A Multi-Baseline PolInSAR Forest Height Inversion Method Taking into Account the Model Ill-posed Problem

Affected by the insufficient information of single baseline observation data,the three-stage method assumes the Ground-to-Volume Ratio(GVR)to be zero so as to invert the vegetation height.However,this assumption introduces much biases into the parameter estimates which greatly limits the accuracy of the vegetation height inversion.Multi-baseline observation can provide redundant information and is helpful for the inversion of GVR.Nevertheless,the similar model parameter values in a multi-baseline model often lead to ill-posed problems and reduce the inversion accuracy of conventional algorithm.To this end,we propose a new step-by-step inversion method applied to the multi-baseline observations.Firstly,an adjustment inversion model is constructed by using multi-baseline volume scattering dominant polarization data,and the regularized estimates of model parameters are obtained by regularization method.Then,the reliable estimates of GVR are determined by the MSE(mean square error)analysis of each regularized parameter estimation.Secondly,the estimated GVR is used to extracts the pure volume coherence,and then the vegetation height parameter is inverted from the pure volume coherence by least squares estimation.The experimental results show that the new method can improve the vegetation height inversion result effectively.The inversion accuracy is improved by 26%with respect to the three-stage method and the conventional solution of multi-baseline.All of these have demonstrated the feasibility and effectiveness of the new method.

Inversion of vegetation height from Pol In SAR using complex least squares adjustment method

In this paper, we propose the novel method of complex least squares adjustment （CLSA） to invert vegetation height accurately using single-baseline polarimetric synthetic aperture radar interferometry （PollnSAR） data. CLSA basically estimates both volume-only coherence and ground phase directly without assuming that the ground-to-volume amplitude radio of a particular polarization channel （e.g., HV） is less than -10 dB, as in the three-stage method. In addition, CLSA can effectively limit errors in interferometric complex coherence, which may translate directly into erroneous ground-phase and volume-only coherence estimations. The proposed CLSA method is validated with BioSAR2008 P-band E-SAR and L-band SIR-C PollnSAR data. Its results are then compared with those of the traditional three-stage method and with external data. It implies that the CLSA method is much more robust than the three-stage method.

Response of small rodents to manipulations of vegetation height in agro-ecosystems

Some small mammal populations require human interference to conserve rare or threatened species or to minimizeadverse effects in plant production. Without a thorough understanding about how small rodents behave in theirenvironment and consideration of how they react to management efforts, management will not be optimal. Socialbehavior, spatial and temporal activity patterns, predator avoidance and other behavioral responses can affect pestrodent management. Some of these behavioral patterns and their causes have been well studied. However, theirimpact on pest rodent management, especially for novel management approaches, is not always clear. Habitatmanipulation occurs necessarily through land use and intentionally to reduce shelter and food availability and toincrease predation pressure on rodents. Rodents often respond to decreased vegetation height with reducedmovements and increased risk sensitivity in their feeding behavior. This seems to result mainly from an elevatedperceived predation risk. Behavioral responses may lessen the efficacy of the management because the desiredeffects of predators might be mediated. It remains largely unknown to what extent such responses can compensateat the population level for the expected consequences of habitat manipulation and how population size and cropdamage are affected. It is advantageous to understand how target and non-target species react to habitatmanipulation to maximize the management effects by appropriate techniques, timing and spatial scale withoutcausing unwanted effects at the system level.

Acoustics in urban parks:Does the structure of narrow urban parks matter in designing a calmer urban landscape?

Urban parks can function as a proper sink of noise pollution.However,lack of universally-agreed upon methodologies and differing urban conditions have fueled controversy surrounding the effectuation of this urban park function around the world.Hence,to address this controversy in narrow urban parks(with a mean width of∼109 m)in Isfahan City,Central Iran,noise levels(Lq30)were measured along two longitudinal transects placed along the interior northern river-and adjacent to the southern edge of the parks bordered by a heavily-conjected road.We used statistical tests and models to determine the association of noise levels measured along the northern transect with the distance to,and the intensity of noise emitted from,the road,vegetation biomass,and vegetation height within two 50 and 100 m buffer rings drawn around northern sites and the richness of bird species.The average Lq30 values differed significantly between the southern(∼73.21 dB)and northern(∼66.43 dB)transects and correlated negatively with species richness(r(98)=−0.324,p<0.01).Three variables including mean NDVIwithin the 100 m buffer ring,distance from the road and mean Lq30 values of the nearest three southern sites were included to build the best predictive multiple-linear regression model through the step-wise procedure with r2 of 0.52.These findings suggest that further attempts aiming to alleviate the parks’interior noise level should be attentive to distance to road,traffic at the nearest road part,and the interior vegetation characteristics.

Characterization of ASTER GDEM elevation data over vegetated area compared with lidar data

Current researches based on areal or spaceborne stereo images with very high resolutions(<1 m)have demonstrated that it is possible to derive vegetation height from stereo images.The second version of the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM)is the state-of-the-art global elevation data-set developed by stereo images.However,the resolution of ASTER stereo images(15 m)is much coarser than areal stereo images,and the ASTER GDEM is compiled products from stereo images acquired over 10 years.The forest disturbances as well as forest growth are inevitable in 10 years time span.In this study,the features of ASTER GDEM over vegetated areas under both flat and mountainous conditions were investigated by comparisons with lidar data.The factors possibly affecting the extraction of vegetation canopy height considered include(1)co-registration of DEMs;(2)spatial resolution of digital elevation models(DEMs);(3)spatial vegetation structure;and(4)terrain slope.The results show that the accurate coregistration between ASTER GDEM and national elevation dataset(NED)is necessary over mountainous areas.The correlation between ASTER GDEM minus NED and vegetation canopy height is improved from 0.328 to 0.43 by degrading resolutions from 1 arc-second to 5 arc-second and further improved to 0.6 if only homogenous vegetated areas were considered.