages of Andean forest and examined its structure using two sampling methods: direct separation and germination. Results: Soil seed bank density was higher (18-fold in old-growth forest and 666-fold in shrubland) with the direct separation method than with germination; however, under the germination method, we found four species that we did not detect through the direct separation method. Soil seed banks from shrublands were mainly dominated by species from disturbed areas (91 %), while those from the old-growth forest presented early, intermediate and late species; e.g., Miconia summa, Myrsine dependens and Solanum sp., respectively. In the old-growth forest (especially for late species), density increased with depth. This pattern was not observed in shrubland. Seeds obtained by using the direct separation method presented low (< 7 %) viability. Conclusion: We consider the two methods to be complementary and recommend the use of both for a thorough characterization of soil seed banks from Andean forests. At different successional stages in the Colombian Andean forest, the soil seed bank may contain early, intermediate and late species, and it therefore plays an important role in the regeneration of this threatened ecosystem.""Antecedentes: Los bancos de semillas del suelo juegan un papel importante en la regeneración de especies de diferentes etapas de sucesión. Preguntas: 1) ¿Cuál es el método más eficaz para la descripción de la composición y la estructura del banco de semillas del suelo de los bosques andinos? y 2) ¿Cómo es la composición y estructura de los bancos de semillas del suelo en un bosque primario y un matorral en el bosque andino en Colombia? Sitio de estudio: Bosque andino en Pamplona, Norte de Santander, Colombia Métodos: Se estudiaron el banco de semillas del suelo en dos etapas de sucesión de bosque andino y se examinó la estructura mediante dos métodos de muestreo: separación directa y la germinación. Resultados: La densidad del banco de semillas en el suelo fue mayor (18 veces en bosques primarios y 666 veces en matorral) con el método de separación directa que con el método de germinación; Sin embargo, bajo el método de germinación, se encontraron cuatro especies que no detectamos a través del método de separación directa. Los bancos de semillas de matorrales fueron dominados principalmente por especies de las áreas perturbadas (91 %), mientras que en el bosque primario se encontraron especies de estados sucesionales tempranos, intermedios y tardíos, por ejemplo, Miconia summa, Myrsine dependens y Solanum sp., respectivamente. En el bosque maduro (especialmente para las especies de estapas sucesionales tardías), la densidad aumenta con la profundidad. Este patrón no se observó en el matorral. Aunado a esto, las semillas obtenidas mediante el método de separación directa presentaron baja (7 % <) viabilidad. Conclusión: Consideramos que los dos métodos son complementarios y recomendamos el uso de las dos metodologías para una adecuada caracterización de los bancos de semillas del suelo de los bosques andinos. El banco de semillas del suelo puede contener especies de diferentes estadios sucesionales, por lo que tiene un papel importante en la regeneración del bosque andino de Colombia.

Chronic leaf harvesting reduces reproductive success of a tropical dry forest palm in northern Mexico

Palm leaves represent one of the most important non-timber forest products in tropical and subtropical regions. Brahea aculeata is an endemic palm of northwest Mexico, whose leaves are intensively exploited for roof thatch and handcrafts. As part of a long-term defoliation experiment, we evaluated the effects of different leaf harvest on foliar and reproductive traits of adults and attributes of their progeny. We conducted a six-year manipulative experiment and applied three harvesting treatments to adults: high harvest, low harvest and no harvest (control). We recorded leaf production and size, flower and fruit production, seed germination and seedling growth. We also explored trade-offs among foliar and reproductive traits. Harvested palms exhibited drastically reduced reproductive activity, producing fewer flowers and fruits (up to 80 and 90% fewer than unharvested palms). However, individuals in both harvest treatments had larger leaves and increased leaf production rates, compared to control palms. For harvested palms, we registered first a slight increase in leaf traits and a decline in reproductive attributes. These traits showed a gradual reduction and for six period attained very low proportional values compared to control palms (similar to 0.10), however individuals in the harvested treatments maintained the greatest leaf lengths and leaf production rates. Seed germination and seedling growth rates of progeny from harvested palms were significantly lower than control palms, with seeds from the high harvest treatment having the lowest seed production and germination rates. Relationships among leaf (size/production) and reproductive traits (flower/fruit production) were positive during the fourth year, but showed negative relationships for the fifth year suggesting a trade-off between reproduction and growth functions. Leaf harvesting in B. aculeata seems to alter patterns of resource allocation away from reproduction as reflected in a decrease in the probability of reproduction, seed number, germination, and vigor, causing a strong decrease in the reproductive success of this species. Results showed that the consequences of long-term leaf harvest not only affect harvested individuals, but also the fitness and vigor of progeny. This type of long-term studies is essential to understand the population dynamics of non-timber forest products and helps inform sustainable harvesting programs considering intensity, frequencies and periods for recovery from defoliation. Also results may help to explain how intensive and non-planned management schemes may negatively affect vital rates and long-term dynamics of populations from non-timber forest products and other components of the ecosystem

