scholarly journals Changes in Long-Term Light Properties of a Mixed Conifer—Broadleaf Forest in Southwestern Europe

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1485
Author(s):  
Ignacio Ruiz de la Cuesta ◽  
Juan A. Blanco ◽  
J. Bosco Imbert ◽  
Javier Peralta ◽  
Javier Rodríguez-Pérez
Keyword(s):  
Species Richness ◽  
Forest Canopy ◽  
Mixed Forest ◽  
Canopy Cover ◽  
Anthropogenic Factors ◽  
Canopy Openness ◽  
Area Index ◽  
Sampling Points ◽  
The Relationship

Natural and anthropogenic factors affect forest structure worldwide, primarily affecting forest canopy and its light properties. However, not only stand-replacing events modify canopy structure, but disturbances of lower intensity can also have important ecological implications. To study such effects, we analyzed long-term changes in light properties of a conifer–broadleaf mixed forest in the Southwestern Pyrenees, placed in the fringe between the Mediterranean and Eurosiberian biogeographical regions. At this site, a thinning trial with different intensities (0%, 20%, and 30–40% basal area removed) took place in 1999 and 2009, windstorms affected some plots in 2009 and droughts were recurrent during the sampling period (2003, 2005, 2011). We monitored light properties during 14 years (2005–2019) with hemispherical photographs. We applied partial autocorrelation functions to determine if changes between years could be attributed to internal canopy changes or to external disturbances. In addition, we mapped the broadleaf canopy in 2003, 2008, and 2016 to calculate broadleaf canopy cover and richness at the sampling points with different buffer areas of increasing surface. We applied generalized linear mixed models to evaluate the effects of light variables on canopy richness and cover. We found that light variables had the most important changes during the period 2008 to 2010, reacting to the changes caused that year by the combined effects of wind and forest management. In addition, we found that an area of 4.0 m radius around the sampling points was the best to explain the relationship between light properties and species richness, whereas a radius of 1.0 m was enough to estimate the relationship between light and canopy cover. In addition, light-related variables such as diffuse light and leaf area index were related to species richness, whereas structural variables such as canopy openness were related to canopy cover. In summary, our study demonstrates that non stand-replacing disturbances such as windstorms, thinning, or droughts can have an important role in modifying structural and light-related canopy properties, which in turn may influence natural processes of stand development and ecological succession.

scholarly journals Growth and clorophyll content dynamics of winter wheat (Triticum aestivum L.) in different cropyear

2013 ◽  
pp. 101-105
Author(s):  
Enikő Vári
Keyword(s):  
Winter Wheat ◽  
Grain Filling ◽  
Triticum Aestivum L ◽  
Area Index ◽  
Rotation System ◽  
Crop Rotation System ◽  
Two Parameters ◽  
The University ◽  
The Relationship

The experiments were carried out at the Látókép experimental station of the University of Debrecen on chernozem soil in a long term winter wheat experiment in the season of 2011 and 2012 in triculture (pea-wheat-maize) and biculture (wheat-maize) at three fertilisation levels (control, N50+P35K40, N150+P105K120). Two different cropyears were compared (2011 and 2012). The research focused on the effects of forecrop and fertilisation on the Leaf Area Index, SPAD values and the amount of yield in two different cropyears. We wanted to find out how the examined parameters were affected by the cropyear and what the relationship was between these two parameters and the changes of the amount of yield. Examining the effects of growing doses of fertilizers applied, results showed that yields increased significantly in both rotations until the N150+PK level in 2011 and 2012. By comparing the two years, results show that in 2011 there was a greater difference in yields between the rotations (7742 kg ha-1 at N150+PK in the biculture and 9830 kg ha-1 at N150+PK in the triculture). Though wheat yields following peas were greater in 2012, results equalized later on at N150+PK levels (8109–8203 kg ha-1). Due to the favorable agrotechnical factors, the leaf and the effects of the treatments grown to a great extent in 2011, while in 2012 the differences between treatments were moderate. Until the N150+PK level, nitrogen fertilisation had a notable effect on the maximum amount of SPAD values (59.1 in the case of the biculture and 54.0 in the triculture). The highest SPAD values were measured at the end of May (during the time of flowering and grain filling) in the biculture. In the triculture, showed high SPAD values from the beginning. The same tendency could be observed in the 2012 cropyear, although increasing doses of fertilizers resulted in higher SPAD values until N150+PK level only from the second measurement. Maximum SPAD values were reached at the end of May in both crop rotation system

