We investigated the spatial distribution, advanced regeneration and stand structure of five
Shorea robusta-dominated forests in 25 1-ha plots subject to disturbances of different intensities. We aim ...to elucidate the relationships of advanced regeneration and spatial patterns of the tree species with degree of disturbance magnitude. Sixty-seven tree species were recorded in the forest plots; 41 species were found in the least disturbed forests, while only 10 species were found in the heavily disturbed forests. We found 5320 trees with >1.5
cm diameter at breast height, in total, and found that moderately disturbed forests contained the highest advanced regeneration (sapling)/pole densities. No significant differences were observed in stem basal area among forests. The overall stand density changed quadratically across the disturbance gradient. A strong inverse relationship was found between the overall stand density and diameter class in the least disturbed and moderately disturbed forests. Ten species showed variation in their dispersion patterns across the disturbance gradient. Most of the socio-economically important tree species analyzed showed little or no regeneration in the least and most heavily disturbed forests. Individual species showed different responses to disturbance ranging from ‘tolerant’ (
Shorea robusta,
Lagerstroemia parviflora and
Symplocos spp
.) to ‘sensitive’ (
Trewia nudiflora,
Adina cardifolia and
Terminalia alata). We concluded that moderate disturbance intensity not only ensures high stand density, but also enhances the advanced regeneration of socio-economically important tree species and affects their dispersion patterns. Future management strategy must balance the consumptive needs of the local community with those of species conservation by allowing regulated access to the forests.
Hadronic reactions producing strange quarks such as exclusive or semi-inclusive kaon production, play an important role in studies of hadron structure and the dynamics that bind the most basic ...elements of nuclear physics. The small-angle capability of the new Super High Momentum Spectrometer (SHMS) in Hall C, coupled with its high momentum reach - up to the anticipated 11-GeV beam energy in Hall C - and coincidence capability with the well-understood High Momentum Spectrometer, will allow for probes of such hadron structure involving strangeness down to the smallest distance scales to date. To cleanly select the kaons, a threshold aerogel Cerenkov detector has been constructed for the SHMS. The detector consists of an aerogel tray followed by a diffusion box. Four trays for aerogel of nominal refractive indices of n=1.030, 1.020, 1.015 and 1.011 were constructed. The tray combination will allow for identification of kaons from 1 GeV/c up to 7.2 GeV/c, reaching 10-2 proton and 10-3 pion rejection, with kaon detection efficiency better than 95%. The diffusion box of the detector is equipped with 14 five-inch diameter photomultiplier tubes. Its interior walls are covered with Gore diffusive reflector, which is superior to the commonly used Millipore paper and improved the detector performance by 35%. The inner surface of the two aerogel trays with higher refractive index is covered with Millipore paper, however, those two trays with lower aerogel refractive index are again covered with Gore diffusive reflector for higher performance. The measured mean number of photoelectrons in saturation is ~12 for n=1.030, ~8 for n=1.020, ~10 for n=1.015, and ~5.5 for n=1.011. Here the design details, the results of component characterization, and initial performance tests and optimization of the detector are presented.
Hadronic reactions producing strange quarks such as the exclusive p(e,e′K+)Λ and p(e,e′K+)Σ0 reactions, or the semi-inclusive p(e,e′K+)X reaction, play an important role in studies of hadron ...structure and the dynamics that bind the most basic elements of nuclear physics. The small-angle capability of the new Super High Momentum Spectrometer (SHMS) in Hall C, coupled with its high momentum reach – up to the anticipated 11-GeV beam energy in Hall C – and coincidence capability with the well-understood High Momentum Spectrometer (HMS), will allow for probes of such hadron structure involving strangeness down to the smallest distance scales to date. To cleanly select the kaons, a threshold aerogel Cerenkov detector has been constructed for the SHMS. The detector consists of an aerogel tray followed by a diffusion box. Four trays for aerogel of nominal refractive indices of n=1.030, 1.020, 1.015 and 1.011 were constructed. The tray combination will allow for identification of kaons from 1GeV/c up to 7.2GeV/c, reaching ∼10−2 proton and 10−3 pion rejection, with kaon detection efficiency better than 95%. The diffusion box of the detector is equipped with 14 five-inch diameter photomultiplier tubes. Its interior walls are covered with Gore diffusive reflector, which is superior to the commonly used Millipore paper and improved the detector performance by 35%. The inner surface of the two aerogel trays with higher refractive index is covered with Millipore paper, however, those two trays with lower aerogel refractive index are again covered with Gore diffusive reflector for higher performance. The measured mean number of photoelectrons in saturation is ∼12 for n=1.030, ∼8 for n=1.020, ∼10 for n=1.015, and ∼5.5 for n=1.011. The design details, the results of component characterization, and initial performance tests and optimization of the detector are presented.
