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| Foranderlige Landskaber - center for strategiske studier i kulturmiljø, natur og landskabshistorie |
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Tilbage til Startside Soil nutrient regimes – who is poor and who is rich? Evaluation framework for forest soils, set-aside land and arable soils Callesen, I., K. Raulund-Rasmussen 1 Danish Centre for Forest, Landscape and Planning
Concepts of soil nutrient regimes Forest ecologists and botanists use ordinal scales (oligothroph -> mesotroph-> eutroph) to characterise nutrient availability and nutrient cycling in ecosystems. Other concepts are acid vs. neutral soils or calcareous/ non calcareous soils. In respect of the soil component these definitions are somewhat ambiguous and not quantitative. Substrate properties should be characterised by quantitative edaphic parameters. These parameters should be stable in the long term (several tree generations). We propose six soil nutrient regimes based on available soil data. Inherited soil properties and present status depend on:
Effect of land-use history
Furthermore present land-use, treespecies, silviculture (slashburning, clear felling), afforestation of set-aside land, fertilisation and liming, deep ploughing N-deposition, S-deposition affect the nutrient availability in forest soils or non-cultivated soils covered by (semi)natural vegetation.
Proposed SNR’s In principle all plant nutrients should be evaluated and the chemical along with chemical and physical restrictions in the soil hampering nutrient availability or root growth, i.e. cementation, dense horizons or strong gleying. We used total pools (concentration x soil volume x bulk density) in depth 0-100 cm + the organic layer to establish a framework of available nutrient pools (i.e. exchangeable cations). The pools were tested against a forest soil data base (NORDSOIL). Data on long term nutrient supply (e.g. extractions in weak acids) are less abundant. Tabel 1. Total reserves of soil nutrient regimes (kg ha-1) 0-100 cm soil depth. Phosphorus- concentrations (mg kg-1).
Test of SNR’s class approach Tested on a population of 98 Danish forest soil profiles covering most sediment types, it appeared that the distributions were not even and may need adjustment. Table 2 98 forest soil profiles distributed in the proposed SNR’s.
Conclusions - rather acid soils with high pools of exchangeable base cations - soils with good reserves of most elements except one, e.g. K or P. soil SNR’s should be evaluated on the basis of multiple criteria PCA analysis - continuous approach
Table 3 PCA analysis (proc princomp, SAS), meancorrected data. N=98. Correlation matrix and the eigen vectors of the 1. and 2. principal component
Eigenvalue of 1.pc: 3.4 (67%) of 2. pc 0.75 (15%).
Conclusions The element pools were highly correlated, whereas correlation with pH was lower. 82% of the total variation was explained by the two principal components. The univariate class approach is intuitively pleasant, whereas the multivariate approach performs better dealing with the highly collinear soil properties. Perspectives SNR’s based on chemical and physical soil properties are meaningful for reference of status. They should furthermore related to long term element pools and ecosystem properties such as net primary producion or other yield measures Til oversigt Landskab og Arealresurser Tilbage til Startside |
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