Spatial heterogeneity of soil available medium- and micro-elements in evergreen-deciduous broadleaved forest in karst.

Understanding the spatial heterogeneity of soil available medium- and micro-elements in karst area can provide a valuable theoretical guideline for soil nutrient management of karst ecosystem. We collected soil samples at a soil depth of 0-10 cm using grid sampling (20 m×20 m) in a 25 hm (500 m×500 m) dynamic monitoring plot. We further analyzed the spatial variability of soil medium- and micro-elements and their drivers, with classic statistics analysis and geo-statistics analysis.

[Effects of tree mortality on the spatial patterns and interspecific associations of individuals in karst evergreen deciduous broad-leaved mixed forests].

Tree mortality is an important ecological process in forests. It is crucial to understand how tree mortality affects spatial patterns and interspecific associations for revealing the mechanisms of tree mortality and community dynamics. We employed the correlation method of spatial point pattern analysis to analyse the variations in spatial patterns and interspecific relations before and after mortality using data obtained from two surveys of a 25 hm plot in the Mulun National Natural Reserve, China.

[Changes of soil microbial biomass carbon, nitrogen, and enzyme activities in East Dongting Lake wetlands at different water levels].

We analyzed soil quality based on soil microbial characteristics of three different vegetation types in the wetlands of East Dongting Lake, including wetland (CTW), wetland (PAW), and wetland (SBW). The soil microbial biomass carbon (MBC), nitrogen (MBN) and enzyme activities were measured and the key influen-cing factors were analyzed during the normal, flood, and dry periods. The results showed that: 1) The amounts of MBC, MBN, and the activities of invertase and cellulase (except cellulase of dry season) in 0-10 cm were higher than those in 10-20 cm for all wetlands, while the catalase activity showed an opposite pattern.

[Biomass and morphological characteristics of fine roots and their affecting factors in diffe-rent vegetation restoration stages in depressions between karst hills].

This study focused on four vegetation restoration stages of grasslands, shrublands, secondary forests and primary forests in the typical karst peak-cluster depression. The soil core method was used to collect fine roots with 2 mm or less in diameter in three layers (0-10, 10-20, 20-30 cm). The biomass, morphological characteristics of fine roots and their relationship with soil properties were analyzed.

[Carbon storage and its allocation in karst forest at different stand ages in Guangxi, China].

Based on a survey of 45 plots (1000 m each) of five different stand ages, i.e., young, middle-aged, pre-mature, mature, and over-mature plantations in the main production area of karst forest in Guangxi, carbon (C) storage and its allocation in vegetation and soil were studied.

[Carbon storage and allocation in Cunninghamia lanceolata plantations with different stand ages.].

Based on survey of 45 plots (1000 m each) of five different stand ages, i.e., young, middle-aged, pre-mature, mature, and over-mature plantations, in the main production area of Cunninghamia lanceolata in the north of Guangxi, China, carbon (C) storage and its allocation in vegetation and soil were studied.

[Soil fertility characteristics under different land use patterns in depressions between karst hills].

Soil samples were collected from the depressions between karst hills by grid sampling method (5 m x 5 m), soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) in surface layer (0-20 cm) under different land use patterns (burning, cutting, cutting plus root removal, enclosure, maize plantation, and pasture plantation) were measured, the main factors of influencing the soil fertility was identified by principal component analysis (PCA), and the relationships between soil nutrients and microorganisms were demonstrated by canonical correlation analysis (CCA). The results showed that the soil was slightly alkaline (pH 7.83-7.

[Stoichiometric characteristics of plant and soil C, N and P in different forest types in depressions between karst hills, southwest China].

The stoichiometric properties of plant carbon (C), nitrogen (N) and phosphorus (P) and their relationships with soil were studied in six dominant plant communities in three forest types, i.e., plantation forest, secondary forest and primary forest in depressions between karst hills, southwest China.

[Characteristics of spatial variation of soil nutrients in sloping field in a gorge karst region, southwest China].

