The amounts of litter produced and nutrients returned play a fundamental role in the productivity and biogeochemical and nutrient cycling of forest ecosystems.We monitored annual litterfall production, nutrient return,and monthly dynamics over a one-year period in Chinese fir plantations aged 10, 22, and 34 years. Our objective was to quantify litterfall and nutrient return over a complete harvest rotation of Chinese fir. Annual litterfall production increased with stand age and was recorded as(3,294.6 ± 360.4),(3,733.9 ± 211.2), and(4,876.1 ± 212.8) kg ha-1a-1in stands aged 10, 22 and 34 years, respectively. Total litter production was significantly greater in the stand aged34 years than in the stand aged 10 years(p \ 0.05). With the exception of miscellaneous components, needle litterfall constituted the highest proportion(27.5–43.6 %), followed by branches/twigs(9.5–16.6 %). In all three plantations,annual total nutrient return to soil was in the order of C(1,119.95–2,709.05 kg ha-1a-1) [ N(39.32–62.04 kg ha-1a-1) [ K(15.95–22.44 kg ha-1a-1) [ P(1.30–1.63 kg ha-1a-1). C, N, K and P input to soil was significantly lower in the 10-year-old stand in comparison to the 22- and34-year-old stands(p \ 0.05). Litterfall production and nutrient return(C, N and K) followed similar patterns, and C and N input to soil was significantly related to litterfall production(needle, branch and total litterfall). C, N, P and K input to soil and total litterfall production were mainly driven by needle litterfall.
Lili ZhouAddo-Danso Daniel ShalomPengfei WuShubin LiYayun JiaXiangqing Ma
Plantations of eucalypts as short-rotation tree crops are rapidly expanding in tropical and sub-tropical regions, including southern China, where the soils are acidic and available phosphorus(P) is limited. We investigated seedling growth, dry matter accumulation, and the dynamics of photosynthetic rate and chlorophyll content of seven Eucalyptus species/hybrids(E. dunnii, E. grandis, E. grandis × E. camaldulensis, E. urophylla × E. camaldulensis, E. urophylla × E. tereticornis, E. grandis × E. tereticornis, E. urophylla × E. grandis) in response to different levels of P supply(0, 6, 12 and 18 mg?kg-1 KH2PO4). The photosynthetic rate and the chlorophyll content significantly declined as the P supply declined in almost a linear fashion for all species as the P stress period extended. In the absence of P supply, height growth of seedlings of all species was significantly impaired, while root collar diameter growth and whole plant dry matter accumulation was not affected by the level of P supply in most of the species. Significant inter-species variations in growth, dry matter accumulation and photosynthetic rate in response to P supply were detected. Eucalyptus dunnii had the lowest growth performance across all levels of P supply while E. urophylla × E. tereticornis showed superior growth performance. From a practical point of view, E. urophylla × E. tereticornis is suggested as a candidate hybrid for planting on slightly P-deficient sites in southern China while E. dunnii, being a slow-growing species, is not suitable for short-rotation plantation. On plantation sites where severe P deficiency exists, P fertilization needs to be considered to boost rapid growth of seedlings so as to meet the management objectives of short-rotation plantation.
