Effects Of Precipitation Regimes Research Articles

Effects of precipitation regime on the structure of soil micro-food web in the grassland of northern China

Effects of precipitation regime on the structure of soil micro-food web in the grassland of northern China

Depth matters: effects of precipitation regime on soil microbial activity upon rewetting of a plant-soil system.

Changes in frequency and amplitude of rain events, that is, precipitation patterns, result in different water conditions with soil depth, andlikely affect plant growth and shape plant and soil microbial activity. Here, we used 18O stable isotope probing (SIP) to investigate bacterial and fungal communities that actively grew or not upon rewetting, at three different depths in soil mesocosms previously subjected to frequent or infrequent watering for 12 weeks (equal total water input). Phylogenetic marker genes for bacteria and fungi were sequenced after rewetting, and plant-soil microbial coupling documented by plant 13C-CO2 labeling. Soil depth, rather than precipitation pattern, was most influential in shaping microbial response to rewetting, and had differential effects on active and inactive bacterial and fungal communities. After rewetting, active bacterial communities were less rich, more even and phylogenetically related than the inactive, and reactivated throughout the soil profile. Active fungal communities after rewetting were less abundant and rich than the inactive. The coupling between plants and soil microbes decreased under infrequent watering in the top soil layer. We suggest that differences in fungal and bacterial abundance and relative activity could result in large effects on subsequent soil biogeochemical cycling.

Shift from ecosystem P to N limitation at precipitation gradient in tropical dry forests at Yucatan, Mexico

The effect of precipitation regime on N and P cycles in tropical forests is poorly understood, despite global climate models project total precipitation reductions during the 21st Century. I investigated the influence of variation in annual precipitation (1240–642 mm yr−1) on N and P intra-system cycling along a precipitation regime gradient at Yucatan including 12 mature, tropical dry forests (TDFs) growing under otherwise similar conditions (similar annual temperature, rainfall seasonality and geological substrate). I analyzed N and P storage and turnover in the forest floor and mineral soil and explored the dependence of these processes and pools on precipitation level. The study findings indicate that with decreasing precipitation the litterfall decreases slightly (10%), while nutrient use efficiency increases by 20% for N, and by 40% for P. Decomposition rate and nutrient release was smallest in the dry extremity of precipitation regime. The difference between N and P turnover times in the forest floor and in organic matter indicates that different nutrients control the ecosystem function across the precipitation gradient. The data from this study reveals a pattern of limitation shifting from P towards N with decreasing annual precipitation. I suggest that the long-term consequences of the expected decrease in precipitation in many tropical dry regions would changes N and P supply could have long-term negative effects on primary productivity and future carbon storage in TDFs.

Variations in soil carbon sequestration and their determinants along a precipitation gradient in seasonally dry tropical forest ecosystems.

The effect of precipitation regime on the C cycle of tropical forests is poorly understood, despite the existence of models that suggest a drier climate may substantially alter the source-sink function of these ecosystems. Along a precipitation regime gradient containing 12 mature seasonally dry tropical forests growing under otherwise similar conditions (similar annual temperature, rainfall seasonality, and geological substrate), we analyzed the influence of variation in annual precipitation (1240 to 642 mm) and duration of seasonal drought on soil C. We investigated litterfall, decomposition in the forest floor, and C storage in the mineral soil, and analyzed the dependence of these processes and pools on precipitation. Litterfall decreased slightly - about 10% - from stands with 1240 mm yr(-1) to those with 642 mm yr(-1), while the decomposition decreased by 56%. Reduced precipitation strongly affected C storage and basal respiration in the mineral soil. Higher soil C storage at the drier sites was also related to the higher chemical recalcitrance of litter (fine roots and forest floor) and the presence of charcoal across sites, suggesting an important indirect influence of climate on C sequestration. Basal respiration was controlled by the amount of recalcitrant organic matter in the mineral soil. We conclude that in these forest ecosystems, the long-term consequences of decreased precipitation would be an increase in organic layer and mineral soil C storage, mainly due to lower decomposition and higher chemical recalcitrance of organic matter, resulting from changes in litter composition and, likely also, wildfire patterns. This could turn these seasonally dry tropical forests into significant soil C sinks under the predicted longer drought periods if primary productivity is maintained.

Effects of precipitation regime and soil nitrogen on leaf traits in seasonally dry tropical forests of the Yucatan Peninsula, Mexico.

