Pre- and Post-Degradation Management of Rangelands: Implications for Sustainable Management

Rangeland degradation directly affects livestock production, resulting in food insecurity and ecological instability. A shift in vegetation from grass to woody plants has severely affected cattle production in Ethiopian rangelands. Those grass species that are perceived by the pastoralists as highly palatable and desirable are currently decreasing in both quality and quantity. A reason for this decline has been claimed to be degradation owing to overgrazing and climate change. While appropriate management of livestock density in rangelands is essential for sustainable production and grassland ecosystem health, the management of dryland ecosystems is mired in controversy due to the complexity of the ecosystem. This region is categorized as a non-equilibrium environment, though at times it experiences equilibrium characteristics, which makes the management of the Borana rangelands highly complex. A better understanding of grass productivity and its controlling factors in modern savanna ecosystems could be a key to understanding the productivity of savannas and to predict responses to future climatic changes. The development of effective management strategies for responding to climatic variability is often impeded by the lack of a systematic framework for analyzing livestock stocking policies and management practices. Further, effective decision making requires an understanding of the important biotic and abiotic components of rangeland systems, such as the response of rangeland vegetation to environmental stressors: climatic change and herbivorous population dynamics. Previous vegetation studies of the Borana rangelands focused mainly on taxonomic descriptions and rangeland condition assessments. Reseeding of degraded rangelands is a potential management option in eastern African rangelands to enhance the resilience of rangelands. Therefore, it is high time to understand how the native perennial grass individuals respond to increased herbivory under higher drought frequency after reseeding

Rangeland Management in a Changing World – Active and Passive Restoration Case Studies from Ethiopia, Tanzania, and South Africa

Rangelands cover almost 50% of the earth’s land surface and are often found in marginal areas that often face climate extremes. The production of herbaceous biomass has strongly declined over the last decades due to overgrazing and adverse climatic conditions such as frequent droughts and flooding. While different rangeland restoration methods are being used, their effect on vegetation quality and quantity over time has rarely been experimentally tested and monitored. Our research comprises experiments of various rangeland restoration tools we have used across eastern and southern Africa. We conducted passive restoration through exclosure experiments and compared vegetation in and outside of exclosures to understand regrowth patterns as well as overall forage quality. The active restoration methods we tested comprised domestic livestock species diversification, i.e., inclusion of browsers in rangeland systems. Further, we investigated how reseeding of nutritious rangeland grass species and subsequent grazing regimes can improve the rangeland health. We found that exclosures strongly improved biomass and productivity but that regular moderate grazing can further enhance those compared to no grazing. Our results further suggest that including browsers might enhance nutrients of herbaceous vegetation and soils of rangeland systems. We also claim that young grass species such as Chloris gayana and Cenchrus ciliaris, which are commonly used for reseeding of rangelands, show higher nutrient contents and productivity under light or moderate grazing pressure while mature grasses did not show this effect. We conclude that a combination of active and passive restoration methods can greatly enhance quality and quantity of African rangelands and enhance their sustainable use and resilience towards climatic shocks such as increasing drought frequencies

A 3,500-year tree-ring record of annual precipitation on the northeastern Tibetan Plateau

An annually resolved and absolutely dated ring-width chronology spanning 4,500 y has been constructed using subfossil, archaeological, and living-tree juniper samples from the northeastern Tibetan Plateau. The chronology represents changing mean annual precipitation and is most reliable after 1500 B.C. Reconstructed precipitation for this period displays a trend toward more moist conditions: the last 10-, 25-, and 50-y periods all appear to be the wettest in at least three and a half millennia. Notable historical dry periods occurred in the 4th century BCE and in the second half of the 15th century CE. The driest individual year reconstructed (since 1500 B.C.) is 1048 B.C., whereas the wettest is 2010. Precipitation variability in this region appears not to be associated with inferred changes in Asian monsoon intensity during recent millennia. The chronology displays a statistical association with the multidecadal and longer-term variability of reconstructed mean Northern Hemisphere temperatures over the last two millennia. This suggests that any further large-scale warming might be associated with even greater moisture supply in this region

Mammalian wildlife diversity in rubber and oil palm plantations.