Expanding tropical forest monitoring into Dry Forests: The DRYFLOR protocol for permanent plots

This is the final version. Available on open access from Wiley via the DOI in this recordSocietal Impact Statement Understanding of tropical forests has been revolutionized by monitoring in permanent plots. Data from global plot networks have transformed our knowledge of forests’ diversity, function, contribution to global biogeochemical cycles, and sensitivity to climate change. Monitoring has thus far been concentrated in rain forests. Despite increasing appreciation of their threatened status, biodiversity, and importance to the global carbon cycle, monitoring in tropical dry forests is still in its infancy. We provide a protocol for permanent monitoring plots in tropical dry forests. Expanding monitoring into dry biomes is critical for overcoming the linked challenges of climate change, land use change, and the biodiversity crisis.Newton FundNatural Environment Research Council (NERC)Fundação de Amparo à Pesquisa do Estado de São PauloCYTE

A conservation assesment of endangered tropical tree species, Guiaicum sanctum and G. coulteri, in Mexico

In this thesis, I propose a general framework to generate robust information on the distribution, abundance and conservation status of threatened species. I used ecological niche modelling techniques to estimate the historic distribution of Guaiacum sanctum and G. coulteri.  These models were then combined with land use maps to estimate habitat loss associated with the conservation of forest to agriculture-pasture and human settlements during the period 1976-2000, and to compute the amount and distribution of suitable habitat contained within existing protected areas. The results showed that by 2000 the distributions of G. sanctum and G. coulteri had been reduced to 72% and 59% of their historic distributions, respectively.  If habitat loss continues to occur at the same rate as during the period 1976-2000, the amount of habitat available for G. sanctum and G. coulteri will decline to 51-70% and 48-56% of the historic ranges, respectively, by 2020. To explore options for sustainable management of G. sactum I compared the demography and dynamics of populations on plots in recently logged forest and in a protected area, and parameterized a transition matrix model to simulate harvesting regimes.  I found that G. sanctum populations had their highest mortality rates in the seedling and juvenile size classes and that mortality rates were very low in the adult size classes.  Although the estimated population growth rate (λ) at the exploited site (Ejido Pich Forest Reserve) was lower than that in the protected area (Calakmul Biosphere Reserve), both populations were growing in size (λ = 1.088 and 1.033, respectively).  This analysis supported the conclusion that harvesting did not have a major impact on the Guaiacum sanctum population growth rate at the stand level. My research suggests that the current management regime implemented at Ejido Pich Forest Reserve would not threaten the existence of the species if extended across similar forests in Campeche.  Land use change is the most important factor threatening the conservation of G. sanctum.  I conclude that avoidance of changes to land use should underpin the conservation strategy for this species, combined with a promotion of sustainable forest management in the area.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Chronic leaf harvesting reduces reproductive success of a tropical dry forest palm in northern Mexico.

Palm leaves represent one of the most important non-timber forest products in tropical and subtropical regions. Brahea aculeata is an endemic palm of northwest Mexico, whose leaves are intensively exploited for roof thatch and handcrafts. As part of a long-term defoliation experiment, we evaluated the effects of different leaf harvest on foliar and reproductive traits of adults and attributes of their progeny. We conducted a six-year manipulative experiment and applied three harvesting treatments to adults: high harvest, low harvest and no harvest (control). We recorded leaf production and size, flower and fruit production, seed germination and seedling growth. We also explored trade-offs among foliar and reproductive traits. Harvested palms exhibited drastically reduced reproductive activity, producing fewer flowers and fruits (up to 80 and 90% fewer than unharvested palms). However, individuals in both harvest treatments had larger leaves and increased leaf production rates, compared to control palms. For harvested palms, we registered first a slight increase in leaf traits and a decline in reproductive attributes. These traits showed a gradual reduction and for six period attained very low proportional values compared to control palms (~0.10), however individuals in the harvested treatments maintained the greatest leaf lengths and leaf production rates. Seed germination and seedling growth rates of progeny from harvested palms were significantly lower than control palms, with seeds from the high harvest treatment having the lowest seed production and germination rates. Relationships among leaf (size/production) and reproductive traits (flower/fruit production) were positive during the fourth year, but showed negative relationships for the fifth year suggesting a trade-off between reproduction and growth functions. Leaf harvesting in B. aculeata seems to alter patterns of resource allocation away from reproduction as reflected in a decrease in the probability of reproduction, seed number, germination, and vigor, causing a strong decrease in the reproductive success of this species. Results showed that the consequences of long-term leaf harvest not only affect harvested individuals, but also the fitness and vigor of progeny. This type of long-term studies is essential to understand the population dynamics of non-timber forest products and helps inform sustainable harvesting programs considering intensity, frequencies and periods for recovery from defoliation. Also results may help to explain how intensive and non-planned management schemes may negatively affect vital rates and long-term dynamics of populations from non-timber forest products and other components of the ecosystem

