Response of Understory Tree Seedling Populations to Spatiotemporal Variation in Soil Moisture

2003 ◽  
pp. 227-254
Author(s):  
Michael A. Huston ◽  
Milena Holmgren ◽  
Michelle B. Kreh
Keyword(s):  
Soil Moisture ◽  
Spatiotemporal Variation ◽  
Tree Seedling ◽  
Understory Tree

scholarly journals Spatiotemporal Variation of the Burned Area and Its Relationship with Climatic Factors in Central Kazakhstan

2021 ◽  
Vol 13 (2) ◽  
pp. 313
Author(s):  
Yongfang Xu ◽  
Zhaohui Lin ◽  
Chenglai Wu
Keyword(s):  
Soil Moisture ◽  
Relative Humidity ◽  
Central Asia ◽  
Climatic Factors ◽  
Spatiotemporal Variation ◽  
Lower Atmosphere ◽  
Burned Area ◽  
Circulation Index ◽  
Precipitation Anomalies ◽  
The Relationship

Central Asia is prone to wildfires, but the relationship between wildfires and climatic factors in this area is still not clear. In this study, the spatiotemporal variation in wildfire activities across Central Asia during 1997–2016 in terms of the burned area (BA) was investigated with Global Fire Emission Database version 4s (GFED4s). The relationship between BA and climatic factors in the region was also analyzed. The results reveal that more than 90% of the BA across Central Asia is located in Kazakhstan. The peak BA occurs from June to September, and remarkable interannual variation in wildfire activities occurs in western central Kazakhstan (WCKZ). At the interannual scale, the BA is negatively correlated with precipitation (correlation coefficient r = −0.66), soil moisture (r = −0.68), and relative humidity (r = −0.65), while it is positively correlated with the frequency of hot days (r = 0.37) during the burning season (from June to September). Composite analysis suggests that the years in which the BA is higher are generally associated with positive geopotential height anomalies at 500 hPa over the WCKZ region, which lead to the strengthening of the downdraft at 500 hPa and the weakening of westerlies at 850 hPa over the region. The weakened westerlies suppress the transport of water vapor from the Atlantic Ocean to the WCKZ region, resulting in decreased precipitation, soil moisture, and relative humidity in the lower atmosphere over the WCKZ region; these conditions promote an increase in BA throughout the region. Moreover, the westerly circulation index is positively correlated (r = 0.53) with precipitation anomalies and negatively correlated (r = −0.37) with BA anomalies in the WCKZ region during the burning season, which further underscores that wildfires associated with atmospheric circulation systems are becoming an increasingly important component of the relationship between climate and wildfire.

Vegetation Control and Soil Moisture Depletion Related to Herbicide Treatments on Forest Plantations in Northeastern Oregon

2018 ◽  
Vol 32 (4) ◽  
pp. 461-474 ◽  
Author(s):  
Elizabeth Cole ◽  
Amanda Lindsay ◽  
Michael Newton ◽  
John D. Bailey
Keyword(s):  
Soil Moisture ◽  
First Year ◽  
Forest Plantations ◽  
Vegetative Cover ◽  
Tree Seedling ◽  
Vegetation Control ◽  
Herbicide Treatments ◽  
Inland Northwest ◽  
Comparable Control ◽  
Second Year

