Rangeland Mismanagement in South Africa: Failure to Apply Ecological Knowledge

Chronic, heavy livestock grazing and concomitant fire suppression have caused the gradual replacement of palatable grass species by less palatable trees and woody shrubs in a rangeland degradation process termed bush encroachment in South Africa. G razing policymakers and cattle farmers alike have not appreciated the ecological role fire and native browsers play in preventing bush encroachment. Unpredictable droughts are common in South Africa but have deflected too much blame for bush encroachment away from grazing mismanagement. Bush encroachment is widespread on both black and white farms, although the contributing socioeconomic, cultural, and political forces differ. Managers at Madikwe Game Reserve have reintroduced fire and native game animals into a formerly overgrazed system in an attempt to remediate bush encroachment, with encouraging preliminary results. A bush control program is needed that educates cattle farmers about the ecological causes of bush encroachment and encourages the use of fire and native browsers as tools for sustainable grazing management.     

Unexpected Conservation of the X-Linked Color Vision Gene in Nocturnal Prosimians: Evidence from Two Bush Babies

Bush babies have had a long history of nocturnal life and it would be interesting to know whether their color vision genes have become degenerate. Therefore, we used PCR techniques to sequence the X-linked pigment gene of two of these nocturnal prosimians: Galago senegalensis and Otolemur garnettii. Southern hybridization of genomic DNA of G. senegalensis showed a single X-linked pigment gene. Interestingly, the deduced pigment sequences of the two bush babies are identical. By comparing the X-linked pigments of bush baby, human, squirrel monkey, and marmoset, 38 variable positions were identified. At those positions that may cause a spectral shift, the bush baby pigment has identical or biochemically similar residues to those of the marmoset cone pigment with a spectral peak of 543 nm. This result is consistent with the estimate of 544–545 nm for the spectral peak of the X-linked pigment of Otolemur crassicaudatus, which is closely related to Otolemur garnettii. The neighbor-joining tree of mammalian X-linked pigments showed a significantly shorter branch in the bush baby lineage than in other primate lineages. A relative rate test showed that the nonsynonymous substitution rate of the bush baby X-linked pigment gene is about three times slower than that of the human red pigment gene, though the synonymous substitution rates of the two genes are similar. The slower nonsynonymous rate in the bush baby lineage suggests that the bush baby X-linked pigment gene is under functional constraints, in spite of its nocturnal life. Two radical changes at positions in the intradiskal surface next to the sixth transmembrane domain were observed in the X-linked cone pigment of bush babies but not in other primates. They are changes from Ala to Ser and from Asn to His, which are similar in function to the corresponding residues in rhodopsins. These two changes may be of importance for dim light sensitivity, which is consistent with our proposal that the evolution of the bush baby X-linked pigment gene is under selective pressure. In addition, the 2.5% divergence in introns 2 and 5 of the X-linked pigment gene between the two bush babies supports their classification into two separate genera. Received: 30 November 1996 / Accepted: 17 June 1997     

Fungal cultures of tar bush and creosote bush for production of two phenolic antioxidants (Pyrocatechol and Gallic acid)

‘Tar bush’ and ‘creosote bush’ were substrates of fungal cultivation for tannase production and gallic acid and pyrocatechol accumulation. Aspergillus niger GH1 grew similarly on both plant materials under solid state culture conditions, reaching maximal levels after 4 d. Fungal strain degraded all tannin content of creosote bush after 4 d of fermentation and >75 % of tar bush after 5 d. Higher level of tannase activity was detected in tar bush fermentation. Biotransformation of tannins to gallic acid was high (93 % in creosote bush and 89 % in tar bush). Pyrocatechol was released poorly. Kinetic parameters of tannin conversion were calculated.     

Identification of volatile compounds released by roots of an invasive plant, bitou bush (Chrysanthemoides monilifera spp. rotundata), and their inhibition of native seedling growth

