scholarly journals Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

2015 ◽  
Vol 12 (1) ◽  
pp. 51-92 ◽  
Author(s):  
M. Moreno-de las Heras ◽  
R. Diaz-Sierra ◽  
L. Turnbull ◽  
J. Wainwright
Keyword(s):  
Primary Production ◽  
Vegetation Change ◽  
Chihuahuan Desert ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Larrea Tridentata ◽  
Shrub Encroachment ◽  
Grass Species ◽  
Natural Habitats ◽  
Herbaceous Vegetation

Abstract. Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. A classic case of vegetation change is the shrub-encroachment process that has been taking place over the last 150 years in the Chihuahuan Desert, where large areas of grasslands dominated by perennial grass species (black grama, Bouteloua eriopoda, and blue grama, B. gracilis) have transitioned to shrublands dominated by woody species (creosotebush, Larrea tridentata, and mesquite, Prosopis glandulosa), accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including exogenous triggering factors such as precipitation variations and land-use change, and endogenous amplifying mechanisms brought about by soil erosion-vegetation feedbacks. In this study, simulations of plant biomass dynamics with a simple modelling framework indicate that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant growth and water-use patterns, and therefore shrub encroachment may be reflected in the analysis of landscape-scale vegetation–rainfall relationships. We analyze the structure and dynamics of vegetation at an 18 km2 grassland-shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000–2013) records of medium-resolution remote sensing of vegetation greenness (MODIS NDVI) and precipitation. Spatial evaluation of NDVI-rainfall relationship at the studied ecotone indicates that herbaceous vegetation shows quick growth pulses associated with short-term (previous 2 months) precipitation, while shrubs show a slow response to medium-term (previous 5 months) precipitation. We use these relationships to (a) classify landscape types as a function of the spatial distribution of dominant vegetation, and to (b) decompose the NDVI signal into partial primary production components for herbaceous vegetation and shrubs across the study site. We further apply remote-sensed annual net primary production (ANPP) estimations and landscape type classification to explore the influence of inter-annual variations in seasonal precipitation on the production of herbaceous and shrub vegetation. Our results suggest that changes in the amount and temporal pattern of precipitation comprising reductions in monsoonal summer rainfall and/or increases in winter precipitation may enhance the shrub-encroachment process in desert grasslands of the American Southwest.

scholarly journals Assessing vegetation structure and ANPP dynamics in a grassland–shrubland Chihuahuan ecotone using NDVI–rainfall relationships

2015 ◽  
Vol 12 (10) ◽  
pp. 2907-2925 ◽  
Author(s):  
M. Moreno-de las Heras ◽  
R. Díaz-Sierra ◽  
L. Turnbull ◽  
J. Wainwright
Keyword(s):  
Plant Growth ◽  
Vegetation Change ◽  
Chihuahuan Desert ◽  
Net Primary Production ◽  
Summer Rainfall ◽  
Remotely Sensed ◽  
Shrub Encroachment ◽  
Grass Species ◽  
Natural Habitats ◽  
Herbaceous Vegetation

Abstract. Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. In the Chihuahuan Desert, large areas of grasslands dominated by perennial grass species have transitioned over the last 150 years to shrublands dominated by woody species, accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including precipitation variations, land-use change, and soil erosion–vegetation feedbacks. In this study, using a simple ecohydrological modelling framework, we show that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant-growth and water-use patterns. Therefore, shrub encroachment may be reflected in the analysis of landscape-scale vegetation–rainfall relationships. We analyse the structure and dynamics of vegetation at an 18 km2 grassland–shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000–2013) records of remotely sensed vegetation greenness (MODIS NDVI) and antecedent rainfall. NDVI–rainfall relationships show a high sensitivity to spatial variations on dominant vegetation types across the grassland–shrubland ecotone, and provide biophysical criteria to (a) classify landscape types as a function of the spatial distribution of dominant vegetation and to (b) decompose the NDVI signal into partial components of annual net primary production (ANPP) for herbaceous vegetation and shrubs. Analysis of remotely sensed ANPP dynamics across the study site indicates that plant growth for herbaceous vegetation is particularly synchronized with monsoonal summer rainfall. For shrubs, ANPP is better explained by winter plus summer precipitation, overlapping the monsoonal period (June–September) of rain concentration. Our results suggest that shrub encroachment was not particularly active in this Chihuahuan ecotone for the period 2000–2013. However, future changes in the amount and temporal pattern of precipitation (i.e. reductions in monsoonal summer rainfall and/or increases in winter precipitation) may enhance the shrub-encroachment process, particularly in the face of expected upcoming increases in aridity for desert grasslands of the southwestern USA.

