Role of Ephemerals in Sustainability of Grazing Lands in Arid Areas

Ephemeral species germinate with onset of rains and complete their lifecycle by setting seeds as the soil moisture declines within one growing season. Though their life cycle is short, they play a multifaceted role in ecological and economic sustenance of arid regions in general and grazing lands in particular. This role of ephemerals emanating from various studies has been synthesized here in respect of Indian arid zone. Nearly half of the reported 682 species in the Indian arid zone are ephemeral and seasonal, the majority being monsoonal. They constitute bulk of alpha diversity on any landscape. These occur on all land uses i.e., croplands and grazing lands. Species composition of ephemerals which varies on different habitats and in varying annual precipitation has been described in this paper. Changes is species composition, cover and biomass of ephemerals due to grazing have been discussed. Comparing phenology of selected seasonals in different grazing pressures with those in protected areas revealed that increasing grazing stress caused a typical shift in their phenophases. Production potential of ephemerals estimated in a large variety of situations indicated that they contribute differently to the total biomass of the grazing lands representing different range conditions. Since ephemerals being palatable offer grazable material, their role in prolonging duration of range use by the livestock has been proved from case studies. Besides, ephemerals occur as weeds of cropland, their composition and biomass on different habitats have been described to assess their contribution to liverstock support. The ecological value of self regenerated ephemerals in rehabilitation of disturbed lands such as mine spoils has been discussed. Many of these ephemerals are also medicinally important with proven economic potential for enhancing the livelihood of desert dwellers.


The Environment
Region facing annual water deficit of two -third or more of the potential evapotranspiration (PET) is classified as arid [2]. Semi arid regions experience this deficit ranging from one third to two third of PET. Using this criteria 9.56 lakh km2 (30.50%) can be classified as semi arid and 3.81 lakh km2 (10.16%) area as arid in India. Arid region of India has over 60% area in western Rajasthan and experience extremes of temperature (0 to 4 °C in winter and 45-48 °C in summer), low annual precipitation ranging from 450mm in the east to 10mm in the west, low humidity, high wind velocity and high evapotranspiration. Soils are sandy, poor in nutrient with low water holding capacity and prone to erosion by wind and water.
Natural vegetation in such edapho climatic conditions is sparse and stunted, predominantly spiny belonging mainly to grass cover type Dichanthium-Cenchrus-Lasiurus-type and very small area having Sehima-Dichanthium type [3].

Dichanthium -Cenchrus_ Lasiurus Cover Type
This grass cover occurs in the region receiving 100-750mm rainfall with higher mean temperature during summer (42-48 °C) and winter temperature as low as 1 to 2 °C). These grasses occur mainly on alluvial soils with varying amount of loam having high soluble salts and pale gray and brown colours. The geographical extent of 4.36 × 10 5 sq km area is distributed in northern portion of Gujarat, Rajasthan (excluding Aravallis), western Uttar Pradesh, Delhi State and semi arid Punjab and Haryana [4]. This cover type has 11 perennial grasses, 45 other herbaceous species of which 19 are legumes. The predominant woody perennials here include Acacia senegal, Calotropis procera and Cassia auriculata. These areas look typical as savanna lands.

Herbage Communties
Vegetation is a reflex of climate, land form and its surface deposit.
Broadly classified on the basis of physiognomy, six characteristic types are recognized in the Indian arid zone [6]. f) Halophytic scrub on low lying saline flats or ranns ( Table   2).

