Implications of Land Use Changes on Carbon Dynamics and Sequestration—Evaluation from Forestry Datasets, India

Forests and soils are a major sink of carbon, and land use changes can affect the magnitude of above ground and below ground carbon stores and the net flux of carbon between the land and the atmosphere. Studies on methods for examining the future consequences of changes in patterns of land use change and carbon flux gains importance, as they provide different options for CO₂ mitigation strategies. In this study, a simulation approach combining Markov chain processes and carbon pools for forests and soils has been implemented to study the carbon flows over a period of time. Markov chains have been computed by converting the land use change and forestry data of India from 1997 to 1999 into a matrix of conditional probabilities reflecting the changes from one class at time t to another class time t+1. Results from Markov modeling suggested Indian forests as a potential sink for 0.94 Gt carbon, with an increase in dense forest area of about 75.93 Mha and decrease of about 3.4 Mha and 5.0 Mha in open and scrub forests, if similar land use changes that occurred during 1997–1999 would continue. The limiting probabilities suggested 34.27 percent as dense forest, 6.90 as open forest, 0.4 percent mangrove forest, 0.1 percent scrub and 58 percent as non-forest area. Although Indian forests are found to be a potential carbon sink, analysis of results from transition probabilities for different years till 2050 suggests that, the forests will continue to be a source of about 20.59 MtC to the atmosphere. The implications of these results in the context of increasing anthropogenic pressure on open and scrub forests and their contribution to carbon source from land use change and forestry sector are discussed. Some of the mitigation aspects to reduce greenhouse gas emissions from land use change and forestry sector in India are also reviewed in the study.     

Agricultural Land Use Effects on Sediment Loading and Fish Assemblages in Two Minnesota (USA) Watersheds

We examined the relationship between water quality and fish communities within two agricultural areas using a computer simulation model. Our analyses focused on a coolwater stream, Wells Creek in southeastern Minnesota, and a warmwater stream, the Chippewa River in western Minnesota. We used the Agricultural Drainage and Pesticide Transport (ADAPT) model in relation to land use to calculate instream suspended sediment concentrations using estimates of sediment delivery, runoff, baseflow and streambank erosion, and quantified the effects of suspended sediment exposure on fish communities. We predicted the effects of agricultural practices on stream fish communities under several possible land use scenarios, with reference to current conditions. Land use changes led to reductions in sediment loading of up to 84% in Wells Creek and 49% in the Chippewa River. The reduction in sediment loading across scenarios may be directly related to a reduction in runoff by about 35% in both study areas. We found a 98% decrease in lethal concentrations of suspended sediment on fish in Wells Creek with an increase in conservation tillage, riparian buffers, and permanent vegetative cover. However, the effects of suspended sediment did not significantly decrease in the Chippewa River. This difference between study areas was likely due to differences in tolerance to suspended sediment between coolwater and warmwater fish communities and differences in topography, runoff and bank erosion between the two streams. The Minnesota Cooperative Fish and Wildlife Research Unit is jointly sponsored by the US Geological Survey, the University of Minnesota, the Minnesota Department of Natural Resources, and the Wildlife Management Institute.     

Wildfire effects on hiking and biking demand in New Mexico: a travel cost study

We use a travel cost model to test the effects of wild and prescribed fire on visitation by hikers and mountain bikers in New Mexico. Our results indicate that net benefits for mountain bikers is $150 per trip and that they take an average of 6.2 trips per year. Hikers take 2.8 trips per year with individual net benefits per trip of $130. Both hikers' and mountain bikers' demand functions react adversely to prescribed burning. Net benefits for both groups fall as areas recover from prescribed burns. Because both visitation and annual recreation benefits decrease to these two types of visitors, this gives rise to multiple use costs associated with prescribed burning. With respect to wildfire, hikers and mountain bikers both exhibit decreased visitation as areas recover from wildfires, however, only hikers indicate an increase in per trip net benefits. Bikers' demand effectively drops to zero. These results differ from previous findings in the literature and have implications for efficient implementation of the National Fire Plan and whether prescribed burning is a cost effective tool for multiple use management of National Forests. Specifically, that fire and recreation managers cannot expect recreation users to react similarly to fire across recreation activities, or different geographic regions. What is cost effective in one region may not be so in another.     