An analysis of primary production in the Daly River, a relatively unimpacted tropical river in northern Australia

2005 ◽  
Vol 56 (3) ◽  
pp. 303 ◽  
Author(s):  
I. T. Webster ◽  
N. Rea ◽  
A. V. Padovan ◽  
P. Dostine ◽  
S. A. Townsend ◽  
...  
Keyword(s):  
Primary Production ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Low Flow ◽  
Nutrient Concentrations ◽  
Tight Coupling ◽  
Tropical River ◽  
Rate Of Photosynthesis ◽  
Curve Method ◽  
Tropical Australia

In this paper, the dynamics of primary production in the Daly River in tropical Australia are investigated. We used the diurnal-curve method for both oxygen and pH to calculate photosynthesis and respiration rates as indicators of whole-river productivity. The Daly River has maximum discharges during the summer, monsoonal season. Flow during the dry season is maintained by groundwater discharge via springs. The study investigated how primary production and respiration evolve during the period of low flow in the river (April–November). The relationship between primary production and the availability of light and nutrients enabled the role of these factors to be assessed in a clear, oligotrophic tropical river. The measured rate of photosynthesis was broadly consistent with the estimated mass of chlorophyll associated with the main primary producers in the river (phytoplankton, epibenthic algae, macroalgae, macrophytes). A significant result of the analysis is that during the time that plant biomass re-established after recession of the flows, net primary production proved to be ~4% of the rate of photosynthesis. This result and the observed low-nutrient concentrations in the river suggest a tight coupling between photosynthetic fixation of carbon and the microbial degradation of photosynthetic products comprising plant material and exudates.

scholarly journals Effects of Controlled SO 2 Exposure on Net Primary Production and Plant Biomass Dynamics

1982 ◽  
Vol 35 (5) ◽  
pp. 572 ◽  
Author(s):  
J. L. Dodd ◽  
W. K. Lauenroth ◽  
R. K. Heitschmidt
Keyword(s):  
Primary Production ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Biomass Dynamics

Effect of precipitation variability on net primary production and soil respiration in a Chihuahuan Desert grassland

2010 ◽  
Vol 17 (4) ◽  
pp. 1505-1515 ◽  
Author(s):  
MICHELL L. THOMEY ◽  
SCOTT L. COLLINS ◽  
RODRIGO VARGAS ◽  
JENNIFER E. JOHNSON ◽  
RENEE F. BROWN ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Primary Production ◽  
Chihuahuan Desert ◽  
Net Primary Production ◽  
Precipitation Variability ◽  
Desert Grassland

Aboveground net primary production dynamics in a northern Chihuahuan Desert ecosystem

Oecologia ◽  
2007 ◽  
Vol 155 (1) ◽  
pp. 123-132 ◽  
Author(s):  
Esteban H. Muldavin ◽  
Douglas I. Moore ◽  
Scott L. Collins ◽  
Karen R. Wetherill ◽  
David C. Lightfoot
Keyword(s):  
Primary Production ◽  
Chihuahuan Desert ◽  
Net Primary Production ◽  
Desert Ecosystem ◽  
Aboveground Net Primary Production ◽  
Production Dynamics

scholarly journals Herbaceous Layer Net Primary Production of Oak-Hornbeam Forest: Comparing Six Methods of Assessment Based on the Seasonal Dynamics of Biomass Increments

Ecosystems ◽  
2021 ◽  
Author(s):  
Mateusz Rawlik ◽  
Andrzej M. Jagodziński
Keyword(s):  
Primary Production ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Carbon Assimilation ◽  
Shoot Biomass ◽  
Individual Species ◽  
Forest Site ◽  
Herb Layer ◽  
Spring Ephemeral ◽  
Galium Odoratum

AbstractProper estimation of the herb layer annual net primary production (ANPP) can help to appreciate the role of this layer in carbon assimilation and nutrient cycling. Simple methods of ANPP estimation often understate its value. More accurate methods take into account biomass increments of individual species but are more laborious. We conducted our study in an oak-hornbeam forest (site area 12 ha) dominated by beech in NW Poland during two growing seasons (2010 and 2011). We collected herb layer biomass from 7 to 10 square frames (0.6 × 0.6 m). We collected plant biomass every week in April and May and every two weeks for the rest of the growing season. We compared six methods of calculating ANPP. The highest current-year standing biomass (1st method of ANPP calculation) was obtained on May 15, 2010—37.8 g m−2 and May 7, 2011—41.0 g m−2. The highest values of ANPP were obtained by the 6th method based on the sum of the highest products of shoot biomass and density for individual species: 74.3 g m−2 year−1 in 2010 and 94.0 g m−2 year−1 in 2011. The spring ephemeral Anemone nemorosa had the highest share of ANPP with 50% of the total ANPP. Two summer-greens, Galeobdolon luteum and Galium odoratum, each had a ca. 10% share of ANPP. The best results of ANPP calculation resulted from laborious tracking of dynamics of biomass and density of individual shoots.

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