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Aims Soil spatial heterogeneity is an important factor partitioning environmental niches and facilitating species coexistence, especially in tropical rainforests. However, fine-scale spatial variability of soil macronutrients and its causative factors are not well understood. We investigate this fine-scale variability and how it relates to environmental factors. Methods We conducted intensive soil sampling (361 samples) in a 1 ha plot in a tropical rainforest in Southwest China to investigate patterns of spatial heterogeneity in soil acidity and macronutrients and explored how the soil properties were influenced by topography and litterfall using a scale-wise wavelet analysis. Results Topography showed great variability at larger scales (>25 m) compared to litterfall properties, which peaked at about 25 m. Soil pH showed variation at large scales and was significantly correlated with topography, whereas soil total nitrogen, ammonium nitrogen, available phosphorus, and potassium showed variation at finer scales and were significantly correlated with litterfall chemical fluxes. A dominant species of canopy tree was non-randomly distributed in high litterfall input sites. Conclusions This study shows that fine-scale spatial variability of soil macronutrients is strongly influenced by litterfall chemical fluxes, highlighting the importance of biotic factors for understanding fine-scale patterns of soil heterogeneity in tropical rainforests.

Aim: Geographical, climatic and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. The aim of this study was to: (1) characterize patterns of beta diversity in global drylands; (2) detect common environmental drivers of beta diversity; and (3) test for thresholds in environmental conditions driving potential shifts in plant species composition. Location: Global. Methods: Beta diversity was quantified in 224 dryland plant communities from 22 geographical regions on all continents except Antarctica using four complementary measures: the percentage of singletons (species occurring at only one site); Whittaker's beta diversity, β(W); a directional beta diversity metric based on the correlation in species occurrences among spatially contiguous sites, β(R²); and a multivariate abundance-based metric, β(MV). We used linear modelling to quantify the relationships between these metrics of beta diversity and geographical, climatic and soil variables. Results: Soil fertility and variability in temperature and rainfall, and to a lesser extent latitude, were the most important environmental predictors of beta diversity. Metrics related to species identity [percentage of singletons and β (W)] were most sensitive to soil fertility, whereas those metrics related to environmental gradients and abundance [(β(R²) and β(MV)] were more associated with climate variability. Interactions among soil variables, climatic factors and plant cover were not important determinants of beta diversity. Sites receiving less than 178 mm of annual rainfall differed sharply in species composition from more mesic sites (> 200 mm). Main conclusions: Soil fertility and variability in temperature and rainfall are the most important environmental predictors of variation in plant beta diversity in global drylands. Our results suggest that those sites annually receiving c. 178 mm of rainfall will be especially sensitive to future climate changes. These findings may help to define appropriate conservation strategies for mitigating effects of climate change on dryland vegetation.

AIMS: Spatial aggregation of soil chemical properties, or nutrient patches, may be generated by topography and plants and can seasonally fluctuate because of climate. Whether nutrient patches maintain consistency (no change in ranking through sequential sampling), through temporal scales, and whether topography and litterfall contribute to the persistence of such ranking is rarely tested. METHODS: In a 1-ha tropical rainforest plot in Southwest China, we measured soil pH, total N, NH₄–N, NO₃–N, and available P and K for four times and assessed the patch structure (patterns of patch distribution) and their temporal consistency. We then tested how structure and consistency of chemical soil properties were affected by topography and chemical inputs from litterfall. RESULTS: All soil chemical properties showed significant seasonal fluctuations, but patch consistency was higher for soil pH, total N, and available P and K compared to NH₄–N or NO₃–N. Topography influenced pH patch consistency while annual litterfall input was important for maintaining patch consistency in total N and available P and K. CONCLUSIONS: Fine-scale consistency of patches in soil pH, total N, and available P and K suggest they may exert stable selection pressures on species for niche differentiation, while consistency of soil NH₄–N and NO₃–N require further study.

