https://commons.ufh.ac.za/vital/access/manager/Index en-us 5 https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56779 Wed 28 Sep 2022 10:25:53 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:53895 Wed 27 Jul 2022 12:54:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56775 Wed 26 Oct 2022 10:14:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46478 Wed 16 Feb 2022 14:50:52 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46708 Wed 16 Feb 2022 12:24:41 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46703 Wed 16 Feb 2022 11:21:40 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46686 Wed 16 Feb 2022 11:07:48 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56075 Wed 14 Sep 2022 14:24:22 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56077 Wed 14 Sep 2022 14:24:19 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56076 Wed 14 Sep 2022 14:24:14 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56071 Wed 14 Sep 2022 14:24:13 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:59921 Wed 13 Mar 2024 14:11:44 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:59944 Wed 13 Mar 2024 14:10:29 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46379 Wed 09 Feb 2022 13:10:34 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46362 Wed 09 Feb 2022 11:30:13 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46302 Wed 09 Feb 2022 10:12:11 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:59241 Wed 08 Feb 2023 10:07:28 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:64770 Wed 07 Jun 2023 08:48:12 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46480 Wed 02 Mar 2022 11:04:31 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56808 65%) occurred in more recent decades. Canopy cover of ~ 50% was found to be rare in each decade. This suggests that ~50% canopy cover maybe a transient, unstable state. The period with the highest rate of canopy cover increase was 2002-2013, and this increase coincided with a high mean annual rainfall 10 years prior to 2002 and a high mean annual rainfall in most years between the 20022013 period. The period between 2002 and 2013 also had the highest number of sites transitioning from lower to higher tree canopy cover classes, indicating that rainfall may have been a factor driving bush encroachment during the past several decades. An increase in canopy cover (a decrease in light transmittance) was accompanied by changes in woody species composition during thicket formation. The low canopy cover (high light transmittance) sites were dominated by Vachellia karroo and Scutia myrtina trees, while high tree cover sites had fewer V. karroo and S. myrtina trees and were rather characterised by an abundance of thicket tree species. Species proportion, NMDS and dendrogram plots indicated that sites with a light transmittance range between 50-100% had similar tree species compositions, different from sites with light transmittances <50%. An increase in tree density was strongly correlated to an increase in canopy cover (from 2019 satellite imagery), density of trees > 3m, maximum height reached by trees, diversity of trees, total canopy volume, total canopy area and leaf area index (LAI), and a decrease in light transmittance. A structural equation model (SEM) was used to explore the relationships between canopy characteristics (maximum canopy area, canopy volume, tree diversity, density of trees, density of trees >3m, individual trees and maximum canopy height), aerial canopy cover in 2019, and light transmittance. The model explained 73% of the variation in light transmittance, mostly via the direct effect of canopy characteristics. Canopy characteristics had a strong influence on both aerial cover in 2019 and directly on light transmittance, but canopy cover in 2019 had a weak influence on light transmittance. The herbaceous layer was rich and dominated by C4 grasses such as Eragrostis plana, Sporobolus fimbriatus, Themeda triandra and Digitaria eriantha) and forbs including Hibiscus aethiopicus, Helichrysum dregeanum, Helichrysum nudifolium and Gerbera viridifolia at low canopy cover sites with high light transmittance. In contrast, high tree cover sites had fewer herbaceous species in general. Grass and forb species characteristic of these sites high canopy cover sites were Panicum maximum, Loudetia flavida, Pellaea viridis and Cyperus spp. Different sites with low light transmittance (<50%) had similar herbaceous species composition. Basal cover, richness, abundance and diversity of herbaceous plants decreased significantly with an increase in tree density, density of trees >3 m, canopy volume, canopy area, canopy cover, LAI, and increased significantly with increasing light transmittance. Most grasses had their highest densities at LAI <0.5, which was estimated to correspond to ~75% light transmittance and ~38% canopy cover and then started to decline thereafter. Herbaceous species basal cover was also highest at LAI <0.5. An SEM model indicated that herbaceous diversity, basal cover and richness responded both to light availability and to the structure of the woody vegetation directly (R2 = 0.53). While the effect of light transmittance on herbaceous communities was strong (0.41), there was little difference between the effect of light transmittance and canopy characteristics (-0.35) on herbaceous communities. Two possible threshold points, relating to two types of transitions in vegetation structure, could be deduced from this study. The first threshold occurred at canopy cover ~ 40% (LAI < ~ 0.5, light transmittance ~ 75%), at which point many of the common herbaceous species, including the dominant C4 grasses, began to decline in abundance while the composition remained characteristic of the savanna state. A canopy cover of less than ~ 40% at a site provides a suitable state for a high abundance of grass and forb species which help maintain an open system by facilitating fires. The second threshold marked a compositional shift between savanna and closed-canopy vegetation states. Savanna species (trees, grasses and forbs) dominated at high light transmittances (>50%) and were significantly reduced at low light transmittances (< 50%), indicating a possible species composition threshold at ~50% light transmittance at which a savanna state switches to a thicket (LAI ~ 1 and canopy cover ~70%). This point indicated the point where there was a significant difference in both tree and herbaceous plant compositions, with a marked reduction in the occurrence of C4 grasses at light transmittance <50%. Fire is supressed when the C4 grass layer is lost, and further thicket encroachment will take place causing complete canopy closure. Land managers in this system should start becoming concerned about a reduction in grass biomass when canopy cover reaches about 40% and would have to reduce tree cover before the threshold of 50% light transmittance (70% canopy cover from aerial photos) is reached to maintain a savanna system.]]