A growing body of evidence shows that aboveground and belowground communities and processes are intrinsically linked, and that feedbacks between these subsystems have important implications for community structure and ecosystem functioning. Almost all studies on this topic have been carried out from an empirical perspective and in specific ecological settings or contexts. Belowground interactions operate at different spatial and temporal scales. Due to the relatively low mobility and high survival of organisms in the soil, plants have longer lasting legacy effects belowground than aboveground. Our current challenge is to understand how aboveground–belowground biotic interactions operate across spatial and temporal scales, and how they depend on, as well as influence, the abiotic environment. Because empirical capacities are too limited to explore all possible combinations of interactions and environmental settings, we explore where and how they can be supported by theoretical approaches to develop testable predictions and to generalise empirical results. We review four key areas where a combined aboveground–belowground approach offers perspectives for enhancing ecological understanding, namely succession, agro-ecosystems, biological invasions and global change impacts on ecosystems. In plant succession, differences in scales between aboveground and belowground biota, as well as between species interactions and ecosystem processes, have important implications for the rate and direction of community change. Aboveground as well as belowground interactions either enhance or reduce rates of plant species replacement. Moreover, the outcomes of the interactions depend on abiotic conditions and plant life history characteristics, which may vary with successional position. We exemplify where translation of the current conceptual succession models into more predictive models can help targeting empirical studies and generalising their results. Then, we discuss how understanding succession may help to enhance managing arable crops, grasslands and invasive plants, as well as provide insights into the effects of global change on community re-organisation and ecosystem processes.
No abstract is provided for this article.
The soil microbial biomass and microbial metabolic quotient (respiration: biomass ratio) was measured in 16 forest and scrubland ecosystems throughout New Zealand, on materials representing successional stages of plant litter and its subsequent incorporation into the F-H and mineral soil layers. Microbial biomass usually peaked in the L 1 layer and then declined. The microbial carbon:organic carbon ratio decreased sharply between the F-H layer and the underlying mineral layer, indicating that a stress factor (possibly pH) reduced the proportion of organic matter immobilized in the microbial biomass at this stage. The microbial respiration: biomass ratio declined between the L 1 and F-H stages
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We agree with Winter and Schweiger that it is important to differentiate between gradually changing and abruptly changing systems. Transformation of tropical regions by land-use change will inevitably have abrupt and profound effects on ecosystem properties, which will be driven both by changes in abiotic factors and by the replacement of one suite of species with another. As such, we maintain that in these cases the species trait concept remains relevant. Even when most or all species are lost, changes in the ecosystem will be driven most strongly by the loss of those species whose traits had the strongest effects on ecosystem processes before the loss occurred.
The influence of capitulum maturity on achene germination was investigated for Senecio jacobaea L. and Carduus nutans L. Germination of achenes from capitula in full flower was negligible for both species but as the floral tissues began to senesce the germination percentage rose to at least 50% for all populations investigated. S. jacobaea achenes with floral parts abscised or absent were generally more viable than achenes with floral parts attached, and seedlings from such achenes exhibited higher growth rates. C. nutans did not exhibit any consistent trends.
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We hypothesised that plant species composition and richness would affect soil chemical and microbial community properties, and that these in turn would aff
When tree seedlings establish beyond the current tree line due to climate warming, they encounter existing vegetation, such as bryophytes that often dominate in arctic and alpine tundra. The stress gradient hypothesis ( SGH ) predicts that plant interactions in tundra become increasingly negative as climate warms and conditions become less harsh. However, for seedlings, climate warming might not result in lower winter stress, if insulating snow cover is reduced. We aimed to understand if bryophytes facilitate seedling survival in a changing winter climate and if these effects of bryophytes on tree seedlings comply with the SGH along elevational gradients under contrasting snow conditions. In the Swedish subarctic, we transplanted intact bryophyte cores covered by each of three bryophyte species and bryophyte‐free control soil from above the tree line to two field common garden sites, representing current and future tree line air temperature conditions (i.e. current tree line elevation and a lower, warmer, elevation below the tree line). We planted seedlings of Betula pubescens and Pinus sylvestris into these cores and subjected them to experimental manipulation of snow cover during one winter. In agreement with the SGH , milder conditions caused by increased snow cover enhanced the generally negative or neutral effects of bryophytes on seedlings immediately after winter. Furthermore, survival of P. sylvestris seedlings after one full year was higher at lower elevation, especially when snow cover was thinner. However, in contrast with the SGH , impacts of bryophytes on over‐winter survival of seedlings did not differ between elevations, and impacts on survival of B. pubescens seedlings after 1 year was more negative at lower elevation. Bryophyte species differed in their effect on seedling survival after winter, but these differences were not related to their insulating capacity. Synthesis . Our study demonstrates that interactions from bryophytes can modify the impacts of winter climate change on tree seedlings, and vice versa . These responses do not always comply with SGH , but could ultimately have consequences for large‐scale ecological processes such as tree line shifts. These new insights need to be taken into account in predictions of plant species responses to climate change.