The effects of glyphosate and triclopyr on common bryophytes and lichens in northwestern Ontario

1999 ◽  
Vol 29 (7) ◽  
pp. 1101-1111 ◽  
Author(s):  
Steven G Newmaster ◽  
F Wayne Bell ◽  
Dale H Vitt
Keyword(s):  
Species Richness ◽  
Community Dynamics ◽  
Herbicide Application ◽  
Northwestern Ontario ◽  
Application Rates ◽  
Open Forest ◽  
Randomized Design ◽  
Completely Randomized Design ◽  
The Relationship

The effects of two silvicultural herbicides (Vision®, Release®) on bryophytes and lichens were studied in a harvested boreal mixedwood ecosystem. A completely randomized design with 115 plots of 1 m2 allowed direct comparison between herbicides and their effects on community dynamics. Regression models were used to analyze the relationship between herbicide application rates (0.71-6.72 kg active ingredient/ha) and changes in bryophyte and lichen abundance and species richness for 2 years following herbicide application. Results showed that bryophyte and lichen abundance and species richness decreased after herbicide treatments. In general, herbicide applications reduced the diversity of forest mesophytes and weedy colonizers to an ecosystem with only a few species of colonizers. A combination of clustering techniques and ANOVA were used to divide bryophytes and lichens into three ecologically defined response groups: herbicide-tolerant colonizers, semi tolerant long-term stayers from dry open forest, and sensitive forest mesophytes.

scholarly journals Mosaics of canopy openness induced by tropical cyclones in lowland rain forests with contrasting management histories in northeastern Australia

2000 ◽  
Vol 16 (6) ◽  
pp. 883-894 ◽  
Author(s):  
SIMON J. GROVE ◽  
STEPHEN M. TURTON ◽  
DANNY T. SIEGENTHALER
Keyword(s):  
Forest Management ◽  
Forest Canopy ◽  
Canopy Openness ◽  
Old Growth ◽  
Lowland Rain Forest ◽  
Forest Sites ◽  
Local Topography ◽  
Marked Points ◽  
Impacted Site

Tropical Cyclone ‘Rona’ crossed the coast of the Daintree lowlands of northeastern Australia in 1999. This study reports on its impact on forest canopy openness at six lowland rain forest sites with contrasting management histories (old-growth, selectively logged and regrowth). Percentage canopy openness was calculated from individual hemispherical photographs taken from marked points below the forest canopy at nine plots per site 3–4 mo before the cyclone, and at the same points a month afterwards. Before the cyclone, when nine sites were visited, canopy openness in old-growth and logged sites was similar, but significantly higher in regrowth forest. After the cyclone, all six revisited sites showed an increase in canopy openness, but the increase was very patchy amongst plots and sites and varied from insignificant to severe. The most severely impacted site was an old-growth one, the least impacted a logged one. Although proneness to impact was apparently related to forest management history (old-growth being the most impacted), underlying local topography may have had an equally strong influence in this case. It was concluded that the likelihood of severe impact may be determined at the landscape-scale by the interaction of anthropogenic with meteorological, physiographic and biotic factors. In the long term, such interactions may caution against pursuing forest management in cyclone-prone areas.

scholarly journals Evaluation of hemispherical photos extracted from smartphone spherical panorama images to estimate canopy structure and forest light environment

2020 ◽  
Author(s):  
A. Z. Andis Arietta
Keyword(s):  
Image Quality ◽  
Forest Canopy ◽  
Dynamic Range ◽  
Canopy Structure ◽  
High Dynamic Range ◽  
Canopy Openness ◽  
Traditional Methods ◽  
Area Index ◽  
Site Factor ◽  
High Dynamic