Distribution and conservation of species is misestimated if biotic interactions are ignored : the case of the orchid Laelia speciosa

The geographic distribution of species depends on their relationships with climate and on the biotic interactions of the species. Ecological Niche Models (ENMs) mainly consider climatic variables only and may tend to overestimate these distributions, especially for species strongly restricted by biotic interactions. We identified the preference of Laelia speciosa for different host tree species and include this information in an ENM. The effect of habitat loss and climate change on the distribution of these species was also estimated. Although L. speciosa was recorded as epiphyte at six tree species, 96% of the individuals were registered at one single species (Quercus deserticola), which indicated a strong biotic interaction. We included the distribution of this host tree as a biotic variable in the ENM of L. speciosa. The contemporary distribution of L. speciosa is 52,892 km 2, which represent 4% of Mexican territory and only 0.6% of the distribution falls within protected areas. Habitat loss rate for L. speciosa during the study period was 0.6% per year. Projections for 2050 and 2070 under optimistic and pessimistic climate change scenarios indicated a severe reduction in its distribution. Climaticaly suitable areas will also shift upwards (200-400 m higher). When estimating the distribution of a species, including its interactions can improve the performance of the ENMs, allowing for more accurate estimates of the actual distribution of the species, which in turn allows for better conservation strategies

Analysis of the Vigor of <i>Pinus hartwegii</i> Lindl. along an Altitudinal Gradient Using UAV Multispectral Images: Evidence of Forest Decline Possibly Associated with Climatic Change

Future climate forecasts predict major changes that will have negative impacts on the distribution, abundance, and dynamics of forest ecosystems. In Mexico, there is evidence of symptoms of massive forest decline; however, there is no consensus in terms of attributing these symptoms to climate change. This study aimed to provide evidence of forest decline possibly associated with climatic change in the highland pine (Pinus hartwegii Lindl.) populations of the Nevado de Toluca Flora and Fauna Protection Area. Using unmanned aerial vehicles (UAV) equipped with multispectral sensors, the study applied digital photogrammetry techniques, automated tree crown detection algorithms, and calculation of the normalized difference vegetation index (NDVI) and leaf chlorophyll index (LCI) to assess forest health across an altitudinal transect (from 3300 m to the timberline at 4040 m elevation). Climate analysis was conducted with TerraClimate data using mean annual temperature (MAT), April temperature, and Palmer Drought Severity Index (PDSI) from the studied altitudinal transect and its xeric limit. We found that lower altitude populations had significantly higher stress levels, indicating forest decline phenomena, while intermediate altitude populations showed greater vigor of the detected trees. Statistically significant differences in the NDVI and LCI values along the altitudinal gradient provided evidence of forest decline in terms of forest vigor and productivity, with the greatest disturbance found at the lower altitude of the examined forest species. The analysis of the climatic data revealed an increase in April temperature +1.4 °C of the xeric limit of the transect (low altitude) when comparing the reference period, 1961–1990 (mean: 12.17 °C), with the decade prior to our study (2011–2020; mean: 13.57 °C). This would be equivalent to an upward shift in elevation of 280 m of the xeric limit. In addition, the PDSI analysis revealed that droughts are becoming increasingly intense at a rate of 0.06 PDSI units per decade, with greater intensity in the last five years. These findings highlight the negative impacts of climate change on forest ecosystems and the urgent need for alternative forest management and conservation practices to increase resilience and adaptation in the temperate forests of Mexico. This study sets a precedent for further research to improve our understanding of the impacts of climate change on forest ecosystems and the development of sustainable management practices

Reciprocal Common Garden Altitudinal Transplants Reveal Potential Negative Impacts of Climate Change on Abies religiosa Populations in the Monarch Butterfly Biosphere Reserve Overwintering Sites

