ISSN 2079-0961, Arid Ecosystems, 2018, Vol. 8, No. 2, pp. 97–110. © Pleiades Publishing, Ltd., 2018.
SYSTEMATIC STUDY OF ARID TERRITORIES
Influences of Physiographic Factors, Vegetation Patterns and Human Impacts on Aeolian Landforms in Arid Environment1 R. H. Abd El-Wahaba, b, *, A. R. Al-Rashedb, and A. Al-Dousaric aSuez
Canal University, Faculty of Science, Botany Department Egypt, Ismailia, 41522 Egypt Public Authority for Applied Education and Training, College of Basic Education, Science Department Kuwait, Adailiya, 73251 Kuwait cKuwait Institute for Scientific Research Kuwait, Kuwait City, 13109 Kuwait *e-mail:
[email protected]
bThe
Received August 8, 2017
Abstract⎯During the last few decades, the inland and coastal aeolian landforms of southern Kuwait showed severe land degradation and deterioration of plant cover due to human impacts such as spring camping, offroad driving and overgrazing. This study aimed to quantify the edaphic conditions and vegetation composition of the main types of aeolian landforms in the southern desert of Kuwait and to investigate the effects of vegetation, climate, physiography and impacts of anthropogenic activities on the features and stability of aeolian sand deposits and subsequently land degradation and vegetation loss. This study classified the southern aeolian deposits into four main landforms: inland active sand sheets, inland stable sand sheets, coastal stable sand sheets and coastal stable sabkhas. These landforms are mostly influenced with soil texture, moisture content, organic matter, salinity, vegetation cover, wind strength and intensity of land use. A total of 46 plant species in 23 families was found in these landforms. Poaceae species dominated the vegetation of inland active and stable sand sheets; however Asteraceae and Chenopodiacea species dominated the vegetation of coastal stable sand sheets and coastal sabkhas. Therefore, the growth of these species in hot deserts is adaptive to the accumulation of wind-borne sediments within or around their canopies. Annuals and perennial herbs were the dominant growth forms in the aeolian landforms. The Shannon-diversity of the plant species was lower at inland stable sand sheets than at inland active sand sheets, coastal stable sand sheets and coastal stable sabkhas. The dominant perennials were Cyperus conglomeratus, Stipagrostis ciliata and Moltkiopsis ciliata at inland aeolian landforms, and Zygophyllum qatarense, Salsola imbricate, Suaeda aegyptiaca, Cyperus conglomeratus and Launaea mucronata, Suaeda vermiculata, Lycium shawii and Halocnemum strobilaceum at coastal aeolian landforms. The dominant annuals were Schismus barbatus at inland aeolian landforms and Polycarpaea repens, Schismus barbatus, and Cornulaca aucheri at coastal aeolian landforms. Deterioration of plant cover, decline in sub-shrubs and shrubs, lacking of trees and severe land degradation in the inland and coastal aeolian landforms of southern Kuwait are attributed to human impacts. Effective management plan for human activities and restoration program for degraded aeolian landforms may include prohibitions of human activities that adversely affect native plant communities, planting of certain native perennial species efficient in trapping sands and stabilization of aeolian landforms, such as Poaceae species and Chenopodiaceae species. In addition, awareness programs and participation of local inhabitants are crucial measures to guarantee successful of restoration plan. Keywords: aeolian deposits, vegetation patterns, sand sheets, coastal sabkha, hot desert, human disturbance, land degradation DOI: 10.1134/S2079096118020026
INTRODUCTION Due to its dry, hot and windy climate, the detrital nature of its bedrock and its location downwind of high deflation area of the Mesopotamian floodplain, desert of Kuwait is mostly covered by a thin layer of recent aeolian deposits (Khalaf et al., 1984). About 75% of the hot desert of Kuwait showed moderate and severe land degradation and deterioration of plant
cover due to high intensity of anthropogenic activities including urbanization, camping, off-road driving, overgrazing, salinization, oil contamination, industrial activities, and quarrying (Brown, 2003; Abd El-Wahab and Al-Rashed, 2010). These activities are contributing to exposure of the dry, loose, recent sediments to wind action and soil loss. During the last few decades, the coastal area of Kuwait, particularly the salt marsh strip, has been altered extensively by human development activities (Abd El-Wahab, 2015).
