Abstract
Aim of the study: Data about the distribution of fine root length density (FRLD) is important to understand the ecophysiology of vegetation. This is particularly true when models are applied to describe ecohydrology and vegetation function. However, there is yet limited knowledge of root distributions in semi－arid regions. The aim of this study is to investigate the distribution of fine roots for six typical afforestation tree species in Loess Plateau and its relationships with soil environmental factors.Area of study: Loess Plateau (NW of China).Material and methods: We quantified the fine root length density distribution of six typical afforestation tree species by soil core method, and the soil properties also were investigated.Main results: More than 50% of fine root length was concentrated at depths between 0 and 40 cm in vertical direction. In horizontal direction, most of fine roots concentrated near the trunk. Results showed a significant negative correlation between vertical distribution of FRLD and soil water content, a positive correlation between FRLD and organic matter and total N is significant, and a negative correlation with bulk density. No relationships were found with total C and particle size distribution in any soil layer for the six tree species. Stepwise multiple linear regression confirmed that changes in different soil properties significantly affected the variation in FRLD for each tree species, total N had strong and positive relationships with FRLD.Research highlights: These measurements provide valuable data for modelling of ecosystem water use and productivity.Keywords: Anjiapo catchment; Core method; Root distribution; Soil moisture; Soil properties.
Highlights
Fine roots are the most dynamic and physiologically active component of below-ground biomass, and they play an important role in nutrient and water uptake (Schenk, 2008; Aanderud & Richards, 2009)
Of the six tree species, the averaged fine root length density (FRLD) was in order of R. pseudoacacia (0.0599 ± 0.0092 cm cm–3) > P. tabuliformis (0.0413 ± 0.0087 cm cm–3) > P. armeniaca (0.0329 ± 0.0072 cm cm–3) > P. tomentosa (0.0292 ± 0.0031cm cm–3) > C. korshinskii (0.00709 ± 0.00088 cm cm–3) > H. rhamnoides (0.00686 ± 0.00067 cm cm–3)
The above-ground growth of the six species in this area has been found to be largely independent of rainfall and to increase as soil moisture reached its lowest values (Wang et al, 2008). These results suggest that the six species have same root foraging strategies as related to soil moisture The soil layers (0-10 cm for P. tabuliformis and R. pseudoacacia; 10-20 cm for P.tomentosa and P. armeniaca; 30-40 cm for C. korshinski and H. rhamnoides) had the lowest soil water content and highest FRLD, indicating each of the six tree species has the dried soil layer (DSL) of different soil depth due to fine roots water uptake and soil evaporation
Summary
Fine roots are the most dynamic and physiologically active component of below-ground biomass, and they play an important role in nutrient and water uptake (Schenk, 2008; Aanderud & Richards, 2009). Fine roots concentrate near the soil surface and exponentially decrease with increasing soil depth (Macinnis-Ng et al, 2010). This enables more soil resource uptake since water enters the soil profile predominantly from the soil surface in most ecosystems, and nutrient concentrations are commonly higher in the upper soil layers (Schenk, 2008). Belsky (1994) found that trees from a dry site had lateral roots extending well beyond the canopy, but that trees from a wetter site concentrated their root growth beneath the canopy She speculated that in more arid conditions trees invested in laterally extensive roots for greater water access, and that when water was less limiting, roots grew under the canopy where nutrients were more plentiful. The properties of fine root distributions often depend on soil water and nutrient availability in soils (Iverson, 2010)
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