Influence of Drought on Acacia senegal (L.) Willd: Gum Yield within a Soil Moisture Gradient in North Eastern Nigeria

There had been a discernible shift in climate affecting the Sahelian zone of northern Nigeria. This attribute of drought influenced the rate of gum Arabic production in the North eastern axis. Therefore, these called for the studied of the Influence of drought on Acacia senegal (L.) Willd. Gum yield within a Soil moisture gradient in north eastern Nigeria. Two studied areas were purposively selected based on the availability (Gujba and Nguru). Complete Randomised Design was employed with three (3) samples examined at six (6) levels in six different tapping periods. Also, systematic line transect of 1Km was laid at the middle of both plantations where 1m by 1m transect were further laid in four transect sample plots. The soil samples were collected with the aid of soil auger at different levels (0-25 cm, 25-50 cm, 50-75 cm, 75-100 cm, 100-150 cm, 150-200 cm). Data was subjected using analysis of variance with statistical analysis system and descriptive statistic was also employed. The results showed that mean yield of Gum Arabic is Gujba is higher than Nguru (45kg and 30kg) respectively. Furthermore, physiochemical properties showed that pH, aluminium calcium and magnesium in both plantations were very high which is harmful for plantation development. Therefore, there is need for proper conservation and silvicultural management for both study areas.

Methane flux measurements along a floodplain soil moisture gradient in the Okavango Delta, Botswana

Data-poor tropical wetlands constitute an important source of atmospheric CH 4 in the world. We studied CH 4 fluxes using closed chambers along a soil moisture gradient in a tropical seasonal swamp in the Okavango Delta, Botswana, the sixth largest tropical wetland in the world. The objective of the study was to assess net CH 4 fluxes and controlling environmental factors in the Delta's seasonal floodplains. Net CH 4 emissions from seasonal floodplains in the wetland were estimated at 0.072 ± 0.016 Tg a −1 . Microbial CH 4 oxidation of approximately 2.817 × 10 −3 ± 0.307 × 10 −3 Tg a −1 in adjacent dry soils of the occasional floodplains accounted for the sink of 4% of the total soil CH 4 emissions from seasonal floodplains. The observed microbial CH 4 sink in the Delta's dry soils is, therefore, comparable to the global average sink of 4–6%. Soil water content (SWC) and soil organic matter were the main environmental factors controlling CH 4 fluxes in both the seasonal and occasional floodplains. The optimum SWC for soil CH 4 emissions and oxidation in the Delta were estimated at 50% and 15%, respectively. Electrical conductivity and pH were poorly correlated ( r 2 ≤ 0.11, p < 0.05) with CH 4 fluxes in the seasonal floodplain at Nxaraga. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part1)'.

Root Reinforcement in Slope Stability Models: A Review

The influence of vegetation on mechanical and hydrological soil behavior represents a significant factor to be considered in shallow landslides modelling. Among the multiple effects exerted by vegetation, root reinforcement is widely recognized as one of the most relevant for slope stability. Lately, the literature has been greatly enriched by novel research on this phenomenon. To investigate which aspects have been most treated, which results have been obtained and which aspects require further attention, we reviewed papers published during the period of 2015–2020 dealing with root reinforcement. This paper—after introducing main effects of vegetation on slope stability, recalling studies of reference—provides a synthesis of the main contributions to the subtopics: (i) approaches for estimating root reinforcement distribution at a regional scale; (ii) new slope stability models, including root reinforcement and (iii) the influence of particular plant species, forest management, forest structure, wildfires and soil moisture gradient on root reinforcement. Including root reinforcement in slope stability analysis has resulted a topic receiving growing attention, particularly in Europe; in addition, research interests are also emerging in Asia. Despite recent advances, including root reinforcement into regional models still represents a research challenge, because of its high spatial and temporal variability: only a few applications are reported about areas of hundreds of square kilometers. The most promising and necessary future research directions include the study of soil moisture gradient and wildfire controls on the root strength, as these aspects have not been fully integrated into slope stability modelling.