From Leaf to Topsoil, a Semi-quantitative Assessment of the Organic Matter Variations in Riparian Forests on a Lake Shore

Glossina palpalis fuscipes Newst. was studied in lake-side forest in north-east Lake Victoria and in riverine forest on the Kuja river, which runs into Lake Victoria. Climatic records are given. Trees counts were made in fifty acres of lake-side forest.Populations of G. palpalis exhibit long-term fluctuations which are not annual and not related to season. On the lake shore, the density of G. palpalis is roughly correlated with the width of the forest, being least where the forest is narrow. In a block 2,200 yeards along the shore by 100 yards wide (this was the widest forest studied) the population was 4,600 non-teneral males. The mean catch along the 2,200 yards of shore was 78 non-teneral males. Calculated on an area basis, this is more than ten times the population which would be inferred from the same catch of G. morsitans or G. swynnertoni. The mean death-rate in this isolated block was 26 per cent. per week, and the mean length of life was 27 days.Analysis of catches indicates that riverine G. palpalis are always more hungry than those on the lake shore, for the percentages of tenerals, of females, and of males attacking, are all higher on the river. Catches from a boat produce more females but fewer males than land catches. Carrying a screen produced more females on some occasions, but not on others, the discrepancy being unexplained.

The area of secondary forest (SF) regenerating from degraded abandoned rubber ( Hevea brasiliensis ) plantation is increasing in the rainforest zone of south southern Nigeria; however, the build-up of soil organic matter following abandonment is not well understood. This study examined the build-up of soil organic matter in a mature forest and three secondary forest fields aged 1, 5 and 10 years of age following the abandonment of degraded rubber ( Hevea brasiliensis ) plantation in Orogun in a part of the rainforest zone of south southern Nigeria. This is in order to ascertain the rate of build-up of organic matter in the soil during the course of forest regeneration from degraded abandoned rubber plantation ( Hevea brasiliensis ). There was a progressive increase in organic matter content of the soil with increasing age of the secondary forest. Organic matter increase was more rapid in the topsoil (0-10cm) than the subsoil (10-30cm): the level of organic matter in the topsoil reached 92.94% of the level of organic matter in the mature forest topsoil by the tenth year and 84.62% of the level of organic matter in the mature forest subsoil by the tenth year. The concentration of organic matter in the topsoil is higher than the subsoil. Reviews of the reported trends in soil organic matter build up during forest establishment after agricultural use show no common trend. This study showed a great variation in soil organic matter build up even within the same locality. Keywords: Organic matter, Rubber plantation, Degraded, Orogun, South Southern Nigeria, Secondary forest.

Policy makers are interested in managing forests to store carbon. Optimizing this strategy requires understanding how carbon storage varies across environmental gradients. We explored variation in tree growth rate, tree longevity, and surface soil organic matter across 135 Connecticut River riparian forest plots. Tree growth rate did not vary significantly with climate but rather increased with sediment accretion rate, soil pH and decreased with plot elevation, where elevation was measured relative to the stage of the 2-year flood. By contrast, surface soil organic matter was negatively related to pH and tree growth rate. Tree species longevities were greater at higher elevations with coarser soils. The faster growth rates at lower elevations allow for restoring forest structure rapidly, whereas flood intolerant but longer-lived tree species allow more durable carbon sequestration at higher elevations. The close associations of growth rate, sediment accretion, and pH suggest that riverine nutrient inputs are important to maintaining the exceptionally high productivity of floodplains. Environmental assessments of river dams should consider impacts of intercepting sediments and reducing flooding on downstream floodplain fertility and productivity. Restoration of riparian locations with high deposition of sediments and associated nutrients may be an opportunity to maximize both nutrient and carbon sequestration.

Radial growth of boreal tree species is only rarely studied in riparian habitats. Here we investigated chronologies of earlywood, latewood, and annual ring widths and blue intensity (BI; a surrogate to latewood density) from riparian lake shore and upland forest interior pines (Pinus sylvestris L.) growing in boreal forest in eastern Finland. Riparian and upland chronologies were compared to examine differences in the pine growth variability and growth response to climatic variation in the two habitats. It was found that the climatic variables showing statistically significant correlations with the tree‐ring chronologies were related to snow conditions at the start of the growing season. Deeper snowpack led to reduced upland pine growth, possibly due to delayed snowmelt and thus postponed onset of the growing season. Warm late winters were followed by increased riparian pine growth because of earlier start of the snow‐melt season and thus a lower maximum early summer lake level. Moreover, riparian pines reacted negatively to increased rainfall in June, whereas the upland pines showed a positive response. Latewood growth reacted significantly to summer temperatures. The BI chronology showed a strong correlation with warm‐season temperatures, indicating an encouraging possibility of summer temperature reconstruction using middle/south boreal pine tree‐ring archives.

Breeding bird community was censused in an area of 15.9 ha in 2000/20001, on the shores of Lake of Varese, in an Alno-Ulmion alluvial forest. The mean number of the territories was 93 pairs/10 ha/year and nests of cavity-nesting birds were actively searched for analysing the selection of dead wood.

Summary1. Single‐station diel oxygen curves were used to monitor the oxygen metabolism of an intermittent, forested third‐order stream (Fuirosos) in the Mediterranean area, over a period of 22 months. Ecosystem respiration (ER) and gross primary production (GPP) were estimated and related to organic matter inputs and photosynthetically active radiation (PAR) in order to understand the effect of the riparian forest on stream metabolism.2. Annual ER was 1690 g O2 m−2 year−1 and annual GPP was 275 g O2 m−2 year−1. Fuirosos was therefore a heterotrophic stream, with P : R ratios averaging 0.16.3. GPP rates were relatively low, ranging from 0.05 to 1.9 g O2 m−2 day−1. The maximum values of GPP occurred during a few weeks in spring, and ended when the riparian canopy was fully closed. The phenology of the riparian vegetation was an important determinant of light availability, and consequently, of GPP.4. On a daily scale, light and temperature were the most important factors governing the shape of photosynthesis–irradiance (P–I) curves. Several patterns could be generalised in the P–I relationships. Hysteresis‐type curves were characteristic of late autumn and winter. Light saturation responses (that occurred at irradiances higher than 90 μE m−2 s−1) were characteristic of early spring. Linear responses occurred during late spring, summer and early autumn when there was no evidence of light saturation.5. Rates of ER were high when compared with analogous streams, ranging from 0.4 to 32 g O2 m−2 day−1. ER was highest in autumn 2001, when organic matter accumulations on the streambed were extremely high. By contrast, the higher discharge in autumn 2002 prevented these accumulations and caused lower ER. The Mediterranean climate, and in its effect the hydrological regime, were mainly responsible for the temporal variation in benthic organic matter, and consequently of ER.