Showing papers on "Growing season published in 2022"

Vegetation greening, extended growing seasons, and temperature feedbacks in warming temperate grasslands of China

Abstract: Vegetation activity and phenology are significantly affected by climate change, and changes in vegetation activity and phenology can in turn affect regional or global climate patterns. As one of the world’s great biomes, temperate grasslands have undergone remarkable changes in recent decades, but the connections between vegetation activity and phenology changes and regional climate there have remained unclear. Using observation minus reanalysis (OMR) method, this study investigated the possible effects of vegetation activity and vegetation growing season changes on air temperatures in temperate grasslands of China. The results showed that average NDVI of the temperate grassland significantly increased by 0.011/decade for the growing season during 1982-2015. The growing season started earlier and ended later, resulting in an extension. Increased vegetation activity during spring and autumn significantly warmed spring and autumn air temperatures by reducing albedo. By contrast, summer greening had no significant effect on summer temperature, due to the opposing effects of decreased albedo and enhanced evapotranspiration on temperature. The earlier start and later end of the growing season contributed to warmer spring and autumn air temperatures. As phenological changes had no significant effect on summer temperature, the extended growing season warmed air temperature. Our results suggest that the climate change-induced increasing vegetation activity and extended growing seasons can further aggravate regional warming in temperate grasslands of China, implying that the effects of vegetation activity and phenology changes on regional climate should be considered in climate models for accurately simulating climate change in temperate grasslands.

An earlier start of the thermal growing season enhances tree growth in cold humid areas but not in dry areas

Abstract: Climatic warming alters the onset, duration and cessation of the vegetative season. While previous studies have shown a tight link between thermal conditions and leaf phenology, less is known about the impacts of phenological changes on tree growth. Here, we assessed the relationships between the start of the thermal growing season and tree growth across the extratropical Northern Hemisphere using 3,451 tree-ring chronologies and daily climatic data for 1948–2014. An earlier start of the thermal growing season promoted growth in regions with high ratios of precipitation to temperature but limited growth in cold–dry regions. Path analyses indicated that an earlier start of the thermal growing season enhanced growth primarily by alleviating thermal limitations on wood formation in boreal forests and by lengthening the period of growth in temperate and Mediterranean forests. Semi-arid and dry subalpine forests, however, did not benefit from an earlier onset of growth and a longer growing season, presumably due to associated water loss and/or more frequent early spring frosts. These emergent patterns of how climatic impacts on wood phenology affect tree growth at regional to hemispheric scales hint at how future phenological changes may affect the carbon sequestration capacity of extratropical forest ecosystems. The authors use tree-ring width data across the extratropical Northern Hemisphere to show that earlier growing season onsets lead to enhanced tree radial growth in cold humid but not in dry areas.

Warm springs alter timing but not total growth of temperate deciduous trees

Abstract: As the climate changes, warmer spring temperatures are causing earlier leaf-out1–3 and commencement of CO2 uptake1,3 in temperate deciduous forests, resulting in a tendency towards increased growing season length3 and annual CO2 uptake1,3–7. However, less is known about how spring temperatures affect tree stem growth8,9, which sequesters carbon in wood that has a long residence time in the ecosystem10,11. Here we show that warmer spring temperatures shifted stem diameter growth of deciduous trees earlier but had no consistent effect on peak growing season length, maximum growth rates, or annual growth, using dendrometer band measurements from 440 trees across two forests. The latter finding was confirmed on the centennial scale by 207 tree-ring chronologies from 108 forests across eastern North America, where annual ring width was far more sensitive to temperatures during the peak growing season than in the spring. These findings imply that any extra CO2 uptake in years with warmer spring temperatures4,5 does not significantly contribute to increased sequestration in long-lived woody stem biomass. Rather, contradicting projections from global carbon cycle models1,12, our empirical results imply that warming spring temperatures are unlikely to increase woody productivity enough to strengthen the long-term CO2 sink of temperate deciduous forests. Warmer spring temperatures affect the timing of stem diameter growth of temperate deciduous trees but have little effect on annual growth.