1 The article is published in the original.
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Mostly the aeolian sand deposits of Kuwait were studied to determine their geneses and to assess their geomorphological and sedimentological trends. These deposits are classified into three main types: (a) mobile, (b) anchored, and (c) stabilized (Cooke et al., 1993). Mobile deposits include sand sheets, star dunes, linear dunes and transverse dunes. Anchored deposits comprise lee, flank, and climbing dunes. Stabilized deposits include clay dunes stabilized by cementation and nabkas stabilized by vegetation. Nabka is an Arabic word denoting accumulation of loose sediments under the canopy of plants in the form of hillocks (El-Bana et al., 2002). Khalaf et al. (1995) recognized several types of aeolian deposits in the desert of Kuwait: (1) rugged vegetated sand sheets; 2) smooth sand sheets; (3) active sand sheets; (4) aeolian wadi fill; (5) sand dunes and sand drifts. Coastal sand drifts vary in size and mode of occurrence. Al-Sarawi et al. (2006) classified the land surface of Kuwait into three types of deposits: (1) fluvial deposits from the delta of wadi Al-Batin, (2) aeolian deposits in the form of dunes or flat sand sheets, and (3) flat desert surface and evoporite deposits in the form of inland and coastal sabkha. Al-Hurban (2014) classified the surface deposits of Kuwait into two main classes; desert deposits and coastal deposits. Desert deposits which are the most abundant types of recent surface deposits in Kuwait consist of six main types of sand deposits: sand sheets, sand dunes, wadi fills, residual gravel, playa deposits, and desert plain deposits. Coastal deposits, which developed from sea shores to the high land, consist of coastal sand deposits or dunes, sabkha deposits, and beach and tidal flat deposits. Sand sheets are sandy plains, mainly flat to low angle aeolian stratification, and commonly exist on the margins or between belts of sand dunes (Fryberger et al., 1979). Sand sheets commonly have coarse grains sediments comparing with other deposits in the desert such as dunes or ripples. Moreover, sand sheets commonly grow by slow vertical accretion and more rapid lateral extension. Active sand sheets cover considerable areas of inland southern desert of Kuwait and in most cases they have a unidirectional ripple surface, indicating the prevailing northwesterly wind direction. Inland stable sand sheets or smooth sand sheets have relatively flat surfaces, covered with a very thin veneer of residual granules of coarse sands and some patches of residual gravels. In addition, vegetation cover plays an important role in the stability of this type of aeolian landform (Al-Hurban, 2014). A rugged vegetated sand sheet used to occupy the shallow wide depression surrounding the ephemeral desert lake areas and mostly covered with widespread vegetated sand drifts (Khalaf et. al., 1984). Aeolian sabkhas consist of flat lying sediments commonly convoluted by evaporation processes. They are more originally brought to the desert locally by wind. Aeolian sabkhas developed due to low
rain fall and high evaporation rate, which characterize the hot desert area (Al-Hurban, 2014). Although several studies have examined the sedimentological aspects of the aeolian deposits of Kuwait (Gunatilaka et al., 1984; Gunatilaka and Mwango, 1987; AI-Sarawi et al., 1988; Khalaf et al., 1995), there has been little attention to link the aeolian landforms to vegetation composition and intensity of human impacts (Al-Hurban, 2014; Abd El-Wahab, 2016). In this study we aim to distinguish the interactions between edaphic conditions, vegetation composition, and human impacts of the main types of aeolian landforms in the southern desert of Kuwait and to discuss how vegetation patterns and human disturbance affect stability of aeolian sand deposits. MATERIAL AND METHODS Site Description The State of Kuwait is located in the north-eastern corner of the Arabian Desert. Geomorphic and sedimentological trends indicate that the surface of Kuwait is carved in a calcretized clastic sequence of Miocene-Pleistocene age, mostly covered by sand sheets of recent aeolian deposits (Khalaf and Al-Ajmi, 1993) with a few low sedimentary hills such as Jal AlZor escarpment (145 m altitude) in the northern Kuwait and Al-Ahmadi hill (125 m altitude) in the southern Kuwait (Al-Sarawi, 1982). Investigation of the inter-relations between vegetation, human disturbance and Aeolian landforms in the southern Kuwait was carried out in four main sites; Shaqaya, Umm Qudeer and Wafra representing desert habitats, and Nuwaiseeb representing coastal habitats (Fig. 1). Kuwait has a typical arid climate characterized by long, hot and dry summer, short winter, a wide range of temperature and low amount of precipitation with a great irregularity in time and space (Abd El-Wahab, 2016). The average monthly climatic data for five years (2011–2015) for certain stations closed to study sites are as follows: average temperature in summer reached 45°C during the day and 23°C during the night. In winter, the average temperature reaches 20°C during the day and 9°C during the night. Generally, coastal sites at Nuwaiseeb were warmer than inland sites at Minagish (Fig. 2). The annual rainfall varies between 30 and 250 mm, most of which falls in winter and spring (Halwagy et al., 1982). The mean annual rainfall for the period 1985–2002 was 128 mm, and for the period 2011–2015 was 100 mm. Relative humidity reaches 60% in winter and 20% in summer. The evaporation rate ranges from 4.6 mm/d in January to 22.9 mm/d in June. The average daily evaporation varied between 2.3 mm in January and 18.9 mm in June at Sulaibiya area and 1.5 mm in January and 11.9 in June at Wafra area. Wind is mostly northwest with an annual average speed of 13.6 km/h. Dust and sand storms are frequent in summer, particularly during June and July when ARID ECOSYSTEMS
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30° N
Iraq
Kuwait
Arabian Gulf
Sulaibiya
Minagish
29° N
Umm Qudeer
Saudi Arabia 0
Shaqaya
40 km Warfa
N
Nuwaiseeb
47° E
48° E
Fig. 1. Location Map showing the study area in the southern of Kuwait at Shaqaya, Umm Qudeer, Wafra and Nuwaiseeb.
