The Role Of Perennial Grasses In The Accumulation Of Organic Matter In Soil-Saving Agriculture

In the farms of the Belgorod region, a comprehensive study was conducted to assess the productivity of perennial grasses using soil-saving technologies in comparison with traditional methods of tillage. The results of the dispersion analysis showed that the value of the indicator of the total aboveground and underground productivity of perennial grasses significantly depends on the species composition of the grass stand. It was found that the difference between the site of a perennial fallow and fields with perennial grasses with the use of soil-saving technologies did not exceed 13.9% in terms of the total aboveground productivity. The aboveground productivity of alfalfa was significantly higher than in the control variant (fallow field) and in the experimental fields with soil conservation technologies – by 73.6 % and 101.6 %, respectively. The accumulation of underground mass in the fallow area and in areas using soil conservation technologies is approximately at the same level – 1.91 kg*(m) − 2 in the control and 1.85-2.25 (average 2.04) kg*(m) − 2 in soil-saving crop rotations. At the same time, the Cv in the control variant was 15.78 %, and in grass mixtures, respectively, it was at the level of 16.47 %; 18.74 % and 18.08 %. In alfalfa crops, the accumulation of mass in the underground layer was inferior to the control variant by an average of 27.2 %, and to soil conservation technologies-by an average of 31.9 %. Alfalfa crops, providing greater aboveground productivity, are more intensive in terms of production, but less effective means of increasing the content of organic matter in the soil compared to cereal-legume grass mixtures. In soil conservation agriculture, it is necessary to use cereal-legume grass mixtures as more natural-like, and to increase the intensification of agricultural production, alfalfa crops should be used.

Estimating the Effects of a Hurricane on Carbon Storage in Mangrove Wetlands in Southwest Florida

Tropical and subtropical mangrove swamps, under normal conditions, can sequester large amounts of carbon in their soils but as coastal wetlands, they are prone to hurricane disturbances. This study adds to the understanding of carbon storage capabilities of mangrove wetlands and explores how these capacities might change within the scope of a changing storm climate. In September 2017, Naples Bay, FL, USA (28°5′ N, 81°47′ W) encountered a direct hit from hurricane Irma, a Saffir–Simpson category 3 storm. By comparing carbon storage, forest community structure, and aboveground productivity collected in 2013 and in 2019, we estimated the effects of hurricane Irma on mangrove functions. Aboveground biomass increased during the study period at a rate of approximately 0.72 kg m−2 yr−1, significantly less than the average found in undisturbed mangrove forests. Soil carbon storage decreased at all study sites. On average, 2.7 kg-C m−2 was lost in the top 20 cm between sample collections. Carbon loss in belowground pools could point to a feedback of mangrove swamps on climate change as they lose their ability to store carbon and increase net atmospheric carbon. Nevertheless, mangrove swamps remain resilient to tropical storms in the long term and can recover their carbon storage capacity in the years following a storm.

Factors controlling the productivity of tropical Andean forests: Climate and soil are more important than tree diversity

Theory predicts positive effects of species richness on the productivity of plant communities through complementary resource use and facilitative interactions between species. Results from manipulative experiments with tropical tree species indicate a positive diversity-productivity relationship (DPR), but the existing evidence from natural forests is scarce and contradictory. We studied forest aboveground productivity in more than 80 humid tropical montane old-growth forests in two highly diverse Andean regions with large geological and topographic heterogeneity, and related productivity to tree diversity and stand structural, edaphic and climatic factors with likely influence on productivity. Main determinants of aboveground productivity in the perhumid study regions were elevation (as a proxy of temperature), soil nutrient (N, P and base cation) availability, and forest structural parameters (wood specific gravity, aboveground biomass). Tree diversity had only a small positive influence on productivity, even though tree species numbers varied largely (6–27 species per 0.04 ha). We conclude that the productivity of Neotropical humid montane forests is primarily controlled by thermal, edaphic and stand structural factors, while tree diversity is of minor importance.

