Importance of overstorey attributes for understorey litter production and nutrient cycling in European forests

Background:In contrast with the negligible contribution of the forest understorey to the total aboveground phytobiomass of a forest,its share in annual litter production and nutrient cycling may be more important.Whether and how this functional role of the understorey differs across forest types and depends upon overstorey characteristics remains to be investigated.Methods:We sampled 209 plots of the FunDivEUROPE Exploratory Platform,a network of study plots covering local gradients of tree diversity spread over six contrasting forest types in Europe.To estimate the relative contribution of the understorey to carbon and nutrient cycling,we sampled non-lignified aboveground understorey biomass and overstorey leaf litterfall in all plots.Understorey samples were analysed for C,N and P concentrations,overstorey leaf litterfall for C and N concentrations.We additionally quantified a set of overstorey attributes,including species richness,proportion of evergreen species,light availability(representing crown density)and litter quality,and investigated whether they drive the understorey’s contribution to carbon and nutrient cycling.Results and conclusions:Overstorey litter production and nutrient stocks in litterfall clearly exceeded the contribution of the understorey for all forest types,and the share of the understorey was higher in forests at the extremes of the climatic gradient.In most of the investigated forest types,it was mainly light availability that determined the contribution of the understorey to yearly carbon and nutrient cycling.Overstorey species richness did not affect the contribution of the understorey to carbon and nutrient cycling in any of the investigated forest types.

Litter Productivity and Nutrient Return Characteristics of Three Typical Forest Stands in Golden Mountain

Objective: The paper aims to analyze the dynamic characteristics of litter production and nutrient return of the forest ecosystems in subtropical areas, and provide a theoretical basis for the nutrient cycling study in southwest Hubei Province and carbon sink function of the whole forest ecosystem. Methods: Three typical forest stands (Chinese fir plantation, Cryptomeria fortunei plantation and evergreen and deciduous broad-leaved mixed forest) in Golden Mountain Forest Farm in southwest Hubei Province were investigated and monitored continuously for the litter types and productivity and nutrient return. Results: The annual litter productivity of the three forest stands ranged from 161.77 to 396.26 kg·hm-2;Litters of branches, leaves and reproductive organs accounted for 14.14% - 20.85%, 33.26% - 78.33%, 7.52% - 42.18% of the total, respectively;The litter productivity and total litter productivity of each composition in the three forest stands show unimodal or bimodal changes over months, and the total litter productivity reached the highest value in January, April and October respectively. For different nutrient contents of the three forest stands, the common feature is C > N. The order of nutrient return amount from greatest to least is evergreen and deciduous broad-leaved mixed forest, Cryptomeria fortunei plantation and Chinese fir plantation. For different nutrient return amounts, the common feature is C > N, and the nutrient return amounts are 76.51-180.69 kg·hm-2 and 2.3 - 5.71 kg·hm-2 respectively. Conclusion: The annual litter productivity and nutrient return amount of the evergreen and deciduous broad-leaved mixed forest are the highest among the three forest stands. Therefore, protecting the evergreen and deciduous broad-leaved mixed forest and studying the litter changes of Chinese fir plantation and Cryptomeria fortunei plantation are of far-reaching significance for the development of sustainable forest management in this region and the further improvement of the carbon sequestration function of the whole forest ecosystem.

Quantification of organic carbon and primary nutrients in litter and soil in a foothill forest plantation of eastern Himalaya

The present study was an effort to understand the amount of litter fall and its subsequent decomposition and quantify the release of available nutrients and soil physicochemical characteristics in plantations of four forest tree species(Lagerstroemia parviflora, Tectona grandis, Shorea robusta and Michelia champaca) in the Chilapatta Reserve Forest of the Cooch Behar Wildlife Division in the Terai zone of West Bengal, India. The most litter(5.61 Mg ha)was produced by T. grandis plantation and the least(4.72 Mg ha) by L. parviflora. The material turnover rate to the soil through decomposition from total litter was fastest during the first quarter of the year and subsequently decreased during the next two quarters. The material turnover rate was only 1 year, which indicates that more than90% of the total litter produced decomposed within a year.The available primary nutrient content in litter varied across the four plantations over the year. The plantations generally did not significantly influence the soil physical characteristics but did significantly influence the availability of primary nutrients and organic carbon at two depths(1–15 and16–30 cm) over the year. The availability of soil primary nutrients in the four plantations also increased gradually from the first quarter of the year to the third quarter and then decreased during the last quarter to the same level as in the first quarter of the year at both depths. The availability for soil organic carbon in the plantations followed a similar trend. The amount of litter produced and the material turnover in the soil in the different plantations differed, influencing the nutrient availability and organic carbon at the plantations. The amount of soil organic carbon was highest for T. grandis(2.52 Mg ha) and lowest for L. parviflora(2.12 Mg ha). Litter is the source of soil organic matter,and more the litter that is produced by the plantations, the higher will be the content and amount of soil organic carbon in the plantation.

The return and loss of litter phosphorus in different types of sand dunes in Horqin Sandy Land,northeastern China

Litter phosphorus （P） return is important to maintain the P cycle and balance in the sandy land of arid areas. In this study, we determined the loss and return of litter P in sand dune areas and elucidated their relation- ship. We investigated litter production and litter P amount, and simulated leaf litter moving dynamics to understand the relationships between the loss of litter P and the total litter P, and between the return of litter P and the total litter P in active （AD）, semi-stabilized （SSD） and stabilized （SD） dunes in Inner Mongolia, northeastern China. The vegetation litter P was 12.6, 94.5, and 201.6 mg P/m2 in AD, SSD, and SD, respectively. A significant movement and loss of leaf litter P with time occurred on the three types of sand dunes. As a result, the loss of P was 7.4, 46.9, and 69.8 mg P/m2 and the return of P was 5.5, 47.6, and 131.8 mg P/m2 in AD, SSD, and SD, respectively. The rela- tionship between both loss and return of P and total litter P in AD, SSD, and SD was revealed by linear regression. The slope of the regression line indicated the rate of loss or return of litter P. From AD to SD, the loss rate showed a declining slope （0.52, 0.32, and 0.17 for AD, SSD, and SD, respectively）, and the return rate showed a rising slope （0.48, 0.67, and 0.83 for AD, SSD, and SD, respectively）. The loss of litter P should be regarded in the local man- agement of vegetation and land in sand dune areas. Improved vegetation restoration measures are necessary to decrease litter P loss to maintain the stability of ecosystems in sand dune areas.

Soil carbon budget in different-aged Chinese fir plantations in south China

Understanding the age effect on soil carbon balance in forest ecosystems is important for other material cycles and forest man-agement. In this research we investigated soil organic carbon density, litter production, litter decomposition rate, soil respiration, and soil mi-crobial properties in a chronosequence of four Chinese fir plantations of 7, 16, 23 and 29 years at Dagangshan mountain range, Jiangxi Province, south China. There was a significant increasing trend in litter production with increasing plantation age. Litter decomposition rate and soil respira-tion, however, declined from the 7-year to the 16-year plantation, and then increased after 16 years. This was largely dependent on soil micro-organisms. Soil carbon output was higher than carbon input before 16 years, and total soil carbon stock declined from 35.98 t＆#183;ha-1 in the 7-year plantation to 30.12 t＆#183;ha-1 in the 16-year plantation. Greater litter produc-tion could not explain the greater soil carbon stock, suggesting that forest growth impacted this microbial process that controlled rates of soil car-bon balance together with litter and soil respiration. The results highlight＆amp;nbsp;the importance of the development stage in assessing soil carbon budget and its significance to future management of Chinese fir plantations.