Anthropogenic and climate influences on biogeochemical dynamics and molecular-level speciation of soil sulfur.

The soil environment is a primary component of the global biogeochemical sulfur (S) cycle, acting as a source and sink of various S species and mediating oxidation state changes. However, ecological significance of the various S forms and the impacts of human intervention and climate on the amount and structural composition of these compounds are still poorly understood. We investigated the long-term influences of anthropogenically mediated transitions from natural to managed ecosystems on molecular-level speciation, biogeochemical dynamics, and the apparent temperature sensitivity of S moieties in temperate, subtropical, and tropical environments with mean annual temperature (MAT) ranging from 5 degrees C to 21 degrees C, using elemental analysis and X-ray absorption near-edge structure (XANES) spectroscopy. Land-use and land-cover changes led to the depletion of total soil S in all three ecoregions over a period of up to 103 years. The largest decline occurred from tropical forest agroecosystems (67% Kakamega and 76% Nandi, Kenya), compared to losses from temperate (36% at Lethbridge, Canada, and 40% at Pendleton, USA) and subtropical (48% at South Africa) grassland agroecosystems. The total S losses correlated significantly with MAT. Anthropogenic interventions profoundly altered the molecular-level composition and resulted in an apparent shift in oxidation states of organic S from native ecosystems composed primarily of S moieties in intermediate and highly reduced oxidation states toward managed agroecosystems dominated by organic S rich in strongly oxidized functionalities. The most prominent change occurred in thiols and sulfides, the proportion of which decreased by 46% (Lethbridge) and 57% (Pendleton) in temperate agroecosystems, by 46% in subtropical agroecosystems, and by 79% (Nandi) and 81% (Kakamega) in tropical agroecosystems. The proportion of organic S directly linked to O increased by 81%, 168%, 40%, 92%, and 85%, respectively. Among the various organic S functionalities, thiols and sulfides seem to have higher apparent temperature sensitivity, and thus these organic S moieties may become prone to losses due to land-use changes, even from the cooler regions of the world if MAT of these regions rise in the future.

Condensed tannins in the diets of primates: a matter of methods?

To understand the ways in which condensed tannins (CT) affect primate diet selection and nutritional status, correct measurements are essential. In the majority of studies of the CT contents of primate foods, a tannin source such as "quebracho" is used to standardize CT assays, but the CT in quebracho tannin may not be similar to those in the plants of interest. We investigated how the choice of standard to calibrate CT assays affects the estimation of CT in the diets of mountain gorillas (Gorilla beringei). We purified the CT from gorilla foods and compared the actual amounts of CT in the foods with estimates produced by using the quebracho tannin. When quebracho was used, the estimates of CT contents of gorilla foods were, on average, 3.6 times the actual content of CT so that the amounts in frequently eaten gorilla foods were substantially overestimated. The overestimation for a given plant could not be predicted reliably and the ranking of plants by tannin content differed according to the standard used. Our results demonstrate that accurate measurements of CT necessitate the use of tannins purified from the plant species of interest. A reevaluation of primatology studies using interspecific comparisons of tannin content will provide new insights into primate food selection and nutritional ecology.

Host-parasite ecology of the helminths in mountain gorillas.

To understand patterns of intestinal parasitism in healthy, undisturbed endangered mountain gorillas (Gorilla beringei), we regularly collected fecal samples from a group of 14 wild gorillas residing in Bwindi Impenetrable National Park (BINP), Uganda, for about 1 yr. The objectives of the study were to collect baseline data in order to document the helminth parasites infecting this group of gorillas and to examine the effects of season and host age-sex class on patterns of parasite infection. In addition to weekly surveys of feces from all group members, fecal samples from 4 identified individuals were examined almost daily. We identified the diagnostic stages of the following parasites: strongylids (Strongylida), Anoplocephala gorillae, Probstmayria sp., Strongyloides fuelleborni, and a trematode. Monthly and daily fluctuations in strongylid egg counts were observed. Infants had lower strongylid egg counts compared with other group members. Both of the silverbacks had higher mean egg counts in the wet season than in the dry season. Examination of fecal samples from identifiable gorillas revealed high day-to-day variation in strongylid egg counts. No evidence of anthropozoonotic transmission of intestinal helminths was found.

Fiber-bound nitrogen in gorilla diets: implications for estimating dietary protein intake of primates.

