Stronger Diversity Effect on Productivity Was Found in Later Successional Stage of Temperate Mixed Forest
As biodiversity of species is rapidly declining worldwide under human disturbance, the relationship between biodiversity and ecosystem functioning (BEF) and their underlying mechanisms have become an important scientific issue. In past decades, many experiments were conducted in small-scale controlled ecosystems, predominantly grasslands, and within relatively short periods (1-10 years) and spatial scales (100 m2) and their results may not reflect structurally complex natural communities. Also, species richness is frequently used as the sole measure of diversity while the importance of other metrics of diversity such as functional and phylogenetic diversity is ignored.
YUAN Zuoqiang and co-authors at Institute of Applied Ecology of Chinese Academy of Sciences took the plots of Broad-leaved Korean Pine Forest and Secondary Poplar-Birch Forest as objects and analyzed the above-ground biomass stock and its dynamics. They collected data of leaf P, N content, leaf area, leaf specific area, wood density and specific root length, and compared the dispersion pattern of these traits with null model. They also calculated the species richness, functional diversity and phylogenetic diversity.
Researchers found that almost all biodiversity indices showed positive correlations with productivity, and the phylogenetic diversity well predicts productivity. However, their findings did not support the conclusion that species richness had weakest predictive power. They revealed that the model including species richness, phylogenetic diversity and single not combined functional trait explained more variation in productivity than other models. Regardless of diversity indices, researchers found stronger positive BEF relationships in the later stage of forest succession, implying that the diversity effect on ecosystem functioning becomes stronger over time.
The study showed that along with the community succession, influence of temperate natural forest in different diversity index of ecosystem function also changed, which means that the relationship between biodiversity and ecosystem function is a dynamic process. Considering the multi-causality in complex world and multi-dimensions of biodiversity at the multi-time and space scales will be the breakthrough to correctly understand and grasp the linkages among biodiversity, ecosystem functioning and the production of ecosystem services.
This work has been published in Oecologia (182(4): 1175-1185) and was financially supported by the external cooperation program of BIC, Chinese Academy of Sciences (151221KYSB20130003), National Natural Science Foundation of China (41301057 and 31370444).
Forest ecosystems play a fundamental role in the global carbon cycle. However, how stand-level changes in tree age and structure influence biomass stock and dynamics in old-growth forests is a question that remains unclear.
In this study, we quantified the aboveground biomass (AGB) standing stock, the coarse woody productivity (CWP), and the change in biomass over ten years (2004–2014) in a 25 ha unmanaged broad-leaved Korean pine mixed forest in northeastern China. In addition, we quantified how AGB stock and change (tree growth, recruitment and mortality) estimations are influenced by the variation in habitat heterogeneity, tree size structure and subplot size.
Our analysis indicated that Changbai forest had AGB of 265.4 Mg ha−1 in 2004, and gained1.36 Mg ha−1 y−1 between 2004 and 2014. Despite recruitment having better performance in nutrient rich habitat, we found that there is a directional tree growth trend independent of habitat heterogeneity for available nutrients in this old growth forest. The observed increases in AGB stock (∼70%) are mainly attributed to the growth of intermediate size trees (30–70 cm DBH), indicating that this forest is still reaching its mature stage. Meanwhile, we indicated that biomass loss due to mortality reduces living biomass, not increment, may be the primary factor to affect forest biomass dynamics in this area.
Also, spatial variation in forest dynamics is large for small sizes (i.e. coefficient of variation in 20 × 20 m subplots is 53.2%), and more than 90 percent of the inherent variability of these coefficients was predicted by a simple model including plot size. Our result provides a mean by which to estimate within-plot variability at a local scale before inferring any directional change in forest dynamics at a regional scale, and information about the variability of forest structure and dynamics are fundamental to design effective sampling strategies in future study.
Publication Name:Yuan Zuoqiang, Gazol Antonio, Wang Xugao, Lin Fei, Ye Ji, Zhang Zhaochen, Suo Yanyan, Kuang Xu, Wang Yunyun, Jia Shihong, Hao Zhanqing.
In forested ecosystems, it remains unclear whether environmental conditions, resource competition or their joint effects explain non-randomly distributed species pattern. Recently, trait-based approaches have been recognized as an important tool to infer processes governing community assembly patterns. In this study, we quantify patterns of functional composition and diversity to study how tree species coexistence is influenced by abiotic factors and biotic interactions in a species-rich temperate old-growth forest. In a 25 ha (500 × 500 m) fully mapped forest plot, we calculated functional composition (community weighted mean) and diversity of five key traits considering two spatial scales (20 × 20 and 50 × 50 m quadrats). We compared the observed patterns in functional diversity with randomly generated null communities to test for the presence of non-random patterns in community assembly, and studied the variation of functional composition and diversity along gradients of soil conditions to test for the shift in assembly processes along resource gradients. Functional diversity differed from null expectations depending on the spatial scale considered. In broad-scale quadrats (50 × 50 m), functional diversity in wood specific gravity (WSG) and leaf area (LA) was lower than expected by chance, whereas functional diversity in specific root length (SRL) was greater than expected. In small quadrats (20 × 20 m), functional diversity was lower than expected by chance in specific leaf area (SLA) and when considering all traits in combination. Functional composition and diversity varied along the soil resource gradient but the results were dependent on the scale considered. We found an increase in functional composition in maximum height (H) and WSG and a reduction in the functional diversity in most of traits suggesting an increase in competition with the increase in soil water content at small scale. The trait dispersion pattern for all traits in combination had no directional changes with some of individual traits generating more clear dispersion trend when the dominant competitor Pinus koraiensis was removed from the community dataset. The results presented here suggest that community assembly is governed by non-random processes in the studied forests. Interestingly, the choice of quadrat size seems to be crucial to describe community patterns and infer the forces governing community assembly. The consideration of different traits and environmental gradients allowed us to discover that different assembly mechanisms operate simultaneously in the studied forest.
Publication Name:Yuan Zuoqiang, Gazol Antonio, Lin Fei, Wang Xugao, Ye Ji, Suo Yanyan, Fang Shuai, Mellard Jarad, Hao Zhanqing.
Biodiversity can be measured by taxonomic, phylogenetic, and functional diversity. How ecosystem functioning depends on these measures of diversity can vary from site to site and depends on successional stage. Here, we measured taxonomic, phylogenetic, and functional diversity, and examined their relationship with biomass in two successional stages of the broad-leaved Korean pine forest in northeastern China. Functional diversity was calculated from six plant traits, and aboveground biomass (AGB) and coarse woody productivity (CWP) were estimated using data from three forest censuses (10 years) in two large fully mapped forest plots (25 and 5 ha). 11 of the 12 regressions between biomass variables (AGB and CWP) and indices of diversity showed significant positive relationships, especially those with phylogenetic diversity. The mean tree diversity-biomass regressions increased from 0.11 in secondary forest to 0.31 in old-growth forest, implying a stronger biodiversity effect in more mature forest. Multi-model selection results showed that models including species richness, phylogenetic diversity, and single functional traits explained more variation in forest biomass than other candidate models. The models with a single functional trait, i.e., leaf area in secondary forest and wood density in mature forest, provided better explanations for forest biomass than models that combined all six functional traits. This finding may reflect different strategies in growth and resource acquisition in secondary and old-growth forests.
Publication Name:Yuan Zuoqiang, Wang Shaopeng, Gazol Antonio, Mellard Jarad, Lin Fei, Ye Ji, Hao Zhanqing, Wang Xugao, Loreau Michel.