Monitoring the Dynamic Changes in Vegetation Cover Using Spatio-Temporal Remote Sensing Data from 1984 to 2020

Abstract: Anthropogenic activities and natural climate changes are the central driving forces of global ecosystems and agriculture changes. Climate changes, such as rainfall and temperature changes, have had the greatest impact on different types of plant production around the world. In the present study, we investigated the spatiotemporal variation of major crops (cotton, rice, wheat, and sugarcane) in the District Vehari, Pakistan, from 1984 to 2020 using remote sensing (RS) technology. The crop identification was pre-processed in ArcGIS software based on Landsat images. After pre-processing, supervised classification was used, which explains the maximum likelihood classification (MLC) to identify the vegetation changes. Our results showed that in the study area cultivated areas under wheat and cotton decreased by almost 5.4% and 9.1% from 1984 to 2020, respectively. Vegetated areas have maximum values of NDVI (> 0.4), and built-up areas showed fewer NDVI values (0 to 0.2) in the District Vehari. During the Rabi season, the temperature was increased from 19.93 °C to 21.17 °C. The average temperature was calculated at 34.28 °C to 35.54 °C during the Kharif season in the District Vehari. Our results showed that temperature negatively affects sugarcane, rice, and cotton crops during the Rabi season, and precipitation positively affects sugarcane, rice, and cotton crops during the Kharif season in the study area. Accurate and timely assessment of crop estimation and relation to climate change can give very useful information for decision-makers, governments, and planners in formulating policies regarding crop management and improving agriculture yields.

Conservation tillage improves soil water storage, spring maize (Zea mays L.) yield and WUE in two types of seasonal rainfall distributions

Abstract: Variations in the rainfall distribution during the growing season are a major limiting factor restricting the spring maize yield on the semiarid Loess Plateau of China. Conservation tillage can improve yield and water use efficiency but the specific effects of conservation tillage with differing rainfall distributions during the growing season remain unclear. Therefore, a 12-year experiment was conducted and the data were divided into two categories based on rainfall distribution type. If poor rainfall occurred during the jointing-tasseling stage of the maize growing season and adequate rainfall occurred in the filling-maturity stage, the rainfall was named type-A. In contrast, if adequate rainfall occurred in the jointing-tasseling stage and poor rainfall occurred in the filling-maturity stage during the maize growing season, the rainfall distribution was categorized as type-B. This research used conventional tillage (CT) as a control to study the productivity of no-tillage (NT) and subsoiling (ST) under the selected rainfall distributions. The results showed that the type-B rainfall distribution increased dry matter accumulation, yield, soil water use efficiency (WUE) and precipitation use efficiency (PUE) by 18.9%, 32.0%, 21.7% and 45.1%, respectively, when compared with the type-A rainfall distribution. However, under type-A rainfall distribution, NT increased soil water storage by 3.7% and 4.4% and ST increased the soil water storage by 6.0% and 7.0% in the tasseling and grain filling stages, respectively, compared with CT. Moreover, NT and ST increased the dry matter accumulation, yield, WUE and PUE. The relationships among the yield, soil water storage and precipitation showed that the water storage in the sowing stage indirectly affected the maize yield through soil water storage at the tasseling stage, and the increase in precipitation from the jointing to tasseling stages had a directly positive effect on the increase in yield. Based on soil water storage with a value of 202.3 mm in the 0–200 cm soil depth during the tasseling stage, the yield increased by 47.8 kg ha−1 as the soil water storage improved by 1 mm. In conclusion, no-tillage and subsoiling improved the soil water conditions, mitigated the soil drought stress caused by variable rainfall distribution and improved the yield. Therefore, no-tillage and subsoiling practices are recommended for agricultural production in semiarid areas.

The Change in Environmental Variables Linked to Climate Change Has a Stronger Effect on Aboveground Net Primary Productivity Than Does Phenological Change in Alpine Grasslands

Abstract: More and more studies have focused on responses of ecosystem carbon cycling to climate change and phenological change, and aboveground net primary productivity (ANPP) is a primary component of global carbon cycling. However, it remains unclear whether the climate change or the phenological change has stronger effects on ANPP. In this study, we compared the effects of phenological change and climate change on ANPP during 2000–2013 across 36 alpine grassland sites on the Tibetan Plateau. Our results indicated that ANPP showed a positive relationship with plant phenology such as prolonged length of growing season and advanced start of growing season, and environmental variables such as growing season precipitation (GSP), actual vapor pressure (Ea), relative humidity (RH), and the ratio of GSP to ≥5°C accumulated temperature (GSP/AccT), respectively. The linear change trend of ANPP increased with that of GSP, Ea, RH, and GSP/AccT rather than phenology variables. Interestingly, GSP had the closer correlation with ANPP and meanwhile the linear slope of GSP had the closer correlation with that of ANPP among all the concerned variables. Therefore, climate change, mainly attributed to precipitation change, had a stronger effect on ANPP than did phenological change in alpine grasslands on the Tibetan Plateau.