Protein is essential for living organisms, but digestibility of crude protein is poorly understood and difficult to predict. Nitrogen is used to estimate protein content because nitrogen is a component of the amino acids that comprise protein, but a substantial portion of the nitrogen in plants may be bound to fiber in an indigestible form. To estimate the amount of crude protein that is unavailable in the diets of mountain gorillas (Gorilla beringei) in Bwindi Impenetrable National Park, Uganda, foods routinely eaten were analyzed to determine the amount of nitrogen bound to the acid-detergent fiber residue. The amount of fiber-bound nitrogen varied among plant parts: herbaceous leaves 14.5+/-8.9% (reported as a percentage of crude protein on a dry matter (DM) basis), tree leaves (16.1+/-6.7% DM), pith/herbaceous peel (26.2+/-8.9% DM), fruit (34.7+/-17.8% DM), bark (43.8+/-15.6% DM), and decaying wood (85.2+/-14.6% DM). When crude protein and available protein intake of adult gorillas was estimated over a year, 15.1% of the dietary crude protein was indigestible. These results indicate that the proportion of fiber-bound protein in primate diets should be considered when estimating protein intake, food selection, and food/habitat quality.

Nutritional quality of gorilla diets: consequences of age, sex, and season.

We tested the effects of age, sex, and season on the nutritional strategies of a group of mountain gorillas (Gorilla beringei) in the Bwindi Impenetrable National Park, Uganda. Through observations of food intake of individual gorillas and nutritional analyses of dietary components over different seasons and environments, we estimated nutrient intake and evaluated diet adequacy. Our results suggest that the nutritional costs of reproduction and growth affect nutrient intake; growing juveniles and adult females ate more food and more protein per kilogram of metabolic body mass than did silverbacks. The diets of silverback males, adult females, and juveniles contained similar concentrations of protein, fiber, and sugar, indicating that adult females and juveniles did not select higher protein foods than silverbacks but rather consumed more dry matter to ingest more protein. Juveniles consumed more minerals (Ca, P, Mg, K, Fe, Zn, Mn, Mo) per kilogram of body mass than adult females and silverback males, and juveniles consumed diets with higher concentrations of phosphorous, iron, and zinc, indicating that the foods they ate contained higher concentrations of these minerals. Seasonally, the amount of food consumed on a dry weight basis did not vary, but with increased frugivory, dietary concentrations of protein and fiber decreased and those of water-soluble carbohydrates increased. Energy intake did not change over the year. With the exception of sodium, gorillas ate diets that exceeded human nutrient requirements. A better understanding of the relative importance of food quantity and quality for different age-sex classes provides insights into the ways in which gorillas may be limited by food resources when faced with environmental heterogeneity.

Complexity of coupled human and natural systems.

Integrated studies of coupled human and natural systems reveal new and complex patterns and processes not evident when studied by social or natural scientists separately. Synthesis of six case studies from around the world shows that couplings between human and natural systems vary across space, time, and organizational units. They also exhibit nonlinear dynamics with thresholds, reciprocal feedback loops, time lags, resilience, heterogeneity, and surprises. Furthermore, past couplings have legacy effects on present conditions and future possibilities.

Coupled human and natural systems.

Humans have continuously interacted with natural systems, resulting in the formation and development of coupled human and natural systems (CHANS). Recent studies reveal the complexity of organizational, spatial, and temporal couplings of CHANS. These couplings have evolved from direct to more indirect interactions, from adjacent to more distant linkages, from local to global scales, and from simple to complex patterns and processes. Untangling complexities, such as reciprocal effects and emergent properties, can lead to novel scientific discoveries and is essential to developing effective policies for ecological and socioeconomic sustainability. Opportunities for truly integrating various disciplines are emerging to address fundamental questions about CHANS and meet society's unprecedented challenges.

Decaying wood is a sodium source for mountain gorillas.

Like several other non-human primates, mountain gorillas (Gorilla beringei beringei) in Bwindi Impenetrable National Park, Uganda consume decaying wood, an interesting but puzzling behaviour. This wood has little obvious nutritional value; it is low in protein and sugar, and high in lignin compared to other foods. We collected pieces of wood eaten and avoided by gorillas, and other foods consumed by gorillas, and measured their sodium content. Wood was substantially higher in sodium than other dietary items, and wood pieces from stumps eaten contained more sodium than those that were avoided. Wood represented only 3.9% of the wet weight food intake of gorillas, but contributed over 95% of dietary sodium, leading us to conclude that decaying wood is an important sodium source for Bwindi gorillas. Because sodium has been leached from the weathered soils characteristic of the subhumid and humid tropics, and because terrestrial plants generally do not require sodium, tropical herbivores, including gorillas, often encounter problems locating the sodium essential for their well-being. Decaying wood is an unexpected sodium source.

