The eco-hydrology of partly cleared,native ecosystems in southern Australia: a review

Water use by the native vegetation that existed in southern Australia prior to European settlement was largely in balance with rainfall. European settlers altered the landscape by clearing land to grow agricultural crops and pastures, and with the introduction of livestock to graze the partly cleared, native ecosystems. The aim of this review is to contrast the hydrology of grazed, partly cleared ecosystems, intact indigenous ecosystems, and entirely cleared agricultural systems in the intensive land-use zone (350–1000 mm annual rainfall zone) of southern Australia. Since European settlement, the areas of forests and woodlands in the Murray–Darling Basin have declined by approximately 64% to make way for agricultural enterprises. Modern-day vegetation surveys estimate between 52 and 58% of the intensive land-use zone of the Murray–Darling Basin has been entirely cleared, while about 40% is in the partly cleared state (disturbed ecosystems with canopy cover exceeding 5%). The replacement of native vegetation by agricultural crops and pastures has disturbed the water cycle that existed prior to European settlement, and has markedly elevated the amount of water leaking beyond the root zone of introduced species, and contributing to groundwater systems. Estimates of annual leakage beneath the root zone of annual crops range from 0 to 63 mm per annum; however, no estimates of leakage for partly cleared woodlands exist. Yet, because the groundwater beneath partly cleared woodlands rises considerably more slowly than under entirely cleared landscapes, it is likely that less water leaks beneath the roots of grazed woody ecosystem. However, aging of these systems by livestock grazing will reduce the numbers of woody individuals and will impact on groundwater recharge.     

Release of Juniperus thurifera woodlands from herbivore‐mediated arrested succession in Spain

Question: Do abiotic constraints maintain monospecific woodlands of Juniperus thurifera? What is the role of biotic (livestock) versus abiotic (climate) drivers in the recruitment and growth of the different tree species? Location: Cabrejas range, Soria, north‐central Spain, 1200 m altitude. Methods: Stand history was reconstructed using dendro‐ecology and spatial pattern analysis, combined with historical data of livestock abundances and climatic records. Results: J. thurifera establishment occurred in two distinct pulses, with a tree component establishing in the late 1800s to early 1900s. Quercus ilex and Pinus sylvestris establishment was evident only from the late 1970s onward. Recruitment events were related to reductions in livestock browsing. J. thurifera spatial structure was clumped and Q. ilex showed a short‐scale aggregation to J. thurifera trees and saplings. Radial growth trends of J. thurifera saplings, Q. ilex and P. sylvestris were negatively related to livestock density. Summer drought limited the radial growth of all the study species, and P. sylvestris and Q. ilex grew faster than J. thurifera even after considering an age effect. Conclusions: The differences in radial growth patterns and recruitment pulses between species indicate that livestock browsing and not abiotic factors is the main factor controlling plant succession and structural development. In this process, J. thurifera acts as a nurse plant, facilitating the establishment of other tree species. Under the current low pressure from herbivores, formerly pure J. thurifera woodlands will change towards dense stands of mixed species composition.     

Fire and stone clearance in Iron Age agriculture: new insights inferred from the analysis of terrestrial macroscopic charcoal in clearance cairns in Hamneda,southern Sweden

Areas with ancient clearance cairns have been studied in Hamneda, Småland Uplands, southern Sweden, by archaeological and palaeoecological methods. Based on numerous radiocarbon dates and stratigraphical analyses, the local introduction of stone clearance is dated to the first century A.D. The clearance cairns reflect a system of semi-mobile cultivation that lasted until c. A.D. 900. Pollen and macrofossil analyses provide information on cereal growing and pastures in these clearance cairn areas, while charcoal analyses reveal details on the agrarian expansion dynamics and the use of fire in vegetation clearance. In the expansion phase, Quercus (oak) woodlands were cleared and transformed to open pastures and arable land, partly by the use of fire. A secondary succession of Betula (birch) and Corylus (hazel) was dealt with by fire clearances to keep pastures open and to prepare new arable plots. In the long run, Betula in particular was favoured by the land-use system. The mobility of the cultivation system is discussed together with the causes behind the introduction of stone clearance. A possible causal relationship with the introduction of hay mowing is also discussed.     