AbstractReforestation in the Inland Northwest, including northeastern Oregon, USA, is often limited by a dry climate and soil moisture availability during the summer months. Reduction of competing vegetative cover in forest plantations is a common method for retaining available soil moisture. Several spring and summer site preparation (applied prior to planting) herbicide treatments were evaluated to determine their efficacy in reducing competing cover, thus retaining soil moisture, on three sites in northeastern Oregon. Results varied by site, year, and season of application. In general, sulfometuron (0.14 kg ai ha–1 alone and in various mixtures), imazapyr (0.42 ae kg ha–1), and hexazinone (1.68 kg ai ha–1) resulted in 3 to 17% cover of forbs and grasses in the first-year when applied in spring. Sulfometuron+glyphosate (2.2 kg ha–1) consistently reduced grasses and forbs for the first year when applied in summer, but forbs recovered in the second year on two of three sites. Aminopyralid (0.12 kg ae ha–1)+sulfometuron applied in summer also led to comparable control of forb cover. In the second year after treatment, forb cover in treated plots was similar to levels in nontreated plots, and some species of forbs had increased relative to nontreated plots. Imazapyr (0.21 and 0.42 kg ha–1) at either rate, spring or summer 2007, or at lower rate (0.14 kg ha–1) with glyphosate in summer, provided the best control of shrubs, of which snowberry was the dominant species. Total vegetative cover was similar across all treatments seven and eight years after application, and differences in vegetation were related to site rather than treatment. In the first year after treatment, rates of soil moisture depletion in the 0- to 23-cm depth were correlated with vegetative cover, particularly late season soil moisture, suggesting increased water availability for tree seedling growth.

Spatiotemporal variation of soil moisture in Northern China based on climate change initiative data

2020 ◽  
Author(s):  
X. L. YAO ◽  
Q. JIANG ◽  
Y. LIU ◽  
L. Y. LI ◽  
Q. Y. WANG ◽  
...  
Keyword(s):  
Climate Change ◽  
Soil Moisture ◽  
Northern China ◽  
Spatiotemporal Variation ◽  
Change Initiative

Spatiotemporal variation of soil moisture under different land use types in a typical karst hill region

2014 ◽  
Vol 34 (18) ◽  
Author(s):  
徐慧芳 XU Huifang ◽  
宋同清 SONG Tongqing ◽  
黄国勤 HUANG Guoqin ◽  
彭晚霞 PENG Wanxia ◽  
曾馥平 ZENG Fuping ◽  
...  
Keyword(s):  
Land Use ◽  
Soil Moisture ◽  
Spatiotemporal Variation ◽  
Hill Region ◽  
Land Use Types

Wildfire-contingent effects of fuel treatments can promote ecological resilience in seasonally dry conifer forests

2014 ◽  
Vol 44 (8) ◽  
pp. 843-854 ◽  
Author(s):  
Jens T. Stevens ◽  
Hugh D. Safford ◽  
Andrew M. Latimer
Keyword(s):  
Soil Moisture ◽  
Forest Restoration ◽  
Strong Support ◽  
Ecological Resilience ◽  
Tree Cover ◽  
Ecological Change ◽  
Conifer Forests ◽  
Tree Seedling ◽  
Fuel Treatments ◽  
Seasonally Dry

Fire suppression has made many seasonally dry conifer forests more susceptible to high-severity wildfires, which cause large changes in forest structure and function. In response, management agencies are applying fuel reduction treatments to millions of acres of forest, with the goal of moderating fire behavior by reducing tree density and understory fuel loads. However, despite their wide application, we still lack basic information about the extent to which these treatments contribute to forest restoration by increasing forest resilience to recurring wildfire events. To address this question, we established 664 plots across 12 different sites in California, USA, where wildfire burned through fuel treatments, and measured a suite of forest characteristics relating to overstory structure, understory cover, and woody plant regeneration. We tested a “wildfire-contingency” hypothesis that there should be strong interactions between treatment and fire, specifically that the direction and magnitude of fuel treatment effects on forest characteristics will depend on subsequent disturbance. This interaction hypothesis had strong support, driven largely by effects on trees: without wildfire, live-tree cover was lower in treated stands than in untreated stands, but after wildfire, it was higher in treated stands than in untreated stands. Treated stands had higher soil moisture and more shrub seedlings than untreated stands without wildfire but had greater soil moisture and fewer shrub seedlings than untreated stands after wildfire. Conversely, litter depth, litter cover, and tree seedling abundance were lower in treated stands than in untreated stands without wildfire but higher in treated stands than in untreated stands after wildfire. Ordination revealed that the magnitude of ecological change attributable to wildfire is lower in treated stands than in untreated stands. We conclude that properly implemented treatments can promote resilience to both first-entry and subsequent wildfires.