AbstractHemispherical photography (HP) is one of the most commonly employed methods to estimate forest canopy structure and understory light environments. Traditional methods require expensive, specialized equipment, are tedious to deploy, and are sensitive to exposure settings. In contrast, modern smartphone cameras are readily available and make use of ever-improving software to produce images with high dynamic range and clarity, but lack suitable hemispherical lenses. Thus, despite the fact that almost all ecologists and foresters carry a high-powered, image processing device in our pockets, we have yet to fully employ it for the purpose of data collection. As an alternative, hemispherical images can be extracted from spherical panoramas produced by many smartphone camera applications. I compared hemispherical photos captured with a digital single lens reflex camera and 180° lens to those extracted from smartphone spherical panoramas (SSP) for 72 sites representing a range of canopy types and densities. I estimated common canopy and light measures (canopy openness, leaf area index, and global site factor) as well as image quality measures (total gap area, number of gaps, and relative gap size) to compare methods. The SSP HP method leverages built-in features of current generation smartphones including exposure metering over restricted field-of-view, high dynamic range tonal correction, computational sharpening, high pixel density, and automatic leveling via the phone’s built-in gyroscope to yield an accurate alternative to traditional HP in canopy estimation. Although the process of stitching together multiple photos occasionally produces artifacts in the SSP HP images, estimates of canopy openness and global site factor are highly correlated with those of traditional methods (R2> 0.9) and are comparable to under- or over-exposing traditional HP by 1-1.5 stops. In addition to superior image quality, SSP HP requires no additional equipment or exposure settings and is likely to prove more robust to uneven lighting conditions by avoiding wide-angles lenses and exploiting HDR images.

scholarly journals Phenological patterns of defoliation and refoliation processes of rubber tree clones in the Colombian northwest

2020 ◽  
Vol 73 (3) ◽  
pp. 9293-9303
Author(s):  
Juan José Guerra-Hincapié ◽  
Óscar De Jesús Córdoba-Gaona ◽  
Juan Pablo Gil-Restrepo ◽  
Danilo Augusto Monsalve-García ◽  
Juan David Hernández-Arredondo ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Management Strategies ◽  
Rubber Tree ◽  
Principal Component ◽  
Canopy Openness ◽  
Area Index ◽  
The Relationship ◽  
Climatic Characteristic

The knowledge of the defoliation-refoliation process in rubber cultivation allows the development of management strategies in the production system to improve rubber yield. The objective of this study was to determine the intensity and duration of defoliation-refoliation of rubber clones FX 3864, IAN 710 and IAN 873 in the municipality of Tarazá and the FX 3864 and IAN 873 clones in the municipality of Nechí (northwestern Colombia). From October 2015 to June 2016, the measurements of the necromass were carried out in each location for each clone. The light environment was quantified, employing the hemispheric photographs technique to estimate canopy openness percentage (CO) and leaf area index. The assessed weeks were grouped by Principal Component Analysis (PCA) based on the original phenology and climatic variables. The defoliation-refoliation process was analyzed descriptively using graphical representations of the trend for the phenological variables that best described this process. The relationship between climatic and phenological variables in the period evaluated was evidenced; the rainfall was the most critical climatic characteristic in the induction of the defoliation process. The leaf area index was reduced to a minimum value in February, with values of 0.52 for IAN 710 clone in Tarazá, and 0.64 for the IAN 873 clone in Nechí, which corresponded to the highest defoliation stage in both locations. The refoliation period was short (4 to 6 weeks) and occurred during the dry season for all the clones in both places.

scholarly journals Tracking the long-term structure changes of a mature deciduous broadleaf forest stand using digital hemispherical photography

2019 ◽  
Vol 70 (1) ◽  
pp. 80-87
Author(s):  
Mait Lang ◽  
Jan Pisek
Keyword(s):  
Term Structure ◽  
Forest Canopy ◽  
Forest Growth ◽  
Repeated Measurements ◽  
Hemispherical Photography ◽  
Area Index ◽  
Plant Area Index ◽  
Plant Area ◽  
Understory Trees

Abstract Hemispherical photography provides permanent records of forest canopy structure. We analysed digital hemispherical images taken during the period of 2007–2018 in a mature silver birch stand located in Järvselja, Estonia. The stand was thinned in 2004. Understory trees were removed in the spring of 2018. Images were processed using the LinearRatioSC method. Effective plant area index Leff during the leafless phenophase increased as a result of tree growth from 0.92 to 1.24 and understory cutting was not detectable. During the full foliage condition Leff increased from 3.6 in 2008 to 5.8 in 2017. After removal of understory trees from the stand Leff decreased, and repeated measurements in the summer of 2018 estimated the plant area index range 4.5 < Leff < 4.8. The results are in agreement with the expected changes following forest growth and demonstrate that LinearRatioSC is a suitable method for the estimation and long-term monitoring of forest canopy properties from digital hemispherical images.

