Changes in carbon and nitrogen fractions of graminaceous straws after burning

Summary Changes in the carbon (C) and nitrogen (N) fractions of graminaceous straws were measured after their combustion under both laboratory and open-air conditions. Volatilization of C and N increased with increasing combustion, and losses exceeded 90% when combustion was nearly complete. The small proportion of total N already present in the inorganic form in straw was not increased during the ashing process.Burning of plant residues decreases the amount of organic microbial substrates returned to the soil, and hence directly affects soil biological processes. In addition, the volatile loss of nutrients occurring during the burning of vegetation must be considered in the long-term nutrient economy of ecosystems, and hence in the full evaluation of fire as a management tool.     

Responses of Plants and Arthropods to Burning and Disking of Riparian Habitats

Abstract: Alteration of Iowa, USA, landscapes for agricultural production has resulted in a loss of >99% of the original prairie and >95% of native wetlands. This conversion has included riparian areas, which, as interfaces between terrestrial and aquatic ecosystems, are important to many wildlife species. Farm Bill programs have resulted in the reestablishment of millions of hectares of grasslands and wetlands nationwide, including >100,000 ha in riparian areas of the Midwest. We assessed plant and arthropod responses to burning and disking of riparian grasslands in east-central Iowa in 2001 and 2002. Burning altered the plant community by removing litter and standing dead vegetation and had negative effects on several arthropod taxa, including Hemiptera and Lepidoptera. However, we observed no differences in vegetation or arthropods between burned and unburned fields during the second year postburning (P > 0.05). Disking decreased the cover of grasses, litter, and standing dead vegetation and increased plant species richness and the cover of forbs and bare ground (P < 0.05). Arthropod abundance and dry biomass were greater on disked than undisked portions of fields (P < 0.05). Increases in the abundance and biomass of arthropods associated with changes in vegetation structure and composition likely improved habitat quality for a number of breeding bird species. Both burning and disking appear to be effective management options for maintaining or enhancing riparian grasslands for wildlife.     

Deer Carrying Capacity in Mid-Rotation Pine Plantations of Mississippi

ABSTRACT Herbicides, commonly used for vegetation management in intensively managed pine (Pinus spp.) forests of the southeastern United States, with and without fire, may alter availability of quality forage for white-tailed deer (Odocoileus virginianus; deer), an economically and socially important game species in North America. Because greater forage quality yields greater deer growth and productivity and intensively managed pine forests are common in the southeastern United States, forest managers would benefit from an understanding of fire and herbicide effects on forage availability to improve habitat conditions for deer. Therefore, we evaluated independent and combined effects of fire and herbicide (i.e., imazapyr) on forage biomass and deer nutritional carrying capacity (CC) on land owned and managed by Weyerhaeuser NR Company in east-central Mississippi, USA. We used a randomized complete block design of 6 pine plantations (blocks) divided into 4 10-ha treatment plots to each of which we randomly assigned a treatment (burn-only, herbicide-only, burn + herbicide, and control). We estimated biomass (kg/ha) of moderate- and high-use deer forage plants during July of 1999–2008, then estimated CC for diets to support either body maintenance (6% crude protein) or lactation (14% crude protein) with a nutritional constraints model. Herbaceous forages responded positively to fire and herbicide application. In most years, CC estimates for maintenance and lactation were greater in burn + herbicide than in controls. Maintenance-level CC was always greater in burn + herbicide than in controls, except at 1 year posttreatment. Burn + herbicide was 2.6–8.3 times greater (x̄ = 4.0) than control for lactation-level CC in 8 of 9 years posttreatment. We recommend fire and selective herbicides to increase high-quality deer forage in mid-rotation, intensively managed pine plantations.     