Based on a grid (20 m x 20 m) sampling, spatial heterogeneity and pattern of soil nutrients in sloping field in the gorge karst region, southwestern China, were explored by using classical statistics and geostatistics methods. The results showed that soil nutrient contents in slope field in the canyon karst region were more abundant, where pH value had a weak variation and the soil organic matter (SOM) had a moderate degree of variation. All the soil nutrients had moderate or strong variation with an order of available phosphorus (AP) > total potassium (TK) > SOM > alkaline nitrogen (AN) > total nitrogen (TN) > total phosphorus (TP) > available potassium (AK).

[Characteristics of soil microbial populations in depressions between karst hills under different land use patterns].

Based on the investigation and analysis of six soil microbial indices, eight soil conventional nutrient indices, six soil mineral nutrient indices, and 15 vegetation indices in the farmland, grassland, scrub, forest plantation, secondary forest, and primary forest in the depressions between karst hills, this paper analyzed the main soil microbial populations, soil microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) and their fractal characteristics, and the relationships of the soil microbes with vegetation, soil nutrients, and soil mineral components under different land use patterns. The soil microbial populations differed in their quantity and composition under different land use patterns. Primary forest and farmland had the highest quantity of soil microbial populations, while forest plantation had the lowest one.

[Profile distribution of soil aggregates organic carbon in primary forests in Karst cluster-peak depression region].

Soil profiles were collected from three primary forests (Itoa orientalis, Platycladus orientalis, and Radermachera sinica) in Karst cluster-peak depression region to study the composition of soil aggregates, their organic carbon contents, and the profile distribution of the organic carbon. In the three forests, >2 mm soil aggregates were dominant, occupying about 76% of the total. The content of soil total organic carbon ranged from 12.

[Compositional characteristics and roles of soil mineral substances in depressions between hills in karst region].

Based on the investigation and analysis of seven soil mineral substance variables, nine vegetation factors, four topographical factors, and ten soil physicochemical factors in the 200 m x 40 m dynamic monitoring plots in farmland, forest plantation, secondary forest, and primary forest in the depressions between hills in karst region, and by using traditional statistical analysis, principal component analysis (PCA), and canonical correlation analysis (CCA), this paper studied the compositional characteristics and roles of soil mineral substances as well as the coupling relationships between the mineral substances and the vegetation, topography, and other soil properties. In the depressions, soil mineral substances were mainly composed of SiO2, Al2O3, K2O, and Fe2O3, whose contents were obviously lower than the mean background values of the soils in the world and in the zonal red soils at the same latitudes. The soil CaO and MgO contents were at medium level, while the soil MnO content was very low.

[Spatial heterogeneity of soil nutrients in Karst area's Mulun National Nature Reserve].

Soil samples were collected from the depression (200 m x 100 m) in Karst area's Mulun National Nature Reserve by grid sampling method (20 m x 20 m), with the spatial heterogeneity of soil nutrients analyzed by the methods of classic statistics and geo-statistics. The soil pH showed small variation, while the soil nutrients showed moderate variation, being in the order of available phosphorus (AP) > available potassium (AK) > available nitrogen (AN) > organic matter (OM) > total potassium (TK) > total phosphorus (TP) > total nitrogen (TN). Spherical model fitted best for soil pH, exponential model fitted best for soil TK and AK, and Gaussian model fitted best for other variables.

[Spatial heterogeneity of soil organic matter and its response to disturbance in karst peak cluster depressions].

By using geostatistic methods, this paper studied the spatial variation and distribution of soil organic matter as well as its ecological processes and related mechanisms in four typical disturbed areas (cropland, man-made forest, secondary forest, and primary forest) of karst peak cluster depressions in northwest Guangxi of China. Eighty soil samples (0-20 cm) were collected from an aligned grid of 10 m x 10 m for the analysis of soil organic matter. The soil organic matter content increased significantly (P < 0.

[A spatial heterogeneity of surface soil moisture content in dry season in Mulun National Natural Reserve in Karst area].

By the methods of classical statistics and geostatistics, the spatial heterogeneity of surface soil (0-5 cm and 5-10 cm layers) moisture content in dry season in the typical sloping fields and depressions in Mulun National Natural Reserve in Karst area were studied. The results indicated that in study area, the surface soil moisture content in dry season was still higher, and showed a fine semivariogram structure as a whole. The spatial distribution of moisture content in 0-5 cm and 5-10 cm soil layers, both for sloping fields and for depressions, fitted exponential model well.