> Tue 27 Sep 2022 11:00:55 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46309 Tue 24 May 2022 13:48:37 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45689 Tue 19 Jul 2022 17:52:06 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:53403 Tue 19 Jul 2022 16:52:56 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:53364 Tue 19 Jul 2022 12:03:39 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:49975 Tue 19 Jul 2022 09:14:51 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46617 Tue 15 Feb 2022 14:58:47 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46618 Tue 15 Feb 2022 13:41:44 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46619 Tue 15 Feb 2022 12:03:49 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46609 Tue 15 Feb 2022 10:32:47 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46603 Tue 15 Feb 2022 10:04:52 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56782 Tue 11 Oct 2022 09:36:40 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:64141 Tue 09 May 2023 07:45:36 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46305 Tue 08 Feb 2022 13:55:42 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46307 Tue 08 Feb 2022 12:31:34 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46025 3000 plastic particles/day), with the relatively natural Sundays River to showing minimal evidence of river macroplastic (<100 plastic particles/day). The types of plastic were noted using the RIMMEL app (premier African implementation), enabling proportional comparison of different plastic litter types to be completed.]]> Tue 01 Feb 2022 14:37:46 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46043 Tue 01 Feb 2022 13:52:39 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46023 Tue 01 Feb 2022 13:48:39 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46026 Tue 01 Feb 2022 13:06:45 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46021 RhMo-AA/Al2O3 (73%) > RhMo-CA/Al2O3 (72%) > RhMo-EDTA/Al2O3 (68%). This could be that the addition of chelating ligand complexed both metallic species retarding sulfidation of both metals, hence lowering the HDS activity. Studies show that it is possible for the citric acid to complex with both promoter and an active metal (Mo), and this might result in the formation of molybdenum dimers, trimers and tetramers which are difficult to sulfide. XPS analysis showed that unchelated catalyst have more MoS2 phases of 63%, hence higher dispersion than the chelated catalyst, this could be the reason for high activity in RhMo/Al2O3 (88%) catalyst.]]> Tue 01 Feb 2022 12:45:40 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45984 Tue 01 Feb 2022 12:10:53 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46016 Tue 01 Feb 2022 12:01:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46005 Tue 01 Feb 2022 11:38:51 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:57012 Thu 29 Sep 2022 16:29:41 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56823 Thu 29 Sep 2022 15:26:40 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:69918 Thu 21 Dec 2023 16:08:45 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:50172 Thu 21 Apr 2022 17:46:55 SAST ]]> 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https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70510 Thu 07 Mar 2024 09:43:59 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46022 Thu 03 Feb 2022 13:55:30 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:69919 Sun 21 Jan 2024 14:16:49 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70248 Sun 03 Dec 2023 19:12:04 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70223 Sun 03 Dec 2023 18:51:33 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:72234 Sun 02 Jun 2024 19:23:41 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45722 Sat 22 Jan 2022 12:11:10 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45721 Sat 22 Jan 2022 11:45:16 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45720 Sat 22 Jan 2022 11:08:19 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45714 Sat 22 Jan 2022 10:36:51 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45713 Sat 22 Jan 2022 10:24:24 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:49974 Sat 16 Apr 2022 19:38:39 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70522 Sat 09 Dec 2023 19:39:22 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:54394 Sat 06 Aug 2022 19:25:38 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:71953 Sat 06 Apr 2024 12:11:21 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:47656 Sat 05 Mar 2022 12:11:37 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45691 Mon 31 Jan 2022 13:44:08 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70259 Mon 29 Jan 2024 11:42:58 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56783 Mon 26 Sep 2022 09:58:04 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:57729 Mon 24 Oct 2022 10:52:53 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70309 Mon 22 Apr 2024 19:39:16 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70220 Mon 18 Dec 2023 12:52:38 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:59934 Mon 16 Jan 2023 09:47:17 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46577 Mon 14 Feb 2022 15:26:49 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46541 Mon 14 Feb 2022 12:03:49 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46517 Mon 14 Feb 2022 10:36:11 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:60122 Mon 12 Dec 2022 15:19:10 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:60080 Mon 12 Dec 2022 10:08:09 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:51737 Mon 06 Jun 2022 10:23:08 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:56834 Fri 30 Sep 2022 11:21:50 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45683 Fri 28 Jan 2022 10:32:56 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45686 Fri 28 Jan 2022 09:28:09 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46381 Fri 18 Mar 2022 09:40:13 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46880 Fri 18 Feb 2022 14:42:37 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46866 Fri 18 Feb 2022 10:40:32 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:70300 Fri 16 Feb 2024 17:40:04 SAST ]]> 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