The link between environmental heterogeneity and diversity is a major tenet of plant ecology. Previous studies designed to test the heterogeneity–diversity hypothesis largely have only included measures characterizing the overall variation in habitat (e.g., CV of soil parameters). Rarely has the spatial structure of that variation been considered in relation to diversity. Here we examined the spatial variability (CV) and spatial structure of that variation (i.e. spatial scale of patchiness) of several main soil variables (C, N, P, pH, and conductivity) in relation to grassland plant species richness and diversity ( H ′). We determined the relationships of plant species richness and diversity at two spatial scales (50 × 50 m plot scale, 1 × 1 m quadrat scale) with the whole-plot soil heterogeneity within an ~750 ha natural area of Kerqin grasslands in northeastern China. We found that the best models describing species richness at the 0.25 ha and 1 m 2 scales included patch size of soil conductivity and N, respectively. For each of the two spatial scales, pairs of models best described H ′; a simple regression with CV of soil N and a multiple regression including soil N patch size and CV at the 0.25 ha scale, and, at the 1 m 2 scale, a simple regression with soil conductivity CV and multiple regression including CV and patch size of soil N. Soil N was negatively associated with conductivity, likely due to sodium, the primary determinant of conductivity in this meadow steppe system, inhibiting plant growth and the capacity of soils to accumulate N. Consequently our results indicated that the heterogeneity of soil N was the principal control of plant species richness and H ′. Moreover, our findings indicate that spatial structure (the average size of a patch), in addition to CV, was important in determining grassland species richness and diversity. Our results indicate that both components of environmental heterogeneity need to be included in future tests of the heterogeneity–diversity hypothesis.

Tiger nut ( Cyperus esculentus L.) is an oil crop with high potential value. This crop has been popularized in the western region of Inner Mongolia, China, in recent years. Currently, tiger nut is planted and managed in the same manner as local traditional crops. Identifying whether traditional crop management is suitable for tiger nut growth and tuber production in arid areas is critical. The spatial relationship between tiger nuts and soil nutrients in the stolon tillering period and the period before tuber maturation was studied based on the integration of geostatistics, point pattern analysis, and spatial comparison (IGPS) method at three different plant row spacings (30 cm, 40 cm, and 50 cm). High organic matter content aggregation occurred in nontypical patches at 30 cm row spacings after tuber expansion. High total nitrogen content significantly aggregated around tiger nuts in nontypical patches. Some row spacings did not exhibit a spatial correlation between tiger nuts and high total phosphorus content. Among the three row spacings, the 30 cm row spacing produced the most biomass, but there was no significant difference in biomass between 40 and 50 cm. A 30 cm row spacing tends to have production effects; a 50 cm row spacing has weak soil nutrient heterogeneity; and a 40 cm row spacing has no obvious advantages. Tiger nut has a significant response to high nitrogen content. Precise management can be adopted based on this response to produce tubers or pastures.

The fine-scale (1 hm super(2)) spatial heterogeneity of the soil physical properties in a primary tropical montane rainforest of Jianfengling, Hainan Island was investigated with geostatistics. The results demonstrated that: (1) the exponential, Gaussian and spherical models separately well fitted the soil data at different layers. The ranges of all the soil physical properties and the ratios of nugget versus sill at the different layers ranged from 10.810 to 48.650 m and 10.2%-87.8%, respectively. The soil porosity and water retention had a large nugget effect in a smaller scale (< 10 m), indicating a strong spatial autocorrelation; (2) Both the ordinary Krige analysis and contour maps showed that there were several remarkable patches of all soil physical properties in the sample area. The spatial patterns of all the soil physical property at different sample depths were concordance with each other to a certain extent; (3) It was identified that the topography was a principal factor resulting the spatial pat

