J. Boone Kauffman

Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems

Recent attention has focused on the high rates of annual carbon sequestration in vegetated coastal ecosystems—marshes, mangroves, and seagrasses—that may be lost with habitat destruction (‘conversion’). Relatively unappreciated, however, is that conversion of these coastal ecosystems also impacts very large pools of previously-sequestered carbon. Residing mostly in sediments, this ‘blue carbon’ can be released to the atmosphere when these ecosystems are converted or degraded. Here we provide the first global estimates of this impact and evaluate its economic implications. Combining the best available data on global area, land-use conversion rates, and near-surface carbon stocks in each of the three ecosystems, using an uncertainty-propagation approach, we estimate that 0.15–1.02 Pg (billion tons) of carbon dioxide are being released annually, several times higher than previous estimates that account only for lost sequestration. These emissions are equivalent to 3–19% of those from deforestation globally, and result in economic damages of

An Ecological Perspective of Riparian and Stream Restoration in the Western United States

US 6–42 billion annually. The largest sources of uncertainty in these estimates stems from limited certitude in global area and rates of land-use conversion, but research is also needed on the fates of ecosystem carbon upon conversion. Currently, carbon emissions from the conversion of vegetated coastal ecosystems are not included in emissions accounting or carbon market protocols, but this analysis suggests they may be disproportionally important to both. Although the relevant science supporting these initial estimates will need to be refined in coming years, it is clear that policies encouraging the sustainable management of coastal ecosystems could significantly reduce carbon emissions from the land-use sector, in addition to sustaining the well-recognized ecosystem services of coastal habitats.

BIOMASS, CARBON, AND NUTRIENT DYNAMICS OF SECONDARY FORESTS IN A HUMID TROPICAL REGION OF MÉXICO

Abstract There is an unprecedented need to preserve and restore aquatic and riparian biological diversity before extinction eliminates the opportunity. Ecological restoration is the reestablishment of processes, functions, and related biological, chemical, and physical linkages between the aquatic and associated riparian ecosystems; it is the repairing of damage caused by human activities. The first and most critical step in ecological restoration is passive restoration, the cessation of those anthropogenic activities that are causing degradation or preventing recovery. Given the capacity of riparian ecosystems to naturally recover, often this is all that is needed to achieve successful restoration. Prior to implementation of active restoration approaches (e.g., instream structures, channel and streambank reconfiguration, and planting programs), a period of time sufficient for natural recovery is recommended. Unfortunately, structural additions and active manipulations are frequently undertaken without ha...

Fire in the Brazilian Amazon: 1. Biomass, nutrient pools, and losses in slashed primary forests

Tropical secondary forests have the capacity to function as large carbon and nutrient sinks and may offset losses resulting from deforestation and land use. In the heavily deforested Los Tuxtlas Region of Mexico, aboveground biomass as well as aboveground and mineral soil C, N, S, and P pools were quantified in 11 secondary forest sites. These sites ranged in age from 6 mo to 50 yr following abandonment and had experienced between 1 and 30 yr of land use prior to abandonment. Total aboveground biomass (TAGB) increased with increasing site age and ranged from 4.8 Mg/ha in a recently abandoned site to 287 Mg/ha in the 50-yr-old secondary forest site. Results indicate that secondary forests would reach TAGB levels equivalent to those of primary forests in the Los Tuxtlas Region after 73 yr. Furthermore, mean annual aboveground biomass accumulation (ABA) of secondary forests was strongly and inversely related to the duration of prior land use. Aboveground pools of C, N, S, and P were also positively correlate...

Biomass and nutrient dynamics associated with slash fires in neotropical dry forests

Deforestation in the Brazilian Amazon has resulted in the conversion of >230,000 km2 of tropical forest, yet little is known on the quantities of biomass consumed or the losses of nutrients from the ecosystem. We quantified the above-ground biomass, nutrient pools and the effects of biomass burning in four slashed primary tropical moist forests in the Brazilian Amazon. Total above-ground biomass (TAGB) ranged from 292 Mg ha-1 to 436 Mg ha-1. Coarse wood debris (>20.5 cm diameter) was the dominant fuel component. However, structure of the four sites were variable. Coarse wood debris comprised from 44% to 69% of the TAGB, while the forest floor (litter and rootmat) comprised from 3.7 to 8.0% of the TAGB. Total biomass consumption ranged from 42% to 57%. Fires resulted in the consumption of >99% of the litter and rootmat, yet <50% of the coarse wood debirs. Dramatic losses in C, N, and S were quantified. Lesser quantities of P, K, and Ca were lost by combustion processes. Carbon losses from the ecosystem were 58–112 Mg ha-1. Nitrogen losses ranged from 817 to 1605 kg ha-1 and S losses ranged from 92 to 122 kg ha-1. This represents losses that are as high as 56%, 68%, and 49% of the total above-ground pools of these nutrients, respectively. Losses of P were as high as 20 kg ha-1 or 32% of the above-ground pool. Losses to the atmosphere arising from primary slash fires were variable among sites due to site differences in concentration, fuel biomass, and fuel structure, climatic fluctuations, and anthropogenic influences. Compared to fires in other forest ecosystems, fires in slashed primary tropical evergreen forests result in among the highest total losses of nutrients ever measured. In addition, the proportion of the total nutrient pool lost from slash fires is higher in this ecosystem compared to other ecosystems due to a higher percentage of nutrients stored in above-ground biomass.

