Picea Crassifolia Forest Research Articles

Correlating the Horizontal and Vertical Distribution of LiDAR Point Clouds with Components of Biomass in a Picea crassifolia Forest

Light detection and ranging (LiDAR) has been widely used to estimate forest biomass. In this study, we aim to further explore this capability by correlating horizontal and vertical distribution of LiDAR data with components of biomass in a Picea crassifolia forest. Airborne small footprint full-waveform data were decomposed to acquire higher density point clouds. We calculated LiDAR metrics at the tree level and subplot level and correlated them to biomass components, including branch biomass (BB), leaf biomass (LB) and above-ground biomass (AGB), respectively. A new metric (Horizcv) describing the horizontal distribution of point clouds was proposed. This metric was found to be highly correlated with canopy biomass (BB and LB) at the tree level and subplot level. Correlation between AGB and Horizcv at the subplot level is much lower than that at tree level. AGB for subplot is highly correlated with the mean height metric (Hmean), canopy cover index (CCI) and the product of them. On the other hand, the relationship between the vertical distribution of LiDAR point and biomass was explored by developing two types of vertical profiles, including LiDAR distribution profiles and a biomass profile. Good relationships were found between these two types of vertical profiles and assessed by Pearson’s correlation coefficient (R) and the area of overlap index (AOI). These good correlations possess potential in predicting the vertical distribution of canopy biomass. Overall, it is concluded that not only the vertical, but also the horizontal distribution of LiDAR points should be taken into account in estimating components of biomass by LiDAR.

A Modified Gash Model for Estimating Rainfall Interception Loss of Forest Using Remote Sensing Observations at Regional Scale

Rainfall interception loss of forest is an important component of water balance in a forested ecosystem. The Gash analytical model has been widely used to estimate the forest interception loss at field scale. In this study, we proposed a simple model to estimate rainfall interception loss of heterogeneous forest at regional scale with several reasonable assumptions using remote sensing observations. The model is a modified Gash analytical model using easily measured parameters of forest structure from satellite data and extends the original Gash model from point-scale to the regional scale. Preliminary results, using remote sensing data from Moderate Resolution Imaging Spectroradiometer (MODIS) products, field measured rainfall data, and meteorological data of the Automatic Weather Station (AWS) over a picea crassifolia forest in the upper reaches of the Heihe River Basin in northwestern China, showed reasonable accuracy in estimating rainfall interception loss at both the Dayekou experimental site (R2 = 0.91, RMSE = 0.34 mm∙d −1) and the Pailugou experimental site (R2 = 0.82, RMSE = 0.6 mm∙d −1), compared with ground measurements based on per unit area of forest. The interception loss map of the study area was shown to be strongly heterogeneous. The modified model has robust physics and is insensitive to the input parameters, according to the sensitivity analysis using numerical simulations. The modified model appears to be stable and easy to be applied for operational estimation of interception loss over large areas.

Spatial variability of canopy interception in a spruce forest of the semiarid mountain regions of China

Canopy interception has large spatial variability which complicates measurements and achievement of spatial representation. In the present study, we measured gross rainfall and throughfall from June 2011 to October 2012, and leaf area index (LAI), plant area index (PAI), and spatial locations of trees within Picea crassifolia forest in Qilian mountains of northwestern China. Spatial variability of canopy interception and related factors, and the minimum number and locations of collectors were analyzed by statistical techniques. The results show that spatial variation of canopy interception has a significant relationship with PAI, but not with LAI. This indicates that PAI is more appropriate parameters for a canopy interception model than LAI. Based on the relationship between canopy interception loss and PAI, the minimum number and locations of collectors were estimated. In this study, 10–12 collectors yielded representative throughfall in the forest, but these collectors required to be placed at the sites of mean values of PAI.

Effect of vegetation on soil water retention and storage in a semi-arid alpine forest catchment

The runoff generated from mountainous regions is recognized as the main water source for inland river basins in arid environments. Thus, the mechanisms by which catchments retain water in soils are to be understood. The water storage capacity of soil depends on its depth and capacity to retain water under gravitational drainage and evapotranspiration. The latter can be studied through soil water retention curve (SWRC), which is closely related to soil properties such as texture, bulk density, porosity, soil organic carbon content, and so on. The present study represented SWRCs using HYDRUS-1D. In the present study, we measured physical and hydraulic properties of soil samples collected from Sabina przewalskii forest (south-facing slope with highest solar radiation), shrubs (west-facing slope with medium radiation), and Picea crassifolia forest (north-facing slope with lowest radiation), and analyzed the differences in soil water storage capacity of these soil samples. Soil water content of those three vegetation covers were also measured to validate the soil water storage capacity and to analyze the relationship between soil organic matter content and soil water content. Statistical analysis showed that different vegetation covers could lead to different soil bulk densities and differences in soil water retention on the three slope aspects. Sand content, porosity, and organic carbon content of the P. crassifolia forest were relatively greater compared with those of the S. przewalskii forest and shrubs. However, silt content and soil bulk density were relatively smaller than those in the S. przewalskii forest and shrubs. In addition, there was a significant linear positive relationship between averaged soil water content and soil organic matter content (P<0.0001). However, this relationship is not significant in the P. crassifolia forest. As depicted in the SWRCs, the water storage capacity of the soil was 39.14% and 37.38% higher in the P. crassifolia forest than in the S. przewalskii forest and shrubs, respectively, at a similar soil depth.