In temperate forests, disturbance by uprooting of trees is a key process in maintaining species richness and diversity. Nevertheless, very little is known about the changing role and abundance of earthworm communities in different windthrow microsites. The aim of the study was to find (i) whether single-tree uprooting causes significant changes in earthworm biomass and species composition and (ii) which changes in chemical and physical soil properties can be related to it. Twelve single-tree gap sites in an Ulmo-Fraxinetum aceretosum were selected, six sites locally dominated by beech ( Fagus sylvatica) and six by poplar ( Populus x euramericana). At each site, 7 microsites were sampled for soil chemical and soil physical properties: undisturbed soil beneath closed canopy, undisturbed soil beneath the gap in the canopy layer, the outer side of the pit, the inner side of the pit, the soil fallen from the mound into and away from the pit, and the mound itself. At six sites also earthworms were collected. The impact of microsite on earthworm biomass and species diversity was more important than the impact of tree species. A significant decrease in earthworm biomass and species number was detected from closed canopy over gaps to zones with soil disturbance and finally to windthrow mounds which never contained earthworms. The most pronounced reaction was the negative impact of uprooting on endogeic biomass. Epigeic biomass or species number of any ecological group changed more moderately. Six years after uprooting, microsites with direct soil disturbance were still adverse for earthworms though some – epigeic – species could profit from the absence of competitive species. It is concluded that in temperate lowland forests, the early uprooting phases induce changes in earthworm communities due to changes in soil physical parameters and food availability.

Soil biological response to management is best evaluated in field-scale experiments within the context of the soil environment and crop; however, cost-effective methods are lacking to relate these data which span multiple spatial scales. We hypothesized that zones of apparent electrical conductivity (ECa) could be used to integrate soil properties (sampling-site scale), microbial-scale measures of vesicular-arbuscular mycorrhizal (VAM) fungi, and field-scale wheat yields from yield maps. An on-farm dryland experiment (~250 ha) was established wherein two (~32-ha) fields were assigned to each phase of a winter wheat (Triticum aestivum L.) - corn (Zea mays L.) - proso millet (Panicum miliaceum L.) - fallow rotation. Each field was mapped and classified into four zones (ranges) of ECa. Soil samples were collected from geo-referenced sites within ECa zones and analyzed for multiple soil properties associated with productivity (0-7.5 and/or 0-30 cm). Additionally, VAM fungi were assessed using C16:1(cis)11 fatty acid methyl ester biomarker (C16vam), glomalin immunoassay, and wet-aggregate stability (WAS) techniques (1-2mm aggregates from 0- to 7.5-cm soil samples). Concentrations of C16vam and WAS increased among cropping treatments as: fallow < wheat < corn < millet. Glomalin across crops and replicates, C16vam and WAS in fallow (crop effect removed), soil properties associated with productivity, and wheat yields were negatively correlated with ECa and different among ECa zones (P < = 0.05). Zones of ECa provide a point of reference for relating data collected at different scales. Monitoring cropping system parameters and profitability, over time, may allow linkage of microbial-scale processes to farm-scale economic and ecological outcomes.

Inspired by previous studies that have indicated consistent or even well-constrained (relatively low variability) relations among carbon (C), nitrogen (N) and phosphorus (P) in soils, we have endeavored to explore general soil C:N:P ratios in China on a national scale, as well as the changing patterns of these ratios with soil depth, developmental stages and climate; we also attempted to determine if well-constrained C: N:P stoichiometrical ratios exist in China's soil. Based on an inventory data set of 2,384 soil profiles, our analysis indicated that the mean C:N, C:P and N:P ratios for the entire soil depth (as deep as 250 cm for some soil profiles) in China were 11.9, 61 and 5.2, respectively, showing a C: N: P ratio of ~ 60: 5:1. C:N ratios showed relatively small variation among different climatic zones, soil orders, soil depth and weathering stages, while C:P and N:P ratios showed a high spatial heterogeneity and large variations in different climatic zones, soil orders, soil depth and weathering stages. No well-constrained C:N:P ratios were found for the entire soil depth in China. However, for the 0-10 cm organic-rich soil, which has the most active organism-environment interaction, we found a well-constrained C:N ratio (14.4, molar ratio) and relatively consistent C:P (136) and N: P (9.3) ratios, with a general C:N:P ratio of 134:9:1. Finally, we suggested that soil C:N, C:P and N:P ratios in organic-rich topsoil could be a good indicator of soil nutrient status during soil development.