[Variation of stem radius of Larix principis-rupprechtii and its influencing factors in the semi-humid Liupan Mountains, China]. / å ­ç›˜å±±åŠæ¹¿æ¶¦åŒºåŽåŒ—è½å¶æ¾æ ‘å¹²åŠå¾„å˜åŒ–ç‰¹å¾åŠå ¶å½±å“å› ç´ .

We measured stem radius of Larix principis-rupprechtii at the semi-humid Liupan Mountains using the automatic band dendrometer over the growing season in 2016. We examined the diurnal and seasonal variations of stem radius, determined the main stem growth period, and analyzed the response of stem radius to environmental factors during the main stem growth period. The aim was to accurately understand the effects of short-term environmental variation on tree growth. The results showed that stem radius had a clear diurnal variation, with the phases of daytime shrin-kage, nighttime recovery, and increment. The seasonal variation of stem radius could be divided into three distinct stages, including stem relatively stable, stem continuous increasing, and stem swell-shrinking fluctuation. Under the meteorological, soil moisture and topographic conditions of 2016, main stem growth period of L. principis-rupprechtii started from 14th May and ended on the 31th July, with the maximum radius growth rate occurred on 8th June. The environmental factors influencing the daily radius shrinkage at different phases (shrinkage phase, daily, cycle) were gene-rally the same, including temperature (including the air and soil temperature), solar radiation intensity, saturation vapor pressure deficit and soil water content. Temperature had the highest contribution (50.3%-71.0%). However, the influencing factors of daily radius increment varied at different phases. Precipitation (with a contribution of 86.9%) and maximum air temperature (13.1%) were the influencing factors at the radius increment phase. Precipitation (50.3%), saturation vapor pressure deficit (29.9%), relative humidity (12.7%) and solar radiation intensity (7.1%) were the factors at stem cycle. Precipitation and solar radiation intensity were the factors at diurnal scale. Radius increment was more sensitive to environmental variation at the time of stem cycle than that at diurnal scale.

Highly conductive, stretchable, and breathable epidermal electrode based on hierarchically interactive nano-network.

Stretchable electrodes have a crucial impact on the development of flexible electronic systems. Most conventionally blended nanocomposite electrodes are incapable of achieving high stretchability, breathability, or durability. In this work, a highly conductive, breathable, and stretchable epidermal electrode (SEE) is demonstrated by designing a hierarchically interactive nano-network that is composed of elastic polymer nano-fibers and multi-level silver nano-wires (AgNWs). The elastic polymer nano-fibers act as a continuous scaffold, and multi-level AgNWs embedded in the nano-fibers form branched conductive pathways. This structure enables high conductivity of the SEE at 4800 S cm-1 (at a significantly low AgNW content of 1.59 vt%), with high stretchability and excellent durability. For example, the SEE remained conductive even at a high strain of 500%, and it also maintained its initial resistance even after 30 000 cycles of strain at 50% or being washed with water for 100 000 cycles. The SEE was prepared by a facile in situ nonequilibrium fabrication process, and can easily be produced into an elastic circuit on a large scale, which provides a foundation for integrated and multifunctional electronic skins. The SEE possesses superior mechanical conformability and permeability of gas and liquid, and therefore, it was successfully applied in measuring electrocardiogram signals and thermal therapy, and exhibited highly robust and comfortable performances even while being washed with water or undergoing complex deformations.

[Evapotranspiration characteristics of artificial and natural forests in Liupan Mountains of Ningxia, China during growth season].

In order to understand the effects of the structure of forest ecosystem on the hydrological processes, a comparative study by using thermal dissipation technique and hydrological methodology was made on the evapotranspiration (ET) and its components of Larix principis-rupprechtii plantation and Pinus armandi natural forest in two adjacent stands in a small catchment Xiangshuihe of Liupan Mountains during the growth season (May-October) in 2009. Throughout the growth season, the total ET from the plantation was 518.2 mm, which accounted for 104.6% of the precipitation and was much higher than that (420.5 mm) of the natural forest. The allocation of ET in the vertical layers performed similarly between the two stands, with the order of canopy layer > herb and soil layer > shrub layer, but the ratio of each component to total ET differed significantly. The plantation consumed 0.2 and 0.9 times more water for canopy interception (19.6 mm per month) and tree transpiration (25.2 mm per month) than the natural forest, respectively. However, the transpiration from the plantation was 4.4 mm per month, and took up 23.4% of the natural forest. In contrast, the sum of soil evaporation and herbage evapotranspiration consumed 37.1 mm water per month in the plantation, which was 0.8 times higher than that in the natural forest. The ET was calculated by Penman-Monteith equation to compare the results estimated by sap flow measurements, and the values estimated by the two methods were similar.

[Relationships between soil moisture and needle-fall in Masson pine forests in acid rain region of Chongqing, Southwest China].

