Abstract
BackgroundSustainable use of our soils is a key goal for environmental protection. As many ecosystem services are supported belowground at different trophic levels by nematodes, soil nematodes are expected to provide objective metrics for biological quality to integrate physical and chemical soil variables. Trait measurements of body mass carried out at the individual level can in this way be correlated with environmental properties that influence the performance of soil biota.ResultsSoil samples were collected across 200 sites (4 soil types and 5 land-use types resulting in 9 combinations) during a long-term monitoring programme in the Netherlands and the functional diversity of nematode communities was investigated. Using three commonly used functional diversity indices applicable to single traits (Divergence, Evenness and Richness), a unified index of overall body-mass distribution is proposed to better illustrate the application of functional metrics as a descriptor of land use. Effects of land use and soil chemistry on the functional diversity of nematodes were demonstrated and a combination of environmental factors accounts for the low functional value of Scots Pine forest soils in comparison to the high functional value of heathland soils, whereas human factors account for the low functional and chemical values of arable fields.ConclusionsThese findings show an unexpected high functional vulnerability of nematodes inhabiting clay-rich soils in comparison to sandy soils and support the notion that soil C:N ratio is a major driver of biodiversity. The higher the C:N ratio, the higher the overall diversity, as soil nematodes cope better with nutrient-poor agroecosystems under less intense fertilization. A trait-based way focusing on size distribution of nematodes is proposed to maintain environmental health by monitoring the overall diversity in soil biota, keeping agriculture and forestry sustainable.
Highlights
Sustainable use of our soils is a key goal for environmental protection
Detrital food webs are less size-structured than aquatic webs, because large, isolated nematodes can be attacked by smaller organisms [7], measurements of the functional diversity of soil nematodes based on their site-specific body-mass distribution are entirely missing
The coefficient of variation of nitrogen concentration was the highest (94.9%), followed by carbon (89.8%) and phosphorus (65.6%), while the coefficient of variation for molar ratios was the highest for C:P (134.1%), followed by N:P (87.6%) and C:N (34%). The latter result is remarkable, as despite its rather low coefficient of variation, the C:N ratio is an important driver of functional diversity metrics (Table 1)
Summary
Sustainable use of our soils is a key goal for environmental protection. As many ecosystem services are supported belowground at different trophic levels by nematodes, soil nematodes are expected to provide objective metrics for biological quality to integrate physical and chemical soil variables. Detrital food webs are less size-structured than aquatic webs, because large, isolated nematodes can be attacked by smaller organisms [7], measurements of the functional diversity of soil nematodes based on their site-specific body-mass distribution are entirely missing. This is rather surprising, as the size of organisms (M) is widely recognized as the best sole predictor in allometric models and plays a dominant role in the delivery of ecosystem services (soil heterotrophs are regarded as ecosystem engineers because they are both motors and moderators of environmental changes). A functional trait like M, which is so strongly correlated with the environment, can be seen as the lowest common denominator among ecological and evolutionary processes, providing a way to mechanistically understand species responses to environmental change
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