Effect of forest on annual water yield in the mountains of an arid inland river basin: a case study in the Pailugou catchment on northwestern China's Qilian Mountains

AbstractThe effect of forests on annual water yield is an unresolved central issue in forest hydrology despite years of study. There has been a particular shortage of research in the mountains of arid inland river basins. In the present study, we examined the effects of forests on hydrology using data on precipitation, evaporation, canopy interception, transpiration, and runoff from 1994 to 2008 for the Pailugou catchment of northwestern China's Qilian Mountains. We modelled the water balance to assess the contribution of different vegetation types to annual water yield. In our study area, Picea crassifolia forest covered 38·5% of the catchment area, but contributed little to annual water yield. For an annual average precipitation of 407·1 mm (from 2003 to 2008) at an elevation of 2700 m, the runoff depth from the forest was 11·6 mm, accounting for only 3·5% of total annual water yield of the catchment. For an annual average precipitation of 374·1 mm (from 1994 to 2002), the runoff depth from the forest was − 14·3 mm (i.e. 5·9% of total annual water yield of the catchment was consumed to sustain tree growth). This has significant implications, because forests are increasingly being planted in the Qilian Mountains, and this may decrease the downstream water supply. Thus, the relationship between the forest and water yield must be better understood to permit the establishment of an appropriate regional level of forest cover. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Successional process of Picea crassifolia forest after logging disturbance in semiarid mountains: A case study in the Qilian Mountains, northwestern China

Selective logging is the most widely employed method of commercial timber production in Asia, and its impact on forest structure, composition, and regeneration dynamics is considerable. However, the successional processes in forest communities after logging in semiarid mountains are poorly understood. To provide more information on these processes, we used data from tree rings, direct and indirect age determinations, and field measurements of stand structure to reconstruct the historical disturbance regime, stand development patterns, and successional processes in a natural Picea crassifolia forest community in the Qilian Mountains of northwestern China. The results showed that the density of P. crassifolia forest increased significantly after logging. The densities of second growth forests 30 and 70 years after logging disturbance had increased to 2874% and 294% of primary forest's density, respectively. Logging disturbance did not alter tree species composition of logged stands. However, the diversity of understory species changed significantly among the successional phases. Logging disturbance decreased the spatial heterogeneity of second growth forest. The spatial distributions of recruitment were affected by the location of the remaining trees. There was less recruitment near the remaining trees than near forest that had been cut. In addition, logging disturbance also induced a growth release for the trees on the sites sampled. Our results imply that the succession and regeneration of P. crassifolia forest may be improved if the remaining trees could be retained relative uniform distribution pattern, thinning or selective logging could be performed to height density, exotic shrubs could be removed or the shrubs cover could be reduced during the earlier successional stages.

A realistic structure model for large-scale surface leaving radiance simulation of forest canopy and accuracy assessment

The radiosity-graphics model (RGM) is an important branch of computer simulation modelling for the vegetation bidirectional reflectance distribution function (BRDF). As the radiosity method is based on a global solving technique, the RGM can only deal with limited numbers of polygons, and has only been used for small-scale flat terrain scenes. However, the land surface is generally rugged, so it is necessary to extend the RGM to simulate the surface leaving radiance of the forest canopy at a large scale with complex topography. The methodology adopted in this paper is: (1) virtual forest scene generation combined with a digital elevation model; (2) scene division method, shadowing effect correction and multiple scattering calculation; (3) merging the simulated sub-scene bidirectional reflectance factors (BRFs) to get the whole-scene BRF. The paper compares this new method with other models by choosing a large-scale conifer forest scene with a GAUSS terrain from RAMI3 (http://rami-benchmark.jrc.it). Multi-angle imaging spectroradiometer (MISR) data are used to validate the extended RGM in a Picea crassifolia forest area at a satellite pixel scale in the field campaign in Gansu Province, China. The root mean square error and correlation coefficient between the simulated BRF and the MISR BRF are 0.018 and 0.98, respectively. The uncertainty and error sources of the large-scale RGM model are thoroughly analysed.

