Effects of heterogeneous habitat use by cattle on nutrient availability and litter decomposition in soils of an Alpine pasture

Abstract

Grazing by free-ranging cattle on Alpine pastures in southern Switzerland creates sharp contrasts in plant species composition between small 'camp areas', which are grazed intensely and receive most cattle excreta, and surrounding pasture dominated by Nardus stricta, which is only lightly grazed. We hypothesised that these contrasts are maintained by positive feedbacks related to nutrient availability in soil, in that (a) plant material with rapid decomposition and nutrient release decomposes in camp areas and (b) litter decomposition is further stimulated by enhanced nutrient availability in soil. We compared nutrient availability at three camp areas with that in surrounding Nardus vegetation and investigated how the decomposition of plant material from both vegetation types responds to nutrient availability in soil, both in the field (during 14 weeks) and in the laboratory (during 4, 10, and 16 weeks). At all three field sites P availability was significantly enhanced in camp areas, whereas differences in N availability were inconsistent among the three sites. Laboratory incubations indicated that microbial activity after the addition of labile C (cellulose) was limited by P availability in the Nardus vegetation but not in camp areas. The camp-area plant substrate decomposed much faster (81.5% vs. 27.1% ash-free dry mass loss in the field) and released more N and P than the Nardus substrate, which tended to immobilise soil nutrients. However, the decomposition rate of neither substrate was influenced by nutrient availability in soil, both in the field (comparing camp areas and Nardus vegetation) and in the laboratory (comparing incubations with and without N or P fertilisation). We conclude that the contrasting quality of plant substrates contributes to the greater nutrient availability in camp areas (feedback a) but that the latter does not influence the decomposition of in situ plant material (feedback b) because the latter is not nutrient-limited.

Plant species selection by sheep in semi-natural dry grasslands extensively grazed in the south-western Italian Alps

“…Such spatial pattern is a common feature in extensive grazing systems in mountain areas (Güsewell et al 2005). Sheep usually concentrate within flat areas because they can maximise the average energy intake rate through optimal foraging (MacArthur and Pianka 1966), but in our study conditions, the arrangement of night pens by the shepherd was the main factor determining the sheep spatial aggregation.…”

Plant nutrient dynamics and stoichiometric homeostasis of invasive species Spartina alterniflora and native Cyperus malaccensis var. brevifolius in the Minjiang River estuarine wetlands

“…发展 到藻类、浮游动物和草本植物 (Rhee, 1978;Andersen & Hessen, 1991;Güsewell et al, 2005)。由于高 等植物体内元素的内稳性和化学计量特征复杂, 对高等植物的研究甚少 (Cernusak et al, 2009;Matzek & Vitousek, 2009;Yu et al, 2010)。生态系统水平上 对内稳性的研究多集中于海洋生态系统和陆地生 态系统 (Güsewell, 2004;苏强, 2012), 对湿地生态 系统的研究较少 (Wang et al, 2014 图3 不同元素、器官以及植物类型的内稳性指数(H)(平均值±标准误差, n = 4)。不同小写字母表示不同因子之间差异显著。 缩写见图2。 Fig. 3 The homeostatic index (H) in different element, organ and plant types (mean ± SE, n = 4).…”

Sheep camping influences soil properties and pasture production in an acidic soil of New South Wales, Australia

“…In the pasture, the process of nutrients recycled from excreta to soil and back to plants affects soil physical, chemical and biological properties (Haynes andWilliams 1993, 1999;Iyyemperuma et al 2007). Grazing also affects plant species composition (Gu¨sewell et al 2005;Proulx and Mazumder 1998), nutrient availability and litter decomposition, and modifies the productivity of the vegetation (Milchunas and Lauenroth 1993;Gu¨sewell et al 2005).…”

“…Animals select particular landscape features for resting and ruminating (Pratt et al 1986), such as beneath trees and hedges, around gateways and water troughs, on areas away from roadsides and on ridges and hillcrests on hill country farms (Haynes and Williams 1999;Rowarth et al 1992). All of these lead to the build up of a large amount of animal excreta in the ''camp areas'' (Haynes and Williams 1999;Gu¨sewell et al 2005) and this transfer of excreta to the camp areas is regarded as nutrients losses for the non-camp areas. The redistribution of nutrients within the pasture results in a heterogeneous pattern of nutrient availability in the soil over the long term (Haynes and Williams 1999;Gu¨sewell et al 2005).…”

“…All of these lead to the build up of a large amount of animal excreta in the ''camp areas'' (Haynes and Williams 1999;Gu¨sewell et al 2005) and this transfer of excreta to the camp areas is regarded as nutrients losses for the non-camp areas. The redistribution of nutrients within the pasture results in a heterogeneous pattern of nutrient availability in the soil over the long term (Haynes and Williams 1999;Gu¨sewell et al 2005). In response to nutrient availability, pasture botanical composition may change and this, in turn, may affect pasture production (Olofsson and Oksanen 2002).…”