ARID ECOSYSTEMS
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(a) Min temp Minagish Max temp Minagish
t, °C
Field Survey and Vegetation Analysis In the spring of 2016, a total of 40 vegetation survey plots (each of approximately 5 × 5 m) were selected randomly and to assess the main features of different aeolian landforms throughout the southern of Kuwait. The distribution of these plots within different landforms was as follows: 8 plots in inland active sand sheets, 14 plots in inland stable sand sheets, 11 plots in coastal stable sand sheets, and 9 plots in coastal sabkha. In each landform, the distance between adjacent plots was about 2 km. The geographical location of each plot (latitude, longitude and altitude) was measured with a global positioning system device (model GPS 315 Magellan, Garmin, United States). The nature of soil surface and features of aeolian landforms were described. Species richness (number of plant species), abundance (number of individuals of each species) were counted in each plot. For each species in each landform, presence (number of plots where each species occurs in divided by the total number of plots) and
abundance (total number of individuals of each species divided by the total number of plots) were estimated. Relative presence (RP) and relative abundance
50 40 30 20 10 0 (b)
t, °C
strong north-westerly winds blow over the dry lowland of Southern Iraq. About 50% of dust storms occur in May, June and July (El-Baz and Al Sarawi, 2000; Almedeij, 2012) The average daily wind speed in June for the period between 2011 and 2015 reached 8.5 m/s at Nuwaiseeb area and 11.1 m/s at Umm Qudeer area (Metrological Department at State of Kuwait; Fig. 3).
Min temp Nuwaiseeb Max temp Nuwaiseeb
50 40 30 20 10 0 Jan.
Mar. May Jul. Sept. Nov. Feb. Apr. Jun. Aug. Oct. Dec.
Fig. 2. Monthly average minimum and maximum temperature data of Kuwait at (a) Minagish and (b) Nuwaiseeb stations through the period between 2011 and 2015.
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Wind speed, m/s
Precipitation, mm
Evaporation, mm
(a) Wafra Sulaibiya
20 15 10 5 0
(b)
Minagish station Umm qudeer Nuwaiseeb
7 6 5 4 3 2 1 0
(c)
Minagish Umm qudeer Nuwaiseeb
14 12 10 8 6 4 2 0 Jan.
Mar. May Jul. Sept. Nov. Feb. Apr. Jun. Aug. Oct. Dec.
Fig. 3. Monthly average climatic data of Kuwait: (a) evaporation, (b) precipitation and (c) wind speed at different stations through the period between 2011 and 2015.
(RA) of each species was calculated according to the following equations:
RP of species % Presence of species = × 100, Total Presences of all species RA of species % Abundance of species = × 100. Total abundances of all species Based on species richness and species abundance in each plot, Shannon diversity index (H′) was calculated according to the following equation (Entsminger, 2014). s
∑ P lnP ,
H' = –
i =1
i
i
where Pi is the proportion of individuals found in the ith species; s is the number of species. Plant cover in each plot was measured using visual assessment of the relative area covered by the different species in three small quadrats (1 × 1 m each) selected randomly in each plot (Kent and Coker, 1992; Bonham, 2013). Plant cover was ranked according to the
following scale: 1 = very low vegetation (30%). Identification, nomenclature, growth form (annual herb, annual grass, perennial herb, sub-shrub, and shrub), importance (fodder, fuel-wood, medicinal) and phytogeographical distribution of the recorded plant species were designated according to Täckholm (1974), Daoud and Al-Rawi (1985), Boulos (1988) and Omar et al. (2007). Human disturbance due to camping, off-road driving, urbanization including beach houses, roads and solid wastes were described. Based on the nearest distance between plots and these human activities, disturbance intensity index was classified into three levels: 1 = low disturbance (distance >3 km), 2 = medium disturbance (distance = 1–3 km) and 3 = high disturbance (distance
