[Effects of Fargesia denudata density on soil nutrient pool]

This paper studied the nutrient storage and its dynamics in different soil layers under three densities of Fargesia denudata communities in Wanglang National Nature Reserve, aimed to understand the effects of F. denudata density on the storage and dynamics of soil nutrients. The results showed that F. denudata density had a significant effect on the total and available nutrient contents in 0 - 30 cm soil layer. The total and available P contents decreased significantly with the increasing F. denudata density (P < 0. 01), being 0.274 kg m(-2) and 1.72 g x m(-2) at D1, 0.222 kg m(-2) and 1.50 g x m(-2) at D2, and 0.158 kg x m(-2) and 1.10 g x m(-2) at D3 sampling site, while the contents of total Ca and Mg increased with the increasing F. denudata density, being 2.64 and 1.70 kg x m(-2) at D1,4.42 and 1.80 kg x m(2-) at D2, and 4.85 and 2.12 kg x m(-2) at D3 sampling site, respectively. The contents of both total and available N and K did not change significantly with F. denudata density. Soil total and available N were 1.10 and 45.15 kg x m(-2) at D1, 1.04 and 44.38 kg x m(-2) at D2, and 1.06 and 42.02 kg x m(-2) at D3, while soil total and available K were 3.19 and 39.62 kg x m(-2) at D1, 3.30 and 36.23 kg x m(-2) at D2, and 3.19 and 37.18 kg x m(-2) at D3, respectively. The total nutrient storage was in order of Ca>K>Mg>N>P, except a higher K storage than Ca under D1 community. The available N, P and K concentration in surface soil (0-10 cm) decreased significantly in July, and then increased slowly in the later growth season. In general, the change magnitude of available nutrients was greater in surface soil (L1) than in lower soil layers (L2 and L3), under higher F. denudata density (D3) than under lower F. denudata density, and for P than for N and K. The distribution pattern of nutrient storage in soil layers differed greatly from that of nutrient concentration, regardless of F. denudata densities. The contents of total N, P, K, Ca and Mg in L (0-10 cm) were lower than those in L2 (10-20 cm) and L3 (20-30 cm). The differences of nutrient contents among soil layers varied with F. denudata density, and particularly with bio-elements. The results suggested that the nutrient storage in soil under F. denudata community was related to F. denudata density, because the density affects the processes of nutrient cycling, such as nutrient absorption, return through litter, and activity of soil microorganisms. It could be concluded that the density of F. denudata communities affected the storage of soil P and Ca significantly, but that of soil Mg, N and K slightly. Soil total and available P contents decreased with the increasing F. denudata density, implying that soil P could be one of the main factors limiting the growth and succession of F. denudata community in these stands, and affecting the flowering and death of bamboo.