Allelopathy has been suggested as a mechanism promoting the monoculture formation of some invasive exotic plants. Previous studies have shown that hydrophobic extracts of the roots and soil of exotic bitou bush (Chrysanthemoides monilifera spp. rotundata (DC.) T. Norl.) inhibited the seedling growth of five Australian native plants, including the dominant acacia (Acacia longifolia var. sophorae (Labill.) F. Muell.). Based on this finding, we compared the hydrophobic root and soil chemical profiles of bitou bush and acacia to determine whether bitou bush roots release allelopathic compounds that are novel to the invaded system. We detected three compounds that were exclusive to the bitou bush root and soil, and seven compounds that were common to the bitou bush and acacia roots but only present in the bitou bush soil. The compounds unique to the bitou bush invaded soil were all sesqui- and diterpenes. Several of these compounds were found to inhibit the seedling growth of a native sedge, Isolepis nodosa (Rott.) R. Br. Of particular interest are the sesquiterpenes: β-maaliene, α-isocomene, β-isocomene, δ-cadinene, 5-hydroxycalamenene and 5-methoxycalamenene which were found in high concentrations in the bitou bush root and soil extracts and exhibited phytotoxic activity. Therefore, we present evidence to suggest that bitou bush exudes low molecular weight volatile compounds into the soil which inhibit native plant seedling growth. The reduced establishment of native plants via allelopathy is likely to create space and contribute to the invasion of bitou bush on the eastern Australian coast.     

Effects of Prescribed Burning and Mechanical Bush Clearing on Ungulate Space Use in an African Savannah

Savannah ecosystems exhibit constant transitions between states dominated by trees and states dominated by a combination of trees and grasses. Transitions between these states are driven by interactions between fire and herbivory. Bush encroachment (i.e. an increase in the density of woody vegetation) is often caused by anthropogenic disturbance such as climate change, invasive plants, fire control, and livestock practices. As bush encroachment alters the dynamics between fire and herbivory, it may have significant impact on savannah ecosystems. Two of the most common measures to mitigate bush encroachment are prescribed burning and bush clearing by mechanical treatments. We studied the effects of these two mitigation measures on ungulate space use in Lapalala Wilderness, a private conservation area within the Waterberg Biosphere Reserve, northern South Africa. Burning and bush clearing affected both the overall abundance and the species composition of ungulates at particular patches, but these effects were influenced by habitat and the type of bush clearing treatment. Contrary to our expectations, most species occurred less frequently in burnt patches, and also less frequently in patches that had been bush cleared. Our results suggest that combined effects of fire and bush clearing may have positive effects on grazers and negative effects on browsers. Although our sampling design did not allow us to fully resolve interactive effects of burning and bush clearing treatments across habitats, our study highlights the fact that there are complex ecological consequences of habitat alterations in savannah ecosystems.     

Directed vertebrate-mediated seed dispersal of a fleshy-fruited amaryllid in a heterogenous habitat

Most plants with fleshy fruits have seeds that are ingested by animals, but a less well-understood mode of seed dispersal involves fleshy fruits containing seeds that are discarded by frugivorous animals because they are too large or toxic to be ingested. We studied the seed dispersal biology of Haemanthus deformis, an amaryllid lily species found in a mosaic of bush clumps in a grassland matrix in South Africa. We asked whether seed dispersal is directed in and among bush clumps and whether germination and survival are greater for seeds dispersed to bush clumps than for those dispersed into grassland. Using camera trapping, we found that fruits are consumed mainly by birds and rodents. The pulp was removed from the seeds which were then discarded without ingestion. While many seeds were dispersed close to the parent plant, most (c. 78.5%) were dispersed further than 1 m away from the parent plant. Longer distance dispersal resulted mainly from birds flying off with fruits in their bill or from rodents engaging in scatter-hoarding behavior. Seedling survival was most successful within bush clumps as compared to grasslands and shade was identified as a primary requirement for seedling survival. Seeds from which the fruit pulp had been removed germinated faster than those in intact fruits. Haemanthus deformis deploys a system of directed seed dispersal, whereby both birds and rodents contribute to the dispersal of seeds within patchy bush clumps that are favorable for seedling survival.     

Soil‐mediated effects on germination and seedling growth of coastal wattle (Acacia sophorae) by the environmental weed,bitou bush (Chrysanthemoides monilifera ssp. rotundata)

Bitou bush (Chrysanthemoides monilifera ssp. rotundata; Asteraceae) is a major woody weed that competes with the native legume Acacia sophorae in coastal ecosystems of eastern Australia. Three glasshouse experiments examined whether litter or soil from beneath bitou bush or Acacia plants could influence seed germination and seedling growth of A. sophorae. The presence of litter decreased seed germinability and this effect was greater for bitou bush litter than for Acacia litter. Shoot growth was increased by the addition of Rhizobium after 40 days, irrespective of soil type. After 78 days, shoot and root biomass were significantly lower for seedlings grown in bitou bush soil than for those grown in Acacia soil. There was a non‐significant trend towards a lower median population of Rhizobium in the soil beneath bitou bush than in that beneath Acacia. The results demonstrated a slight effect of bitou bush on the growth of A. sophorae, which could, however, be overshadowed by the judicious use of herbicides or fire for weed control and revegetation.     

