Biodiversity and Plant Litter: Experimental Evidence Which Does Not Support the View That Enhanced Species Richness Improves Ecosystem Function

Drivers of nitrogen leaching from organic layers in Central European beech forests

“…plant N uptake) of vascular plants in diverse communities. Decreased N release during decomposition seems unlikely because several studies on the relationship between plant diversity and organic matter turnover reported no or a positive e ect of plant diversity on N release (e.g., Blair et al 1990;Wardle et al 1997;Fornara et al 2009;Rosenkranz et al 2012). Lower dissolved N uxes in more diverse forests could instead have resulted from increased N demand of the vegetation as related to the greater productivity of more diverse forests (Morin et al 2011;Paquette and Messier 2011;Brassard et al 2013).…”

“…The N release during litter decomposition di ers among functional plant groups because leaf traits like N and lignin concentrations impact both litter decomposition and N immobilization (Wardle et al 1997;Berg 2000). Functional traits other than growth form (e.g., leaf N, nitrate reductase activity) were not determined in the studied communities and could thus not be examined directly.…”

Charcoal does not change the decomposition rate of mixed litters in a mineral cambisol: a controlled conditions study

“…For 49 example, nitrogen depleted organic product decomposition can be improved by being 50 mixed with a N-rich substrate (Wardle et al 1997 Charcoal is aromatic in nature, chemically highly condensed and poor in nitrogen. 58…”

Effects of mixture of branch order-based roots and nitrogen addition on root decay in a subtropical pine plantation

“…This implies that the tissue N concentration increases in proportion to acidunhydrolyzable residue of order-based roots and much of the N in lower-order roots is tightly bound in acid-unhydrolyzable residue (Xiong et al 2013). Hence, the complementary resource (e.g., N) use by microbial decomposers (Vos et al 2013) or priming effects of high-quality litters on low-quality litters (Wardle et al 1997) may, to some extent, be hindered due to the limited N release. Alternatively, the high amount of polyphenols (e.g., chitin and tannin, collectively referred to as acid-unhydrolyzable residue) in lower-order roots typically exerts negative effects on decomposition (Langley et al 2006) and thus may offset the positive effects of N transfer (if any) on decomposition of root mixture.…”

“…Therefore, regardless of the branch order-or diameterbased root mixture, the synergistic effect commonly observed in decomposition of root mixtures among species (Robinson et al 1999;De Graaff et al 2011) may not hold within species. The synergistic effect is generally driven by the chemical heterogeneity of mixed litters via the priming effects (Wardle et al 1997;Chapman and Koch 2007) or niche complementarity among microdecomposer groups (Hector et al 1999). Lower-order roots are the primary plant structures for nutrient uptake within the branching fine root systems (Xia et al 2010) and are commonly associated with mycorrhizal fungi (Guo Table 2 Results of the repeated measures two-way ANOVA for residual mass, residual acid-unhydrolyzable residue, and residual N, with different N addition rates (CK, low N, and high N) and decomposition conditions ( "isolation" vs. "mixture" for each root group, or "observed" vs. "expected" for the whole mixture) as factors , and thus they have higher N and P concentrations than higher-order roots (Pregitzer et al 2002;Li et al 2010).…”