Life Cycle Of Ephemerals
Besides showing spatial specificity, some ephemerals are unique in their temporal presence; being 'accidental vegetation [8].
Accidental vegetation appears only during high rainfall; say once in the years when rainwater collects in depression where these species come up. Monsoon herbage act as 'rain-gauges' i.e. these will germinate only after a particular amount of rain is received in one event. In contrast, there are species which germinate at the very first event of rainfall irrespective of amount. These include large number of species of Indigofera, Aristida and Cenchrus. If there is no successive rain with in a span of 15-20 days these will start flowering and set seeds as early as 20 days to 40-50 days. This has been confirmed by sequential sampling of permanent plots where seasonal variation in monsoonal vegetation has been charted and measured on rocky habitats [9], alluvial plains [10] and semi rocky habitats [11]. Their findings are: Within 21 days of rain, annuals were maximum 33.58% in August and declined to 13.6% by end of September on rocky habitats of Kailana, near Jodhpur. Likewise, maximum dominance of annual grasses was 14% within 18 days of rain and it declined to almost 1/3 i.e., 4.6% by the end of September on alluvial plains in Jodhpur. It has been found that at each germination event, 20-25% seeds of entire seed bank germinate and remaining are dormant. This is an ecological adaptation in annuals to germinate only a fraction of total seed bank so as to preserve the rest for next rain event. This ensures that if seedlings die or disappear without completing life cycle and formation of seeds, the remaining seed bank portion held with in soil is able to regenerate and continue the progeny. If however, there are continuously well distributed spells of rain, they continue to grow vegetatively till they face water stress. Growth up to 50-60 cm height has been observed in these species in case of prolonged wet spell. This indicates the plasticity in annual habit of these plants.

Production Potential
There are a large number of studies on estimation of dry matter yield of rainy season ephemerals at regional, landscape and local level. Shankar and Kumar [13] estimated Aristida -Oropetium cover on 2526sq. km area in Jaisalmer with their yield as low as in Jalore district [14]. At landscape level, production of palatable monsoonals in 3 landscapes in Churu district was 174, 250 and 567kg/ha on forest floor, a planted grazingland and moderately degraded natural grazing land (Table 4). In Sikar, a protected site has 491kg/ha (92.9%) palatable and 40kg (7.1%) unpalatable herbage. The adjoining unprotected site had 230kg/ha palatable (71%) and 95kg/ha unpalatable herbage biomass [12]. Not only the total herbage yield but also yield of palatable species decline upon indiscriminate grazing. This also indicated a potential of regeneration of seasonal palatable herbage to the tune of nearly half a ton per hectare by mere protection.  their exact contribution was not reported by [17]. But this estimate amply proves that monsoon seasonals not only make up 34% of floristic composition, they also make up over 50% of biomass of grazing lands which is palatable too, in both protection and degraded conditions. grazing pressure, the other forbs species also increased up to September and declined later, with increasing grazing pressure.
This was also confirmed by positive significant correlation between cover and grazing intensity i.e., increases in cover with increasing grazing pressure in Aristida mutabilis. Importantly, correlation coefficient between grazing pressure and cover of Indigofera hochstetteri, I. cordifolia, I. linifolia at arid site and C.
pumila at semi arid site was strongly negative. Thus same species behaves differently in two different rainfall situations. It emerged from above that annual species after being nibbled or partly grazed by sheep re-sprout and assume growth in semi arid situation, behaving much as multi cut fodder corp. These findings were in conformity with results of an earlier grazing experiment of three years at Kailana, Jodhpur where per cent plant cover increased from 4.8 to 7.42% and forage yield, 28.3 to 29.8kg/ha after grazing [20].
In the same experimental paddocks at Chandan in Jaisalmer district of western India, phenological changes at monthly intervals were also recorded under different grazing pressures.
Concurrently, palatability of species as and when the sheep bites was also noted for one hour each during morning (8-10AM), noon (12-2PM) and evening (4-8PM). Results revealed that vegetative phase was shortened and flowering, fruiting and seed set occurred earlier in perennial like Lasiurus sindicus as the grazing pressure increased [21]. Thus compressing the vegetative phase emerged as a mechanism of evading grazing pressure in this perennial grass.
Reverse was noted in all the ephemeral species. Vegetative phase was prolonged with increasing intensity of grazing and thus seed setting was delayed in ephemeral species Aristida funiculata, Indigofera cordifolia, Indigofera linifolia and Corchorus tridense.