In situ treatment of metals in contaminated soils with phytate

Batch experiments were conducted to evaluate the ability of various forms of phytate, the hexaphosphoric form of myo-inositol (IP6), to immobilize U, Ni, and other inorganic contaminants in soils and sediments. A Ca-phytate precipitate (Ca(n)-IP6), dodeca sodium-phytate (Na12-IP6), and hydroxyapatite (HA) were added to contaminated soil at rates of 0, 10, 25, and 50 g kg(-1) and equilibrated in 0.001 M CaCl2. The samples were then centrifuged, the solution pH was measured, and the supernatants were filtered prior to analysis for dissolved organic carbon (DOC), U, Ni, P, and other inorganic contaminants, such as As, Cr, Se, and Pb. The residual sediments were air-dried prior to characterization by analytical electron microscopy and extraction with the Toxicity Characteristic Leaching Procedure (TCLP). The solubility of several metals (e.g., U, Pb, Cu) increased with increasing Na12-IP6 when compared with the nonamended control. In some cases immobilization was observed at the lowest Na12-IP6 application rate (10 g kg(-1)) with an increase in solubility observed at the higher rates, demonstrating the importance of metal to ligand ratio. In contrast, Ca(n)-IP6 and HA decreased the solubility of U, Ni, Al, Pb, Ba, Co, Mn, and Zn. For example, soluble U decreased from 2242 to 76 microg kg(-1) and Ni from 58 to 9.6 mg kg with the Ca(n)-IP6 addition, similar to the results observed for HA. Arsenic and Se solubility increased for HA and both forms of IP6, but to a much greater degree for Na12-IP6, suggesting that the increase in pH observed for HA and Na12-IP6, combined with added competition from PO4 and IP6 for sorption sites, resulted in the release of sorbed oxyanion contaminants. The analytical electron microscopy results indicated that metals such as U and Ni were closely associated with secondary Al-rich precipitates in the HA-treated soils, rather than unreacted HA. The analytical electron microscopy results were less definitive for the Ca(n)-IP6-treated soil, although the residual P-containing material was enriched in Al, with lesser amounts of U and Ni.     

Oxidation of organic impurities in the recycle and reclaim loops of ultra-pure water plants

 The oxidation of trace organic impurities in ultrapure water by ultraviolet light (UV), ozone, and the combination of UV/ozone is investigated. The emphasis is on the development of a global model to simulate the process that take place in the typical oxidation reactors used in ultrapure water plants. The study also focuses on reaction mechanism for oxidation of multi-component organic impurities. Eighteen organic model compounds are chosen as representative contaminants. The results demonstrate and confirm a significant synergistic effect between UV and ozone oxidation. A mechanism for the synergistic oxidation of organic impurities is proposed and validated with experimental data. The combination of the reaction and the reactor models is used to determine the fundamental kinetic parameters involved in the three oxidation processes. Received: 3 July 1998 / Accepted: 4 September 1998     

An analysis of assessment outcomes from eight years' operation of the Australian border weed risk assessment system

The majority of Australian weeds are exotic plant species that were intentionally introduced for a variety of horticultural and agricultural purposes. A border weed risk assessment system (WRA) was implemented in 1997 in order to reduce the high economic costs and massive environmental damage associated with introducing serious weeds. We review the behaviour of this system with regard to eight years of data collected from the assessment of species proposed for importation or held within genetic resource centres in Australia. From a taxonomic perspective, species from the Chenopodiaceae and Poaceae were most likely to be rejected and those from the Arecaceae and Flacourtiaceae were most likely to be accepted. Dendrogram analysis and classification and regression tree (TREE) models were also used to analyse the data. The latter revealed that a small subset of the 35 variables assessed was highly associated with the outcome of the original assessment. The TREE model examining all of the data contained just five variables: unintentional human dispersal, congeneric weed, weed elsewhere, tolerates or benefits from mutilation, cultivation or fire, and reproduction by vegetative propagation. It gave the same outcome as the full WRA model for 71% of species. Weed elsewhere was not the first splitting variable in this model, indicating that the WRA has a capacity for capturing species that have no history of weediness. A reduced TREE model (in which human-mediated variables had been removed) contained four variables: broad climate suitability, reproduction in less or than equal to 1year, self-fertilisation, and tolerates and benefits from mutilation, cultivation or fire. It yielded the same outcome as the full WRA model for 65% of species. Data inconsistencies and the relative importance of questions are discussed, with some recommendations made for improving the use of the system.