Mesityl or imide acridinium photocatalysts: accessible versus inaccessible charge-transfer states in photoredox catalysis

A study on C9-imide acridinium photocatalysts with enhanced photoredox catalytic activity with respect to the well-established C9-mesityl acridinium salt is presented. The differences observed rely on the diverse accessibility of singlet chargetransfer excited states, which have been proven by CASPT2/CASSCF calculations, fluorescence and quenching studiesThe Boehringer Ingelheim Stiftung (Exploration Grant), the Deutsche Forschungsgemeinschaft (DFG), Spanish Government (CTQ2015-64561-R, CTQ2015-63997-C2, ENE2016-79608-C2-1-R) and Community of Madrid (2016-T1/AMB-1275) are acknowledged. The authors wish to thank ’’Comunidad de Madrid’’ for its support to the FotoArt-CM Project (S2018/NMT-4367) through the Program of R&D activities between research groups in Technologies 2013, co-financed by European Structural Fun

Factors that influence the success of conservation programs in communal property areas in Mexico

More than half of the natural vegetation in Mexico is managed collectively within common property systems. The appropriation and continuity of government programs related to the conservation of land that is communally used is proposed to depend on the level of organization of the communities and the interaction between the local and governmental institutions, as well as the benefits derived from conservation projects. Patterns of what drives the conservation of common natural resources were analyzed in order to propose improvements to conservation policy. Changes in primary and secondary vegetation cover in common and private properties were identified by performing a historical spatial analysis. Questionnaires were used to survey 32 populations of seven states of the Mexican Republic to determine the conservation status of common property resources, as well as the ability of the community to continue conservation activities initially undertaken by government programs. Some 53% of the primary and secondary vegetation in Mexico is found in common property areas, but the change from primary and secondary vegetation to other uses is the same for common and private property. Communities with a high level of conservation of communal areas and with the ability to continue conservation projects were those that had dedicated the areas to recreation and conservation, had stronger community organization and were less marginalized. A recognition of the heterogeneity of the socioeconomic and cultural context of communities with common property is necessary to design governmental conservation programs that achieve long-term conservation. To meet the needs of a region that is both degraded and marginalized, the creation of synergies between programs that combat poverty and programs that promote conservation is needed. In addition, the continuation of payments with public funds for work that preserves or rehabilitates natural areas is needed, thereby acknowledging the environmental services that these areas generate

Effects of Harvest on the Sustainability and Leaf Productivity of Populations of Two Palm Species in Maya Homegardens

<div><p>Traditional management practices are usually thought to be sustainable. The Maya manage <i>Sabal</i> (Arecaceae) palms in homegardens, using their leaves for thatching. The sustainability of such production systems depends on the long-term persistence of palm populations, whereas resource availability also depends on the number of leaves on individual palms. We examined how leaf harvest affects <i>Sabal yapa</i> and <i>S</i>. <i>mexicana</i> population growth rates (λ) and leaf production, comparing traditional and alternative harvest regimes in terms of sustainability and productivity. Demographic, harvest and leaf production data were recorded for three years in two homegardens. We used general integral projection models linked to leaf-production models to describe population dynamics and productivity. Harvest had no effect on <i>S</i>. <i>yapa</i>’s vital rates or on λ, but it changed the growth rate of individuals of <i>S</i>. <i>mexicana</i>, with a negligible impact on λ. Homegardens affected λ values, reflecting the species’ ecological affinities. <i>S</i>. <i>mexicana</i>, introduced from mesic forests, required watering and shade; therefore, its population declined rapidly in the homegarden that lacked both water and shade. The λ of the xerophilic <i>S</i>. <i>yapa</i> was slightly larger without watering than with watering. Palms usually compensated for leaf extraction, causing the number of leaves harvested per individual to increase with harvest intensity. Nevertheless, traditional management is relatively mild, allowing standing leaves to accumulate but reducing the homegarden’s yield. Apparently, the Maya do not seek to maximize annual production but to ensure the availability of large numbers of leaves in homegardens. These leaves may then be used when the entire roof of a hut needs to be replaced every few years.</p></div

Cultural or Ecological Sustainability? The Effect of Cultural Change on Sabal Palm Management Among the Lowland Maya of Mexico