Stone marten (Martes foina) habitat in a Mediterranean ecosystem: effects of scale, sex, and interspecific interactions

Mediterranean ecosystems are inherently patchy, challenging habitat-use behavior. Certain mammalian carnivores take advantage of this patchiness by a strategy of habitat complementation/supplementation, which is invariant to the scale of analysis. To test if the same behavior is adopted by the stone marten, we used a combined data set of capture and radio-tracking data at three scales of analysis (1-m, 25-m, and 452-m radius plots). We used compositional analysis to test if there were sex-specific differences in foraging and resting habitat use of stone martens and if these patterns were affected by the presence of other mesocarnivores. Our results showed that stone martens are found both in rural and forested landscapes. Foraging and resting activities occurred far from roads in large and complex patches of cork oak woodlands, riparian vegetation, orchards, and pastureland. Use varied with the scale of analysis and the sex. At smaller scales, females use pastures for foraging and orchards for resting, whereas riparian vegetation and sparse cork oak forests influenced this use at larger scales. Males, on the other hand, were more consistent across scales, using riparian areas and dense cork oak woodlands for foraging and pastures for resting. Stone martens shared the same areas with other coexisting mesocarnivores. Stone martens use cork oak woodlands and complement/supplement this use with other land cover types. The consistent use of cork oak woodlands across scales emphasizes the importance of this land cover to the preservation of functional Mediterranean ecosystems in southern Portugal.     

Scale-dependent effects of land use on plant species richness of mountain grassland in the European Alps

Traditionally managed mountain grasslands in the Alps are species‐rich ecosystems that developed during centuries of livestock grazing. However, changes in land use including fertilisation of well accessible pastures and gradual abandonment of remote sites are increasingly threatening this diversity. In five regions of the Swiss and French Alps we assessed the relationship between land use, soil resource availability, cover of the unpalatable species Veratrum album, species richness and vegetation composition of mountain grasslands across four spatial scales ranging from 1 to 1000 m². Mean species richness and the increase in the number of species with increasing area were lower in intensively grazed, fertilised pastures than in traditional pastures or in abandoned pastures. Species composition of abandoned pastures differed from that of the other management types. Plant species richness was influenced by different factors at different spatial scales. At the 1 m² scale, plant species richness was negatively related to soil nitrate and influenced by the cover of V. album, depending on land use: species richness and cover of V. album were negatively correlated in abandoned pastures, but positively correlated in fertilised grasslands. At the 1000 m² scale, a negative effect of fertilization on richness was evident. These results indicate that at small scales species richness in mountain grasslands is determined by competition for light, which should be more important if nutrient availability is high, and by positive and negative interactions with unpalatable plants. In contrast, species richness at the large scale appears to be mainly influenced by land use. This result emphasizes the importance of studying such inter‐relationships at multiple scales. Our study further suggests that the maintenance of the traditional land use scheme is crucial for the conservation of plant species richness of mountain pastures as both intensification and abandonment changed species composition and reduced plant species diversity.     

Colonization of Abandoned Land by Juniperus thurifera Is Mediated by the Interaction of a Diverse Dispersal Assemblage and Environmental Heterogeneity

Land abandonment is one of the most powerful global change drivers in developed countries where recent rural exodus has been the norm. Abandonment of traditional land use practices has permitted the colonization of these areas by shrub and tree species. For fleshy fruited species the colonization of new areas is determined by the dispersal assemblage composition and abundance. In this study we showed how the relative contribution to the dispersal process by each animal species is modulated by the environmental heterogeneity and ecosystem structure. This complex interaction caused differential patterns on the seed dispersal in both, landscape patches in which the process of colonization is acting nowadays and mature woodlands of Juniperus thurifera, a relict tree distributed in the western Mediterranean Basin. Thrushes (Turdus spp) and carnivores (red fox and stone marten) dispersed a high amount of seeds while rabbits and sheeps only a tiny fraction. Thrushes dispersed a significant amount of seeds in new colonization areas, however they were limited by the presence of high perches with big crop size. While carnivores dispersed seeds to all studied habitats, even in those patches where no trees of J. thurifera were present, turning out to be critical for primary colonization. The presence of Pinus and Quercus was related to a reduced consumption of J. thurifera seeds while the presence of fleshy fruited shrubs was related with higher content of J. thurifera seeds in dispersers’ faeces. Therefore environmental heterogeneity and ecosystem structure had a great influence on dispersers feeding behaviour, and should be considered in order to accurately describe the role of seed dispersal in ecological process, such as regeneration and colonization. J. thurifera expansion is not seed limited thanks to its diverse dispersal community, hence the conservation of all dispersers in an ecosystem enhance ecosystems services and resilience.     

