The paper provides an empirical analysis of the macroeconomic factors that enhance revenue gap in South Africa using the multivariate cointegration techniques for the period 1965 to 2012. The results from the cointegration analysis indicate that the revenue gap in South Africa is negatively associated with the level of imports while positively related to external debt and underground economy. The former finding is consistent with the notion that imports are subjected to more taxation than domestic activities because of certain features of international trade that tend to make tax evasion difficult. On the other hand, the positive relationship between external debt and tax gap shows that the South African government relies upon external debt to finance its budget deficit resulting from missing revenues. Furthermore, the observed negative effect of the post-apartheid dummy confirms that the tax policy reforms that South Africa introduced following the liberation in 1994 have led to a reduction in missing revenues. The results from the Granger causality test also show that there is a unidirectional causality running from imports and underground economy to revenue gap, while revenue gap on the other hand is found to Granger-cause national income and external debt in South Africa.

© iForest -Biogeosciences and Forestry IntroductionNorway spruce is the second most abundant tree species in Latvian forests, occupying 0.52 million hectares, and nearly 0.14 million are second age class (21-40 years old) forest stands (Latvian State Forest Service 2011). Therefore, it is critical to assess the management risks in growing stand volume now, because it is these stands that will comprise the majority of the cutting volume in 40-60 years. Spruce is a species quite vulnerable to biotic and abiotic factors; therefore its cultivation is increasingly associated with high-risk levels. One of the most widespread causes of Norway spruce stand damage is development of large spruce bud scale colonies.The first cases of Norway spruce damage were observed in 2009 in middle-aged stands on drained soils. In August of 2010, monitoring by Riga Forests revealed 24% of the stands were damaged, and 10% of Picea abies stands were reported dead. Management made the decision to avoid further spruce bud scale propagation by felling 300 ha of Norway spruce forests in sanitary clear-cuts . Physokermes piceae Schrnk. belongs to the Coccidae family, order Hemiptera, and are characterized by sexual dimorphisms, with a high ability to adapt to a parasitic lifestyle on host plants (Rasina & Rupais 1994). Adult females are globular with a pronounced curvature, shiny, and brown to reddishbrown in color. Female length averages 3.5 mm, width 3.0 mm, and height 3.5-4.0 mm.Males are winged, average 1 mm long, and rarely encountered (Ozols 1985). Males have a discernable head, chest and abdomen, three pairs of legs, and one pair of wings (Graora et al. 2012). The species develops one generation per year. Immature stages winter at the base of terminal buds, less often on needles. In May, the instar larvae move to the base of new buds by old bud fissures. By the end of May or beginning of June, the females have already developed. Settling on the trunk and twigs, individuals suck sap through the bark vascular tissue. At the end of June or beginning of July, the insects lay eggs beneath themselves, and soon die (Ozols 1985). Several studies report one female lays 800-3 000 reddish eggs (Novak 1974, Turguter & Ülgenturk 2006, State Forest Service 2010. Pink first instars, called "crawlers" hatch in July, and attach themselves to new buds or the underside of needles. In October, crawlers molt into the second instar, and change color from pink to brown. The second instar larvae continue to suck sap, and subsequently overwinter on the branching parts or the lower side of the spruce needles. In spring, a small portion of the overwintering population travels to the needles, where in May the individuals pass through prepupal and pupal stages, developing into winged males (State Forest Service 2011, Lazdins et al. 2011. After wintering, most second instars attach themselves among the budding forked branch apices, where molting occurs, and round yellowish females emerge that gradually darken, and are easily noticeable (State Forest Service 2010.Sp...

Wood ash recycling can be a reasonable method for energy producers to decrease waste problems. Using wood ash as a fertilizer or liming material could improve soil macro and micronutrient content in peat soils. Therefore, the effect of wood ash on Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.) juvenile growth and nutrient content in the soil after spreading wood ash in medium to high doses before and after planting seedlings was investigated in peat forests in the Eastern part of Latvia. The aim of the study was to evaluate the effect of high doses of wood ash on soil properties and the growth of planted Norway spruce and Scots pine seedlings up to 10 years after experiment establishment. Wood ash was applied a year before planting seedlings in doses of 5 and 10 t ha−1 and right after planting in concentrations of 5, 10, 15, and 20 t ha−1. Changes in macronutrient content (i.e., phosphorus [P], and potassium [K]) and tree height and diameter at breast height were measured at one and 10 years after establishing the experiment. Fertilization one year prior to planting the seedlings exhibited a positive response on tree height and diameter growth compared to fertilization after the seedlings were planted. Soil samples from fertilized plots one year after establishment contained more P and K in the soil than the control plots. Wood ash application of the highest doses did not reach the overdose limit, as the tree growth (height and diameter at breast height) results of fertilized plots were similar to those of the control fields; therefore, no significant negative effect on tree growth was discovered.

Abstract. One of the most feasible options for utilization of wood ash obviously is to improve the forest growth conditions, particularly in fertilization of drained forests and peatlands, where the positive impact on tree growth response is observed by many studies in boreal and temperate moist climate zone. Forest fertilization as forestry measure meets several obstacles. One of the main is evenness of mechanized spreading, which is affected by the strip road configuration and stand density. It is also difficult to provide even spread of ash because of variable texture if untreated ash is used. The aim of this study is to determine how far from the fertilized area tree growth is affected. Experiment was established in 3 Norway spruce stands on drained forest soils. In each stand 9 systematically located 20×20 m sample plots were set. Tree measurements were made before fertilization and increment cores were collected 5 growing seasons after fertilization from trees in the sample plots and trees in different distances from the sample plots to determine annual radial increments. Cumulative additional radial increment varied from 0.95 to 3.58 mm in the ash fertilized plots. Significant and positive (t = 4.68 > t 0.05;37 = 1.69) effect of wood ash in outer 10 m zone of the fertilized plots was observed only in 1 spruce stand, which could be partly explained by leaching of biogenic elements and distribution of roots.