This shift in phenophase could be related to their relative palatability. Since annual species germinate and grow with their fresh foliage during the monsoon rains, annuals (due to fresh foliage) were eaten in preference over the perennials. This preferred removal of annuals due to their palatability, if continued unabated, would finally remove them completely due to overgrazing. In fact, such a shift in phenophases, induced by increase in grazing intensity, can effectively be used as indicator of beginning of deterioration of rangeland health. And this becomes the start point of desertification in grazing lands in deserts. Moderate grazing is therefore, desirable for maintaining range health for sustainable grazing. On the other hand, it is also important to realize this potential of monsoon ephemerals as grazing material as by way of corollary these can be sown and then cut, not grazed, and fed to animals.
In order to further understand the role of herbaceous annual and seasonal vegetation, another grazing study was undertaken for two consecutive years in Lasiurus sindicus dominated protected grazingland at experimental area at Chandan in Jaisalmer district by Kumar et al. [22]. There were five grazing treatments:T-1: Control (T-5) kgha-1. In rain driven ecosystem of arid lands, even a small variation in the quantum, spread and timing of rainfall causes major effect on vegetation composition [23]. These have cascading effects making the whole system vulnerable to drought and adversely affecting sustainable productivity of the rangeland ecosystem [24].
This study thus, concluded that rainy season ephemerals by way of their preferential consumption give temporary or seasonal rest to perennials like L. sindicus enabling it to grow and recover. Vetter et al. [25] while discussing such differences in composition, structure, diversity and forage production potential of vegetation under different grazing intensities reasoned that these ephemerals can draw water from whole soil profile throughout the growing seasons where as climax grasses withdraw water from deeper layers of 2-5m during droughts [23].
Thus, resource utilization is partitioned to be optimally used among ephemerals and perennials resulting in better growth of both these components. Consequently, grazable material becomes available from the same grazing land for a longer duration and that imparts resilience to the grazing land system. Fynn [26] also reported that short, nutritious grasses in functional wet seasons habitats facilitate optimum intake of nutrients and energy for lactating females, for optimal calf growth and building body stores.
Heterogeneity in vegetation composition due to ephemerals was also emphasized for achieving optimum grazing use by [28].
Evidently, Kumar et al. [22] in their study also related the spatial patterns created by patches of seasonal vegetation in the landscape and temporal patterns of biomass (= productivity) availability of seasonals in post monsoon and perennials in winter and summer with long term sustainability. Fynn [26] also concluded that grazing based on spatial and temporal variability in forage quality and quantity would be more sustainable. Nutritionally also, seasonal vegetation having higher crude protein than perennial grasses 560 [28] meets the nutritional needs of the livestock. Utilizing above mentioned spatial and temporal patterns was also recommended as best range utilization strategy by [27]. But Kumar et al. [23] found that free range animals in monsoonal rangelands themselves do selective grazing based on seasonal availability of biomass i.e., they graze annuals first (August to November) and then perennials   [30] i.e., their biomass was 2 to 4 times more than crop (

Role of Ephemerals in Rehabilitation of Mine Spoils
Though perennials are preferred for rehabilitation of degraded lands like mine spoils, but once the seeds bank is added to soil, annuals   This aspect has helped to design conservation strategy of critically endangered Great Indian Bustard in its native landscape by way of provisioning of foraging material by just enabling buried ephemerals seeds to come up on surface through ploughing and then germinating during rains.

Ephemerals as Medicinal Plants
They contribute up to 500-600kg/ha dry matter without any management in natural conditions. Grown properly under managed conditions, their yield can be enhanced many folds. This can be achieved by providing moisture just before flowering so that vegetative phase is prolonged, thus capitalizing its ecological properties to further increase its yield to double or treble.
Experiments are however needed to confirm whether these could be used as multicut fodder crop in sole or as intercrop. In view of rich ephemeral flora in the Indian desert, we are advantageously placed to select a few chosen species for testing their potential as future livestock feed either raw or as feed cake. Not merely a source of livestock feed, these grazing lands are also cradle of as many as medicine; many of them having immense trade potential that can add to the kitty of local farmers. In the ecological management of mine spoiled lands, ephemerals as an adjunct to perennial species have proved their potential as a cheaper and faster rehabilitation material.