Levels Of Structural Diversity Research Articles

6′-Amino-5,7-dibromo-2-oxo-3′-(trifluoromethyl)-1′H-spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-5′-carbonitrile

The multicomponent reactions are environmentally benign synthetic methods of building-up of complex molecules and several levels of structural diversity for diverse applications. Spirooxindoles are an important synthetic target possessing extended biological activity and drug discovery applications. In this communication, the multicomponent transformation of 5,7-dibromoisatin, malononitrile, and 5-(trifluoromethyl)-2,4-dihydro-3H-pyrazol-3-one in EtOH at reflux in the presence of sodium acetate was carefully investigated to give 6′-amino-5,7-dibromo-2-oxo-3′-(trifluoromethyl)-1′H-spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-5′-carbonitrile in excellent yield. The structure of the new compound was established by means of elemental analysis, mass and nuclear magnetic resonance, and infrared spectroscopy.

Alternative approaches to mixed conifer forest restoration: partitioning the competitive neighborhood

Forest restoration efforts in the intermountain west of North America generally seek to promote the continuation of pine dominance, enhance wildlife habitat, and decrease hazardous fuels, thereby mitigating catastrophic losses from various stressors and disturbances. We propose a method of focal tree release thinning that partitions the competitive neighborhood to provide alternative approaches to managers. Specifically, we sought to examine how competition index (CI) derived harvest simulations alter forest structure, composition, and variability, and evaluate the ecological implications and efficacy of achieving management recommendations. We used a tree inventory collected across 38 experimental plots in the mixed conifer forest of the Sierra Nevada and simulated post-harvest structure using common silvicultural prescriptions to the ownership and cover type. We calculated competition values for all trees using 10 CIs and simulated harvests from two defined integrals of each corresponding probability density function to compare with the standard marking scenario, for a total of 21 harvest simulations. We assessed post-harvest structure through tree density and diameter distributions, basal area by species, and a structural diversity index. Post-harvest conditions exhibited differences in levels of structural diversity and species dominance; however we did not detect any influence on tree density across diameter classes. Most simulations resulted in a decline of non-pine species basal area relative to the default, while only 3 thinning scenarios showed concomitant increases in pine. Every simulation resulted in greater variance of structural diversity than the default marking guidelines. Review of this method highlighted the variability in tree ranked competitive status across indices. We emphasize that no harvest simulation by CI was clearly superior in all aspects of achieving desired objectives, and there was no clear benefit to incorporating inter-tree distances to calculate CI. We consistently observed favorable outcomes in harvest simulations derived from an open-grown crown width parameter which averts the need for tree distance measurements. This approach can be tailored across multiple individual plots, each maintaining unique competitive environments that reflect local tree neighborhoods.

‘Dieback’ (chronic decline) of Eucalyptus viminalis on the Monaro is not new, unique or difficult to explain

ABSTRACTRoss and Brack (2015) reported a widespread decline over the past decade in the health of Eucalyptus viminalis on the Monaro Tablelands in southern New South Wales. They were unable to attribute this to changes in management, lack of fire, or ‘declining levels of structural diversity’. They noted consistent infestation of trees by a native weevil and recommended further work on the role of climate and rainfall in ‘Monaro dieback’. However, chronic decline involving a wide range of arbivores has affected a wide range of eucalypts across Australia since European settlement, and is currently rampant in many areas of forest and woodland. Pasture improvement and/or exclusion of fire and grazing are the major causes of chronically declining health of eucalypts. The data presented by Ross and Brack (2015) provide some support for this conclusion and no contrary evidence.

Response of ground-dwelling spider assemblages to prescribed fire following stand structure manipulation in the southern Cascade RangeThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.

We assessed spider (Arachnida: Araneae) responses to prescribed fire following stand structure treatments in ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) stands in the Cascade Range of California. Stands were logged or left untreated to create three levels of structural diversity. We logged one treatment to minimize old-growth characteristics (low diversity) and one to enhance old-growth characteristics (high diversity) and we used unlogged Research Natural Areas (RNAs) as old-growth, highest-diversity reference stands. We conducted low-intensity prescribed fire on half of each plot following harvest. Spider assemblages in unburned, logged stands were similar to one another but diverged from those in RNAs, with increased abundance, species richness, and diversity in more structurally diverse stands. Prescribed fire, which altered habitat in the organic soil layer where many spiders forage, resulted in altered spider assemblages and population declines in most plots. Fire generally reduced spider species richness, evenness, and diversity. Several taxa were potential indicators of fire and old-growth structure, and we discovered one species and one genus that were previously unknown. There was evidence that old-growth characteristics intensified the effects of fire on spider abundance. This outcome probably results from the deep litter layers in high-diversity stands and RNAs, which constituted greater fuel loads than low-diversity stands.

Response of small mammals to alternative stand structures in the mixed-conifer forest of northeastern CaliforniaThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.

A common, but largely untested, strategy for maintaining forest biodiversity is to enhance stand structural complexity. A silvicultural experiment was implemented from 1996 to 1998 at Blacks Mountain Experimental Forest, California, to test the efficacy of two levels of structural diversity (high versus low) and two levels of prescribed underburning (burn versus no burn) for maintaining or restoring biodiversity. Small mammals were trapped and tagged in experimental units for 2 noncontiguous weeks in fall 2003 and 2004. Total number of captures and number of captured individuals varied by year (P < 0.002). No treatment effects were detected for all species lumped together or for the three most frequent species analyzed separately ( Tamias amoenus J.A. Allen, 1890, Peromyscus maniculatus (Wagner, 1845), and Spermophilus lateralis (Say, 1823)), with the exception that T. amoenus was captured more often in burned units in 2004 (P = 0.004 for year × burn interaction). Mixed-effects regression models indicated that the number of captures and captured individuals of T. amoenus and P. maniculatus decreased with increasing residual basal area of overstory trees, but opposite results were obtained for S. lateralis. After accounting for residual stand density differences, T. amoenus was captured more frequently in units of low structural diversity and S. lateralis in units of high structural diversity.