Fecal bacterial diversity in a wild gorilla.

We describe the bacterial diversity in fecal samples of a wild gorilla by use of a 16S rRNA gene clone library and terminal-restriction fragment length polymorphism (T-RFLP). Clones were classified as Firmicutes, Verrucomicrobia, Actinobacteria, Lentisphaerae, Bacteroidetes, Spirochetes, and Planctomycetes. Our data suggest that fecal populations did not change temporally, as determined by T-RFLP.

Nutritional chemistry of foods eaten by gorillas in Bwindi Impenetrable National Park, Uganda.

Foods eaten by gorillas (Gorilla beringei) in Bwindi Impenetrable National Park (BINP), Uganda, were analyzed for their nutrient content. The goal of the study was to assess the amounts of fiber, protein, and sugars in the foods eaten by the Bwindi gorillas, and to determine whether condensed tannins and cyanide are present in these foods. A total of 127 food plant parts representing 84 plant species eaten by two groups of Bwindi gorillas were collected, processed, and analyzed for their chemical contents. The Bwindi gorilla ate foods that contain 2-28% crude protein (CP), 21-88% neutral detergent fiber (NDF), 14-60% acid detergent fiber (ADF), 2-42% acid detergent lignin (ADL), and

Plant choice in the construction of night nests by gorillas in the Bwindi Impenetrable National Park, Uganda.

We investigated the choice of plants in nest sites and individual night nests of a group of gorillas (Gorilla beringei) in Bwindi Impenetrable National Park, Uganda. Most of the nests were built on the ground in secondary forest or canopy gaps. The gorillas used 62 plant genera in their nests out of a possible 108 plant genera available in the immediate environment. This group of Bwindi gorillas chose nest sites nonrandomly with respect to habitat type and selected nest sites in which Pteridium spp. or Mimulopsis spp. were the dominant plants. The Bwindi gorillas selected Pteridium spp. and Ipomea spp. to construct their individual night nests in greater quantities compared to their proportional availability in the immediate environment.

Assessment of biases associated with profiling simple, model communities using terminal-restriction fragment length polymorphism-based analyses.

Community profiles based on terminal-restriction fragment length polymorphism (T-RFLP) analyses of amplified ribosomal RNA genes are used to monitor changes in microbial community structure and are sometimes employed for semi-quantitative estimates of species richness and abundance in environmental samples. To assess the accuracy of T-RFLP community profiles representing the relative abundance of bacteria in a sample, five species of ruminal bacteria were used to construct simple "communities". Template DNA for PCR amplification was generated either by mixing equal quantities of genomic DNA from pure cultures or by mixing equal numbers of cells prior to DNA extraction. Pairwise mixtures of Fibrobacter succinogenes S85 with Ruminococcus albus 8, Ruminococcus flavefaciens FD-1, Butyrivibrio fibrisolvens 49 and Streptococcus bovis JB1 were created and a 5-member community was constructed. With genomic DNA mixes, relative abundance calculations based on T-RFLP patterns did not reflect input ratios. These discrepancies could not be accounted for by differences in genome size and rRNA operon copy number. In cell mixing experiments, easily lysed cells were overrepresented. To determine if a numerical correction factor could be used to compensate for observed discrepancies, we attempted to quantify biases attributed to DNA extraction and PCR amplification. Biases attributable to these factors led to deviations from expected PCR product ratios by 6% to 38%. We found that interactions were so complex that a suitable factor could not be derived. The unsystematic dependence of T-RFLP peak ratios on variability of DNA extraction and PCR amplification prevents accurate quantification of the relative abundance of microorganisms designed to represent simplified natural populations.

Intestinal parasites found in the research group of mountain gorillas in Bwindi Impenetrable National Park, Uganda: preliminary results.

Mountain gorillas (Gorilla gorilla beringei) are critically endangered, remaining only in two isolated populations in Central Africa. The objective of this study was to determine the prevalence and intensity of intestinal parasites in a single group of mountain gorillas in Bwindi Impenetrable National Park, Uganda over 7 weeks from June to August 2000. Fecal samples were collected from night nests and transported in formalin for examination at Cornell University and the Centers for Disease Control. All fecal samples were examined microscopically for parasitic larvae, cysts, and eggs. The following were found: strongylid eggs, Probstymaria sp. larvae, and two parasitic nematode larvae that were not identified. Additional examination techniques will be used to further examine the fecal material specifically for protozoan cysts. An increasing threat to this group of gorillas is the presence of local field assistants and researchers. We found no evidence of human parasites in the fecal samples from this gorilla group.