Ruth Sherman

A comparison of biodiversity-ecosystem function relationships in alpine grasslands across a degradation gradient on the Qinghai-Tibetan Plateau

To examine biodiversity–ecosystem function relationships in alpine grasslands of the Qinghai–Tibetan Plateau, we compared differences in plant species and functional group diversity (sedges, grasses, legumes and non-leguminous forbs) to aboveground biomass, soil carbon (C) and nitrogen (N) pools and soil loss in five sites that ranged from healthy to severely degraded grasslands. Plant diversity decreased from 36 species in the healthy grassland to 15 species in the severely degraded grassland, and the plant functional groups changed from predominantly grasses and sedges to mostly forbs as the level of degradation increased. Plant biomass and soil pools of C and N decreased whereas soil loss and the amount of bare ground increased across the degradation gradient from healthy to severely degraded grasslands. Simple linear regressions showed strong positive relationships between species diversity and aboveground biomass of sedges, grasses and legumes and between soil C and N pools, but negative relationships between species diversity and non-leguminous forbs and soil loss. Our results provide strong evidence that plant diversity in grasslands on the Qinghai–Tibetan Plateau is positively related to primary productivity, C and N storage in soils and soil conservation, and that grassland degradation is impairing ecosystem function resulting in a loss in ecosystem services.

Enhancing the resilience of coupled human and natural systems of alpine rangelands on the Qinghai-Tibetan Plateau

This special issue covers a wide range of topics on the protection and sustainable management of alpine rangelands on the Qinghai-Tibetan Plateau (QTP), including Indigenous knowledge of sustainable rangeland management, science-policy interface for alpine rangeland biodiversity conservation, adaptations of local people to social and environmental changes and policy design for managing coupled human-natural systems of alpine rangelands.

Local-Scale Carbon Budgets and Mitigation Opportunities for the Northeastern United States

Economic and political realities present challenges for implementing an aggressive climate change abatement program in the United States. A high-efficiency approach will be essential. In this synthesis, we compare carbon budgets and evaluate the carbon-mitigation potential for nine counties in the northeastern United States that represent a range of biophysical, demographic, and socioeconomic conditions. Most counties are net sources of carbon dioxide (CO2) to the atmosphere, with the exception of rural forested counties, in which sequestration in vegetation and soils exceed emissions. Protecting forests will ensure that the regions largest CO2 sink does not become a source of emissions. For rural counties, afforestation, sustainable fuelwood harvest for bioenergy, and utility-scale wind power could provide the largest and most cost-effective mitigation opportunities among those evaluated. For urban and suburban counties, energy-efficiency measures and energy-saving technologies would be most cost effective. Through the implementation of locally tailored management and technology options, large reductions in CO2 emissions could be achieved at relatively low costs.

Changes in vegetation composition and plant diversity with rangeland degradation in the alpine region of Qinghai-Tibet Plateau

The changes in vegetation composition and plant diversity of three different alpine ecosystems: alpine meadow, alpine steppe and alpine desert, impacted by different levels of degradation (healthy, lightly degraded and moderately degraded) were examined across a large-scale transect on the Qinghai-Tibet Plateau. The alpine meadow was dominated by sedges, the alpine steppe was dominated by grasses and the alpine desert was dominated by shrubs. The alpine meadow had the highest species diversity, whereas the alpine steppe had the lowest and tended to be dominated by a few species. Forbs were the dominant and most diverse functional group in the alpine meadow and the alpine steppe, which was different from the alpine desert. The importance values of the dominant species and levels of diversity measured by various vegetation indices were only slightly different in the degraded sites as compared with the non-degraded alpine meadow and steppe, whereas the alpine desert showed large changes in the composition and diversity of the plant community in response to degradation. In conclusion, the plant composition of the alpine meadow and alpine steppe ecosystems was more stable and appeared more resistant to disturbance than that of the alpine desert ecosystem.

Derivation of a cooling-rate quotient for high-methoxyl pectin jelly sols

Abstract A common setting-rate index for pectin jelly sols was computed from an equation that was derived from consideration of the straight-line relationships between viscosity, reciprocal, absolute temperature and time, prior to gelation. The equation describes three major indices ( n ), that is, 0 n ⩽ 1 and n ⪢ 1, which should generally increase from slow-set to rapid-set pectins, according to the mathematical logic. This new system is mostly compatible with the existing trade classifications, while simultaneously eliminating the arbitrariness on which the latter are based. Inasmuch as the equation originates from a common time denominator, this mathematical method of classification requires fixed boundaries of the temperature-controlling events. The numerical values inserted in the derived equation have less significance than has the algebraic logic leading to n .

Application of intrinsic viscosity and the interaction coefficient to some ionic galacturonan dispersions

Abstract Aqueous dispersions of a number of galacturonans, commercially called pectins, were made to contain different concentrations of ethanol, and the corresponding slope ([η]2k′) of the viscosity number versus concentration graphs was factored into intrinsic viscosity ([η]) and an interaction coefficient (k′). Factoring was also done for purely aqueous dispersions at different temperatures. Low-OMe pectins appeared to be more susceptible to ethanol and heat than high-OMe pectins. This susceptibility is believed to arise from a tendency toward greater hydrogen bonding which in turn is quite sensitive to solution (dispersion) forces. At ethanol concentrations of 15–25%, all pectins exhibited large increases in [η]2k′, a development that is attributable to OMe—OMe bonding and a consequent increase in the frictional component of viscosity. Squaring or multiplication of small numerical differences in [η] and k′ leads to the conclusion that the slope is a more reliable index of dispersion behavior than is [η] or k′ separately. Although [η] is basically an inherent molecular property, theoretically free of interference in a given solvent system, and k′ is an independent property of that pectin-solvent system, any numerical value acquired by one will automatically impose a limit on the other. Comparisons of [η] or k′ under variable conditions are therefore meaningless without an appraisal of the impact of those conditions on the other parameter. Ageing the dispersions did not show any trend in either factor, but it was expected that OMe—OMe contacts would increase as a pre-condition of fractional deposition of solute.