12/11/2023 0 Comments Ephemeral definition forestry![]() Separately, estimating fine-root life spans of both trees and understory is thus essential to accurately model stand fine-root turnover. ![]() Since herbs and shrubs are generally the dominant components of understory vegetation in many forest ecosystems, it is reasonable to expect shorter fine-root life spans for understory than for the trees with which they grow. A global meta-analysis by Chen and Brassard ( 2012) showed that fine roots of trees generally have longer life span, followed by grasses, lianas, shrubs, and forbs. However, apart from knowledge of fine-root biomass, so far, we know little about how the fine-root life spans of understory plants differ from those of trees in the same forest stand. ( 2013) estimated that as much as 68 % of the total fine-root biomass was composed of fine roots of understory vegetation in an overmature Chinese fir ( Cunninghamia lanceolata (Lamb) Hook.) stand in southern China. This omission could underestimate belowground C and nutrient fluxes derived from fine-root turnover data, especially in subtropical forests where the understory vegetation develops vigorously under the tree canopy. This possibility remains untested because most root studies in forest ecosystems have focused on tree fine roots, while understory fine roots are generally excluded from analyses or are not distinguished from those of trees (Yang et al. Although understory plants represent a relatively minor component of the whole biomass of forest ecosystems, their roots could contribute significantly to the total fine-root biomass and belowground C dynamics of a forest stand particularly if they had faster turnover times than the fine roots of trees (Bakker et al. Depending on the calculation assumptions used, typical ratios of belowground to aboveground biomasses of vegetation in forests range from about 0.3 to 0.5, but for grasslands, the corresponding ratios are about five times larger (Robinson 2007). Many forests have substantial understory communities (mainly herbs and shrubs), which can allocate a greater percentage of their photosynthate belowground than do trees (Raich and Tufekciogul 2000). One major area of uncertainty in mixed-species forests is the contribution made to root turnover at the stand level by understory vegetation. However, ecosystem models have incomplete understanding on this critical belowground process (Jackson et al. Fine-root life span can range from a few days to more than a decade and varies among species and across sites (Eissenstat and Yanai 1997 Peek 2007 Guo et al. Root life span, or root turnover rate, determines how fast C is cycled through the root biomass pool, reliable estimates of which are required by many ecosystem models. ![]() Therefore, fine-root turnover represents a major pathway of C and nutrient flow from plant to soil and is fundamental to both forest NPP and C sequestration (Strand et al. These results highlight the importance of taking into account understory fine-root life span estimates when assessing the dynamics of fine-root recycling in Chinese fir forests.Īnnually, between 10 and 60 % of net primary productivity (NPP) in terrestrial ecosystems can be cycled through fine roots (≤2 mm in diameter) (Jackson et al. Root diameter at appearance, rooting depth, and season of emergence had a significant effect on fine-root life span. Fine-root life spans for both trees and understory plants were longer in the older than in the younger plantation. Resultsįine roots were more ephemeral in understory plants than in trees in the two plantations. Factors controlling fine-root life spans were identified with Cox proportional hazards regression. We measured fine-root (≤2 mm in diameter) life span for trees and understory vegetation in 16- and 88-year-old Chinese fir plantations in southern China during 4 years with minirhizotron. This study aimed to document fine-root life spans in trees and understory plants in two Chinese fir plantations with different ages. Potential differences in fine-root life span between understory and trees remain poorly known. The contribution of understory vegetation to belowground carbon and nutrient cycling is often neglected in forest stands. Understory fine root can contribute significantly to total fine root biomass and belowground carbon. The life span of fine roots of understory plants and Chinese fir was shorter in the younger than in the older stand, although most of the factors affecting fine-root life spans were similar between trees and understory plants. Fine roots from understory plants were much more ephemeral than those from trees. We tested the life span of fine roots of Chinese fir trees and understory plants in two stands in subtropical China.
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