This research article published by CABI, 2016In the face of globally diminishing natural habitats in biodiversity-rich regions, agricultural landscapes around protected areas have increasingly gained importance as extended habitat for wildlife species. Rubber (Hevea brasiliensis) and oil palm (Elais guineensis) plantations are two of the dominant land-use systems in Southeast Asia that have seen a tremendous expansion over the last decades. Despite far-reaching ecological consequences of these intensively cropped monocultures on natural ecosystems, relatively little is known about their utilization by wildlife populations. With this review we want to give an overview of mammalian diversity in rubber and oil palm plantations with reference to human-wildlife conflicts occurring as a result of overlapping resource use. We searched the literature for studies on wild mammalian diversity in rubber and oil palm plantations and found 17 publications. We considered 29 additional publications that provided information on single species in such plantations. We discuss the potential of 'wildlife-friendly' farming for mammalian assemblages in plantations and its importance in the case of rubber and oil palm production. Our review showed that most wild mammal species found in these plantations were likely to be visitors that use cultivated landscapes as fringe habitat but some adapted well to plantations and few even became resident. We conclude that although plantations in the tropics and subtropics cannot substitute for forests and the preservation of natural habitats is indispensable, the reality of ongoing forest degradation and transformation into plantations will make wildlife-friendly farming a key strategy in maintaining mammalian diversity, particularly in land-use matrices surrounding natural habitats

Anthropogenic disturbance and chimpanzee (Pan troglodytes) habitat use in the Masito-Ugalla Ecosystem, Tanzania

This research article published by the American Society of Mammalogists, 2020The habitat quality of chimpanzee (Pan troglodytes), including the availability of plant food and nesting species, is important to ensure the long-term survival of this endangered species. Botanical composition of vegetation is spatially variable and depends on soil characteristics, weather, topography, and numerous other biotic and abiotic factors. There are few data regarding the availability of chimpanzee plant food and nesting species in the Masito-Ugalla Ecosystem (MUE), a vast area that lies outside national park boundaries in Tanzania, and how the availability of these resources varies with human disturbance. We hypothesized that chimpanzee plant food species richness, diversity, and abundance decline with increasing human disturbance. Further, we predicted that chimpanzee abundance and habitat use is influenced negatively by human disturbance. Published literature from Issa Valley, Gombe, and Mahale Mountains National Parks, in Tanzania, was used to document plant species consumed by chimpanzees, and quantify their richness, diversity, and abundance, along 32 transects totaling 63.8 km in length across four sites of varying human disturbance in MUE. We documented 102 chimpanzee plant food species and found a significant difference in their species richness (H = 55.09, P 0.964). The least disturbed site exhibited the highest encounter rate of chimpanzee nests/km, with rates declining toward the highly disturbed sites. Our results show that severe anthropogenic disturbance in MUE is associated with the loss of chimpanzee plant food species and negatively influences chimpanzee habitat use, a relationship that threatens the future of all chimpanzee populations outside national parks

Uniform growth trends among central Asian low and high elevation juniper tree sites. Trees

Abstract We present an analysis of 28 juniper tree-ring sites sampled over the last decades by several research teams in the Tien Shan and Karakorum mountains of western central Asia. Ring-width chronologies were developed on a site-by-site basis, using a detrending technique designed to retain low-frequency climate variations. Site chronologies were grouped according to their distance from the upper timberline in the Tien Shan ( ∼ 3,400 m a.s.l.) and Karakorum ( ∼ 4,000 m), and low-and high-elevation composite chronologies combining data from both mountain systems developed. Comparison of these elevational subsets revealed significant coherence (r = 0.72) over the 1438-1995 common period, which is inconsistent with the concept of differing environmental signals captured in tree-ring data along elevational gradients. It is hypothesized that the uniform growth behavior in central Asian juniper trees has been forced by solar radiation variations controlled via cloud cover changes, but verification of this assumption requires further fieldwork. The high-elevation composite chronology was further compared with existing temperature reconstructions from the Karakorum and Tien Shan, and long-term trend differences discussed. We concluded that the extent of warmth during medieval times cannot be precisely estimated based on ring-width data currently available. Communicated by M. Adam