Surface pollen and its relationship to vegetation on the southern slope of the eastern Qilian Mountains

The objective of this study is to investigate pollen-vegetation relationship in the Qilian Mountains. The eastern Qilian Mountains are located in the transitional zone of the Tibetan Plateau, the Loess Plateau and the arid region of Northwest China, which is one of the key areas of global environmental change. A total of 13 surface pollen samples from main vegetation have been collected. Pollen percentages were calculated in all samples. In order to reveal the relationship between pollen composition and the vegetation types from which the soil samples have been collected, Detrended Correspondence Analysis (DCA) ordination method was employed on the pollen data. The results show that dominating vegetation types can be recognized by their pollen spectra: Picea crassifolia forest, alpine shrub and alpine meadow as well. Altitude and temperature determine the distribution of the surface pollen and the vegetation. The good agreement between modern vegetation and surface samples across this area provides a measure of the reliability of using pollen data to reconstruct paleoenvironment and paleovegetation patterns in this or other similar regions. However the loss of Betula pollen in forest needs further investigation. Pollen oxidation is the most important factor contributing to the damage of modern pollen in the study area. Pollen concentrations decrease with the increase of pH values of soils, and decrease sharply when the pH exceeds 7.6.

The Water Balance of Picea Crassifolia Forests in Qilian Mountains Based on Spatial Data Structure

The establishment of spatial data structure includes the relation between the system function and the data,the classification of data and the codes,the importation of the data and edit etc.This text researched the distribution and variety regulation of precipitation,interception,throughfall,stemflow runoff,evapotranspiration of Picea crassifolia in Qilian Mountains.The results indicated that the total precipitation was 433.5mm and the throughfall 287.37 mm;stemflow 0.294 mm,interception 145.83 mm,taking up to 66.29%,0.068% and 33.64% of the total precipitation respectively.and the runoff was 239.98 mm which took up to 55.36% Evapotranspiration.water storage in soil and that in litter were 156.54 mm、23.63 mm and 7.92 mm respectively.Taking up to 36.11%,5.45% and 1.83% of the precipitation respectively.

Hydrological Effects of Forest Landscape Patterns in the Qilian Mountains

Abstract The relationship between vegetation and water budgets in mountain catchments has been the subject of intense debate from an ecological as well as a hydrological point of view. In the present article, we evaluate forest landscape patterns and their hydrological effects on the Qilian Mountains of northwest China, using GIS and 15 years (1987 to 2001) of hydrological databases to illustrate the cases of 2 catchments, Dayekou (DYK) and Haichaoba (HCB). Landsat ETM+ remote sensing satellite data (1:50,000) taken in May 2001 and topographic maps (1:50,000) were used to produce the landscape maps. The results showed that the main landscape elements affecting hydrological processes were grassland and Picea crassifolia forest in the lower areas in DYK, while the main landscape elements affecting hydrological processes in the higher areas in HCB were shrub-land and barren land. Observations over many years indicate that the water retention capacity of Picea crassifolia forest makes it the best of all veget...

Simulation of energy and water balance in Soil-Vegetation-Atmosphere Transfer system in the mountain area of Heihe River Basin at Hexi Corridor of northwest China

In the mountain area of inland Heihe River Basin at Hexi Corridor of northwest China during the vegetation growing season from May to September, the Simultaneous Heat and Water (SHAW) model of Soil-Vegetation-Atmosphere Transfer (SVAT) system is applied to simulating and studying energy and water balance of the soil-residue-plant canopy layers in the Picea crassifolia forest and the grassland by the forest at the shaded slope and the grassland at the sun-facing slope. The simulation of energy balance indicates that net radiation of the grass-land at the sun-facing slope is more than that of the Picea crassifolia forest and the grassland by the forest at the shaded slope. The energy outgoing components are the first latent heat and next sensible heat from the grassland both at the shaded slope and the sun-facing slope, but those at the former are less. The energy outgoing components are the first sensible heat and next latent heat from the Picea crassifolia forest. The composition and distribution of energy in the soil-residue-plant canopy layers in the Picea crassifolia forest and the grassland by the forest at the shaded slope make the soil layer receive less energy, which therefore, especially the forest possesses the energy conditions for soil water conservation. The simulation of water balance indicates that the water loss of the grassland at the sun-facing slope is mainly caused by soil evaporation, while evapotranspiration of the Picea crassifolia forest and the grassland by the forest at the shaded slope is less than that of the grassland at the sun-facing slope. Half of the evapotranspiration of the Picea crassifolia forest and the grassland by the forest at the shaded slope is consumed by transpiration. After precipitation, the soil water storage is increased much more for the Picea crassifolia forest and also more for the grassland by the forest at the shaded slope. Therefore the shaded slope vegetation, especially the forest is favorable for soil water storage.