Compound hydroclimatic extremes in a semi‐arid grassland: Drought, deluge, and the carbon cycle

Abstract: Climate change is predicted to increase the frequency and intensity of extreme events including droughts and large precipitation events or “deluges.” While many studies have focused on the ecological impacts of individual events (e.g., a heat wave), there is growing recognition that when extreme events co‐occur as compound extremes, (e.g., a heatwave during a drought), the additive effects on ecosystems are often greater than either extreme alone. In this study, we assessed a unique type of extreme—a contrasting compound extreme—where the extremes may have offsetting, rather than additive ecological effects, by examining how a deluge during a drought impacts productivity and carbon cycling in a semi‐arid grassland. The experiment consisted of four treatments: a control (average precipitation), an extreme drought (<5th percentile), an extreme drought interrupted by a single deluge (>95th percentile), or an extreme drought interrupted by the equivalent amount of precipitation added in several smaller events. We highlight three key results. First, extreme drought resulted in early senescence, reduced carbon uptake, and a decline in net primary productivity relative to the control treatment. Second, the deluge imposed during extreme drought stimulated carbon fluxes and plant growth well above the levels of both the control and the drought treatment with several additional smaller rainfall events, emphasizing the importance of precipitation amount, event size, and timing. Third, while the deluge's positive effects on carbon fluxes and plant growth persisted for 1 month, the deluge did not completely offset the negative effects of extreme drought on end‐of‐season productivity. Thus, in the case of these contrasting hydroclimatic extremes, a deluge during a drought can stimulate temporally dynamic ecosystem processes (e.g., net ecosystem exchange) while only partially compensating for reductions in ecosystem functions over longer time scales (e.g., aboveground net primary productivity).

Conservation tillage improves soil water storage, spring maize (Zea mays L.) yield and WUE in two types of seasonal rainfall distributions

Abstract: Variations in the rainfall distribution during the growing season are a major limiting factor restricting the spring maize yield on the semiarid Loess Plateau of China. Conservation tillage can improve yield and water use efficiency but the specific effects of conservation tillage with differing rainfall distributions during the growing season remain unclear. Therefore, a 12-year experiment was conducted and the data were divided into two categories based on rainfall distribution type. If poor rainfall occurred during the jointing-tasseling stage of the maize growing season and adequate rainfall occurred in the filling-maturity stage, the rainfall was named type-A. In contrast, if adequate rainfall occurred in the jointing-tasseling stage and poor rainfall occurred in the filling-maturity stage during the maize growing season, the rainfall distribution was categorized as type-B. This research used conventional tillage (CT) as a control to study the productivity of no-tillage (NT) and subsoiling (ST) under the selected rainfall distributions. The results showed that the type-B rainfall distribution increased dry matter accumulation, yield, soil water use efficiency (WUE) and precipitation use efficiency (PUE) by 18.9%, 32.0%, 21.7% and 45.1%, respectively, when compared with the type-A rainfall distribution. However, under type-A rainfall distribution, NT increased soil water storage by 3.7% and 4.4% and ST increased the soil water storage by 6.0% and 7.0% in the tasseling and grain filling stages, respectively, compared with CT. Moreover, NT and ST increased the dry matter accumulation, yield, WUE and PUE. The relationships among the yield, soil water storage and precipitation showed that the water storage in the sowing stage indirectly affected the maize yield through soil water storage at the tasseling stage, and the increase in precipitation from the jointing to tasseling stages had a directly positive effect on the increase in yield. Based on soil water storage with a value of 202.3 mm in the 0–200 cm soil depth during the tasseling stage, the yield increased by 47.8 kg ha−1 as the soil water storage improved by 1 mm. In conclusion, no-tillage and subsoiling improved the soil water conditions, mitigated the soil drought stress caused by variable rainfall distribution and improved the yield. Therefore, no-tillage and subsoiling practices are recommended for agricultural production in semiarid areas.