Aims
We aim to examine the canopy gap characteristics and evaluate their influence on regeneration, dominance and the early growth of woody species in seasonally dry Shorea robusta forests (Sal ...forests).
Methods
Sixty canopy gaps were surveyed in six randomly located transects belts in seasonally dry subtropical Sal forests of central Nepal. Each transect belt was followed until 10 gap sites were encountered. The equation for the area of an ellipse was used to calculate the size of canopy gap, measuring the longest axis and its perpendicular shorter axis. Number, sizes, ages and causes of tree falls creating canopy gaps along with number and sizes of border trees were identified and recorded. Detailed gap inventories were carried out using square 25-m2 quadrats placed in the middle of each gap. All individuals >2 m in height within the quadrat were identified at the species level and their diameter at breast height was measured. We assigned a nested 4-m2 quadrat to the corner of each 25-m2 quadrat, within which all woody individuals >10 cm tall were identified at the species level, and counted them and their regeneration mechanisms were identified. The height and collar diameter of the tallest individuals were measured. Descriptive statistics was calculated for the variables of interests and Pearson correlation, linear regression, independent-sample t-test and chi-square test were used to relate them and to test for their associations.
Important Findings
The study found mean gap size of 283 m2 and ∼50% gaps of 10-15 years old. Gaps created by natural single-tree falls were significantly more numerous, and their mean size was significantly smaller than those resulting from artificial causes or multiple-tree falls. Gap size correlated with the basal area of felled trees, but it did not correlate with the number of tree falls. While tree fall basal area was significantly positively correlated to the seed-originated seedling to resprout ratio, it was negatively correlated, along with gap area and the basal size of retained trees, to seedling growth. The relative seedling density of Terminalia alata increased with increases in gap areas, while that of S.robusta decreased with increases in tree fall basal area, thereby lowering the plot-level dominance. However, the relative seedling densities of Eugenia operculata and Syzigium cumini were negatively and positively correlated, respectively, with tree fall basal area.
Many have recognized community forestry as Nepal's most successful development initiative. It empowers communities not only to take responsibility for management of their forest resources, but also ...provides them with an economic base to lead local development efforts. For the past ten years, Nepal has been embroiled in a Maoist led insurgency that has limited official government access to many rural areas. This paper examines the impact of the insurgency on the community forestry programme, with special respect to the functioning of forestry user groups.
Note: Recent political events in Nepal have taken a positive turn. Future research will tell the complete story of the impact of the period on community forestry and on the resiliency of forest user groups.
1
We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q\(^2\)) up to 15.75~\gevsq. Combined with existing data, these provide an ...improved extraction of the proton magnetic form factor at high Q\(^2\) and double the range over which a longitudinal/transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q\(^2\) and attributed to hard two-photon exchange (TPE) effects, extending to 8~(GeV/c)\(^2\) the range of Q\(^2\) for which a discrepancy is established at \(>\)95\% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q\(^2\).
We report high-precision measurements of the Deeply Virtual Compton
Scattering (DVCS) cross section at high values of the Bjorken variable $x_B$.
DVCS is sensitive to the Generalized Parton ...Distributions of the nucleon, which
provide a three-dimensional description of its internal constituents. Using the
exact analytic expression of the DVCS cross section for all possible
polarization states of the initial and final electron and nucleon, and final
state photon, we present the first experimental extraction of all four
helicity-conserving Compton Form Factors (CFFs) of the nucleon as a function of
$x_B$, while systematically including helicity flip amplitudes. In particular,
the high accuracy of the present data demonstrates sensitivity to some very
poorly known CFFs.
Phys. Rev. Lett. 127, 152301 (2021) We report measurements of the exclusive neutral pion electroproduction cross
section off protons at large values of $x_B$ (0.36, 0.48 and 0.60) and $Q^2$
(3.1 to ...8.4 GeV$^2$) obtained from Jefferson Lab Hall A experiment E12-06-014.
The corresponding structure functions $d\sigma_L/dt+\epsilon d\sigma_T/dt$,
$d\sigma_{TT}/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{LT'}/dt$ are extracted as a
function of the proton momentum transfer $t-t_{min}$. The results suggest the
amplitude for transversely polarized virtual photons continues to dominate the
cross-section throughout this kinematic range. The data are well described by
calculations based on transversity Generalized Parton Distributions coupled to
a helicity flip Distribution Amplitude of the pion, thus providing a unique way
to probe the structure of the nucleon.
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