Pasture intensification is insufficient to relieve pressure on conservation priority areas in open agricultural markets

Agricultural expansion is a leading driver of biodiversity loss across the world, but little is known on how future land‐use change may encroach on remaining natural vegetation. This uncertainty is, in part, due to unknown levels of future agricultural intensification and international trade. Using an economic land‐use model, we assessed potential future losses of natural vegetation with a focus on how these may threaten biodiversity hotspots and intact forest landscapes. We analysed agricultural expansion under proactive and reactive biodiversity protection scenarios, and for different rates of pasture intensification. We found growing food demand to lead to a significant expansion of cropland at the expense of pastures and natural vegetation. In our reference scenario, global cropland area increased by more than 400 Mha between 2015 and 2050, mostly in Africa and Latin America. Grazing intensification was a main determinant of future land‐use change. In Africa, higher rates of pasture intensification resulted in smaller losses of natural vegetation, and reduced pressure on biodiversity hotspots and intact forest landscapes. Investments into raising pasture productivity in conjunction with proactive land‐use planning appear essential in Africa to reduce further losses of areas with high conservation value. In Latin America, in contrast, higher pasture productivity resulted in increased livestock exports, highlighting that unchecked trade can reduce the land savings of pasture intensification. Reactive protection of sensitive areas significantly reduced the conversion of natural ecosystems in Latin America. We conclude that protection strategies need to adapt to region‐specific trade positions. In regions with a high involvement in international trade, area‐based conservation measures should be preferred over strategies aimed at increasing pasture productivity, which by themselves might not be sufficient to protect biodiversity effectively.     

不同草地所有权下家庭牧场生产效率比较分析

选取了甘肃祁连山区肃南县春夏秋冬四季草场均已分配到户的15个牧户和天祝县夏秋草场或四季草场均为公共草场的15个农牧户,从草地生态系统生产功能的角度,通过野外调查、DEA模型(数据包络分析模型)分析,比较两地牧民草场面积,冷季补饲,牧工费,家庭劳动力等投入,出售活畜、毛、奶等畜产品的产出等项目,探讨不同的草地所有权下牧民生产效率平均值、效率分布的差异性以及影响生产效率的因素。结果显示:天祝县农牧民生产效率的平均值大于肃南县(P0.05),且天祝县牧户生产效率的分布优于肃南县。进一步分析得出造成牧业生产效率低的原因从大到小顺序为:补饲投入、能繁母畜、草场面积和劳动力投入。验证了草地所有权会影响家庭牧场生产效率的假设,并且就生产效率角度来说,不完全承包到户的草地所有权优于完全承包到户的。     

Moms are better nurses than dads: gender biased self‐facilitation in a dioecious Juniperus tree

Questions: Can gender of nurse plants affect regeneration patterns and spatial population structure? Is there a seed‐seedling conflict in the regeneration process? What factors are responsible for the clumped spatial population structure observed for adult trees? Location: Mediterranean cold semi‐arid high mountains in Spain. Methods: The spatial pattern of adult Juniperus thurifera trees was studied by means of Ripley's K‐analysis. χ² analyses were used to test for natural seedling frequency in each of three main microhabitats: (1) under female and (2) male tree canopies and (3) in open interspaces. The observed pattern was explained experimentally by studying seed and seedling survival for two years. Survival probabilities were calculated across life stages for each of three main microhabitats. Results: Adult J. thurifera trees were aggregated in space. Most seedlings were found underneath female J. thurifera trees. Experimental studies demonstrated that from seed dispersal to seedling survival all life stages showed the same positive or negative trend within a given microhabitat, indicating stage coupling and no seed‐seedling conflicts. Attraction of frugivo‐rous birds by reproductive female junipers and improvement of environmental conditions beneath tree canopies were the main factors responsible for the variation in seedling density among microhabitats; highest underneath female trees and lowest in open interspaces. Conclusions: In dioecious species, the gender of nurse plants can significantly determine the spatial population structure. In J. thurifera forests, facilitation beneath female trees occurs among all life stages without any sign of seed‐seedling conflict. The most critical factors shaping the spatial population structure were directed seed dispersal and environmental amelioration beneath female conspecific trees.     

Stress‐Driven Changes in the Strength of Facilitation on Tree Seedling Establishment in West African Woodlands

The strength of competitive and facilitative interactions in plant communities is expected to change along resource gradients. Contrasting theoretical models predict that with increasing abiotic stress, facilitative effects are higher, lower, or similar than those found under more productive conditions. While these predictions have been tested in stressful environments such as arid and alpine ecosystems, they have hardly been tested for more productive African woodlands. We experimentally assessed the strength of tree seedling facilitation by nurse trees in mesic and dry woodlands in Benin, West Africa. We planted seedlings of the drought‐sensitive Afzelia africana and the drought‐tolerant Khaya senegalensis under three microsite conditions (closed woodland, woodland gap, and open fields). Seedling survival was greater within woodlands compared with open fields in both the mesic and dry woodlands. The relative benefits in seedling survival were larger at the dry site, especially for the drought‐sensitive species. Nevertheless, plant interactions became neutral or negative during the dry season in the drier woodland, indicating that the net positive effects may be lost under very stressful abiotic conditions. We conclude that facilitation also occurs in the relatively more productive conditions of African woodlands. Our results underscore the role of environmental variation in space and time, and the stress tolerance of species, in explaining competitive and facilitative interactions within plant communities. Abstract in French is available at http://www.blackwell‐synergy.com/loi/btp .