Fire and riparian ecosystems in landscapes of the western USA

Unprecedented rates of deforestation and biomass burning in tropical dry forests are dramatically influencing biogeochemical cycles, resulting in resource depletion, declines in biodiversity, and atmospheric pollution. We quantified the effects of deforestation and varying levels of slash-fire severity on nutrient losses and redistribution in a second-growth tropical dry forest ([open quotes]Caatinga[close quotes]) near Serra Talhada, Pernambuco, Brazil. Total aboveground biomass prior to burning was [approx]74 Mg/ha. Nitrogen and phosphorus concentrations were highest in litter, leaves attached to slash, and fine wood debris (

Fuel biomass and combustion factors associated with fires in savanna ecosystems of South Africa and Zambia

Despite the numerous values of riparian areas and the recognition of fire as a critical natural disturbance, few studies have investigated the behavior, properties, and influence of natural fire in riparian areas of the western USA. Riparian areas frequently differ from adjacent uplands in vegetative composition and structure, geomorphology, hydrology, microclimate, and fuel characteristics. These features may contribute to different fire environments, fire regimes, and fire properties (frequency, severity, behavior, and extent) in riparian areas relative to uplands. In certain forested riparian areas, fire frequency has generally been lower, and fire severity has been more moderate than in adjacent uplands, but in other areas, fires have appeared to burn riparian areas with comparable frequency. Impacts of land use and management may strongly influence fire properties and regimes in riparian areas. Fire suppression, livestock grazing, logging, damming and flow regulation, agricultural diversions, channel modifications, and introduction of invasive species have led to shifts in plant species composition, structure and distribution of fuel loads, and changes in microclimate and areal extent of riparian areas. Cumulative impacts of human alterations are likely to exert the most pronounced influence on fire behavior during periods of drought and under conditions of extreme fire weather. Riparian plant species possess adaptations to fluvial disturbances that facilitate survival and reestablishment following fires, thus contributing to the rapid recovery of many streamside habitats. Given the critical resource values of riparian zones, additional data are needed to understand interactions between fire and riparian ecosystems, and how riparian zones affect spatial and temporal patterns of fires at the landscape scale. An improved understanding of fire ecology and effects in riparian areas is needed to prescribe ecologically sound rehabilitation projects following fire.

Survival by Sprouting Following Fire in Tropical Forests of the Eastern Amazon

Fires are dominant factors in shaping the structure and composition of vegetation in African savanna ecosystems. Emissions such as CO 2 , NO x , CH 4 , and other compounds originating from these fires are suspected to contribute substantially to changes in global biogeochemical processes. Limited quantitative data exist detailing characteristics of biomass, burning conditions, and the postfire environment in African savannas. Fourteen test sites, differentiated by distinct burn frequency histories and land- use patterns, were established and burned during August and September 1992 in savanna parklands of South Africa and savanna woodlands of Zambia. Vegetation physiognomy, available fuel loads, the levels of biomass consumed by fire, environmental conditions, and fire behavior are described. In the South African sites, total aboveground fuel loads ranged from 2218 to 5492 kg ha -1 where fire return intervals were 1-4 years and exceeded 7000 kg ha -1 at a site subjected to 38 years of fire exclusion. However, fireline intensity was only 1419 kW m -1 at the fire exclusion site, while ranging from 480 to 6130 kW m -1 among the frequent fire sites. In Zambia, total aboveground fuel loads ranged from 3164 kg ha -1 in a hydromorphic grassland to 7343 kg ha -1 in a fallow shifting cultivation site. Dormant grass and litter constituted 70-98% of the total fuel load among all sites. Although downed woody debris was a relatively minor fuel component at most sites, it constituted 43-57% of the total fuel load in the fire exclusion and shifting cultivation sites. Fire line intensity ranged between 1734 and 4061 kW m -1 among all Zambian sites. Mean grass consumption generally exceeded 95%, while downed woody debris consumption ranged from 3 to 73% at all sites. In tropical savannas and savanna woodlands of southern Africa, differences in environmental conditions, land- use patterns, and fire regimes influence vegetation characteristics and thus influence fire behavior and biomass consumption.