Effects of hedgerows on bats and bush crickets at different spatial scales

Biodiversity is threatened by the loss and fragmentation of habitats. The role of hedgerows in maintaining biodiversity is well established, but few studies have addressed the importance for biodiversity of the intrinsic characteristics of hedgerows and the quality of hedgerow networks along a spatial scale. We examined three quality indices providing information at different territorial levels: density in the landscape, structural diversity and wood production. We performed an acoustic survey in a grassland to estimate the species abundance and community composition of bats (9 taxa) and bush crickets (11 species). Using an approach based on species and traits, we assessed how hedgerow quality influenced the activity of these taxa at different spatial scales (from 50 to 1000 m) and focused on three types of traits: bush cricket mobility ability, bat foraging strategy and habitat specialization. In general, our results showed the importance of hedgerow quality for bats and bush crickets, but the strength of the association between taxa and hedgerows varied substantially among the species and the spatial scales. Although it depends on the taxa, the production, density and structural diversity of hedgerows each had an overall positive effect. Our results suggested that these effects were generally more important at large scales. The scale effect of the production index is the best predictor of activity for bat and bush cricket taxa and traits. Our results showed the importance of hedgerow quality for the ecology of bat and bush cricket communities and could be used to improve conservation management.     

Cool-season whole-plant gas exchange of exotic and native semiarid bunchgrasses

The success of invasive aridland plants may depend on their utilization of precipitation not fully exploited by native species, which could lead to seasonally altered ecosystem carbon and water fluxes. We measured volumetric soil water across 25-cm profiles (??_25cm) and springtime whole-plant water- and carbon-fluxes of the exotic Lehmann lovegrass (Eragrostis lehmanniana) and a native bunchgrass, bush muhly (Muhlenbergia porteri), following typical (55?mm in 2009) and El Ni?o-enhanced accumulations (154?mm in 2010) in a SE Arizona savanna. Across both years, ??_25cm was higher under lovegrass plots, with similar evapotranspiration (ET) between lovegrass and bush muhly plots. However, in 2010 transpiration (T) was higher in bush muhly than lovegrass, implying higher soil evaporation in lovegrass plots maintained similar ET. Net ecosystem carbon dioxide exchange (NEE) was similar between lovegrass and bush muhly plots in 2009, but was more negative in bush muhly plots following El Ni?o, indicating greater CO₂ assimilation. Ecosystem respiration (R _eco) and gross ecosystem photosynthesis (GEP) were similar between lovegrass and bush muhly plots in 2009, but were higher in bush muhly plots in 2010. As a result, lovegrass plots reduced ecosystem water-use efficiency (WUE_e?=?NEE/ET), while bush muhly WUE_e remained constant between 2009 and 2010. Concurrent whole-plant WUE (WUE_p?=?GEP/T) did not change in lovegrass plots, but increased in bush muhly plots between these years. We concluded that cool-season precipitation use is not a component of Lehmann lovegrass invasive success, but that the change in ET partitioning and attendant shifts in cool-season WUE_e may increase interannual variation in ecosystem water- and carbon-exchange dynamics in the water-limited systems it dominates.     

Relationship between the heat tolerance of photosynthesis and the thermal stability of rubisco activase in plants from contrasting thermal environments

Inhibition of net photosynthesis (Pn) by moderate heat stress has been attributed to an inability of Rubisco activase to maintain Rubisco in an active form. To examine this proposal, the temperature response of Pn, Rubisco activation, chlorophyll fluorescence, and the activities of Rubisco and Rubisco activase were examined in species from contrasting environments. The temperature optimum of Rubisco activation was 10 degrees C higher in the creosote bush (Larrea tridentata) compared with the Antarctic hairgrass (Deschampsia antarctica), resembling the temperature response of Pn. Pn increased markedly with increasing internal CO(2) concentration in Antarctic hairgrass and creosote bush plants subjected to moderate heat stress even under nonphotorespiratory conditions. Nonphotochemical quenching of chlorophyll fluorescence, the effective quantum yield of photochemical energy conversion (DeltaF/F(m)') and the maximum yield of PSII (F(v)/F(m)) were more sensitive to temperature in Antarctic hairgrass and two other species endemic to cold regions (i.e. Lysipomia pumila and spinach [Spinacea oleracea]) compared with creosote bush and three species (i.e. jojoba [Simmondsia chinensis], tobacco [Nicotiana tabacum], and cotton [Gossypium hirsutum]) from warm regions. The temperature response of activity and the rate of catalytic inactivation of Rubisco from creosote bush and Antarctic hairgrass were similar, whereas the optimum for ATP hydrolysis and Rubisco activation by recombinant creosote bush, cotton, and tobacco activase was 8 degrees C to 10 degrees C higher than for Antarctic hairgrass and spinach activase. These results support a role for activase in limiting photosynthesis at high temperature.     