The Dynamics of tropical forest ecosystem with special reference to gap dynamics, regeneration and succession

2021 ◽  
Vol 03 (01) ◽  
pp. 114-120
Author(s):  
A. R. R. Menon
Keyword(s):  
Tropical Forest ◽  
Forest Ecosystem ◽  
Forest Canopy ◽  
Canopy Cover ◽  
Long Span ◽  
Long Time ◽  
Biodiversity Change ◽  
Profile Changes ◽  
Tropical Forest Ecosystem

The ecosystem stability in forests is highly dependent on ecological efficiency of species to the changed habitat. Thus, in forest ecosystems, the biodiversity change, interruption of migration patches, changes in soil profile, changes in habitat and watershed, and changes in wildlife status etc are the major impacts of climate change. The forest canopy is not homogenous and dense canopy cover is often interspaced with openings, where tree saplings along with shrubby vegetation co-exist. The species in the openings or fewer dens region determining the forest structure for a very long time because of the long span of tree maturity phase, sometimes centuries. New species seedlings occupy the canopy openings, most of them are light demanding, and establish the community at the risk of shade loving species present under dense canopy region. This building phase of forest is the most important part of the life cycle. The survival of seedlings and transformation to the sapling stage can be more complex due to long-term environmental factors. The regeneration dynamics of the tropical forest ecosystem is poorly understood. The details are discussed in the paper.

scholarly journals Exploring Spatiotemporal Pattern of Grassland Cover in Western China from 1661 to 1996

2019 ◽  
Vol 16 (17) ◽  
pp. 3160 ◽  
Author(s):  
Yang ◽  
He ◽  
Li ◽  
Li
Keyword(s):  
Land Cover ◽  
Agricultural Development ◽  
Sharp Decrease ◽  
Western China ◽  
Anthropogenic Factors ◽  
Spatiotemporal Pattern ◽  
The Qing Dynasty ◽  
Development Policies ◽  
The Relationship

Historical grassland cover change is vital for global and regional environmental change modeling; however, in China, estimates of this are rare, and therefore, we propose a method to reconstruct grassland cover over the past 300 years. By synthesizing remote sensing-derived Chinese land use and land cover change (LULCC) data (1980–2015) and potential natural vegetation data simulated by the relationship between vegetation and environment, we first determined the potential extent of natural grassland vegetation (PENG) in the absence of human activities. Then we reconstructed grassland cover across western China between 1661 and 1996 at 10 km resolution by overlaying the Chinese historical cropland dataset (CHCD) over the PENG. As this land cover type has been significantly influenced by anthropogenic factors, the data show that the proportion of grassland in western China continuously decreased from 304.84 × 106 ha in 1661 to 277.69 × 106 ha in 1996. This reduction can be divided into four phases, comprising a rapid decrease between 1661 and 1724, a slow decrease between 1724 and 1873, a sharp decrease between 1873 and 1980, and a gradual increase since 1980. These reductions correspond to annual loss rates of 7.32 × 104 ha, 2.90 × 104 ha, 17.04 × 104 ha, and −2.37 × 104 ha, respectively. The data reconstructed here show that the decrease in grassland area between 1661 and 1724 was mainly limited to the Gan-Ning region (Gansu and Ningxia) and was driven by the early agricultural development policies of the Qing Dynasty. Grassland was extensively cultivated in northeastern China (Heilongjiang, Jilin, and Liaoning) and in the Xinjiang region between 1724 and 1980, a process which resulted from an exponential increase in immigrants to these provinces. The reconstruction results enable provide crucial data that can be used for modeling long-term climate change and carbon emissions.

scholarly journals Comparison of GF2 and SPOT6 Imagery on Canopy Cover Estimating in Northern Subtropics Forest in China