Study on Spatiotemporal Variation of Soil Moisture in China in the Past 71 Years

2021 ◽  
Author(s):  
Mengqing Geng ◽  
Mengyuan Zang ◽  
Feng Zhang ◽  
Qiulan Wu ◽  
Yong Liang
Keyword(s):  
Soil Moisture ◽  
Spatiotemporal Variation ◽  
The Past

Phenology and ecophysiology of Aesculus sylvatica, a vernal understory tree

1989 ◽  
Vol 67 (7) ◽  
pp. 2161-2167 ◽  
Author(s):  
Claude W. DePamphilis ◽  
Howard S. Neufeld
Keyword(s):  
Soil Moisture ◽  
Environmental Changes ◽  
Stomatal Closure ◽  
Woody Species ◽  
Moisture Stress ◽  
Leaf Nitrogen ◽  
Daily Maximum ◽  
Canopy Closure ◽  
Spring Ephemeral ◽  
Understory Tree

Aesculus sylvatica, the Georgia buckeye, is a deciduous, understory tree of oak–hickory forests in the southeastern United States. It is the first woody species to produce leaves (mid-March) and the first to lose its leaves (beginning in June, complete by 1 September). Fruit maturation, however, continues through the season and dehiscence occurs in mid-September. To investigate this unusual phenology, environmental changes and ecophysiological responses of a population in Georgia were followed through one season. Light levels declined from 74% of full sun in March to around 4% after canopy closure in May. At that time, leaves began to senesce, as indicated by discoloration and declining levels of chlorophyll a and leaf nitrogen. Senescing leaves were often colonized by powdery mildew and (or) aphids, but these were not the primary cause of leaf death. Drought effects, such as midday wilting or stomatal closure were not observed, but daily maximum leaf conductances were correlated with soil moisture at 0–10 cm. Prior to canopy closure, maximum conductances were reached at PAR levels of 500 μmol m−2 s−1, while afterwards they occurred at 30 μmol m−2 s−1. Visibly senescent leaves had much lower conductances than healthy leaves. While seasonal soil moisture stress may affect the timing of leaf senescence, it does not seem to be the primary physiological trigger mechanism. Aesculus sylvatica appears to be a woody analog of shade-intolerant spring ephemeral herbs.

Stability of wooded patches in a South African nutrient-poor grassland: do nutrients, fire or herbivores limit their expansion?

2007 ◽  
Vol 23 (5) ◽  
pp. 529-537 ◽  
Author(s):  
Anja A. Mourik ◽  
Frank van Langevelde ◽  
Esther van Tellingen ◽  
Ignas M. A. Heitkönig ◽  
Ian Gaigher
Keyword(s):  
Soil Moisture ◽  
South African ◽  
Nutrient Availability ◽  
Negative Impact ◽  
Nutrient Concentrations ◽  
Tree Seedlings ◽  
Tree Seedling ◽  
Tree Recruitment ◽  
Islands Of Fertility ◽  
Patch Boundary

Patches of wooded vegetation in nutrient-poor grassland characteristically contain high soil moisture and nutrient availability compared with surrounding grassland. These ‘islands of fertility’ appear stable in size, suggesting that tree recruitment at the patch boundary is limited. We hypothesize that tree establishment in adjacent grassland is limited by (1) competition for resources, (2) fire or (3) herbivory. In a South African grassland, we measured moisture availability and conducted a bioassay experiment to analyse whether soil nutrient limits tree recruitment at the patch boundary. We thus measured nutrient concentrations of maize plants grown in patch, boundary and grassland soil. To investigate whether browsing or fire affected tree seedlings at the patch boundary, we burned plots including patches, and used fences to exclude browsers. Neither soil moisture nor nutrient availability at the boundary differed from inside the patches, suggesting that tree recruitment at the boundary is not resource limited. Both fire and browsing combined caused a significantly lower tree seedling growth at the patch boundary, suggesting that these two factors can impede tree recruitment. The balance between positive feedback mechanisms facilitating tree recruitment, and the negative impact of fire and browsing can explain the apparent stability of these islands of fertility.

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