Manuel Maass

Phosphorus cycling in a Mexican tropical dry forest ecosystem

The study was conducted in five contiguous small watersheds (12–28 ha) gauged for long-term ecosystem research. Five 80 × 30 m plots were used for the study. We quantified inputs from the atmosphere, dissolved and particulate-bound losses, throughfall and litterfall fluxes, standing crop litter and soil available P pools. Mean P input and output for a six-year period was 0.16 and 0.06 kg⋅ha−1⋅yr−1, respectively. Phosphorus concentration increased as rainfall moved through the canopy. Annual P returns in litterfall (3.88 kg/ha) represented more than 90% of the total aboveground nutrient return to the forest floor. Phosphorus concentration in standing litter (0.08%) was lower than that in litterfall (0.11%). Phosphorus content in the litterfall was higher at Chamela than at other tropical dry forests. Mean residence time on the forest floor was 1.2 yr for P and 1.3 yr for organic matter. Together these results suggest that the forest at Chamela may not be limited by P availability and suggest a balance between P immobilization and uptake. Comparison of P losses in stream water with input rates from the atmosphere for the six-year period showed that inputs were higher than outputs. Balances calculated for a wet and a dry year indicated a small P accumulation in both years.

Electrical capacitance as a rapid and non-invasive indicator of root length

Measurement of tree root systems by conventional methods is a Herculean task. The electrical capacitance method offers a rapid and non-destructive alternative, but it has largely been restricted to herbaceous species. The Dalton Model has been the main concept for understanding equivalent root circuitry; it proposed that roots were cylindrical capacitors with epidermis and xylem being the external and internal electrodes. Capacitance (C) therefore varied in proportion to root surface area (A), mass (M), length (L) and relative permittivity of the plant tissue ε(r). We used the capacitance method on forest and plantation trees (13 to circa 100 y.o.) in situ to test hypotheses derived from implicit assumptions about tree-root-soil circuitry. We concluded: C was not confounded by intermingled root systems; C was strongly related to diameter at breast height (DBH); C was less strongly related to DBH for multiple species at the same site; and C was a poor indicator of DBH, M and L across species, ages and sites. We proposed that ε(r) was proportional to root tissue density ρ and fitted a model with P < 0.05 and R(2) = 0.70 when the three immature (13 y.o.) trees were excluded. There was no significant difference (P = 0.28) between the parameters of the tree model (excluding the immature trees) and one of the same form fitted to data from bean (Vicia faba L.; R(2) = 0.55). Together, the data sets suggested (R(2) = 0.94; n = 26) that there may exist a general relationship of this form applied over two orders of magnitude of L.

Water Dynamics at the Ecosystem Level in Seasonally Dry Tropical Forests

Water availability is one of the most important factors controlling species distribution in terrestrial ecosystems (Holdridge 1967). Organisms have developed remarkable physiological adaptations to withstand, avoid, or tolerate water limitations. It is crucial to recognize and understand these adaptations, and there is an ample literature addressing this subject. However, very few of these studies have focused their attention on seasonally dry tropical forest (SDTF) species, and fewer still have examined the study of water dynamics at the ecosystem level. This is the aim of this chapter.

Seasonal balance and vertical pattern of photosynthetically active radiation within canopies of a tropical dry deciduous forest ecosystem in Mexico

Major components of the flux density of global photosynthetically active radiation (PAR) were measured above and within canopies in a tropical deciduous forest on the Pacific coast of Mexico. At each of 69 locations grouped along a topographic sequence the PAR reflected from the top of the canopy, the vertical profile of transmittance, and the reflectance from the ground, were measured as many as four times in the year, including the extremes of the wet and dry seasons. With these observations an annual balance of the portion of PAR radiation reflected and absorbed by the canopy and ground was assembled and the detailed spatial and temporal dynamics of PAR within canopy layers were estimated. Canopy stature declined along the topographic sequence and the shape of the transmittance profiles reflected this. In locations of declining moisture availability the fraction of PAR absorbed by the ground increased and the fraction absorbed by non-foliar tissues decreased. Seasonal variation in canopy structure was the dominant influence on the partitioning of radiation - spatial variation was less important. Of a total annual PAR input of 15 200 mol m -2 , about 95% of incident PAR was absorbed, 50% by leaves, 2 5% by non-foliar tissues and 20% by the ground. The remaining 5% was reflected by the top of the canopy.

