Post-fire recovery of ecosystem carbon pools in a tropical mixed pine-hardwood forest

Aim of the study: To analyze the recovery pattern of carbon pools in terms of size and the relative contribution of each pool to total ecosystem C along a fire chronosequence of tropical mixed pine-hardwood forest.Area of the study: Las Joyas Research Station (LJRS), core zone of Sierra de Manantlán Biosphere Reserve (SMBR) in the state of Jalisco, central western Mexico.Materials and methods: Carbon stored in aboveground plant biomass, standing dead trees, downed woody debris, forest floor, fine roots and mineral soil, was compared with a nested analysis of variance (ANOVA) in post-fire stands of eight-year-old, 28- and 60-year-old stands of mixed Pinus douglasiana-hardwood forest.Main results: The total ecosystem carbon in eight-year-old stands was 50% lower than that of 60-year-old stands. Carbon content in the biomass and mineral soil increased with stand age. The carbon in the biomass recovered to the undisturbed forest in the 28 years of succession. The main C storage in the eight-year-old stands were the mineral soil (64%) and downed woody debris (18%), while in the 28- and 60-year-old stands, live tree biomass and mineral soil were the two largest components of the total C pool (43% and 46%, respectively).Research highlights: We found a significant effect of high-severity fire events on ecosystem C storage and a shift in carbon distribution. The relatively fast recovery of C in ecosystem biomass suggests that mixed Pinus douglasiana hardwood forest possess functional traits that confer resilience to severe fire events.Key words: chronosequence; carbon dynamics; mineral soil; Pinus douglasiana; fire effects.Abbreviations used: LJRS, Las Joyas Research Station; DBH, diameter at breast height; DL, duff layer; LL, litter layer; DWD, downed woody debris; ANOVA, analysis of variance; CO2, carbon dioxide; SMBR, Sierra de Manantlán Biosphere Reserve; C, carbon. AGV, above ground vegetation

Ecosystem services of tropical dry forests : insights from longterm ecological and social research on the Pacific coast of Mexico

In the search for an integrated understanding of the relationships among productive activities, human well-being, and ecosystem functioning, we evaluated the services delivered by a tropical dry forest (TDF) ecosystem in the Chamela Region, on the Pacific Coast of Mexico. We synthesized information gathered for the past two decades as part of a long-term ecosystem research study and included social data collected in the past four years using the Millennium Ecosystem Assessment (MA) conceptual framework as a guide. Here we identify the four nested spatial scales at which information has been obtained and emphasize one of them through a basin conceptual model. We then articulate the biophysical and socio-economic constraints and drivers determining the delivery of ecosystem services in the Region. We describe the nine most important services, the stakeholders who benefit from those services, and their degree of awareness of such services. We characterize spatial and temporal patterns of the services&rsquo; delivery as well as trade-offs among services and stakeholders. Finally, we contrast three alternative future scenarios on the delivery of ecosystem services and human well-being. Biophysical and socioeconomic features of the study site strongly influence human&minus;ecosystem interactions, the ecosystem services delivered, the possible future trajectories of the ecosystem, and the effect on human well-being. We discuss future research approaches that will set the basis for an integrated understanding of human&minus;ecosystem interactions and for constructing sustainable management strategies for the TDF.<br /

Differential ecological filtering across life cycle stages drive old-field succession in a neotropical dry forest

Abiotic and biotic filters may play differential roles in the plant community organization along forest succession in abandoned fields. However, little is known about how life stage-specific filters influence species replacement during succession. We approach this issue by analyzing changes in community attributes (abundance, species density, species diversity, species composition) and the phylogenetic structure of shrubs and trees at different life stages during the old-field succession of a seasonally tropical dry forest (TDF) in Western Mexico. We raised two main questions: (1) How different are the trajectories of change in community attributes and phylogenetic structure along succession for shrub and tree species at different life-stages? (2) Do different stage-specific trajectories result from differential filtering mechanisms? We used a chronosequence of abandoned pastures and forest sites, classified in five successional categories (with three sites each): Pasture ( 100 cm height and < 2.5 cm diameter at breast height (DBH)], adults (shrubs and trees with DBH ≥ 2.5 cm). Additionally, we quantified the phylogenetic mean parwise distance (MPD) among species, and analyzed the phylogenetic community structure, for each successional category and life stage. We found that early in succession the resprout stage was more abundant and diverse than the seedling stage, while the inverse occurred late in succession. Along the first 15 years of succession, the seedling stage showed a clumped phylogenetic structure (with a strong dominance of legume species), while the resprout stage tended to have an overdispersed one (with species from a wide range of clades). Also, community attributes of the juvenile and adult stages approached those of the old-growth forest, and in both stages the phylogenetic structure changed from clustered to random. Overall, our results suggest that the assembly of shrub and trees communities along succession resulted from a combination of abiotic filtering processes, operating mostly on seedlings (selecting primarily legume drought-tolerant species), and biotic filtering processes, operating mostly in resprouts (generating a taxonomic and phylogenetically diverse regenerative pool). The implications of these results for the management of secondary TDF in human modified landscapes are discussed.</p