Sabal palm has been used for thatching the traditional Maya house for over 3000 yr. The great importance of this resource has promoted its management within home gardens. Although traditionally managed populations in home gardens are capable of ecological long-term persistence, the impact of cultural change on sustainable resource management is poorly understood. By means of interviews in 108 households, we obtained information about Sabal management practices, leaf demand, and sociocultural data. Density and size structure of the palm populations in the respective home gardens were also measured. By means of principal components analysis, the sociocultural data were summarized into a cultural change index, which was then statistically related to palm density, size structure, leaf demand, and management practices. Leaf demand along the cultural change gradient was estimated. Sabal populations were affected by the cultural change index. Palm density and the proportion of harvestable individuals were higher in the more traditional households. The number of management practices decreased, and the probability of felling adult palms increased with cultural change. As a result, the percentage of the total leaf demand satisfied by home garden production diminished from 118.2-69.4% as cultural change increased. Traditional practices seem oriented to increasing the palm availability. Seed sowing and the protection of seedlings and adults affect the life stages with the largest impact on the population growth rate, as measured through sensitivity analysis. This means that abandoning traditional practices and felling adults more frequently should reduce rapidly, which is consistent with the low palm density observed in less traditional households. The application of demographic models to Sabal tells us that traditional management warrants the persistence of the resource as long as the current conditions remain unchanged. In contrast, our data show that Sabal management may not be sustainable from a cultural perspective, since the cultural attitudes that affect palm management and demand change over time. Both approaches assess the same problem from different viewpoints reaching different but complementary conclusions. In this study, we propose new methods that integrate the ecological and cultural processes, which affect the sustainable management of the natural resources

Leaf production for different harvest intensities in both homegardens.

<p>Two different harvest procedures are shown: leaving a fixed number of leaves on the palm (left) and harvesting a constant proportion of leaves (right). For each method, simulations were performed harvesting either all plants with stems (all) or only those measuring less than 3 m (<3 m). I3 individuals were always harvested. A-B: Per capita number of leaves harvested annually from <i>S</i>. <i>yapa</i> individuals. C-D: The same as A-B but for <i>S</i>. <i>mexicana</i>.</p

Population stationary size structures of <i>Sabal mexicana</i> under different harvest procedures: leaving a fixed number of leaves on the palm (left) and harvesting a constant proportion of leaves (right).

<p>Lighter colors correspond to more intense harvesting. In all cases, I3 individuals were harvested, together with either all stemmed palms (all) or only those measuring less than 3 m (<3 m). A-B: homegarden 1, <3 m. C-D: homegarden 1, all. E-F: homegarden 2, <3 m. G-H: homegarden 2, all.</p

Compensation by different-sized plants of <i>Sabal yapa</i> and <i>S</i>. <i>mexicana</i> in different years and homegardens.

<p>A-C: <i>S</i>. <i>yapa</i>, homegarden 1; D-F: <i>S</i>. <i>yapa</i>, homegarden 2; G-I: <i>S</i>. <i>mexicana</i>, homegarden 1; J-L: <i>S</i>. <i>mexicana</i>, homegarden 2.</p

Growth of <i>Sabal mexicana</i> stems depending on the proportion of harvested leaves in homegarden 1 (left) and homegarden 2 (right).

<p>Axes’ scale is square root transformed.</p

Number of leaves available in plants of different sizes under different harvest regimes.

<p>Two different harvest methods are shown: leaving a fixed number of leaves on the palm (left) and harvesting a constant proportion of leaves (right). Lighter colors correspond to more intense harvesting. In the simulations, I3 and all stemmed palms were harvested. A-B: <i>S</i>. <i>yapa</i>, homegarden 1. C-D: <i>S</i>. <i>yapa</i>, homegarden 2. E-F: <i>S</i>. <i>mexicana</i>, homegarden 1. G-H: <i>S</i>. <i>mexicana</i>, homegarden 2.</p

Criteria for classifying plants in the D domain based on leaf morphology.

<p>Plants in this domain do not have a developed aboveground stem.</p><p>Criteria for classifying plants in the D domain based on leaf morphology.</p