Changes in biodiversity and trade-offs among ecosystem services, stakeholders, and components of well-being: the contribution of the International Long-Term Ecological Research network (ILTER) to Programme on Ecosystem Change and Society (PECS)

The International Long-Term Ecological Research (ILTER) network comprises > 600 scientific groups conducting site-based research within 40 countries. Its mission includes improving the understanding of global ecosystems and informs solutions to current and future environmental problems at the global scales. The ILTER network covers a wide range of social-ecological conditions and is aligned with the Programme on Ecosystem Change and Society (PECS) goals and approach. Our aim is to examine and develop the conceptual basis for proposed collaboration between ILTER and PECS. We describe how a coordinated effort of several contrasting LTER site-based research groups contributes to the understanding of how policies and technologies drive either toward or away from the sustainable delivery of ecosystem services. This effort is based on three tenets: transdisciplinary research; cross-scale interactions and subsequent dynamics; and an ecological stewardship orientation. The overarching goal is to design management practices taking into account trade-offs between using and conserving ecosystems toward more sustainable solutions. To that end, we propose a conceptual approach linking ecosystem integrity, ecosystem services, and stakeholder well-being, and as a way to analyze trade-offs among ecosystem services inherent in diverse management options. We also outline our methodological approach that includes: (i) monitoring and synthesis activities following spatial and temporal trends and changes on each site and by documenting cross-scale interactions; (ii) developing analytical tools for integration; (iii) promoting trans-site comparison; and (iv) developing conceptual tools to design adequate policies and management interventions to deal with trade-offs. Finally, we highlight the heterogeneity in the social-ecological setting encountered in a subset of 15 ILTER sites. These study cases are diverse enough to provide a broad cross-section of contrasting ecosystems with different policy and management drivers of ecosystem conversion; distinct trends of biodiversity change; different stakeholders’ preferences for ecosystem services; and diverse components of well-being issues.

Key features for more successful place-based sustainability research on social-ecological systems: A Programme on Ecosystem Change and Society (PECS) perspective

The emerging discipline of sustainability science is focused explicitly on the dynamic interactions between nature and society and is committed to research that spans multiple scales and can support transitions toward greater sustainability. Because a growing body of place-based social-ecological sustainability research (PBSESR) has emerged in recent decades, there is a growing need to understand better how to maximize the effectiveness of this work. The Programme on Ecosystem Change and Society (PECS) provides a unique opportunity for synthesizing insights gained from this research community on key features that may contribute to the relative success of PBSESR. We surveyed the leaders of PECS-affiliated projects using a combination of open, closed, and semistructured questions to identify which features of a research project are perceived to contribute to successful research design and implementation. We assessed six types of research features: problem orientation, research team, and contextual, conceptual, methodological, and evaluative features. We examined the desirable and undesirable aspects of each feature, the enabling factors and obstacles associated with project implementation, and asked respondents to assess the performance of their own projects in relation to these features. Responses were obtained from 25 projects working in 42 social-ecological study cases within 25 countries. Factors that contribute to the overall success of PBSESR included: explicitly addressing integrated social-ecological systems; a focus on solution- and transformation-oriented research; adaptation of studies to their local context; trusted, long-term, and frequent engagement with stakeholders and partners; and an early definition of the purpose and scope of research. Factors that hindered the success of PBSESR included: the complexities inherent to social-ecological systems, the imposition of particular epistemologies and methods on the wider research group, the need for long periods of time to initiate and conduct this kind of research, and power asymmetries both within the research team and among stakeholders. In the self-assessment exercise, performance relating to team and context-related features was ranked higher than performance relating to methodological, evaluation, and problem orientation features. We discuss how these insights are relevant for balancing place-based and global perspectives in sustainability science, fostering more rapid progress toward inter- and transdisciplinary integration, redefining and measuring the success of PBSESR, and facing the challenges of academic and research funding institutions. These results highlight the valuable opportunity that the PECS community provides in helping build a community of practice for PBSESR.

