Differences in nitrogen cycling between tropical dry forests with contrasting precipitation revealed by stable isotopes of nitrogen in plants and soils

Abstract

Despite the known links between climate and biogeochemical cycling of N in tropical forests, fundamental knowledge of N cycling is still far from complete. Our objective was to ascertain differences in the N cycle of two tropical dry forests under contrasting precipitation regime (1240 or 642 mm of mean annual rainfall). To do so, we examined a short-term metric of N cycling (N concentration) and a more integrated metric of N cycling (natural abundance 15 N) in plants and soils at both sites. At both the relatively wet and dry sites, N cycling associated with two non-N 2 -fixing species was compared to N cycling associated with two potential N 2 -fixing species; all four tree species considered were dominant at both sites. The 15 N abundance in plants was highest in the site with low rainfall, showing that N losses from the system may be large. By contrast, short-term N metrics did not vary with rainfall. Although there was a trend for leaf N concentration to be elevated in trees that have potential associations with N 2 -fixers, only 15 N in the forest floor was significantly greater under trees with high canopy N (N 2 -fixing species) than those with low canopy N (non-N 2 -fixing species). Within each site, the influence of N 2 -fixing species on N cycling increased with a reduction in rainfall. Overall, our results demonstrate the role of climate as a driver of N cycling in the region, such that the projected decrease in precipitation in this region may lead to larger N losses in these forests. This study also shows how changes in tree species with and without N 2 -fixing associations may impact N cycling in tropical dryland forests in the future.Abstract in Spanish is available with online material.

Effects of Initial Soil Properties on Three-Year Performance of Six Tree Species in Tropical Dry Forest Restoration Plantings

“…Soils in the TDF are extremely poor in nitrogen [76], and the availability of N for plants decreases with environmental disturbance [77]. Given that plants require N to achieve high growth rates [78], and stable isotopes of nitrogen reveal that TDFs have an open N cycle (i.e., high losses of NO 3 − by leaching and losses by N 2 O emissions [79]), a high initial NO 3 − availability in the soil favored the growth rates of fast-growing species. For example, two fast-growing tree species from the TDF had a higher ability to forage for soil nutrients by producing more roots than two slow-growing species under high light availability in greenhouse conditions [66].…”

Spectrometric Prediction of Nitrogen Content in Different Tissues of Slash Pine Trees

“…Therefore, it is necessary and helpful to understand the internal cycling process of N in trees for plant ecology and management. However, the dearth of research on the variation of N storage and consumption is mainly ascribed to the cost and time-consuming methods, e.g., a large number of samples need to be considered for multiple plant species and methods such as atomic absorption spectrometry [ 9 , 10 ] and chromatography [ 11 ] need to be deployed.…”

Association of spectroscopically determined leaf nutrition related traits and breeding selection in Sassafras tzumu

“…However, research on plant growth and the variation of N storage and remobilization have typically required labour intensive methods to measure the N concentration and index properties (NBI, ANTH, and FLAV), such as atomic absorption spectrometry [ 8 , 32 ], chromatography [ 68 ] and so on. These analytical methods will limit the breeding selection of tree growth with a large number of samples.…”