Seed dispersal potential of Asian elephants

This research article published by Elsevier, 2016Elephants, the largest terrestrial mega-herbivores, play an important ecological role in maintaining forest ecosystem diversity. While several plant species strongly rely on African elephants (Loxodonta africana; L. cyclotis) as seed dispersers, little is known about the dispersal potential of Asian elephants (Elephas maximus). We examined the effects of elephant fruit consumption on potential seed dispersal using the example of a tree species with mega-faunal characteristics, Dillenia indica L., in Thailand. We conducted feeding trials with Asian elephants to quantify seed survival and gut passage times (GPT). In total, 1200 ingested and non-ingested control seeds were planted in soil and in elephant dung to quantify differences in germination rates in terms of GPT and dung treatment. We used survival analysis as a novel approach to account for the right-censored nature of the data obtained from germination experiments. The average seed survival rate was 79% and the mean GPT was 35 h. The minimum and maximum GPT were 20 h and 72 h, respectively. Ingested seeds were significantly more likely to germinate and to do so earlier than non-ingested control seeds (P = 0.0002). Seeds with the longest GPT displayed the highest germination success over time. Unexpectedly, seeds planted with dung had longer germination times than those planted without. We conclude that D. indica does not solely depend on but benefits from dispersal by elephants. The declining numbers of these mega-faunal seed dispersers might, therefore, have long-term negative consequences for the recruitment and dispersal dynamics of populations of certain tree species

Western Indian Ocean marine and terrestrial records of climate variability: a review and new concepts on land-ocean interactions since AD 1660

We examine the relationship between three tropical and two subtropical western Indian Ocean coral oxygen isotope time series to surface air temperatures (SAT) and rainfall over India, tropical East Africa and southeast Africa. We review established relationships, provide new concepts with regard to distinct rainfall seasons, and mean annual temperatures. Tropical corals are coherent with SAT over western India and East Africa at interannual and multidecadal periodicities. The subtropical corals correlate with Southeast African SAT at periodicities of 16–30 years. The relationship between the coral records and land rainfall is more complex. Running correlations suggest varying strength of interannual teleconnections between the tropical coral oxygen isotope records and rainfall over equatorial East Africa. The relationship with rainfall over India changed in the 1970s. The subtropical oxygen isotope records are coherent with South African rainfall at interdecadal periodicities. Paleoclimatological reconstructions of land rainfall and SAT reveal that the inferred relationships generally hold during the last 350 years. Thus, the Indian Ocean corals prove invaluable for investigating land–ocean interactions during past centuries

Quality dating: a well-defined protocol implemented at ETH for high-precision 14c-dates tested on late glacial wood

Advances in accelerator mass spectrometry have resulted in an unprecedented amount of new high-precision radiocarbon (14C) -dates, some of which will redefine the international 14C calibration curves (IntCal and SHCal). Often these datasets are unaccompanied by detailed quality insurances in place at the laboratory, questioning whether the 14C structure is real, a result of a laboratory variation or measurement-scatter. A handful of intercomparison studies attempt to elucidate laboratory offsets but may fail to identify measurement-scatter and are often financially constrained. Here we introduce a protocol, called Quality Dating, implemented at ETH-Zürich to ensure reproducible and accurate high-precision 14C-dates. The protocol highlights the importance of the continuous measurements and evaluation of blanks, standards, references and replicates. This protocol is tested on an absolutely dated German Late Glacial tree-ring chronology, part of which is intercompared with the Curt Engelhorn-Center for Archaeometry, Mannheim, Germany (CEZA). The combined dataset contains 170 highly resolved, highly precise 14C-dates that supplement three decadal dates spanning 280 cal. years in IntCal, and provides detailed 14C structure for this interval

The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean

This paper is not subject to U.S. copyright. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 297 (2010): 299-310, doi:10.1016/j.palaeo.2010.08.009.A new 2400-year paleoclimate reconstruction from Chesapeake Bay (CB) (eastern US) was compared to other paleoclimate records in the North Atlantic region to evaluate climate variability during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Using Mg/Ca ratios from ostracodes and oxygen isotopes from benthic foraminifera as proxies for temperature and precipitation-driven estuarine hydrography, results show that warmest temperatures in CB reached 16–17 °C between 600 and 950 CE (Common Era), centuries before the classic European Medieval Warm Period (950–1100 CE) and peak warming in the Nordic Seas (1000–1400 CE). A series of centennial warm/cool cycles began about 1000 CE with temperature minima of ~ 8 to 9 °C about 1150, 1350, and 1650–1800 CE, and intervening warm periods (14–15 °C) centered at 1200, 1400, 1500 and 1600 CE. Precipitation variability in the eastern US included multiple dry intervals from 600 to 1200 CE, which contrasts with wet medieval conditions in the Caribbean. The eastern US experienced a wet LIA between 1650 and 1800 CE when the Caribbean was relatively dry. Comparison of the CB record with other records shows that the MCA and LIA were characterized by regionally asynchronous warming and complex spatial patterns of precipitation, possibly related to ocean–atmosphere processes