Earth Stewardship, Socioecosystems, the Need for a Transdisciplinary Approach and the Role of the International Long Term Ecological Research Network (ILTER)

The way we see ourselves and understand the world we live in guides and determines the types of solutions we are designing and implementing to deal with our global change problems. System thinking is helping us to recognize humanity as complex, self-organized, multi-level, and highly integrated socio-bio-physical entities that we refer to as socioecosystems. This new ontological paradigm requires new epistemological tools, and transdisciplinary research is inducing changes in different aspects of our scientific endeavor, including: the philosophical approach we use to observe our world; the level of commitment we put in our scientific work; the extent and scope we envision in our research goals; the geographical scale and context in which we focus our case-studies; the type of collaboration we engage in with other scientists; and the institutional arrangements we construct to accomplish our research efforts. The International Long Term Ecological Research Network (ILTER) includes national-level networks of scientists engaged and committed to conducting long-term and site-based ecological and socio-economic research and monitoring, with a strong interest in capacity building. ILTER members have expertise in the collection, management, and analysis of long-term environmental data and, together, they are responsible for creating and maintaining a large number of unique long-term datasets. ILTER has been a natural partner for global initiatives dealing with environmental issues, and many members of its community have been participating in these international programs. We should not underestimate the urgency, nor the level of commitment, required to foster worldwide socioecosystem research with a transdisciplinary approach, which are essential for the success of the sustainable Earth Stewardship initiative.

Redes de Investigación Ecológica y Socio-Ecológica a Largo Plazo (LTER y LTSER) en Iberoamérica: Los casos de México y España

Las profundas diferencias economicas entre los paises, combinadas con igualmente diferentes contextos historicos, sociales y culturales complican enormemente la organizacion de procesos de investigacion cientifica a escala regional y global. Los diferentes paises miembros de la Red Internacional de Investigacion Ecologica a Largo Plazo (ILTER) han armado sus propias redes atendiendo a las necesidades, caracteristicas y restricciones nacionales, pero con miras a participar de manera firme en el proceso internacional. En este articulo se presenta una resena pormenorizada de las experiencias de dos paises iberoamericanos, Mexico y Espana, en su proceso de conformacion de redes LTER nacionales. Los paises comparten muchas similitudes culturales, pero con algunas diferencias importantes que han determinado la forma particular en que cada uno de ellos ha disenado e implementado sus propias redes LTER. Se aborda para ambos casos el proceso de conformacion de sus Redes Nacionales en el contexto de su entorno internacional. Asimismo, describe brevemente la manera como ambos grupos estan participando en un primer esfuerzo de la red ILTER por detonar un proyecto de colaboracion cientifica a nivel internacional sobre las relaciones existentes entre los motores socioeconomicos y los servicios ambientales de los ecosistemas.

Integrating Food-Water-Energy Research through a Socio-Ecosystem Approach

The nexus approach helps in recognizing the link between water, energy and food production systems, emphasizing the need to manage them in a more integrated way. The socio‑ecosystem (SES) approach, however, goes beyond that, by incorporating the regulation and supporting services in the management equation. Changes in ecosystem integrity affect the delivery of ecosystem services to society, which affects local people’s well-being, creating a feedback mechanism regarding management strategies. The SES approach makes explicit the “human‑bio‑physical” nature of our interaction with ecosystems, highlighting the need for a more integrated and interconnected social‑ecological research perspective. In addition, the SES approach makes more explicit the multi-scale character of the ecological processes that structure and maintain social‑ecological systems. Water dynamics have an important role in shaping ecosystem’s structure and functioning, as well as determining the systems capacity for delivering provisioning services. The tropical dry-deciduous forest, is particularly useful in studying water-food-energy trade-off interactions. Recently, a category 5 hurricane landed in the study area (Mexico’s Pacific coast), triggering various social and ecological problems. This event is challenging the current forest management strategies in the region. The extreme hydrometeorological event created an excellent opportunity to test and promote the SES approach for more integrated food‑water‑energy research. By using the SES approach within our long-term socio-ecological research project, it was easier to identify opportunities for tackling trade‑offs between maintaining the transformation of the system and a more sustainable alternative: promoting the maintenance of the ecosystem’s integrity and its capacity to deliver provisioning and regulating services.

La Red Internacional de Investigación Ecológica a Largo Plazo (ILTER) a 20 años de su creación: sus avances y retos

Twenty years after being established, the ILTER network embraces more than 600 groups from 37 countries. The ecological research at the ILTER network has mov...