Leaf traits are closely associated with nutrient use by plants and can be utilized as a proxy for nutrient cycling processes. However, open questions remain, in particular regarding the variability of leaf traits within and across seasonally dry tropical forests. To address this, we considered six leaf traits (specific area, thickness, dry matter content, N content, P content and natural abundance (15)N) of four co-occurring tree species (two that are not associated with N2-fixing bacteria and two that are associated with N2-fixing bacteria) and net N mineralization rates and inorganic N concentrations along a precipitation gradient (537-1036 mm per year) in the Yucatan Peninsula, Mexico. Specifically we sought to test the hypothesis that leaf traits of dominant plant species shift along a precipitation gradient, but are affected by soil N cycling. Although variation among different species within each site explains some leaf trait variation, there is also a high level of variability across sites, suggesting that factors other than precipitation regime more strongly influence leaf traits. Principal component analyses indicated that across sites and tree species, covariation in leaf traits is an indicator of soil N availability. Patterns of natural abundance (15)N in foliage and foliage minus soil suggest that variation in precipitation regime drives a shift in plant N acquisition and the openness of the N cycle. Overall, our study shows that both plant species and site are important determinants of leaf traits, and that the leaf trait spectrum is correlated with soil N cycling.

The effects of precipitation regime on soil carbon pools on the Yucatan Peninsula

Abstract:The effects of precipitation regime on the size of soil carbon (C) pools were compared in mature tropical dry forests of the Yucatan Peninsula. Our study included three forest stands in each, a dry site (potential evapotranspiration ratio = 3.2 mm mm−1; mean annual precipitation = 537 mm), a wetter site (2.0 mm mm−1; 993 mm) and a site in which water was comparatively less limiting (1.3 mm mm−1; 1086 mm). At each site, soil C pools in dead fallen phytomass (includes leaves, flowers, fruits, small twigs and deadwood debris) deposited on the litter layer and in roots and organic matter of the mineral soil (from the upper 10 cm) were measured in samples collected during the dry season. A high proportion of the total C pool (93–95%) was in the top 10 cm of soil in all forest sites. The smallest C pool was in roots (1.8–2.4% of the total C), meanwhile the C in the litter layer represented 3–5% of the total pool. These patterns were observed irrespective of study site. However, distribution of C (i.e. wood debris vs. fine litter) varied across sites; the proportion of the forest-floor C pool in wood debris decreased from 80% in the driest site, to 51% and 42% in 993-mm and 1086-mm sites, respectively. Overall, we observed that three pools (wood debris, roots and soil organic C) provide evidence for the significant decrease in soil C storage with increase in mean annual precipitation in Yucatan Peninsula. A potential explanation for this unexpected pattern includes an increasing C turnover time with decreasing mean annual precipitation, resulting in higher C accumulation per unit of C input in the driest site.

Effect of precipitation regime on δD values of soil n-alkanes from elevation gradients – Implications for the study of paleo-elevation

We measured dD values of long chain n-alkanes isolated from 30 surface soil samples along two elevation transects on the Tibetan Plateau differing in precipitation regime and water source. The East Asian Monsoon precipitation dominates the wetter regime on the eastern slope (from 1230 to 4300 m) of Gongga Shan on the eastern Tibetan Plateau. Precipitation from the Polar Westerlies dominates the drier region on the slope from 1900 to 5000 m in the West Kunlun Shan on the northwestern Tibetan Plateau. The decrease in dD value with elevation in the wetter region greatly exceeded that in drier region by, � 1.9 ± 0.1‰/100 m and � 1.4 ± 1.0‰/100 m respectively. The apparent fractionation between leaf wax and precipitation ewax–p values in the wetter region (ca. � 164‰) were more negative than those in drier region (ca. � 125‰ above 3200 m). We also measured dD values in leaves of six common living trees (values from � 287‰ to � 193‰) from Gongga Shan, ranging from about 2900–4200 m. The abundance-weighted average values of the nalkanes (dDwax) show a strong reverse correlation with sample source elevation (R 2 0.78 for soils from 2 0.85 for soils from West Kunlun Shan above 3200 m), suggesting that n-alkane dDwax faithfully records the precipitation dD and that the isotopic altitude effect of precipitation controls dDwax altitudinal gradients in the mountains. The data show a fairly strong monotonic dependency of n-alkane dD values on elevation for the eastern Plateau, but a complex relationship between n-alkane dD values and elevation for the northwestern Plateau. The dDwax values at sites below 3200 m from the Kunlun Shan area exhibit an unexpected positive correlation with elevation. The study confirms the potential for using sediment dDwax values to reconstruct paleo-elevation in wetter regions, but suggests caution in applying the approach to dry regions. Our results also show it is essential to consider the intricacy of the pattern of atmospheric circulation and water sources and their influence on the lapse rate of dD values with elevation.