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Soil: An indicator of grazing pressure around watering holes in the Namib Desert

Introduction

Summer Drylands Programme (SDP) is a two month research methodology course offered by Gobabeb Research and Training Centre and the Desert Research Foundation of Namibia (DRFN).

SDP aims to equip emerging Namibian researchers with experience and training in integrated sustainable land management through applied research approaches, critical thinking and problem solving. The main objective of this year’s research is to determine the impact of artificial water points on wildlife conservation in the Namib Desert. These impacts will be determined using different variables, including soil which is one of the most critical variables. The study is carried out by SDP 20 which is composed of 12 Namibian students from different universities. The study was conducted at four sites in the Namib Desert: Natab, Ghemsbok water point (Ganab), Sossusvlei and Escourt. This research will also be included in a global project known as Biodeserts, to aid in gaining a holistic understanding of rangeland management in dry lands around the world.

Soil as a priority consideration in sustainable land or rangeland management

Soil is associated with nearly all ecosystem processes and thus it is the basic component of rangeland ecosystems. Although many people do not value soil, it is fundamental for life. Soil is a non-renewable resource because the formation process is very slow, especially in arid and semi arid environments. Land or rangeland management decisions should be made with careful consideration of the impacts on the soil. The type of soil present in an area is an important consideration for appropriate management. When too much vegetation is removed, for instance by grazing, soil erosion, loss of top soil, can become a major problem leading to reduction in soil quality, soil degradation, due to improper use.

Soil Sampling

At each water point, three plots were demarcated, at varying distances from the water point. We then collected soil samples from each plot using a coring cylinder and a hammer. Soil samples were taken from 10 randomly selected micro-sites within a plot, five at bare ground and five close to the stem of the dominant perennial plant species. Samples were collected for biodeserts, SDP and bulk density (the weight of soil per unit volume). We collected soil samples to find the level of disturbance due to grazing and trampling which can be determined by analyzing changes in the soil properties as you move away from the water point.

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Soil processing in the laboratory

After collecting the soil samples from the field, they were taken to the lab for processing. In the lab, the biodeserts soil samples were sieved with a 2mm mesh sieve. Out of the sieved soil, 40 g samples were weighed into 10 small bags (for each micro-site). These bags were stored in the freezer in order to preserve the soil microbial community before analysis. Microorganisms play a vital role in recycling nutrients, improving soil tilth (suitability for plant growth) and enhancing water infiltration.

For the SDP soil samples, the soil was weighed immediately after collection. These samples will be dried in the oven and weighed later to calculate the soil moisture content. For bulk density determination, the soil will be weighed after drying.

Soil properties to be analyzed

Soil as one of the variables that is considered in this research, was taken to determine the levels of some of its properties. Such properties include bulk density, water holding capacity (amount of water soil can hold for vegetation use), colour, total organic content (plant and animals residues in the soil) conductivity (ability of soil to conduct electric current) as well as pH (alkalinity and acidity of the soil).

Oops! There are always challenges

Taking soil samples is fun and easy, but can depend on the soil collection site. At places where the soil is soft and sandy, the process is very fast. However, when sampling at a very rocky area, such as the Sossusvlei plots one and two, one had to apply a lot of force and sweat for one bag of soil sample. Working under the hot sun of the Namib Desert requires one to have passion and be physically fit! Field work went well, now it’s time for analyses and write-ups. We will communicate the findings very soon!

 


By Taimi Uushona, Jagadguru Sri Shivarathreeswara University, MSc Environmental Science Martha Linus, Namibia University of Science and Technology, BSc Agriculture

 

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