From March 2009 to November 2011, an investigation was conducted on the spatiotemporal variation of soil moisture and its effects on the needle-fall in Masson pine (Pinus massoniana) forests in acid rain region of Chongqing, Southeast China, with the corresponding soil moisture thresholds determined. No matter the annual precipitation was abundant, normal or less than average, the seasonal variation of soil moisture in the forests could be obviously divided into four periods, i.e., sufficient (before May), descending (from June to July), drought (from August to September), and recovering (from October to November). With increasing soil depth, the soil moisture content increased after an initial decrease, but the difference of the soil moisture content among different soil layers decreased with decreasing annual precipitation. The amount of monthly needle-fall in the forests in growth season was significantly correlated with the water storage in root zone (0-60 cm soil layer), especially in the main root zone (20-50 cm soil layer). Soil field capacity (or capillary porosity) and 82% of field capacity (or 80% of capillary porosity) were the main soil moisture thresholds affecting the litter-fall. It was suggested that in acid rain region, Masson pine forest was easily to suffer from water deficit stress, especially in dry-summer period. The water deficit stress, together with already existed acid rain stress, would further threaten the health of the Masson forest.

[Canopy interception characteristics of main vegetation types in Liupan Mountains of China].

Based on field observation and modeling analysis, this paper studied the canopy interception, interception capacity, and some parameters for interception modeling of main forest types in Liupan Mountains of China. For the test main forest types, the ratio of their canopy interception to precipitation ranged from 8.59% to 17.94%, throughfall was more than 80%, and stemflow ranged from 0.23% to 3.10%. The canopy interception capacity was 0.78-1.88 mm, among which, leaf interception capacity was 0.62-1.63 mm, and stem interception capacity was 0.13-0.29 mm. Conifer forest had a higher canopy interception capacity than broad-leaved forest. The modified model considering the change of leaf area index, which was used in this paper, had a higher simulating precision than the interception model used before. The simulation results for Betula albo-sinensis forest, Pinus armandii forest, Prunus shrub, and Quercus liaotungensis-Tilia paucicostata forest were good, but those for Quercus liaotungensis forest, Pinus tabulaeformis forest, and Acer tetramerum and Euonymus sanguineus shrub were bad, which might be related to the differences in canopy structure, leaf area index, and precipitation characteristics.

[Growth process of Larix principis-rupprechtii stands with different density on south slope of Liupan Mountains].

By the method of sample trees stem analysis, this paper studied the growth process and diameter structure of 21-year-old Larix principis-rupprechtii plantations with the densities of 1200, 1500, and 2000 stems x hm(-2) in the head-water area on the southern slope of Liupan Mountain in Ningxia Hui Autonomous Region. The results showed that there were no significant differences in the growth status of L. principis-rupprechtii stands among the three densities when the stand age was less than 10 years. However, obvious differences were observed in the diameter and timber volume of individual trees and in the stand volume when the stand age was more than 10 years. The tree growth status in low-density stand was apparently better than that in medium- and high-density stands, but the height growth had no significant difference among the three densities. There was a significant difference in the skewness coefficient (Sk) of diameter distribution among the stands with different density, being higher (Sk = 0.338) in high-density stand than in medium-density stand (Sk = 0.072) and low-density stand (Sk = 0.015). The diameter distribution in high-density stand deviated from normal distribution, with a zenith tending to left, while that in medium- and low-density stands approached a normal distribution, with a more reasonable density structure. The kurtosis coefficient (K = 1.691) of medium-density stand was higher than that of high-density stand (K = 1.532) and low-density stand (K = 0.665), indicating a lower degree of polarization of tree growth in medium-density stand than in other two stands. The reasonable remaining density of 21-year-old L. principis-rupprechtii plantations was suggested to be 1200 stems x hm(-2).

[Soil macropore characteristics under typical vegetations in Liupan Mountains].

The radius and density of soil macropores under eight typical vegetations in Liupan Mountains of Northwest China were studied by using water breakthrough curves and Poiseuille equation. The results indicated that the radii of soil macropores ranged from 0.4 mm to 2.3 mm, and the weighted mean radii ranged from 0.57 mm to 1.21 mm, with a mean of 0.89 mm. The density of soil macropores ranged from 57 individuals per dm2 to 1 117 individuals per dm2, with a mean of 408 individuals per dm2. The macropores with radii bigger than 1.4 mm had a lower density, accounting for only 6.86% of the total. The area proportion of soil macropores ranged from 0.76% to 31.26%, with a mean of 10.82%. In study area, the density of soil macropores was higher in broadleaf forest than in coniferous forest, but basically the same in sub-alpine meadow and in broadleaf forest, as well as in shrubs and in coniferous forest. As for the area proportion of soil macropores, it was also higher in broadleaf forest than in coniferous forest, but basically the same in shrubs and in broadleaf forest soil, as well as in sub-alpine meadow and in coniferous forest.