Populations of the bush fly (Musca vetustissima Walker) in arid Australia

Populations of the bush fly Musca vetustissima were usually low in arid south-western Australia. Herbaceous plants that grew only after rain resulted in changes to cattle dung that increased its attractiveness to bush flies for oviposition in laboratory tests. Larvae reared in such dung consistently produced large flies of high fecundity, and larval survival was usually high. Similar responses to the dung were evident from examination of flies sampled in the field. Although greatly increased bush fly abundance was possible only after major improvement in cattle dung, it was not a general phenomenon as immature survival did not always increase. Even major population increases resulted from periods of high immature survival that were brief relative to the duration of favourable dung. Nematodes Heterotylenchus sp. appeared to be an important mortality factor of the immature stages at such times. Build-up of high bush fly populations occurred only in cattle-grazing areas, but base-level abundance was similar regardless of the presence of cattle. Almost all female flies were gravid when cattle dung was unfavourable for breeding, and in areas without cattle. In arid areas, acceptable oviposition sites probably are more limiting than are sources of protein for oögensis.     

Transmission of Indigenous Knowledge and Bush Skills Among the Western James Bay Cree Women of Subarctic Canada

The transmission of 93 items of women's indigenous knowledge and bush skills was studied in two subarctic Omushkego (West Main) Cree Indian communities, Moose Factory and Peawanuck, Ontario, Canada. About half of all bush skills were still being transmitted at the hands-on learning stage. Some skills such as setting snares and fishnets, beadwork, smoking geese, and tanning moose and caribou hides were transmitted well. Many skills no longer essential for livelihoods, such as some fur preparation skills and food preservation techniques, were not. Loss of certain skills and incomplete transmission of others (a lower level of mastery than in older generations) were attributable to changes in the educational environment, diminished time available in the bush, problems related to learning bush skills at later ages, and changes in value systems. These factors seemed to impair the traditional mode of education based on participant observation and apprenticeship in the bush, which provided the essential self-disciplining educational environment. Policy measures to counteract these trends may include the institution of a hunters' income security program to provide incentives for family units to go on the land, rather than all-male hunting parties.     

Evidence for allelopathy as a mechanism of community composition change by an invasive exotic shrub, Chrysanthemoides monilifera spp. rotundata

Chemical interference is increasingly suggested as a mechanism facilitating exotic plant invasion and plant community composition. In order to explore this further, we employed a comprehensive extract-bioassay technique that facilitated detection and demarcation of phytotoxicity, direct allelopathy and indirect allelopathy of bitou bush (Chrysanthemoides monilifera spp. rotundata) compared to an indigenous dominant of the invaded system, acacia (Acacia longifolia var. sophorae). Extracts of the leaves and roots of both species exhibited phytotoxic effects against five indigenous plant species. Evidence for allelopathy between co-evolved indigenous plants was detected between acacia and Isolepis nodosa. Allelopathy between bitou bush and four indigenous plant species was also detected. Therefore we propose that both the acacia and bitou bush have the potential to chemically inhibit the establishment of indigenous plants. Eventual dominance of bitou bush is predicted, however, based on more ubiquitous effects on seedling growth.     