A Review on the Observed Climate Change in Europe and Its Impacts on Viticulture

Abstract: The European climate is changing displaying profound on agriculture, thus strongly reaching the scientific community’s attention. In this review, the compilation of selected scientific research on the agroclimatic conditions’ changes and their impact on the productivity parameters (phenology timing, product quality and quantity) of grapevines and on the spatiotemporal characteristics of the viticultural areas are attempted for the first time. For this purpose, a thorough investigation through multiple search queries was conducted for the period (2005–2021). Overall, increasing (decreasing) trends in critical temperature (precipitation) parameters are the reality of the recent past with visible impacts on viticulture. The observed climate warming already enforces emerging phenomena related to the modification of the developmental rate (earlier phenological events, shortening of phenological intervals, lengthening of the growing season, earlier harvest), the alteration of product quality, the heterogeneous effects on grapevine yield and the emergence of new cool-climate viticulture areas highlighting the cultivation’s rebirth in the northern and central parts of the continent. The vulnerability of the wine-growing ecosystem urges the integration of innovative and sustainable solutions for confronting the impacts of climate change and safeguarding the production (quantity and quality) capacity of viticultural systems in Europe under a continuously changing environment.

Combined amendment reduces soil Cd availability and rice Cd accumulation in three consecutive rice planting seasons

Abstract: The scientific application of stabilized materials has been considered an effective method for the in situ remediation of Cd-contaminated soil. This study aimed to investigate the persistence of the effect of a combined amendment of limestone and sepiolite (LS) on soil Cd availability and accumulation in rice grown in a mildly Cd-contaminated paddy field (0.45 mg/kg of Cd) over three consecutive rice seasons. 1125–4500 kg/ha of LS was applied to the soil before the first rice planting season and 562.5–2250 kg/ha of LS was supplemented before the third rice planting season. The application of LS (1125–4500 kg/ha) increased the soil pH by 0.44–1.09, 0.18–0.53, and 0.42–0.68 in the first, second, and third season, respectively, and decreased the soil acid-extractable Cd content by 18.2–36.4%, 17.7–33.5%, and 9.6–17.6%. LS application significantly decreased the Cd contents in the rice tissues. The application of 4500 kg/ha of LS decreased the Cd content in brown rice to below the National Food Limit Standard of 0.2 mg/kg (GB 2762-2017) in the three consecutive rice seasons. However, the effect of LS on the soil-rice system was significantly weakened in the third season. The supplementary application of 562.5–2250 kg/ha of LS further decreased the Cd content in brown rice by 26.1–56.5% and decreased the health risk index by 23.7–43.8%. Therefore, it was recommended to apply 4500 kg/ha of LS in the first season and to supplement 2250 kg/ha of LS in the third season to effectively guarantee the clean production of rice in three consecutive rice seasons.

Comparison of yield performance between direct-seeded and transplanted double-season rice using ultrashort-duration varieties in central China

Abstract: Labor scarcity requires double-season rice to be planted by direct seeding as an alternative to transplanting. Only ultrashort-duration varieties can be used in direct-seeded, double-season rice (DSD) in central China where thermal time is limited. Whether ultrashort-duration varieties grown in DSD can be as productive and efficient in nitrogen (N) use as transplanted double-season rice (TPD) remains unclear. Field experiments were conducted in Hubei province, central China with two establishment methods (DSD, TPD) and three N rates in the early and late seasons of 2017 and 2018. Nitrogen treatments included zero-N control (N0), total N rate of 60 kg N ha −1 with equal splits at basal, midtillering, and panicle initiation (N1), and weekly N application at 15 kg ha −1 from seeding/transplanting to heading (N2). Both early- and late-season rice under DSD matured within 95 days, on average 9 days shorter than rice under TPD. The grain yield of DSD was comparable to or higher than that of TDP in both seasons, although the daily yield was significantly higher under DSD than under TDP. Before heading, DSD had higher leaf area, stem number, intercepted radiation, and radiation use efficiency than TPD, which compensated for the negative effect of short growth duration on biomass production. Total dry weight and harvest index under DSD were comparable to or higher than those under TDP. In general, the recovery efficiency of fertilizer-N under DSD was higher than that under TPD, but the reverse was true for physiological N use efficiency. Thus, there was no significant difference in agronomic N use efficiency between DSD and TPD. These results suggested that DSD with ultrashort-duration varieties is a promising alternative to TPD in central China for maintaining high grain yield and N fertilizer use efficiency with less labor input.