Research Highlights: Reciprocal altitudinal transplants of Abies religiosa seedlings within the Monarch Butterfly Biosphere Reserve (MBBR) allow prediction of the impacts of climatic change, because they grow in sites with a climate that differs from that of their origin. Background and Objectives: Climatic change is generating a mismatch between the sites currently occupied by forest populations and the climate to which they have adapted. This study determined the effect on the survival and growth of A. religiosa seedlings of transfer to sites that were warmer or colder than that of the origin of their seeds. Materials and Methods: Eleven provenances of A. religiosa, collected along an altitudinal gradient (3000 to 3550 m a.s.l.), were assayed in common gardens in three sites of contrasting altitude: 3400, 3000 and 2600 m a.s.l. The results were evaluated by fitting a response curve with a mixed model. Results: The climate transfer distance for the seasonal balance between the temperature conducive to growth (degree days above 5 °C) and the available precipitation (a ratio expressed as dryness index) dominated the shape of the response function curve. The rainy season (June–October) dryness index transfer distance was critical for survival, while that of the cold and dry season (November–February) was critical for aerial biomass, and the annual index was critical for the increase in basal diameter. The effect of climatic transfer distance is much more negative (triggering about 45% mortality) when transfer is toward warmer and dryer sites (at 400 m lower in altitude, +1.9 °C warmer and 16% less precipitation), than when shifting toward colder and wetter sites (400 m higher in altitude, resulting in 95% survival). Conclusions: The projected higher temperatures and lower precipitation due to climatic change will undoubtedly cause severe mortality in young A. religiosa seedlings. A 400 m shift upwards in altitude to compensate for climatic change (assisted migration) appears to be a feasible management action

Reciprocal Common Garden Altitudinal Transplants Reveal Potential Negative Impacts of Climate Change on <em>Abies religiosa</em> Populations in the Monarch Butterfly Biosphere Reserve Overwintering Sites

Research Highlights: Reciprocal altitudinal transplants of Abies religiosa seedlings within the Monarch Butterfly Biosphere Reserve (MBBR) allow prediction of the impacts of climatic change, because they grow in sites with a climate that differs from that of their origin. Background and Objectives: Climatic change is generating a mismatch between the sites currently occupied by forest populations and the climate to which they have adapted. This study determined the effect on the survival and growth of A. religiosa seedlings of transfer to sites that were warmer or colder than that of the origin of their seeds. Materials and Methods: Eleven provenances of A. religiosa, collected along an altitudinal gradient (3000 to 3550 m a.s.l.), were assayed in common gardens in three sites of contrasting altitude: 3400, 3000 and 2600 m a.s.l. The results were evaluated by fitting a response curve with a mixed model. Results: The climate transfer distance for the seasonal balance between the temperature conducive to growth (degree days above 5 °C) and the available precipitation (a ratio expressed as dryness index) dominated the shape of the response function curve. The rainy season (June–October) dryness index transfer distance was critical for survival, while that of the cold and dry season (November–February) was critical for aerial biomass, and the annual index was critical for the increase in basal diameter. The effect of climatic transfer distance is much more negative (triggering about 45% mortality) when transfer is toward warmer and dryer sites (at 400 m lower in altitude, +1.9 °C warmer and 16% less precipitation), than when shifting toward colder and wetter sites (400 m higher in altitude, resulting in 95% survival). Conclusions: The projected higher temperatures and lower precipitation due to climatic change will undoubtedly cause severe mortality in young A. religiosa seedlings. A 400 m shift upwards in altitude to compensate for climatic change (assisted migration) appears to be a feasible management action

Data from: Impact of a hurricane on the herpetofaunal assemblages of a successional chronosequence in a tropical dry forest

Land‐use change is the main cause of deforestation and degradation of tropical forest in Mexico. Frequently, these lands are abandoned leading to a mosaic of natural vegetation in secondary succession. Further degradation of the natural vegetation in these lands could be exacerbated by stochastic catastrophic events such as hurricanes. Information on the impact of human disturbance parallel to natural disturbance has not yet been evaluated for faunal assemblages in tropical dry forests. To evaluate the response of herpetofaunal assemblages to the interaction of human and natural disturbances, we used information of pre‐ and post‐hurricane herpetofaunal assemblages inhabiting different successional stages (pasture, early forest, young forest, intermediate forest, and old growth forest) of dry forest. Herpetofaunal assemblages were surveyed in all successional stages two years before and two years after the hurricane Jova that hit the Pacific Coast of Mexico on October 2011. We registered 4093 individuals of 61 species. Overall, there were only slight effects of successional stage, hurricane Jova or the interaction between them on abundance, observed species richness and diversity of the herpetofauna. However, we found marked changes in estimated richness and composition of frogs, lizards, and snakes among successional stages in response to hurricane Jova. Modifications in vegetation structure as result of hurricane pass promoted particular changes in each successional stage and taxonomic group (anurans, lizards, and snakes). Secondary forests at different stages of succession may attenuate the negative effects of an intense, short‐duration, and low‐frequency natural disturbance such as hurricane Jova on successional herpetofaunal trajectories and species turnover