Local-scale and spatially explicit response of tropical forests to climate change

<p>Currently applied dynamic vegetation models do not realistically represent forest ecosystem processes and thus are not able to reproduce in-situ observations of forest ecosystem responses to drought. This is due to the fact that models typically rely on plant functional types to forecast the functional response of vegetation to climate change and to anthropogenic disturbance. However, recent observations of divergent ecosystem responses between topographic forest sites, differing in the availability of water and nutrients, indicate that we should no longer rely on this outdated concept but rather should explore new avenues of representing vegetation dynamics and associated climate change response in next-generation approaches.</p><p>Global climate change scenarios forecast increasing severity of climate extremes in association with El Niño–Southern Oscillation (ENSO). Such climate anomalies have been shown to affect forest ecosystem processes such as net primary productivity, which is determined by climate (precipitation, temperature, and light) and soil fertility (geology and topography). However, more recently it has been suggested that the impact of such climate fluctuations on forest productivity was strongly related to local site characteristics, which determined the sensitivity of forest ecosystem processes to climate anomalies.</p><p>We propose a novel approach integrating in-situ observations with remotely sensed estimates of forest aboveground productivity for parameterization of next-generation vegetation models capable of forecasting realistic forest ecosystem responses under future scenarios. Our approach considers local site characteristics associated with topography and disturbance history, both of which determine the sensitivity of forest aboveground productivity to projected climate anomalies. Our results therefore should have crucial implications for management and restoration of forest ecosystems and could be used to refine estimates of forest C sink-strength under future scenarios.</p>

The Economy of Canopy Space Occupation and Shade Production in Early- to Late-Successional Temperate Tree Species and Their Relation to Productivity

Light capture is linked to occupation of canopy space by tree crowns, which requires investment of carbon and nutrients. We hypothesize that (i) late-successional trees invest more in casting shade than in occupying space than early-successional trees, and (ii) shade production and crown volume expansion are generally greater in more productive species. For six Central European early-successional (Betula pendula, Pinus sylvestris), mid/late-successional (Quercus petraea, Carpinus betulus), and late-successional tree species (Tilia cordata, Fagus sylvatica), we measured through full-tree harvests (1) crown volume, (2) the costs of canopy space exploration (carbon (C) and nutrients invested to fill crown volume), of space occupation (annual foliage production per volume), and of shade production (foliage needed to reduce light transmittance), and (3) related the costs to aboveground productivity (ANPP). The C and nutrient costs of canopy volume exploration and occupation were independent of the species’ seral stage, but increased with ANPP. In contrast, the cost of shade production decreased from early-to late-successional species, suggesting that the economy of shade production is more decisive for the competitive superiority of late-successional species than the economy of canopy space exploration and occupation.

Clipping defoliation eliminates the stimulating effects of nitrogen enrichment on the aboveground productivity of an alpine meadow

To investigate how clipping (CL) regulates the effects of nutrient addition, an experiment, including CL and nitrogen (N) addition, was conducted in an alpine meadow. Nitrogen treatment increased community coverage (48–113% higher than the control) and aboveground biomass (29–117% higher than the control), which was mainly attributed to grass growth. Both N and N + CL treatments showed a tendency to reducing species richness, while significant reduction only occurred in 2016 and 2017 in CL treatment. Clipping showed a tendency to decrease community cover (3–37% lower than the control) and aboveground biomass (2–34% lower than the control), while N + CL treatment had no effect, indicating that clipping can eliminate the simulated effects of N addition. Nitrogen addition significantly increased soil inorganic N (SIN, 528–1230% higher than the control), while SIN in N + CL was 25–48% lower than N treatment. The decrease in stimulated effects in N + CL was attributed to SIN decrease, which resulted from the aboveground biomass removal by clipping. Our results show that clipping can take away aboveground biomass and cause soil nutrients to decrease, which slows down the degraded grassland recovery. This suggests that grazing exclusion may eliminate the effect of nitrogen deposition on aboveground production in alpine grasslands.