Linkages between the temperature sensitivity of soil respiration and microbial life strategy are dependent on sampling season

Abstract: The temperature sensitivity (Q10) of soil respiration (Rs) is crucial to assess the carbon (C) budget of terrestrial ecosystems under global warming. The Q10 changes along a climatic gradient as well as its seasonal dynamics remain unclear, and the underlying microbial mechanisms are not well known. Here, the seasonal Q10 of Rs at the northern, middle, and southern sites of a natural temperate mixed forest was examined. The mean annual temperature (MAT) of the sampling sites spanned from 0.5 to 4.9 °C. The Q10 pattern over the climatic zones was highly dependent on season, with Q10 increasing toward the southern region in spring and autumn, but having a similar level across the sampling sites in summer. In spring, Q10 was independent of microbial community composition and functions. Instead, spring Q10 increased with decreasing C availability from north to south, consistent with the Carbon-Quality-Temperature theory. In summer, Q10 was closely associated with the dominance of microbial r-strategy features, characterized by high copiotroph/oligotroph and labile/recalcitrant C degradation gene ratios. In autumn, however, Q10 was driven by the K-selected microbial communities, which might have been ascribed to the priming effects mediated by fresh plant litter. The seasonality of Q10 was site-dependent. The southern and middle sites had the lowest Q10 in summer, consistent with the Seasonal Plasticity Hypothesis, which predicts lower temperature sensitivity in warmer seasons. In contrast, the Q10 at the northern site remained stable during the growing season due to minor seasonal fluctuations in plant litter inputs and microbial community composition and functions. This work deepens our understanding on the complex relationships between Q10, carbon availability and microorganisms over spatial and temporal scales by translating microbial phylogenetic data into life strategies.

Combined amendment reduces soil Cd availability and rice Cd accumulation in three consecutive rice planting seasons

Abstract: The scientific application of stabilized materials has been considered an effective method for the in situ remediation of Cd-contaminated soil. This study aimed to investigate the persistence of the effect of a combined amendment of limestone and sepiolite (LS) on soil Cd availability and accumulation in rice grown in a mildly Cd-contaminated paddy field (0.45 mg/kg of Cd) over three consecutive rice seasons. 1125-4500 kg/ha of LS was applied to the soil before the first rice planting season and 562.5-2250 kg/ha of LS was supplemented before the third rice planting season. The application of LS (1125-4500 kg/ha) increased the soil pH by 0.44-1.09, 0.18-0.53, and 0.42-0.68 in the first, second, and third season, respectively, and decreased the soil acid-extractable Cd content by 18.2-36.4%, 17.7-33.5%, and 9.6-17.6%. LS application significantly decreased the Cd contents in the rice tissues. The application of 4500 kg/ha of LS decreased the Cd content in brown rice to below the National Food Limit Standard of 0.2 mg/kg (GB 2762-2017) in the three consecutive rice seasons. However, the effect of LS on the soil-rice system was significantly weakened in the third season. The supplementary application of 562.5-2250 kg/ha of LS further decreased the Cd content in brown rice by 26.1-56.5% and decreased the health risk index by 23.7-43.8%. Therefore, it was recommended to apply 4500 kg/ha of LS in the first season and to supplement 2250 kg/ha of LS in the third season to effectively guarantee the clean production of rice in three consecutive rice seasons.

No evidence for a negative effect of growing season photosynthesis on leaf senescence timing

Abstract: The length of the growing season has a large influence on the carbon, water, and energy fluxes of global terrestrial ecosystems. While there has been mounting evidence of an advanced start of the growing season mostly due to elevated spring air temperatures, the mechanisms that control the end of the growing season (EOS) in most ecosystems remain relatively less well understood. Recently, a strong lagged control of EOS by growing season photosynthesis has been proposed, suggesting that more productive growing seasons lead to an earlier EOS. However, this relationship has not been extensively tested with in‐situ observations across a variety of ecosystems. Here, we use observations from 40 eddy‐covariance flux tower sites in temperate and boreal ecosystems in the northern hemisphere with more than 10 years of observations (594 site‐years), ground observations of phenology, satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS), and three leaf senescence models to test the extent of a relationship between growing season photosynthesis and end of season senescence. The results suggest that there is no significant negative relationship between growing season photosynthesis and observed leaf senescence, flux‐inferred EOS estimates, or remotely sensed phenological metrics, in most ecosystems. On the contrary, while we found negative effects of summer air temperatures and autumn vapor pressure deficit on EOS, more productive growing seasons were typically related to a later, not earlier, EOS. Our results challenge recent reports of carry‐over effects of photosynthesis on EOS timing, and suggest those results may not hold over a large range of ecosystems.