Global climate change and litter decomposition: more frequent fire slows decomposition and increases the functional importance of invertebrates

Of the many mechanisms by which global climate change may alter ecosystem processes perhaps the least known and insidious is altered disturbance regimes. We used a field-based experiment to examine the climate change scenario of more frequent fires with altered invertebrate assemblages on the decomposition of Eucalyptus leaves. Our design comprised three fire regimes [long-term fire exclusion (FE), long-term frequent burning (FB) and FE altered to FB (FEFB)] and two litter bag mesh sizes (8.0 and 0.2 mm) that either permitted or denied access to the leaf litter by most invertebrates. We found a significant interaction effect between fire regime and mesh size in losses of litter mass and net carbon (C). Compared with the regime of FE, with more frequent burning (FB and FEFB) the pace of decomposition was slowed by 41% (when access to litter by most invertebrates is not impeded). For the regime of FE, denying access to leaf litter by most invertebrates did not alter the pace of decomposition. Conversely, under regimes of frequently burning, restricting access to the litter by most invertebrates altered the pace of decomposition by 46%. Similar results were found for net C. For net losses of nitrogen (N), no interaction effects between fire regime and mesh size were detected, although both main effects were significant. Our results show that by modifying disturbance regimes such as fire frequency, global climate change has the potential to modify the mechanism by which ecosystems function. With more FB, decomposition is driven not only by fire regime induced changes in substrate quality and/or physiochemical conditions but through the interaction of disturbance regime with animal assemblages mediating ecosystem processes.     

Drought effects on fine-root and ectomycorrhizal-root biomass in managed Pinus oaxacana Mirov stands in Oaxaca, Mexico

The effects of a severe drought on fine-root and ectomycorrhizal biomass were investigated in a forest ecosystem dominated by Pinus oaxacana located in Oaxaca, Mexico. Root cores were collected during both the wet and dry seasons of 1998 and 1999 from three sites subjected to different forest management treatments in 1990 and assessed for total fine-root biomass and ectomycorrhizal-root biomass. Additionally, a bioassay experiment with P. oaxacana seedlings was conducted to assess the ectomycorrhizal inoculum potential of the soil for each of the three stands. Results indicated that biomasses of both fine roots and ectomycorrhizal roots were reduced by almost 60% in the drought year compared to the nondrought year. There were no significant differences in ectomycorrhizal and fine-root biomass between the wet and dry seasons. Further, the proportion of total root biomass consisting of ectomycorrhizal roots did not vary between years or seasons. These results suggest that both total fine-root biomass and ectomycorrhizal-root biomass are strongly affected by severe drought in these high-elevation tropical pine forests, and that these responses outweigh seasonal effects. Forest management practices in these tropical pine forests should consider the effects of drought on the capacity of P. oaxacana to maintain sufficient levels of ectomycorrhizae especially when there is a potential for synergistic interactions between multiple disturbances that may lead to more severe stress in the host plant and subsequent reductions in ectomycorrhizal colonization.     

Bird Community Changes in Response to Single and Repeated Fires in a Lowland Tropical Rainforest of Eastern Borneo

Our current understanding of bird community responses to tropical forest fires is limited and strongly geographically biased towards South America. Here we used the circular plot method to carry out complete bird inventories in undisturbed, once burned (1998) and twice burned forests (1983 and 1998) in East Kalimantan (Indonesia). Additionally, environmental variables were measured within a 25 m radius of each plot. Three years after fire the number of birds and bird species were similar for undisturbed and burned forests, but species diversity and turnover were significantly lower in the burned forests. The bird species composition also differed significantly between undisturbed and burned forests, with a strong decline of closed forest preferring bird species accompanied by a strong increase in degraded forest preferring species in burned forests. These differences were strongly related to differences in environmental conditions such as shifts in vegetation cover and layering and differences in ground and understorey vegetation structure. We also found significant shifts in body mass distribution, foraging height and feeding guilds between the bird communities in unburned and burned forests. Surprisingly, repeated burning did not lead to increasing impoverishment of the avifauna, and both once and twice burned forests still contained most of the bird species that were also present in undisturbed forest, even though their densities were considerably lowered.