Population structure of woody plants in the arid cloud forests of Dhofar, southern Oman

Abstract

-This study evaluates the size frequency distribution of 11 trees and shrubs in the cloud forest in Wadi Garziz, southern Oman, in order to assess their current situation, which is affected by cutting, overgrazing and other constraints. A size class distribution and a vegetation structure analysis were applied in order to analyze the dynamics of this forest using census data from 51 plots selected across 5 transects covering the hill-slope and wadi-bed habitats. Some of the trees inhabiting the hill-slopes (e.g. Acacia senegal and Commiphora spp.) were found to exhibit an inverse J-shaped distribution with constant regeneration, whilst in the wadi bed these same trees exhibited a J-shaped distribution (i.e. of declining populations). On the other hand, Acacia etbaica inhabiting the hill-slopes exhibited a tendency towards a J-shaped distribution and an inverse J-shaped distribution in the wadi-bed. All the populations (i.e. inhabiting the hill-slopes and the beds) of Anogeissus dhofarica had a J-shaped distribution whereas all the populations of Blepharispermum hirtum had a more or less inverse J-shaped distribution. The Ziziphus spina--christi and Acacia tortilis populations, meanwhile, exhibited the bi-modal shape of size distribution. The shrubs inhabiting the hill-slopes (e.g. Coroton confertus and Ormocarpum dhofarense) exhibited a tendency towards a J-shaped distribution; such distribution characterizes a declining population with a limited regenerational capacity. Overall, most of the examined populations, except those of Acacia etbaica in wadi-bed and Blepharispermum hirtum, seemed to be under stress from both environmental and human factors, particularly in the wadi bed. This type of study can provide a basis for the development of a management plan to support the conservation and sustainable use of forest vegetation in an arid region.

Stand Structure, Diversity and Regeneration Status of Woody Species in Open and Exclosed Dry Woodland Sites around <i>Molapo</i> Farming Areas of the Okavango Delta, Northeastern Botswana

“…Based on the assessment of diameter class distributions, the population structure patterns of the woody species recorded from Island Safari, Shorobe and Xobe were categorized into two groups. In the first group, the number of individuals decreased with the increasing diameter class, resulting in an inverted J-shaped population, an indication of stable population structure or healthy regeneration status (Teketay 1997a;Alelign et al, 2007;Tesfaye et al, 2010;Zegeye et al, 2011;Helm & Witkowski, 2012;El-Sheikh, 2013). This pattern was exhibited by about 29%, 20% and 15% of the woody species recorded at Island Safari, Shorobe and Xobe, respectively.…”

“…This might suggest signs of bush encroachment due to overgrazing and over-exploitation of woody species at Xobe (DEA, 2008;Neelo et al, 2013). Acacia mellifera is known to form impenetrable patches of thickets at Xobe, and also it encroaches eroded sites (Ellery & Ellery, 1997) and heavily grazed areas (El-Sheikh, 2013). Acacia tortilis is also a common and widespread species in Botswana, which occurs on clay or loam soils in a variety of woodlands, generally near floodplains and pans.…”

Dewfall and its ecological significance in semi-arid coastal south-western Madagascar

“…Best known are the ancient fog harvesting systems of the Atacama desert in Chile and Peru which use water for irrigation of field crops (Fessehaye et al, 2014), and natural dew collection in desert ecosystems in the Negev of Israel (Kidron et al, 2002). Similarly impressive are the Indian Summer Monsoon-dependent Anogeissus dhofarica (Combretaceae) forests in Dhofar region of southern Oman and Yemen (El-Sheikh, 2013;Hildebrandt and Eltahir, 2006;Kürschner et al, 2004). Dew may also play a role in maintaining plant water status through foliar uptake of moisture, which has been documented for several species in arid and humid environments (Goldsmith et al, 2013;, as well as in the reduction of transpiration rates in early morning hours (Ben-Asher et al, 2010;Raman et al, 1973;Richards, 2004).…”

Diversity, stand structure and regeneration status of woody species, and spatial cover of herbaceous species in Mokolodi Nature Reserve, Southeastern Botswana

“…This might suggest signs of bush encroachment due to overgrazing and over-exploitation of woody species (DEA, 2008;Neelo et al, 2013;Neelo et al, 2015). Acacia mellifera is known to form impenetrable patches of thickets as well as encroach eroded sites (Ellery and Ellery, 1997;Neelo et al, 2015) and heavily grazed areas (El-Sheikh, 2013;Neelo et al, 2015). The relatively high density of Acacia species, which are indicative of heavy grazing and encroachment, is consistent with the fact that MNR, as alluded in the introduction, has been used as an open grazing area in the past.…”