纸坊沟流域植被恢复区灌木林昆虫群落时间结构及动态

通过对纸房沟流域不同植被恢复区昆虫进行调查,结果表明:昆虫种类数以天然灌木林最高,混交林次之,单纯林分较低,个体数量以柠条林昆虫数量最高,其次为混交林和沙棘林,天然灌木林变化幅度最小。各植被昆虫种类和数量季节变化符合y=ax3 bx2 cx d函数变化规律。从特征指数来分析:昆虫群落多样性指数5～9月份大小次序均为天然灌木林>混交林>单纯林分,均匀度以单纯林和混交林的昆虫群落变化幅度较大,天然灌木林变化幅度最小。群落的优势度与均匀度值的变化呈相反趋势。主分量分析表明:植物类型不同的昆虫群落,其主导因素和时间格局不同,且结构越复杂,主导因素和时间格局越明显;相反,则主导因素和时间格局分化不明显;通过排序植食性昆虫、捕食性昆虫、寄生性昆虫在各植被昆虫群落变化的不同时期占主导因素。     

Useful native plants in the American southwestern deserts

In addition to yuccas, creosote bush, prickly pear cactus, a?aves and the wax-producin? candelilla bush, all of which have already yielded to some commercial exploitation, scores of other plants listed in this article also ?row in the re?ion and contain industrial potentialities.     

A framework for managing and monitoring bush regeneration programs: a case study from Lake Macquarie,NSW

It is widely recognised that effective bush regeneration and ecological restoration programmes must be well planned and require effective management and monitoring. While general guidelines for monitoring are available, few examples of effective site monitoring and reporting exist in practice. The note describes a framework developed for managing and monitoring a bush regeneration programme for coastal NSW and evaluates it against a set of principles for monitoring ecological restoration programmes. The example illustrates how tools could be developed to improve management and monitoring practice.     

Timing and intensity of bush cricket predation on egg batches of pine processionary moth: no evidence of population control

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Spatial autocorrelation analysis offers new insights into gene flow in the Australian bush rat,Rattus fuscipes

Dispersal is a fundamental process that influences the response of species to landscape change and habitat fragmentation. In an attempt to better understand dispersal in the Australian bush rat, Rattus fuscipes, we have combined a new multilocus autocorrelation method with hypervariable microsatellite genetic markers to investigate fine-scale (< or = 1 km) patterns of spatial distribution and spatial genetic structure. The study was conducted across eight trapping transects at four sites, with a total of 270 animals sampled. Spatial autocorrelation analysis of bush rat distribution revealed that, in general, animals occurred in groups or clusters of higher density (< or = 200 m across), with intervening gaps or lower density areas. Spatial genetic autocorrelation analysis, based on seven hypervariable microsatellite loci (He = 0.8) with a total of 80 alleles, revealed a consistent pattern of significant positive local genetic structure. This genetic pattern was consistent for all transects, and for adults and sub-adults, males and females. By testing for autocorrelation at multiple scales from 10 to 800 m we found that the extent of detectable positive spatial genetic structure exceeded 500 m. Further analyses detected significantly weaker spatial genetic structure in males compared with females, but no significant differences were detected between adults and sub adults. Results from Mantel tests and hierarchical AMOVA further support the conclusion that the distribution of bush rat genotypes is not random at the scale of our study. Instead, proximate bush rats are more genetically alike than more distant animals. We conclude that in bush rats, gene flow per generation is sufficiently restricted to generate the strong positive signal of local spatial genetic structure. Although our results are consistent with field data on animal movement, including the reported tendency for males to move further than females, we provide the first evidence for restricted gene flow in bush rats. Our study appears to be the first microsatellite-based study of fine-scale genetic variation in small mammals and the first to report consistent positive local genetic structure across sites, age-classes, and sexes. The combination of new forms of autocorrelation analyses, hypervariable genetic markers and fine-scale analysis (< 1 km) may thus offer new evolutionary insights that are overlooked by more traditional larger scaled (> 10 km) population genetic studies.     

Time structure and dynamics of the insect communities in bush vegetation restoration areas of Zhifanggou watershed in Loess hilly region

The insects were investigated in Zhifanggou watershed, Ansai County, Shaanxi Province, China. The results showed that the insect species varied spatially in the following order: the natural bush forests, the mixed forests and the simple forests. The individual number of insects in Caragana korshinskii was the highest, followed by mixed forests and Hippaphae rhamnoides, and the change range of the insect individuals in the natural bush forests was the smallest. The species number of insects with seasonal changes and the individual number of insects in various types of vegetation can be described by the Univariate cubic equation. The order of the diversity index of the insect communities in various types of vegetation from May to September was the natural bush forests, the mixed forests and the simple forests. The change ranges of the evenness values of the simple forests and the mixed forests were higher, and that of the natural bush forests was smaller. The reverse trend was assumed between the dominance values and the evenness values in the time course. Moreover, the main factors and temporal patterns of the insect communities in the natural bush forests were more complicated, fluctuative and obvious than those in the mixed forests and the simple forests by using the principal component analysis.