Biomass, Carbon, and Nitrogen Pools in Mexican Tropical Dry Forest Landscapes

Current anthropogenic activities in Amazonia are resulting in the widespread occurrence of fire; an ecosystem that is believed to have evolved in a fire-free environment. Even in areas away from intensified human land use, warmer and drier climatic conditions could increase the probability of fire in tropical forests. In this study the capacity of tree species to sprout following fire in disturbed moist tropical evergreen forests was quantified. Additionally, mortality and the modes of survival of standing forest trees at four sites were measured. Crown mortality ranged from 64-97 percent. Eight months after fire, 36-69 percent of all trees present on the sites at the time of burning were dead (i.e., no sprouting occurred). Out of 124 species measured (500 total individuals), 46 percent had the capacity to sprout from subterranean tissues and 27 percent sprouted from epicormic tissues. Forty-one percent of the sampled species were found to lack any capacity to sprout vegetatively. The percentage of individuals that survived by sprouting varied among tree species. Survival of the 14 most common species encountered ranged from 15-83 percent. Survival also varied among sites and this was primarily attributed to differences in fire severity. Fire severity and plant mortality were greatest in selectively logged forests that were intentionally burned for pasture conversion (> 65% mortality). One ecological advantage of sprouting over establishment from seeds is rapid regrowth and a greater capacity for exploitation of limited resources in tropical forests. Mean sprout height was 0.8-1.6 m for 8-month old sprouts and 4.2 m for 20-month old sprouts. IT IS WIDELY ACCEPTED that in undisturbed, closed canopy evergreen tropical forests, fire is an extremely rare, if not an impossible event under current climatic conditions (Mueller-Dombois 1981, Uhl et al. 1988b, Uhl & Kauffman 1990). However, with changes in land use, fire is becoming a widespread disturbance factor in Amazonia. Mosaics of logged forests, cattle pastures, settlements, and farm plots represent a new landscape in which fire is a very common phenomenon. Even in undisturbed rain forest, minor shifts towards warmer and drier conditions would greatly increase the probability of fire. Such shifts are likely if current technological, economic, and demographic trends continue (Salati 1987, Schneider 1989). As a result of an almost complete absence of naturally occurring fires (fire-return intervals of 600 or more years [Sanford et al. 19851), Amazonian moist and rain forest species are believed to have evolved with very few adaptations related specifically to postfire survival (Kauffman & Uhl, in press). Regardless of evolutionary derivation, all plants possess characteristics that may greatly influence their calacity to survive fire or some other disturbance. The capacity to sprout from epicormic tissues (i.e., dormant meristematic tissues beneath bark on trunks and branches) or from subterranean tissues following fire or other disturbance is a very widespread and probably an ancestral trait among many woody dicots (Wells 1969). Sprouting from subterranean tissues, coppicing, and epicormic sprouting has been reported to be a common means of regeneration among tropical forest species following disturbance (Knight 1975, Uhl et al. 1981, Putz & Brokaw

Fire in the Brazilian Amazon 2. Biomass, nutrient pools and losses in cattle pastures

Tropical dry forest is the most widely distributed land-cover type in the tropics. As the rate of land-use/land-cover change from forest to pasture or agriculture accelerates worldwide, it is becoming increasingly important to quantify the ecosystem biomass and carbon (C) and nitrogen (N) pools of both intact forests and converted sites. In the central coastal region of México, we sampled total aboveground biomass (TAGB), and the N and C pools of two floodplain forests, three upland dry forests, and four pastures converted from dry forest. We also sampled belowground biomass and soil C and N pools in two sites of each land-cover type. The TAGB of floodplain forests was as high as 416 Mg ha–1, whereas the TAGB of the dry forest ranged from 94 to 126 Mg ha–1. The TAGB of pastures derived from dry forest ranged from 20 to 34 Mg ha–1. Dead wood (standing and downed combined) comprised 27%–29% of the TABG of dry forest but only about 10% in floodplain forest. Root biomass averaged 32.0 Mg ha–1 in floodplain forest, 17.1 Mg ha–1 in dry forest, and 5.8 Mg ha–1 in pasture. Although total root biomass was similar between sites within land-cover types, root distribution varied by depth and by size class. The highest proportion of root biomass occurred in the top 20 cm of soil in all sites. Total aboveground and root C pools, respectively, were 12 and 2.2 Mg ha–1 in pasture and reached 180 and 12.9 Mg ha–1 in floodplain forest. Total aboveground and root pools, respectively, were 149 and 47 kg ha–1 in pasture and reached 2623 and 264 kg ha–1 in floodplain forest. Soil organic C pools were greater in pastures than in dry forest, but soil N pools were similar when calculated for the same soil depths. Total ecosystem C pools were 306. The Mg ha–1 in floodplain forest, 141 Mg ha–1 in dry forest, and 124 Mg ha–1 in pasture. Soil C comprised 37%–90% of the total ecosystem C, whereas soil N comprised 85%–98% of the total. The N pools lack of a consistent decrease in soil pools caused by land-use change suggests that C and N losses result from the burning of aboveground biomass. We estimate that in México, dry forest landscapes store approximately 2.3 Pg C, which is about equal to the C stored by the evergreen forests of that country (approximately 2.4 Pg C). Potential C emissions to the atmosphere from the burning of biomass in the dry tropical landscapes of México may amount to 708 Tg C, as compared with 569 Tg C from evergreen forests.