Forests ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 407
Author(s):  
Jingjing Zhou ◽  
Yuanyong Dian ◽  
Xiong Wang ◽  
Chonghuai Yao ◽  
Yongfeng Jian ◽  
...  
Keyword(s):  
Ensemble Learning ◽  
Spatial Resolution ◽  
Forest Canopy ◽  
High Spatial Resolution ◽  
Mixed Forest ◽  
Canopy Cover ◽  
Learning Model ◽  
Gradient Boosting ◽  
Learning Models ◽  
Adaptive Boosting

Canopy cover is an important vegetation attribute used for many environmental applications such as defining management objectives, thinning and ecological modeling. However, the estimation of canopy cover from high spatial resolution imagery is still a difficult task due to limited spectral information and the heterogeneous pixel values of the same canopy. In this paper, we compared the capacity of two high spatial resolution sensors (SPOT6 and GF2) using three ensemble learning models (Adaptive Boosting (AdaBoost), Gradient Boosting (GDBoost), and random forest (RF)), to estimate canopy cover (CC) in a Chinese northern subtropics forest. Canopy cover across 97 plots was measured across 41 needle forest plots, 24 broadleaf forest plots, and 32 mixed forest plots. Results showed that (1) the textural features performed more importantly than spectral variables according to the number of variables in the top ten predictors in estimating canopy cover (CC) in both SPOT6 and GF2. Moreover, the vegetation indices in spectral variables had a lower relative importance value than the band reflectance variables. (2) GF2 imagery outperformed SPOT6 imagery in estimating CC when using the ensemble learning model in our data. On average across the models, the R2 was almost 0.08 higher for GF2 over SPOT6. Likewise, the average RMSE and average MAE were 0.002 and 0.01 lower in GF2 than in SPOT6. (3) The ensemble learning model showed good results in estimating CC, yet the different models performed a little differently in the results. Additionally, the GDBoost model performed the best of all the ensemble learning models with R2 = 0.92, root mean square error (RMSE) = 0.001 and mean absolute error (MAE) = 0.022.

scholarly journals Estimating Interception from Near-Surface Soil Moisture Response

2019 ◽  
Author(s):  
Subodh Acharya ◽  
Daniel McLaughlin ◽  
David Kaplan ◽  
Matthew J. Cohen
Keyword(s):  
Soil Moisture ◽  
Forest Canopy ◽  
Surface Soil ◽  
Forest Type ◽  
Mixed Forest ◽  
Surface Soil Moisture ◽  
Empirical Estimation ◽  
Potential Cost ◽  
Area Index ◽  
Near Surface

Abstract. Interception is the storage and subsequent evaporation of rainfall by above-ground structures, including canopy and groundcover vegetation and surface litter. Accurately quantifying interception is critical for understanding how ecosystems partition incoming precipitation, but it is difficult and costly to measure, leading most studies to rely on modeled interception estimates. Moreover, forest interception estimates typically focus only on canopy storage, despite the potential for substantial interception by groundcover vegetation and surface litter. In this study, we developed an approach to quantify total interception losses (i.e., including forest canopy, understory, and surface litter layers) using measurements of shallow soil moisture dynamics during rainfall events. Across 36 pine and mixed forest stands in Florida (USA), we used soil moisture and rainfall data to estimate the interception storage capacity (βs), a parameter required to estimate total annual interception losses (Ia) relative to rainfall (R). Estimated values for βs (mean βs = 0.30 cm; 0.01 ≤ βs ≤ 0.62 cm) and Ia/R (mean Ia/R = 0.14; 0.06 ≤ Ia/R ≤ 0.21) were consistent with reported literature values for these ecosystems and were significantly predicted by forest structural attributes (leaf area index and percent groundcover), as well as other site variables (e.g., water table depth). The best-fit model was dominated by LAI and explained nearly 80 % of observed βs variation. These results suggest that whole-forest interception can be measured using a single near-surface soil moisture time series and highlight the variability in interception losses across a single forest type, underscoring the need for expanded empirical measurement. Potential cost savings and logistical advantages of this method relative to conventional, labor-intensive interception measurements may improve empirical estimation of this critical water budget element.

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