摘要:

Hierarchical classification based on proportional species composition of the grass layer was used to identify and classify semi‐arid rangeland into range types. The relation between range types produced by the classification and the environmental parameters measured were investigated using a two‐group, and a multi‐group stepwise linear discriminant function analysis. The first split of the TWINSPAN dendrogram separated savanna from open grassveld. The open grassveld was characterized byThemeda triandra, Microchloa caffra, Eragrostis capensisandE. planaand the savanna bySetaria neglecta, Sporobolus fimbri atus,Panicum stapfianumandCymbopogon plurinodis. The two range types were best discriminated by rainfall, soil depth and altitude with sites in the grassveld corresponding to deep soils and receiving rainfall of more than 450 mm a‐1, and sites in savanna corresponding to shallow soils and receiving rainfall of 400–500 mm a‐1. Further divisions within these two range types were related to soil textural and chemical characteristics of the A‐horizon. Multi‐group discriminant function analysis identified eight environmental variables which best discriminate between range types at level 3 of the hierarchical dendrogram. Rainfall, soil depth and altitude were selected as the most important environmental variables discriminating between range types. Reclassification by discriminant analysis using the eight selected environmental factors resulted in a 67% concurrence with range types. It is proposed that the area be stratified on the basis of the current classification for monitoring and management purposes.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638360

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The production of an irrigated grass/clover pasture was evaluated under continuous grazing at a range of stocking rates (20.6 to 35.9 Merino ewe units ha‐1and two nitrogen fertiliser treatments (0 and 300 kg N ha‐1a‐1) over a period of four years. The clover content of the pastures declined, while the grass component increased with increased pasture age on both nitrogen treatments, leading to grass domination by the end of the trial period. The clover content (%) of the green dry matter (DM) was higher and the grass content (%) lower on the zero‐nitrogen than the nitrogen‐fertilised pastures, with the average daily gain of the sheep and wool production per ewe unit highest at low stocking rates on the zero‐nitrogen treatment. However, the total amount of green DM was higher on the nitrogen‐fertilised than on the unfertilized treatment, resulting in higher stocking rates for maximum wool and meat production per hectare. A higher profit margin was realised at lower stocking rates on the zero‐nitrogen treatment when compared with the fertilised treatment. The low weaning mass of the lambs at high stocking rates on the fertilised pastures questions the profitability of using nitrogen fertiliser on irrigated grass/clover pastures.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9647850

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The mountain catchments above 2 750 m a.s.l. in eastern Lesotho are a proclaimed Managed Resource Area (MRA) as a result of official concern about degradation of the grasslands of the alpine belt, and of recent parastatal interventions in the local livestock economy. However, the demarcation of the MRA may be inappropriate because it ignores recent changes in the transhumance system which threatens to cause greater degradation of the grasslands in the subalpine belt, particularly in the lower subalpine zone. In response to a variety of ecological and social factors, Basotho have modified the transhumance system by establishing winter grazing posts in this zone which lies between the summer grazing post areas in the subalpine zone and the alpine belt and the villages. The former areas are now used more intensively than the latter areas, thereby increasing the potential for greater degradation in the lower subalpine than in the upper subalpine zone and in the alpine belt. It is argued that the conservationist perspective, by which the MRA was demarcated needs to be broadened to include these lower valleys in view of these ecological dynamics.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9647851

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Hydraulic, non‐floating lysimeters were used to determine evapotranspiration (Et) and water‐use efficiency (WUE) of several dryland planted pasture species over a period of three years. The species wereAnthephora pubescens, Cenchrus ciliaris, Chloris gayana, Digitaria eriantha subsp. eriantha, Eragrosiis curvulaandPanicum maximum. The WUE was expressed as the amount of above‐ground phytomass as well as the crude protein produced per unit volume of water evapotranspired. The water‐balances of the planted pastures were also compared with that of a natural grassland (veld) in good condition. Differences in Et between the various species were not significant (P>0.05). Deep percolation, beyond the root zone (i.e. more than 0.8 m), did not occur in any of the species nor in the veld treatment throughout the study.Chloris gayanaproduced more above‐ground phytomass (P≤0.01) than all the other species in both wet and drier conditions. The average WUE (7.2 kg dry matter (DM) ha‐1mm‐1and 0.39 kg crude protein (CP) ha‐1mm‐1) of this species was the highest (P≤0.01) throughout the experimental period. During the first half of the season (July ‐ December) the crude protein content (7.94%) ofPanicumwas the highest (P≤0.01), while thatof Anthephora(5.02%) was the highest (P≤0.01) during the second half (January – June). The exceptionally low (P≤0.01) crude protein content of natural grassland andEragrostisduring the second half of the season indicated that these are not well suited for use as foggage (grown out forage), while the high values forAnthephoraandDigitariasuggests these to be suitable foggage species.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9647852

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Wetland loss rates remain high as the full value of wetland services is understated. This is partly due to the benefits of wetland preservation (non‐use) being unpriced, as they are not traded in markets. These benefits are reflected by option, existence and bequest demands for wetland preservation. The contingent valuation method (CVM) was used to estimate the value of non‐market wetland preservation benefits, by asking members of the Wakkerstroom Natural Heritage Association (WNHA) to, state their willingness‐to‐pay (WTP) to preserve the Wakkerstroom wetland. For option value, the median WTP class ranged from R17.51 to R20.00 per month, whilst existence and bequest values had the same median WTP class which ranged from R15.01 to R.17.50 per month. Well‐designed CVM studies can help to make the public, policy‐makers and individual farmers more aware of the benefits of wetland preservation, leading to more informed decisions being made about wetland use.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9647853

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638359

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor